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


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

A CCD (charge coupled device) sensor

A photographic sensor used in various types of equipment, which ensures the conversion of a light signal into an electronic signal. This technology, introduced in 1969, has been used in astronomy since the end of the 1970s.

Abbey Road

A mythical recording studio in London, belonging to the EMI record company. Abbey Road has, picking out randomly, seen the Beatles, Pink Floyd and the group Oasis come and go.

Abbott RealTime

In vitro test by PCR (polymerase chain reaction) in order to determine the quantity of ARN of the virus in the plasma of infected individuals. It is a tried and tested technique for measuring the viral load.

Academia Belgica

Inaugurated in 1939, the Academia Belgica is a residence for Belgian artists and researchers in Rome. Even if it is above all visited by archaeologists and historians – specialists in Antiquity – it is open to all disciplines. Welcoming researchers, organising conferences and exhibitions and possessing its own library, it is an important window on the world for Belgian university personnel. See http://www.academiabelgica.it

Academia Belgica

Inaugurated in 1939, the Academia Belgica is a residence for Belgian artists and researchers in Rome. Even if it is above all visited by archaeologists and historians – specialists in Antiquity – it is open to all disciplines. Welcoming researchers, organising conferences and exhibitions and possessing its own library, it is an important window on the world for Belgian university personnel. (see http://www.academiabelgica.it).


This is a sub-class of the order of arachnids. The Acari have eight legs, like spiders and scorpions. There are about 50,000 species of Acaria. These arachnids look like small, thick, disks (the disk is their abdomen), and attached to this is a thorax that incorporates the head (cephalothorax). The species of the order Acaria are parasites that eat blood and/or dead skin from a host animal. Contact with them can provoke allergies in the host and various kinds of dermatitis, as well as providing an opportunity for the transmission of infectious diseases.


Also called ‘dubbing’, it consists of a Mediaeval ceremony whereby a young noble became a knight through the handing over of arms. By extension: consecration, the recognition of merits.

Accoustic wave – gravity wave (asteroseismology )

A wave is generated by a disturbance that a restoring force propagates in its environment. It can be very different according to the process that causes it. For example, the physics which describes the waves created by throwing a stone onto the surface of water (gravity wave) differs from that which underlies the propagation of sound in the air (acoustic sound). In the same way, various mechanisms can disturb the interior of the Earth or a star and thus cause oscillations of different kinds. Asteroseismology studies the internal structure of stars through observation of its oscillation modes. The acoustic-type waves have a restoring force linked to the variation of the pressure that exists inside the star. Gravity waves are subjected to the principle of Archimedes.


The capture of matter by a star, or a black hole, under the effect of gravity. The matter captured by orbiting the central object forms an accretion disk, acquires thermal energy and generates luminous radiation.

Accursed poets

A term which appeared, through the pen of Verlaine (1844-1896), in the review Lutèce in 1883, and then in an expanded volume the following year. It consists of an anthology-collection of poets termed ‘accursed’ – ‘absolute through the imagination, absolute in expression’ – because they live on the margins of their time and, through their writing, decisively break with former practices. On this list feature names such as Corbière (1847-1875), Mallarmé (1842-1898), Rimbaud (1854-1891), Villers de l'Isle-Adam (1838-1889) and Pauvre Lelian (Paul Verlaine himself). But this label has been widely adopted by literary history, beyond solely the 19th century, to designate rebel writers, more often than not transgressive, amongst whom feature notably Villon (before 1431-after 1463), Lautréamont (1846-1870), Sade (1740-1814), Gérard de Nerval (1808-1855) and Baudelaire (1821-1867).


A word which springs from the Greek akèdia meaning ‘indifference’, ‘negligence’. Historically, this notion was applied to a restricted group of monks who had decided to lead a solitary existence, in distinction to those who had chosen a community life. Thinking through courage from the basis of this notion thus means first of all thinking it through on the basis of solitude and discouragement.


A potentially toxic synthetic molecule (C3H5NO) which generally forms during cooking of certain foods particularly during frying at temperatures higher than 120°C. Crisps, French fries, bread, pastries and coffee are the foods that have the highest levels of contamination.

Actes Sud

A French publishing house founded in 1978 by Hubert Nyssen.


ubiquitous protein, component of the cell cytoskeleton and important for the architecture and movements of the cells.

Action potential: (or nerve impulse)

An electrical signal crossing the neurons and causing the liberation of neurotransmitters within the synapses. The action potential is the neuron’s information unit. It is generated by a series of diverse ion channels opening and closing following an excitation stimulus.

Active site

The active site of an enzyme is the part of this enzyme that interacts with the substrate to form the product.

Adaptive Radiation

Adaptive radiation describes a rapid evolution from a common ancestor of a set of species characterized by great ecological and morphological diversity. Each new species is adapted to a particular niche.

Adaptive immune system

a component of the immune system corresponding to the specific defence mechanisms involving the T lymphocytes and B lymphocytes, allowing the body to acquire an immune memory following infection.

Adaptive optics

When we observe a star with the naked eye we have the impression that it twinkles. Nevertheless the star does not emit fluctuating light. This apparent twinkling in fact results from a perturbation brought about by the luminous rays crossing the atmosphere. Adaptive optics is a technique born in the 1990s which allows such non-predictable distortions of the observations to be corrected in real time, thanks to telescopes equipped with deformable mirrors which are capable of compensating atmospheric turbulence exactly.

