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
P
Pagan

A word which etymologically designates an inhabitant of the pagus (‘rural territory’) and which is also applied to followers of the polytheistic cults of the ancient Roman and Germanic religions, and then more widely, since the 3rd century, to ‘non-Christians.’ The common origin of the terms ‘peasant’ and ‘pagus’ is explained by the fact that the progress of Christianity was slower in the countryside than it was in the towns.

Pain (Nociception Coma Scale)

The question of pain is an essential one for patients in a minimally conscious state or for LIS patients, as it is known that they are faced with it. But when and according to what posology? Not only can these patients not say that they are in pain, but they are also incapable of signalling that they are no longer experiencing pain (whilst difficult, a form of communication is possible in LIS patients after a correct diagnosis of their condition). To get round this stumbling block the Coma Science Group team has developed a scale called the Nociception Coma Scale (1), inspired by the scales used on newborns and permanently bedridden dementia patients.

The Nociception Coma Scale, developed by Caroline Schnakers, allows the evaluation of pain to be standardised. It is graduated from 0 to 12. If the score obtained is 7 or higher at the end of tests which evaluate motor, visual and vocal responses as well as facial expressions, treatment must be administered. At first not very powerful analgesics will be given. The treatment will be progressively intensified until the patient’s score, re-evaluated, remains below 7.

(1) Schnakers C, Chatelle C, Vanhaudenhuyse A, Majerus S, Ledoux D, Boly M, Bruno MA, Boveroux P, Demertzi A, Moonen G, Laureys S, The Nociception Coma Scale : A new tool to assess nociception in disorders of consciousness, Pain 148 (2010) 215-9.

Paleo-oceanography

The study and reconstruction of the oceans and marine depths during the different geological eras.

Paléoanthropologique

Paléo, vient du grec palaios, qui désigne "ancien". Anthropologique, vient du grec anthropos, "homme" et logia, "science"

Palynology

From the Ancient Greek ‘palunein’, which means to ‘scatter’, palynology is the study of pollens and fossils. Archaeologists use palynology to date, trace or evaluate the context linked to an object or an era. This discipline also enables retrospective evaluations of the responses made by ecosystems to climate changes and to reconstruct ancient plant populations.

Pancreatitis

inflammation of the pancreas.

Pancytopenia

Lowering of levels of different blood corpuscles in the blood. More precisely it is the pathological and simultaneous reduction of red corpuscles (erythrocyte), white corpuscles (leukocytes) and blood platelets.

pandemic

An epidemic that extends to a vast geographic zone, for instance, a continent.

Panleucopenia

Diminution of the leukocytes (or white corpuscules).

Pantheon

With its origins in the Greek prefix pan (‘everything’) and the Greek name theos (‘god’), this term designates the whole of the divinities of a polytheistic system.

Papain

An enzyme present in the latex of papaya and pineapple. As a protease, it has the ability to fragment proteins.

Papillomavirus

Human papillomaviruses (HPV) are the viruses responsible for contagious lesions on the skin and mucus membranes (warts, for instance). Some lead to the appearance of cervical cancer in women.

Papyrus/papyrology

The word papyrus designates, firstly, a plant (Cyperus papyrus) once common on the banks of the Nile. In ancient times its stalks (similar to those of the elderberry) were cut into strips which were glued together to make leaves on which one could write. Hence, the second meaning of papyrus: the material that can be written on and the manuscript produced in this way. Papyrus made in Egypt was exported throughout the Mediterranean. Papyrology is the science of papyri.

Paramagnetic

Substances which, when placed within a magnetic field, become very weakly magnetic in the same sense or direction as the field.

parastatal (or paragovernmental)

An adjective and noun, from the Ancient Greek para, besides, next to, and the Latin status, the State. In a general sense this word can be considered a synonym of semi-public, para-public, on the fringes of the State. Frequently used in Belgian administrative law, this word designates organisations totally or in part confined to or controlled by the government. These public interest organisations are, more precisely, legal persons in public law created through or in accordance with a legislative Act. The budgets of these organisations have to be approved by the Chamber of Representatives. These bodies are divided up into four categories: A, B, C and D.

Type A public interest organisations are legally distinct from the State, but are subjected to the hierarchical line management of a Minister who exercises managerial powers. Examples: the Buildings Agency, the Federal Agency for the reception of Asylum Seekers (FEDASIL), the Federal Agency for the Safety of the Food Chan (AFSCA), the Federal Planning Bureau, etc.

Type B public interest organisations have a certain technical autonomy from an administrative and financial point of view, and an organic autonomy in terms of decision making and management, but are subject to the supervision of the Minister they are accountable to. Examples: the National War Invalids Institute, the Théâtre Royal de la Monnaie, the Fine Arts Museum, etc.

Type C public interest organisations, which exercise financial activity, have wide reaching autonomy. Examples: the National Export Credit Agency, the Insurance Ombudsman, the National Lottery, etc.

Type D public interest organisations carry out their activities in the area of social security. Their autonomy is more limited than that of the category C bodies. They are in principle subject to the joint management of the social security organisms. Examples: the National Social Security Office (ONSS), the National Employment Office (ONEM), the National Annual Holidays Office, the Accident at Work Fund, the National Office for Family Allowance for Salaried Employees, etc.

Paratype

Designates a specimen within a typological series other than the holotype, and which allows the intraspecific morphological variation of this series to be determined.

Parenchyma

Tissue assuring the essential functions of an organ (as opposed to the stroma).

Pareto, Vilfredo (1848-1923)

Italian sociologist known for his research on the concept of efficiency. In his “Treatise of General Sociology” (1916), he places logical action which is linked to the economy alongside non-logical action which is linked to sociology. He also prioritised the importance of elites and the concept of the “circulation of elites”.

Parkinson’s disease

a neurodegenerative disease characterised by shaking, a stiffness and slowness of movement whose initial causes remain unknown. It is the most frequent neurodegenerative disease as it affects 1% of the population aged over 50. It is described as a degeneration of the nerve cells of the central grey core (substantia nigra) and brings about a deficiency of dopamine secretion (see also the article ‘Dopamine at the service of movement’).

