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Sample records for bacteries etude experimentale

  1. Hydration of swelling clay and bacteria interaction. An experimental in situ reaction study; Hydratation des argiles gonflantes et influence des bacteries. Etude experimentale de reaction in situ

    Energy Technology Data Exchange (ETDEWEB)

    Berger, J

    2008-01-15

    observed between Na- and Ca-smectite. The hydration mechanisms of compacted smectite occurring within a confined volume system are presented in a schematic model involving different scales, ranging from the Angstrom-scale of lattice layers to the bulk clay structure. Whereas the nature of interlayer cation affects hydration on all scales, the ionic strength of the infiltrating solution primarily affects the bulk texture. The impact of selected smectites (SWy-2, MX80 and nontronite) on the growth of S. putrefaciens was studied using agitated batch solution experiments combined with viable cell counts. The prolonged survival of bacteria in smectite suspensions compared to growth in culture medium is attributed to i) a continuous and sustainable supply of cationic nutrients and Corg, ii) the buffering capacity of the smectite clay and iii) the large clay surface areas, which accumulate nutrients, serve as attachment sites and sorb toxic waste products. The rate of bacterially induced smectite alteration/dissolution in batch solutions, as monitored by ICPOES and microscopy (confocal, ESEM and TEM coupled to EDX), shows depletion of the main cations in the nontronite extracted solution. This is attributed to the initial consumption and/or binding of cations by S. putrefaciens, which is probably related to the production of chelating agents. The constantly depleted Ca is most likely stored in the abundant EPS (exo-polymeric substance). Enhanced cation release in the case of nontronite in long-term experiments was especially evident for Fe and Al that corresponds to more than 10% partial dissolution. In contrast, the Fe-poor, Na-smectite was not seen to be affected by bacterial activity in this way and the increased release of Al by acid leaching corresponds to only 1.4% partial smectite dissolution. The presence of S. putrefaciens induced abundant textural changes as observed by microscopic investigations (confocal microscopy, ESEM), associated with the formation of smectite

  2. Hydration of swelling clay and bacteria interaction. An experimental in situ reaction study; Hydratation des argiles gonflantes et influence des bacteries. Etude experimentale de reaction in situ

    Energy Technology Data Exchange (ETDEWEB)

    Berger, J

    2008-01-15

    observed between Na- and Ca-smectite. The hydration mechanisms of compacted smectite occurring within a confined volume system are presented in a schematic model involving different scales, ranging from the Angstrom-scale of lattice layers to the bulk clay structure. Whereas the nature of interlayer cation affects hydration on all scales, the ionic strength of the infiltrating solution primarily affects the bulk texture. The impact of selected smectites (SWy-2, MX80 and nontronite) on the growth of S. putrefaciens was studied using agitated batch solution experiments combined with viable cell counts. The prolonged survival of bacteria in smectite suspensions compared to growth in culture medium is attributed to i) a continuous and sustainable supply of cationic nutrients and Corg, ii) the buffering capacity of the smectite clay and iii) the large clay surface areas, which accumulate nutrients, serve as attachment sites and sorb toxic waste products. The rate of bacterially induced smectite alteration/dissolution in batch solutions, as monitored by ICPOES and microscopy (confocal, ESEM and TEM coupled to EDX), shows depletion of the main cations in the nontronite extracted solution. This is attributed to the initial consumption and/or binding of cations by S. putrefaciens, which is probably related to the production of chelating agents. The constantly depleted Ca is most likely stored in the abundant EPS (exo-polymeric substance). Enhanced cation release in the case of nontronite in long-term experiments was especially evident for Fe and Al that corresponds to more than 10% partial dissolution. In contrast, the Fe-poor, Na-smectite was not seen to be affected by bacterial activity in this way and the increased release of Al by acid leaching corresponds to only 1.4% partial smectite dissolution. The presence of S. putrefaciens induced abundant textural changes as observed by microscopic investigations (confocal microscopy, ESEM), associated with the formation of smectite

  3. Etude theorique et experimentale des evaporateurs de dioxyde de carbone operant dans des conditions de givrage

    Science.gov (United States)

    Bendaoud, Adlane Larbi

    Les evaporateurs de refrigeration sont surtout du type tube a ailettes, appeles serpentins, et fonctionnent dans l'une des conditions suivantes: seche, humide ou avec formation de givre. Il a ete demontre que la formation du givre sur la paroi exterieure de l'echangeur engendre une surconsommation energetique a cause des operations de degivrage puisque 15 a 20% seulement de la chaleur produite sert au degivrage tandis que le reste est dissipee dans l'environnement [1]. Avec l'avenement des nouveaux refrigerants, moins nocifs envers l'environnement, l'industrie du froid se trouve penalisee du fait que peu ou pas de composantes mecaniques (compresseur, pompe, echangeur...etc.) adaptees sont disponibles [3]. Il s'agit pour la communaute des frigoristes de combler ce retard technologique en redeveloppant ces composantes mecaniques afin qu'elles soient adaptees aux nouveaux refrigerants. Dans cette optique, et afin de mieux comprendre le comportement thermique des evaporateurs au CO2 fonctionnant dans des conditions seches, qu'un groupe de chercheurs du CanmetENERGIE avaient lance, en 2000, un programme de R & D. Dans le cadre de programme un outil de simulation des evaporateurs au CO2 a ete developpe et un banc d'essai contenant une boucle secondaire de refrigeration utilisant le CO2 comme refrigerant a ete construit. Comme continuite de ce travail de recherche, en 2006 ce meme groupe de recherche a lance un nouveau projet qui consiste a faire une etude theorique et experimentale des evaporateurs au CO2 operants dans des conditions de givrage. Et, c'est exactement dans le cadre de ce projet que se positionne ce travail de these. Ce travail de recherche a ete entrepris pour mieux comprendre le comportement thermique et hydrodynamique des serpentins fonctionnant dans des conditions de givrage, l'effet des circuits de refrigerant ainsi que celui des parametres geometriques et d'operation. Pour cela, un travail theorique supporte par une etude experimentale a ete effectue

  4. Etude experimentale des excitations topologiques de l'effet Hall quantique a nu = 1 dans les heterostructures semiconductrices a double puits quantique

    Science.gov (United States)

    Charlebois, Serge

    De nombreux travaux theoriques et experimentaux ont ete publies sur les excitations topologiques de gaz electroniques bidimensionnels (GE2D), appellees skyrmions, dans le regime de l'effet Hall quantique a remplissage unitaire. On attend des excitations semblables appellees bimerons dans les systemes formes de deux GE2D couples. Contrairement au cas des GE2D simples, aucune experience n'a, a notre connaissance, presente la mesure d'une propriete specifique aux bimerons. Nous presentons dans cette these des travaux experimentaux ayant pour objectif l'etude d'excitations topologiques dans les heterostructures a double puits quantique. Une manifestation attendue (les bimerons est la presence d'une anisotropie dans la conductivite a travers une constriction. Nous avons concu un dispositif original a point de contact a trois grilles non-coplanaires. Ce dispositif a trois grilles a la particularite de permettre la creation d'une constriction etroite dans le double GE2D tout en permettant l'equilibrage de la densite electronique entre les deux puits dans l'etroit canal de conduction. Nous avons fabrique ce dispositif de taille submicronique par electrolithographie sur des heterostructures a double puits. Les dispositifs ainsi fabriques ont ete etudies a basse temperature (0.3K) et ont montre un fonctionnement conforme aux attentes. Les travaux n'ont pas permis de mettre en evidence une anisotropie de transport revelatrice de l'existence de bimerons. Cette these est a notre connaissance la premiere etude experimentale visant la realisation de l'experience d'anisotropie de transport et est ainsi une contribution significative a l'avancement des connaissances dans ce domaine. Les travaux theoriques que nous presentons ont permis de montrer l'effet des excitations topologiques sur la capacite grille-GE2D du systeme. Ces travaux ouvrent la voie de la detection des bimerons par l'intermediaire de la mesure de la capacite grille-GE2D ou encore de la susceptibilite electrique du

  5. Experimental study of the hydrodynamic instabilities occurring in boiling-water reactors; Etude experimentale des instabilites hydrodynamiques survenant dans les reacteurs nucleaires a ebullition

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-10-01

    The subjects is an experimental out-of pile loop study of the hydrodynamic oscillations occurring in boiling-water reactors. The study was carried out at atmospheric pressure and at pressure of about 8 atmospheres, in channels heated electrically by a constant and uniform specified current. In the test at 8 atmospheres the channel was a round tube of approximately 6 mm interior diameter. At 1 atmosphere a ring-section channel was used, 10 * 20 mm in diameter, with an inner heating tube and an outer tube of pyrex. It was possible to operate with natural convection and also with forced convection with test-channel by-pass. The study consists of 3 parts: 1. Preliminary determination of the laws governing pressure-drop during boiling. 2. Determination of the fronts at which oscillation appears, within a wide range of the parameters involved. 3. A descriptive study of the oscillations and measurement of the periods. The report gives the oscillation fronts with natural and forced convection for various values of the singular pressure drop at the channel inlet and for various riser lengths. The results are presented in non-dimensional form, which is available, in first approximation, for all geometric scales and for all fluids. Besides the following points were observed: - the wall (nature and thickness) can be an important factor ; - oscillation can occur in a horizontal channel. (author) [French] II a ete effectue une etude experimentale, en boucle hors-pile, des oscillations hydrodynamiques survenant dans les reacteurs a ebullition. L'etude a ete effectuee a la pression atmospherique et a une pression voisine de 8 atmospheres dans des canaux chauffes electriquement a puissance imposee constante et uniforme. Dans les essais a 8 atmospheres le canal etait un tube circulaire de diametre interieur 6 mm environ. A 1 atmosphere le canal etait de section annulaire 10 * 20 mm avec un tube interieur chauffant et un tube exterieur en pyrex. Le fonctionnement etait possible

  6. Pegase: safety studies - experimental study of burn-out risks in transient operation; Pegase: etude de surete - etude experimentale des risques de burn out en regime transitoire

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-07-01

    permet de conclure que le canal chaud se met en etat de calefaction au bout de 0.1 s et que sa temperature atteint 500 C en 0.8 s. Les regimes hydrodynamiques rencontres dans les canaux apres l'accident sont des regimes d'expulsion periodiques de periodes courtes 0.2 a 0.5 s, caracteristiques de l'ebullition a basse pression. L'etude en regime permanent de la redistribution de debit dans un by-pass a donne des flux PHI{sub R} de redistribution de 190 W/cm{sup 2} pour une vitesse de 4.5 m/s a 50 C et de 175 W/cm{sup 2} a 60 C. Ces valeurs sont a majorer de 25 pour cent pour une vitesse de 6 m/s. On a montre la distinction a faire entre flux critique PHI{sub C} en regime periodique d'expulsion et flux de redistribution PHI{sub R} en regime permanent. (auteur)

  7. Radio-vulcanization of natural rubber in the latex phase. Study of an experimental 1 tonne per hour production; Radio-vulcanisation du caoutchouc naturel en phase latex. Etude d'une production experimentale de 1 tonne par heure

    Energy Technology Data Exchange (ETDEWEB)

    Leveque, P.; Puig, J.R.; Roudeix, H. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    After briefly reviewing the main research carried out on the radio-vulcanization of latex and elastomers, a description is given of 4 types of cell which have been used successively with a view to industrial irradiation. They have made it possible to acquire the information necessary for resolving the main problem arising during irradiation - the formation of coagulum. The first two cell are designed for irradiation by a horizontal beam ('Dynamitron'), the two others use a vertical beam ('Circe'). The study of the properties of the rubber obtained shows it to compare favorably with 'Revultex'. In the appendix are given some characteristics of natural latex and information about its processing. (authors) [French] Apres un rappel des principales etudes sur la radio-vulcanisation du latex et des elastomeres, on decrit les quatre types de cellules successivement essayes en vue de l'irradiation industrielle. Ils ont permis d'acquerir les informations necessaires a la resolution du probleme principal pose par l'irradiation, la formation de coagulum au cours de celle,-ci. Les deux premiers sont concus pour l'irradiation par un faisceau horizontal ('Dynamitron'), les derniers par un faisceau vertical ('Circe'). L'etude des proprietes du caoutchouc obtenu montre qu'il se compare favorablement au 'Revultex'. Un apercu est donne en annexe des caracteristiques du latex naturel et de sa mise en oeuvre. (auteurs)

  8. Modelos experimentales de anafilaxia

    Directory of Open Access Journals (Sweden)

    Yazmín Ravelo Calzado

    2009-01-01

    Full Text Available Los modelos experimentales constituyen una herramienta clave en la búsqueda de nuevas opciones para el tratamiento y profilaxis de diversas condiciones patológicas. La anafilaxia, síndrome clínico con manifestaciones multisistémicas como urticaria, asma, vasodilatación sistémica, hipotensión y shock, entre otras, no resulta una excepción. El objetivo del presente trabajo consistió en presentar algunos de los modelos experimentales utilizados en la evaluación de sustancias con potenciales efectos antianafilácticos, específicamente aquellos en los que la anafilaxia se produce como consecuencia de un mecanismo inmunológico mediado por inmunoglobulina E (IgE, que da lugar a la liberación de mediadores inflamatorios (histamina, prostaglandinas, leucotrienos, factor de activación plaquetario, tromboxano A2 a partir de mastocitos y basófilos. Para ello, se resumen diferentes modelos de anafilaxia experimentales in vivo e in vitro, y se agrupan según el método de inducción de anafilaxia, mostrando así, mecanismos moleculares comunes, pero también especificidades distintivas en cuanto a la especie utilizada, el tipo de antígeno que desencadena la reacción y su tipo (sistémica o local, entre otros aspectos. Se enfatiza la importancia de la adecuada selección de modelos experimentales que garanticen la mayor reproducibilidad y fiabilidad de los resultados, para lo cual se precisan algunos criterios para dicha selección, teniendo en mente que ningún modelo satisface todos los criterios involucrados en la etiopatogenia de una determinada patología.

