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CRITICAL REACTION [12 records]

Record 1 2025-04-23

English

Subject field(s)
  • Chemical Elements and Compounds
CONT

High-purity solvents are essential for applications requiring minimal interference and maximum solvation efficiency. They are used in the synthesis of advanced materials, purification processes, and reaction media in pharmaceutical and chemical research. Their exceptional purity ensures accurate results and reproducibility in critical experiments and productions.

Key term(s)
  • high purity solvent

French

Domaine(s)
  • Éléments et composés chimiques
OBS

Un solvant de grande pureté peut être utilisé pour le nettoyage d'une grande variété de surfaces sans laisser de résidu graisseux ou d'odeur résiduelle.

Spanish

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Record 2 2015-04-29

English

Subject field(s)
  • Atomic Physics
DEF

The average number of neutrons with the velocity and position of type B which must be added to a critical system to keep the chain reaction rate constant after removal of a neutron with the velocity and position of type A.

OBS

relative importance: term and definition standardized by ISO.

French

Domaine(s)
  • Physique atomique
DEF

Nombre moyen de neutrons ayant la vitesse et la position de B qui doivent être ajoutés à un système critique pour maintenir constant le taux de réaction en chaîne après suppression d'un neutron ayant la position et la vitesse de A.

OBS

importance relative : terme et définition normalisés par l'ISO.

Spanish

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Record 3 2014-11-03

English

Subject field(s)
  • Atomic Physics
  • CBRNE Weapons
DEF

The action which sets off a chain reaction in a fissile mass which has reached the critical state(generally by the emission of a "spurt" of neutrons).

OBS

initiation: term and definition standardized by NATO in the AAP-6 standard published in 1998, but not included in the 2014 version.

French

Domaine(s)
  • Physique atomique
  • Armes CBRNE
DEF

Action provoquant la réaction en chaîne dans une masse fissile ayant atteint l'état critique (en général par émission d'une «bouffée» de neutrons).

OBS

amorçage : terme et définition normalisés par l'OTAN dans la norme AAP-6 de 1998, mais non repris dans l'édition de 2014.

Spanish

Campo(s) temático(s)
  • Física atómica
  • Armas QBRNE
DEF

La acción que origina una reacción en cadena en una masa fisionable, que ha alcanzado el estado crítico (generalmente por la emisión de neutrones acelerados).

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Record 4 2011-08-09

English

Subject field(s)
  • Biological Sciences
DEF

Temperature at which an enzyme exhibits maximal activity under specified conditions.

CONT

Although enzyme-catalyzed reactions often appear to have an optimum temperature, the peak in such a plot of catalytic activity vs. temperature results because enzymes, being proteins, are denatured by heat and become inactive as the temperature is raised beyond a certain point. The apparent temperature "optimum" is thus the resultant of two processes :(1) the usual increase in reaction rate with temperature and(2) the increasing rate of thermal denaturation of the enzyme above a critical temperature.

French

Domaine(s)
  • Sciences biologiques
DEF

Température à laquelle la vitesse de réaction enzymatique atteint une valeur maximale.

CONT

La température optimale est un compromis entre le fait que l'élévation de température augmente la vitesse de réaction et qu'en même temps, elle dénature l'enzyme. Il est difficile de donner une valeur précise à la température optimale d'une réaction enzymatique, la vitesse de dénaturation de l'enzyme étant fonction du pH et de la durée de la réaction. (...) Plus le temps est court, plus la température optimale peut être élevée.

Spanish

Campo(s) temático(s)
  • Ciencias biológicas
Save record 4

Record 5 2009-10-07

English

Subject field(s)
  • Nuclear Fission Reactors
CONT

Unlike reactor cores, nuclear fuel cycle installations do not have their own resources provided at the design stage to regulate or stop any uncontrolled chain reaction. Critical excursion is a phenomenon that occurs quickly and of which there are few physical warning signs.

