Mojave Desert

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https://en.wikipedia.org/wiki/Mojave_Desert

Mojave Desert Hayyikwiir Mat'aar (Mohave)
Sand dunes in Death Valley
Location within North America
Ecology
Realm	Nearctic
Biome	Deserts and xeric shrublands
Borders

List
Bird species	230
Mammal species	98
Geography
Area	81,000 km2 (31,000 sq mi)
Country	United States
States	Arizona, California, Nevada and Utah
Coordinates	35°N 116°WCoordinates: 35°N 116°W
Rivers	Colorado River, Mojave River
Conservation
Conservation status	Relatively Stable/Intact

The Mojave Desert (/moʊˈhɑːvi, mə-/ moh-HAH-vee, mə-; Mohave: Hayikwiir Mat'aar; Spanish: Desierto de Mojave) is a xeric desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in southeastern California and southwestern Nevada, with small portions extending into Arizona and Utah.

The Mojave Desert, together with the Sonoran, Chihuahuan, and Great Basin deserts, forms a larger North American Desert. Of these, the Mojave is the smallest and driest. The Mojave Desert displays typical basin and range topography, generally having a pattern of a series of parallel mountain ranges and valleys. It is also the site of Death Valley, which is the lowest elevation in North America. The Mojave Desert is often colloquially called the "high desert", as most of it lies between 2,000 and 4,000 feet (610 and 1,220 m). It supports a diversity of flora and fauna.

The 20 million acres (81,000 km²) desert supports a number of human activities, including recreation, ranching, and military training. The Mojave Desert also contains various silver, tungsten, iron and gold deposits.

The spelling Mojave originates from the Spanish language, while the spelling Mohave comes from modern English. Both are used today, although the Mojave Tribal Nation officially uses the spelling Mojave. Mojave is a shortened form of Hamakhaave, an endonym in their native language, which means "beside the water".

Geography

The Joshua tree (Yucca brevifolia) is endemic and exclusive to the Mojave Desert.

The Mojave Desert is bordered to the west by the Sierra Nevada mountain range and the California montane chaparral and woodlands, and to the south and east by the Sonoran Desert. The boundaries to the east of the Mojave Desert are less distinctive than the other boundaries because there is no presence of an indicator species, such as the Joshua tree (Yucca brevifolia), which is endemic to the Mojave Desert. The Mojave Desert is distinguished from the Sonoran Desert and other deserts adjacent to it by its warm temperate climate, as well as flora and fauna such as ironwood (Olneya tesota), blue Palo Verde (Parkinsonia florida), chuparosa (Justicia californica), spiny menodora (Menodora spinescens), desert senna (Cassia armata), California dalea (Psorothamnus arborescens), and goldenhead (Acamptopappus shockleyi). Along with these other factors, these plants differentiate the Mojave from the nearby Sonoran desert.

The Mojave Desert is bordered by the San Andreas fault to the Southwest and the Garlock fault to the North. The mountains elevated along the length of the San Andreas fault provide a clear border between the Mojave desert and the coastal regions to the West. The Garlock fault separates the Mojave Desert from the Sierra Nevada and Tehachapi mountains, which provide a natural border to the Mojave Desert. There are also abundant alluvial fans, which are called bajadas, that form around the mountains within the Mojave desert and extend down toward the low altitude basins, which contain dried lake beds called playas, where water generally collects and evaporates, leaving large volumes of salt. These playas include Rogers Dry Lake, and China Lake. Dry lakes are a noted feature of the Mojave landscape. The Mojave Desert is also home to the Devils Playground, about 40 miles (64 km) of dunes and salt flats going in a northwest-southeasterly direction. The Devil's Playground is a part of the Mojave National Preserve and is between the town of Baker, California and Providence Mountains. The Cronese Mountains are within the Devil's Playground.

There are very few surface rivers in the Mojave Desert, even given the low precipitation level: two major rivers generally flow underground. The intermittent Mojave River, which begins on the San Bernardino mountains and disappears underground in the Mojave Desert. The Amargosa River also flows partly underground through the Mojave Desert along a southward path. The Manix, Mojave, and the Little Mojave lakes are all large but shallow. Soda Lake is the principal saline basin of the Mojave desert. Natural springs are typically rare throughout the Mojave desert, however, there are two notable springs, Ash Meadows, and Oasis Valley. Ash Meadows is formed from several other springs, which all draw from deep underground. Oasis Valley draws from the nearby Amargosa River.

Climate

Extremes in temperatures throughout the seasons characterize the climate of the Mojave Desert. Freezing temperatures as well as strong winds are not uncommon in the winter, as well as precipitation such as rain and snow in the mountains. In contrast, temperatures above 100 °F (38 °C) are not uncommon during the summer months. There is an annual average precipitation of 2 to 6 inches (51 to 152 mm), although regions at high altitudes such as the portion of the Mojave desert in the San Gabriel mountains. Most of the precipitation in the Mojave comes from the Pacific Cyclonic storms that are generally present passing Eastward in November to April. Such storms generally bring rain and snow only in the mountainous regions, as a result of the effect of the Sierra Nevada mountains, which creates a drying effect on its leeward slopes.

During the late summer months, there is also the possibility of strong thunderstorms, which bring heavy showers or cloudbursts. These storms can result in flash flooding.

The Mojave Desert has not historically supported a fire regime because of low fuel loads and connectivity. However, in the last few decades, invasive annual plants such as some within the genera Bromus, Schismus and Brassica have facilitated fires by serving as a fuel bed for fires. This has significantly altered many areas of the desert. At higher elevations, fire regimes are regular but infrequent.

Cities and regions

Main article: List of cities in the Mojave Desert

For a description of the metropolitan areas of the Mojave, see High Desert (California).

 

Las Vegas is in the Mojave Desert

While the Mojave Desert is generally sparsely populated, it has increasingly become urbanized in recent years. The metropolitan areas include Las Vegas, the largest urban area in the Mojave and the largest urban area in Nevada with a population of about 2.3 million. St. George, Utah, is the northeasternmost metropolitan area in the Mojave, with a population of around 180,000 in 2020, and is located at the convergence of the Mojave, Great Basin, and Colorado Plateau. The Los Angeles exurban area of Lancaster-Palmdale has more than 400,000 residents, and the Victorville area to its east has more than 300,000 residents. Smaller cities or micropolitan areas in the Mojave Desert include Helendale, Lake Havasu City, Kingman, Laughlin, Bullhead City and Pahrump. All have experienced rapid population growth since 1990. The California portion of the desert also contains Edwards Air Force Base and Naval Air Weapons Station China Lake, noted for experimental aviation and weapons projects.

The Mojave Desert has several ghost towns. The most significant are the silver and copper-mining town of Calico, California, and the old railroad depot of Kelso, California. Some of the other ghost towns are more modern, created when U.S. Route 66 (and the lesser-known U.S. Route 91) were abandoned in favor of the construction of Interstates.

Geology

Rock formations in Joshua Tree National Park

The rock that forms the Mojave Desert was likely created under shallow water in the Precambrian. Under this shallow coat of water, a large volume of sedimentary processes were likely taking place, causing in large deposits of limestones, silicates, and dolomites. During the Paleozoic era, the area that is now the Mojave was again likely submerged under a greater sea. During the Mesozoic era, major tectonic activities such as thrust faulting and folding resulted in distinctive shaping as well as intrusion. During the Cenozoic, more tectonic deformation occurred whilst the Mojave was partly submerged. Major volcanic activity is thought to have occurred during the Oligocene. Large downpours during the Miocene likely significantly eroded the rock in the Mojave and accelerated deposition.

The Mojave Desert is a source of various minerals and metallic materials. Due to the climate, there is an accumulation of weathered bedrock, fine sand and silt, both sand and silt sediments becoming converted into colluvium. The deposits of gold, tungsten, and silver have been mined frequently prior to the Second World War. Additionally, there have been deposits of copper, tin, lead-zinc, manganese, iron, and various radioactive substances but they have not been mined for commercial use.

Ecology

Flora

The flora of the Mojave desert consists of various endemic plant species, notably the Joshua Tree, which is a notable endemic and indicator species of the desert. There is more endemic flora in the Mojave desert than almost anywhere in the world. Mojave Desert flora is not a vegetation type, although the plants in the area have evolved in isolation because of the physical barriers of the Sierra Nevadas and the Colorado Plateau. Predominant plants of the Mojave desert include all-scale (Atriplex polycarpa), creosote bush (Larrea tridentata), brittlebush (Encelia farinosa), desert holly (Atriplex hymenelytra), white burrobush (Hymenoclea salsola), and most notably, the Joshua tree (Yucca brevifolia). Additionally, the Mojave desert is also home to various species of cacti, such as silver cholla (Cylindropuntia echinocarpa), Mojave prickly pear (O. erinacea), beavertail cactus (O. basilaris), and many-headed barrel cactus (Echinocactus polycephalus). Less common but distinctive plants of the Mojave desert include ironwood (Olneya tesota), blue Palo Verde (Parkinsonia Florida), chuparosa (Justicia californica), spiny menodora (Menodora spinescens), desert senna (Cassia armata), California dalea (Psorothamnus arborescens), and goldenhead (Acamptopappus shockleyi). The Mojave desert is generally abundant in winter annuals. The plants of the Mojave desert each generally correspond to an individual geographic feature. As such, there are distinctive flora communities within the desert.