  9. Contribution to the theoretical and experimental study of the electron-volt effect in N-P junctions; Contribution a l'etude theorique et experimentale de l'effet electronvoltaique dans les jonctions N-P

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Van, Dong [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-07-15

    , taking into account other phenomena which occur at low temperature. In the fourth part, results concerning the healing of the defects and protection measures against too energetic {beta} rays are described. A healing difference was observed between the lifetime and the conductivity. Finally, interesting results were obtained from experiments using a cadmium sulphide film to transform the {beta} particles of {sup 90}Sr-{sup 90}Y into photons. (author) [French] Le but propose dons le cadre de ce travail est d'etudier le comportement d'une jonction semi-conductrice sous l'action des rayons {beta}. L'etude a porte d'une part sur la conversion directe de l'energie rayonnee par une source radioactive en energie electrique utilisable a l'aide des jonctions N-P, et d'autre part sur la cinetique des defauts produits dans les cristaux de semi-conducteur par les rayons {beta} de grande energie. Dans la premiere partie du travail, on a essaye de completer les theories anterieures de l'effet electron-voltaique dans les jonctions en faisant une analyse mathematique de l'effet. Ceci a permis d'atteindre une equation unique dans laquelle figurent les parametres electriques et geometriques du semi-conducteur, de la jonction et les proprietes du rayonnement incident. D'autre part, on a etudie d'une maniere plus approfondie le courant de diffusion des porteurs de charge crees par le bombardement en tenant compte de tous les facteurs intervenant dans l'expression de l'efficacite de collection de charge d'une jonction. Dans la deuxieme partie, ou des experiences d'irradiation des jonctions N-P ont ete effectuees avec une source de {sup 90}Sr- {sup 90}Y, on a signale l'interet particulier d'une jonction d'arseniure de gallium susceptible de travailler a des temperatures relativement elevees (voisines de 100 deg. C). La troisieme partie presente l'etude des defauts crees dans un cristal de

  10. Theoretical and experimental study of ions focusing systems in order to improve the ions beam brightness by suppressing aberration causes; Etude theorique et experimentale de la focalisation des ions afin d'ameliorer la brillance du faisceau ionique par la suppression des causes d'aberration

    Energy Technology Data Exchange (ETDEWEB)

    Faure, J

    1966-07-01

    It is shown that a beam brightness can be improved by an order of magnitude when the sources of aberrations are suppressed in the anode region source, as well as in the extraction region and in the electrostatic focusing system. A calculation was first set up to determine a simple focusing system. The aberration ratio due to this focusing system is smaller than 10 to 15 per cent. The experimental study was developed by using an ion source and its extraction system capable of producing an aberration free beam at an energy of 20 keV and an accelerating unit up to 190 keV that confirms that the qualities of a 35 mA beam produced by the said ion source are not spoiled when the beam goes through the focusing and accelerating system that was designed to be aberration free. (author) [French] Dans ce travail, on s'attache a demontrer que la brillance d'un faisceau peut etre amelioree d'un ordre de grandeur lorsque l'on supprime les causes d'aberration aussi bien a la sortie de la source, dans la zone d'extraction, que dans le systeme de focalisation electrostatique. Un calcul est, tout d'abord, mis au point pour determiner un systeme de focalisation simple. Cette focalisation n'entraine pas un taux d'aberrations superieur a 10 ou 15 pour cent. Puis l'etude experimentale conduit: a) a la realisation d'une source et de son systeme d'extraction fournissant un faisceau sans aberration a une energie de 20 keV. b) et a l'elaboration d'un petit accelerateur a 190 keV qui verifie que les proprietes d'un faisceau de 35 mA issu de la source ne sont pas affectees par la traversee des systemes focalisateur et accelerateur lorsque ceux-ci n'apportent pas d'aberration. (auteur)

  11. Matemáticas experimentales

    OpenAIRE

    Pérez, Antonio

    1992-01-01

    En primer lugar, quiero manifestar mi más sincero agradecimiento a los organizadores de estos II Encuentros Extremeños por la amabilidad que han tenido al invitame. Antes que nada, una aclaración. Al hablar de matemáticas experimentales me estaré refiriendo siempre a la enseñanza de nuestra materia. Nada más lejos de mis posibilidades que intentar adjetivar las propias matemáticas. Hablaré de enseñanza de las matemáticas y, en general, de la utilización de recursos que posibiliten la acción d...

  12. Numerical and experimental investigation of industrial electrostatic precipitators; Etude numerique et experimentale d`electrofiltres industriels

    Energy Technology Data Exchange (ETDEWEB)

    Tochon, P.

    1997-10-17

    This work deals with electrostatic precipitators or ESP used for gas-solid particles separation. By means of a dust-controlled testing loop created and realised at the GRETh`s plate-form (Research Group on Heat Exchangers) and a numerical model developed during this work from TRIO software, the study of the performances of different ESP geometries has been carried out. Many electrical, hydraulic and particular parameters governing solid particles collection under ionised electric field have been identified, measured and modelled. The numerical model, ratified with experimental data obtained during this study and from literature, allows to describe local and global phenomena occurring in any geometries. Furthermore, parametric studies have been carried out in order to propose some optimised geometries. allowing to increase collection efficiencies. At least, on-site measurements with CETIAT (Centre Technique des Industries Aerauliques et Thermiques) allow to identify dust particles likely to be thrown out to the atmosphere, and troubles peculiar to large scales industrial plants. The numerical model has also been tested on these data. At the end of this study, an efficient dust-controlled experimental tool, PACIFIC loop, and a numerical simulation allowing ESP sizing are available. (author)

  13. Experimental study of the Rapsodie protections; Etude experimentale des protections de rapsodie

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-07-01

    This report gives details of the protection tests which have been carried out by the Protection Sub-Commission during the starting-up trials on the reactor Rapsodie. The main types of tests reported concern the flux measurements in the core, the reflectors, the sodium and the near biological protections, the radio-protection measurements in the premises, and the activation of the principal fluids. In the last part, the results obtained are analyzed and compared to the forecast calculations. (author) [French] Ce rapport rend compte des essais de protection qui ont ete effectues dans le cadre des essais de demarrage de RAPSODIE par la Sous Commission Protection. Les principaux types d'essais rapportes sont les mesures de flux dans le coeur, les reflecteurs, le sodium et les protections biologiques proches, les mesures de radioprotection dans les locaux, et l'activation des principaux fluides. Dans la derniere partie, les resultats obtenus sont analyses et compares aux calculs previsionnels. (auteur)

  14. ETUDE THEORIQUE ET EXPERIMENTALE DU SECHAGE SOLAIRE DES FEUILLES DE LA MENTHE VERTE (MENTHA VIRIDIS).

    OpenAIRE

    BOUMEDIENE, TOUATI

    2014-01-01

    LES PLANTES MÉDICINALES ET AROMATIQUES ET EN PARTICULIER LES FEUILLES DE LA MENTHE VERTE ONT BEAUCOUP D'IMPORTANCE POUR LA PHARMACOPÉE, LA PARFUMERIE ,LA CONFISERIE ET LA LIQUORISTE RIE . CE TRAVAIL ENTRE DANS LE CADRE DE LA VALORISATION DE CETTE PLANTE PRODUITE EN GRANDE QUANTITÉ DANS LE SUD ET LE SUD-OUEST ALGÉRIEN .IL S'AGIT RÉÉTUDIER LE SÉCHAGE DE CETTE PLANTE ET DE DÉVELOPPER L'UTILISATION DE L’ÉNERGIE POUR SE'CHER LA MENTHE VIRIDES.

  15. NMR study of the 1-{sup 13}C glucose colon bacterial metabolism; Etude du metabolisme bacterien colique du 1-{sup 13}C glucose par RMN

    Energy Technology Data Exchange (ETDEWEB)

    Briet, F.; Flourie, B.; Pochart, P.; Rambaud, J.C.; Desjeux, J.F. [Hopital Saint-Lazare, 75 - Paris (France); Dallery, L. [Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France); Grivet, J.P. [Centre National de la Recherche Scientifique (CNRS), 45 - Orleans-la-Source (France)

    1994-12-31

    The aim of the study is to examine in-vitro and by nuclear magnetic resonance the biological pathways for the fermentation of the 1-{sup 13}C labelled glucose (99 atoms percent) by human colon bacteria. The preparation of the bacterial suspension and the glucose degradation kinetics are presented; the NMR analysis sensitivity and quantification features are discussed and results are presented. 2 figs., 1 ref.

  16. El estudio de Trichinella spiralis en modelos experimentales.

    OpenAIRE

    Alejandra Moreno G; Claudia Maldonado T; Isabel Chávez Ruvalcaba; Rosa G Reveles H; Zuleika Quiroz Núñez; José J. Muñoz E

    2012-01-01

    ResumenSe presenta una breve descripción del estudio de Trichinella spiralis en modelos experimentales, enfocándonos al estudio de la epidemiología, técnicas diagnósticas directas e indirectas, tratamiento y biología del parasito.

  17. El estudio de Trichinella spiralis en modelos experimentales.

    Directory of Open Access Journals (Sweden)

    Alejandra Moreno G

    2012-07-01

    Full Text Available ResumenSe presenta una breve descripción del estudio de Trichinella spiralis en modelos experimentales, enfocándonos al estudio de la epidemiología, técnicas diagnósticas directas e indirectas, tratamiento y biología del parasito.

  18. Etude des etats electroniques en champ magnetique dans le niveau de Landau N=0 de la tricouche ABC de graphene

    Science.gov (United States)

    Rondeau, Maxime

    Dans cet ouvrage nous etudions les phases du gaz d'electrons bidimensionnel dans la tricouche de graphene en empilement ABC. En partant du modele des liaisons fortes et en faisant l'approximation du continuum autour des vallees K +, K-, nous obtenons un modele effectif a deux bandes qui permet de decrire la physique de basse energie des electrons en champ magnetique dans cette structure. Ce modele contient trois orbitales degenerees dans le niveau de Landau N = O. Ce dernier est donc 12N φ, fois degeneres en incluant les degres de liberte de spin et de vallee. En ajoutant l'interaction de Coulomb au systeme et en considerant seulement les remplissages v = -5, -4, -4, 5 afin d'avoir un systeme a trois niveaux, nous etudions le diagramme de phase du gaz d'electrons en fonction d'un biais electrique entre les couches externes. Nous trouvons une phase d'onde de densite de charge bidimensionnelle (ODC2D) comme etat fondamental du systeme. Cette ODC2D se nomme cristal dans ce memoire et nous derivons ses proprietes de transports et ses modes collectifs. Nous discutons egalement du caractere topologique de ce cristal. Notre etude englobe aussi les phases liquides avec ou sans coherence orbitale. Nous concluons notre memoire par l'etude de quelques signatures experimentales des phases du gaz d'electrons dans la tricouche.

  19. Experimental study of drop breakup in a turbulent flow; Etude experimentale de la rupture de gouttes dans un ecoulement turbulent

    Energy Technology Data Exchange (ETDEWEB)

    Galinat, S.

    2005-04-15

    This work presents the drop breakup phenomenon in a turbulent flow induced by a cross-section restriction in a pipe. A global analysis of single-drop breakup, in a finite volume downstream of the orifice, has allowed deriving statistical quantities such as the break-up probability and the daughter-drop distribution. These parameters are function of a global Weber number based on the maximal pressure drop through the orifice. At a local scale, the locations of breakup events are distributed heterogeneously and depend on the flow Reynolds number. The local hydrodynamic study in downstream of the orifice, which has been done by using Particle Image Velocimetry, reveals the specific breakup zones. Otherwise, this analysis has proved that the turbulence is the predominant external stress at the drop scale. The relation between drop deformation and the external stress along the trajectory has been simulated numerically by the response of a damped oscillator to the locally measured instantaneous turbulence forcing. The results of statistical analysis have allowed to introduce a breakup criterion, based on a unique deformation threshold value for all experiments. This multi-scale approach has been conducted to study drop breakup mechanisms in a concentrated dispersion. The breakup probability decrease with the increase of dispersed phase concentration, which influences the turbulent Weber number distribution in downstream of the orifice. (author)

  20. Etude de la transmission sonore a travers un protecteur de type "coquilles" : modelisation numerique et validation experimentale

    Science.gov (United States)

