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Thursday, July 12, 2018

Synapse

From Wikipedia, the free encyclopedia

Structure of a typical chemical synapse

In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target efferent cell.

Santiago Ramón y Cajal proposed that neurons are not continuous throughout the body, yet still communicate with each other, an idea known as the neuron doctrine.[2] The word "synapse" – from the Greek synapsis (συνάψις), meaning "conjunction", in turn from συνάπτεὶν (συν ("together") and ἅπτειν ("to fasten")) – was introduced in 1897 by the English neurophysiologist Charles Sherrington in Michael Foster's Textbook of Physiology.[1] Sherrington struggled to find a good term that emphasized a union between two separate elements, and the actual term "synapse" was suggested by the English classical scholar Arthur Woollgar Verrall, a friend of Michael Foster.[3][4] Some authors generalize the concept of the synapse to include the communication from a neuron to any other cell type,[5] such as to a motor cell, although such non-neuronal contacts may be referred to as junctions (a historically older term).

Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of a molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon and the postsynaptic part is located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission.[6] Synapses (at least chemical synapses) are stabilized in position by synaptic adhesion molecules (SAMs) projecting from both the pre- and post-synaptic neuron and sticking together where they overlap; SAMs may also assist in the generation and functioning of synapses.[7]

Chemical or electrical

An example of chemical synapse by the release of neurotransmitters like acetylcholine or glutamic acid.

There are two fundamentally different types of synapses:
  • In a chemical synapse, electrical activity in the presynaptic neuron is converted (via the activation of voltage-gated calcium channels) into the release of a chemical called a neurotransmitter that binds to receptors located in the plasma membrane of the postsynaptic cell. The neurotransmitter may initiate an electrical response or a secondary messenger pathway that may either excite or inhibit the postsynaptic neuron. Chemical synapses can be classified according to the neurotransmitter released: glutamatergic (often excitatory), GABAergic (often inhibitory), cholinergic (e.g. vertebrate neuromuscular junction), and adrenergic (releasing norepinephrine). Because of the complexity of receptor signal transduction, chemical synapses can have complex effects on the postsynaptic cell.
  • In an electrical synapse, the presynaptic and postsynaptic cell membranes are connected by special channels called gap junctions or synaptic cleft that are capable of passing an electric current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell. The main advantage of an electrical synapse is the rapid transfer of signals from one cell to the next.[8]
Synaptic communication is distinct from an ephaptic coupling, in which communication between neurons occurs via indirect electric fields.

An autapse is a chemical or electrical synapse that forms when the axon of one neuron synapses onto dendrites of the same neuron.

Types of interfaces

Synapses can be classified by the type of cellular structures serving as the pre- and post-synaptic components. The vast majority of synapses in the mammalian nervous system are classical axo-dendritic synapses (axon synapsing upon a dendrite), however, a variety of other arrangements exist. These include but are not limited to axo-axonic, dendro-dendritic, axo-secretory, somato-dendritic, dendro-somatic, and somato-somatic synapses.

The axon can synapse onto a dendrite, onto a cell body, or onto another axon or axon terminal, as well as into the bloodstream or diffusely into the adjacent nervous tissue.

Different types of synapses

Role in memory

It is widely accepted that the synapse plays a role in the formation of memory. As neurotransmitters activate receptors across the synaptic cleft, the connection between the two neurons is strengthened when both neurons are active at the same time, as a result of the receptor's signaling mechanisms. The strength of two connected neural pathways is thought to result in the storage of information, resulting in memory. This process of synaptic strengthening is known as long-term potentiation.[9]

By altering the release of neurotransmitters, the plasticity of synapses can be controlled in the presynaptic cell. The postsynaptic cell can be regulated by altering the function and number of its receptors. Changes in postsynaptic signaling are most commonly associated with a N-methyl-d-aspartic acid receptor (NMDAR)-dependent long-term potentiation (LTP) and long-term depression (LTD) due to the influx of calcium into the post-synaptic cell, which are the most analyzed forms of plasticity at excitatory synapses.[10]

Study models

For technical reasons, synaptic structure and function have been historically studied at unusually large model synapses, for example:

Synaptic polarization

The function of neurons depends upon cell polarity. The distinctive structure of nerve cells allows action potentials to travel directionally (from dendrites to cell body down the axon), and for these signals to then be received and carried on by post-synaptic neurons or received by effector cells. Nerve cells have long been used as models for cellular polarization, and of particular interest are the mechanisms underlying the polarized localization of synaptic molecules. PIP2 signaling regulated by IMPase plays an integral role in synaptic polarity.

Phosphoinositides (PIP, PIP2, and PIP3) are molecules that have been shown to affect neuronal polarity.[12] A gene (ttx-7) was identified in Caenorhabditis elegans that encodes myo-inositol monophosphatase (IMPase), an enzyme that produces inositol by dephosphorylating inositol phosphate. Organisms with mutant ttx-7 genes demonstrated behavioral and localization defects, which were rescued by expression of IMPase. This led to the conclusion that IMPase is required for the correct localization of synaptic protein components.[13][14] The egl-8 gene encodes a homolog of phospholipase Cβ (PLCβ), an enzyme that cleaves PIP2. When ttx-7 mutants also had a mutant egl-8 gene, the defects caused by the faulty ttx-7 gene were largely reversed. These results suggest that PIP2 signaling establishes polarized localization of synaptic components in living neurons.[13]

Additional images

Wednesday, July 11, 2018

Dialectic

From Wikipedia, the free encyclopedia

Dialectic or dialectics (Greek: διαλεκτική, dialektikḗ; related to dialogue), also known as the dialectical method, is at base a discourse between two or more people holding different points of view about a subject but wishing to establish the truth through reasoned arguments. Dialectic resembles debate, but shorn of subjective elements such as emotional appeal and the modern pejorative sense of rhetoric. It may be contrasted with the didactic method where one side of the conversation teaches the other. Dialectic is alternatively known as minor logic, as opposed to major logic or critique.

Within Hegelianism, dialectic acquires a specialised meaning of a contradiction of ideas that serves as the determining factor in their interaction; comprising three stages of development: a thesis, giving rise to its reaction; an antithesis, which contradicts or negates the thesis; and the tension between the two being resolved by means of a synthesis.

Dialectical materialism, built mainly by Karl Marx and Friedrich Engels, adapted the Hegelian dialectic into traditional materialism.