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  A depiction of cassia armata, which is particularly characteristic of the Mojave

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  California Dalea, an indicator species of the Mojave Desert

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  Goldenhead (Acamptopappus shockleyi) an indicator species of the Mojave

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  Silver cholla (Opuntia echinocarpa), a common species of cacti in the Mojave

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  A creosote bush, which is common in the Mojave

Fauna

A desert tortoise, which can be found in the Mojave Desert

Notable species of the Mojave desert include bighorn sheep (Ovis canadensis), mountain lions (Puma concolor), black-tailed jackrabbits (Lepus californicus), and desert tortoises (Gopherus agassizii). Various other species are particularly common in the Mojave Desert, such as the LeConte's thrasher (Toxostoma lecontei), banded gecko (Coleonyx variegatus), desert iguana (Dipsosaurus dorsalis), chuckwalla (Sauromalus obesus), and regal horned lizard (Phrynosoma solare). Species of snake include the rosy boa (Lichanura trivirgata), Western patch-nosed snake (Salvadora hexalepis), and Mojave rattlesnake (Crotalus scutulatus). These species can also occur in the neighboring Sonoran and Great Basin deserts.

The animal species of the Mojave Desert have generally fewer endemics than its flora. However, endemic fauna of the Mojave Desert include Kelso Dunes jerusalem cricket (Ammopelmatus kelsoensis), the Kelso Dunes shieldback katydid (Eremopedes kelsoensis), the Mohave ground squirrel (Spermophilus Mohavensis) and Amargosa vole (Microtus californicus scirpensis). The Mojave fringe-toed lizard (Uma Scoparia) is not endemic, but almost completely limited to the Mojave desert. There are also aquatic species that are found nowhere else, such as the Devils Hole pupfish, limited to one hot spring near Death Valley.

In society

History

Before the European exploration of North America, tribes of Native Americans, such as the Mohave, were hunter-gatherers living in the Mojave Desert.

European explorers started exploring the deserts beginning in the 18th century. Francisco Garcés, a Franciscan friar, was the first explorer of the Mojave desert in 1776. Garcés recorded information about the original inhabitants of the deserts.

Later, as American interests expanded into California, American explorers started probing the California deserts. Jedediah Smith travelled through the Mojave deserts in 1826, finally reaching the San Gabriel Mission.

Human development

In recent years, human development in the Mojave desert has become increasingly present. Human development at the major urban and suburban centers of Las Vegas and Los Angeles has had an increasingly damaging effect on the wildlife of the Mojave Desert. An added demand for landfill space as a result of the large metropolitan centers of Las Vegas and Los Angeles also has the real potential to drastically affect flora and fauna of the Mojave Desert. Agricultural development along the Colorado river, close to the Eastern boundary of the Mojave Desert, also causes habitat loss and degradation. Areas that are particularly affected by human development include Ward Valley and Riverside county. The United States military also maintains installations in the Mojave Desert, making the Mojave a critical training location for the United States Department of Defense. The Mojave Desert has long been a valuable resource for people, and as its human population grows, its importance will only grow. Miners, ranchers, and farmers rely on the desert for a living. The desert is also helping California meet its renewable energy objectives: the desert is an excellent place to site wind and solar energy systems, although they can cause their own environmental impact.

Tourism

Panorama of Zabriskie point

The Mojave Desert is one of the most popular spots for tourism in North America, primarily because of the international destination of Las Vegas. The Mojave is also known for its scenery, playing host to Death Valley National Park, Joshua Tree National Park, and the Mojave National Preserve. Lakes Mead, Mohave, and Havasu provide water sports recreation, and vast off-road areas entice off-road enthusiasts. The Mojave Desert also includes three California State Parks, the Antelope Valley California Poppy Reserve, in Lancaster, Saddleback Butte State Park, in Hi Vista and Red Rock Canyon State Park. Mojave Narrows Park, operated by San Bernardino County, is a former ranch along the Mojave River.

Several attractions and natural features are in the Calico Mountains. Calico Ghost Town, in Yermo, is administered by San Bernardino County. The ghost town has several shops and attractions and inspired Walter Knott to build Knott's Berry Farm. The Bureau of Land Management also administers Rainbow Basin and Owl Canyon. The Calico Early Man Site, in the Calico Hills east of Yermo, is believed by some archaeologists, including the late Louis Leakey, to show the earliest evidence with lithic stone tools found here of human activity in North America.

Conservation status

A field of California poppies in the California Poppy Reserve in Antelope Valley

The Mojave Desert has a relatively stable and intact conservation status. The Mojave Desert is one of the best protected distinct ecoregions in the United States, as a result of the California Desert Protection Act, which established the Death Valley, Joshua Tree National Parks and the Mojave National Preserve. However, the southwest and central east portions of the Mojave Desert are particularly threatened as a result of off-road vehicles, human development, and agricultural grazing. The World Wildlife Fund lists the Mojave Desert as relatively "stable/intact".

Various habitats and regions of the Mojave Desert have been protected by statute. Notably, Joshua Tree National Park, Death Valley National Park, and the Mojave National Preserve by the California Desert Protection Act of 1994. (Pub.L. 103–433). Various other national parks and state parks have regions within the Mojave Desert. These include Antelope Valley California Poppy Reserve, which protects the fields of California poppies, Desert Tortoise Natural Area, Arthur B. Ripley Desert Woodland State Park, Desert National Wildlife Refuge, Lake Mead National Recreation Area, Providence Mountains State Recreation Area, Red Cliffs National Conservation Area, Red Rock Canyon State Park, Saddleback Butte State Park, Snow Canyon State Park and Valley of Fire State Park.

2009 litigation

In 2009, U.S. District Judge Susan Illston ruled against the Bureau's proposed designation of additional off-road vehicle use allowance in the western Mojave Desert. According to the ruling, the Bureau of Land Management violated its own regulations when it designated approximately 5,000 miles (8,000 km) of off-roading routes in 2006. According to Judge Illston, the Bureau's designation was significantly "flawed because it does not contain a reasonable range of alternatives" to limit damage to sensitive habitats. Judge Illston found the bureau had inadequately analyzed the routes' impacts on air quality, soils, plant communities, riparian habitats, and sensitive species such as the endangered Mojave fringe-toed lizard, pointing out that the desert and its resources are "extremely fragile, easily scarred, and slowly healed".

Atomic absorption spectroscopy

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy

Flame atomic absorption spectroscopy instrument

 

A scientist preparing solutions for atomic absorption spectroscopy, reflected in the glass window of the AAS's flame atomizer cover door

Atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state. Atomic absorption spectroscopy is based on absorption of light by free metallic ions.

In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electrothermal vaporization, and is used in pharmacology, biophysics, archaeology and toxicology research.

Atomic emission spectroscopy was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.

The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.

Atomic absorption spectrometry has many uses in different areas of chemistry such as clinical analysis of metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, hair, muscle tissue. Atomic absorption spectrometry can be used in qualitative and quantitative analysis.

Principles

The technique makes use of the atomic absorption spectrum of a sample in order to assess the concentration of specific analytes within it. It requires standards with known analyte content to establish the relation between the measured absorbance and the analyte concentration and relies therefore on the Beer–Lambert law.

Instrumentation

Atomic absorption spectrometer block diagram

In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through a monochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector.

Atomizers

The atomizers most commonly used nowadays are spectroscopic flames and electrothermal atomizers. Other atomizers, such as glow-discharge atomization, hydride atomization, or cold-vapor atomization, might be used for special purposes.

Flame atomizers

The oldest and most commonly used atomizers in AAS are flames, principally the air-acetylene flame with a temperature of about 2300 °C and the nitrous oxide system (N₂O)-acetylene flame with a temperature of about 2700 °C. The latter flame, in addition, offers a more reducing environment, being ideally suited for analytes with high affinity to oxygen.

A laboratory flame photometer that uses a propane operated flame atomizer

Liquid or dissolved samples are typically used with flame atomizers. The sample solution is aspirated by a pneumatic analytical nebulizer, transformed into an aerosol, which is introduced into a spray chamber, where it is mixed with the flame gases and conditioned in a way that only the finest aerosol droplets (< 10 μm) enter the flame. This conditioning process reduces interference, but only about 5% of the aerosolized solution reaches the flame because of it.

On top of the spray chamber is a burner head that produces a flame that is laterally long (usually 5–10 cm) and only a few mm deep. The radiation beam passes through this flame at its longest axis, and the flame gas flow-rates may be adjusted to produce the highest concentration of free atoms. The burner height may also be adjusted, so that the radiation beam passes through the zone of highest atom cloud density in the flame, resulting in the highest sensitivity.

The processes in a flame include the stages of desolvation (drying) in which the solvent is evaporated and the dry sample nano-particles remain, vaporization (transfer to the gaseous phase) in which the solid particles are converted into gaseous molecule, atomization in which the molecules are dissociated into free atoms, and ionization where (depending on the ionization potential of the analyte atoms and the energy available in a particular flame) atoms may be in part converted to gaseous ions.

Each of these stages includes the risk of interference in case the degree of phase transfer is different for the analyte in the calibration standard and in the sample. Ionization is generally undesirable, as it reduces the number of atoms that are available for measurement, i.e., the sensitivity.

In flame AAS a steady-state signal is generated during the time period when the sample is aspirated. This technique is typically used for determinations in the mg L⁻¹ range, and may be extended down to a few μg L⁻¹ for some elements.

Electrothermal atomizers

GFAA method development

 

Graphite tube

Electrothermal AAS (ET AAS) using graphite tube atomizers was pioneered by Boris V. L’vov at the Saint Petersburg Polytechnical Institute, Russia, since the late 1950s, and investigated in parallel by Hans Massmann at the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) in Dortmund, Germany.

Although a wide variety of graphite tube designs have been used over the years, the dimensions nowadays are typically 20–25 mm in length and 5–6 mm inner diameter. With this technique liquid/dissolved, solid and gaseous samples may be analyzed directly. A measured volume (typically 10–50 μL) or a weighed mass (typically around 1 mg) of a solid sample are introduced into the graphite tube and subject to a temperature program. This typically consists of stages, such as drying – the solvent is evaporated; pyrolysis – the majority of the matrix constituents are removed; atomization – the analyte element is released to the gaseous phase; and cleaning – eventual residues in the graphite tube are removed at high temperature.