    Boyer, Sylvain

    On estime que sur les 3,7 millions des travailleurs au Quebec, plus de 500 000 sont exposes quotidiennement a des niveaux de bruits pouvant causer des lesions de l'appareil auditif. Lorsqu'il n'est pas possible de diminuer le niveau de bruit environnant, en modifiant les sources de bruits, ou en limitant la propagation du son, le port de protecteurs auditifs individualises, telles que les coquilles, demeure l'ultime solution. Bien que vue comme une solution a court terme, elle est communement employee, du fait de son caractere peu dispendieux, de sa facilite d'implantation et de son adaptabilite a la plupart des operations en environnement bruyant. Cependant les protecteurs auditifs peuvent etre a la fois inadaptes aux travailleurs et a leur environnement et inconfortables ce qui limite leur temps de port, reduisant leur protection effective. Afin de palier a ces difficultes, un projet de recherche sur la protection auditive intitule : " Developpement d'outils et de methodes pour ameliorer et mieux evaluer la protection auditive individuelle des travailleur ", a ete mis sur pied en 2010, associant l'Ecole de technologie superieure (ETS) et l'Institut de recherche Robert-Sauve en sante et en securite du travail (IRSST). S'inscrivant dans ce programme de recherche, le present travail de doctorat s'interesse specifiquement a la protection auditive au moyen de protecteurs auditifs " passifs " de type coquille, dont l'usage presente trois problematiques specifiques presentees dans les paragraphes suivants. La premiere problematique specifique concerne l'inconfort cause par exemple par la pression statique induite par la force de serrage de l'arceau, qui peut reduire le temps de port recommande pour limiter l'exposition au bruit. Il convient alors de pouvoir donner a l'utilisateur un protecteur confortable, adapte a son environnement de travail et a son activite. La seconde problematique specifique est l'evaluation de la protection reelle apportee par le protecteur. La methode des seuils auditifs REAT (Real Ear Attenuation Threshold) aussi vu comme un "golden standard" est utilise pour quantifier la reduction du bruit mais surestime generalement la performance des protecteurs. Les techniques de mesure terrains, telles que la F-MIRE (Field Measurement in Real Ear) peuvent etre a l'avenir de meilleurs outils pour evaluer l'attenuation individuelle. Si ces techniques existent pour des bouchons d'oreilles, elles doivent etre adaptees et ameliorees pour le cas des coquilles, en determinant l'emplacement optimal des capteurs acoustiques et les facteurs de compensation individuels qui lient la mesure microphonique a la mesure qui aurait ete prise au tympan. La troisieme problematique specifique est l'optimisation de l'attenuation des coquilles pour les adapter a l'individu et a son environnement de travail. En effet, le design des coquilles est generalement base sur des concepts empiriques et des methodes essais/erreurs sur des prototypes. La piste des outils predictifs a ete tres peu etudiee jusqu'a present et meriterait d'etre approfondie. L'utilisation du prototypage virtuel, permettrait a la fois d'optimiser le design avant production, d'accelerer la phase de developpement produit et d'en reduire les couts. L'objectif general de cette these est de repondre a ces differentes problematiques par le developpement d'un modele de l'attenuation sonore d'un protecteur auditif de type coquille. A cause de la complexite de la geometrie de ces protecteurs, la methode principale de modelisation retenue a priori est la methode des elements finis (FEM). Pour atteindre cet objectif general, trois objectifs specifiques ont ete etablis et sont presentes dans les trois paragraphes suivants. (Abstract shortened by ProQuest.).

  1. Les entit\\'es spatiales dans la langue : \\'etude descriptive, formelle et exp\\'erimentale de la cat\\'egorisation

    CERN Document Server

    Aurnague, Michel; Vieu, Laure

    2010-01-01

    While previous linguistic and psycholinguistic research on space has mainly analyzed spatial relations, the studies reported in this paper focus on how language distinguishes among spatial entities. Descriptive and experimental studies first propose a classification of entities, which accounts for both static and dynamic space, has some cross-linguistic validity, and underlies adults' cognitive processing. Formal and computational analyses then introduce theoretical elements aiming at modelling these categories, while fulfilling various properties of formal ontologies (generality, parsimony, coherence...). This formal framework accounts, in particular, for functional dependences among entities underlying some part-whole descriptions. Finally, developmental research shows that language-specific properties have a clear impact on how children talk about space. The results suggest some cross-linguistic variability in children's spatial representations from an early age onwards, bringing into question models in wh...

  2. An experimental study of mixed convection; Contribution a l'etude experimentale de la convection mixte

    Energy Technology Data Exchange (ETDEWEB)

    Saez, M.

    1998-10-20

    The aim of our study is to establish a reliable database for improving thermal hydraulic codes, in the field of turbulent flows with buoyancy forces. The flow considered is mixed convection in the Reynolds and Richardson number range: Re = 10{sup 3} to 6.10{sup 4} and Ri = 10{sup -4} to 1. Experiments are carried out in an upward turbulent flow between vertical parallel plates at different wall temperatures. Part 1 gives a detailed database of turbulent mixed flow of free and forced convection. Part 2 presents the installation and the calibration system intended for probes calibration. Part 3 describes the measurement technique (constant temperature probe and cold-wire probe) and the method for measuring the position of the hot-wire anemometer from the wall surface. The measurement accuracy is within 0.001 mm in the present system. Part 4 relates the development of a method for near wall measurements. This correction procedure for hot-wire anemometer close to wall has been derived on the basis of a two-dimensional numerical study. The method permits to obtain a quantitative correction of the wall influence on hot-wires and takes into account the velocity profile and the effects the wall material has on the heat loss. Part 5 presents the experimental data obtained in the channel in forced and mixed convection. Results obtained in the forced convection regime serve as a verification of the measurement technique close to the wall and give the conditions at the entrance of the test section. The effects of the buoyancy force on the mean velocity and temperature profiles are confirmed. The buoyancy strongly affects the fluid structure and deforms the distribution of mean velocity. The velocity profiles are asymmetric. The second section of part 5 gives an approach of analytical wall functions with buoyancy forces, on the basis of the experimental data obtained in the test section. (author)

  3. Etude experimentale de l'utilisation des revetements glaciophobes et/ou hydrophobes sur les pales d'eoliennes

    Science.gov (United States)

    Adomou, Maryelle C.

    2011-12-01

    Blade icing is a major problem of windmill use in northern climates. At present, the use of anti-icing protection on blades is little used because it is energy intensive and unsafe. An interesting current alternative is the use of ice-shedding coatings because they are proving to be less energy hungry, but their efficiency and durability have yet to be proven in windmills. Since windmills have a special dynamic structure and icing events can be of several types, an understanding of the accretion process on a variety of coatings is necessary to advance general knowledge in this field. To explore this problem, experiments were performed in the refrigerated wind tunnel at the Anti-icing Materials International Laboratory of the Universite du Quebec a Chicoutimi on a static-blade section covered with three commercial ice-shedding coatings chosen using well-defined criteria. Experimental conditions were based on several real extreme icing events. Scaling of the parameters of the icing events gave two air speeds for the wind tunnel (21 and 33m/s), two air temperatures (5 and -20°C) and one humidity level (0.4g/m 3). The experimental runs were carried out on blades covered with the coatings alone and also in combination with an electrothermal deicing system. The efficiency of the apparatus was evaluated by analysing the shape of the ice formed, the energy consumption of each anti-icing and de-icing combination and also by analysing the internal distribution of temperatures in the system. When used as a protective anti-icing system, none of the icephobic coatings was effective in reducing ice accumulation significantly on the blades. However, combined with an electrothermal anti-icing system, these types of coatings proved to be effective. Nevertheless, the power must be high enough to cause runoff. Hydrophobic coatings reduce energy consumption of electric anti-icing systems by about 7% whereas a super hydrophobic coating can reduce energy consumption by more than twice this amount. In de-icing mode and using a super hydrophobic coating, a reduction of 15% was recorded. These power reductions are largely due to the hydrophobic nature of the surfaces.

  4. Experimental contribution to the study of gas bearings; Contribution experimentale a l'etude des paliers a gaz

    Energy Technology Data Exchange (ETDEWEB)

    Gobert, G

    1962-07-01

    Developments for gas-lubricated bearings are discussed. The study of how the fluid film behaves compared to what one can expect is discussed. Various devices are described which have allowed us to go up to peripheral velocity greater than 400 m/s, leading to rotational speed of several thousand revolutions per second. This is obtained by using an automatic setting for the distance between fixed and rotating walls. (author) [French] Le present travail debute par un apercu de l'etat actuel des connaissances sur le processus de la lubrification, notamment sur les paliers a lubrification par gaz. Apres une analyse effectuee au moyen des recentes theories de R. Comolet sur le film fluide entre disques paralleles, nous decrivons des machines dont les charges axiales et radiales specialement etudiees ont permis, au moyen d'un reglage automatique des jeux entre parois fixes et parois tournantes, d'atteindre des vitesses peripheriques superieures a 400 m/s correspondant a des vitesses de plusieurs milliers de tours par seconde. (auteur)

  5. Experimental study of a water thermo-capillary loop; Etude experimentale d`une boucle thermocapillaire a eau

    Energy Technology Data Exchange (ETDEWEB)

    Lefriec, C.; Alexandre, A. [Ecole Nationale Superieure de Mecanique et d`Aerotechnique (ENSMA), 86 - Poitiers (France)

    1996-12-31

    This paper presents a bench scale experiment of a water thermo-capillary loop which allows to improve the understanding of its functioning mechanisms thanks to the internal visualisation of each component using transparent walls. The advantages of water are its non-toxicity, its high chemical compatibility with several materials and its low functioning pressure. The experimental device is presented and the functioning regimes of each component is analyzed: condenser (flow visualization, influence of tilt), evaporator (quality of heat exchange between teeth and porous medium, bubbles, heat exchange coefficient). (J.S.)

  6. Modelos experimentales de enfermedad cardiovascular Experimental models of cardiovascular disease

    Directory of Open Access Journals (Sweden)

    A. Gil Hernández

    2007-04-01

    Full Text Available El presente trabajo describe los modelos experimentales de utilidad clínica en el estudio de las enfermedades cardiovasculares y hace énfasis en los modelos usados para determinar los mecanismos fisiopatológicos de la aterosclerosis, así como para evaluar los efectos de productos nutricionales y farmacológicos sobre el desarrollo de este proceso inflamatorio complejo común a muchas enfermedades cardiovasculares. Se revisan los modelos animales en los que se puede inducir aterosclerosis por cambios en la composición de la dieta y los modelos animales en los que la alteración de uno o más genes (animales knock-out y knock-in, o la incorporación de genes foráneos de otras especies, da lugar a la aparición de hiperlipidemia con riesgo asociado de aparición de enfermedad cardiovascular temprana. Por otra parte, se consideran algunas de las líneas celulares más utilizadas en el estudio de los mecanismos moleculares de la aterogénesis y de evaluación de sustancias con interés nutricional o farmacológico.The present work describes clinically useful experimental models for the study of cardiovascular disease and emphasites the models used to determine the pathophysiologic mechanisms of atherosclerosis, as well as to evaluate the effects of nutritional and pharmacological products on the development of this complex inflammatory process present in many cardiovascular diseases. Animal models in which ahterosclerosis may be induced by dietary changes are reviewed, as well as those in which modification in one or more genes (knock-out and knock-in animals, or the incorporation of foreign genes from other species lead to early cardiovascular disease. On the other hand, some of the cell lines most frequently used in studying molecular mechanisms of atherosclerosis and assessment of substances with nutritional or pharmacological interest are considered.

  7. L’onomastique comorienne: etude linguistique

    OpenAIRE

    Yahaya, Moinaecha Cheikh

    2012-01-01

    Dans cette etude nous nous sommes fixé commee objectif principal la recherche des morphèmes nominaux altérés dans la langue courante et qui se manifestent au niveau des noms propres surtout au niveau des composés. Ces éléments nous permettront de mieux comprendre le système morphologique du comorien et compléter une etude en cours sur la morphologie des nominaux. L’étude morphologique du nom propre sera complétée par une étude syntaxique des différents éléments qui le composent. Les indicatio...

  8. Sucesiones experimentales en pastizales con diferente uso y edad de abandono

    Directory of Open Access Journals (Sweden)

    Vargas Ríos Orlando

    2006-06-01

    Full Text Available Se presentan los resultados de la diversidad y cobertura de las especies vegetales presentes en parcelas después
    de generar disturbios experimentales (remoción epígea y remoción epígea-hipógea, en dos pastizales con diferente
    uso y edad de abandono, en la Reserva Forestal Municipal de Cogua, Cundinamarca (Colombia. Se observaron
    diferencias significativas entre los tratamientos y los pastizales en cuanto a diversidad y cobertura de las especies, dado el comportamiento diferencial de las especies a los disturbios experimentales realizados. En
    las parcelas con remoción epígea se obtuvo una regeneración rápida de la cobertura vegetal, con una composición de especies similar a la presentada antes de los disturbios experimentales. En los tratamientos con
    remoción epígea-hipógea la regeneración de la vegetación y el aumento de la cobertura es lento pero con un
    aumento en la diversidad con respecto a las especies presentes antes de los disturbios experimentales.

  9. Las ciencias experimentales en el aula: el agua como fuente de recursos didácticos

    OpenAIRE

    Sánchez Peñil, Verónica

    2016-01-01

    RESUMEN Este Trabajo Fin de Grado muestra la importancia de las Ciencias experimentales en el aula de Educación Primaria, concretamente el uso del agua como un recurso didáctico. A lo largo de este proyecto se expone la evolución histórica de las Ciencias Naturales y de la Educación Ambiental tanto a nivel social como a nivel educativo. Es a nivel educativo donde se hace mayor hincapié mostrando los distintos modelos pedagógicos y la selección de una enseñanza de las ciencias basada en el des...