Dialectic tends to imply a process of evolution, and so does not naturally fit within formal logic; see logic and dialectic. This is particularly marked in Hegelian and even more Marxist dialectic which may rely on the time-evolution of ideas in the real world; Dialectical logic attempts to address this.

Western dialectical forms

Classical philosophy

In classical philosophy, dialectic (διαλεκτική) is a form of reasoning based upon dialogue of arguments and counter-arguments, advocating propositions (theses) and counter-propositions (antitheses). The outcome of such a dialectic might be the refutation of a relevant proposition, or of a synthesis, or a combination of the opposing assertions, or a qualitative improvement of the dialogue.

Moreover, the term "dialectic" owes much of its prestige to its role in the philosophies of Socrates and Plato, in the Greek Classical period (5th to 4th centuries BCE). Aristotle said that it was the pre-Socratic philosopher Zeno of Elea who invented dialectic, of which the dialogues of Plato are the examples of the Socratic dialectical method.[5]

According to Kant, however, the ancient Greeks used the word "dialectic" to signify the logic of false appearance or semblance. To the Ancients, "it was nothing but the logic of illusion. It was a sophistic art of giving to one's ignorance, indeed even to one's intentional tricks, the outward appearance of truth, by imitating the thorough, accurate method which logic always requires, and by using its topic as a cloak for every empty assertion."[6]

Socratic method

The Socratic dialogues are a particular form of dialectic known as the method of elenchus (literally, "refutation, scrutiny"[7]) whereby a series of questions clarifies a more precise statement of a vague belief, logical consequences of that statement are explored, and a contradiction is discovered. The method is largely destructive, in that false belief is exposed[8] and only constructive in that this exposure may lead to further search for truth. The detection of error does not amount to a proof of the antithesis; for example, a contradiction in the consequences of a definition of piety does not provide a correct definition. The principal aim of Socratic activity may be to improve the soul of the interlocutors, by freeing them from unrecognized errors; or indeed, by teaching them the spirit of inquiry.

In common cases, Socrates used enthymemes as the foundation of his argument.

For example, in the Euthyphro, Socrates asks Euthyphro to provide a definition of piety. Euthyphro replies that the pious is that which is loved by the gods. But, Socrates also has Euthyphro agreeing that the gods are quarrelsome and their quarrels, like human quarrels, concern objects of love or hatred. Therefore, Socrates reasons, at least one thing exists that certain gods love but other gods hate. Again, Euthyphro agrees. Socrates concludes that if Euthyphro's definition of piety is acceptable, then there must exist at least one thing that is both pious and impious (as it is both loved and hated by the gods)—which Euthyphro admits is absurd. Thus, Euthyphro is brought to a realization by this dialectical method that his definition of piety is not sufficiently meaningful.

For example, in Plato's Gorgias, dialectic occurs between Socrates, the Sophist Gorgias, and two men, Polus and Callicles. Because Socrates' ultimate goal was to reach true knowledge, he was even willing to change his own views in order to arrive at the truth. The fundamental goal of dialectic, in this instance, was to establish a precise definition of the subject (in this case, rhetoric) and with the use of argumentation and questioning, make the subject even more precise. In the Gorgias, Socrates reaches the truth by asking a series of questions and in return, receiving short, clear answers.

There is another interpretation of the dialectic, as a method of intuition suggested in The Republic.[9] Simon Blackburn writes that the dialectic in this sense is used to understand "the total process of enlightenment, whereby the philosopher is educated so as to achieve knowledge of the supreme good, the Form of the Good".[10]

Aristotle

Aristotle stresses that rhetoric is closely related to dialectic. He offers several formulas to describe this affinity between the two disciplines: first of all, rhetoric is said to be a “counterpart” (antistrophos) to dialectic (Rhet. I.1, 1354a1); (ii) it is also called an “outgrowth” (paraphues ti) of dialectic and the study of character (Rhet. I.2, 1356a25f.); finally, Aristotle says that rhetoric is part of dialectic and resembles it (Rhet. I.2, 1356a30f.). In saying that rhetoric is a counterpart to dialectic, Aristotle obviously alludes to Plato's Gorgias (464bff.), where rhetoric is ironically defined as a counterpart to cookery in the soul. Since, in this passage, Plato uses the word ‘antistrophos’ to designate an analogy, it is likely that Aristotle wants to express a kind of analogy too: what dialectic is for the (private or academic) practice of attacking and maintaining an argument, rhetoric is for the (public) practice of defending oneself or accusing an opponent. The analogy to dialectic has important implications for the status of rhetoric. Plato argued in his Gorgias that rhetoric cannot be an art (technê), since it is not related to a definite subject, while real arts are defined by their specific subjects, as e.g. medicine or shoemaking are defined by their products, i.e., health and shoes.[11]

Medieval philosophy

Logic, which could be considered to include dialectic, was one of the three liberal arts taught in medieval universities as part of the trivium; the other elements were rhetoric and grammar.[12][13]

Based mainly on Aristotle, the first medieval philosopher to work on dialectics was Boethius (480–524).[16] After him, many scholastic philosophers also made use of dialectics in their works, such as Abelard,[17] William of Sherwood,[18] Garlandus Compotista,[19] Walter Burley, Roger Swyneshed, William of Ockham,[20] and Thomas Aquinas.[21]

This dialectic (a quaestio disputata) was formed as follows:
  1. The question to be determined (“It is asked whether...”);
  2. A provisory answer to the question (“And it seems that...”)
  3. The principal arguments in favor of the provisory answer;
  4. An argument against the provisory answer, traditionally a single argument from authority ("On the contrary...");
  5. The determination of the question after weighing the evidence ("I answer that...");
  6. The replies to each of the initial objections. (“To the first, to the second etc., I answer that...”)

Modern philosophy

The concept of dialectics was given new life by Georg Wilhelm Friedrich Hegel (following Johann Gottlieb Fichte), whose dialectically synthetic model of nature and of history made it, as it were, a fundamental aspect of the nature of reality (instead of regarding the contradictions into which dialectics leads as a sign of the sterility of the dialectical method, as Immanuel Kant tended to do in his Critique of Pure Reason).[22][23] In the mid-19th century, the concept of "dialectic" was appropriated by Karl Marx (see, for example, Das Kapital, published in 1867) and Friedrich Engels and retooled in a dynamic, nonidealistic manner. It would also become a crucial part of later representations of Marxism as a philosophy of dialectical materialism. These representations often contrasted dramatically[24] and led to vigorous debate among different Marxist groupings, leading some prominent Marxists to give up on the idea of dialectics completely.[25]

Hegelian dialectic

Hegelian dialectic, usually presented in a threefold manner, was stated by Heinrich Moritz Chalybäus[26] as comprising three dialectical stages of development: a thesis, giving rise to its reaction; an antithesis, which contradicts or negates the thesis; and the tension between the two being resolved by means of a synthesis. In more simplistic terms, one can consider it thus: problem → reaction → solution. Although this model is often named after Hegel, he himself never used that specific formulation. Hegel ascribed that terminology to Kant.[27] Carrying on Kant's work, Fichte greatly elaborated on the synthesis model and popularized it.