The graphite tubes are heated via their ohmic resistance using a low-voltage high-current power supply; the temperature in the individual stages can be controlled very closely, and temperature ramps between the individual stages facilitate separation of sample components. Tubes may be heated transversely or longitudinally, where the former ones have the advantage of a more homogeneous temperature distribution over their length. The so-called stabilized temperature platform furnace (STPF) concept, proposed by Walter Slavin, based on research of Boris L’vov, makes ET AAS essentially free from interference. The major components of this concept are atomization of the sample from a graphite platform inserted into the graphite tube (L’vov platform) instead of from the tube wall in order to delay atomization until the gas phase in the atomizer has reached a stable temperature; use of a chemical modifier in order to stabilize the analyte to a pyrolysis temperature that is sufficient to remove the majority of the matrix components; and integration of the absorbance over the time of the transient absorption signal instead of using peak height absorbance for quantification.

In ET AAS a transient signal is generated, the area of which is directly proportional to the mass of analyte (not its concentration) introduced into the graphite tube. This technique has the advantage that any kind of sample, solid, liquid or gaseous, can be analyzed directly. Its sensitivity is 2–3 orders of magnitude higher than that of flame AAS, so that determinations in the low μg L⁻¹ range (for a typical sample volume of 20 μL) and ng g⁻¹ range (for a typical sample mass of 1 mg) can be carried out. It shows a very high degree of freedom from interferences, so that ET AAS might be considered the most robust technique available nowadays for the determination of trace elements in complex matrices.

Specialized atomization techniques

While flame and electrothermal vaporizers are the most common atomization techniques, several other atomization methods are utilized for specialized use.

Glow-discharge atomization

A glow-discharge device (GD) serves as a versatile source, as it can simultaneously introduce and atomize the sample. The glow discharge occurs in a low-pressure argon gas atmosphere between 1 and 10 torr. In this atmosphere lies a pair of electrodes applying a DC voltage of 250 to 1000 V to break down the argon gas into positively charged ions and electrons. These ions, under the influence of the electric field, are accelerated into the cathode surface containing the sample, bombarding the sample and causing neutral sample atom ejection through the process known as sputtering. The atomic vapor produced by this discharge is composed of ions, ground state atoms, and fraction of excited atoms. When the excited atoms relax back into their ground state, a low-intensity glow is emitted, giving the technique its name.

The requirement for samples of glow discharge atomizers is that they are electrical conductors. Consequently, atomizers are most commonly used in the analysis of metals and other conducting samples. However, with proper modifications, it can be utilized to analyze liquid samples as well as nonconducting materials by mixing them with a conductor (e.g. graphite).

Hydride atomization

Hydride generation techniques are specialized in solutions of specific elements. The technique provides a means of introducing samples containing arsenic, antimony, selenium, bismuth, and lead into an atomizer in the gas phase. With these elements, hydride atomization enhances detection limits by a factor of 10 to 100 compared to alternative methods. Hydride generation occurs by adding an acidified aqueous solution of the sample to a 1% aqueous solution of sodium borohydride, all of which is contained in a glass vessel. The volatile hydride generated by the reaction that occurs is swept into the atomization chamber by an inert gas, where it undergoes decomposition. This process forms an atomized form of the analyte, which can then be measured by absorption or emission spectrometry.

Cold-vapor atomization

The cold-vapor technique is an atomization method limited only for the determination of mercury, due to it being the only metallic element to have a large vapor pressure at ambient temperature. Because of this, it has an important use in determining organic mercury compounds in samples and their distribution in the environment. The method initiates by converting mercury into Hg²⁺ by oxidation from nitric and sulfuric acids, followed by a reduction of Hg²⁺ with tin(II) chloride. The mercury, is then swept into a long-pass absorption tube by bubbling a stream of inert gas through the reaction mixture. The concentration is determined by measuring the absorbance of this gas at 253.7 nm. Detection limits for this technique are in the parts-per-billion range making it an excellent mercury detection atomization method.

Radiation sources

We have to distinguish between line source AAS (LS AAS) and continuum source AAS (CS AAS). In classical LS AAS, as it has been proposed by Alan Walsh, the high spectral resolution required for AAS measurements is provided by the radiation source itself that emits the spectrum of the analyte in the form of lines that are narrower than the absorption lines. Continuum sources, such as deuterium lamps, are only used for background correction purposes. The advantage of this technique is that only a medium-resolution monochromator is necessary for measuring AAS; however, it has the disadvantage that usually a separate lamp is required for each element that has to be determined. In CS AAS, in contrast, a single lamp, emitting a continuum spectrum over the entire spectral range of interest is used for all elements. Obviously, a high-resolution monochromator is required for this technique, as will be discussed later.

Hollow cathode lamp (HCL)

Hollow cathode lamps

Hollow cathode lamps (HCL) are the most common radiation source in LS AAS. Inside the sealed lamp, filled with argon or neon gas at low pressure, is a cylindrical metal cathode containing the element of interest and an anode. A high voltage is applied across the anode and cathode, resulting in an ionization of the fill gas. The gas ions are accelerated towards the cathode and, upon impact on the cathode, sputter cathode material that is excited in the glow discharge to emit the radiation of the sputtered material, i.e., the element of interest. In the majority of cases single element lamps are used, where the cathode is pressed out of predominantly compounds of the target element. Multi-element lamps are available with combinations of compounds of the target elements pressed in the cathode. Multi element lamps produce slightly less sensitivity than single element lamps and the combinations of elements have to be selected carefully to avoid spectral interferences. Most multi-element lamps combine a handful of elements, e.g.: 2 - 8. Atomic Absorption Spectrometers can feature as few as 1-2 hollow cathode lamp positions or in automated multi-element spectrometers, a 8-12 lamp positions may be typically available.

Electrodeless discharge lamps

Electrodeless discharge lamps (EDL) contain a small quantity of the analyte as a metal or a salt in a quartz bulb together with an inert gas, typically argon gas, at low pressure. The bulb is inserted into a coil that is generating an electromagnetic radio frequency field, resulting in a low-pressure inductively coupled discharge in the lamp. The emission from an EDL is higher than that from an HCL, and the line width is generally narrower, but EDLs need a separate power supply and might need a longer time to stabilize.

Deuterium lamps

Deuterium HCL or even hydrogen HCL and deuterium discharge lamps are used in LS AAS for background correction purposes. The radiation intensity emitted by these lamps decreases significantly with increasing wavelength, so that they can be only used in the wavelength range between 190 and about 320 nm.

Xenon lamp as a continuous radiation source

Continuum sources

When a continuum radiation source is used for AAS, it is necessary to use a high-resolution monochromator, as will be discussed later. In addition, it is necessary that the lamp emits radiation of intensity at least an order of magnitude above that of a typical HCL over the entire wavelength range from 190 nm to 900 nm. A special high-pressure xenon short arc lamp, operating in a hot-spot mode has been developed to fulfill these requirements.

Spectrometer

As already pointed out above, there is a difference between medium-resolution spectrometers that are used for LS AAS and high-resolution spectrometers that are designed for CS AAS. The spectrometer includes the spectral sorting device (monochromator) and the detector.

Spectrometers for LS AAS

In LS AAS the high resolution that is required for the measurement of atomic absorption is provided by the narrow line emission of the radiation source, and the monochromator simply has to resolve the analytical line from other radiation emitted by the lamp. This can usually be accomplished with a band pass between 0.2 and 2 nm, i.e., a medium-resolution monochromator. Another feature to make LS AAS element-specific is modulation of the primary radiation and the use of a selective amplifier that is tuned to the same modulation frequency, as already postulated by Alan Walsh. This way any (unmodulated) radiation emitted for example by the atomizer can be excluded, which is imperative for LS AAS. Simple monochromators of the Littrow or (better) the Czerny-Turner design are typically used for LS AAS. Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio.

Spectrometers for CS AAS

When a continuum radiation source is used for AAS measurement it is indispensable to work with a high-resolution monochromator. The resolution has to be equal to or better than the half-width of an atomic absorption line (about 2 pm) in order to avoid losses of sensitivity and linearity of the calibration graph. The research with high-resolution (HR) CS AAS was pioneered by the groups of O’Haver and Harnly in the US, who also developed the (up until now) only simultaneous multi-element spectrometer for this technique. The breakthrough, however, came when the group of Becker-Ross in Berlin, Germany, built a spectrometer entirely designed for HR-CS AAS. The first commercial equipment for HR-CS AAS was introduced by Analytik Jena (Jena, Germany) at the beginning of the 21st century, based on the design proposed by Becker-Ross and Florek. These spectrometers use a compact double monochromator with a prism pre-monochromator and an echelle grating monochromator for high resolution. A linear charge-coupled device (CCD) array with 200 pixels is used as the detector. The second monochromator does not have an exit slit; hence the spectral environment at both sides of the analytical line becomes visible at high resolution. As typically only 3–5 pixels are used to measure the atomic absorption, the other pixels are available for correction purposes. One of these corrections is that for lamp flicker noise, which is independent of wavelength, resulting in measurements with very low noise level; other corrections are those for background absorption, as will be discussed later.

Background absorption and background correction

The relatively small number of atomic absorption lines (compared to atomic emission lines) and their narrow width (a few pm) make spectral overlap rare; there are only few examples known that an absorption line from one element will overlap with another. Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line. This kind of absorption might be caused by un-dissociated molecules of concomitant elements of the sample or by flame gases. We have to distinguish between the spectra of di-atomic molecules, which exhibit a pronounced fine structure, and those of larger (usually tri-atomic) molecules that don't show such fine structure. Another source of background absorption, particularly in ET AAS, is scattering of the primary radiation at particles that are generated in the atomization stage, when the matrix could not be removed sufficiently in the pyrolysis stage.

