Magnesium

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From Wikipedia, the free encyclopedia

Magnesium,  ₁₂Mg

Spectral lines of magnesium
General properties
Name, symbol	magnesium, Mg
Pronunciation	/mæɡˈniːziəm/ mag-NEE-zee-əm
Appearance	shiny grey solid
Magnesium in the periodic table
Be ↑ Mg ↓ Ca sodium ← magnesium → aluminium
Atomic number	12
Standard atomic weight	24.305[1] (24.304–24.307)[2]
Element category	alkaline earth metal
Group, block	group 2 (alkaline earth metals), s-block
Period	period 3
Electron configuration	[Ne] 3s2
per shell	2, 8, 2
Physical properties
Phase	solid
Melting point	923 K ​(650 °C, ​1202 °F)
Boiling point	1363 K ​(1091 °C, ​1994 °F)
Density near r.t.	1.738 g·cm−3
when liquid, at m.p.	1.584 g·cm−3
Heat of fusion	8.48 kJ·mol−1
Heat of vaporization	128 kJ·mol−1
Molar heat capacity	24.869 J·mol−1·K−1
vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 701 773 861 971 1132 1361
Atomic properties
Oxidation states	+2, +1[3] ​(a strongly basic oxide)
Electronegativity	Pauling scale: 1.31
Ionization energies	1st: 737.7 kJ·mol−1 2nd: 1450.7 kJ·mol−1 3rd: 7732.7 kJ·mol−1 (more)
Atomic radius	empirical: 160 pm
Covalent radius	141±7 pm
Van der Waals radius	173 pm
Miscellanea
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound thin rod	4940 m·s−1 (at r.t.) (annealed)
Thermal expansion	24.8 µm·m−1·K−1 (at 25 °C)
Thermal conductivity	156 W·m−1·K−1
Electrical resistivity	43.9 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Young's modulus	45 GPa
Shear modulus	17 GPa
Bulk modulus	45 GPa
Poisson ratio	0.290
Mohs hardness	1–2.5
Brinell hardness	44–260 MPa
CAS Registry Number	7439-95-4
History
Naming	after Magnesia, Greece
Discovery	Joseph Black (1755)
First isolation	Humphry Davy (1808)
Most stable isotopes
Main article: Isotopes of magnesium
iso NA half-life DM DE (MeV) DP 24Mg 78.99% 24Mg is stable with 12 neutrons 25Mg 10.00% 25Mg is stable with 13 neutrons 26Mg 11.01% 26Mg is stable with 14 neutrons

Magnesium is a chemical element with symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (Group 2, or alkaline earth metals) of the periodic table: they each have the same electron configuration in their outer electron shell to explain their similar crystal structure.

Magnesium is the ninth most abundant element in the universe.^[4][5] It is synthesized in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such a star explodes as a supernova, much of its magnesium is expelled into the interstellar medium, where it can be recycled into new star systems. Consequently, magnesium is the eighth most abundant element in the Earth's crust^[6] and the fourth most common element in the Earth (below iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's mantle. It is the third most abundant element dissolved in seawater, after sodium and chlorine.^[7]

Magnesium only occurs naturally in combination with other elements, where it uniformly takes on the +2 oxidation state. The free element (metal) can be produced artificially, and is highly reactive (though once produced, it is coated in a thin layer of oxide {see passivation}, which partly masks this reactivity). The free metal burns with a characteristic brilliant-white light, making it a useful ingredient in flares. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine. In commerce, the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys, sometimes called magnalium or magnelium. Since magnesium is less dense than aluminium, this alloy is prized for its properties of lightness combined with strength.

Magnesium is the eleventh most abundant element by mass in the human body. Its ions are essential to all cells. They interact with polyphosphate compounds such as ATP, DNA, and RNA. Hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia), and to stabilize abnormal nerve excitation or blood vessel spasm such as in eclampsia. Magnesium ions are sour to the taste, and in low concentrations they help to impart a natural tartness to fresh mineral waters. Magnesium is the metallic ion at the center of chlorophyll, and is a common additive to fertilizers.^[8]

§Characteristics

§Physical properties

Elemental magnesium is a gray-white light-weight metal, two-thirds the density of aluminium. It tarnishes slightly when exposed to air, although, unlike the other alkali metals, an oxygen-free environment is unnecessary for storage because magnesium is protected by a thin layer of oxide that is fairly impermeable and difficult to remove. Magnesium reacts with water at room temperature, though it reacts much more slowly than the similar earth alkali metal calcium. When submerged in water, hydrogen bubbles almost unnoticeably begin to form on the surface of the metal—though, if powdered, it reacts much more rapidly. The reaction occurs faster with higher temperatures (see precautions). Magnesium's ability to react with water can be harnessed to produce energy and run a magnesium-based engine. Magnesium also reacts exothermically with most acids, such as hydrochloric acid (HCl). As with aluminium, zinc, and many other metals, the reaction with HCl produces the chloride of the metal and releases hydrogen gas.

§Chemical properties

Magnesium is a highly flammable metal, especially when powdered or shaved into thin strips. It is, however, difficult to ignite in mass or bulk. Once ignited, it is difficult to extinguish, being able to burn in nitrogen (forming magnesium nitride), carbon dioxide (forming magnesium oxide, and carbon) and water (forming magnesium oxide and hydrogen). This property was used in incendiary weapons used in the firebombing of cities in World War II, the only practical civil defense being to smother a burning flare under dry sand to exclude the atmosphere. On burning in air, magnesium produces a brilliant-white light that includes strong ultraviolet. Thus, magnesium powder (flash powder) was used as a source of illumination in the early days of photography. Later, magnesium ribbon was used in electrically ignited flashbulbs. Magnesium powder is used in the manufacture of fireworks and marine flares where a brilliant white light is required. Flame temperatures of magnesium and magnesium alloys can reach 3,100 °C (3,370 K; 5,610 °F),^[9] although flame height above the burning metal is usually less than 300 mm (12 in).^[10] Magnesium may be used as an ignition source for thermite, a mixture of aluminium and iron oxide powder that is otherwise difficult to ignite.

§Occurrence

Magnesium is the eighth-most-abundant element in the Earth's crust by mass and tied in seventh place with iron in terms of molarity.^[6] It is found in large deposits of magnesite, dolomite, and other minerals, and in mineral waters, where magnesium ion is soluble.
Although magnesium is found in over 60 minerals, only dolomite, magnesite, brucite, carnallite, talc, and olivine are of commercial importance.

The Mg2+ cation is the second-most-abundant cation in seawater (occurring at about 12% of the mass of sodium there), which makes seawater and sea-salt an attractive commercial source of Mg. To extract the magnesium, calcium hydroxide is added to seawater to form magnesium hydroxide precipitate.

MgCl
2 + Ca(OH)
2 → Mg(OH)
2 + CaCl
2

Magnesium hydroxide (brucite) is insoluble in water, so it can be filtered out and reacted with hydrochloric acid to obtain concentrated magnesium chloride.

Mg(OH)
2 + 2 HCl → MgCl
2 + 2 H
2O

From magnesium chloride, electrolysis produces magnesium.