On the other hand, Hegel did use a three-valued logical model that is very similar to the antithesis model, but Hegel's most usual terms were: Abstract-Negative-Concrete. Hegel used this writing model as a backbone to accompany his points in many of his works.

The formula, thesis-antithesis-synthesis, does not explain why the thesis requires an antithesis. However, the formula, abstract-negative-concrete, suggests a flaw, or perhaps an incompleteness, in any initial thesis—it is too abstract and lacks the negative of trial, error, and experience. For Hegel, the concrete, the synthesis, the absolute, must always pass through the phase of the negative, in the journey to completion, that is, mediation. This is the essence of what is popularly called Hegelian dialectics.

According to the German philosopher Walter Kaufmann:
"Fichte introduced into German philosophy the three-step of thesis, antithesis, and synthesis, using these three terms. Schelling took up this terminology. Hegel did not. He never once used these three terms together to designate three stages in an argument or account in any of his books. And they do not help us understand his Phenomenology, his Logic, or his philosophy of history; they impede any open-minded comprehension of what he does by forcing it into a scheme which was available to him and which he deliberately spurned [...] The mechanical formalism [...] Hegel derides expressly and at some length in the preface to the Phenomenology.[28][29]
Kaufmann also cites Hegel's criticism of the triad model commonly misattributed to him, adding that "the only place where Hegel uses the three terms together occurs in his lectures on the history of philosophy, on the last page but one of the section on Kant—where Hegel roundly reproaches Kant for having 'everywhere posited thesis, antithesis, synthesis'".[30]

To describe the activity of overcoming the negative, Hegel also often used the term Aufhebung, variously translated into English as "sublation" or "overcoming," to conceive of the working of the dialectic. Roughly, the term indicates preserving the useful portion of an idea, thing, society, etc., while moving beyond its limitations. (Jacques Derrida's preferred French translation of the term was relever.)[31]

In the Logic, for instance, Hegel describes a dialectic of existence: first, existence must be posited as pure Being (Sein); but pure Being, upon examination, is found to be indistinguishable from Nothing (Nichts). When it is realized that what is coming into being is, at the same time, also returning to nothing (in life, for example, one's living is also a dying), both Being and Nothing are united as Becoming.[32]

As in the Socratic dialectic, Hegel claimed to proceed by making implicit contradictions explicit: each stage of the process is the product of contradictions inherent or implicit in the preceding stage. For Hegel, the whole of history is one tremendous dialectic, major stages of which chart a progression from self-alienation as slavery to self-unification and realization as the rational constitutional state of free and equal citizens. The Hegelian dialectic cannot be mechanically applied for any chosen thesis. Critics argue that the selection of any antithesis, other than the logical negation of the thesis, is subjective. Then, if the logical negation is used as the antithesis, there is no rigorous way to derive a synthesis. In practice, when an antithesis is selected to suit the user's subjective purpose, the resulting "contradictions" are rhetorical, not logical, and the resulting synthesis is not rigorously defensible against a multitude of other possible syntheses. The problem with the Fichtean "thesis–antithesis–synthesis" model is that it implies that contradictions or negations come from outside of things. Hegel's point is that they are inherent in and internal to things. This conception of dialectics derives ultimately from Heraclitus.

Hegel stated that the purpose of dialectics is "to study things in their own being and movement and thus to demonstrate the finitude of the partial categories of understanding."[33]

One important dialectical principle for Hegel is the transition from quantity to quality, which he terms the Measure. The measure is the qualitative quantum, the quantum is the existence of quantity.[34]
"The identity between quantity and quality, which is found in Measure, is at first only implicit, and not yet explicitly realised. In other words, these two categories, which unite in Measure, each claim an independent authority. On the one hand, the quantitative features of existence may be altered, without affecting its quality. On the other hand, this increase and diminution, immaterial though it be, has its limit, by exceeding which the quality suffers change. [...] But if the quantity present in measure exceeds a certain limit, the quality corresponding to it is also put in abeyance. This however is not a negation of quality altogether, but only of this definite quality, the place of which is at once occupied by another. This process of measure, which appears alternately as a mere change in quantity, and then as a sudden revulsion of quantity into quality, may be envisaged under the figure of a nodal (knotted) line".[35]
As an example, Hegel mentions the states of aggregation of water: "Thus the temperature of water is, in the first place, a point of no consequence in respect of its liquidity: still with the increase or diminution of the temperature of the liquid water, there comes a point where this state of cohesion suffers a qualitative change, and the water is converted into steam or ice".[36] As other examples Hegel mentions the reaching of a point where a single additional grain makes a heap of wheat; or where the bald tail is produced, if we continue plucking out single hairs.

Another important principle for Hegel is the negation of the negation, which he also terms Aufhebung (sublation): Something is only what it is in its relation to another, but by the negation of the negation this something incorporates the other into itself. The dialectical movement involves two moments that negate each other, something and its other. As a result of the negation of the negation, "something becomes its other; this other is itself something; therefore it likewise becomes an other, and so on ad infinitum".[37] Something in its passage into other only joins with itself, it is self-related.[38] In becoming there are two moments:[39] coming-to-be and ceasing-to-be: by sublation, i.e., negation of the negation, being passes over into nothing, it ceases to be, but something new shows up, is coming to be. What is sublated (aufgehoben) on the one hand ceases to be and is put to an end, but on the other hand it is preserved and maintained.[40] In dialectics, a totality transforms itself; it is self-related, then self-forgetful, relieving the original tension.

Marxist dialectic

Marxist dialectic is a form of Hegelian dialectic which applies to the study of historical materialism. It purports to be a reflection of the real world created by man. Dialectic would thus be a robust method under which one could examine personal, social, and economic behaviors. Marxist dialectic is the core foundation of the philosophy of dialectical materialism, which forms the basis of the ideas behind historical materialism.