All these phenomena, molecular absorption and radiation scattering, can result in artificially high absorption and an improperly high (erroneous) calculation for the concentration or mass of the analyte in the sample. There are several techniques available to correct for background absorption, and they are significantly different for LS AAS and HR-CS AAS.

Background correction techniques in LS AAS

In LS AAS background absorption can only be corrected using instrumental techniques, and all of them are based on two sequential measurements: firstly, total absorption (atomic plus background), secondly, background absorption only. The difference of the two measurements gives the net atomic absorption. Because of this, and because of the use of additional devices in the spectrometer, the signal-to-noise ratio of background-corrected signals is always significantly inferior compared to uncorrected signals. It should also be pointed out that in LS AAS there is no way to correct for (the rare case of) a direct overlap of two atomic lines. In essence there are three techniques used for background correction in LS AAS:

Deuterium background correction

This is the oldest and still most commonly used technique, particularly for flame AAS. In this case, a separate source (a deuterium lamp) with broad emission is used to measure the background absorption over the entire width of the exit slit of the spectrometer. The use of a separate lamp makes this technique the least accurate one, as it cannot correct for any structured background. It also cannot be used at wavelengths above about 320 nm, as the emission intensity of the deuterium lamp becomes very weak. The use of deuterium HCL is preferable compared to an arc lamp due to the better fit of the image of the former lamp with that of the analyte HCL.

Smith-Hieftje background correction

This technique (named after their inventors) is based on the line-broadening and self-reversal of emission lines from HCL when high current is applied. Total absorption is measured with normal lamp current, i.e., with a narrow emission line, and background absorption after application of a high-current pulse with the profile of the self-reversed line, which has little emission at the original wavelength, but strong emission on both sides of the analytical line. The advantage of this technique is that only one radiation source is used; among the disadvantages are that the high-current pulses reduce lamp lifetime, and that the technique can only be used for relatively volatile elements, as only those exhibit sufficient self-reversal to avoid dramatic loss of sensitivity. Another problem is that background is not measured at the same wavelength as total absorption, making the technique unsuitable for correcting structured background.

Zeeman-effect background correction

Main article: Zeeman effect

An alternating magnetic field is applied at the atomizer (graphite furnace) to split the absorption line into three components, the π component, which remains at the same position as the original absorption line, and two σ components, which are moved to higher and lower wavelengths, respectively. Total absorption is measured without magnetic field and background absorption with the magnetic field on. The π component has to be removed in this case, e.g. using a polarizer, and the σ components do not overlap with the emission profile of the lamp, so that only the background absorption is measured. The advantages of this technique are that total and background absorption are measured with the same emission profile of the same lamp, so that any kind of background, including background with fine structure can be corrected accurately, unless the molecule responsible for the background is also affected by the magnetic field and using a chopper as a polariser reduces the signal to noise ratio. While the disadvantages are the increased complexity of the spectrometer and power supply needed for running the powerful magnet needed to split the absorption line.

Background correction techniques in HR-CS AAS

In HR-CS AAS background correction is carried out mathematically in the software using information from detector pixels that are not used for measuring atomic absorption; hence, in contrast to LS AAS, no additional components are required for background correction.

Background correction using correction pixels

It has already been mentioned that in HR-CS AAS lamp flicker noise is eliminated using correction pixels. In fact, any increase or decrease in radiation intensity that is observed to the same extent at all pixels chosen for correction is eliminated by the correction algorithm. This obviously also includes a reduction of the measured intensity due to radiation scattering or molecular absorption, which is corrected in the same way. As measurement of total and background absorption, and correction for the latter, are strictly simultaneous (in contrast to LS AAS), even the fastest changes of background absorption, as they may be observed in ET AAS, do not cause any problem. In addition, as the same algorithm is used for background correction and elimination of lamp noise, the background corrected signals show a much better signal-to-noise ratio compared to the uncorrected signals, which is also in contrast to LS AAS.

Background correction using a least-squares algorithm

The above technique can obviously not correct for a background with fine structure, as in this case the absorbance will be different at each of the correction pixels. In this case HR-CS AAS is offering the possibility to measure correction spectra of the molecule(s) that is (are) responsible for the background and store them in the computer. These spectra are then multiplied with a factor to match the intensity of the sample spectrum and subtracted pixel by pixel and spectrum by spectrum from the sample spectrum using a least-squares algorithm. This might sound complex, but first of all the number of di-atomic molecules that can exist at the temperatures of the atomizers used in AAS is relatively small, and second, the correction is performed by the computer within a few seconds. The same algorithm can actually also be used to correct for direct line overlap of two atomic absorption lines, making HR-CS AAS the only AAS technique that can correct for this kind of spectral interference.

Second Life

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Second_Life 

 

Second Life Viewer

Developer(s)	Linden Lab
Initial release	June 23, 2003; 19 years ago
Stable release	6.6.1.572458 / June 29, 2022; 4 months ago
Engine	Havok (physics engine)
Platform	Windows macOS Linux (development paused)
License	Open-source
Website	secondlife.com

Second Life Server

Developer(s)	Linden Lab
Initial release	June 23, 2003; 19 years ago
Stable release	2022-07-06.573149 / July 6, 2022
Platform	Linux
License	Proprietary
Website	secondlife.com

Second Life is an online multimedia platform that allows people to create an avatar for themselves and then interact with other users and user created content within a multi player online virtual world. Developed and owned by the San Francisco-based firm Linden Lab and launched on June 23, 2003, it saw rapid growth for some years and in 2013 it had approximately one million regular users. Growth eventually stabilized, and by the end of 2017 the active user count had declined to "between 800,000 and 900,000". In many ways, Second Life is similar to massively multiplayer online role-playing games; nevertheless, Linden Lab is emphatic that their creation is not a game: "There is no manufactured conflict, no set objective".

The virtual world can be accessed freely via Linden Lab's own client software or via alternative third-party viewers. Second Life users, also called 'residents', create virtual representations of themselves, called avatars, and are able to interact with places, objects and other avatars. They can explore the world (known as the grid), meet other residents, socialize, participate in both individual and group activities, build, create, shop, and trade virtual property and services with one another.

The platform principally features 3D-based user-generated content. Second Life also has its own virtual currency, the Linden Dollar (L$), which is exchangeable with real world currency.

Second Life is intended for people ages 16 and over, with the exception of 13–15-year-old users, who are restricted to the Second Life region of a sponsoring institution (e.g., a school).

History

Philip Rosedale, founder of Second Life

Philip Rosedale formed Linden Lab in 1999 with the intention of developing computer hardware to allow people to become immersed in a virtual world. In its earliest form, the company struggled to produce a commercial version of the hardware, known as "The Rig", which in prototype form was seen as a clunky steel contraption with computer monitors worn on shoulders. That vision changed into the software application Linden World, in which people participated in task-based games and socializing in a three-dimensional online environment. That effort eventually transformed into the better known, user-centered Second Life. Although he was familiar with the metaverse of Neal Stephenson's novel Snow Crash, Rosedale has said that his vision of virtual worlds predates that book, and that he conducted early virtual world experiments during his college years at the University of California, San Diego, where he studied physics.

Second Life began to receive significant media attention in 2005 and 2006, including a cover story in BusinessWeek magazine featuring the virtual world and Second Life avatar Anshe Chung. By that time, Anshe Chung had become Second Life's poster child and symbol for the economic opportunities that the virtual world offers to its residents. At the same time, the service saw a period of exponential growth of its user base.

One of the principal developers, Cory Ondrejka, was forced to resign as chief technology officer in December 2007, with Rosedale citing irreconcilable differences in the way the company was run. Nevertheless, the platform continued to grow rapidly, and by January 2008, residents spent a total of 28,274,505 hours "inworld" and on average 38,000 residents were logged in at any moment. The maximum concurrency (number of avatars inworld) recorded was set at 88,200 in the first quarter of 2009.

Second Life was honored at the Technology & Engineering Emmy Awards for advancing the development of online sites with user-generated content in 2008, adding to the media attention. Rosedale accepted the award. although he had announced plans to step down from his position as Linden Lab CEO and to become chairman of Linden Lab's board of directors instead in March 2008. Rosedale announced Mark Kingdon as the new CEO effective May 15, 2008. In 2010, Kingdon was replaced by Rosedale, who took over as interim CEO. After four months, Rosedale abruptly stepped down from the Interim CEO position. It was announced in October 2010 that Bob Komin, Linden Lab's chief financial officer and chief operating officer, would take over the CEO job for the immediate future.

With the platform's failure to continue its high rate of growth after 2009, Linden Lab announced layoffs of 30% of its workforce in 2010. Some 21.3 million accounts were registered by this point, although the company did not make public any statistics regarding actual long-term consistent usage and numbers of dormant accounts.

Despite speculation as to the actual size of the user base, Second Life continued as a commercial success. In 2015, Second Life users cashed out approximately $60,000,000 (60 million US dollars) and Second Life had an estimated GDP of $500,000,000 (500 million US dollars), higher than some small countries.

Recognizing improvements in computing power and particularly in computer graphics, Linden Lab began work on a successor to Second Life, a VR experience called Sansar, launching a public beta in July 2017. Uptake was low and Linden Lab halted development in 2020 to focus their attention fully on Second Life. The rights to Sansar's assets were sold to Wookey Search Technologies, who are expected to continue development on the title without Linden Lab. Second Life, the usage of which peaked in the first decade of the 21st-century, has been cited as the first example of the metaverse, a concept which has been taken up by other major corporations such as Facebook in 2021. As a notable precursor (which retains a small and loyal following), it provides several examples of virtual reality social issues and lessons learned.

Classification

During a 2001 meeting with investors, Rosedale noticed that the participants were particularly responsive to the collaborative, creative potential of Second Life. As a result, the initial objective-driven, gaming focus of Second Life was shifted to a more user-created, community-driven experience.