§Forms

§Alloy

As of 2013, magnesium alloy consumption was less than one million tons per year, compared with 50 million tons of aluminum alloys. Its use has been historically limited by its tendency to corrode, high-temperature creep, and flammability.^[11]

§Corrosion

The presence of iron, nickel, copper, and cobalt strongly activates corrosion. This is due to their low solid solubility limits (above a very small percentage, they precipitate out as intermetallic compounds) and because they behave as active cathodic sites that reduce water and cause the loss of magnesium.^[11] Reducing the quantity of these metals improves corrosion resistance. Sufficient manganese overcomes the corrosive effects of iron. This requires precise control over composition, increasing costs.^[11] Adding a cathodic poison captures atomic hydrogen within the structure of a metal. This prevents the formation of free hydrogen gas, which is required for corrosive chemical processes. The addition of about one-third of a percent of arsenic reduces its corrosion rate in a salt solution by a factor of nearly ten.^[11][12]

§High-temperature creep and flammability

Research and development eliminated magnesium's tendency toward high-temperature creep by inclusion of scandium and gadolinium. Flammability was greatly reduced by introducing a small amount of calcium into the mix.^[11]

§Compounds

Magnesium forms a variety of industrially and biologically important compounds, including magnesium carbonate, magnesium chloride, magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium oxide, magnesium sulfate, and magnesium sulfate heptahydrate (Epsom salts).

§Isotopes

Magnesium has three stable isotopes: ²⁴Mg, ²⁵Mg and ²⁶Mg. All are present in significant amounts (see table of isotopes above). About 79% of Mg is ²⁴Mg. The isotope ²⁸Mg is radioactive and in the 1950s to 1970s was made commercially by several nuclear power plants for use in scientific experiments. This isotope has a relatively short half-life (21 hours) and so its use was limited by shipping times.

²⁶Mg has found application in isotopic geology, similar to that of aluminium. ²⁶Mg is a radiogenic daughter product of ²⁶Al, which has a half-life of 717,000 years. Large enrichments of stable ²⁶Mg have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteorites. The anomalous abundance of ²⁶Mg is attributed to the decay of its parent ²⁶Al in the inclusions. Therefore, the meteorite must have formed in the solar nebula before the ²⁶Al had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its early history.

It is conventional to plot ²⁶Mg/²⁴Mg against an Al/Mg ratio. In an isochron dating plot, the Al/Mg ratio plotted is²⁷Al/²⁴Mg. The slope of the isochron has no age significance, but indicates the initial ²⁶Al/²⁷Al ratio in the sample at the time when the systems were separated from a common reservoir.

§Production

Country	2011 production (tonnes)[13]
China	661,000
U.S.[note 1]	63,500
Russia	37,000
Israel	30,000
Kazakhstan	21,000
Brazil	16,000
Ukraine	2,000
Serbia	1,500
Total	832,000

Magnesium sheets and ingots

China is the dominant supplier of magnesium, with approximately 80% of the world market share. China is almost completely reliant on the silicothermic Pidgeon process (the reduction of the oxide at high temperatures with silicon, often provided by a ferrosilicon alloy in which the iron is but a spectator in the reactions) to obtain the metal.^[14] The process can also be carried out with carbon at approx 2300 °C:

2MgO_(s) + Si_(s) + 2CaO_(s) → 2Mg_(g) + Ca₂SiO_4(s)

MgO_(s) + C_(s) → Mg_(g) + CO_(g)

In the United States, magnesium is obtained principally with the Dow process, by electrolysis of fused magnesium chloride from brine and sea water. A saline solution containing Mg²⁺ ions is first treated with lime (calcium oxide) and the precipitated magnesium hydroxide is collected:

Mg²⁺_(aq) + CaO_(s) + H₂O → Ca²⁺_(aq) + Mg(OH)_2(s)

The hydroxide is then converted to a partial hydrate of magnesium chloride by treating the hydroxide with hydrochloric acid and heating of the product:

Mg(OH)_2(s) + 2 HCl → MgCl_2(aq) + 2H₂O_(l)

The salt is then electrolyzed in the molten state. At the cathode, the Mg2+ ion is reduced by two electrons to magnesium metal:

Mg2+ + 2 e− → Mg

At the anode, each pair of Cl− ions is oxidized to chlorine gas, releasing two electrons to complete the circuit:

2 Cl− → Cl
2 (g) + 2 e−

A new process, solid oxide membrane technology, involves the electrolytic reduction of MgO. At the cathode, Mg2+ ion is reduced by two electrons to magnesium metal. The electrolyte is Yttria-stabilized zirconia (YSZ). The anode is a liquid metal. At the YSZ/liquid metal anode O2− is oxidized. A layer of graphite borders the liquid metal anode, and at this interface carbon and oxygen react to form carbon monoxide. When silver is used as the liquid metal anode, there is no reductant carbon or hydrogen needed, and only oxygen gas is evolved at the anode.^[15] It has been reported that this method provides a 40% reduction in cost per pound over the electrolytic reduction method.^[16] This method is more environmentally sound than others because there is much less carbon dioxide emitted.

The United States has traditionally been the major world supplier of this metal, supplying 45% of world production even as recently as 1995. Today, the US market share is at 7%, with a single domestic producer left, US Magnesium, a Renco Group company in Utah born from now-defunct Magcorp.^[17]

§History

The name magnesium originates from the Greek word for a district in Thessaly called Magnesia.^[18] It is related to magnetite and manganese, which also originated from this area, and required differentiation as separate substances. See manganese for this history.

In 1618, a farmer at Epsom in England attempted to give his cows water from a well there. The cows refused to drink because of the water's bitter taste, but the farmer noticed that the water seemed to heal scratches and rashes. The substance became known as Epsom salts and its fame spread. It was eventually recognized as hydrated magnesium sulfate, MgSO₄·7 H₂O.

The metal itself was first produced by Sir Humphry Davy in England in 1808. He used electrolysis on a mixture of magnesia and mercuric oxide.^[19] Antoine Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium,^[19] but the name magnesium is now used.

§Uses

§As a metal

An unusual application of magnesium as an illumination source while wakeskating in 1931

Magnesium is the third-most-commonly-used structural metal, following iron and aluminium. It has been called the lightest useful metal by The Periodic Table of Videos.^[20]

The main applications of magnesium are, in order: component of aluminium alloys, in die-casting (alloyed with zinc),^[21] to remove sulfur in the production of iron and steel, the production of titanium in the Kroll process.^[22]

Historically, magnesium was one of the main aerospace construction metals and was used for German military aircraft as early as World War I and extensively for German aircraft in World War II.

The Germans coined the name "Elektron" for magnesium alloy. The term is still used today. The application of magnesium in the commercial aerospace industry was generally restricted to engine-related components, due either to perceived hazards with magnesium parts in the event of fire or to corrosion. Currently, the use of magnesium alloys in aerospace is increasing, mostly driven by the increasing importance of fuel economy and the need to reduce weight.^[23] The development and testing of new magnesium alloys continues, notably Elektron 21, which has successfully undergone extensive aerospace testing for suitability in engine and internal and airframe components.^[24] The European Community runs three R&D magnesium projects in the Aerospace priority of Six Framework Program.

