WorldWideScience

Sample records for des neutrons lents

  1. Fission ionisation chamber for the measurement of low fluxes of slow neutrons; Chambre d'ionisation a fission pour la mesure des faibles flux de neutrons lents

    Energy Technology Data Exchange (ETDEWEB)

    Weill, J; Duchene, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The ionisation chamber described is designed for the measurement of slow neutron fluxes of average or low intensity, in the presence, eventually, of very high gamma fluxes. The capture of a slow neutron by a fissile material, in this case {sup 235}U, gives rise to fission fragments, high-energy particles which ionise the gas contained in the chamber. The neutrons are detected by virtue of the potential pulses, on the collecting electrode of the chamber, deriving from the collection of the ions produced by the fission fragments. The pulses are counted by means of a measuring system consisting of a preamplifier, a 2 Mc amplifier, a discriminator and an electronic scale with numerator or integrator. The general characteristics are as follows: sensitivity to neutrons: 0.07 kicks/n/cm{sup 2}.s, sensitivity to {gamma} rays: zero up to 3.10{sup 4} R/H, a background noise at the normal discrimination voltage: 0.01 kicks/s, working H.T.: -500 V, capacity: 40 {mu}{mu}F, average height of pulse: 8 mV, limits of use: from several neutrons to 10{sup 6} n/cm{sup 2}.s. This chamber may be used in all cases where low fluxes of slow neutrons must be measured, especially in the presence of high gamma fluxes, for example in the checking of Pu concentrations in an extraction plant or for the starting up of reactors. (author) [French] La chambre d'ionisation decrite est destinee a la mesure des flux de neutrons lents d'intensite moyenne ou faible, en presence eventuelle de flux gamma tres importants. La capture d'un neutron lent par un materiau fissile, en l'occurrence {sup 235}U, donne naissance a des fragments de fission, particules de grande energie qui ionisent le gaz contenu dans la chambre. Les neutrons sont detectes grace aux impulsions de potentiel, sur l'electrode collectrice de la chambre, provenant de la collection des ions produits par les fragments de fission. Une chaine de mesure comprenant un preamplificateur, un amplificateur 2 Mc, un discriminateur, une echelle

  2. The Scattering of Slow Neutrons from Hydrogen and Ethylene; Diffusion des neutrons lents par l'hydrogene et par l'ethylene; O rasseyanii medlennykh nejtronov vodorodom i ehtilenom; Dispersion de neutrones lentos por hidrogeno y etileno

    Energy Technology Data Exchange (ETDEWEB)

    Bally, D; Tarina, V; Todireanu, S [Institute of Atomic Physics, Bucharest (Romania)

    1963-01-15

    The angular distribution of 1.61 A wavelength neutrons scattered from hydrogen and ethylene has been measured. For ethylene the pressure was varied from 15 to 60 atm and for hydrogen from 60 to 110 atm. The investigated angular range was between 5''o and 90{sup o}. The experimental results obtained have been compared with the differential cross-section calculated using the Krieger-Nelkin formulae. (author) [French] Les auteurs ont mesure la distribution angulaire des neutrons ayant une longueur d'onde de 1,61 A diffuses par de l'hydrogene et par l'ethylene. Ils ont fait varier la pression de l'ethylene de 15 a 60 atm et celle de l'hydrogene de 60 a 110 atm. Le domaine angulaire etudie etait compris entre 5{sup o} et 90{sup o}. Les resultats des experiences ont ete compares aux sections efficaces differentielles calculees au moyen des formules de Krieger-Nelkin. (author) [Spanish] Los autores han medido la distribucion angular de neutrones de longitud de onda igual a 1,61 A, despersados por hidrogeno y etileno. En el caso del etileno, la presion vario de 15 a 60 atm y en el del higrogeno, de 60 a 110 atm. Los autores han explorado angulos comprendidos entre 5{sup o} y 90{sup o}. comparan los resultados experimentales obtenidos con el valor de la seccion eficaz diferencial calculado con ayuda de las formulas de Kriger-Nelkin. (author)

  3. A Double Slow Neutron Spectrometer; Spectrometre double pour neutrons lents; Dvojnoj spektrometr medlennykh nejtronov; Espectrometro doble para neutrones lentos

    Energy Technology Data Exchange (ETDEWEB)

    Bondarenko, I I; Liforov, V G; Nikolaev, M N; Orlov, V V; Parfenov, V A; Semenov, V A; Smirnov, V I; Turchin, V F [Fehi, Moscow, SSSR (Russian Federation)

    1963-01-15

    The neutron spectrometer described in the paper is intended for measurements of the angular and energy distribution of monochromatic slow neutrons, inelasticaily scattered by liquid and solid bodies. Experiments of this type permit detailed information to be obtained concerning the dynamics of the atoms in various aggregate states of a substance. The spectromeeter is based on the time-of-flight method. The pulse source of neutrons is the IBR (1) reactor. A mechanical interrupter, rotating synchronously with the disc of the IBR and having a prescribed phase shift, serves as the monochromator. A special phasing system ensures a phasee stability better than 0.5{sup o}. The neutrons scattered by the sample are recorded by a scintillation detector set at a given angle to the neutron beam. The resolving power of the spectrometer is - 15 {mu}s/m. The paper gives a detailed description of the construction of the spectroscope and its characteristics. (author) [French] Le spectrometre neutronique decrit dans le memoire est destine a mesurer la distribution en energie, la distribution angulaire et la diffusion inelastique des neutrons lents monochromatiques dans des liquides et des solides. Les experiences de ce genre permettent d'obtenir des renseignements detailles sur la dynamique des atomes dans de divers etats de la matiere. Le spectrometre est fonde sur la mesure du temps de vol. Comme source puisee de neutrons on a utilise le reacteur IBR-1. Le systeme monochromateur etait constitue par un interrupteur mecanique en rotation synchronisee avec celle du disque du reacteur IBR, avec un dephasage determine. Un dispositif special de dephasage assure la stabilite de la phase a 0,5{sup o} pres. La diffusion des neutrons par l'echantillon est enregistree a l'aide d'un detecteur a scintillations dispose sous un angle determine par rapport au faisceau de neutrons. Le pouvoir de resolution du spectrometre est d'environ 15 {mu}s/m. Les auteurs decrivent en detail la construction du

  4. Measure of the efficiency of a long counter of Hanson's type and use of this counter for the survey of the slow neutrons coming from the reactor of Chatillon; Mesure de l'efficacite d'un long compteur du type Hanson et utilisation de ce compteur a l'etude des neutrons lents sortant de la pile de Chatillon

    Energy Technology Data Exchange (ETDEWEB)

    Barloutaud, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1953-07-01

    A detection device of fast neutrons of efficiency almost independent of the energy of the neutrons has been achieved. It efficiency has been measured in absolute value for groups of neutrons of different energies. This device allowed to get some indications on the energy composition of the neutrons leaving from the reactor of Chatillon. (author) [French] Un dispositif de detection de neutrons rapides d'efficacite pratiquement independante de l'energie des neutrons a ete realise. Son efficacite a ete mesuree en valeur absolue pour des groupes de neutrons de diverses energies. Ce dispositif a permis obtenir quelques indications sur la composition energetique des neutrons sortant de la pile de Chatillon. (auteur)

  5. Experiments on the thermalization of slow neutrons by liquid hydrogen (1962); Experience de thermalisation de neutrons lents par de l'hydrogene liquide (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Cribier, D; Jacrot, B; Lacaze, A; Roubeau, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Institut Fourier, 38 - Grenoble (France)

    1962-07-01

    In order to increase the flux of neutrons of long wave-length ({lambda} > 4 A) emerging from a channel in the EL-3, a liquid hydrogen device was introduced into a channel of the reactor (Channel H{sub 1}). The principle of the device is simple. A volume of liquid hydrogen is introduced as close as possible to the reactor core into a region of intense isotropic flux. This hydrogen slows down the slow neutrons; because of the very small mean free diffusion path of slow in hydrogen, this slowing down is considerable even in a small volume of liquid hydrogen, and the spectrum temperature of neutrons emerging from the volume of liquid hydrogen can therefore be shifted. The intensity gain for neutrons with a wave length {lambda}, is a G ({lambda}) function which, for perfect thermalization and ignoring capture, is expressed by: G ({lambda}) = 225 exp (- 45.3/{lambda}{sup 2}), assuming a temperature of 300 deg. K for the neutrons before cooling and is 20 deg. K after cooling. For a wave-length of 5 A, the theoretical maximum gain of thus about 37. (authors) [French] Dans le but d'accroitre le flux des neutrons de grande longueur d'onde ({lambda} > 4 A) sortant d'un canal de la pile EL-3, un dispositif a hydrogene liquide a ete introduit dans un canal de la pile (canal H{sub 1}). Le principe du dispositif est simple. Un volume d'hydrogene liquide est introduit le plus pres possible du coeur de ia pile dans une region de flux intense et isotrope. Les neutrons lents sont ralentis par cet hydrogene; a cause du tres faible libre parcours moyen de diffusion des neutrons lents dans l'hydrogene, ce ralentissement est important meme dans un faible volume d'hydrogene liquide et l'on peut ainsi deplacer la temperature du spectre des neutrons sortant du volume d'hydrogene liquide. Le gain en intensite des neutrons de longueur d'onde {lambda} est une fonction G ({lambda}) qui pour une thermalisation parfaite et en negligeant la capture, s'exprime par: G ({lambda}) = 225 exp (- 45

  6. Comparison of fission probabilities with emission of long range particles under the action of slow and fast neutrons on various materials; Probabilites comparees de fission avec emission de particules de long parcours pour divers materiaux sous l'action des neutrons lents et rapides

    Energy Technology Data Exchange (ETDEWEB)

    Netter, F; Faraggi, H; Garin-Bonnet, A; Julien, J; Corge, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Turkiewicz, J [Institut de Recherches Nucleaire de Varsovie (Poland)

    1958-07-01

    The authors describe relative cross-section measurements of fission of the isotopes of uranium and plutonium (more particularly {sup 235}U, {sup 238}U, {sup 239}Pu), with emission of long range particles, under the action of neutrons of various energies: thermal neutrons, pile neutrons, neutrons produced with the Van de Graaff accelerator by reaction of protons on tritium. The measurements are carried out: 1) with the aid of photographic plates, by submitting to the action of the neutrons a layer of fissile material coupled with an Ilford nuclear emulsion of 200 microns; a tin sheet laying between the plate and the layer stops the {alpha} particles and the fission fragments. By an appropriate development the tracks of the long range particles can be distinguished in the emulsion, from the tracks of the recoil protons resulting of fission neutrons, or of the last primary neutrons. For neutrons of energy under 1 MeV, the compared frequency of the tracks of long range particles and of the recoils caused by the fission neutrons gives a measurement of the fission cross-section with emission of long range particles relative to the product of the fission cross-section by the mean number of neutrons emitted by fission. For neutrons of higher energy, one measures only the frequency of the tracks of long range particles, comparatively with the flux of primary neutrons. Some precautions are taken to eliminate the action of thermal neutrons in the measurements with fast neutrons. 2) with the aid of a system of ionization chamber and proportional counter, the rate of coincidence between the impulsions caused by the long range particles and the impulsions provided by one of the fission fragments is measured comparatively with the counting rate of fission fragme (author) [French] Les auteurs decrivent des mesures relatives a la section efficace de fission des isotopes de l'uranium et du plutonium (notamment {sup 235}U, {sup 238}U, {sup 239}Pu) avec emission de particules de long

  7. A New Apparatus for Inelastic, Quasi-Elastic and Elastic Cold Neutron Measurements; Un nouveau appareil pour les mesures de diffusion inelastique , quasi-elastique et elastique des neutrons lents; Novyj pribor dlya izmereniya neuprugogo, kvaziuprugogo i uprugogo rasseyaniya kholodnykh nejtrohov; Nuevo aparato para mediciones inelastic as, cuasi elasticas y elasticas de neutrones frios

    Energy Technology Data Exchange (ETDEWEB)

    Otnes, K; Palevsky, H [Brookhaven National Laboratory, Upton, NY (United States)

    1963-01-15

    despersion de la longueur d'onde (largeur totale a mi-hauteur) seront respectivement de 16 {mu}s et 0,16 A pour des neutrons incidents ayant une longueur d'onde de 4 A; l'intensite de la bouffee sur l'echantillon (4 x 1,6 cm) sera de 2 x 10{sup 6} n/s pouf mesures de diffusion quasi-elastique et elastique, la configuration a trois rotors conviendra parfaitement. La duree de la bouffee et la dispersion de longueur d'onde correspondante peuvent atteindre des valeurs aussi faibles que 8 {mu}s et 0, 04 A, ce qui donne une intensite de 10{sup 4} n/s sur un echantillon de 4 x 0, 8 cm. La longueur d'onde et la resolution en temps peuvent etre ajustees entre les; deux limites susmentionnees, de maniere a obtenir l'intensite de flux maximum pour une experience determinee. (author) [Spanish] Se esta construyendo un nuevo selector mecanico destinado al reactor de flujo intenso de Brookhaven. El aparato es del tipo de tres elementos rotores en fase. Los rotores, de 80 cm de diametro, giran a una velo- cidad maxima de 15000 rev/min y se han disenado de modo que emitan tres rafagas de neutrones monocromaticos por revolucion. Dos de los rotores giran alrededor de un eje horizontal, mientras que el tercero lo hace verticalmente. El sistma puede funcionar con uno, dos or tres elementos selectores, segun el tipo de medicion que se quiera efectuar. Para las mediciones inelasticas en que los neutrones ganan energia, lo mas indicado es utilizar un sistema de dos rotores. En este sistema, la duracion de las rafagas sera de 16 {mu}s y el ensanchamiento de longitudes de onda (amplitud plena a la mitad del valor maximo) de 0,16 A para neutrones incidentes de 4 A; la intensidd en la muestra (4 x 1,6 cm) sera de 2 x 10{sup 6} n/s. para las mediciones cuasi elasticas y elasticas resultara mas apropiado el sistema de tres rotores. La duracion de las rafagas y el ensanchamiento de longitudes de onda pueden llegar a un minimo de 8 {mu}s y 0,04 A, respectivamente, lo que representa una intensidad de 10{sup

  8. Time-of-flight spectrometer for slow neutrons in use at the reactor in Saclay. Its application for the study of the inelastic diffusion of cold neutrons; L'appareillage de spectrometrie a temps-de-vol pour neutrons lents en service a la pile de Saclay. Son application a l'etude de la diffusion inelastique des neutrons froids

    Energy Technology Data Exchange (ETDEWEB)

    Jacsot, B; Netter, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Galula, M [Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France)

    1955-07-01

    The time-of-flight spectrometers is constituted of a mechanic swivel obturator which absorbs neutrons until energies above 1 KeV, a mechanic filter which allow to retain only high wave length components and a delayed pulses selector with 100 channels. Its main application field is the thermic region where it allowed to measure the inelastic scattering of neutrons using various materials as H{sub 2}O, D{sub 2}O, Be, BeO, etc... (M.P.)

  9. Apport de l’IRM dans la prise en charge des compressions médullaires lentes non traumatiques

    Science.gov (United States)

    Badji, Nfally; Deme, Hamidou; Akpo, Geraud; Ndong, Boucar; Toure, Mouhamadou Hamine; Diop, Sokhna Ba; Niang, El Hadji

    2016-01-01

    Les compressions médullaires lentes sont dues au développement dans le canal médullaire d’une lésion expansive. C’est une pathologie très fréquente dont le diagnostic est essentiellement clinique. L’imagerie par résonnance magnétique occupe une place incontournable dans le diagnostic de localisation et la recherche étiologique. En Europe l’étiologie tumorale est prépondérante. Le but de cette étude était de décrire les aspects IRM des compressions médullaires lentes et de déterminer le profil étiologique. Il s’agit d’une étude rétrospective portant sur 97 observations colligées au service de radiologie du CHUN de Fann sur une période de 30 mois (du 08/03/10 au 29/09/12). On été inclus dans l’étude, tous les patients adressés pour un tableau de compression médullaire lente survenu dans un contexte non traumatique. L’âge moyen des patients était de 42,6 ans avec des extrêmes compris entre 04 mois et 85 ans. Nous avons étudié la topographie des lésions (étage rachidien, compartiments canalaires) leur rehaussement et les critères d’orientation étiologique. Le protocole d’examen permettait la réalisation de séquence pondérées T1 sans avec injection de gado, T2, STIR et T2 DRIVE centrées sur les niveaux lésionnels ou les zones suspectes. L’IRM a permis de préciser le siège exact et l’étendue des lésions. L’atteinte du rachis dorsal représentait 42% des cas, suivi du rachis cervical avec 32% des cas. Les atteintes lombo-sacrées et pluri-étagées représentaient respectivement 18% et 08% des cas. Les lésions extradurales représentaient 87% des cas, suivi des lésions intradurales extramédullaires avec 08% des cas et des lésions intramédullaires dans 05% des cas. La particularité du profil étiologique de notre étude est la prédominance des épidurites infectieuses et la fréquence relative des épidurites métastatiques comparée aux séries occidentales. L’IRM vertébro-médullaire occupe

  10. Study and production of polarized monochromatic thermal neutron beams; Etude et production de faisceaux monochromatiques polarises de neutrons lents

    Energy Technology Data Exchange (ETDEWEB)

    Beiln, H. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-06-15

    Results obtained with a recently built neutron spectrometer producing monochromatic polarized neutron beams,in the energy rang (10{sup -3} - 10) eV and using a series of artificial (Co: 92 per cent - Fe: 8 per cent) monocrystal as polarizers and analysers, are given. A high precision method for cutting monocrystals is explained. A description of the installation itself as well as some results obtained with Fe{sub 3}O{sub 4} crystals are also given. Experimental result pertaining to various magnetic guide and 'spin flip' system, as required in the handling of such polarized neutron beams, are also discussed. (author) [French] Nous donnons les resultats obtenus avec un spectrometre produisant des neutrons monochromatiques polarises d'energie comprise entre quelques milliemes d'electronvolts et quelques electronvotts qui utilise une serie de monocristaux artificiels de Co: 92 pour cent - Fe: 8 pour cent, comme polariseurs et analyseurs. Nous discutons egalement une methode de taille de monocristaux a tres haute precision. Le dispositif experimental ainsi que quelques resultats preliminaires obtenus avec des monocristaux de Fe{sub 3}O{sub 4} sont egalement donnes. Nous discutons egalement des resultats experimentaux obtenus avec differents systemes de guidage magnetique et de renversement du spin. (auteur)

  11. Study and production of polarized monochromatic thermal neutron beams; Etude et production de faisceaux monochromatiques polarises de neutrons lents

    Energy Technology Data Exchange (ETDEWEB)

    Beiln, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-06-15

    Results obtained with a recently built neutron spectrometer producing monochromatic polarized neutron beams,in the energy rang (10{sup -3} - 10) eV and using a series of artificial (Co: 92 per cent - Fe: 8 per cent) monocrystal as polarizers and analysers, are given. A high precision method for cutting monocrystals is explained. A description of the installation itself as well as some results obtained with Fe{sub 3}O{sub 4} crystals are also given. Experimental result pertaining to various magnetic guide and 'spin flip' system, as required in the handling of such polarized neutron beams, are also discussed. (author) [French] Nous donnons les resultats obtenus avec un spectrometre produisant des neutrons monochromatiques polarises d'energie comprise entre quelques milliemes d'electronvolts et quelques electronvotts qui utilise une serie de monocristaux artificiels de Co: 92 pour cent - Fe: 8 pour cent, comme polariseurs et analyseurs. Nous discutons egalement une methode de taille de monocristaux a tres haute precision. Le dispositif experimental ainsi que quelques resultats preliminaires obtenus avec des monocristaux de Fe{sub 3}O{sub 4} sont egalement donnes. Nous discutons egalement des resultats experimentaux obtenus avec differents systemes de guidage magnetique et de renversement du spin. (auteur)

  12. Study of the critical scattering of neutrons by iron; Etude de la diffusion critique des neutrons par le fer

    Energy Technology Data Exchange (ETDEWEB)

    Galula, M; Jacrot, B; Mangin, J P [Commissariat a l' Energie Atomique, Saclay (France)

    1959-07-01

    The critical scattering of very slow neutrons by iron near critical point is measured by time of flight techniques. The VAN HOVE formula is verified and the geometrical parameters K{sub 1} et r{sub 1} introduced in this theory are determined. (author) [French] On etudie la diffusion critique des neutrons tres lents par le fer dans la region du point de Curie par une methode de temps de vol. On verifie la formule de VAN HOVE et on determine les parametres geometriques K{sub 1} et r{sub 1} introduit par ce dernier. (auteur)

  13. Slow Neutron Spectrometers at the Swedish Reactors; Spectrometres a Neutrons Lents des Reacteurs Suedois; 0421 041f 0415 041a 0422 0420 041e 041c 0415 0422 0420 042b 041c 0415 0414 041b 0415 041d 041d 042b 0425 041d 0415 0419 0422 0420 041e 041d 041e 0412 041d 0410 0428 0412 0415 0414 0421 041a 0418 0425 0420 0415 0410 041a 0422 041e 0420 0410 0425 ; Espectrometros para Neutrones Lentos en los Reactores de Suecia

    Energy Technology Data Exchange (ETDEWEB)

    Dahlborg, U.; Skoeld, K. [AB Atomenergi, Stockholm (Sweden); Larsson, K. -E. [Royal Institute of Technology, Stockholm (Sweden)

    1965-06-15

    is briefly discussed for illustrational purposes. A comparison between the light- and heavy-water moderated reactors for beam tube work shows the distinct advantages of the heavy-water type. (author) [French] Aux centres crees autour des deux, reacteurs de recherche suedois, Rl a Stockholm et R2 a Studsvik, on a maintenant la possibilite d'utiliser quatre spectrometres differents pour les experiences de diffusion inelastique des neutrons. A Stockholm, le reacteur Rl de 600 kW, ralenti a l'eau lourde, est equipe de deux spectrometres mecaniques a neutrons lents qui fonctionnent simultanement, Avec l'un, on utilise toujours un monochromateur a filtre en Be; avec l'autre, on peut employer soit le meme genre de monochromateur, soit un monochromateur a cristal. On a constate que pour les mesures de distribution angulaire, on obtient d'excellents resultats en combinant un monochromateur a cristal et un spectrometre mecanique, meme si l'intensite et le pouvoir de resolution sont relativement faibles. Recemment on a fait l'essai d'un selecteur de vitesse mecanique ayant un pouvoir de separation des longueurs d'onde de 4,2%. Cependant, cet instrument n'est pas encore utilise pour les experiences. Le spectrometre mecanique de Studsvik, avec lequel le reacteur R2 de 30 MW ralenti a l'eau legere est equipe, utilise pour la monochromatisation l'action combinee d'un monochromateur a filtre de Be et d'un hacheur a courbe de transmission etroite. Dans ce spectrometre, de meme que dans celui de Stockholm, le hacheur est place avant l'echantillon, ce qui permet l'enregistrement simultane de donnees pour des angles d'observation differents. Un spectrometre a cristal triaxial est aussi en service pres du reacteur R2. Les auteurs donnent certaines caracteristiques de ces instruments, notamment l'intensite, le pouvoir de resolution, et indiquent dans quelle mesure ils conviennent pour certaines operations. Ainsi, il ressort des donnees numeriques mentionnees qu'une amelioration assez

  14. The magnetic diffusion of neutrons; La diffusion magnetique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, W C [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The purpose of this report is to examine briefly the diffusion of neutrons by substances, particularly by crystals containing permanent atomic or ionic magnetic moments. In other words we shall deal with ferromagnetic, antiferromagnetic, ferrimagnetic or paramagnetic crystals, but first it is necessary to touch on nuclear diffusion of neutrons. We shall start with the interaction of the neutron with a single diffusion centre; the results will then be applied to the magnetic interactions of the neutron with the satellite electrons of the atom; finally we shall discuss the diffusion of neutrons by crystals. (author) [French] Le but de ce rapport est d'examiner, brievement, la diffusion des neutrons par les substances, et surtout, par des cristaux qui contiennent des moments magnetiques atomiques ou ioniques permanents. C'est-a-dire que nous nous interesserons aux cristaux ferromagnetiques, antiferromagnetiques, ferrimagnetiques ou paramagnetiques; il nous faut cependant rappeler d'abord la diffusion nucleaire des neutrons. Nous commencerons par l'interaction du neutron avec un seul centre diffuseur; puis les resultats seront appliques aux interactions magnetiques du neutron avec les electrons satellites de l'atome; enfin nous discuterons la diffusion des neutrons par les cristaux. (auteur)

  15. Dosimetry techniques of thermal neutrons and {gamma} radiation in reactor cores; Techniques de dosimetrie des neutrons thermiques et du rayonnement {gamma} dans les piles

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, J; Draganic, I; Hering, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    Chemical studies under radiation done in the reactor cores require to be followed by dosimetry. When the irradiations are done in the reflector, one can limit to the measure of the {gamma} and the neutron radiation. For the dosimetry of the {gamma} radiation, a dosimeter of ferrous sulfate is convenient until doses of about 10{sup 6} rep. The use of aired oxalic acid solutions permits to reach 10{sup 7} rep. The dosimetry of thermal neutrons has been made with solutions of cobalt sulphate or paper filter impregnated with this salt. The total chemical effect of the {gamma} and of the slow neutrons radiation is obtained with solutions of ferrous sulfate added with lithium sulphate. (M.B.) [French] Les etudes de chimie sous radiation faites dans les piles exigent d'etre suivies par dosimetrie. Lorsque les irradiations sont effectues dans le reflecteur, on peut se limiter a doser le rayonnement {gamma} et les neutrons. Pour la dosimetrie du rayonnement {gamma}, un dosimetre a sulfate ferreux convient jusqu'a des doses d'environ 10{sup 6} rep. L'emploi de solutions aerees d'acide oxalique permet d'atteindre 10{sup 7} rep. La dosimetrie des neutrons thermiques a ete faite avec des solutions de sulfate de cotalt ou du papier filtre impregne de ce sel. L'effet chimique total du rayonnement {gamma} et des neutrons lents est obtenu avec des solutions de sulfate ferreux additionne de sulfate de lithium. (M.B.)

  16. Problems Associated with the Monochromatisation of Slow Neutrons; Quelques aspects de la monochromatisation des neutrons thermiques; Nekotorye voprosy monokhromatizatsii medlennykh nejtronov; Algunos problemas de la monocromatizacion de neutrones lentos

    Energy Technology Data Exchange (ETDEWEB)

    Vertebnyj, V P; Kolotyj, V V; Majstrenko, A N

    1963-01-15

    The paper sets out the result of calculations to determine the shape of the spectral line of twin-rotor, pulsing, slow-neutron monochromators, as a function of the shifts in the phases between the rotors. Consideration is also given to die possibility of using certain light elements as slow-neutron filters. (author) [French] Les auteurs exposent les resultats de leurs calculs relatifs a la forme du spectre des monochromateurs a impulsions et a deux rotors pour neutrons thermiques en fonction de la distance et du dephasage entre les rotors. Ils examinent egalement la possibilite d*utiliser certains elements legers comme filtres a neutrons lents. (author) [Spanish] Los autores exponen ios resultadas de sus calculos relativos a la forma de la linea espectral de los monocromadores pulsantes de dos rotores para neutrones lentos en funcion de la distancia y del desias amiento de los rotores. Examinan asimismo la posibilidad de utilizar algunos elementos ligeros como filtros de neutrones lentos. (author)

  17. Cross section measurements of fissile nuclei for slow neutrons; Mesures de sections efficaces de noyaux fissiles pour les neutrons lents

    Energy Technology Data Exchange (ETDEWEB)

    Auclair, J M; Hubert, P; Joly, R; Vendryes, G; Jacrot, B; Netter, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Galula, M [Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France)

    1955-07-01

    It presents the experimental measurements of cross section of fissile nuclei for slow neutrons to improve the understanding of some heavy nuclei of great importance in the study of nuclear reactors. The different experiments are divided in three categories. In the first part, it studied the variation with energy of the cross sections of natural uranium, {sup 233}U, {sup 235}U and {sup 239}Pu. Two measurement techniques are used: the time-of-flight spectrometer and the crystal spectrometer. In a second part, the fission cross sections of {sup 233}U and {sup 239}Pu for thermal neutrons are compared using a neutron flux from EL-2 going through a double fission chamber. The matter quantity contained in each source is measured by counting the {alpha} activity with a solid angle counter. Finally, the average cross section of {sup 236}U for a spectra of neutrons from the reactor is measured by studying the {beta} activity of {sup 237}U formed by the reaction {sup 236}U (n, {gamma}) {sup 237}U in a sample of {sup 236}U irradiated in the Saclay reactor (EL-2). (M.P.)

  18. Neutron Dosimetry and Irradiation of Solids; Dosimetrie des neutrons et irradiation des solides

    Energy Technology Data Exchange (ETDEWEB)

    Perriot, G; Schmitt, A P [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1962-07-01

    Results of work at C.E.A. from 1958 to 1960 are reviewed. The possibilities offered by classical dosimetry methods are discussed. The tests which led to the utilization, for fast neutron dosimetry, of resistivity variations induced in solid W by such neutrons are described. Experimental W irradiation results led to a definition of neutron efficiency which describes the relations between neutron energy and their effects on materials. Possibilities offered by detectors which make use of radiation damage and are sensitive to neutrons at keV energies were explored. In other work, the principal French reactors were classified according to their ability to produce damage in materials such as W. (authors) [French] Dans ce rapport on a presente les resultats essentiels de travaux qui ont ete effectues de 1958 a 1980 par des chercheurs du CEA issus de differents services. En meme temps qu'une revue des possibilites offertes a l'epoque par les methodes classiques de dosimetrie (utilisation des detecteurs par activation), on a decrit les essais qui devaient permettre d'utiliser, a la dosimetrie les neutrons rapides, les variations de resistivite qu'ils creent dans un corps solide (tungstene). L'irradiation du tungstene a montre l'importance qu'il y avait a definir 'l'efficacite' des neutrons, c'est-a-dire leur aptitude plus ou moins grande, selon leur energie, a creer des defauts dans les materiaux. L'efficacite d'un emplacement d'irradiation se trouvant liee au spectre neutronique, on a vu les difficultes qu'il y avait a utiliser les detecteurs par activation des qu'on n'avait plus affaire a un spectre en 1/E ou de fission et on a pu entrevoir les possibilites offertes par les detecteurs utilisant la creation des defauts qui repondent a tous les neutrons d'energies, superieures a quelques keV. Enfin, on a classe les principaux types de Piles Francaises selon leur aptitude a creer plus ou moins rapidement des dommages dans des materiaux comme le tungstene. (auteur)

  19. Contribution to the study of the interaction of slow neutrons with {sup 235}U using the time-of-flight method; Contribution a l'etude par la methode du temps de vol de l'interaction de neutrons lents avec l'U{sup 235}

    Energy Technology Data Exchange (ETDEWEB)

    Michaudon, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-05-15

    This study concerns the properties of the excited levels of uranium 236 obtained by interaction of slow neutron with uranium 235. The experiments have been carried out at the Saclay linear electron accelerator by use of the time of flight method. In the first part of this paper, we examine the technical and physical conditions which rule the experiments: compromise between resolution and counting rate, time dispersion due to the slowing down of the neutrons and crystalline binding effects. In a second part the experimental results i.e. total, fission and ternary fission cross sections are given. The third part deals with the analysis of these results: the resonance parameters determination ({tau}{sub n}, {tau}{sub {gamma}}, {tau}{sub f}), the study of their statistical distribution and of their correlations. We tried some classifications of the resonances according to their parameters and compared these classifications to each other and to other results. At least the evidence of a cross section correlation with a range smaller than 100 eV seems to be confirmed. (author) [French] Cette etude porte sur les proprietes des niveaux excites de l'Uranium-236 obtenus par l'interaction de neutrons lents avec le {sup 235}U. La technique experimentale est celle de la spectrometrie par temps de vol, les experiences ayant ete realisees aupres de l'accelerateur lineaire d'electrons de Saclay, Dans une premiere partie nous examinons les donnees techniques et physiques conditionnant les experiences: compromis entre resolution et taux de comptage, dispersion en temps due au ralentissement des neutrons, effet des liaisons cristallines. Dans une deuxieme partie sont exposes les resultats experimentaux: sections efficaces totales, de fission et de fission ternaire du {sup 235}U. Une troisieme partie porte sur l'analyse de ces resultats: determination des parametres ({tau}{sub n}, {tau}{sub {gamma}}, {tau}{sub f}), etude de leurs distributions statistiques et des correlations entre ces

  20. Contribution to the study of the interaction of slow neutrons with {sup 235}U using the time-of-flight method; Contribution a l'etude par la methode du temps de vol de l'interaction de neutrons lents avec l'U{sup 235}

    Energy Technology Data Exchange (ETDEWEB)

    Michaudon, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-05-15

    This study concerns the properties of the excited levels of uranium 236 obtained by interaction of slow neutron with uranium 235. The experiments have been carried out at the Saclay linear electron accelerator by use of the time of flight method. In the first part of this paper, we examine the technical and physical conditions which rule the experiments: compromise between resolution and counting rate, time dispersion due to the slowing down of the neutrons and crystalline binding effects. In a second part the experimental results i.e. total, fission and ternary fission cross sections are given. The third part deals with the analysis of these results: the resonance parameters determination ({tau}{sub n}, {tau}{sub {gamma}}, {tau}{sub f}), the study of their statistical distribution and of their correlations. We tried some classifications of the resonances according to their parameters and compared these classifications to each other and to other results. At least the evidence of a cross section correlation with a range smaller than 100 eV seems to be confirmed. (author) [French] Cette etude porte sur les proprietes des niveaux excites de l'Uranium-236 obtenus par l'interaction de neutrons lents avec le {sup 235}U. La technique experimentale est celle de la spectrometrie par temps de vol, les experiences ayant ete realisees aupres de l'accelerateur lineaire d'electrons de Saclay, Dans une premiere partie nous examinons les donnees techniques et physiques conditionnant les experiences: compromis entre resolution et taux de comptage, dispersion en temps due au ralentissement des neutrons, effet des liaisons cristallines. Dans une deuxieme partie sont exposes les resultats experimentaux: sections efficaces totales, de fission et de fission ternaire du {sup 235}U. Une troisieme partie porte sur l'analyse de ces resultats: determination des parametres ({tau}{sub n}, {tau}{sub {gamma}}, {tau}{sub f}), etude de leurs distributions statistiques et

  1. Neutron cooling and cold-neutron sources (1962); Refroidissement des neutrons et sources de neutrons froids (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Jacrot, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    Intense cold-neutron sources are useful in studying solids by the inelastic scattering of neutrons. The paper presents a general survey covering the following aspects: a) theoretical considerations put forward by various authors regarding thermalization processes at very low temperatures; b) the experiments that have been carried out in numerous laboratories with a view to comparing the different moderators that can be used; c) the cold neutron sources that have actually been produced in reactors up to the present time, and the results obtained with them. (author) [French] Des sources intenses de neutrons froids sont utiles pour l'etude des solides par diffusion inelastique des neutrons. On presente une revue d'ensemble: a) des considerations theoriques faites par divers auteurs sur les processus de thermalisation a tres basse temperature; b) des experiences faites dans de nombreux laboratoires pour comparer les divers moderateurs possibles; c) des sources de neutrons froids effectivement realisees dans des piles a ce jour, et des resultats obtenus avec ces sources. (auteur)

  2. Thermal neutron flux measurements using neutron-electron converters; Mesure de flux de neutrons thermiques avec des convertisseurs neutrons electrons

    Energy Technology Data Exchange (ETDEWEB)

    Le Meur, R; Lecomte, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    The operation of neutron-electron converters designed for measuring thermal neutron fluxes is examined. The principle is to produce short lived isotopes emitting beta particles, by activation, and to measure their activity not by extracting them from the reactor, but directly in the reactor using the emitted electrons to deflect the needle of a galvanometer placed outside the flux. After a theoretical study, the results of the measurements are presented; particular attention is paid to a new type of converter characterized by a layer structure. The converters are very useful for obtaining flux distributions with more than 10{sup 7} neutrons cm{sup -2}*sec{sup -1}. They work satisfactorily in pressurized carbon dioxide at 400 Celsius degrees. Some points still have to be cleared up however concerning interfering currents in the detectors and the behaviour of the dielectrics under irradiation. (authors) [French] On examine le fonctionnement de convertisseurs neutrons electrons destines a des mesures de flux de neutrons thermiques. Le principe est de former par activation des isotopes a periodes courtes et a emission beta et de mesurer leur activite non pas en les sortant du reacteur, mais directement en pile, utilisant les electrons emis pour faire devier l'aiguille d'un galvanometre place hors flux. Apres une etude theorique, on indique des resultats de mesures obtenus, en insistant particulierement sur un nouveau type de convertisseur, caracterise par sa structure stratifiee. Les convertisseurs sont tres interessants pour tracer, des cartes de flux a partir de 10{sup 7} neutrons cm{sup -2}*s{sup -1}. Ils sont utilisables pour des flux de 10{sup 14} neutrons cm{sup -2}*s{sup -1}. Ils fonctionnent correctement dans du gaz carbonique sous pression a 400 C. Des points restent cependant a eclaircir concernant les courants parasites dans les detecteurs et le comportement des dielectriques pendant leur irradiation. (auteur)

  3. Prompt neutron emission; Emission des neutrons prompts de fission

    Energy Technology Data Exchange (ETDEWEB)

    Sher, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    It is shown that Ramanna and Rao's tentative conclusion that prompt fission neutrons are emitted (in the fragment system) preferentially in the direction of fragment motion is not necessitated by their angular distribution measurements, which are well explained by the usual assumptions of isotropic emission with a Maxwell (or Maxwell-like) emission spectrum. The energy distribution (Watt spectrum) and the angular distribution, both including the effects of anisotropic emission, are given. (author) [French] On montre que la conclusion experimentale de Ramanna et Rao selon laquelle les neutrons prompts de fission sont emis (dans le systeme de reference des fragments) preferentiellement dans la direction du mouvement du fragment, ne decoule pas necessairement de leurs mesures de distribution angulaire. Celles-ci sont bien expliquees par l'hypothese classique de l'emission isotrope et d'un spectre d'emission maxwellien (ou quasi-maxwellien). On donne la distribution en energie (ou spectre de Watt) et la distribution angulaire, comprenant toutes les deux les effets d'emission anisotrope. (auteur)

  4. A Cold Neutron Monochromator and Scattering Apparatus; Monochromateur et appareillage pour la diffusion de neutrons lents; Monokhromator dlya ''kholodnykh'' nejtronov i pribor dlya rasseyaniya; Monocromador y aparato de dispersion para neutrones frios

    Energy Technology Data Exchange (ETDEWEB)

    Harris, D; Cocking, S J; Egelstaff, P A; Webb, F J [Nuclear Physics Division, Aere, Harwell, Didcot, Berks (United Kingdom)

    1963-01-15

    A narrow band of neutron wavelengths (4 A and greater) is selected from a collimated neutron beam obtained from the Dido reactor at Harwell. These neutrqps are scattered by various samples and the energy transfer of the scattered neutrons measured using time-of-flight techniques. The neutrons, moderated by a liquid hydrogen source in the reactor pass through first a liquid nitrogen- cooled filter, then a single crystal of bismuth and finally they are ''chopped'' by a magnesium-cadmium high- speed curved slot rotor. In this apparatus the wavelength spread of 0. 3 A at 4 . 1 A is determined primarily by the Be-Bi filter, while the time spread (8 {mu}s) is determined by the rotor. The monochromated neutron bursts from this rotor are scattered by a sample and detected in one of two counter arrays. When studying liquid or polycrystalline samples an array of six BF{sub 3}, counter assemblies (each 2 inches x 24 inches in area)are used covering scatter angles from 20{sup o} to 90{sup o}. This array is placed below the neutron beam. Above the line of the neutron beam is a second array consisting of three scintillators 2 inches in diameter, which is used for the study of single crystal samples. The output of each counter is fed into a tape recording system which has 500 time channels available for each counter. This apparatus has been used to study neutron scattering from several gaseous, liquid and crystalline samples and the most recent measurements are presented in other papers in these proceedings. [French] Les auteurs extraient une bande etroite de neutrons ( 4 A et plus) d'un faisceau collimate de neutrons produits par le reacteur Dido de Harwell. On fait diffuser ces neutrons au moyen de divers echantillons et on mesure le transfert d'energie des neutrons diffuses par la methode du temps de vol. Les neutrons ralentis par de l'hydrogene liquide place dans le reacteur passent d'abord dans un filtre refroidi a l'azote liquide, puis dans un monocristal de bismuth

  5. Retention in Solid KIO{sub 3} Activated with Fast and Slow Neutrons; Retention dans KIO{sub 3} Solide Active par des Neutrons Rapides et des Neutrons Lents; 0423 0414 0415 0420 0416 0410 041d 0418 0415 0412 0422 0412 0415 0420 0414 041e 041c KIO{sub 3}, 0410 041a 0422 0418 0412 0418 0420 041e 0412 0410 041d 041d 041e 041c 0411 042b 0421 0422 0420 042b 041c 0418 0418 041c 0415 0414 041b 0415 041d 041d 042b 041c 0418 041d 0415 0418 0422 0420 041e 041d 0410 041c 0418 ; Retencion en KIO{sub 3} Solido Activado con Neutrones Rapidos y Lentos

    Energy Technology Data Exchange (ETDEWEB)

    Aten, A.H.W. Jr.; Lindner-Groen, M.; Lindner, L. [Instituut voor Kernphysisch Onderzoek, Amsterdam (Netherlands)

    1965-04-15

    A simple model of recoil reactions in a solid would suggest that primary (unannealed) retention should demonstrate isotope effects (which would presumably be due to the way in which the product nucleus loses its excess nuclear energy), and that this quantity should be insensitive to the condition of the crystal lattice. On the other hand, annealing in this simple model should be dependent on the condition (and pretreatment) of the crystal, but show the same behaviour for different isotopes. A test for these arguments is provided by a series of experiments in which solid KIO{sub 3} was activated by means of fast and thermal neutrons. With fast neutrons the retention of I{sup 128} was appreciably higher than that of I{sup 126} but the retention of I{sup 128} obtained with thermal neutrons was even higher than that obtained with fast neutrons. This indicates that apart form the decay scheme the recoil energy may also constitute a factor determining the retention. The annealing of I{sup 128} and I{sup 126} (both obtained with fast neutrons) also proved to be different. Under post-irradiation treatment at temperatures up to 100 Degree-Sign C the retention of both isotopes increased by the same percentage of the total activity, i.e. the difference in retention remained constant. Thus the fraction of the I{sup 126} which is reduced by the recoil process in excess of the reduced fraction of I{sup 128} is much less affected by heating than the fraction which is reduced in both isotopes. It is evident that such complicated chemical behaviour of the radioactive recoil atom can only be explained by a fairly detailed model. (author) [French] Un modele simple de reactions de recul dans un solide donnerait a penser que la retention primaire (sans recuit) devrait manifester des effets isotopiques (probablement dus a la maniere dont le noyau du produit perd son excedent d'energie nucleaire) et que cette valeur devrait etre independante de l'etat du reseau cristallin. En revanche

  6. Conservative treatment of soft tissue sarcomas of the extremities. Functional evaluation with LENT-SOMA scales and the Enneking score; Traitement conservateur des sarcomes des tissus mous des membres. Evaluation du resultat fonctionnel selon l'echelle LENT-SOMA et le score de Enneking

    Energy Technology Data Exchange (ETDEWEB)

    Tawfiq, N.; Lagarde, P.; Thomas, L.; Kantor, G. [Institut Bergonie, Centre Regional de Lutte Contre le Cancer, Service de Radiotherapie, 33 - Bordeaux (France); Stockle, E. [Institut Bergonie, Centre Regional de Lutte Contre le Cancer, Service de Chirurgie, 33 - Bordeaux (France); Bui, B.N. [Institut Bergonie, Centre Regional de Lutte Contre le Cancer, Service d' Oncologie Medicale, 33 - Bordeaux (France)

    2000-12-01

    Objective. - The aim of this prospective study is the feasibility of late effects assessment by LENT-SOMA scales after conservative treatment of soft tissue sarcomas of the extremities and a comparison with the functional evaluation by the Enneking score. Patients and methods. - During the systematic follow-up consultations, a series of 32 consecutive patients was evaluated in terms of late effects by LENT SOMA scales and functional results by the Enneking score. The median time after treatment was 65 months. The treatment consisted of conservative surgery (all cases) followed by radiation therapy (29 cases), often combined with adjuvant therapy (12 concomitant radio-chemotherapy association cases out of 14). The assessment of the toxicity was retrospective for acute effects and prospective for the following late tissue damage: skin/subcutaneous tissues, muscles/soft tissues and peripheral nerves. Results. -According to the Enneking score, the global score for the overall series was high (24/30) despite four the scores zero for the psychological acceptance. According to LENT SOMA scales, a low rate of severe sequelae (grade 3-4) was observed. The occurrence of high-grade sequelae and their functional consequences were not correlated with quality of exeresis, dose of radiotherapy or use of concomitant chemotherapy. A complementarity was observed between certain factors of the Enneking score and some criteria of the LENTSOMA scales, especially of muscles/soft tissues. Conclusion. -The good quality of functional results was confirmed by the two mean scoring systems for late normal tissue damage. The routine use of LENT-SOMA seems to be more time consuming than the Enneking score (mean time of scoring: 1 3 versus five minutes). The LENT-SOMA scales are aimed at a detailed description of late toxicity and sequelae while the Enneking score provides a more global evaluation, including the psychological acceptance of treatment. The late effects assessment by the LENT

  7. Materiales. Lentes de contacto. (I)

    OpenAIRE

    Lozano Prieto, Beatriz

    2017-01-01

    La función de una lente de contacto, al igual que la de unas lentes oftálmicas en gafas, es la compensación de las ametropías ya sea miopía, hipermetropía o astigmatismo. En este trabajo se realiza un estudio metodológico basado principalmente en la evolución de las lentes de contacto y de sus materiales, desde las primeras lentes de vidrio esclerales y corneales, pasando por las lentes de material plástico, las rígidas permeables a los gases, las de hidrogel, y finalmente a las lentes de ...

  8. Improvements in fast-neutron spectroscopy methods (1961); Amelioration des methodes de spectrometrie des neutrons rapides (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Cambou, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-02-15

    This research aimed at improving fast-neutron electronic detectors based on n-p elastic scattering. The first part concerns proportional counters; careful constructional methods have made it possible to plot mono-energetic neutron spectra in the range 700 keV - 3 MeV with a resolution of 7 per cent. The second part concerns scintillation counters: an organic scintillator and an inorganic scintillator covered with a thin layer of a scattering agent. An exact study of the types of scintillation has made it possible to develop efficient discriminator circuits. Different neutron spectra plotted in the presence of a strong gamma background are presented. The last part deals with the development of form discrimination methods for the study, in the actual beam, of the elastic scattering of 14.58 MeV electrons. With hydrogen, the distribution f ({phi}) of the recoil protons is f({phi}) = 1 + 0.034 cos {phi} + 0.042 cos{sup 2} {phi}. With tritium the scattering is strongly anisotropic; the curve representing the variation of the differential cross-section for the elastic scattering in the centre of mass system is obtained with a target containing 1 cm{sup 3} of tritium. (author) [French] Le travail a porte sur l'amelioration des detecteurs electroniques de neutrons rapides bases sur la diffusion elastique n-p. La premiere partie est relative aux compteurs proportionnels; des methodes soignees de fabrication ont permis des traces de spectres de neutrons monoenergetiques dans le domaine 700 keV - 3 MeV avec une resolution de 7 pour cent. La deuxieme partie est relative au compteur a scintillations; scintillateur organique et scintillateur mineral recouvert d'un diffuseur mince. Une etude precise des formes de scintillations a permis la mise au point de circuits discriminateurs efficaces. Differents spectres de neutrons traces en presence d'un fond gamma intense sont presentes. La derniere partie est relative a la mise en oeuvre des methodes de discrimination de forme pour l

  9. The epithermal critical experiments; Experiences critiques avec des neutrons epitliermiques; Nadteplovye kriticheskie ehksperimenty; Experimentos criticos con neutrones epitermicos

    Energy Technology Data Exchange (ETDEWEB)

    Morewitz, H A; Carpenter, S O [Atomics International, Canoga Park, CA (United States)

    1962-03-15

    The epithermal critical experiments. The present phase of the advanced-epithermal-thorium-reactor programme consists of integral-reactor-physic s experiments designed to provide neutron-cross-section information in the 10-MeV to 1-keV range. A series of nine, multi-region, slow-fast, pseudospherica l critical assemblies of the honey- comb, split-table type are being studied. So far, three assemblies have' been run. The outer driver-decouple r region drives an interior U{sup 233}-Th fuelled spherical test region whose neutron-flux spectrum is successively degraded by increasing the graphite moderator to fuel ratio. A square-wave oscillator experiment defines the central reactivity worths of forty small samples of different materials to 10{sup -8} {Delta}k for each assembly. Additionally, intercalibrated artificial neutron sources are oscillated to determine the various central neutron importance functions. The spectra are obtained by fission-counter measurements with calibrated foils of different thresholds and by a Li{sup 6}-solid-state- counter sandwich spectrometer. A digital computer routine will be used to compile all measurements into a self-consistent library of spectrum averaged cross-sections. (author) [French] La phase actuelle du programme de reacteur au thorium a neutrons epithermiques comprend des experiences integrales de physique des reacteurs pour obtenir des renseignements sur les sections efficaces neutroniques pour la gamme d'energie comprise entre 1 keV et 10 MeV. Les auteurs etudient une serie de neuf ensembles critiques pseudospheriques, a plusieurs regions, a couplage neutrons lents et neutrons rapides du type a alveoles et a coeur divise. A ce jour, trois de ces ensembles ont ete mis en service. La region exterieure, mettant en service ou hors service, commande une zone d'essai interieure de forme spherique ou le combustible est constitue de {sup 233}U-Th, dont le spectre du flux de neutrons est degrade progressivement par augmentation du

  10. Monte-Carlo method for studying the slowing down of neutrons in a thin plate of hydrogenated matter; Methode de Monte-Carlo pour l'etude du ralentissement des neutrons dans une plaque mince de matiere hydrogenee

    Energy Technology Data Exchange (ETDEWEB)

    Ribon, P; Michaudon, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    The studies of interaction of slow neutrons with atomic nuclei by means of the time of flight methods are made with a pulsed neutron source with a broad energy spectrum. The measurement accuracy needs a high intensity and an output time as short as possible and well defined. If the neutrons source is a target bombarded by the beam of a pulsed accelerator, it is usually required to slow down the neutrons to obtain a sufficient intensity at low energies. The purpose of the Monte-Carlo method which is described in this paper is to study the slowing down properties, mainly the intensity and the output time distribution of the slowed-down neutrons. The choice of the method and parameters studied is explained as well as the principles, some calculations and the program organization. A few results given as examples were obtained in the line of this program, the limits of which are principally due to simplifying physical hypotheses. (author) [French] l'etude de l'interaction des neutrons lents avec les noyaux atomiques par la methode du temps de vol s'effectue avec une source pulsee de neutrons dont le spectre en energie est assez etendu. La precision des mesures demande que la source soit intense et que la duree d'emission des neutrons soit breve et bien definie. Si la source est une cible bombardee par le faisceau de particules d'un accelerateur pulse, il est generalement indispensable de ralentir les neutrons pour avoir une intensite suffisante a basse energie. Nous presentons ici une methode de Monte-Carlo pour l'etude detaillee de ce ralentissement, notamment l'intensite et la distribution des temps de sortie des neutrons ralentis. Cette presentation comprend: la justification du choix de la methode de Monte-Carlo, les principes generaux, les differentes etapes du calcul et du programme ecrit pour le calculateur electronique IBM 7090. Nous indiquons aussi les restrictions qui sont apportees au domaine d'application de ce programme et qui proviennent surtout des

  11. Fast neutron spectrometry and dosimetry; Spectrometrie et dosimetrie des neutrons rapides

    Energy Technology Data Exchange (ETDEWEB)

    Blaize, S; Ailloud, J; Mariani, J; Millot, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    We have studied fast neutron spectrometry and dosimetry through the recoil protons they produce in hydrogenated samples. In spectrometric, we used nuclear emulsions, in dosimetric, we used polyethylene coated with zinc sulphide and placed before a photomultiplier. (author)Fren. [French] Nous avons etudie la spectrometrie et la dosimetrie des neutrons rapides en utilisant les protons de recul qu'ils produisent dans une matiere hydrogenee. En spectrometrie, nous avons employe des emulsions nucleaires, en dosimetrie, du polyethylene recouvert de sulfure de zinc place devant un photomultiplicateur. (auteur)

  12. Compétition et coexistence : la motorisation des transports terrestres et le lent processus de substitution de la traction équine

    NARCIS (Netherlands)

    Mom, G.P.A.

    2009-01-01

    Cet article interroge les liens entre la mécanisation des moyens de transport terrestre et la disparition du cheval comme outil de locomotion. Trois domaines différents sont successivement analysés : le chemin de fer et le tramway dans la seconde moitié du xixe siècle, le développement des flottes

  13. Neutrons moderation theory; Theorie du ralentissement des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Vigier, J P

    1949-07-01

    This report gives a summarized presentation of the theory of fast neutrons diffusion and moderation in a given environment as elaborated by M. Langevin, E. Fermi, R. Marshak and others. This statistical theory is based on three assumptions: there is no inelastic diffusion, the elastic diffusion has a spherical symmetry with respect to the center of gravity of the neutron-nucleus system (s-scattering), and the effects of chemical bonds and thermal agitation of nuclei are neglected. The first chapter analyzes the Boltzmann equation of moderation, its first approximate solution (age-velocity equation) and its domain of validity, the extension of the age-velocity theory (general solution) and the boundary conditions, the upper order approximation (spherical harmonics method and Laplace transformation), the asymptotic solutions, and the theory of spatial momenta. The second chapter analyzes the energy distribution of delayed neutrons (stationary and non-stationary cases). (J.S.)

  14. Studies of the Solid and Liquid Phases of HF, HCl and HBr by Slow-Neutron Inelastic Scattering; Etude des Phases Solide et Liquide de HF, HCl Et HBr par la Diffusion Inelastique des Neutrons Lents; 0418 0417 0423 0427 0415 041d 0418 0415 0422 0412 0415 0420 0414 042b 0425 0418 0416 0418 0414 041a 0418 0425 0424 0410 0417 HF, HCl I HBr 0421 041f 041e 041c 041e 0429 042c 042e 041d 0415 0423 041f 0420 0423 0413 041e 0413 041e 0420 0410 0421 0421 0415 042f 041d 0418 042f 041c 0415 0414 041b 0415 041d 041d 042b 0425 041d 0415 0419 0422 0420 041e 041d 041e 0412 ; Estudio de las Fases Solida y Liquida del HF, HCl Y HBr por Dispersion Inelastica de Neutrones Lentos

    Energy Technology Data Exchange (ETDEWEB)

    Boutin, H. [Picatinny Arsenal, Dover, NJ (United States); Brookhaven National Laboratory, Upton, NY (United States); Safford, G. J. [Brookhaven National Laboratory, Upton, NY (United States)

    1965-06-15

    be attributed to a weaker degree of association, which is expected from the decreasing electronegativity of the anion. The systematic study of these spectra in the various phases and at variais temperatures allows a distinction to be made between the low frequency motions characteristic of the lattice or of an hydrogen-bonded chain and those low frequency motions which involve nearest-neighbour interactions or short-range forces. The results of these measurements are in agreement with previous infrared data and indicate that hydrogen bonding is an influential factor in explaining the spectra of the solid phases of both HCl and HBr. These data are not in agreement, however, with theories that account for the solid phases of these compounds only in terms of simple dipole arrays or in terms of long-range interactions involving the dipole moment of one single unit interacting with an average electric field. (author) [French] Les auteurs ont etudie les phases liquide et solide de HF, HCl et HBr entre les raies d'absorption 30 et 1200 cm{sup -1} employant la methode de la diffusion inelastique des neutrons froids (0, 005 eV). Ils ont procede a ces mesures pour examiner systematiquement l'influence qu'un accroissement du degre d'electronegativite et la dimension des anions exercent sur les mouvements moleculaires de basse frequence dans la phase solide et la phase liquide. L'etude a d'abord porte sur HF du fait que les donnees obtenues par diffraction des rayons X avaient montre que dans ce compose a l'etat solide apparaissaient de longues chaines en zigzag liees par l'hydrogene. Les spectres des neutrons inelastiquement diffuses par les phases liquide et solide de HF font ressortir le haut degre d'association qui existe dans toute la phase liquide en raison de la liaison hydrogenee. Aux fins d'interpretation, les auteurs comparent les donnees relatives a HF a des donnees analogues relatives aux ions HF{sub 2}{sup -} et H{sub 2}F{sub 3}{sup -} dont les structures sont

  15. Commentaire : Récits des contentieux : ce qu'ils révèlent des liens sociaux et des rapports aux autorités

    Directory of Open Access Journals (Sweden)

    Jack Thomas

    2009-10-01

    Full Text Available Les trois papiers présentés lors de cette session mettent en lumière plusieurs grands types de sources juridiques. Pour élise Chopin-Tufel, il s’agit de sources qui relèvent de la justice personnelle du roi ; ce sont des demandes d’enfermement adressées au roi par des particuliers mais traitées par les intendants des généralités. Marc Vacher explore les fonds judiciaires de la sénéchaussée de Lyon pour traquer les tentatives d’accommodement entre parties adverses. Les différentes pièces de pr...

  16. The determination of sulphur in materials of high neutron absorption cross-section by fast-neutron activation analysis; Determination du soufre dans les matieres de forte section efficace d'absorption neutronique, au moyen d'une analyse par activation avec des neutrons rapides; Opredelenie sery v materialakh s bol'shim secheniem pogloshcheniya nejtronov metodom aktivatsionnogo analiza bystrykh nejtronov; Determinacion del azufre en sustancias de elevada seccion eficaz de absorcion neutronica mediante analisis por activacion con neutrones rapidos

    Energy Technology Data Exchange (ETDEWEB)

    Gibbons, D; Simpson, H [Wantage Research Laboratory (A.E.R.E.), Wantage, Berks. (United Kingdom)

    1962-01-15

    The production of radiophosphorus by the fast neutron (n, p) reaction on sulphur is used for the determination of sulphur by activation analysis. Using this technique it is possible to determine sulphur in materials of high thermal-neutron absorption cross-section because the absorption cross-sections for fast neutrons are, in general, much lower than those for slow neutrons, so that self-shielding errors are considerably reduced. Interference due to the slow neutron (n, {gamma}) reaction on neutral phosphorus is eliminated by a double irradiation technique involving irradiation in regions of differing slow/fast flux-ratios. The method has been applied to the determination of sulphur in chromium and arsenic. (author) [French] La production de radiophosphore par reaction (n, p) de neutrons rapides sur le soufre est utilisee pour la determination du soufre au moyen d'une analyse par activation. Cette methode permet la determination du soufre dans les matieres de forte section efficace d'absorption des neutrons thermiques; en effet, les sections efficaces d'absorption des neutrons rapides sont, d'une maniere generale, beaucoup plus faibles que pour les neutrons lents, de sorte que les erreurs d'autoprotection se trouvent considerablement reduites. L'interference due a la reaction (n, {gamma}) des neutrons lents sur le phosphore naturel est eliminee par une double irradiation, qui implique une irradiation dans les regions ou le rapport du flux de neutrons lents au flux de neutrons rapides a des valeurs differentes. La methode a ete appliquee a la determination du soufre dans le chrome et l'arsenic. (author) [Spanish] La formacion de fosforo radiactivo por la accion de los neutrones rapidos sobre el azufre, reaccion (n, p), puede servir para determinar este elemento mediante analisis por activacion. El empleo de esta tecnica permite efectuar determinaciones de azufre en materiales de elevada seccion eficaz de absorcion de neutrones termicos porque, en general, las

  17. Theoretical study of the paramagnetic scattering of neutrons; Etude theorique de la diffusion paramagnetique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Saint-James, D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-02-15

    General paramagnetic scattering of neutrons is investigated in the situation where the orbital moment of the magnetic scattering ions is not quenched. The general relevant expression of the cross-section is given. The proceeding results are applied to rare earths and iron group ions. It is shown that if crystalline actions lift the free ion ground state degeneracy the neutron may induce transitions between the various levels, the distances of which are typically of the order of several hundred cm{sup -1}. The various scattering cross-sections (elastic and inelastic) are calculated for the rare earths in a cubic crystal field, for the holmium and erbium sesquioxide and for the anhydrous iron chloride (Cl{sub 2}Fe). These cross-sections are high enough to allow for an experimental detection, thus providing a direct determination of the levels distances through the measurement of the neutron wave-length shift. Moreover it is shown that, for neodymium, holmium, erbium, the total cross-section for neutrons of one angstrom wave length is rather insensitive to the crystal field effects. The results are then compared with the available experimental studies. The influence of the orbital moment on the angular dependence of the scattering for polarised ions is then investigated. The well-known formula: I = I{sub 0}sin{sup 2}{beta} is only an approximation, the validity of which is discussed. (author) [French] On envisage le cas general de la diffusion paramagnetique de neutrons. Le moment orbital des ions magnetiques ne peut etre considere comme bloque. On donne l'expression generale de la section efficace. Les resultats obtenus sont appliques au cas des terres rares et des ions du groupe du fer. On montre que, si les actions cristallines levent la degenerescence du niveau fondamental de l'ion libre, le neutron peut induire des transitions entre les divers sous-niveaux, dont la distance est ordinairement de l'ordre de quelques centaines de cm{sup -1}. La section efficace des

  18. A lente moderna

    Directory of Open Access Journals (Sweden)

    Maria Elisa Baptista

    2012-11-01

    Full Text Available Belo Horizonte, cidade moderna, abriga registros do surgimento da arquitetura moderna brasileira, flagrados na sua construção pela lente moderna do fotógrafo Wilson Baptista. Associar fragmentos das histórias arquitetônica e fotográfica nas décadas de 1930-1960 é o objetivo com este ensaio, baseado no relato pessoal da experiência de cada imagem. As referências arquitetônicas não se estendem além do necessário, por já terem sido publicadas por outros autores, limitando-se a referenciar o trabalho inventivo do fotógrafo, que traduz, em uma estética também moderna, a beleza da arquitetura belo-horizontina.

  19. Queratocone e lentes de contacto

    OpenAIRE

    Coutinho, I; Ramalho, M; Pedrosa, C; Pina, S; Mota, M; Santos, C; Vendrell, C

    2014-01-01

    Nos doentes com queratocone quando os óculos não possibilitam boa visão, as lentes de contacto são uma boa alternativa terapêutica. Há vários desenhos de lentes de contacto que podem ser utilizados na correção óptica do queratocone e a sua adaptação deve assegurar o menor trauma da córnea e conforto ao doente. Este trabalho pretende fazer fazendo-se breve revisão das lentes de contacto disponíveis no tratamento do queratocone.

  20. Neutron moderation at very low temperatures (1691); Moderation des neutrons aux tres basses temperatures (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Lacaze, A [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1961-04-15

    Starting from Harwell experiment carried out inside a low-power reactor, we intended to maintain a liquid hydrogen cell in a channel of the EL3 reactor (at Saclay) whose thermal neutrons flux is 10{sup 14} neutrons/cm{sup 2}/s. We tried to work out a device giving off an important beam of cold neutrons and able to operate in a way as automatic as possible during many consecutive day without a stop. Several circuits have already been achieved at very low temperatures but they brought out volumes and fluxes much lower than those we used this time. The difficulties we have met in carrying out such a device arose on the one hand from the very high energy release to which any kind of experiment is inevitably submitted when placed near the core of the reactor, on the other, hand from the very little room which is available in experimental channels of reactors. In such condition, it is necessary to use a moderator as effective as possible. This study is divided into three parts ; in the first part, we try to determine: a) conditions in which moderation takes place, hence the volume of the cell; b) materials likely to be used at low temperature and in pile; c) cooling system; hence we had to study fluid flow conditions at very low temperatures in very long ducts. The second part is devoted to the description of the device. The third part ventilates the results we have obtained. (author) [French] Partant de l'experience de Harwell faite dans une pile de faible puissance, nous nous sommes propose de maintenir une cellule d'hydrogene liquide dans un canal de la pile EL3 de Saclay dont le flux de neutrons thermiques est de 10{sup 14} neutrons par seconde et par cm{sup 2}. Nous avons cherche a realiser une installation donnant un faisceau de neutrons froids important, et pouvant fonctionner d'une maniere aussi automatique que possible, pendant des periodes de plusieurs jours sans arret. Plusieurs circuits aux tres basses temperatures ont deja ete realises, mais ils ne mettaient

  1. Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Samour, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

  2. Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Samour, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

  3. Calculation of actual cross sections and thermalization of neutrons; Calcul des sections efficaces effectives et thermalisation des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Naudet, R.

    1963-05-15

    This report gathers and presents in a simple way results of studies performed at the CEA on issues of spectra in thermal reactors. It is in fact a synthesis of results eventually published in different documents. It first presents the notion of actual cross section as it was introduced by Westcott to characterize the dependence of neutron behaviour on speed distribution. It addresses the case of a homogeneous medium with a conventional model, with the heavy gas model, and with the hydrogen gas model. It generalizes the approach by the differential model. The next part addresses the case of a heterogeneous medium, and the case of presence of moderator nuclei within the fuel [French] Le present rapport a pour objet de rassembler et de presenter de maniere simple les resultats des etudes effectuees au CE.A. sur les problemes de spectres dans les reacteurs thermiques. Ces resultats se trouvaient disperses dans plusieurs documents, ou n'etaient pas encore rediges, et bien que les etudes se poursuivent, il a paru utile d'en faire une synthese provisoire. On a cherche d'autre part a en donner une presentation elementaire, accessible aux lecteurs peu familiarises avec les problemes de thermalisation; dans cet esprit l'expose a une forme didactique, et comporte des rappels de notions bien connues comme par exemple le formalisme de Westcott. (auteur)

  4. Frequency Spectrum of Liquids and Cold Neutron Scattering; Spectre de frequences des liquides et diffusion de neutrons froids; Chastotnyj spektr zhidkostej i rasseyanie kholodnykh nejtronov; Espectro de frecuencias de los liquidos y dispersion de neutrones frios

    Energy Technology Data Exchange (ETDEWEB)

    Singwi, K S; Sjolander, A; Rahman, A [Argonne National Laboratory, Argonne, IL (United States)

    1963-01-15

    An important question which arises in connection with slow neutron scattering by liquids is: does there exist a frequency spectrum tor liquids analogous to that in solids? The answer to this question is given by showing that the width function {gamma}(t) of the Gaussian space-time self-correlation function G{sub s}(r,t) can be expressed, by using the frequency spectrum of the velocity auto-correlation function, in a form which is formally identical with that of a harmonic solid. Thus a knowledge of the frequency spectrum of the velocity auto-correlation function should enable one to calculate slow neutron scattering by liquids as has been emphasized by Egelstaff and co-workers. Using a stochastic model of a liquid, the frequency spectrum f({omega}) of the velocity auto-correlation function is calculated for water at 300{sup o}K and for liquid lead at 620{sup o}K. In the case of water a maximum in f({omega}) corresponding to {Dirac_h} 75{sup o}K is predicted. For lead the maximum also occurs at nearly the same {omega}-value. There also occurs a minimum in f({omega})in both cases. Larsson and Dahlborg have observed a maximum in f({omega}) at the above predicted {omega}-value. A recent observation in liquid lead of Cotter et al. probably confirms our prediction too. (author) [French] Dans le domaine de la diffusion des neutrons lents par des liquides une question importante se pose: existe-t-il un spectre de frequences pour les liquides analogue au spectre pour les solides? On peut repondre d cette quesnon en montrant que la fonction de largeur {gamma}(t) de la fonction gaussienne spatio-temporelle d'auto-correlation G{sub s}(r,t) peut etre exprimee, en employant le spectre de frequences de la fonction d'auto-correlation des vitesses, sous uune forme qui presente le membe aspect formel que celle d'un solide harmonique. par consequent, la connaissance du spectre de frequences de la fonction d'auto-correlation des vitesses devrait permettre de calculer la diffusion des

  5. Scattering of Neutrons by Liquid Bromine; Diffusion des neutrons par le brome liquide; R; Dispersion de neutrones por bromo liquido

    Energy Technology Data Exchange (ETDEWEB)

    Coote, G E; Haywood, B C [Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada)

    1963-01-15

    Neutrons of 0.037 eV and 0.0088 eV were scattered from a thin sample of liquid bromine at room temperature, and the energy distributions of the scattered neutrons measured at angles from 10{sup o} to 160{sup o} by the time-of-flight method. The angular distribution confirms the results of a previous study by Caglioti. Spectra were expressed in the form of the ''scattering law'' S({alpha},{beta}) of Egelstaff and analysed to derive the generalized frequency distribution p({beta}) of atomic motions in the liquid. The function p({beta}) has a broad smooth peak centred at {beta}{approx}0.3, and shows no evidence for discrete levels in the measured range 0<{beta}< 0.8: the general shape of the curve supports the 'quasi-crystalline' picture of the liquid. Difficulty in the absolute normalization of p({beta}) is discussed. (author) [French] Des neutrons de 0,037 eV et 0,0088 eV ont ete dissuses par un echantillon mince de brome liquide a la temperature ambiante; on a mesure, par la methode du temps de vol, les distributions d'energies des neutrons diffuses, pour des angles compris entre 10{sup o} et 160{sup o}. La distribution angulaire confirme les resultats d'une etude anterieure faite par Caglioti. Les spectres ont ete exprimes d'apres la ''loi de dispersion'' S({alpha},{beta}) d'Egelstaff et analyses pour determiner la distribution generalisee des frequences p({beta}) des mouvements atomiques dans le liquide. La fonction p({beta}) comporte un pic large et a faible pente dont le centre est a {beta} {approx} 0,3 et ne presente aucune indication de niveaux discrets dans la gamme mesuree 0 < {beta} < 0,8; la forme generale de la courbe confirme l'image ''quasi cristalline'' du liquide. Les auteurs examinent les difficultes qui s'opposent a la normalisation absolue de p({beta}). (author) [Spanish] Los autores han estudiado la dispersion de neutrones de 0,037 eV y 0,0088 eV en una muestra de bromo liquido de espesor reducido, a temperatura ambiente. La distribucion

  6. Theoretical Interpretation of Pulsed Neutron Phenomena; Interpretation Theorique des Phenomenes dus aux Neutrons Pulses; Teoreticheskaya interpretatsiya yavlenij, svyazannykh s impul'snymi nejtronami; Interpretacion Teorica de los Fenomenos Debidos a Neutrones Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Corngold, N. [Brookhaven National Laboratory, Upton, NY (United States)

    1965-08-15

    , au moyen des neutrons puises, portant sur des milieux non multiplicateurs, ainsi qu'a leur interpretation en fonction des modes espace-energie et des constantes de decroissance (en temps). Les etudes theoriques dans ce domaine, dont la plupart one ete executees au Laboratoire national de Brookhaven, sont fondees sur la solution exacte de plusieurs problemes particuliers et sur des solutions numeriques approximatives de problemes serrant la realite de plus pres. A une data recente, on a propose une interpretation unjforme fondee sur la theorie de la diffusion des neutrons lents etablie par Van Hove et Glauber. On a constate que le comportement a long terme de la fonction de correlation de paire, qui permet de distinguer entre les differents types de ralentisseurs, determine egalement le genre du spectre des constantes de decroissance que l'on obtient. Au cours de son examen critique, l'auteur met en evidence le cas des solutions relatives a un milieu infini, qui sont proportionnelles a exp(iB * r) dans les milieux a absorption 1/v. Le calcul analytique porte sur des solutions modales, egalement proportionnelles a exp({lambda}t), alors que le calcul numerique vise a obtenir la solution complete pour toute la duree depuis l'origine, ainsi que les solutions modales. Le memoire traite aussi de phenomenes qui se produisent lorsque l'absorption n'est pas 1/v et que l'echantillon de ralentisseur est si petit que les solutions a long terme ne peuvent plus Etre separees selon l'espace et l'energie. Enfin, l'auteur examine l'influence de ces faits nouveaux sur l'interpretation des experiences au moyen de neutrons puises - il mentionne notamment la mesure des coefficients de diffusion et de refroidissement par diffusion - ainsi que sur la nature de la methode a employer pour etudier la distribution asymptotique. (author) [Spanish] El autor discute los conocimientos y las teorias modernas sobre los efectos transitorios en las variaciones de la distribucion de los neutrones en el

  7. Lentes plegables suturadas a iris

    Directory of Open Access Journals (Sweden)

    Dunia Cruz Izquierdo

    Full Text Available Para la corrección quirúrgica de la afaquia existen en la actualidad varias técnicas quirúrgicas que permiten fijar los lentes intraoculares plegables o rígidos en cámara posterior suturados al iris o al sulcus ciliar. En estas circunstancias el cirujano determinará cuándo, dónde y el tipo de lente mejor a implantar. Se presenta un paciente con una afaquia traumática del ojo izquierdo, con agudeza visual sin corrección de movimiento de mano a 1 m. Se le realizó implante secundario de lente intraocular plegable de cámara posterior suturada al iris. En el examen biomicroscópico en lámpara de hendidura del ojo izquierdo se observó midriasis media paralítica, refracción dinámica de +11,00 (0,6 y tensión ocular normal. Se le realizó examen por bimicroscopía indirecta sin alteración. Al mes de operado la agudeza visual mejor corregida alcanzó la unidad de visión. Las complicaciones presentadas fueron ovalización de la pupila y depósitos de pigmentos de iris en el lente intraocular.

