Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège

Glossary

Vous trouverez dans ce glossaire les définitions de termes présents dans les différents articles, classés de manière alphabétique.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
D
Dalton

A unit of measure of molecular mass, equivalent to grams/mole.

Dark energy

This is a form of energy about which we know nothing, except that it must exhibit a kind of negative pressure that allows it to act like a gravitational force, only one that is repulsive instead of attractive. Dark energy is supposed to be responsible for the acceleration of the expansion of the universe. Together with dark matter, dark energy makes up most of the matter in the universe.

Dark matter

Research concerning the matter in the universe indicates the presence of non-luminous matter, and also non-baryonic matter (that is, matter not made up of quarks), which is called black or dark matter. This dark matter was predicted based on the properties of gravitation. Each body, in effect, creates a gravitational field, and undergoes the influences of all the other bodies. By studying the movement of a body it is possible to calculate its gravitational field, and also to localize and calculate the size of masses that create this field. Since 1933 (the work of Zwicky) many galaxies have been observed that contain stars whose rotational speed is not what theory says it should be: their rotation is too fast to maintain itself in those galaxies. The only explanation is that there is some matter (which must be much larger than the mass of the galaxies themselves) that is influencing those stars, and preventing centrifugal force from scattering them far from the center of their galaxies. This matter must be made up of electrically neutral elements, because it does not emit radiation. Hence the name, dark matter.

Dark matter constitutes about 23% of the total amount of matter in the universe. Baryonic matter (of which we ourselves, and the planets, and the “visible” stars are composed) represents only 4.5% of the total amount of matter in the universe. All the rest is dark energy (about 72%).

Darwin, Charles (1809-1882)

Charles Robert Darwin, a British biologist, is at the root of the theory of evolution. From his journeys to the Galapagos Islands, Darwin brought back numerous fossil and living animal specimens. He noticed particularly that each island possessed its own specific types of turtle and bird, whose appearance and diet differed in small ways, but which were in addition a lot alike. He thus developed his theory according to which, for example, each sort of turtle originates from the same species, each having adapted in a different way to life on the different islands. In doing this, he abandoned the idea of the divine creation of the species.

Database

A structure which allows the storage of and access to a vast quantity of information in an efficient manner.

DC Comics

One of the most famous American comics publishing houses, created in 1935 and today belonging to the Time Warner group. It was this publishing house that created particular superheroes such as Batman, Flash Gordon, Superman and Wonder Woman.

http://www.dccomics.com/

DDT

Dichlorodiphenyltrichloroethane, a colorless crystalline substance, almost completely insoluble in water but very soluble in fats and organic solvents. It was synthesized for the first time in 1874 but its insecticidal properties were not discovered until 1939. After that time, it was widely used by military forces, especially in Italy, to fight against insects carrying malaria and typhus. After the war, it was widely used in agriculture. The WHO (World Health Organization) relied upon DDT in its worldwide program to stamp out malaria in 1955. But during the 1950s, the first doubts began to arise about the effect of DDT on the environment (deaths of birds and fish following spraying with DDT). Gradually, its use in agriculture was prohibited in developed countries during the 1970s and 1980s. The use of DDT is nowadays largely limited, but as for PCBs, it is a very stabile molecule. We can still find a lot of DDT in the environment, notably in the sea.

de Bosschère, Jean (1878-1953)

A Belgian French speaking writer, born in Uccle (Brussels), who acquired French nationality in 1948 and died in Châteauroux (in the department of Indre). After a grim adolescence he threw himself heart and soul not only into writing but also painting, drawing and sculpture. His literary work, if we restrict ourselves to just that, is protean, which only adds to the ‘unclassifiable’ character of this individual, who has remained unknown to the general public. On the other hand a good number of his peers recognised and admired him: Antonin Artaud, for example, wrote a preface for his Marthe et l'Enragé (1927), a novel with an autobiographical dimension; Max Elskamp, André Suarès, Ezra Pound, Oscar Vladislas, Lubicz-Milosz and many others were amongst his circle of friends. But whilst he broke with Symbolist aesthetics he at no time enrolled in one of the literary movements of his day. Independently of his novelistic output, of which Satan l'Obscur (1933) in particular predominates, it is through his poems and poetic prose that he made a mark on the French literature of the first half of the twentieth century. In them we rub shoulders with a soul which is both solitary and rebellious, certainly tormented and perpetually seeking the absolute.