§Aircraft

• Wright Aeronautical used a magnesium crankcase in the WWII-era Wright Duplex Cyclone aviation engine. This presented a serious problem for the earliest examples of the Boeing B-29 heavy bomber, as engine fires in flight could ignite the engine crankcases, literally "torching" the wing spar apart.^[25][26]

§Automotive

Mg alloy car engine blocks

• Mercedes-Benz used the alloy Elektron in the body of an early model Mercedes-Benz 300 SLR; these cars ran (with successes) at Le Mans, the Mille Miglia, and other world-class race events in 1955.
• Porsche used magnesium alloy frames in the 917/053 that won Le Mans in 1971, and continues to use magnesium alloys for its engine blocks due to the weight advantage.
• Volkswagen Group has used magnesium in its engine components for many years.^{[citation needed]}
• Mitsubishi Motors also uses magnesium for its paddle shifters.
• BMW used magnesium alloy engine blocks in the 2006 325i and 330i models, including an aluminium alloy insert for the cylinder walls and cooling jackets surrounded by a high-temperature magnesium alloy AJ62A.
• Chevrolet used the magnesium alloy AE44 in the 2006 Corvette Z06.

Both AJ62A and AE44 are recent developments in high-temperature low-creep magnesium alloys. The general strategy for such alloys is to form intermetallic precipitates at the grain boundaries, for example by adding mischmetal or calcium.^[27] New alloy development and lower costs that make magnesium competitive with aluminium will increase the number of automotive applications.

§Electronics

Because of low weight and good mechanical and electrical properties, magnesium is widely used for manufacturing of mobile phones, laptop and tablet computers, cameras, and other electronic components.

Products made of magnesium:
firestarter and shavings, sharpener, magnesium ribbon

§Niche uses of the metal

Magnesium, being readily available and relatively nontoxic, has a variety of uses:

• Magnesium is flammable, burning at a temperature of approximately 3,100 °C (3,370 K; 5,610 °F),^[9] and the autoignition temperature of magnesium ribbon is approximately 473 °C (746 K; 883 °F).^[28] It produces intense, bright, white light when it burns. Magnesium's high combustion temperature makes it a useful tool for starting emergency fires. Other uses include flash photography, flares, pyrotechnics, and fireworks sparklers. Magnesium is also often used to ignite thermite or other materials that require a high ignition temperature.
  
  

  Magnesium firestarter (in left hand), used with a pocket knife and flint to create sparks that ignite the shavings
• In the form of turnings or ribbons, to prepare Grignard reagents, which are useful in organic synthesis.
• As an additive agent in conventional propellants and the production of nodular graphite in cast iron.
• As a reducing agent to separate uranium and other metals from their salts.
• As a sacrificial (galvanic) anode to protect underground tanks, pipelines, buried structures, and water heaters.
• Alloyed with zinc to produce the zinc sheet used in photoengraving plates in the printing industry, dry-cell battery walls, and roofing.^[21]
• As a metal, this element's principal use is as an alloying additive to aluminium with these aluminium-magnesium alloys being used mainly for beverage cans, sports equipment such as golf clubs, fishing reels, and archery bows and arrows.
• Specialty, high-grade car wheels of magnesium alloy are called "mag wheels", although the term is often more broadly misapplied to include aluminium wheels. Many car and aircraft manufacturers have made engine and body parts from magnesium.

§In compounds

Magnesium compounds, primarily magnesium oxide (MgO), are used as a refractory material in furnace linings for producing iron, steel, nonferrous metals, glass, and cement. Magnesium oxide and other magnesium compounds are also used in the agricultural, chemical, and construction industries. Magnesium oxide from calcination is used as an electrical insulator in fire-resistant cables.^[29]

Magnesium reacted with an alkyl halide gives a Grignard reagent, which is a very useful tool for preparing alcohols.

Magnesium salts are frequently included in various foods, fertilizers (magnesium is a component of chlorophyll), and culture media.

Magnesium sulfite is used in the manufacture of paper (sulfite process).

Magnesium phosphate is used to fireproof wood used in construction.

Magnesium hexafluorosilicate is used in mothproofing of textiles.

In the form of turnings or ribbons, Mg is useful in purification of solvents, for example the preparation of super-dry ethanol.

§Biological

Pharmaceutical preparations of magnesium are used to treat magnesium deficiency and hypomagnesemia, as well as eclampsia.^[30] Usually in lower dosages, magnesium is commonly included in dietary mineral preparations, including many multivitamin preparations.
Sorted by type of magnesium salt, biological applications of magnesium include:

• Magnesium sulfate, as the heptahydrate called Epsom salts, is used as bath salts, as a laxative, and as a highly soluble fertilizer.^[31]
• Magnesium hydroxide, suspended in water, is used in milk of magnesia antacids and laxatives.
• Magnesium chloride, oxide, gluconate, malate, orotate, glycinate and citrate are all used as oral magnesium supplements. Some have claimed that oral magnesium supplements are therapeutic for restless leg syndrome (RLS) in some individuals.^[32]
• Magnesium borate, magnesium salicylate, and magnesium sulfate are used as antiseptics.
• Magnesium bromide is used as a mild sedative (this action is due to the bromide, not the magnesium).
• Magnesium stearate is a slightly flammable white powder with lubricating properties. In pharmaceutical technology, it is used in the manufacturing of numerous kinds of tablets to prevent the tablets from sticking to the equipment during the tablet compression process (i.e., when the tablet's substance is pressed into tablet form).
• Magnesium carbonate powder is used by athletes such as gymnasts, weightlifters, and climbers to eliminate moisture and improving the grip on a gymnastic apparatus, lifting bar, and climbing rocks.
• Magnesium L-threonate is used a dietary magnesium supplement

§Biological roles

§Mechanism of action

Because of the important interaction between phosphate and magnesium ions, magnesium ions are essential to the basic nucleic acid chemistry of life, and thus are essential to all cells of all known living organisms. Over 300 enzymes require the presence of magnesium ions for their catalytic action, including all enzymes utilizing or synthesizing ATP, or those that use other nucleotides to synthesize DNA and RNA. ATP exists in cells normally as a chelate of ATP and a magnesium ion.^[33]

§Dietary sources, recommended intake, and supplementation

Examples of food sources of magnesium

Spices, nuts, cereals, cocoa and vegetables are rich sources of magnesium.^[34] Green leafy vegetables such as spinach are also rich in magnesium since they contain chlorophyll.

The UK recommended daily values for magnesium is 300 mg for men and 270 mg for women.^[35] Observations of reduced dietary magnesium intake in modern Western countries compared to earlier generations may be related to food refining and modern fertilizers that contain no magnesium.^[36]

Numerous pharmaceutical preparations of magnesium, as well as magnesium dietary supplements are available. Magnesium oxide, one of the most common forms in magnesium dietary supplements because it has high magnesium content per weight, has been reported the least bioavailable.^[37][38]

There is limited evidence that magnesium supplementation may play a role in the prevention and treatment of migraine.^[39]

§Metabolism

An adult has 22-26 grams of magnesium,^[40] with 60% in the skeleton, 39% intracellular (20% in skeletal muscle), and 1% extracellular.^[41] Serum levels are typically 0.7–1.0 mmol/L or 1.8–2.4 mEq/L. Serum magnesium levels may be normal even when intracellular magnesium is deficient. The mechanisms for maintaining the magnesium level in the serum are varying gastrointestinal absorption and renal excretion. Intracellular magnesium is correlated with intracellular potassium. Increased magnesium lowers calcium^[42] and can either prevent hypercalcemia or cause hypocalcemia depending on the initial level.^[42] Low and high protein intake inhibit magnesium absorption, as does the amount of phosphate, phytate, and fat in the gut. Excess dietary magnesium is excreted in feces, urine, and sweat.^[36] Magnesium status may be assessed via serum and erythrocyte magnesium concentrations coupled with urinary and fecal magnesium content, but intravenous magnesium loading tests are more accurate and practical.^[43] A retention of 20% or more of the injected amount indicates deficiency.^[44] No biomarker has been established for magnesium.^[45]