Second Life's status as a virtual world, a computer game, or a talker, is frequently debated. Unlike a traditional computer game, Second Life does not have a designated objective, nor traditional game play mechanics or rules. It can also be argued that Second Life is a multi-user virtual world, because its virtual world facilitates interaction between multiple users. As it does not have any stipulated goals, it is irrelevant to talk about winning or losing in relation to Second Life. Likewise, unlike a traditional talker, Second Life contains an extensive world that can be explored and interacted with, and it can be used purely as a creative tool set if the user so chooses. In March 2006, while speaking at Google TechTalks, Rosedale said: "So, we don't see this as a game. We see it as a platform."

Second Life used to offer two main grids: one for adults (18+) and one for teens. In August 2010, Linden Lab closed the teen grid due to operating costs. Since then, users 16 and over can sign up for a free account. Other limited accounts are available for educators who use Second Life with younger students.

There are three activity-based classifications, called "Ratings", for sims in Second Life:

1. General (formerly "PG"—no extreme violence or nudity)
2. Moderate (formerly "Mature"—some violence, swearing, adult situations, some nudity)
3. Adult (may contain overt sexual activity, nudity, and violence)

Residents and avatars

Several avatars together

There is no charge for creating a Second Life account or for making use of the world for any period of time. Linden Lab reserves the right to charge for the creation of large numbers of multiple accounts for a single person (5 per household, 2 per 24 hours) but at present does not do so. A Premium membership (US$11.99 monthly, US$32.97 quarterly, or US$99 annually) extends access to an increased level of technical support, and also pays an automatic stipend of L$300/week into the member's avatar account, and after 45 days that resident will receive a L$700 bonus, making it L$1,000 for that week. This amount has decreased since the original stipend of L$500, which is still paid to older accounts. Certain accounts created during an earlier period may receive L$400. This stipend, if changed into USD, means that the actual cost for the benefit of extended tech support for an annual payment of US$72 is only about US$14, depending on the currency exchange rates. However, the vast majority of casual users of Second Life do not upgrade beyond the free "basic" account.

Avatars may take any form users choose (human, animal, vegetable, mineral, or a combination thereof) or residents may choose to resemble themselves as they are in real life. They may choose even more abstract forms, given that almost every aspect of an avatar is fully customizable. Second Life Culture consists of many activities and behaviors that are also present in real life. A single resident account may have only one avatar at a time, although the appearance of this avatar can change between as many different forms as the Resident wishes. Avatar forms, like almost everything else in Second Life, can be either created by the user, or bought pre-made. A single person may also have multiple accounts, and thus appear to be multiple Residents (a person's multiple accounts are referred to as alts).

Avatars can travel via walking, running, vehicular access, flying, or teleportation. Because Second Life is such a vast virtual world, teleportation is used when avatars wish to travel instantly and efficiently. Once they reach their destination, they may travel in more conventional means at various speeds.

Avatars can communicate via local chat, group chat, global instant messaging (known as IM), and voice (public, private and group). Chatting is used for localized public conversations between two or more avatars, and is visible to any avatar within a given distance. IMs are used for private conversations, either between two avatars, or among the members of a group, or even between objects and avatars. Unlike chatting, IM communication does not depend on the participants being within a certain distance of each other. As of version 1.18.1.2 (2007-Aug-02), voice chat, both local and IM, was also available. Instant messages may optionally be sent to a Resident's email when the Resident is logged off, although message length is limited to 4096 bytes.

Identities in Second Life can relate to the users' personality or creating their own character. It is based on their decisions on how to express themselves. Most avatars are human, but they can choose to be vampires or animals. Sometimes, what they choose does not relate to their offline selves.

In Coming of Age in Second Life: An Anthropologist Explores the Virtually Human, anthropologist Tom Boellstorff notes that the interface of Second Life is designed with the purpose of disconnecting a player's virtual identity from their physical identity in mind. As of 2015 Second Life has made it possible to display one's legal name in the player's profile or as their screen name, but when Boellstorff first published the book in 2008 users were required to select a last name from a pre-determined list of options. Boellstorff describes this mentality as being in direct contrast to the one held by other mainstream social media websites, where anonymity is shunned and users are encouraged to make the link between their online and physical presence clear.

Content

The ability to create content and shape the Second Life world is one of the key features that separate this from online games.

Built into the software is a 3D modeling tool based on simple geometric shapes that allows residents to build virtual objects. There is also a procedural scripting language, Linden Scripting Language, which can be used to add interactivity to objects. Sculpted prims ("sculpties"), 3D mesh, textures for clothing or other objects, animations, and gestures can be created using external software and imported. The Second Life terms of service provide that users retain copyright for any content they create, and the server and client provide simple digital rights management (DRM) functions. However, Linden Lab changed their terms of service in August 2013 to be able to use user-generated content for any purpose. The new terms of service prevent users from using textures from third-party texture services, as some of them pointed out explicitly.

Economy

Main article: Economy of Second Life

 

An avatar in the virtual world Second Life

 

User-generated content in the virtual world Second Life

Second Life has an internal economy and closed-loop virtual token called the "Linden dollar (L$)". L$ can be used to buy, sell, rent or trade land or goods and services with other users. The "Linden Dollar" is a closed-loop virtual token for use only within the Second Life platform. Linden Dollars have no monetary value and are not redeemable for monetary value from Linden Lab. A resident with a surplus of Linden Dollars earned via a Second Life business or experiential play can request to refund their Linden Dollar surplus to PayPal. Linden Lab reports that the Second Life economy generated US$3,596,674 in economic activity during the month of September 2005, and in September 2006 Second Life was reported to have a GDP of $64 million. In 2009, the total size of the Second Life economy grew 65% to US$567 million, about 25% of the entire U.S. virtual goods market. Gross resident earnings are US$55 million in 2009 – 11% growth over 2008. In 2013, Linden Labs released an info graphic that showed that over 10 years $3.2 billion in transactions for virtual goods had exchanged between Second Life residents, with an average of 1.2 million daily transactions.

There is a high level of entrepreneurial activity in Second Life. Residents of Second Life are able to create virtual objects and other content. Second Life is unique in that users retain all the rights to their content which means they can use Second Life to distribute and sell their creations, with 2.1 million items listed on its online marketplace. At its height circa 2006, hundreds of thousands of dollars were changing hands daily as residents created and sold a wide variety of virtual commodities. Second Life also quickly became profitable due to the selling and renting of virtual real estate. 2006 also saw Second Life's first real-world millionaire; Ailin Graef, better known as Anshe Chung (her avatar), converted an initial investment of US$9.95 into over one million dollars over the course of two and a half years. She built her fortune primarily by buying, selling, and renting virtual real estate.

Major tech corporations have tried to use Second Life to market products or services to Second Life's tech-savvy audience. IBM, for example, purchased 12 islands within Second Life for virtual training and simulations of key business processes, but has since moved on to other platforms due to maintaining costs. Others, like musicians, podcasters, and news organizations (including CNET, Reuters, NPR's The Infinite Mind, and the BBC) have all had a presence within Second Life.

Virtual goods include buildings, vehicles, devices of all kinds, animations, clothing, skin, hair, jewelry, flora and fauna, and works of art. Services include business management, entertainment, and custom content creation (which can be broken up into the following six categories: building, texturing, scripting, animating, art direction, and the position of producer/project funder). L$ can be purchased using US dollars and other local currencies on the LindeX exchange provided by Linden Lab. Customer USD wallets obtained from Linden Dollar sales on the Lindex are most commonly used to pay Second Life's own subscription and tier fees; only a relatively small number of users earn enough profit to request a refund to PayPal. According to figures published by Linden Lab, about 64,000 users made a profit in Second Life in February 2009, of whom 38,524 made less than US$10, while 233 made more than US$5000. Profits are derived from selling virtual goods, renting land, and a broad range of services.

Technology

Second Life comprises the viewer (also known as the client) executing on the user's personal computer, and several thousand servers operated by Linden Lab.

Client

Linden Lab provides official viewers for the operating systems Windows, macOS, and most distributions of Linux where the more known Chrome OS has been excluded so far. The viewer renders 3D graphics using OpenGL technology. The viewer source code was released under the GPL in 2007 and moved to the LGPL in 2010.

There are now several mature third party viewer projects, like Firestorm as the most popular one, that contain features not available in the Linden Lab 'Official' client, target other platforms or cater to specialist & accessibility needs. The main focus of third party development is exploring new ideas and working with Linden Lab to deliver new functionality.

An independent project, libopenmetaverse, offers a function library for interacting with Second Life servers. libopenmetaverse has been used to create non-graphic third party viewers.

There are several Alternate Viewers published by Linden Lab used for software testing by volunteers for early access to upcoming projects. Some of these clients only function on the "beta grid" consisting of a limited number of regions running various releases of unstable test server code.

Server

Each full region (an area of 256×256 meters) in the Second Life "grid" runs on a single dedicated core of a multi-core server. Homestead regions share 3 regions per core and Openspace Regions share 4 regions per core, running proprietary software on Debian Linux. These servers run scripts in the region, as well as providing communication between avatars and objects present in the region.

Every item in the Second Life universe is referred to as an asset. This includes the shapes of basic 3D polygon objects formally known as Primitive Mesh (commonly known as primitives or prims for short), the digital images referred to as textures that decorate primitives, digitized audio clips, avatar shape and appearance, avatar skin textures, LSL scripts, information written on notecards, and so on. Each asset is referenced with a universally unique identifier or UUID.

Assets are stored on Isilon Systems storage clusters, comprising all data that has ever been created by anyone who has been in the Second Life world. Infrequently used assets are offloaded to S3 bulk storage. As of December 2007, the total storage was estimated to consume 100 terabytes of server capacity. The asset servers function independently of the region simulators, though the region simulators act as a proxy for the client, request object data from the asset servers when a new object loads into the simulator. Region simulators areas are commonly known as sims by residents.