Karl Marx and Friedrich Engels proposed that Hegel's dialectic is too abstract:
The mystification which dialectic suffers in Hegel's hands, by no means prevents him from being the first to present its general form of working in a comprehensive and conscious manner. With him it is standing on its head. It must be turned right side up again, if you would discover the rational kernel within the mystical shell.[41]
In contradiction to Hegelian idealism, Marx presented his own dialectic method, which he claims to be "direct opposite" of Hegel's method:
My dialectic method is not only different from the Hegelian, but is its direct opposite. To Hegel, the life-process of the human brain, i.e. the process of thinking, which, under the name of 'the Idea', he even transforms into an independent subject, is the demiurgos of the real world, and the real world is only the external, phenomenal form of 'the Idea'. With me, on the contrary, the ideal is nothing else than the material world reflected by the human mind, and translated into forms of thought.[42]
In Marxism, the dialectical method of historical study became intertwined with historical materialism, the school of thought exemplified by the works of Marx, Engels, and Vladimir Lenin. In the USSR, under Joseph Stalin, Marxist dialectics became "diamat" (short for dialectical materialism), a theory emphasizing the primacy of the material way of life; social "praxis" over all forms of social consciousness; and the secondary, dependent character of the "ideal". The term "dialectical materialism" was coined by the 19th-century social theorist Joseph Dietzgen who used the theory to explain the nature of socialism and social development. The original populariser of Marxism in Russia, Georgi Plekhanov used the terms "dialectical materialism" and "historical materialism" interchangeably. For Lenin, the primary feature of Marx's "dialectical materialism" (Lenin's term) was its application of materialist philosophy to history and social sciences. Lenin's main input in the philosophy of dialectical materialism was his theory of reflection, which presented human consciousness as a dynamic reflection of the objective material world that fully shapes its contents and structure. Later, Stalin's works on the subject established a rigid and formalistic division of Marxist–Leninist theory in the dialectical materialism and historical materialism parts. While the first was supposed to be the key method and theory of the philosophy of nature, the second was the Soviet version of the philosophy of history.

A dialectical method was fundamental to Marxist politics, e.g., the works of Karl Korsch, Georg Lukács and certain members of the Frankfurt School. Soviet academics, notably Evald Ilyenkov and Zaid Orudzhev, continued pursuing unorthodox philosophic study of Marxist dialectics; likewise in the West, notably the philosopher Bertell Ollman at New York University.

Friedrich Engels proposed that Nature is dialectical, thus, in Anti-Dühring he said that the negation of negation is:
A very simple process, which is taking place everywhere and every day, which any child can understand as soon as it is stripped of the veil of mystery in which it was enveloped by the old idealist philosophy.[43]
In Dialectics of Nature, Engels said:
Probably the same gentlemen who up to now have decried the transformation of quantity into quality as mysticism and incomprehensible transcendentalism will now declare that it is indeed something quite self-evident, trivial, and commonplace, which they have long employed, and so they have been taught nothing new. But to have formulated for the first time in its universally valid form a general law of development of Nature, society, and thought, will always remain an act of historic importance.[44]
Marxist dialectics is exemplified in Das Kapital (Capital), which outlines two central theories: (i) surplus value and (ii) the materialist conception of history; Marx explains dialectical materialism:
In its rational form, it is a scandal and abomination to bourgeoisdom and its doctrinaire professors, because it includes in its comprehension an affirmative recognition of the existing state of things, at the same time, also, the recognition of the negation of that state, of its inevitable breaking up; because it regards every historically developed social form as in fluid movement, and therefore takes into account its transient nature not less than its momentary existence; because it lets nothing impose upon it, and is in its essence critical and revolutionary.[45]
Class struggle is the primary contradiction to be resolved by Marxist dialectics, because of its central role in the social and political lives of a society. Nonetheless, Marx and Marxists developed the concept of class struggle to comprehend the dialectical contradictions between mental and manual labor, and between town and country. Hence, philosophic contradiction is central to the development of dialectics – the progress from quantity to quality, the acceleration of gradual social change; the negation of the initial development of the status quo; the negation of that negation; and the high-level recurrence of features of the original status quo. In the USSR, Progress Publishers issued anthologies of dialectical materialism by Lenin, wherein he also quotes Marx and Engels:
As the most comprehensive and profound doctrine of development, and the richest in content, Hegelian dialectics was considered by Marx and Engels the greatest achievement of classical German philosophy.... "The great basic thought", Engels writes, "that the world is not to be comprehended as a complex of ready-made things, but as a complex of processes, in which the things, apparently stable no less than their mind images in our heads, the concepts, go through an uninterrupted change of coming into being and passing away... this great fundamental thought has, especially since the time of Hegel, so thoroughly permeated ordinary consciousness that, in its generality, it is now scarcely ever contradicted.

But, to acknowledge this fundamental thought in words, and to apply it in reality in detail to each domain of investigation, are two different things.... For dialectical philosophy nothing is final, absolute, sacred. It reveals the transitory character of everything and in everything; nothing can endure before it, except the uninterrupted process of becoming and of passing away, of endless ascendancy from the lower to the higher. And dialectical philosophy, itself, is nothing more than the mere reflection of this process in the thinking brain." Thus, according to Marx, dialectics is "the science of the general laws of motion both of the external world and of human thought".[46]
Lenin describes his dialectical understanding of the concept of development:
A development that repeats, as it were, stages that have already been passed, but repeats them in a different way, on a higher basis ("the negation of the negation"), a development, so to speak, that proceeds in spirals, not in a straight line; a development by leaps, catastrophes, and revolutions; "breaks in continuity"; the transformation of quantity into quality; inner impulses towards development, imparted by the contradiction and conflict of the various forces and tendencies acting on a given body, or within a given phenomenon, or within a given society; the interdependence and the closest and indissoluble connection between all aspects of any phenomenon (history constantly revealing ever new aspects), a connection that provides a uniform, and universal process of motion, one that follows definite laws – these are some of the features of dialectics as a doctrine of development that is richer than the conventional one.[46]

Dialectical theology

Neo-orthodoxy, in Europe also known as theology of crisis and dialectical theology,[47][48] is an approach to theology in Protestantism that was developed in the aftermath of the First World War (1914–1918). It is characterized as a reaction against doctrines of 19th-century liberal theology and a more positive reevaluation of the teachings of the Reformation, much of which had been in decline (especially in western Europe) since the late 18th century.[49] It is primarily associated with two Swiss professors and pastors, Karl Barth[50] (1886–1968) and Emil Brunner (1899–1966),[47][48] even though Barth himself expressed his unease in the use of the term.[51]

In dialectical theology the difference and opposition between God and human beings is stressed in such a way that all human attempts at overcoming this opposition through moral, religious or philosophical idealism must be characterized as 'sin'. In the death of Christ humanity is negated and overcome, but this judgment also points forwards to the resurrection in which humanity is reestablished in Christ. For Barth this meant that only through God's 'no' to everything human can his 'yes' be perceived. Applied to traditional themes of Protestant theology, such as double predestination, this means that election and reprobation cannot be viewed as a quantitative limitation of God's action. Rather it must be seen as its "qualitative definition".[52] As Christ bore the rejection as well as the election of God for all humanity, every person is subject to both aspects of God's double predestination.