  8. Other applications of neutron beams in material sciences; Autres utilisations des faisceaux de neutrons en science des materiaux

    Energy Technology Data Exchange (ETDEWEB)

    Novion, C.H. de

    1997-12-31

    The various applications of neutron beams are reviewed. The different mechanisms involved in neutron interaction with matter are explained. We notice that generally neutron radiation effects are unfavorable but can be turned into efficient tools to add new structures or properties to materials, silicon doping is an example. The basis principles of neutron activation analysis and neutron radiography are described. (A.C.)

  9. Que peut-on voir avec des neutrons? Une introduction pour des non spécialistes

    Science.gov (United States)

    Schweizer, J.

    2005-11-01

    Le neutron est une particule élémentaire qui a été découverte en 1932 par James Chadwick. Ses caractéristiques principales sont résumées dans le tableau I. Il a été utilisé pour la première fois par Clifford Shull en 1946 comme outil pour des expériences de diffusion. Cette technique s'est depuis constamment développée pour concerner tous les aspects de la matière condensée: physique, chimie, matériaux, biologie. Il s'agit d'un outil tout à fait exceptionnel car le neutron possède des propriétés uniques et particulièrement adaptées pour ces études.

  10. The study of neutron transport by oscillation method; Etude du transport des neutrons par la methode de modulation

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, V

    1959-07-01

    The oscillation method is of very general use for studying the behavior of thermal neutrons in media. The main experiments are described and a general theory of them is given. This theory, which is presented in the first part, is established using the two-group approximation which has proved its efficiency in the case of thermal neutron piles. The validity of the two-group approximation is recalled. This allows definition of the meaning of the parameters used in the theory and which are measured in these experiments. The experiments carried out by this method are described, especially those performed at the Centre d'Etudes Nucleaires de Saclay where the method has been extensively used. These experiments are interpreted by means of the general theory given previously. In this way, the identity of parameters measured by this method and those given by the theory is proved. This is particularly conclusive is the case of the mean life of neutrons in a pile. (author) [French] La methode de modulation est un procede tres general d'etude des proprietes neutroniques des milieux contenant des neutrons thermiques. Le present rapport a pour but de decrire les principales de ces experiences et d'en donner une theorie generale. Cette theorie, exposee dans la premiere partie, est etablie dons le cadre de l'approximation a deux groupes de vitesse qui a prouve son efficacite dons le cas des piles a neutrons thermiques. Le domaine de validite de l'approximation a deux groupes est rappele au debut, ce qui permet de definir avec precision la signification des parametres qui entrent dons la theorie et qui font l'objet de ces mesures. La deuxieme partie decrit les experiences realisees, en particulier celles effectuees au Centre d'Etudes Nucleaires de Saclay ou la methode a ete considerablement developpee. Ces experiences sont interpretees dans le cadre de la theorie generale exposee precedemment. On prouve ainsi l'identite des parametres mesures par cette methode et de ceux figurant

  11. Fast neutron dosimetry and spectrometry using radioactivation (1963); Dosimetrie et spectrometrie des neutrons rapides par radioactivation (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Lamberieux, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    The author first recalls rapidly a few generalities concerning induced radioactivity detectors and gives, in an appendix, tables summarizing the properties of detector elements which may be used in radioprotection. The excitation functions found in the literature and also given. The technological characteristics of the detectors used are given, together with the counting methods. The many advantages of activation dosimetry for strong or periodic neutron fluxes and for those in the presence of {gamma}-radiation are stressed. The main problem in activation dosimetry is, however, the calculation of the dose absorbed from the results of the measurements. It is shown how the dose is expressed, fairly accurately, as a function of the radioactivities induced in a series of detectors. As an example, the spectrometry and the dosimetry of the neutron flux emitted by a Po-Be source are presented. (author) [French] L'auteur fait d'abord un bref rappel des generalites sur les detecteurs a radioactivite induite, accompagne, en annexe, des tableaux resumant les proprietes d'elements detecteurs utilisables en radioprotection. Les fonctions d'excitation trouvees dans la litterature y sont egalement annexees. On donne ensuite les caracteristiques technologiques des detecteurs employes ainsi que les methodes de comptage utilisees. On souligne les nombreux avantages de la dosimetrie par activation dans les flux de neutrons intenses ou periodiques et en presence de rayonnement {gamma}. Il reste que le probleme central de la dosimetrie par activation est le calcul de la dose absorbee a partir des resultats de mesure. On montre comment la dose s'exprime, de maniere approchee, en fonction des radioactivites induites dans une serie de detecteurs. A titre d'exemple, la spectrometrie et la dosimetrie du flux de neutrons emis par une source de Po-Be sont presentees. (auteur)

  12. Study of the propagation of fast neutrons in water, by Monte-Carlo methods; Etude de la propagation des neutrons rapides dans l'eau par des methodes de Monte-Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Lafore, P; Lattes, R; Millot, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    We have studied the propagation in water of neutrons from mono-directional plane sources with energies ranging from 300 keV to 19,66 MeV, placed in an infinite water medium. The exact paths of a number of neutrons are determined, taking into account the microscopic sections, assuming that inelastic collisions of the neutrons on oxygen are absorptions, and neglecting the loss of energy by elastic collisions on oxygen. The neutron lifetimes have been made use of to study the propagation of neutrons from fission sources, Po-Be, Po-B and Ra-Be, as well as the reflection of fast neutrons on a semi-infinite water medium. We have taken complete account of the first collision in order to improve the precision of the results. The calculations were carried out by Mrs J. VASSEUR and Mr A. GUILLOU. (author)Fren. [French] Nous etudions la propagation dans l'eau des neutrons a partir de sources planes monodirectionnelles dont les energies sont repartis de 300 keV a 19,66 MeV, placees dans un milieu infini d'eau. Nous determinons les trajectoires exactes d'un certain nombre de neutrons en tenant compte des sections microscopiques, en supposant que les chocs inelastiques des neutrons sur l'oxygene sont des absorptions, et en negligeant la perte d'energie par chocs elastiques sur l'oxygene. Les vies de neutrons ont ete exploitees pour etudier la propagation des neutrons a partir de sources de fission, Po-Be, Po-B et Ra-Be, ainsi que la reflexion des neutrons rapides sur un milieu semi-infini d'eau. On a tenu compte integralement du premier choc pour ameliorer la precision des resultats. Les calculs ont ete effectues par Mme J. VASSEUR et M.A. GUILLOU. (auteur)

  13. Experiments on neutron-attenuation by ordinary concrete; Etude experimentale de l'attenuation des neutrons dans le beton ordinaire

    Energy Technology Data Exchange (ETDEWEB)

    Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The penetration of fission-neutrons in water and glass mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 15 per cent. For smaller water-contents the measurements show the evidence of streaming, presumably due to slowing-down neutrons of energy smaller than 300 keV. Since a volume proportion of about 15 per cent of water in glass corresponds to the composition of ordinary concrete, the present work enables to predict the effects of a desiccation of concrete. Moreover, it is seen that there is no interest in increasing the proportion of water in ordinary concrete beyond the usual values (15-20 per cent). (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges verre-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 15 pour cent en volume. Pour des proportions d'eau inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. La composition des melanges verre-eau aux environs de 15 pour cent d'eau en volume correspondant au beton ordinaire, la presente etude permet de prevoir les effets d'une dessication du beton, et montre, en outre, qu'il n'y a pas interet a essayer d'augmenter la proportion d'eau dans le beton ordinaire au dela des valeurs usuelles (15 a 20 pour cent). (auteur)

  14. Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, V D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-06-01

    Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

  15. Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, V.D. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-06-01

    Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

  16. Delayed neutron detection in canning burst detection studies (1961); Etude sur la detection des neutrons differes en vue de la detection des ruptures de gaines (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Perlini, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    This paper describes a theoretical and experimental study on the detection of neutrons present in the primary cooling circuit of a reactor cooled by heavy or light water, with a view to the installation of a canning burst detection unit. The concentration of background neutrons is first calculated, taking into account the neutrons from nitrogen 17 decay, and the photoneutrons produced by the decay of nitrogen 16 and sodium 24. The emission of delayed fission neutrons, originating at a given crack in the canning, has been estimated. Using the D{sub 2}O circuit of the pile EL-3, three units have been developed by means of which the following three types of detector may be compared: 1) BF{sub 3} proportional counter 2) Boron scintillator 3) Fission chamber Under the present experimental conditions the BF{sub 3} counter gave the best results. The influence on these detectors of the {gamma} flux, which in certain cases reaches 200 R/h, is analysed. Finally a calibration is carried out with an experimental crack of 30 mm{sup 2} of uranium exposed to a flux of 5.8 x 10{sup 13} n.cm{sup -2}.s{sup -1}. The sensitivity obtained with the BF{sub 3} counter during this test is 2 counts/s per mm{sup 2} of exposed uranium. (author) [French] Le present rapport est une etude theorique et experimentale sur la detection des neutrons presents dans le circuit primaire de refroidissement d'un reacteur refrigere par l'eau lourde ou l'eau legere, en vue d'une installation de detection de ruptures de gaines. On fait d'abord un calcul sur la concentration des neutrons de bruit de fond en tenant compte: des neutrons de decroissance de l'azote 17 et des photoneutrons produits par les decroissances de l'azote 16 et du sodium 24. L'emission des neutrons differes de fission, qui ont pour origine une fissure de gaine donnee, a ete evaluee. Utilisant le circuit D{sub 2}O de la pile EL3, trois installations ont ete mises au point permettant de comparer les trois types de detecteurs suivants: 1

  17. Randvere Kool = Randvere School / Kristi Lents

    Index Scriptorium Estoniae

    Lents, Kristi, 1981-

    2013-01-01

    Kristi Lents-Esnari ja Marita Mätase (Allianss Arhitektid) kujundatud Randvere Kooli (G.H. Schüdlöffeli tee 4, Randvere küla, Viimsi) interjöörist. Hoone arhitekt Inga Raukas. Lühidalt Kristi Lents-Esnarist ja Marita Mätasest

  18. Measurement of the C / H ratio using neutrons; Mesure du rapport C / H au moyen des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Martinelli, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Ricci, H [Universite de Lima (Peru)

    1960-07-01

    A probe made up of a Ra ({alpha}, n) Be neutron source and a proportional counter filled with boron trifluoride has been used to measure the C/H ratio in hydrocarbons. The intensity of the thermal neutron flux in the neighbourhood of the detector increases with the concentration of the hydrocarbon hydrogen surrounding it. By measuring the density it is possible to deduce the C/H ratio. It is thus possible to evaluate the C/H ratio with a precision equal to that given by the {beta}-ray transmission method. The errors arising from the chemical nature of the hydrocarbon can be reduced to a minimum. This method has the advantage of allowing the measurement of the C/H ratio of hydrocarbons contained in recipients or thick steel tubing by means an independent portable apparatus. (author) [French] Une sonde constituee d'une source de neutrons Ra ({alpha}, n) Be et d'un compteur proportionnel a remplissage de trifluorure de bore a ete utilisee pour mesurer le rapport C/H dans les hydrocarbures. Le flux des neutrons thermiques au voisinage du detecteur est d'autant plus intense que la concentration en hydrogene de l'hydrocarbure qui entoure la sonde est plus elevee. Une mesure de densite permet d'en deduire le rapport C/H. On peut ainsi evaluer le rapport C/H avec une precision aussi bonne que celle que l'on obtient par transmission de rayons {beta}. Les erreurs provenant de la nature chimique de l'hydrocarbure peuvent etre minimisees. Cette methode presente l'avantage de permettre la mesure du rapport C/H d'hydrocarbures contenus dans des recipients ou des canalisations epaisses en acier a l'aide d'un appareil exterieur transportable. (auteur)

  19. Propagation of thermal neutrons in mock-up screw-shaped steel elements with water protection; Propagation des neutrons thermiques dans des fausses cartouches d'acier en helice dans une protection d'eau. Programme tournesol 3

    Energy Technology Data Exchange (ETDEWEB)

    Devillers, C L; Lanore, J M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1967-07-01

    This report treats the streaming of thermal neutrons in a cylindrical duct in light water. The duct contains a spiral iron shield. Transmission and reflection matrices are used to describe the probabilities for the thermal neutrons to be absorbed or to be scattered on the surfaces. The neutron paths across the void are represented by geometrical matrices. The numerical resolution is performed by the Monte-Carlo method. (authors) [French] Dans ce rapport on traite un probleme de fuites de neutrons thermiques dans un canal cylindrique plonge dans l'eau et obture par un ecran helicoidal en acier. On utilise des matrices de transmission-reflexion pour decrire les probabilites d'absorption et de diffusion des neutrons sur les parois et l'helicoide et des matrices de correspondance geometrique pour representer la propagation dans le vide. La resolution numerique se fait par une methode de Monte-Carlo. (auteur)

  20. Basic physics with ultra cold neutrons; Physique fondamentale avec des neutrons ultra froids

    Energy Technology Data Exchange (ETDEWEB)

    Protasov, K. [Laboratoire de Physique Subatomique et de Cosmologie, CNRS-IN2P3, Universite Joseph Fourier, INPG, Grenoble (France)

    2007-07-01

    A short introduction to the physics of Ultra Cold Neutrons (UCN) is given. It covers different aspects from their discovery, their major properties as well as their using in the three experiments of fundamental physics: measurements of the neutron life time and of its electric dipole moment and studies of neutrons quantum states in the Earth's gravitational field. (author)

  1. Irradiation and development of the nuclear emulsions exposed to intense fluxes of thermal neutrons with {gamma} rays; Irradiation et developpement des emulsions nucleaires exposees a des flux intenses de neutrons thermiques, accompagnes de rayons {gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, H; Bonnet, A; Cohen, J [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1952-07-01

    The thermal neutron fluxes provided by nuclear reactors permit the survey of relatively rare phenomenons, and dosage of very weak quantities of some elements. One of the most favorable detection technique are constituted by the use of the nuclear emulsions. one can mention: - the dosage of uranium by counting in the emulsion the number of traces due to fission fragments after irradiation. - The dosage of the lithium and the boron as trace amounts with the help of nuclear reactions (n, {alpha}) and thermal neutrons. - The research of reactions (n, {alpha}) or (n, p) of very weak cross section for middle or heavy elements. These different applications require however important neutrons fluxes. It had therefore obliged us to search for the most favorable irradiation and development of the emulsions conditions, to get the best visibility of the trajectories and decrease the phenomena of fog on the emulsion, which prevents any observation. (M.B.) [French] Les flux de neutrons thermiques fournis par les reacteurs nucleaires permettent l'etude de phenomenes relativement rares, et le dosage de tres faibles quantites de certains elements. Un des moyens de detection les plus favorables est constitue par l'utilisation des emulsions nucleaires. on peut citer: - le dosage de l'uranium par comptage dans l'emulsion du nombre de traces dues aux fragments de fission apres irradiation. - Le dosage du lithium et du bore a l'etat de traces a l'aide des reactions (n, {alpha}) sous l'action des neutrons thermiques. - La recherche de reactions (n,{alpha}) ou (n,p) de tres faible section efficace pour des elements moyens ou lourds. Ces differentes applications necessite cependant des flux de neutrons important. On a donc ete amene a rechercher les conditions les plus favorables d'irradiation et de developpement des emulsions, de maniere a obtenir la meilleure visibilite des trajectoires et diminuer les phenomenes de voile de l'emulsion, qui empeche toute observation. (M.B.)

  2. Neutron noise in nuclear reactors; Le bruit neutronique des reacteurs nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Blaquiere, A. [Institut National des Sciences et Techniques Nucleaires (France); Pachowska, R. [Universite Technique de Varsovie (Poland)

    1961-06-15

    The power of a nuclear reactor, in the operating conditions, presents fluctuations due to various causes. This random behaviour can be included in the study of 'noises'. Among other sources of noise, we analyse hereafter the fluctuations due: a) to the discontinuous emissions of neutrons from an independent source; b) to the multiplication of neutrons inside the reactor. The method which we present makes use of the analogies between the rules governing a nuclear reactor in operation and a number of radio-electrical systems, in particular the feed-back loops. The reactor can be characterized by its 'passing band' and is described as a system submitted to a sequence of random pulses. In non linear operating condition, the effect of neutron noise is defined by means of a non-linear functional, this theory is thus related to previous works the references of which are given at the end of the present report. This leads us in particular in the case of nuclear reactors to some results given by A. Blaquiere in the case of radio-electrical loops. (author) [French] La puissance d'un reacteur nucleaire, dans les conditions du regime, est affectee de fluctuations dont les causes sont tres diverses. Ce comportement aleatoire rentre dans le cadre general de l'etude des 'bruits'. Entre autres sources ce bruit, nous analysons ici les fluctuations dues: a) a l'emission discontinue des neutrons provenant d'une source autonome; b) a la multiplication des neutrons au sein du reacteur. La methode que nous introduisons exploite les analogies entre les lois qui regissent un reacteur nucleaire au regime et certains systemes radioelectriques, en particulier les circuits a boucle de reaction. Le reacteur est caracterise par sa 'bande passante' et est decrit comme un systeme soumis a une succession d'impulsions aleatoires. Dans les conditions de fonctionnement non lineaires, l'effet du bruit neutronique est precise en utilisant une fonctionnelle non lineaire, ce qui relie cette theorie a

  3. Measurement of the diffusion length of thermal neutrons in the beryllium oxide; Mesure de la longueur de diffusion des neutrons thermiques dans l'oxyde de beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Koechlin, J C; Martelly, J; Duggal, V P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The diffusion length of thermal neutrons in the beryllium oxide has been obtained while studying the spatial distribution of the neutrons in a massive parallelepiped of this matter placed before the thermal column of the reactor core of Saclay. The mean density of the beryllium oxide (BeO) is 2,95 gr/cm{sup 3}, the mean density of the massif is 2,92 gr/cm{sup 3}. The value of the diffusion length, deducted of the done measures, is: L = 32,7 {+-} 0,5 cm (likely gap). Some remarks are formulated about the influence of the spectral distribution of the neutrons flux used. (authors) [French] La longueur de diffusion des neutrons thermiques dans l'oxyde de beryllium a ete obtenue en etudiant la repartition spatiale des neutrons dans un massif parallelepipedique de cette matiere placee devant la colonne thermique de la Pile de Saclay. La densite moyenne de l'oxyde de beryllium (BeO) est de 2,95 gr/cm{sup 3}, la densite moyenne du massif de 2,92 gr/cm{sup 3}. La valeur de la longueur de diffusion, deduite des mesures effectuees est: L 32,7 {+-} 0,5 cm (ecart probable). Des remarques sont formulees quant a l'influence de la repartition spectrale du flux de neutrons utilise. (auteurs)

  4. Use of the helium-3 proportional counter for neutron spectrometry; Utilisation du compteur proportionnel a helium 3 pour la spectrometrie des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Vialettes, H; Le Thanh, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    Up to now, two methods have been mainly used for neutron spectrometry near nuclear installations: - photographic emulsion spectrometry - the so-called, 'multisphere' technique spectrometry. The first method, which is fairly difficult to apply, has a threshold energy of about 500 keV; this is a big disadvantage for an apparatus which has to be used for spectrometry around nuclear installations where the neutron radiation is very much degraded energetically. The second method does not suffer from this disadvantage but the results which it yields are only approximate. In order to extend the energy range of the neutron spectra studied with sufficient accuracy the use of a helium-3 proportional counter has been considered. This report presents the principles of operation of the helium-3 spectrometer, and the calculation methods which make it possible to take into account the two main effects tending to deform the spectra obtained: - energy absorption by the walls of the counter, - energy loss of the incident neutrons due to elastic collisions with helium-3 nuclei. As an example of the application, the shape of the neutron spectrum emitted by a polonium-lithium source is given; the results obtained are in excellent agreement with theoretical predictions. (authors) [French] Jusqu'ici deux methodes ont ete utilisees principalement pour la spectrometrie des neutrons autour des installations nucleaires: - la spectrometrie par emulsions photographiques - la spectrometrie par la technique dite des multispheres. La premiere methode, d'un emploi assez delicat presente un seuil en energie d'environ 500 keV qui est un obstacle serieux a la spectrometrie autour des installations nucleaires ou le rayonnement neutronique est tres degrade en energie. La deuxieme methode ne presente pas cet inconvenient mais les resultats qu'elle permet d'obtenir ne sont qu'approches. Pour etendre la gamme d'energie des spectres de neutrons etudies avec une precision suffisante, l'utilisation du

  5. Rotor calculations for neutron spectroscopy; Calculs des rotors de spectrometres a neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Gobert, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    The determination of stress in a rotating disk plane of symmetry normal to the axis of rotation has been studied by a number of investigators. In a recent paper Reich gives an operating process for an analytical solution in an asymmetric rotating disk. In the report we give the calculation of finite difference stress solutions applicable to the two rotating disks. The equations are then programmed for the 360.75 computer by Fortran methods concerning the rotors of choppers. (author) [French] La determination des contraintes dans les disques symetriques, en rotation a ete etudiee par de nombreux auteurs. Dans un recent rapport, Reich donne une solution pour le calcul des disques asymetriques. Ce rapport concerne l'application du calcul des contraintes par differences finies aux deux types de rotors. Les equations ecrites en langage Fortran pour l'ordinateur 360.75 concerne les rotors de choppers. (auteur)

  6. Neutronic study of the two french heavy water reactors; Etude neutronique des deux piles francaises a eau lourde

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The two french reactors - the reactor of Chatillon, named Zoe, and the reactor of Saclay - P2 - were the object of detailed neutronic studies which the main ideas are exposed in this report. These studies were mostly done by the Department of the Reactor Studies (D.E.P.). We have thus studied the distribution of neutronic fluxes; the factors influencing reactivity; the link between reactivity and divergence with the formula of Nordheim; the mean time life of neutrons; neutron spectra s of P2; the xenon effect; or the effect of the different adjustments of the plates and controls bar. (M.B.) [French] Les deux reacteurs francais - la pile de Chatillon, appelee ZOE, et la pile de Saclay, designee dans la suite par P2 - ont fait l'objet d'etudes neutroniques detaillees dont les principales sont exposees dans ce rapport. Ces etudes ont ete pour la plupart effectuees dans le cadre du Departement des Etudes de Piles (D.E.P.). Nous avons ainsi entre autre etudie la distribution du flux neutronique; les facteurs influencants la reactivite; le lien entre reactivite et divergence par la formule de Nordheim; le temps de vie moyen des neutrons; les spectres de neutrons de P2; l'effet xenon; ou encore l'effet des differents reglages des plaques et barres de controles. (M.B.)

  7. Experiments on neutron-attenuation by water-lead mixtures; Etude experimentale de l'attenuation des neutrons dans les melanges plomb-eau

    Energy Technology Data Exchange (ETDEWEB)

    Beauge, R; Millot, J P; Rastoin, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The penetration of fission neutrons in water-lead mixtures has been investigated in the NAIADE facility. The slopes of the thermal and fast fluxes (the latter measured with a dosimeter) remain similar when the volume proportion of water is greater than 65 per cent. For smaller water contents, the measurements show the evidence of streaming presumably due to slowing-down neutrons of energy smaller than 300 keV. (author) [French] La propagation des neutrons de fission a ete etudiee dans les melanges plomb-eau au moyen du dispositif NAIADE. La pente du flux thermique et la pente du flux rapide (obtenue au moyen d'un dosimetre) restent voisines lorsque la proportion d'eau dans le melange depasse 65 pour cent en volume. Pour des proportions inferieures les mesures mettent en evidence un 'streaming' de neutrons en ralentissement d'energie probablement inferieure a 300 keV. (auteur)

  8. A new detector for the measurement of neutron flux in nuclear reactors; Nouvelle methode de mesure des flux de neutrons dans les reacteurs atomiques

    Energy Technology Data Exchange (ETDEWEB)

    Koch, L; Labeyrie, J; Tarassenko, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The detector described is designed for the instantaneous measurement of thermal neutron fluxes, in the presence of high {gamma} ray activity; this detector can withstand temperatures as high as 500 deg. C. It is based on the following principle: radioactive atoms resulting from heavy-nucleus fission are carried by a gas flow to a detector recording their {beta} and {gamma} disintegration. Thermal neutron fluxes as low as few neutrons per cm{sup 2} per second can be measured. This detector may be used to control a nuclear reactor, to plot the thermal flux distribution with an excellent definition (1 mm{sup 2}) for fluxes higher than 10{sup 8} n/cm{sup 2}/s. The time response of the system to a sharp variation of flux is limited, in case of large fluxes, to the transit time of the gas flow between the fission product emitter and the detector; of the order of one tenth of a sec per meter of piping. The detector may also be applied for spectroscopy of fission products eider than 0,1 s. (author)Fren. [French] On decrit un appareil permettant la mesure instantanee des flux de neutrons thermiques accompagnes de flux intenses de rayons {gamma} et situes dans des enceintes pouvant etre portees a des temperatures superieures a 500 deg. C. On utilise la radioactivite des atomes resultant de la fission des noyaux lourds; ces atomes sont entraines par un courant gazeux vers un detecteur de radioactivite qui enregistre leurs desintegrations {beta} et {gamma}. On peut mesurer des flux partir de quelques neutrons thermiques par cm{sup 2} et par seconde. L'appareil permet de suivre la puissance d'un reacteur atomique, de tracer des cartes de densite de neutrons avec une tres bonne definition (1 mm{sup 2}) dans le cas de flux superieurs a 10{sup 8} cm{sup 2}/s. Le temps de reponse du systeme a une variation du flux de neutrons est limite, poes flux importants, par le temps de transit du gaz entre l'emetteur de produits de fission et le detecteur: soit quelques dizaines de

  9. Thermal, intermediate and fast neutron flux measurements using activation detectors; Mesure des flux de neutrons thermiques, intermediaires et rapides au moyen de detecteurs par activation

    Energy Technology Data Exchange (ETDEWEB)

    Brisbois, J; Lott, M; Manent, G [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1964-07-01

    The problem of neutron flux measurements using activation detectors is studied in the particular case of protection research. It is shown how it possible, it is possible, using a known thermal flux, to organise a coherent calibration system for all the detectors. The rapid neutron detectors are calibrated with respect to a reference detector (phosphorus) in a natural uranium converter; the intermediate neutron detectors with respect to gold in the axial channel of ZOE. This method makes it possible to minimise the errors due to the activation cross-sections. A brief description is given of the counting room of the Pile Safety Study Service, as well of the practical utilisation characteristics of the counters employed. (authors) [French] Le probleme de la mesure des flux de neutrons au moyen de detecteurs par activation est etudie dans le cas particulier des etudes de protections. On montre comment, a partir d'un flux thermique connu, on peut organiser un systeme coherent d'etalonnage de tous les detecteurs. Les detecteurs de neutrons rapides sont etalonnes par rapport a un detecteur de reference (phosphore) dans un convertisseur en uranium naturel; les detecteurs de neutrons intermediaires, par rapport a l'or dans le canal axial de ZOE, Cette methode permet de minimiser les erreurs dues aux sections efficaces d'activation. On decrit sommairement la salle de comptage du Service d'Etudes de Protections de Piles et on indique les caracteristiques d'emploi pratique des detecteurs utilises. (auteurs)

  10. The structure of para-toluidine by X-ray and neutron diffraction; Etude de la structure de la para-toluidine par la diffraction des rayons X et des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Bertinotti, A L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-12-01

    The crystal and molecular structure of para-toluidine has been solved by X-ray and neutron diffraction counter techniques. The molecules are arranged in the form of infinite chains in the crystal, each molecule being linked to two neighbours by hydrogen bonds. The presence of the H bonds makes clear the difference in the melting points between para-toluidine and benzene hydrocarbons of related symmetry and molecular weight. Their direction accounts for the (001) cleavage and the growth anisotropy of crystals from supersaturated vapour phase. A structure-seeking method by computer has been elaborated, using lattice energy calculations applied to molecules treated as rigid bodies and making use of a simplex method for function minimization without calculation of derivatives. The way the available information is handled allows to increase the range of convergence, as shown in the case of para-toluidine. (author) [French] La structure cristalline et moleculaire de la para-toluidine a ete resolue a l'aide de la diffraction des rayons X et des neutrons. L'analyse a revele que la structure presentait un encha ement particulier des molecules, liees entre elles par des ponts hydrogene. La presence des liaisons rend compte de l'elevation du point de fusion de la para-toluidine par rapport a celui des carbures benzeniques de symetrie et de poids moleculaires voisins. La direction des liaisons explique le clivage facile (001) des cristaux obtenus par fusion et l'anisotropie de croissance des cristaux en phase vapeur. Une methode de recherche de structures par ordinateur a ete elaboree, faisant usage du concept d'energie reticulaire applique aux molecules considerees comme rigides et faisant appel a une methode de simplexe pour la minimisation des fonctions sans calcul de derivees. La maniere dont est exploitee l'information disponible permet d'accro re, comme cela est montre dans le cas de la para-toluidine, l'etendue du domaine de convergence. (auteur)

  11. Contribution to the study of neutron propagation in cavities; Contribution a l'etude de la propagation des neutrons dans les cavites

    Energy Technology Data Exchange (ETDEWEB)

    Hasselin, G [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1965-07-01

    In large size cavities where the dimensions of the holes are greater than the mean free path of the radiations, the neutron propagation calculations are carried out by taking into account the effect of the medium surrounding the hole using a reflection coefficient or albedo. In this work the fast neutron albedos are obtained for various materials and these results are applied for a Monte-Carlo propagation calculation. A comparison of this calculation with experimental results shows the validity of the method. (author) [French] Dans les cavites de grandes dimensions, ou les dimensions des vides sont superieures au libre parcours moyen des rayonnements, le calcul de la propagation des neutrons se fait en essayant de rendre compte de l'effet du milieu entourant le vide, par un coefficient de reflexion ou albedo. Dans cette etude, sont d'une part obtenus des albedo en neutrons rapides sur divers materiaux, d'autre part ces resultats sont appliques pour un calcul de MONTE-CARLO de propagation. La comparaison entre le calcul et l'experience montre la validite de la methode. (auteur)

  12. Contribution to the study of neutron propagation in cavities; Contribution a l'etude de la propagation des neutrons dans les cavites

    Energy Technology Data Exchange (ETDEWEB)

    Hasselin, G. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1965-07-01

    In large size cavities where the dimensions of the holes are greater than the mean free path of the radiations, the neutron propagation calculations are carried out by taking into account the effect of the medium surrounding the hole using a reflection coefficient or albedo. In this work the fast neutron albedos are obtained for various materials and these results are applied for a Monte-Carlo propagation calculation. A comparison of this calculation with experimental results shows the validity of the method. (author) [French] Dans les cavites de grandes dimensions, ou les dimensions des vides sont superieures au libre parcours moyen des rayonnements, le calcul de la propagation des neutrons se fait en essayant de rendre compte de l'effet du milieu entourant le vide, par un coefficient de reflexion ou albedo. Dans cette etude, sont d'une part obtenus des albedo en neutrons rapides sur divers materiaux, d'autre part ces resultats sont appliques pour un calcul de MONTE-CARLO de propagation. La comparaison entre le calcul et l'experience montre la validite de la methode. (auteur)

  13. Diffraction des neutrons : principe, dispositifs expérimentaux et applications

    Science.gov (United States)

    Muller, C.

    2003-02-01

    La diffraction de neutrons, sur monocristal ou sur échantillon polycristallin (ou poudre), est une technique très largement utilisée, en science des matériaux comme en biologie, lorsque l'on souhaite déterminer la structure cristalline d'un composé ou d'une molécule. Toutefois, le degré de précision de la détermination structurale est très corrélé au choix de l'instrument utilisé. Il s'en suit que la question “comment choisir l'instrument le mieux adapté au composé et à la problématique ?" apparaît comme fondamentale. L'objectif de ce cours est de tenter de répondre à cette question en décrivant brièvement les caractéristiques instrumentales de différents diffractomètres, en exposant les avantages spécifiques des expériences de diffraction de neutrons et en donnant quelques exemples d'application.

  14. Experimental methods of reactor physics; Methodes experimentales de physique des reacteurs a neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Breton, D; Lafore, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    This paper is a synthesis of various experimental methods in use with the reactors of the Commissariat a l'Energie Atomique. The main techniques used are mentioned and the difficulties encountered and the accuracy obtained are particularly dwelt upon. The application of these various methods to reactors in order to obtain specific results is also indicated. This paper consists of five parts. I - General methods. Macroscopic and microscopic flux distribution (anisotropy effect), power distribution, etc... II - Kinetic measurements a) pulsed neutron technique: apparatus and accuracy; application to {lambda}t and to anti reactivity measurements; application to graphite, light water and beryllium oxide. b) oscillation techniques: equipment and accuracy; application to the measurements of effective cross sections and resonance integrals. c) fluctuations: apparatus and technique of measurement. III - Poison methods. Description of methods for introducing and extracting the poison, difficulties encountered with light and heavy water, measurement of temperature coefficients and anti-reactivity. IV - Spectra measurements. Choice and development of foils, problems of measurement, application to spectral measurements for thermalization studies, application to dosimetry. V - Experimental shielding measurements. The technique and apparatus recently developed in this field are presented. (authors) [French] Cette communication fait une synthese des differentes methodes experimentales mises en oeuvre sur les reacteurs du CEA. Elle presente les principales techniques utilisees et insiste plus particulierement sur les difficultes rencontrees et la precision obtenue; elle indique egalement l'application de ces differentes methodes sur les reacteurs, en vue de l'obtention des resultats determines. Elle comporte cinq parties: I - METHODES GENERALES: Distribution de flux macroscopique et microscopique (effet d'anisotropie), distribution de puissance, etc... II - MESURES CINETIQUES: a

  15. Studies and modeling of cold neutron sources; Etude et modelisation des sources froides de neutron

    Energy Technology Data Exchange (ETDEWEB)

    Campioni, G

    2004-11-15

    With the purpose of updating knowledge in the fields of cold neutron sources, the work of this thesis has been run according to the 3 following axes. First, the gathering of specific information forming the materials of this work. This set of knowledge covers the following fields: cold neutron, cross-sections for the different cold moderators, flux slowing down, different measurements of the cold flux and finally, issues in the thermal analysis of the problem. Secondly, the study and development of suitable computation tools. After an analysis of the problem, several tools have been planed, implemented and tested in the 3-dimensional radiation transport code Tripoli-4. In particular, a module of uncoupling, integrated in the official version of Tripoli-4, can perform Monte-Carlo parametric studies with a spare factor of Cpu time fetching 50 times. A module of coupling, simulating neutron guides, has also been developed and implemented in the Monte-Carlo code McStas. Thirdly, achieving a complete study for the validation of the installed calculation chain. These studies focus on 3 cold sources currently functioning: SP1 from Orphee reactor and 2 other sources (SFH and SFV) from the HFR at the Laue Langevin Institute. These studies give examples of problems and methods for the design of future cold sources.

  16. Irradiation and development of the nuclear emulsions exposed to intense fluxes of thermal neutrons with {gamma} rays; Irradiation et developpement des emulsions nucleaires exposees a des flux intenses de neutrons thermiques, accompagnes de rayons {gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, H.; Bonnet, A.; Cohen, J. [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1952-07-01

    The thermal neutron fluxes provided by nuclear reactors permit the survey of relatively rare phenomenons, and dosage of very weak quantities of some elements. One of the most favorable detection technique are constituted by the use of the nuclear emulsions. one can mention: - the dosage of uranium by counting in the emulsion the number of traces due to fission fragments after irradiation. - The dosage of the lithium and the boron as trace amounts with the help of nuclear reactions (n, {alpha}) and thermal neutrons. - The research of reactions (n, {alpha}) or (n, p) of very weak cross section for middle or heavy elements. These different applications require however important neutrons fluxes. It had therefore obliged us to search for the most favorable irradiation and development of the emulsions conditions, to get the best visibility of the trajectories and decrease the phenomena of fog on the emulsion, which prevents any observation. (M.B.) [French] Les flux de neutrons thermiques fournis par les reacteurs nucleaires permettent l'etude de phenomenes relativement rares, et le dosage de tres faibles quantites de certains elements. Un des moyens de detection les plus favorables est constitue par l'utilisation des emulsions nucleaires. on peut citer: - le dosage de l'uranium par comptage dans l'emulsion du nombre de traces dues aux fragments de fission apres irradiation. - Le dosage du lithium et du bore a l'etat de traces a l'aide des reactions (n, {alpha}) sous l'action des neutrons thermiques. - La recherche de reactions (n,{alpha}) ou (n,p) de tres faible section efficace pour des elements moyens ou lourds. Ces differentes applications necessite cependant des flux de neutrons important. On a donc ete amene a rechercher les conditions les plus favorables d'irradiation et de developpement des emulsions, de maniere a obtenir la meilleure visibilite des trajectoires et diminuer les phenomenes de voile de l'emulsion, qui

  17. Lentes de contacto en el deporte

    Directory of Open Access Journals (Sweden)

    Lluïsa Quevedo i Junyent

    2007-06-01

    Full Text Available Tras una completa evaluación optométrica, la primera responsabilidad del especialista, es procurar al deportista amétrope (miope, hipermétrope, astígmata... una óptima calidad de visión, ya sea con gafas o, preferiblemente, con lentes de contacto, por las numerosas ventajas que éstas presentan para el deportista. En los últimos años, especialmente, la industria de las lentes de contacto viene experimentando una evolución imparable, con grandes innovaciones a nivel de materiales, diseños y frecuencias de reemplazo que se traducen en mayor calidad de visión, confort y seguridad para el usuario. Las lentes de contacto desechables (usar y tirar, suelen ser de primera elección para los deportistas. En esta línea se encuentra la lente de contacto Nike Max Sight, de reciente comercialización en nuestro país, y que sin duda, como ya está sucediendo en los EUA, puede comportar una pequeña revolución en el contexto deportivo

  18. Nuevas aplicaciones de las lentes de contacto

    OpenAIRE

    Blanco Menéndez, Patricia

    2017-01-01

    Revisión bibliográfica de los estudios para el seguimiento y monitorización de patologías de elevada prevalencia (glaucoma y diabetes mellitus) de una forma no invasiva y administración de fármacos mediante el uso de lentes de contacto. Grado en Optica y Optometría

  19. 7 CFR 1710.107 - Amount lent for acquisitions.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Amount lent for acquisitions. 1710.107 Section 1710... GUARANTEES Loan Purposes and Basic Policies § 1710.107 Amount lent for acquisitions. The maximum amount that will be lent for an acquisition is limited to the value of the property, as determined by RUS. If the...

  20. Study of fast neutron scattering. The displacement cross-section (1962); Etude de la diffusion des neutrons rapides. Section efficace de deplacement (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Millot, J P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1962-07-01

    We propose a method for calculating the biological efficiency of fast neutrons emitted by in-pile fission sources. This method justifies the empirical theory of Albert and Welton. In making simple assumptions concerning the cross-sections, we have supposed that the propagation can ben reduced to a mono-kinetic problem. A system of orthonormal functions is then set up making it possible to calculate the flux leaving a planar source. This method generalises the results obtained by Platzek to the case where the elastic cross-sections are not isotropic, and make it possible in particular to define a displacement cross-section: extension of the diffusion coefficient. This method can be generalised to the case of neutron diffraction as a function of time, and to the study of slowing-down. Numerical results are given in an appendix for the following: H{sub 2}O, D{sub 2}O, Fe, Be, Pb, CH, CH{sub 2}. These cross-sections have been verified experimentally in water and in graphite for neutrons of 2.5 and 14 MeV using a SAMES accelerator and a 2 MeV Van De Graaff. (author) [French] Nous proposons une methode permettant de calculer l'efficacite biologique des neutrons rapides issus des sources de fission dans la protection d'une pile. Cette methode justifie la theorie empirique d'Albert et Welton. En faisant des hypotheses simples sur les sections efficaces, nous avons suppose que la propagation pouvait etre ramenee a un probleme monocinetique. Nous construisons alors un systeme de fonctions orthonormales qui permet de calculer le flux issu d'une source plane. Cette methode generalise les resultats obtenus par Platzek au cas ou les sections efficaces elastiques ne sont pas isotropes et en particulier permet de definir une section efficace de deplacement: extension du coefficient de diffusion. Cette methode peut etre generalisee a la diffusion des neutrons en fonction du temps et a l'etude du ralentissement. Les resultats numeriques sont donnes en annexe pour les corps. H{sub 2

  1. Measurement of the temperature of the neutrons in reactor G1; Mesure de la temperature des neutrons dans la pile G1

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, V; Sautiez, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    A precise experimental method has been adapted to the analysis of the spectrum of neutrons in the thermal region. This method uses the technique of modulation applied to a beam of neutrons issuing from a characteristic point in the pile. The analysis of the spectrum is made by adjusting, by the method of least squares, an analytical form to the experimental results. In this report are given the results obtained with a beam from the centre of the moderator of G1. The spectrum of this beam essentially represents the spectrum of the neutrons in the moderator. The most probable velocity was determined by means of Maxwell's functions. The measurements were made of different moderator temperatures between 304 deg. K and 435 deg. K. (author) [French] Une methode experimentale precise a ete mise au point pour l'analyse du spectre des neutrons dans le domaine thermique. Cette methode utilise la technique de la modulation appliquee a un faisceau de neutrons issu d'un point caracteristique de la pile. L'analyse du spectre est faite en ajustant par la methode des moindres carres une forme analytique aux resultats experimentaux. Dans ce rapport, on donne les resultats obtenus sur un faisceau du centre du moderateur de G1. Le spectre de ce faisceau represente convenablement le spectre des neutrons dans le moderateur. On s'est limite ici a une fonction de Maxwell dont on a recherche la vitesse la plus probable. Les mesures ont ete faites avec une temperature du moderateur variant entre 304 deg. K et 435 deg. K. (auteur)

  2. Installation for Studying the Scattering of Cold Neutrons; Installation pour l'etude de la diffusion des neutrons thermiques; Ustanovka dlya izucheniya rasseyaniya kholodnykh nejtronov; Instalacion para estudiar la dispersion de neutrones frios

    Energy Technology Data Exchange (ETDEWEB)

    Golikov, V V; Shapiro, F L; Shkatula, A; Yanik, E A [Ob' edinennyj institut yadernykh issledovanij, Dubna, Union of Soviet Socialist Republics (Russian Federation)

    1963-01-15

    Using the pulsed fut reactor in the Joint Institute for Nuclear Research, an installation was set up to investigate the spectrometry of cold neutrons. The moderator, adjoining the reactor reflector, and the beryllium filter were at the temperature of liquid nitrogen. The scatterer, located at a distance of about 0. 6 m from the moderator, was irradiated by flashes of cold neutrons, whose duration was determined by the lifetime of the neutrons in the moderator and the dispersion of the times-of-flight over a distance of 0. 6 m. The frequency of the flashes was 8/s. The steep beryllium edge of the spectrum, lying around 200 {mu}s, was used for spectrometry in the quasi-elastic range. The energy of the scattered neutrons was determined by the time-of-flight over the distance between scatterer and detector, which was about 10-40 m. ZnS + 10{sub 2}{sup 10} O{sub 3} scintillation detectors with surfaces of 300 and 2 000 cm{sup 2} were used and the efficiency, for fast neutrons, was about 60%. (author) [French] A l'aide du reacteur a flux pulse de neutrons rapides de l'Institut unifie de recherches nucleaires, les auteurs ont mis au point une installation pour la spectrometrie des neutrons thermiques. Le ralentisseur contigu au reflecteur du reacteur et le filtre deberyllium sont maintenus a la temperature de l'azote liquide. Le diffuseur, place a environ 60 cm du ralentisseur, est irradie par une bouffee de neutrons thermiques dont la duree est determinee par la vie moyenne des neutrons dans le ralentisseur et par l'etalement des temps de vol necessaires pour parcourir la distance de 60 cm. La frequence des bouffees est de 8/s. Pour la spectrometrie dans la region quasi-elastique, on utilise la bande en bordure du spectre qui correspond au beryllium et s'etale sur environ 200 {mu}s. L'energie des neutrons diffuses est determinee par la duree du parcours entre le diffuseur et le detecteur. Les auteurs ont utilise des detecteurs a scintillation a ZnS + 10{sub 2}{sup 10} O

  3. Application of the pulsed neutron technique on the reactors ALIZE - AQUILON (1963); Application de la methode des neutrons pulses sur les piles ALIZE et AQUILON (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Jacquemart, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    Different methods of measuring the ratio effective delayed fraction / prompt neutron lifetime, {alpha}{sub c}, are described. According to the classic pulsed neutron technique the negative reactivity due to a localized absorber is given by {rho} / {beta}{sub eff} = {alpha} / {alpha}{sub c} -1 Experiments are reported which show that in this case {alpha}{sub c} can not be considered constant for large reactivities. The absorber element distorts the flux in the system, increasing the importance of the reflector. An application of the pulsed neutron method to the measurement of critical distributed boron concentrations of various absorber elements is described. Less time is required than for the usual super-critical techniques, and the experimental analysis is simplified. It is interesting to note that the results are not influenced by the spectral sensitivity of the control element. A modified pulsed neutron method has been tried out. This procedure was used to determine by measurements at sub-critical the critical water level of uranium-heavy water lattices with a high precision. (author) [French] Differents modes operatoires pour definir la valeur du rapport pourcentage effectif de neutrons retardes / temps de vie, {alpha}{sub c}, sont exposes. La methode classique par neutrons pulses definit l'anti-reactivite d'un element absorbant a partir de la relation: {rho} / {beta}{sub eff} {alpha} / {alpha}{sub c} -1 Les manipulations effectuees montrent qu'on ne peut considerer dans ce cas {alpha}{sub c} constant pour de tres grandes anti-reactivites. L'absorbant introduit dans la pile deforme le flux et augmente l'importance du reflecteur. Une application de la methode des neutrons pulses pour mesurer le titre critique en mg de B/l de divers absorbants est signalee. Les operations sont effectuees en regime sous-critique avec un certain gain de temps et une grande facilite de depouillement. Il est interessant de noter que les resultats ne sont pas

  4. Application of the pulsed neutron technique on the reactors ALIZE - AQUILON (1963); Application de la methode des neutrons pulses sur les piles ALIZE et AQUILON (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Jacquemart, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    Different methods of measuring the ratio effective delayed fraction / prompt neutron lifetime, {alpha}{sub c}, are described. According to the classic pulsed neutron technique the negative reactivity due to a localized absorber is given by {rho} / {beta}{sub eff} = {alpha} / {alpha}{sub c} -1 Experiments are reported which show that in this case {alpha}{sub c} can not be considered constant for large reactivities. The absorber element distorts the flux in the system, increasing the importance of the reflector. An application of the pulsed neutron method to the measurement of critical distributed boron concentrations of various absorber elements is described. Less time is required than for the usual super-critical techniques, and the experimental analysis is simplified. It is interesting to note that the results are not influenced by the spectral sensitivity of the control element. A modified pulsed neutron method has been tried out. This procedure was used to determine by measurements at sub-critical the critical water level of uranium-heavy water lattices with a high precision. (author) [French] Differents modes operatoires pour definir la valeur du rapport pourcentage effectif de neutrons retardes / temps de vie, {alpha}{sub c}, sont exposes. La methode classique par neutrons pulses definit l'anti-reactivite d'un element absorbant a partir de la relation: {rho} / {beta}{sub eff} {alpha} / {alpha}{sub c} -1 Les manipulations effectuees montrent qu'on ne peut considerer dans ce cas {alpha}{sub c} constant pour de tres grandes anti-reactivites. L'absorbant introduit dans la pile deforme le flux et augmente l'importance du reflecteur. Une application de la methode des neutrons pulses pour mesurer le titre critique en mg de B/l de divers absorbants est signalee. Les operations sont effectuees en regime sous-critique avec un certain gain de temps et une grande facilite de depouillement. Il est interessant de noter que les resultats ne sont pas affectes par la

  5. Study by {alpha}-particle scattering, of the collective states of closed shell nuclei with 28 neutrons, 28 and 50 protons; Etude des etats a caractere collectif des noyaux au voisinage des couches fermees par diffusion inelastique des particules {alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Bruge, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-01-01

    This report gives the results from a systematic study by 44 MeV {alpha} particle scattering on the collective states of closed shell nuclei with 28 neutrons, 28 and 50 protons especially in the energy region corresponding to the two phonon vibrational triplet. The nuclei studied are: {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn and {sup 124}Sn. The theoretical analysis has been made with the Austern and Blair model using a phase shift analysis of the elastic scattering. Deformation lengths {delta}{sub I} = {beta}{sub I}R and transition probabilities obtained are compared with several experimental and theoretical data. (author) [French] Ce rapport donne les resultats d'une etude systematique par diffusion de particules {alpha} de 44 MeV des etats collectifs des noyaux au voisinage des couches fermees a 28 neutrons et 28 et 50 protons, specialement dans la region correspondant au triplet vibrationnel a deux phonons. Les noyaux etudies sont: {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn et {sup 124}Sn. L'analyse theorique a ete faite a l'aide du modele de Austern et Blair utilisant une analyse en dephasages de la diffusion elastique. Les longueurs de deformation {delta}I = {beta}{sub I}R obtenues pour chaque niveau sont comparees a plusieurs donnees experimentales et theoriques. (auteur)

  6. The structure of para-toluidine by X-ray and neutron diffraction; Etude de la structure de la para-toluidine par la diffraction des rayons X et des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Bertinotti, A.L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-12-01

    The crystal and molecular structure of para-toluidine has been solved by X-ray and neutron diffraction counter techniques. The molecules are arranged in the form of infinite chains in the crystal, each molecule being linked to two neighbours by hydrogen bonds. The presence of the H bonds makes clear the difference in the melting points between para-toluidine and benzene hydrocarbons of related symmetry and molecular weight. Their direction accounts for the (001) cleavage and the growth anisotropy of crystals from supersaturated vapour phase. A structure-seeking method by computer has been elaborated, using lattice energy calculations applied to molecules treated as rigid bodies and making use of a simplex method for function minimization without calculation of derivatives. The way the available information is handled allows to increase the range of convergence, as shown in the case of para-toluidine. (author) [French] La structure cristalline et moleculaire de la para-toluidine a ete resolue a l'aide de la diffraction des rayons X et des neutrons. L'analyse a revele que la structure presentait un encha ement particulier des molecules, liees entre elles par des ponts hydrogene. La presence des liaisons rend compte de l'elevation du point de fusion de la para-toluidine par rapport a celui des carbures benzeniques de symetrie et de poids moleculaires voisins. La direction des liaisons explique le clivage facile (001) des cristaux obtenus par fusion et l'anisotropie de croissance des cristaux en phase vapeur. Une methode de recherche de structures par ordinateur a ete elaboree, faisant usage du concept d'energie reticulaire applique aux molecules considerees comme rigides et faisant appel a une methode de simplexe pour la minimisation des fonctions sans calcul de derivees. La maniere dont est exploitee l'information disponible permet d'accro re, comme cela est montre dans le cas de la para-toluidine, l'etendue du domaine de

  7. Study of niobium isotopes having excess neutrons and a short half-life; Etude des isotopes du niobium excedentaires en neutrons et de courte periode

    Energy Technology Data Exchange (ETDEWEB)

    Huebenthal, K [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-02-01

    By irradiating Mo with 14 MeV neutrons isomers have been found for {sup 98}Nb (2.8 s half-life) {sup 99}Nb (9 s) and {sup 100}Nb (2.4 s). No isomer of this type seems to exist for {sup 96}Nb. Rapid separation methods are developed for isolating {sup 98}Zr from fission products, and for separating Zr and Nb. The half-life of {sup 98}Zr is measured (31 s) and the formation of {sup 98}Nb (2.8 s) from {sup 98}Zr (31 s) is shown by milking. Rough {beta} and {gamma} measurements of these nuclei are described. The {gamma} spectrum of {sup 98}Nb (51 mn) is studied with a high-resolution Ge/Li - detector. (authors) [French] Des irradiations des isotopes de molybdene avec des neutrons de 14 MeV ont mis en evidence l'existence des isomeres de {sup 98}Nb (periode 2.8 s) {sup 99}Nb (9 s) et {sup 100}Nb (2.4 s). Pour le {sup 96}Nb un isomere de ce type ne semble pas exister. Des methodes rapides de separation sont mises au point pour isoler le zirconium 98 des produits de fission, et pour separer ensuite le niobium du zirconium. La periode du {sup 98}Zr est de 3l s, et on demontre la formation du {sup 98}Nb (2.8 s) a partir du Zr (31 s). Ces corps sont etudies sommairement en spectroscopie {beta} et {gamma}. Le spectre gamma de {sup 98}Nb (periode 51 mn) est etudie avec un detecteur Ge/Li de haute resolution. (auteurs)

  8. Differential Neutron Scattering from Hydrogenous Moderators; Diffusion Differentielle des Neutrons par des Ralentisseurs Hydrogenes; Differentsial'noe rasseyanie nejtronov iz vodorodosoderzhashchikh zamedlitelej; Dispersion Diferencial de Neutrones en Moderadores Hidrogenados

    Energy Technology Data Exchange (ETDEWEB)

    Beyster, J. R.; Young, J. C.; Neill, J. M.; Mowry, W. R. [General Atomic Division of General Dynamics Corporation, John Jay Hopkins Laboratory for Pure and Applied Science, San Diego, CA (United States)

    1965-08-15

    experiments, which are sensitive mainly to P{sub 0} scattering. In particular one may test the P{sub 1} scattering kernel appropriate to a given molecular model. Third, the transport cross-section may be calculated directly from the experiments for use in multigroup reactor analysis. (author) [French] On mesure par les methodes du temps de vol les sections efficaces differentielles de diffusion simple (d{sigma}/d {Omega}) pour les ralentisseurs usuels. On utilise des neutrons thermiques produits par une source puisee intense (accelerateur lineaire de la General Atomic) avec un parcours de vol de 12 m a l'extremite duquel est place un echantillon mince du ralentisseur a l*etude. En outre, on a egalement prevu un petit parcours de vol terminal pour les neutrons diffuses, entre l'echantillon et plusieurs detecteurs de neutrons entierement absorbants. Cette methode permet de mesurer simultanement la distribution angulaire de diffusion pour plus de 50 energies des neutrons incidents. Les intensites sont-elevees, le bruit de fond est faible et bien defini et on peut proceder a des mesures rapides pour tous les angles de diffusion compris entre 10 et 155 degres. Les auteurs presentent des mesures de la section efficace differentielle de diffusion pour le vanadium, H{sub 2}O, D{sub 2}O et ZrH. On a etudie le vanadium pour controler le dispositif experimental. On a fait des mesures avec H{sub 2}O pour diverses epaisseurs et orientations des echantillons en vue de les comparer aux calculs fondes sur divers modeles de diffusion par l'hydrogene lie et aux resultats obtenus par Springer et Reinsch. Toutes les mesures experimentales ont ete corrigees pour tenir compte des effets importants de la diffusion multiple dans les echantillons. Pour l'instant, on n'a pas observe experimentalement la variation accusee que fait prevoir le modele de diffusion de Nelkin lorsque l'energie des neutrons est d'environ 0,06 eV; ceci est du au fait que l'hypothese du rotateur unique inhibe a 0,06 eV n'a pas

  9. Reactor AQUILON. The hardening of neutron spectrum in natural uranium rods, with a computation of epithermal fissions (1961); Pile AQUILON. Durcissement du spectre des neutrons dans les barreaux d'uranium et calcul des fissions epithermiques (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Durand -Smet, R; Lourme, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    - Microscopic flux measurements in reactor Aquilon have allowed to investigate the thermal and epithermal flux distribution in natural uranium rods, then to obtain the neutron spectrum variations in uranium, Wescott '{beta}' term of the average spectrum in the rod, and the ratio of epithermal to therma fissions. A new definition for the infinite multiplication factor is proposed in annex, which takes into account epithermal parameters. (authors) [French] - Un certain nombre de mesures effectuees dans la pile Aquilon ont permis d'etablir la distribution fine des flux thermique et epithermique dans les barreaux d'uranium, et d'en deduire les variations du spectre des neutrons dans l'uranium, le terme {beta} du spectre de Wescott moyen dans le barreau et le nombre de fissions epithermiques. En annexe, il est propose une definition nouvelle du coefficient de multiplication infini, qui fait intervenir les parametres epithermiques. (auteurs)

  10. New modelling method for fast reactor neutronic behaviours analysis; Nouvelles methodes de modelisation neutronique des reacteurs rapides de quatrieme Generation

    Energy Technology Data Exchange (ETDEWEB)

    Jacquet, P.

    2011-05-23

    Due to safety rules running on fourth generation reactors' core development, neutronics simulation tools have to be as accurate as never before. First part of this report enumerates every step of fast reactor's neutronics simulation implemented in current reference code: ECCO. Considering the field of fast reactors that meet criteria of fourth generation, ability of models to describe self-shielding phenomenon, to simulate neutrons leakage in a lattice of fuel assemblies and to produce representative macroscopic sections is evaluated. The second part of this thesis is dedicated to the simulation of fast reactors' core with steel reflector. These require the development of advanced methods of condensation and homogenization. Several methods are proposed and compared on a typical case: the ZONA2B core of MASURCA reactor. (author) [French] Les criteres de surete qui regissent le developpement de coeurs de reacteurs de quatrieme generation implique l'usage d'outils de calcul neutronique performants. Une premiere partie de la these reprend toutes les etapes de modelisation neutronique des reacteurs rapides actuellement d'usage dans le code de reference ECCO. La capacite des modeles a decrire le phenomene d'autoprotection, a representer les fuites neutroniques au niveau d'un reseau d'assemblages combustibles et a generer des sections macroscopiques representatives est appreciee sur le domaine des reacteurs rapides innovants respectant les criteres de quatrieme generation. La deuxieme partie de ce memoire se consacre a la modelisation des coeurs rapides avec reflecteur acier. Ces derniers necessitent le developpement de methodes avancees de condensation et d'homogenisation. Plusieurs methodes sont proposees et confrontees sur un probleme de modelisation typique: le coeur ZONA2B du reacteur maquette MASURCA

  11. Neutron thermalization in absorbing infinite homogeneous media: theoretical methods; Methodes theoriques pour l'etude de la thermalisation des neutrons dans les milieux absorbants infinis et homogenes

    Energy Technology Data Exchange (ETDEWEB)

    Cadilhac, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-11-15

    After a general survey of the theory of neutron thermalization in homogeneous media, one introduces, through a proper formulation, a simplified model generalizing both the Horowitz model (generalized heavy free gas approximation) and the proton gas model. When this model is used, the calculation of spectra is reduced to the solution of linear second order differential equations. Since it depends on two arbitrary functions, the model gives a good approximation of any usual moderator for reactor physics purposes. The choice of these functions is discussed from a theoretical point of view; a method based on the consideration of the first two moments of the scattering law is investigated. Finally, the possibility of discriminating models by using experimental informations is considered. (author) [French] Apres un passage en revue de generalites sur la thermalisation des neutrons dans les milieux homogenes, on developpe un formalisme permettant de definir et d'etudier un modele simplifie de thermaliseur. Ce modele generalise l'approximation proposee par J. HOROWITZ (''gaz lourd generalise'') et comporte comme cas particulier le modele ''hydrogene gazeux monoatomique''. Il ramene le calcul des spectres a la resolution d'equations differentielles lineaires du second ordre. Il fait intervenir deux fonctions arbitraires, ce qui lui permet de representer les thermaliseurs usuels de facon satisfaisante pour les besoins de la physique des reacteurs. L'ajustement theorique de ces fonctions est discute; on etudie une methode basee sur la consideration des deux premiers moments de la loi de diffusion. On envisage enfin la possibilite de discriminer les modeles d'apres des renseignements d'origine experimentale. (auteur)

  12. Some Results of the Research Work on the Biological Effect of Neutrons and Protons; Quelques Resultats des Etudes sur les Effets Biologiques des Neutrons et des Protons; Nekotorye itogi izucheniya biologicheskogo dejstviya nejtronov i protonov; Algunos Resultados del Estudio de los Efectos Biologicos de los Neutrones y Protones

    Energy Technology Data Exchange (ETDEWEB)

    Moskalev, Ju. I. [Institut Biofiziki AMN SSSR, SSSR (Russian Federation)

    1964-03-15

    The author correlates and analyses the experimental data obtained over the past two or three years regarding the biological effects of neutrons and high-energy protons, and shows that it is a matter of prime concern for present-day radiobiology to investigate the relative biological effectiveness of the various types of radiation under various irradiation conditions and the reasons for the qualitative differences in their effect on the animal organism. Attention is drawn to the need for more research into the combined effect of various types of radiation and other agents. Specific examples are cited to demonstrate the main progress achieved in studying the prophylaxis of radiation injury induced by neutrons or high-energy protons and to show the contribution such research can make towards understanding the specific way in which various types of radiation act. (author) [French] L'auteur generalise les resultats des recherches experimentales qui ont ete faites au cours des deux ou trois dernieres annees sur les effets biologiques des neutrons et protons de haute energie. Il montre qu'une des taches importantes de la radiobiologie moderne est d'etudier a la fois l'efficacite biologique relative des divers types de rayonnements dans des conditions d'irradiation differentes et les differences qualitatives que presente leur action sur l'organisme vivant. Le memoire souligne qu'il est indispensable de developper les recherches sur l'effet combine des divers facteurs: rayonnements et autres. En partant d'exemples concrets, l'auteur expose les principaux resultats des recherches-sur la prophylaxie des radiolesions provoquees par les neutrons et les protons de haute energie; il montre egalement a quel point ces travaux sont necessaires pour mieux comprendre le caractere specifique de l'e ffet des divers types de rayonnements. (author) [Spanish] En esta memoria se generalizan los resultados de los estudios experimentales efectuados en los ultimos dos o tres anos en materia de

  13. Etude de la diagraphie neutron du granite de Beauvoir. Effet neutron des altérations et de la matrice du granite. Calibration granite. Porosité totale à l'eau et porosité neutron Analysis of the Beauvoir Granite Neutron Log. Neutron Effect of Alterations and of the Granite Matrix. Granite Calibration. Total Water Porosity and Neutron Porosity

    Directory of Open Access Journals (Sweden)

    Galle C.

    2006-11-01

    Full Text Available Cet article rend compte des travaux effectués sur la porosité du granite de Beauvoir (Sondage GPF 1 d'Echassières, Massif Central français. L'objectif de notre étude est de pouvoir obtenir des valeurs représentatives de la saturation en eau (porosité totale à l'eau n du granite de Beauvoir à partir des mesures de porosité neutron PorositéN (diagraphie neutron BRGM sans avoir recours aux mesures sur carottes. Notre démarche est expérimentale et nous avons tenté d'approfondir certains problèmes liés à l'utilisation de la diagraphie neutron dans une roche granitique. Deux facteurs principaux conditionnent la réponse neutron : la concentration en hydrogène de la formation (eau libre et eau de constitution de certains minéraux et la présence d'éléments absorbeurs à forte section de capture comme le gadolinium, le cadmium, le bore, . . . et dans le cas du granite de Beauvoir, le lithium. A partir des mesures de porosité totale à l'eau n sur carottes, des essais de pertes au feu sur poudre qui nous permettent de déterminer la porosité neutron liée à l'eau de constitution PorositéN(OH- et des analyses chimiques avec lesquelles nous évaluons la porosité neutron thermique PorositéN(ox (Programme SNUPAR, Schlumberger liée à la capture neutronique, nous reconstituons la porosité neutron totale PorositéNR du granite de Beauvoir. Pour 7 échantillons caractéristiques du granite de Beauvoir, nous réalisons grâce à ces résultats une nouvelle calibration du taux de comptage neutron initial corrigé du gradient thermique et de l'effet de trou. Grâce à cette opération, il est possible de déterminer, pour les échantillons traités, la porosité neutron du granite avec une calibration granite (PorositéNg et non calcaire (PorositéNc. La connaissance de l'effet neutron de la matrice nous permet enfin d'évaluer la teneur en eau du granite (porosité totale à l'eau et de comparer celle-ci avec la porosité mesurée sur

  14. Lentes progressivas x lentes multifocais: um estudo baseado na geometria analítica do cone

    Directory of Open Access Journals (Sweden)

    Araújo Marília Cavalcante

    2004-01-01

    Full Text Available OBJETIVO: Compreender, por meio de figuras e funções matemáticas do cone, as lentes progressivas e mostrar que elas não são lentes multifocais porque, nelas, a refração da luz não obedece as leis da geometria euclidiana. MÉTODOS: Foi feito um estudo da geometria analítica do cone, com o programa de computador Auto-CAD 14, dando enfoque óptico às figuras geométricas obtidas com a sua secção. RESULTADOS: Pela análise das figuras obtidas da secção do cone, pudemos observar as superfícies que compõem as lentes progressivas. Estas superfícies são compostas de elipse, círculo, parábola e hipérbole. Diferente do que é dito na literatura, encontramos as elipses com diâmetro maior nas ordenadas e de mesmo sentido seguida por duas superfícies inferiores que são parábola e hipérbole e não o contrário. CONCLUSÕES: As lentes progressivas diferentemente das lentes multifocais apresentam prismas nos centros ópticos como decorrência da sua estrutura. No final, fizemos análise das suas formas mostrando o limite teórico da sua evolução.

  15. Neutron detection in an atomic reactor core using semi-conductors; Detection des neutrons par semi-conducteur dans un coeur de reacteur atomique

    Energy Technology Data Exchange (ETDEWEB)

    Divoux, F [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    In this paper, the first part describes the principle of nuclear particle detection by means of semiconductor diodes and the general application of these. The second part describes fabrication of the device used to estimate thermic neutron fluxes in core of a swimming pool type reactor. The useful volume (2.9 mm thickness) is in the light water moderator, between combustible elements plates. The results, principally obtained in the core of Siloette reactor at the 'Centre d'Etudes Nucleaires de Grenoble' at low power, are mentioned in the third part. Flux maps have been set and comparison between converter's products: Bore 10, Lithium 6, Uranium 235 is made. (author) [French] Dans ce rapport, une premiere partie porte sur la description du principe de detection des particules nucleaires par diodes a semi-conducteur et sur l'application generale de celles-ci. Une deuxieme partie s'attache a decrire la fabrication du materiel utilise pour evaluer les flux de neutrons thermiques dans un coeur de reacteur type pile piscine. L'espace de mesure (2,9 mm d'epaisseur) se situe entre les plaques des elements combustibles, dans le moderateur eau legere. Les resultats, obtenus principalement dans le coeur du reacteur Siloette du Centre d'Etudes Nucleaires de Grenoble aux basses puissances de fonctionnement, sont rapportes dans la troisieme partie. Des cartes de flux ont ete dressees et une comparaison est faite entre les produits 'convertisseurs' suivants: Bore 10, Lithium 6, Uranium 235. (auteur)

  16. Inelastic Neutron Scattering from Doped Germanium and Silicon; Diffusion Inelastique des Neutrons dans du Germanium et du Silicium Contenant une 'Impurete'; Neuprugoe rasseyanie nejtronov na germanii i kremnii s prisadkoj; Dispersion Inelastica de Neutrones en Germanio y Silicio Deliberadamente Impurificados

    Energy Technology Data Exchange (ETDEWEB)

    Dolling, G. [Chalk River Nuclear Laboratories, Chalk River, ON (Canada)

    1965-04-15

    The normal modes of vibration of the pure semiconductors germanium and silicon have been extensively studied by means of coherent one-phonon scattering of slow neutrons from single-crystal specimens. The present paper describes similar experiments performed (i) on germanium heavily doped ({approx}0.1%) with (a) arsenic and (b) gallium, and also (ii) on silicon doped with phosphorus. In each case, control experiments were carried out on high- purity crystals. All measurements were performed with the triple-axis crystal spectrometer at Chalk River Nuclear Laboratories. The elastic constant C{sub 44} for germanium is known to be appreciably dependent on the dopant concentration, and so certain transverse acoustic (TA) modes of long wavelength were studied to see if such effects persisted into the dispersive region. Other TA modes whose frequencies could be measured with high precision were also studied in both materials to check as sensitively as possible for small effects which might be ascribed to the existence of excess electrons or holes. A particularly careful study was made of modes having the following wave vectors (aq/2{pi}, where a is the cubic unit cell side): (i) in germanium, (1,0,0), (ii) in silicon, (0.85, 0.85, 0) and (0.3, 0, 0). Such normal modes might be expected to show anomalous behaviour in the n-type crystals, since inter-valley scattering of electrons between adjacent conduction band minima would require their co-operation in order to conserve ''crystal momentum''. The results in all cases were negative, i. e. no differences in phonon frequencies or energy widths between pure and doped specimens were observed, within the experimental accuracy. In the most favourable cases, this (relative) accuracy is about 0.5% in frequency, rising to 2.0% for certain longitudinal optic modes in silicon. (author) [French] L'auteur a etudie, a l'aide d'experiences de diffusion coherente (a un phonon) de neutrons lents par des monocristaux, les modes normaux de

  17. X-ray diffraction studies of neutron irradiated beryllium oxide; Etude par diffraction des rayons X de glucine irradiee aux neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Belbeoch, B; Rodot, J; Roulliay, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-07-01

    X-ray diagrams of neutron irradiated sintered BeO (E > 1 MeV) can be classified into 3 types depending on the value of the c/a ratio, independently of the characteristics of the sinters, (hot pressed or cold pressed, material, variable density and grain size, pure BeO or BeO with additions). The anisotropic expansion of the BeO lattice caused by irradiation depends not only on the dose of irradiation, but also on the intergranular stresses of the samples. The sintered samples which resist most satisfactorily to irradiation consist of cold pressed high density and small grain size material for which the c/a ratio varies little with increasing dosage. The single crystal diagrams show the same classification as the polycrystalline material in respect with the c/a ratio. Furthermore, in addition to the Bragg reflections, X-ray diffusions are observed; the distribution of the defects is no longer isotropic; a description is given in particular of the scattering which occurs when 1.625 < c/a < 1.645. It appears that the defects start to congregate and cause pronounced distortion of the lattice. The defects are stabilized in the form of large aggregates only when a later irradiation stage is reached. (author) [French] Les diagrammes de rayons X obtenus a l'aide d'echantillons frittes de BeO irradies aux neutrons (E > 1 MeV) peuvent etre classes en trois types qui dependent de la valeur du rapport c/a, quelles que soient les caracteristiques du fritte (fritte sous charge ou fritte naturel, densite et taille de grains variables, BeO pur ou avec additions). La dilatation anisotrope de la maille de BeO observee par irradiation ne depend pas seulement de la dose recue, mais aussi des etats de contraintes intergranulaires des echantillons; ainsi les frittes qui resistent le mieux sous irradiation sont les frittes naturels a forte densite et a petits grains pour lesquels le rapport c/a varie peu en fonction de la dose d'irradiation. Les diagrammes de monocristaux presentent la

  18. Lentes de contacto em idade pediátrica

    OpenAIRE

    Mota, M; Vendrell, C; Ramalho, M; Santos, C; Pedrosa, C; Coutinho, I; Lopes, AS; Silva, D

    2015-01-01

    Revisão sobre os tipos de lentes de contacto para utilização na idade pediátrica. Regras de adaptação, indicações e contraindicações ao uso de lentes de contacto na criança. Descrição das melhores opções na afaquia.

  19. Le statut vitaminique des individus et des populations…

    Directory of Open Access Journals (Sweden)

    Icart Jean-Claude

    2000-05-01

    Full Text Available Comme le souligne un récent rapport du Haut comité de santé publique, le statut vitaminique des individus et des populations demeure une question d’actualité. Si les études ne révèlent plus de signes évocateurs de carence, au plus des problèmes de déficiences pour certains groupes à risque, des interrogations, demeurent malgré le contexte d’abondance, concernant la couverture des besoins, laquelle pourrait s’avérer inférieure aux valeurs considérées comme satisfaisantes.

  20. Study of the radiation around a high energy accelerator. Production and scattering of cascade neutrons; Etude du rayonnement autour d'un accelerateur de haute energie. Production et diffusion des neutrons de cascade

    Energy Technology Data Exchange (ETDEWEB)

    Tardy-Joubert, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-03-01

    The cascade induced in protective screens by a 3 GeV proton beam has been studied using activation detectors; the results have been compared with the cosmic neutron spectrum in the atmosphere. A study of the secondary neutron spectrum has made, it possible to obtain the distribution of the dose and to determine the maximum permissible fluxes expressed in terms of the energy, taking into account all the daughter products present. The dose calculated has been checked experimentally. The proportion of cascade neutrons has been studied using the idea of an imaginary source. The parameters which have to be introduced into the general equations to take into account scattering in the the air have been determined. (author) [French] La cascade induite dans les ecrans de protection par un faisceau de protons de 3 GeV a ete etudiee au moyen de detecteurs a activation et la comparaison a ete faite avec le spectre des neutrons cosmiques dans l'atmosphere. L'etude du spectre des neutrons secondaires a permis de preciser la distribution de la dose et de determiner les flux maximaux admissibles qui sont exprimes en fonction de l'energie, en tenant compte de l'ensemble des descendants presents. La dose calculee a ete verifiee experimentalement. La propagation des neutrons de cascade a ete etudiee en introduisant la notion de source fictive. Les parametres a introduire dans les equations generales pour rendre compte de la diffusion dans l'air ont ete determines. (auteur)

  1. Neutron distribution in the central cell and a peripheral cell of the Fontenay-aux-Roses pile; Repartition des neutrons dans la cellule centrale et une cellule peripherique de la pile de Fontenay-aux-Roses

    Energy Technology Data Exchange (ETDEWEB)

    Roullier, F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1958-07-01

    The distribution of the neutron density has been determined in the central cell and a peripheral cell of the pile at Fontenay-aux-Roses. This measurement was carried out by the autoradiographic method with manganese detectors. The neutron density distribution in the uranium rod has already been studied. The measurement was completed by the study of the neutron density in the complete cell by means of detectors placed in the uranium and in the heavy water. (author) [French] La repartition de la densite des neutrons a ete determinee dans la cellule centrale et une cellule peripherique de la pile de Fontenay-aux-Roses. Cette mesure a ete effectuee par la methode d'autoradiographie avec des detecteurs de manganese. La repartition de la densite des neutrons dans la barre d'uranium a deja ete etudiee. La mesure a ete completee par l'etude de la densite des neutrons dans la cellule complete a l'aide de detecteurs places dans l'uranium et dans l'eau lourde. (auteur)

  2. The spectrometer PERKEO III and the decay of free neutrons; Das Spektrometer PERKEO III und der Zerfall des freien Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Maerkisch, B.M.