Parnassus

A French literary movement which emerged during the second half of the 19th century around the figure of Leconte de Lisle. The movement was opposed to Romanticism and the bourgeois idea of the individual. According to the Parnassian movement art finds it true meaning not in political commitment but in contemplation of the beautiful. There is no other outcome for art than the beautiful. The Parnassians thus looked for no utility for art and believed in the principle of ‘art for art’s sake’, from which arises the reference to Antiquity through the word Parnassus, the mountain of Apollo and his nine muses. The name appeared in 1866 when the first edition of Parnasse contemporain was published.

Parrêsia

A Greek word designating the freedom of expression, the frankness or the courage of truth. It was one of the fundamental rights of Greek democracy with isegoria (equality of speech) and isonomia (equality before the law).

Parsec

Unit of length used in astronomy corresponding to 3.26 light-years. A megaparsec corresponds to 3.26 million light years.

Parsons, Talcott (1902-1979)

American sociologist who elaborated the theory of the systemic functionalism of action. Among those who influenced his research were Freud and Durkheim.

Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Commonly used are ppm (parts-per-million, 10–6), ppb (parts-per-billion, 10–9), ppt (parts-per-trillion, 10–12) and ppq (parts-per-quadrillion, 10-15).

Pascal

The pascal is a unit of pressure. One pascal is equivalent to the uniform pressure which, when applied to a flat surface area of one square metre, exerts a total force of one Newton perpendicularly to it. The bar is another commonly used unit of pressure: one bar equals 100,000 pascal.

Pascal, Blaise (1623-1662)

A French mathematician, physicist and philosopher. Picking up on the work of the Italian Torricelli, he pronounced himself in favour of the existence of vacuums and wrote two dissertations on the equilibrium of liquids and the weight of air. He subsequently studied phenomena linked to gambling and in so doing sparked reflections on it which were at the origin of the calculation of probabilities. He then deepened the field of geometry, for which he sidelined the ancient organisation of Euclid, and tackled infinitesimal calculus. The final part of his life was more mystical; he devoted himself to faith and piety. He concluded that only faith in God and the hope for salvation can give meaning to existence. Betting on the existence of God and acting accordingly was thus the safest attitude to adopt.

Pastorius, Jaco (1951-1987)

A virtuoso bassist. He gave to the electric bass guitar, up until then a rhythmic instrument, its first badges of honour as a solo and melodic instrument. He had a solo career as well as playing in the Jazz Fusion group Weather Report.

Patent ambush

Also called ‘patent hold-up’, this ambush involving patents consists of a company which has participated in a process of standard setting to conceal patents or requests for patents, of which it is the titleholder and which are essential for the application of the standard, in order to refuse them to actors in the market after the standard has been adopted. The patent holder is thus in a position to demand users of the standard higher royalty fees than it would have received if the technology had not been standardised.

Pathogenicity

The capability of an organism (virus, bacteria) or a substance to cause a disease.

patriarch

A title accorded, from the 5th century, to certain Bishops of the Eastern Church whose sees were considered preeminent: Rome, Constantinople, Alexandria, Antioch, and Jerusalem.

patristic

Adjective derived from the Greek patêr (‘father’) and which concerns the Fathers of the Church, or the Christian writers of the early days – in other words generally up until the 6th century – who distinguished themselves through their orthodoxy and their doctrine and whose lives were considered as exemplary. Amongst the best known in the West are Saint Cyprian, Saint Hilary, Saint Jerome and Saint Augustine.

Paul-Henri Spaak (1899-1972)

Belgian politician. Elected as a member of parliament for the socialist party from 1932, he became a Minister in 1935 and Prime Minister in 1938. He was Foreign Minister in the Belgian government in exile in London during the war. After this, he followed a brilliant Ministerial career and was widely known on the international scene. Among other things, he was considered as one of the founding fathers of Europe. He was to be present of the General Assembly of the United Nations, President of the Parliamentary Assembly of ECSC (European Coal and Steel Community) and General Secretary of NATO.

pays de par-deçà

A name (translated as ‘countries over here’) distinguishing the ensemble formed by the northern territories of the Dukes of Bourgogne, in other words the Netherlands, from their southern territories, called ‘pays de par-delà,’ (‘countries over there), in other words Bourgogne itself and the Franche-Comte.

PBDE (polybrominated diphenyl ethers)

These are chemical products that act as fire retardants. They are used to protect plastic materials and textiles. They are found in large quantities in homes. They were very commonly used in the 1970s and 1980s for oil extraction. They are not soluble in water but can dissolve in fats, they are very volatile. They are biodegradable but only over a period of two years maximum and they are very present in the food web.

PCB

The PCBs or polychlorinated biphenyls are a family of 209 organochloride compounds, with a strong aromatic odour. They are very stable compounds which only decompose at temperatures higher than 1000°C. The PCBs are pollutants which can be persistent (a lifespan of between 94 days and 2,700 years, depending on the molecule) and which is capable of bioaccumulating in the fat of animals and notably humans, including in a mother’s breast milk. Widely used in the old days – mostly in electric material -  PCBs were banned from most countries at the beginning of the 70s. As the PCBs are stabile, we can still find some trace in the environment nowadays.

Pedicel

Part of a flower's stalk, located just beneath it.

Pedology

The science of soil. It is concerned with its origin, formation and development as well as its constituent parts.

pelagic

From the Greek pelagos, which means “in open sea”. The term is applied to a fish or organism such as plankton which lives in water close to the surface.

pelagic zone

Pelagic ZoneFrom the Greek, Pelagos, meaning the high sea. The pelagic zone of lakes, seas or oceans corresponds to the area comprising the water column in whivh live diferent species (pelagic, demersal, demersal benthic and benthic). Therefore, the pelagic zone doesn’t include water close to the coastline or the sea bed.

pelvic anteversion

Forward rotation of the pelvis. Contrary to retroversion which is a backwards movement.

Penal

From the Latin poenalis, of poena, punishments. Related to sentences and offences which bring about sentences. Criminal law is the ensemble of the regulations which determine offences (crimes, misdemeanours, minor offences) and the sanctions which are applied to them. Only decisions given in criminal cases can figure on a criminal record. Not on it are therefore judgements or decrees given in civil cases (e.g., a divorce), business cases (a bankruptcy) social cases, or cases of administrative law, etc.