Legacy

Dialectics has become central to "Continental" philosophy, but it plays no part in "Anglo-American" philosophy. In other words, on the continent of Europe, dialectics has entered intellectual culture as what might be called a legitimate part of thought and philosophy, whereas in America and Britain, the dialectic plays no discernible part in the intellectual culture, which instead tends toward positivism. A prime example of the European tradition is Jean-Paul Sartre's Critique of Dialectical Reason, which is very different from the works of Popper, whose philosophy was for a time highly influential in the UK where he resided (see below). Sartre states:
"Existentialism, like Marxism, addresses itself to experience in order to discover there concrete syntheses. It can conceive of these syntheses only within a moving, dialectical totalisation, which is nothing else but history or—from the strictly cultural point of view adopted here—'philosophy-becoming-the world'."[53]

Criticisms

Karl Popper has attacked the dialectic repeatedly. In 1937 he wrote and delivered a paper entitled "What Is Dialectic?" in which he attacked the dialectical method for its willingness "to put up with contradictions".[54] Popper concluded the essay with these words: "The whole development of dialectic should be a warning against the dangers inherent in philosophical system-building. It should remind us that philosophy should not be made a basis for any sort of scientific system and that philosophers should be much more modest in their claims. One task which they can fulfill quite usefully is the study of the critical methods of science" (Ibid., p. 335).

In chapter 12 of volume 2 of The Open Society and Its Enemies (1944; 5th rev. ed., 1966) Popper unleashed a famous attack on Hegelian dialectics, in which he held that Hegel's thought (unjustly, in the view of some philosophers, such as Walter Kaufmann,[55]) was to some degree responsible for facilitating the rise of fascism in Europe by encouraging and justifying irrationalism. In section 17 of his 1961 "addenda" to The Open Society, entitled "Facts, Standards and Truth: A Further Criticism of Relativism," Popper refused to moderate his criticism of the Hegelian dialectic, arguing that it "played a major role in the downfall of the liberal movement in Germany,... by contributing to historicism and to an identification of might and right, encouraged totalitarian modes of thought.  . . . [and] undermined and eventually lowered the traditional standards of intellectual responsibility and honesty".[56]

The philosopher of science and physicist Mario Bunge repeatedly criticized Hegelian and Marxian dialectics, calling them "fuzzy and remote from science"[57] and a "disastrous legacy",[58] and he concluded: "The so-called laws of dialectics, such as formulated by Engels (1940, 1954) and Lenin (1947, 1981), are false insofar as they are intelligible."[58]

Formalism

In the past few decades, European and American logicians have attempted to provide mathematical foundations for dialectical logic or argument.[59]:201–372 There had been pre-formal and partially-formal treatises on argument and dialectic, from authors such as Stephen Toulmin (The Uses of Argument),[59]:203–256 Nicholas Rescher (Dialectics),[59]:330–336 and van Eemeren and Grootendorst (pragma-dialectics).[59]:517–614 One can include the communities of informal logic and paraconsistent logic.[59]:373–424 However, building on theories of defeasible reasoning (see John L. Pollock), systems have been built that define well-formedness of arguments, rules governing the process of introducing arguments based on fixed assumptions, and rules for shifting burden. Many of these logics appear in the special area of artificial intelligence and law, though the computer scientists' interest in formalizing dialectic originates in a desire to build decision support and computer-supported collaborative work systems.

Exoplanet Ross 128b Likely Has Temperate Climate: Study

Understanding which chemical elements are present in a star in what abundances can help astronomers estimate the makeup of planets that orbit them, which can help predict how similar the planets are to the Earth. Dr. Diogo Souto of Brazil’s National Observatory and co-authors have determined detailed chemical abundances of Ross 128, a cool star just 11 light-years from Earth that’s known to host a potentially habitable planet 1.35 times more massive than our own. The team’s work appears in the Astrophysical Journal Letters (arXiv.org preprint).

This artist’s impression shows Ross 128b, with the red dwarf star Ross 128 in the background. This system is located in the constellation of Virgo, about 11 light-years away.  Ross 128b is 20 times closer to the star than the Earth is to the Sun, and takes just 9.9 days to circle it. The planet’s equilibrium temperature is estimated to be 70 degrees Fahrenheit (21 degrees Celsius). Image credit: Sci-News.com.
This artist’s impression shows Ross 128b, with the red dwarf
star Ross 128 in the background. This system is located in the
constellation of Virgo, about 11 light-years away. Ross 128b is
20 times closer to the star than the Earth is to the Sun, and
takes just 9.9 days to circle it. The planet’s equilibrium
temperature is estimated to be 70 degrees Fahrenheit (21
degrees Celsius). Image credit: Sci-News.com.

Ross 128, also known as Proxima Virginis, Gliese 447 and HIP 57548, is a red dwarf star, meaning that it is much smaller, and much cooler, than our Sun.

“Until recently, it was difficult to obtain detailed chemical abundances for this kind of star,” Dr. Souto said.

Using SDSS’s Apache Point Galactic Evolution Experiment (APOGEE) spectrographs, he and his colleagues measured Ross 128’s near-infrared light to derive abundances of carbon, oxygen, magnesium, aluminum, potassium, calcium, titanium, and iron.

“When stars are young, they are surrounded by a disk of rotating gas and dust from which rocky planets accrete,” the astronomers said.

“The star’s chemistry can influence the contents of the disk, as well as the resulting planet’s mineralogy and interior structure. For example, the amount of magnesium, iron, and silicon in a planet will control the mass ratio of its internal core and mantle layers.”

The researchers determined that Ross 128 has iron levels similar to the Sun.

Although they were not able to measure its abundance of silicon, the ratio of iron to magnesium in the star indicates that the core of Ross 128b, an Earth-like exoplanet in the inner edge of the star’s habitable zone, should be larger than Earth’s.