    2006-10-18

    The Standard Model of particle physics describes neutron decay with three parameters. In contrast to that, a multitude of observables are accessible experimentally. With precision measurements sensitive tests of the Standard Model are thus possible. The neutron decay spectrometer PERKEO III was designed and built as part of this work. It will replace its predecessor PERKEO II, which has reached its systematical and statistical limits. With the new instrument measurements with continuous and pulsed neutron beams become feasible. This either provides an increase in statistics of up to two orders of magnitude, or eliminates the two major instrument specific sources of systematical corrections. In our first measurement in winter 2006/2007, the available event rate will be used to determine weak magnetism from the electron asymmetry A. Previously, this value was not statistically accessible in neutron decay. Systematics are analyzed with the help of our measurement with PERKEO II. For this measurement PERKEO III will be installed at the neutron guide H113 at the Institute Laue-Langevin, Grenoble. The neutron beam from this guide is characterized and a model is given, which allows the rapid calculation of beam profiles and absolute event rates from such a beam. In preparation of a future neutron decay instrument the reflective properties of two non-magnetic neutron mirrors were measured. (orig.)

  3. [Present conceptions of the C.E.A. concerning] the development of fast neutron reactors in France; [Les conceptions actuelles du C.E.A. concernant] la filiere des reacteurs a neutrons rapides en France

    Energy Technology Data Exchange (ETDEWEB)

    Vendryes, G; Gaussens, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Pasquer, R [Electricite de France (EDF), 75 - Paris (France)

    1964-07-01

    . (authors) [French] 1 - Situation des reacteurs a neutrons rapides dans le programme d'energie nucleaire francais. En developpant un programme base sur l'uranium naturel, la France se trouvera dotee d'un stock important de plutonium riche on isotopes superieurs. L'existence de ce plutonium et de l'uranium appauvri provenant des memes reacteurs a pour consequence logique leur emploi dans des reacteurs a neutrons rapides. Justifiee par cet interet a court terme, la mise au point de reacteurs a neutrons rapides repond par ailleurs a une necessite pour l'avenir. 2 - Enonce des caracteristiques d'une centrale a neutrons rapides de 1000 MW el. Nous indiquons les caracteristiques d'une future centrale a neutrons rapides chargee au plutonium et refroidie au sodium. Si incertaines qu'elles soient, elles constituent un guide necessaire a l'orientation de nos travaux. 3 - Etudes effectuees a ce jour: Nous donnons un apercu des etudes souvent tres preliminaires qui ont permis de retenir les caracteristiques citees plus haut. Les principaux domaines techniques abordes sont les suivants: - Neutronique (masses critiques, taux de regeneration, enrichissements, aplatissement du flux de neutrons, coefficients de reactivite, evolution de la reactivite en fonction de l'irradiation), - Dynamique, controle et surete, - Combustible, - Technologie (conception du bloc-pile, des circuits de sodium, des dispositifs pour la manutention des assemblages). Ces etudes techniques se completent de considerations economiques. Le choix de caracteristiques optimales est lie a l'existence de programmes de production d'electricite et, dans ces programmes, a celle des reacteurs a neutrons thermiques producteurs de plutonium. On montre comment il y a lieu de tenir compte de l'existence du plutonium dans ce contexte, et quels sont les mecanismes qui rattachent l'economie de ce plutonium au choix des parametres essentiels des reacteurs surgenerateurs. 4 - Reacteur prototype: On justifie l'interet d'une etape

  4. The pulsed neutron method applied to the determination of the nuclear constants of graphite (1961); La methode des neutrons pulses appliquee a la determination des constantes nucleaires du graphite (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Lalande, J [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1961-07-01

    A method for determining the nuclear constants {sigma}{sub a} and {lambda}{sub t} of a moderator is described. The disappearance of a burst of neutrons introduced into a finite medium is studied as a function of time. This decrease in the thermal neutron density is the product of two exponentials; one representing the absorption, the other the leakage. By varying one or other of these factors, the constants of the factor left unvaried can be determined, and from this the nuclear constant values are deduced. (author) [French] On decrit une methode permettant de determiner les constantes nucleaires {sigma}{sub a} et {lambda}{sub t} d'un moderateur. On etudie la decroissance dans le temps d'une bouffee de neutrons introduite dans un milieu fini. Cette decroissance de la densite en neutrons thermiques est le produit de deux exponentielles; l'une represente l'absorption, l'autre les fuites. Par variation de l'un ou l'autre de ces facteurs, on determine les constantes du facteur laisse invariant dont on deduit les valeurs des constantes nucleaires. (auteur)

  5. RBE of Monoenergetic Fast Neutrons: Cytogenetic Effects in Maize; EBR des Neutrons Rapides Monoenergeniques: Effets Cytogenetiques sur le Mais; Obeh monoehnergeticheskikh bystrykh nejtronov: tsitogeneticheskie izmeneniya u kukuruzy; EBR de los Neutrones Rapidos Monoenergeticos: Efectos Citogeneticos en el Maiz

    Energy Technology Data Exchange (ETDEWEB)

    Smith, H. H.; Bateman, J. L.; Quastler, H.; Rossi, H. H. [Biology and Medical Departments, Brookhaven National Laboratory, Upton, NY (United States)

    1964-05-15

    The maize used in these experiments has the advantage for RBE studies of yielding a basically first-order dose-response curve with low as well as with high LET radiations. An exposure apparatus was used which produced essentially equal dose rates in five rings of seeds placed so as to intercept neutrons of 0.43, 0.65, 1.00, 1.50 and 1.80 MeV. The mutant sectors produced in leaves are believed to be due mostly to simple chromosome breakage and deletion. Experiments were performed at dosages that gave responses which were linear, below saturation levels, and overlapping in range for the monoenergetic fast neutrons and 250 kVp X-rays. RBE values, calculated from relative slopes of linear-regression lines for neutrons and X-rays ranged from 42 to 135 with an overall average of about 70. Fast neutrons of 0.43 MeV energy were the most efficient, of those used, in producing g{sub 2} mutant sectors. (author) [French] Pour les etudes sur l'EBR, le maft utilise au cours des experiences offre l'avantage de donner une courbe dose-reponse qui est essentiellement de premier ordre, que le TLE du rayonnement soit faible ou eleve. Les auteurs ont utilise un appareil d'irradiation assurant des debits de dose pratiquement egaux dans cinq couronnes de semences disposees de maniere a intercepter les neutrons de 0,43, 0,65, 1,00, 1,50 et 1,80 MeV. On pense que les secteurs mutants produits dans les feuilles sont dus essentiellement a une rupture et une disparition de chromosomes simples. Les auteurs ont fait des experiences a des doses qui ont donne des reponses lineaires, inferieures au niveau de saturation et se chevauchant dans le cas des neutrons rapides et des rayons X de 250 kV-crete. Les valeurs de l'EBR calculees d'apres la comparaison des pentes des courbes de regression lineaire pour les neutrons et les rayons X varient de 42 a 135, avec une valeur moyenne d'environ 70. Parmi les neutrons utilises, les neutrons rapides de 0,43 MeV ont ete les plus efficaces pour produire des

  6. Experimental Study of the Process of Neutron Thermalization in Time in Aqueous Moderators; Etude Experimentale du Processus de Thermalisation des Neutrons en Fonction du Temps dans les Ralentisseurs Contenant de l'Eau; Ehksperimental'noe izuchenie protsessa termalizatsii nejtronov vo vremeni v vodorodosoderzhashchikh zamedlitelyakh; Estudio Experimental del Proceso de Termalizacion de Neutrones en Funcion del Tiempo en Moderadores Acuosos

    Energy Technology Data Exchange (ETDEWEB)

    Ishmaev, S. N.; Mostovoj, V. I.; Sadikov, I. P.; Chernyshov, A. A. [Gosudarstvennyj Komitet po Ispol' zovaniju Atomnoj Ehnergii SSSR, Institut Atomnoj Ehnergii Im. I.V.Kurchatova, Moskva, SSSR (Russian Federation)

    1965-08-15

    }s. Les spectres ont ete determines au moyen d'un prisme de ZrH de grande dimension (B{sup 2} = 3,8 * 10{sup -2} cm{sup -2}) pour des temps de ralentissement superieurs a 30 {mu}s; pour ces valeurs du temps, l'energie moyenne des neutrons est inferieure a 0,13 eV et l'echange d'energie entre le gaz neutronique et le milieu s'opere essentiellement du fait de l'apparition d'oscillations acoustiques dans le reseau; en outre, le processus de thermalisation suit un rythme relativement lent et le temps necessaire pour obtenir un spectre de neutrons a l'etat d'equilibre est de l'ordre de 400 {mu}s. Dans un assemblage a ZrH de petite dimension (B{sup 2} Asymptotically-Equal-To 20 * 10{sup -2} cm{sup -2}) on constate un puissant effet de refroidissement par diffusion. Les spectres mesures pour des temps de ralentissement prolonges different sensiblement de la distribution maxwellienne a la temperature ambiante. Le temps requis pour obtenir une distribution equilibree de l'energie augmente avec la reduction des dimensions dy systeme. Les auteurs presentent les spectres energetiques des neutrons dans l'eau (B{sup 2} = 2,56 * 10{sup -2} cm{sup -2}) pour des temps de ralentissement superieurs a 13 {mu}s ou les deformations provoquees aux depens du pouvoir de resolution sont insignifiantes. La forme du spectre ne concorde entierement avec la distribution maxwellienne a la temperature ambiante qu'apres un delai d'environ 100 {mu}s apres la bouffee de neutrons rapides. Dans l'experience, le temps necessaire a la formation d'un spectre de neutrons a l'etat d'equilibre etait de trois a quatre fois superieur a celui qu'indiquent les calculs effectues par differents auteurs. Les causes possibles de ces divergences font l'objet d'un examen critique. (author) [Spanish] Con ayuda del metodo descrito en otra memoria presentada a este Simposio, los autores han medido en funcion del tiempo de moderacion los espectros neutronicos no estacionarios en hidruro de circonio y en agua a temperatura

  7. The n,{gamma} discrimination in recoil-proton proportional counters. Application to the measurement of fast neutron spectra; Discrimination n,{gamma} dans les compteurs proportionnels a protons de recul. Application a la mesure des spectres de neutrons rapides

    Energy Technology Data Exchange (ETDEWEB)

    Jeandidier, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A description is given of a spectrometry chain working in the energy range of a few keV to 1 MeV, and designed for measurement of fast neutron spectra. It consists of detectors, recoil proton proportional counters built especially for this work by R. COMTE (DEG/SER) and which make it possible to cover the energy range and also associated electronic equipment. A brief description is first given of the physical processes involved: (n,p) collisions in the gas, influence of {gamma} radiation; the method of discrimination is then presented. It is based on the difference in the rise-times of the pulses. In the experiments described here the use of a bi-parametric system made it possible to employ the most simple discrimination device, based on the fact that the high frequency gamma pulse components are, at a given energy, weaker than those of the neutron pulses. Results are given of measurements carried out on the Van der Graaff (mono-energetic neutrons for testing the linearity of the chain and the resolving power of the counters), and of those made in a sub-critical system Hug at Cadarache. (author) [French] On decrit une chaine de spectrometrie travaillant dans le domaine d'energie de quelques keV a 1 MeV destinee a la mesure des spectres de neutrons rapides. Elle comprend les detecteurs, compteurs proportionnels a protons de recul, realises specialement pour cette etude par M. R. COMTE (DEG/SER), permettant de couvrir la gamme d'energie et l'electronique associee. Apres un rappel des processus physiques mis en jeu: chocs (n,p) dans les gaz, influence des rayonnements {gamma}, on expose la methode de discrimination utilisee. Celle-ci est basee sur la difference des temps de montee des impulsions. Au cours des experiences rapportees ici, la mise en oeuvre d'un ensemble bi-parametrique a permis d'utiliser le dispositif de discrimination le plus simple, base sur la remarque que les composantes a haute frequence des impulsions {gamma} sont, a energie egale, plus faibles

  8. The n,{gamma} discrimination in recoil-proton proportional counters. Application to the measurement of fast neutron spectra; Discrimination n,{gamma} dans les compteurs proportionnels a protons de recul. Application a la mesure des spectres de neutrons rapides

    Energy Technology Data Exchange (ETDEWEB)

    Jeandidier, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A description is given of a spectrometry chain working in the energy range of a few keV to 1 MeV, and designed for measurement of fast neutron spectra. It consists of detectors, recoil proton proportional counters built especially for this work by R. COMTE (DEG/SER) and which make it possible to cover the energy range and also associated electronic equipment. A brief description is first given of the physical processes involved: (n,p) collisions in the gas, influence of {gamma} radiation; the method of discrimination is then presented. It is based on the difference in the rise-times of the pulses. In the experiments described here the use of a bi-parametric system made it possible to employ the most simple discrimination device, based on the fact that the high frequency gamma pulse components are, at a given energy, weaker than those of the neutron pulses. Results are given of measurements carried out on the Van der Graaff (mono-energetic neutrons for testing the linearity of the chain and the resolving power of the counters), and of those made in a sub-critical system Hug at Cadarache. (author) [French] On decrit une chaine de spectrometrie travaillant dans le domaine d'energie de quelques keV a 1 MeV destinee a la mesure des spectres de neutrons rapides. Elle comprend les detecteurs, compteurs proportionnels a protons de recul, realises specialement pour cette etude par M. R. COMTE (DEG/SER), permettant de couvrir la gamme d'energie et l'electronique associee. Apres un rappel des processus physiques mis en jeu: chocs (n,p) dans les gaz, influence des rayonnements {gamma}, on expose la methode de discrimination utilisee. Celle-ci est basee sur la difference des temps de montee des impulsions. Au cours des experiences rapportees ici, la mise en oeuvre d'un ensemble bi-parametrique a permis d'utiliser le dispositif de discrimination le plus simple, base sur la remarque que les composantes a haute frequence des impulsions {gamma} sont, a

  9. Pärt, Arvo: "Miserere", "Festina lente" / Volkmar Fischer

    Index Scriptorium Estoniae

    Fischer, Volkmar

    1991-01-01

    Uuest heliplaadist Pärt, Arvo: "Miserere", "Festina lente", "Sarah Was Ninety Years Old". The Hilliard Ensemble. Orchester der Beethovenhalle Bonn. Dirigent Dennis Russel Davies (ECM Records, distr Amigo)

  10. The study of neutron propagation in natural uranium; Etude de la propagation des neutrons dans l'uranium naturel

    Energy Technology Data Exchange (ETDEWEB)

    Campan, J L; Clauzon, P P; Kirchner, B; Ribon, P; Zaleski, C P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    Fast exponential experiment. Experimental facilities are described; the experimental results obtained with the block of natural uranium are then presented. Detectors used were fission chambers, activation detectors and nuclear emulsions. One tries to explain the results, which are, then compared with theoretical values obtained by calculations based on diffusion theory. Measured spectrum (pseudo equilibrium) may be characterised by the following values: diffusion length: 95,25 {+-} 0,5; {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 238} : 230 {+-} 10, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Np{sub 237} : 14 {+-} 0.5, {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 233} : 0.67 {+-} 0.03, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Pu{sub 239} : 0.90 {+-} 0.05, {sigma}{sub f}U{sub 235}/{sigma}(ny) In : 230 {+-}10. (author) [French] Experience exponentielle rapide. Apres une description du dispositif experimental, on presente des resultats de mesures effectuees dans un massif d'uranium naturel. Les detecteurs utilises sont des chambres a fission, des detecteurs d'activation et des emulsions nucleaires. Une interpretation des resultats est donnee; ceux-ci sont compares a des valeurs theoriques obtenues par des calculs utilisant la theorie de la diffusion. Le spectre mesure (pseudo equilibre) peut etre caracterise par les valeurs suivantes: Longueur de diffusion: 95,25 {+-} 0,5; {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 238} : 230 {+-} 10, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Np{sub 237} : 14 {+-} 0.5, {sigma}{sub f}U{sub 235}/{sigma}{sub f}U{sub 233} : 0.67 {+-} 0.03, {sigma}{sub f}U{sub 235}/{sigma}{sub f}Pu{sub 239} : 0.90 {+-} 0.05, {sigma}{sub f}U{sub 235}/{sigma}(ny) In : 230 {+-}10. (auteur)

  11. Neutron penetrabilities using an optical model potential (1963); Penetrabilites des neutrons selon le modele du potentiel optique (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Mani, G S; Melkanoff, M A; Iori, I [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    The neutron penetrabilities and reaction cross-sections are presented in these tables for the case of an optical model potential for the nucleus, for nuclei up to mass 230. (authors) [French] Les penetrabilites et les sections efficaces de reaction pour les neutrons sont donnees dans ces tables en utilisant le modele du potentiel optique, pour les noyaux cibles jusqu'a la masse 230. (auteurs)

  12. Neutron penetrabilities using an optical model potential (1963); Penetrabilites des neutrons selon le modele du potentiel optique (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Mani, G.S.; Melkanoff, M.A.; Iori, I. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    The neutron penetrabilities and reaction cross-sections are presented in these tables for the case of an optical model potential for the nucleus, for nuclei up to mass 230. (authors) [French] Les penetrabilites et les sections efficaces de reaction pour les neutrons sont donnees dans ces tables en utilisant le modele du potentiel optique, pour les noyaux cibles jusqu'a la masse 230. (auteurs)

  13. Neutronic measurements of radioactive waste; Les mesures neutroniques des dechets radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Perot, B

    1997-12-31

    This document presents the general matters involved in the radioactive waste management and the different non destructive assays of radioactivity. The neutronic measurements used in the characterization of waste drums containing emitters are described with more details, especially the active neutronic interrogation assays with prompt or delayed neutron detection: physical principle, signal processing and evaluation of the detection limit. (author).

  14. Artus code. Calculation of the energy transfer from neutrons to a solid; Programme Artus. Calcul des quantites d'energie cedees par des neutrons a un solide

    Energy Technology Data Exchange (ETDEWEB)

    Barre, B

    1967-07-01

    The described codes have been realized for a particular study concerning the ionization influence of the CO{sub 2} by neutrons on the reaction: CO{sub 2} - graphite. The code hypothesis and formulation are presented and the application to more general physical problems is proposed. (A.L.B.)

  15. Artus code. Calculation of the energy transfer from neutrons to a solid; Programme Artus. Calcul des quantites d'energie cedees par des neutrons a un solide

    Energy Technology Data Exchange (ETDEWEB)

    Barre, B

    1967-07-01

    The described codes have been realized for a particular study concerning the ionization influence of the CO{sub 2} by neutrons on the reaction: CO{sub 2} - graphite. The code hypothesis and formulation are presented and the application to more general physical problems is proposed. (A.L.B.)

  16. Methods for determining fast neutron spectra using threshold detectors; Les methodes de determination des spectres de neutrons rapides a l'aide de detecteurs a seuil

    Energy Technology Data Exchange (ETDEWEB)

    Delattre, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    We propose to examine all the methods by which fast neutron spectra can be determined using the response of threshold detectors (activation or fission chamber detectors). Most of these methods have been proposed and often even used by various authors of which a list will be found in the bibliography. The aim of the present report is thus not to present original work but rather to gather into a single article and to present in a rational form a whole series of methods which have already been described in articles scattered throughout the specialised literature. Up to the present, each author has in general studied one or two methods and no comparative study of all the possible methods seems to have been made. The most comprehensive study on this topic is that of P.M. UTHE from whose article much has been borrowed. We have tried here to develop a useful tool which should facilitate the systematic experimental study leading to the recognition of the respective merits of the methods proposed. (author) [French] On se propose d'examiner l'ensemble des methodes permettant de determiner les spectres de neutrons rapides a partir des reponses de detecteurs a seuil (detecteurs par activation ou chambre a fission). La plupart de ces methodes ont deja ete proposees, et souvent meme utilisees, par differents auteurs dont on trouvera la liste en bibliographie. Le but du present rapport n'est donc pas de faire oeuvre originale mais plutot de rassembler dans un meme document et de presenter de maniere homogene toute une serie de methodes qui ont deja fait l'objet d'articles disperses dans la litterature specialisee. Jusqu'a present, chaque auteur s'est en general limite a l'etude experimentale d'une ou deux methodes et aucune etude comparative de l'ensemble des methodes possibles ne semble avoir ete faite. Le rapport le plus complet a ce sujet est celui de P.M. UTHE auquel de larges emprunts ont ete faits. On s'est efforce ici d'elaborer un outil de travail commode qui devrait

  17. The neutronic method for measuring soil moisture; La methode neutronique de mesure de l'humidite des sols

    Energy Technology Data Exchange (ETDEWEB)

    Couchat, Ph [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

    1967-07-01

    The three group diffusion theory being chosen as the most adequate method for determining the response of the neutron soil moisture probe, a mathematical model is worked out using a numerical calculation programme with Fortran IV coding. This model is fitted to the experimental conditions by determining the effect of different parameters of measuring device: channel, fast neutron source, detector, as also the soil behaviour under neutron irradiation: absorbers, chemical binding of elements. The adequacy of the model is tested by fitting a line through the image points corresponding to the couples of experimental and theoretical values, for seven media having different chemical composition: sand, alumina, line stone, dolomite, kaolin, sandy loam, calcareous clay. The model chosen gives a good expression of the dry density influence and allows {alpha}, {beta}, {gamma} and {delta} constants to be calculated for a definite soil according to the following relation which gives the count rate of the soil moisture probe: N = ({alpha} {rho}{sub s} +{beta}) H{sub v} +{gamma} {rho}{sub s} + {delta}. (author) [French] La theorie a trois groupes etant choisie comme le moyen le plus adequat pour determiner la reponse de l'humidimetre, une mise en forme d'un modele mathematique est effectuee grace a un programme de calcul numerique ecrit en code Fortran IV. Cette representation est adaptee a l'experience par l'etude de l'influence de parametres du systeme de mesure: tubage, source, detecteur, et du comportement du sol vis-a-vis des neutrons: presence d'absorbeurs, liaison chimique des elements. La validite du modele est testee par ajustement d'une droite aux points images des couples de valeurs experimentales et theoriques, ceci pour sept milieux distincts definis par leur composition chimique: sable, alumine, calcaire, dolomie, kaolin, limon sableux, argile calcaire. Le modele prevoit, bien l'influence de la densite seche et permet de calculer pour un sol donne les constantes

  18. Contribution to the study of the inelastic scattering of neutrons from a to 5 MeV (1961); Contribution a l'etude de la diffusion inelastique des neutrons de 1 a 5 MeV (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Abramson - Szteinsznaider, D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    - The aim of this work is to see if this reaction occurs only by compound nucleus formation or involves some contribution of direct interaction. In the first case, the angular distribution of inelastic neutrons is symmetric about 90 degree. In the second case, this distribution must be asymmetric and must change slowly with energy of incident neutrons. The neutrons corresponding at the excitation of a given level of the residual nucleus are selected by their coincidence with the {gamma} rays of deexcitation of this level. From the results of our measurements on iron, iodine and bismuth and of other laboratories on different elements, we can conclude that generally, the inelastic scattering of neutrons of some MeV occurs only by compound nucleus. (author) [French] - Le but de ce travail est de determiner si cette reaction s'effectue uniquement par passage par un noyau compose ou fait intervenir un processus d'interaction directe. Dans le premier cas, la distribution angulaire des neutrons inelastiques est symetrique par rapport a 90 degree. Dans le deuxieme cas, cette distribution doit etre asymetrique et doit varier lentement avec l'energie des neutrons incidents. Les neutrons correspondant a l'excitation d'un niveau determine du residuel sont selectionnes par leur cofncidence avec les rayonnements {gamma} de desexcitation de ce niveau. D'apres les resultats de nos mesures sur le fer, l'iode et le bismuth et de celles des autres laboratoires sur differents elements, nous pouvons conclure que, en general, la diffusion inelastique des neutrons de quelques MeV s'effectue uniquement par noyau compose. (auteur)

  19. Study of the neutron slowing-down in graphite; Etude du ralentissement des neutrons dans le graphite

    Energy Technology Data Exchange (ETDEWEB)

    Martelly, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Duggal, V P [Commission a l' Energie atomique indienne (India)

    1955-07-01

    Study of the slowing-down age of neutrons in graphite. In the aim to eliminate the effect of resonance neutrons on the detector, neutrons captured by cadmium are studied with a classic method consisting of calculating the difference between the activity measured with and without screens. This method is described and screening properties of cadmium and gadolinium are compared. The experimental parameters and detectors details are described. The radioactive source is Ra-{alpha}-Be. The experimental results are given and the experimental distribution is compared with theoretical formula. In a second part, the spatial distribution of resonance neutrons in indium is discussed. Finally, the neutron slowing-down between the indium resonance and the thermal equilibrium is discussed as well as the research for the effective value of slowing-down age. The slowing-down age definition is given before calculating its effective value. It compared the slowing-down law with the experiment and the Gurney theory. (M.P.)

  20. Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites

    Energy Technology Data Exchange (ETDEWEB)

    Benoist, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-01-15

    In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only. These formulae are very accurate, as seen from the results of a variational method which was studied as a reference. Various correction effects are reviewed. Expressions which allow the exact treatment of fuel rod clusters are presented. The theory is confronted with various experimental results, and a new method of measuring the radial coefficient is proposed. (author) [French] Dans une publication anterieure, on a etablie une formulation simple et generale du coefficient de diffusion, qui definit le mode de ponderation des libres parcours des differents milieux constituants en faisant apparaitre les probabilites de collision dans chaque milieu. On redemontre ici cette expression d'une maniere plus directe, tout en introduisant la variable

  1. Theory of the diffusion coefficient of neutrons in a lattice containing cavities; Theorie du coefficient de diffusion des neutrons dans un reseau comportant des cavites

    Energy Technology Data Exchange (ETDEWEB)

    Benoist, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-01-15

    In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only. These formulae are very accurate, as seen from the results of a variational method which was studied as a reference. Various correction effects are reviewed. Expressions which allow the exact treatment of fuel rod clusters are presented. The theory is confronted with various experimental results, and a new method of measuring the radial coefficient is proposed. (author) [French] Dans une publication anterieure, on a etablie une formulation simple et generale du coefficient de diffusion, qui definit le mode de ponderation des libres parcours des differents milieux constituants en faisant apparaitre les probabilites de collision dans chaque milieu. On redemontre ici cette expression d'une maniere plus directe, tout en introduisant la variable

  2. Determination of the mean free path of the thermal neutrons transport by the measure of a complex diffusion length; Determination du libre parcours moyen de transport des neutrons thermiques par la mesure d'une longueur de diffusion complexe

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, V; Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The further method is the outcome of a technique used in the study of neutrons in scattering and slowing-down environment. In this technique, we replace the constant sources used in the classic experiences by modulated sources with a variable frequency. The object of this article is to describe the extension of the method for the mean free path for transport of thermal neutrons and also to indicate the possible applications for other sizes, as the slowing length, or the absolute value of the cross-section of the boron. (M.B.) [French] La methode qui va etre decrite est l'aboutissement d'une technique utilisee dans l'etude des milieux ou diffusent et se ralentissent des neutrons. Dans cette technique, on remplace les sources constantes utilisees dans les experiences classiques par des sources modulees, a frequence variable. L'objet de cet article est de decrire l'extension de la methode a la mesure du libre parcours moyen de transport des neutrons thermiques et egalement d'indiquer les applications possibles a la mesure d'autres grandeurs, telles que la longueur de ralentissement, ou la valeur absolue de la section de capture du bore. (M.B.)

  3. Radiolysis of some aqueous solutions of neutron absorbers; Etude des effets de certains absorbeurs de neutrons en solution sur la radiolyse de l'eau

    Energy Technology Data Exchange (ETDEWEB)

    Rozenberg, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-12-15

    The initial yield of molecular hydrogen formed by radiolytic decomposition of water in reactor and {sup 60}Co gamma radiation is decreased by the presence of salts of polyvalent elements possessing only one stable valence, i.e cadmium, zinc, magnesium, gadolinium. This effect is favourable for the use of cadmium and gadolinium as soluble neutron absorber in heavy water reactors. Cations of these salts are not inert toward the primary products of water radiolysis. They have a high degree of reactivity toward the hydrated electron, which is the precursor of molecular hydrogen in neutral or alkaline aqueous media. The value of the rate constant for the reaction between cadmium ion and hydrated electron was shown to be (6.1 {+-} 1.8) 10{sup 10} M{sup -1} s{sup -1}. Boric acid at low concentration has no effect on the radiation chemistry of water. An isotope effect has been found in the radiolysis of heavy water, corresponding to a lowering of initial yield [G{sub 0}(D{sub 2}) < G{sub 0}(H{sub 2})]. additionally it was necessary to determine the influence of organic impurities, remaining after the purification of water, on the mechanism of its radiolytic decomposition. (author) [French] Le rendement initial de la formation d'hydrogene moleculaire dans la decomposition radiolytique de l'eau, sous l'effet du rayonnement des reacteurs nucleaires ou du cobalt 60, est diminue si le solute est un sel d'element polyvalent ne possedant qu'un seul etat stable de valence (cadmium, zinc, magnesium, gadolinium). Cet effet est favorable au choix des elements cadmium et gadolinium pour servir d'absorbeur soluble de neutrons dans un reacteur a eau lourde. Les cations de ces sels ne sont pas inertes vis-a-vis des produits primaires de la radiolyse. Ils ont une affinite notable pour l'electron solvate, precurseur de l'hydrogene moleculaire en milieu neutre ou alcalin. En particulier, la constante de vitesse de la reaction du cadmium ionise avec l'electron solvate a pu etre calculee. Sa

  4. Absolute measurement of {beta} activities and application to the determination of neutronic densities; Mesure absolue d'activites {beta} et application a la determination des densites neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, R [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1951-01-15

    M. Berthelot, to my entrance to the ''Commissariat a l 'Energie Atomique'', proposed me to study the absolute measurement of neutron densities. Very quickly the problem of the absolute activity of {beta} sources became the central object of this work. In a first part, we will develop the methods of absolute determination for {beta} activities. The use of a 4{pi} counter permits to get the absolute activity of all beta radioactive source, susceptible to be put as thin leaf and of period superior than some minutes. The method is independent of the spectra of the measured radioelement. we will describe in the second part some applications which use neutron densities measurement, neutron sources intensities and ratio of cross sections of capture of thermal neutrons. (M.B.) [French] M. Berthelot, a mon entree au ''Commissariat a l 'Energie Atomique'', m'a propose d'etudier la mesure absolue des densites neutroniques. Tres rapidement le probleme de l'activite absolue des sources beta est devenu l'objet central de ce travail. Dans une premiere partie, on abordera les methodes de determination absolue des activites beta. L'utilisation d'un compteur 4{pi} permet d 'obtenir l'activite absolue de toute source radioactive beta, susceptible d'etre mise sous forme de feuille mince et de periode superieure a quelques minutes. La methode est independante du spectre du radioelement mesure. On decrira dans la seconde partie quelques applications a des mesures de densites neutroniques, d'intensites de sources de neutrons et de rapport de sections efficaces de capture de neutrons thermiques. (M.B.)

  5. Absolute measurement of {beta} activities and application to the determination of neutronic densities; Mesure absolue d'activites {beta} et application a la determination des densites neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, R. [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1951-01-15

    M. Berthelot, to my entrance to the ''Commissariat a l 'Energie Atomique'', proposed me to study the absolute measurement of neutron densities. Very quickly the problem of the absolute activity of {beta} sources became the central object of this work. In a first part, we will develop the methods of absolute determination for {beta} activities. The use of a 4{pi} counter permits to get the absolute activity of all beta radioactive source, susceptible to be put as thin leaf and of period superior than some minutes. The method is independent of the spectra of the measured radioelement. we will describe in the second part some applications which use neutron densities measurement, neutron sources intensities and ratio of cross sections of capture of thermal neutrons. (M.B.) [French] M. Berthelot, a mon entree au ''Commissariat a l 'Energie Atomique'', m'a propose d'etudier la mesure absolue des densites neutroniques. Tres rapidement le probleme de l'activite absolue des sources beta est devenu l'objet central de ce travail. Dans une premiere partie, on abordera les methodes de determination absolue des activites beta. L'utilisation d'un compteur 4{pi} permet d 'obtenir l'activite absolue de toute source radioactive beta, susceptible d'etre mise sous forme de feuille mince et de periode superieure a quelques minutes. La methode est independante du spectre du radioelement mesure. On decrira dans la seconde partie quelques applications a des mesures de densites neutroniques, d'intensites de sources de neutrons et de rapport de sections efficaces de capture de neutrons thermiques. (M.B.)

  6. Bacilos gram negativos, contaminantes más prevalentes en lentes de contacto blandos usados

    OpenAIRE

    Castiblanco, Diana; Rodríguez, Martha Fabiola; Mayorga C., Myriam Teresa

    2007-01-01

    Las bacterias son los contaminantes más frecuentes de los lentes de contacto. Objetivo: identificar el tipo de depósitos microbiológicos en lentes de contacto blando (LCB) usados. Materiales y Métodos: 100 lentes de contacto blandos de usuarios o de prueba  de las ópticas, recolectándose 25 lentes para cada grupo de la FDA (Grupo1, 2, 3 y 4, según el contenido de agua e ionicidad del polímero). Los lentes se almacenaron por 20 días en sus estuches individuales hasta su estudio. A cada lente, ...

  7. Innova on pour la santé des mères et des enfants d'Afrique

    International Development Research Centre (IDRC) Digital Library (Canada)

    19 janv. 2018 ... Les conclusions révèlent des similitudes parmi les cas de divers contextes na onaux, fournissant une riche base de preuves afin d'inspirer des ini a ves visant à améliorer l'équité en ma ère de santé. OUVRIR LE PDF | COMMANDER LE LIVRE. Innova on pour la santé des mères et des enfants d'Afrique.

  8. Étude de la compétitivité de complexation des métaux issus des ...

    African Journals Online (AJOL)

    Les analyses chimiques effectuées sur le phosphate naturel révèlent la présence des métaux lourds. Pour étudier les risques de rétrogradation de ces engrais phosphatés, notre étude s'est portée sur la complexation des substances humiques naturelles extraites des sols sur des ions métalliques tels que le calcium, ...

  9. Studies on the rice seed (Oryza sativa) sensitivity to gama radiation, neutrons di-enthyl sulphate (DES) and sodium azide (SA)

    International Nuclear Information System (INIS)

    Guimaraes, E.P.

    1978-04-01

    Dry rice seeds of 'Dourado Precoce' variety were treated with gama-rays, thermal and fast neutrons, di-ethyl sulphate (DES) and sodium azide (SA). Biologial effects on survival, seedling height, plant fertility and chlorophy 11 mutation frequency were studied in the M 1 generation. The data obtained were analysed by 'independent test'. Survival was not affected by increased gama ray dosage, but by increased DES and SA dosages, as well as by SA treatments with increased solution acidity for seeds pretreated in distilled water. Seedling height was decreased with the increase of gama-ray dosage, DES concentration. SA acidity and concentration. Plant fertility was reduced drastically with higher gama-ray and neutron dosages and with high SA acidity and concentrations. The maximum chlorophy 11 mutation frequency was obtained in the SA treatment. Seeds pretreated with distilled water showed larger physiological damages in the SA treatments and higher mutation frequencies. Regarding chlorophyll mutation frequency, thermal neutrons were more efficient than gama-rays. SA was the most efficient mutagen used . DES showed lower physiological damages in the M 1 plants, but did not induce mutations in the used conditions [pt

  10. Investigation of correlations in light neutron-rich nuclei; Etude des correlations dans les noyaux legers riches en neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Normand, G

    2004-10-01

    Correlations play a crucial role in understanding the structure of light nuclei at and beyond the neutron drip-line. In this context, the two-neutron halo nucleus He{sup 6} and the unbound systems H{sup 5}, He{sup 7,9} and Li{sup 10} have been studied via measurements of the breakup of beams of He{sup 6} and Be{sup 11,12}. The CHARISSA and DEMON detector arrays were employed. The interpretation was facilitated by a simulation code (SILLAGE) which provided for the setup. In the case of He{sup 7}, the existence of an excited state with E{sub r} {approx} 1 MeV and gamma {approx} 0.75 MeV was confirmed. The virtual character of the s-wave ground state of Li{sup 10} was also confirmed and a scattering length of as {approx} -16 fm deduced. The results obtained for He{sup 9} suggest that a virtual s-wave state may exist just above threshold. The study of the three-body breakup of He{sup 6} found that the decay of the first 2+ state is essentially direct, while the decay of the remaining continuum strength is sequential - passage via He{sup 5}. Using the technique of intensity interferometry an rms separation between the halo neutrons of 7.7 +- 0.8 fm was derived. This result was confirmed by a complementary method utilizing Dalitz plots. In the case of H{sup 5}, the invariant mass spectrum was found to exhibit a broad (gamma {approx} 2 MeV) structure some 1.8 MeV above threshold. Comparison with recent three-body model calculations suggest that this corresponds to the predicted 1/2+ ground state. An rms valence neutron separation of some 5.5 fm was estimated. A search was also carried out for the 4n system using the Be{sup 12*} (2 alpha + Xn decay channel). No signal was observed beyond that expected on the basis of the known background processes. (author)

  11. Modelling of heterogenous neutron leakages in a nuclear reactor; Modelisation des fuites heterogenes de neutrons dans un reacteur nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Wohleber, X

    1997-11-17

    The TIBERE Model is a neutron leakage method based on B{sub 1} heterogeneous transport equation resolution. In this work, we have studied the influence of the reflection mode at the boundary of the assembly. In particular the White boundary condition has been implemented in the APOLLO2 neutron transport code. We have compared the two TIBERE kinds of boundary conditions (specular and white) with the classical B{sub 1} homogeneous leakage method in the modelling of some reactors. We have remarked the better capability of the TIBERE Model to compute voided assemblies. The white boundary condition is also able to compute a completely voided assembly and, besides, wins a factor 10 in CPU time in comparison with the specular boundary condition. These two heterogenous leakage formalisms have been tested on a partially voided experiment and have shown that the TIBERE Model can compute this kind of situation with a greater precision than the classical B{sub 1} homogeneous leakage method, and with a shorter computational time. (author)

  12. Total cross-section measurements on aluminium, carbon, fluorine and hydrogen for d, d reaction neutrons using the coincidence method (1963); Mesure de la section efficace totale de l'aluminium, du carbone, du fluor et de l'hydrogene pour des neutrons de la reaction d, d par la methode des coincidences (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosino, G; Sorriaux, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    The experiment described consists in the measurement of the total cross-section of various materials: aluminium, carbon, fluorine and hydrogen, for mono-energetic 2.77 MeV neutrons obtained from the d,d reaction. The measurement is carried out by transmission. The neutrons are detected by means of a plastic scintillator mounted on a 56 AVP photomultiplier, and are isolated from all secondary phenomena (background noise, scattered neutrons) by coincidence with helium 3. which particles are associated to the neutrons from the reaction {sup 2}{sub 1}D ({sup 2}{sub 1}D, n) {sup 3}{sub 2}H The helium 3 particles are detected by a PN junction diode used with inverted polarisation. An absorption exponential has been traced out using measurements made on seven aluminium bars. The accuracy of the total cross-section measurements is about 10{sup -2}. (authors) [French] L'experience exposee dans ce rapport consiste en la mesure des sections efficaces totales de differents materiaux: aluminium, carbone, fluor et hydrogene, pour des neutrons monoenergetiques de 2,77 MeV, obtenus par la reaction d,d. La mesure est faite par transmission. Les neutrons sont detectes par un scintillateur plastique monte sur un photomultiplicateur 56 AVP, et sont separes de tout phenomene secondaire (bruit de fond, neutrons diffuses) par coincidence avec les helium 3, particules associees aux neutrons de la reaction {sup 2}{sub 1}D ({sup 2}{sub 1}D, n) {sup 3}{sub 2}H Les helium 3 sont detectes par une diode a jonction PN utilisee en polarisation inverse. Une exponentielle d'absorption a ete tracee a partir de mesures faites sur sept barreaux d'aluminium. La precision des mesures des sections efficaces totales est de l'ordre de 10{sup -2}. (auteurs)

  13. Applications des techniques de diffusion de la lumière, des rayons X et des neutrons a l'étude des systèmes colloïdaux. Troisième partie : caractérisation des microémulsions et des composés solides. Étude de différents systèmes d'intérêt industriel Application of Light, X-Ray and Neutron Diffusion Techniques to the Study of Colloidal Systems. Part Three: Microemulsions, Solid Materials, Liquids and Miscellaneous Systems with Industrial Uses

    Directory of Open Access Journals (Sweden)

    Espinat D.

    2006-11-01

    Full Text Available Cette troisième partie clôt une revue bibliographique concernant la caractérisation des systèmes colloïdaux par les techniques de diffusion (lumière, rayons X, neutrons (Rev. Inst. Franç. du Pétrole, Vol. 45, No 6, novembre-décembre 1990. Nous poursuivrons cette présentation en nous intéressant aux microémulsions. Après la présentation des informations que l'on peut obtenir sur les systèmes polymériques, les solutions micellaires ou les systèmes fractals, qui ont fait l'objet de multiples travaux, nous reviendrons sur les applications plus restreintes à des systèmes colloïdaux parfois moins bien définis et d'origine industrielle, telles les fractions lourdes des pétroles, les asphaltènes ou encore les additifs de lubrification. Les possibilités de la diffusion des rayons X et des neutrons à l'étude de matériaux solides seront présentées à travers la caractérisation des solides poreux et en particulier des catalyseurs. Nous terminerons cette présentation par les liquides purs ou les mélanges; les techniques de diffusion ont contribué fortement à la description des structures des phases liquides. This article is the second one (the first one was published in Revue de l'Institut Français du Pétrole No. 6, November-December 1990 concerning the application of techniques of light scattering, X rays and neutrons to the analysis of colloidal systems and more specifically to the theoretical description of the three methods. The aim of this second part is to make a nonexhaustive description of several fields of applications. A special effort is made to describe the potential of these methods for characterizing colloidal or divided systems encountered in a great many activities involving the petroleum industry. The first part of this article takes up polymer and colloidal solutions. Particular attention is paid to the importance of scattering techniques for characterizing polymers in solution and micellar solutions. A

  14. Contribution to the radio crystallographic study of the effect of neutrons on LiF monocrystals (1962); Contribution a l'etude radiocristallographique de l'effet des neutrons sur les monocristaux de LiF (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, M; Tournarie, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    We have studied the changes in the 200 and 400 reflections in LiF monocrystals irradiated by neutrons, for doses of between 10{sup 17} and 10{sup 18} n/cm{sup 2}. The reflections are distinctly dissymmetric and in the case of doses under 5.10{sup 17} appear to consist of a fine peak associated with a wide and diffuse base. These appear to exist organised groups of point defects which lead to perturbed zones whose number varies very little with the irradiation and which exist perhaps beforehand. (authors) [French] Nous avons etudie l'evolution des reflexions 200 et 400 de monocristaux de LiF irradie aux neutrons pour des doses variant de 10{sup 17} a 10{sup 18} n/cm{sup 2}. Les reflexions presentent une nette dissymetrie et pour des doses inferieures a 5.10{sup 17} semblent constituees d'un pic fin associe a une base large et diffuse. Il semble qu'il y ait des rassemblements organises de defauts ponctuels pour donner des zones perturbees dans le nombre varierait peu avec l'irradiation et lui serait peut-etre preexistant. (auteurs)

  15. Contribution to the experimental study of the critical scattering of cold neutrons in iron; Contriiution a l'etude experimentale de la diffusion critique des neutrons froids par le fer

    Energy Technology Data Exchange (ETDEWEB)

    Konstantinovic, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-03-15

    The aim of the present work is a study of magnetic fluctuations which are produced in iron in the neighbourhood of the Curie temperature, by neutron scattering. We start by briefly recalling the theory of scattering of neutrons by magnetic substances and Landau's theory of second order phase transitions which enables one to derive the magnetic cross section near the Curie temperature. Following this is a description of the experimental apparatus after which we present the experimental results. The analysis of the results confirms the four-third law obeyed by the magnetic susceptibility near the Curie point, predicted by recent theories based on the Heisenberg model. However, the analysis reveals a non-zero relaxation time for the magnetic fluctuations at the Curie point, which is in disagreement with theoretical conclusions. (author) [French] L'objet du present travail est l'etude des fluctuations d'aimantation qui prennent naissance dans le fer au voisinage de sa temperature de Curie par la diffusion des neutrons. Nous commencons par rappeler brievement les generalites sur la diffusion des neutrons par les substances magnetiques et la theorie de Landau des transitions de phase du second ordre qui permet de deriver une expression de la section efficace magnetique pres de la temperature de Curie. Ensuite, apres la description du dispositif experimental, nous presentons les resultats experimentaux. L'analyse de ces resultats confirme les theories recentes suivant le modele d'Heisenberg en ce qui concerne la 'loi en 4/3' de la susceptibilite magnetique au voisinage du point de Curie; mais par ailleurs elle revele l'existence d'un temps de relaxation des fluctuations d'aimantation non nul en ce point, ce qui est en desaccord avec les previsions theoriques actuelles. (auteur)

  16. Methods of Particle Detection in Free Neutron Decay; Methode de detection des particules dans une desintegration de neutrons libres; Metod obnaruzheniya chastits pri raspade svobodnogo nejtrona; Metodo para la deteccion de particulas en la desintegracion de neutrones libres

    Energy Technology Data Exchange (ETDEWEB)

    Novey, T B [Argonne National Laboratory, Lemont, IL (United States)

    1960-06-15

    A number of experimental studies have recently been completed by the Argonne Group on the decay of polarized neutrons in order to elucidate the structure of the weak nuclear interaction. These studies have taken the form of the measurement of the. angular distributions of electrons and protons with respect to the spin direction of the decaying free neutrons. The basic components of the apparatus which will be discussed are: 1. The one-meter iron-cobalt mirror which selects a beam of highly polarized neutrons and the methods for determination of the polarization. 2. The electron detector comprising a 10 cm diameter, 6 mm thick mosaic of anthracene crystals, and its light pipe system. 3. The proton detector, a 14-stage electron multiplier system, the first stage with a 15x15 cm opening, tapering in four stages to a standard 10-stage multiplier structure, and its entrance baffles for angular resolution. 4. The electronic system which selects pulses from the detectors having the proper time sequence, relative time-delay and pulse-height to allow indentification of a neutron decay. (author) [French] Le groupe Argonne a termine recemment des etudes experimentales sur la desintegration des neutrons polarises, en vue de mettre en lumiere le processus de l'interaction nucleaire faible. Ces etudes consistaient a mesurer les distributions angulaires d'electrons et de protons par rapport a la direction du spin des neutrons libres en voie de desintegration. Les principaux elements de l'appareillage qui sera decrit sont: 1. Le miroir de ferro-cobalt d'un metre, qui isole un faisceau de neutrons hautement polarises, ainsi que les methodes permettant de determiner la polarisation. 2. Le detecteur electronique qui comprend une mosaique de 10 cm de diametre et de 6 mm d'epaisseur en cristaux d'anthracene, et son systeme selectif. 3. Le detecteur de protons, un systeme multiplicateur electronique a 14 etages, le premier ayant une ouverture de 15x15 cm se retrecissant en 4 etages pour

  17. Study by neutron diffusion of magnetic fluctuations in iron in the curie temperature region; Etude des fluctuations d'aimantation dans le fer au voisinage de la temperature de curie par diffusion des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Ericson-Galula, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-12-15

    Heinsenberg model and a simple band model; our values in good agreement with those calculated in the Heisenberg model and exclude the band model used. Finally, in chapter IV we recall the chief results obtained. (author) [French] La diffusion critique des neutrons dans le fer est due aux fluctuations d'aimantation qui existent dans les substances ferromagnetiques au voisinage de la temperature de Curie. Les fluctuations peuvent se decrire en termes de correlations; on definit une fonction de correlation: {gamma}{sub R{sub vector}} (t), {gamma}{sub R{sub vector}} (t) , valeur moyenne du produit scalaire d'un spin de reference et d'un spin situe a la distance (R) du premier et considere a l'instant t. Dans le chapitre I nous rappelons les generalites sur les sections efficaces de diffusion des neutrons; nous donnons un bref resume de la theorie de VAN HOVE qui a montre que la section efficace de diffusion magnetique des neutrons est la transformee de FOURIER de la fonction de correlation. Dans le chapitre II nous etudions la dependance spatiale de la fonction de correlation, supposee independante du temps. On peut alors la caracteriser par deux parametres K{sub 1} et r{sub 1} qui permettent de calculer respectivement la portee et l'intensite des correlations. Apres avoir expose le principe de la mesure de ces parametres, nous decrirons l'appareillage experimental. Les valeurs experimentales obtenues sont en bon accord avec celles calculees, l'accord est meilleur si on suppose que ce sont les deuxiemes et non les premiers voisins d'un atome de fer qui sont magnetiquement actifs, ainsi que l'a propose NEEL. Dans le chapitre III nous etudions l'evolution dans le temps de la fonction de correlation; cette evolution est caracterisee par un parametre {lambda} dependant de la temperature, qui intervient dans l'equation de diffusion, a laquelle obeissent les fluctuations d'aimantation {delta}M{sub vector}/{delta}t = {lambda} {nabla

  18. Study of heterogeneous multiplying and non-multiplying media by the neutron pulsed source technique; Etude des milieux heterogenes multiplicateurs et non-multiplicateurs par la technique de la source pulsee de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Deniz, V [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-06-01

    The pulsed neutron technique consists essentially in sending in the medium to be studied a short neutron pulse and in determining the asymptotic decay constant of the generated population. The variation of the decay constant as a function of the size of the medium allows the medium characteristics to be defined. This technique has been largely developed these last years and has been applied as well to moderator as to multiplying media, in most cases homogeneous ones. We considered of interest of apply this technique to lattices, to see if useful informations could be collected for lattice calculations. We present here a general theoretical study of the problem, and results and interpretation of a series of experiments made on graphite lattices. There is a good agreement for non-multiplying media. In the case of multiplying media, it is shown that the age value used until now in graphite lattices calculations is over-estimated by about 10 per cent. [French] La technique de la pulsation neutronique consiste essentiellement a envoyer dans le milieu a etudier une courte bouffee de neutrons et a determiner la constante de decroissance asymptotique de la population engendree. La variation de cette constante de decroissance en fonction des dimensions du milieu permet de determiner ses caracteristiques. Cette technique a connu ces dernieres annees un grand essor et a ete appliquee a des moderateurs et des milieux multiplicateurs. Il s'agissait dans la plupart des cas de milieux homogenes. Il nous a semble interessant de l'utiliser dans le cas des reseaux, afin de voir si ces experiences peuvent fournir des renseignements utiles aux calculs. Nous presentons ici une etude theorique generale du probleme, ainsi que les resultats et l'interpretation d'une serie d'experiences faites sur des reseaux a graphite. L'accord est bon dans le cas des reseaux non-multiplicateurs. Dans le cas des reseaux multiplicateurs, on montre que la valeur de l'age utilisee jusqu'ici dans les calculs

  19. Theory of Pulsed Neutron Experiments in Highly Heterogeneous Multiplying Media; Theorie des Experiences au Moyen des Neutrons Pulses, dans les Milieux Multiplicateurs Tres Heterogenes; O teorii ehksperimentov s impul'snymi neitronami v geterogennykh razmnozhayushchikh sredakh; Aspectos Teoricos de los Experimentos con Neutrones Pulsados en Medios Multiplicadores Muy Heterogeneos

    Energy Technology Data Exchange (ETDEWEB)

    Corno, S. E. [Instituto di Fisica ' ' A. Volta' ' (Italy); Unversity of Pavia, Pavia (Italy); SNAM, Milan [Italy

    1965-10-15

    In this work we investigate the time and space dependence of the neutron flux within a highly heterogeneous assembly, in which pulsed or sinusoidally modulated neutrons are injected. We consider, for the sake of simplicity, a device consisting of a cylindrical block of heavy moderator, along the axis of which a line-shaped region of fissionable material is located. The driving neutron source is assumed to be located on one of the end faces of the cylinder. The extent of the fissionable region allows us to deal with it as with an absorbing and multiplying singularity of the neutron field. As our attention is mostly concentrated on space and time variation of the neutron flux, rather crude approximations are assumed as far as the energy dependence of the neutron population is concerned. Within the limits of the age-diffusion theory, the response of the device to any neutron excitation may be found in closed form. For a sinusoidally modulated source of given frequency, it may easily be shown that, if the axial singularity were a purely absorbing one, the neutron waves being propagated along the device would possess a phase shift; a wavelength and an attenuation constant depending on the absorbing properties of the singularity. This picture becomes more and more complicated when neutron multiplication occurs. For this general case the solution derived in our paper obviously turns out to be dependent on both absorption and multiplication properties of the singularity. This circumstance suggests, among others, the idea of using a device of the type described above for testing fuel elements of heterogeneous reactors. (author) [French] L'auteur etudie les variations du flux de neutrons en fonction du temps et du lieu dans un assemblage tres heterogene ou l'on injecte des neutrons puises ou modules sinusoidalement. Il envisage, pour des raisons de simplicite, un dispositif constitue par un ralentisseur lourd en forme de bloc cylindrique sur l'axe duquel est placee une zone

  20. Continuous measurement of neutron flux with the help of a converter; Mesure continue des flux de neutrons a l'aide d'un dispositif convertisseur

    Energy Technology Data Exchange (ETDEWEB)

    Mas, P; Sciers, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-07-01

    The device described in this report is working from this following principle: an element, the thermal neutron activate of which has a short period and is emitter of a {beta} particle, is surrounded with a dielectric which is itself surrounded by a conducting metal. {beta} particles are stopped in the conducting metal. Thus an electric current rises between the emitter element and the collector metal. The experimental study has been-done with rhodium as emitter. The linearity as function of thermal flux of the power of the pile, the accuracy, the efficiency of the device have been measured and are satisfactory. Just the stability of the measure equipment is not very good. This method gives, us at moment the instantaneous flux and the integrated flux, is well adapted for the measurements in pile to execute on loops. It is possible to continue to perfect the process. (authors) [French] Le dispositif decrit dans ce rapport fonctionne d'apres le principe suivant: un corps, dont le produit d'activation en neutrons thermiques a une courte periode et est emetteur d'une particule {beta}, est entoure d'un dielectrique lui-meme entoure d'un metal conducteur. Les particules {beta} sont arretees dans le metal conducteur. Il y a ainsi naissance d'un courant electrique entre le corps emetteur et le metal collecteur. L'etude experimentale a ete menee avec le rhodium comme emetteur. La linearite en fonction du flux thermique, de la puissance de la pile, la precision, le rendement du dispositif ont ete mesures et sont satisfaisants. Seule la stabilite de l'appareillage de mesure n'est pas tres bonne. Cette methode, qui peut nous donner a tout instant le flux instantane et le flux integre, est tout a fait adaptee aux mesures en pile a effectuer. sur des boucles. On peut poursuivre la mise au point du procede. (auteurs)

  1. Compression medullaire lente secondaire a un lymphome de Burkitt ...

    African Journals Online (AJOL)

    faciale à la fin du 1er mois et une récupération neurologique au bout d'un an. La localisation secondaire intra rachidienne d'un LB bien que rare doit être présente à l'esprit surtout en face d'une compression médullaire lente survenue dans un ...

  2. Moderation of Neutrons Emitted by a Pulsed Source and Neutron Spectrometry Based on Slowing-Down Time; Ralentissement des Neutrons Emis par une Source Pulsee et Leur Spectrometrie en Fonction du Temps de Ralentissement; Zamedlenie nejtronov, ispuskaemykh impul'snym istochnikom, i spektrometriya nejtronov po vremeni zamedleniya; Moderacion de Neutrones Emitidos por una Pitente Pulsada y Espectrometria Neutronica Basada en el Tiempo de Frenado

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, A. A.; Isakov, A. I.; Kazarnovskij, M. V.; Popov, Ju. P.; Shapiro, F. L. [Fizicheskij Institut Im. P.N. Lebedeva AN SSSR, Moskva, SSSR (Russian Federation)

    1965-08-15

    -sections. Measurements carried out on a large number of substances, including separated isotopes, have led to the discovery of hitherto unknown resonance levels with small neutron widths and have made it possible to determine for many nuclei the magnitude of the force function for the capture of neutrons with orbital angular momentum 1 = 1. (author) [French] A l'Institut de physique P. N. Lebedev de l'Academie des sciences de l'URSS, on a procede, au cours de ces six dernieres annees, a une serie de travaux visant a etudier le ralentissement non stationnaire des neutrons dans les milieux lourds, a elaborer une methode de spectro- metrie des neutrons en fonction du temps de ralentissement et a appliquer cette methode a l'etude de l'influence que l'energie exerce sur les sections efficaces des reactions nuceaires provoquees par des neutrons d'une energie de 30 keV ou moins. Les auteurs donnent un apercu de ces recherches et en analysent les resultats. Apres avoir examine brievement la theorie du ralentissement non stationnaire et de la thermalisation des neutrons, ils indiquent les donnees fournies par une etude experimentale du ralentissement des neutrons dans le graphite, le fer et le plomb et par l'etude de leur thermalisation dans le plomb. En utilisant une source de neutrons puisee et des detecteurs a resonance, ils ont mesure la distribution des temps de ralentissement pour une serie de valeurs determinees de l'energie finale des neutrons. Ils comparent les resultats obtenus a la theorie qui tient compte du mouvement thermique des atomes du ralentisseur, lequel provoque, dans le cas du plomb, une dispersion mesurable des temps de ralentissement pour des energies inferieures a 10 eV. Dans le domaine d'energies inferieures au seuil cadmium, on a mesure l'influence du temps de ralentissement sur la vitesse moyenne des neutrons dans le plomb; une comparaison a ete faite avec la theorie a plusieurs groupes. Les auteurs decrivent la methode employee pour determiner, selon le temps de

  3. Contribution to the study of magnetic diffusion of neutrons; Contribution a l'etude de la diffusion magnetique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Gennes, P.G. de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-07-01

    Certain statistical aspects of a large collection of electronic spins coupled by exchange forces are examined. The treatment is limited to substances where the orbital magnetic moment can be considered fixed, and where the effect of thermal agitation of the ions can be neglected. A system of this kind can be followed experimentally by elastic and inelastic diffusion of neutrons. At high temperatures, inelastic diffusion allows the microscopic aspect, reversible, and the macroscopic aspect, irreversible, to be studied simultaneously and these 2 fields to be linked. At temperatures around the Curie point, the average phenomenon is the appearance of a critical opalescence. At low temperatures, collective spin excitations can be observed. In the neighborhood of the Curie point, the spin coefficient {lambda}, which governs the relaxation of fluctuations of magnetization, is calculated. An intrinsic factor is discussed in {lambda}, bound to the microscopic frequency of the spin exchanges, and to a factor due to the damping of the diffusion by the magnetic field. At the transition point, {lambda} is cancelled. The spectrum of the spin excitations in metals is discussed. (author)

  4. A critical summary of microscopic fast-neutron interactions with reactor structural, fissile and fertile materials; Apercu critique des interactions microscopiques des neutrons rapides avec les materiaux de construction et les matieres fissiles et fertiles utilisees dans les reacteurs; Kriticheskij obzor mikroskopicheskog o vzaimodejstviya bystrykh nejtronov s konstruktsionnymi, rasshcheplyayushchimis ya i vosproizvodyashchim i reaktornymi materialami; Resumen critico de las interacciones microscopicas de los neutrones rapidos con los materiales estructurales fisionables y fertiles utilizados en los reactores

    Energy Technology Data Exchange (ETDEWEB)

    Smith, A B [Argonne National Laboratory, Argonne, IL (United States)

    1962-03-15

    Prevailing knowledge of fast-neutron-induced reactions utilized in the nuclear design of reactor systems is reviewed. Principal emphasis is placed upon microscopic experimental methods, results and precisions. Fast-neutron scattering is considered in detail, including the results of experimental determinations of scattering from oxygen, iron, zirconium, niobium, tungsten, thorium and uranium. Representative results of experimental studies of fast-neutron capture and fast-neutron-induced fission are given. The measurements discussed not only provide results of considerable applied usefulness but axe also examples of the application of advanced experimental nuclear techniques. Areas of limited, conflicting or non-existent experimental information are outlined. A prognosis of future knowledge of fast-neutron reactions is made, with emphasis on the fulfillment of reactor requirements for basic nuclear data. (author) [French] L'auteur fait le point des connaissances sur les reactions provoquees par les neutrons rapides sur lesquelles on tend a fonder les projets de reacteurs. Il met en relief les methodes, les resultats et la precision de mesures experimentales a l'echelle microscopique. Il etudie en detail la diffusion des neutrons rapides, et donne les resultats de mesures experimentales de diffusion dans l'oxygene, le fer, le zirconium, le niobium, le tungstene, le thorium et l'uranium. Il donne les resultats les plus significatifs d'etudes experimentales sur la capture des neutrons rapides et sur la fission provoquee par des neutrons rapides. Les mesures etudiees, non seulement fournissent des renseignements d'une utilite pratique considerable, mais aussi constituent des exemples de l'application de techniques experimentales nucleaires a la pointe du progres. L'auteur indique les domaines ou les donnees experimentales sont limitees, contradictoires ou inexistantes. Il se livre a des pronostics sur le developpement des connaissances experimentales en matiere de

  5. The Biological Effect of Fast Neutrons and High-Energy Protons; Effets Biologiques des Neutrons Rapides et des Protons de Haute Energie; Biologicheskoe dejstvie bystrykh nejtronov i protonov vysokikh ehnergii; Efectos Biologicos de los Neutrones Rapidos y de los Protones de Elevada Energia

    Energy Technology Data Exchange (ETDEWEB)

    Moskalev, Ju. I.; Petrovich, I. K.; Strel' cova, V. N.

    1964-03-15

    tumour of the thyroid gland also appear. With proton irradiation, the minimum tumour dose for haemopoietic tissue and the thyroid gland is in the neighbourhood of 250 rad, for the testicles 300 rad, for the prostate, the pancreas and the subcutaneous tissue 100 rad. After irradiation with fast neutrons the incidence of tumours of the testicles, the large intestine, the kidneys and the liver is increased at doses between 42.5 and 85 rad. The same is true for tumours of the skin and the subcutaneous tissue at a dose of 85 rad. With fast neutron irradiation tumours appeared at approximately three to five times lower radiation doses than with proton irradiation. (author) [French] Le memoire expose les resultats d'experiences visant a comparer l'e ffe t des neutrons rapides et celui des protons de haute energie (500 MeV) sur la duree de vie, le sang peripherique, la frequence et la rapidite d'apparition des tumeurs chez le rat, en tenant compte de la dose efficace et du delai d'observation. Les travaux ont porte sur 573 rats blancs pour les neutrons et sur 490 rats blancs pour les protons. Les animaux etaient exposes a des doses de neutrons rapides de 8,5 a 510 rad et a des doses de protons de 28 a 1008 rad. Pour les neutrons rapides et les protons, les auteurs ont determine les valeurs des doses effectives aiguees, sub-aiguees et chroniques. La DL{sup 30}{sub 50} est de 408 rad pour les neutrons et de 600 rad pour les protons; la DL{sup 120}{sub 50} s'eleve a 380 et 600 rad, respectivement. On a procede a une etude critique des lois qui regissent la mortalite des rats a breve echeance et apres des delais prolonges. D'apres les constatations, la survie moyenne des rats irradies par des neutrons rapides est independante de leur sexe. En ce qui concerne les differents indices du sang peripherique, la forme de la courbe dose/effet depend dans une forte mesure, non seulement de la radiosensibilite des cellules correspondantes du sang, mais aussi de la duree d'observation. Elle

  6. Neutron spin echo spectroscopy. Its application to the study of the dynamics of polymers in solution; La spectrometrie par echos de spins de neutrons. Application a l'etude de la dynamique des polymeres en solution

    Energy Technology Data Exchange (ETDEWEB)

    Papoular, Robert

    1992-06-15

    This work focuses on Neutron Spin Echo (NSE) spectroscopy and on the NSE spectrometer MESS, which we have built at the L.L.B. (CE Saclay). After analyzing in detail the classical and quantum principles of this type of instrument, and illustrated them with optical analogies, we expound a simple formalism for the interpretation of polarized neutron experiments of the most general type. In a second part, we describe the MESS spectrometer extensively; its characteristics and performances as well as the first results obtained with this instrument. In particular, we include two papers showing how the neutron depolarization, spin rotation and echoes can be used to investigate high-Tc superconductors. The last part deals with the dynamics of Polymer-Polymer-Solvent ternary solutions and demonstrates how the Neutron Spin Echo technique becomes a privileged tool for such physico-chemical studies thanks to the joint use of NSE and contrast variation methods, coupled with the adequate ranges of time and scattering vectors accessible. Finally, we describe the specific case of partially deuterated polydimethyl-siloxane (PDMS) in semi-dilute solution in Toluene. We have experimentally and separately evidenced the cooperative and inter-diffusive diffusion modes predicted by the theory of Akcasu, Benoit, Benmouna et al. These results, obtained at the L.L.B. (CE Saclay) are the subject matter of the last paper included in this work. (author) [French] Ce memoire est centre sur la spectroscopie par echos de spins de neutrons, et plus particulierement, sur le spectrometre a echos de spins MESS que nous avons construit au L.L.B (CE/Saclay). Apres avoir detaille les principes classique et quantique de ce type d'instrument et les avoir illustres par des analogies optiques, nous detaillons un formalisme simple permettant d'interpreter les experiences utilisant les neutrons polarises dans le cas le plus general. Une seconde partie decrit de maniere approfondie le spectrometre MESS de Saclay

  7. Procedimiento para elaborar una lente intraocular monofocal asférica isoplanática y lente obtenida empleando dicho procedimiento

    OpenAIRE

    Barbero, Sergio; Marcos, Susana; Dorronsoro, Carlos; Montejo, Javier; Salazar Salegui, Pedro

    2010-01-01

    Procedimiento para elaborar una lente intraocular monofocal asférica isoplanática y lente obtenida empleando dicho procedimiento. Permite obtener lentes oftálmicas monofocales asféricas isoplanáticas en un rango visual de hasta 25º (preferentemente hasta 10º) de amplitud. El procedimiento comprende las etapas de: 1.- Definición matemática de un modelo de ojo afáquico; 2.- Definición matemática de un modelo de lente intraocular; 3.- Definición matemática de la implantac...

  8. The determination by irradiation with a pulsed neutron generator and delayed neutron counting of the amount of fissile material present in a sample; Determination de la quantite de matiere fissile presente dans un echantillon par irradiation au moyen d'une source pulsee de neutrons et comptage des neutrons retardes

    Energy Technology Data Exchange (ETDEWEB)

    Beliard, L; Janot, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    A preliminary study was conducted to determine the amount of fissile material present in a sample. The method used consisted in irradiating the sample by means of a pulsed neutron generator and delayed neutron counting. Results show the validity of this method provided some experimental precautions are taken. Checking on the residual proportion of fissile material in leached hulls seems possible. (authors) [French] Ce rapport rend compte d'une etude preliminaire effectuee en vue de determiner la quantite de matiere fissile presente dans un echantillon. La methode utilisee consiste a irradier l'echantillon considere au moyen d'une source puisee de neutrons et a compter les neutrons retardes produits. Les resultats obtenus permettent de conclure a la validite de la methode moyennant certaines precautions. Un controle de la teneur residuelle en matiere fissile des gaines apres traitement semble possible. (auteurs)

  9. Carcinogenesis by Fast Neutrons Relative to X-Rays in Mice; Carcinogenese chez les Souris sous l'Effet des Neutrons Rapides et des Rayons X; Sravnitel'naya chastota vozniknoveniya rakovykh opukholej u myshej pri obluchenii bystrymi nejtronami i rentgenovskimi luchami; Accion Carcinogenica Comparada de los Neutrones Rapidos y de los Rayos X en el Raton

    Energy Technology Data Exchange (ETDEWEB)

    Cole, L. J.; Nowell, P. C. [Division of Biological and Medical Sciences, U.S. Naval Radiological Defense Laboratory, San Francisco, CA (United States); Department of Pathology, School of Medicine, University of Pennsylvania, Philadelphia, PA (United States)

    1964-05-15

    Young adult LAF{sub 1} mice received a single sublethal exposure to fission-spectrum neutrons, and were treated as follows: Group 1 - 195 to 199 rad, followed by a single subcutaneous injection of CCI{sub 4} one month later; Group II - CCl{sub 4} injected one day prior to neutron irradiation (280 - 329 rad); Group III - CCI{sub 4} only; no irradiation; Group IV - unilateral nephrectomy carried out one day before neutron irradiation (320 - 328 rad); Group V - neutron irradiation only (200 - 320 rad> In the Group I-mice, sacrificed 12-16 months post-irradiation, 75% exhibited hepatomas, while 92% of the mice in Group II showed hepatomas. By contrast, liver tumours appeared in 14% of mice receiving neutron irradiation only (Group V), and in 2.4% of mice exposed to a single dose (500 rad) of 250 kVp X-rays. The incidence of kidney neoplasms approached 100% in the uninephrectomized irradiated mice (Group IV), whereas such lesions were infrequent in control mice. The induction of these neoplasms is discussed in terms of initiation by the neutron radiation, and promotion by the specific proliferative stimuli exployed. The data indicate a potency factor of approximately 2 for fission neutrons relative to 250 kVp X-rays for initiation of kidney neoplasms in mice. With respect to the occurrence of lymphoma in this strain, the neutron-irradiated mice showed a reduced incidence (11 %) as compared with the X-irradiated animals (29%). (author) [French] On a expose a une dose sub letale unique de neutrons de fission des jeunes sujets adultes de souche LAF, que l'on a traites de la facon suivante: Groupe 1 - injection souscutanee de CCl{sub 4} un mois apres l 'exposition(195 a 199rad); Groupe II - injection de CCl{sub 4} un jour avant l'exposition aux neutrons (280 a 329 rad); Groupe III - CCl{sub 4} seulement, pas d'exposition; Groupe IV - nephrectomie unilaterale un jour avant l'exposition aux neutrons (320 a 328 rad); Groupe V - exposition aux mettrons seulement (200 a 320 rad

  10. Structural and dynamical study about denatured states of yeast phosphoglycerate kinase by neutrons scattering and X-rays; Etude structurale et dynamique des etats denatures de la phosphoglycerate kinase de levure par diffusion des neutrons et des rayons X

    Energy Technology Data Exchange (ETDEWEB)

    Receveur, V

    1997-04-28

    During a long time, the neutron scattering and X-rays techniques have not been used for the studies bearing on the folding of proteins. The compactness and the globularness of a protein are two structural characteristics describing the denatured states and the intermediate states of folding, and the neutrons and x-rays scattering are probably the two techniques the most appropriate to give this kind of information; they are sensible to the spatial extent and to the molecules compactness, and to their general shape. For these three or four last years, the works using these techniques are increasing, giving precious knowledge on the different steps of folding and on the interactions stabilizing the denatured or intermediate states. This thesis falls into this category. (N.C.).

  11. Homogenization of neutronic diffusion models; Homogeneisation des modeles de diffusion en neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Capdebosq, Y

    1999-09-01

    In order to study and simulate nuclear reactor cores, one needs to access the neutron distribution in the core. In practice, the description of this density of neutrons is given by a system of diffusion equations, coupled by non differential exchange terms. The strong heterogeneity of the medium constitutes a major obstacle to the numerical computation of this models at reasonable cost. Homogenization appears as compulsory. Heuristic methods have been developed since the origin by nuclear physicists, under a periodicity assumption on the coefficients. They consist in doing a fine computation one a single periodicity cell, to solve the system on the whole domain with homogeneous coefficients, and to reconstruct the neutron density by multiplying the solutions of the two computations. The objectives of this work are to provide mathematically rigorous basis to this factorization method, to obtain the exact formulas of the homogenized coefficients, and to start on geometries where two periodical medium are placed side by side. The first result of this thesis concerns eigenvalue problem models which are used to characterize the state of criticality of the reactor, under a symmetry assumption on the coefficients. The convergence of the homogenization process is proved, and formulas of the homogenized coefficients are given. We then show that without symmetry assumptions, a drift phenomenon appears. It is characterized by the mean of a real Bloch wave method, which gives the homogenized limit in the general case. These results for the critical problem are then adapted to the evolution model. Finally, the homogenization of the critical problem in the case of two side by side periodic medium is studied on a one dimensional on equation model. (authors)

  12. Automation on computers of the partial area method for the analysis of 's' neutron induced resonances. I. Without interference terms. (1962); Automatisation sur ordinateur de la methode des aires partielle dans l'analyse des resonances induites par les neutrons 's'. I. sans terme d'interference. (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, G; Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    This report deals with numerical analysis of transmission resonances induced by 's' wave neutrons in time of flight experiments. The analysis method used is the partial area one. The only case treated here, in this first part, is the one when the interference term can be neglected. Programs and subroutines are thoroughly described, which determine from experimental raw data the resonant transmission, the partial areas, and the resonance parameters. (authors) [French] Le present rapport a pour objet l'analyse numerique sur ordinateur IBM 7090, des resonances dues aux neutrons 's' dans les experiences de transmission par temps de vol, la methode d'analyse utilisee etant la methode des aires partielles. Dans cette premiere partie, seul a ete envisage le cas ou le terme d'interference peut etre neglige. On y trouvera une description detaillee des programmes et sous programmes elabores pour determiner les transmissions resonantes avec leur trace, a partir des donnees experimentales brutes, les aires partielles afferentes ainsi que les parametres caracteristiques des resonances. (auteurs)

  13. Úlceras corneales en usuarios de lentes de contacto

    Directory of Open Access Journals (Sweden)

    Darlen Rodríguez Rivero

    Full Text Available El empleo de lentes de contacto se ha incrementado a nivel mundial. En la actualidad su uso no se restringe solamente a la corrección óptica, sino que se utilizan con fines terapéuticos, ya que generan comodidad y estética en múltiples afecciones oculares. Es de esperar el creciente aumento de las complicaciones relacionadas con el uso de estos, por ser la queratitis bacteriana potencialmente grave y devastadora para el globo ocular. Se realizó una revisión bibliográfica acerca de las úlceras corneales en portadores de lentes de contacto con el objetivo de describir su epidemiología y las formas de prevenir esta complicación.