De Coster, Charles (1827-1879)

A Belgian francophone writer born in Munich to a Walloon mother and a Flemish father who held the functions of a steward of the Bavarian city’s Apostolic Nuncio. Having arrived very young in Belgium, he studied humanities at the Brussels Collège Saint-Michel, and then began studies at the capital’s Free University, without nevertheless ever completing them. But it was within this institution that he was taken by the spirit of the free exam, which would lead him to adopt democratic and anti-clerical convictions. He then became a journalist and a Professor of the Brussels ‘École de guerre’. His Légendes flamandes (1857) knew a certain success. The same would not be true of his Contes brabançons (1861), and even less so for his La Légende et les Aventures héroïques, joyeuses et glorieuses d'Ulenspiegel et de Lamme Goedzak au pays de Flandres et ailleurs (1867), which remains known under its abridged title La Légende d'Ulenspiegel: this novel, written in a deliberately archaic language, and mixing history and myth, places on the stage Thyl Ulenspiegel (or Till the Mischievous), a symbol of the resistance to the oppression of King Philippe II and the Duke of Alba during the time of the Spanish Netherlands in the 16th century. The fact remains that, coldly welcomed by non-conformist backgrounds, this magnum opus new universal success after the death of its author and is generally considered as foundational in Belgian literature of French expression.

De Gasperi, Alcide (1881-1954)

Male Italian politician. He was elected to the Austrian parliament in 1911 when his region, Trentin, was still a part of the Austro-Hungarian empire. The victory of Italy over Austria in 1918 made him an Italian citizen. He opposed the fascism of Mussolini from the very beginning – he was imprisoned for four years – and subsequently took part in the founding of Christian democracy. After the Second World War he was Prime Minister and Foreign Minister. He was also an ardent architect of the construction of Europe. In 1954 he was elected President of the ESCS.

de Gaulle, Charles (1890-1970)

French poltician and General. An officer by training, Charles de Gaulle pursued a military career during the First World War and between the two wars, while publishing several works of political history and military strategy. At the start of the Second World War, he commanded an armoured division. On the 6th of June 1940, mid-battle, he was named Under-Secretary of National Defence and set himself against supporters of the Armistice. He arrived in London on the 17th of June to continue the fight against Germany; the following day he launched his “18th of June Call”, inciting all French people to back the Allies. As and when French territory was liberated, he imposed himself as the legitimate leader, under the title of President of the Provisional Government of the French Republic (GPRF). In disagreement with the political parties, which he reproached for wanting to go back to the pre-1940 “system” (biased decision-making, triumphant parliamentarism, weakness of the Executive, Ministerial instability), he stepped down in January 1946.

He only regained power on the 1st of June 1958, following the rebellion of Algiers and the deterioration of the situation in Algeria, and then the entire French Departments. The new constitution was approved by referendum in September, giving France a regime that ensured the primacy of the Executive and made the President of the Republic the keystone of all public institutions. The Fifth Republic was born. Charles de Gaulle was elected President of the French Republic in December 1958. Negotiations with the Algerian leaders led to Algerian independence in 1962. General de Gaulle practiced a foreign policy that led to affirmation of the independence of France from the two big powers of the time and reached reconciliation with Germany. He was re-elected President in 1965, but this time through universal suffrage, but the economic, social and cultural malaise present in France for several years exploded in May 1968. This crisis caught de Gaulle unprepared; he was only able to call a halt to it in June by winning the long-awaited legislative elections. He abandoned power the following year following defeat in a referendum on regionalisation and reform of the Senate.

De Geest, Dirk (1957 - )

Professor of literary theory and contemporary Flemish literature at the KUL (Leuven). Along with Reine Meylaerts, and with the collaboration of Gina Blanckhaert, he edited Littératures en Belgique / Literaturen in België. Diversités culturelles et dynamiques littéraires / Culturele diversiteit en literaire dynamiek (2004).

de Ghelderode, Michel (1898-1962)

Pseudonym of Adémar Adolphe Louis Martens. A Belgian writer who wrote in French. He wrote numerous stories and numerous  theatre plays, for which he earned international recognition.

de Noé, Amédée (known as Cham) (1818 – 1879)

A French cartoonist. He is above all known as one of the great humorists of the satirical illustrated journal, Le Charivari, to which he contributed for numerous years.

Debord, Guy (1931-1994)

A French Cinematographer and writer. He founded Situationist International in 1958, a movement that sought to overtake art so that it would become a form of communication, with the participation of everyone, and that it would integrate poetry into daily life transformed into a game of events. His most famous work remains The society of the spectacle, which appeared in 1967. In 1965, Guy Debord patented his war game of which he said “It is perhaps the only one of [his] works which will be acknowledged to have some value”.