Because they knew Ross 128b’s minimum mass, and stellar abundances, the scientists were also able to estimate a range for the planet’s radius.

“Knowing a planet’s mass and radius is important to understanding what it’s made of, because these two measurements can be used to calculate its bulk density,” they said.

“What’s more, when quantifying planets in this way, astronomers have realized that planets with radii greater than about 1.7 times Earth’s are likely surrounded by a gassy envelope, like Neptune, and those with smaller radii are likely to be more-rocky, as is our own home planet.”

“The estimated radius of Ross 128 b indicates that it should be rocky.”

Lastly, by measuring the temperature of Ross 128 and estimating the radius of the planet, the team was able to determine how much of the host star’s light should be reflecting off the surface of Ross 128b, revealing that the planet likely has a temperate climate.

“It’s exciting what we can learn about another planet by determining what the light from its host star tells us about the system’s chemistry,” Dr. Souto said.

“Although Ross 128b is not Earth’s twin, and there is still much we don’t know about its potential geologic activity, we were able to strengthen the argument that it’s a temperate planet that could potentially have liquid water on its surface.”
_____
Diogo Souto et al. 2018. Stellar and Planetary Characterization of the Ross 128 Exoplanetary System from APOGEE Spectra. ApJL 860, L15; doi: 10.3847/2041-8213/aac896

Socratic method

From Wikipedia, the free encyclopedia
 
The Socratic Method, also can be known as maieutics, method of elenchus, elenctic method, or Socratic debate, is a form of cooperative argumentative dialogue between individuals, based on asking and answering questions to stimulate critical thinking and to draw out ideas and underlying presumptions. It is a dialectical method, involving a discussion in which the defense of one point of view is questioned; one participant may lead another to contradict themselves in some way, thus weakening the defender's point. This method is named after the Classical Greek philosopher Socrates and is introduced by him in Plato's Theaetetus as midwifery (maieutics) because it is employed to bring out definitions implicit in the interlocutors' beliefs, or to help them further their understanding.

The Socratic Method, is a method of hypothesis elimination, in that, better hypotheses are found by steadily identifying and eliminating those that lead to contradictions. The Socratic method searches for general, commonly held truths that shape beliefs and scrutinizes them to determine their consistency with other beliefs. The basic form is a series of questions formulated as tests of logic and fact intended to help a person or group discover their beliefs about some topic, exploring definitions or logoi (singular logos) and seeking to characterize general characteristics shared by various particular instances.

Development

In the second half of the 5th century BC, sophists were teachers who specialized in using the tools of philosophy and rhetoric to entertain, impress, or persuade an audience to accept the speaker's point of view. Socrates promoted an alternative method of teaching which came to be called the Socratic method.

Socrates began to engage in such discussions with his fellow Athenians after his friend from youth, Chaerephon, visited the Oracle of Delphi, which confirmed that no man in Greece was wiser than Socrates. Socrates saw this as a paradox, and began using the Socratic method to answer his conundrum. Diogenes Laërtius, however, wrote that Protagoras invented the “Socratic” method.[1][2]

Plato famously formalized the Socratic elenctic style in prose—presenting Socrates as the curious questioner of some prominent Athenian interlocutor—in some of his early dialogues, such as Euthyphro and Ion, and the method is most commonly found within the so-called "Socratic dialogues", which generally portray Socrates engaging in the method and questioning his fellow citizens about moral and epistemological issues. But in his later dialogues, such as Theaetetus or Sophist, Plato had a different method to philosophical discussions, namely dialectic.

Method

Elenchus (Ancient Greek: ἔλεγχος, translit. elengkhos, lit. 'argument of disproof or refutation; cross-examining, testing, scrutiny esp. for purposes of refutation'[3]) is the central technique of the Socratic method. The Latin form elenchus (plural elenchi) is used in English as the technical philosophical term.[4] The most common adjectival form in English is elenctic; elenchic and elenchtic are also current.

In Plato's early dialogues, the elenchus is the technique Socrates uses to investigate, for example, the nature or definition of ethical concepts such as justice or virtue. According to Vlastos,[5] it has the following steps:
  1. Socrates' interlocutor asserts a thesis, for example "Courage is endurance of the soul", which Socrates considers false and targets for refutation.
  2. Socrates secures his interlocutor's agreement to further premises, for example "Courage is a fine thing" and "Ignorant endurance is not a fine thing".
  3. Socrates then argues, and the interlocutor agrees, that these further premises imply the contrary of the original thesis; in this case, it leads to: "courage is not endurance of the soul".
  4. Socrates then claims that he has shown that his interlocutor's thesis is false and that its negation is true.
One elenctic examination can lead to a new, more refined, examination of the concept being considered, in this case it invites an examination of the claim: "Courage is wise endurance of the soul". Most Socratic inquiries consist of a series of elenchi and typically end in puzzlement known as aporia.

Frede[6] points out that Vlastos' conclusion in step #4 above makes nonsense of the aporetic nature of the early dialogues. Having shown that a proposed thesis is false is insufficient to conclude that some other competing thesis must be true. Rather, the interlocutors have reached aporia, an improved state of still not knowing what to say about the subject under discussion.

The exact nature of the elenchus is subject to a great deal of debate, in particular concerning whether it is a positive method, leading to knowledge, or a negative method used solely to refute false claims to knowledge.[7]

W. K. C. Guthrie in The Greek Philosophers sees it as an error to regard the Socratic method as a means by which one seeks the answer to a problem, or knowledge. Guthrie claims that the Socratic method actually aims to demonstrate one's ignorance. Socrates, unlike the Sophists, did believe that knowledge was possible, but believed that the first step to knowledge was recognition of one's ignorance. Guthrie writes, "[Socrates] was accustomed to say that he did not himself know anything, and that the only way in which he was wiser than other men was that he was conscious of his own ignorance, while they were not. The essence of the Socratic method is to convince the interlocutor that whereas he thought he knew something, in fact he does not."{pg 74}

Application

Socrates generally applied his method of examination to concepts that seem to lack any concrete definition; e.g., the key moral concepts at the time, the virtues of piety, wisdom, temperance, courage, and justice. Such an examination challenged the implicit moral beliefs of the interlocutors, bringing out inadequacies and inconsistencies in their beliefs, and usually resulting in aporia. In view of such inadequacies, Socrates himself professed his ignorance, but others still claimed to have knowledge. Socrates believed that his awareness of his ignorance made him wiser than those who, though ignorant, still claimed knowledge. While this belief seems paradoxical at first glance, it in fact allowed Socrates to discover his own errors where others might assume they were correct. This claim was known by the anecdote of the Delphic oracular pronouncement that Socrates was the wisest of all men. (Or, rather, that no man was wiser than Socrates.)