  14. Observaci\\'on de lentes gravitatorias con ALMA

    OpenAIRE

    Bonilla, A.; Toloza, O.; Fuentes, I.; Motta, V.

    2016-01-01

    Gravitational lensing is a fundamental tool for cosmology. A recent instrument which will provide more information for models of these objects is ALMA. Our goal is to select lens candidates to observe with ALMA and then model them using GravLens Software. We had selected 12 quadruple images systems from the CASTLES database, which show a high probability of observing extended sources in the submillimetric range. These new data will allow us to improve existing models. Las lentes gravitatorias...

  15. Effects of Monoenergetic Neutron Radiation on Human Cells in Tissue Culture; Effets des Neutrons Monoenergetiques sur des Cellules de Tissus Humains en Culture; Dejstvie oblucheniya monoehnergeticheskimi nejtronami na kletki kul'tury tkanej cheloveka; Efectos de la Radiacion Neutronica Monoenergetica sobre las Celulas Humanas en Cultivos de Tejidos

    Energy Technology Data Exchange (ETDEWEB)

    Broerse, J. J.; Barendsen, G. W. [Radiobiological Institute of the Organization for Health Research TNO, Rijswijk (Z.H.) (Netherlands)

    1964-03-15

    Dose effect relations concerning inhibition of clone formation by kidney cells of human origin in culture after irradiation with monoenergetic neutrons of about 3-MeV and about 15-MeV energy, are reported. For 3-MeV neutrons the dose rate was equal to 0.2 rad/min, while for 15-MeV neutrons dose rates of 2.7 rad/min and 12 rad/min were obtained. The cells were irradiated in culture dishes with a thin Melinex bottom and in small flexible nylon and silicon rubber tubes. Neutron fluxes were determined by measuring the activation of sulphur pellets mounted respectively between the dishes and the tubes. Calculation of the dose on the basis of the neutron flux presented a number of problems which are discussed. Because no radiation equilibrium exists around the cells, the resulting inaccuracies in the dose determinations are investigated. Dose-survival curves for both types of neutrons are presented. For 3-MeV neutrons an RBE was found ranging from 6.5 at low doses to about 3.1 at high doses, while for 15-MeV neutrons the RBE varied from 1.9 to 1.6. By comparison of these RBE-values with the RBE-LET relation obtained in earlier experiments with deuterons and {alpha}-particles, it is possible to derive an effective LET for the neutrons used. In order to elucidate certain problems related to the death of experimental animals after X- or neutron- irradiation, a technique has been developed whereby the cells, contained in small tubes, are used to measure the effective dose (i.e . dose corrected for the RBE) at sites of interest in phantoms or animals. (author) [French] Les auteurs indiquent les relations dose-effet pour l 'inhibition de la formation de lignees par les cellules renales d' origine humaine apres irradiation par des neutrons monoenergetiques de 3 MeV et de 15 MeV. Pour les neutrons de 3 MeV, le debit de dose etait egal a 0,2 rad/min, alors que pour les neutrons de 15 MeV on a obtenu des debits de dose de 2,7 rad/min et de 12 rad/min. L'irradiation des cellules

  16. Lentes esclerales: características e indicaciones

    Directory of Open Access Journals (Sweden)

    Oreste Mariño Hidalgo

    Full Text Available Los lentes de contacto esclerales o de apoyo escleral constituyen una de las opciones terapéuticas más relevantes en el tratamiento y corrección óptica de las enfermedades corneales primaria o secundarias, que traen como consecuencia alteraciones de la curvatura, de la regularidad de la superficie y de su transparencia. La evolución y el desarrollo de este tipo de lentes han abierto un diapasón de múltiples opciones para su uso. En la actualidad se prescriben por numerosos especialistas y ópticas del mundo con una gran aceptación y confort de los pacientes que los utilizan, lo que ha popularizado su comercialización. Realizamos una búsqueda de diversos artículos publicados en los últimos diez años para profundizar en el conocimiento de las características e indicaciones de los lentes de contacto esclerales.

  17. Application des techniques de diffusion de la lumière des rayons X et des neutrons à l'étude des systèmes colloïdaux. Première partie : Présentation théorique des trois techniques Application of Light, X-Ray and Neutron Diffusion Techniques to the Study of Colloidal Systems. Part One : Theoretical Description of Three Techniques

    Directory of Open Access Journals (Sweden)

    Espinat D.

    2006-11-01

    Full Text Available Les techniques de diffusion, des rayons X, des neutrons et de la lumière, jouent un rôle très important pour la compréhension des milieux colloïdaux. Peu d'articles de la littérature s'attachent à présenter conjointement les trois méthodes. Nous avons, dans la première partie de cet article, détaillé les principes théoriques en insistent tout particulièrement sur les spécificités de chacune. Après les rappels concernant la diffusion par les systèmes dilués, nous nous sommes intéressés aux systèmes concentrés pour lesquels les entités diffusantes sont en interaction. Les milieux dispersés montrent souvent une certaine polydispersité que l'on cherche à mesurer; les techniques de diffusion permettent cette mesure. Nous terminerons cette revue par une description des appareillages utilisés. La deuxième partie de cet article concernera une large illustration des possibilités de ces méthodes d'analyse à l'étude des systèmes colloïdaux, sur la base de travaux effectués à I'IFP (Institut Français du Pétrole ou dans de nombreux laboratoires de recherche extérieurs. This article aims to describe X-ray, neutron and light scattering techniques with emphasis on their specific nature and their scope of application. Indeed, whereas light diffusion has been used for a long time in research laboratories, in particular for characterizing polymers in solution, small angle X-ray scattering has been the subject of renewed interest in recent years. Neutron scattering, which is obviously more difficultly accessible, has proven to be extremely useful for studying various systems for which light and X-ray scattering remain relatively powerless. Whereas there is an abundant literature concerning various applications of the three methods, it should be noted that only a few articles have attempted to describe all three techniques at the same time. In this article we have tried to make up for this lack, and as such it was

  18. Survey of Pulsed Neutron Source Methods for Multiplying Media; Methodes des Neutrons Pulses Pour l'Etude des Milieux Multiplicateurs; Obzor metodov s ispol'zovaniem istochnikov impul'snykh nejtronov dlya razmnozhayushchej sredy; Estudio Panoramico de los Metodos de Empleo de Fuentes de Neutrons Pulsados en Medios Multiplicadores

    Energy Technology Data Exchange (ETDEWEB)

    Garelis, E. [General Electric Company, Vallecitos Atomic Laboratory, Pleasanton, CA (United States)

    1965-10-15

    . Thus, this makes it possible to apply the methods developed for the repetitive to that of the pseudo-random technique. (author) [French] Depuis quelques annees, il existe deux opinions sur la maniere la plus efficace de mesurer la reactivite d'arret au moyen de generateurs de neutrons puises, savoir: a) les mesures classiques au moyen d'une source puisee a repetition; b) des methodes qui sont fondees sur la reponse a des impulsions pseudo-aleatoires et utilisent une correlation entre l'entree et la sortie. Dans les deux cas, les renseignements pertinents que l'on obtient sont identiques, en d'autres termes, idealement les deux methodes servent a determiner la fonction de reponse. L'auteur retrace l'evolution des methodes de mesure de la reactivite fondees sur les sources puisees dans les systemes a neutrons thermiques, depuis les premieres tentatives de Sjoestrand jusqu'a la recente methode de (k{beta}/ Script-Small-L ). Dans la methode habituelle, la fonction de Green relative a l'assemblage sous-critique - la reponse du reacteur a une source de neutrons a fonction delta - constitue la propriete recherchee. La decroissance exponentielle, exp(-{alpha}t), de la fonction de Green donne une constante de decroissance des neutrons instantanes independante du lieu. L'auteur examine les methodes permettant de deduire la reactivite de la mesure de a , par exemple, la mesure de a a l'etat critique retarde et la recente methode de (k{beta}/ Script-Small-L ). Il etudie notamment les traitements du mode fondamental a la lumiere de la theorie des methodes des neutrons puises, telles qu'elle a ete mise au point pour le modele (k{beta}/ Script-Small-L )- L'auteur examine les incidences de la theorie des neutrons puises en vue d'obtenir des constantes de decroissance precises et les donnees voulues pour l'analyse des systemes puises. Il passe en revue les travaux experimentaux qui font ressortir a la fois les avantages et les limitations de la technique de (k{beta}/ Script

  19. Automation on computer of the partial area method in the analysis of resonances induced by 'S' neutrons 2. with an interference term and extension of the method to the treatment of multi resonances (1963); Automatisation sur ordinateur de la methode des aires partielles dans l'analyse des resonances induites par les neutrons ''S''. 2, avec terme d'interference et extension de la methode au traitement des multiresonances (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, G; Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    This report deals with the numerical analysis on an I.B.M. 7090 computer of transmission resonances induced by 's' wave neutrons in time of flight experiments. The analysis method used is the partial area one. In this second part the interference term is taken into account. Modifications have been made in the programs and subroutines described in the first part, to determine the resonant transmissions from experimental raw data, and the relating partial areas. Also programs and subroutines are thoroughly described, which estimate the resonance parameters. The field of the partial area method has been extended to cover the case where several resonances have to be treated simultaneously, provided they do not interfere. (authors) [French] Le pretent rapport a pour objet l'analyse numerique sur ordinateur I.B.M. 7090 des resonances dues aux neutrons ''s'' dans les experiences de transmission par temps de vol, la methode d'analyse utilisee etant la methode dea aires partielles. Dans cette deuxieme partie il a ete tenu compte du terme d'interference. On y trouvera une description des amenagements apportes aux programmes et sous-programmes decrits dans la premiere partie pour determiner les transmissions interfero-resonnantes a partir des donnees experimentales brutes et les aires partielles afferentes. Sont egalement decrits les programmes et sous-programmes necessaires au calcul des parametres caracteristiques des resonances. Le domaine d'application de la methode a ete etendu au traitement simultane de plusieurs resonances groupees n'interferant pas entre elles. (auteurs)

  20. Mass measurement project by determination of Q{sub {beta}} for neutron-rich nuclei; Projet de mesure des masses par determination des Q{sub {beta}} pour des noyaux tres riches en neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Pautrat, M; Lagrange, J M; Petizon, L [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Vanhorenbeeck, J; Duhamel, P [Brussels Univ. (Belgium). Inst. d` Astronomie et d` Astrophysique; Binon, F [Universite Libre de Bruxelles (Belgium)

    1994-12-31

    The aim of the project described hereafter is to collect new data on the exotic neutron rich nuclei of the Fe to Zn region, and in particular to determine their masses, for both nuclear physics and astrophysics purposes. These isotopes will be produced through projectile fragmentation at the GANIL facility and selected by the LISE3 spectrometer. Their half-lives will be measured as well as the energy of their main {gamma} rays; {gamma} - {gamma} coincidences will then allow to build a preliminary level scheme. The analysis of {beta} spectra and {beta} - {gamma} coincidences will finally provide the maximum {beta} decay energies of the studied nuclei leading to their masses. The difficulties arising from the low production rates, the {beta} detection, the data handling are discussed together with the solutions proposed to overcome them. (authors). 17 refs.

  1. Experimental measurement of neutron spectrum in the reflector of a light water reactor; Determination experimentale du spectre des neutrons dans le reflecteur d'une pile a eau legere

    Energy Technology Data Exchange (ETDEWEB)

    Brethe, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-09-15

    1. Thermal neutrons: The temperature of the thermal neutron spectrum was calculated using Au-Lu foils. This temperature varies from 300 deg. K (temperature of the moderator) at 30 cm of the core to 350 deg. K in a hole of the core. 2. Slowing down of neutron: Four resonance detectors have been used (Au, In, Co, Mn). We can write a 1/E form of the spectrum. The linking up energy E{sub M} between thermal neutron spectrum and slowing down spectrum is about 0.23 eV and is free from the Maxwell spectrum temperature. The decrease of slowing down flux regarding thermal flux, farther from the core, has been showed. 3. Fast neutrons: We used 3 threshold detectors (Ni, Al, Mg). We supposed a E{sup 1/2} e{sup -{beta}}{sup E} from of the spectrum above 3 MeV. The values of {beta} are in a range from 0.775, at the centre of the core and in a loop-hole, to 0,64 at about 30 cm of the core. 4. Continuous shape of the spectrum: The following interpolations give useful informations between the field where measurements have been made: between 340 eV and 10 keV: 1/E form between 10 keV and 330 keV: 1/(E {sigma}{sub S}(E)) form ({sigma}{sub S}(E) elastic scattering section on hydrogen) between 330 keV and 3 MeV: calculated form by the moments method (ref. BSR). (author) [French] 1. Neutrons thermiques: La temperature du spectre des neutrons thermiques a ete determinee par la methode (or-lutecium). Cette temperature varie de 300 deg. K (temperature du moderateur) a 30 cm du coeur, a 350 deg. K dans une encoche du coeur. 2. Neutrons en ralentissement: 4 detecteurs resonnants ont ete employes (Au, In, Co, Mn). Le spectre peut etre mis sous la forme 1/E quelle que soit la distance a la limite coeur-reflecteur. L'energie de raccordement E{sub M} entre spectre des neutrons thermiques et spectre en ralentissement est environ 0,23 eV et independante de la temperature du spectre de Maxwell. La diminution relative du flux en ralentissement par rapport au flux thermique quand la distance au coeur

  2. Pathogenesis of Intrapulmonary Haemorrhage in Dogs Exposed to Pulsed Fission-Spectrum Neutrons; Pathogenese de l'Hemorragie Intrapulmonaire chez des Chiens Exposes a des Neutrons de Fission Pulses; Patogenez vnutrilegochnykh krovoizliyanij u sobak pri obluchenii impul'snymi nejtronami spektra deleniya; Patogenesis de la Hemorragia Intrapulmonar en Perros Expuestos a Neutrones de Fision Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R. K.; Engel, R. E.; Godden, W. R. [Kirtland AFB, New Mexico (United States)

    1964-05-15

    marrow megakaryocytes was found to be inversely proportional to the severity of intrapulmonary haemorrhage. (author) [French] Des comparaisons precedemment effectuees dans le laboratoire des auteurs entre les modifications tissulaires observees chez des chiens exposes a des rayons X de 250 kV-crete et a des neutrons de fission puises ont montre que, dans les deux cas, les reactions etaient en general semblables. Cependant, les poumons des animaux exposes aux neutrons de fission ont ete beaucoup plus souvent le siege d'hemorragies peribronchiales et peri vasculaires. On a essaye de determiner la pathogenese de cette lesion en exposant cinq bigles a une dose de 400 rad (DMA) de neutronsrapides emanant d'un reacteur du type GODIVA et en sacrifiant successivement les animaux a intervalles reguliers. Cinq jours apres l 'exposition, on a pu discerner un ensemble d'alterations pathologiques constituees par de petites hemorragies pulmonaires sporadiques a la peripherie. Leur nombre a augmente progressivement vers le neuvieme jour. Les modifications les plus frappantes sont survenues au bout de 13 j sous forme de grandes hemorragies perivasculaires autour des ramuscules des arteres pulmonaires, depuis le hile jusqu' a la suriace de la plevre. Les premieres modifications histologiques observees dans les poumons sont survenues le cinquieme jour, sour forme de foyers nettement demarques de congestion alveolaire,- de gonflement des cellules capillaires endotheliales et d'extravasion alveolaire legere des globules rouges. Ces alterations se sont generalisees au bout de neuf jours et on.a pu observer en outre des foyers d'extravasion peribronchiale du sang autour des deux bronches primaires. On a constate, chez les animaux autopsies le treizieme jour apres l ' exposition, une grosse hemorragie-peri vasculaire autour des grandes et des petites arteres pulmonaires. Le sang se trouvait dans le tissu conjonctif externe et dans les vaisseaux lymphatiques periarteriels. Les vaisseaux

  3. [Therapeutic qualities of a lente preparation of swine insulins manufactured by Pharmachem].

    Science.gov (United States)

    Andreev, D; Bozadzhieva, E; Pampulov, L; Penchev, I; Uzunova, B

    1977-01-01

    The therapeutic effect of swine insulin preparation Lente, "Pharmachim" production was studied in 50 diabetics. Its hypoglycemizing activitis compared with that of standardized insulin Lente--"Novo", extract of bovine pancreas. The Bulgarian preparation was found to be very similar to the preparation Lente-Novo in its pharma-codynamic properties and could successfully be used in the diabetes melitus treatment. Insulin Lente Pharmachim is presumed to have lower antigenicity as an extract of swine pancreas, which is actually its great advantage for the therapeutic practice.

  4. Measurement of the fission cross-section of {sup 235}U and {sup 239}Pu for thermal neutrons; Mesures des sections de fission de {sup 235}U et de {sup 239}Pu en neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Fraysse, G; Prosdocimi, A; Netter, F; Samour, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    Improved techniques of fast detection have been applied for determining the fission cross-sections of {sup 235}U and {sup 239}Pu with reference to the absorption cross-section of Boron. Monochromatic neutron beams of 0.0322 eV, 0.0626 eV and 0.275 eV have been employed. Use has been made of a Xe-filled gaseous scintillator and of a low-geometry solid state ion chamber. Both measured alpha and fission rates. The results at the reference energy of 0.0253 eV are: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (authors) [French] Des techniques avancees de comptage rapide ont ete mise en oeuvre pour determiner la section efficace de fission de {sup 235}U et de {sup 239}Pu par rapport a celle d'absorption du bore. Des faisceaux de neutrons monochromatiques de 0,0322 eV, 0,0626 eV et 0,275 eV ont ete employes. Les detecteurs utilises sont un scintillateur gazeux rempli de xenon et une chambre d'ionisation a etat solide a basse geometrie. Les deux ont mesure les taux des desintegrations alpha et des fissions. Les resultats a l'energie de reference de 0,0253 eV sont: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (auteurs)

  5. Analysis and development of spatial hp-refinement methods for solving the neutron transport equation; Analyse et developpement de methodes de raffinement hp en espace pour l'equation de transport des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, D.

    2011-10-10

    flux behaviour is very different depending on the energy, there is no reason to use the same spatial discretization. Such an approach implies to modify the initial estimators in order to take into account the coupling between groups. This study is done from a theoretical as well as from a numerical point of view. (author) [French] Pour la conception des coeurs de reacteurs de 4eme generation, une precision accrue est requise pour les calculs des differents parametres neutroniques. Les ressources memoire et le temps de calcul etant limites, une solution consiste a utiliser des methodes de raffinement de maillage afin de resoudre l'equation de transport des neutrons. Le flux neutronique, solution de cette equation, depend de l'energie, l'angle et l'espace. Les differentes variables sont discretisees de maniere successive. L'energie avec une approche multigroupe, considerant les differentes grandeurs constantes sur chaque groupe, l'angle par une methode de collocation, dite approximation SN. Apres discretisation energetique et angulaire, un systeme d'equations hyperboliques couplees ne dependant plus que de la variable d'espace doit etre resolu. Des elements finis discontinus sont alors utilises afin de permettre la mise en place de methodes de raffinement dite hp. La precision de la solution peut alors etre amelioree via un raffinement en espace (h-raffinement), consistant a subdiviser une cellule en sous-cellules, ou en ordre (p-raffinement) en augmentant l'ordre de la base de polynomes utilisee. Dans cette these, les proprietes de ces methodes sont analysees et montrent l'importance de la regularite de la solution dans le choix du type de raffinement. Ainsi deux estimateurs d'erreurs permettant de mener le raffinement ont ete utilises. Le premier, suppose des hypotheses de regularite tres fortes (solution analytique) alors que le second utilise seulement le fait que la solution est a variations bornees. La

  6. Neutron-Phonon Interaction Studies in Copper, Zinc and Magnesium Single Crystals; Etude des interactions neutron-phonon dans des monocristaux de cuivre, de zinc et de magnesium; Izuchenie vzaimodejstviya nejtronov i fononov v monokristallakh medi, ninki i magniya; Estudio de las interacciones neutron-fonon en monocristales de cobre, cinc y magnesio

    Energy Technology Data Exchange (ETDEWEB)

    Maliszewski, E.; Sosnowski, J.; Blinowski, K.; Kozubowski, J.; Padlo, L.; Sledziewska, D. [Institute of Nuclear Research, Warsaw (Poland)

    1963-01-15

    The phonon dispersion relations in copper single crystals has been studied by means of a triple-axis crystal neutron spectrometer. In the [100] direction the transversal branch, not reported in the papers of Cabie and Jacrot, has been found. This branch fits well to the recent data of sound velocity; however, it differs partly from the X-ray results of Jacobsen. For the longitudinal branch in the [100] direction the dispersion curve obtained by Cribier and Jacrot is lying well above the Jacobsen's curve, and the experimental points reported in the present paper support the results of Cribier and Jacrot. The phonon dispersion relations in zinc and magnesium single crystals has been studied using the cold neutron method and by means of a triple-axis crystal neutron spectrometer as well. The scattering surfaces in the [1010] plane were traced, the AT and AL branches found and the phonon dispersion relations in the [001] and [010] directions obtained. The results have been compared with those obtained by Johnson with X-rays. In the [001] direction the present results fit well lo Johnson's foe the AL branch. In the [010] direction for the AT branch a large discrepancy has been found between Johnson's and the present results. Some explanation of this discrepancy is given. Similar measurements in the same directions in magnesium single crystals are under way and will be reported. (author) [French] Les auteurs ont etudie les relations de dispersion des phonons dans des monocristaux de cuivre, au moyen d'un spectrometre neutronique a cristal triaxe. Ils ont trouve, dans la direction [100] , la branche transversale que n'ont pas signalee Cribier et Jacrot dans leurs travaux. Cette branche s'adapce bien aux donnees recentes relatives a la vitesse du son, mais elle differe partiellement de celles qui ont ete obtenues par Jacobsen pour les rayons X . En ce qui concerne la branche longitudinale dans la direction [100] , la courbe de dispersion obtenue par Cribier et Jacrot se

  7. Thermal Neutron Spectral and Spatial Distributions in Light-Water-Moderated Uranium Lattices; Distributions Spectrale et Spatiale des Neutrons Thermiques dans des Reseaux a Uranium et a Eau Leger; Spektral'noe i prostranstvennoe raspredelenie teplovykh nejtronov v uranovykh reshetkakh s vodnym zamedlitelem; Distribuciones Espectral y Espacial de los Neutrones Termicos en los Reticulados de Uranio Moderados por Agua Ligera

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, J.; Volpe, J. J.; Klein, D.; Schmidt, E.; Gelbard, E. [Bettis Atomic Power Laboratory, Pittsburgh, PA (United States)

    1964-02-15

    distorted by cadmium poison. Calculations with each kernel were done, for this experiment, in a 12-energy group, P{sub 3} approximation. The slowing-down source shape was obtained by means of an eigenvalue calculation of the spatial modal shapes, decaying exponentially in lethargy, which are sustained by the system, supplemented by measured epicadmium activation shapes. Between the poisoned and unpoisoned cases, calculated relative activation rates predicted by the two kernels differed by as much as 10%. Comparisons of the experimental results with calculations using the Radkowsky kernel and the Nelkin kernel were made. Results strongly favour the harder spectrum predicted by the Nelkin kernel. (author) [French] Les auteurs passent en revue certaines experiences sur le comportement des neutrons thermiques dans les reseaux a uranium et a eau legere. Les experiences sont de deux types principaux: mesures de l'utilisation thermique et mesures par activation de la distribution spatiale des neutrons thermiques dans un milieu aqueux uniformement empoisonne. Ces experiences ont ete concues pour verifier la validite des modeles theoriques actuels en separant les effets spectraux des effets spatiaux a l'interieur d'un reacteur. On a procede a des comparaisons avec des modeles theoriques impliquant differentes approximations touchant la theorie du transport et le noyau de diffusion des neutrons thermiques. La premiere serie d'experiences a consiste en mesures par activation des facteurs de desavantage pour le flux thermique dans differentes cellules du reseau de l'assemblage TRX, qui est un reacteur a uranium faiblement enrichi et a eau legere et dont les barreaux de combustible cylindriques sont disposes en un faisceau hexagonal. Les auteurs ont compare les mesures de l'utilisation thermique avec les resultats de calculs faits par une methode de Monte-Carlo. Ils ont fait usage du noyau de Radkowsky et du noyau de Nelkin. Le noyau de Radkowsky est une approximation de premier ordre

  8. Study of the influence of the fast neutron spectrum on the production of defects in solids and liquids; Etude de l'influence du spectre des neutrons rapides sur la creation de defauts dans les solides et les liquides

    Energy Technology Data Exchange (ETDEWEB)

    Mas, P; Droulers, Y [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-07-01

    les neutrons rapides dans le carbone, l'oxygene et l'hydrogene. Dans une zone de 25 cm entourant le coeur d'une pile piscine, ces integrales de degagement d'energie sont a peu pres proportionnelles au flux de neutrons au-dessus de 1 MeV. La determination du degagement d'energie en provenance des neutrons dans les liquides organiques se ramene donc a la determination du flux au-dessus de 1 MeV sous le spectre reel. Une verification calorimetrique a ete faite pour l'eau. (auteurs)

  9. The Pulsed Neutron Technique Applied to Fast Non-Multiplying Assemblies; Application de la Methode des Neutrons Pulses aux Assemblages Non Multiplicateurs a Neutrons Rapides; Primenenie metoda impul'snykh nejtronov pri izuchenii povedeniya bystrykh nejtronov v nerazmnozhayushchikh sborkakh; Aplicacion de la Tecnica de los Neutrones Pulsados a Conjuntos Rapidos de Materiales No Multiplicadores

    Energy Technology Data Exchange (ETDEWEB)

    Beghian, L. E.; Wilensky, S. [Massachusetts Institute of Technology, Cambridge, MA (United States)

    1965-10-15

    Graaff a impulsions de l'ordre de la nanoseconde pour etudier le comportement de neutrons rapides dans des assemblages metalliques non multiplicateurs. Ils ont mesure les sections efficaces non elastiques du fer pour les neutrons rapides. La methode employee est semblable a celle qu'on utilise pour mesurer les sections efficaces d'absorption dans des assemblages a neutrons thermiques, avec cette difference que les temps de decroissance pour les neutrons rapides sont de l'ordre de la nanoseconde et non de la microseconde. Des bouffees de neutrons monoenergetiques d'une nanoseconde sont introduites dans des assemblages en fer de dimensions diverses. On remarque que dans ces assemblages le flux de neutrons decroit exponentiellement avec une constante de decroissance caracteristique. La constante de decroissance est composee d'une somme de termes qui representent la perte de neutrons due aux fuites et a la degradation en energie. La degradation en energie represente une perte de neutrons, car un detecteur de neutrons dont les donnees sont entachees d'une erreur systematique est utilise. On peut determiner le terme correspondant a la diffusion elastique et inelastique en mesurant la constante de decroissance consideree comme une fonction des dimensions de l'assemblage. Suit un developpement theorique pour le calcul de la fraction de ce terme qui est due a la diffusion elastique et, par consequent, pour la determination de la section efficace non elastique. Le procede theorique de calcul de cette fraction a fait l'objet de verifications experimentales. Les auteurs ont mesure la section efficace non elastique du fer par cette methode pour des energies de neutrons primaires comprises entre 0,8 et 1,5 MeV. La methode de la source puisee decrite ci-dessus a ete utilisee pour mesurer des constantes de decroissance pour des plaques de plomb. Les conditions de l'experience sont approximativement conformes aux hypotheses generalement admises lorsqu'on resout l'equation de transport de

  10. Measure of the slowing down area of thermal state 1,45 eV neutrons in the graphite; Mesure de l'aire de ralentissement des neutrons dans le graphite de 1,45 eV a l'etat thermique

    Energy Technology Data Exchange (ETDEWEB)

    Robert, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1956-12-15

    The life of a neutron emitted as a fast one within a moderating medium may be divided into two parts; at first it is slowed down colliding with the nuclei of the medium; later on, as soon as its energy is of the order of the thermal agitation energy, it diffuses until captured by some nucleus. As a matter of fact, dividing the evolution of a neutron into two phases, a slowing down phase and a diffusing phase is arbitrary, since the thermal equilibrium is attained stepwise. This report is intended to examine the means of inferring the distribution of thermal neutrons from the distribution of fast neutrons on the basis of the distribution of nascent thermal neutrons and of the law of scattering. (author) [French] La vie d'un neutron emis a l'etat rapide dans un milieu moderateur comprend 2 parties: au debut il se ralentit par chocs sur les noyaux du milieu; ensuite, lorsque son energie est de l'ordre de l'energie d'agitation thermique, il diffuse jusqu'a sa capture par un noyau. La separation de l'evolution d'un neutron en deux phases, phase de ralentissement, puis phase de diffusion, est, en realite, arbitraire; un neutron doit atteindre l'equilibre thermique progressivement. L'objet de ce rapport est de voir comment on peut deduire la repartition des thermiques de la repartition des rapides connaissant la repartition des thermiques naissants et la loi de diffusion. (au0010te.

  11. Theory of the Influence of Phonon-Phonon and Electron-Phonon Interactions on the Scattering of Neutrons by Crystals; Theorie de l'influence des interactions phonon-phonon et electron-phonon sur la diffusion des neutrons par des cristaux; Teoriya vliyaniya vzaimodejstvij fonon-fonon iehlvktron-fonon na rasseyanie nejtronov kristalla-; Teoria de la influencia de las interacciones fonon-fonon y electron-fonon en la dispersion de neutrones por cristales

    Energy Technology Data Exchange (ETDEWEB)

    Kokkedee, J J.J. [Institute for Theoretical Physics of the University of Utrecht (Netherlands)

    1963-01-15

    interatomic or interionic distance in the crystal). Approximate calculations are performed to give some insight into the orders of magnitude of the effects under study. (author) [French] Comme le predit la theorie harmonique, le spectre de la diffusion inelastique coherente de neutrons par un monocristal non conducteur, pour un angle de diffusion donne, se compose d'une serie de pics de fonction delta, qui se superposent a un bruit de fond continu. Les pics correspondent a des phenomenes a un phonon, dans lesquels un phonon est absorbe ou emis par le neutron; le bruit de fond provient de phenomenes a plusieurs phonons. Lorsqu'il existe des forces anharmoniques (interaction phonon-phonon) les pics de fonction delta s'elargissent pour former des pics finis et leur frequence centrale est dephasee par rapport aux valeurs harmoniques. Dans le cas d'un metal il y a, en plus des interactions phonon-phonon, une interaction entre les phonons et les electrons de conduction, laquelle contribue a dephaser et elargir encore davantage les pics a un phonon. Continuant les travaux de Van Hove (qui avait considere le cas relativement simple d'un cristal non conducteur a l'etat fondamental, soit T = 0{sup o}K) l'auteut a etudie les deplacements et les largeurs des pics de diffusion resultant des interactions indiquees plus haut, a l'aide de la theorie de la perturbation a plusieurs particules, en ayant largement recours a la methode des diagrammes. Il admet, avant tout examen du probleme, que quelle que soit la force des interactions, la largeur de chaque pic est petite par rapport a la valeur de la frequence en son centres dans ces conditions seulement, on peut considerer que les pics sont bien definis par rapport au bruit de fond, si les calculs d'interaction sont pousses jusqu'aux ordres superieurs. On estime que cette hipothbse est realisee tant que les temperatures ne sont pas trop elevees et que les valeurs du vecteur d'onde des phonons ne sont pas trop considerables. La methode

  12. Diffusion Parameters of BeO by the Pulsed Neutron Method; Calcul des Parametres de Diffusion de BeO par la Methode des Neutrons Pulses; Opredelenie diffuzionnykh parametrov BeO s pomoshch'yu metoda impul'snykh nejtronov; Determinacion de los Parametros de Difusion en el BeO por el Metodo de los Neutrones Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, B. V.; Nargundkar, V. R.; Subbarao, K. [Atomic Energy Establishment Trombay, Bombay (India)

    1965-08-15

    The use of the pulsed neutron method for the precise determination of the diffusion parameters of moderators is described. The diffusion parameters of BeO have been obtained by this method. The neutron bursts were produced from a cascade accelerator by pulsing the ion source and using the Be (d, n) reaction. The detector was an enriched boron trifluoride proportional counter. It is shown that by a proper choice of the counter position arid length, and the source position, most of the space harmonics can be eliminated. Any constant background can be accounted for in the calculation of the decay constant. Very large bucklings were not used to avoid time harmonics. Any remaining harmonic content was rendered ineffective by the use of adequate time delay. The decay constant of the fundamental mode of the thermal neutron population was determined for several bucklings. Conditions to be satisfied for an accurate determination of the diffusion cooling constant C are discussed. The following values are obtained for BeO: {lambda}{sub 0} = absorption constant = 156.02 {+-} 4.37 s{sup -1} D = diffusion coefficient = (1.3334 {+-} 0.0128) x 10{sup 5} cm{sup 2}/s C = diffusion cooling constant = (-4.8758 {+-} 0.5846) x 10{sup 5} cm{sup 4}/s. The effect of neglecting the contribution of the B{sup 6} term on the determination of the diffusion parameters was estimated and is shown to be considerable. The reason for the longstanding discrepancy between the values of C obtained for the same moderator by different workers is attributed to this. (author) [French] Les auteurs decrivent l'emploi de la methode des neutrons puises pour la determination precise des parametres de diffusion des ralentisseurs. Ils ont calculi ceux de la glucine par cette methode. Des deuterons puises au moyen d'un accelerateur a cascade produisaient les bouffees de neutrons par la reaction Be (d, n). Le detecteur etait constitue par un compteur proportionnel au BF{sub 3} enrichi. En choisissant convenablement

  13. Non-destructive analysis of major components in plant materials by mean of 14-MeV neutrons; Analyse ''non destructrice'' des principaux constituants de la matiere vegetale apres irradiation aux neutrons de 14 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Garrec, J P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    Although reactors are an important source of neutrons for activation analysis, it is sometimes convenient to have recourse to other, less expensive neutron sources. The Centre d'Etudes Nucleaires at Grenoble has small electrostatic accelerators which generate fast neutrons of 14 MeV energy. These SAMES-type generators are used for directing a deuton beam at 150 kV onto a tritiated target, the resulting flux of monoenergetic neutrons attaining 5 x 10{sup 11} ns{sup -1} in 4 {pi} geometry by the {sup 3}H(d,n){sup 4}He reaction. Numerous elements found in plant material can be activated in this flux, mainly by (n,p), (n,{alpha}) and (n,2n) reactions. Current research is directed towards making use of the entire gamma spectrum of activated plant matter. A computer is used to break down the spectrum into seven main spectral regions by the least-squares method. As a first approximation, these regions are those obtained from aluminium, calcium, potassium, magnesium, phosphorus, silicon and chlorine standards in standard activation and radioactive decay conditions. The wanted advantage of this way of analysis is not acute sensibility, but great fastness. Therefore radioactivation with 14 MeV neutrons is particularly well adapted to quick and simultaneous dosages of useful elements in agronomy. (author) [French] Bien que les reacteurs constituent une source de neutrons importante en analyse par activation, il est parfois commode de recourir a d'autres sources neutronigenes exigeant un investissement moindre. Le Centre d'Etudes Nucleaires de Grenoble dispose de petits accelerateurs electrostatiques generateurs de neutrons rapides de 14 MeV. Ces generateurs, de type SAMES, accelerent un faisceau de deutons sous 150 kV vers une cible tritiee. Celle-ci fournit un flux de neutrons mono-energetiques atteignant 5 x 10{sup 11} n/s/4 {pi} par la reaction {sup 3}H(d,n){sup 4}He. De nombreux elements composant les matieres vegetales s'activent dans ce flux principalement par reactions

  14. Apprentissage en collaboration pour la cogestion des ressources ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Les prairies et les steppes de la Mongolie abritent actuellement quelque 35 millions de têtes de bétail et 180 000 familles de pasteurs. Les écosystèmes des prairies sont fragiles, très vulnérables à la dénudation des sols et lents à se rétablir, surtout à cause du climat froid et sec. Partout au pays, les pasteurs sont confrontés ...

  15. Monilapsisten perheiden lentäen tapahtuvat valmismatkat ulkomaille

    OpenAIRE

    Argillander, Rita

    2015-01-01

    Tässä opinnäytetyössä pyrittiin selvittämään ulkomaille lentäen matkuste-levien monilapsisten perheiden valmismatkan sisältöä sekä osto- ja valin-taprosessiin vaikuttavia tekijöitä. Työssä kartoitettiin mitä monilapsiset perheet arvostavat ja tarvitsevat viihtyäkseen valmismatkalla. Työn tarkoi-tus oli auttaa matkantarjoaja Apollomatkoja kehittämään vanhoja ja tuot-tamaan uusia palveluja monilapsisten perheiden toiveiden mukaan. Työssä käsiteltiin lisäksi mitä tekijöitä lapsiperheiden itse tu...

  16. Conservation, transformation et composition chimique des arilles ...

    African Journals Online (AJOL)

    Les solutions basiques de bicarbonate de sodium et de potassium apparaissent plus adaptées pour la conservation (2 – 3 mois) des arilles frais. Séchés, ces arilles se révèlent riches en lipides (48,46±0,42%) et peuvent être exploités pour une extraction industrielle d'huile. Ils se prêtent bien à la transformation en une ...

  17. Patterns of Lethality and Absorbed Dose Distributions in Mice for Monoenergetic Neutrons; Letalite et Distribution de la Dose Absorbee chez la Souris pour des Neutrons Monoenergetiques; Letal'nost' i raspredelenie pogloshchennoj dozy pri obluchenii myshej monoehnergeticheskimi neitronami; Letalidad y Distribucion de las Dosis Absorbidas por el Raton para Neutrones Monoenergeticos

    Energy Technology Data Exchange (ETDEWEB)

    Frigerio, N. A.; Jordan, D. L. [Argonne National Laboratory, Argonne, IL (United States)

    1964-03-15

    gamma and epithermal contaminations, produce the early ''intestinal death'' almost exclusively. (author) [French] La presence de fortes resonances de C, N et O dans la region du spectre situee entre 100 et 1500 keV a permis d'etudier les interactions specifiques neutrons-nucleides d'apres-la letalite, les valeurs maxima de l'EBR, etc. Grace a la reaction {sup 7}Li(p, n){sup 7}Be, on a produit des neutrons monoenergetiques avec des protons de 62 {mu}A resolus a leur sortie d*une machine van de Graaf et dont l'energie allait de 1882 a 2738 keV. Des souris femelles vierges CF-1, placees dans des capsules en celluloide, ont ete exposees aux neutrons monoenergetiques, a des distances de 3,1 a 11,3 cm de la source, sous des angles de 0 a 1 radian. On les a exposees bilateralement, au cours d*un deplacement sur une orbite, circulaire ou elliptique, normale a l'axe du faisceau. On pouvait ainsi controler la distribution de la dose dans le corps de l'animal. On a procede a des mesures absolues du flux avec des compteurs a fission a {sup 235}U et par comptage absolu a l'aide de fils et de feuilles d'or actives a revetement de cadmium. On a mesure les doses absorbees a l'aide de chambres a ionisation et d'un dosimetre a FeSO{sub 4}-NH{sub 4}SCN de haute sensibilite, tout specialement etudie a cette fin. On a procede ensuite a des mesures relatives de la dose avec des compteurs de Hurst a gaz et protons de recul et avec des scintillateurs a {sup 10}B, {sup 6}Li et protons de recul. Les energies des neutrons ont ete mesurees avec des spectrometres speciaux a {sup 10}B, {sup 3}H, {sup 6}Li et semi-conducteurs. On a mesure l'action des rayons gamma avec des chamb rescompteuis a Ne/Ar. Ces mesures ont montre que les rayons gamma constituent moins de 0,8% et les neutrons thermo-epithermiques moins de 0 ,01% de la dose totale exprimee en rad. Les animaux ont ete exposes a des doses moyennes dans l'axe median de 180 a 1200 rad, les energies des neutrons s' echelonnant de 396 a 658 ke

  18. Fast neutron dosimetry for radioprotection near large accelerators. Application to the proton synchrotron Saturne; Dosimetrie des neutrons rapides en vue de la radioprotection aupres des grands accelerateurs. Application au synchrotron a protons Saturne

    Energy Technology Data Exchange (ETDEWEB)

    Tardy-Joubert, P

    1963-07-01

    Methods are described that are used for the measurement of a neutron flux, and of the corresponding energy flux and dose absorbed. The methods are checked experimentally by the use of neutron sources of known energy distribution. The conditions of use of a proportional counter for recoil protons are described. The experimental results obtained with the synchrotron SATURNE at Saclay are described. (author) [French] L'auteur presente les methodes utilisables pour la mesure d'un flux de neutrons, du flux d'energie et de la dose absorbee correspondants. Les methodes sont verifiees experimentalement au moyen de sources de neutrons de spectre connu. Les conditions d'emploi d'un compteur proportionnel a protons de recul sont definies. Les resultats experimentaux obtenus aupres du synchrotron Saturne de Saclay sont presentes. (auteur)

  19. Estimation of the {alpha} particles and neutron distribution generated during a fusion reaction; Evaluation de la distribution des particules {alpha} et des neutrons issus de la reaction de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Dellacherie, S.

    1997-12-01

    The respective distributions (or density probabilities) of {alpha} particles and neutrons have been modeled using a Monte-Carlo method for the thermonuclear fusion reaction D + T {yields} {alpha} + n + 17.6 MeV. (N.T.).

  20. The fortran programme for the calculation of the absorption and double scattering corrections in cross-section measurements with fast neutrons using the monte Carlo method (1963); Programme fortran pour le calcul des corrections d'absorption et de double diffusion dans les mesures de sections efficaces pour les neutrons rapides par la methode de monte-carlo (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    A calculation for double scattering and absorption corrections in fast neutron scattering experiments using Monte-Carlo method is given. Application to cylindrical target is presented in FORTRAN symbolic language. (author) [French] Un calcul des corrections de double diffusion et d'absorption dans les experiences de diffusion de neutrons rapides par la methode de Monte-Carlo est presente. L'application au cas d'une cible cylindrique est traitee en langage symbolique FORTRAN. (auteur)

  1. Simulation des fuites neutroniques a l'aide d'un modele B1 heterogene pour des reacteurs a neutrons rapides et a eau legere

    Science.gov (United States)

    Faure, Bastien

    The neutronic calculation of a reactor's core is usually done in two steps. After solving the neutron transport equation over an elementary domain of the core, a set of parameters, namely macroscopic cross sections and potentially diffusion coefficients, are defined in order to perform a full core calculation. In the first step, the cell or assembly is calculated using the "fundamental mode theory", the pattern being inserted in an infinite lattice of periodic structures. This simple representation allows a precise modeling for the geometry and the energy variable and can be treated within transport theory with minimalist approximations. However, it supposes that the reactor's core can be treated as a periodic lattice of elementary domains, which is already a big hypothesis, and cannot, at first sight, take into account neutron leakage between two different zones and out of the core. The leakage models propose to correct the transport equation with an additional leakage term in order to represent this phenomenon. For historical reasons, numerical methods for solving the transport equation being limited by computer's features (processor speeds and memory sizes), the leakage term is, in most cases, modeled by a homogeneous and isotropic probability within a "homogeneous leakage model". Driven by technological innovation in the computer science field, "heterogeneous leakage models" have been developed and implemented in several neutron transport calculation codes. This work focuses on a study of some of those models, including the TIBERE model from the DRAGON-3 code developed at Ecole Polytechnique de Montreal, as well as the heterogeneous model from the APOLLO-3 code developed at Commissariat a l'Energie Atomique et aux energies alternatives. The research based on sodium cooled fast reactors and light water reactors has allowed us to demonstrate the interest of those models compared to a homogeneous leakage model. In particular, it has been shown that a heterogeneous

  2. Measurement of the diffusion length of thermal neutrons inside graphite; Mesure de la longueur de diffusion des neutrons thermiques dans le graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ertaud, A; Beauge, R; Fauquez, H; De Laboulay, H; Mercier, C; Vautrey, L

    1948-11-01

    The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra {alpha} {yields} Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm {+-} 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)

  3. Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1; Mesures relatives des flux thermique, resonnant et rapide dans le reacteur G1

    Energy Technology Data Exchange (ETDEWEB)

    Carle, R.; Mazancourt, T. de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [French] Nous avons cherche a determiner le comportement des differents flux, thermique, resonnant et rapide a la transition milieu multiplicateur-reflecteur dans les deux directions principales du reseau. Nous avons egalement mesure la variation de ces differents flux au sein du milieu multiplicateur dans un canal rempli de graphite et dans un canal vide. Les resultats sont donnes sous forme de courbe representant: - La variation du rapport du flux thermique au flux rapide aux transitions axiale et radiale - L'allure des flux thermique et resonnant et la variation de leur rapport dans les memes regions. (auteur)

  4. Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1; Mesures relatives des flux thermique, resonnant et rapide dans le reacteur G1

    Energy Technology Data Exchange (ETDEWEB)

    Carle, R; Mazancourt, T de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [French] Nous avons cherche a determiner le comportement des differents flux, thermique, resonnant et rapide a la transition milieu multiplicateur-reflecteur dans les deux directions principales du reseau. Nous avons egalement mesure la variation de ces differents flux au sein du milieu multiplicateur dans un canal rempli de graphite et dans un canal vide. Les resultats sont donnes sous forme de courbe representant: - La variation du rapport du flux thermique au flux rapide aux transitions axiale et radiale - L'allure des flux thermique et resonnant et la variation de leur rapport dans les memes regions. (auteur)

  5. Angular distributions of fast neutrons scattered by Al, Si, P, S and Zn; Distributions angulaires des neutrons rapides diffuses par Al, Si, P, S et Zn; Usloviya raspredeleniya bystrykh nejtronov, rasseyannykh alyuminiem, kremniem, fosforom i tsinkom; Distribuciones angulares de neutrones rapidos dispersados por Al, Si, P, S y Zn

    Energy Technology Data Exchange (ETDEWEB)

    Tstjkaija, K; Tanaka, S; Maeuyama, M; Tomita, Y [Japan Atomic Energy Research Institute, Tokai-Mtjea (Japan)

    1962-03-15

    Differential scattering cross-sections of Al, Si, P, S and Zn for fast neutrons have been measured in an energy range of 3.4 to 4.6 MeV by using the time-of-flight method. Angular distributions of the inelastically scattered neutrons are nearly isotropic in all cases. These results are discussed on the basis of the Hauser-Feshbach theory. (author) [French] Les sections efficaces differentielles de diffusion de Al, Si, P, S et Zn pour des neutrons rapides ont ete mesurees dans la gamme d'energies de 3,4 a 4,6 MeV, en employant la methode du temps de vol. Les distributions angulaires des neutrons diffuses inelastiquement sont presque isotropes dans tous les cas. Les auteurs analysent ces resultats en se fondant sur la theorie de Hauser-Feshbach. (author) [Spanish] Los autores han medido por el metodo del tiempo de vuelo las secciones eficaces diferenciales de dispersion del Al, Si, P, S y Zn para neutrones rapidos de energia comprendida entre 3,4 y 4,6 MeV. Las distribuciones angulares de los neutrones dispersados inelasticamente son casi isotropicas en todos los casos. Los autores analizan los resultados obtenidos basandose en la teoria de Hauser-Feshbach . (author) [Russian] Differentsial'no e sechenie rasseyaniya alyuminiya, kremniya, fosfora, sery i tsinka dlya bystrykh nejtronov izmereno v diapazone ehnergii ot 3,4 do 4,6 Megaehlektronvol't ispol'zovanie m metoda vremeni proleta. Uglovye raspredeleniya neuprugo rasseyannykh nejtronov yavlyayutsya pochti vo vsekh sluchayakh izotropnymi. Jeti rezul'taty obsuzhdayutsya na osnove teorii Hauzera-Feshbakha. (author)

  6. Application des techniques de diffusion de la lumière des rayons x et des neutrons à l'étude des systèmes colloïdaux. Deuxième partie : étude des différents systèmes : polymères en solution à l'état solide, solutions micellaires, systèmes fractals Application of Light, X-Ray and Neutron Diffusion Techniques to the Study of Colloidal Systems. Part Two: Research on Different Systems: Polymers in Solution in the Solid State, Micellar Solutions, Fractals Systems

    Directory of Open Access Journals (Sweden)

    Espinat D.

    2006-11-01

    Full Text Available Cet article fait suite à la première partie (Revue Inst. Franç. du Pétrole, vol. 45, n°6, novembre-décembre 1990 concernant l'application des techniques de diffusion de la lumière, des rayons X et des neutrons à l'étude des systèmes colloïdaux et plus précisément à la présentation théorique des trois méthodes. L'objet de cette deuxième partie est la présentation non exhaustive de quelques domaines d'applications. Nous nous attacherons tout particulièrement à présenter les potentialités des méthodes pour la caractérisation de systèmes colloïdaux ou divisés rencontrés dans de nombreuses branches d'activité de l'industrie pétrolière. Nous aborderons dans une première partie les solutions polymériques et colloïdales. En particulier nous nous attarderons sur l'importance des techniques de diffusion pour la caractérisation des polymères en solution et des solutions micellaires. Nous verrons également quelles informations la diffusion centrale peut apporter sur la macrostructure des polymères cristallisés ou amorphes à l'état solide. De nombreux systèmes présentent une structure de type fractal ; après présentation de quelques exemples, nous montrerons que les méthodes de diffusion peuvent apporter certaines informations sur ces matériaux, notamment la dimension fractale. This article is the second one (the first one was published in Revue de l'Institut Français du Pétrole No. 6, NovemberDecember 1990 concerning the application of techniques of light scattering, X rays and neutrons to the analysis of colloidal systems and more specifically to the theoretical description of the three methods. The aim of this second part is to make a nonexhaustive description of several fields of applications. A special effort is made to describe the potential of these methods for characterizing colloidal or divided systems encountered in a great many activities involving the petroleum industry. The first part of this

  7. Effects of atmospheric neutrons on advanced micro-electronic devices, standards and applications; Effets des neutrons atmospheriques sur les dispositifs microelectroniques avances, normes et applications

    Energy Technology Data Exchange (ETDEWEB)

    Leray, J.L. [CEA, 75 - Paris (France); Baggio, J.; Ferlet-Cavrois, V.; Flament, O. [CEA Bruyeres-le-Chatel, 91 (France)

    2005-10-01

    Since the 1980's, it is known that terrestrial cosmic rays, mainly reported as atmospheric neutrons, can penetrate the natural shielding of buildings, equipments and circuit package and induce soft errors in integrated circuits and breakdown of power devices. The high-energy neutron fluxes of interest, larger than 10 MeV, range between 10 particles/cm{sup 2}/hour at sea level and 10{sup 4} particles/cm{sup 2}/hour at typical airplanes flight altitude of 30000 feet, with modulation due to solar flares. In the 1990's, the phenomenon has pervaded as a consequence of the road-map of electronic devices especially the down-scaling of transistor dimensions, the increase of signal bandwidth and the increase of the size of DRAM and SRAM memory, stand-alone or embedded on processors and system-on-chips. Failure-in-time and soft error rate became unacceptable. Test standards and design solutions have been proposed to maintain reliability of commercial products and improve those used in special high-reliability equipments such as avionic computers. The paper describes the atmospheric neutron flux, the effects in the main classes of devices and specific cases such as neutron induced single event upset observed in CMOS vs. CMOS/SOI and some mitigation issues. In this paper, a model called CCPM (critical cross-point model) is proposed to provide critical graphs of technology node sensitivity along the scaling trend of CMOS. (authors)

  8. Pärt: Fratres in sechs Versionen. Festina lente. Summa / C. S.

    Index Scriptorium Estoniae

    C. S.

    1997-01-01

    Uuest heliplaadist "Pärt: Fratres in sechs Versionen. Festina lente. Summa. Cantus in memoriam Benjamin Britten. Orchester der Ungarischen Staatsoper, Tamas Benedek". Naxos CD 8 553 750 (WD:79'06") DDD

  9. Lentes progressivas: análise da potência do astigmatismo induzido

    Directory of Open Access Journals (Sweden)

    Celso Marcelo Cunha

    2013-06-01

    Full Text Available OBJETIVO: Avaliar a potência do astigmatismo induzido nas lentes progressivas em um deflexômetro. MÉTODOS: Foram incluídas onze lentes progressivas com poder longe de +1,00D e adição 2,00D para perto. Avaliou-se o astigmatismo induzido em doze pontos do campo intermediário, sendo seis de cada lado do corredor progressivo no deflexômetro. RESULTADOS: Existem diferenças significativas entre as somas dos astigmatismos induzidos de cada lado do corredor progressivo e no total geral nestas lentes estudadas, com coeficiente de variação com forte dispersão (CV 10 a 13%. CONCLUSÃO: Existe uma variação importante das potências dos astigmatismos induzidos nas lentes progressivas.

  10. Fuel material neutron crystallography texture and structure determinations (1960); Etudes sur l'evolution des structures cristallines de l'uranium par neutrocristallographie (1960)

    Energy Technology Data Exchange (ETDEWEB)

    Laniesse, J; Englander, M; Meriel, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    {beta} {yields} {alpha} transformation at 333 deg. K of a bulk U alloy containing 1000 ppm chromium. (author) [French] La methode utilisee permet d'obtenir d'une maniere plus rapide et plus statistique que par difraction de rayons X des informations sur la texture d'agregats polycristallins d'uranium-metal et sur les cours de l'evolution de leurs structures crystallines pendant leurs transformations allotropiques. Elle emploie un faisceau neutronique sortant du reacteur EL3 au CEN Saclay, monochromatise a {lambda} = 1,143 A {+-} 0,030 Angstrom; l'axe de ce faisceau rigoureusement collimate, est dirige perpendiculairement a l'axe de fibre de l'echantillon de forme cylindrique et de dimensions optimales. Les neutrons diffuses sont recus dans un compteur BF3 qui peut decrire un cercle centre sur l'echantillon (R = 1,30 m), dans un plan horizontal passant par l'axe du faisceau; de plus, le dispositif de fixation de l'echantillon permet la rotation de celui-ci autour de son axe longitudinal. Le spectre de reference des raies de diffraction neutronique de la phase {alpha} de l'uranium pur est ainsi obtenu a la temperature ordinaire, en utilisant un echantillon pour lequel il est certain qu'il n'existe aucune texture parasite ou residuaire. Il en est de meme pour la phase {beta} d'une solution solide metastable d'uranium contenant la concentration nominale d'impuretes metalliques telles que le Cr ou le Si. Ces deux spectres sont compares aux spectres theoriques ainsi qu'aux spectres de diffraction roentgenographiques. En choisissant ensuite convenablement un certain nombre de ces raies de diffraction, les evaluations d'orientations predominantes eventuelles peuvent etre suivies qualitativement et semi-quantitativement, en fonction des differents traitements mecaniques et/ou thermiques subis simultanement ou non par l'echantillon. De meme en enregistrant d'une maniere continue l'intensite d'une raie mixte judicieusement placee par rapport aux raies des spectres {alpha} et {beta

  11. Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrijevic, Z.; Rzany, H.; Todorovic, J.; Wanic, A. [Institute for Nuclear Physics Cracow (Poland)

    1965-04-15

    faites a Vinea, dans le reacteur RA, au moyen d'un spectrometre a cristal. Des neutrons monochromatiques ({lambda} = 1.314A) ont ete diffuses par un grand monocristal d'hematite ({alpha}-Fe{sub 2}O{sub 3}). Les auteurs ont etudie la distribution angulaire des neutrons diffuses inelastiquement. Pour plusieurs angles de decalage {Delta}{theta} du cristal, ils ont mesure la largeur {Gamma} du faisceau de neutrons diffuses (appele cone de diffusion). Ils ont attribue ce cone a la surface de diffusion des magnons qui entoure le point du reseau reciproque (1,1,1). Pour plusieurs vitesses de magnons, ils ont mesure {Gamma}, en fonction de l'angle de decalage, et l*ont comparee aux points experimentaux. Ils ont constate que dans la direction [111], la vitesse avait une valeur egale a 25,5{+-}1,0 km/s. Ils ont decouvert une anisotropie structurelle de la relation de dispersion des magnons. Ils ont note que la vitesse etait plus elevee pour les directions de propagation paralleles a l'axe [111], ce qui concorde qualitativement avec les mesures anterieures (faites par Riste et d'autres) qui ont donne v = 38 km/s. Il n'a pas ete possible de mettre en evidence l'existence d'une discontinuite Eg dans la bande acoustique de l'energie des magnons. Selon les evaluations, Eg doit avoir une valeur inferieure a 1 meV. En utilisant le formalisme de Wallace, les auteurs ont calcule les relations de dispersion des magnons dans l'hematite. A cet effet, ils ont admis l'existence de deux integrales d'echange J{sub 1} et J{sub 2} qui ne disparaissent pas. J{sub 1} et J{sub 2} expriment le couplage a superechange d'energie entre les spins d'ions Fe voisins lies par l'intermediaire d'un ion oxygene. Les angles Fe-O-Fe des liaisons considerees sont respectivement de 132 et 126 Degree-Sign . Les resultats theoriques et les donnees experimentales actuelles concordent de facon satisfaisante lorsque SJ{sub 1} = SJ{sub 2} = 5,1 meV. Outre la branche acoustique des magnons, les calculs ont revele l

  12. Localizing by autoradiography at -195 deg radioactive areas in rats exposed to a high flux of thermal neutrons, importance of phosphorus 32 in consecutive internal irradiation; Localisation par autoradiographie a -195 deg des zones radioactives chez le rat expose a un haut flux de neutrons thermiques, importance du phosphore 32 dans l'irradiation interne consecutive

    Energy Technology Data Exchange (ETDEWEB)

    Chanteur, J; Pellerin, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1961-07-01

    Rats weighing 25 g were exposed for 5 mn to a flux of 6.10{sup 12} thermal neutrons/cm{sup 2}/s. Anatomical autoradiography at -195 deg. C has enabled the radioactive organs to be easily localised, to follow in course of time the decrease of radioactivity, and from it to deduce the probable nature of the numerous emitters in question. In particular, the phosphorus 32 has thus appeared to be one of those responsible for internal irradiation, general, on the one hand, by activating cellular phosphorus, local, on the other, by activating bony phosphates. Owing to this, an accidental irradiation by neutrons might have consequences that are both somatic (elective irradiation of the bone marrow) and genetic (activation of nucleic acids). The gamma spectrometry has confirmed the nature of certain other emitters. (author) [French] Des rats de 25 g ont ete exposes pendant 5 mn a un flux de 6.10{sup 12} neutrons thermiques/cm{sup 2}/s. L'autoradiographie anatomique a -195 deg. C a permis de localiser facilement les organes radioactifs, de suivre dans le temps la decroissance de la radioactivite, et d'en deduire la nature probable des nombreux emetteurs en cause. En particulier, le phosphore 32 est ainsi apparu comme l'un des responsables de l'irradiation interne, d'une part generale par activation du phosphore cellulaire, d'autre part locale par activation des phosphates osseux. Une irradiations accidentelle par neutrons aurait, de ce fait, des consequences a la fois somatiques (irradiation elective de la moelle osseuse) et genetiques (activation des acides nucleiques). La spectrometrie gamma a confirme la nature de certains autres emetteurs. (auteur)

  13. Calculation of the Inelastic Scattering of Neutrons from Polyethylene and Water; Calcul de la diffusion inelastique des neutrons par le polyethylene et l'eau; Raschet neuprugogo rasseyaniya nejtronov poliehtilenom i vodoj; Calculo de la dispersion inelastica de neutrones por polietileno y agua

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, D T; Federighi, F D [Knolls Atomic Power Laboratory, General Electric Company, Schenectady, NY (United States)

    1963-01-15

    A model for the calculation of the scattering of thermal neutrons from chemical system was proposed by Nelkin. This model considered the actual dynamics of the scattering system as composed of a set of oscillatory motions, each describable by a Hamiltonian which commuted with each of the others. It was then possible to express the differential scattering cross-section in closed form. This model has been used to calculate the scattering of neutrons by water. Some care must be taken in performing the numerical integration over angle and energy. The scattering model has been extended to the calculation of neutron scattering from polyethylene C{sub n}H{sub 2n}. Analogous levels of polyethylene can be noted at 0.089 eV, 0.182 eV, 0.354 eV, and 0.533 eV. The differential and total cross-sections have been calculated for the scattering and the latter has been seen to be in reasonable agreement with experiment at room temperature. Scattering kernels have been calculated for a number of temperatures and where possible the results have been compared with experiment. In addition, neutron flux spectra and diffusion lengths have been calculated using the equations of reactor physics. Comparison of these Results with experimental data indicates that such integral measurements are indicative of at least the gross features of the scattering system and should be analysed in conduction with the detailed differential cross-section results. (author) [French] Nelkin a propose un modele pour calculer la diffusion de neutrons thermiques dans des systemes chimiques. Dans ce mod and le on considere que la dynamique reelle du systeme de diffusion se compose d'un ensemble de mouvements oscillatoires, chaque mouvement pouvant 6tre decrit par un hamiltonien commutant avec chacun des autres. Il est alors possible d'exprimer la section efficace differentielle de diffusion sous une forme fermee. Les auteurs ont employe ce modele pour calculer la diffusion des neutrons par l'eau. Il faut prendre

  14. Study of portable particle accelerators used as neutron sources. Report 7-9. Characteristics of accelerators currently available on the market; Etude sur les accelerateurs de particules du type transportable utilises en tant que sources de neutrons. Rapport 7-9. Caracteristiques des accelerateurs actuellement sur le marche

    Energy Technology Data Exchange (ETDEWEB)

    Godar, Serge [Communaute europeenne de l' energie atomique - Euratom, Brussels (Belgium)

    1964-08-15

    This report indicates characteristics of available accelerators adapted to neutron production. Indicated information are for example: brand and type, brief description, maximum high voltage, ion source, ion current, gas introduction system, titanium self-target, beam focusing system, target diameter, reaction used for neutron production, target cooling, generator use temperature, dimensions, weight, manufacturer address, and so on [French] L'ensemble de cette etude bibliographique est traitee dans une serie de huit rapports, chacun ayant trait a un aspect ou un domaine particulier. Ce rapport (No. 7-9) a pour but de donner des renseignements generaux aux chercheurs desirant acquerir un accelerateur de particules adapte a la production de neutrons. Les recherches concernant les caracteristiques des appareils actuellement sur le marche ont ete arretees a la date du 15 octobre 1963. Il n'est malheureusement pas possible de garantir toutes les caracteristiques fournies, etant donne les modifications continuelles apportees a ces generateurs.

  15. A study on structure defects in irradiated lithium fluoride (thermal neutrons); Etude des imperfections de structure du fluorure de lithium irradie (neutrons thermiques)

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, M

    1958-06-19

    A study was made of the behavior of atomic defects, vacancies and interstitials, generated from the Li{sup 6}(n,{alpha})H{sup 3} reaction in Lip crystals. Defects appear as cavities and platelets around ten angstrom in size and increase both with neutron dose and annealing temperature. For longer irradiations, metallic lithium precipitates out, in epitaxy with LiF lattice, and later, lithium salts appear due to the penetration of atmospheric gases through the cracks present in the damaged crystal. Various x-ray experiments followed the formation and evolution of these imperfections when their atomic concentration reached 10{sup -4}. (author)

  16. Resultados da troca de lente intra-ocular de hidrogel opacificada

    Directory of Open Access Journals (Sweden)

    Salera Cristina Moreira

    2004-01-01

    Full Text Available OBJETIVO: Avaliar os resultados da explantação e substituição das lentes intra-oculares (LIO de hidrogel opacificadas. MÉTODOS: Foram analisados retrospectivamente os prontuários de 12 pacientes (15 olhos submetidos à explantação e substituição das lentes intra-oculares de hidrogel opacificadas. RESULTADOS: A opacificação das lentes intra-oculares de hidrogel causou perdas de linhas de visão em 13 olhos (86,7%. A troca das lentes intra-oculares opacificadas promoveu o ganho de linhas de visão em 11 olhos (73,3%. As complicações peroperatórias ocorreram em três olhos (20% e foram as seguintes: perda de óleo de silicone, ruptura total de zônula com perda do saco capsular e ruptura parcial de zônula. Durante a explantação das lentes intra-oculares foi necessária a realização de incisões relaxantes na borda da capsulorrexe anterior em três olhos (20% e em dois olhos (13,3% os hápticos foram cortados sendo retirada somente a zona óptica das lentes intra-oculares. CONCLUSÃO: A cirurgia para explantação e substituição das lentes intra-oculares opacificadas mostrou-se eficaz naqueles pacientes com perdas de linhas de visão (p > 0,05.

  17. Portfolio langagier : Les finissants des programmes d’immersion se révèlent

    Directory of Open Access Journals (Sweden)

    Lucille Mandin

    2010-02-01

    Full Text Available This article presents a research conducted with French Immersion graduates in the context of an introductory language methodology course in a francophone institution. The participants completed a language portfolio, created by Laplante & Christiansen (2001. The portfolio consisted of a two-page autobiographical narrative entitled 'My Life in French till now', an action plan which included an analysis of the errors they identified as targets for that semester and the means or the tools they chose to correct the errors. An analysis of the autobiographical narrative, a document written by the individual participants, stemming from their life experiences since they were exposed to the French language, is presented. The narrative is inspired by the values they have developed and the choices they have made concerning learning French (Baumeister, 1991; Kenyon, 1999. This study also presents a profile of significant experiences these French Immersion graduates identify as pivotal in their motivation to pursue their postsecondary studies in French. They also highlight teachers, friends and family who played an important role during 'their lives in French' till now. In their action plan, the students identified categories of linguistic challenges in areas such as semantics, syntax and phonology. These results shed light on questions pertaining to best practices in French Immersion programs.

  18. Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II; Methodes d'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol et automatisation de ces methodes sur ordinateur IBM 7094 II

    Energy Technology Data Exchange (ETDEWEB)

    Corge, Ch [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-01-01

    Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [French] L'automatisation, sur ordinateur IBM 7094/II, de l'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol a ete accomplie en la decomposant selon un schema articule en quatre phases: 1 - le traitement des donnees experimentales brutes pour obtenir les transmissions interfero-resonnantes, 2 - la determination des grandeurs d'analyse a partir des transmissions precedentes, 3 - l'analyse proprement dite des resonances dont les parametres sont obtenus par la resolution d'un systeme surabondant. Quatre methodes d'analyse sont groupees en un meme programme, 4 - la procedure de verification graphique. (auteur)

  19. Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II; Methodes d'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol et automatisation de ces methodes sur ordinateur IBM 7094 II

    Energy Technology Data Exchange (ETDEWEB)

    Corge, Ch. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-01-01

    Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [French] L'automatisation, sur ordinateur IBM 7094/II, de l'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol a ete accomplie en la decomposant selon un schema articule en quatre phases: 1 - le traitement des donnees experimentales brutes pour obtenir les transmissions interfero-resonnantes, 2 - la determination des grandeurs d'analyse a partir des transmissions precedentes, 3 - l'analyse proprement dite des resonances dont les parametres sont obtenus par la resolution d'un systeme surabondant. Quatre methodes d'analyse sont groupees en un meme programme, 4 - la procedure de verification graphique. (auteur)

  20. Study of magnetic interactions in some ferri- and antiferromagnetic normal spinels studied by neutron diffraction; Contribution a l'etude des interactions magnetiques dans quelques spinelles ferri-et antiferromagnetiques normaux etudies par diffraction des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Plumier, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    Magnetic structure determination of a few ferri- and antiferromagnets normal spinels has led us to study what are, besides nearest neighbour magnetic interactions, the magnetic terms which have to be considered in the establishment of such or such magnetic structure. Tetragonal distortion which is frequently observed in such compounds is of the order of magnetic exchange striction (10{sup -3}). Such a distortion leads to two effects. First it decreases the total energy of the system. Secondly it introduces term of axial magnetic anisotropy. Besides this term of axial anisotropy, the possibility of basal anisotropy in the case of coplanar magnetic structure has to be considered. This last term explained why the magnetic structures of such antiferromagnetic spinels frequently have one or more cell parameters which are twice that of the chemical cell. Finally the comparison between various magnetic structures of antiferromagnetic spinels in which the leading term is the magnetic energy between first nearest neighbours, shows that the part played by magnetic interactions between non nearest neighbours is not negligible. Such indirect superexchange interactions through two anions or two anions and a cation on tetrahedral site, although of the order of a few percent of the preceding one, join a given ion to its twelve second nearest neighbours, six third nearest neighbours and twelve fourth nearest neighbours. (author) [French] La determination des structures magnetiques de quelques spinelles ferri- et antiferromagnetiques normaux nous a conduit a preciser quels sont, en dehors du terme dominant d'interaction magnetique entre ions premiers voiins, les termes d'energie magnetique a considerer dans l'apparition de telle ou telle structure magnetique. La distorsion quadratique que l'on observe frequemment dans ces composes est de l'ordre de grandeur de celle attribuable a la striction d'echange (10{sup -3}). L'effet d'une telle distorsion est double. Non seulement elle

  1. Neutron elastic scattering cross-sections measurement on carbon and fluorine in epithermal energy range using PEREN platform; Mesure des sections efficaces de diffusion elastique des neutrons sur le carbone et le fluor dans le domaine epithermique sur la plate-forme PEREN

    Energy Technology Data Exchange (ETDEWEB)

    Thiolliere, N

    2005-10-15

    Molten Salt Reactor (MSR) based on Th/U cycle is one of the new generation concepts for nuclear energy production. A typical MSR is a graphite-moderated core with liquid fuel ({sup 7}LiF +ThF{sub 4} + UF{sub 4}). Many numerical studies based on Monte-Carlo codes are currently carried out but the validity of these numerical result relies on the precise knowledge of neutron cross sections used such as elastic scattering on carbon ({sigma}{sub C}), fluorine ({sigma}{sub F}) and lithium 7 ({sigma}{sub Li}). The goal of this work is to obtain {sigma}{sub C} and {sigma}{sub F} between 1 eV and 100 keV. Such measurements have been performed at the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) de Grenoble on the experimental platform PEREN using slowing-down time spectrometers (C and CF{sub 2}) associated to a pulsed neutron generator (GENEPI). Capture rates are obtained for reference materials (Au, Ag, Mo and In) using YAP scintillator coupled to a photo-multiplier. Very precise simulations (MCNP code) of the experimental setup have been performed and comparison with experiments has led to the determination of {sigma}{sub C} and {sigma}{sub F} with accuracies of 1% and 2% respectively. These results show a small discrepancy to evaluated nuclear data file (ENDF). Measures of total cross-sections {sigma}{sub C} and {sigma}{sub F} at higher energy (200 - 600 keV) were also carried out at Centre des Etudes Nucleaires de Bordeaux using a transmission method. Mono-energetic neutrons were produced by protons accelerated by a Van de Graaff accelerator on a LiF target and transmitted neutrons are counted in a proportional hydrogen gaseous detector. Discrepancies of 5% and 9% for {sigma}{sub C} and {sigma}{sub F} respectively with ENDF have been shown. (author)

  2. Study of the influence of chemical binding on resonant absorption and scattering of neutrons; Etude de l'influence des liaisons chimiques sur l'absorption et la diffusion des neutrons aux energies de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Naberejnev, D.G. [Aix-Marseille-1 Univ., 13 - Marseille (France)

    1999-02-01

    At present time the problem of taking into account of the crystalline binding in the heavy nuclei resonance range is not correctly treated in nuclear data processing codes. The present work deals separately with resonant absorption and scattering of neutrons. The influence of crystalline binding is considered for both types of reactions in the harmonic crystal frame work. The harmonic crystal model is applied to the study of resonant absorption cross sections to show the inconsistency of the free gas model widely in use in reactor neutronics. The errors due to the use of the latter were found to be non negligible. These errors should be corrected by introducing a more elaborated harmonic crystal model in codes for resonances analysis and on the nuclear data processing stage. Currently the influence of crystalline binding on transfer cross section in the resonance domain is taken into account in a naive manner using the model of the free nucleus at rest in the laboratory system. In this work I present a formalism (Uncoupled Phonon Approximation) which permits to consider in more detail the crystalline structure of the nuclear fuel. This formalism shows new features in comparison with the static model. (author)

  3. Study of the influence of chemical binding on resonant absorption and scattering of neutrons; Etude de l'influence des liaisons chimiques sur l'absorption et la diffusion des neutrons aux energies de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Naberejnev, D G [Aix-Marseille-1 Univ., 13 - Marseille (France)

    1999-02-01

    At present time the problem of taking into account of the crystalline binding in the heavy nuclei resonance range is not correctly treated in nuclear data processing codes. The present work deals separately with resonant absorption and scattering of neutrons. The influence of crystalline binding is considered for both types of reactions in the harmonic crystal frame work. The harmonic crystal model is applied to the study of resonant absorption cross sections to show the inconsistency of the free gas model widely in use in reactor neutronics. The errors due to the use of the latter were found to be non negligible. These errors should be corrected by introducing a more elaborated harmonic crystal model in codes for resonances analysis and on the nuclear data processing stage. Currently the influence of crystalline binding on transfer cross section in the resonance domain is taken into account in a naive manner using the model of the free nucleus at rest in the laboratory system. In this work I present a formalism (Uncoupled Phonon Approximation) which permits to consider in more detail the crystalline structure of the nuclear fuel. This formalism shows new features in comparison with the static model. (author)

  4. Improved Techniques for Low-Flux Measurement of Prompt Neutron Lifetime, Conversion Ratio and Fast Spectra; Methodes Perfectionnees de Mesure de la Duree de Vie des Neutrons Instantanes, du Rapport de Conversion et des Spectres de Neutrons Rapides, dans un Reacteur a Bas Flux; Usovershenstvovannye metody izmereniya vremeni zhizni mgnovennykh nejtronov, koehffitsienta konversii i spektra bystrykh nejtronov pri slabykh potokakh nejtronov; Tecnicas Perfeccionadas para la Determinacion del Periodo de los Neutrones Inmediatos, la Razon de Conversion y los Espectros de Neutrones Rapidos, con Flujos Reducidos

    Energy Technology Data Exchange (ETDEWEB)

    Armani, R. J.; Bennett, E. F.; Brenner, M. W.; Bretscher, M. M.; Cohn, C. E.; Huber, R. J.; Kaufmann, S. G.; Redman, W. C. [Argonne National Laboratory, Argonne, IL (United States)

    1964-02-15

    been concentrated on the use of pulse shape analysis to reject gamma-ray initiated events in hydrogen recoil proportional counters and the introduction of collimation in Li{sup 6}F solid-state detector ''sandwiches'' to improve the resolution obtained. A number of such instruments have been built and their response to mono-kinetic and reactor neutrons has been investigated. Use of the gamma-ray rejection technique was equivalent to a several hundred-fold effective reduction in gamma-ray sensitivity of the recoil counter and extends the usable range down to at least 30 keV. For the Li{sup 6} solid-state devices, resolutions as low as 70 keV full-width at half maximum (1.5%) have been observed for the sum pulse in thermal neutron irradiation. (author) [French] Dans le programme des reacteurs de puissance zero, on a utilise diverses methodes statistiques pour mesurer le rapport duree de vie des neutrons instantanes/duree de vie des neutrons differes. Les auteurs ont mis au point une methode nouvelle, qui consiste a analyser le bruit du reacteur a l'aide d'un filtre passe-bande, et ont perfectionne d'autres methodes telles que la mesure, a l'aide d'un compteur a impulsions, de la frequence des coincidences retardees en fonction du temps de retard et celle de la variance relative des flux de neutrons integres en fonction du temps d'integration. Ils ont etudie les domaines dans lesquels les differentes methodes peuvent etre utilisees avec le plus d'interet. II se sont aussi preoccupes de l'interpretation des resultats de ces mesures, et montrent que l'interpretation fondee sur un modele cinetique simple peut s'appliquer dans la pratique a une grande diversite de cas. Les auteurs decrivent plusieurs perfectionnements de leur methode d'activation pour la determination du rapport de conversion: application de techniques chimiques tres sensibles pour confirmer les resultats obtenus; correction pour les coups parasites en utilisant, dans la determination de la capture, des

  5. Use of the Neutron Die-Away Technique to Test Control Rod Effectiveness Theories; Emploi de la Methode d'Absorption des Neutrons pour Verifier les Theories sur l'Efficacite des Barres de Commande; Ispol'zovanie metoda spada potoka nejtronov dlya proverki teorij ehffektivnosti reguliruyushchikh sterzhnej; Aplicacion de la Tecnica de Extincion Neutronica a la Verificacion de las Teorias sobre la Eficacia de las Barras de Control

    Energy Technology Data Exchange (ETDEWEB)

    Perez, R. B. [University of Florida, Gainesville, FL (United States); De Saussure, G.; Silver, E. G. [University of Florida, Gainesville, FL (United States); Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    1964-04-15

    extremely accurate. The disagreement found for the thick rods is to be expected when diffusion theory is used to describe the effect of absorbers with cross-sectional dimensions comparable to the neutron mean free path in the moderator. Measurements with rods of intermediate sizes are being carried out to determine the point at which diffusion theory becomes inadequate. (author) [French] Le calcul de l'efficacite des barres de commande se trouve complique par le fait qu'elle depend a la fois de la repartition energetique des neutrons et de la geometrie de l'ensemble. La comparaison entre la theorie et les resultats experimentaux obtenus sur des reacteurs ou des systemes sous- critiques souleve des difficultes, en raison de la complexite intrinseque de ces systemes. La methode d'absorption des neutrons permet d'utiliser un modele a neutrons exclusivement thermiques, dans lequel on peut dissocier la repartition energetique des neutrons.des effets spatiaux. Il s'ensuit que l'on peut etudier ie facteur geometrique de l'efficacite de la barre de commande sans ten ir compte des details du spectre des neutrons, et comparer les resultats a un dispositif experimental simple non empoisonne. La methode est fondee sur le fait que, dans une experience d'absorption des neutrons du genre de celle que decrivent les autetits, le laplacien de l'ensemble est fonction de la constante de decroissance du mode fondamental. B{sup 2} = ({lambda} - {lambda}{sub a})/D {lambda}{sub a} = inverse de la periode des neutrons dans le moderateur (s{sup -1}) D = constante de diffusion (cm{sup 2}/s) Le milieu ralentisseur utilise pour ces experiences etait constitue par des prismes rectangulaires de. beryllium, de dimensions diverses, dont les plus petits etaient des blocs de 2,54 cm de haut et 7,3 de cote. Trois types de barres de cadmium ont ete utilises: des barres minces de 0,476 cm de diametre, une barre de section cruciforme, et des barres creuses et 'epaisses' ayant une section carree de 7,3 de ctfte

  6. Continuous and discreet methods in the aggregation and des fuzzy stages of a diffuse controller of neutron power

    International Nuclear Information System (INIS)

    Najera H, M.C.; Benitez R, J.S.