Decadence

Beyond its habitual meaning, this term is applied to a literary movement whose representatives, inscribed within the symbolist nebula, cultivate a deliberate pessimism laced with humour and mobilised for provocation. ‘I am the empire at the end of decadence,’ wrote Verlaine (1844-1896) in Le Chat noir in 1883: he thus expressed in his manner a sensibility which would irrigate the work of young poets such as Laforgue (1860-1887), who treats the more familiar subjects of existence with melancholy or ironic detachment. A ‘fin de siècle’ atmosphere which Paul Bourget (1852-1935) traces back to Baudelaire (1821-1867), amongst others, and in which he detects a degeneration of classical language: ‘a decadent style is that in which the unity of the book breaks down to be give way to the independence of the page, where the page breaks down to give way to the independence of the sentence and the sentence gives way to the independence of the word’ (Essais de psychologie contemporaine, 1883).

Defamatory

(in French, Infamant) from the Latin infamare, to dishonour. Which sullies honour, reputation. Demeaning, degrading, dishonouring, shameful.

deflector

A massive celestial body located between a luminous source and its observer and which can generate multiple images of the back ground source . These bodies are typically galaxies or clusters of galaxies.

Defoe, Daniel (1659? - 1731)

An English adventurer and writer, whose real name is Daniel Foe. He is the author of major work, whose best known title is without a doubt The Life and Adventures of Robinson Crusoe (1719), which narrates the life of a shipwrecked man on a desert island. We also owe to him A Journal of the Plague Year (1720), which describes the London of the 1665 plague epidemic. His books provide precious testimony to the customs, values and politics of England and Scotland at the end of the 17th and the beginning of the 18th centuries.

Degeneracy of a theoretical model

In science it is said that a theoretical model is degenerate when the same prediction can be made by several sets of values of the model’s parameters or when a measurement does not allow a single output of the model to be selected.

Deletion

loss of a fragment of chromosome

Deleuze, Gilles (1925-1995)

French philosopher. He wrote many essays that were influential in many areas, including philosophy, film criticism, literature, painting and politics in contemporary societies.

Demaret, Albert (1933-2011)

A psychiatrist from Liège and a pioneer in evolutionary psychology, he was known for his work on mental anorexia and manic-depression. In his book Ethologie et psychiatrie: Valeur de Survie et Phylogenèse des Maladies Mentales, published in 1979, he determined that human pathological behaviour contained the fundamental characteristics of evolutionary adaptive behaviours to the natural environment.

deme

The territorial dominion of certain Greek City-States.

Dementia

Dementia is an acquired reduction in cognitive capacities which is sufficiently large to affect people significantly and lead to a loss of autonomy. Areas which are particularly affected include memory, attention spans, language and problem solving.

In the last stages of dementia, people affected can become very disorientated in terms of time (not knowing the day, week, month or year), place (not knowing where they are) and people (not knowing who they are).

Demeter

A goddess who encourages agriculture and favours the fertility of the land and of women.

demotic

A simplification of the hieratic script. Demotic defined a state of the Egyptian language at a particular time, as much as a system of writing that appeared in the seventh century B.C.E. The simplification and signs in demotic writing is so extensive that the connection between this script and the hieroglyphic system is considered to have been broken. Along with Greek and the hieroglyphic system, this was one of the three languages/writing systems represented on the Rosetta Stone.

Denaturing Gradient Gel Electrophoresis (DGGE)

When we want to extract a DNA sequence from a mixture of sequences coming from a core sediment sample, for example, we must use techniques in order to succeed in pinning down this sequence. DGGE is one of these techniques. It is a method of separation and isolation of DNA sequences based on their denaturation characteristics (see Polymerase Chain Reaction).

Each DNA is different. What differentiates them is the chain of nucleotides. The As are linked to Ts, and the Gs are linked to Cs. The AT links are less solid than GC links and these denature more easily. 

In the case of DGGE, the denaturation is not done by means of an increase in temperature but with the help of a chemical denaturant placed in an electrically charged gel. The nearer to the positive pole of the gel the more the solution is concentrated in chemical denaturant. When placed on the gel, the negatively charged DNA migrates towards the positive pole. The DNA having more AT connections denatures more quickly and become immobilised in the gel. Conversely, the DNA composed of more GC connections migrates further in the gel where the denaturant is more concentrated. 