  10. Assistance orale \\`a la recherche visuelle - \\'etude exp\\'erimentale de l'apport d'indications spatiales \\`a la d\\'etection de cibles

    CERN Document Server

    Kieffer, Suzanne

    2006-01-01

    This paper describes an experimental study that aims at assessing the actual contribution of voice system messages to visual search efficiency and comfort. Messages which include spatial information on the target location are meant to support search for familiar targets in collections of photographs (30 per display). 24 participants carried out 240 visual search tasks in two conditions differing from each other in initial target presentation only. The isolated target was presented either simultaneously with an oral message (multimodal presentation, MP), or without any message (visual presentation, VP). Averaged target selection times were thrice longer and errors almost twice more frequent in the VP condition than in the MP condition. In addition, the contribution of spatial messages to visual search rapidity and accuracy was influenced by display layout and task difficulty. Most results are statistically significant. Besides, subjective judgments indicate that oral messages were well accepted.

  11. Theoretical and experimental study of cyclotronic waves in a fusion plasma; Etude theorique et experimentale des ondes cyclotroniques electroniques dans un plasma de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Vezard, D.

    1994-12-20

    This thesis presents a study concerning cyclotronic waves in a plasma. It starts with an illustration of the elementary interaction between electromagnetic waves and matter.It shows that electrons from tokamak absorbs waves at cyclotronic frequency. Cyclotronic waves are studied by solving the dispersion relation in plasma; it concerns polarisation, absorption, dispersion, extinction. Then, classical theories are reminded in order to speak about decoupled electrons and their interactions. Absorption and emission properties of cyclotronic waves by electrons from a queue are described. After that, cyclotronic waves propagation is studied taking into account resonance. The last part of this thesis is dedicated to the electronic distribution function that is made by a wave spectra at a inferior hybrid frequency. (TEC). 129 refs., 75 figs.

  12. Experimental study of turbulence on Tore Supra by plasma micro-waves interaction; Etude experimentale de la turbulence sur Tore Supra par interaction plasma micro-ondes

    Energy Technology Data Exchange (ETDEWEB)

    Colas, L

    1996-09-23

    Internal small-scale magnetic turbulence is a serious candidate to explain the anomalous heat transport in tokamaks. This turbulence is badly known in the gradient region of large machines. In this work internal magnetic fluctuations are measured on Tore Supra with an original diagnostic : Cross Polarization Scattering (CPS). This experimental tool relies on the Eigenmode change of a probing polarised microwave beam scattered by magnetic fluctuations, close to a cut-off layer for the incident wave. In this work, the diagnostic is first qualified to assess its sensitivity to magnetic fluctuations, and the spatial localisation for its measurements. The magnetic fluctuation behaviour is then analysed over a wide range of plasma current, density and additional power, and interpreted with a simple 1-D scattering model. A scan of the plasma density or magnetic field is used to move the CPS measurement location from r/a = 0.3 to r/a = 0.75. A fluctuation radial profile is obtained by two means. In L-mode discharges, the relation between magnetic fluctuations, temperature profiles and local heat diffusivities is investigated. With all measurements, it is also possible to look for a local parameter correlated to the turbulence in a large domain of plasma conditions. The fluctuation-induced local heat diffusivity expected from the measured fluctuations is estimated using the non-collisional quasi-linear formula: X{sup mag}{sub e} = {pi}qRV{sub te}({delta}B / B){sup 2}. Both the absolute values and the parametric dependence of calculated X{sup mag}{sub e} are close to the electron thermal diffusivities Xe determined by transport analysis. In particular, a threshold is evidenced in the dependence of fluctuation-induced heat fluxes on local {nabla}T{sub e}, which is analogous to the critical gradient for measured heat fluxes. The experimental setup is also sensitive to the Thomson scattering of the probing wave by density fluctuations. Its measurements are analysed as the fluctuations of the amplitude and the phase of an interferometer, thanks to a simple modelling of the plasma poloidal motion. Thus one than measure from the spectra shapes statistical quantities of the plasma movement. (author)

  13. Experimental and numerical study of the active control of jets inside combustion chambers; Etude experimentale et numerique du controle actif de jets dans des chambres de combustion

    Energy Technology Data Exchange (ETDEWEB)

    Faivre, V.

    2003-12-15

    Combustion instabilities occur when the flame heat release couples with the acoustic waves propagating in the combustion chamber. This phenomenon can lead to strong vibrations and noise but also, sometimes, to the complete combustion device failure. That is the reason why so many studies focus on the control of those instabilities. The method chosen in this study consists in an active control device (or set of actuators) having a strong effect on the mixing of the burner exhaust flow with the ambient fluid. The model configuration studied consists in a non reactive jet of air controlled by four small tangential secondary jets. Experiments have been carried out to optimize the control device geometry. The configuration identified as the most efficient, in terms of mixing enhancement, has been simulated through Large Eddy Simulations (LES). The objective of the numerical part of the present work is double. First, the numerical simulations provide a better understanding of the phenomena occurring when the control is on. Then, it is shown that LES can be considered as a tool to predict the effects of a control device on a flow. (author)

  14. Multi scale experimental study of water and ionic transport in porous charged media: clays; Etude experimentale multiechelle du transport ionique et aqueux en milieu poreux charge: argiles

    Energy Technology Data Exchange (ETDEWEB)

    Cadene, A

    2005-10-15

    Clays are porous media of industrial interest. Due to their retention capacities and low permeability to water, they are the principal candidate for the conception of engineered barriers radioactive waste disposal. The main interest of this study is the experimental determination of the cationic and water dynamics in montmorillonite and fluoro-hectorite at low water contents This latter synthetic smectite has been used as a model clay to help the interpretation of the results issued from the first natural one. After a summary on the clayey system, this work reports the many experimental techniques (Atomic Force Microscopy, Photo-Correlation Spectroscopy, Micro-calorimetry, Powder Diffraction) used during the preliminary study concerning structural characterisation of the samples. The study of the sodic form of smectites with the use of a combination of quasi-elastic neutron scattering techniques (Time of Flight and Spin Echo) succeeded to water diffusion coefficients but also to a discernment of the limits of such techniques. Experiments with montmorillonite samples are in agreement with the simulations, so tending to a validation of the models. Experimental data obtained from synthetic hectorites will be in the near future compared to simulations In the last part, this work shows the application of Broad Band Dielectric Spectroscopy for the investigation of ionic dynamic in these porous media. Many models have been developed for the interpretation of the experimental raw data obtained with this technique. (author)

  15. Thermal design of horizontal tube boilers. Numerical and experimental investigation; Modelisation thermique de bouilleurs a tubes horizontaux. Etude numerique et validation experimentale

    Energy Technology Data Exchange (ETDEWEB)

    Roser, R.

    1999-11-26

    This work concerns the thermal design of kettle reboilers. Current methods are highly inaccurate, regarded to the correlations for external heat transfer coefficient at one tube scale, as well as to two-phase flow modelling at boiler scale. The aim of this work is to improve these thermal design methods. It contains an experimental investigation with typical operating conditions of such equipment: an hydrocarbon (n-pentane) with low mass flux. This investigation has lead to characterize the local flow pattern through void fraction measurements and, from this, to develop correlations for void fraction, pressure drop and heat transfer coefficient. The approach is original, since the developed correlations are based on the liquid velocity at minimum cross section area between tubes, as variable characterizing the hydrodynamic effects on pressure drop and heat transfer coefficient. These correlations are shown to give much better results than those suggested up to now in the literature, which are empirical transpositions from methods developed for inside tube flows. Furthermore, the numerical code MC3D has been applied using the correlations developed in this work, leading to a modeling of the two-phase flow in the boiler, which is a significant progress compared to current simplified methods. (author)

  16. Experimental study of different histologic types of lung cancers after irradiation. Etude experimentale des differents types histologiques de cancers pulmonaires induits par l'irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Morin, M.; Masse, R.; Lafuma, J. (CEA Centre d' Etudes de Fontenay-aux-Roses, 92 (France). Dept. de Pathologie et de Toxicologie Experimentales)

    1994-01-01

    Recent epidemiologic studies suggested that some histologic types of carcinomas were preferentially induced in the lung by irradiation, whatever the mode of exposure and the radiation quality. Since smoking and other environmental airborne pollutants may be strong confounding factors in humans, we have investigated whether histological subtypes were dependent or not on the mode of exposure, in a large series of 9000 rats exposed to external and internal sources at high and low Linear Energy Transfer. Despite comparable overall risk coefficients in rats and humans, our results show that histological types are influenced not only by dose but also by radiation quality and heterogeneity of dose delivering. We suggest that extrapolation from one group to an other take this information in consideration. (authors). 10 refs., 1 tab.

  17. 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)

  18. Experimental study of heat and mass transfer across a density interface; Etude experimentale des transferts de chaleur et de masse a travers une interface de densite

    Energy Technology Data Exchange (ETDEWEB)

    Zellouf, Y.

    2004-11-15

    This work is part of a major research program on stratified flows encountered in the storage tanks of liquid natural gas. The subject of this dissertation concerns more particularly the problem of heat and mass transfer across a density interface. These flows are complex by nature due to the combination of three parameters: density difference {delta}{rho} across the interface, turbulence intensity u' in the homogeneous layers and the diffusivity K of the stratifying components. To control the operational conditions of the liquid gas storage, it is crucial to have a universal physical model to estimate the fluxes across the interface and to predict the brutal mixing of homogeneous layers commonly called the 'roll-over' event. In this work heat and mass transfer across an interface is measured in the presence of turbulence generated by vertical oscillation of two grids. Turbulent velocity field is measured in a homogeneous environment by Particle Image velocimetry (PIV). It shows that the turbulence generated by the two grids is homogeneous and isotropic in the vertical plan. We have established, based on this measurements, an experimental decay law of the turbulence intensity as a function of the flow parameters and the distance from the grids. Stratifications have been followed in time by recording the vertical profiles of temperature and density. Measured heat and mass fluxes are presented as a function of the three flow parameters (u', {delta}{rho}, K) through the non-dimensional numbers: Richardson number Ri g({delta}{rho}/{rho}{sub 0})(l'/u'{sup 2}) and Peclet number Pe = u'l'/K. Measurements show that these two parameters have opposite effects on transfer phenomena. While thermal diffusivity favours the entrainment near the interface, the stratification effect limits this entrainment. This fact is explained by analysing the interface structure. A phenomenological model is then proposed which takes into account these parameters. (author)

  19. Experimental study of the topological aspect of the ergodic divertor in Tore-supra tokamak; Etude experimentale des aspects topologiques du divertor ergodique de Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Costanzo, L

    2001-10-01

    The control of power deposition onto plasma facing components in tokamaks is a determining factor for future thermonuclear fusion reactors. Plasma surface interaction can be performed using limiters or divertors. The ergodic divertor installed on Tore Supra is an atypical example of a magnetic divertor. It consists in applying a magnetic perturbation which establishes a particular topology of the plasma in contact with the wall (edge plasma). We carried out dedicated experiments in order to study parallel heat flux which strike the divertor neutralizers. This quantitative and qualitative analysis of heat flux as a function of experimental conditions allows to determine the profiles of power deposition along the neutralizers. The influence of plasma electron density, additional heating, impurities and injected gas was established. An experimental study of the sheath heat transmission factor {gamma} was carried out by correlating measurements made with Langmuir probes and infrared imaging. This study gave rise to a major conclusion: for ohmic discharges with deuterium injection and most of the time with helium, it was experimentally confirmed that {gamma}=7 in agreement with classical sheath theory. However, an increase of this factor with additional power has been shown. Detached plasma, which is an attractive regime in order to reduce the power deposition, requires an optimized control. A new measurement of the detachment onset has been developed. It is based on the variation of heat flux onto the plates derived from infrared measurements. A detachment cartography with the determination of a new 2D 'IR' Degree of Detachment was carried out allowing to locate the zone where the detachment starts. We can apply this concept both to other tokamaks such as JET and ITER. A comparison between the axisymmetric divertor and the ergodic divertor is also presented concerning the power deposition in the two configurations. Low heat flux with the ergodic divertor is a major advantage. (author)

  20. Contribution to the experimental study of the polarized liquid helium-3; Contributions a l'etude experimentale de l'helium-3 liquide polarise

    Energy Technology Data Exchange (ETDEWEB)

    Villard, B

    1999-07-15

    Spin-polarized liquid helium-3 is prepared by laser optical pumping in low magnetic field and at room temperature, prior to fast liquefaction of the polarized sample. The use of a new helium-3 cryostat enabled us to obtain liquid helium-3 with polarization rates up to 25 % at well-stabilized temperatures (around 0.5 K). We could thereby study the effect of nuclear polarization on liquid-vapour equilibrium, and particularly on the saturated vapour pressure. Very sensitive capacitive gauges were developed. We estimated (to first order in M{sup 2}) the expected effects when the polarization M is suddenly destroyed. These effects were experimentally observed in helium-3/helium-4 mixtures, in pure helium-3, only a transient increase in pressure has been recorded. We then describe in a third part a preliminary experiment which aimed at determining the longitudinal relaxation time T1 in mixtures. Relaxation on the walls is efficiently reduced by a cesium coating and T1s of order 20 minutes were observed. A careful determination of the helium-3 concentration in the liquid phase was made. Finally we studied the effects of dipolar field on transverse polarisation decay in our strongly polarized samples. We observed the free precession of polarization after a NMR pulse, and analysed in detail its decay time constant as a function of different parameters. This time constant drastically varied with the tipping angle, an effect which could be linked to NMR dynamical instabilities. (author)

  1. Experimental study of a finned-tubes coil with wet wall conditions; Etude experimentale d'une batterie froide en condition de paroi mouillee

    Energy Technology Data Exchange (ETDEWEB)

    Khalfi, M.S. [Institut Algerien du Petrole, Boumerdes (Algeria); Benelmir, R.; Feidt, M. [Universite Henri Poincare, Lab. d' Energetique et de Mecanique Theorique et Appliquee, 54 - Vandoeuvre-les-Nancy (France)