Penicillin-Binding Protein

PBPs play an important role in the formation of peptidoglycan, a key component in the bacterial wall. These proteins are the targets of beta-lactamine type antibiotics, such as penicillin.

Peptide

Basic element of a protein, with several peptides forming a protein. A molecule consisting of at least two amino acids linked by a peptide bond, or a CO-NH bond, a result of condensation between the amino group (-NH2) of the first amino acid and the carboxyl group (-CO2H) of the second amino acid.

Peptide sequence

A peptide sequence is the chain of amino acids that make up a given peptide. The sequence is generally read from the N-terminal end to the C-terminal end. It can be expressed by using the name of the amino acid (example: Glycine-Asparagine-Valine), a 3-letter abbreviation (Gly-Asn-Val), or more commonly, a 1-letter abbreviation (G-N-V).

Perceived pubertal timing

Perceived pubertal timing is a relative term which corresponds to the physical development of individuals in comparison with their peers of the same sex and the same age (Angold & Costello, 2006).

Percolation zone

a zone situated in the accumulation zone (I.e. where the mass gained by snowfall is higher than the mass lost by surface melt in summer) where melt is observed each year but in which the meltwater percolates and then refreezes inside the snowpack without necessarily reaching the ocean.

Perestroïka

This word (which means ‘reconstruction’ in Russian) names the whole of the economic reforms carried out by Mikhail Gorbachov, the General Secretary of the Communist Party, in the USSR from the end of 1985. Its failure widely contributed to the end of the communist regime and the break up of the USSR in December 1991.

Périer, Odilon-Jean (1901-1928)

A Belgian French speaking poet who was born and died in Brussels. Born into a rich and cultivated bourgeois family, he was forced to abandon his studies at the Free University of Brussels, but quickly launched into literature in publishing La Vertu par le chant (1921) and Le Citadin ou Eloge de Bruxelles (1924). His poetry collections stand out for a research into language which in no way affects the concern for form. Prose poetry an also be picked out in Le Passage des anges (1926). In his short life he moreover mixed with Franz Hellens and Henri Michaux and, close to the daily realities of the city of his birth, he also shone because, amongst other things, the composition of the poem Je t'offre un verre d'eau glacée...

Perihelion

A heavenly body which orbits its star takes an elliptical orbit with the star at one of the two foci.  The point where the body is nearest its star is called the perihelion, while the point at which it is furthest from its star is called the aphelion.

Periosteum

Tissue which covers the bone. Periosteum has an important role in bone growth.

peripartum cardiomyopathy

Heart disease due to the dilation of the left ventricle of the heart which occurs in women who are in the latter phases of pregnancy or six months following the birth of their babies. The disease is infrequent in Europe (1 case in 3,500) but is frequent in Africa and it affects one in three hundred individuals in Haiti.

Peripheral nervous system

The peripheral nervous system is made up of the complex of nerves attached to the central nervous system. There are two kinds of peripheral nerves, cranial nerves and rachidian nerves. We distinguish two peripheral nervous systems: the somatic nervous system (motor and sensation) and the vegetative (autonomous).

Peritoneum

Membrane covering the abdominal cavity and the exterior of the internal organs. Inflammation of the peritoneum is called peritonitis.

permafrost

Soil that is permanently frozen and is therefore impermeable. Since its dynamics are linked to climatic variations, permafrost is studied within the framework of research on climate change. In some places, for instance Siberia, the permafrost is thawing and is releasing large amounts of greenhouse gases.

Perovskite structure

A cubic structure whose form is seen in many ABO3 oxides, in which the A atom is at the corners of the cube, the B atom in the middle, and the oxygen atoms in the centre of the face edges. Identified for the first time in the form of CaTiO3, this structure is named after the Russian mineralogist L. A. Perovski (1792-1856).

persistent organic pollutants (POPs)

A set of organic substances which have four different properties. They are persistent which means that they degrade slowly. They are bioaccumulative, that is to say they accumulate in living beings and cannot dissolve in water. They are toxic and can travel over long distances. They are found as far away as the Antarctic. Some of them are now banned in most countries of the world. This is the case with PCBs and DDTs. Others have not yet been banned. Examples of these are pesticides, industrial chemical substances or accidental by-products of industrial or other processes. Twelve of them have been recognised by the United Nations as very dangerous chemical substances because their effect on human and animal health is considerable. Les POPs can cause lesions of the central and peripheral nervous system, reproductive and immune system disorders.

Pesticide

A chemical substance aimed at driving back or combating pests or undesirable plant or animal species which cause damage to farming products.

Petri dish

a cylindrical shallow transparent container made of glass or plastic containing a cover and which is used in microbiology for growing micro-organisms.

Petrochemistry

Petrochemistry is the science which focuses on the fabrication of synthetic materials (such as plastics) from the chemical derivatives of petrol.

Petrography

science which focuses on the description of rocks and the analysis of their structural, mineralogical and chemical structures.

Petrology

The scientific study of rocks, their formation, their structure and their constituents.

Phage

Abbreviation of bacteriophage. Any virus that infects bacteria and can destroy them. Bacteriophages have a high level of specificity not only in a certain group of bacteria, but also in a species or even a bacterial strain.

Pharyngeal teeth

The pharyngeal teeth of the clownfish are located within the branchial arches. In some species they are used to chew food, whilst in others they can be compared to a treadmill which carries food into the oesophagus. Fish also possess buccal teeth whose principal role is to grip food.

phenol

Molecule whose industrial production is confined mainly to the fabrication of plastics.

Evénements périodiques dans le monde végétal (floraison, feuillaison des végétaux). ">

Evénements périodiques dans le monde végétal (floraison, feuillaison des végétaux).

This refers to periodic events in the plant kingdom (flowering, coming into leaf of plants).

Phenotype

The ensemble of the corporal characteristics of a living organism. It is the morphological expression of certain elements of the genotype.

Pheromones

The term pheromone – from the Greek pherein (to carry) and hormân (excite) – was introduced in 1959 by the German biochemists Peter Karlson and Martin Lüscher, who gave it the following definition: ‘A pheromone is a substance (or a mixture of substances) which, after having been secreted by an individual (emitter), is perceived by an individual of the same species (receiver) in which it produces a specific behavioural reaction, even a physiological modification.’ Pheromones are thus chemical substances comparable to hormones; they are emitted by most animals and certain plants. They act as messages between individuals of the same species, transmitting to other organisms information which plays a role, notably in sexual attraction.

phocidae

Family including trueseals, leopard seals and elephant seals.