The different DNA chains will therefore be isolated. It only remains to extract the required DGGE bandand apply the PCR to amplify and analyse its sequence, and finally to know to which species the sequence belongs, thanks to the ribosomal 16S rRNA sequence.

DGGE is only one method among many others. DNA sequencing has been constantly evolving over the last thirty years or so. Effective high-throughput sequencing techniques are being born and are becoming widely accessible.

Dendrites

Multiple and ramified projections of a nerve cell that receive numerous synaptic contacts with the axonal endings, collect the signals they produce and transmit them to the body of the neuron (soma).

Dendritic cells

Dendritic cells are the cells in the immune system that present dendrites, as their name indicates, in certain cases (cytoplasmic prolongations). They are phagocytic cells that express a wide range of proteins allowing the presence of pathogens to be detected. It is these cells that are especially responsible for triggering an immune response.

Dendrochronology

Method allowing dating to be carried out or climatic and environmental variations to be determined by studying the growth rings of a tree trunk.

deoxyhaemoglobin

Haemoglobin to which no oxygen is attached, thus loaded with CO2.

Depardon Raymond

Raymond Depardon (1942 - ) is a French photographer and filmmaker. His documentaries deal with social issues. His first feature length film in 1974 is a documentary which traces the presidential campaign of Valéry Giscard d'Estaing. He would also become interested in the press, the police and psychiatric institutions. He has a particular passion for Africa and he has shot numerous films and photographic reports on the subject. More recently he has become interested in the peasant world, which he originates from, through his triptyque ‘Peasant Profiles.’

Deposit

In geology, a deposit, or ore bed, is a place where one or more useful minerals are concentrated.

depth of field

A zone of space in which should be found an object for which one can obtain a clear image.

Derain, André (1880-1954)

Derain met Matisse at the Louvre when he was young (he would rejoin him much later at Collioure). He was friends with de Vlaminck and worked beside him in a workshop. He had an interest in Seurat, Van Gogh and Cezanne. All these influences meant that Derain would always put colour first. He applied it in large fragments, and appeared at one point to be one of the most daring of Fauvists. He left Bateau-Lavoir and went to Montmartre, where Picasso was living, and began to do sculpture. His style gradually became more traditional. His work includes portraits, landscapes, still lifes and fantastic creations, as well as stage sets (he was the scene designer for La Boutique by Diaghilev) and book illustrations, including L’Enchanteur pourrissant by Apollinaire, poems by Max Jacob and André Breton’s first book, Mont de Piété.

Dermis

The dermis is one of three main layers of the skin. It is below the epidermis (superficial layer of skin) and above the hypodermis (essentially composed of fat that is traversed by blood vessels, and containing sudoriferous glands and the roots of longer hairs). The dermis is made up of conjunctive tissue, a gelatinous structure that assembles proteins and serves as a connection and support for various other tissues and organs.

Descartes, René (1596 – 1650)

A French mathematician, physicist and philosopher. After studying at the Jesuit school in La Flèche, Descartes became a soldier, crossing Europe and settling in Holland in 1629. On a scientific level, he simplified mathematical writing, developed analytical geometry, and discovered the laws of light refraction. He is most well-known for having defined a deductive method that leads from doubt to certainty (Discours de la Méthode, 1637).

Descola, Philippe

Philippe Descola is a French anthropologist born in 1949. He devotes his theories to the modes of the socialisation of nature and to the relationships between human beings and what surrounds them. With the goal of going beyond the nature/culture dichotomy he has suggested an analysis reading grid of four modes of social identification which are ways of establishing a border between self and other, according to the perception of resemblances or differences in the interiority and physicality between the human and the non-human. These four modes are naturalism, totemism, animism and analogism, described in his work "Par delà nature et culture" (Beyond Nature and Culture).

Descola TAB

Desnos, Robert (1900-1945)

Robert Desnos was born in Paris in the neighbourhood of the Halles, which he celebrated in all his work. He was a great reader; in 1919 he published Prospectus, which was significantly influenced by Apollinaire. He was a member of a group that formed around André Breton at the beginning of the 1920s, and he participated in the birth of Surrealism. His writings testify to his taste for automatic writing and for language games, although he affirmed that dreams and desires were all-powerful. He was proficient in experiments concerning hypnotic sleep, in which the group was much interested, and he captivated his friends with prophetic words and mysterious drawings. L’Aumonyme and Le Langage cuit are evidence of his desire to regenerate language. He published several collections of poetry, including Corps et biens (1930), and he broke away from the surrealists. He was a supporter of the Republicans in the Spanish Civil War, and later he fought with the Resistance. He wrote an autobiographical novel entitled Le vin est tiré… (1943) and the following year published Chantefables (1944). He was arrested on February 22, 1944, and sent to the concentration camp at Terezin, where he died of typhus on June 8, 1945.