Adenauer, Konrad (1876-1967)

A German Christian Democrat male politician. He was first of all Mayor of Cologne, and deposed by the Nazis when they came to power in 1933. After the Second World War he became the first Chancellor of the Federal Republic of Germany (1949), a mandate which he occupied for fourteen years. He was the architect of Franco-German reconciliation and instrumental in post-war Germany gaining recognition on the international map, as well as its integration in nascent Europe. In this respect he is considered one of the founding fathers of Europe.


Benign tumor on a gland or mucosa.


An element which plays an important role in biochemical processes, such as the transfer of energy – such as adenosine triphosphate (ATP) and adenosine diphosphate (ADP) – as well as in signal transduction, such as cyclic adenosine monophosphate, cAMP.


Fat cells.


Substance added to a vaccine which allows its immunogenicity and effectiveness to be strengthened.

Adrenal glands

Endocrine glands situated at the upper section of each of the two kidneys. They are made up of two parts: the adrenal cortex and the adrenal medulla. The first is responsible for the secretion of mineralocorticoids, glucocorticoids and sex steroids, whilst the second is responsible for the secretion of noradrenaline and its derivative, adrenaline.

Adsorbent, Adsorption

Adsorbent products possess an extremely porous structure. Their physical properties allow them to capture and to store water and humidity in their microscopic orifice, which are laid out in layers, pores and canals. Adsorbents are insoluble in water. Following the example of clays and zeolites, active carbon is an excellent adsorbent: its ability to absorb gas and organic molecules is remarkable, from which springs its use in protective masks, as a universal antidote or in medicines to counter dyspepsia. Adsorption, not to be confused with absorption, is a process in which gas or liquid molecules attach themselves to the solid surfaces of adsorbents in various ways. Adsorption consists of the fixing of hydrogen onto the surface of the internal cavities of a porous substance, or its being locked into carbon nanotubes. It should also be noted that adsorption constitutes the first stage of reactions which require the use of solid catalysts.


'Fact of a spouse having sexual relations with someone other than his/her spouse.'


The transport of an additive quantity – heat, internal energy, an arbitrary chemical element, electrical charges – by a moving fluid, no matter what the origin of the movement, gravitational instability or an impetus given by some force. In oceanography, for example, advection refers in particular to the horizontal transport of certain properties by the fluids considered, including transport by wind or by the currents: advection of water vapour, heat, salinity, etc.


In the case of an organism or process, it means that the latter require oxygen to survive and develop.


P period of variable duration which follows the neuronal action potential and over the course of which the membrane is less excitable as the membranal potential is further from the action potential threshold than at rest.

Age-related macular degeneration (ARMD)

A chronic retinal degenerative disease, sometimes associated with the development of neovessels under the macula. It causes the progressive loss of central vision while leaving peripheral (or lateral) vision intact. The loss of central vision is due to the degeneration of the photoreceptors, photosensitive cells (i.e. reacting to light) located in the macula. The degree of central vision loss varies according to the type of macular degeneration, its severity, and other individual characteristics. In Western countries, ARMD is the principal cause of severe vision loss in people over 50 years of age. Approximately 20 to 30 million individuals are currently affected and this figure could double in the next 35 years due to ageing of the population.


Proteoglycan. An essential component of cartilage and joints as it allows them to bear heavy and compressive loads.


From the ancient Greek agôn which describes any form of competition or sparring match. In the areas of art or sport, the agôn was a competition organized during religious ceremonies. In the structure of a tragedy or an ancient Greek comedy, the agôn was the technical term describing the part of the room where a scene of debate or combat took place.


A substance that attaches itself to a receptor and causes its response to be produced. In general, the agonist agent mimics the operation of the messenger substance that normally attaches itself to be receptor in question.

Agricultural land abandonment

A decline or reduction of the agricultural pressure on a given site.


Agrometeorology, or agricultural meteorology, aims to understand the interactions which exist between soils, plants and the atmosphere. It studies the action of meteorological, climatological and hydrological actions with a view to improving the management of agricultural enterprises.

AIDS (acquired immune deficiency syndrome)

The fourth and last stage of infection by HIV. The immune system is then very weak which increases the risks of dangerous or fatal infections for the HIV-positive individual. These infections are called “opportunistic infections”.

AKP (Adalet ve Kalkınma Partisi)

Party for justice and development, has been in power in Turkey since 2002.


In Arab, al-Qaeda signifies the base. A terrorist movement created in 1988 by Osama Bin Laden to fight the Soviets in Afghanistan. From 1996 onwards it has engaged in a holy war (jihad) against the United States. It is considered to be the instigator of attacks on American embassies in Kenya and Tanzania in 1998 and the September 11th, 2001, suicide attacks in New York and Washington.


The albedo is a unit understood to be between 0 and 1 which measures the sunlight reflected back into space by a planet. The brighter the planet, like a block of ice for example, the more light it reflects and the less heat it keeps. It will have an albedo of around 1. By way of example, the houses with white facades in Greece insulate against heat by reflecting light. Conversely, the darker the planet, the more it will absorb light and heat, its albedo will be around 0.


The albedo is the ratio of the intensity of light reflected from an object. For instance, the albedo of snow is much higher than that of the sea: snow reflects nearly all the rays, while the sea absorbs the majority.

Albert and Isabelle

Shortly before his death, the King of Spain Philip II ceded (in an Act of 6th May 1598) the Netherlands to his daughter Isabelle, who was soon to be married to Archduke Albert. In practice what were ceded were only the southern provinces as the seven northern provinces, which had a Protestant majority, declared themselves to be a sovereign state from 1579 onwards (the United Provinces, whose independence was not recognised until 1648).