Socrates used this claim of wisdom as the basis of his moral exhortation. Accordingly, he claimed that the chief goodness consists in the caring of the soul concerned with moral truth and moral understanding, that "wealth does not bring goodness, but goodness brings wealth and every other blessing, both to the individual and to the state", and that "life without examination [dialogue] is not worth living". It is with this in mind that the Socratic method is employed.

The motive for the modern usage of this method and Socrates' use are not necessarily equivalent. Socrates rarely used the method to actually develop consistent theories, instead using myth to explain them. The Parmenides dialogue shows Parmenides using the Socratic method to point out the flaws in the Platonic theory of the Forms, as presented by Socrates; it is not the only dialogue in which theories normally expounded by Plato/Socrates are broken down through dialectic. Instead of arriving at answers, the method was used to break down the theories we hold, to go "beyond" the axioms and postulates we take for granted. Therefore, myth and the Socratic method are not meant by Plato to be incompatible; they have different purposes, and are often described as the "left hand" and "right hand" paths to good and wisdom.

Socratic Circles

A Socratic Circle (also known as a Socratic Seminar) is a pedagogical approach based on the Socratic method and uses a dialogic approach to understand information in a text. Its systematic procedure is used to examine a text through questions and answers founded on the beliefs that all new knowledge is connected to prior knowledge, that all thinking comes from asking questions, and that asking one question should lead to asking further questions.[8] A Socratic Circle is not a debate. The goal of this activity is to have participants work together to construct meaning and arrive at an answer, not for one student or one group to “win the argument”.[9]

This approach is based on the belief that participants seek and gain deeper understanding of concepts in the text through thoughtful dialogue rather than memorizing information that has been provided for them.[9] While Socratic Circles can differ in structure, and even in name, they typically involve the following components: a passage of text that students must read beforehand and two concentric circles of students: an outer circle and an inner circle. The inner circle focuses on exploring and analysing the text through the act of questioning and answering. During this phase, the outer circle remains silent. Students in the outer circle are much like scientific observers watching and listening to the conversation of the inner circle. When the text has been fully discussed and the inner circle is finished talking, the outer circle provides feedback on the dialogue that took place. This process alternates with the inner circle students going to the outer circle for the next meeting and vice versa. The length of this process varies depending on the text used for the discussion. The teacher may decide to alternate groups within one meeting, or they may alternate at each separate meeting.[8][10]

The most significant difference between this activity and most typical classroom activities involves the role of the teacher. In Socratic Circles the students lead the discussion and questioning. The teacher's role is to ensure the discussion advances regardless of the particular direction the discussion takes.[8][10]

Various approaches to Socratic Circles

Teachers use Socratic Circles in different ways. The structure it takes may look different in each classroom. While this is not an exhaustive list, teachers may use one of the following structures to administer Socratic Seminar:
  1. Inner/outer circle or fishbowl: Students need to be arranged in inner and outer circles. The inner circle engages in discussion about the text. The outer circle observes the inner circle, while taking notes. The outer circle shares their observations and questions the inner circle with guidance from the teacher/facilitator. Students use constructive criticism as opposed to making judgements. The students on the outside keep track of topics they would like to discuss as part of the debrief. Participants of the outer circle can use an observation checklist or notes form to monitor the participants in the inner circle. These tools will provide structure for listening and give the outside members specific details to discuss later in the seminar.[8][10] The teacher may also sit in the circle but at the same height as the students.[11]
  2. Triad: Students are arranged so that each participant (called a “pilot”) in the inner circle has two “co-pilots” sitting behind them on either side. Pilots are the speakers because they are in the inner circle; co-pilots are in the outer circle and only speak during consultation. The seminar proceeds as any other seminar. At a point in the seminar, the facilitator pauses the discussion and instructs the triad to talk to each other. Conversation will be about topics that need more in-depth discussion or a question posed by the leader. Sometimes triads will be asked by the facilitator to come up with a new question. Any time during a triad conversation, group members can switch seats and one of the co-pilots can sit in the pilot’s seat. Only during that time is the switching of seats allowed. This structure allows for students to speak, who may not yet have the confidence to speak in the large group. This type of seminar involves all students instead of just the students in the inner and outer circles.[10]
  3. Simultaneous seminars: Students are arranged in multiple small groups and placed as far as possible from each other. Following the guidelines of the Socratic Seminar, students engage in small group discussions. Simultaneous seminars are typically done with experienced students who need little guidance and can engage in a discussion without assistance from a teacher/facilitator. According to the literature, this type of seminar is beneficial for teachers who want students to explore a variety of texts around a main issue or topic. Each small group may have a different text to read/view and discuss. A larger Socratic Seminar can then occur as a discussion about how each text corresponds with one another. Simultaneous Seminars can also be used for a particularly difficult text. Students can work through different issues and key passages from the text.[12]
No matter what structure the teacher employs, the basic premise of the seminar/circles is to turn partial control and direction of the classroom over to the students. The seminars encourage students to work together, creating meaning from the text and to stay away from trying to find a correct interpretation. The emphasis is on critical and creative thinking.[8]

Text selection

Socratic Circle texts
A Socratic Circle text is a tangible document that creates a thought-provoking discussion.[13] The text ought to be appropriate for the participants' current level of intellectual and social development.[14] It provides the anchor for dialogue whereby the facilitator can bring the participants back to the text if they begin to digress. Furthermore, the seminar text enables the participants to create a level playing field – ensuring that the dialogical tone within the classroom remains consistent and pure to the subject or topic at hand.[13] Some practitioners argue that "texts" do not have to be confined to printed texts, but can include artifacts such as objects, physical spaces, and the like.

Pertinent elements of an effective Socratic text

Socratic seminar texts are able to challenge participants’ thinking skills by having these characteristics:
  1. Ideas and values
  2. Complexity and challenge
  3. Relevance to participants' curriculum
  4. Ambiguity
1. Ideas and values - The text must introduce ideas and values that are complex and difficult to summarize.[13] Powerful discussions arise from personal connections to abstract ideas and from implications to personal values.

2. Complexity and challenge - The text must be rich in ideas and complexity [10] and open to interpretation.[15] Ideally it should require multiple readings,[16] but should be neither far above the participants' intellectual level nor very long.