§Detection in serum and plasma

Magnesium concentrations in plasma or serum may be measured to monitor for efficacy and safety in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage. The newborn children of mothers having received parenteral magnesium sulfate during labor may exhibit toxicity with normal serum magnesium levels.^[46]

§Deficiency

Magnesium deficiency (hypomagnesemia) is common: it is found in 2.5 - 15% of the general population.^[47] The primary cause of deficiency is decreased dietary intake: only 32% of people in the United States meet the recommended daily allowance.^[48] Other causes are increased renal or gastrointestinal loss, an increased intracellular shift, and proton-pump inhibitor antacid therapy. Most are asymptomatic, but symptoms referable to neuromuscular, cardiovascular, and metabolic dysfunction may occur.^[47] Alcoholism is often associated with magnesium deficiency. Chronically low serum magnesium levels are associated with metabolic syndrome, diabetes mellitus type 2 and hypertension.^[49]

§Therapy

• Intravenous magnesium is recommended by the ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death for patients with ventricular arrhythmia associated with torsades de pointes who present with long QT syndrome; and for the treatment of patients with digoxin induced arrhythmias.^[50]
• Magnesium is the drug of choice in the management of pre-eclampsia and eclampsia.^[51]
• Hypomagnesemia, including that caused by alcoholism, is reversible by oral or parenteral magnesium administration depending on the degree of deficiency.^[52]

§Overdose

Overdose from dietary sources alone is unlikely because excess magnesium in the blood is promptly filtered by the kidneys.^[47] Overdose with magnesium tablets is possible in the presence of impaired renal function. There is a single case report of hypermagnesemia in a woman with normal renal function using high doses of magnesium salts for catharsis.^[53] The most common symptoms of overdose are nausea, vomiting and diarrhea; other symptoms include hypotension, confusion, slowed heart and respiratory rate, deficiencies of other minerals, coma, cardiac arrhythmia, and death from cardiac arrest.^[42]

§Function in plants

Plants require magnesium to synthesize chlorophyll. Magnesium in the center of the porphyrin ring in chlorophyll functions in a manner similar to the iron in the center of the porphyrin ring in heme. Magnesium deficiency in plants causes late-season yellowing between leaf veins, especially in older leaves, and can be corrected by applying to the soil either Epsom salts (which is rapidly leached), or crushed dolomitic limestone.

§Safety precautions for the metal

The combusting magnesium-bodied Honda RA302 at the 1968 French Grand Prix, after the crash that killed driver Jo Schlesser.

Magnesium metal and its alloys are explosive hazards; they are highly flammable in their pure form when molten or in powder or ribbon form. Burning or molten magnesium metal reacts violently with water. When working with powdered magnesium, safety glasses with welding eye protection are employed, because the bright-white light produced by burning magnesium contains ultraviolet light that can permanently damage the retinas of the eyes.^[54]

Magnesium is capable of reducing water to highly flammable hydrogen gas:^[55]

Mg (s) + 2 H
2O (l) → Mg(OH)
2 (s) + H
2 (g)

As a result, water cannot extinguish magnesium fires. The hydrogen gas produced only intensifies the fire. Dry sand is an effective smothering agent, but only on relatively level and flat surfaces.

Magnesium also reacts with carbon dioxide to form magnesium oxide and carbon:

2 Mg + CO
2 → 2 MgO + C (s)

hence, carbon dioxide fire extinguishers are also ineffective for extinguishing magnesium fires.^[56]

Burning magnesium is usually quenched by using a Class D dry chemical fire extinguisher, or by covering the fire with sand or magnesium foundry flux to remove its air source.

Life extension

From Wikipedia, the free encyclopedia

Life extension science, also known as anti-aging medicine, indefinite life extension, experimental gerontology, and biomedical gerontology, is the study of slowing down or reversing the processes of aging to extend both the maximum and average lifespan. Some researchers in this area, and "life extensionists", "immortalists" or "longevists" (those who wish to achieve longer lives themselves), believe that future breakthroughs in tissue rejuvenation, stem cells, regenerative medicine, molecular repair, pharmaceuticals, and organ replacement (such as with artificial organs or xenotransplantations) will eventually enable humans to have indefinite lifespans (agerasia^[1]) through complete rejuvenation to a healthy youthful condition.

The sale of putative anti-aging products such as nutrition, physical fitness, skin care, hormone replacements, vitamins, supplements and herbs is a lucrative global industry, with the US market generating about $50 billion of revenue each year.^[2] Some medical experts state that the use of such products has not been proven to affect the aging process and many claims regarding the efficacy of these marketed products have been roundly criticized by medical experts, including the American Medical Association.^{[2][3][4][5][6]}

However, it has not been shown that the goal of indefinite human lifespans itself is necessarily unfeasible; some animals such as hydra, planarian flatworms, and certain sponges, corals, and jellyfish do not die of old age and exhibit potential immortality.^{[7][8][9][10]} The ethical ramifications of life extension are debated by bioethicists.

§Public opinion

Life extension is a controversial topic due to fear of overpopulation and possible effects on society.^[11] Religious people are no more likely to oppose life extension than the unaffiliated,^[12] though some variation exists between religious denominations. Blacks and Hispanics are more likely to support life extension than white people.^[12] Biogerontologist Aubrey De Grey counters the overpopulation critique by pointing out that the therapy could postpone or eliminate menopause, allowing women to space out their pregnancies over more years and thus decreasing the yearly population growth rate.^[13] Moreover, the philosopher and futurist Max More argues that, given the fact the worldwide population growth rate is slowing down and is projected to eventually stabilize and begin falling, superlongevity would be unlikely to contribute to overpopulation.^[11]

A Spring 2013 Pew Research poll in the United States found that 38% of Americans would want life extension treatments, and 56% would reject it. However, it also found that 68% believed most people would want it and that only 4% consider an "ideal lifespan" to be more than 120 years. The median "ideal lifespan" was 91 years of age and the majority of the public (63%) viewed medical advances aimed at prolonging life as generally good. 41% of Americans believed that radical life extension would be good for society, while 51% said they believed it would be bad for society.^[12] One possibility for why 56% of Americans claim they would reject life extension treatments may be due to the cultural perception that living longer would result in a longer period of decrepitude, and that the elderly in our current society are unhealthy.^[14]

§Average and maximum lifespans

During the process of aging, an organism accumulates damage to its macromolecules, cells, tissues, and organs. Specifically, aging is characterized as and thought to be caused by "genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication."^[15] Oxidation damage to cellular contents caused by free radicals is believed to contribute to aging as well.^[16][16][17]
The longest a human has ever been proven to live is 122 years, the case of Jeanne Calment who was born in 1875 and died in 1997, whereas the maximum lifespan of a wildtype mouse, commonly used as a model in research on aging, is about three years.^[18] Genetic differences between humans and mice that may account for these different aging rates include differences in efficiency of DNA repair, antioxidant defenses, energy metabolism, proteostasis maintenance, and recycling mechanisms such as autophagy.^[19]

Average lifespan in a population is lowered by infant and child mortality, which are frequently linked to infectious diseases or nutrition problems. Later in life, vulnerability to accidents and age-related chronic disease such as cancer or cardiovascular disease play an increasing role in mortality. Extension of expected lifespan can often be achieved by access to improved medical care, vaccinations, good diet, exercise and avoidance of hazards such as smoking.