Destrée, Jules (1863-1936)

Lawyer, writer and Belgian politician. He was elected to the office of Deputy as a member of the POB (the precursor to the Belgian Socialist Party) beginning in 1894, and he would be reelected to that office continuously, until his death. In 1912, he published in the “Revue de Belgique” a letter to the King in which he observed that Belgium was composed of two distinct peoples, and that there were no Belgians. This letter is considered as a foundation for the recognition of a Walloon identity, and the Walloon federalist movement. During the First World War, he travelled through Italy denouncing atrocities committed by the Germans in Belgium, and he attempted to win Italy over to the side of the Allies. In 1917, following the Russian Revolution, he was named ambassador extraordinaire to the provisional government of Kerensky; later he was named ambassador to China, a post he held up until the time of the armistice. After the war he became Minister of Arts and Sciences (1919-1921). He was responsible for the creation of the Royal Academy of French language and literature.

Detrez, Conrad (1937-1985)

A Walloon writer born at Roclenge-sur-Geer (province of Liège) into a modest rural family, who became a naturalised French person in 1982 and died in Paris. At the end of brilliant studies in Greek-Latin humanities and an adolescence marked by strong religious impregnation, he undertook studies in philosophy and theology at the Catholic University of Louvain. Contact with young students from the Third World nevertheless led him to interrupt them: becoming aware of the socio-economic conditions experienced in the lands of his fellow students from overseas literally shattered him. Saving lives thus became more urgent than saving souls. He left Belgium and emigrated to Brazil where, after having received an arts degree, he became a Professor at Rio de Janeiro. There he discovered at the same homosexuality the Castro inspired guerrilla. Arrested, then tried and condemned, he was expelled, and went to France, Algeria and Portugal by turn: it was in the latter country that he gave accounts, from Lisbon and in his capacity as a RTB correspondent, of the 1974 Carnation Revolution. After having translated Brazilian revolutionary authors, he wrote successively Ludo (1974), Les Plumes du coq (1975) and L'Herbe à brûler (Renaudot Prize 1978): these novels bring to life his first Belgian years as his youth drunk on liberty far from his native land; with them, we are in the presence of a genuine ‘hallucinatory’ autobiography’ and, to all appearances, a literature lived as a substitute for militant activity.

Dévi, Savitri (1905-1982)

Born in Lyon under her real name Maximine Portas, Savitry Dévi had a Greek father and an English mother. A chemist and philosopher, she is above all known for her admiration for Hinduism and Nazism, whose merits she continued extol after the war – which earned her a fixed six year prison term. She spent a large part of her life travelling in India, a country whose independence she firmly stood up for.

Dewey, John (1859-1952)

An American philosopher whose field of study, sowed with concerns of a democratic and humanist nature, extended to applied psychology and pedagogy. He has remained particularly known for his theory of empirically founded knowledge: an initiator of learning processes through action, making experience the springboard of knowledge, he has considerably influenced current concepts in teaching. Witness to this are the scores of publications, amongst which stands out the book Democracy and Teaching.

Dexamethasone

A synthetic hormone used in the treatment of inflammatory or auto-immune diseases. It is also administered to certain cancer patients who are undergoing chemotherapy in order to counter the therapy’s side effects. Dexamethasone is also used to curb the formation of oedema in the treatment of brain tumours.

Diabetes

A disease characterised by the excessive elimination of a substance in urine. Several types of diabetes exist but the best known remains the so called sugar diabetes. The latter is expressed by an overabundant presence of sugar in urine and is due to a hyperglycemia or an insufficiency in the secretion of insulin. Sugar diabetes is a common disease which affects 5% of the population of industrialised nations. Only 15% of these people suffer from type 1 diabetes (a major deficit of insulin secretion whose treatment rests on obligatory and daily injection of synthetic insulin) whilst the rest (85%) suffer from type 2 diabetes (a reduction in the effect of insulin on the cells, generally due to people being overweight. Losing weight and maintaining a balanced diet often allows this glycaemia to be normalised.

diachrony

The point of view that focuses on the development of events over time.