3. Relevance to participants and curriculum - An effective text has identifiable themes that are recognizable and pertinent to the lives of the participants.[14] Themes in the text should relate to the curriculum.

4. Ambiguity - The text must be approachable from a variety of different perspectives, including perspectives that seem mutually exclusive, thus provoking critical thinking and raising important questions. The absence of right and wrong answers promotes a variety of discussion and encourages individual contributions.[10][16]

Two different ways to select a text

Socratic texts can be divided into two main categories:

1. Print texts (e.g. short stories, poems, and essays) and non-print texts (e.g. photographs, sculptures, and maps); and

2. Subject area, which can draw from print or non-print artifacts. As examples, language arts can be approached through poems, history through written or oral historical speeches, science through policies on environmental issues, math through mathematical proofs, health through nutrition labels, and physical education through fitness guidelines.[10][13]

Questioning methods in Socratic Circles

Socratic Circles are based upon the interaction of peers. The focus is to explore multiple perspectives on a given issue or topic. Socratic questioning is used to help students apply the activity to their learning. The pedagogy of Socratic questions is open-ended, focusing on broad, general ideas rather than specific, factual information.[8] The questioning technique emphasizes a level of questioning and thinking where there is no single right answer.

Socratic circles generally start with an open-ended question proposed either by the leader or by another participant.[14] There is no designated first speaker; as individuals participate in Socratic circles, they gain experience that enables them to be effective in this role of initial questioner.[10]

The leader keeps the topic focused by asking a variety of questions about the text itself, as well as questions to help clarify positions when arguments become confused. The leader also seeks to coax reluctant participants into the discussion, and to limit contributions from those who tend to dominate.[10] She or he prompts participants to elaborate on their responses and to build on what others have said. The leader guides participants to deepen, clarify, and paraphrase, and to synthesize a variety of different views.[10]

The participants share the responsibility with the leader to maintain the quality of the Socratic circle. They listen actively in order to respond effectively to what others have contributed. This teaches the participants to think and speak persuasively using the discussion to support their position.[8] Participants must demonstrate respect for different ideas, thoughts and values, and must not interrupt each other.[10]

Questions can be created individually or in small groups.[15] All participants are given the opportunity to take part in the discussion.[17] Socratic Circles specify three types of questions to prepare:
  1. Opening questions generate discussion at the beginning of the seminar in order to elicit dominant themes.[10][15]
  2. Guiding questions help deepen and elaborate the discussion, keeping contributions on topic and encouraging a positive atmosphere and consideration for others.
  3. Closing questions lead participants to summarize their thoughts and learning[10] and personalize what they’ve discussed.[15]

Psychotherapy

The Socratic method, in the form of Socratic questioning, has been adapted for psychotherapy, most prominently in Classical Adlerian psychotherapy, Logotherapy,[18] Rational Emotive Behavioral Therapy, Cognitive Therapy[19][20][21][22] and Reality Therapy. It can be used to clarify meaning, feeling, and consequences, as well as to gradually unfold insight, or explore alternative actions.

The Socratic method has also recently inspired a new form of applied philosophy: socratic dialogue, also called philosophical counseling. In Europe Gerd B. Achenbach is probably the best known practitioner, and Michel Weber has also proposed another variant of the practice.

Brains Improved by Graphene Are on the Horizon

Researchers gain better understanding of how graphene interacts with brain cells to increase neuron activity

Single-layer graphene (SLG) increases neuronal firing by altering membrane-associated functions in cultured cells.
Image: SISSA

While graphene has been tapped to deliver on everything from electronics to optoelectronics, it’s a bit harder to picture how it may offer a key tool for addressing neurological damage and disorders. But that’s exactly what researchers have been looking at lately because of the wonder material’s conductivity and transparency.

In the most recent development, a team from Europe has offered a deeper understanding of how graphene can be combined with neurological tissue and, in so doing, may have not only given us an additional tool for neurological medicine, but also provided a tool for gaining insights into other biological processes.

In research described in the journal Nature Nanotechnology, a group from the International School for Advanced Studies (SISSA), in Trieste, Italy and the Catalan Institute of Nanoscience and Nanotechnology (ICN2) in Spain have demonstrated that single-layer graphene increases neuronal firing by altering membrane-associated functions in cultured cells.

“The results demonstrate that, depending on how the interface with [single-layer graphene] is engineered, the material may tune neuronal activities by altering the ion mobility, in particular potassium, at the cell/substrate interface,” said Laura Ballerini, a researcher in neurons and nanomaterials at SISSA.

Ballerini provided some context for this most recent development by explaining that graphene-based nanomaterials have come to represent potential tools in neurology and neurosurgery.

“These materials are increasingly engineered as components of a variety of applications such as biosensors, interfaces, or drug-delivery platforms,” said Ballerini. “In particular, in neural electrode or interfaces, a precise requirement is the stable device/neuronal electrical coupling, which requires governing the interactions between the electrode surface and the cell membrane.”

This neuro-electrode hybrid is at the core of numerous studies, she explained, and graphene, thanks to its electrical properties, transparency, and flexibility represents an ideal material candidate.

 
In all of this work, the real challenge has been to investigate the ability of a single atomic layer to tune neuronal excitability and to demonstrate unequivocally that graphene selectively modifies membrane-associated neuronal functions.

The researchers hypothesized that there would be specific interactions between graphene and potassium ions in the extracellular solution, crucially regulating cell excitability. By experimental and theoretical approaches, they further hypothesized that crucial to these effects are the graphene specific cation-pi interactions, which are non-covalent molecular interactions between a cation—an ion with fewer electrons than protons, giving it a positive charge—and an electron-rich system (the pi). These cation-pi interactions are maximized by the single-layer graphene, according to Ballerini, which in turn impacts cell excitability.

“Our work provides important insights on the deep interactions of technology with nature,” said Ballerini. “Novel and outstanding materials might then represent, in general, unconventional and exciting tools to gain insights into genuine biological processes. In turn, biological processes may hint at describing unconventional properties, new physics, and applications of the materials.”

Ballerini notes that for this line of research, the group will ultimately have to move to in vivo conditions, which poses different challenges both in engineering devices to be tested in real life and in analyzing biological outcome. However, for now Ballerini and her colleagues will focus on the design of a smart device that takes advantage of their expertise in biology and nanomaterials.

Entropy (information theory)

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Entropy_(information_theory) In info...