French

Domaine(s)
  • Réacteurs nucléaires de fission
CONT

Si, dans une configuration fissile donnée, le coefficient de multiplication [...] dépasse accidentellement 1, la source de neutrons dans le système croît, en première approximation, exponentiellement à partir de sa valeur initiale S0 en un temps très court, le taux de fissions variant de la même façon. La source initiale de neutrons résulte du rayonnement cosmique et de réactions internes au système [...]. Cette réaction en chaîne, appelée excursion critique, provoque une émission de chaleur croissante et des flux intenses de rayons bêta, gamma et de neutrons à l'intérieur et à l'extérieur du système.

Spanish

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Record 6 2006-08-08

English

Subject field(s)
  • Animal Diseases
  • Poultry Production
CONT

Gizzard erosion is a condition seen in broiler chickens caused by gizzerosine toxicity.

OBS

Gizzerosine is formed by a reaction between the 3 amino group of lysine with free histidine during the heating of fish meal. The amount of heat to which fish meal is exposed during the drying process is critical in the formation of gizzerosine.

OBS

So far gizzerosine toxicity have only been described in chickens, possibly due to the high level of fish meal in the diets of this species ... The question of the influence of gizzerosine on horses and other species is however still unanswered.

French

Domaine(s)
  • Maladies des animaux
  • Élevage des volailles
CONT

Une équipe japonaise vient de reproduire expérimentalement une forte érosion du gésier sur des poulets de chair de différents âges, en leur inoculant un Adénovirus aviaire de type I (souche 99ZH).

OBS

Il a été signalé que la gizzérosine provoque l'érosion du gésier (EG) chez les poulets [...]

OBS

érosion : lésion de la peau ou d'une muqueuse avec perte de substance très superficielle.

Spanish

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Record 7 2003-12-10

English

Subject field(s)
  • Combustion and Fuels (Fireplaces)
  • Heat (Physics)
CONT

A certain class of ceramic and metallic materials can be manufactured by the self-propagating high-temperature synthesis method. Even though by now this process has included reaction systems of the solid-gas and solid-liquid types, the original work was directed towards the reactions investigated where not only the reactants but also the final products formed in the solid phase. These reactions are therefore generally referred to as gasless, solid-solid or condensed phase combustion reactions.

CONT

Condensed phase combustion is a complex phenomenon of theoretical and practical interest, in particular, as a method to synthesize materials. This combustion synthesis process involves a self-sustained combustion wave which propagates through initial reactants converting them into a desired product. In condensed phase combustion the initial reactants as well as final, and possibly intermediate products, remain in the condensed phase throughout the reaction. Though the combustion process occurs in a heterogeneous medium composed of reactive particles, typical models of condensed phase combustion treat the medium as homogeneous.

CONT

A deflagration analysis of porous energetic materials with two-phase flow and a multiphase sequential reaction mechanism. ... A theoretical analysis for the unconfined deflagration of a porous energetic material is developed for a two-step global reaction mechanism that consists of the condensed-phase combustion of the reactive material to produce gas-phase intermediates, followed by a gas-phase reaction that produces final gas-phase products.

OBS

Combustion is a chemical reaction, it gives off heat and is self-sustaining. It can occur in a condensed-phase(glowing), a gas-phase(flame) or both. Fire results when a combustible material(fuel) in the presence of an oxidizing agent(oxygen) is heated to a critical temperature(ignition temperature).

French

Domaine(s)
  • Combustion et combustibles (Foyers)
  • Chaleur (Physique)
CONT

Synthèse auto-propagée à haute température. La synthèse auto-propagée est un processus de combustion en phase condensée (en anglais «SHS» - «self-propagating high temperature synthesis») développé pour produire des céramiques et des matériaux refractaires.

OBS

état condensé : État de la matière dans lequel les atomes du corps sont très proches les uns des autres. (Les états solide et liquide sont des états condensés).

Spanish

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Record 8 2003-06-17

English

Subject field(s)
  • Biological Sciences
  • Biotechnology
CONT

A critical reaction in all organisms is the transfer of an amino group from one carbon skeleton to another by the process of transamination. Frequently, the most active exchange is between glutamate and aspartate.... This reaction is catalyzed by aspartate aminotransferase(also known as glutamate-oxaloacetate transaminase, glutamate-aspartate transaminase, and similar permutations).