Diagenesis

The ensemble of the physico-chemical phenomena which transform fresh sediment into consistent rock, in the conditions of low temperatures and pressures which prevail in the subsurface environment. It concerns the phenomena of cementation, dissolution, recristallisation and replacement affecting the sediments. It stops where metamorphosis starts, in other words the transformation of rocks in higher temperature and pressure conditions.

diamagnetism

The conduct of certain materials which, when they are subjected to a magnetic field, are magneticised in the opposite direction of the latter. That is the case for practically all of the organic molecules and gases. In general this magneticisation is so weak that it is almost imperceptible.

diapause

Spontaneous temporary cessation of the development of an organism

diaspora

A term that derives from the ancient Greek diasporá – dispersal, originally used in botany to speak of seed dispersal.
The term was first used to talk about the Jewish diaspora, but today it is used to describe more broadly the dispersal of a population or an ethnic community around the world (Italian, African or Palestinian diaspora). The first diasporas date back to antiquity. Although it is impossible to calculate exactly the extent of the diasporas, it is possible to estimate the overall number at over 600 million people, so about 10% of the world’s population.

diatom

A unicellular microalga protected by two silica valves.

Diderot, Denis (1713-1784)

After having studied theology and English and lived the life of a Bohemian, Diderot began his career as a translator. In 1746, he published the Pensées Philosophiques, his first major work in which he opposed the religious opinions of a Christian, a deist, a sceptic and an atheist through aphorisms. This work was condemned to be thrown on the fire because he put all religions on the same footing. In 1749, he published his Lettre sur les aveugles à l’usage de ceux qui voient, a revolutionary work since he defended the idea of a chaotic universe, in constant evolution, in which all species – including Man – are not created by a creator but are the fruit of evolution. What comes first is chaos, and what we consider to be “normal” is therefore only one case. Understandably, such thoughts led their author to be imprisoned on 24th July 1749. However, Diderot only remained a short while in prison, thus allowing him to continue with the work he had devoted himself to since 1745: with the assistance of D’Alembert, the future Encyclopédie (Encyclopedia)whose publication was spread over more than 20 years. Diderot was also responsible for works on art and aesthetics, ethics and politics, but also tales and novels, such as La Religieuse (1780), Jacques le Fataliste et son Maître (1778 to 1780) and Le Neveu de Rameau (posthumous).

Un matériau est dit diélectrique lorsqu’il ne contient pas de charges électriques susceptibles de se déplacer. Autrement dit, il ne peut pas conduire le courant et est donc un isolant électrique.

When a dielectric is placed in an electrical field, electric charges don’t flow through the material as they do in a conductor. In other words, it can’t conduct the current and is therefore an electrical insulator.

Dielectric constant

The dielectric constant of a material is a measure of its capacity to induce an electric charge displacement when placed in an electric field.

Diète

An institution within the Holy Roman Empire, which had the task of resolving differences between States within the Empire. This was not a parliament in the modern sense of the term, but an assembly of sovereigns (princes, counts, dukes and bishops) that met at various times in different German cities.

Diffusible Protein

Protein capable of circulating freely in the organism.

digital pathology

A branch of medicine that studies and uses tissue samples whose images have been digitized at a very high resolution.

Dionysus

A god who is the purveyor of wine and the vital humours, transgression and the definition of limits

Dioxins

Dioxins belong to the chemical family of polychlorinated aromatic hydrocarbons, which consists of over 200 identified molecules. They are substances which result essentially from industrial processes: waste incineration, foundries, metallurgy, welding, bleaching paper pulp, the manufacture of herbicides and pesticides, etc. They can also be produced by natural events such as volcanic eruptions and forest fires. Once introduced into the environment they last for a long time thanks to their chemical stability.

Diphosphonate

Diphosphonate exists in various forms. It is used as a treatment against osteoporosis or as a tracer for the medical imaging of bones.

direct current

An electrical current that is independent of time, with a unidirectional flow. It's the type of current produced by batteries or car batteries, for example.

Direct line of descent or vertical gene transfer

A process by which an organism receives genetic material from its ancestor.

discrete dynamic model

In mathematics a dynamic model represents a system which evolves over time. Stochastic data are conventionally excluded, as they are more inherent to theories of probability. It is discrete when it represents a discontinuous evolution over time. In other words time intervals are fixed between the data (these intervals are counted in hours, days, months, years, etc.). In the opposite case it is called continuous.