Maximum lifespan is determined by the rate of aging for a species inherent in its genes and by environmental factors. Widely recognized methods of extending maximum lifespan in model organisms such as nematodes, fruit flies, and mice include caloric restriction, gene manipulation, and administration of pharmaceuticals.^[20] Another technique uses evolutionary pressures such as breeding from only older members or altering levels of extrinsic mortality.^[21][22]

Theoretically, extension of maximum lifespan in humans could be achieved by reducing the rate of aging damage by periodic replacement of damaged tissues, molecular repair or rejuvenation of deteriorated cells and tissues, reversal of harmful epigenetic changes, or the enhancement of telomerase enzyme activity.^[23][24]

Research geared towards life extension strategies in various organisms is currently under way at a number of academic and private institutions. As of 2009, investigators had founds ways to increase the lifespan of nematode worms and yeast by 10-fold; the record in nematodes was achieved through genetic engineering and the extension in yeast by a combination of genetic engineering and caloric restriction.^[25] A 2009 review of longevity research noted: "Extrapolation from worms to mammals is risky at best, and it cannot be assumed that interventions will result in comparable life extension factors. Longevity gains from dietary restriction, or from mutations studied previously, yield smaller benefits to Drosophila than to nematodes, and smaller still to mammals. This is not unexpected, since mammals have evolved to live many times the worm's lifespan, and humans live nearly twice as long as the next longest-lived primate. From an evolutionary perspective, mammals and their ancestors have already undergone several hundred million years of natural selection favoring traits that could directly or indirectly favor increased longevity, and may thus have already settled on gene sequences that promote lifespan. Moreover, the very notion of a “life-extension factor” that could apply across taxa presumes a linear response rarely seen in biology."^[25]

§Current anti-aging strategies and issues

§Diets and supplements

Much life extension research focuses on nutrition—diets or supplements—as a means to extend lifespan, although few of these have been systematically tested for significant longevity effects. The many diets promoted by anti-aging advocates are often contradictory.^{[original research?]} A dietary pattern with some support from scientific research is caloric restriction.^[26][27]

Preliminary studies of caloric restriction on humans using surrogate measurements have provided evidence that caloric restriction may have powerful protective effect against secondary aging in humans. Caloric restriction in humans may reduce the risk of developing Type 2 diabetes and atherosclerosis.^[28] More research is needed.

The free-radical theory of aging suggests that antioxidant supplements, such as Vitamin C, Vitamin E, Q₁₀, lipoic acid, carnosine, and N-acetylcysteine, might extend human life. However, combined evidence from several clinical trials suggest that β-Carotene supplements and high doses of Vitamin E increase mortality rates.^[29] Resveratrol is a sirtuin stimulant that has been shown to extend life in animal models, but the effect of resveratrol on lifespan in humans is unclear as of 2011.^[30]

There are many traditional herbs purportedly used to extend the health-span, including a Chinese tea called Jiaogulan (Gynostemma pentaphyllum), dubbed "China's Immortality Herb."^[31] Ayurveda, the traditional Indian system of medicine, describes a class of longevity herbs called rasayanas, including Bacopa monnieri, Ocimum sanctum, Curcuma longa, Centella asiatica, Phyllanthus emblica, Withania somnifera and many others.^[31]

§Hormone treatments

The anti-aging industry offers several hormone therapies. Some of these have been criticized for possible dangers to the patient and a lack of proven effect. For example, the American Medical Association has been critical of some anti-aging hormone therapies.^[2]

Although some recent clinical studies have shown that low-dose growth hormone (GH) treatment for adults with GH deficiency changes the body composition by increasing muscle mass, decreasing fat mass, increasing bone density and muscle strength, improves cardiovascular parameters (i.e. decrease of LDL cholesterol), and affects the quality of life without significant side effects,^[32][33][34] the evidence for use of growth hormone as an anti-aging therapy is mixed and based on animal studies. An early study suggested that supplementation of mice with growth hormone increased average life expectancy.^[35] Additional animal experiments have suggested that growth hormone may generally act to shorten maximum lifespan; knockout mice lacking the receptor for growth hormone live especially long.^[36] Furthermore, mouse models lacking the insulin-like growth factor also live especially long and have low levels of growth hormone.^[36]

§Insulin like growth factor (IGF-1) restriction

People suffering from a rare condition known as Laron syndrome have a mutation in the gene that makes the receptor for growth hormone. It is theorised that this mutation may hold a key to life extension.

Longo said that some level of IGF-1 was necessary to protect against heart disease, but that lowering the level might be beneficial. A drug that does this is already on the market for treatment of acromegaly, a thickening of the bones caused by excessive growth hormone. “Our underlying hypothesis is that this drug would prolong life span,” Longo said. He said he was not taking the drug, called pegvisomant or Somavert, which is very hard to obtain.

^[37]

§Scientific controversy regarding anti-aging nutritional supplementation and medicine

Some critics dispute the portrayal of aging as a disease. For example, Leonard Hayflick, who determined that fibroblasts are limited to around 50 cell divisions, reasons that aging is an unavoidable consequence of entropy. Hayflick and fellow biogerontologists Jay Olshansky and Bruce Carnes have strongly criticized the anti-aging industry in response to what they see as unscrupulous profiteering from the sale of unproven anti-aging supplements.^[4]

§Ethics and politics of anti-aging nutritional supplementation and medicine

Politics relevant to the substances of life extension pertain mostly to communications and availability.^{[citation needed]}

In the United States, product claims on food and drug labels are strictly regulated. The First Amendment (freedom of speech) protects third-party publishers' rights to distribute fact, opinion and speculation on life extension practices. Manufacturers and suppliers also provide informational publications, but because they market the substances, they are subject to monitoring and enforcement by the Federal Trade Commission (FTC), which polices claims by marketers. What constitutes the difference between truthful and false claims is hotly debated and is a central controversy in this arena.^{[citation needed]}

§Consumer motivations for using anti-aging products

Research by Sobh and Martin (2011) suggests that people buy anti-aging products to obtain a hoped-for self (e.g., keeping a youthful skin) or to avoid a feared-self (e.g., looking old). The research shows that when consumers pursue a hoped-for self, it is expectations of success that most strongly drive their motivation to use the product. The research also shows why doing badly when trying to avoid a feared self is more motivating than doing well. Interestingly, when product use is seen to fail it is more motivating than success when consumers seek to avoid a feared-self.^[38]

§Proposed strategies of life extension

§Anti-aging drugs

There are a number of drugs intended to slow the aging process currently being studied in animal models. One type of research is related to the observed effects a calorie restriction (CR) diet, which has been shown to extend lifespan in some animals^[39] Based on that research, there have been attempts to develop drugs that will have the same effect on the aging process as a caloric restriction diet, which are known as Caloric restriction mimetic drugs. Drugs that have been studied for possible longevity effects on laboratory animals because of a possible CR-mimic effect include rapamycin,^[40] metformin,^[41] and resveratrol.^[42]