    2003-01-01

    The results of a comparative study are presented of: to) A denominated diffuse controller 'exact', designed by means of an innovative method that determines analytically so much the group of exit resultant in the aggregation stage like the de fuzzy process, and b) a diffuse controller denominated 'discreet' based on the discretization of the variable of having left as much for the aggregation as for the de fuzzy. These stages incorporated to the control algorithms whose objective is the ascent and regulation of the neutron power, carrying out an analysis of its performance. (Author)

  7. Study of neutron deficient iridium isotopes by using laser spectroscopy; Etude des noyaux d'iridium deficients en neutrons par spectroscopie laser

    Energy Technology Data Exchange (ETDEWEB)

    Verney, D

    2000-12-19

    Resonance ionization spectroscopy was performed on neutron deficient iridium isotopes {sup 182-189}Ir, {sup 186}Ir{sup m} and stable isotopes {sup 191,193}Ir. Hyperfine spectra were recorded from the optical transition at 351,7 nm between the 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2} ground state and the 5d{sup 7}6s6p {sup 6}F{sub 11/2} excited state. Radioactive iridium isotopes were obtained from {beta}{sup +}/EC decay of radioactive mercury nuclei deposited on a graphite substrate. The radioactive mercury nuclei were produced at the ISOLDE facility at CERN through spallation reactions, by bombarding a molten lead target with the 1 GeV proton beam delivered by the PS-Booster. Magnetic dipole moments and spectroscopic quadrupole moments were extracted from the hyperfine spectra. The mean square charge radius variations, as deduced from the measured isotopic shift, show a sharp change between {sup 187}Ir and {sup 186}Ir{sup g}, accompanied by a sudden increase in deformation: from {beta}2 {approx} 0,16 to {beta}2 > 0, 2. These results were analysed in the framework of an axial rotor plus one or two quasiparticles. The wave functions of the osmium and platinum cores which are used in order to describe the iridium nuclei were calculated from the HF+BCS method with the Skyrme SIII effective interaction. The cores were constrained to take the deformation parameters extracted from the isotopic shift measurements. One shows then that this sudden deformation change corresponds also to a change in the proton state that describes the odd nuclei ground state or that participates in the coupling with the neutron in odd-odd nuclei. This state is identified with the {pi}3/2{sup +}[402] orbital for the smaller deformations nuclei and with the {pi}1/2{sup -}[541] orbital stemming from the h{sub 9/2} subshell for bigger deformations nuclei. (author)

  8. Lentes intraoculares fácicas de câmara posterior

    Directory of Open Access Journals (Sweden)

    Mara Barreto Theiss

    Full Text Available Resumo O objetivo deste artigo foi reunir estudos que reportam resultados disponíveis na literatura científica, considerando a previsibilidade, segurança, eficácia, e estabilidade das lentes intraoculares fácicas de câmara posterior. E relatar as complicações documentadas para estas lentes. A revisão criteriosa dos estudos publicados na literatura ate o momento revelam resultado satisfatórios quanto à eficácia, elevada previsibilidade, estabilidade e segurança do implante de lente intraocular de câmara posterior, para correção das miopia, hipermetropia e astigmatismo.

  9. Evaluation of residual stresses in composite materials by using neutron diffraction; study of elasto-plasticity; Etude des composites a matrice metallique par la technique de la diffraction de neutrons: analyse du comportement elastoplastique et evaluation des contraintes residuelles

    Energy Technology Data Exchange (ETDEWEB)

    Levy-Tubiana, R

    1999-11-05

    This work deals with the study of Metal Matrix Composites (MMC) using neutrons diffraction method and the analysis of the elastoplastic behavior in such materials. First, we evaluated macro-stresses in aluminium MMC reinforced with 17%vol. of SiC particles. One of the analyzed sample has been 4 point bending deformed, measurements have been performed after relaxation. The difference between the coefficients of thermal expansion constrains the matrix to be in tensile state and the particles in compressive state in the sample which has not be deformed. In the sample deformed, the MMC response is predicted by the science of Resistance Materials applied to a bent bar. We assume that macro-stresses are the sum of stresses with different origins (elastic, plastic, thermal mismatch): elastic mismatch is evaluated by Eshelby model and we determined micro-stresses in the unbent bar: they are equivalent and constant along width direction. For the bent bar, we observe relaxation of thermal stresses in the surface region. Theses results are confirmed by measurements of tensile/compressive sample using neutrons diffraction method. We also observed the influence of mechanical and thermal treatment on such MMC: the shear stress (established by the auto-coherent model) depends only on the way of cooling. Finally, a study was performed on titanium MMC for SNECMA on rotor beings used in the gas turbine engine industry. Evolution of stresses between felloe and boring is confirmed by a finite elements modeling and they are the first experimental results in this application. (author)

  10. A study of the fluorescence of the rare gases excited by nuclear particles. Use of the principle for the detection of nuclear radiation by scintillation; Etude de la fluorescence des gaz rares excites par des particules nucleaires. Utilisation pour la detection des rayonnements nucleaires par scintillation

    Energy Technology Data Exchange (ETDEWEB)

    Koch, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-12-15

    composantes, l'une tres breve due a la desexcitation directe du gaz rare, l'autre relativement plus lente, due au transfert d'energie sur les impuretes. La mesure des durees de vie des etats excites a confirme l'hypothese precedente, la partie breve de l'impulsion est extremement courte: inferieure a 2,25.10{sup -9} s dans le cas du xenon, la partie plus lente a une duree qui depend etroitement de la concentration d'azote, l'azote etant l'impurete dont le role est preponderant dans tous les cas. L'etude des gaz rares soumis a un champ electrique a permis de montrer que la quantite de lumiere produite par une particule {alpha} peut etre multipliee (par 60 dans un champ de 600 V/cm par exemple) ce qui correspond a un rendement de luminescence superieur a celui de INa TI. Dans la deuxieme partie on a etudie les caracteristiques des gaz rares comme scintillateurs, la plus importante est l'absence de saturation de la fluorescence lorsque la densite d'excitation transmise au gaz devient tres grande. Ceci joint au temps de scintillation tres court a permis d'etudier un certain nombre d'applications a la physique nucleaire (mesure d'energie des particules lourdes, etude cinetique des reacteurs nucleaires, spectroscopie des neutrons...). (auteur)

  11. Contribution to the study of recoil species produced by potassium ferrocyanide neutron irradiation; Contribution a l'etude de la reactivite des especes de recul dans le ferrocyanure de potassium irradie aux neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Meriadec Vernier de Byans, B. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    The chemical species produced by potassium ferrocyanide neutron irradiation were separated and identified. The study of their behaviour upon thermal annealing has allowed to establish a scheme of reaction as well as a kinetic treatment of the data. Activation energies are determined in different conditions and the effects of radiation dose, oxygen and water of crystallisation upon the activation energies were studied. Preliminary E.S.R. data and its relevance to the decomposition process is also discussed. (authors) [French] On a separe et identifie les differentes especes chimiques produites par irradiation neutronique de ferrocyanure de potassium. L'etude de leur comportement au cours du recuit thermique a permis l'application de differentes cinetiques et l'etablissement d'un schema de reaction. On a deterrmine la valeur des energies d'activation dans differentes conditions de recuit ainsi que l'influence de la dose de radiations, de l'oxygene et de l'eau de cristallisation sur ces energies. Une serie de mesures de resonance paramagnetique electronique a complete cette etude. (auteurs)

  12. Measurement of Diffusion Parameters and of Anisotropy of Graphite with a Pulsed Source of Neutrons; Mesure des parametres de diffusion et de l'anisotropie du graphite a l'aide d'une source pulsee de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Sagot, M; Tellier, H [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1963-07-01

    The diffusion coefficient, cooling coefficient, and anisotropy of graphite were determined to be (2.19 {+-} 0.03) x 10{sup 5} cm{sup 2} sec{sup -1}, (37.9 {+-} 4) x 10{sup 5} cm{sup 4} sec{sup -1}, and 1.017 {+-} 0.008, respectively. The range of geometrical buckling was from 7 to 155 m{sup -2}. The values obtained are compared with published values. (authors) [French] Un programme experimental utilisant la methode de la source pulsee de neutrons a ete realise sur le graphite. La gamme des laplaciens couverte est de 7 m{sup -2} a 155 m{sup -2}. Les resultats en sont presentes dans ce rapport: - coefficient de diffusion D{sub 0} = (2,19 {+-} 0,03) x 10{sup 5} cm{sup 2} s{sup -1} - coefficient de refroidissement C = (37,9 {+-} 4) x 10{sup 5} cm{sup 4} s{sup -1} - anisotropie du graphite (D parall./D perp.) = 1,017 {+-} 0,008. Ils sont compares aux valeurs deja publiees. (auteurs)

  13. Development of a new time-amplitude converter with tunnel diodes for improving fast neutron spectrometry by time of flight; Realisation d'un nouveau convertisseur temps-amplitude a diodes ''tunnel'' ameliorant la spectrometrie des neutrons rapides par temps de vol

    Energy Technology Data Exchange (ETDEWEB)

    Van Zurk, R [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-11-15

    New time-amplitude converter with Esaki diodes, the events being preselected before analysis, allows for realizing a fast neutron spectrometer by time-of-flight with an 1.5 * 10{sup -9} s overall time resolution for {sup 12}C (n,n') at 14 MeV. (author) [French] Realisation d'un convertisseur temps-amplitude a diodes 'tunnel', avec preselection des impulsions; l'application pour un spectrometre de neutrons rapides a temps-de-vol permet d'obtenir une resolution totale en temps de 1,5 nanoseconde dans la diffusion {sup 12}C (n,n') a 14 MeV. (auteur)

  14. Contribution to the study of 14 MeV neutron scattering by {sup 12}C using a time-of-flight spectrometer (1963); Contribution a l'etude de la diffusion des neutrons de 14 MeV par {sup 12}C, a l'aide d'un spectrometre a temps de vol (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, P [Commisariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-07-15

    Experimental measurements of 14 MeV fast neutrons scattering by {sup 12}C by time-flight spectrometer, with a 1.7 n. sec over-all resolution. The excitation of the 7.65 MeV level is observed. (author) [French] Etude experimentate de la diffusion par {sup 12}C des neutrons rapides de 14 MeV a l'aide d'un spectrometre de resolution totale de 17 n/s. Observation de l'excitation du niveau 0+ de 7,65 MeV. (auteur)

  15. Analysis of resonances due to 'S' neutrons in experiments on transmission by time-of-flight. 1. without the interference term; Analyse des resonances dues aux neutrons 'S' dans les experiences de transmission par temps de vol. 1. sans terme d'interference

    Energy Technology Data Exchange (ETDEWEB)

    Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    Various methods of transmission resonance analysis for 's' wave neutrons in time of flight experiments are described in this report. Only the case when the interference term can be neglected is treated in this first part. Results are given relative to a more complete partial area method and also to a new method so-called the width at half depth method. (author) [French] Le present rapport est consacre a l'expose de differentes methodes d'analyse des resonances dues aux neutrons d'ondes 's' dans les experiences de transmission par temps de vol, cette premiere partie traitant uniquement le cas ou l'on peut negliger le terme d'interference. Y figurent en particulier sous forme de reseaux de courbes, les resultats relatifs a une methode des aires partielles amelioree et ceux relatifs a une nouvelle methode dite de la largeur a mi-profondeur. (auteur)

  16. {gamma} ray spectroscopy of neutron rich nuclei around N=20; Spectroscopie {gamma} des noyaux riches en neutrons autour de N=20

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, M

    2007-09-15

    There is an island of inversion around {sup 32}Mg (12 protons, 20 neutrons) in contradiction with a shell closure N=20. It means a coexistence of spherical and deformed shapes. This work is devoted to the study of {gamma}-ray spectroscopy for nuclei in this region, based on an experiment done at GANIL with a composite secondary beam produced by fragmentation. The originality of the method used here lies in the possibility to study simultaneously several nuclei, and for each of them to explore several reaction channels. The VAMOS spectrometer was used for the identification of the ejectiles. The {gamma}-rays were detected with EXOGAM, a germanium clover array. The detectors used before and after the target allowed for a unique identification and a selection of the reaction channel: inelastic scattering, transfer and fragmentation reaction. In this thesis the following nuclei were studied: {sup 28}Ne, {sup 30-32}Mg {sup 31-34}Al, {sup 33-35}Si, {sup 35}P. New {gamma}-rays have been observed. The {gamma}-ray angular distributions and {gamma}-{gamma} angular correlations have been measured for some transitions. Assignment of spins and parities has been proposed for some states. In particular, in {sup 34}Si, the 3{sup -} assignment is confirmed and a new candidate for the second 0{sup +} has been proposed. In {sup 32}Mg, the state at 2.321 MeV, for which conflicting assignment existed, is deduced from the present data as a 4{sup +}, and a 6{sup +} state is proposed. (author)

  17. Measurement of resonance parameters of cross-sections affecting fast-neutron propagation in various media; Mesure des parametres de resonance de sections efficaces lies a la propagation des neutrons dans differents milieux; Izmerenie parametrov rezonansnoj struktury sechenij, vliyayushchikh na rasprostranenie bystrykh nejtronov v sredakh; Medicion de los parametros de resonancia de las secciones eficaces que afectan a la propagacion de los neutrones rapidos en distintos medios

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaev, M N; Filippov, V V; Bondarenko, I I [Academy of Sciences, Moscow, Union of Soviet Socialist Republics (Russian Federation)

    1962-03-15

    In compiling a system of multi-group constants for fast- and intermediate-reactor calculations, it is frequently necessary to account for the self-shielding effect associated with the resonance structure of the cross-sections. The energy region in which the resonance structure has a considerable influence on neutron propagation in the material extends up to several decades of kilo-electron- volts for heavy nuclei and to several mega-electron-volts for intermediate nuclei. To compute resonance effects in calculating group parameters, it is essential to know not only the average interaction cross-sections between neutrons and materials, but also values such as (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}), etc. - the brackets signify averaging over the energy group. Present information about resonance parameters for fast neutrons is not sufficient to calculate these values with the necessary precision. In this connection it is interesting to take direct measurements of the values (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}) and other analogous characteristics. The paper describes the results obtained from measurements of a number of parameters such as ({Sigma}{sub t}), ({Sigma}{sub t}{sup 2}), (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}), (1/{Sigma}{sub t}{sup 3}), etc. which characterize the cross-section structure of a number of intermediate nuclei within the range from 300 keV to 3 MeV. These values were arrived at by an analysis of transmission curves obtained by good geometry for transmissions up to {approx}10{sup -2}. The data show that resonance effects exercise a strong influence on the diffusion characteristics of the material. (author) [French] Lorsqu'on etablit un systeme de constantes multi-groupes pour les calculs de reacteurs a neutrons rapides et intermediaires, il est souvent necessaire de tenir compte de l'effet d'auto-protectio n lie a la structure de resonance des sections efficaces. Le domaine d'energie dans lequel la structure de resonance a

  18. Study of problems arising from the use of thermal neutron detectors in a pulsed regime. Application to the development of a digital transferometer adapted to receive signals from these detectors; Etude des problemes poses par l'utilisation des detecteurs de neutrons thermiques fonctionnant en regime impulsionnel. Application a la realisation d'un transferometre numerique adapte aux signaux fournis par ces detecteurs

    Energy Technology Data Exchange (ETDEWEB)

    Le Tilly, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-12-01

    The instantaneous value of the counting rate of the pulses given by a fission detector settled in a reactor follows the neutron flux, but it is shown that the counter adds a white noise to the measured signal. This report deals with some possibilities of on line numerical handling afforded by this kind of signals. One considers first the influence of a by N numerical divider and one shows that, acting like a quantifier, it adds to the signal a white noise with the power N{sup 2}/{sub 12}. One, studies afterwards the principle of a digital filter aimed to Fourier analyse the signal. The realization of this device is described. It can be used in transfer function measurements at frequencies below 125 kHz. Some examples of experiments performed with this apparatus are presented. One discusses finally the design, according to the same principle, of a power spectral density analyser in the frequency range 0,01 - 10 000 Hz for random signal of the same kind. (author) [French] La valeur instantanee de la frequence de recurrence des impulsions issues d'un detecteur a fission place dans un reacteur est proportionnelle au flux neutronique. Apres avoir montre que le detecteur ajoute un bruit blanc au signal mesure, on etudie clans ce rapport certaines possibilites de traitement numerique en temps reel offertes par ce type de signaux. On examine d'abord l'influence d'un diviseur numerique par N, et l'on montre que son action, semblable a une quantification, ajoute au signal un bruit blanc de puissance N{sup 2}/{sub 12}. On, etudie ensuite le principe d'un filtre numerique destine a effectuer l'analyse de Fourier du signal, et l'on decrit la realisation de cet appareil qui peut etre utilise pour mesurer des fonctions de transfert a une frequence quelconque inferieure a 10 kHz. Des exemples de mesures faites avec cet appareil sont presentes. On discute enfin la possibilite de realiser suivant le meme principe un analyseur de densite spectrale dans la bande de frequence 0,01 Hz

  19. Fast neutron breeder reactor Rapsodie - situation of physics, hydraulic, thermal and dynamics studies and studies of stability early in 1963; Pile rapide rapsodie - point des etudes neutroniques, hydrauliques, thermiques et dynamiques et des etudes de stabilite au debut de l'annee 1963

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1964-07-01

    ) [French] Au debut de 1963, il a ete necessaire de faire un choix entre les deux combustibles etudies pour Rapsodie: l'alliage UPuMo avec double gainage Nb et acier inoxydable et l'oxyde mixte UO{sub 2}-PuO{sub 2}. Ce rapport donne les resultats des etudes menees avec les deux types de combustible. On rappelle d'abord les differents modeles qui ont ete etudies et on donne une description detaillee de coeurs alliage et oxyde tels qu'ils sont envisages au debut de 1963. On rapporte ensuite les principales caracteristiques neutroniques des deux coeurs: flux et spectre des neutrons, valeur des barres de securite - compensation, economie des neutrons, puissance specifique, fraction effective des neutrons retardes, temps de vie des neutrons prompts, coefficients de reactivite. On decrit les etudes et essais hydrauliques qui ont ete faits a propos de ces deux coeurs. On discute les criteres qui ont ete a l'origine des calculs de debits. On donne les resultats des essais de pertes de charge, de soulevement des assemblages, de vibration et d'ecoulement fin entre les aiguilles. On discute les constantes utilisees pour les calculs thermiques et on donne les temperatures maximales du sodium et des combustibles alliage et oxyde, les majorations dues aux points chauds et la limitation du taux de combustion de l'aiguille oxyde ayant pour origine la pression des gaz de fission. On rapporte les hypotheses qui ont ete utilisees pour les calculs dynamiques et l'on decrit les differents incidents qui ont ete etudies. On donne les resultats des calculs, pour chaque incident et pour chaque combustible et l'on montre que l'on peut eviter la fusion du combustible ou l'ebullition du sodium, meme dans le cas des hypotheses les plus pessimistes, en agissant sur les caracteristiques de la pile (valeur de la barre de pilotage ou puissance de la pile avec un seul circuit de refroidissement). La stabilite de la pile a ete evaluee avec les hypotheses utilisees pour les calculs dynamiques, a l

  20. DIANE, a simulation code for the interaction of neutrons with living tissues. Application to low doses of fast neutrons on human tumoral cells; DIANE, un code de simulation de l'interaction des neutrons avec la matiere vivante. Applications aux faibles doses de neutrons rapides sur des cellules tumorales humaines

    Energy Technology Data Exchange (ETDEWEB)

    Nenot, M.L

    2003-07-15

    Our work deals with the irradiation of cells and living tissues by 14 MeV neutrons at very low doses (a few 10{sup -2} Gy). Such experiments require an accurate knowledge of the values of neutron dose rates and fluences at the level of cell cultures. We have performed measurements of fluence rates through an activation method applied to gold and copper foils. The fluence rate is deduced from the gamma rays emitted by the irradiated foils. Neutron doses and dose rates have been measured through varied methods: PIN diodes, ionization tissue equivalent chambers, and Geiger-Mueller counters. We have designed the DIANE code to simulate the impact of energetic neutrons on cells. This code can be used with isolated cells or macroscopic tissues, it takes into account the roles of the ionisation electrons produced by recoil nuclei entering the cell. This point is all the more important since recent works have highlighted the impact of very low energy electrons on DNA. (A.C.)

  1. Resolution of crystal structures by X-ray and neutrons powder diffraction using global optimisation methods; Resolution des structures cristallines par diffraction des rayons X et neutrons sur poudres en utilisant les methodes d'optimisation globale

    Energy Technology Data Exchange (ETDEWEB)

    Palin, L

    2005-03-15

    We have shown in this work that X-ray diffraction on powder is a powerful tool to analyze crystal structure. The purpose of this thesis is the resolution of crystal structures by X-ray and neutrons diffraction on powder using global optimisation methods. We have studied 3 different topics. The first one is the order-disorder phenomena observed in some globular organic molecular solids. The second is the opiate family of neuropeptides. These neurotransmitters regulate sensory functions including pain and control of respiration in the central nervous system. The aim of our study was to try to determine the crystal structure of Leu-enkephalin and some of its sub-fragments. The determination of the crystal structures has been done performing Monte Carlo simulations. The third one is the location of benzene in a sodium-X zeolite. The zeolite framework was already known and the benzene has been localized by simulated annealing and by the use of maximum entropy maps.

  2. Conformation and arrangement of polyelectrolytes in semi-diluted solution. A study by small angle neutrons scattering; Conformation et arrangement des polyelectrolytes en solution semi-diluee. Etude par diffusion des neutrons aux petits angles

    Energy Technology Data Exchange (ETDEWEB)

    Spiteri, M N

    1997-03-25

    Polyelectrolytes have particular physical and chemical properties and can thus be used for instance for petroleum production. Some of their microscopic properties have been studied in this work. With the particular zero average contrast technique, the small angle neutron scattering allows to directly know the form factors in semi-diluted solutions of polyelectrolytes where the chains are mixed. Another measure leads to the crystal structure. The electrostatic screen effects when salt is added in aqueous solutions of completely charged PSSNa solutions (f=1) (sodium polystyrene sulfonate) are studied. It seems that the chains take a vermiform conformation. Their persistence length varies as I{sup -1/3} (I is the ionic force). The hydrophobicity effects in partially charged PSSNa solutions (f<1) are given too. They lead to a progressive collapse of the chains when their charge rates decrease. The screen and condensation effects when the charge rate f of the PSSNa (f>f(Manning)) varies in a polar solvent (DMSO) are studied. The vermiform chains have the same persistence length (for each f) which varies as I{sup -1/4}. Lastly, the f variation effects in the case of a weakly charged hydrophilic poly-ion (f

  3. In Vivo and Air Dosimetry of Fission-Spectrum Neutrons; Dosimetrie In Vivo et dans l'Air du Spectre des Neutrons de Fission; Dozimetriya v vozdukhe i dozimetriya In Vivo nejtronov spektra deleniya; Dosimetria In Vivo y en el Aire de Neutrones de un Espectro de Fision

    Energy Technology Data Exchange (ETDEWEB)

    Mobley, T. S.; Engel, R. E.; Godden, W. R. [Kirtland Airforce Base, New Mexico (United States); Penikas, V. T. [AFIT, Wright-Patterson Air Force Base, Ohio, with Duty Station at University of Rochester, School of Medicine and Dentistry, Rochester, NY (United States)

    1964-03-15

    internal package varied with burst temperature rise, distance from the reactor, orientation of the foils with respect to the reactor, and the thickness and composition of the attenuating tissues. (author) [French] En vue d'evaluer la dose profonde du fait de l'exposition au spectre des neutrons de fission, les auteurs ont mis au point une methode de dosimetrie in vivo sur le mouton. On a utilise pour ces etudes un reacteur a flux puise semblable a l'appareil GODIVA II du Laboratoire scientifique de Los Alamos. En regime puise, le reacteur donne une impulsion d'une largeur de 50 {mu}s a la moitie du maximum d'amplitude pour une elevation de temperature du combustible d'environ 100 Degree-Sign C. Une insertion sous-cutanee contient une feuille d'or recouverte de cadmium, une feuille d'or nue et trois dosimetres en verre thermoluminescent places dans un etui de lithium et de plomb double de verre. On a place les insertions dans le tissu sous-cutane des deux cotes du corps pour detecter la dose totale de neutrons thermiques-gamma, les neutrons etant delivres sur les flancs. Des insertions abdominales sont preparees a peu pres de la meme facon que les insertions sous-cutanees; elles sont constituees d'une boule de bore contenant des feuilles a seuil de fission (Pu, Np, Ue) recouvertes de cadmium, d'un comprime de soufre et de trois dosimetres identiques a ceux des insertions sous-cutanees. On les a placees dans l'abdomen des sujets 18 h avant l'exposition, en les fixant au pilier anterieur du rumen. Les auteurs decrivent un procede de rumenotomie. On a determine la dose de neutrons au moyen de la feuille a seuil. On a utilise les feuilles d'or et les feuilles d'or recouvertes de cadmium pour determiner le flux integre de neutrons thermiques, le plutonium-239, le neptumum-237, l'uranium-238 et le soufre-32 pour determiner le flux integre de neutrons rapides, et les batonnets de verre radiophotoluminescents pour determiner la dose gamma. Les moutons ont subi des expositions

  4. Measurements of the neutron capture cross sections and incineration potentials of minor-actinides in high thermal neutron fluxes: Impact on the transmutation of nuclear wastes; Mesures des sections efficaces de capture et potentiels d'incineration des actinides mineurs dans les hauts flux de neutrons: Impact sur la transmutation des dechets

    Energy Technology Data Exchange (ETDEWEB)

    Bringer, O

    2007-10-15

    This thesis comes within the framework of minor-actinide nuclear transmutation studies. First of all, we have evaluated the impact of minor actinide nuclear data uncertainties within the cases of {sup 241}Am and {sup 237}Np incineration in three different reactor spectra: EFR (fast), GT-MHR (epithermal) and HI-HWR (thermal). The nuclear parameters which give the highest uncertainties were thus highlighted. As a result of fact, we have tried to reduce data uncertainties, in the thermal energy region, for one part of them through experimental campaigns in the moderated high intensity neutron fluxes of ILL reactor (Grenoble). These measurements were focused onto the incineration and transmutation of the americium-241, the curium-244 and the californium-249 isotopes. Finally, the values of 12 different cross sections and the {sup 241}Am isomeric branching ratio were precisely measured at thermal energy point. (author)

  5. Bijdragen aan Hoofdstukken 2-6: Landschapsbiografie Dijkteruglegging Nijmegen-Lent

    NARCIS (Netherlands)

    Heunks, Eckhart

    2016-01-01

    Contributions to a synthesis of landscape archaeological activities carried out in Nijmegen-Lent as part of heritage management by Gemeente Nijmegen during expansion of the city and reconstruction of the Waal river dike and bridges in the past decade. In 2014-2015, Dr. Kim Cohen advised to the

  6. Implante de lente intraocular trifocal difractivo: análisis y resultado de la agudeza visual

    Directory of Open Access Journals (Sweden)

    Miguel Ángel Ibáñez-Hernández

    2017-09-01

    Conclusiones: El implante de un lente intraocular trifocal difractivo es capaz de proporcionar una excelente visión lejana, intermedia y cercana, con escasas aberraciones ópticas, permitiendo una mejor calidad visual útil en actividades desarrolladas a diferentes distancias.

  7. Relationship between subcutaneous blood flow and absorption of lente type insulin

    DEFF Research Database (Denmark)

    Hildebrant, P; Mehlsen, J; Birch, K

    1987-01-01

    To study the relationship between the absorption of intermediate acting insulin and the local subcutaneous blood flow (SBF) 8 diabetic patients were given subcutaneous injections of 125I labeled human lente type insulin and 133Xenon in the abdominal wall. External measurements of the tracer...

  8. Evolution of the nondestructive testing equipment for neutron radiography in the framework of the programs of the Services des Piles de Saclay

    International Nuclear Information System (INIS)

    1980-10-01

    The progress made in neutron radiography testing equipment is made with respect to (a) the devices located inside reactor ponds (collimation, leak-tightness, irradiation devices, detection systems), (b) neutron radiography of active parts outside the reactor ponds (testing of fuel rods several metres long by a neutron radiography system by dry feed through), (3) neutron radiography on inactive materials (fitting an axial channel and a side channel in the Triton reactor), (4) neutron radiography on a neutron guide set up at the end of the Neutron Guide Hall associated with the Orphee reactor, i.e. 70 metres from it [fr

  9. Etude de la dynamique en régimes quasiharmonique et anharmonique de la phase basse température de la triéthylènediamine par diffusion cohérente inélastique des neutrons

    OpenAIRE

    Hedoux , A.; Sauvajol , J.L.; More , M.

    1988-01-01

    La triéthylènediamine N(CH2CH2)3N cristallise jusqu'à Tc = 351 K dans une phase solide ordonnée de symétrie hexagonale compacte. Les expériences de diffusion cohérente inélastique des neutrons réalisées dans la phase basse température s'inscrivent dans le cadre de l'étude du processus de la transition martensitique à Tc à partir de l'évolution avec la température des paramètres dynamiques. Ainsi les courbes de dispersion ont été déterminées à 190 K, 245 K et 295 K. Les mesures effectuées à te...

  10. Lentes fáquicos como alternativa de tratamiento en el queratocono

    Directory of Open Access Journals (Sweden)

    Raúl Barroso Lorenzo

    Full Text Available El queratocono es una enfermedad degenerativa que se caracteriza por un adelgazamiento progresivo del estroma corneal y la deformidad en forma de cono de la córnea, lo cual provoca astigmatismo irregular y miopía elevada. Se realizó una revisión de artículos publicados referentes al implante de lentes intraoculares fáquicos como alternativa de tratamiento en esta entidad, la cual continúa siendo de difícil manejo en la actualidad. En ametropías con alto componente esférico y cilíndrico, el uso de lente fáquico tórico mostró óptimos resultados visuales. De igual modo el uso de lentes de soporte angular "estira" la córnea y achata el área apical central a través de sus hápticas, con lo que reduce la ectasia corneal y el astigmatismo irregular asimétrico. A su vez, la presencia del lente intraocular entre la pupila y la córnea crea una barrera física que evita la acción de la corriente de humor acuoso contra la córnea y, por consiguiente, hay una estabilización de todos los parámetros de la córnea después de la implantación del lente. La literatura reporta combinación de implantes de lentes fáquicos posterior a anillos intraestromales y crosslinking con un excelente resultado funcional: incrementa en forma importante la agudeza visual sin corrección, mejora las topografías corneales y las aberraciones de alto orden y disminuye la posibilidad de requerir un trasplante de córnea. El uso de lentes fáquicos tóricos en queratoconos estables es una alternativa terapéutica válida como tratamiento de la ametropía que acompaña a esta patología.

  11. Crystal Dynamics from Neutron Spectrometry; Etude de la dynamique des cristaux par la spectrometrie neutronique; Izuchenie voprosov dinamiki kristallov metodami nejtronnoj spektrometrii; Estudio de la dinamica de redes cristalinas por espectrometria neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Woods, A. D.B. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

    1963-01-15

    This paper reviews investigations carried out at Chalk River on the lattice dynamics of various crystals including lead, sodium, alkali halides, semi-conductors, and other more complex compounds. Analysis of the low temperature results (-{approx}100{sup o}K) gives considerable insight into the nature of the interatomic forces. In sodium, a simple metal, the interatomic forces are very nearly derivable from a potential. Lead, a more complicated metal, has extremely long range forces accompanied by strong electronic effects. At higher temperatures anharmonic effects are very pronounced in both metals, especially in lead. The alkali halide results can be interpreted on a ''shell'' model, with polarizable ions. Even at low temperature neutron groups corresponding to the longitudinal optical modes. (author) [French] Dans ce memoire, l'auteur decrit les recherches faites a Chalk River sur la dynamique des reseaux de certains cristaux, y compris le plomb, le sodium, les halogenures alcalins, les semi-conducteurs et d'autres composes complexes. L'analyse des resultats obtenus a basse temperature (environ 100{sup o}K) fournit de nombreux renseignements sur la nature des forces interatomiques. Dans le sodium (metal simple), les forces interatomiques peuvent presque etre derivees d'un potentiel. Dans un metal plus complique, tel que le plomb, on trouve des forces ayant une portee extremement grande et comportant des effets electroniques marques. A des temperatures plus elevees, il se produit des effets anharmoniques tres prononces dans les deux metaux et particulierement dans le plomb. On peut interpreter les resultats obtenus pour les halogenures alcalins en se fondant sur le modele en couche comportant des ions polarisables. Meme aux basses temperatures, les groupes de neutrons correspondant aux modes optiques longitudinaux possedent des largeurs dependant de la temperature, que l'on ne comprend pas encore parfaitement. (author) [Spanish] Los autores pasan revista a las

  12. The Measurement of Reactivity In Multiregion Subcritical Systems by the Pulsed Neutron Technique; Mesure de la Reactivite dans les Systemes Sous-Critiques a Plusieurs Regions par la Methode des Neutrons Pulses; Izmerenie reaktivnosti v mnogozonnykh podkriticheskikh sistemakh metodom impul'snykh nejtronov; Mediciones de la Reactividad en Sistemas Subcriticos de Varias Regiones Mediante la Tecnica de los Neutrones Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Sherwin, J.; Leng, J. H. [United Kingdom Atomic Energy Authority, Windscale Works, Cumberland (United Kingdom)

    1965-10-15

    The prompt decay of a thermalized burst of neutrons in a multiregion subcritical system is examined using a two-group diffusion theory. It is shown that a relationship can be established between the prompt decay constant of the fundamental mode and the effective multiplication factor of the system in terms of two parameters, defined, for the purposes of this paper, as the reactor response coefficient and the prompt decay correction and which depend to a large extent on the spatial flux patterns within the system. For the uniform bare system, the response coefficient can be identified with the mean neutron lifetime in the system; for a multiregion system it represents a compound of the lifetimes in each region weighted by perturbation type integrals. The second parameter, the decay correction, can have no physical meaning in that it arises from an attempt to relate the two scales of reactivity involved; that is the scale using the prompt decay constant and the scale derived using the effective multiplication factor. The properties of these parameters are examined here with reference to an enriched uranium graphitemoderated reactor consisting of uniform core and reflector and it is shown that the two parameters are not uniquely defined by the reactivity of the system but depend on the method chosen to make the system subcritical. Two sets of measurements are treated by the theory. In one, the Windscale Advanced Gas-Cooled Reactor was shut down by a uniform poison. In the other the reactivity of a core in the zero-energy reactor HERO was varied by altering the loaded radius. The neutron pulse measurements are all shown to be in good agreement with more conventional methods of reactivity determination. Some discussion of the experimental techniques and the difficulties encountered in the graphite-moderated systems is presented. (author) [French] Les auteurs etudient la decroissance des neutrons instantanes d'une bouffee thermalisee de neutrons dans un systeme sous

  13. Principle of the determination of neutron multiplication coefficients by the Monte Carlo method. Application. Description of a code for ibm 360-75; Principe de la determination des coefficients de multiplication neutronique par methode de Monte-Carlo. Application. Description d'un code pour IBM 360-75

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, J; Parisot, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    The determination of neutron multiplication coefficients by the Monte Carlo method can be carried out in different ways; the are first examined particularly complex geometries; it makes use of multi-group isotropic cross sections. The performances of this code are illustrated by some examples. (author) [French] La determination des coefficients de multiplication neutronique par methode de Monte Carlo peut se faire par differentes voies, elles sont successivement examinees et comparees. On en deduit un code rapide pour des geometries particulierement complexes, il utilise des sections efficaces multigroupes isotropes. Les performances de ce code sont demontrees par quelques exemples. (auteur)

  14. Biological Effects of Thermal Neutrons and the B{sup 10}(n, {alpha}) Li{sup 7} reaction; Effets Biologiques des Neutrons Thermiques et la Reaction {sup 10}B(n, {alpha}){sup 7}Li; Biologicheskoe dejstvie teplovykh nejtronov i reaktsiya B{sup 10}(n, {alpha}) Li{sup 7}; Efectos Biologicos de los Neutrones Termicos y la Reaccion {sup 10}B(n, {alpha}){sup 7}Li

    Energy Technology Data Exchange (ETDEWEB)

    Archambeau, J. O.; Alcober, V.; Calvo, W. G.; Brenneis, H. [Medical Research Center, Brookhaven National Laboratory, Upton, NY (United States)

    1964-05-15

    into eight applications over 12 days does not reduce the severity of the reaction as it does with gamma-irradiation. This effect is attributed primarily to the alpha-particle irradiation from the thermal-neutron capture of boron-10. (author) [French] En exposant des animaux aux neutrons thermiques du Reacteur de recherches medicales, on constate dans les tissus des effets qui sont dus aux rayons gamma et aux rayonnements corpusculaires emis lors de la capture des neutrons thermiques par des elements du tissu et des matieres de protection, ainsi qu'aux rayons gamma et aux neutrons rapides provenant du processus de fission dans le coeur du reacteur. L' e ffe t globa l de l ' irradiation par les neutrons thermiques est fonction du nombre de neutrons incidents par centimetre carre et par unite de temps. Comme le flux de neutrons thermique decroit rapidement dans le tissue (couche de demi-attenuation Approximately-Equal-To 8 cm), il faut que les doses incidentes a la suriace soient elev ees pour obtenir une dose profonde suffisante. C 'est pourquoi les reactions des poumons, des intestins, de la moelle osseuse et des muqueuses sont essentiellement attribuees aux rayons gamma provenant de la capture de neutrons thermiques dans les couches superficielles du tissu. En exposant la tete d' un chien a un flux de 1.4 x 10{sup 14}/cm{sup 2}, on constate une chute de poils, un erytheme et une desquamation humide, ces symptomes etant accompagnes d'une deficience hematologique. Cependant, la restauration de la moelle osseuse et la guerison de la peau s' operent dans l'espace de 25 a 30 j. Chez les animaux exposes a un flux de 5 x 10{sup 13} n/cm{sup 2}, 30 min apres une injection intraveineuse de 35 mg de {sup 10}B/kg de matiere vivante, on observe une epidermite qui tend a se necroser, des oedemes de la peau du crane et une conjonctivite. Le cerveau est le siege d'hemorragies et de stagnations dans les vaisseaux capillaires, accompagnees de lesions au niveau des neutrons et

  15. Neutron diffraction study at 0.3 K of the magnetic properties of rare-earth aluminium or gallium garnets; Etude par diffraction des neutrons a 0,3 K des proprietes magnetiques de grenats de terre rare et d'aluminium ou de gallium

    Energy Technology Data Exchange (ETDEWEB)

    Hammann, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-03-01

    In order to study ordered magnetic states below 1.5 deg. K by neutron diffraction measurements, a helium-3 cryostat has been realised in which the thermalization of a great quantity of powdered sample is performed by a helium-4 superfluid film, and which leaves the possibility of applying an external magnetic field. We thus studied essentially the magnetic phase transitions of rare-earth aluminium or gallium garnets. First we determined the antiferromagnetic structures of the erbium gallium garnet (T{sub N} = 0.79 deg. K) and of the neodymium gallium garnet (T{sub N} = 0.516 deg. K). The metamagnetic behavior of the erbium gallium garnet has been observed and compared to that of the dysprosium aluminium garnet. Second we considered the 'non-Kramers' ions Tb{sup 3+} and Ho{sup 3+} in the aluminium garnets. In this case, only two single ground states (well isolated from upper levels) have to be considered. A molecular field model with purely magnetic dipolar interactions, leads then to the existence of magnetic phase transition with antiferromagnetic ordering. This has been observed for the terbium-aluminium garnet below T{sub N} 1.35 deg. K and for the holmium-aluminium garnet below T{sub N} {approx} 0.98 deg. K. (author) [French] Afin d'acceder a l'etude par diffraction des neutrons des etats magnetiques ordonnes en-dessous de 1,5 deg. K, nous avons realise un cryostat a helium-3 qui assure la mise en temperature de la quantite importante d'echantillon en poudre a l'aide d'un film d'helium-4-superfluide, et qui laisse la possibilite d'application d'un champ magnetique exterieur. Nous avons essentiellement etudie avec cette technique les transitions de phase magnetique de grenats de terre rare et d'aluminium ou de gallium. C'est ainsi qu'on a determine l'ordre antiferromagnetique dans les grenats de gallium-erbium (T{sub N} = 0,79 deg. K) et de gallium-neodyme (T{sub N} = 0,516 deg. K). Le comportement metamagnetique du grenat de gallium-erbium a ete mis en evidence

  16. Opacificación capsular posterior en lentes intraoculares hidrofílicos en comparación con lentes intraoculares hidrofóbicos usando imágenes de Scheimpflug

    Directory of Open Access Journals (Sweden)

    Arturo Olguin Manríquez

    2016-03-01

    Conclusiones: Los resultados de la función visual son comparables entre ambos lentes. La opacificación de la cápsula posterior se vio en menor proporción con el LIO Akreos MI60 cuando se midió por imágenes de Scheimpflug, debido probablemente al diseño del lente. No se demostraron correlación entre ambas pruebas.

  17. Determination by neutron activation of the uranium-235 concentration in uranium oxides; Determination par activation neutronique de la concentration d'uranium-235 dans des oxydes d'urane

    Energy Technology Data Exchange (ETDEWEB)

    May, S; Leveque, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    Classical methods of measuring isotopic abundance have the disadvantage of being long and of requiring chemical separation. A non-destructive method of measuring the uranium-235 content is described. It is based on an overall measurement of the short lived fission product activity formed during a 15 s neutron irradiation. The precision is of the order {+-} 1.5 per cent for 20 per cent enriched samples. The error due to the contribution from fast fission is discussed in detail. (author) [French] Les methodes classiques de mesure de l'abondance isotopique presentent le gros inconvenient d'etre longues et de necessiter des separations chimiques. Nous exposons une methode non destructive de mesure de la concentration d'uranium-235. Elle est basee sur la mesure globale de l'activite des produits de fission de courte periode formes par une irradiation neutronique de 15 s de l'echantillon. La precision est de l'ordre de {+-} 1,5 pour cent pour des echantillons enrichis jusqu'a 20 pour cent. L'erreur a la contribution de la fission rapide est discutee en detail. (auteur)

  18. Study of neutrons resonances as a function of spin for the nuclei I = 1/2 (silver, thulium, platinum) between 1 and 800 eV; Etude des resonnances de neutrons en foncton de leur spin pour les noyaux I = 1/2 (argent, thulium et platine) entre 1 et 800 eV

    Energy Technology Data Exchange (ETDEWEB)

    De Barros, S M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-04-01

    The assignment of spins has been made for 120 levels of 239 detected. From these data we have deduced that: - The ratio of average spacing of each state of spin obeys the law of 2 J + 1. - The values of the strength function of {sup 195}Pt and {sup 169}Tm are in agreement with the model of Chase et Al and has the same values for the two states of spin. - The fluctuations of total radiation widths of resonances are observed in the case of {sup 195}Pt for the two spin-states. - The neutron widths are governed by the distributions of Porter and Thomas with one degree of freedom; the observed spacings are consistent with the Wigner distribution for two populations. (author) [French] L'attribution de spin a ete faite pour 120 niveaux sur 239 detectes. On en deduit: - Le rapport des espacements moyens pour chaque etat de spin qui obeit a la loi en (2j + 1). - Les valeurs des fonctions densites de {sup 195}Pt et {sup 169}Tm sont en accord avec le modele du noyau deforme de Chase et al. et ont la meme valeur pour les deux etats de spin. - Des fluctuations, dans les largeurs radiatives totales des resonances sont observees dans le cas de {sup 195}Pt pour les deux etats de spin. - Les largeurs de diffusion suivent les distributions de Porter et Thomas a un degre de liberte; les espacements celles de Wigner a deux populations. (auteur)

  19. Estudo comparativo do desempenho óptico de diversas lentes intra-oculares (LIO) multifocais

    OpenAIRE

    Antunes, Telma Nicole Nogueira

    2012-01-01

    A cirurgia da catarata tem vindo a evoluir ao longo dos anos, tendo sido realizado o primeiro implante de uma lente intra-ocular em 1949. Desde então, várias técnicas foram utilizadas e descontinuadas devido a insucessos. Actualmente é utilizada a técnica de facoemulsificação. Tal como a técnica cirúrgica a lente implantada também tem vindo a evoluir, tanto a nível do material como a nível de design. Com as evoluções, tanto a nível de técnica cirúrgica como a nível de forma e material das len...

  20. Diabetes mellitus y lentes de contacto Diabetes mellitus related to use of contact lenses

    Directory of Open Access Journals (Sweden)

    Beatriz Zozaya Aldana

    2009-04-01

    Full Text Available Cada día aumenta el número de diabéticos diagnosticados que demandan como método de compensación para los defectos de refracción las lentes de contacto. Debido a la escasa información que se tiene sobre el tema, dedicamos nuestro trabajo a realizar una revisión sobre la relación de estos dos temas: lentes de contacto y diabetes, con el justo ánimo de brindar una atención más completa a nuestros pacientes.Every day increases the figure of diagnosed diabetic patients requiring a compensatory method for refraction defects the use of contact lenses. Due to the non-available information on this matter, this paper is aimed to make a review on relation between these two topics: contact lenses and diabetes to offer a more complete care to our patients.

  1. 12 CFR 7.1003 - Money lent at banking offices or at other than banking offices.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Money lent at banking offices or at other than banking offices. 7.1003 Section 7.1003 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE... without violating 12 U.S.C. 36, 12 U.S.C. 81 and 12 CFR 5.30, provided that a third party is used to...

  2. Infiltrados corneales asociados al uso de lentes de contacto Corneal infiltrates associated with contact lens wear

    Directory of Open Access Journals (Sweden)

    Vivian Padrón Álvarez

    2001-12-01

    Full Text Available Se estudiaron 15 pacientes que usan lentes de contacto rígidas, permeables al gas (LCRPG y lentes de contacto blandas (LCB que presentaron infiltrados corneales. Se realizó estudio microbiológico de las lesiones y seguimiento clínico de estos casos. En 3 de los casos estudiados el cultivo fue positivo a estafilococo aureus, el resto de los estudios microbiológicos fueron negativos. Todos los pacientes respondieron rápidamente al retirar la lente de contacto y al tratamiento con antibióticos tópicos y ninguno tuvo afectación permanente de la agudeza visual. El diagnóstico exacto y el manejo apropiado de los infiltrados corneales en pacientes que usan lentes de contacto es de gran importancia por la posibilidad de infección o de secuela visual permanente.15 patients wearing gas permeable rigid contact lenses (GPRCL and soft contanct lenses (SCL that presented corneal infiltrates were studied. A microbiological study of the injuries and a clinical follow-up of these cases were conducted. In 3 of the studied cases the culture was positive to Staphyloccocus aureus. The rest of the mircobiological studies were negative. All the patients responded rapidly to the contact lens removal and to the treatment with topical antibiotics. None of them had permanent affection of visual acuity. The accurate diagnosis and the appropiate management of the corneal infiltrates in patients wearing contact lenses is very important due to the possibility of infection or of permanent visual sequela.

  3. Development of an experimental device based on the digitalization of the signal and dedicated to the characterization of fission fragments and prompt neutrons; Developpement d'un dispositif experimental base sur la digitalisation des signaux et dedie a la caracterisation des fragments de fission et des neutrons prompts emis

    Energy Technology Data Exchange (ETDEWEB)

    Varapai, N

    2006-12-15

    The present work demonstrates the application of the digital technique for nuclear measurements. This new technique is based on the digitalization of the signals from the detectors and has several advantages. This technique allows us to extract the maximum amount of information contained in the signal shape. In the case of an ionization chamber this signal contains the necessary information on the particle kinetic energy, emission angle and mass. This method has been implemented for measurements of promptly emitted fission neutrons in coincidence with fission fragments from {sup 252}Cf(sf). A double Frisch-grid ionization chamber is used as fission fragment detector. The promptly emitted neutrons are detected by a NE213 liquid scintillation detector. This work displays how delicate analysis of the digitalized signals permitted us to infer the mass and kinetic energy distributions of the fission fragments as well as the neutron energy spectrum and multiplicity. The outline of this thesis is as follows: Chapter 2 gives an overview of the experimental tools used in this work. Chapter 3 explains the analysis procedure of the digitalized anode signal from an ionization chamber. Chapter 4 gives a detailed explanation of the analysis procedure of the digitalized signal from a neutron detector. In Chapter 5 the analysis procedure of the fission fragment events in coincidence with neutrons is given.

  4. Avaliação da qualidade de vida em pacientes submetidos à cirurgia de catarata, com implantes de lentes monofocais bifocais e multifocais

    Directory of Open Access Journals (Sweden)

    Beogival Wagner Lucas Santos

    2014-04-01

    Full Text Available Objetivo: Fornecer uma avaliação objetiva e subjetiva da qualidade de vida e o nível de satisfação de pacientes que se submeteram à cirurgia de catarata, com implante de lentes bifocais, multifocais e monofocais. Métodos: Lentes bifocais foram implantadas em 72 pacientes; lentes multifocais asférica em 16 pacientes; lentes multifocais apodizada em 20 pacientes e lentes monofocais em 63 pacientes. Foi aplicado um questionário de 47 perguntas cujos resultados foram avaliados e analisados. Resultados: O nível de satisfação dos pacientes implantados com lentes bifocais e multifocais foi significantemente mais alto do que aqueles com lentes monofocais (teste Kruskal-Wallis p<0,01, seguido do teste Dunn, p<0,05. Quanto à comparação de lentes monofocais com lentes bifocais e multifocais, a visão para perto sem correção foi consideravelmente mais baixa em pacientes com lentes monofocais (teste Z, p<0,001. Os pacientes com lentes monofocais sem correção apresentaram uma menor capacidade de ler jornais ou livros e no que diz respeito a trabalhos manuais do que aqueles com lentes bifocais e multifocais (teste Z, p<0,001. Conclusão: Os resultados deste estudo mostram que os pacientes que receberam as lentes bifocais e multifocais tiveram uma melhora notável em sua acuidade visual para perto, estando satisfeitos com sua visão geral, sem óculos. A satisfação foi atribuída ao fato de conseguirem ler livros e jornais, preencher cheques, preencher formulários, praticar esportes, se barbear ou se maquiar sem correção.

  5. Pulsed Neutron Studies of BeO-Natural Uranium Lattices; Etudes de Reseaux Uranium Naturel-Glucine, par la Methode des Neutrons Pulses; Issledovanie reshetok BeO-prirodnyj uran s pomoshch'yu impul'snykh nejtronov; Estudio de Reticulados de Beo-Uranio Natural con Ayuda de Neutrones Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, B. V.; Nargundkar, V. R.; Subbarao, K. [Atomic Energy Establishment Trombay, Bombay (India)

    1965-10-15

    The use of the pulsed neutron method for determination of the diffusion parameters and multiplication constants of lattices is described. The diffusion parameters and multiplication constants of BeO-natural uranium lattices are obtained by this method. The uranium rods used were 2.92 cm diameter clad in aluminium 0.072 cm thick and were arranged vertically in channels of square cross-section 5 cm x 5 cm, in a square lattice of pitch 15 cm. The neutron bursts were produced from a cascade accelerator by pulsing the ion source and using the Be(d,n) reaction. The detectors were enriched boron trifluorfde proportional counters. The space and time harmonics were eliminated as described by the authors in another paper at this Symposium. The decay constant of the fundamental mode was determined for several bucklings, far from criticality. In these calculations the effect of diffusion cooling and anisotropy was taken into account. All the diffusion and multiplication constants were determined by the method of least squares fit by three different approaches. The prompt critical buckling was determined by solving the decay constant equation for {lambda} = 0. The final results are: Diffusion length L = 15.2 cm Absorption constant {lambda}{sub 0} = 762.5 s{sup -1}. Diffusion coefficient D = 1.761 x 10{sup 5} cm{sup 2}/s Diffusion cooling constant C = -8.766 x 10{sup 5} cm{sup 4}/s Age {tau} = 150.7 cm{sup -2} Infinite multiplication factor k{sub {infinity}} = 1.126 Prompt critical buckling B{sup 2} = 3.00 x 10{sup -4} cm{sup -2}. (author) [French] Les auteurs decrivent l'utilisation de la methode des neutrons puises pour la determination des parametres de diffusion et des constantes de multiplication des reseaux. Cette methode permet d'obtenir les parametres de diffusion et les constantes de multiplication du reseau uranium naturel-glucine. Les barres d'uranium utilisees avaient un diametre de 2,92 cm et un gainage'd'aluminium d'une epaisseur de 0,072 cm elles etaient disposees

  6. Development of the neutron-transport code TransRay and studies on the two- and three-dimensional calculation of effective group cross sections; Entwicklung des Neutronentransportcodes TransRay und Untersuchungen zur zwei- und dreidimensionalen Berechnung effektiver Gruppenwirkungsquerschnitte

    Energy Technology Data Exchange (ETDEWEB)

    Beckert, C.

    2007-12-19

    Conventionally the data preparation of the neutron cross sections for reactor-core calculations pursues with 2D cell codes. Aim of this thesis was, to develop a 3D cell code, to study with this code 3D effects, and to evaluate the necessarity of a 3D data preparation of the neutron cross sections. For the calculation of the neutron transport the method of the first-collision probabilities, which are calculated with the ray-tracing method, was chosen. The mathematical algorithms were implemented in the 2D/3D cell code TransRay. For the geometry part of the program the geometry module of a Monte Carlo code was used.The ray tracing in 3D was parallelized because of the high computational time. The program TransRay was verified on 2D test problems. For a reference pressured-water reactor following 3D problems were studied: A partly immersed control rod and void (vacuum or steam) around a fuel rod as model of a steam void. All problems were for comparison calculated also with the programs HELIOS(2D) and MCNP(3D). The dependence of the multiplication factor and the averaged two-group cross section on the immersion depth of the control rod respectively of the height of the steam void were studied. The 3D-calculated two-group cross sections were compared with three conventional approximations: Linear interpolation, interpolation with flux weighting, and homogenization, At the 3D problem of the control rod it was shown that the interpolation with flux weighting is a good approximation. Therefore here a 3D data preparation is not necessary. At the test case of the single control rod, which is surrounded by the void, the three approximation for the two-group cross sections were proved as unsufficient. Therefore a 3D data preparation is necessary. The single fuel-rod cell with void can be considered as the limiting case of a reactor, in which a phase interface has been formed. [German] Standardmaessig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte fuer

  7. Dynamics of water and ions in clays of type montmorillonite by microscopic simulation and quasi-elastic neutron scattering; Dynamique de l'eau et des ions dans des argiles de type montmorillonite par simulation microscopique et diffusion quasi-elastique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Malikova, N

    2005-09-15

    Montmorillonite clays in low hydration states, with Na{sup +} and Cs{sup +} compensating counter ions, are investigated by a combination of microscopic simulation and quasi-elastic neutron scattering to obtain information on the local structure and dynamics of water and ions in the interlayer. At first predictions of simulation into the dynamics of water and ions at elevate temperatures are shown (0 deg C 80 deg C, pertinent for the radioactive waste disposal scenario) Marked difference is observed between the modes of diffusion of the Na{sup +} and C{sup +} counter ions. In water dynamics, a significant step towards bulk water behaviour is seen on transition from the mono- to bilayer states. Secondly, a detailed comparison between simulation and quasi-elastic neutron scattering (Neutron Spin Echo and Time-of-Flight) regarding ambient temperature water dynamics is presented. Overall, the approaches are found to be in good agreement with each other and limitations of each of the methods are clearly shown. (author)

  8. Measurement of the anti reactivity of a control rod of G1, by a slow oscillation method; Mesure de l'antireactivite d'une barre de reglage de G1 pour une methode d'oscillation lente

    Energy Technology Data Exchange (ETDEWEB)

    Breton, D; Leroy, J; Vidal, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    It is possible to determine the effect of the end of a control rod on the reactivity of the pile by measuring the modulation induced in the neutron flux by the slow oscillation of this control rod. The total effect of the control rod can be deduced, given certain hypothesis and corrections, from the experimental curve giving the effect of the end of the rod as a function of its position. This method has the advantage of permitting the measurement of very large anti reactivities, such as p= 10{sup -2} for example, which would not be possible by other kinetic methods. Thus the control rod B{sub 3}, in the low position, brings about a reduction in reactivity equal to 1130 p.c.m. {+-} 30 in the pile charged with 518 fuel elements, on one side only of the slit. We have compared the oscillation method with the classical divergence method, in the fields where the two measurements were possible: a satisfactory agreement was found. We have established that the phase displacement between the oscillation of the rod and the modulation of the flux varied greatly with the position of the rod. This variation cannot be explained on the basis of the dynamic model independent of space; we have attributed it to the influence of spatial harmonics of the flux distribution, and have determined a correction which frees the measurements of this influence. (author) [French] II est possible de determiner l'effet de l'extremite d'une barre de reglage sur la reactivite de la pile, a partir de la mesure de la modulation induite dans le flux neutronique par l'oscillation lente de cette barre de reglage. L'effet total de la barre de reglage peut etre deduit, moyennant certaines hypotheses et certaines corrections, de la courbe experimentale donnant l'effet de l'extremite de la barre en fonction de sa position. Cette methode a l'avantage de rendre possible la mesure d'antireactivites tres grandes, telles que p = 10{sup -2} par exemple, ce qui ne serait pas possible par d'autres methodes

  9. Study of the response of a silicon detector irradiated with 1 MeV neutrons; Etude de la reponse d`un detecteur Si irradie par des neutrons de 1 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Roy, P [Montreal Univ., PQ (Canada). Lab. de Physique Nucleaire

    1994-12-31

    The author studied the response of an n-type silicon detector irradiated with 1 MeV neutrons at fluences ranging from 0.26x10{sup 13} to 11.19x10{sup 13} neutrons/cm{sup 2}. The response of the irradiated detector to {sup 241}Am alpha particles was measured. 13 refs., 7 figs.

  10. Determination of the neutron-induced fission cross section of {sup 242}Pu; Bestimmung des neutroneninduzierten Spaltquerschnitts von {sup 242}Pu

    Energy Technology Data Exchange (ETDEWEB)

    Koegler, Toni Joerg

    2016-04-26

    Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For {sup 242}Pu, current uncertainties are of around 21%. Sensitivity studies show that the total uncertainty has to be reduced to below 5% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of {sup 235}U and {sup 242}Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of {sup 242}Pu relative to {sup 235}U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of {sup 242}Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using results of different neutron transport simulations (Geant 4, MCNP 6 and FLUKA).

  11. The liquid hydrogen cell in the EL3 Saclay reactor; Cellule a hydrogene liquide dans la pile EL3 de Saclay

    Energy Technology Data Exchange (ETDEWEB)

    Jacrot, B; Lacaze, A; Weil, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; [Grenoble-1 Univ., 38 (France)

    1960-07-01

    Description and results in connection with the liquid hydrogen cell, for obtaining slow neutrons, in the EL3. (author) [French] Description et resultats concernant la cellule a hydrogene liquide de EL3 utilisee pour obtenir des neutrons lents. (auteur)

  12. Neutron Depolarization in Superconductors

    Science.gov (United States)

    Zhuchenko, N. K.

    1995-04-01

    The dependences of neutron depolarization on applied magnetic field are deduced along the magnetization hysteresis loop in terms of the Bean model of the critical state. The depolarization in uniaxial superconductors with the reversible magnetization, including uniaxial magnetic superconductors, is also considered. A strong depolarization is expected if the neutrons travel along the vortex lines. On calcule la dépendance en champ magnétique de la dépolarisation des neutrons le long du cycle d'hystérésis en termes du modèle critique de Bean. On considère aussi la dépolarisation dans les supraconducteurs uniaxiaux en fonction de l'aimantation réversible, y compris pour les supraconducteurs magnétiques. On attend une forte dépolarisation si les neutrons se propagent le long des vortex.

  13. A practical contribution to the dosimetry of fast neutrons in radio-protection - determination of the integrated dose in man using the {sup 32}S(n, p){sup 32}P reaction (1963); Contribution pratique a la dosimetrie des neutrons rapides en radioprotection - determination de la dose integree par reaction {sup 32}S(n, p){sup 32}P chez l'homme (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Scheidhauer, J; Chabidon, M [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

    1963-07-01

    The problem of fast neutron dosimetry using activation is studied from the radio-protection point of view. The practical development of methods for analyzing phosphorus 32 produced by the activation of sulphur 32 in human hair by the reaction {sup 32}S(n, p){sup 32}P is described. The sensitivity obtained is 5 rad. A preliminary study was made of the variations in the natural sulphur and phosphorus concentrations. (authors) [French] Le probleme de la dosimetrie des neutrons rapides par activation est etudie sous l'angle de la radioprotectlon. Une mise au point pratique de methodes d'analyae du phosphore 32 induit par activation du soufre 32 des cheveux humains par reaction {sup 32}S(n, p){sup 32}P est exposee. La sensibilite obtenue est de 5 rad. Les variations du soufre et du phosphore naturels ont fait l'objet d'une etude preliminaire. (auteurs)

  14. Determination of a PWR key neutron parameters uncertainties and conformity studies applications; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustible et applications aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2002-07-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and lifetime. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimised. (author)

  15. Determination of a PWR key neutron parameters uncertainties and conformity studies applications; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustible et applications aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2002-07-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and lifetime. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimised. (author)

  16. Neutron Activation for Studying Hydroelectrolytic Disorders in Child Pathology; Application de l'Activation Neutronique a l'Etude des Troubles Hydroelectrolytiques en Pathologie Infantile

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, J. [Hopital Universitaire St-Pierre, Bruxelles (Belgium); Colard, J. [Centre d' Etude de l' Energie Nucleaire, Mol (Belgium); Vis, H. L. [Institut pour la Recherche Scientifique en Afrique Centrale, Bukavu (Congo, The Democratic Republic of the)

    1967-10-15

    The authors describe a method of determining electrolytes (Na, K, CI) and phosphorus in small fragments of muscle taken from child patients by needle biopsy. This method has been used to study muscular disturbances in hydroelectrolytic illnesses of childhood, whether acute, such as dehydration or toxicosis in infants, or chronic, such as malnutrition or marasmus. The results are discussed in the light of parallel data obtained by other methods of investigation. The authors also discuss the possibility of using this method to estimate intra-cellular hydroelectrolytic disorders in child pathology. (author) [French] Les auteurs presentent la description d'une methode permettant le dosage des electrolytes (Na, K, Cl) et du phosphore sur de petits fragments musculaires preleves par ponction-biopsie chez l'enfant. Cette methode a ete appliquee a l'etude des perturbations du milieu musculaire dans des troubles hydroelectrolytiques aigus (deshydratation et toxicose des nourrissons) et chroniques (malnutrition et denutrition) de l'enfance. Les resultats obtenus sont discutes a la lumiere de donnees recueillies parallelement par d'autres methodes d'investigation. Les auteurs discutent egalement la possibilite d'estimer par cette methode les perturbations hydroelectrolytiques intra-cellulaires en pathologie pediatrique. (author)

  17. Assessment of morbidity in carcinoma of the cervix: a comparison of the LENT SOMA scales and the Franco-Italian glossary

    International Nuclear Information System (INIS)

    Davidson, Susan E.; Burns, Meriel P.; Routledge, Jacqueline A.; Swindell, Ric; Bentzen, Soeren M.; West, Catharine M.L.

    2003-01-01

    Background and purpose: To assess the correlation between the LENT (late effects on normal tissue) SOMA (subjective objective management analytic) system and the Franco-Italian glossary scores of late morbidity in cervical cancer patients treated with radiation, and to compare the ability of the scoring systems to detect differences between radiation treatment groups. Materials and methods: The study was retrospective. Patients, invited to take part in the study, had radiotherapy for cervical cancer and had a minimum of 3 years follow-up with no evidence of recurrence. One hundred patients agreed to take part. LENT subjective data were obtained using a patient questionnaire approach in order to complete the scales as published. The LENT objective, management and Franco-Italian glossary scores were obtained by a physician. Correlations between scores and differences between treatment groups were examined using non-parametric tests. Results: The average LENT SOMA scores had a greater resolution than the maximum scores, and using the maximum score alone underestimated treatment morbidity. The Franco-Italian glossary scores correlated strongly with the LENT objective scores (ρ=0.61, P<0.0005), and less strongly with the LENT subjective scores (ρ=0.45, P<0.0005). Significant differences in morbidity between the radiation treatment groups were measured using both the LENT SOMA system and the Franco-Italian glossary. Conclusions: The maximum and average LENT scores should be reported for each subsite. The LENT objective scores correlated well with the scores obtained using the established Franco-Italian glossary, but the LENT system provided additional information on subjective treatment effects. Both systems were able to measure significant differences in morbidity between radiation treatment groups. In conclusion, the LENT SOMA system is a valid and comprehensive approach for scoring the late normal tissue effects of radiotherapy

  18. Adaptação de lente de contato gelatinosa especial para ceratocone Keratoconus special soft contact lens fitting

    Directory of Open Access Journals (Sweden)

    Ester Sakae Yamazaki

    2006-08-01

    Full Text Available OBJETIVO: Relatar a experiência inicial com o uso de lentes de contato gelatinosas especiais para ceratocone. MÉTODOS: Estudo retrospectivo de 80 olhos de 66 pacientes usuários de lentes de contato gelatinosas especial para ceratocone, no Setor de Lentes de Contato da UNIFESP e em clínicas particulares. Os pacientes foram classificados de acordo com o grau de gravidade da doença pela avaliação ceratométrica. Foram coletados os seguintes dados: idade, sexo, diagnóstico, ceratometria, acuidade visual com a lente, equivalente esférico (ES, curvatura da lente e indicação para o seu uso. RESULTADOS: Foram estudados 80 olhos de 66 pacientes usuários de lente gelatinosa para ceratocone. A média de idade foi de 29 anos, sendo 51,5% homens e 48,5% de mulheres. De acordo com os grupos: incipiente: 15,0%, moderado: 53,7%, avançado: 26,3%, grave: 5,0%. A maioria dos olhos estudados (91,25% apresentou acuidade visual melhor que 20/40 com a lente. Foram adaptadas 58% lentes de poder esférico (média de -5,45 dioptrias e 41% lentes com grau esferocilíndrico (variando de -0,50 a -5,00 dioptrias cilíndricas. A curva esférica mais utilizada foi de 7,6 mm (61% dos olhos. As principais razões para a escolha e adaptação desta lente foram devido à intolerância e ao padrão de adaptação insatisfatório com outras lentes. CONCLUSÃO: A lente gelatinosa para ceratocone pode ser usada em casos de difícil adaptação, como uma opção para melhorar o conforto e possibilitar a reabilitação visual em pacientes que não obtiveram alternativas a não ser algum procedimento cirúrgico.PURPOSE: To evaluate the fitting and use of a soft contact lens in keratoconic patients. METHODS: Retrospective study on 80 eyes of 66 patients, fitted with a special soft contact lens for keratoconus, at the Contact Lens Section of UNIFESP and private clinics. Keratoconus was classified according to degrees of disease severity by keratometric pattern. Age, gender

  19. Cálculo del poder de la lente intraocular mediante biometría ultrasónica

    Directory of Open Access Journals (Sweden)

    Yileika Elías García

    Full Text Available Objetivo: caracterizar el comportamiento del cálculo de la lente intraocular mediante biometría ultrasónica. Métodos: se realizó un estudio descriptivo y prospectivo, con un grupo de pacientes atendidos por el Servicio de Catarata del Centro Oftalmológico «Enrique Cabrera», que recibieron tratamiento quirúrgico por catarata con implante de lente intraocular, mediante técnica de Blumenthal. La muestra se conformó con 160 ojos y se estudiaron las variables: sorpresa refractiva, edad, longitud axial y promedio queratométrico según resultado refractivo, poder dióptrico de la lente y componente esférico según edad. Resultados: como resultados más sobresalientes, se obtuvo que el 78,7 % no presentó error en el cálculo de la lente, la mayoría de los pacientes tenían 60 años y más, predominó el rango de longitud axial entre 22 y 24,4 (67,5 %, el promedio queratométrico de 43 a 44,99 (64,3 %, el poder dióptrico del lente de + 20 a + 23 dioptrías (48,2 % y el componente esférico entre 0,00 y +/-1,00 dioptrías (78,8%. Conclusiones: se considera que la biometría ultrasónica resulta adecuada para el cálculo correcto del lente.