The reign of Albert and Isabelle over the regions in question lasted from 1598 until 1621. They enjoyed relative independence from the Spanish crown, even if they were obliged to continue the war against the northern provinces. In 1609 they nevertheless signed a truce with them, from which they profited by rebuilding the ruined country. But it was above all its cultural life which was extraordinarily energetic. Architecture adopted the baroque style: the Marian basilica at Montaigu, the Jesuit church of Saint Ignatius at Antwerp (which became Saint Charles Borromée when the religious order was suppressed), and the church of the Holy Trinity at Ixelles are good examples. Their reign was also marked by the high point of the Antwerp school of painting: Rubens, the official painter to the royal rulers, Van Dyck, Teniers the Younger and the sons of Pierre Breugel contributed to the fame of the Netherlands.

The couple being childless, when Albert died in 1621, the Netherlands were once again placed under the direct control of Spain. The ‘Unhappy Century’ as historians have called it, thus began for our provinces.

Album amicorum

Literally, a book of friends in Imageries (2001), Philippe Hamon defines it thus: ‘a collection of handwritten manuscripts, (lines of verse, pictures, thoughts, bons mots, fragments of pieces of music, little caricatures, statements of thanks or friendship) brought together on the white pages of an album which is made available to a small circle of friends, and which is often attached to a fixed location (salon, café, workshop, college; etc.) which is frequented by this circle, and written by the location’s guests in an ongoing process.’


Derived from alginic acid extracted from brown algae. Used in the food industry for their gelification, thickening, emulsifying and stabilising properties, they are also used in medicine to encapsulate medicaments or fragile biological substances (enzyme, microorganisms, human or animal cells).


An algorithm is a finite sequential series of rules applied to a finite number of data, allowing for similar classes of problem to be solved. By extension it is also the whole set of operational rules specific to a calculation or a computer data processing operation.

Alimentary support

'Support made for maintenance, that is, in executing an alimentary obligation (e.g. between separated spouses or to an ascendant in need) or an obligation to maintain (parental contribution to the maintenance of a minor child)'. The 'maintenance' is the amounts paid over to a person to ensure he/she can cover the expenses associated with the needs necessary for his/her day-to-day life. Nevertheless, when the beneficiary of the maintenance is a school-aged child, the maintenance generally includes the costs necessary for his/her education. The word thus covers a broader area than the needs specifically related to maintenance.


A version of a gene, a fixed variant of a DNA sequence in a species.


A natural proteinic substance belonging to the environment and the cause of an allergic reaction. When an allergen of animal, plant or chemical origin penetrated the body, this leads to a variety of pathological symptoms. An allergen is sometimes constituted through the association of several substances.

Allergic rhinitis

Irritation and inflammation of the upper airways in people who are sensitive to the presence of an allergen.


Related to a sacred wood.

alternating current

An electrical current that reverses directions twice per period. It transmits alternating quantities of energy first in one direction, then another. It thus has a frequency, which is the number of times the current changes direction in a second (in Hertz or Hz).

Alternative world (alter-globalisation) activist

A partisan of alter-globalisation, a recent word which refers to a movement which is fighting against neo-liberal globalisation and clamouring for other economic, social, ecological and social models. Its militants want to see the setting up of another society, one which would be more attentive to the sustainable development of humanity and a fair distribution of its resources.

Alzheimer's disease

Alzheimer’s disease is a neuro-degenerative which progressively brings about the loss of cognitive mental functions, following the degeneration of cerebral tissue, and leading to a form of dementia. The most striking symptom of the disease is short term memory loss, whilst the oldest memories remain relatively intact. Other developments involve a loss of dexterity in controlling movements and losing recognition skills. Its exact cause is still unknown, but it is thought that both environmental and genetic factors contribute towards it. Until the 1960s the disease was believed to be rare, and it was attributed to ageing aspects and a slowing down of vital activity. The disease was discovered by Aloïs Alzheimer (1864-1915), a German psychiatric doctor and neuro-pathologist who studied the brains of people affected by dementia.

Alzheimer EN

Amino acis

Small molecules with a carboxyl group acid (COOH) and an amino group base (NH2) grafted on to a central carbon atom. They are the basic building blocks of proteins.


Also called batracians, amphibians form a class of tetrapod vertebrates. They are considered to be the oldest land vertebrates having separated from fish some 360 million years ago. The class of modern amphibians includes three orders, urodela (salamanders and newts), anura (toads and frogs) and gymnophiona (amphibians resembling worms). As their name suggests, (amphi, on both sides; bios, life), at least in our regions, they live just as well in either an aquatic or land environment.


These are molecules which have a hydrophilic part (polar) and a hydrophobic part (apolar).


Small crustacean with a body that is compressed laterally. They are no bigger than one centimetre and are very abundant in littoral zones.

Amsterdam Treaty

The Maastricht Treaty made provision for the meeting of an intergovernmental conference on treaty revision in 1996. Opened in March 1996, it led to the Amsterdam Treaty, signed on October 2, 1997.

The Amsterdam Treaty proclaims that the Union is founded on the principles of liberty, democracy, respect for human rights and basic freedoms, as well as the rule of law, principles which the member states have in common. At the same time the treaty envisaged the hypothesis of a member state violating these principles and legislates on the steps the Union would have to take against the state concerned.