Each server instance runs a physics simulation to manage the collisions and interactions of all objects in that region. Objects can be nonphysical and non-moving, or actively physical and movable. Complex shapes may be linked together in groups of up to 256 separate primitives. Additionally, each player's avatar is treated as a physical object so that it may interact with physical objects in the world. As of 9 July 2014, Second Life simulators use the Havok 2011.2 physics engine for all in-world dynamics. This engine is capable of simulating thousands of physical objects at once.

Linden Lab pursues the use of open standards technologies, and uses free and open source software such as Apache, MySQL, Squid and Linux. The plan is to move everything to open standards by standardizing the Second Life protocol. Cory Ondrejka, former CTO^[63] of Second Life, stated in 2006 that a while after everything has been standardized, both the client and the server will be released as free and open source software.

In January 2021, Linden Labs completed the migration of all of its services and databases to AWS servers.

OpenSimulator

Main article: OpenSimulator

In January 2007, OpenSimulator was founded as an open-source simulator project. The aim of this project is to develop a full open-source server software for Second Life clients. OpenSIM is BSD Licensed and it is written in C# and can run under Mono environment. From 2008, alternative grids began to emerge and many of these allow cross visits from other grids through the hypergrid protocol using OpenSimulator.

Applications

Arts

Main article: Arts in Second Life

Second Life residents express themselves creatively through virtual world adaptations of art exhibits, live music, live theater and machinima, as well as other art forms.

Competitive entertainment

A wide variety of recreational activities, both competitive and non-competitive, take place on the Second Life Grid, including both traditional sports and video game-like scenarios.

Education

Main article: Education in Second Life

Second Life is used as a platform for education by many institutions, such as colleges, universities, libraries and government entities. Since 2008, the University of San Martin de Porres of Peru has been developing Second Life prototypes of Peruvian archeological buildings, and training teachers for this new paradigm of education. The West Virginia University (WVU) Department of Special Education has used Second Life widely in education, and it provided teaching certification and certificates of degree in seven different distance education programs. WVU started a pilot program in the college's computer lab in spring 2011.

Embassies

The Maldives was the first country to open an embassy in Second Life. The Maldives' embassy is located on Second Life's "Diplomacy Island", where visitors will be able to talk face-to-face with a computer-generated ambassador about visas, trade and other issues. "Diplomacy Island" also hosts Diplomatic Museum and Diplomatic Academy. The Island is established by DiploFoundation as part of the Virtual Diplomacy Project.

In May 2007, Sweden became the second country to open an embassy in Second Life. Run by the Swedish Institute, the embassy serves to promote Sweden's image and culture, rather than providing any real or virtual services. The Swedish Minister for Foreign Affairs, Carl Bildt, stated on his blog that he hoped he would get an invitation to the grand opening.

In September 2007, Publicis Group announced the project of creating a Serbia island as a part of a project Serbia Under Construction. The project is officially supported by Ministry of Diaspora of Serbian Government. It was stated that the island will feature the Nikola Tesla Museum, the Guča Trumpet Festival and the Exit Festival. It was also planned on opening a virtual info terminals of Ministry of Diaspora.

On Tuesday December 4, 2007, Estonia became the third country to open an embassy in Second Life. In September 2007, Colombia and Serbia opened embassies. As of 2008, North Macedonia and the Philippines have opened embassies in the "Diplomatic Island" of Second Life. In 2008, Albania opened an embassy in the Nova Bay location. SL Israel was inaugurated in January 2008 in an effort to showcase Israel to a global audience, though without any connection to official Israeli diplomatic channels. In 2008 Malta opened an embassy on Second Life.

Religion

The Anglican Cathedral of Second Life.

Religious organizations have also begun to open virtual meeting places within Second Life. In early 2007, LifeChurch.tv, a Christian church headquartered in Edmond, Oklahoma, and with eleven campuses in the US, created "Experience Island" and opened its twelfth campus in Second Life. In July 2007, an Anglican cathedral was established in Second Life; Mark Brown, the head of the group that built the cathedral, noted that there is "an interest in what I call depth, and a moving away from light, fluffy Christianity".

The First Unitarian Universalist Congregation of Second Life was established in 2006. Services have been held regularly, making the FUUCSL Congregation one of the longest-running active congregations in Second Life.

The Egyptian-owned news website Islam Online has purchased land in Second Life to allow Muslims and non-Muslims alike to perform the ritual of Hajj in virtual reality form, obtaining experience before actually making the pilgrimage to Mecca in person.

Second Life also offers several groups that cater to the needs and interests of humanists, atheists, agnostics, and freethinkers. One of the most active groups is SL Humanism which has been holding weekly discussion meetings inside Second Life every Sunday since 2006.

Relationships

Romantic relationships are common in Second Life, including some couples who have married online. The social engagement offered by the online environment helps those who might be socially isolated. In addition, sex is often encountered. However, to access the adult sections requires age verification. There are also large BDSM and Gorean communities.

Second Life relationships have been taken from virtual online relationships into personal, real-world relationships. Booperkit Moseley and Shukran Fahid were possibly the first couple to meet in Second Life and then marry in real life. Booperkit travelled to the United States to meet Shukran and he returned to England with her after one week. They married in 2006, had twin boys in 2009, and are still married. Some couples meet online, form friendships, and eventually move to finding one another in the real world. Some even have their weddings on Second Life, as well as in a real-world setting.

Relationships in virtual worlds have an added dimension compared to other social media, because avatars give a feeling of proximity making the voyeur experience more intense than simply a textual encounter. The complexities of those encounters depend on the engagement levels of the people behind the avatars, whether they are engaging disassociatively (entertainment only), immersively (as if the avatar was them), or augmentatively (meaning they engage for a real-life purpose).

Science

Second Life is used for scientific research, collaboration, and data visualization. Examples include SciLands, American Chemical Society's ACS Island, Genome, Virginia Tech's SLATE, and Nature Publishing Group's Elucian Islands Village.

Social network

Second Life can be a real-time, immersive social space for people including those with physical or mental disabilities that impair their first lives, who often find comfort and security interacting through anonymous avatars. (Indeed, some academics believe using Second Life might even help improve motor ability for people with Parkinson’s disease.). An example of how Second Life has been used by disabled people is Wheelies, the widely publicised disability themed nightclub founded by Simon Stevens.

Music streams

ShoutCast and Icecast Internet radio stations can be streamed into a land parcel in Second Life. Streaming codecs are currently MP3 as AAC and OGG are not currently supported. There are internet radio providers that offer these services or select from a list compiled by Lindal Kidd and is updated whenever by whoever as there's no officiant for it. At the time of this writing, media on a prim (MOAP) is not a reliable enough way of displaying media and such, sites listed work best with Parcel Media or Parcel Audio.

Work spaces

Second Life gives companies the option to create virtual workplaces to allow employees to virtually meet, hold events, practice any kind of corporate communications, conduct training sessions in 3D immersive virtual learning environment, simulate business processes, and prototype new products.

In 2020, CEO of Second Life Ebbe Altberg announced a microsite for Second Life to serve as a space for digital meetings to take place amidst global social distancing, self-isolation, and quarantine orders during the COVID-19 pandemic.

Notable events and influence

Ban of Woodbury University

The controversial campus of Woodbury University's School of Media, Culture and Design, which was deleted in 2010 by Linden Lab

Linden Lab has twice, in 2007 and 2010, banned a California educational institution, Woodbury University, from having a representation within Second Life. On April 20, 2010, four simulators belonging to the university were deleted and the accounts of several students and professors terminated, according to The Chronicle of Higher Education. Edward Clift, dean of the School of Media, Culture and Design at Woodbury University, told The Chronicle of Higher Education that their campus "was a living, breathing campus in Second Life", including educational spaces designed mostly by students, such as a mock representation of the former Soviet Union and a replica of the Berlin Wall. According to Clift, the virtual campus did not "conform to what Linden Lab wanted a campus to be".

The article in The Chronicle of Higher Education concluded with: "Meanwhile, many people in Second Life expressed on blogs that they were glad to see the virtual campus go, arguing that it had been a haven for troublemakers in the virtual world."

The Alphaville Herald

Main article: The Alphaville Herald

In 2004, the newspaper The Alphaville Herald, founded and edited by the philosopher Peter Ludlow, migrated to Second Life, and in the following years the newspaper played a prominent role in reporting on Second Life and in the public discussion of the game. The newspaper, which was known as The Second Life Herald from 2004 to 2009, was later edited by the Internet pioneer Mark P. McCahill. According to scholars Constantinescu and Decu, The Alphaville Herald was the first "virtual free press," pioneering mass communication in virtual worlds.

2007 "Virtual Riot"

In January 2007, a "virtual riot" erupted between members of the French National Front (FN) who had established a virtual HQ on Second Life, and anti-racism activists, including Second Life Left Unity, a socialist and anti-capitalist user-group. Since then, several small Internet-based organizations have claimed some responsibility for instigating the riots.

Marketing

Corporate marketers, especially during the height of Second Life in the cultural zeitgeist of 2005–2010, have been accused of being overly credulous of the actual reach and influence of Second Life. Journalists have theorized this might be partially due to blithely accepting total account statistics rather than harder-to-discern active player counts. Reasons for account "inflation" can include in-world systems which encourage the creation of bogus extra accounts such as "traffic bots" which simply remain stationary in a store, causing the system to rank the store as popular because there are people there, as well as simply idle and long inactive accounts. One article in Wired featured a marketer for Coca-Cola who found Second Life to be essentially deserted when personally inspecting it, yet still funded a marketing campaign there anyway from fear of missing out.