Two drugs that may have potential benefits of combating age-related maladies are resveratrol and rapamycin. These drugs are considered to be the forefront drugs in anti-aging research.^[43] Before these drugs had been tested, the best-characterized anti-aging therapy was, and still is, CR. In some studies calorie restriction has been shown to extend the life of mice, yeast, and rhesus monkeys significantly.^[44][45] However, a more recent study has shown that in contrast, calorie restriction has not improved the survival rate in rhesus monkeys.^[46] Long-term human trials of CR are now being done. It is the hope of the anti-aging researchers that resveratrol and rapamycin may act as CR mimetics to increase the life span of humans.^[43]

Resveratrol was first thought to be an activator of sirtuins, a family of deacetylases, that would promote anti aging effects without having to restrict caloric intake.^[47] However, recent replication studies have failed to show that Resveratrol increases the life span in yeast or mice and that Resveratrol may not activate sirtuins that are biologically beneficial to age reduction.^{[48][49][50][51]} Another study was done showing that resveratrol activates or inhibits fifteen or more different enzymes.^[52] Of those enzymes, one stands out with potential for reducing age-related disease. AMP-activated protein kinase (AMPK) has shown to increase life span of nematodes and prevent obesity in mice.^[53] Although resveratrol has not been proven to extend the life-span of mammals at the current doses tested, resveratrol could be used to access some of the same molecular pathways that CR does. Several examples would include diet induced obesity, some cancers, cardiovascular disease, and neurodegenerative diseases.^[54]

While resveratrol has not been proven to increase life span, rapamycin has shown much more promise.^[43] Rapamycin is shown to increase longevity by inhibiting the mammalian target of rapamycin (mTOR) the same way CR does.^[55] Study systems including yeast, nematodes, flies, and mammals, have shown that reduction of TOR signaling will result in an increased life span.^[56][40] Additionally, rapamycin has similar effects of resveratrol in protecting against several cancers, cardiovascular, and neurodegenerative diseases.^[43][56] Rapamycin also has been shown to act as an immunosuppressant, however more testing is needed to show if the life extending dose comes at the cost of an impaired immune system.^[56]

Resveratrol and rapamycin have both shown protection against cancers, cardiovascular disease, and neurodegenerative diseases in multiple study systems.^[54][56] Rapamycin looks to have more potential in life span extension than resveratrol, but may come at a price of immune system impairment.^[43][56] Clinical trials are now being performed to see if rapamycin or resveratrol will have anti-aging effects in humans.

Other attempts to create anti-aging drugs have taken different research paths. One notable direction of research has been research into the possibility of using the enzyme telomerase in order to counter the process of telomere shortening.^[57] However, there are potential dangers in this, since some research has also linked telomerase to cancer and to tumor growth and formation.^[58]

§Nanotechnology

Future advances in nanomedicine could give rise to life extension through the repair of many processes thought to be responsible for aging. K. Eric Drexler, one of the founders of nanotechnology, postulated cell repair machines, including ones operating within cells and utilizing as yet hypothetical molecular computers, in his 1986 book Engines of Creation. Raymond Kurzweil, a futurist and transhumanist, stated in his book The Singularity Is Near that he believes that advanced medical nanorobotics could completely remedy the effects of aging by 2030.^[59]

§Cloning and body part replacement

Some life extensionists suggest that therapeutic cloning and stem cell research could one day provide a way to generate cells, body parts, or even entire bodies (generally referred to as reproductive cloning) that would be genetically identical to a prospective patient. Recently, the US Department of Defense initiated a program to research the possibility of growing human body parts on mice.^[60] Complex biological structures, such as mammalian joints and limbs, have not yet been replicated. Dog and primate brain transplantation experiments were conducted in the mid-20th century but failed due to rejection and the inability to restore nerve connections. As of 2006, the implantation of bio-engineered bladders grown from patients' own cells has proven to be a viable treatment for bladder disease.^[61] Proponents of body part replacement and cloning contend that the required biotechnologies are likely to appear earlier than other life-extension technologies.

The use of human stem cells, particularly embryonic stem cells, is controversial. Opponents' objections generally are based on interpretations of religious teachings or ethical considerations. Proponents of stem cell research point out that cells are routinely formed and destroyed in a variety of contexts. Use of stem cells taken from the umbilical cord or parts of the adult body may not provoke controversy.^[62]

The controversies over cloning are similar, except general public opinion in most countries stands in opposition to reproductive cloning. Some proponents of therapeutic cloning predict the production of whole bodies, lacking consciousness, for eventual brain transplantation.

§Cyborgs

Replacement of biological (susceptible on diseases) organs with mechanical ones could extend life. This is the goal of 2045 Initiative.^[63]

§Cryonics

For cryonicists (advocates of cryopreservation), storing the body at low temperatures after death may provide an "ambulance" into a future in which advanced medical technologies may allow resuscitation and repair. They speculate cryogenic temperatures will minimize changes in biological tissue for many years, giving the medical community ample time to cure all disease, rejuvenate the aged and repair any damage that is caused by the cryopreservation process.
Many cryonicists do not believe that legal death is "real death" because stoppage of heartbeat and breathing—the usual medical criteria for legal death—occur before biological death of cells and tissues of the body. Even at room temperature, cells may take hours to die and days to decompose. Although neurological damage occurs within 4–6 minutes of cardiac arrest, the irreversible neurodegenerative processes do not manifest for hours.^[64] Cryonicists state that rapid cooling and cardio-pulmonary support applied immediately after certification of death can preserve cells and tissues for long-term preservation at cryogenic temperatures. People, particularly children, have survived up to an hour without heartbeat after submersion in ice water. In one case, full recovery was reported after 45 minutes underwater.^[65] To facilitate rapid preservation of cells and tissue, cryonics "standby teams" are available to wait by the bedside of patients who are to be cryopreserved to apply cooling and cardio-pulmonary support as soon as possible after declaration of death.^[66]

No mammal has been successfully cryopreserved and brought back to life, with the exception of frozen human embryos. Resuscitation of a postembryonic human from cryonics is not possible with current science. Some scientists still support the idea based on their expectations of the capabilities of future science.^[67][68]

§Strategies for Engineered Negligible Senescence (SENS)

Another proposed life extension technology would combine existing and predicted future biochemical and genetic techniques. SENS proposes that rejuvenation may be obtained by removing aging damage via the use of stem cells and tissue engineering, removal of telomere-lengthening machinery, allotopic expression of mitochondrial proteins, targeted ablation of cells, immunotherapeutic clearance, and novel lysosomal hydrolases.^[69]
While many biogerontologists find these ideas "worthy of discussion"^[70][71] and SENS conferences feature important research in the field,^[72][73] some contend that the alleged benefits are too speculative given the current state of technology, referring to it as "fantasy rather than science".^[3][5]

§Genetic modification

Gene therapy, in which nucleic acid polymers are delivered as a drug and are either expressed as proteins, interfere with the expression of proteins, or correct genetic mutations, has been proposed as a future strategy to prevent aging.^[74][75]

A large array of genetic modifications have been found to increase lifespan in model organisms such as yeast, nematode worms, fruit flies, and mice. As of 2013, the longest extension of life caused by a single gene manipulation was roughly 150% in mice and 10-fold in nematode worms.^[76]