The Amsterdam Treaty creates a new title of competences for the European Community called ‘Visas, asylum, immigration and other policies linked to the free movement of persons.’ It requires the fifteen states at the time – and those who subsequently join the Union – to adopt:
The norms and modalities of monitoring the crossing of the European Union’s external borders: minimal norms and measures concerning asylum and the protection of refugees; the procedure and conditions for granting visas for stays of a maximum of three months and for long term stays, including those granted in the context of family reunification; the fight against clandestine immigration and illegal stays; the procedures for repatriating offenders.
The measures aiming at ensuring the free movement of persons between the member states.

At the end of a period of five years after the ratification of the Amsterdam Treaty, the Council of the European Union unanimously decided that decisions taken within the framework of this chapter would be made by qualified majority, as a co-decision with the European Parliament.

The latter are to ensure a level of security and protection at least equivalent to that provided by the Schengen Agreement, the application of which would from now on be within the Community wide framework and its procedures. This intergovernmental agreement abolishes the monitoring of people within the internal borders and organises it at its external borders. The Amsterdam Treaty incorporates the Schengen agreement within the European Union, but the United Kingdom, Ireland and Denmark obtained the right to delay its application.


Part of the brain situated in the anterointernal region of the temporal lobe, near the hypothalamus and the hippocampus, and which plays an important role in emotions and conditionin

amyloid plaques 

Also known as senile plaques, these plaques are extracellular pathological aggregates of fragments of the APP protein (Amyloid Precursor Protein) which is present in the membranes of brain cells. With the effects of age and/or illness (such as Alzheimer's Disease), this APP protein is spliced into small fragments (amyloid peptides) which aggregate to form extracellular plaques, compressing the neurons, leading to the malfunctions observed in patients.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a neurological condition that affects the nervous system of adults, causing lesions on nerve cells (neurons) that eventually result in progressive paralysis. The disease is characterized by damage to motor neurons (neurons that transmit messages that cause movements). These neurons are located in the spinal marrow, and more precisely in their anterior sheath. They are also located in the motor nodes (islands of gray matter located within the white matter) of certain cranial nerves.

Amyotropic lateral sclerosis (ALS)

Disease (also known as Charcot's disease or Lou Gehrig's disease) which affects motor neurons located in the internal horn of the spinal cord as well as motor nuclei of the last cranial nerves. The incidence of ALS in Europe is 2 cases per 100,000. The most famous people afflicted with ALS are Mao Tse-tung, Stephen Hawking (astrophysicist), Lou Gehrig (American baseball player), and David Niven (actor).


The opposite of aerobic. In the case of an organism or process, it means that the latter don't require oxygen to survive. As regards an oxygen-free environment, it is usually referred to as an anoxic environment.

Anaerobic conditions

In an environment without oxygen


One of the four modes of identification for humans in relation to the non-human, according to the theory proposed by Philippe Descola. According to analogism the world is constituted of an infinity of individualities. To be able to think it, to render it accessible to our understanding, the only way is to draw up a series of analogies between the species and class them accordingly, through being aware of their differences. There is thus a strong consciousness of a discontinuity which is both internal or external, or mental and physical, between humans and non-humans. This paradigm is found for example in Chinese culture.


Infection caused by the pathogenic bacterium Anaplasma phagocytophilum. Anaplasmosis first manifests itself in symptoms that are flu-like, appearing from 5-15 days after the tick bite: high fever, muscle aches, headaches and sometimes aching joints. This disease is on the rise in Belgium; the number of cases detected is quite low, but nonetheless the highest in Europe.

anatomical pathology

Medical speciality that is concerned with the diagnosis of a disease through the observation of the lesions the disease causes in organs, tissue or cells (cytology). The main tool of the anatomical pathologist is the microscope (with all its technical refinements), and the object of his studies is the various samples that can be taken from a living (biopsies, smears, surgical removal) or deceased subject (autopsy parts). 
In disciplines such as cancer research, the contribution of pathologists is  essential in assessing the seriousness of the condition and to choose the most appropriate treatment.

Ancien Régime

Name given to the period of French history preceding the French Revolution of 1789. By extension the term Ancien Regime (Old Regime) designates the same period in the countries – Belgium, notably – and regions strongly influenced by the French political, economic and cultural institutions of before the Revolution.

Andrea Mantegna

Italian painter and engraver (1431-1506), born in Venice but worked for a long time in Padua. His works marked a break with the Gothic style; first influences by artists such as Uccello, Fra Filippo Lippi and Donatello, announce the Renaissance, if only through a taste for the ancient and because of his mastery of perspective. A notable example is the painting Lamentation for the dead Christ (ca. 1480-1490).


19 carbon hormone steroids responsible, during embryonic life, for the masculinisation of male embryos, and at adult age for the development of male characteristics (masculine) such as the largest muscular mass, the distribution of hair and sexual motivation. Testosterone is the prototype of the androgens.


A localised and irreversible dilation of an artery wall.


The mechanism responsible for the formation of new blood vessels from pre-existing ones.


plant whose reproductive organs are condensed into a flower and whose fertilised seeds are enclosed in a fruit.

Angot, Christine (1959- )

A French novelist and playwright. She published her first novel (Vu du ciel) in 1990. Her books are often termed ‘autofiction,’ but the author refuses this label.

angular diamteter

Or apparent size is the angle under which an object is seen

Angular moment

The angular or kinetic moment of a point or a body describes the rotation of this point or body around an origin.

Angular velocity

A measurement of rotational speed. This is expressed in radians per second in the international system (rad.s-1) as well as in rotations per minute in current usage.