Griefing and denial of service attacks

See also: Griefer

Second Life has been attacked several times by groups of residents abusing the creation tools to create objects that harass other users or damage the system. This included grey goo objects which infinitely reproduce, eventually overwhelming the servers; orbiters which throw an avatar so far upwards they cannot get back down in a reasonable timeframe without teleporting; cages which surround avatars, preventing them from moving, and similar tools. Although combat between users is sanctioned in certain areas of the world, these objects have been used to cause disruption in all areas. Attacks on the grid itself, such as Grey Goo, are strictly forbidden anywhere on the grid. It was possible to perpetrate denial-of-service attacks (DoS) on other users simply by scripting objects that spew screen filling characters from anywhere on the grid to another avatar's location, thereby disabling a clear view to the virtual world. Bugs in the client and server software were also exploited by griefers to kick users, crash servers, and revert content before being patched out.

The Emerald client and in-world logging scripts

The Emerald client was developed by a group of users based on Snowglobe, an opensource fork of the Second Life client. Several groups alleged that the Emerald viewer contained Trojan code which tracked user details and demographics in a way that the developers could later recover. One of these groups was banned from Second Life by Linden Lab after publishing their discovery. Shortly afterward, a member of the Emerald team was accused of a DDOS attack against another website. In response, Linden Lab revoked Emerald's third-party viewer approval and permanently banned several of Emerald's developers. Due to what happened with Emerald, Linden Lab instituted a new third-party viewer policy.

The support staff and one of the developers of the Emerald project, who was not banned, left to work on a new viewer project, Phoenix (using some of the Emerald codebase, but without Off-the-Record Messaging nor any potentially malicious code). The Phoenix team are now the developers behind Firestorm Viewer, a fork of Second Life's "viewer 2.0" open source client.

Criticism and controversy

Second Life has seen a number of controversies, as well. Issues range from the technical (budgeting of server resources), to moral (pornography), to legal (legal position of the Linden Dollar, Bragg v. Linden Lab). Security issues have also been a concern.

Regulation

In the past, large portions of the Second Life economy consisted of businesses that are regulated or banned. Changes to Second Life's terms of service in this regard have largely had the purpose of bringing activity within Second Life into compliance with various international laws, even though the person running the business may be in full compliance with the law in their own country.

On July 26, 2007, Linden Lab announced a ban on in-world gambling due to federal and state regulations on Internet gambling that could affect Linden Lab if it was permitted to continue. The ban was immediately met with in-world protests.

In August 2007, a $750,000 in-world Linden Dollar bank or Ponzi scheme called Ginko Financial collapsed due to a bank run triggered by Linden Lab's ban on gambling. The aftershocks of this collapse caused severe liquidity problems for other virtual "Linden Dollar banks", which critics had long asserted were scams. On Tuesday, January 8, 2008, Linden Lab announced the upcoming prohibition of payment of fixed interest on cash deposits in unregulated banking activities in-world. All banks without real-world charters closed or converted to virtual joint stock companies by January 22, 2008. After the ban, a few companies continue to offer non-interest bearing deposit accounts to residents, such as the e-commerce site XStreet, which had already adopted a zero-interest policy 3 months before the Linden Lab interest ban.

Technical issues

Second Life has suffered from difficulties related to system instability. These include increased system latency, and intermittent client crashes. However, some faults are caused by the system's use of an "asset server" cluster, on which the actual data governing objects is stored separately from the areas of the world and the avatars that use those objects. The communication between the main servers and the asset cluster appears to constitute a bottleneck which frequently causes problems. Typically, when asset server downtime is announced, users are advised not to build, manipulate objects, or engage in business, leaving them with little to do but chat and generally reducing confidence in all businesses on the grid.

Another problem is inventory loss, in which items in a user's inventory, including those which have been paid for, can disappear without warning or permanently enter a state where they will fail to appear in-world when requested (giving an "object missing from database" error). Linden Lab offers no compensation for items that are lost in this way, although a policy change instituted in 2008 allows accounts to file support tickets when inventory loss occurs. Many in-world businesses will attempt to compensate for this or restore items, although they are under no obligation to do so and not all are able to do so. A recent change in how the company handles items which have "lost their parent directory" means that inventory loss is much less of a problem and resolves faster than in recent years. "Loss to recovery times" have gone from months (or never) to hours or a day or two for the majority of users, but inventory loss does still exist.

Second Life functions by streaming all data to the user live over the Internet with minimal local caching of frequently used data. The user is expected to have a minimum of 300kbit/s of Internet bandwidth for basic functionality. Due to the proprietary communications protocols, it is not possible to use a network proxy service to reduce network load when many people are all using the same location, such as when used for group activities in a school or business.

Quality assurance

Criticism of quality assurance of Second Life states that Linden Lab focuses too much on bringing new features to the production environment instead of fixing long-standing bugs that, in the worst case, cause financial loss for the users. On April 30, 2007, an open letter signed by over 3,000 users was sent to Linden Lab to protest the quality assurance process of the company. Linden Lab has responded to the open letter.

Frame rate

Computer hardware and Internet connections capable of smoothly rendering high quality content in other MMOGs may perform poorly in Second Life, resulting in low frame rates and unresponsive controls on even minimal graphical configurations. The problem is especially prevalent when large numbers of avatars congregate in one area. The problem is largely due to the fact that the world is entirely user created, and the majority of content created by users is made without any sort of basic graphical optimization. As a result, objects with both unnecessarily high polygon counts, and unnecessarily high resolution textures are prevalent. It is not uncommon for users to have to download and use upwards of a dozen times the amount of resources than would actually be required for the equivalent visual result. Certain areas have guidelines for script usage, which helps reduce lag by reducing resources used server-side, but does nothing to alleviate the primary issue above.

Congestion

A single region (65,536 m² of land hosted on a single CPU) is set to accommodate a limited number of Residents (40 on 'mainland' regions, up to 100 on private islands), causing some popular locations such as teleportation points to become inaccessible at times. It is possible for an area of land a Resident has paid for to become inaccessible because another area in the same region has exhausted the avatar limit.

Customer security

On September 8, 2006, Linden Lab released a news bulletin that revealed their Second Life database had been compromised and customer information, including encrypted passwords and users' real names, had likely been accessed. However, it was later revealed that the hacker had in fact been focused on trying to cheat the in-world money system and their access to personal information was believed incidental, although a full alert was still raised for safety's sake.

Fraud and intellectual property protection

Although Second Life's client and server incorporate digital rights management technology, the visual data of an object must ultimately be sent to the client in order for it to be drawn; thus unofficial third-party clients can bypass them. One such program, CopyBot, was developed in 2006 as a debugging tool to enable objects to be backed up, but was immediately hijacked for use in copying objects; additionally, programs that generally attack client-side processing of data, such as GLIntercept, can copy certain pieces of data. Such use is prohibited under the Second Life TOS and could be prosecuted under the Digital Millennium Copyright Act.

Linden Lab may ban a user who is observed using CopyBot or a similar client, but it will not ban a user simply for uploading or even selling copied content; in this case, Linden Lab's enforcement of intellectual property law is limited to that required by the "safe harbor" provisions of the DMCA which used to require a regular mail DMCA complaint. However, since 2019 an electronic DMCA complaint form is also available.

A few high-profile businesses in Second Life have filed such lawsuits, none of the cases filed to date have gone to trial, and most have been dismissed pursuant to a settlement agreement reached between the parties. Another case where settlement and dismissal was gained may be found in the matter of Eros, LLC v. Linden Research, Inc. As of October 7, 2010, the case was transferred to private mediation and the plaintiffs filed for dismissal of charges on March 15, 2011.

Most users in the world as paying, private individuals are, likewise, effectively unprotected. Common forms of fraud taking place in-world include bogus investment and pyramid schemes, fake or hacked vendors, and failure to honor land rental agreements. A group of virtual landowners online have filed a class action lawsuit against the company, claiming the company broke the law when it rescinded their ownership rights. The plaintiffs say a change in the terms of service forced them to either accept new terms that rescinded their virtual property ownership rights, or else be locked out of the site.

OpenSpaces

Linden Lab, for a period, offered Openspace regions to users: regions which were purchased in packs of four, with all four running on a single CPU core, intended to be placed next to an existing region to create the effect of larger size. The fee for 4 Openspaces was identical to that for a single private region. However, in March 2008, this rule was modified to permit Openspaces to be bought individually and placed elsewhere, as well as increasing the prim load each one could handle. Openspaces were made available for a US$415 downpayment plus a US$75 monthly fee.

In October 2008, Linden Lab announced that the Openspaces being used for this purpose were being misused; there was in fact no technical throttle limiting their usage. Linden Lab raised the monthly fee per Openspace to US$125, the same cost as half a region; added an avatar limit of 20; and renamed it to Homestead.

A week after the initial announcement Linden Lab stated its intention to add technical limits. A revised Openspace product, with far fewer prims, a no-residency rule, and costing the same monthly amount, was announced.

In May 2009, Linden Lab announced they were "grandfathering" Openspace sims (now rebranded as "Homesteads"), after a protracted protest movement caused a major amount of negative publicity and funded potential litigation.

Sex

Some media attention has been given to sexual activity involving avatars with a childlike appearance. The United Kingdom and Germany are among the countries investigating new laws to combat simulated child pornography. The USA has attempted to pass several laws forbidding simulated child pornography; however, each one has been struck down by the US Supreme Court as an infringement on the First Amendment right to free speech.

As of May 2007, two such countries, Germany and Belgium, have launched a police investigation into age of consent-related offenses in Second Life (including both trading of non-virtual photography and involuntary virtual sexual activity with childlike avatars by means of virtual identity theft). Linden Lab responded by issuing a statement that any "depiction of sexual or lewd acts involving minors" was a bannable offence.