Phoneme

The smallest sound unit of a spoken language. Thus the word ‘flag’ consists of four phonemes: ‘f’, ‘l’, ‘a’ and ‘g’.

phoniatrics

The medical field focused on diagnosing and curing voice disorders.

phonogram

In hieroglyphic writing, the phonogram is a figurative character that no longer has any semantic value. It is the arbitrary transmission of the phoneme. Its value is only phonetic and it serves only to transmit oral speech. For example, take a hieroglyphic sign that represents a house; if it is employed as a phonogram, it will be uniquely attached to the phonetic value /pr/ and it will be present in a word that does not at all suggest the idea of a house. Thus a restricted list of uniliteral phonograms would have allowed Egyptian civilization to come up with an alphabetic system, if the need or desire for such a system had been great enough.

Phonological neighbour

A word similar to the target word which differs by a single phoneme.

phoretic

Refers to an association between two organisms where one (the phoront) is transported by the other (the host). This association benefits both sides.

Phosphate

A salt formed by phosphoric acid combining with a base. Phosphates are produced by the replacement of all or part of the hydrogen in phosphoric acid with metals.

Phosphorylation

Addition of a phosphate group (PO4) to a protein in one of the three potential phosphorylation sites or amino acids: serine, tyrosine or threonine. The phosphorylation of a protein often profoundly changes its activity as an enzyme or a receptor.

Photobioreactor

An apparatus that allows fine control of various parameters that influence the growth of photosynthetic microorganisms, and of the photoproduction of hydrogen.

photolysis

In chemistry, photolysis is a reaction during which a chemical compound is decomposed by light. The photons are carriers of a sufficient amount of energy to separate the atoms assembled into molecules.

photometry

The observation of the transit of a planet by photometry (mesurement of the light intensity) aims to detect the presence of the planet  in question by the variation in the luminous flux of its star when it passes between the star and the observer. Telescopes that operate by means of photometry do not cover the entire light spectrum, but rather cover certain precise wavelengths (visible, near infrared, etc.), which make it possible to give different indications on the planet. According to the wavelength, photometry can give indications about the presence and composition of an atmosphere, for example (its gas or metal content or whether it is hazy or not).

This technique is therefore ideal to find new planets, or study smaller bodies such as asteroids or comets. In both cases, it is possible to establish a good estimate of their size.

The more a planet is observed during its transits at different wavelengths, the more its luminous spectrum will be precisely known, and the more researchers will be able to learn about it. The MOST satellite, for example, observes the variation in the luminous flux at wavelengths of around  0.5 microns, like the human eye. The Hubble satellite makes it possible to record the spectrum between 1 and 1.6 microns, in the infrared, while Spitzer make possible a photometric observation at 3.6 and 4.5 microns, still in the infrared.

Photometry simply takes into account the light intensity of a star and should not be confused with spectroscopy, which separates light into different wavelengths. Depending on the absorption or the emission of light by the material, it enables us to work out the chemical composition of the object observed.

Photon

A quantum of electromagnetic energy carrying light.

Photoperiod

Time during a day from dawn to dusk; the number of hours of daylight.

Photophysics

Photophysics studies the interactions between light and matter. It finds itself at the basis of a good number of events which all in all are quite everyday: sight, photography, radiology, microscopy, astronomical observations, scanners, etc.

Photosphere

A great orange peel, the photosphere is a thin surface layer which covers the stars. The Sun's photosphere has a thickness of 200km, whilst its rays are of the order of 700.000km. Its average temperature is in the neighbourhood of 6000°C.

Sun Layers

Photosynthesis

Process that allows plants to synthesise their organic matter from light energy (solar or artificial).

Phylogenetic tree

A diagram in the form of a tree which shows the family relationships between living organisms. Each node of the tree represents the common ancestor of its descendents. Charles Darwin was one of the first scientists to offer a history of the species in the form of a tree.

Phylogeny

A study of the family relationships between living beings, with a view to understanding their evolution. It is based on the identification of homology, in other words the resemblances between organisms, at a morphological level (the only way of classifying fossil species whose DNA is recently preserved) or a molecular level (DNA, proteins). The results are represented by a phylogenetic tree or a cladogram in which each node corresponds to a common ancestor. Two organisms are all the more related if they share a common ancestor close by in the tree.

phytopathology

This is the study of plant diseases. It is divided into several disciplines and concentrates on the diagnosis of diseases or deals with the study of pathogens from an epidemiological point of view. It can also involve the study of the interaction between the plant and the pathogen. This type of study makes it possible to find ways of fighting disease used by the plant and which can be adapted by mankind in order to stem the tide of certain diseases. This type of research makes it possible to replace traditional pesticides while minimizing losses in crop yields.

Phytoplancton

Or plant plankton (in opposition to zooplankton). This term groups together the ensemble of the eukaryote and photosynthetic unicellular organisms (above all unicellular and filamentous algae). The phytoplankton produces the greatest part of the oxygen we breathe. It also plays an essential role in climate feedback, as it sucks up the CO2 (greenhouse gas) from the air.

Phytoremediation

A technology which uses plants to clean up soils.

Picard, Edmond (1836-1924)

A Belgian francophone jurisconsult and writer, born in Brussels and died in the neighbourhood of Dave, which is today a part of Namur. After brilliant studies at the Free University of Brussels, he began a career as a lawyer, established the Pandectes belges (encyclopedia of Belgian legislation, doctrine and jurisprudence and created the Journal des tribunaux. But his activities were not restricted to law: his passion for letters led him to found r L'Art moderne in 1881, a journal which defended the idea of a national literature and a social art setting itself up against the conception of art for art’s sake advocated by the authors of Jeune Belgique. But this personality, which was omnipresent in his time – he was a law Professor, journalist, patron, socialist senator and welcomed as interns the major intellectuals of his era, and moreover anxious to theorise the ‘Belgian spirit’, was also a notorious anti-Semite.