A British rock group formed in 1962, inspired by the Rhythm & Blues. Its main success remains the song The House of The Rising Sun.


One of the four modes of identification for humans in relation to the non-human, according to the theory proposed by Philippe Descola. Animism grants to non-humans an interiority similar to that of humans. It is the body, the physical, which differentiates them from us. It is thus possible to have social relationships with other species. This paradigm is to be found for example amongst the Amazonian Amerindians.

Anne of Brittany (1477-1514)

A unique destiny for this young woman, who possessed heart and character, and who was married to two kings of France, Charles VIII and Louis XII. She had to battle hard, and marry, to bring peace to her Duchy. Dating from 1508, her famous Book of Hours, the Great-Hours, contains not only pages for religious inspiration, but also a herbarium (more than 750 plants are identified!) which constitute the bases of the works illuminations. The magnificent illuminations are the work of Jehan Bourdichon and Jehan Poyet.


Invertebrate vermiform organisms (‘worms’), most of which live in the water with the exception of a few species, e.g. earthworms, which live in the ground.


species of lizards, they are the unique representatives of the family of Dactyloidae. Found in America, they are diurnal, mainly tree dwelling and mainly eat insects although many species also eat fruit.


Sociologists define anomie as the state of a group or society whose members no longer share – or barely share – common values.


A reduction or complete loss of the sense of smell.


Anosognosia describes a disorder in which a person affected by an illness or handicap does not appear to be aware of their state.


A reduction or the absence of dissolved oxygen in an aquatic environment or in a submerged semident.


An environment without oxygen.

ANRS (National Agency for Research into AIDS)

A French public organization created in 1988 and whose objective is to “federate, coordinate, lead and finance all public research into AIDS”. A mission which extends to the developing countries, particularly those affected by the disease. It is also the name given to a method of measuring the viral load.


Discipline based on the study of charcoal exposed during archaeological digs. It allows the woody vegetation of the past but also traditional practices (metallurgy, building...).to be reconstructed.

anthropomorphic measurements

Technique for surveying the characteristics of the human body.

Anthropomorphic robot

A ‘robot’ (a term coined in 1924 from the Czech ‘Robota,’ meaning ‘forced work’) is an electronically controlled automatic mechanism which can replace human beings for the carrying out of certain operations. It is ‘anthropomorphic’ if it has human appearance.


Qui mange de la chair humaine. Synonyme : cannibale

Anti-complement factor

A substance in the blood that inhibits the activation of the complement system, a cascade of biochemical substances that help the organism destroy invading pathogens.


Antibiotics are substances of microbial origin, which prevent other micro-organisms from growing or which destroy them. Unlike simple disinfectants, they perform a specific action, i.e. they deregulate the metabolism of these targeted micro-organisms without attacking the cells of the human body. The first antibiotic (*) was discovered in 1928 by Alexander Fleming, a Scottish doctor. Alexander Fleming had noticed that a strain of Staphylococcus aureus (one of his bacterial cultures) was invaded by a mould called Penicillium notatum and that bacteria stopped growing where this mould was present. He deduced that the mould secreted an inhibitive substance which he called penicillin. On February 12, 1941, a patient diagnosed with septicemia was the first person to be miraculously saved following the administration of penicillin. Since then, other classes of antibiotics have been discovered, such as gramicidin, tyrocidin and streptomycin. There are now some 10,000 antibiotics of natural origin, 80% of which come from bacteria and 20% from moulds. Not all are used for medical purposes.

(*) The same observation seems to have been made a few years earlier by a young French doctor called Ernest Duchesne, but there was no follow-up.


Also called immunoglobulins, these are molecules produced by the body in response to the penetration of foreign bodies in the body.


An antigen is a natural or synthetic macromolecule, considered as a foreign body by the body, recognised by antibodies or cells in the immune system and capable of generating an immune response. Antigens are at the basis of the adaptive immune response. It is the recognition of the antigen by the immunocompetent cells that activate specific immunity.

Antigen presenting cells

Cell that displays foreign antigen complexes circulating in the the organism using T-cell receptors thus triggering a targeted immune response.


Molecule which reduces or prevents the process of oxidation, a chemical reaction during which there is a transfer of electrons. This type of reaction can produce free radicals.

antiretroviral (ARV)

Class of medicines used for treatment of infections linked to the retrovirus, a category of virus to which HIV belongs. The administration of such a treatment, if it is effective, prevents the virus from reproducing itself or multiplying.

Apastron – Perisastron

In astronomy, when one body gravitates around another, it in reality turns around the centre of the system’s common mass. Its orbit, which generally has the form of an ellipsis, has a perisastron and an apastron. The perisastron is the orbital point at which the two bodies pass the closest to one another, whilst the apastron is the orbital point where the distance between the bodies is at its maximum.


An apathogenic organism is one that does not cause problems for another organism that may serve as its host.


Loss of voice.


The goddess of sexual union and the attraction between people, sometimes in the form of the violence of a battle field.

apical meristem

Plant tissue consisting of undifferentiated cells responsible for plant growth, i.e. edification of the stem and leaves.


A non political character or attitude, particular to someone who displays no political opinions and who feels very distant from public affairs.