In France, a conservative family union, Familles de France, sued Linden Lab in June 2007, alleging that Second Life gave minors access to sexual content, including bondage, zoophilia and scatophilia, as well as gambling, and advertisements for alcohol, drugs or tobacco. Linden Lab pointed out that the virtual world is not meant for children (people under the age of 18) because of the mature content and interactions within Second Life. However, minors aged between 13 and 17 can access Second Life, but they will be restricted to what they can see or do based on age. The Second Life world is split into sections/worlds and each one is given a maturity rating similar to films: General, Moderate and Adult. Minors aged 13–17 can access areas with a General Rating only.

Second Life Main Grid regions are rated either "General", "Moderate", or "Adult" (previously "PG", "Mature", or "Adult"). Builds, textures, actions, animations, chat, or businesses that are of an adult nature are regulated by the Second Life Terms of Service to only occur in simulators with a Moderate or Adult rating. General rated sims exist as an alternative for residents who do not wish to reside in areas where adult-oriented activities and businesses are permitted.

Linden Lab has created an Adult rated "mainland" continent named Zindra in response to its other "mainland" continents being mostly General.

Unauthorized copying of content

Second Life features a built-in digital rights management system that controls the movement of textures, sounds, scripts, and models with the Second Life servers at Linden Lab. At some point, though, this data must be sent to a user's computer to be displayed or played—an issue fundamental to any system attempting to apply restrictions to digital information.

In November 2006 controversy arose over a tool called CopyBot, developed as part of libsecondlife and was intended to allow users to legitimately back up their Second Life data. For a brief period, an unmodified CopyBot allowed any user to replicate SL items or avatars (although not scripts, which run only on the servers at Linden Lab). Later changes to the SecondLife protocols prevented unmodified copies of CopyBot from working. Nevertheless, the basic issue of users being able to duplicate content that is sent to them remains.

Residents who copy content belonging to other users face being banned from Second Life, but Linden Lab has so far never sued any of these users for copyright infringement; since the resident creators (and not Linden Lab) retain ownership of the rights, it is not clear whether Linden Lab would legally be able to do so. Linden Lab does, however, comply with DMCA takedown notices served to them against resident content; serving a DMCA Takedown Notice is the normal procedure recommended by Linden Lab for having copyrighted content illegally resold on Second Life.

Any user who uploads, publishes or submits any content keeps the intellectual property rights of that content, however both Linden Lab and other users gain their own rights from your content. Linden Lab receives a content license from anything a user uploads to the server. Section 7.3 of the Second Life terms of service states; "you hereby automatically grant Linden Lab a non-exclusive, worldwide, royalty-free, sub-license able, and transferable licence to use, reproduce, distribute, prepare derivative works of, display, and perform the content solely for the purpose of providing and promoting the service".

A user who uploads their content to a public area also gives a content licence to other users as well, which allows other users to replicate and record for use in Machinima (as outlined in section 7.4, Snapshot and Machinima Policy).

Regardless of what rights and licences are given, Linden Lab takes no responsibility for the outcome of any dispute between users or the server regarding content. Section 10.2 states; "you release Linden Lab (and its officers, directors, shareholders, agents, subsidiaries, and employees) from claims, demands, losses, liabilities and damages (actual and consequential) of every kind nature, known and unknown, arising out of or in any way connected with any dispute you have or claim to have with one or more users, including whether or not Linden Lab becomes involved in any resolution or attempted resolution of the dispute". Section 10.3 repeats a similar passage but regarding the responsibility of Linden Lab during any data or technical fault.

Litigation

Bragg v. Linden Lab

Main article: Bragg v. Linden Lab

In 2006, attorney Marc Bragg sued Linden Lab, claiming that it had illegally deprived him of access to his account after he discovered a loophole in the online land auction system which allowed regions to be purchased at prices below reserve. Although most users and commentators believed that Bragg would have no chance of winning, a number of legal developments occurred as a result of the case, including a court ruling that parts of the Second Life Terms of Service were unenforceable, due to being an unconscionable contract of adhesion. The case eventually ended with Bragg's virtual land and account being restored to him in a confidential out-of-court settlement. Since the settlement created no legal precedent, it left users with confusion as to what legal rights they truly had with respect to their virtual land, items, and account. Many of Bragg's legal arguments rested on the claim—advertised on Linden Lab web site—that virtual land within Second Life could be "owned" by the purchasing user, which was removed shortly after the settlement.

Eros, LLC and Grei v. Linden Lab

Eros, LLC and Shannon Grei brought forth a class action suit in US District Court in Northern California against Linden Research, Inc on September 15, 2009 (Case4:09-cv-04269-PJH). Court papers allege the defendants knowingly and profitably turned a blind eye to copyright and trademark violations within the Second Life service.

Evans et al. v. Linden Lab

In 2010, a group of banned SL users filed suit against Linden Lab and CEO Philip Rosedale, in the same Pennsylvania Federal District Court that the Bragg case was adjudicated in, with the same judge, to deal with further land seizures and account suspensions by the Lab against various customers. Due to the Terms of Service agreement changes since the Bragg case, defendants attorneys successfully argued to move the suit to federal court in California, where the case lingered for several years. The judge did rule that there was a basis to turn the litigation into a class action, and that there were two classes under which claimants could file claims. The primary class was those who suffered economic damages to their livelihoods, through loss of their business revenues in SL. The secondary class was those who suffered property losses from loss of land, money on hand, and virtual goods in avatar inventories. In May 2013, attorney for defendants negotiated a settlement agreement with one of the lead attorneys that, in plain language, agreed to refund region setup fees for private island owners, pay land owners 2 Linden Dollars per square meter of virtual land, refund all L$ and USD amounts in the plaintiffs' accounts at the time of suspension, and allow the plaintiffs the option of either receiving $15US as compensation for loss of accounts and inventory virtual goods OR restoration of their accounts in order to sell their goods on the SL Marketplace. The settlement agreement went to final hearing in March 2014, with an objection from claimant Mike Lorrey as to the vagueness of certain terms in the settlement as to which fees exactly would be refunded. With the resolution of that objection, claimants who had filed claims prior to March 28, 2014, began to receive settlement money a few months later.

In popular culture

Since its debut in 2003, Second Life has been referred to by various popular culture media, including literature, television, film and music. In addition, various personalities in such media have themselves used or employed Second Life for both their own works and for private purposes.

In September 2006, former Governor of Virginia Mark Warner became the first politician to appear in a MMO when he gave a speech in Second Life. Musicians followed suit, with Redzone being credited by Wired and Reuters as the first band to tour in Second Life in February 2007. Then, in June 2008, author Charles Stross held a conference in Second Life to promote an upcoming novel. Second Life was also featured prominently, and used as a tool to locate a suspect, in the television show CSI: NY in 2007. In the American sitcom The Office, Dwight Schrute (Rainn Wilson) is known to play the game, most notably in the episode "Local Ad".

Research

Much of the published research conducted in Second Life is associated with education and learning. Unlike computer games, Second Life does not have a pre-defined purpose and allows for highly realistic enactment of real life activities online. One such study tested the usefulness of SL as an action learning environment in a senior course for management information systems students. Another presented a case study in which university students were tasked with building an interactive learning experience using SL as a platform. Both problem-based learning and constructionism acted as framing pedagogies for the task, with students working in teams to design and build a learning experience which could be possible in real life.

Situated learning has also been examined in SL, in order to determine how the design and social dynamics of the virtual world support as well as constrain various types of learning. The paper, "The future for (second) life and learning", published in the British Journal of Educational Technology, examines the potential of Second Life to further innovative learning techniques. It notes trends within the SL innovation to date, including the provision of realistic settings, the exploitation of pleasant simulated environments for groups, and the links with other learning technologies. It also considers the creativity sparked by SL's potential to offer the illusion of 3-D ‘spaces’ and buildings, and points to infinite imaginative educational possibilities.

HealthInfo Island provides tips on staying healthy to Second Life residents.

Second Life has also offered educational research potential within the medical and healthcare fields. Examples include in-world research facilities such as the Second Life Medical and Consumer Health Libraries (Healthinfo Island—funded by a grant from the US National Library of Medicine), and VNEC (Virtual Neurological Education Centre—developed at the University of Plymouth, UK).

There have also been healthcare related studies done of SL residents. Studies show that behaviors from virtual worlds can translate to the real world. One survey suggests that users are engaged in a range of health-related activities in SL which are potentially impacting real-life behaviors.

Another focus of SL research has included the relationship of avatars or virtual personas to the 'real' or actual person. These studies have included research into social behavior and reported two main implications. The first is that SL virtual selves shape users' offline attitudes and behavior. The research indicated that virtual lives and physical lives are not independent, and our appearances and actions have both online and offline consequences. The second deals with experimental research and supports the idea that virtual environments, such as SL, can enable research programs in that people behave in a relatively natural spread of behavioral patterns.

The SL avatar-self relationship was also studied via resident interviews, and various enactments of the avatar-self relationship were identified. The study concluded that SL residents enacted multiple avatar-self relationships and cycled through them in quick succession, suggesting that these avatar-self relationships might be shaped and activated strategically in order to achieve the desired educational, commercial, or therapeutic outcomes.

Anthropologist Tom Boellstorff describes the anthropological applications of studying Second Life and its userbase in Coming of Age in Second Life: An Anthropologist Explores the Virtually Human. Boellstorff explores the relationship between anonymity and community when everyone in a community belongs to varying degrees of anonymity, and how this feeds into the idea of digital collectivity. He also comments on the phenomenon of data becoming "part of social context" that has been observed both inside and outside of Second Life as surveillance becomes more integrated into everyday life. He stresses the difference between the concepts of anonymity and pseudonymity, identifying Second Life users as belonging to the latter group of people - though their avatars are not directly linked to their real identities and reputations, they have forged new ones in this online space, a unique effect of creating an online persona in the digital age.