Piccard, Auguste (1884-1962)

 

Physicien suisse, professeur à l’Université Libre de Bruxelles à partir de 1922. Le 27 mai 1931, il s’élève en ballon libre dans la stratosphère, atteignant l’altitude de 15.781 mètres. Il conçoit également des sous-marins pour plongées à grande profondeur (10.916 m dans le Pacifique), les bathyscaphes.

 

Piccolomini, Enea Silvio (1405-1464)

A humanist and poet, he was born in Sienna and died in Ancona (1405-1464). Educated in Tuscany, then a hotbed of humanism, he became Pope in 1458 under the name of Pius II. Apart from a rich diplomatic life and the activities he carried out during his pontificate, he remains known for prolific literary work, written in Latin, notably composed of chronicles, a treatise on the education and upbringing of children and what has been termed an erotic tale (De duobus amantibus).

Picoeukaryote

Also called picoplanktonic eukaryotes, the picoeukaryotes represent the fraction of plankton consisting eukaryotic organisms which have a size between 0.2 and 2µm.

piezoelectric

A material capable of being distorted under the effect of a difference of potential or, reciprocally, generating a voltage when deformed. Used in ultrasound imaging in sonars and to manipulate AFM peaks.

Piezoelectric

A material is piezoelectric when it can be distorted when in an electric field. Conversely, the distortion of a piezoelectric crystal generates a difference in electric potential at its terminals. The piezoelectric effect is at the root of many applications, such as sonar and ultrasound.

pigments

Colouring substance, insoluble in the medium it is used to colour. This insolubility distinguishes pigments from colorants or dyes. Pigments can be natural or synthetic.

pilot whale (Globicephala melas)

Its Latin name means “globulous head”. Equipped with a very long pectoral fin, this cetacean belongs to the same family as dolphins. It is present all year round in the Mediterranean. An adult male can reach up to six metres in length and weigh up to 3.5 tonnes.

Pilote

A comic trip magazine founded in 1959, a weekly at first, before becoming a monthly in 1974. From 1963, and with René Goscinny (the author of Asterix and Obelix) occupying the position of editor in chief, the magazine set itself apart from Tintin and Spirou by progressively offering comic strips aimed at older teenagers and young adults. After being very successful at first, the magazine died out like so many others and stopped of its activities in 1989.

Pinelli, Joe Giusto

Joe G. Pinelli (Bertrand Dehuy, by his real name) is a Belgian comic strip illustrator and writer born in 1960. In the 1980s he became the pioneer of autobiographical and autofiction comic strips.

Piron, Maurice (1814-1986)

Former professor of dialectology, Walloon literature and French literature at the University of Ghent and at the ULg. He is a specialist in the poetry of Guillaume Apollinaire and the writing of Georges Simenon, and in francophone literatures. He published the Anthologie de la littérature dialectale de Wallonie (1979) and a collection of articles entitled Aspects et profils de la culture romane en Belgique (1978).

Placebo

The simple fact of receiving a treatment may have an influence on symptoms, regardless of the biological effects of the administered substance. This is called a placebo effect. In clinical experiments, it is essential to determine the effects linked to the treatment and those that are linked to the placebo effect. Therefore, it is common practice to compare the effects of the substance to be tested with those of a preparation with no biological effect but which looks exactly the same at first glance. This is a placebo. Neither the person taking part in the experiment nor the experimenter know whether the product administered corresponds to the drug or vaccine to tested or the placebo. This is called a double-blind test.

Placenta

All the tissues and blood vessels from which an embryo takes all the nutrients it needs. It contains both the mother’s blood and the foetus’ blood. But the two never come into contact with each other, separated by the hemato-placental barrier. The placenta plays the following roles: - to feed and oxygenate the foetus; - to eliminate the toxins (urine, carbon dioxide, etc.) produced by the foetus since the organs that perform these roles (kidneys, liver) are not yet able to do so; - to act as an immunological shield, i.e. to prevent the microbes from getting through. However, substances pass through this barrier such as certain types of medication, certain viruses (aids, rubella, etc.) and pollutants such as tobacco, alcohol and drugs.

Plaminogen

Inactive plasmatic protein involved, once activated, in numerous biological processes, including the coagulation and activation of growth factors.

Plankton

(From the Ancient Greek planktos – drifting). The ensemble of aquatic organisms drifting on the surface of water flows, living in fresh, brackish or salt waters. They depend on vertical or horizontal currents to move about. We distinguish between three large plankton groups: phytoplankton, zooplankton and bacterioplankton (essentially composed of bacteria).

Plantin, Christopher (1520-1589)

An Antwerp printer and bookbinder, he was born near Tours and died in Antwerp. From 1555 he printed classical, learned and religious works, including a polyglot Bible in eight volumes. His ‘Officina Plantiniara’, preserved in its actual state since the sixteenth century, has become the Plantin-Moretus Museum in the Sheldt metropolis.

plasma

Plasma is one of the four fundamental states of matter, the others being solid, liquid and gas. The matter becomes plasma when heated at a very high temperature (more or less 2000°C depending on the matter).

Plasma cell

Variety of leukocyte-type blood cell  which produces antibodies in the Immune system

Plasmide

A DNA molecule in bacteria, other than chromosomal DNA. Plasmides are not necessary for the survival of bacteria and reproduce autonomously.

Illustration of a bacterium with plasmid enclosed showing chromosomal DNA (1) and plasmids (2).

platelets

Small cell fragments in the blood produced in the bone marrow, which intervene in the coagulation process. Also called thrombocytes.

Plato (428-348 or 347)

Greek philosopher. A disciple of Socrates, he created at Athens the Academy, where he taught whilst writing and publishing his dialogues in which tackled the great philosophical problems. Amongst his 28 works recognized as authentic The Republic stands out, devoted to the organization of the ideal city, as does The Banquet, a search into the nature of love. He devotes to courage a dialogue, The Laches, subtitled precisely ‘on courage.’ As for The Apology of Socrates, Phaedo and Crito, they describe the trial and death of his master. His thought is principally known for his concept of Forms or Ideas, abstract entities beyond time and space, pre-existing through the very fact of their ephemeral inscription into the daily life of human beings. An individual’s courageous act, for example, proceeds from the very essence of the universal and indestructible concept of courage.