Apollinaire, Guillaume (1880-1918)

A French poet – whose real name is Wilhelm Apollinaris Albertus de Kostrowitzky – who was born in Rome and died in Paris. The son of an exiled Polish aristocrat mother and an Italian officer who did not acknowledge him. After somewhat chaotic years of school study in Monaco, Cannes and Nice, he travelled across Europe in his youth: Stavelot in the Belgian Ardennes, Rhineland, Austro-Hungary and finally London. Voyages which would remain for him, and in particular as a result of the romances that went hand in hand with them, a precious source of poetic inspiration. Having returned to Paris he published his first texts in literary journals such as La Revue blanche and La Plume, regularly met up with a group of poets amongst whom were Alfred Jarry, André Salmon, Paul Fort and Max Jacob, struck up friendships with painters of the first rank, amongst whom Pablo Picasso stood out, not to mention his in many respects decisive encounter with the artist Marie Laurencin. It was in this Montmartre bohemia that he took part in all the avant-garde movements in aesthetics, whilst also stimulating them as no-one else did. His works bear witness to a person who, from his L'Enchanteur pourrissant (1909) and L'Hérésiarque et Cie (1910) up to Alcools (1913) and Calligrammes (1918), decisively opened the door to Modernism: free verse, the abolition of punctuation, the use of blank spaces, a cascade of images, out of the ordinary associations, typographical representations of the objects invoked; all these procedures, which largely evoke Cubism, express the New Spirit of which Apollinaire was the pioneer and which he defined as a means of ‘exalting life’ in all its forms. And yet this innovator was also a continuer of tradition, if only for the Romantic echoes in his poems, elegiac when he feels ‘starved of love,’ lyrical when he declares his love for Lou during the war. Because this poet, an occasional art critic, enrolled in the artillery in 1914; but who, having suffered a head injury due to shrapnel in 1916, died two days before the Armistice, struck down by the Spanish Flu.


The son of Zeus, who transmits the wishes of his father via oracles and inspires poets through the intermediation of the Muses; his image, that of a young man, reflects that of the youth who pay homage to him.


Programmed cell death process responsible for the physiological suppression of cells in an organism.

appendicular skeletal muscle mass

This is obtained by adding the appendicular skeletal muscle mass of the two arms and legs.

Arago, François (1786 – 1853)

A French physician and politician. He is responsible for many works in the domain of optics and astronomy. He was the director of the Paris Observatory. But he was also a key figure in the republican party under the July Monarchy. After the Revolution of 1848, which established the 2nd Republic, he became Minister of War and the Navy in the provisional government. However, he refused to swear an oath of allegiance to Louis-Napoleon Bonaparte, the future Napoléon III.

Aragon, Louis (1897-1982)

Aragon was a medical student in 1919 when he met Breton and Soupault. Together they founded a magazine, Littérature, which in 1924 became Révolution surréaliste. He published his first collections (Feu de joie, Le Mouvement perpétuel) soon after, and a group of novels, Anicet ou le Panorama, Les Aventures de Télémaque and Le Paysan de Paris. All his life, went back and forth between poetry and prose. In 1927 he joined the Communist Party and met Elsa Triolet. Traité du Style, which appeared the following year and made fun of automatic writing, was a first step toward a break with Breton that became evident in 1932. He sympathized with the Soviet government, and brought Hourra l’Oural back from Russia in 1934. He wrote a cycle of novels in which he attacked the bourgeoisie (Les Cloches de Bâle, Les Beaux Quartiers, Les Voyageurs de l’Impériale). He was in the Resistance during the German occupation, and published poems clandestinely through the éditions de Minuit (Le Musée Grévin). With Les Yeux d’Elsa, he began an ode to his wife (Le Fou d’Elsa, Il ne m’est Paris que d’Elsa…) that would structure their life together until the death of the author of Roses à crédit in 1970. In addition to the six volumes of Communistes, attesting his faithfulness to a doctrine, even when it was represented by Stalin, and which he never repudiated, he authored Aurélien, Le Roman inachevé, his poetic autobiography, La Semaine sainte, Blanche ou l’Oubli, Henri Matisse, roman and, in 1980, Le Mentir-vrai.


Group of single-celled microorganisms classed as prokaryotes.


Archaebacteria are one of the two living components of prokaryotes, the second being bacteria. Archaebacteria differ from bacteria in terms of their structure, biochemistry and physiology.

Arendt, Hannah (1906-1975)

An American Jewish philosopher of German origin. A pupil of Jaspers and then Heidegger, she fled Nazism shortly after Hitler came to power to end up settling in the United States in 1941. Her political thought endeavours to decode – in particular in her book The Origins of Totalitarianism – the phenomenon of totalitarianism, seeing in Nazism and Stalinism obvious points of convergence. In addition she has examined without respite the soul of modern man, so frequently pulverized and thus become easy prey to anti-libertarian regimes. Finally, amongst the concepts she has introduced is that of ‘the banality of evil,’ brought to light during the trial of Eichmann in Jerusalem in 1961.


The Ariane programme aimed at providing Europe with the ability to launch satellites. The first designed model (Ariane I) had a take-off mass of 210 tons and was capable of placing 1.85 kg in orbit. Its first flight took place on 24th December, 1979. Eleven Ariane I rockets were fired between 1979 and 1986.

Other versions followed, allowing for larger and larger satellites to be placed in orbit. The first Ariane V flight took place on 4th June, 1996. Its take-off mass is around 750 tons and it can place satellites weighing over 9 tons in orbit.