    2001-01-01

    The use of a global pseudo-conductance in the mathematical model of heat and mass transfer within a heat exchanger allowed us to take into account the water condensate on the wall as well as air humidity. The application of this dual consideration to our experimental investigation shows a 'critical' Reynolds number at which we observe an inversion of thermal behavior. The heat exchanger considered in this work has been used in a previous published work where heat transfer occurred only with dry wall condition. (authors)

  2. Adsorption of trace elements on a bentonite sample: experimental study and modelling; Retention d'elements trace sur une bentonite: etude experimentale et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Hurel, Ch

    2002-12-15

    Radioactive waste storage in deep underground is studied in France. The alteration of the radioactive waste can mobilize the elements that can migrate to the geosphere. Clays (bentonite) are investigated as major materials constituting the barriers because of their low permeability and high retention capacity. A thermodynamic surface complexation model, based on the component additivity principle was investigated, in order to predict the adsorption behaviour of pollutants in contact with clay. This principle allows an independent determination of each parameter of the model, limiting the fitting procedure of correlated data, and it allows the use of an adsorption thermodynamic database for a solid. The predictions obtained were in good accordance with experimental data. The model could then be applied successfully in performance assessment. (author)

  3. An experimental study of electrical and dielectric properties of consolidated clayey materials; Etude experimentale des proprietes electriques et dielectriques des materiaux argileux consolides

    Energy Technology Data Exchange (ETDEWEB)

    Comparon, L

    2005-06-15

    This study is devoted to the electrical and dielectric properties of consolidated clays. A better understanding of the conduction and polarization phenomena in clays is necessary to better interpret in situ measurements in terms of water saturation and texture. An experimental study was carried out on synthetic clay samples (kaolinite and smectite) compacted with various water contents, porosities and mineralogical compositions, on a large frequency range, using three laboratory setups. The electrical properties of natural argillites (from ANDRA) were then investigated. We found that the response of the synthetic samples is mainly controlled by water content on the whole frequency range; two polarization phenomena were observed, which were related to the Maxwell-Wagner polarization and the electrical double layer polarization around the clay particles. The electrical response of argillites is more complex; it is controlled by water content but also by the microstructure of the rock. In these rocks, the electrical and dielectric anisotropies are high; anisotropy was also measured for the synthetic clays. The existing models explain the high frequency limit of the dielectric permittivity of the clayey materials, but the low frequency part of the spectra ({<=}1 MHz) needs theoretical developments. (author)

  4. Experimental and theoretical study of phase transitions under ball milling; Etude experimentale et modelisation des changements de phases sous broyage a haute energie

    Energy Technology Data Exchange (ETDEWEB)

    Pochet, P

    1997-12-31

    The aim of this work was to determine how phase transition s under ball-milling depend on the milling conditions and to find out if one can rationalize such transitions with the theory of driven alloys. We have chosen two phase transitions: the order-disorder transition in Fe Al and the precipitation-dissolution NiGe. In the case of Fe Al we have found that the steady-state long range order parameter achieved under ball milling intensity; moreover the same degree of order is achieved starting from an ordered alloy or a disordered solid solution. On the way to fully disordered state the degree of order either decreases monotonically or goes through a short lived transient state. This behaviour is reminiscent of a first order transition while the equilibrium transition is second order. All the above features are well reproduced by a simple model of driven alloys, which was originally build for alloys under irradiation. The stationary degree of order results of two competitive atomic jump mechanisms: the forced displacements induced by the shearing of the grains, and the thermally activated jumps caused by vacancies migrations. Finally we have performed atomistic simulations with a Monte Carlo kinetic algorithm, which revealed the role of the fluctuations in the intensity of the forcing. Moreover we have shown that specific atomistic mechanisms are active in a dilute NiGe solid solution which might lead to ball milling induced precipitation in under-saturated solid solution. (author). 149 refs.

  5. The transition radiation. 2. experimental study of the optical transition radiation; Le rayonnement de transition: 2. etude experimentale du rayonnement de transition optique

    Energy Technology Data Exchange (ETDEWEB)

    Couillaud, Ch.; Haouat, G.; Seguin, S.; Striby, S

    1999-07-01

    Optical-transition-radiation-based diagnostics have been widely used for many years on electron accelerators in order to measure beam energy and transverse and longitudinal emittances. These diagnostics are very attractive for high brightness electron beams used as drivers for radiation sources. Such diagnostics have been performed on the ELSA facility (18 MeV electron energy, 100 A peak current) using both a single interface and an OTR-Wartski interferometer. We present the accelerator, the experimental set-up and the method for analyzing the OTR angular distribution. Then, the experimental results are described and compared with those from the three gradient method. In addition, we present a beam energy measurement using OTR interferogram analysis. (author)

  6. Lanthanides in geological fluids: experimental study of standard thermodynamic properties and of solubilities; Les lanthanides dans les fluides geologiques: etude experimentale des proprietes thermodynamiques standard et des solubilites

    Energy Technology Data Exchange (ETDEWEB)

    Pourtier, E

    2006-11-15

    Standard thermodynamic properties (STP) of lanthanides (Ln{sup 3+}) are necessary to predict their transport in hydrothermal fluids. New STP (apparent molal volumes and heat capacities) of Ln{sup 3+} are determined with dilute (La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Yb{sup 3+}) triflates solutions, up to 300 deg. C and 300 bars, using a vibrating tube flow densimeter and a differential heat flow calorimeter. The triflate anion (CF{sub 3}SO{sub 3}), stable at high temperature, does not form complexes with Ln{sup 3+}. The STP of HCF{sub 3}SO{sub 3} and NaCF{sub 3}SO{sub 3} are measured in order to get the STP of CF{sub 3}SO{sub 3}. The solubility of the Nd-pure pole of monazite (NdPO{sub 4}) studied between 300 and 800 deg. C at 2 kbars in H{sub 2}O and H{sub 2}O+NaCl using weight loss and isotope dilution methods, is prograde for neutral pH. The study of Nd{sup 3+} speciation at 650 deg. C and 300 deg. C, 2 kbars, shows that only hydroxylated species are present. These data allow the revision of Ln{sup 3+} parameters in the HKF model. (author)

  7. Experimental and theoretical study of the atmospheric boundary layer over the paris area; Etude experimentale et theorique de la couche limite atmospherique en agglomeration parisienne

    Energy Technology Data Exchange (ETDEWEB)

    Menut, L

    1997-12-15

    This thesis studied the urban boundary layer dynamic behaviour over the Paris area by comparing urban (Paris) and suburban (Palaiseau) dynamic data such as lidars, sodars, sonic anemometers. All the data were obtained during the ECLAP experiment, specifically performed to characterize the differences between a city and its near environment. (author)

  8. Experimental study of the electric charge process of the radioactive aerosols beta emitter; Etude experimentale du processus de charge electrique des aerosols radioactifs emetteurs beta

    Energy Technology Data Exchange (ETDEWEB)

    Gensdarmes, F.; Boulaud, D. [CEA/Saclay, Inst. de Protection et de Surete Nucleaire, IPSN/DPEA/SERAC, 91 - Gif-sur-Yvette (France); Renoux, A. [Paris-12 Univ., Lab. de Physique des Aerosols et de Transfert des Contaminations, 94 - Creteil (France)

    2000-07-01

    An aerosol radioactivity may change its electrical properties and then modify its evolution in a closed room. In order to define the electric charge state of a radioactive aerosol, an experimental device has been developed to produce a calibrated radioactive aerosol of cesium 137. The results show an increase of the aerosol average charge when the particles specific activity increase. (A.L.B.)

  9. etude experimentale de la propagation de fissures de fatigue dans la zone affectee thermiquement de joints soudes de roues de turbines hydrauliques

    Science.gov (United States)

    Trudel, Alexandre

    This thesis presents the results of a comprehensive experimental study on the fatigue crack propagation behavior in aqueous environment of the heat affected zone of CA6NM stainless steel hydraulic turbine runner welds. The initial objective of this project was to determine the fatigue crack growth properties of the heat affected zone. To achieve this, standardized fatigue crack growth tests in aqueous environment were performed to determine the crack growth threshold DeltaKth, and the Paris relationship constants C and m of the heat affected zone. Given potential experimental uncertainties arising from the growth of a crack confined to the heat affected zone, fatigue crack growth tests in an aqueous environment at constant stress intensity factor range (DeltaK) were performed so that the crack would propagate across the heat affected zone. These tests allowed to better appreciate the fatigue crack growth resistance variation between the three zones of the weld, i.e., the filler metal, the heat affected zone and the base metal. Various experimental objectives were supplemented to these two primary objectives. A CA6NM plate was welded to generate a layer of filler metal over its entire surface. The welded plate was cut in two equal pieces, one of which was post-weld heat treated in order to study the effect of this treatment on the fatigue crack growth behavior. Compact tension type fatigue specimens were machined from the welded plates. Rectangular samples were also collected to allow the characterization of the weld. Metallographic observations and X-ray diffraction measurements of the three zones of the weld (filler metal, heat affected zone and base metal) were conducted in order to characterize the microstructure. This microstructural characterization combined with metallographic observations of the crack path profiles were useful in assessing the microstructural effects acting on the fatigue crack growth behavior of the weld. Microhardness measurements were carried out across the weld in order to quantify the heat affected zone width and to allow a relative mechanical characterization of the three weld zones. Residual stresses were measured in fatigue specimens to determine their influence on the fatigue crack growth behavior. Finally, the fracture surfaces were observed using a scanning electron microscope in order to identify the main fracture mechanisms. This work led to several conclusions about the fatigue crack growth behavior in aqueous environment of hydraulic turbine runner welds, and especially in the heat affected zone. First, the measured crack tip tensile residual stresses inhibited crack closure, which resulted in a deteriorated resistance to fatigue crack growth. On the other hand, the beneficial effect of post-weld heat treatment was explained by its ability to sufficiently reduce the tensile residual stresses to allow crack closure to occur. Secondly, the martensitic microstructure of the three weld zones was identified as influencing the fatigue crack growth behavior. The varying martensite coarseness between the three weld zones influenced the path of the crack. A fine martensitic microstructure, as observed in the weld metal, resulted in a linear crack path, while a coarse microstructure, as observed in the heat affected zone and base metal, resulted in a tortuous crack path. The degree of crack path tortuosity was related to the fatigue crack growth resistance, which revealed that a coarse martensitic microstructure that leads to a tortuous crack path, promotes toughening by local mixed modes of crack advance and roughness-induced crack closure. Thirdly, when the crack propagated in the heat affected zone, a tendency to gradually deviate towards the base metal was observed. This behavior was rationalized by considering the yield strength mismatch between the three weld zones. The yield strength decreased in the heat affected zone from filler metal to base metal. Finally, the presence of residual and/or reformed austenite in the three zones of the weld, as well as the occurrence of an intergranula

  10. Experimental study and modelling of iron ore reduction by hydrogen; Etude experimentale et modelisation de la reduction du minerai de fer par l'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, D

    2008-01-15

    In an effort to find new ways to drastically reduce the CO{sub 2} emissions from the steel industry (ULCOS project), the reduction of iron ore by pure hydrogen in a shaft furnace was investigated. The work consisted of literature, experimental, and modelling studies. The chemical reaction and its kinetics were analysed on the basis of thermogravimetric experiments and physicochemical characterizations of partially reduced samples. A specific kinetic model was designed, which simulates the successive reactions, the different steps of mass transport, and possible iron sintering, at the particle scale. Finally, a 2-dimensional numerical model of a shaft furnace was developed. It depicts the variation of the solid and gas temperatures and compositions throughout the reactor. One original feature of the model is using the law of additive characteristic times for calculating the reaction rates. This allowed us to handle both the particle and the reactor scale, while keeping reasonable calculation time. From the simulation results, the influence of the process parameters was assessed. Optimal operating conditions were concluded, which reveal the efficiency of the hydrogen process. (author)

  11. Technical and harmonic analysis of Carl Czerny op. 299 number 34 etude

    Directory of Open Access Journals (Sweden)

    Mehmet Serkan Umuzdas

    2012-11-01

    Full Text Available In this study, the 34th etude of the book Czerny Op. 299 that is one of the commonly employed books in the piano training was analysed in terms of technique and harmony. The etude was examined in terms of its technical features and contributions to technical development. If an etude is analysed before it is played, time and effort can be amanged much more efficiently. In turn, it may contribute to play the etude or work in accordance with its objectives and to produce outcomes. The aims of this study are to make the students aware of the goals and methods of etudes and to provide them with the suggestions for studying. It is suggested that any etude written with the 2/4 rhythm pattern should be played very vividly and energytically. Any etude written in the octave width of 5.5 is made up of 43 scales in two section. The etude is composed of two sections, each with four sentences and two periods. It also involves 43 scales. Of them, 16 scales are in the first section and the remaining 27 scales are in the second section. The etude has very regular system in terms of harmonic continuity and motives. It has a homogenious pattern in terms of the order of the sentences with half-decsion and those with full-decision.