Pleistocene

the first geological era of the quaternary. It lasted from 2,000,000 to 10,000 years B.C. This era includes the appearance of Homo erectus, the golden age of mammoths, wooly rhinoceros, sabre-toothed tigers and the famous ice age which covered Europe up to 30,000 years ago.

polar

Tthe polarity of a molecule is due to the difference in electronegativity (ability to attract electrons during a chemical combination) between the elements it is composed of and their distribution in space. The more electrical charges are distributed in an asymmetrical manner, the more the molecule is said to be polar. Conversely, if the charges are perfectly symmetrical and cancel each other out, they are said to be apolar.

Polieus

That which relates to the polis.

Polis

A specific term which, since the archaic period at least, designates a Greek City-State, in other words a city and its territory.

polygenic

Relating to a disease or characteristic whose appearance depends on the expression of several genes.

polymer

Macromolecule formed by the stringing of monomers. A copolymer results when the monomers are different and homopolymer when they are the same.

Polymer

A polymer is a molecule with a very high molecular weight, composed of elements that have weak molecular weight.

Polymerase Chain Reaction (PCR)

Polymerase Chain Reaction is an in vitro molecular gene amplification technique which allows significant quantities of DNA or RNA sequences to be produced from a small quantity of nucleic acids.

polymerization

Repeated addition of small molecules, called monomers to each other in macromolecules called polymers.

polymorphism

Refers to the possibility of different arrangements of molecules within the elementary lattice of a given crystalline compound.

Polymorphism

A property individuals of the same species have to be different from each other. Genetic polymorphism is expressed by the fact that several alleles can exist for the same gene.

polyphenols

The polyphenols or phenolic compounds are organic molecules present in plants. They are part of vitamin E and vitamin C, the best-known antioxidants. They are widely used in supplements and nutritional complements containing antioxidants. Among the polyphenol are the flavonoids, for example, which are found in red wine.

Polytheism

A system that conceives of the superhuman world in plural form. However, the ancient Greeks did not define their religion in this way. What we call Greek polytheism is a set of cultural practices and representations of the divine world which went across the whole of Hellenic society, flying in the face of the usual distinction between religion and laity, sacred and profane, public and private. In this multi-god system, deities are not simply juxtaposed with each other; their respective abilities are intertwined. Polytheistic language links deities to each other in configurations which vary according to places and circumstances, for which reason a deity cannot be studied in isolation.

Polyvalence (in ancient Greek religion)

The plurality that characterizes the divine world of ancient Greece is also found in each deity. The multiple abilities of a god, and the innumerable faces through which he is feared by the Greeks, constitute a veritable, well-linked, cohesive network. This network is a deity’s polyvalence.

Ponchon, Raoul (1848-1931)

French poet and writer, he was one of the founders of the Vivants.

Pontiff

Originating from the Latin pontifex, this word designated for the Romans ‘bridge builders,’ maybe in the sense of those thanks to whom prayers and rites reached the residence of the Gods. Already under the Roman Kingship, the college of Pontiffs, or ministers of the cult, occupied the high echelons of the leadership of the Roman religion. And under the Empire, from Augustine onwards, all the Emperors carried the name ‘Great Pontiff.’ The Catholic Church reserved the title Pontifex maximus – or Sovereign Pontiff or Roman pontiff – for the Bishop of Rome, the Pope, whilst the term ‘pontiff’ more generally refers to Episcopal Dignity.

Populism

A polemical discourse pitting the honest, hard working and homogenous people against lazy, dishonest and minority elites. Populism proposes to do away with intermediaries and mediations between the people and the exercise of power and promises a society in which the popular will would coincide on a daily basis with its being effective carried out.

porphyrin

A molecule involved in the transport of oxygen and which can play a role as a co-factor of certain enzymes.

Poseidon

The brother of Zeus, who received a share of the sea, but who also exercises his powers within the very depths of the Earth, which he shakes when moods of anger take him over.

Positive discrimination

A concept born in the United States in the 1960s-70s the purpose of which was to favour the integration of black and Hispanic minorities. The measures taken gave priority to members of these groups over white people through a system of quotas.  Positive discrimination therefore refers to a set of measures aimed at making up for certain inequalities and favouring one group over another. Some people object to this system, claiming that these measures are ineffective and lead to the stigmatisation of the group in question. The categories of people involved can be defined according to gender, ethnic, religious, socio-economic, cultural, territorial or linguistic criteria. In Europe positive discrimination measures exist but the criteria never apply to religious affiliation or ethnicity.

Positron

Positron is the antiparticle linked to the electron – same mass, same spin, with an equal but opposite charge (positive).

potassium hydroxide

Also known as “caustic potash”. This is a chemical compound used for a large number of industrial applications. Its most important use is for the production of saturated potassium carbonate which is used mainly for the fabrication of special glass including television tubes.  This compound is also used in food, soaps, dyes and pigments, anti-scaling agents, substantive dyeing and fabric printing. Very soluble in water and alcohol, it is a powerfully corrosive agent which has been known to be a potent poison since antiquity.

potestative

We speak of potestative conditions when the coming into being of an obligation or its execution depends entirely on the will of only one of the parties

Potvin, Charles (1818-1902)

Historian, writer, journalist and critic of Belgian literature. He has authored a number of patriotic poems and essays, many short political or literary works, and the “Aperçu général de l'histoire des lettres en Belgique”, which appeared in Nos premiers siècles littéraires, choix de conférences données à l'Hôtel de ville de Bruxelles dans les années 1865 et 1868 (1870).

Poulet, Robert (1893-1991)

A Belgian francophone writer, literary critic and journalist, born in Liège into a Catholic petit-bourgeois background and who died in Marly-le-Roi in France. After a turbulent, resolutely non-conformist childhood, he made a name for himself in 1931 with the publication of Handji ou la femme illusion, a novel which recounts the lives of soldiers on the Russian front during the First World War. This oeuvre led him to be considered as the creator of a new literary genre, in other words magic realism, in which reality and the invisible world are brought together. Over the course of the Second World War he founded the daily Le Nouveau Journal and advocated a collaboration policy with the Nazi occupier. Arrested and sentenced to death in 1945, a punishment commuted to exile, he established himself in the Paris region without for all that abandoning his extreme rightwing convictions (essays and articles in the weekly Rivarol, publishing Louis-Ferdinand Céline’s Pont de Londres, etc.).