Aristotle (384-322)

Greek philosopher who was first of all a disciple of Plato before distancing himself from him and becoming the tutor of Alexander the Great. Above all a scholar and teacher, he founded in Athens his own school, the Lyceum. His intellectual activity embraced every domain of thought, as the titles of his principal works signal: Physics, Metaphysics, Logic, Rhetoric, and Nicomachean Ethics. Setting himself against the Platonic world of Ideas – too abstract for his taste – he anchored his thinking essentially on the concrete or the material. The morality he moreover advocated, opposed to a too acute idealism, is that of the happy medium: the courageous attitude, for example, must as much avoid the foibles of cowardice as that of an unbridled recklessness.

Armed Israeli-Arab conflicts

1948-1949: Israeli-Arab war following the creation of Israel in 1948 1956: Suez Canal crisis 1967: The Six Day War 1973: The Yom Kippur War 1982: The first Lebanese war 2006: The second Lebanese war 2008-2009: The Gaza war Certain analysts add to this list the crushing of two large Palestinian uprisings by the Israeli army: the first Intifada launched in 1987 and the second Intifada in 2000. In this respect the 2009-2009 war in Gaza could be regarded as the third strictly Israeli-Palestinian conflict.


Enzyme that catalyses the transformation of androgens, such as testosterone, into oestrogens, such as oestradiol. Aromatase is significantly expressed in the ovaries but also in the brains of males and females in most species of vertebrates.

Aromatic Polycyclic Hydrocarbons (APH)

Aromatic polycyclic hydrocarbons are natural constituents of coals  and oils or which result from the incomplete combustion of organic compounds  such as fuel , wood or tobacco. They are present in the air, water or in food.

Aron, Paul (1956 - )

Professor of Belgian literature and French literature at the ULB, and research director at the FRS-FNRS. His work primarily concerns the history of the literary life and the genre of pastiche. He published Les écrivains belges et le socialisme. 1880-1913: L'Expérience de l'art social, d'Edmond Picard à Emile Verhaeren (1985), La Mémoire en jeu. Une histoire du théâtre de langue française en Belgique (1995). Le Dictionnaire du littéraire (2002) and Sociologie de la littérature (2006) were published as a collaboration, while Les 100 mots du surréalisme (2010) and Les 100 mots du symbolisme (2011) were a collaboration with Jean-Pierre Bertrand.


An acronym of 'Advanced Research Projects Agency Network', the first delocalised data packet transfer computer network, and thus the basis of transferring data over the Internet. It was developed in the USA in 1969. The first users were two universities, the first to be linked up in such a way, the University of California, Los Angeles campus (UCLA) and Stanford.

Arrhenius, Svante August (1859-1927)

Swedish chemist who carried out work on electrolysis and the speed of chemical reactions. He is mostly known today for his work on the growth of concentration of CO₂ in the atmosphere. He was the first who, in 1896, estimated that a doubling of this concentration would be translated by an increase in the average temperature of the Earth’s surface of aroun 5°C. Nobel Prize for Chemistry in 1903.


Goddess of the margins and the wilderness, who honours both hunters as much as young girls on the point of marrying, women in childbirth, and new mothers with their babies.


A branch of invertebrates which includes crustaceans, insects, arachnids etc. It is therefore the branch which groups together the most species and the most individuals of the animal kingdom.


Son of Apollo who, from being a hero-doctor, over the course of time became a genuine god-doctor.


The Ashkenazic culture is culture of Jews from Germany, Poland, Russia, the former empire of Austria-Hungary, and Central and Eastern Europe in general.

ASPCR (Allele-Specific Polymerase Chain Reaction)

A technique which makes it possible to detect a resistance mutation in small proportions (1 %) in a sample.


Contract by which the holder of intellectual rights (or other property) transfers all or part of it to a third party, whether or not quid pro quo.


A small deformed object of the solar system composed of rock and ice. We can distinguish two groups: those which evolve in the “main asteroid belt” (between Mars and Jupiter) and those which orbit in the “Kuiper belt” (beyond Neptune, called trans Neptunian objects or OTNs). Their size can vary from a few metres to several hundred kilometers.


Extreme fatigue that can be due to physical effort, prolonged stress or any other “normal” everyday situation, or a disease.


An incurable condition that affects the airways – the small tubes that carry air in and out of the lungs. An asthma attack can be triggered when a person with asthma comes into contact with something that irritates their airways (an asthma trigger, such as pollen or dust mites). Then the muscles around the walls of the airways tighten so that the airways become narrower and the lining of the airways becomes inflamed and starts to swell. Symptoms of the narrowing include wheezing, chest tightness, breathing problems, and coughing. Environmental factors such as pollen, dust mites, pollution, ozone levels and high levels of humidity are important, and genetic factors are also involved, though much work remains to be done for greater understanding of these hereditary factors to be reached.


Glial cells in the shape of a star found in the brain and more generally in the central nervous system.

Astronomical unit

It is the distance which separates the Earth and the Sun which comprises an astronomical unit. The distance is 150 million kilometres.

asymmetric warfare

This can be defined as the absence of any correspondence between the aims, objectives and means of opposing forces. An asymmetric war is a conflict which opposes combatants whose forces are incompatible; where military, sociological and political imbalance between the sides is absolute: a regular strong army against a guerrilla movement which is supposedly weak, a nation against a terrorist movement etc.


A straight line that continually approaches a given curve but does not meet it at any finite distance.