  20. Contact lens-associated microbial keratitis Ceratites microbianas relacionadas a lente de contato

    Directory of Open Access Journals (Sweden)

    Aline Silveira Moriyama

    2008-12-01

    Full Text Available PURPOSE: Contact lens-associated microbial keratitis is a severe condition with sight-threatening potential and increasing incidence. Information regarding the etiological agents is essential in guiding management and may vary geographically. The aim of this study was to analyze the microbiological results of corneal scrapings collected from patients presenting with contact lens-associated microbial keratitis. METHODS: Retrospective analysis of the records of all patients who were clinically diagnosed with contact lens-associated microbial keratitis and had corneal scrapings sent to the Laboratory of Ocular Microbiology, UNIFESP/EPM during a 5-year period from January 2002 to December 2007. RESULTS: The etiological agent was identified in 239 patients. Bacterial isolates accounted for 166 (69.46% cases, Acanthamoeba for 95 (39.75% cases and fungi for 4 (1.67% cases. Among the bacterial infections, coagulase-negative Staphylococcus was demonstrated in 74 cases, while Pseudomonas spp was found in 32 patients. All coagulase negative Staphylococcus and Pseudomonas were susceptible to ciprofloxacin and ofloxacin. Resistance to gentamicin was documented in a single case of Pseudomonas. Fourth-generation flouoroquinolone resistance was not observed among Pseudomonas cases. CONCLUSION: Coagulase-negative Staphylococcus was the most frequent isolate, and such data must be considered when determining empiric treatment. Second-generation fluoroquinolones ciprofloxacin and ofloxacin and fourth-generation fluoroquinolones moxifloxacin and gatifloxacin showed a good antibacterial profile and therefore could be good options for initial management.OBJETIVO: A ceratite microbiana associada ao uso de lente de contato é uma condição clínica grave, com risco de perda visual e cuja incidência vem aumentando progressivamente. Os principais agentes etiológicos podem variar geograficamente e informações referentes aos agentes causais são essenciais para

  1. Formulation of the energetic spectral distribution of in pile neutron flux (energies greater than a few hundred electron volts) (1963); Formulation des repartitions spectrales energetiques de flux neutroniques en pile (energies superieures a quelques centaines d'electrons-volts) (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Genthon, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    In the present report an expression is deduced for the spectral distribution of flux of over a few hundred electron volts; it is valid for most cases of thermal neutron reactors. This expression is: {psi}(E) = K [{psi}{sub o}(E) + h {psi}{sub e}(E)] {psi}{sub o}(E) is the so-called 'homogeneous' constituent of the flux; it corresponds approximately to the case of an infinite homogeneous medium; it is of the type: Y(V - E) e{sup (b{radical}}{sup E)}/E + Y(E-V) F E{sup {upsilon}} e{sup -{beta}}{sup E} The parameters V and F are such that {psi}{sub o}(E) and its derivative are continuous at the junction energy V. {psi}{sub e}(E) is the 'heterogeneous' constituent of the flux; it is of the type: E{sup {upsilon}} e{sup -{beta}}{sup E}. The various parameters of {psi}(E) are on the one hand characteristic of the nature of the reactor moderator, and on the other hand determined by a resonant flux measurement and one, or possibly two, measurements using a fast neutron threshold detector. We have been led furthermore to define an expression for the threshold reaction section which is more exact than the conventional transition function. (author) [French] Il est etabli, dans le present rapport, une formulation {psi}(E) des repartitions spectrales de flux au-dessus de quelques centaines d'electron-s volts, valable dans la majeure partie des cas de piles dites a neutrons thermiques. Cette formulation s'exprime: {psi}(E) = K [{psi}{sub o}(E) + h {psi}{sub e}(E)] {psi}{sub o}(E) est la composante dite 'homogene' du flux; elle correspond a peu pres au cas d'un milieu infini homogene; elle est du type: Y(V - E) e{sup (b{radical}}{sup E)}/E + Y(E-V) F E{sup {upsilon}} e{sup -{beta}}{sup E} les parametres V et F sont tels que {psi}{sub o}(E) et sa derivee soient continues a l'energie de jonction V. {psi}{sub e} est la composante dite 'heterogene' du flux ; elle est du type: E{sup {upsilon}} e{sup -{beta}}{sup E}. Les differents parametres de {psi}(E) sont, d'une part

  2. Simulation of complete neutron scattering experiments: from model systems to liquid germanium; Simulation complete d'une experience de diffusion de neutrons: des systemes modeles au germanium liquide

    Energy Technology Data Exchange (ETDEWEB)

    Hugouvieux, V

    2004-11-15

    In this thesis, both theoretical and experimental studies of liquids are done. Neutron scattering enables structural and dynamical properties of liquids to be investigated. On the theoretical side, molecular dynamics simulations are of great interest since they give positions and velocities of the atoms and the forces acting on each of them. They also enable spatial and temporal correlations to be computed and these quantities are also available from neutron scattering experiments. Consequently, the comparison can be made between results from molecular dynamics simulations and from neutron scattering experiments, in order to improve our understanding of the structure and dynamics of liquids. However, since extracting reliable data from a neutron scattering experiment is difficult, we propose to simulate the experiment as a whole, including both instrument and sample, in order to gain understanding and to evaluate the impact of the different parasitic contributions (absorption, multiple scattering associated with elastic and inelastic scattering, instrument resolution). This approach, in which the sample is described by its structure and dynamics as computed from molecular dynamics simulations, is presented and tested on isotropic model systems. Then liquid germanium is investigated by inelastic neutron scattering and both classical and ab initio molecular dynamics simulations. This enables us to simulate the experiment we performed and to evaluate the influence of the contributions from the instrument and from the sample on the detected signal. (author)

  3. A contribution to the development of the modular neutron detector (DEMON): performance evaluation through measurements and simulations; Contribution a la realisation du detecteur modulaire de neutrons (DEMON): etudes des performances par mesures et simulations

    Energy Technology Data Exchange (ETDEWEB)

    Mouatassim, S

    1994-07-01

    The modular neutron detector is dedicated to the study of heavy ion reaction mechanisms. Monte Carlo simulations are performed for the optimization of the NE213 scintillator cell size and the general geometrical setup for the DEMON multidetector of neutrons with a minimum of cross-talk. Tests are performed with various types of photomultiplier tubes and scintillators. Using high energy neutron beams, more than six different reaction processes were identified with pulse shape discrimination by the charge comparison method. Cross sections were estimated. Light yields of charged particles p, d, t and alpha in the NE213 organic scintillator were analyzed using different theoretical approaches, and the intrinsic efficiency of the DEMON`s modules was measured and compared to Monte Carlo calculations. The DEMON experimental filter was simulated and has been associated with the Gemini physical events generator to study the performance of such a multidetector. Thus, the DEMON response for neutron evaporation of excited nuclei and its influence on energy measurement and temperature determination were studied. The same filter was used to simulate pre- and post-fission emission of neutrons for the fission process of the composite {sup 126}Ba system formed in the {sup 19}F + {sup 107}Ag entrance channel. (from author) 70 figs., 99 refs.

  4. Fission gas pressure build-up and fast-breeder economy; Accumulation de la pression des gaz de fission et economie des reacteurs surgenerateurs a neutrons rapides; Nakoplenie davleniya gazov produktov deleniya i ehkonomika reaktorov-razmnozhitelej na bystrykh nejtronakh; Aumento de la presion de los gases de fision y economia de los reactores reproductores rapidos

    Energy Technology Data Exchange (ETDEWEB)

    Engelmann, P [Kernforschungszentrum, Karlsruhe (Germany)

    1962-03-15

    Fuel-cycle costs and doubling time of fast-breeder reactors are strongly affected by the fuel-burn-up obtainable. Use of oxide or carbide fuel offers the possibility of reaching a burn-up of 100 000 MWd/t. In fuel-clad elements, a limiting factor is the fission-gas-pressure build-up. At the high burn-up considered, an appreciable fraction of the fission gases gets into the pores and thus contributes to the pressure on the can. Starting from the known fission-product yields and decay chains, gas production and pressure build-up have been calculated. Three physical models have been employed in calculating the pressure acting upon the can : the gas is contained either in interconnected pores, in separate pores, or in a central hole. The pressure-dependence upon free volume (fuel density) and temperature will be discussed. Cans made of high-strength materials as Ineonel-X and molybdenum could stand the fission-gas pressure at operating temperatures. Unfortunately, these materials have higher absorption cross-sections than stainless steel. Results of a multi-group calculation are given, showing the effect of using these can materials and of decreasing the fuel density on critical mass and breeding ratio in small and medium-size breeders. (author) [French] Le cout du cycle de combustible et la periode de doublement des reacteurs surgenerateurs a neutrons rapides dependent etroitement du taux de combustion. En utilisant pour combustible un oxyde ou un carbure, on peut atteindre un taux de combustion de 100 000 MW j/t. Avec des combustibles gaines, l'accumulation de la pression des gaz de fission est un facteur limitatif. Pour le fort taux de combustion envisage, une fraction non negligeable des gaz de fission penetre dans les interstices et contribue ainsi a la pression sur la gaine. A partir des rendements en produits de fission et des chaines de desintegration connus, l'auteur a calcule la production de gaz et l'accumulation de pression. Pour calculer la pression

  5. The Determination of Uranium in Urine by Delayed Neutron Counting; Dosage de l'Uranium dans l'Urine par Comptage des Neutrons Differes; Opredelenie soderzhaniya urana v moche putem scheta zapazdyvayushchikh nejtronov; Determinacion del Uranio Contenido en la Orina por Recuento de Neutrones Retardados

    Energy Technology Data Exchange (ETDEWEB)

    Brookes, I. R. [Atomic Weapons Research Establishment, Aldermaston, Berks. (United Kingdom)

    1965-10-15

    For this method {sup 235}U is assayed by counting delayed neutrons emitted following the fission of {sup 235}U in the sample with thermal neutrons. The three groups of neutrons of interest have half-lives of 55.72, 22.72 and 6.22 s. A 100-ml sample of urine is evaporated to dryness on a water bath. The residue is transferred with about 4-5 ml of water to a 1-oz polythene bottle which is then heat sealed. The sample bottle is put into a ''rabbit'' and sent through a pneumatic tube system to the HERALD reactor core where it is irradiated in a thermal flux of 3.94 x 10{sup 12} n cm{sup 2}/s. The sample automatically returns to the laboratory after 60 s irradiation where the sample bottle is transferred to the counter. This counter is switched on 25 s after the sample has left the reactor and counts the sample for 1 min. Blank samples consist of urine from persons occupationally unexposed to uranium and the calibration standard is a known amount of {sup 235}U (as natural uranium). The limit of detection is 0.020 pCi of 93% enriched uranium (0.007 of the maximum permissible body- burden) and 0.036 {mu}g of natural uranium per 100 ml of urine. The limit of detection is governed by the magnitude of the blank count. The main component of the blank is the response of the counter to {gamma}-radiation from activation products in irradiated urine. The counting and irradiation cycle takes about 3 Vulgar-Fraction-One-Half min and 50 samples at one time may be evaporated and bottled in the working day. Interference from {sup 239}Pu is likely to be negligible for the purposes of urine analysis. (author) [French] U methode decrite consiste a doser l'uranium-235 d'un echantillon en comptant les neutrons differes emis lors de la fission de {sup 235}U par neutrons thermiques. Les trois groupes de neutrons qui presentent un interet ont des periodes de 55,72, 22, 72 et 6, 22 s. On fait evaporer 100 ml d'urine au bain-marie. Le residu est transvase avec 4 a 5 ml d'eau dans un flacon en

  6. Desempenho visual dos pacientes pseudofácicos com diferentes lentes intraoculares

    Directory of Open Access Journals (Sweden)

    Wilson Takashi Hida

    2013-10-01

    Full Text Available OBJETIVO: Comparar a performance visual dos pacientes submetidos ao implante das lentes intraoculares multifocais difrativas Tecnis® MF ZM900, Acrysof® Restor® SN60D3, Acrysof® SN60WF e Acrysof® SN60AT. MÉTODOS: Estudo prospectivo comparativo, não randomizado, que incluiu 142 olhos de 71 pacientes com catarata, provenientes do ambulatório de oftalmologia do HC-FMUSP. A avaliação oftalmológica contou com medida da acuidade visual para longa, intermediária e curta distância, sem correção e com a melhor correção óptica, teste de sensibilidade ao contraste, pupilometria e análise de frente de onda por meio do aberrômetro. Todos os exames foram realizados com seis meses de pós-operatório. RESULTADOS: A média de idade dos pacientes foi de 60,7±6,6 anos no grupo Tecnis, 63,1±4,4 anos no grupo Restor e 63,7±4,2 anos no grupo monofocal (SN60AT no olho contralateral SN60WF. A acuidade visual para perto não corrigida e corrigida para longe foi estatisticamente superior nos grupos multifocal Restor e multifocal Tecnis em comparação ao grupo monofocal SN60AT/SN60WF (p<0,001. Não houve diferença estatística entre os grupos na comparação da acuidade visual para longe (p=0,56. A sensibilidade ao contraste fotópica monocular foi estatisticamente inferior nos grupos Restor e Tecnis (p<0,001. A SN60AT apresentou maior aberração esférica comparada a todas as outras lentes (p<0,001. A Tecnis se mostrou com menores valores médios de aberrações esféricas na comparação com a Restor (p<0.001. CONCLUSÃO: A Restor e Tecnis apresentaram melhor acuidade visual para perto do que o grupo monofocal SN60AT/SN60WF. Todas as lentes intraoculares promoveram boa visão para longe. O grupo da Tecnis apresentou melhor sensibilidade de contraste, menos aberrações ópticas e melhor visão intermediária que o grupo Restor.

  7. Lentes fácicas de câmara anterior

    Directory of Open Access Journals (Sweden)

    Walton Nosé

    2012-08-01

    Full Text Available Os implantes em olhos fácicos apresentam-se como uma opção para a correção de altas ametropias. De acordo com sua localização podem ser classificados como de câmara anterior ou posterior, sendo que os primeiros subdividem-se em fixação iriana ou de suporte angular. Além da correção da miopia, as lentes de fixação iriana apresentam modelos para hipermétropes e astigmatas. Várias modificações no desenho das lentes foram propostas nas últimas décadas com a finalidade de reduzir complicações tardias, como a perda endotelial progressiva. Cuidados no intraoperatório devem ser tomados de forma a diminuir a perda endotelial aguda relacionada ao trauma. Avanços nos métodos de triagem pré-operatória também melhoraram a segurança do procedimento. A estimativa do poder dióptrico é baseada nos cálculos de Van der Heijde, sendo dependente da profundidade de câmara anterior, do equivalente esférico da refração e da média ceratométrica. Resultados a longo prazo demonstram a eficácia, previsibilidade e segurança do procedimento. Dependendo do modelo, além da possibilidade de perda endotelial, outras possíveis complicações incluem: irite, dispersão pigmentar, atrofia de íris, ovalização pupilar, rotação, descentração ou deslocamento da lente, hipertensão ocular e bloqueio pupilar. Modelos dobráveis atualmente disponíveis vêm apresentado resultados bastante promissores com redução da taxa de complicações.

  8. Study of the variation with the energy of the fission cross-sections of {sup 233}U, {sup 235}U, {sup 239}Pu for the fast neutrons; Etude de la variation avec l'energie des sections efficaces de fission de {sup 233}U, {sup 235}U, {sup 239}Pu pour les neutrons rapides

    Energy Technology Data Exchange (ETDEWEB)

    Szteinsznaider, D; Naggiar, V; Netter, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    This measurements have been done while taking the value of the fission cross-sections of {sup 238}U as reference. The neutrons are produced by the reaction {sup 7}Li(p,n) in the Van de Graaff generator of Saclay. The explored domain spreads from some tenths to 2000 keV. We find: for {sup 239}Pu: {sigma}{sub f} = 2,04 {+-} 0,12 barns, cross-section constant between 150 and 2000 keV, for {sup 235}U: {sigma}{sub f} = 1,15 {+-} 0,15 barns, cross-section constant between 700 and 1000 keV, for {sup 233}U: {sigma}{sub f} = 1,92 {+-} 0,25 barns, for neutrons of 850 keV. (authors) [French] Ces mesures ont ete effectuees en prenant la valeur de la section efficace de fission de {sup 238}U comme reference. Les neutrons sont produits par la reaction {sup 7}Li(p,n) au generateur Van de Graaff de Saclay. Le domaine explore s'etend de quelques dizaines de kev a 2000 kev. Nous trouvons: pour {sup 239}Pu: {sigma}{sub f} = 2,04 {+-} 0,12 barns, section efficace constante entre 150 et 2000 kev. pour {sup 235}U: {sigma}{sub f} = 1,15 {+-} 0,15 barns, section efficace constante entre 700 et 1000 kev. pour {sup 233}U: {sigma}{sub f} = 1,92 {+-} 0,25 barns, pour des neutrons de 850 kev. (auteurs)

  9. Neutrons produced in thick targets of Be, {sup 238}U and C by means of 100 MeV/A deutons and 95 MeV/A {sup 36}Ar. Dose rate due to uranium activation; Neutrons produits dans des cibles epaisses de Be et {sup 238}U par des deutons de 100 MeV/A et de C par des {sup 36}Ar de 95 MeV/A. Debit de dose resultant de l`activation de l`uranium

    Energy Technology Data Exchange (ETDEWEB)

    Pauwels, N.; Proust, J.; Clapier, F.; Gara, P.; Mirea, M.; Obert, J. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Granier, T.; Belier, G.; Ethvignot, T. [CEA, Service de Physique Nucleaire, 91 - Bruyeres-le-Chatel (France)

    1998-12-01

    This study presents the results of two experiments, one lead in GANIL facilities and the other at Saturn National Laboratory. Both aim at neutron production. The energy spectra of neutrons are given for different targets and ion beams. The efficiency of deuteron beams in term of neutron production is reinforced. The neutron flux appears to be higher in any forward direction when using a beryllium target. In order to optimize shielding the neutron attenuation length in 15 cm thick concrete slab is revalued. (A.C.) 13 refs.

  10. Delayed Neutrons and Photoneutrons from Fission Products; Neutrons Retardes et Photoneutrons Emis par des Produits de Fission; 0417 0410 041f 0410 0417 0414 042b 0412 0410 042e 0429 0418 0415 041d 0415 0419 0422 0420 041e 041d 042b 0418 0424 041e 0422 041e 041d 0415 0419 0422 0420 041e 041d 042b 041f 0420 041e 0414 0423 041a 0422 041e 0412 0414 0415 041b 0415 041d 0418 042f ; Neutrones Retardados y Fotoneutrones de los Productos de Fision

    Energy Technology Data Exchange (ETDEWEB)

    Amiel, S. [Soreq Nuclear Research Centre, Atomic Energy Commission, Yavne (Israel)

    1965-07-15

    photoneutron emission after fission represents the composite decay of the corresponding gamma- ray-emifting nuclides in the mixture of fission product chains. The gross photoneutron decay curves from both D{sub 2}O and beryllium have been resolved into nine groups with half-lives ranging from a few seconds to {approx}13 d. Each of these groups represents a complex composite of nuclides. Derailed information on the constituents of these groups is important for reactors in which fission products fractionation may take place and affect relative group abundances. Such information exists only for the longer-lived fission products whose properties and yields are well known, and where experimental results are in agreement with calculated values based on fission mass and charge distributions and decay schemes. The characterization of individual nuclides in the more complex short-lived groups is indeed a formidable task, but this information is of considerable practical and theoretical importance, and warrants further extensive study. (author) [French] Neutrons retardes: La plupart des etudes sur les neutrons retardes emis par des produits de fission impliquent l'analyse du comportement cinetique des systemes qui subissent une reaction de fission en chaine, l'analyse de la desintegration totale des neutrons (se resolvant en six groupes avec des periodes d'environ 0,2, 0,5, 2, 6, 22 et 55 s) et cettaines mesures des spectres de neutrons - ayant une energie comprise entre 0,1 et 1.2 MeV, avec des pics dans la gamme de 0,2 a 0,5 MeV. Des separations rapides des halogenes produits par fission ont mis en evidence la presence de sept isotopes ({sup 87,88,89,90}Br et {sup 137,138,139}I) et le dosage des gaz rares a permis d'identifier Kr (1,5 s) et Rb (6 s), comme precurseurs de neutrons retardes. Environ 80% des rendements totaux en neutrons retardes doivent etre attribues aux precurseurs ainsi identifies. A la suite de recherches theoriques, quelques dizaines de ces nucleides ont ete

  11. Lentes progressivas: análise dos campos intermediário e de perto por deflexometria

    Directory of Open Access Journals (Sweden)

    Celso Marcelo Cunha

    2013-02-01

    Full Text Available OBJETIVO: Avaliar por deflexometria as diferentes regiões das lentes progressivas e determinar as áreas dos campos de visão intermediário e de perto. MÉTODOS: Foram incluídas vinte e duas lentes progressivas com poder +1,00 DE para longe e duas adições diferentes (adição 1,00 e 2,00, 11 de cada. Mediram-se as áreas dos campos intermediário e de perto entre as isoastigmáticas de 0,5 DC. RESULTADOS: Encontraram-se diferenças significativas entre as áreas dos campos intermediário e de perto das lentes estudadas. Entre a área do campo intermediário e a adição observou-se correlação inversa; entre a área do campo intermediário e a extensão vertical do corredor encontrou-se correlação direta. CONCLUSÃO: Com esses dados permitem-se recomendar as lentes de acordo com o campo de maior necessidade visual de cada usuário.

  12. Estrutura de populações de Rhodnius neglectus Lent e Psammolestes tertius Lent & Jurberg (Hemiptera, Reduviidae em ninhos de pássaros (Furnariidae presentes na palmeira Mauritia flexuosa no Distrito Federal, Brasil Population structure of Rhodnius neglectus Lent and Psammolestes tertius Lent & Jurberg (Hemiptera, Reduviidae in bird nests (Furnariidae on Mauritia flexuosa palm trees in Federal District of Brazil

    Directory of Open Access Journals (Sweden)

    Rodrigo Gurgel-Gonçalves

    2007-03-01

    Full Text Available Rhodnius neglectus Lent, 1954 {Rn}e Psammolestes tertius Lent & Jurberg, 1965 {Pt} são triatomíneos que ocorrem em ninhos de aves, principalmente da família Furnariidae. O ciclo biológico dessas espécies é conhecido em condições de laboratório, sendo poucos estudos em ecótopos silvestres. Para analisar a infestação e estrutura de populações de Rn e Pt em ninhos de aves presentes na palmeira Mauritia flexuosa Linnaeus, em duas estações climáticas do Brasil Central, foram amostradas 41 palmeiras com evidências de nidificação de Phacellodomus ruber Vieillot, 1817 (22 na estação chuvosa e 19 na estação seca em quatro áreas do Distrito Federal. Os insetos foram capturados usando-se coleta manual na copa da palmeira, identificados morfologicamente, separados por sexo e estádio ninfal. Fezes e glândulas salivares de Rn foram examinadas para verificar infecção por Trypanosoma cruzi Chagas, 1909 e/ou T. rangeli Tejera, 1920. Trinta e cinco palmeiras com ninhos de P. ruber estavam infestadas por Rn (85% e 22 por Pt (53%. 442 indivíduos foram coletados na estação seca (200 Rn e 242 Pt e 267 na estação chuvosa (136 Rn e 131 Pt. O único fator relacionado significativamente com a densidade de triatomíneos nas palmeiras foi a área. A estrutura etária das populações mostrou: a maior abundância de adultos nas populações de Pt, b maior abundância de machos em ambas as espécies e c presença de fêmeas ovipondo em ambas as estações. Nenhum dos 177 triatomíneos examinados estava infectado por T. cruzi ou T. rangeli. A estrutura etária das populações de Rn e Pt não diferiu significativamente entre as estações amostradas, indicando ausência de marcada sazonalidade para essas espécies.Rhodnius neglectus Lent, 1954 {Rn}and Psammolestes tertius Lent & Jurberg, 1965 {Pt} are triatomines that occur in bird nests, mainly furnarid nests. Their biological cycles are known in laboratory conditions and few studies were

  13. Luz y gravedad (Reflexiones geométricas sobre cáusticas y lentes gravitacionales

    Directory of Open Access Journals (Sweden)

    Elena Ortiz García

    2011-04-01

    Full Text Available Cuando los rayos de luz iluminan una taza de café en una tardesoleada, podemos observar la curva que más brilla sobre la superficie del líquido. Quizá sea ésta una oportunidad para plantearse el siguiente experimento mental: ¿cómo juegan los rayos de luz al reflejarse en diferentes “tazas” geométricas? Esta comunicación pretende proseguir esta discusión con algunas consideraciones sencillas que nos sitúen ante el fenómeno de las lentes gravitacionales, allí donde los efectos de la gravedad afectan, incluso, a la manera de propagarse de la luz, mostrando un sistema dinámico idealizado que resulta, a la vez, sencilloy (matemáticamente caótico.

  14. CURED I - LENT. Late effects of cancer treatment on normal tissues

    International Nuclear Information System (INIS)

    Rubin, P.; Okunieff, P.; Constine, L.S.; Rochester Univ. School of Medicine and Dentistry, Rochester, NY; Marks, L.B.

    2008-01-01

    The search for the most favorable therapeutic ratio - at which ablation of cancer is achieved while normal tissues are conserved - has been modern radiation oncology's equivalent of the quest for the Holy Grail. Our awareness of the late effects of radiation grew during the past century as new modalities were introduced. Heightened normal tissue reactions accompanied the higher rates of cancer ablation achieved by escalation of radiation doses, accelerated fractionated radiotherapy, and aggressive concurrent chemotherapy and radiation regimens. This volume is based on the LENT V NCI-sponsored meeting held in May 2004 and the CURED I conference held in 2006. Written by experts in the field, it addresses a number of critical topics relating to late effects, such as mechanisms of injury, the role of screening, options for interventions, second malignancies, and prevention. It is hoped that it will assist the reader in understanding how to prevent and treat the long-term side-effects of irradiation. (orig.)

  15. Lente intra-ocular multifocal difrativa apodizada: resultados Diffractive apodized multifocal intraocular lens: results

    Directory of Open Access Journals (Sweden)

    Virgilio Centurion

    2007-12-01

    Full Text Available OBJETIVO: Mostrar os resultados visuais e refracionais com lente intra-ocular multifocal difrativa apodizada. MÉTODOS: Estudo de 100 olhos de 50 pacientes com catarata, submetidos à facoemulsificação com implante bilateral de lente intra-ocular (LIO multifocal difrativa apodizada. Foi avaliada a acuidade visual binocular sem e com correção para longe e perto, a previsibilidade refracional e a freqüência de uso de óculos. RESULTADOS: A acuidade visual sem correção para longe foi de e " 20/30 em 97,56% dos olhos operados e e" J2 em 100%, sendo que 82% dos pacientes nunca usam óculos e 16% usam de forma esporádica. CONCLUSÃO: A LIO multifocal difrativa apodizada mostrou ser uma opção previsível, reproduzível e segura na correção dos vícios de refração para longe e perto durante a cirurgia da catarata, permitindo elevado índice de independência ao uso de óculos.OBJECTIVE: To show visual and refraction results using multifocal diffractive apodized intraocular lens. METHODS: The study of 100 eyes of 50 patients with cataract, submitted to phacoemulsification with bilateral implant of multifocal diffractive apodized intraocular lens (IOL. Binocular visual acuity was evaluated with and without correction for near and distance, and refraction previsibility and frequency of wearing glasses. RESULTS: Visual acuity without correction for distance was e" 20/30 in 97.56% of eyes operated on and e" J2 in 100%, of these 82% of patients never wear glasses and 16% wear glasses sporadically. CONCLUSION: Multifocal diffractive apodized IOL proved to be a foreseeable option, reproducible and safe in the correction of refraction errors for distance and near during cataract surgery, enabling a high rate of independence from the use of glasses.

  16. Neutron stars

    International Nuclear Information System (INIS)

    Irvine, J.M.

    1978-01-01

    The subject is covered in chapters entitled: introduction (resume of stellar evolution, gross characteristics of neutron stars); pulsars (pulsar characteristics, pulsars as neutron stars); neutron star temperatures (neutron star cooling, superfluidity and superconductivity in neutron stars); the exterior of neutron stars (the magnetosphere, the neutron star 'atmosphere', pulses); neutron star structure; neutron star equations of state. (U.K.)

  17. Analyze of phase's mechanical behaviour of a multiphase polycrystalline alloy by X-ray and neutron diffraction; Analyse du comportement mecanique des constituants d'un alliage polycristallin multiphase par diffraction des rayons X et neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Dakhlaoui, R

    2006-12-15

    The aim of this work is to propose a methodology using diffraction methods and theoretical approaches of self-consistent modeling in order to analyze and better understand the mechanical behavior of each phase of hot-rolled duplex stainless steel. The purpose of the experimental study is to characterize the local mechanical behavior of phases under uniaxial loading. X-ray and neutron diffraction which enable to measure strains in each phase separately were used in this aim. Austenitic and ferritic phase stresses are determined by X-ray diffraction during tensile tests. Evolution of the elastic strains in each phase was measured by neutron diffraction using 'time-of-flight' method during tensile and compression tests. Elastic constants were given using the self-consistent model for a purely elastic deformation. To reproduce the mechanical behaviour of the studied material, self-consistent polycrystalline micro-mechanical model for elastoplastic deformation has been adapted and confronted to experimental results. Crystallographic texture and initial residual stresses were considered in this analysis. Critical shear stresses and hardening parameters of each phase of the studied duplex steel have been identified. Results of this study showed that the austenitic phase represents the softest and the most hardenable phase. Taking into account in calculations the initial residual stresses in the non deformed sample leads to the conclusion that the initial stresses modify considerably the values of phase's yield stresses. Good agreement has been noted comparing results obtained by XRD to those obtained by neutron diffraction. The problem of relaxation of normal stresses in the analysed layer by X-rays was analysed and discussed. Using XRD and self-consistent modelling, the effect of the chemical composition of the duplex stainless steel and the influence of ageing at 400 C degrees for 1000 h on the mechanical behaviour of austenitic and ferritic phases have

  18. Medindo o poder refrativo de lentes de contato gelatinosas personalizadas Measuring the refractive power of customized soft contact lenses

    Directory of Open Access Journals (Sweden)

    Luis Alberto Vieira de Carvalho

    2007-02-01

    Full Text Available OBJETIVO: Lentes de contato gelatinosas com curvas-base esféricas têm sido usadas há anos. O cálculo do poder refrativo de lentes deste tipo é fácil, bastando utilizarmos a equação do fabricante de lentes para lentes espessas. No entanto, para projetos de lentes de contato personalizadas, não há ainda métodos confiáveis para medida das aberrações ópticas de ordem mais alta. Esse trabalho foi desenvolvido no laboratório do Centro de Ciências da Visão (Center for Visual Science da Universidade de Rochester, Nova York, com aparelho óptico que permite realizar medidas precisas de aberrações de ordem baixa e alta de lentes de contato gelatinosas personalizadas. Este é um passo essencial na verificação e obtenção de lentes de contato personalizadas de qualidade, e o instrumento desenvolvido na Universidade de Rochester permite verificar a qualidade de fabricação destas lentes. MÉTODOS: Um aparelho óptico de bancada foi montado em laboratório. Este aparelho consiste de uma célula úmida onde as lentes de contato são depositadas. Consiste também de uma série de lentes e espelhos e um sensor de frente-de-onda de Hartmann-Shack. As lentes de contato personalizadas utilizadas neste projeto foram fabricadas pela empresa Bausch & Lomb. Das dezenas de lentes de contato mensuradas no aparelho, restringimos aqui a apresentar os resultados de uma lente personalizada para ceratocone. RESULTADOS: O erro quadrático médio (EQM do instrumento foi de 0,04 micrômetro, sendo que o EQM das aberrações induzidas na lente está entre 4 e 6 micrômetros, ou seja, a precisão do aparelho está em torno de 1%. Este valor é mais do que suficiente para medidas precisas destes tipos de lentes de contato, algo até então inviável utilizando-se os sensores ou aparelhos convencionais de aberrometria. CONCLUSÃO: Com o instrumento desenvolvido neste trabalho foi possível realizar medidas precisas de aberrações de alta ordem. Esta

  19. Impact des TIC sur la motivation et la réussite des étudiants Enquête à l’Université d’Abomey-Calavi au Bénin

    Directory of Open Access Journals (Sweden)

    Serge Armel Attenoukon

    2013-01-01

    Full Text Available Cette étude tente d’explorer, dans un contexte de forts taux d’échec des apprenants des facultés classiques à l’Université d’Abomey-Calavi (Bénin, les perceptions des étudiants et des enseignants quant à l’impact des TIC tant sur la motivation que sur la réussite des apprenants. L’étude est tout particulièrement importante dans notre contexte où les TIC sont de plus en plus utilisées en pédagogie universitaire et où les étudiants y recourent dans leur pratique plus que les formateurs dans la leur. Au total, 171 questionnaires ont été remplis par les étudiants et les enseignants; 11 apprenants et 6 enseignants ont passé des entrevues semi-dirigées. Des analyses statistiques et qualitatives de ces données révèlent que les étudiants et les enseignants soulignent, dans leur majorité, le potentiel motivationnel des TIC, notamment de l’ordinateur et d’Internet, pour l’apprentissage. Elles ont cependant montré une position plus mitigée entre les étudiants et les enseignants en ce qui concerne l’effet positif des TIC pour la réussite des études.

  20. Determination of elements in citrus leaves; Dosage des elements dans les feuilles de citrus

    Energy Technology Data Exchange (ETDEWEB)

    Masozera, C.; Compernolle, G. van; Brandstetr, J.; Krivanek, M. [Centre nucléaire TRICO, Kinshasa (Congo, The Democratic Republic of the); Université Lovanium, Kinshasa (Congo, The Democratic Republic of the)

    1970-01-15

    facteurs, entre autres l'épuisement du sol ou l'application d'engrais dont la formule n’ est pas appropriée. L' appauvrissement chimique du sol est lié à deux causes: d' une part au phénomène de lessivage, d’entrainement de bases, d’autre part aux «exportations» d'éléments fertilisants sous forme de récoltes pendant des années sans contrepartie. Ces pertes sont particulièrement néfastes si la roche-mère ne contient pas suffisamment de réserves minérales susceptibles de les compenser par altération lente. Cet appauvrissement est mis en évidence par les analyses du sol et par les analyses foliaires. Les auteurs ont essayé de doser les éléments suivants: Mn, P, Cu, Cl, et K (ces derniers pour trois échantillons seulement) pour le Citrus. Après prélèvement ils ont traité les échantillons selon la méthode utilisée par Bransolten (Rapport de recherche TRICO n° 15/1968), séchage pendant au moins 12 h à 105°C et broyage des feuilles en poudre, puis ils ont procédé au dosage. Le dosage du Mn et du Cl est très facile, tout comme celui du Cu. Ce dernier est dosé par activation aux neutrons lents pour éviter la formation de Zn. Quant au phosphore, il a été dosé en mesurant le rayonnement ß émis par les radioéléments. Ici, des précautions particulières doivent être prises pour avoir la même couche pour les échantillons et les étalons vu que le rayonnement ß est absorbé par ces couches. Le K et le Na ont été dosés en utilisant les neutrons thermiques pour l'activation et un détecteur au Ge(Li) pour les mesures des spectres y. La grande résolution du détecteur a permis de doser ces deux éléments sans séparation. (author)

  1. Domain decomposition methods for the mixed dual formulation of the critical neutron diffusion problem; Methodes de decomposition de domaine pour la formulation mixte duale du probleme critique de la diffusion des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Guerin, P

    2007-12-15

    The neutronic simulation of a nuclear reactor core is performed using the neutron transport equation, and leads to an eigenvalue problem in the steady-state case. Among the deterministic resolution methods, diffusion approximation is often used. For this problem, the MINOS solver based on a mixed dual finite element method has shown his efficiency. In order to take advantage of parallel computers, and to reduce the computing time and the local memory requirement, we propose in this dissertation two domain decomposition methods for the resolution of the mixed dual form of the eigenvalue neutron diffusion problem. The first approach is a component mode synthesis method on overlapping sub-domains. Several Eigenmodes solutions of a local problem solved by MINOS on each sub-domain are taken as basis functions used for the resolution of the global problem on the whole domain. The second approach is a modified iterative Schwarz algorithm based on non-overlapping domain decomposition with Robin interface conditions. At each iteration, the problem is solved on each sub domain by MINOS with the interface conditions deduced from the solutions on the adjacent sub-domains at the previous iteration. The iterations allow the simultaneous convergence of the domain decomposition and the eigenvalue problem. We demonstrate the accuracy and the efficiency in parallel of these two methods with numerical results for the diffusion model on realistic 2- and 3-dimensional cores. (author)

  2. Study of some properties of 's' neutron resonance parameters for target nuclei I = 1/2 and I = 3/2 in function of spin value J = I + 1/2 in the energy range 1 {yields} 5000 eV; Etude de quelques proprietes des parametres de resonances des neutrons ''s'' pour des noyaux cibles I = 1/2 et I = 3/2 en fonction de la valeur du spin J = I + 1/2 dans le domaine d'energie 1 eV {yields} 5000 eV

    Energy Technology Data Exchange (ETDEWEB)

    Julien, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-05-15

    Different kinds of experiments and analysis methods allowing to achieve neutron resonances parameters in the low energy range (1 eV {yields} 5000 eV) are described. A great deal of effort to improve experimental conditions and data processing in order to know the spin value J = I {+-} 1/2 has been spent. The time of flight method was used. A few target nuclei I = 3/2 and 1 = 1/2 have been studied. For I = 3/2 (Ga, As, 3r, Au) we find S{sub o} J = 2 {approx_equal} 2 S{sub o} J = 1 and S{sub o} J = 1 {approx_equal} S{sub o} J = 0 for I = 1/2 (Tm, Pt) but {sup 77}Se. Fluctuations of the total radiative width {gamma}{sub {gamma}} depend on the spin value I = I {+-} 1/2 when E1 transition, are enhanced for one of the both spin states. The magnitude of these fluctuations can be explained of the strength of E1 transitions (E{sub {gamma}} {approx} 7 MeV) is supposed to be proportional to E{sup 5}{sub {gamma}} instead of E{sup 3}{sub {gamma}}. The distribution of levels spacings against spin value J are considered and are compared to theoretical predictions. (author) [French] On decrit les differentes methodes d'analyse permettant d'obtenir les parametres des resonances de neutron dans le domaine d'energie 1 eV {yields} 5000 eV. Un effort particulier a ete fait pour connaitre la valeur du spin J = I {+-} 1/2. Les types d'experience et les analyses des donnees, developpes et ameliores pour determiner J sont decrits. Les resultats obtenus ont permis l'etude de differentes proprietes en fonction du spin J. On trouve: S{sub o} J 2 {approx_equal} 2 S{sub o} J = 1 pour les noyaux I = 3/2 etudies (Ga, As, Br, Au) et S{sub o} J = 1 {approx_equal} S{sub o} J = 0 Pour le Tm et {sup 195}Pt de spin I = 1/2. On constate que les largeurs radiatives totales {gamma}{sub {gamma}} fluctuent si des transitions E1 aux premiers etats excites sont favorisees. Ces fluctuations peuvent etre expliquees si on suppose que les intensites de ces transitions sont proportionnelles a E{sup 5}{sub {gamma

  3. Relative Biological Effectiveness of 14-MeV Fast Neutrons to Co{sup 60} Gamma-Rays in Einkorn Wheat; Efficacite Biologique Relative des Neutrons Rapides de 14 MeV par Rapport aux Rayons Gamma de {sup 60}Co sur l'Engrain; Otnositel'naya biologicheskaya ehffektivnost' bystrykh nejtronov s ehnergiej 14 MeV i gamma-luchej CO{sup 60} pri ikh dejstvii na pshenitsu odnozernyanku; EBR de los Neutrones Rapidos de 14 MeV y de los Rayos Gamma del {sup 60}Co en el Trigo Escanda Menor

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, T. [National Institute of Genetics, Misima (Japan)

    1964-05-15

    somatic mutation. (author) [French] L' auteur a etudie l'EBR des neutrons de 14 MeV par rapport aux rayons gamma de {sup 60}Co en appliquant a l'engrain la methode des loci specifiques. Il a utilise pour cette etude des semences Fi resultant du croisement entre l'espece originale et un mutant chlorina (le mutant chlorina e ta it le produit d'une mutation recessive induite par les rayons X ; depuis le stade de plantule jusqu'a sa maturite, le m utant a conserve une couleur vert c la ir uniforme ainsi qu'un taux de survie et une fe rtilite relativement eleves). Les plantes Fi avaient une couleur verte et une croissance normales. Des semences dormantes de F{sub 1} ont e te irradiees avec 0,5 , 1,0 et 1,4 krad de neutrons rapides et avec 4,3 , 8,6 et 12,9 krad de rayons gamma. Sous l'effet des deux types de rayonnements, il s'est produit des mutations de vert normal dominant en chlorina, sous forme de bandes longitudinales. Sur les feuilles et les tiges des heterozygotes X{sub 1}. Environ 80% des semences ont germe dans le lot temoin ainsi que dans les deux lots ayant recu la plus faible dose de neutrons et de rayons gamma; les taux de germination ont diminue a mesure qu'augmentaient les doses de neutrons et de rayons gamma. En outre, on a observe un phenomene analogue au debut de lacroissance de la plantule, qui etait progressivement inhibee a mesure qu'augmentait la dose de rayonnement. Les resultats obtenus montrent que l'irradiation par les neutrons est environ 13 fois plus efficace que celle par les rayons gamma. Le taux de survie des semences non irradiees du lo t temoin a e te de 90% environ; 60 a 80% des plantules ont survecu aux doses de 0,5 et 1,0 krad de neutrons; toutes les plantilles irradiees par les rayons gamma ont survecu. En revanche, 4% seulement des plantules ont survecu a 1,4 krad de neutrons. L'auteur n 'a pas observe de mutations chez les plantes du lo t temoin; le nombre des plantes a talles rayees a augmente en meme temps que les doses des deux types

  4. Cross-Sections for Low-Energy Neutron-Induced Fission; Sections Efficaces de Fission pour des Neutrons de Faible Energie; 0421 0415 0427 0415 041d 0418 042f 0414 0415 041b 0415 041d 0418 042f , 0412 042b 0417 0412 0410 041d 041d 041e 0413 041e 041d 0415 0419 0422 0420 041e 041d 0410 041c 0418 041d 0418 0417 K 041e 0419 042d 041d 0415 0420 0413 0418 0418 ; Secciones Eficaces en la Fision Inducida por Neutrones de Baja Energia

    Energy Technology Data Exchange (ETDEWEB)

    Rae, E. R. [Atomic Energy Research Establishment, Harwell, Didcot, Berks. (United Kingdom)

    1965-07-15

    The cross-sections of the heavy nuclei for neutron-induced fission are of fundamental importance to the technology of nuclear energy production. The manner in which these cross-sections vary with the neutron energy and with the mass and charge of the target nuclei also provides much information on the structure of heavy nuclei. In the case of a thermally fissile target nucleus, as the neutron energy is increased from thermal the cross-section first exhibits an inverse velocity dependence, followed by a region in which sharp resonance peaks appear, and finally a continuum region where the cross-section exhibits relatively smooth steps and breaks. All these phenomena can be explained in principle, but certain features of the data have proved very difficult to explain quantitatively. Recent cross-section measurements, stimulated by the needs of reactor technology, have concentrated on improving the energy resolution and accuracy of the data on fuel materials, and this has led to a more detailed study of the resonance region, which is of considerable interest for reactor Doppler effect calculations. More accurate measurements at rather higher energies have established the existence of appreciable fission cross-sections below the so-called fission threshold in certain cases. Careful measurements of this nature have in turn stimulated interest in the interpretation of the cross-sections in terms of nuclear models on a firm quantitative basis. This paper outlines the main features of neutron-induced-fission cross-sections and their interpretation. Some emphasis is placed on recent improvements in the quality of the measurements and in attempts at quantitative interpretation of certain aspects of the data. (author) [French] Les sections efficaces de fission des noyaux lourds ont une importance essentielle pour la technologie de la production d'energie d'origine nucleaire. La maniere dont ces sections efficaces varient Selon l'energie des neutrons et Selon la masse et la

  5. Conservative treatment of soft tissue sarcomas of the extremities. Functional evaluation with LENT-SOMA scales and the Enneking score

    International Nuclear Information System (INIS)

    Tawfiq, N.; Lagarde, P.; Thomas, L.; Kantor, G.; Stockle, E.; Bui, B.N.

    2000-01-01

    Objective. - The aim of this prospective study is the feasibility of late effects assessment by LENT-SOMA scales after conservative treatment of soft tissue sarcomas of the extremities and a comparison with the functional evaluation by the Enneking score. Patients and methods. - During the systematic follow-up consultations, a series of 32 consecutive patients was evaluated in terms of late effects by LENT SOMA scales and functional results by the Enneking score. The median time after treatment was 65 months. The treatment consisted of conservative surgery (all cases) followed by radiation therapy (29 cases), often combined with adjuvant therapy (12 concomitant radio-chemotherapy association cases out of 14). The assessment of the toxicity was retrospective for acute effects and prospective for the following late tissue damage: skin/subcutaneous tissues, muscles/soft tissues and peripheral nerves. Results. -According to the Enneking score, the global score for the overall series was high (24/30) despite four the scores zero for the psychological acceptance. According to LENT SOMA scales, a low rate of severe sequelae (grade 3-4) was observed. The occurrence of high-grade sequelae and their functional consequences were not correlated with quality of exeresis, dose of radiotherapy or use of concomitant chemotherapy. A complementarity was observed between certain factors of the Enneking score and some criteria of the LENTSOMA scales, especially of muscles/soft tissues. Conclusion. -The good quality of functional results was confirmed by the two mean scoring systems for late normal tissue damage. The routine use of LENT-SOMA seems to be more time consuming than the Enneking score (mean time of scoring: 1 3 versus five minutes). The LENT-SOMA scales are aimed at a detailed description of late toxicity and sequelae while the Enneking score provides a more global evaluation, including the psychological acceptance of treatment. The late effects assessment by the LENT

  6. Caractéristiques musculaires des bovins sélectionnés pour la croissance musculaire

    OpenAIRE

    Hocquette, Jean-François; Cassar-Malek, Isabelle; Jurie, Catherine; Bauchart, Dominique; Picard, Brigitte; Renand, Gilles

    2015-01-01

    La sélection génétique en faveur du potentiel de croissance musculaire aux dépens de l’engraissement des carcasses peut affecter les caractéristiques des muscles, et de ce fait modifier la qualité de la viande. Une expérience a donc été conduite avec deux lots extrêmes de 6 taurillons parmi un effectif total de 64 taurillons Charolais classés selon leur potentiel génétique de croissance musculaire. Différentes caractéristiques de deux muscles [Rectus abdominis (RA, lent oxydatif) et Semitendi...

  7. Structure of simple liquids; Structure des liquides simples

    Energy Technology Data Exchange (ETDEWEB)

    Blain, J F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-07-01

    The results obtained by application to argon and sodium of the two important methods of studying the structure of liquids: scattering of X-rays and neutrons, are presented on one hand. On the other hand the principal models employed for reconstituting the structure of simple liquids are exposed: mathematical models, lattice models and their derived models, experimental models. (author) [French] On presente d'une part les resultats obtenus par application a l'argon et au sodium des deux principales methodes d'etude de la structure des liquides: la diffusion des rayons X et la diffusion des neutrons; d'autre part, les principaux modeles employes pour reconstituer la structure des liquides simples sont exposes: modeles mathematiques, modeles des reseaux et modeles derives, modeles experimentaux. (auteur)

  8. Neutron resonance spectroscopy

    International Nuclear Information System (INIS)

    Gunsing, F.

    2005-06-01

    The present document has been written in order to obtain the diploma 'Habilitation a Diriger des Recherches'. Since this diploma is indispensable to supervise thesis students, I had the intention to write a document that can be useful for someone starting in the field of neutron resonance spectroscopy. Although the here described topics are already described elsewhere, and often in more detail, it seemed useful to have most of the relevant information in a single document. A general introduction places the topic of neutron-nucleus interaction in a nuclear physics context. The large variations of several orders of magnitude in neutron-induced reaction cross sections are explained in terms of nuclear level excitations. The random character of the resonances make nuclear model calculation predictions impossible. Then several fields in physics where neutron-induced reactions are important and to which I have contributed in some way or another, are mentioned in a first synthetic chapter. They concern topics like parity nonconservation in certain neutron resonances, stellar nucleosynthesis by neutron capture, and data for nuclear energy applications. The latter item is especially important for the transmutation of nuclear waste and for alternative fuel cycles. Nuclear data libraries are also briefly mentioned. A second chapter details the R-matrix theory. This formalism is the foundation of the description of the neutron-nucleus interaction and is present in all fields of neutron resonance spectroscopy. (author)

  9. Neutron resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gunsing, F

    2005-06-15

    The present document has been written in order to obtain the diploma 'Habilitation a Diriger des Recherches'. Since this diploma is indispensable to supervise thesis students, I had the intention to write a document that can be useful for someone starting in the field of neutron resonance spectroscopy. Although the here described topics are already described elsewhere, and often in more detail, it seemed useful to have most of the relevant information in a single document. A general introduction places the topic of neutron-nucleus interaction in a nuclear physics context. The large variations of several orders of magnitude in neutron-induced reaction cross sections are explained in terms of nuclear level excitations. The random character of the resonances make nuclear model calculation predictions impossible. Then several fields in physics where neutron-induced reactions are important and to which I have contributed in some way or another, are mentioned in a first synthetic chapter. They concern topics like parity nonconservation in certain neutron resonances, stellar nucleosynthesis by neutron capture, and data for nuclear energy applications. The latter item is especially important for the transmutation of nuclear waste and for alternative fuel cycles. Nuclear data libraries are also briefly mentioned. A second chapter details the R-matrix theory. This formalism is the foundation of the description of the neutron-nucleus interaction and is present in all fields of neutron resonance spectroscopy. (author)

  10. Neutrons detection by scintillation; Detection de neutrons par scintillations

    Energy Technology Data Exchange (ETDEWEB)

    Giraudon, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-01-15

    The absence of charge of neutrons and their elevated penetration power make difficult their detection. Techniques vary otherwise with the energy of the particle. The author proposes the realization of a scintillation detector with a big volume of liquid scintillator and containing boron for the detection of slowing-down neutrons in the domain of intermediate energies from 1 to 10{sup 5} eV about. (M.B.) [French] L'absence de charge du neutron et son pouvoir de penetration eleve rendent difficile sa detection. Les techniques par ailleurs varient avec l'energie de cette particule. L'auteur propose la realisation d'un detecteur a scintillations comprenant un grand volume de scintillateur liquide et contenant du bore pour la detection des neutrons en ralentissement dans le domaine des energies intermediaires de 1 a 10{sup 5} eV environ. (M.B.)

  11. Neutrons detection by scintillation; Detection de neutrons par scintillations

    Energy Technology Data Exchange (ETDEWEB)

    Giraudon, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-01-15

    The absence of charge of neutrons and their elevated penetration power make difficult their detection. Techniques vary otherwise with the energy of the particle. The author proposes the realization of a scintillation detector with a big volume of liquid scintillator and containing boron for the detection of slowing-down neutrons in the domain of intermediate energies from 1 to 10{sup 5} eV about. (M.B.) [French] L'absence de charge du neutron et son pouvoir de penetration eleve rendent difficile sa detection. Les techniques par ailleurs varient avec l'energie de cette particule. L'auteur propose la realisation d'un detecteur a scintillations comprenant un grand volume de scintillateur liquide et contenant du bore pour la detection des neutrons en ralentissement dans le domaine des energies intermediaires de 1 a 10{sup 5} eV environ. (M.B.)

  12. Evaluation of Dose: Comparative Effect of Fast Neutrons and other Types of Radiation on the Survival of E. Coli and S. Cerevisiae; Evaluation de la Dose Delivree et Actions Comparees des Neutrons Rapides et d'Autres Radiations sur la Survie de E. Coli et S. Cerevisiae; Otsenka dozy i sravnitel'noe vliyanie bystrykh nejtronov i drugikh vidov izlucheniya na vyzhivaemost' E. Coli i S. Cerevisiae; Evaluacion de la Dosis Suministrada y Comparacion de la Accion de los Neutrones Rapidos sobre la Supervivencia del E. Coli y del S. Cerevisiae con la de Otras Radiaciones

    Energy Technology Data Exchange (ETDEWEB)

    Arnaud, Y.; Bocquet, C. [Centre d' Etudes Nucleaires de Saclay (France)

    1964-05-15

    The EL-3 reactor is equipped with auranium converter by means of which fast neutrons can be obtained. A bank of fission chambers measures the flux and spectral distribution of the fast neutrons. These miniature detectors are placed at various points in the target zone and make possible the experimental evaluation of the absorbed tissue-dose. This apparatus and dosimetric technique can be used to compare the effect of fast neutrons and other types of ionizing radiation (e.g. X-rays) on unicellular organisms. The authors study the percentage of survivals and the frequency of a mutation in Saccharomyces cerevisiae. The survival curve for Escherichia coli is also determined for X-rays and neutrons. It is found that the RBE's of these various types of radiation depend not only on the species and the biological criterion adopted, but also on the irradiation dose-level at which the comparison is made. These experiments show the RBE to be also a function of dose. The effects of fast neutrons and X-rays are often brought about by differing radiobiological processes. It is arbitrary to establish linear relationships between the doses for these various types of radiation. (author) [French] Nous disposons aupres du reacteur EL3 d'un convertisseur a uranium permettant d'obtenir des neutrons rapides. Une batterie de chambres a fission mesure le flux et la repartition spectrale des neutrons rapides. Ces detecteurs miniatures sont places en divers points du volume a irradier et permettent d'evaluer experimentalement la dose absorbee dans les tissus. Ce dispositif et cette dosimetrie nous servent a comparer l'action des neutrons rapides et d'autres radiations ionisantes (X, {gamma}) sur des organismes monocellulaires. Nous etudions ici le pourcentage de survie et la frequence d'une mutation morphologique chez Saccharomyces cerevisiae. La courbe de survie d'Escherichia coli est aussi etablie pour les rayons X et les neutrons. On observe que les effets biologiques relatifs de ces

  13. Study of magnetic thin films by polarized neutron reflectivity. Off-specular diffusion on periodical structures; Etude de couches minces magnetiques par reflectivite de neutrons polarises. Diffusion non speculaire sur des structures periodiques

    Energy Technology Data Exchange (ETDEWEB)

    Ott, F

    1998-11-26

    Theoretical (Zeeman energy effects) and experimental (beam polarisation problems) progress have been made in the understanding of polarized neutron reflectivity with polarisation analysis. It has been shown that modelization and numerical simulations makes it possible to avoid to have to systematically measure a full set of reflectivity curves for each field and temperature condition. It has been possible to determine a magnetic profile as a function of the field in a magnetic bilayer system by using only a few points in the reciprocal space. This technique allows to considerable reduce the experiment time. In single nickel layer systems, we have shown that it is possible to induce magnetic rotation inhomogeneities when these systems are subjects to deformation strains. The effect are related to magneto-elastic constants gradients. In trilayer systems, with a ME constant modulation, we have been able to induce large magnetic rotation gradients. A new magneto-optic technique to measure the magnetization direction without rotating the magnetic field has been developed. The field of neutron reflectivity has been extended to off-specular studies. It has been possible to account quantitatively of the off-specular diffusion on 2-D model systems (prepared by optical lithography). This new technique should make it possible in the future to determine magnetic structures with a in-depth as well as lateral resolution. (author)

  14. New experimental determination of the neutron resonance parameters of {sup 99}Tc; Nouvelle determination experimentale des parametres de resonances neutroniques de {sup 99}Tc

    Energy Technology Data Exchange (ETDEWEB)

    Brienne-Raepsaet, C. [CEA Bruyeres-le-Chatel, 91 (France). Dept. de Physique Theorique et Appliquee]|[Aix-Marseille-1 Univ., 13 - Marseille (France)

    1999-04-01

    In order to improve nuclear data for nuclear waste transmutation cross-sections of Tc{sup 99} in the resonance energy region have been performed using the time-of-flight method at the pulsed white neutron source GELINA of the Institute for Reference Materials and Measurements, Geel, Belgium. The energy range studied spreads from 3 eV to 100 KeV. 2 kinds of measurements have been performed: capture and transmission measurements. In the energy range between 0 and 2 KeV, more than 220 resonances have been analyzed. About 130 resonances which had stayed previously undiscovered, have been detected and analyzed. Because of instability problems concerning the process of measuring itself, the systematic error is not yet determined. The accuracy which takes into account statistical and systematic errors is expected to be between 4 and 5%.

  15. Cronos 2: a neutronic simulation software for reactor core calculations; Cronos 2: un logiciel de simulation neutronique des coeurs de reacteurs

    Energy Technology Data Exchange (ETDEWEB)

    Lautard, J J; Magnaud, C; Moreau, F; Baudron, A M [CEA Saclay, Dept. de Mecanique et de Technologie (DMT/SERMA), 91 - Gif-sur-Yvette (France)

    1999-07-01

    The CRONOS2 software is that part of the SAPHYR code system dedicated to neutronic core calculations. CRONOS2 is a powerful tool for reactor design, fuel management and safety studies. Its modular structure and great flexibility make CRONOS2 an unique simulation tool for research and development for a wide variety of reactor systems. CRONOS2 is a versatile tool that covers a large range of applications from very fast calculations used in training simulators to time and memory consuming reference calculations needed to understand complex physical phenomena. CRONOS2 has a procedure library named CPROC that allows the user to create its own application environment fitted to a specific industrial use. (authors)

  16. Data Evaluation Problems in the Pulsed Neutron Source Method; Problemes d'Evaluation des Donnees dans les Applications de la Methode de la Source Pulsee; Problemy otsenki dannykh pri primenenii metoda istochnika impul'snykh nejtronov; Problemas de Evaluacion de Datos en el Metodo de la Fuente de Neutrones Pulsados

    Energy Technology Data Exchange (ETDEWEB)

    Pal, L.; Bod, L.; Szatmary, Z. [Central Research Institute for Physics, Hungarian Academy of Sciences, Budapest (Hungary)

    1965-08-15

    the weighted least-squares method using the decay constants of minimum standard deviation evaluated from the maximum likelihood function. Since, for the materials investigated, the values of the transport mean free path were not known, a fast converging iteration procedure was elaborated for the determination of the transport mean free path. The computer evaluation made it possible to determine the coefficients of the B{sup 6} and higher order terms of the decay constant. The diffusion parameters of the hydrogenous materials investigated were calculated by the Radkowsky prescription from the energy dependence of the integral scattering cross-sections. The calculations have shown that the Radkowsky prescription is a useful empirical method for the evaluation of the transport mean free path of numerous hydrogenous materials. (author) [French] Pour obtenir les parametres de diffusion des neutrons thermiques, on emploie depuis plus de dix ans la methode des neutrons puises. Cette methode convient tout particulierement pour l'etude des ralentisseurs hydrogenes. Les auteurs donnent les resultats des mesures pour l'eau, le benzene, le toluene, le xylene, le cyclohexane, le n-hexane et le diphenyle et discutent les methodes permettant d'evaluer avec le minimum d'erreurs les parametres de diffusion interessants, a partir des donnees mesurees. Ils etudient en detail au point de vue theorique et experimental l'effet du temps de vol qui se fait sentir lors des recherches sur les ralentisseurs a des temperatures elevees pour des raisons techniques, et influe sur la valeur de la constante de decroissance; ils indiquent les conditions geometriques dans lesquelles on peut obtenir une bonne precision. Ilsdeterminent en outre l'effet du temps mort du detecteur de neutrons et du systeme d'amplification sur la valeur de la constante de decroissance: l'effet du temps mort peut etre neglige si [i(t) {tau}]{sup 2} << 1, ou i (t) dt est le nombre des neutrons detectes dans l'intervalle de

  17. Guía Clínica para la Adaptación de Lentes de Contacto Multifocales Tóricas Hidrofílicas

    OpenAIRE

    García Valencia, Lidia

    2015-01-01

    Elaboración de una guía clínica para la adaptación de lentes de contacto multifocales tóricas, basada en la bibliografía existente sobre ese tipo de lentes de contacto y un caso clínico utilizado para faciltar su comprensión. Grado en Óptica y Optometría

  18. A gaseous scintillation counter filled with He{sup 3} for neutron spectrometry; Compteur a scintillateur gazeux rempli de {sup 3}He pour la spectrometrie des flux de neutrons; Gazovyj stsintillyatsionnyj schetchik napolnennyj He{sup 3} dlya spektrometrii potokov nejtronov; Contador de centelleador gaseoso cargado con helio-3 para la espectrometria neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Baldin, S A; Matveev, V V

    1962-04-15

    The paper describes a gas plant and gaseous scintillation counter, and gives the results of experiments on the recording and spectrometry of neutron beams using a gaseous scintillation counter filled with a mixture of 10% xenene and 90% helium-3 at an overall pressure of 20 ata. Data are given on the design of the gas plant, which makes it possible to operate the counter continuously over long periods of time, as well as providing the required gas mixtures at overall pressures of up to 60 atm and ensuring constant freedom of the gas from contamination. In addition, the paper presents the results of research on the counter's energy resolution and linearity at different energy levels and indicates its efficiency in gamma fields of intensity up to 3 r/h; the possibility of extending the working energy-range of gaseous scintillation counters filled with helium-3 is also considered. (author) [French] FLes auteurs decrivent un compteur a scintillateur gazeux ainsi que les resultats des experiences d'enregistrement et de spectrometrie des flux de neutrons qui ont ete faites au moyen d'un compteur a scintillateur gazeux rempli d'un melange de 10% de xenon et de 90% d'helium-3 sous une pression de 20 atmospheres. Ils exposent les donnees relatives a la construction d'un appareillage qui assure le fonctionnement ininterrompu du compteur durant un laps de temps prolonge, l'obtention des melanges de gaz indispensables sous une pression totale de 60 atmospheres et l'epuration continue du gaz. En outre, ils examinent les resultats de l'etude du pouvoir de resolution en energie et de la linearite du compteur en fonction de l'energie, le fonctionnement du compteur dans les champs de rayonnement gamma d'une intensite allant jusqu'a 3 r/h, ainsi que la possibilite d'elargir la gamme d'energie dans laquelle on peut employer des compteurs a scintillateurs gazeux de {sup 3}He. (author) [Spanish] En esta memoria se describe un aparato de suministro de gas y un contador de centelleador

  19. Reorganization of Students Disability Support Unit in Bülent Ecevit University

    Directory of Open Access Journals (Sweden)

    Hakan KALYON

    2012-01-01

    Full Text Available Universities are the centers where science and knowledge can be produced and shared freely. In these centers, it is probable that disabled people can be in the audience and benefit from these training and education activities. Therefore, removing inequalities defined as “inequitable differences of individuals not caused by personal characteristics” and solving problems in accessing information and education is an indispensible target for our country.The highest step among the needs of the human beings is self-perform. Especially, in the social order of 21st century, the disabled people who aim to meet the expectations of life should be supported allover.Turkey has a young and dynamic population; there is a significant increase in the number of the disabled students who reach and graduate from higher education in 2000s. In 2000, 97 disabled students graduated from universities and this number reached 410 in 2008 and 1090 in 2009. Number of disabled students in the Universities of Turkey reached 3584 in 2011.One of the most important examples in the process of legislative changes about the education of disabled people is the “Institutions of Higher Education Disabled People Consultation and Coordination Regulation.” The purpose of the regulation is to take steps in order to ease the education lives of the disabled people in higher education. In the context of applicable law, the unit of disabled students is restructured at Bülent Ecevit University.

  20. Late effects of normal tissues (lent) scoring system: the soma scale

    International Nuclear Information System (INIS)

    Mornex, F.; Pavy, J.J.; Denekamp, J.

    1997-01-01

    Radiation tolerance of normal tissues remains the limiting factor for delivering tumoricidal dose. The late toxicity of normal tissues is the most critical element of an irradiation: somatic, functional and structural alterations occur during the actual treatment itself, but late effects manifest months to years after acute effects heal, and may progress with time. The optimal therapeutic ratio ultimately requires not only complete tumor clearance, but also minimal residual injury to surrounding vital normal tissues. The disparity between the intensity of acute and late effects and the inability to predict the eventual manifestation of late normal tissue injury has made radiation oncologists recognize the importance of careful patient follow-up. There is so far no uniform toxicity scoring system to compare several clinical studies in the absence of a 'common toxicity language'. This justifies the need to establish a precise evaluation system for the analysis of late effects of radiation on normal tissues. The SOMA/LENT scoring system results from an international collaboration. European Organization Treatment of Cancer (EORTC) and Radiation Therapy Oncology Group (RTOG) have created subcommittees with the aim of addressing the question of standardized toxic effects criteria. This effort appeared as a necessity to standardize and improve the data recording, to then describe and evaluate uniform toxicity at regular time intervals. The current proposed scale is not yet validated, and should be used cautiously. (authors)

  1. Development of a slow mono-kinetic electron source; Etude et realisation d'une source d'electrons lents monocinetiques

    Energy Technology Data Exchange (ETDEWEB)

    Ballu, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-06-01

    A comparative study of already existing slow mono-kinetic electron guns shows that those using a 127 degrees electrostatic selector can be improved still further to arrive at the performances obtained with spherical 180 degrees selectors for example. For this reason we have examined the 127 degrees selector theoretically in more detail; it appears that it should be possible to obtain a resolving power better than 30 mV for a current of about 10{sup -10} A, on condition that certain improvements be made to the instrument as normally designed, in particular concerning the entrance and exit slides. As a result, the usual suppressors for the scattered electrons are no longer necessary. The development of this apparatus has been carried out with particular care: the dimensional characteristics are fixed to an accuracy of a few microns, although the instrument can be baked out at 300 C. The experimental results are in excellent agreement with the theoretical predictions: for a current of 10{sup -10} A, the measured resolving power is 24 {+-} 4 mV. The easy detection of the He{sup -} resonance line at 19.3 eV has confirmed the advantages of this apparatus for the study of atomic collisions. (author) [French] L'etude comparative des canons a electrons lents monocinetiques realises jusqu'a present montre que ceux qui utilisent un selecteur electrostatique a 127 degres peuvent etre encore perfectionnes en vue de parvenir aux performances obtenues avec les selecteurs spheriques a 180 degres par exemple. D'ou notre etude theorique approfondie du selecteur a 127 degres qui nous a conduit a esperer une resolution meilleure que 30 mV pour un courant de l'ordre de 10{sup -10} A a condition d'apporter certaines ameliorations a la conception usuelle de cet instrument notamment au niveau des fentes d'entree et de sortie. Par voie de consequence les suppresseurs habituels d'electrons parasites deviennent inutiles. L'etude et la mise au point de l'appareil ont fait l'objet de soins

  2. Evaluation of uncertainties of key neutron parameters of PWR-type reactors with slab fuel, application to neutronic conformity; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustibles et application aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2001-12-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and life-time. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then, neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimized. (author)

  3. Evaluation of uncertainties of key neutron parameters of PWR-type reactors with slab fuel, application to neutronic conformity; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustibles et application aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2001-12-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and life-time. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then, neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimized. (author)

  4. Multi-domain/multi-method numerical approach for neutron transport equation; Couplage de methodes et decomposition de domaine pour la resolution de l'equation du transport des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Girardi, E

    2004-12-15

    A new methodology for the solution of the neutron transport equation, based on domain decomposition has been developed. This approach allows us to employ different numerical methods together for a whole core calculation: a variational nodal method, a discrete ordinate nodal method and a method of characteristics. These new developments authorize the use of independent spatial and angular expansion, non-conformal Cartesian and unstructured meshes for each sub-domain, introducing a flexibility of modeling which is not allowed in today available codes. The effectiveness of our multi-domain/multi-method approach has been tested on several configurations. Among them, one particular application: the benchmark model of the Phebus experimental facility at Cea-Cadarache, shows why this new methodology is relevant to problems with strong local heterogeneities. This comparison has showed that the decomposition method brings more accuracy all along with an important reduction of the computer time.

  5. Neutron cross section evaluations of europium isotopes in 1 keV - 30 MeV energy range. Format - validation - comparison; Evaluation de sections efficaces pour des neutrons incidents sur des isotopes d'europium aux energies 1 keV - 30 MeV. Format - validation - comparaison

    Energy Technology Data Exchange (ETDEWEB)

    Dossantos-Uzarralde, P.; Le Luel, C.; Bauge, E. [CEA Bruyeres le Chatel, 91 (France). Dept. de Physique Theorique et Appliquee

    2004-07-01

    This paper presents neutron cross section evaluations of Europium isotopes. The cross sections are evaluated in 1 keV - 30 MeV energy range for the isotopes {sup 146}Eu, {sup 147}Eu, {sup 148}Eu, {sup 149}Eu, {sup 150}Eu, {sup 151}Eu, {sup 152}Eu, {sup 153}Eu, {sup 154}Eu in their ground state. This evaluation includes cross section productions of the long life isomeric states. Special attention is put on the options used for the description of the files written in ENDF-6 format. The final issue is a proposal of a new breed of ENDF-6 formatted neutron activation file. (authors)

  6. A novel time-to-pulse height converter for fast-neutron time-of-flight techniques; Nouveau convertisseur temps-amplitude d'impulsions pour les mesures du temps de vol des neutrons rapides; Novyj vremya-amplitudnyj preobrazovatel' impul'sov dlya izmereniya vremeni proleta bystrykh nejtronov; Nuevo convertidor tiempo-altura de impulsos para tecnicas de tiempo de vuelo de neutrones rapidos

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, J [Physikalisches Staatsinstitut, Hamburg, Federal Republic of Germany (Germany)

    1962-04-15

    An electronic time-to-pulse height converter is described which uses a multiplicative method instead of the usual one of adding overlapping pulses. This is achieved by a coincidence of a linear sawtooth and a sharply clipped needle-pulse. The sawtooth is fed to the grid of a beam-deflecting tube (E80T) and the needle-pulse is applied to the deflecting plates and opens the tube only during a time-interval of about 5.10{sup -9} s. The plate gets a charge proportional to the time-difference between the start of the sawtooth and the needle pulse. The plate-pulse is stretched and amplified and its height represents a measurement of the time-difference. With this method we got a time resolution of 2{tau} = 7 x 10{sup -12}s with artificial pulses, 2{tau} = 3 x 10{sup -10}s with Co{sup 60} {gamma}-coincidences by using NE 102 plastic crystals and 2{tau} = 1.4 x 10{sup -9} s with 511-keV {gamma}-coincidences using NaI(Te) crystals. The method was also used with pulsed beam techniques. In this case we got from the pulsing RF an 8-Mc, sharply-peaked pulse-sequence, which was fed to the E80T plates. We had a time-resolution of 2{tau} = 1.1 x 10{sup -9} s with 4-MeV neutrons using plastic crystals 0.7 in long. Normally the region of linear response was 30 ns but it was possible to go up to 120 ns. (author) [French] L'auteur decrit un convertisseur electronique temps en amplitude d'impulsions fonctionnant d'apres une methode de multiplication au lieu de la methode habituelle qui consiste a ajouter des impulsions qui se chevauchent. On fait coincider une impulsion lineaire en dents de scie avec une impulsion en forme d'aiguille fortement ecretee. L'impulsion en dents de scie est envoyee sur la grille d'un tube a faisceaux electroniques diriges (E80T) ; et l'impulsion en forme d'aiguille est appliquee aux plaques de deflexion et n'ouvre le tube que pendant un intervalle de temps d'environ 5 {center_dot} 10{sup -9} s. La plaque recoit une charge proportionnelle a la difference de

  7. Experimental studies of some of the physical features of beryllium-moderated intermediate reactors; Etude experimentale de quelques particularites physiques des reacteurs a neutrons intermediaires, ralentis au beryllium; Ehksperimental'ny e issledovaniya nekotorykh fizicheskikh osobennostej promezhutochnykh reaktorov s berillievym zamedlitelem; Estudios experimentales de algunas caracteristicas fisicas de los reactores intermedios moderados con berilio

    Energy Technology Data Exchange (ETDEWEB)

    Lejpunskij, A I; Kuznetsov, V A; Artyukhov, G Ya; Mogil' ner, A I; Prokhorov, Yu A; Steklovski, V M; Chernov, L A [Akademiya Nauk, Moskva, Union of Soviet Socialist Republics (Russian Federation)

    1962-03-15

    of neutrons absorbed by the uranium. The paper provides data, derived from the same assembly, on the efficiency of rods made of various absorbing materials. It gives the experimentally measured distribution of neutron density for neutrons of various energies in the neighbourhood of a boron-carbide rod, and the density of neutron captures by a 1/v detector within the rod. The paper also discusses methods used and the results obtained from experiments designed to assess the efficiency of recompensation, cylinders placed on the boundary between core and reflector. (author) [French] Le memoire analyse les resultats de plusieurs experiences effectuees sur l'ensemble critique PF-4, qui est destine a l'etude detaillee des particularites physiques des reacteurs a neutrons intermediaires. Les coeurs et les reflecteurs des differents esembles critiques etaient constitues par un assemblage compact de tubes en acier ou en aluminium dans lesquels etaient inseres des diques de diverses matieres. En combinant selon differentes proportions les disques d'uranium enrichi a 90% et les matieres de ralentissement et en introduisant dans le reflecteur des couches de ralentisseur de diverses epaisseurs, on a pu obtenir de grandes modifications du spectre des neutrons provoquant la fission. Le memoire decrit l'ensemble critique PF-4 et les differents assemblages qui le composent. Les auteurs analysent l'efficacite relative du ralentissement interieur et exterieur pour des reacteurs dans lesquels le rapport noyaux du ralentisseur noyaux d'uranium dans le coeur est tres peu eleve. Il ressort des experiences que, meme lorsqu'on emploie des reflecteurs tres epais, la faible dilution de l'uranium par le ralentisseur (le rap- port entre les noyaux du beryllium et de l'uranium-235 etant: {partial_derivative}Be/{partial_derivative}{sup 235}U{approx_equal}1) entraine un accroissement de la masse critique. Une partie importante du memoire est consacree a une analyse des effets hetero- genes produits

  8. Tracking techniques for the characteristics method applied to the resolution of the neutrons transport equation in multi scale domains; Techniques de tracage pour la methode des caracteristiques appliquee a la resolution de l'equation du transport des neutrons en domaines multi-dimensionnels

    Energy Technology Data Exchange (ETDEWEB)

    Fevotte, F. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DEN/DANS/DM2S/SERMA), 91 - Gif sur Yvette (France)

    2008-07-01

    At the various stages of a nuclear reactor's life, numerous studies are needed to guaranty the safety and efficiency of the design, analyse the fuel cycle, prepare the dismantlement, and so on. Due to the extreme difficulty to take extensive and accurate measurements in the reactor core, most of these studies are numerical simulations. The complete numerical simulation of a nuclear reactor involves many types of physics: neutronics, thermal hydraulics, materials, control engineering, Among these, the neutron transport simulation is one of the fundamental steps, since it allows computation - among other things - of various fundamental values such as the power density (used in thermal hydraulics computations) or fuel burn-up. The neutron transport simulation is based on the Boltzmann equation, which models the neutron population inside the reactor core. Among the various methods allowing its numerical solution, much interest has been devoted in the past few years to the Method of Characteristics in unstructured meshes (MOC), since it offers a good accuracy and operates in complicated geometries. The aim of this work is to propose improvements of the calculation scheme bound on the two dimensions MOC, in order to decrease the needed resources number. (A.L.B.)