Poussin, Nicolas (1594-1665)

French painter who spent his productive years mostly in Rome. He is considered to be a major exponent of classicism. He invented a new pictorial genre during the 17th century: the “ideal landscape”. In his paintings, nature and human beings are represented in majestic fashion, and are intimately bound up with one another, and thus reconciled.

Pre-Raphaelites

A group of English painters (William Hunt (1827-1910), John Everett Millais (1829-1896) and Dante Gabriel Rossetti (1828-1882)) who in 1848 determined to distance themselves from all forms of academism and return to Gothic art as well as to the Quattrocento, thus before the work of Raphael (1483-1520). These artists were innovative, as much for the meticulous pictorial style as for the themes they drew from various cultures’ stock of legends. Bourget (1852-1935), in his novel L'Irréparable (1883), identified the group as ‘the paragon of modern aestheticism.’

Presley, Elvis (1935 - 1977)

American singer and actor. Born in 1935 and died in 1977. In 1954, he recorded an album at the Sun studios and became one of the first legends of Rock & Roll.

prevalence

The number of individuals affected by an illness, for example, in a given population at a given moment in time.

Prevalence

Numerous diseases, or any other medical event, recorded in a determined population and including new cases as well as the old ones.

Primary

Adjective designating that which is of the first degree, of what concerns a beginning. Attached to the substantive delinquent, it designates the person who commits a misdemeanour for the first time. By opposition the recidivist delinquent is one commits the same offence for the second time, or commits another one.

primary atmosphere

The primary atmosphere is a gaseous envelope that a planet has captured during its formation from gases present in the protoplanetary nebula as distinct from the secondary atmosphere.

Primary cerebral tumour

Primary cerebral tumours are those which develop in the specialised cells which constitute the brain and its envelope. Metastatic cerebral tumours come from another organ such as the lungs, the breasts, the kidneys or the skin.

primary energy:

Energy that can be used without being transformed, mainly thermal and mechanical energy; electrical energy is a secondary form of energy (for example, the mechanical energy of a river has to be transformed to obtain electrical energy).

Primary lymphoid organ

Organs where specific cells called lymphocytes mature. Among these organs are: the thymus gland, bone marrow, lymph nodes, amygdales, Peyer’s patches (in the small intestine), the appendix and some parts of the skin and mucous membrane. (source : vulgaris-medical)

Prime number

A prime number is an integer that can only be divided by 1 and itself.

Prince (1958 - )

American singer, multi-instrument player and producer. He was born Prince Rogers Nelson  in 1958 and was musically active from 1978 onwards: he achieved international success with the album Purple Rain. He was one of the first to break up the codes of music distribution, in offering an album on the internet at the end of the 1990s, and then in 2007 offering another album (Planet Earth) to the readers of the English newspaper, the Mail on Sunday.

Principle of precaution

The principle of precaution is a guarantee against potential risks that are not yet identifiable given the actual state of our knowledge. This principle affirms that in the absence of formal scientific certainty, the existence of a risk of serious or irreversible damage imposes a responsibility, that some means of warning should be provided prior to the beginning of such damage.

Probabilistic inference

Inference is a logical operation by which one accepts a proposition in accordance with its link with other propositions already held to be true. Probabilistic inference thus combines a degree of probability to a proposition, action or event in conjunction with another proposition, action or event.

prodromal

Relating to prodrome, an early symptom indicating the onset of a disease or illness.

projection neuron

Neurons whose axons project towards one or several structures of the central nervous system situated at greater or lesser distances from their  somas (central parts of neurons).

Prokaryotes

Prokaryotes are living organisms whose cells, unlike those of eukaryotes, do not have a nucleus.

prolactin

Hormone secreted by the anterior pituitary. In women, it triggers and maintains the lactation process, among other things.

pronotum

Dorsal surface of the 1st thoracic segment of an insect (situated behind the head).

Propellant

A substance, or combination of substances, whose decomposition or chemical reactions generates the energy for rocket self-propulsion.

Property law

The very definition of the word “property” is complex. Authors are divided over it: some only see it as covering tangible assets, whereas others include intangible assets, including certain rights. For ordinary mortals, it can be defined as any asset that is part of a person’s patrimony. New assets have appeared that aren’t always easy to classify, which has an effect on the effectiveness of their legal regime For example, the emissions quotas in the Kyoto Protocol: they can be exchanged, bought and sold, so it should be possible to classify them as property...but in which category?! Symposiums regularly deal with these new assets but it is very difficult to know which legal regime they fall under.

Prostaglandin

Prostaglandins are fatty acids produced by cells. They work as mediators to stimulate adjacent cells. The signals they send activate the cells, increasing or reducing cell reactions.

prostate

A gland of the male genital apparatus which secretes part of the seminal liquid, one of the constituents of sperm.

Prostates

Originating from the Greek ‘prostatês’ (‘that which stands before’), this word designates a college of five elected magistrates, responsible for the administration of the city, whose existence is known on Kos and other Doric cities.

Protease

Enzyme that breaks the protein peptide bonds

Protein

A molecule consisting of chains of amino acids linked together. Proteins determine the greatest part of living organism’s cell structures and functions. In this respect they are considered to be the major tools of the living world.

Proteolysis

Protein degradation.

Proteolytic Enzymes

Enzymes, also called proteases, which break the peptide binding of proteins.

proteome

The entire set of proteins expressed by a genome, a cell, a tissue, an organ or an organism.

proteomic

Relating to the proteome, the set of proteins expressed by a genome, cell, tissue, or organism.

Proterozoic era

The Proterozoic is a geological era which on its own covers nearly half the history of the Earth as it stretches from 2.5 to 0.5 billions of years ago. It is marked by the oxygenation of the oceans and the atmosphere, giving rise to a complexification of mono and pluricellular forms of life.