  12. Initiation of detonation by impact on granular explosives; Contribution a l'etude de la generation de la detonation provoquee par impact sur un explosif

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-05-15

    A good number of experiments have shown up the particular behaviour of granular explosives when they are detonated by barrier transmitted shocks. Similar results can be obtained when the shock is induced by impact. In this case the pressure signal shape applied at the explosive is better known and both its intensity and duration can be varied. By using a mathematical model in which the law of chemical kinetics is a linear function of pressure, and different temperatures are used for solids and gases, it is possible to describe most of the behaviour of detonation initiation in solid granular explosives. (author) [French] De nombreuses etudes experimentales ont montre le comportement particulier des explosifs granulaires lors de la detonation provoquee par choc transmis a travers une barriere. Les memes resultats peuvent etre obtenus lorsque la detonation est engendree par impact. Dans ce cas, la forme du signal de pression induit dans l'explosif est mieux connue, et il est possible d'en faire varier l'intensite et la duree d'application. Un modele mathematique utilisant une loi de cinetique chimique fonction lineaire de la pression et ou les temperatures des etats solide et gazeux pendant la reaction sont differenciees, permet de retrouver la plupart des caracteres specifiques de la generation dans un explosif solide granulaire. (auteur)

  13. Modelos matemáticos y experimentales sobre el secado de biomasa

    Directory of Open Access Journals (Sweden)

    Jorge Armando Villalba Vidales

    2015-01-01

    Full Text Available El secado de biomasa como proceso previo a la combustión se ha convertido en la actualidad en un factor decisivo para mejorar la eficiencia de dichos procesos en los sectores industrial y residencial. Debido a la creciente importancia de este proceso, los investigadores han desarrollado una gran cantidad de modelos, tanto teóricos como experimentales, que buscan predecir la cinética de secado de diferentes tipos de biomasa. Si bien se han logrado grandes avances en el desarrollo de modelos, aún no existe un modelo unificado que permita predecir los perfiles de temperatura y humedad para diversos materiales. Dichas dificultades se generan fundamentalmente por la amplia diversidad de biomateriales y las grandes diferencias entre los procesos existentes. El propósito de este artículo es brindar una panorámica sobre el estado del arte relativo a modelos, tanto matemáticos como experimentales, utilizados en la actualidad para simular procesos de secado de la biomasa. Asimismo, proponer los elementos fundamentales que deberá poseer un modelo de secado unificado.

  14. Nuclear study of Melusine; Etude nucleaire de Melusine

    Energy Technology Data Exchange (ETDEWEB)

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

    1959-07-01

    In this report are reviewed - with respect to starting of experiments - the main nuclear characteristics of a 20 per cent enriched uranium lattice, with light water as moderator and reflector. The reactor is to operate at 1 MW. 1) Study of various critical masses. 2) Control. Effectiveness of cadmium. Control rods and of a stainless steel regulating rod. 3) Study of the effect on reactivity of disturbances in the core center. 4) Study of xenon and samarium poisoning. 5) Temperature factor. 6) Heat exchanges in a fuel element. (author) [French] On etudie, dans ce rapport, les principales proprietes nucleaires d'un reseau a uranium enrichi (20 pour cent), dont le moderateur et le reflecteur sont l'eau legere en vue des experiences de demarrage. Ce reacteur devra fonctionner a 1 MW. 1) Etude de diverses masses critiques. 2) Controle. Efficacite des barres de controle en cadmium et d'une barre de reglage en acier inoxydable. 3) Etude de l'effet sur la reactivite de perturbation au centre du coeur. 4) Etude de l'empoisonnement xenon et samarium. 5) Coefficient de temperature. 6) Echanges thermiques dans un element. (auteur)

  15. Métodos Experimentales de Estudio de la Percepción Temprana del Habla

    Directory of Open Access Journals (Sweden)

    LEONARDO FRANCISCO BARÓN BIRCHENALL

    2014-01-01

    Full Text Available El estudio de la percepción temprana del habla surgió a comienzos de la década de los setenta, pero solo se desarrolló plenamente diez años después, debido a la aparición y adaptación de nuevos métodos empíricos y herramientas tec - nológicas. En este artículo se presenta una revi - sión de los métodos experimentales que pueden ser utilizados para el estudio de la percepción del habla en niños menores de un año. También se refieren algunas de las conclusiones teóricas más relevantes que se han alcanzado gracias a su aplicación. Se pretende brindar un panorama del estado metodológico y teórico del estudio de la percepción del lenguaje hablado durante el pri - mer año de vida.

  16. Etude par spectroscopie de Coulomb de points quantiques lateraux individuels et couples

    Science.gov (United States)

    Pioro-Ladriere, Michel

    Des points quantiques contenant un nombre discret et variable d'electrons sont formes dans un gaz bi-dimensionnel d'electrons a l'aide de grilles metalliques. Le transport electrique, le blocage de spin et la detection de charge sont employes comme outils spectroscopiques permettant de sonder les proprietes de ces nanostructures. Ces techniques permettent aussi de controler exactement le nombres d'electrons confines dans des points quantiques individuels et couples en utilisant un patron de grille judicieux. Une technique de refroidissement en tension est developpee afin de minimiser les effets parasites du bruit telegraphique. Ce type de bruit de charge deteriore la stabilite des nanostructures laterales par l'activation d'un minuscule courant de fuite entre les grilles et le gaz bi-dimensionnel. Un modele expliquant le role du refroidissement en tension sur le courant de fuite est presente. L'activation du courant de fuite est confirmee par detection de charge. Les effets des interactions entre les electrons pieges dans un point quantique sont ensuite etudies dans un regime ou il est possible de comparer les resulats experimentaux avec ceux obtenus par diagonalisation exacte. L'etude demontre que la phase associee au facteur de remplissage nu = 2 est instable au-dessus d'un nombre critique d'electrons. Cette instabilite est confirmee experimentalement par blocage de spin. On demontre aussi l'existence d'etats correles dans le regime des renversements de spin, associe au passage de la phase nu = 2 a nu = 1. Les etats correles sont identifies par spectroscopie en transport non lineaire. Cette caracterisation du diagramme de phase de points individuels permet de coupler deux points quantiques configures a nu = 2. Pour ce regime, la nanostructure se comporte comme un systeme a deux niveaux pouvant contenir entre un et quatre electrons de valence et ce, meme si le nombre total d'electrons est plus eleve. Les degres de liberte de charge et de spin des deux points

  17. Ciencias Experimentales en la Educación Infantil y en la Educación Primaria

    OpenAIRE

    Naves Pineda, Francisco Javier; Feliu Ortega, María José; Fernández-Lorenzo, Concepción

    2010-01-01

    Este curso engloba los conocimientos básicos que deben ser adquiridos por los alumnos en los grados de Magisterio en Educación Infantil y en Educación Primaria sobre las Ciencias Experimentales. De esta forma, se desarrollan temas que versan sobre la materia, la energía, la luz, los estados de agregación de la materia, etc, y se incluyen los conocimientos sobre el entorno que nos rodea desde un punto de vista físico y químico.

  18. Aplicación combinada de métodos de aprendizaje en temas transversales de ciencias experimentales

    OpenAIRE

    Torregrosa Maciá, Rosa; Molina Sabio, Miguel

    2011-01-01

    Muchos temas científicos de actualidad no pueden encasillarse en las clásicas divisiones de las Ciencias Experimentales (Matemáticas, Fisica, Química Biología y Geología). La comprensión de estos temas obtenida por alumnos senior, cuyo perfil de formación puede no estar ubicado en ciencias, requiere la aplicación de variados métodos de aprendizaje, incluyendo tanto los convencionales (exposiciones teóricas, dinamización de grupos, trabajo en laboratorio, visitas a instalaciones etc.) como aqu...

  19. Innovación educativa para integrar la seguridad en asignaturas experimentales

    Directory of Open Access Journals (Sweden)

    José Miguel Arnal

    2014-12-01

    Full Text Available La formación es uno de los pilares esenciales para consolidar una auténtica cultura de la prevención que luego repercuta en el ámbito laboral. En Ingeniería Química, la formación en Higiene y Seguridad es absolutamente necesaria, por el tipo de equipos y productos manejados. Sin embargo, la integración de la prevención de riesgos en los nuevos planes de estudio de Ingeniería Química es muy variable, y todavía insuficiente para que los egresados estén capacitados para desarrollar su actividad profesional aplicando los principios de la prevención de riesgos. Aprovechando la puesta en marcha de los nuevos grados, se pensó desarrollar alguna estrategia para mejorar la formación en Seguridad de los estudiantes del Grado de Ingeniería Química (GIQ de la Universitat Politècnica de València (UPV. Para ello, se solicitó un Proyecto de Innovación Educativa, que fue concedido para su ejecución en el curso 2012-2013. En dicho Proyecto se planteó mejorar la formación en Higiene y Seguridad de los estudiantes a través de las tres asignaturas de Experimentación en Ingeniería Química. Para ello, la innovación contemplaba la incorporación de procedimientos y modos de actuación enfocados a la prevención de riesgos en el trabajo desarrollado en estas asignaturas experimentales. Tras la implantación de la innovación, en este trabajo se describen las acciones llevadas a cabo; y se presentan algunos resultados referentes a la evaluación del grado de aprendizaje de los estudiantes a lo largo de las tres asignaturas A partir de los resultados y de las reflexiones del profesorado implicado, se plantean líneas de actuación futuras para mejorar el aprendizaje de los estudiantes de GIQ en materia de Seguridad.

  20. Stabilization of mixed carbides of uranium-plutonium by zirconium. Part 1.: uranium carbide with small additions of zirconium; Etude de la stabilisation des carbures mixtes d'uranium et de plutonium par addition de zirconium. 1. partie: etude des carbures d'uranium avec de faibles additions de zirconium

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-07-01

    Cast carbide samples, being of a high density and purity, are preferable for research purposes, to samples produced by powder metallurgy methods. Samples of uranium carbide with small additions of zirconium (1 to 5 per cent) were cast, as rods, in an arc furnace. A single phase carbide with interesting qualities was produced. As cast, a dendrite structure is observed, which does not disappear, after a treatment at 1900 deg. C during 110 hours. In comparison with uranium monocarbide the compatibility with stainless steel is much improved. The specific heat (between room temperature and 2500 deg. C) is similar to the specific heat of uranium monocarbide. A study of these mixed carbides, but having a part of the uranium replaced by plutonium is under way. (author) [French] Les echantillons de monocarbures obtenus par coulee sont tres interessants pour les recherches experimentales a cause de leur grande purete, de leur densite tres elevee et de la facilite d'obtention des lingots de forme et dimensions variees. On a prepare et coule dans un four a arc des echantillons de carbures d'uranium avec de faibles additions de zirconium (1 a 5 at. pour cent). On obtient ainsi des carbures monophases presentant de meilleures proprietes que le monocarbure d'uranium. A l'etat brut de coulee on observe une structure dendritique qui n'est pas detruite par un traitement thermique de 110 heures a 1900 deg. C. La compatibilite avec l'acier inoxydable 316 (a 925 deg. C pendant 500 heures) est nettement amelioree par rapport a UC. La chaleur specifique (entre la temperature ordinaire et 2500 deg. C) et la densite sont tres peu differentes de celles du monocarbure d'uranium. Une etude concernant les composes U-Pu-Zr-C est actuellement en cours. (auteur)

  1. Electrofisiologia de los receptores y vias neuronales del sistema audio-vestibular en seres humanos y en animales experimentales

    Directory of Open Access Journals (Sweden)

    José A. A. de Oliveira

    1987-01-01

    Full Text Available El estudio electrofisiológico del sistema audio-vestibular en animales y humanos es muy importante en fisiología sensorial y en laberintología. En este estudio se presentan los métodos para el regístro coclear y de los potenciales de acción nerviosa con electrodos implantados en la ventana oval en animales experimentales normales (conejillos de indias. Se muestran también los métodos de registro de respuestas del tallo cerebral en animales experimentales normales y en seres humanos. Además se discutió la importancia de estos métodos en el estudio de la ototoxidad experimental en la evaluación de niños sordos y en la localización de lesiones en el tallo cerebral. Fueron descritos el método de registro de nistagmos por medio de estimulación térmica y rotatoria en animales y humanos, y se mostraron los resultados en individuos normales. Se enfatizó la importancia de la electronistagmografía para el estudio de la ototoxidad experimental y la detección de patologías vestibulares

  2. Respuesta hidrológica en medios semiáridos: Las cuencas experimentales de la Sierra de El Picarcho, Murcia (España)

    OpenAIRE

    Castillo Sánchez, Victor Manuel; Gomez-Plaza, A.; Martínez-Mena García, M. Dolores; Albaladejo Montoro, Juan

    2000-01-01

    [ES] Las cuencas experimentales de la Sierra del Picarcho se establecieron en 1997 para estudiar los factores que controlan la generación de escorrentía en distintas escalas de trabajo, analizar la variabilidad de estos factores y desarrollar modelos hidrológicos de simulación adaptados a estos ambientes.

  3. EL DILEMA DE LA CONTRIBUCIÓN VOLUNTARIA A BIENES PÚBLICOS: UNA REVISIÓN DE TRABAJOS EXPERIMENTALES

    Directory of Open Access Journals (Sweden)

    Luis Alejandro Palacio García

    2014-01-01

    Full Text Available El artículo presenta una revisión de los experimentos realizados sobre bienes públicos apoyados en el mecanismo de contribución voluntaria. La evidencia empírica existente muestra que los individuos no son solo los seres egoístas y competitivos que supone la teoría económica ortodoxa, sino que también son seres bondadosos y altruistas. Aunque los diversos trabajos experimentales concuerdan en la existencia de estos sentimientos catalogados como "bondad", no es claro si los sujetos actúan así para mejorar el bienestar de los demás (altruismo o porque se sienten bien realizando este tipo acciones (satisfacción moral.