§Fooling genes

In The Selfish Gene, Richard Dawkins describes an approach to life-extension that involves "fooling genes" into thinking the body is young.^[77] Dawkins attributes inspiration for this idea to Peter Medawar. The basic idea is that our bodies are composed of genes that activate throughout our lifetimes, some when we are young and others when we are older. Presumably, these genes are activated by environmental factors, and the changes caused by these genes activating can be lethal. It is a statistical certainty that we possess more lethal genes that activate in later life than in early life. Therefore, to extend life, we should be able to prevent these genes from switching on, and we should be able to do so by "identifying changes in the internal chemical environment of a body that take place during aging... and by simulating the superficial chemical properties of a young body".^[78]

§Reversal of informational entropy

According to some lines of thinking, the ageing process is routed into a basic reduction of biological complexity,^[79] and thus loss of information. In order to reverse this loss, gerontologist Marios Kyriazis suggested that it is necessary to increase input of actionable and meaningful information both individually (into individual brains),^[80] and collectively (into societal systems).^[81] This technique enhances overall biological function through up-regulation of immune, hormonal, antioxidant and other parameters, resulting in improved age-repair mechanisms. Working in parallel with natural evolutionary mechanisms that can facilitate survival through increased fitness, Kyriazis claims that the technique may lead to a reduction of the rate of death as a function of age, i.e. indefinite lifespan.^[82]

§Mind uploading

One hypothetical future strategy that, as some suggest, "eliminates" the complications related to a physical body, involves the copying or transferring (e.g. by progressively replacing neurons with transistors) of a conscious mind from a biological brain to a non-biological computer system or computational device. The basic idea is to scan the structure of a particular brain in detail, and then construct a software model of it that is so faithful to the original that, when run on appropriate hardware, it will behave in essentially the same way as the original brain.^[83] Whether or not an exact copy of one's mind constitutes actual life extension is matter of debate.

§History of the life extension movement

In 1970, the American Aging Association was formed under the impetus of Denham Harman, originator of the free radical theory of aging. Harman wanted an organization of biogerontologists that was devoted to research and to the sharing of information among scientists interested in extending human lifespan.

In 1976, futurists Joel Kurtzman and Philip Gordon wrote No More Dying. The Conquest Of Aging And The Extension Of Human Life, (ISBN 0-440-36247-4) the first popular book on research to extend human lifespan. Subsequently, Kurtzman was invited to testify before the House Select Committee on Aging, chaired by Claude Pepper of Florida, to discuss the impact of life extension on the Social Security system.

Saul Kent published The Life Extension Revolution (ISBN 0-688-03580-9) in 1980 and created a nutraceutical firm called the Life Extension Foundation, a non-profit organization that promotes dietary supplements. The Life Extension Foundation publishes a periodical called Life Extension Magazine. The 1982 bestselling book Life Extension: A Practical Scientific Approach (ISBN 0-446-51229-X) by Durk Pearson and Sandy Shaw further popularized the phrase "life extension".

In 1983, Roy Walford, a life-extensionist and gerontologist, published a popular book called Maximum Lifespan. In 1988, Walford and his student Richard Weindruch summarized their research into the ability of calorie restriction to extend the lifespan of rodents in The Retardation of Aging and Disease by Dietary Restriction (ISBN 0-398-05496-7). It had been known since the work of Clive McCay in the 1930s that calorie restriction can extend the maximum lifespan of rodents. But it was the work of Walford and Weindruch that gave detailed scientific grounding to that knowledge.^{[citation needed]} Walford's personal interest in life extension motivated his scientific work and he practiced calorie restriction himself. Walford died at the age of 80 from complications caused by amyotrophic lateral sclerosis.

Money generated by the non-profit Life Extension Foundation allowed Saul Kent to finance the Alcor Life Extension Foundation, the world's largest cryonics organization. The cryonics movement had been launched in 1962 by Robert Ettinger's book, The Prospect of Immortality. In the 1960s, Saul Kent had been a co-founder of the Cryonics Society of New York. Alcor gained national prominence when baseball star Ted Williams was cryonically preserved by Alcor in 2002 and a family dispute arose as to whether Williams had really wanted to be cryopreserved.

Regulatory and legal struggles between the Food and Drug Administration (FDA) and the Life Extension Foundation included seizure of merchandise and court action. In 1991, Saul Kent and Bill Faloon, the principals of the Foundation, were jailed. The LEF accused the FDA of perpetrating a "Holocaust" and "seeking gestapo-like power" through its regulation of drugs and marketing claims.^[84]

In 2003, Doubleday published "The Immortal Cell: One Scientist's Quest to Solve the Mystery of Human Aging," by Michael D. West. West emphasised the potential role of embryonic stem cells in life extension.^[85]

§Scientific research

In 1991, the American Academy of Anti-Aging Medicine (A4M) was formed as a non-profit organization to create what it considered an anti-aging medical specialty distinct from geriatrics, and to hold trade shows for physicians interested in anti-aging medicine. The A4M trains doctors in anti-aging medicine and publicly promotes the field of anti-aging research. It has about 26,000 members, of whom about 97% are doctors and scientists.^[86] The American Board of Medical Specialties recognizes neither anti-aging medicine nor the A4M's professional standing.^[87]

In 2003, Aubrey de Grey and David Gobel formed the Methuselah Foundation, which gives financial grants to anti-aging research projects. In 2009, de Grey and several others founded the SENS Research Foundation, a California-based scientific research organization which conducts research into aging and funds other anti-aging research projects at various universities.^[88] In 2013, Google announced Calico, a new company based in San Francisco that will harness new technologies to increase scientific understanding of the biology of aging.^[89] It is led by Arthur D. Levinson,^[90] and its research team includes scientists such as Hal V. Barron, David Botstein, and Cynthia Kenyon. In 2014, biologist Craig Venter founded Human Longevity Inc., a company dedicated to scientific research to end aging through genomics and cell therapy. It subsequently began building the a human genotype, microbiome, and phenotype database in the world to aid in its research.^[91]

Aside from private initiatives, aging research is being conducted in university laboratories, and includes universities such as Harvard and UCLA. University researchers have made a number of breakthroughs in extending the lives of mice and insects by reversing certain aspects of aging.^{[92][93][94][95]}

§Ethics and politics of life extension

Though many scientists state^[96] that life extension and radical life extension are possible, there are still no international or national programs focused on radical life extension. There are political forces staying for and against life extension. By 2012, in Russia, the United States, Israel, and the Netherlands, the Longevity political parties started. They aimed to provide political support to radical life extension research and technologies, and ensure the fastest possible and at the same time soft transition of society to the next step - life without aging and with radical life extension, and to provide access to such technologies to most currently living people.^{[97] [98]}

Leon Kass (chairman of the US President's Council on Bioethics from 2001 to 2005) has questioned whether potential exacerbation of overpopulation problems would make life extension unethical.^[99] He states his opposition to life extension with the words:

"simply to covet a prolonged life span for ourselves is both a sign and a cause of our failure to open ourselves to procreation and to any higher purpose ... [The] desire to prolong youthfulness is not only a childish desire to eat one's life and keep it; it is also an expression of a childish and narcissistic wish incompatible with devotion to posterity."^[100]

John Harris, former editor-in-chief of the Journal of Medical Ethics, argues that as long as life is worth living, according to the person himself, we have a powerful moral imperative to save the life and thus to develop and offer life extension therapies to those who want them.^[101]