  9. Comparison of Clinical and Laboratory Responses in Sheep and Dogs following Whole-Body Exposures to 250-Kvp X-Rays and Fission-Spectrum Neutrons; Etude Comparee Clinique et en Laboratoire, des Reactions de Moutons et de Chiens a la Suite d'une Exposition du Corps Entier a des Rayons X de 250 Kv-Crete et a des Neutrons de Fission; Sravnenie klinicheskikh i laboratornykh dannykh o reaktsii ovets i sobak na obluchenie vsego tela rentgenovskimi luchami pri pikovom napryazhenii 250 Kv i nejtronami spektra deleniya; Estudio Comparado, Clinico y de Laboratorio, de las Reacciones de Ovejas y Perros Consecutivas a la Irradiacion del Cuerpo Entero con Rayos X de 250 KVp y Neutrones de Fision

    Energy Technology Data Exchange (ETDEWEB)

    Quaife, M. A.; Boer, J. de; Jones, R. K.; Ichiki, A. T.; Godden, W. R.; Davis, H.; Engel, R. E. [Kirtland AFB, New Mexico (United States)

    1964-05-15

    fission puises, ainsi que 15 moutons et 14 chiens a une dose de 400 r (dose mediane dans l'a ir ) de rayons X de 250 kV-crete. Sept moutons et quatre chiens ont servi de temoins. On a fait des observations pendant les deux semaines qui ont precede les expositions, puis a intervalles frequents et reguliers apres l'irradiation. Chez les moutons, l'alteration clinique la plus constante a ete la perte complete de la laine 51 j apres l'exposition. La peau ainsi mise a nu etait d'une couleur rose semblable a celle que produit parfois chez les humains un leger rougissement. Il n'y a pas eu de chute de poils chez les chiens. Le nombre des polynucleaires neutrophiles, des lymphocytes et des plaquettes a baisse rapidement apres l 'irradiation chez les moutons et les chiens. Environ 24 j apres l 'exposition, on a note une restauration du nombre des globules blancs uniquement dans les groupes exposes aux neutrons. Le nombre des plaquettes a baisse dans la meme proportion chez les moutons et les chiens, mais un peu plus tot chez les chiens. Dans les deux cas, une restauration a ete constatee au cours de la troisieme semaine apres l'exposition aux neutrons, mais il n'en a pas ete de meme chez les animaux exposes aux rayons X. Neuf jours apres l 'exposition, le nombre des globules rouges avait sensiblement diminue chez les deux groupes de chiens; on n'a pas constate de diminution notable chez les moutons. On a determine le taux d'elimination du {sup 59}Fe dans le plasma des animaux d'experience, comme parametre de mesure de la fonction hematopoieetique. Les auteurs discutent l'influence sur le pronostic des modifications survenant dans ce parametre de l'hematopoieese. Les modifications pathologiques les plus significatives ont ete limitees aux poumons, ou on a constate une importante hemorragie perivasculaire autour des arteres. L'observation microscopique a revele que la zone d'hemorragie se trouvait dans les tissus conjonctifs adventices et les vaisseaux periarteriels. Au trentieme

  10. Study of shell closures N=40 and N=50 in neutron-rich nuclei; Etude des fermetures de couches N=40 et N=50 dans les noyaux riches en neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Perru, O

    2004-12-01

    For this thesis I have studied 2 neutron shell closures: N=40 and N=50. On N=50, an experiment was done in February 2001 on the ISOL line PARRNe, the issue was to measure the first excited states of {sup 83}Ge (Z=32, N=51) by studying the beta decay of {sup 83}Ga produced by fission of {sup 238}U.The extreme precision of the experimental device, with the operation of hot plasma ion sources made it possible to reach spectroscopic information of the Ge isotopes beyond the magic gap N=50. Two transitions have been attributed to {sup 83}Ge: at 867 keV and at 1238 keV. The level scheme of {sup 83}Ge could be interpreted in terms of weak coupling: the excited states of this nucleus are due to the couplings between the single neutron beyond N=50 and the remaining nucleons.On N=40, we wanted to determine the transition probability between ground state and first excited state, called B(E2), in {sup 70}Ni (N=42) and {sup 74}Zn (N=44) from Coulomb excitation. These exotic nuclei are produced by fragmentation of a primary beam of {sup 76}Ge on a target of {sup 58}Ni, selected by the spectrometer LISE, then interact with a secondary {sup 208}Pb target to induce the Coulomb excitation. At the end of this analysis, the following values have been obtained: B(E2,{sup 70}Ni)=860(170) e{sup 2}fm{sup 4}, B(E2,{sup 74}Zn)=1960(140) e{sup 2}fm{sup 4}. These values have been compared on the one hand to variational calculations which I have realised, on the other hand to published shell model calculations.These calculations point out the complex aspect of the Ni nuclei, which do not seem to have a typical behaviour of semi magic nuclei although they are located on a closed shell in protons (Z=28). (author)

  11. Precisão da retinoscopia sem lentes neutralizadoras na hipermetropia experimental de olho artificial

    Directory of Open Access Journals (Sweden)

    Beatriz Simões-Corrêa

    2012-10-01

    Full Text Available OBJETIVO: Avaliar a acurácia e a precisão da retinoscopia sem lentes neutralizadoras na hipermetropia experimental de olho artificial. MÉTODOS: Observação da projeção da faixa do retinoscópio em olho artificial preparado para apresentar hipermetropias de +1,00 D a +8,00 D. A movimentação da faixa é feita simultaneamente com a variação da sua largura, deslocando a luva do retinoscópio até a obtenção da neutralização do movimento. O retinoscópio foi preparado para dois modos de medida: com escala milimétrica sob a luva e com acoplamento a potenciômetro ligado a multímetro de leitura digital em ohms (Ù. Oito médicos oftalmologistas realizaram 1200 retinoscopias em cada modo de medida, num total de 2400. Calculou-se a média e o desvio padrão das observações. Para comparar os resultados em mm e em ohms (Ù calculou-se o coeficiente de variação (CV a partir dos desvios padrão das observações em cada modo. RESULTADOS: Pelos modos descritos foi possível estimar hipermetropias até +4,00 dioptrias. CONCLUSÃO: A acurácia e a reprodutibilidade experimentais foram boas na identificação de hipermetropias até +4 ,00 D.

  12. Characterization of the hydrogen bond in molecular systems of biological interest by neutron scattering; Caracterisation de la liaison hydrogene dans des systemes moleculaires d'interet biologique par diffusion de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Cavillon, F

    2004-10-15

    This work presents a methodology for the analysis of the scattering spectra of neutrons on molecular liquids. This method is based on the adjustment of the molecular form factor concerning great momentum transfer. The subtraction of the intra-molecular contributions gives access to information on inter-molecular interactions such as the hydrogen bond. 3 systems with increasing levels of difficulty have been studied: the ammonia molecule, the N-methyl-formamide (NMF) and the N-methyl-acetamide (NMA). The value we get for the N-D intermolecular distance of the liquid ammonia molecule is 1.7 angstrom, this value is different from the value generally admitted (2.3 angstrom) but we have validated it by studying the isotopic substitution N{sup 14}/N{sup 15}. The adjustment to the NMF is obtained with a good accuracy but the characterization of the hydrogen bound is more delicate to infer. A preliminary study of the NMA molecule shows that this method can give relevant results on complex molecules.

  13. Measurement of the fission cross section induced by fast neutrons of the {sup 232}Th/{sup 233}U nuclei within the innovating fuel cycles framework; Mesure de la section efficace de fission induite par neutrons rapides des noyaux {sup 232}Th/{sup 233}U dans le cadre des cycles de combustible innovants

    Energy Technology Data Exchange (ETDEWEB)

    Grosjean, C

    2005-03-15

    The thorium-U{sup 233} fuel cycle might provided safer and cleaner nuclear energy than the present Uranium/Pu fuelled reactors. Over the last 10 years, a vast campaign of measurements has been initiated to bring the precision of neutron data for the key nuclei (Th{sup 232}, Pa{sup 233} and U{sup 233}) at the level of those for the U-Pu cycle. This is the framework of these measurements, the energy dependent neutron induced fission cross section of Th{sup 232} and U{sup 233} has been measured from 1 to 7 MeV with a target accuracy lesser than 5 per cent. These measurements imply the accurate determination of the fission rate, the number of the target nuclei as well as the incident neutron flux impinging on the target, the latter has been obtained using the elastic scattering (n,p). The cross section of which is very well known in a large neutron energy domain ({approx} 0,5 % from 1 eV to 50 MeV) compared to the U{sup 235}(n,f) reaction. This technique has been applied for the first time to the Th{sup 232}(n,f) and U{sup 233}(n,f) cases. A Hauser-Feshbach statistical model has been developed. It consists of describing the different decay channels of the compound nucleus U{sup 234} from 0,01 to 10 MeV neutron energy. The parameters of this model were adjusted in order to reproduce the measured fission cross section of U{sup 233}. From these parameters, the cross sections from the following reactions could be extracted: inelastic scattering U{sup 233}(n,n'), radiative capture U{sup 233}(n,{gamma}) and U{sup 233}(n,2n). These cross sections are still difficult to measure by direct neutron reactions. The calculated values have allowed us to fill the lack of experimental data for the major fissile nucleus of the thorium cycle. (author)

  14. Polarized neutrons

    International Nuclear Information System (INIS)

    Williams, W.G.

    1988-01-01

    The book on 'polarized neutrons' is intended to inform researchers in condensed matter physics and chemistry of the diversity of scientific problems that can be investigated using polarized neutron beams. The contents include chapters on:- neutron polarizers and instrumentation, polarized neutron scattering, neutron polarization analysis experiments and precessing neutron polarization. (U.K.)

  15. Neutron--neutron logging

    International Nuclear Information System (INIS)

    Allen, L.S.

    1977-01-01

    A borehole logging tool includes a steady-state source of fast neutrons, two epithermal neutron detectors, and two thermal neutron detectors. A count rate meter is connected to each neutron detector. A first ratio detector provides an indication of the porosity of the formation surrounding the borehole by determining the ratio of the outputs of the two count rate meters connected to the two epithermal neutron detectors. A second ratio detector provides an indication of both porosity and macroscopic absorption cross section of the formation surrounding the borehole by determining the ratio of the outputs of the two count rate meters connected to the two thermal neutron detectors. By comparing the signals of the two ratio detectors, oil bearing zones and salt water bearing zones within the formation being logged can be distinguished and the amount of oil saturation can be determined. 6 claims, 2 figures

  16. Utilisation des sous-produits agroalimentaires dans l’alimentation des poissons d’élevage en Côte d’Ivoire

    Directory of Open Access Journals (Sweden)

    Kimou Nestor B.

    2016-03-01

    Full Text Available Cette étude évalue l’impact de l’utilisation des sous-produits agroalimentaires dans l’alimentation des poissons d’élevage en Côte d’Ivoire. Une enquête a été réalisée en 2013 dans quinze principales zones piscicoles sur les caractéristiques technico-économiques des fermes, le profil socio-économique des promoteurs et les pratiques aquacoles, particulièrement l’alimentation des poissons. Les résultats révèlent que 71 % des pisciculteurs enquêtés utilisent des sous-produits agricoles durant au moins un stade de production. Parmi eux, 53 % utilisent exclusivement des sous-produits. Le son de riz (52 % et le mélange de sons de riz et de maïs (28 % sont les plus utilisés. Les prix moyens de ces sous-produits varient entre 20 et 105 FCFA/kg. Oreochromis niloticus et Heterotis niloticus sont les principales espèces élevées en polyculture sur les fermes. Les sous-produits sont utilisés en système semi-intensif, extensif et en rizipisciculture, en majorité en zone rurale. Les pisciculteurs sont pour la plupart des agriculteurs, âgés de plus de 40 ans. Les taux d’utilisation des sous-produits sont plus élevés dans les régions de l’Ouest, du Centre-Ouest et du Sud-Ouest de la Côte d’Ivoire, par rapport à celles du Sud et de l’Est. Les rendements des fermes sont relativement faibles (544 à 2445 kg/ha/an, avec des gains moyens quotidiens de 0,87 et 9,97 g/j pour le tilapia et l’heterotis respectivement. L’analyse des stratégies des acteurs suggère la nécessité de définir des mécanismes d’accompagnement et de financement de la pisciculture, afin que ces acteurs puissent améliorer les formulations alimentaires à partir des matières premières locales et accessibles.

  17. The impact of radiotherapy for carcinoma of the cervix on sexual function assessed using the LENT SOMA scales

    International Nuclear Information System (INIS)

    Davidson, Susan E.; Burns, Meriel P.; Routledge, Jacqueline A.; Swindell, Ric

    2003-01-01

    Background and purpose: As there are few studies examining the impact of radiotherapy on sexuality, we assessed the effect of radiotherapy for carcinoma of the cervix on sexual health and the ability of the LENT system to assess sexual function. Materials and methods: Using the vagina and sexual dysfunction scales of the LENT SOMA scales, subjective scores were measured prospectively before initiation of radiotherapy for 89 women, and at the following times after the start of treatment: 21, 70, 200, 400, 600 and 800 days. Results: There was considerable variation in pre-radiotherapy scores that was not related to disease stage (P=0.054), but was related to patient age (P=0.037, for the average vagina scores and P=0.039 for the maximum vagina scores) The scores were influenced by prior surgery (P<0.0005 for maximum and average vagina scores, P=0.042 average and 0.017 maximum sexual dysfunction scores). For 48 patients for whom data were available at the first three time points, the vagina scores decreased significantly by 70 days compared to pre-radiotherapy scores, but not for sexual dysfunction. There was heterogeneity in the pattern of changes of scores over time: for some women there was no change in vagina subsection score, some increased, and some decreased. Conclusions: The work has shown variation both in pre-treatment sexual function and in the pattern of changes seen following radiotherapy. Our questionnaire proved useful to score subjective sexual and vaginal problems as given in the LENT subjective scales. Further study is needed to assess the effectiveness of the scales in assessing late effects

  18. Principios para el cálculo de la lente intraocular tras cirugía refractiva corneal

    Directory of Open Access Journals (Sweden)

    Taimí Cárdenas Díaz

    Full Text Available Se estima que aproximadamente un millón o más de pacientes se realizan cirugía refractiva al año. Es por eso que con el envejecimiento son cada día más frecuentes los pacientes con catarata, a quienes previamente se les ha efectuado cirugía refractiva. El cálculo inexacto de la potencia dióptrica de la lente a implantar en la intervención de estos es también un problema de importancia creciente y con él la sorpresa refractiva. Este es mucho más complejo de lo normal, ya que existen dos fuentes de error: la incorrecta predicción de la posición efectiva de la lente por parte de la fórmula y la determinación errónea de la potencia de la córnea por parte de la queratometría. La corrección de estos dos factores permitirá realizar un cálculo correcto en estos ojos. De ahí la motivación para realizar una búsqueda actualizadas de los últimos diez años de diversos artículos publicados, con el objetivo de describir los principios para el cálculo de la lente intraocular tras cirugía refractiva corneal. Se utilizó la plataforma Infomed, específicamente la Biblioteca Virtual de Salud, con todos sus buscadores.

  19. Development of the control assembly pattern and dynamic analysis of the generation IV large gas-cooled fast reactor (GFR); Developpement du design d'un assemblage de controle et analyse dynamique des reacteurs a neutrons rapides de quatrieme generation refroidis au gaz

    Energy Technology Data Exchange (ETDEWEB)

    Girardin, G.

    2009-07-09

    Among the systems selected by the GIF, the Gas-cooled Fast Reactor (GFR) is a highly innovative system with advanced fuel geometry and materials. It is in the context of the large, 2400 MWth reference GFR design that the present doctoral research has been conducted, the principal aim having been to develop and qualify the control assembly (CA) pattern and corresponding CA implementation scheme for this system. The work has been carried out in three successive and complementary phases: (1) validation of the neutronics tools, (2) the CA pattern development and related static analysis, and (3) dynamic core behavior studies for hypothetical CA driven transients. During the first phase of the thesis, the reference PROTEUS test lattice from these experiments has been analyzed with ERANOS-2.0 and its associated, adjusted nuclear data library ERALIB1. Additionally, benchmark calculations were performed with the Monte Carlo code MCNPX, allowing one to both check the deterministic results and to analyze the sensitivity to different modern data libraries. It has been found that, for the main reaction rate ratios, the new analysis of the GCFR-PROTEUS reference lattice generally yields good agreement - within 1{sigma} measurement uncertainty - with experimental values and with the Monte Carlo simulations. As shown by the analysis, the predictions were in somewhat better agreement in the case of the adjusted ERALIB1 library. The applicability of ERANOS-2.0/ERALIB1 as the reference neutronics tool for the GFR analysis could thus be demonstrated. Furthermore, neutronics aspects related to the novel features of the GFR, for which new experimental investigations are needed, were highlighted. In the second phase of the research, the CA pattern was developed for the GFR, based on iterative neutronics and thermal-hydraulics calculations, 2D and 3D neutronics models for the reactor core having first been set up using the reference ERANOS-2.0/ERALIB1 computational scheme. For the thermal

  20. The Control of Fast Reactors: Current Methods and Future Prospects; Controle des Reacteurs a Neutrons Rapides. Methodes Actuelles et Perspectives d'Avenir; Upravlenie reaktorami na bystrykh nejtronakh. sushchestvuyushchie metody i dal'nejshie perspektivy; Control de Reactores Rapidos: Metodos Actuales y Perspectivas

    Energy Technology Data Exchange (ETDEWEB)

    Loewenstein, W. B. [Argonne National Laboratory, IL (United States)

    1964-06-15

    regarding the specification of this parameter. These considerations are discussed in terms of control reactivity in existing fast reactors as opposed to the amount that is really required for fast power-breeder reactor operation. Typical power- and temperature-dependent feedback parameters are cited for determination of their influence upon the control reactivity requirements. The methods used to predict the reactivity worth of control mechanisms have evolved from crude estimates to quite reliable calculations which can be confirmed by experimental data from critical assemblies. Experimental results and currently reliable analytical techniques are described. Critical experiments for the current generation of fast reactors included many investigations pertaining to the reactivity worth of their control mechanisms as well as peripheral experiments for larger-core-volume advanced systems. Exploratory analytical studies, which indicate that detailed experimental mockup investigations may not be required in the future, are cited. (author) [French] L'auteur examine dans ce memoire les aspects pratiques du probleme qui consiste a fournir une reactivite suffisante pour le controle des reacteurs a neutrons rapides; ce probleme differe dans une grande mesure de celui du controle des reacteurs a neutrons thenniques. Ces differences sont dues en premier lieu au fait que les sections efficaces d'absorption des neutrons rapides sont assez faibles. Il n'existe pas de poisons forts dans un reacteur a neutrons rapides. En consequence, les poisons forts que sont certains produits de fission dans un reacteur thermique (par exemple Xe et Sm) exigent un exces de reactivite beaucoup moins important que n'en exige la perte de reactivite due a la destruction de produit fissile par fission et capture. Comme les sections efficaces pour les neutrons rapides sont relativement petites comparees aux valeurs correspondantes pour les neutrons thermiques, la densite atomique du materiau joue un role

  1. The diode pump: its application to nuclear particle counting and to the detection of rapid neutronic power excursions in atomic piles (1962); La pompe a diodes, son application au comptage de particules nucleaires et a la detection des excursions rapides de puissance neutronique d'une pile atomique (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Nicolo, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-05-15

    This work deals in particular with three applications of an electronic device whose principle is based on that of the diode pump. 1- Linear response circuit 2- Logarithmic response circuit 3- Detection of neutronic power excursions in atomic piles using a circuit or a combination of several circuits of the linear response type. Each of the applications has been studied theoretically and experimentally. Finally, the detection of rapid power excursions is extensively discussed with reference to the many methods available, emphasis being laid on the rapidity of the electronic response. (author) [French] Cet ouvrage traite plus particulierement de trois applications d'un dispositif electronique dont le principe de fonctionnement est base sur celui de la pompe a diodes. 1- Circuit a reponse lineaire 2- Circuit a reponse logarithmique 3- Detection des excursions de puissance neutronique d'une pile atomique a l'aide d'un circuit ou d'une association de plusieurs circuits a reponse lineaire. Chacune des applications fait l'objet d'une etude theorique et experimentale. Enfin, la detection des excursions rapides de puissance est tres largement discutee a travers plusieurs methodes, notamment sur la partie concernant la rapidite de reponse de l'electronique. (auteur)

  2. Structural and energetical studies of the adsorption of para and meta-isomers of xylene on pre-hydrated zeolite BaX. Characterization by neutron diffraction and temperature programmed desorption; Etude structurale et energetique de l'adsorption des isomeres para- et meta- du xylene dans la zeolithe BaX prehydratee. Caracterisation par diffraction des neutrons et thermodesorption programmee

    Energy Technology Data Exchange (ETDEWEB)

    Pichon, Ch.

    1999-10-19

    The separation of p-xylene from C{sub 8} aromatics is performed industrially by selective adsorption on zeolitic materials. FAU-type zeolites are currently used for this separation and especially the partially hydrated BaX. The aim of this work is to characterize from a structural (by low temperature neutron powder diffraction) and an energetical (by temperature programmed desorption) point of view, the adsorption of para- and meta- isomers of xylene, for different fillings, as pure substances as well as mixtures, on pre-hydrated zeolite BaX. The influence of the water pre-adsorption on xylene adsorption selectivity is carefully discussed. The crystalline structure of the zeolite BaX (framework and compensation of charge cations) and of the adsorbed phase (water, p- and m-xylene molecules) are completely characterized by neutron diffraction. The location and the distribution of water and xylene molecules on their adsorption sites is especially followed as a function of the filling of the zeolite and of the composition of the adsorbed phase. Microscopic measurements were correlated to the energetical analysis (at a macroscopic level) in order to obtain a consistent description of adsorption phenomenon and to propose a possible origin for adsorption selectivity.

  3. A review of calculation methods for fast and intermediate reactors; Expose des methodes pour le calcul de reacteurs a neutrons rapides et intermediaires; Obzor metodov rascheta reaktorov na promezhutochnykh i bystrykh nejtronakh; Estudio panoramico de los metodos de calculo de los reactores rapidos e intermedios

    Energy Technology Data Exchange (ETDEWEB)

    Marchuk, G I [Akademiya Nauk, Moskva, Union of Soviet Socialist Republics (Russian Federation)

    1962-03-15

    This paper discusses the development of methods for calculating intermediate and fast reactors. It deals with various approaches to the problems of physical calculation. The calculation of resonance effects is discussed. Consideration is given to multi-group systems of fundamental and conjugate equations, various applications of perturbation theory to the problems of physical reactor calculation, and numerical methods of solving fundamental and conjugate reactor equations, which approximate the method of spherical harmonics. The paper describes an application of the response method to the solution of critical-mass problems, and methods of calculating reactors with hydrogeneous moderators. The fundamental features of an effective one-group reactor model are described. (author) [French] L'auteur examine la mise au point de methodes pour le calcul de reacteurs a neutrons rapides et intermediaires . Il decrit diverses manieres d'aborder les problemes des calculs sur la physique des reacteurs, notamment le calcul des effets de resonance. Il s'attache particulierement aux points suivants: systemes d'equations fondamentales et conjuguees a plusieurs groupes; diverses applications de la theorie des perturbations aux problemes de calculs sur la physique des reacteurs; methodes numeriques pour resoudre les equations fondamentales et conjuguees, voisines de la methode des harmoniques spheriques. L'auteur decrit ensuite une maniere d'appliquer la methode de la reponse aux problemes de la masse critique ainsi que des methodes pour le calcul de reacteurs ralentis a l'hydrogene. Il decrit les caracteristique s fondamentale s d'un modele de reacteur a un groupe effectif. (author) [Spanish] El autor analiza el desarrollo de los metodos de calculo de los reactores nucleares que trabajan con neutrones rapidos y con neutrones intermedios. Examina diversos planteos de los problemas del calculo fisico. Indica la forma de tomar en cuenta los efectos de resonancia y menciona los sistemas

  4. Ultracold neutrons

    International Nuclear Information System (INIS)

    Steenstrup, S.

    Briefly surveys recent developments in research work with ultracold neutrons (neutrons of very low velocity, up to 10 m/s at up to 10 -7 eV and 10 -3 K). Slow neutrons can be detected in an ionisation chamber filled with B 10 F 3 . Very slow neutrons can be used for investigations into the dipole moment of neutrons. Neutrons of large wave length have properties similar to those of light. The limit angle for total reflection is governed by the wave length and by the material. Total reflection can be used to filter ultracold neutrons out of the moderator material of a reactor. Total reflection can also be used to store ultracold neutrons but certain problems with storage have not yet been clarified. Slow neutrons can be made to lose speed in a neutron turbine, and come out as ultracold neutrons. A beam of ultracold neutrons could be used in a neutron microscope. (J.S.)

  5. Experimental Determination of the Neutron Characteristics of UO{sub 2}-PuO{sub 2}-H{sub 2}O Lattices; Determination Experimentale Des Caracteristiques Neutroniques De Reseaux UO{sub 2}-PuO{sub 2}-H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Debrue, J.; Fabry, A.; Leenders, L.; Motte, F.; Van Den Broeck, H. [Centre d' Etude de l' Energie Nucleaire, Mol (Belgium)

    1967-09-15

    plutonium: fission density measurements by direct counting of the fission products formed in the mixed fuel as a result of irradiation, and measurements of spectral indices by means of fission detectors and detectors having resonances close to those of the isotopes of plutonium. The optimum conditions for applying these techniques are described and the effect on the fuel cycle of uncertainties in the values for the spectral indices (ratios of cross-sections) is discussed. A brief reference is finally made to a programme of sub-critical experiments conducted hitherto with two batches of UO{sub 2} fuel enriched to 5% and 7% {sup 235}U, and having the purpose of studying possible methods of exciting a sub-critical lattice by means of an external neutron source in pulsed and modulated operation. The aim of this programme is to ascertain to what extent these methods, which employ a quantity of fuel considerably less than the critical mass, can help in determining the characteristics of a lattice. The advantages of such methods are particularly obvious in the case of plutonium fuels. (author) [French] Au cours de l'etude dans l'installation critique VENUS du coeur a moderation variable du reacteur BR3/VULCAIN, un assemblage combustible constitue de 37 crayons UO{sub 2}-PuO{sub 2} (94% UO{sub 2} naturel, PuO{sub 2}) a ete substitue a un des assemblages combustibles UO{sub 2} enrichi a 7% {sup 235}U constituant le coeur de ce reacteur. Des experiences ont ete effectuees dans le but de permettre l'ajustement des modeles du calcul des performances de cet assemblage special: on a notamment mesure la distribution de la densite de fission ainsi que l'evolution du rapport des sections efficaces effectives de fission dans {sup 239}Pu et {sup 235}U. Une experience critique directement orientee sur les problemes de recyclage du plutonium dans les reacteurs thermiques a eau legere pressurisee est en cours d'execution dans la meme installation critique. A cette fin, on dispose de deux

  6. The influence of the (n, 2n) and (n, {alpha}) reactions of beryllium on the neutron balance in a BeO or Be moderated reactor and its consequences on the long term reactivity changes; Influence des reactions (n, 2n) et (n, {alpha}) du beryllium sur le bilan neutronique d'un reacteur modere a l'oxyde de beryllium ou au beryllium. Consequences sur l'evolution a long terme de la reactivite

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, K; Benoist, P; Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The reaction probabilities in an infinite and homogeneous medium of BeO or Be have been calculated from neutron cross-section curves, for a neutron produced with an energy distribution similar to a fission spectrum; the calculation shows that, after several elastic collisions, the neutron has yet an appreciable probability to undergo a reaction, in spite of the energy degradation in the spectrum due to each collision. This degradation has been calculated, taking into account of anisotropy of the collisions. The gain of the reactivity in a reactor has been obtained after correcting these probabilities for the attenuation of the flux of fission neutrons due to the inelastic scattering in the uranium. Finally, the calculation shows that in a power reactor, this gain of reactivity is in practice destroyed in a few years by the accumulation of poisonous nuclei such as Li{sup 6} and He{sup 3} following (n, {alpha}) reaction. (author) [French] Les probabilites de reaction en milieu infini et homogene de glucine (BeO) ou de beryllium ont ete calculees a partir des courbes de section efficace pour un neutron naissant suivant un spectre de fission; le calcul montre qu'apres plusieurs diffusions elastiques le neutron a encore une probabilite appreciable de subir une reaction, malgre la degradation du spectre a chaque diffusion; cette degradation a ete calculee en tenant compte de l'anisotropie du choc. Le gain de reactivite dans un reacteur a ensuite ete obtenu en corrigeant les probabilites en milieu homogene de l'effet l'attenuation du flux des neutrons de fission par les chocs inelastiques dans les barres d'uranium. Enfin, le calcul montre que, dans un reacteur de puissance, ce gain de reactivite est pratiquement detruit en peu d'annees par l'accumulation de noyaux poisons Li{sup 6} et He{sup 3} consecutive a la reaction (n, {alpha}). (auteur)

  7. Influence of i{sub 13/2} proton and j{sub 15/2} neutron intruding orbitals on the behaviour of 190 mass region superdeformed nuclei; Influence des orbitales intruses proton i{sub 13/2} et neutron j{sub 15/2} sur le comportement des noyaux superdeformes de la region de masse 190

    Energy Technology Data Exchange (ETDEWEB)

    Duprat, J

    1995-01-01

    This work concerns the study of the nuclear superdeformation phenomenon in the A = 190 mass region. The superdeformed (SD) states in {sup 193}Tl, {sup 194}Tl {sup 195}Tl were produced via heavy-ion induced reactions and studied with the EUROGAM gamma multidetector array. The analysis of high-multiplicity events allowed the study of the magnetic properties of the SD states in these nuclei. For the first time, the g-factor of a proton orbital in a SD nucleus in the A = 190 mass region has been extracted. This measurement indicates that the two known bands in {sup 195}Tl-SD are built on the i{sub 13/2} proton intruder orbital. A new SD band has been found in this isotope: it is the first SD band built on an excited proton state found in the A = 190 region. Finally an interaction between two pairs of bands has been established in {sup 194}Tl; this interaction indicate the crossing of two neutron orbitals above the N = 112 gap. The magnetic properties of the states of the SD bands in {sup 194}Tl reveals that these bands are built on configurations in which the single proton and neutron intrinsic spins are aligned. Comparison between different SD bands in the Thallium isotopes shows the prominent role of the i{sub 13/2} proton and the j{sub 15/2} neutron intruder orbitals in the smooth increase of the dynamical moment of inertia as a function of the rotational frequency. In addition, this work reports on the first observation of a SD rotational band produced in a (HI, {alpha}xn) reaction channel. The study of the maximum spin reached by the SD bands indicates both a competition between alpha emission and fission of the compound nucleus, and the limitation due to the fission process in the population of the SD nuclei in the A = 190 region. (author). 120 refs., 112 figs., 22 tabs., 2 ann.

  8. Control of radioactive wastes and coupling of neutron/gamma measurements: use of radiative capture for the correction of matrix effects that penalize the fissile mass measurement by active neutron interrogation; Controle des dechets radioactifs et couplage de mesures neutron/gamma: exploitation de la capture radiative pour corriger les effets de matrice penalisant la mesure de la masse fissile par interrogation neutronique active

    Energy Technology Data Exchange (ETDEWEB)

    Loche, F

    2006-10-15

    In the framework of radioactive waste drums control, difficulties arise in the nondestructive measurement of fissile mass ({sup 235}U, {sup 239}Pu..) by Active Neutron Interrogation (ANI), when dealing with matrices containing materials (Cl, H...) influencing the neutron flux. The idea is to use the neutron capture reaction (n,{gamma}) to determine the matrix composition to adjust the ANI calibration coefficient value. This study, dealing with 118 litres, homogeneous drums of density less than 0,4 and composed of chlorinated and/or hydrogenated materials, leads to build abacus linking the {gamma} ray peak areas to the ANI calibration coefficient. Validation assays of these abacus show a very good agreement between the corrected and true fissile masses for hydrogenated matrices (max. relative standard deviation: 23 %) and quite good for chlorinated and hydrogenated matrices (58 %). The developed correction method improves the measured values. It may be extended to 0,45 density, heterogeneous drums. (author)

  9. A pulsed fast reactor; Un reacteur pulse a neutrons rapides; Impul'snyj reaktor na bystrykh nejtronakh; Reactor rapido pulsado

    Energy Technology Data Exchange (ETDEWEB)

    Blokhin, G. E.; Blokhintsev, D. I.; Blyumkina, Yu. A.; Bondarenko, I. I.; Deryagin, B. N.; Zajmovskij, A. S.; Zinov' ev, V. P.; Kazachkovskij, O. D.; Krasnoyarov, N. V.; Lejpunskij, A. I.; Malykh, V. A.; Nazarov, P. M.; Nikolaev, S. K.; Stavisskij, Yu. Ya.; Ukraintsev, F. I.; Frank, I. M.; Shapiro, F. Ji.; Yazvitskij, Yu. S. [Akademiya Nauk, Moscow, SSSR (Russian Federation)

    1962-03-15

    fonctionne a la puissance nominale depuis le mois de decembre 1960. Ce reacteur est utilise comme source puisee de neutrons pour les experiences de physique fondees sur la methode du temps de vol. On l'emploie pour etablir la section efficace totale et la section efficace de capture des neutrons intermediaires, pour etudier l'interaction des neutrons lents et des corps solides ou liquides et pour mesurer les spectres neutroniques dans differents milieux. Le memoire decrit les caracteristique s essentielles de la construction du reacteur et les resultats d'experiences faites a l'aide de ce reacteur. Le regime de fonctionnemen t normal est celui des impulsions periodiques. Les impulsions de puissance sont produites par un deplacement rapide de la partie mobile du coeur a travers sa partie immobile. La partie mobile se trouve fixee sur un disque tournant et se deplace a une vitesse d'environ 230 m/s. Une zone mobile auxiliaire permet de modifier la frequence des impulsions de puissance entre 2,3 et 88 ips. Le reacteur a une puissance moyenne de 1 kW. La demi-largeur d'une impulsion de puissance est de 36 {mu}/s. Le reacteur est dote d'un systeme de commande et de securite qui assure le maintien automatique de la puissance moyenne et un arret rapide en cas de fonctionnement irregulier. Il est equipe d'un systeme de canalisations sous vide pour le passage des neutrons, qui permettent de mesurer le temps de vol. Le canal principal a 1000 m de long. Lors du demarrage du reacteur et durant les experiences de physique dont il a fait l'objet, on a etudie l'effet que produit sur la reactivite le deplacement des organes de commande et des parties mobiles du coeur; on a mesure la longueur des impulsions a des regimes de fonctionnement differents et etudie les fluctuations d'amplitude des impulsions de puissance. En outre, les auteurs ont procede a des mesures en vue de determiner la duree de vie des neutrons instantanes, la fraction effective de neutrons retardes et les coefficients de

  10. Rapid Estimation of Fast-Neutron Doses following Radiation Exposure in Criticality Accidents: The S{sup 32}(n, p)P{sup 32} Reaction in Body Hair; Prompte Evaluation des Doses de Neutrons Rapides apres une Exposition au Rayonnement a la Suite d'Accidents de Criticite: Reaction {sup 32}S(n, p){sup 32}P dans le Systeme Pileux; 0411 042b 0421 0414 ; Evaluacion Acelerada de Dosis de Neutrones Rapidos Despues de una Irradiacion Consecutiva a un Accidente de Criticidad: La Reaccion {sup 32}S(n, p){sup 32}P en el Pelo

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, D. F. [Los Alamos Scientific Laboratory, University of California, Los Alamos, NM (United States)

    1965-06-15

    information for comparison with average total-body neutron exposure estimates based on blood Na{sup 24} measurements. Fission yield estimates based on deduced geometries in each case were in good agreement with independent determinations of total fissions by more conventional analytical procedures. For rapid approximations of fast neutron dose, P{sup 32} activity in dpm/g hair at T = 0 from any counting system of known efficiency is simply multiplied by 0.49 to obtain ''sulphur-level'' neutron dose in rads. (author) [French] Etant donne sa composition chimique constante, sa situation anatomique fixe et sa facilite de prelevement, le systeme pileux de l'homme offre un materiau de choix permettant d'evaluer en peu de temps des doses de neutrons rapides recues par le personnel implique dans des accidents de criticite. La teneur en soufre du cheveu ou du poil est remarquablement constante, independente du sexe, de la couleur ou de la region ou il pousse; comme cette teneur est de 0,048 {+-} 0,005 g au gramme, on peut prendre le chiffre de 5% pour les estimations preliminaires de dose, sans avoir a proceder chaque fois a un dosage individuel du soufre. En l'absence d'une contamination externe facile a eliminer, le cheveu ou le poil contient moins de 0,025% de phosphore; etant donne que les sections efficaces d'activation du soufre et du phosphore sont semblables, l'absence virtuelle de phosphore permet d'utiliser le soufre du cheveu ou du poil comme un detecteur biologique a seuil pour la mesure du flux de neutrons de 2,5 MeV et plus, en appliquant la reaction {sup 32}S(n, p){sup 32}P. On a mis au point des methodes d'isolement rapide de {sup 32}P radiochimiquement pur pour permettre des estimations a des fins cliniques de l'exposition aux neutrons rapides des victimes des accidents de criticite. En l'absence d'une forte contamination par les produits de fission, on peut proceder aux evaluations dans les deux heures. Le procede plus complet qui comporte l'elimination des produits

  11. Study of the effect of neutron and electron irradiations on the low temperature thermal conductivity of germanium and silicon; Etude de l'effet des irradiations neutronique et electronique sur la conductibilite thermique aux basses temperatures du germanium et du silicium

    Energy Technology Data Exchange (ETDEWEB)

    Vandevyver, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-06-15

    The main results obtained from this work are the following: 1 Neutron irradiation (at 300 deg. K) produces lattice defects in germanium and silicon, and a corresponding very large lowering of the thermal conductivity is observed in the low temperature region (4-300 ). The results obtained have been explained with the help of the following hypotheses: for silicon a scattering of phonons by the stress fields produced by the defects; for germanium, a supplementary scattering of the electron phonon type. 2 Annealing treatments carried out on these materials above 373 deg. K restored the thermal conductivity over the whole temperature range of the measurements (4-300 deg. K); in the case of both germanium and silicon there were two steps in the annealing process. 3 A study of the thermal conductivity of germanium (initially P or N) after an electronic irradiation showed that the scattering of phonons could depend on the state of charge of the defects thus produced. (author) [French] Les principaux resultats obtenus au cours de ce travail sont les suivants : 1 Les irradiations neutroniques (a 300 deg. K) introduisent des defauts de reseau dans le germanium et le silicium et l'on observe correlativement pour ces materiaux, une tres importante diminution de conductibilite thermique dans le domaine des basses temperatures (4-300 deg. K). Les resultats obtenus ont pu etre interpretes en admettant principalement: pour le silicium, une diffusion des phonons par les champs de contrainte dus aux defauts; pour le germanium, une diffusion additionnelle du type electron-phonon. 2 Des recuits effectues sur ces materiaux au-dessus de 373 deg. K ont montre une restauration de la conductibilite thermique dans tout l'intervalle de temperature de mesure (4-300 deg. K) et comportant pour le germanium et le silicium, deux etapes de recuit 3 L'etude de la conductibilite thermique de germanium (initialement N ou P) apres une irradiation electronique, a montre que la diffusion des phonons

  12. ANALYSE DES PERCEPTIONS LOCALES ET DES FACTEURS ...

    African Journals Online (AJOL)

    AISA

    1Faculté des Sciences Agronomiques (FSA), Université d'Abomey-Calavi (UAC), 01 BP 526 Cotonou Bénin. Email : cgbemavo@yahoo.fr. 2Institut National des Recherches Agricoles du Bénin, Centre de Recherches Agricoles d'Agonkanmey (CRA-A),. Laboratoire des Sciences du Sol, Eau et Environnement (LSSEE).

  13. Resultados topográficos en pacientes portadores de lentes de contacto Topographic results achieved patients wearing contact lens

    Directory of Open Access Journals (Sweden)

    Tania Aymeé Díaz Martínez

    2009-06-01

    Full Text Available OBJETIVOS: Analizar los resultados topográficos en pacientes portadores de lentes de contacto y candidatos a cirugía refractiva con excimer láser, en el Hospital "Carlos Juan Finlay"; determinar el comportamiento según edad y sexo; conocer el tipo de lente de contacto empleado y su tiempo de uso; conocer el comportamiento según la edad y el sexo; identificar la relación del patrón topográfico corneal inducido en portadores de lentes de contacto con el moldeamiento corneal y el queratocono. MÉTODOS: Es un estudio retrospectivo de las topografías de los candidatos para cirugía refractiva durante los últimos 2 años, de 80 pacientes (todos ellos portadores de lentes de contacto. Para las exploraciones se emplearon los topógrafos OPTIKON AMF510P y el HUMPHREY. A todos se les realizó un examen oftalmológico completo (refracción manifiesta, biomicroscopia, queratometría, paquimetría y topografía corneal. Se compararon los resultados y su estabilidad. También se analizó la edad, el sexo, el tipo de lentes de contacto, así como su tiempo de utilización. RESULTADOS: Se trataron 158 ojos, de ellos 83 presentaron un patrón topográfico normal, 58 moldeamiento corneal inducido por el uso de lentes de contacto y en 17 se evidenció queratocono. La edad media de los pacientes fue de 27 años. El astigmatismo corneal medio en los pacientes con queratocono fue de -3,25 dioptrías, y de -1,12 dioptrías en pacientes con moldeamiento corneal. La lectura del meridiano más plano en pacientes con queratocono fue de 46,75 dioptrías, y en moldeamiento corneal 43,25 dioptrías. En los queratoconos el meridiano más curvo fue de 54,75 dioptrías, y en el moldeamiento corneal 46,00 dioptrías. CONCLUSIONES: El tipo de lente de contacto, así como su tiempo de uso influyen en la aparición del moldeamiento corneal inducido y el queratocono subclínico, y ambos presentaron un patrón topográfico similar.OBJECTIVES: To analyze the topographic

  14. Lente de contato em crianças: aspectos epidemiológicos Contact lens in children: epidemiological aspects

    Directory of Open Access Journals (Sweden)

    André Luiz Alves Salame

    2008-06-01

    Full Text Available OBJETIVO: Traçar o perfil epidemiológico de crianças encaminhadas para adaptação de lente de contato. MÉTODOS: Foi realizado estudo retrospectivo de pacientes registrados no Setor de lente de contato da Universidade Federal de São Paulo. Os pacientes com até 12 anos de idade foram avaliados quanto ao sexo, idade, diagnóstico, indicação e tipo de lente de contato testada na primeira consulta. RESULTADOS: Dos 73 prontuários avaliados, 34 (46,6% pertenciam a crianças do sexo masculino e 39 (53,4% a crianças do sexo feminino. A idade variou de 2 a 12 com média de 10,2 e desvio-padrão de 2,42 anos. O diagnóstico mais encontrado foi afacia em 16 (21,9% crianças, seguido de ceratocone em 14 (19,1%, leucoma em 11 (15%, anisometropia em 10 (13,7%, ametropia em 9 (12,3%, astigmatismo irregular em 7 (9,5% e ectopia lentis em 4 (5,4%. Uma criança era alta míope (1,3% e outra emétrope (1,3% que possuía desejo de usar lente de contato estética. Em relação às indicações, 52 (71,2% pacientes tinham indicação médica, 9 (12,3% indicação óptica e 12 (16,4% indicação cosmética. Foram testadas lentes em 103 olhos sendo as mais testadas a rígida gás permeável esférica em 43 (41,7%, a gelatinosa esférica em 41 (39,8% e a gelatinosa cosmética em 11 (10,6%. CONCLUSÃO: O perfil epidemiológico dos usuários de lente de contato nessa faixa etária tem como diagnóstico mais prevalente a afacia, a indicação mais freqüente a de ordem médica e a lente mais testada a rígida gás permeável esférica.PURPOSE: To describe the epidemiology of children submitted to contact lens fit. METHODS: Retrospective study of 73 children that had been submitted to contact lens fit at the "Universidade Federal de São Paulo". This study analyzed sex distribution, age, diagnosis, indications and contact lens fitted at first examination. RESULTS: 34 children (46.6% were male and 39 (53.4% female, aged between 2 and 12 years with mean of 10.2 and

  15. Resultados de implante de lente intraocular en niños Results of intraocular lens implantation in children

    Directory of Open Access Journals (Sweden)

    Nashelly I. Mejía Cruz

    2007-12-01

    Full Text Available En este estudio se describen los resultados obtenidos del implante de lente intraocular en niños, quienes acudieron al servicio de Oftalmología Pediátrica de Instituto Cubano de oftalmología “Ramón Pando Ferrer” con el diagnóstico de catarata de diversas etiologías, en período comprendido entre abril del 2002 al 2005 cuyo seguimiento fue durante un año. En nuestro universo de estudio se determinan algunos parámetros como la edad del paciente, etiología de las cataratas, agudeza visual, defecto refractivo preoperatorio y posoperatorio. Se identificó el poder dióptrico del lente intraocular más frecuente, la presencia de complicaciones durante la cirugía y después de esta. Se evaluaron finalmente, los pacientes que requerían de tratamiento adicional como la capsulotomía con láser o membranectomía quirúrgica. El implante del lente intraocular a temprana edad se relacionó con buenos resultados quirúrgicos: mejoría de la agudeza visual corregida, presentándose el astigmatismo como el error refractivo más frecuente. La complicación transoperatorio y postoperatoria más frecuente fue la membrana inflamatoria, mientras que la complicación posoperatoria más frecuente fue la opacidad de la cápsula posterior.This paper described the results of the intraocular lens implantation performed in children, who had been seen at the Pediatric Ophthalmologic Service of " Ramon Pando Ferrer " Cuban Institute of Ophthalmology and had been diagnosed as having cataract of various etiologies, from April 2002 to April 2005. They were all followed-up for a year. Some parameters like the patient’s age, the etiology of cataract, visual acuity, pre-operative and post-operative refractive defect were considered in our study. The dioptric power of the most common intraocular lens and the most frequent complications during and after surgery were identified. The patients requiring additional treatment such as laser capsulotomy and surgical

  16. Determination of neutron resonance parameters of Neptunium 237 between 0 and 500 eV. The covariance matrices of statistical and of systematic origin, relating the resonance parameters, are also given; Determination des parametres des resonances neutroniques du neptunium 237, en dessous de 500eV, et obtention des matrices de covariances statistiques et systematiques entre les parametres de ces resonances

    Energy Technology Data Exchange (ETDEWEB)

    Lepretre, A.; Herault, N. [CEA Saclay, Dept. d' Astrophysique de Physique des Particules, de Physique Nucleaire et de l' Instrumentation Associee, 91- Gif sur Yvette (France); Brusegan, A.; Noguere, G.; Siegler, P. [Institut des Materiaux et des Metrologies - IRMM, Joint Research Centre, Gell (Belgium)

    2002-12-01

    This report is a follow up of the report CEA DAPNIA/SPHN-99-04T of Vincent Gressier. In the frame of a collaboration between the 'Commissariat a l'Energie Atomique (CEA)' and the Institute for Reference Materials and Measurement (IRMM, Geel, Belgique), the resonance parameters of neptunium 237 have been determined in the energy interval between 0 and 500 eV. These parameters have been obtained by using the Refit code in analysing simultaneously three transmission experiments. The covariance matrix of statistical origin is provided. A new method, based on various sensitivity studies is proposed for determining also the covariance matrix of systematic origin, relating the resonance parameters. From an experimental viewpoint, the study indicated that, with a large probability, the background spectrum has structure. A two dimensional profiler for the neutron density has been proved feasible. Such a profiler could, among others, demonstrate the existence of the structured background. (authors)

  17. Analysis of space and energy homogenization techniques for the solving of the neutron transport equation in nuclear reactor; Analyse des techniques d'homogeneisation spatiale et energetique dans la resolution de l'equation du transport des neutrons dans les reacteurs nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Magat, Ph

    1997-04-01

    Today neutron transport in PWR's core is routinely computed through the transport-diffusion(2 groups) scheme. This method gives satisfactory results for reactors operating in normal conditions but the 2 group diffusion approximation is unable to take into account interface effects or anisotropy. The improvement of this scheme is logically possible through the use of a simplified P{sub N} method (SP{sub N}) for the modeling of the core. The comparison between S{sub N} calculations and SP{sub N} calculations shows an excellent agreement on eigenvalues as well as on power maps. We can notice that: -) it is no use extending the development beyond P{sub 3}, there is no effect; -) the P{sub 1} development is adequate; and -) the P{sub 0} development is totally inappropriate. Calculations performed on the N4 core of the Chooz power plant have enabled us to compare diffusion operators with transport operators (SP{sub 1}, SP{sub 3}, SP{sub 5} and SP{sub 7}). These calculations show that the implementation of the SP{sub N} method is feasible but the extra-costs in computation times and memory are important. We recommend: SP{sub 5}P{sub 1} calculations for heterogeneous 2-dimension geometry and SP{sub 3}P{sub 1} calculations for the homogeneous 3-dimension geometry. (A.C.)

  18. Analysis of space and energy homogenization techniques for the solving of the neutron transport equation in nuclear reactor; Analyse des techniques d'homogeneisation spatiale et energetique dans la resolution de l'equation du transport des neutrons dans les reacteurs nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Magat, Ph

    1997-04-01

    Today neutron transport in PWR's core is routinely computed through the transport-diffusion(2 groups) scheme. This method gives satisfactory results for reactors operating in normal conditions but the 2 group diffusion approximation is unable to take into account interface effects or anisotropy. The improvement of this scheme is logically possible through the use of a simplified P{sub N} method (SP{sub N}) for the modeling of the core. The comparison between S{sub N} calculations and SP{sub N} calculations shows an excellent agreement on eigenvalues as well as on power maps. We can notice that: -) it is no use extending the development beyond P{sub 3}, there is no effect; -) the P{sub 1} development is adequate; and -) the P{sub 0} development is totally inappropriate. Calculations performed on the N4 core of the Chooz power plant have enabled us to compare diffusion operators with transport operators (SP{sub 1}, SP{sub 3}, SP{sub 5} and SP{sub 7}). These calculations show that the implementation of the SP{sub N} method is feasible but the extra-costs in computation times and memory are important. We recommend: SP{sub 5}P{sub 1} calculations for heterogeneous 2-dimension geometry and SP{sub 3}P{sub 1} calculations for the homogeneous 3-dimension geometry. (A.C.)

  19. Estimation de la survie des alevins de carpe (C. carpio au cours de leur premier mois d'existence

    Directory of Open Access Journals (Sweden)

    MOREAU J.

    1979-10-01

    Full Text Available Des observations réalisées sur deux stations piscicoles de Madagascar, dans des étangs ne recevant ni engrais ni nourriture, révèlent qu'au cours de leur premier mois les alevins de carpe (C. carpio subissent des mortalités voi-sines de 50 %. Ces dernières sont encore plus élevées en début et en fin de saison de reproduction. Au début, les fortes mortalités sont dues à la température trop basse et aux disponibilités alimentaires insuffisantes ; en fin de saison de reproduction, la température trop élevée et la mauvaise qualité des œufs sont sans doute en cause. Une fumure adéquate des étangs de grossissement des alevins et une alimentation correcte des géniteurs permettront peut-être de diminuer ces mortalités.

  20. Au-delà du plan. La topologie urbaine des livreurs

    Directory of Open Access Journals (Sweden)

    Céline Cholez

    2011-03-01

    Full Text Available Nombreuses sont les activités professionnelles au sein desquelles s’orchestrent des « défis » classant les professionnels en fonction de leur degré d’expertise. Parmi les livreurs, une joute fréquente consiste à soumettre à un collègue un nom et un numéro de rue au hasard pour qu’il indique le plus rapidement possible le plus court chemin pour y parvenir. Ces jeux professionnels révèlent un aspect essentiel de l’engagement dans l’activité de travail : l’ancrage dans un espace approprié comme territoire, le secteur de tournée. Les livreurs maîtrisent en effet leurs tâches grâce à leur connaissance des zones géographiques qu’ils sillonnent quotidiennement.

  1. Development of a semiconductor counter telescope with low background for the investigations of charged particles produced in reactions induced by neutrons; Realisation et mise au point d'un telescope a semi-conducteurs et a faible bruit-de-fond pour l'etude des reactions neutronsparticules chargees

    Energy Technology Data Exchange (ETDEWEB)

    Helleboid, J M [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-08-15

    A AE-E counter telescope for charged particles (p, d, t) produced in reactions with neutrons has been constructed. The semiconductor counter telescope method allows the investigations of two and three-body reactions {sup 6}Li(n,p), D(n,np)n induced by 14 MeV neutrons. By using a coincidence of associated alpha particle pulses with those ({delta}E,E) in the telescope, the background is considerably reduced for all angles outside the coincidence cone, i.e. larger than 15 deg. (L). For forward angles, the same telescope ({delta}E{sub 2}/E) plus a thin semiconductor ({delta}E{sub 1}) allows keeping a low background. The multiparameter analysing method ({delta}E{sub 1}, {delta}E{sub 2}, E) from the experimental range-energy data gives a linearity, an efficiency and an identifying power which are satisfactory. The identification is performed by differed time on a IBM 7044 computer. (author) [French] On a realise un spectrometre de particules chargees (p, d, t) avec identification des particules, pour l'etude des reactions neutrons-particules chargees. La methode du telescope a semi-conducteurs permet d'effectuer l'etude de reactions a deux corps [{sup 6}Li(n,p)] et de reactions a trois corps [D(n,pn)n] a 14 MeV. L'utilisation de la particule alpha associee en coincidence avec les impulsions ({delta}E,E) du telescope permet d'obtenir un bruit-de-fond tres faible pour tous les angles situes en dehors du cone de coincidence, c'est-a-dire superieurs a {approx_equal} 15 deg. (L). Pour les angles avant, le meme telescope ({delta}E{sub 2}/E) plus un semi-conducteur mince ({delta}E{sub 1}) permet de conserver un faible bruit-de-fond. La methode d'analyse multiparametrique ({delta}E{sub 1}, {delta}E{sub 2}, E) a partir des donnees experimentales parcours-energie, donne une linearite, une efficacite et un pouvoir d'identification satisfaisants. L'identification est effectuee en temps differe sur un calculateur numerique IBM 7044. (auteur)

  2. Sistemas atuais de cuidados e manutenção de lentes de contato Current care and maintenance systems for contact lenses

    Directory of Open Access Journals (Sweden)

    César Lipener

    2008-12-01

    Full Text Available A correta manutenção das lentes de contato é fundamental para se obter sucesso e manter a continuidade de seu uso. É grande o número de pacientes que abandonam o uso de suas lentes por problemas que poderiam ser solucionados com tratamentos relativamente simples ou com uma orientação mais adequada. O mau uso das lentes, associado à má adaptação, contaminação, doenças oculares prévias e fatores ambientais, podem aumentar o número de infecções corneanas através da proliferação de microorganismos. O presente artigo visa apresentar as atualizações em relação aos cuidados e manutenção com as lentes de contato.The proper maintenance of contact lenses is crucial for their success and to maintain the continuity of their use. Many patients abandon the use of their lenses due to problems that could be solved with relatively simple treatments. The misuse of lenses, coupled with poor adjustment, contamination, eye disease and environmental factors may increase the number of corneal infections through the proliferation of microorganisms. This article aims to provide contact lens care and maintenance updates.

  3. Alteraciones oculares y visuales en personas que trabajan con ordenador y son usuarias de lentes de contacto: una revisión bibliográfica

    Directory of Open Access Journals (Sweden)

    Ana Tauste Francés

    2014-01-01

    Full Text Available Fundamentos: El elevado número de personas que trabajando con ordenador utiliza lentes de contacto plantea la cuestión sobre si la suma de estos dos factores de riesgo para la salud visual puede originar un agravamiento del Síndrome Visual Informático. El objetivo de esta revisión es sintetizar el conocimiento científico sobre las alteraciones oculares y visuales relacionadas con la exposición a ordenador en usuarios de lentes de contacto. Métodos: Revisión de artículos científicos (2003-2013 en español e inglés, realizando una búsqueda bibliográfica, en Medline a través de PubMed y en Scopus. Resultados: La búsqueda inicial aportó 114 trabajos, después de aplicar criterios de inclusión/exclusión se incluyeron seis artículos. Todos ellos ponen de manifiesto que las alteraciones al utilizar el ordenador son más frecuentes en las personas usuarias de lentes de contacto, con prevalencias que oscilan de 95,0% al 16,9% que en las que no utilizan lentes de contacto, cuya prevalencia va del 57,5% al 9,9% y con una probabilidad cuatro veces mayor de padecer ojo seco [OR: 4,07 (IC 95%: 3,52-4,71]. Conclusiones: Las personas usuarias de ordenador padecen más alteraciones oculares y visuales cuando además son usuarias de lentes de contacto, pero los estudios son escasos y poco contundentes. Se precisan nuevas investigaciones que analicen la influencia según los tipos de lentes y sus condiciones de uso, tanto en la sintomatología como en la calidad de la lágrima y la superficie ocular. Las lentes de hidrogel de silicona son las que se asocian a mayor confort.

  4. Construcción de un microscopio simple con la lente de un teléfono celular

    Directory of Open Access Journals (Sweden)

    Ernesto Cyrulies

    2014-01-01

    Full Text Available En este artículo se propone la construcción de un microscopio simple recreando el principio de funcionamiento del microscopio de Leeuwenhoek, empleando en este caso una lente de cámara fotográfica de teléfono celular. El dispositivo permite observar y fotografiar estructuras celulares, cuyas imágenes ampliadas posibilitan ver ciertos detalles minúsculos. Se describe una manera sencilla de construirlo con materiales comunes. También se relata la implementación de la propuesta con alumnos de un instituto de formación docente y cuáles fueron sus resultados.

  5. Neutron reflectometry

    International Nuclear Information System (INIS)

    Van Well, A.A.

    1999-01-01

    Neutron research where reflection, refraction, and interference play an essential role is generally referred to as 'neutron optics'. The neutron wavelength, the scattering length density and the magnetic properties of the material determine the critical angle for total reflection. The theoretical background of neutron reflection, experimental methods and the interpretation of reflection data are presented. (K.A.)

  6. Study of magnetic excitations in the high critical temperature La{sub 2-x}Sr{sub x}CuO{sub 4} superconductor with neutrons inelastic scattering; Etude des excitations magnetiques dans le supraconducteur a haute temperature critique La{sub 2-x}Sr{sub x}CuO{sub 4} par diffusion inelastique des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Petit, S

    1997-11-25

    In this work, we question the relevance of spin correlations in the problem of high-T{sub c} superconductivity. To characterize these correlations, we present a detailed inelastic neutron scattering study of the magnetic excitations spectrum, in the high T{sub c} La{sub 2-x}Sr{sub x}CuO{sub 4} copper oxide superconductor, as a function of temperature and strontium content x. Our study demonstrates the existence of two distinct types of fluctuations. The first type corresponds to two-dimensional isotropic fluctuations peaked at incommensurate points around the antiferromagnetic wavevector. These fluctuations show a gap below T{sub c}. The second type of fluctuations corresponds to two-dimensional very low energy, typically 1 MeV, antiferromagnetic correlations. They arise at low temperatures, for T {<=}T{sub f} {approx} 10 K {<=}T{sub c}. Different scenarios are discussed, namely particle-hole excitation arising because of nesting properties of the Fermi surface, stripes, and localized carriers in the CuO{sub 2} plane because of the La/Sr substitution disorder. Next, aiming to study the interrelation between magnetism and superconductivity, we present a theoretical perturbative treatment of the t-t`-J model. This model is believed to describe the physics of the CuO{sub 2} plane. The considered quasiparticles describe the motion of a doped hole, followed by localized spins on the copper sites. For a given doping x, two phases can exist, containing either x or 1 + x of these quasiparticles. We show at in the second phase, the exchange interaction between localized spins, combined to the intrinsic anharmonicity of these quasiparticles leads to an attractive interaction between them. We study the stability and the symmetry of a superconducting phase based on this mechanism. (author) 215 refs.

  7. Tracking techniques for the method of characteristics applied to the neutron transport problem in multi-dimensional domains; Techniques de tracage pour la methode des caracteristiques appliquee a la resolution de l'equation du transport des neutrons en domaines multi-dimensionnels

    Energy Technology Data Exchange (ETDEWEB)

    Fevotte, F

    2008-10-15

    In the past years, the Method of Characteristics (MOC) has become a popular tool for the numerical solution of the neutron transport equation. Among its most interesting advantages are its good precision over computing time ratio, as well as its ability to accurately describe complicated geometries using non structured meshes. In order to reduce the need for computing resources in the method of characteristics, we propose in this dissertation two lines of improvement. The first axis of development is based on an analysis of the transverse integration technique in the method of characteristics. Various limitations have been discerned in this regard, which we intend to correct by proposing a new variant of the method of characteristics. Through a better treatment of material discontinuities in the geometry, our aim is to increase the accuracy of the transverse integration formula in order to decrease the computing resources without sacrificing the quality of the results. This method has been numerically tested in order to show its interest. Analysing the numerical results obtained with this new method also allows better understanding of the transverse integration approximations. Another improvement comes from the observation that industrial reactor cores exhibit very complex structures, but are often partly composed of a lattice of geometrically identical cells or assemblies. We propose a systematic method taking advantage of repetitions in the geometry to reduce the storage requirements for geometric data. Based on the group theory, this method can be employed for all lattice geometries. We present some numerical results showing the interest of the method in industrial contexts. (author)

  8. Some physics aspects of cermet and ceramic fast systems; Quelques aspects de la physique des reacteurs a neutrons rapides utilisant des cermets et des ceramiques comme combustibles; Nekotorye fizicheskie aspekty kermetnykh i keramicheskikh sistem na bystrykh nejtronakh; Algunos aspectos fisicos de los sistemas rapidos a base de combustibles cermet y ceramicos

    Energy Technology Data Exchange (ETDEWEB)

    Codd, J; James, M F; Mann, J E [United Kingdom Atomic Energy Authority, Reactor Group (United Kingdom)

    1962-03-15

    The characteristics of a system using an iron-based oxide cermet as fuel material are discussed. A transport theory investigation to develop methods of predicting the effect of core heterogeneity on reactivity and flux distribution is described. Some preliminary calculations are also given of resonance self-shielding and Doppler temperature effects in a cermet system. (author) [French] Les auteurs etudient les caracteristique s d'un reacteur utilisant comme combustible un cermet d'oxydes a armature de fer. Ils exposent une application de la theorie du transport a la mise au point des methodes permettant de prevoir l'effet de l'heterogeneite du coeur sur la reactivite et sur la distribution du flux. Ils donnent egalement quelques calculs preliminaires d'effets d'autoprotection due a la resonance et d'effet Doppler du a la chaleur dans un reacteur utilisant un cermet. (author) [Spanish] La memoria discute las caracteristicas de un sistema que emplea como combustible un oxido tipo cermet a base de hierro. Describe una investigacion de la teoria de transporte con miras a desarrollar metodos para evaluar el efecto de la heterogeneidad del cuerpo sobre la reactividad y la distribucion de flujo. Tambien da algunos calculos preliminares de los efectos del autoblindaje por resonancia y de la temperatura de Doppler en un sistema de tipo cermet. (author) [Russian] Obsuzhdayutsya kharakteristiki sistemy, ispol'zuyushchej v kachestve toplivnogo materiala oksidnye kermety, razrabotannye na osnove zheleza. Opisyvaetsya issledovanie teorii perenosa, chtoby razvit' metody predskazaniya vliyaniya geterogennosti aktivnoj zony na reaktivnost' i raspredelenie potoka. Dayutsya takzhe nekotorye predvaritel'nye raschety ehffektov rezonansnoj samozashchity i temperaturnogo ehffekta Dopplera v kermetnoj sisteme. (author)

  9. Kinetic study of the alkaline metals oxidation by dry oxygen; Etude cinetique de l'oxydation des metaux alcalins par l'oxygene sec

    Energy Technology Data Exchange (ETDEWEB)

    Touzain, Ph. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [French] L'oxydation du lithium, du sodium, du potassium, du rubidium, du cesium et des alliages sodium-potassium par l'oxygene sec est etudiee a diverses temperatures et a des pressions comprises entre 40 et 400 mmHg d'oxygene. On distingue trois processus d'oxydation differents (l'inflammation, l'ignition et la combustion lente) dont les domaines en fonction de la temperature sont precises. Les lois cinetiques d'oxydation lente, la nature des oxydes formes ainsi que les causes des colorations de ces oxydes sont determinees. Enfin les resultats obtenus sont interpretes theoriquement. (auteur)

  10. Kinetic study of the alkaline metals oxidation by dry oxygen; Etude cinetique de l'oxydation des metaux alcalins par l'oxygene sec

    Energy Technology Data Exchange (ETDEWEB)

    Touzain, Ph [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [French] L'oxydation du lithium, du sodium, du potassium, du rubidium, du cesium et des alliages sodium-potassium par l'oxygene sec est etudiee a diverses temperatures et a des pressions comprises entre 40 et 400 mmHg d'oxygene. On distingue trois processus d'oxydation differents (l'inflammation, l'ignition et la combustion lente) dont les domaines en fonction de la temperature sont precises. Les lois cinetiques d'oxydation lente, la nature des oxydes formes ainsi que les causes des colorations de ces oxydes sont determinees. Enfin les resultats obtenus sont interpretes theoriquement. (auteur)

  11. Principales métodos para el cálculo de la lente intraocular después de la cirugía refractiva corneal

    Directory of Open Access Journals (Sweden)

    Taimí Cárdenas Díaz

    Full Text Available Con el surgimiento y el desarrollo de la cirugía refractiva corneal se han podido corregir quirúrgicamente a millones de pacientes con defectos refractivos. Con el cursar de los años comienza a opacarse fisiológicamente el cristalino, y disminuye la agudeza visual en estos pacientes a quienes se les modificó la curvatura corneal. Ante la necesidad de remover el cristalino y de calcular una lente intraocular de potencia adecuada para conseguir la emetropía, surge un nuevo reto a la Oftalmología. El cálculo de la lente intraocular en pacientes con cirugía refractiva corneal es mucho más complejo, pues además de tener longitudes axiales extremas, se añaden factores por la intervención previa que alteran la predictibilidad del resultado visual, con la aplicación de las fórmulas de cálculo de lente intraocular existentes. Se han descrito varios métodos que permiten determinar correctamente la potencia de la lente a implantar, dependiendo de los datos de los que se dispongan; de ahí la motivación para realizar una revisión de diferentes publicaciones con el propósito de describir los principales métodos empleados para realizar el cálculo de la lente intraocular en estos pacientes. Se utilizó la plataforma Infomed, específicamente la Biblioteca Virtual de Salud, con todos sus buscadores.

  12. Modelisation des effets physico-techniques pour la conception des ...

    African Journals Online (AJOL)

    automatisation dans les installations industrielles a besoin d'une régulation automatique des commandes des processus technologiques pour lesquelles certaines contraintes sont à relever compte tenu des exigences des innovations scientifiques de ...

  13. Contribution to the study of nuclear structure using neutron total cross-section measurements between 400 and 1200 keV: isolated resonances and intermediate structure; Contribution a l'etude de la structure nucleaire par des mesures de sections efficaces neutroniques entre 400 keV et 1200 keV. Resonances isolees et structure intermediaire

    Energy Technology Data Exchange (ETDEWEB)

    Cabe, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-06-15

    The neutron total cross sections have been measured over the energy range 400 keV - 1200 keV for fluorine, aluminium, silicon, phosphorus, vanadium, chromium, manganese, iron, nickel, cobalt and lead with an energy spread of 3 keV. The neutrons were produced by the T (p,n) {sup 3}He reaction, the proton beam was supplied by a 2 MeV Van de Graaff. The structure in {sup 56}Fe has been studied in a more detailed way by measuring six angular distributions in the above range and the elastic scattering excitation curves at four angles. The measurements have made it possible to show the existence of the compound nucleus, as well as the presence of an intermediate structure in certain nuclei. (author) [French] Nous avons mesure les sections efficaces totales neutroniques entre 400 keV et 1200 keV du fluor, de l'aluminium, du silicium, du phosphore, du vanadium, du chrome, du manganese, du fer, du nickel, du cobalt et du plomb avec une dispersion en energie de 3 keV. Les neutrons etaient produits a l'aide de la reaction T (p,n) {sup 3}He, les protons etant acceleres par un Van de Graaff 2 MeV. Nous presentons de plus quatre courbes d'excitation de la diffusion elastique des neutrons sur le fer ainsi que six distributions angulaires. Ces mesures ont permis de mettre en evidence un certain nombres de resonances du noyau compose, ainsi que la presence d'une structure intermediaire dans. certains noyaux. (auteur)

  14. Neutron radiography with ultracold neutrons

    International Nuclear Information System (INIS)

    Bates, J.C.

    1981-01-01

    The neutron transmission factor of very thin films may be low if the neutron energy is comparable to the pseudo-potential of the film material. Surprisingly, perhaps, it is relatively easy to obtain neutrons with such low energies in sufficient numbers to produce neutron radiographs. (orig.)

  15. High resolution neutron spectroscopy - a tool for the investigation of dynamics of polymers and soft matter; La spectroscopie de neutrons a haute resolution-un outil pour l'etude de la dynamique des polymeres et de la matiere molle

    Energy Technology Data Exchange (ETDEWEB)

    Monkenbusch, M.; Richter, D. [Institut fur Festkorperforschung (IFF), Forschungszentrum Julich, Julich (Germany)

    2007-09-15

    Neutron scattering, with the ability to vary the contrast of molecular items by hydrogen/deuterium exchanges, is an invaluable tool for soft matter research. Besides the structural information on the mesoscopic scale that is obtained by diffraction methods like small angle neutron scattering, the slow dynamics of molecular motion on mesoscopic scale is accessible by high resolution neutron spectroscopy. The basic features of neutron backscattering spectroscopy, and in particular neutron spin-echo spectroscopy, are presented, in combination with illustrations of results from polymer melt dynamics to protein dynamics which are obtained by these techniques. (authors)

  16. Analyse des effets de deux modalités de constitution des groupes dans un dispositif hybride de formation à distance

    Directory of Open Access Journals (Sweden)

    Christian Depover

    2004-01-01

    Full Text Available Cette étude porte sur les effets de deux modalités de constitution des groupes (spontané versus contrasté dans un dispositif hybride de formation à distance destiné à des étudiants universitaires. Les scénarios d’apprentissage mis en œuvre à l’occasion de cette expérience reposent sur l’utilisation des cartes conceptuelles comme support au travail collaboratif. Les résultats observés n’ont pas permis de mettre en évidence de différence quant à la densité conceptuelle des cartes ou au nombre d’unités de sens produites. Par contre, il apparaît que les unités de sens qui concernent les activités de planification et les commentaires métacognitifs sont nettement plus nombreuses au sein des groupes constitués par pairage contrasté. Une corrélation positive entre l’intensité des interactions à l’intérieur du forum et la densité conceptuelle des cartes produites a également été mise en évidence pour les groupes constitués sur la base d’un pairage contrasté. En ce qui concerne le pairage spontané, nos résultats indiquent que les paires constituées témoignent d’un comportement plus homogène, se révèlent plus collaboratives et consacrent moins d’effort à la planification du travail de groupe.

  17. Neutron Skins and Neutron Stars

    OpenAIRE

    Piekarewicz, J.

    2013-01-01

    The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ("PREX") at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in 208Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron be...

  18. variabilite des productions et des revenus des exploitations

    African Journals Online (AJOL)

    3Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UMR Innovation,. Montpellier, France. Doubangolo COULIBALY, Email kone_b@yahoo.fr. RESUME. La durabilité des systèmes de production à base de coton dans un contexte de variabilité des prix aux producteurs et de ...

  19. Neutron Dosimetry

    International Nuclear Information System (INIS)

    Vanhavere, F.