  4. Study of a case of essential hypoproteinaemia using the isotopes {sup 131}I and {sup 15}N; Etude a l'aide des isotopes {sup 131}I et {sup 15}N d'un cas d'hypoproteinemie essentielle

    Energy Technology Data Exchange (ETDEWEB)

    Dubert, A.; Coursaget, J.; Fallot, P.; Royer, P. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Hopital des Enfants Malades, 75 - Paris (France)

    1959-07-01

    Hypoproteinaemia both human and experimental has been studied with the help of nuclear labelling. A comparative study has been made of the fate of serum proteins labelled by an endogenous path after administration of nitrogen-15 glycine and also of serum albumin labelled by exogenous path using iodine-131. We have determined the biological period of the serum albumin and serum globulins and also the magnitude of the vascular and extravascular pools of serum albumin. In this way it has been possible to measure the speed of replacement of plasma proteins. A presentation of results taken from both clinical observation and experiment leads to a discussion on the pathogenic mechanism of hypoproteinaemia. (author) [French] Les hypoproteinemies humaine et experimentale ont ete explorees a l'aide d'indicateurs nucleaires. Une etude comparative du devenir des proteines seriques marquees par voie endogene, apres administration de glycocolle-{sup 15}N et de l'albumine serique marquee par voie exogene a l'iode-131 a ete realisee. On a determine la periode biologique de la serumalbumine et des globulines seriques ainsi que la grandeur des 'pools' vasculaire et extravasculaire de la serumalbumine. Il a ete ainsi possible d'evaluer la vitesse de renouvellement des proteines plasmatiques. La confrontation des resultats tires de l'observation clinique et de l'experimentation conduit a une discussion sur le mecanisme pathogenique de l'hypoproteinemie. (auteur)

  5. Contribution to the study of detonation initiation by shock in solid explosives (1961); Contribution a l'etude de l'initiation de la detonation par choc dans les explosifs solides (1961)

    Energy Technology Data Exchange (ETDEWEB)

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

    1961-05-15

    When a shock wave is induced in an explosive, it can initiate chemical reactions which lead more or less rapidly to a stable detonation state. In this study more particular attention was paid to the transition phase, in which has been evaluated the increases in the wave velocity, the pressure, and the electrical conductivity. The influence of the nature of the medium in front of the wave and in contact with the explosive has also been the subject of an experimental study designed to determine the extent to which its nature can be ignored and, subsequently, to characterise the initiation conditions using only the shock intensity induced in the explosive. Finally, the results were generalized for various explosive compositions and led to the development of a possible mechanism for shock initiation. (author) [French] Lorsqu'une onde de choc est induite dans un explosif, elle peut y amorcer des reactions chimiques qui conduisent plus ou moins rapidement a un regime de detonation stable. Dans cette etude, on s'est interesse plus particulierement a la phase transitoire dans laquelle on a evalue l'accroissement de la vitesse d'onde, de la pression et de la conductibilite electrique. L'influence du milieu amont, au contact de l'explosif, a egalement fait l'objet de recherches experimentales de facon a determiner dans quelle mesure on pouvait s'affranchir de sa nature et, par suite, caracteriser les conditions d'initiation par la seule intensite du choc induit dans l'explosif. Enfin, les resultats ont ete generalises a diverses compositions explosives et ont conduit a l'elaboration d'un schema possible du mecanisme de l'initiation par choc. (auteur)

  6. Study of secondary electronic emission in some piezo-electric materials: application to ultrasonic visualization; Etude de l'emission electronique secondaire de quelques materiaux piezoelectriques: application a la visualisation ultrasonore

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-07-01

    Methods allowing the visualization of acoustic images appear at the moment to be of great interest in the field of non-destructive testing as well as in that of underwater detection. In order to carry out certain calculations on the operation of an ultrasonic camera, it has been necessary to study the secondary electron emission of some piezoelectric materials liable to be incorporated into the equipment. The secondary electron emission of insulators is a rather complex phenomenon; in order to find a rational explanation for the observations made, a theory has been developed for the energy spectrum of the emitted electrons. The experimental results of this work have then been used to build an ultrasonic visualization installation. Some examples of acoustic images which have been visualized are also presented. (author) [French] Les methodes qui permettent de visualiser des images acoustiques trouvent a l'heure actuelle un grand interet dans le domaine du controle non destructif comme dans celui de la detection sous-marine. De maniere a effectuer certains calculs sur le fonctionnement d'une camera ultrasons, il a ete necessaire d'etudier l'emission electronique secondaire de quelques materiaux piezoelectriques susceptibles d'etre utilises dans sa construction. L'emission electronique secondaire des isolants est un phenomene assez complexe et de maniere a trouver des explications coherentes aux observations effectuees, une theorie du spectre energetique des electrons emis a ete elaboree. Une installation de visualisation ultrasonore a alors ete realisee a partir des donnees experimentales de cette etude. Quelques exemples d'images acoustiques visualisees par cette methode sont egalement presentees. (auteur)

  7. E. P. R. spectroscopic study of nitroxide mono- and bi-radicals; Etude par spectroscopie de resonance paramagnetique electronique de monoradicaux et de biradicaux nitroxydes

    Energy Technology Data Exchange (ETDEWEB)

    Lemaire, H. [Commissariat a l' Energie Atomique, Grenoble, 38 (France). Centre d' Etudes Nucleaires

    1967-07-01

    experimentales d'etude de produits parfaitement bien definis au point de vue structure chimique. L'etude par resonance paramagnetique electronique de monoradicaux nitroxydes conduit a la determination des axes et des elements du tenseur d'interaction hyperfine electron-noyau d'azote et du tenseur d'anisotropie du facteur de Lande: les resultats sont relies a la structure electronique des radicaux. On interprete qualitativement l'influence du solvant sur les elements des tenseurs, ainsi que les elargissements selectifs des raies hyperfines en milieu visqueux. Dans les biradicaux nitroxydes, la structure hyperfine depend non seulement des interactions magnetiques propres a chaque monomere, mais egalement de la grandeur de l'interaction d'echange separant les etats singulet et triplet du dimere; les biradicaux etudies ici sont les premiers composes organiques pour lesquels l'influence de l'echange sur la structure hyperfine est clairement mise en evidence. La presence de deux electrons non apparies introduit egalement une interaction magnetique dipolaire electron-electron, que l'on peut mettre a profit, dans le cas d'un echange intermediaire, pour determiner le signe de l'echange en etudiant le biradical dans un cristal liquide. Ces composes presentent egalement des elargissements selectifs de transitions hyperfines lorsque la viscosite du solvant croit. La theorie utilisee pour interpreter les largeurs de raie des monoradicaux est etendue au cas des biradicaux; elle rend compte des resultats experimentaux si l'on introduit simultanement les anisotropies des facteurs de Lande et des interactions dipolaires electrons-noyaux et electron-electron, en conduisant a une autre determination du signe de l'echange. (auteur)

  8. Bacterial Vaginosis

    Science.gov (United States)

    ... 586. Related Content STDs during Pregnancy Fact Sheet Pregnancy and HIV, Viral Hepatitis, and STD Prevention Pelvic Inflammatory Disease ( ... Bacterial Vaginosis (BV) Chlamydia Gonorrhea Genital Herpes Hepatitis HIV/AIDS & STDs Human Papillomavirus ... STDs See Also Pregnancy Reproductive ...

  9. Bacterial Meningitis

    Science.gov (United States)

    ... Schedules Preteen & Teen Vaccines Meningococcal Disease Sepsis Bacterial Meningitis Recommend on Facebook Tweet Share Compartir On this ... serious disease. Laboratory Methods for the Diagnosis of Meningitis This manual summarizes laboratory methods used to isolate, ...

  10. Contribution to the crystallographic study of the uranium-oxygenated system; Contribution a l'etude cristallographique du systeme uranium-oxygene

    Energy Technology Data Exchange (ETDEWEB)

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

    1955-04-15

    Three uranium oxides, UO{sub 2}, U{sub 3}O{sub 8} and UO{sub 3} are known since a long time. The existence of a fourth, U{sub 2}O{sub 5}, is discussed. The mechanisms of decomposition between UO{sub 3} and U{sub 3}O{sub 8} have even some shadow zones. The aim of this report is the study of the phase relations in an uranium - oxygen system, from the metal until UO{sub 3}. We considered, on the one hand, the equilibrium relations, what should result in a diagram of phases in pressures and temperatures, on the other hand, the transformations bringing one oxide to the other, often by a continuous way and through intermediate of metastable phases. The introduction of the temperature and the consideration of the kinetics effects have permitted to raise the ambiguities. We adopted, to facilitate the presentation of the results, a partition a few arbitrary but convenient, in three chapters,: I - experimental Techniques II - Crystallographic species between U and UO{sub 3}. III - Kinetic of oxidisation of UO{sub 2}. (M.B.) [French] Trois oxydes d'uranium, UO{sub 2}, U{sub 3}O{sub 8} et UO{sub 3} sont connus depuis longtemps. L'existence d'un quatrieme, U{sub 2}O{sub 5}, est en suspend. Les mecanismes de decomposition entre UO{sub 3} et U{sub 3}O{sub 8} possedent encore quelques zones d mbres. Le but propose dans ce memoire est l'etude des relations de phase dans le systeme uranium - oxygene, du metal jusqu'a UO{sub 3}. Nous avons ete amene a considerer, d'une part, les relations a l'equilibre, ce qui devrait se traduire par un diagramme de phases en pressions et temperatures, d'autre part, les transformations amenant, souvent d'une facon continue et par l'intermediaire de phases metastables, d'un oxyde a l'autre. L'introduction de la temperature et la consideration des effets de cinetique ont le plus souvent permis de lever les ambiguites rencontrees. Nous avons adopte, pour faciliter la presentation des

  11. 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

  12. Laser-matter interaction studies at Centre d'Etudes de Limeil

    International Nuclear Information System (INIS)

    A review is made of the laser-matter interaction and implosion experiments carried out at Centre d'Etudes de Limeil with the two following neodymium glass lasers; the monobeam 50 J - 1ns P102 laser for the interaction with foils and the eight beam 400 J - 0.5ns OCTAL laser for the implosion of glass microballoons

  13. Fundamentos para una enseñanza y difusión del patrimonio desde una perspectiva integradora de las ciencias sociales y experimentales

    OpenAIRE

    Estepa Giménez, Jesús; Wamba Aguado, Ana María; Jiménez Pérez, Roque

    2005-01-01

    En este trabajo se formula una propuesta teórica que revisa el papel del patrimonio desde una perspectiva integradora y holística, en la educación formal y no formal de las cienciaO sociales y de las ciencias experimentales, así como su relevancia en el desarrollo de programas de educación ambiental, de alfabetización científica y de educación del ciudadano.

  14. Bacterial carbonatogenesis

    International Nuclear Information System (INIS)

    Several series of experiments in the laboratory as well as in natural conditions teach that the production of carbonate particles by heterotrophic bacteria follows different ways. The 'passive' carbonatogenesis is generated by modifications of the medium that lead to the accumulation of carbonate and bicarbonate ions and to the precipitation of solid particles. The 'active' carbonatogenesis is independent of the metabolic pathways. The carbonate particles are produced by ionic exchanges through the cell membrane following still poorly known mechanisms. Carbonatogenesis appears to be the response of heterotrophic bacterial communities to an enrichment of the milieu in organic matter. The active carbonatogenesis seems to start first. It is followed by the passive one which induces the growth of initially produced particles. The yield of heterotrophic bacterial carbonatogenesis and the amounts of solid carbonates production by bacteria are potentially very high as compared to autotrophic or chemical sedimentation from marine, paralic or continental waters. Furthermore, the bacterial processes are environmentally very ubiquitous; they just require organic matter enrichment. Thus, apart from purely evaporite and autotrophic ones, all Ca and/or Mg carbonates must be considered as from heterotrophic bacterial origin. By the way, the carbon of carbonates comes from primary organic matter. Such considerations ask questions about some interpretations from isotopic data on carbonates. Finally, bacterial heterotrophic carbonatogenesis appears as a fundamental phase in the relationships between atmosphere and lithosphere and in the geo-biological evolution of Earth. (author)

  15. RECHERCHE DES BACTERIES LACTIQUES ET ETUDE IN VITRO DE LEURS PROPRIETES PROBIOTIQUES

    Directory of Open Access Journals (Sweden)

    B. MIDASSIROU

    2012-12-01

    Full Text Available The bacteria mainly used as potentials probiotic belong to the group of the lactic bacteria. In order to fulfill this function, these bacteria must answer a certain number of properties (antagonistic activity, tolerance to acidity, capacity of adhesion etc. In this study, 6 strains: Enterococcus faecium, d’Enterococcus faecalis, Lactococcus lactis ssp lactis, Lactobacillus collinoides, Lactobacillus delbrueckii ssp delbrueckii and Lactobacillus fermentum, have been isolated and characterized. Our data revealed that these strains were susceptible to most used antimicrobial drugs, have an antibacterial activity against pathogenic strains: (Listeria monocytogenes ATCC 19115, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis CIP 106510, Enterococcus faecalis ATCC 9212, Micrococcus luteus NCIMB 816, Salmonella typhimurium NRRLB 4420, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 35218. The tested strains showed a aptitude to produce acidity, and tolerated the bile Oxgall 0,3% and pH 3. Adherence assay to polystyrene revealed that these strains are fairly adherent. The studied strains present in vitro interesting probiotic properties (inhibiting effect, production of acids... independently of their biotope.