French

Domaine(s)
  • Sciences biologiques
  • Biotechnologie
CONT

On connaît maintenant la quasi-totalité des amino-transférases (transaminases) capables d'assurer la transamination de tous les amino-acides (E.C. 2.6.1....). Toutes ces transaminases fonctionnent avec un coenzyme commun, le phosphate de pyridoxal, selon un mécanisme moléculaire bien connu. Dans les cellules encaryotes, ces enzymes sont localisés à la fois dans le cytosol et dans les mitochondries : il en existe ainsi plusieurs variétés moléculaires séparables par électrofocalisation.

Spanish

Campo(s) temático(s)
  • Ciencias biológicas
  • Biotecnología
Save record 8

Record 9 1989-10-16

English

Subject field(s)
  • Helicopters (Military)
  • Flight Controls (Aeroindustry)
CONT

The natural reaction of applying lift pedal and aft cyclic in an attempt to stop the sudden yaw and rolling moments of the aircraft would only exacerbate this already critical situation.

French

Domaine(s)
  • Hélicoptères (Militaire)
  • Commandes de vol (Constructions aéronautiques)

Spanish

Save record 9

Record 10 1989-05-23

English

Subject field(s)
  • Blasting Work (Mining)
CONT

The second aspect of performance sensitivity is usually distinguished by the name of Propagation Sensitivity, which is a measure of the ability of an explosive to support or reinforce a detonation that has already been created. Since the tendency for the detonation wave to fail or fade increases as the hole diameter is reduced, it has become customary to measure propagation sensitivity by the(minimum) critical diameter of a charge at least six diameters long that will support the detonation process once created. At a point below this value, a detonation wave cannot be consistently propagated, and a misfire... may occur; or otherwise the reaction may be incomplete, resulting in a poor blast effect and significant fume.

French

Domaine(s)
  • Travail aux explosifs (Exploitation minière)
CONT

Sensibilité à l'onde explosive. C'est une caractéristique très importante car elle conditionne la transmission de la détonation dans une file de cartouches. La Commission de Normalisation a adopté comme critère le coefficient de transmission de détonation (CTD), (...) La sensibilité à l'onde explosive est fonction de la densité de l'explosif et de son état (pulvérulent, gélatineux, fondu). Quand la densité est trop élevée, surtout avec les explosifs nitratés, l'onde explosive provoquée par le détonateur peut ne pas agir, ou s'arrêter en cours de propagation : on a alors un raté, ou un culot d'explosif.

Spanish

Save record 10

Record 11 1988-10-26

English

Subject field(s)
  • Blasting Work (Mining)
CONT

The second aspect of performance sensitivity is usually distinguished by the name of Propagation Sensitivity, which is a measure of the ability of an explosive to support or reinforce a detonation that has already been created. Since the tendency for the detonation wave to fail or fade increases as the hole diameter is reduced, it has become customary to measure propagation sensitivity by the(minimum) critical diameter of a charge at least six diameters long that will support the detonation process once created. At a point below this value, a detonation wave cannot be consistently propagated, and a misfire... may occur; or otherwise the reaction may be incomplete, resulting in a poor blast effect and significant fume.

French

Domaine(s)
  • Travail aux explosifs (Exploitation minière)
DEF

Diamètre d'une charge cylindrique de substance explosive au-dessous duquel cette substance ne peut pas détoner.

Spanish

Save record 11

Record 12 1986-03-27

English

Subject field(s)
  • Semiconductors (Electronics)
  • Industrial Techniques and Processes
CONT

In most metallic [solar collector] systems, especially those using a number of metals or a reactive metal such as aluminum, the heat transfer fluid can have a significant impact on corrosion. In aqueous solutions, the concentration of dissolved chemicals, heavy metal ions, and pH of the fluid must be controlled. Deionized or demineralized water has been used successfully but additional steps are usually taken. These include the use of a gettering column to trap heavy metal ions before they enter critical parts of the system and inhibitors which stabilize the metal ions and reduce their reaction with less noble metals.

French

Domaine(s)
  • Semi-conducteurs (Électronique)
  • Techniques industrielles

Spanish

Save record 12

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