Transhumanist philosopher Nick Bostrom has argued that any technological advances in life extension must be equitably distributed and not restricted to a privileged few.^[102] In an extended metaphor entitled "The Fable of the Dragon-Tyrant", Bostrom envisions death as a monstrous dragon who demands human sacrifices. In the fable, after a lengthy debate between those who believe the dragon is a fact of life and those who believe the dragon can and should be destroyed, the dragon is finally killed. Bostrom argues that political inaction allowed many preventable human deaths to occur.^[103]

§Aging as a disease

Most mainstream medical organizations and practitioners do not consider aging to be a disease. David Sinclair says: "I don't see aging as a disease, but as a collection of quite predictable diseases caused by the deterioration of the body".^[104] The two main arguments used are that aging is both inevitable and universal while diseases are not.^[105] However not everyone agrees. Harry R. Moody, Director of Academic Affairs for AARP, notes that what is normal and what is disease strongly depends on a historical context.^[106] David Gems, Assistant Director of the Institute of Healthy Ageing, strongly argues that aging should be viewed as a disease.^[107] In response to the universality of aging, David Gems notes that it is as misleading as arguing that Basenji are not dogs because they do not bark.^[108] Because of the universality of aging he calls it a 'special sort of disease'. Robert M. Perlman, coined the terms ‘aging syndrome’ and ‘disease complex’ in 1954 to describe aging.^[109]

The discussion whether aging should be viewed as a disease or not has important implications. It would stimulate pharmaceutical companies to develop life extension therapies and in the United States of America, it would also increase the regulation of the anti-aging market by the FDA. Anti-aging now falls under the regulations for cosmetic medicine which are less tight than those for drugs.^[108][110]

Cosmic radiation causes fluctuations in global temperatures, but doesn't cause climate change

4 hours ago by Christopher Packham  

Original link:  http://phys.org/news/2015-03-cosmic-fluctuations-global-temperatures-doesnt.html

Enlarge

The Crab Nebula from VLT . Credit: FORS Team, 8.2-meter VLT, ESO

(Phys.org)—Unlike electromagnetic radiation, which consists of massless and accelerated charged particles, galactic cosmic rays (CR) are composed mostly of atomic nuclei and solitary electrons, objects that have mass. Cosmic rays originate via a wide range of processes and sources including supernovae, galactic nuclei, and gamma ray bursts. Researchers have speculated for decades on the possible effects of galactic cosmic rays on the immediate environs of Earth's atmosphere, but until recently, a causal relationship between climate and cosmic rays has been difficult to establish.

A research collaborative has published a paper in the Proceedings of the National Academy of Sciences that mathematically establishes such a causal link between CR and year-to-year changes in global temperature, but has found no causal relationship between the CR and the warming trend of the 20th century.

Understanding cosmic radiation and global climate

In 1911, Charles Thomas Rees Wilson determined that ionizing radiation leads to atmospheric cloud nucleation. Increased cloudiness in the upper troposphere reduces long-wave radiation and results in warmer temperatures. Increased cloudiness in the lower troposphere leads to reduced incoming radiation, thereby decreasing global temperatures.

But the flux of cosmic rays interacting with the atmosphere is affected by the solar wind and Earth's own magnetic field. The solar wind, particularly at the region between the sun's termination shock and the heliopause, acts as a barrier to cosmic rays and decreases the flux of low-energy cosmic radiation. Earth's magnetic field deflects cosmic rays toward the poles, which produces the aurorae observed at certain latitudes. Therefore, researchers have theorized that the extent to which cosmic rays affect the Earth's climate depends on this combination of factors.

Going to the data

To study the effects of cosmic radiation on global temperature, the researchers compared two sets of data and devised a method to examine their causal connection. Past statistical analyses, while suggesting correlation of the effects of CR and temperature flux, were unable to actually establish causation. The authors applied a recently developed analytical method called convergent cross mapping (CCM) that was specifically designed to measure causality in nonlinear dynamical systems.

The data sets they analyzed included a CR proxy called the aa index that characterizes magnetic activity resulting from the interaction of the solar wind and Earth's magnetic field. In the set, a stronger solar wind and stronger magnetic disturbances yield a higher aa index. They compared it with the United Kingdom's Met Office HadCRUT3 data set of global temperature in the post-1900 period.

CCM helps to distinguish causality from spurious correlations in the time systems of dynamical systems, detecting whether two variables belong to the same dynamical system. If variable X is influencing variable Y, causality is established—but only if states of X can be recovered from the time series of Y. "Simply put," the authors write, "CCM measures the extent to which the historical record of the affected variable Y (or its proxies), reliably estimates states of causal variable X (or its proxies)."

Modestly cosmic results

The CCM method can identify both bidirectional causality (in which X and Y are mutually coupled) and unidirectional causality (in which X influences Y, but Y has no influence on X). The analysis produced the expected unidirectional causality between global temperature change and cosmic radiation—information about global temperature is not present in the cosmic radiation time series, but mapping from global temperature change to cosmic radiation succeeded, indicating that CR information was actually recoverable from analysis of GT fluctuations.

"Our results suggest weak to moderate coupling between CR and year-to-year changes of GT," they write. "However, we find that the realized effect is modest at best, and only recoverable when the secular trend in GT is removed." This "secular trend" is the warming widely believed to be caused by excess carbon in the atmosphere, an effect the researchers accounted for by first-differencing. "We show specifically that CR cannot explain secular warming, a trend that the consensus attributes to anthropogenic forcing. Nonetheless, the results verify the presence of a nontraditional forcing in the climate system, an effect that represents another interesting piece of the puzzle in our understanding of factors influencing climate variability," they write.

Explore further: Next solar maximum may be safest time for manned missions to Mars

More information: "Dynamical evidence for causality between galactic cosmic rays and interannual variation in global temperature." PNAS 2015 ; published ahead of print March 2, 2015, DOI: 10.1073/pnas.1420291112

Abstract

As early as 1959, it was hypothesized that an indirect link between solar activity and climate could be mediated by mechanisms controlling the flux of galactic cosmic rays (CR) [Ney ER (1959) Nature 183:451–452]. Although the connection between CR and climate remains controversial, a significant body of laboratory evidence has emerged at the European Organization for Nuclear Research [Duplissy J, et al. (2010) Atmos Chem Phys 10:1635–1647; Kirkby J, et al. (2011) Nature 476(7361):429–433] and elsewhere [Svensmark H, Pedersen JOP, Marsh ND, Enghoff MB, Uggerhøj UI (2007) Proc R Soc A 463:385–396; Enghoff MB, Pedersen JOP, Uggerhoj UI, Paling SM, Svensmark H (2011) Geophys Res Lett 38:L09805], demonstrating the theoretical mechanism of this link. In this article, we present an analysis based on convergent cross mapping, which uses observational time series data to directly examine the causal link between CR and year-to-year changes in global temperature. Despite a gross correlation, we find no measurable evidence of a causal effect linking CR to the overall 20th-century warming trend. However, on short interannual timescales, we find a significant, although modest, causal effect between CR and short-term, year-to-year variability in global temperature that is consistent with the presence of nonlinearities internal to the system. Thus, although CR do not contribute measurably to the 20th-century global warming trend, they do appear as a nontraditional forcing in the climate system on short interannual timescales.