Workshop for research and urban action (Atelier de recherche et d’action urbaines - ARAU)

Since 1969, ARAU has never stopped mobilizing and generating energy on the part of Brussels’ citizens, all trying to get decisions about urban matters into the public eye and out of the secrecy of agencies, in order to make what is at stake for residents of the city public, and thus to give some meaning and vitality to the democratic process. ARAU stands for thinking and acting in the framework of a global and nuanced approach to the urban phenomenon, paying particular attention to realities on the ground that are part of the everyday life of the inhabitants of the city. The objective of ARAU is to bring greater transparency to decisions that affect the life of the city, and to continue to take positions on questions about urban development.


The daughter of Zeus, from whom she gained the cunning intelligence which she put into practice in the activities of war in order to protect the city.


American record company which today belongs to the Warner group. In the 1950s it in particularly contributed to making Rhythm & Blues popular. Over the decades it signed renowned artists such as Ray Charles, Aretha Franklin, Sonny & Cher, Crosby, Still, Nash & Young, ACDC, Dire Straits and Led Zeppelin.






A ring-shaped coral island in the tropical seas surrounding a lagoon.


From the Ancient Greek atomos, that which cannot be divided. The basic constituent of matter, an assembly of fundamental particles. A particle of a chemical element which forms the smallest quantity capable of combining with others. An example: the water molecule (H2O) contains 2 hydrogen atoms and 1 oxygen atom. An atom is formed by a nucleus and a cloud of electrons 40,000 times more extensive than the nucleus itself. The latter is made up of protons, with a positive charge, and neutrons, electrically neutral.

Atomic absorption spectroscopy

In analytical chemistry the atomic absorption spextroscopy is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. It can be used to determine over 70 different elements in solution or directly in solid samples employed in pharmacology, biophysics and toxicology research.

Atomic force microscope (AFM)

An instrument which allows the topography of a surface to be determined at the atomic level. It is equipped with an extremely small and sharp tip (some nanometres) placed on a flexible cantilever. This tip is both attracted and repelled by the atoms on the surface. These repulsion/attraction forces cause the tip to move, making the cantilever drift. These deviations are recorded and then transformed into topography. An ‘image’ of the surface is thus obtained, atom by atom.


The adenosine triphosphate is a molecule found in every living organism and which is in particular the main source of immediately available energy for cell activity.

ATP synthesis

ATP synthesis (adenosine triphosphate) is the last stage in cell respiration (during which the cells of all living organisms produce energy from organic molecules). This is a chemical reaction which takes place in the mitochondrial membrane, during which ATP is synthesised from ADP (adenosine diphosphate) and inorganic phosphate.

Attenuated virus

A virus whose pathogenic power has been weakened considerably, or totally eliminated, but which still stimulates the production of antibodies involved in the immune response to the pathogen.

Augustine (Saint) (354-430)

A Father of the Church and bishop of Hippo, in present day Algeria, whose immense philosophical work – situated at the crossroads of Platonism and Christianity – has considerably marked Western thought. With his Confessions first of all, the first autobiography in world literature; then with his The City of God, a book which makes of each individual the site where two kingdoms coexist: that of God, of immutable character and founded on love, and that of life on Earth, of an unstable nature and grounded on pride. Amongst the several of his ideas which prevailed after his death was that of predestination, according to which the salvation of each and all depends intimately on divine grace.

Aurora polaris

An aurora polaris is called an aurora borealis – or Northern Lights – in the Northern hemisphere and an aurora australis in the Southern hemisphere. It manifests itself through the appearance of coloured veils in the nocturnal sky and are caused by the interaction of charged particles sent out by the Sun (solar wind) and the upper atmosphere. They occur in areas close to the magnetic poles.

Auschwitz Birkenau

The largest Nazi concentration and extermination camps, located in Southern Poland. In five years more than one million deportees died there. 

Auto-immune diseases

Auto-immune diseases are due to a hyperactivity of the immune system, which attacks certain constituents of its own host as if they were foreign substances. The body then produces autoantibodies which are directed against the antibodies. It is in some ways a phenomena partial self destruction.

Autonoetic Awareness

According to Endel Tulving of the University of Toronto, this is the capacity of a person to be aware of his prolonged existence in time. Autonoetic conscience allows us to mentally «travel» in time in order to «relive»our past experiences and project us into the future.


The ability certain animals have to deliberately lose a part of their bodies, in particular certain reptiles and invertebrates. Certain rodents can also lose a part of their tails.


Organisms capable of producing organic matter from inorganic material. According to the etymology of the word 'autotroph' (from Ancient Greek: auto, self and trophos, nutrition), autrophy designates any living being which does not need another living being to feed itself. Autrophic organisms constitute the basis of every food chain.


An Oriental nomadic people, related to the Huns. Having emigrated from central Asia, they reached southern Russia around the middle of the 6th century, invaded present-day Hungary and Austria, and then launched raids on Bavaria in particular. They were finally defeated by Charlemagne during the Summer of 796.

Avicenna (980-1037)

A Persian philosopher who studied very varied domains in the field of knowledge, such as logic, linguistics, mathematics, physics, metaphysics and medicine. He greatly influenced both Islamic and Western culture. His Canon of Medicine had significant influence in Europe up until the 17th century.


Unique projection of a nerve cell that conducts electrical impulses away from the neuron’s soma (cell body) to a target. It is the nerve cell’s “lead cable”.

Azores High

An anticyclone is an atmospheric area of high pressure. The Azores High refers to such a semi-permanent subtropical zone in the North Atlantic. It influences the climate in eastern North America, western Europe and North Africa. Its centre moves from Bermuda (summer-autumn), hence its name the Bermuda High/Anticyclone in the USA, to the archipelago of the Azores (winter-spring), hence its name in Europe.

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