Discretisation

A digital translation of the laws of physics. It is thus the creation of a digital code on the basis of mathematical equations during a modelling procedure. It is in the manner that these calculations and laws of physics are applied which makes the model correspond to reality or not.

disparity

Morphological diversity within a clade. Not to be confused with specific diversity, which is the number of species within a clade, ecosystem, etc.

Disulphide bond

A disulphide bond (or SS-bond) is a strong covalent bond which, by way of oxidation, couples the thiol groups of two cysteine amino acids in a peptide sequence (or protein). In the case of toxins, these disulphide bonds allow peptides to maintain the three-dimensional conformation needed to bond with their target receptors.

divine power (in ancient Greek religion)

A Greek deity is not, strictly speaking, a “person”, or an individual with a well-defined personality comparable to that of human beings. Even when it is represented with anthropomorphic traits, a god remains above all a divine power, a supernatural force that extends itself into all fields of experience, at all levels (nature, society, institutions, individuals), although without identifying completely with any one of its manifestations.

DNA

An abbreviation of DeoxyriboNucleic Acid, a molecule vehicle for storing and passing on hereditary genetic information. In human beings, they are located within the cells’ nuclei. Unwound, DNA molecules stretch out in a very long line made up of a precise chain (sequence) of base structural units called nucleotides. Each nucleotide is made up of a base (the bars of the helix), a sugar and a phosphate (the verticals of the helix). The structure of DNA, made up of the two complementary strands of a rolled up helix (double helix), allows it duplicate itself into two molecules which are identical to each other and identical to the mother gene when they are replicated or duplicated. DNA is one of the component parts of chromosomes. Genes are segments of DNA.

DNA-Microarray/DNA chip

The DNA chip method, biochip or DNA microarray makes it possible to analyze the level of expression of genes in a cell at given moment and in a given state. This technique is based on the single-strand DNA property of reforming a double helix when it is in the presence of a complementary single-strand. In concrete terms, it consists in extracting the mRNA from the cells of interest. After amplification of these mRNA in order to obtain a sufficient amount of material for the experiment, these are transformed into complementary DNA (cDNA) and labeled. This cDNA is then placed in the presence of single-strand DNA chosen according to the genes tested and fixed to a glass, plastic or silicon surface. Thanks to the labeling, one can observe which strands of DNA and cDNA have assembled to reform a double helix.

Flash animation of the microarray methodology

Doctrine (in law)

Ensemble of juridical works aimed at presenting or interpreting the law. Doctrine also constitutes one of the sources of law, besides law and jurisprudence.

Dodo

The dodo was a large bird belonging to the pigeon family and which was incapable of flight, populating the island of Mauritius up until the end of the seventeenth century. It became extinct following the colonisation of the island by human beings.

Doggy Dog, Snoop (1971 - )

Birth name Calvin Cordozar Broadus Jr. A Californian rapper whom, at the beginning of the 1990s  became one of the spearheads of the G-Funk movement (Gangsta-Funk), West coast rap which drew its main influences from the funk of the end of the 1970s.

Dogma

An assertion considered as the absolute truth, fundamental, incontestable and intangible, even though it is not demonstrable.

Donnay, Auguste (1862-1921)

A painter and illustrator from Liège, Auguste Donnay began his career by designing numerous posters for the printer and editor Bénard. In 1900, he was nominated Professor of Decorative Arts at the Academy of Fine Arts in Liège. He settled shortly after in Méry (Esneux) a small village in the valley of the Ourthe. This was to be an important source of inspiration to him. He painted numerous undulating landscapes of the Meuse valley. He also illustrated numerous books.

Dopamine

Chemical substance produced by the brain which acts as a neurotransmitter, involved notably in movement control and reward processes.

DPS (Dried Plasma Spot) / DBS (Dried Blood Spot)

These describe a technique of blood sample-taking on buvard filter paper. The first requires a plasma sample while the other is done from blood. In both cases, the sample must first be dried at room temperature.

DRAM

Dynamic Random Access Memory chips. Chips used as electronic memory for computer material. DRAMs which conform to the JEDEC standard represent around 95% of the market and are used in just about all personal computers. In 2008 world sales of DRAMs exceeded 34 billion dollars (or 23 billion Euros).

dual use technology product

It consists of ‘goods’ (materials, products, devices) which are not specifically nuclear, but which are capable of contributing substantially to a nuclear explosion process or to a nuclear fuel cycle process.

dual-energy X-ray absorptiometry

A technique for measuring the density of tissues by two x-rays with different energy levels. It does not require an injection, is painless and low in radiation.