Protestantism

A doctrine of Christian churches stemming from the Reformation. Despite the large diversity of Protestant churches (Lutherans, Calvinists, Anglicans, etc.) and their independence, they are united by a number of characteristics. It is thus that Protestants consider the Bible as the sole source of faith and try to eliminate from religion everything that is not prescribed by the scriptures and the church’s early fathers, those most close in time to the apostolic era. It is for that reason that they translated and disseminated the holy texts in vernacular languages and encouraged education for the people. It is also generally agrees that, in Calvinist areas above all, the importance placed on personal judgement encouraged the appearance of democratic forms of government and that the abolition of the authority of the clergy opened up the path to modern capitalism.

Protist

A eukaryotic unicellular organism that may be similar to plants (such as diatoms), but may also be similar to animals (such as amoebae).

Protists

In order to classify the 30 million living organisms which today exist on the Earth, biologists group them together on the basis of their relatedness over the course of evolution. They are divided into three domains and six kingdoms. The first two domains, Archea and Bacteria, gather together the prokaryotes, unicellular organisms whose cell has neither a nucleus nor any other internal compartment. Each of these domains contains just a single kingdom, the archaebacteria and the eubacteria. The third domain, the Eukarya, brings together unicellular eukaryotes (a cell with a nucleus and complex internal compartments called organelles). This domain is divided into four kingdoms: the protists, the fungi, the plants and the animals (including human beings). The protist kingdom groups together the unicellular organisms and it is thought that the three other kingdoms (whose members are generally pluricellular) come from the protists.

Protocols of the Elders of Zion

A forged piece of anti-Semitism, a complete fabrication put together in Paris in 1900-1901 by the Tsar's secret police service, whose foreign section was led from the French capital by Pierre Ivanovitch Ratchkovski. This document presented itself as the minutes or an account of secret meetings of the leaders at the highest level of ‘global Judaism’; it was supposed to reveal their programme for world domination and, at the same time, to warn the Russian leaders – and more widely the worldwide population – against the bosses of these supposedly dangerous conspirators.

Protoplanetary disk

A disk of gas and dust which surrounds a young star and in which planets will be formed.

Protozoan

Unicellular eukaryote micro-organism without cellular wall.

protractor muscle

A muscle that operates the protraction, which tracts, or pulls forward. Like the protraction of a tongue, for example.

Proudhon, Pierre-Joseph (1809-1865)

French journalist, economist, philosopher and sociologist. Member of the First Socialist International. He held that “property is theft”, but believed that the social revolution could be carried out peacefully. He was opposed to profit, to worker exploitation and even to public property, and he rejected both capitalism and communism, preferring the form of associations called mutualism. For Proudhon the goods produced by cooperatives or individuals should be exchanged by persons, using barter instead of money; the State was supposed to be limited to a federation of “free” municipalities (communes).

Proust, Marcel (1871-1922)

A French writer and author of Remembrance of Things Past, a novel written between 1908-1909 and 1922 and published between 1913 and 1927. More than the narration of a sequence of given events, this work is interested in the memory of the narrator: his recollections and the connections between them. In the framework of Recherche are mounted Swann’s Way (1913), Within a Budding Grove (1919) and Time Regained, a posthumous work which appeared in 1927.

psychological perspective

In sociology, there are two main currents that attempt to explain the receptivity of members of society and their capacity for action. There is the sociological perspective on the one hand, which is deterministic and claims that the environment influences the individual without any possibility for the individual to reclaim this environment. He or she therefore passively submits to this influence. The psychological perspective, on the other hand, considers that the environment does have influence as part of a social heritage, but it may be reclaimed by individuals in light of their own experiences. Thus individuals are not seen as passive receptacles. The social construction of an individual is accomplished through negotiation between heritage and experience.  

The advantage of the sociological perspective is that places the actions of individuals in a larger context. It allows us to make generalities that don't consider the complexity of a group's existence, but can reveal major trends and allow us to move forward more quickly with quantitative studies. The psychological perspective is based more on the individual’s experience. No generalities are possible, but it ensures that data is more complete and complex, and is the preferred methodological tool in qualitative studies.  

Ptolemy V

Pharaoh of the dynasty of the Ptolemies, the last Egyptian dynasty. He was married to Cleopatra I and reigned from 204 to 181 B.C.E.

Pulitzer Prize

It takes its name from Joseph Pulitzer, an American journalist of Hungarian origins (1847-1911). In 1883 he bought the New York World. He subsequently founded a journalism school at the University of Columbia (New York), which has since 1917 annually awarded Pulitzer Prizes, encouraging excellence in literature and journalism. The fields of music and theatre have been subsequently added. All in all 24 categories are considered amongst the four branches. To receive a Pulitzer Prize in literature, music or theatre it is necessary to be an American citizen. The journalism Prizes can be attributed to any journalist who has had an article published in an American newspaper.

Pulmonary alveoli

These spherical outcroppings of the respiratory bronchioles are the primary sites of gas exchange with the blood. In the alveoli, the air releases part of its oxygen to transform the dark red venous blood into bright red arterial blood. This transformation is called haematosis. Carbon dioxide enters the alveoli and is evacuated through expiration.

Putin, Vladimir Vladimirovitch (1952 - )

Russian statesman. A member of the KGB, he spent five years in the GDR (German Democratic Republic) from the year 1985. In 1991 he became the international affairs advisor to the Mayor of Saint Petersburg, and then became one of the close advisors to the President of the Russian Federation, Boris Yeltsin, who in 1998 nominated him the Director of the FSS (Federal Security Service, the body which succeeded the KGB), and then, one year later, the President of his government.
President of the Russian Federation from December 31, 1999, to May 7, 2008, he carried out a policy of reforms marked by a recovery of the national economy and an institutional politics geared towards a concentration of Presidential powers.
In 2008 the Constitution forbade him a third consecutive Presidential mandate and he supported his government’s Vice-President, Dimitri Medvedev, who, once elected, made him the government’s President. He subsequently became the leader of the political party, ‘United Russia.’ It was under this party’s flag that he was once again elected President of the Russian Federation in March, 2012.

Pyrite

an iron sulphide with the formula FeS2, is a mineral that can contain traces of other chemical elements such as nickel (Ni), cobalt (Co), arsenic (As), copper (Cu), zinc (Zn), silver (Ag), gold (Au), thallium (Tl), selenium (Se) and vanadium (V).



© 2007 ULi�ge