    2001-01-01

    The objective of SCK-CEN's R and D programme on neutron dosimetry is to improve the determination of neutron doses by studying neutron spectra, neutron dosemeters and shielding adaptations. In 2000, R and D focused on the contiued investigation of the bubble detectors type BD-PND and BDT, in particular their sensitivity and temperature dependence; the updating of SCK-CEN's criticality dosemeter, the investigation of the characteristics of new thermoluminescent materials and their use in neutron dosemetry; and the investigation of neutron shielding

  20. Neutron Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Vanhavere, F

    2001-04-01

    The objective of SCK-CEN's R and D programme on neutron dosimetry is to improve the determination of neutron doses by studying neutron spectra, neutron dosemeters and shielding adaptations. In 2000, R and D focused on the contiued investigation of the bubble detectors type BD-PND and BDT, in particular their sensitivity and temperature dependence; the updating of SCK-CEN's criticality dosemeter, the investigation of the characteristics of new thermoluminescent materials and their use in neutron dosemetry; and the investigation of neutron shielding.

  1. Experiencia con la lente intraocular RAYNER 620H Experience gained with the use of intraocular lens RAYNER 620 H

    Directory of Open Access Journals (Sweden)

    Juan Raúl Hernández Silva

    2008-06-01

    Full Text Available Un importante eslabón en el progreso alcanzado en la cirugía de cataratas, está fundamentado en el desarrollo industrial paralelo que ha ocurrido durante los últimos años con la introducción de nuevos modelos de lentes intraoculares, como el Rayner 620 H; el perfeccionamiento del instrumental quirúrgico, sistemas de aspiración e irrigación bimanual y bisturí con la medida exacta para colocar el inyector de la lente intraocular. La lente intraocular Rayner 620H significó un gran paso para la facoemulsificación y el control de la opacidad de la cápsula posterior posoperatoria por el diseño peculiar de su óptica y hápticos, que permiten un implante seguro, fácil y una incisión mínima. Se realizó un estudio prospectivo y descriptivo, cuyo universo de estudio fueron 28 ojos con diagnóstico de cataratas a los cuales se les realizó facoemulsificación con implante de lente intraocular Rayner 620 H, en el Centro de Microcirugía Ocular del Instituto Cubano de oftalmología "Ramón Pando Ferrer" en el período comprendido entre junio de 2006 a febrero de 2007. El grupo de edades donde se encontró el de mayor número de pacientes fue en el de más de 60 años. En todos los casos hubo un aumento significativo de la agudeza visual sin corrección y con ella, del preoperatorio al posoperatorio. Hubo un aumento del cilindro queratométrico del preoperatorio al posoperatorio, pero este fue mínimo La pérdida de células endoteliales fue baja del preoperatorio al posoperatorio, respectivamente. No hubo ninguna complicación durante la cirugía ni después de esta. Evaluamos como satisfactoria la efectividad del lente intraocular Rayner 620 H, por el aumento de la agudeza visual del paciente, el bajo astigmatismo inducido, mejoría del campo visual por confrontación, mínima pérdida de células endoteliales, y ausencia de complicaciones y de deslumbramiento posoperatorio en los pacientes.An important link in the advances made by the

  2. Instruments used to measure or check {alpha}, {beta}, {gamma} activity and neutron emission in the course of processing ore or irradiated fuel; Appareils de mesure ou de controle {alpha}, {beta}, {gamma}, n, des circuits des usines de traitement du minerai ou du combustible irradie

    Energy Technology Data Exchange (ETDEWEB)

    Blanc, A; Brunet, M; Kermagoret, M; Labeyrie, J; Roux, G; Vasseur, J; Weil, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-07-01

    One of the methods checking ores in the course of treatment is the rapid quantitative determination of thorium. This measurement is carried out by means of a scintillation instrument which shows the {beta} and {alpha} coincidences of ThC and ThC'. The treatment of irradiated fuel is accompanied by a large number of radioactive checks relative to the performance of the fixation and elution operations of uranium in the ion exchangers, to the concentration of radioactivity of effluent sent from the plant into watercourses. The operations of fixation and elution of the uranium are checked automatically by an instrument which takes a sample of 5 cm{sup 3} of solution, evaporates it and measures its activity every 10 or 20 minutes. Plutonium concentrations are measured: - in the presence of strong {beta} {gamma} activities, by means of rotating cylinder detectors; - in the presence of weak {beta} {gamma} activities, by means of {alpha} detectors scanning a constant level liquid surface; - by means of fission chambers relatively insensitive to {gamma}. Fission product concentrations are measured by chambers, counters or scintillators, according to the amount of {gamma} activity present. Finally, the activity of effluent to be emptied into watercourses is checked by means of a scintillation instrument, which measures the {alpha} activity on the one hand, and on the other hand the {beta} {gamma} activity of residue from a 100 cm{sup 3} sample taken and evaporated in 20 minutes. (author) [French] Parmi les controles relatifs au minerai en cours de traitement, figure le dosage rapide de thorium. Cette mesure est realisee au moyen d'un appareillage a scintillation qui met en evidence la coincidence des emissions {beta} et {alpha} du ThC et du ThC'. Le traitement des combustibles irradies s'accompagne d'un grand nombre de controles radioactifs portant sur le fonctionnement des operations de fixation et d'elution de l'uranium dans les echangeurs d'ions, sur la concentration du

  3. Neutron radiography

    International Nuclear Information System (INIS)

    Hrdlicka, Z.

    1977-01-01

    Neutron radiography is a radiographic method using a neutron beam of a defined geometry. The neutron source usually consists of a research reactor, a specialized neutron radiography reactor or the 252 Cf radioisotope source. There are two types of the neutron radiography display system, viz., a system producing neutron radiography images by a photographic process or a system allowing a visual display, eg., using a television monitor. The method can be used wherever X-ray radiography is used except applications in the radiography of humans. The neutron radiography unit at UJV uses the WWR-S reactor as the neutron source and both types of the above mentioned display system. (J.P.)

  4. Géomorphologie et sédimentologie d'une plate-forme carbonatée isolée: l'Archipel des Glorieuses, SO Océan Indien

    OpenAIRE

    Prat, Sophie; Jorry, Stephan; Jouet, Gwenael; Le Roy, Pascal; Camoin, Gilbert; Vella, Claude; Caline, Bruno

    2013-01-01

    Améliorer nos connaissances sur la distribution des sédiments carbonatés dans les systèmes récifaux actuels sert à définir des analogues afin de mieux comprendre les réservoirs à hydrocarbures exploités dans les formations récifales fossiles. Bien que le rôle des changements du niveau marin, de la tectonique et de la sédimentation sur la dynamique et l'évolution des plates-formes carbonatés tropicales ait été largement étudié, la variabilité sédimentaire et les facteurs qui contrôlent cette h...

  5. Molecular Dynamics Investigated by Neutron Scattering; Etude de la Dynamique Moleculaire au Moyen de la Diffusion des Neutrons; 0418 0421 0421 041b 0415 0414 041e 0412 0410 041d 0418 0415 041c 041e 041b 0415 041a 0423 041b 042f 0420 041d 041e 0419 0414 0418 041d 0410 041c 0418 041a 0418 0421 041f 041e 041c 041e 0429 042c 042e 0420 0410 0421 0421 0415 042f 041d 0418 042f 041d 0415 0419 0422 0420 041e 041d 041e 0412 ; Estudio de la Dinamica Molecular por Dispersion Neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Janik, J. A. [Institute for Nuclear Physics, Cracow (Poland)

    1965-06-15

    is discussed from the point of view of molecular dynamics. (author) [French] L'auteur fait le point de l'etat actuel des connaissances touchant le probleme de l'applicabilite des theories de Krieger- Nelkin et de Griffing dans le cas des gaz. Ensuite, sur la base d'experiences faites avec du methane liquide, il examine d'une maniere critique l'applicabilite du concept du tenseur de masse a des molecules dans l'etat condense. Les arguments les plus puissants qui militent contre l'application de la theorie de Krieger-Nelkin aux etats condenses sont: a) un deplacement dans la distribution des neutrons en energie, apres diffusion, vers les grandes energies; b) l'absence d'une relation de dependance entre la fraction inelastique et l'angle de diffusion. D'autres parties du memoire traitent de la dynamique de rotation des groupes ammonium dans les composes d'ammonium. L'auteur discute la plupart des donnees d'experience relatives aux halogenures d'ammonium en se fondant sur les experiences de differents auteurs. Far des mesures de neutrons, il a obtenu une liberte de rotation des groupes NH{sub 4} pour certaines substances, tandis que pour d'autres la rotation evolue en vibration de torsion. Dans le dernier cas, il a compare les frequences des vibrations de torsion obtenues par divers auteurs au cours d'experiences sur les neutrons avec celles qui resultent de la spectroscopie infrarouge et des mesures de la chaleur specifique. L'auteur discute egalement l'obstacle qui s'oppose a l'evaluation de la rotation a l'aide de mesures des sections efficaces totales pour les neutrons. En outre, il compare la dynamique de rotation des groupes NH{sub 4} dans NH{sub 4}ClO{sub 4} et des groupes H{sub 3}O dans H{sub 3}OCIO{sub 4}, en se fondant sur des experiences de diffusion inelastique des neutrons. Il a obtenu une rotation libre du groupe NH4 dans le perchlorate d'ammonium, meme a des temperatures ne depassant pas celle de l'azote liquide. Pour H{sub 3}OCIO{sub 4} il a obtenu une

  6. Analysis methods of neutrons induced resonances in the transmission experiments by time-of-flight and automation of these methods on IBM 7094 II computer; Methode d'analyse des resonances induites par les neutrons dans les experiences de transmission par temps-de-vol et automatisation de ces methodes sur ordinateur IBM-7094 II

    Energy Technology Data Exchange (ETDEWEB)

    Corge, C

    1967-07-01

    The neutron induced resonances analysis aims to determine the neutrons characteristics, leading to the excitation energies, de-excitation probabilities by gamma radiation emission, by neutron emission or by fission, their spin, their parity... This document describes the methods developed, or adapted, the calculation schemes and the algorithms implemented to realize such analysis on a computer, from data obtained during time-of-flight experiments on the linear accelerator of Saclay. (A.L.B.)

  7. Analysis methods of neutrons induced resonances in the transmission experiments by time-of-flight and automation of these methods on IBM 7094 II computer; Methode d'analyse des resonances induites par les neutrons dans les experiences de transmission par temps-de-vol et automatisation de ces methodes sur ordinateur IBM-7094 II

    Energy Technology Data Exchange (ETDEWEB)

    Corge, C

    1967-07-01

    The neutron induced resonances analysis aims to determine the neutrons characteristics, leading to the excitation energies, de-excitation probabilities by gamma radiation emission, by neutron emission or by fission, their spin, their parity... This document describes the methods developed, or adapted, the calculation schemes and the algorithms implemented to realize such analysis on a computer, from data obtained during time-of-flight experiments on the linear accelerator of Saclay. (A.L.B.)

  8. Civili, langue des Baloango

    DEFF Research Database (Denmark)

    Mavoungou, Paul Achille; Ndinga-Koumba-Binza, Hugues Steve

    , Congo, Angola, etc.) issus de la décolonisation. Il présente de façon succincte quelques phénomènes historiques, phonologiques, morphosyntaxiques, homonymiques et analogiques de la langue. Des faits sémantiques des emprunts linguistiques y sont également décrits dans le cadre des changements...

  9. The neutron

    International Nuclear Information System (INIS)

    Kredov, B.M.

    1979-01-01

    The history of the neutron is displayed on the basis of contributions by scientists who produced outstanding results in neutron research (part 1), of summarizing discoveries and theories which led to the discovery of the neutron and the resulting development of nuclear physics (part 2), and of fundamental papers written by Rutherford, Chadwick, Iwanenko, and others (appendix). Of interest to physicists, historians, and students

  10. Neutron techniques

    International Nuclear Information System (INIS)

    Charlton, J.S.

    1986-01-01

    The way in which neutrons interact with matter such as slowing-down, diffusion, neutron absorption and moderation are described. The use of neutron techniques in industry, in moisture gages, level and interface measurements, the detection of blockages, boron analysis in ore feedstock and industrial radiography are discussed. (author)

  11. Des racines et des ailes

    Directory of Open Access Journals (Sweden)

    Stéphanie Vincent-Geslin

    2012-05-01

    Full Text Available Les mobilités pendulaires semblent être en augmentation en Europe depuis une dizaine d’années. Cette croissance du temps passé à se déplacer amène à remettre en question la conjecture de Zahavi et apparaît relativement inexplicable en regard du paradigme classique de l’acteur rationnel traditionnellement utilisé dans le champ des transports. Si, dans la littérature, les temps de déplacements sont principalement expliqués par le contexte résidentiel, la forme urbaine et le travail, ce cadre explicatif ne dit rien des processus de décision eux-mêmes qui amènent aux pendularités intensives.À partir d’une enquête qualitative menée auprès de pendulaires français, suisses et belges, cette contribution propose d’analyser les arbitrages et les éléments déterminants des processus de la grande pendularité. Les mobilités quotidiennes pendulaires apparaissent comme le résultat de compromis entre activité professionnelle, attachement résidentiel et choix de vie et prennent ainsi la forme de stratégies de conciliation entre vie privée et vie professionnelle. Ces mobilités spatiales permettent alors paradoxalement la préservation des ancrages résidentiels, sociaux et familiaux.Roots and wings. Long-distance commuting patterns, or how to conciliate professional and personal lifeLong-distance commuting patterns appear to be increasing in Europe over the last ten years. These raising mobility patterns lead to reappraise the Zahavi conjecture and appear largely inexplicable by the classical rational actor paradigm traditionally used in transportation research. In literature, commuting is mainly explained by residential contexts, urban forms and job. Nevertheless this theoretical frame says little about the decision-making processes themselves. Based on a qualitative survey conducted in three European countries - France, Belgium and Switzerland – among a population of high commuters, this paper proposes an analysis of

  12. Adaptação de lentes de contato após cirurgia refrativa Contact lens fitting after refractive surgery

    Directory of Open Access Journals (Sweden)

    Adimara da Candelária Renesto

    2005-02-01

    Full Text Available OBJETIVO: Avaliar a adaptação e o uso de lente de contato em pacientes que foram submetidos à cirurgia refrativa. MÉTODOS: Foi realizado estudo retrospectivo de 53 pacientes submetidos à cirurgia refrativa, que posteriormente passaram a usar lente de contato, no período de 1999 a 2003. Foram avaliados a ametropia prévia, tipo de cirurgia realizada, refração pós-cirúrgica, equivalente esférico pós-cirurgia, ceratometria pós-operatória, curva base da lente adaptada, tipo de lente de contato adaptada, acuidade visual com óculos no pós-operatório, acuidade visual final com lente de contato, complicações e motivo da interrupção do uso. O tempo de seguimento variou de 1 mês a 84 meses (média de 42,5 meses. RESULTADOS: Dos 53 pacientes analisados, 19 pacientes foram submetidos a LASIK (Laser Assisted in Situ Keratomileusis, 29 pacientes foram submetidos à RK (ceratotomia radial, 4 pacientes foram submetidos a PRK (ceratectomia fotoablativa e em um paciente não foi possível obter o tipo de cirurgia realizado. Em 61,29% dos pacientes, (57 olhos de um total de 93, foram adaptadas lentes de contato rígidas gás-permeáveis esféricas. Houve melhora da acuidade visual em 60,21% dos casos (AV>20/40, com poucas complicações. CONCLUSÃO: Devido ao número cada vez maior de cirurgias refrativas realizadas, espera-se que aumente o número de pacientes insatisfeitos com o resultado no pós-operatório e para os quais o uso de lentes de contato venha a ser a melhor opção. A adaptação de lentes de contato pós-cirurgia refrativa exige conhecimento e dedicação e em geral tem bons resultados principalmente pela melhora da acuidade visual.PURPOSE: To evaluate the fitting and use of contact lens in patients submitted to refractive surgery. METHODS: This was a retrospective study in 53 patients submitted to refractive surgery who later started to use contact lens, from 1999 to 2003. The parameters were: previous ametropia, refractive

  13. Acuidade visual em implantes bilaterais de lentes intra-oculares monofocais e multifocais Visual acuity of bilateral implants of monofocal and multifocal intraocular lenses

    Directory of Open Access Journals (Sweden)

    Leonardo Akaishi

    2003-01-01

    Full Text Available OBJETIVO: Comparar a acuidade visual de longe e perto de pacientes submetidos à facoemulsificação binocular não simultânea com implante de lentes multifocais ou monofocais. MÉTODOS: Foram selecionados 20 pacientes com lentes multifocais bilaterais e outros 20 pacientes com lentes monofocais também bilaterais, com acuidade visual sem correção melhor ou igual a 0,63 (20/30, medidos separadamente, nos três primeiros meses de pós-operatório. Foi medida a acuidade visual para longe e perto com e sem correção e testes de sensibilidade ao contraste e ofuscamento. RESULTADOS: A acuidade visual sem correção para longe no grupo das monofocais teve média de 0,82 (DP± 0,16 e no grupo das multifocais, 0,94 (DP±0,12, valor de p 0,001. Os dois grupos de lentes tiveram visão com correção para longe igual a 1. No grupo das multifocais, 75% tiveram J1 e 100% tiveram J3 ou melhor sem correção. No grupo das lentes monofocais, 10% tiveram J1 e 70% tiveram J3 ou melhor sem correção. Não houve diferença significante na avaliação com o teste de sensibilidade ao contraste entre os grupos pesquisados. No teste de ofuscamento, os dois grupos tiveram redução da visão, que foi mais acentuada no grupo dos pacientes com lentes multifocais. CONCLUSÃO: A acuidade visual para longe com correção nos pacientes com implante multifocal foi semelhante a dos pacientes com implantes monofocais, embora a acuidade visual para perto no grupo em que foi implantado lente multifocal foi bastante superior ao grupo da lente monofocal. A sensibilidade ao contraste manteve-se semelhante nos dois grupos, já o ofuscamento ("glare test" no grupo multifocal foi maior que no grupo monofocal.PURPOSE: To compare distant and near visual acuity between patients submitted to bilateral nonsimultaneous facoemulsification and implantation of multifocal or monofocal intraocular lenses (IOL. METHODS: Twenty patients with bilateral multifocal IOL and 20 patients with

  14. Revisión bibliográfica sobre los beneficios del coloreado de las lentes destinadas a las actividades deportivas

    Directory of Open Access Journals (Sweden)

    Carlos Montaner Sesmero

    2010-09-01

    Full Text Available El desarrollo de productos comerciales específicos para cada usuario es una línea de actuación preferente para cada vez más empresas del sector deportivo. Algunos de estos productos personalizados, como es el caso de las gafas deportivas con lentes coloreadas, ofrecen prestaciones que aseguran un mejor confort y/o rendimiento deportivo en determinados contextos. Sin embargo, la base científica que apoya el beneficio de dichos artículos es desconocida. Así, el propósito de este estudio es realizar una revisión del trabajo científico publicado que explique el posible beneficio que puede suponer el uso de un tipo de coloreado u otro en las lentes de las gafas deportivas. Para ello, se ha llevado a cabo una revisión bibliográfica centrada en aspectos de confort y de rendimiento visual en la práctica deportiva, a través de bases documentales científicas, de páginas web y de normativa referente al uso de lentes deportivas. La principal conclusión que se puede extraer es que el estado del arte ofrece una limitada base científica para soportar los productos existentes en el mercado, así como para proponer lentes de color para deportes concretos. Queda establecido que a través de determinados filtros coloreados puedan mejorarse los tiempos de reacción y la habilidad visual, pero en caso de abordar esta línea de I+D, sería incluso necesario poner a punto métodos de medida adecuados.

  15. Vitrectomía pars plana y reimplante de lente intraocular en surco Pars plana vitrectomy and intraocular lens repositioning in the sulcus

    Directory of Open Access Journals (Sweden)

    Alejandro Guerra García

    2010-01-01

    Full Text Available Se presentó un caso de lente intraocular luxado a vítreo en paciente con conteo bajo de células endoteliales e intolerancia a lentes de contacto. Se practicó vitrectomía pars plana con reimplante de lente en surco ciliar con el objetivo de demostrar la fiabilidad de la técnica para casos que presenten condiciones adecuadas y situaciones especiales. Se revisó la bibliografía para conocer las tendencias actuales con respecto al manejo de esta patología. El paciente alcanzó una agudeza visual de 20/30. El lente permaneció estable en el surco 3 meses después de practicada la vitrectomía. El manejo de esta entidad debe ser personalizado. La técnica utilizada debe ser siempre la primera opción de tratamiento y parece ser segura en casos cuidadosamente escogidos.A case of dislocated intraocular lens moved to the vitreous cavity in a patient with low endothelial cell count and contact lens intolerance was reported. A pars plana vitrectomy with lens repositioning was performed to demonstrate the safety of this technique for some special cases under adequate conditions. The literature was reviewed to learn about the current management of this pathology. Finally, patient's best visual acuity was 20/30. The stability of the lens was confirmed three month l after the vitrectomy. Management of this disorder should be customized. This technique should be considered as the first option of treatment and seems to be safe in selected cases.

  16. Comparison of patient-reported late treatment toxicity (LENT-SOMA) with quality of life (EORTC QLQ-C30 and QLQ-H and N35) assessment after head and neck radiotherapy

    International Nuclear Information System (INIS)

    Ho, Kean Fatt; Farnell, Damien J.J.; Routledge, Jacqueline A.; Burns, Meriel P.; Sykes, Andrew J.; Slevin, Nick J.; Davidson, Susan E.

    2010-01-01

    Purpose: The patient's role in toxicity reporting is increasingly acknowledged but requires the adaptation and validation of toxicity reporting instruments for patient use as most toxicity scales are designed for physician use. Recording of radiotherapy related late toxicity is important and needs to be improved. A patient-scored symptom questionnaire of late treatment effects using LENT-SOMA was compared with a recognised quality of life tool (EORTC QLQ-C30/H and N35). Materials/methods: LENT-SOMA and EORTC QLQ-C30 patient questionnaires were prospectively completed by 220 head and neck cancer patients over 3 years and 72 completed EORTC QLQ-H and N35 questionnaires at 2 years post-radiotherapy. Results: Endpoints common to both questionnaires (pain, swallowing, dental pain, dry mouth, opening mouth, analgesics) were matched. Spearman rank correlation coefficients with ρ > 0.6 (P < 0.001) were obtained for all 'matched' scales except for analgesics scale, ρ = 0.267 (P < 0.05). There was good agreement between LENT-SOMA and EORTC QLQ-H and N35 except for analgesic endpoints. Global quality of life scores correlated negatively with average LENT-SOMA scores (P < 0.001). Significant differences in average LENT-SOMA scores between treatment modalities were found. The LENT-SOMA questionnaire has demonstrated a high Cronbach's α value (0.786) indicating good reliability. Conclusions: LENT-SOMA patient questionnaire results agreed well with those from the EORTC QLQ-H and N35 questionnaire for toxicity items where they could be compared explicitly, particularly for subjective endpoints. Patient-reported late toxicity had a negative impact on quality of life. The LENT-SOMA patient questionnaire is both reliable and sensitive to differences between patients treated with different modalities. A patient-based questionnaire is an important contributor to capturing late radiotherapy effects.

  17. Avaliação do nível de conhecimento quanto ao uso de lentes de contato entre os estudantes de medicina da Faculdade de Medicina do ABC

    Directory of Open Access Journals (Sweden)

    Giovana Arlene Fioravanti Lui

    2010-12-01

    Full Text Available OBJETIVO: Analisar o nível de conhecimento dos usuários de lentes de contato entre os estudantes de medicina da Faculdade de Medicina do ABC (SP quanto aos cuidados, formas de uso, às complicações e à aquisição das lentes. MÉTODOS: Foi aplicado um questionário a todos os alunos usuários de lentes de contato do 1º ao 6º ano de medicina da Faculdade de Medicina do ABC (SP, analisando-se por fim os resultados encontrados. Todos os questionários aplicados foram respondidos. RESULTADOS: 61 estudantes responderam ao questionário. 52,5% afirmaram já terem tido algum tipo de complicação ocular decorrente do uso de lentes de contato. Apesar de a maioria (70,5% estar satisfeito com o uso das lentes de contato, 67% dos que responderam ao questionário estão esperando o grau estabilizar para realizar cirurgia para correção de grau. CONCLUSÃO: Observou-se uma adaptação inadequada, aquisição de lentes de contato em ópticas ou farmácias e complicações oculares graves ocorreram em usuários de lentes de contato considerados diferenciados. Podemos concluir que o médico oftalmologista deverá dar mais atenção ao tema, para que haja menos complicações ao realizar adaptações de lentes de contato.

  18. Late radiation effects to the rectum and bladder in gynecologic cancer patients: the comparison of LENT/SOMA and RTOG/EORTC late-effects scoring systems

    International Nuclear Information System (INIS)

    Anacak, Yavuz; Yalman, Deniz; Oezsaran, Zeynep; Haydaroglu, Ayfer

    2001-01-01

    Purpose: To test the correlation of LENT/SOMA and RTOG/EORTC late-effect scales for rectum and bladder, 116 cases with gynecologic malignancies that were treated with radiotherapy were assessed with both scales. Methods and Materials: All cases had been treated at least 6 months before the date of assessment with external beam radiotherapy (50-54 Gy to midline) and 1-2 fractions of HDR brachytherapy (2x8.5 Gy to point-A for 32 inoperable cases; 1x9.25 Gy to 5-9 mm from the ovoid surface for 84 postoperative cases). The patients were questioned with both scales, and the correlation between the two scales was analyzed by Spearman's rho (rank correlation) test. Results: There were 64 cases with uterine cervix carcinoma and 52 cases with endometrium carcinoma, The overall (external + brachy) doses to ICRU points were 57.8±3.8 Gy for rectum and 59.3±4.9 Gy for bladder. The statistical analysis of LENT/SOMA and RTOG/EORTC scales revealed a very good correlation for rectum (r=0.81; p<0.01) and a good correlation for bladder (r=0.72; p<0.01). Conclusion: The LENT/SOMA system is a further step on the reporting of late radiation effects. Some modifications will improve its precision, and multicentric randomized studies are needed to test its validity

  19. Les déterminants de l’intention entrepreneuriale des jeunes diplômés

    Directory of Open Access Journals (Sweden)

    Ali Maâlej

    2013-11-01

    Full Text Available En nous inspirant du modèle psychosocial du comportement planifié d’Ajzen, nous avons expliqué l’intention entrepreneuriale à travers les caractéristiques individuelles et le milieu environnant. Nous avons envisagé de jeter la lumière sur un échantillon de diplômés issus de l’école supérieure de commerce de Sfax. Nos résultats révèlent l’importance des attitudes associées au comportement ainsi que l’importance des normes sociales dans l’intention entrepreneuriale. À contrario, les contraintes financières, la formation en création d’entreprise et tout ce qui se rapporte aux perceptions du contrôle comportemental sont d’un effet non significatif sur l’intention.

  20. L’EPURATION TERTIAIRE DES EAUX USEES DE L’INDUSTRIE DE LA CELLULOSE

    Directory of Open Access Journals (Sweden)

    Constantin STANCIU

    2010-05-01

    Full Text Available Les processus de fabrication de la cellulose représentent des sources importantes de pollution tant pour les eaux, que pour l’aire et le sol. La pollution de l’eau est du, essentiellement, aux substances organiques dissous, aux substances en suspension et aux substances colorantes. Les évacuations des substances polluantes résultant de l’industrie de la cellulose se classifient en : substances solides en suspension, composés avec une biodégradabilité rapide ou lente, sels anorganiques, composés toxiques et échangeurs de valeur de pH. On a analysé les substances filtrées résultant du processus de blanchiment de la cellulose pour l’industrie papetière fabriquée du bois des arbres à feuilles caduques (hêtre et l’efficacité de l’épuration par oxydation électrochimique, par oxydation à l’ozone, l’épuration avec des résines échangeuses d’ions et l’épuration par l’ajout de charbon actif.

  1. Technique of nuclear reactors controls; Technique des controles des reacteurs nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Weill, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1953-12-15

    This report deal about 'Techniques of control of the nuclear reactors' in the goal to achieve the control of natural uranium reactors and especially the one of Saclay. This work is mainly about the measurement into nuclear parameters and go further in the measurement of thermodynamic variables,etc... putting in relief the new features required on behalf of the detectors because of their use in the thermal neutrons flux. In the domain of nuclear measurement, we indicate the realizations and the results obtained with thermal neutron detectors and for the measurement of ionizations currents. We also treat the technical problem of the start-up of a reactor and of the reactivity measurement. We give the necessary details for the comprehension of all essential diagrams and plans put on, in particular, for the reactor of Saclay. (author) [French] Nous avons aborde le probleme de la ''Technique du Controle des reacteurs nucleaires'' dans le but de realiser le controle du reacteur de Saclay. C'est ainsi que nous avons ete amene a etudier le probleme dans son ensemble, tel qu'il se pose pour tout reacteur a uranium naturel. Ce travail traite principalement du domaine des mesures a caractere nucleaire et s'etend dans le domaine des mesures thermodynamque de niveaux, etc... mettant en relief les caracteristiques nouvelles exigees de la part des detecteurs du fait de leur utilisation dans le flux de neutrons thermiques. Dans le domaine de mesures nucleaires, nous indiquons principalement les realisations et les resultats obtenus pour les detecteurs de neutrons thermiques et pour la mesure de courants d'ionisations. Nous traitons egalement du probleme technique du demarrage d'un reacteur et du probleme de la mesure de la reactivite. Nous donnons les details necessaires a la comrehension de tous les schemas et plans de cablages essentiels mis au point, en particulier, pour le reacteur de Saclay. (auteur)

  2. Usages différenciés des TIC chez les seniors au prisme de l’âge, du genre et de la classe sociale

    OpenAIRE

    Bourdeloie, Hélène; Boucher-Petrovic, Nathalie

    2014-01-01

    Selon le modèle expressiviste (Allard, 2007 ; 2009), les technologies de l’information et de la communication (TIC) recèlent des potentialités expressives permettant à l’individu de performer son identité et, ipso facto, de reconfigurer son identité socialement assignée au profit d’une identité façonnée individuellement. Dans une société marquée par les valeurs individualistes et dans laquelle les TIC prennent une place qui rivalise désormais avec les grands cadres de socialisation traditionn...

  3. New experimental determination of the neutronic resonance parameters of {sup 237}Np below 500 eV; Nouvelle determination experimentale des parametres de resonances neutroniques de {sup 237}Np en dessous de 500 eV

    Energy Technology Data Exchange (ETDEWEB)

    Gressier, V

    1999-10-01

    For studies of future nuclear reactors dedicated to nuclear waste transmutation, an improvement of the accuracy of the neutron radiative capture cross section of {sup 237}Np appears necessary. In the framework of a collaboration between the Commissariat a l'Energie atomique (CEA) and Institute for Reference Materials and Measurement (IRMM, Geel, Bergium), a new determination of the resonance parameters of {sup 237}Np has been performed. Two types of experiments are carried out at GELINA, the IRMM pulsed neutron source, using the time of flight method: a transmission experiment which is related to the neutron total cross section and a capture experiment which gives the neutron radiative capture cross section. The resonance parameters presented in this work are extracted from the transmission data between 0 and 500 eV with the least square code REFIT, using the Reich-Moore formalism. In parallel, the Doppler effect is investigated. The commonly used free gas model appears inadequate below 20 eV for neptunium dioxide at room temperature. By the use of the program DOPUSH, which calculates the Doppler broadening with a harmonic crystal model according to Lamb's theory, we are able to produce abetter fit of the experimental data for the resonances of {sup 237}Np in NpO{sub 2} at low energy or temperatures. In addition to the resonance parameters, a study of their mean value and distribution is included in this work. (authors)

  4. Lentes de contato filtrantes coloridas nas discromatopsias: relato de casos Absorptive and colored contact lenses in color-vision defects: case report

    Directory of Open Access Journals (Sweden)

    Luciene Chaves Fernandes

    2003-06-01

    Full Text Available As autoras propõem a utilização de lentes de contato filtrantes coloridas para melhora da discriminação de cores e do ofuscamento, em portadores de discromatopsia, na impossibilidade de montagem de filtros coloridos em óculos. Foram adaptadas lentes de contato filtrantes coloridas em dois portadores de discromatopsias, um com deutanopia e outro com acromatopsia. No primeiro, adaptou-se lente rígida filtrante, de polimetilmetacrilato (PMMA, vermelha, no olho não dominante, com o objetivo de melhorar a discriminação de cores. No segundo, colocou-se lente filtrante gelatinosa, de uso diário, de coloração marrom escuro com pupila âmbar, visando melhorar o ofuscamento. No primeiro caso, o paciente manteve inalterada a acuidade visual e também o contraste, porém demonstrou melhora na discriminação das cores ao teste de PV-16. No segundo caso, houve melhora subjetiva acentuada do ofuscamento tanto em ambiente interno, como externo. A acuidade visual e a visão de cores permaneceram sem alterações. Os achados sugerem a possibilidade de contarmos com as lentes de contato filtrantes coloridas como importante auxílio para a melhora na discriminação de cores e ofuscamento, nas discromatopsias.The authors propose the use of absorptive and colored contact lenses as an aid to color defects in making color judgments and reduce glare sensitivity in dichromatic subjects, when the use of filter in glasses is not possible. Absorptive and colored contact lenses were adapted in two dichromatic subjects, one deutanope and the other with achromatopsia. In the former, a hard absorptive, red-colored, polymethacrylate lens was adapted monocularly, in the non-dominant eye to help color judgments. In the latter, a soft absorptive, dark brown-colored lens with amber pupil was worn in both eyes to reduce glare sensitivity. Subject # 1 remained with the same visual acuity and contrast sensitivity and demonstrated a better color perception on the PV-16

  5. Neutron radiography

    International Nuclear Information System (INIS)

    Hiraoka, Eiichi

    1988-01-01

    The thermal neutron absorption coefficient is essentially different from the X-ray absorption coefficient. Each substance has a characteristic absorption coefficient regardless of its density. Neutron deams have the following features: (1) neutrons are not transmitted efficiently by low molecular weight substances, (2) they are transmitted efficiently by heavy metals, and (3) the transmittance differs among isotopes. Thus, neutron beams are suitable for cheking for foreign matters in heavy metals and testing of composites consisting of both heavy and light materials. A neutron source generates fast neutrons, which should be converted into thermal neutrons by reducing their energy. Major neutron souces include nuclear reactors, radioisotopes and particle accelerators. Photographic films and television systems are mainly used to observe neutron transmission images. Computers are employed for image processing, computerized tomography and three-dimensional analysis. The major applications of neutron radiography include inspection of neclear fuel; evaluation of material for airplane; observation of fuel in the engine and oil in the hydraulic systems in airplanes; testing of composite materials; etc. (Nogami, K.)

  6. Small-Angle Scattering of Neutrons by Iron and Nickel Close to the Curie Point; Diffusion aux petits angles des neutrons par le fer et le nickel au voisinage du point de curie; Rasseyanie nejtronov pod malymi uglami zhelezom i nikelem, blizkikh k tochke kyuri; Dispersion de neutrones en angulos pequenos por el hierro y el niquel cerca del punto de curie

    Energy Technology Data Exchange (ETDEWEB)

    Jacrot, B.; Konstantinovic, J.; Parette, G.; Cribier, D. [Centre d' etudes Nucleaires de Saclay (France)

    1963-01-15

    Recent studies on critical scattering by iron have thrown fresh light on the results obtained previously and shown that: (1) At the Curie point, scattering is inelastic. The Lorentzian form of the lines and their angular dependence establish the existence of a scattering process having the diffusion coefficient 2m {Omega}/n = 7. (2) At the Curie point, the coefficient K{sub 1}{sup 2} is less than 5 x 10{sup -5} A{sup -2}. Iron and nickel have very different angular distribution. Small-angle scattering below T{sub c} has also been studied. (author) [French] De nouveaux travaux sur la diffusion critique par le fer ont permis de completer les resultats obtenus anterieurement. Ils etablissent les faits suivants: 1. Au point de Curie la diffusion est inelastique. La forme lorentzienne des raies et leur dependance angulaire etablissent l'existence d*un processus de diffusion avec un coefficient de diffusion 2m{Omega}/n = 7. 2. Au point de Curie le coefficient K{sub 1}{sup 2} est inferieur a 5 x 10{sup -5} A{sup -2}. La distribution angulaire est tres differente dans le cas du fer et du nickel. On a egalement etudie la diffusion aux petits angles en dessous de T{sub c}. (author) [Spanish] Nuevos trabajos sobre la dispersion critica por el hierro han permitido completar los resultados obtenidos anteriormente. Dichos trabajos prueban los hechos siguientes: 1) La dispersion es inelastica en el punto de Curie. La forma lorentziana de las rayas y su dependencia angular demuestran la existencia de un proceso de dispersion con un coeficiente de dispersion igual a 2m {Omega}/n = 7. 2) En el punto de Curie, el coeficiente K{sub 1}{sup 2} es inferior a 5 x 10{sup -5} A{sup -2}. La distribucion angular es muy diferente en el caso del hierro y del ni quel. Se ha estudiado tambien la dispersion en pequenos angulos por debajo de T{sub c}. (author)

  7. Contribution to the study of neutron-neutron interactions using the three-nucleon experiment D(n,nnp) at 14.5 MeV: evaluation of parasitic events; Contribution a l'etude de l'interaction neutron-neutron a l'aide de l'experience a trois nucleons D(n,nnp) A 14.5 MeV: evaluation des evenements parasites

    Energy Technology Data Exchange (ETDEWEB)

    Ducharme, C [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    This work is related to the interpretation of the results concerning the three nucleon experiment, D(n,nnp), at 14.5 MeV, carried out by double time-of-flight spectrometry. The present work consists in the simulation of the main parasitic events using the Monte-Carlo method for extracting them from the experimental distribution around the n-n pole. (author) [French] Cette etude rentre dans le cadre de l'interpretation des resultats de l'experience a trois nucleons D(n,nnp) a 14.5 MeV effectuee par spectrometrie a double temps-de-vol. Le present travail consiste a simuler les evenements parasites principaux par une methode de Monte-Carlo pour les soustraire de la distribution experimentale autour du pole n-n. (auteur)

  8. Neutron detector

    Science.gov (United States)

    Stephan, Andrew C [Knoxville, TN; Jardret,; Vincent, D [Powell, TN

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  9. Fusion neutronics

    CERN Document Server

    Wu, Yican

    2017-01-01

    This book provides a systematic and comprehensive introduction to fusion neutronics, covering all key topics from the fundamental theories and methodologies, as well as a wide range of fusion system designs and experiments. It is the first-ever book focusing on the subject of fusion neutronics research. Compared with other nuclear devices such as fission reactors and accelerators, fusion systems are normally characterized by their complex geometry and nuclear physics, which entail new challenges for neutronics such as complicated modeling, deep penetration, low simulation efficiency, multi-physics coupling, etc. The book focuses on the neutronics characteristics of fusion systems and introduces a series of theories and methodologies that were developed to address the challenges of fusion neutronics, and which have since been widely applied all over the world. Further, it introduces readers to neutronics design’s unique principles and procedures, experimental methodologies and technologies for fusion systems...

  10. Neutron spectometers

    International Nuclear Information System (INIS)

    Poortmans, F.

    1977-01-01

    Experimental work in the field of low-energy neutron physics can be subdivided into two classes: 1)Study of the decay process of the compound-nucleus state as for example the study of the capture gamma rays and of the neutron induced fission process; 2)Study of the reaction mechanism, mainly by measuring the reaction cross-sections and resonance parameters. These neutron cross-sections and resonance parameters are also important data required for many technological applications especially for reactor development programmes. In general, the second class of experiments impose other requirements on the neutron spectrometer than the first class. In most cases, a better neutron energy resolution and a broader neutron energy range are required for the study of the reaction mechanism than for the study of various aspects of the decay process. (author)

  11. Development, improvement and calibration of neutronic reaction rate measurements: elaboration of a base of standard techniques; Developpement, amelioration et calibration des mesures de taux de reaction neutroniques: elaboration d`une base de techniques standards

    Energy Technology Data Exchange (ETDEWEB)

    Hudelot, J.P

    1998-06-19

    In order to improve and to validate the neutronic calculation schemes, perfecting integral measurements of neutronic parameters is necessary. This thesis focuses on the conception, the improvement and the development of neutronic reaction rates measurements, and aims at building a base of standard techniques. Two subjects are discussed. The first one deals with direct measurements by fission chambers. A short presentation of the different usual techniques is given. Then, those last ones are applied through the example of doubling time measurements on the EOLE facility during the MISTRAL 1 experimental programme. Two calibration devices of fission chambers are developed: a thermal column located in the central part of the MINERVE facility, and a calibration cell using a pulsed high flux neutron generator and based on the discrimination of the energy of the neutrons with a time-of-flight method. This second device will soon allow to measure the mass of fission chambers with a precision of about 1 %. Finally, the necessity of those calibrations will be shown through spectral indices measurements in core MISTRAL 1 (UO{sub 2}) and MISTRAL 2 (MOX) of the EOLE facility. In each case, the associated calculation schemes, performed using the Monte Carlo MCNP code with the ENDF-BV library, will be validated. Concerning the second one, the goal is to develop a method for measuring the modified conversion ratio of {sup 238}U (defined as the ratio of {sup 238}U capture rate to total fission rate) by gamma-ray spectrometry of fuel rods. Within the framework of the MISTRAL 1 and MISTRAL 2 programmes, the measurement device, the experimental results and the spectrometer calibration are described. Furthermore, the MCNP calculations of neutron self-shielding and gamma self-absorption are validated. It is finally shown that measurement uncertainties are better than 1 %. The extension of this technique to future modified conversion ratio measurements for {sup 242}Pu (on MOX rods) and

  12. Neutron exposure

    International Nuclear Information System (INIS)

    Prillinger, G.; Konynenburg, R.A. van

    1998-01-01

    As a result of the popularity of the Agencies report 'Neutron Irradiation Embrittlement of Reactor Pressure Vessel Steels' of 1975, it was decided that another report on this broad subject would be of use. In this report, background and contemporary views on specially identified areas of the subject are considered as self-contained chapters, written by experts. In chapter 6, LWR-PV neutron transport calculations and dosimetry methods and how they are combined to evaluate the neutron exposure of the steel of pressure vessels are discussed. An effort to correlate neutron exposure parameters with damage is made

  13. Atmospheric neutrons

    International Nuclear Information System (INIS)

    Preszler, A.M.; Moon, S.; White, R.S.

    1976-01-01

    Additional calibrations of the University of California double-scatter neutron and additional analysis corrections lead to the slightly changed neutron fluxes reported here. The theoretical angular distributions of Merker (1975) are in general agreement with our experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current J 2 /sub pi/ (Merker, 1972; Armstrong et al., 1973) is in agreement with the experimental values from 10 to 100 MeV. Our experimental fluxes agree with those of the Kanbach et al. (1974) in the overlap region from 70 to 100 MeV

  14. Neutron Albedo

    CERN Document Server

    Ignatovich, V K

    2005-01-01

    A new, algebraic, method is applied to calculation of neutron albedo from substance to check the claim that use of ultradispersive fuel and moderator of an active core can help to gain in size and mass of the reactor. In a model of isotropic distribution of incident and reflected neutrons it is shown that coherent scattering on separate grains in the case of thermal neutrons increases transport cross section negligibly, however it decreases albedo from a wall of finite thickness because of decrease of substance density. A visible increase of albedo takes place only for neutrons with wave length of the order of the size of a single grain.

  15. Study by neutrons diffusion and X-rays of structural and magnetic properties of Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} type superconductive cuprates; Etude par diffusion des neutrons et des rayons X des proprietes structurales et magnetiques des cuprates supraconducteurs de type Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Vasiliu-Doloc, L

    1995-09-22

    In this work we have used inelastic and elastic neutron and X-ray scattering techniques for characterizing the incommensurate structural distortions in compounds belonging to the family Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4+{delta}} of high-Tc superconducting cuprates. We have searched the existence of structural instabilities specific of the CuO{sub 2} planes and of magnetic instabilities. The modulated structure of the 2212 phase has been refined from single-crystal neutron diffraction results and importance of distortion of CuO{sub 2} planes has thus been determined. It is shown that the additional oxygen is not ordered three-dimensionally within the modulated structure and that the information about it is contained in diffuse scattering results. A model of the short-range order associated with additional oxygen atoms is proposed and discussed. The temperature studies of the long-range order have shown a great stability of the amplitude and period of the incommensurate distortion wave in the one-layer, as well as in the double-layer compounds, either superconducting or insulating. We find such a behaviour to be highly incompatible with a distortion resulting from a charge-density-wave instability. The results we have obtained indicate that the bismuth-based high-Tc superconducting cuprates have essentially the same physics of the CuO{sub 2} planes as the previous two families, La{sub 2-x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}, being at the proximity of three instabilities: a metal-insulator transition, an antiferromagnetic instability and a structural instability specific of the CuO{sub 2} planes. (author).

  16. Shape difference between scintillation pulses due to γ rays and to neutrons

    International Nuclear Information System (INIS)

    Cambou, Francis; Ambrosino, Georges

    1960-01-01

    A simple method is described which allows to clearly show the shape differences between γ ray- and neutron-induced pulses. In the neutrons case the intensity of the slow component is 2.4 times higher than in the γ ray case. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1034-1036, sitting of 8 February 1960 [fr

  17. Des Connaissances Aux Politiques

    International Development Research Centre (IDRC) Digital Library (Canada)

    Les synergies ont été mises en commun au fur et à mesure des progrès de la recherche. .... Recherche normative (sur le rôle et la performance des institutions .... Système national d'information sur la gestion environnementale connecté à 19 ...... Un fort contrôle centralisé sur l'élaboration des politiques nationales peut ...

  18. Apparatus for the measurement of the distribution of neutron flux (band and wire continuous recorders); Appareillage pour la mesure des repartitions de flux neutroniques (derouleurs a bandes et a fils)

    Energy Technology Data Exchange (ETDEWEB)

    Derrien, H; Lemerle, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    The apparatus of which we describe the principles and the operation, makes it possible to know the thermal neutron flux distribution in a pile channel or along a fuel element by the measurement of the {beta} activity of continuous detectors. It is also possible thereby to show the presence of a very localised sudden discontinuity in the distribution curve. (authors) [French] Les appareils dont nous decrivons le principe et le fonctionnement, permettent de connaitre la repartition du flux de neutrons thermiques dans un canal de pile ou le long d'un element combustible, par la mesure de l'activite {beta} de detecteurs continus. Ils permettent en outre de mettre en evidence un accident brutal, tres localise, de la courbe de repartition. (auteurs)

  19. Study of spectral response of a neutron filter. Design of a method to adjust spectra; Etude des moyens de conditionnement de la reponse spectrale d'un filtre a neutrons. Mise au point d'une methode d'ajustement rapide de spectre

    Energy Technology Data Exchange (ETDEWEB)

    Colomb-Dolci, F. [Universite Louis Pasteur, 67 - Strasbourg (France)

    1999-02-01

    The first part of this thesis describes an experimental method which intends to determine a neutron spectrum in the epithermal range [1 eV -10 keV]. Based on measurements of reaction rates provided by activation foils, it gives flux level in each energy range corresponding to each probe. This method can be used in any reactor location or in a neutron beam. It can determine scepter on eight energy groups, five groups in the epithermal range. The second part of this thesis presents a study of an epithermal neutron beam design, in the frame of Neutron Capture Therapy. A beam tube was specially built to test filters made up of different materials. Its geometry was designed to favour epithermal neutron crossing and to cut thermal and fast neutrons. A code scheme was validated to simulate the device response with a Monte Carlo code. Measurements were made at ISIS reactor and experimental spectra were compared to calculated ones. This validated code scheme was used to simulate different materials usable as shields in the tube. A study of these shields is presented at the end of this thesis. (author)

  20. Neutron dosimetry; Dosimetria de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fratin, Luciano

    1993-12-31

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is

  1. Neutron dosimetry; Dosimetria de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fratin, Luciano

    1994-12-31

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is

  2. Contribution to the determination of the neutronic parameters uncertainties of a compact heterogeneous core: the material testing Jules Horowitz reactor; Contribution a l'etude des incertitudes des parametres neutroniques d'un coeur compact et heterogene: le reacteur d'irradiation Jules Horowitz

    Energy Technology Data Exchange (ETDEWEB)

    Di Salvo, J

    2002-07-01

    The design studies of the future Material Testing Reactor Jules Horowitz require the development of an adapted neutronic calculation route. To guarantee good accuracy and save time cost, some approximations with deterministic modelling (APOLLO2 / CRONOS2) are needed. As no relevant integral experiments are yet available to ensure the accuracy of the calculation, the results need to be validated by a rigorous methodical approach, which is based on comparison against numerical benchmarks (Monte Carlo TRIPOLI4 code). In order to complete the validation results, sensitivity coefficients of main neutronic parameters to nuclear data are very useful to get an estimate of the final uncertainty on the calculation. Unfortunately, most of covariance information is missing in the recent evaluated files such as JEF-2.2. To generate missing covariance matrices, a method based on the comparison of different independent evaluations is used in this study. Special attention is paid to the determination of sensitivity coefficients, using perturbation methods and direct calculations. This study points out the importance of the non-diagonal elements of the covariance matrices as well as the neutron capture cross section uncertainty of the 27Al in the thermal range. In complement to uncertainty studies, it will be still necessary to obtain integral experimental validation of the Jules Horowitz Reactor neutronic parameters calculations. (author)

  3. Contribution to the determination of the neutronic parameters uncertainties of a compact heterogeneous core: the material testing Jules Horowitz reactor; Contribution a l'etude des incertitudes des parametres neutroniques d'un coeur compact et heterogene: le reacteur d'irradiation Jules Horowitz

    Energy Technology Data Exchange (ETDEWEB)

    Di Salvo, J

    2002-07-01

    The design studies of the future Material Testing Reactor Jules Horowitz require the development of an adapted neutronic calculation route. To guarantee good accuracy and save time cost, some approximations with deterministic modelling (APOLLO2 / CRONOS2) are needed. As no relevant integral experiments are yet available to ensure the accuracy of the calculation, the results need to be validated by a rigorous methodical approach, which is based on comparison against numerical benchmarks (Monte Carlo TRIPOLI4 code). In order to complete the validation results, sensitivity coefficients of main neutronic parameters to nuclear data are very useful to get an estimate of the final uncertainty on the calculation. Unfortunately, most of covariance information is missing in the recent evaluated files such as JEF-2.2. To generate missing covariance matrices, a method based on the comparison of different independent evaluations is used in this study. Special attention is paid to the determination of sensitivity coefficients, using perturbation methods and direct calculations. This study points out the importance of the non-diagonal elements of the covariance matrices as well as the neutron capture cross section uncertainty of the 27Al in the thermal range. In complement to uncertainty studies, it will be still necessary to obtain integral experimental validation of the Jules Horowitz Reactor neutronic parameters calculations. (author)

  4. Lignes directrices canadiennes sur l’utilisation sécuritaire et efficace des opioïdes pour la douleur chronique non cancéreuse

    Science.gov (United States)

    Kahan, Meldon; Mailis-Gagnon, Angela; Wilson, Lynn; Srivastava, Anita

    2011-01-01

    Résumé Objectif Présenter aux médecins de famille un résumé clinique pratique des lignes directrices canadiennes sur l’utilisation sécuritaire et efficace des opioïdes pour la douleur chronique non cancéreuse, produites par le National Opioid Use Guideline Group. Qualité des données Pour produire les lignes directrices, les chercheurs ont effectué une synthèse critique de la littérature médicale sur l’efficacité et l’innocuité des opioïdes pour la douleur chronique non cancéreuse et ont rédigé une série de recommandations. Un panel de 49 cliniciens experts de toutes les régions du Canada ont passé en revue l’ébauche et ont atteint un consensus sur 24 recommandations. Message principal Il est recommandé de faire un dépistage du risque de dépendance avant de prescrire des opioïdes. On recommande des opioïdes faibles (codéine et tramadol) pour une douleur de légère à modérée qui n’a pas répondu aux traitements de première intention. On peut essayer l’oxycodone, l’hydromorphone et la morphine chez les patients qui n’ont pas eu de soulagement avec des opioïdes plus faibles. Une faible dose initiale et une lente hausse du titrage sont recommandées, ainsi qu’une étroite surveillance du patient qu’on a d’abord renseigné. Les médecins doivent surveiller l’apparition de complications comme l’apnée du sommeil. La dose optimale est celle qui améliore le fonctionnement ou atténue les cotes d’évaluation de la douleur d’au moins 30 %. Pour la grande majorité des patients, la dose optimale sera bien en deçà de l’équivalent de 200 mg de morphine par jour. On recommande le sevrage progressif pour les patients qui n’ont pas répondu à un essai d’opioïdes adéquat. Conclusion Les opioïdes jouent un rôle important dans la prise en charge de la douleur chronique non cancéreuse, mais il faut en prescrire avec prudence pour limiter les dommages potentiels. Les nouvelles lignes directrices

  5. Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

    African Journals Online (AJOL)

    SARAH

    30 sept. 2017 ... ... de Biochimie et Immunologie Appliquée, Centre de Recherche en Sciences Biologiques, Alimentaires et .... l'intoxication des agriculteurs et des consommateurs, ... source d'alimentation en eau et au pouvoir d'achat des.

  6. Neutronic reactor

    International Nuclear Information System (INIS)

    Wende, C.W.J.

    1976-01-01

    A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield

  7. Neutron polarization

    International Nuclear Information System (INIS)

    Firk, F.W.K.

    1976-01-01

    Some recent experiments involving polarized neutrons are discussed; they demonstrate how polarization studies provide information on fundamental aspects of nuclear structure that cannot be obtained from more traditional neutron studies. Until recently, neutron polarization studies tended to be limited either to very low energies or to restricted regions at higher energies, determined by the kinematics of favorable (p, vector n) and (d, vector n) reactions. With the advent of high intensity pulsed electron and proton accelerators and of beams of vector polarized deuterons, this is no longer the case. One has entered an era in which neutron polarization experiments are now being carried out, in a routine way, throughout the entire range from thermal energies to tens-of-MeV. The significance of neutron polarization studies is illustrated in discussions of a wide variety of experiments that include the measurement of T-invariance in the β-decay of polarized neutrons, a search for the effects of meson exchange currents in the photo-disintegration of the deuteron, the determination of quantum numbers of states in the fission of aligned 235 U and 237 Np induced by polarized neutrons, and the double- and triple-scattering of fast neutrons by light nuclei

  8. Neutron holography

    International Nuclear Information System (INIS)

    Beynon, T.D.

    1986-01-01

    the paper concerns neutron holography, which allows an image to be constructed of the surfaces, as well as the interiors, of objects. The technique of neutron holography and its applications are described. Present and future use of the method is briefly outlined. (U.K.)

  9. Comparison of Spin Wave Theory with Neutron Scattering Results for MnF{sub 2}; Comparaison entre la Theorie de l'Onde de Spin et les Resultats Obtenus par la Diffusion des Neutrons dans MnF{sub 2}; Sravnenie teorij spinovoj volny s rezul'tatami rasseyaniya nejtronov dlya MnF{sub 2}; Estudio Comparativo, en el MnF{sub 2}, de la Teoria Ondulatoria del Spin y de los Resultados de la Dispersion Neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Low, G. G. [Atomic Energy Research Establishment, Harwell, Berks (United Kingdom)

    1965-04-15

    Recent inelastic neutron scattering experiments carried out by Okazaki and Turberfield have provided a direct measure of spin wave dispersion in MnF{sub 2} both at 4.2 Degree-Sign K and at higher temperatures approaching the Neel point. The low temperature results taken together with other magnetic data allow the various exchange constants in MnF{sub 2} to be evaluated with some precision. Using these constants, the spin wave formalism for anti-ferromagnets described by Oguchi has been employed to predict theoretically the temperature dependence of the spin wave dispersion. No disposable parameters are involved and theoretical dispersion curves may be compared with the experimental results for higher temperatures as a test of the spin wave theory. The spin wave energies were evaluated numerically and integrations over the Brillouin zone were carried out, thus avoiding the use of some form of series expansion in temperature. Account was taken of dynamical interactions between pairs of spin waves but kinematical effects were neglected. Renormalization of the spin wave energies was performed. This is an important factor for T/T{sub N}{>=} Vulgar-Fraction-One-Half The agreement between theory and experiment is in fact remarkably good up to temperatures corresponding to about 90% of the Neel point. It would be dangerous to extrapolate this result to systems of lower spin as kinematical effects are likely to play a much greater part in such cases. For MnF{sub 2} where S= 5/2 a rough estimate suggests that kinematical effects will not be important until M/M{sub O}-20% and this occurs only within a degree or so of the Neel point. A brief discussion of the likely consequences of a biquadratic exchange term in MnF{sub 2} is given and it is concluded that, if present, such exchange is quite small. (author) [French] Des experiences recentes, executees par Okazaki et Turberfield au moyen de la diffusion inelastique des neutrons, ont fourni une mesure directe de la dispersion de

  10. Neutron source

    International Nuclear Information System (INIS)

    Cason, J.L. Jr.; Shaw, C.B.

    1975-01-01

    A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap

  11. Neutron transport

    International Nuclear Information System (INIS)

    Berthoud, Georges; Ducros, Gerard; Feron, Damien; Guerin, Yannick; Latge, Christian; Limoge, Yves; Santarini, Gerard; Seiler, Jean-Marie; Vernaz, Etienne; Coste-Delclaux, Mireille; M'Backe Diop, Cheikh; Nicolas, Anne; Andrieux, Catherine; Archier, Pascal; Baudron, Anne-Marie; Bernard, David; Biaise, Patrick; Blanc-Tranchant, Patrick; Bonin, Bernard; Bouland, Olivier; Bourganel, Stephane; Calvin, Christophe; Chiron, Maurice; Damian, Frederic; Dumonteil, Eric; Fausser, Clement; Fougeras, Philippe; Gabriel, Franck; Gagnier, Emmanuel; Gallo, Daniele; Hudelot, Jean-Pascal; Hugot, Francois-Xavier; Dat Huynh, Tan; Jouanne, Cedric; Lautard, Jean-Jacques; Laye, Frederic; Lee, Yi-Kang; Lenain, Richard; Leray, Sylvie; Litaize, Olivier; Magnaud, Christine; Malvagi, Fausto; Mijuin, Dominique; Mounier, Claude; Naury, Sylvie; Nicolas, Anne; Noguere, Gilles; Palau, Jean-Marc; Le Pallec, Jean-Charles; Peneliau, Yannick; Petit, Odile; Poinot-Salanon, Christine; Raepsaet, Xavier; Reuss, Paul; Richebois, Edwige; Roque, Benedicte; Royer, Eric; Saint-Jean, Cyrille de; Santamarina, Alain; Serot, Olivier; Soldevila, Michel; Tommasi, Jean; Trama, Jean-Christophe; Tsilanizara, Aime; Behar, Christophe; Provitina, Olivier; Lecomte, Michael; Forestier, Alain; Bender, Alexandra; Parisot, Jean-Francois; Finot, Pierre

    2013-10-01

    This bibliographical note presents a reference book which addresses the study of neutron transport in matter, the study of conditions for a chain reaction and the study of modifications of matter composition due to nuclear reactions. This book presents the main nuclear data, their measurement, assessment and processing, and the spallation. It proposes an overview of methods applied for the study of neutron transport: basic equations and their derived forms, deterministic methods and Monte Carlo method of resolution of the Boltzmann equation, methods of resolution of generalized Bateman equations, methods of time resolution of space kinetics coupled equations. It presents the main calculation codes, discusses the qualification and experimental aspects, and gives an overview of neutron transport applications: neutron transport calculation of reactors, neutron transport coupled with other disciplines, physics of fuel cycle, criticality

  12. Set up of an innovative methodology to measure on-line the incineration potential of minor actinides under very high neutron sources in the frame of the future prospects of the nuclear waste transmutation; Mise au point d'une methodologie innovante pour la mesure du potentiel d'incineration d'actinides mineurs sous des sources tres intenses de neutrons, dans la perspective de transmutation des dechets nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Fadil, M

    2003-03-01

    This work deals generally with the problem of nuclear waste management and especially with the transmutation of it to reduce considerably its radiotoxicity potential. The principal objective of this thesis is to show the feasibility to measure on-line the incineration potential of minor actinides irradiated under very high neutron flux. To realize this goal, we have developed fission micro-chambers able to operate, for the first time in the world, in saturation regime under a severe neutron flux. These new chambers use {sup 235}U as an active deposit. They were irradiated in the high flux reactor at Laue-Langevin Institute in Grenoble. The measurement of the saturation current delivered by these chambers during their irradiation for 26 days allowed to evaluate the burn-up of {sup 235}U. We have determined the neutron flux intensity of 1,6 10{sup 15} n.cm{sup -2}.s{sup -1} in the bottom of the irradiation tube called 'V4'. The relative uncertainty of this value is less than 4 %. This is for the first time that such high neutron flux is measured with a fission chamber. To confirm this result, we have also performed independent measurements using gamma spectroscopy of irradiated Nb and Co samples. Both results are in agreement within error bars. Simple Deposit Fission Chambers (SDFC) as above were the reference of the new generation of fission chambers that we have developed in the framework of this thesis: Double Deposit Fission Chambers (DDFC). The reference active deposit was {sup 235}U. The other deposit was the actinide that we wanted to study (e.g. {sup 237}Np and {sup 241}Am). At the end of the thesis, we present some suggestions to ameliorate the operation of the DDFC to be exploited in other transmutation applications in the future. (author)

  13. Long-term radiation sequelae after breast-conserving therapy in women with early-stage breast cancer: an observational study using the LENT-SOMA scoring system

    International Nuclear Information System (INIS)

    Fehlauer, Fabian; Tribius, Silke; Hoeller, Ulrike; Rades, Dirk; Kuhlmey, Antje; Bajrovic, Amira; Alberti, Winfried

    2003-01-01

    Purpose: To evaluate the long-term toxicity after breast-conserving therapy in women with early-stage breast cancer. Methods and Materials: Late toxicity according to the late effects of normal tissue-subjective, objective, management, and analytic (LENT-SOMA) criteria and cosmetic outcome (graded by physicians) were evaluated in 590 of 2943 women with early-stage breast cancer who were irradiated between 1983 and 1995 using the following fractionation schedules: group A, 1983-1987, 2.5 Gy 4x/wk to 60 Gy; group B, 1988-1993, 2.5 Gy 4x/wk to 55 Gy, group C, 1994-1995, 2.0 Gy 5x/wk to 55 Gy. Results: LENT-SOMA Grade 3-4 toxicity was observed as follows: group A (median follow-up 171 months; range 154-222 months), fibrosis 16% (7 of 45), telangiectasia 18% (8 of 45), and atrophy 4% (2 of 45); group B (median follow-up 113 months; range 78-164 months), pain 2% (8 of 345), fibrosis 10% (34 of 345), telangiectasia 10% (33 of 345), arm edema 1% (2 of 345), and atrophy 8% (27 of 345); and group C (median follow-up 75 months, range 51-96 months, n = 200), occurrence of Grade 3-4 late morbidity ≤2%. The cosmetic outcome was very good to acceptable in 78% (35 of 45) of patients in group A, 83% (286 of 345) in group B, and 94% (187 of 200) in group C. Conclusion: In our population, the long-term side effects after breast-conserving therapy were not rare, but were mainly asymptomatic. The LENT-SOMA breast module is a practical tool to assess radiation-induced long-term toxicity

  14. Lente fácica de câmara posterior para correção de hipermetropia consecutiva à ceratotomia radial

    Directory of Open Access Journals (Sweden)

    Salera Cristina Moreira

    2003-01-01

    Full Text Available OBJETIVO: Avaliar a eficácia, previsibilidade e segurança do implante de lente fácica de câmara posterior para a correção de hipermetropia consecutiva à ceratotomia radial. MÉTODOS: Foram analisados retrospectivamente os prontuários de seis pacientes (10 olhos com hipermetropia consecutiva à hipercorreção após ceratotomia radial submetidos ao implante de lente fácica de câmara posterior para sua correção. RESULTADOS: O equivalente esférico pré-operatório médio da refração dinâmica foi de +4,65 dioptrias (variando de +2,50 a +6,50 dioptrias e o equivalente esférico pós-operatório médio foi de +0,3375 dioptrias (variando de -0,875 a +2,25 dioptrias. Quando comparamos as acuidades visuais com correção pré e pós-operatórias observamos que três olhos (30% ganharam duas linhas de acuidade visual, dois (20% ganharam uma linha de acuidade visual, um (10% manteve a mesma acuidade visual, três olhos (30% perderam uma linha de acuidade visual e um olho (10% perdeu duas linhas. CONCLUSÃO: O implante da lente fácica de câmara posterior para correção da hipermetropia consecutiva à ceratotomia radial mostrou-se como uma nova opção para o tratamento desta indesejável complicação, entretanto, fazem-se necessários estudos abrangendo maior número de casos e um acompanhamento a longo prazo destes casos.

  15. Mensurações do bulbo ocular e cálculo do poder dióptrico de lentes intraoculares em coelhos

    Directory of Open Access Journals (Sweden)

    M.A.R. Valinhos

    2012-02-01

    Full Text Available Determinaram-se as dimensões oculares de coelhos, empregando ultrassonografia modo-A e ceratometria, a fim de utilizá-las como subsídios para calcular o poder dióptrico de lentes intraoculares a serem implantadas experimentalmente nessa espécie e avaliar se existe diferença entre as mensurações oculares de machos e fêmeas e entre olho esquerdo e olho direito. Foram utilizados 58 animais do grupo genético Botucatu, distribuídos entre 30 fêmeas e 28 machos, com idade média de 85,8±8,29 dias e peso médio de 2,3±0,46kg. O cálculo da lente intraocular foi realizado por meio do software Holladay IOL Consultant®. As fórmulas empregadas para o cálculo foram: Holladay II, Holladay I, Hoffer Q e SRK-T, que calcularam lentes de aproximadamente 48,5 D; 50,27 D; 59,67 D e 49,24 D, respectivamente. A fórmula SRK-T mostrou-se semelhante às fórmulas Holladay II e Holladay I, enquanto entre as demais ocorreram diferenças. As características biométricas oculares avaliadas, assim como o poder dióptrico calculado por uma mesma fórmula, não apresentaram diferenças significativas com relação ao sexo e à lateralidade.

  16. Neutron scattering by normal liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gennes, P.G. de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    Neutron data on motions in normal liquids well below critical point are reviewed and classified according to the order of magnitude of momentum transfers {Dirac_h}q and energy transfers {Dirac_h}w. For large momentum transfers a perfect gas model is valid. For smaller q and incoherent scattering, the major effects are related to the existence of two characteristic times: the period of oscillation of an atom in its cell, and the average lifetime of the atom in a definite cell. Various interpolation schemes covering both time scales are discussed. For coherent scattering and intermediate q, the energy spread is expected to show a minimum whenever q corresponds to a diffraction peak. For very small q the standard macroscopic description of density fluctuations is applicable. The limits of the various (q) and (w) domains and the validity of various approximations are discussed by a method of moments. The possibility of observing discrete transitions due to internal degrees of freedom in polyatomic molecules, in spite of the 'Doppler width' caused by translational motions, is also examined. (author) [French] L'auteur examine les donnees neutroniques sur les mouvements dans les liquides normaux, bien au-dessous du point critique, et les classe d'apres l'ordre de grandeur des transferts de quantite de mouvement {Dirac_h}q et des transferts d'energie {Dirac_h}w. Pour les grands transferts de, quantite de mouvement, un modele de gaz parfait est valable. En ce qui concerne les faibles valeurs de q et la diffussion incoherente, les principaux effets sont lies a l'existence de deux temps caracteristiques: la periode d'oscillation d'un atome dans sa cellule et la duree moyenne de vie de l'atome dans une cellule determinee. L'auteur etudie divers systemes d'interpolation se rapportant aux deux echelles de temps. Pour la diffusion coherente et les valeurs intermediaires de q, on presume que le spectre d'energie accuse un minimum chaque fois que q correspond a un pic de

  17. Calculation of correlation between spins in a magnetic substance; Calcul des correlations entre spins dans une substance magnetique

    Energy Technology Data Exchange (ETDEWEB)

    Gennes, P.G. de [Commissariat a l' Energie Atomique, Saclay (France)

    1959-07-01

    The report states an elementary calculation of the correlation between spins in a magnetic substance, and particularly of their asymptotic form with regard to relatively wide-spaced spins. This permits the determination of the phenomenological parameters introduced by Var Hove to describe the magnetic scatter of neutrons in the critical opalescent area. (author) [French] On donne un calcul elementaire des correlations entre spins dans une substance magnetique, et notamment de leur forme asymptotique pour des spins assez eloignes. Ceci permet de determiner les parametres phenomenologiques introduits par Van Hove pour decrire la diffusion magnetique des neutrons dans la region d'opalescence critique. (auteur)

  18. Correcting the effects of the matrix using capture gamma-ray spectrometry: Application to measurement by Active Neutron Interrogation; Correction des effets de matrice par spectrometrie des rayonnements gamma de capture: Application a la mesure par Interrogation Neutronique Active (I.N.A.)

    Energy Technology Data Exchange (ETDEWEB)

    Baudry, G.

    2003-11-15

    In the field of the measurement of low masses of fissile material ({sup 235}U, {sup 239}Pu, {sup 241}Pu) in radioactive waste drums, the Active Neutron Interrogation is a non-destructive method achieving good results. It does however remain reliant upon uncertainties related to the matrix effects on interrogation and fission neutrons. The aim of this thesis is to develop a correction method able to take into account these matrix effects by quantifying the amount of absorbent materials (chlorine and hydrogen) in a 118- liter homogeneous matrix. The main idea is to use the gamma-ray spectrometry of gamma emitted by neutron captures to identify and quantify the composition of the matrix. An indicator from its chlorine content is then deduced in order to choose the calibration coefficient which best represents the real composition of the matrix. This document firstly presents the needs of control and characterization of radioactive objects, and the means used in the field of nuclear measurement. Emphases is put in particular on the Active Neutron Interrogation method. The matrices of interest are those made of light technological waste (density {<=} 0,4 g/cm{sup 3}) containing hydrogenated and chlorinated materials. The advantages of gamma-rays emitted by neutron captures for the determination of a chlorine content indicator of the matrices and the principles of the correction method are then explained. Measurements have been firstly realized with an existing Neutron Interrogation device (PROMETHEE 6). Such measurements have proven its inadequacy: no signal from the matrix hydrogen was detected, due to an intense signal from the polyethylene contained in some cell elements. Moreover, the matrix chlorine content appeared difficult to be measured. A new and specific device, named REGAIN and dedicated to active gamma-rays spectrometry, was defined with the Monte-Carlo N-Particle (MCNP) code. The experiments conducted with this new device made it possible to detect the

  19. Gestion des risques

    CERN Document Server

    Louisot, Jean-Paul

    2009-01-01

    Depuis le début du lie siècle, la gestion des risques connaît une véritable révolution culturelle. Jusqu'alors fonction technique, centrée autour de l'achat de couverture d'assurances, elle est devenue une discipline managériale et transversale : une valise d'instruments que chaque manager doit connaître et appliquer quels que soient son domaine de compétence et ses missions au sein de l'organisation. En effet, la gestion des risques est une culture qui doit être assimilée par chacun des acteurs. C'est précisément l'ambition des 101 questions rassemblées dans cet ouvrage : apporter à chaque manager d'entreprise, de collectivité, d'établissement de santé..., des réponses claires au " pourquoi " et au " comment " : Comment identifier les risques ? Comment analyser les risques ? Quels sont les objectifs de la gestion des risques ? Une carte des risques pour quoi faire ? Pourquoi faut-il financer les risques ? Les entreprises ont-elles des responsabilités pénales ? En quoi consiste la gestion...

  20. Elaboración y gestión de un programa de mantenimiento para una fábrica de lentes oftálmicos

    OpenAIRE

    Garrafa Ayquipa, Henry Calixto; Garrafa Ayquipa, Henry Calixto

    2007-01-01

    La fabricación de lentes oftálmicos es una industria de poco desarrollo en el Perú. Sin embargo, Topsa se ha preocupado por ser una empresa competitiva, realizando inversiones en tecnología y mejora de sus procesos, convirtiéndola en una empresa lideren la industria. En la última década, las ventas de Topsa crecieron a razón del 20 % anual, por ello se amplió la capacidad de planta adquiriendo nuevas maquinarias. También, se incrementaron los reclamos de los clientes por productos defec...

  1. Continuous and discreet methods in the aggregation and des fuzzy stages of a diffuse controller of neutron power; Metodos continuo y discreto en las etapas de agregacion y desdifusificacion de un controlador disfuso de potencia neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Najera H, M.C.; Benitez R, J.S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    The results of a comparative study are presented of: to) A denominated diffuse controller 'exact', designed by means of an innovative method that determines analytically so much the group of exit resultant in the aggregation stage like the de fuzzy process, and b) a diffuse controller denominated 'discreet' based on the discretization of the variable of having left as much for the aggregation as for the de fuzzy. These stages incorporated to the control algorithms whose objective is the ascent and regulation of the neutron power, carrying out an analysis of its performance. (Author)

  2. La gouvernance des risques naturels et la problematique des ...

    African Journals Online (AJOL)

    Depuis quelques années, la gouvernance des risques naturels dus aux inondations remet en cause les processus de mise en oeuvre des politiques urbaines et la qualité de la structure des aménagements dans les grandes villes du Golfe de Guinée. La perception de la gouvernance et l'application des politiques de ...

  3. Special concretes for protection in piles (1963); Les betons speciaux dans la protection des piles (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Condat, M.J.; Lafore, P.; Rastoin, J. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1963-07-01

    The report reviews the main concretes used for the protection of reactors. First are examined the general factors affecting the selection of concretes for protection; some of the general aspects of radiation attenuation (fast and thermal neutrons, {gamma}) are then recalled. After an enumeration of the qualities and defects of conventional concretes, d