Duane Michals

American photographer born in 1932 in Pennsylvania; his work is nourished by his working-class origin and his taste for Surrealists such as Magritte and Balthus. The themes of his black and white photographs – weather, dreams, absence, memory, etc. – are generally abstract, but he manages to give them a startling visual presence.

Dufy, Raoul (1877-1953)

Dufy was born in Havre, and went to Paris to study at the workshop of Bonnat. His first canvases show the influence of Toulouse-Lautrec, and of Boudin and Monet in the area of landscapes and pictures of the sea. He discovered Matisse and began to use bright colours and more schematic forms. He drifted away from Fauvism, and following a period of contact with Braque, he turned to a more sober palette and moved nearer to a kind of Cubism that recalls Cezanne. Following this he turned to engravings, and then created a number of fabric designs for the couturier Paul Poiret. Still later, travels to the south of France, Italy and Morocco inspired in him a new luminosity.

Duhamel, Georges (1884-1966)

Duhamel was a medical student from Paris when in 1906 he began to participate in the activities of the group known as l’Abbaye, which included poets and painters. For a while the group was associated with the “unanimist” school of Jules Romains, but quickly rejected him. In 1912, he published his fourth book of poetry, Compagnons. He was an Army doctor during the war and he wrote of his experiences in Vie des martyrs and then in Civilisation, which was awarded the Prix Goncourt in 1918. In the period between the World Wars he created two ambitious novel cycles, Vie et Aventures de Salavin and Chronique des Pasquier, completed in 1945. Later he wrote autobiographical pieces in Lumières sur ma vie. He was named a member of the Académie française in 1935.

Dumas, Alexandre (1802-1870)

A French writer. He started of by writing plays for the theatre. The staging of his play Henry III and his Court (1829) brought him to public awareness. This success continued throughout the whole of his literary career in the genres of his choice: drama, the historical novel, and sagas: this prolific author put his hand to great works such as The Three Musketeers (1844) and The Count of Monte Cristo (1845-1846)

His son, also given the first name of Alexandre (1824-1895), was also a writer, the author in particular of The Lady of the Camellias (1848).

Dürer, Albrecht

Born in 1471, died 1528. Albrecht Dürer was a theoretician of art, and a mathematician, painter and engraver. From Nuremberg, he is a major figure in the German Renaissance

Durkheim, Emile (1858-1917)

Now recognised as one of the founders of modern sociology, the French sociologist set out to bring moral fact back into social fact, which are for him independent of individual conscience. His best-known work is, without a doubt, “_The Division of Labour in Society_” (1893) in which he classifies societies with regard to the conception they have of social solidarity.

Dwarf planet

A dwarf planet is a type of heavenly body of the solar system somewhere between a planet and a small body (comets, asteroids and trans-neptunian objects). The term was adopted in 2006 by the International Astronomical Union in order to clarify the classification of objects orbiting the sun. Today, five objects are recognised as dwarf planets: Eris, Pluto, Makemake, Haumea and Ceres.

Dylan, Bob (1941 - )

Born in Minnesota in 1941 and still musically active today in 2011. At the beginning of the 1960s he went to New York and rapidly became one of the principal figures of folk movement and the protest song, before using the electric guitar at the end of the same decade. He was thus denounced by his initial fans but acquired an international aura, in particularly thanks to the first double album in the history of rock, Blonde on Blonde. In using the electric guitar to play folk, he was also the instigator of folk rock.

dynamic (relating to mechanics)

The study of the movements of a mobile element considered in relation to the forces which cause these movements.

dynamometer

A piece of equipment which makes it possible to measure strength, by means of a spring to which the desired resistance can be applied. When it is manual, it evaluates the strength of the hand.

Dysphasia

This refers to problems affecting the learning and development of oral language, which may take many forms: words that are not distinct, syntax problems, expression through isolated words rather than constructed phrases, etc.

dysphonic

Vocal disorder which results in reduced vocal quality.

dysplasia

Medical term used to designate the abnormal development of a tissue or organ. In the case of cancer screening, the word dysplasia refers to precancerous lesions.

Dyspraxia

This refers to problems with motor development and in particular motor coordination. Children who suffer from this have difficulty in coordinating their movements and repeating these movements in an automatic fashion.

Dystopia

A dystopia is a negative utopia. Rather than describing a perfect world, the author of a dystopia presents a world about which he warns the reader, one in which political or social constraints are so great they interfere with individuals’ search for happiness. The control exercised upon them is crushing, almost total.



© 2007 ULi�ge