  16. Electrochemical study in molten potassium thiocyanate; Etude electrochimique dans le thiocyanate de potassium fondu

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-07-01

    2}, Hg{sup 2+}, Cu{sup +}, Co{sup 2+}, Ni{sup 2+}, Cr{sup 3+}. La comparaison des valeurs des potentiels trouves dans le thiocyanate avec celles qui sont connues pour d'autres solvants fondus, nous a permis de rapprocher les proprietes du thiocyanate de celles de certains sels comme les chlorures ou les nitrates fondus. Ainsi les proprietes complexantes de SCN{sup -} vis-a-vis de Cu{sup +} exaltent les proprietes oxydantes de Cu{sup 2+}. Une etude polarographique de complexes dans le bain fondu, nous a revele l'existence de deux complexes cupro-cyanures de formules Cu(CN){sup -}{sub 2} et Cu(CN){sup 3-}{sub 4}, dont nous avons determine, experimentalement les constantes de dissociation. (auteur)

  17. Experimental study of the MHD activity associated to the mode m=2, n=1 in the Tore Supra tokamak; Etude experimentale de l`activite MHD associee au mode m=2, n=1 dans le tokamak Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Turlur, S.

    1996-09-20

    In tokamaks such as Tore Supra, the plasma confinement magnetic structure can be severely affected when Magnetohydrodynamic (M.H.D.) instabilities are destabilized. Experimentally, these instabilities are detected as magnetic fluctuations with captors located against the inner wall of the vacuum vessel. Fourier analysis provides amplitude, frequency and wave numbers of magnetic modes. In case of fast or transient phenomena, the analysis of magnetic fluctuations is completed using the singular value decomposition. In this dissertation, these analysis techniques are used to study two specific examples of M.H.D. activity related to the m = 2, n = 1 mode. On Tore Supra, the onset of this mode have strong consequences on the stability of partially or fully non inductive discharges. A regular and persistent sawtooth-like regime is observed on the electronic temperature leading to a significant degradation of the central confinement. Heat exhaust and particle balance are also essential parameters to achieve stationary discharges. On Tore Supra, these are studied with the ergodic divertor which produces stochastic magnetic field lines at the plasma edge. For optimal operating conditions of the ergodic divertor, the growth of the m = 2, N = 1 mode can lead to sudden destruction of magnetic equilibrium. For both cases, understanding and characterization of mechanisms leading to the observed m = 2, n = 1 M.H.D. activity are fundamental to obtain stationary discharges. (author). 115 refs.

  18. Experimental studies on extinction of opposed jet: turbulent premixed flames with water mists; Etudes experimentales sur l'extinction par brouillards d'eau des flammes turbulentes de premelanges stebilisees entre deux jets opposes

    Energy Technology Data Exchange (ETDEWEB)

    Mesli, B.

    2000-12-15

    The security against unwanted fires and explosive systems is of primary importance. The phase out of Halon constitutes a real challenge for their replacement. As one of the most effective fire suppression solutions, water mists represent a good alternative because of their neutrality with respect to the environment and their various advantages. In order to improve their efficiency and to determine the predominant mechanisms in the extinction of premixed flames, an experimental work through this PhD thesis have be initiated in the laboratory. The main objective of the present study is the characterization of water mist efficiency for the extinction of opposed jet turbulent premixed methane/air flames, as a function of parameters related to the flame and to the water mist. To this aim, an experimental set-up has been developed, in particular, an air blast atomizer to produce and control the water mist was inserted into the opposed jet burner system. Typical water mist mean droplet diameters range in this study around 4 {mu}m. Phase Doppler Anemometry and Particle Imaging Velocimetry were used for the characterization of the water mist. The dynamic field and the size of the water droplets were determined for the various experimental conditions explored. The extinction limits of the flame were determined with and without the addition of the water mist. A new parameter defining the water mist efficiency was introduced and used in the interpretation of the results. The various mechanisms of flame extinction by water mist have been analyzed by investigating three different configurations of the water mist /flame interaction. The effect of the injected water mist flow rate and its application time were also studied. Finally, a part of this work was devoted to the use of sea water for the extinction of the flame. (author)

  19. Turbulent precipitation of uranium oxalate in a vortex reactor - experimental study and modelling; Precipitation turbulente d'oxalate d'uranium en reacteur vortex - etude experimentale et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Sommer de Gelicourt, Y

    2004-03-15

    Industrial oxalic precipitation processed in an un-baffled magnetically stirred tank, the Vortex Reactor, has been studied with uranium simulating plutonium. Modelling precipitation requires a mixing model for the continuous liquid phase and the solution of population balance for the dispersed solid phase. Being chemical reaction influenced by the degree of mixing at molecular scale, that commercial CFD code does not resolve, a sub-grid scale model has been introduced: the finite mode probability density functions, and coupled with a model for the liquid energy spectrum. Evolution of the dispersed phase has been resolved by the quadrature method of moments, first used here with experimental nucleation and growth kinetics, and an aggregation kernel based on local shear rate. The promising abilities of this local approach, without any fitting constant, are strengthened by the similarity between experimental results and simulations. (author)

  20. Modeling and experimental study of heat transfer in innovate building components for industrial production; Modelisation et etude experimentale des echanges de chaleur dans des composants innovants de batiment industriels

    Energy Technology Data Exchange (ETDEWEB)

    Lacena-Neildez, A.

    2000-05-15

    The main objective of the thesis is the study of a new roof thermal behaviour with the thermal transfer by radiation and convection in order to propose an alternative to the mechanical air-conditioning in the overseas islands, and to determine the way of improving the energy performance. Two fundamental results were obtained. First, the coating has a great importance in relation with the radiative properties. Secondly, air channel geometries can complete insufficient coatings in their cooling purpose. In this thesis, both experimental and modelling analyses were carried out. A solar simulator was used for the experiment to carry out a comparative study of prototypes. A performance indicator was defined; it is the eliminated flux, because the temperature is not sufficient to describe the heat exchange. At the same time, the radiative properties of coatings were measured and a characterisation of paints allows to start a new research of innovative infrared reflective paints. A mono-dimensional model was developed describing thermal exchanges in an air channel component. A sensibility study was carried out which allows to determine the main parameters. The experimental study validated the model in rear flux, more realistic than stagnation. Finally, the feasibility of this new steel component was concluded by a technical-economical study. (author)

  1. Experimental study of X-ray emission in laser-cluster interaction; Etude experimentale de l'emission X issue de l'interaction laser-agregats

    Energy Technology Data Exchange (ETDEWEB)

    Caillaud, T

    2004-09-01

    Rare gas cluster jets are an intermediate medium between solid and gas targets. Laser-cluster jets interaction may generate a great number of energetic particles as X-rays, UV, high harmonics, ions, electrons and neutrons. To understand all the mechanisms involved in such an interaction we need to make a complete study of individual cluster response to an ultra-short laser pulse. We studied the laser interaction with our argon cluster gas jet, which is well characterized in cluster size and density, to enlarge the knowledge of this interaction. We measured absorption, heating and X-ray emission spectra versus laser parameters and clusters size ({approx} 15-30 nm). We show that there is a strong refraction effect on laser propagation due to the residual gas density. This effect was confirmed by laser propagation simulation with a cylindrical 2-dimensional particle code WAKE. The role played by refraction was to limit maximum laser intensity on the focal spot and to increase interaction volume. By this way, X-ray emission was observed with laser intensity not so far from the ionization threshold (few 10{sup 14} W.cm{sup -2}). We also studied plasma expansion both at cluster scale and focal volume scale and deduced the deposited energy distribution as a function of time. Thanks to a simple hydrodynamic model, we used these results to study cluster expansion. X-ray emission is then simulated by TRANSPEC code in order to reproduce X-ray spectra and duration. Those results revealed an extremely brief X-ray emission consistent with a preliminary measure by streak camera (on ps scale). (author)

  2. Experimental study of the influence of partner structure in the fusion of the almost symmetrical systems; Etude experimentale de l`influence de la structure des partenaires dans la fusion de systemes presque symetriques

    Energy Technology Data Exchange (ETDEWEB)

    Stodel-Le Lay, Christelle [Lab. de Physique Corpusculaire, Caen Univ., 14 - Caen (France)

    1998-12-04

    The cross-sections for the formation of evaporation residues in {sup 70}Zn and {sup 86}Kr reactions with {sup 150}Nd and {sup 130,136}Xe isotopes were measured for excitation energies of the compound nuclei ({sup 216,220,222}Th) varied from 7 MeV to 70 MeV, at the linear accelerator UNILAC of the nuclear facility GSI, Darmstadt (Germany). After de-excitation by evaporation (xn,pxn and {alpha}xn), the residual nuclei are separated from the primary beam and from spurious reaction products by the velocity filter SHIP and implanted into a silicon localization detector. Their subsequent decay via alpha particles with characteristic energies allows us to identify them and to deduce their yields. Experimental fusion-evaporation excitation functions are compared with those leading to the same compound nuclei obtained with other projectile and target combinations and with those calculated with a code developed at GSI. This code allows us to evaluate the evolution of the fission probability as a function of the incident energy for each system. The variation of cross-sections and of the fusion probability is studied as a function of the macroscopic and microscopic variables of the partners. For the synthesis of super-heavy elements, these results demonstrate quantitatively the interest in using partners of fusion with closed shell structures and rich in neurons (the fusion cross-section increases by a factor of 9 for a complementary pair of neutrons). On the other hand, closed shell compound nuclei do not influence the fusion cross-section. It will be worth synthesizing isotopes approaching the predicted stability region, nuclei with Z greater than 110 using neutron rich projectiles coming from secondary beams. (author) 104 refs., 71 figs., 11 tabs.

  3. Strontium and caesium transport in unsaturated soil from Chernobyl Pilot Site under steady flow conditions; Transfert de radioelements en zone non saturee. Etude experimentale et modelisation appliquees au Site Pilote de Tchernobyl

    Energy Technology Data Exchange (ETDEWEB)

    Szenknect, St

    2003-10-15

    This work is devoted to the quantification and the identification of the predominant processes involved in strontium and caesium transport in unsaturated soil from Chernobyl Pilot Site under steady flow conditions. The transport and fate of radionuclides in the subsurface is affected by various physical and chemical processes including advective and diffusive transport as well as chemical and biological transformations. Laboratory experiments and the use of a multiple tracer approach allow to isolate the contributions of each elementary process and to control the physico-chemical conditions in the system. To be more representative of the field conditions, we decided to perform column miscible displacement experiments. We perform batch and flow-through reactor experiments to characterize the radionuclides sorption mechanisms. Miscible displacement experiments within homogeneous columns and modeling allow to characterize the hydrodynamic properties of the soil and to describe the radionuclides behaviour under dynamic conditions at different water contents. We show that the water content of porous media affect the transport behaviour of inert and strongly sorbing radionuclides. Our results demonstrate that a parametrized transport model that was calibrated under completely saturated conditions was not able to describe the advective-dispersive transport of reactive solutes under unsaturated steady state conditions. Under our experimental conditions, there is no effect of a decrease of the mean water content on the sorption model parameters, but the transport parameters are modified. We established for the studied soil the relation between hydrodynamic dispersion and water content and the relation between pore water velocity and water content. (author)

  4. Experimental study of anti-icing coatings' use on wind turbine blades; Etudes experimentale de l'utilisation de revetements a caractere glaciophobe sur les pales d'eolienne

    Energy Technology Data Exchange (ETDEWEB)

    Adomou, M.; Fortin, G.; Perron, J. [Quebec Univ., Chicoutimi, PQ (Canada). Anti-Icing Materials International Laboratory

    2010-07-01

    Ice accumulation on wind turbine blades can result in energy production losses, mechanical overloads, and ice shedding. The de-icing systems which are currently used are energy intensive. This poster reported on a study that investigated the use of ice-phobic coatings as a means of protecting wind turbines during cold weather. The study examined the behaviour of various coatings on wind turbine blades under icing conditions and investigated the feasibility of reducing the surface temperature of heated blades with the addition of ice-phobic or hydrophobic coatings. The performance of the thermal systems combined with the coatings was also investigated. The coatings included a polyurethane plastic film; a silicone-epoxy composite; a fluorinated resin; and a fluoroethane compound. The coatings were applied to a NACA airfoil placed in an icing wind tunnel. Various ice accumulation regimes, wind speeds, and temperatures were studied. The coatings proved to be effective against run-back effects during anti-icing operations, and may increase production. tabs., figs.

  5. Experimental study of the drying in dense fluidized beds of a synthetic mud coated with support particulates; Etude experimentale du sechage en lit fluidise dense d'une boue synthetique enrobee sur des particules supports

    Energy Technology Data Exchange (ETDEWEB)

    Gode, C.; Shakourzadeh, K. [Universite de Technologie de Compiegne, L.G.P.I., 60 (France)

    2001-07-01

    This article presents the results of an experimental study of a new drying process for muddy materials and based on the fluidization technique. The granular phase has been obtained by the coating with mud of a porous mineral support, inert and recyclable in the process. Activated porous particulates of alumina (2-5 mm) have been chosen because of their heat transfer properties. A first part of the experimental study concerns the drying process. The second part concerns the attrition and elutriation mechanisms. The experimental measurements have been performed with a laboratory fluidized column (internal diameter = 150 mm) and with a fluidized column (internal diameter = 400 mm) from a semi-industrial facility. The air velocity and the drying temperature are the main adjustment parameters. The working temperatures have been fixed between 20 and 150 deg. C. (J.S.)

  6. Results of experimental study of heat insulated diesel turbo-compound engine working processes; Resultats de l'etude experimentale des processus de fonctionnement du diesel turbocompound avec limitation des pertes thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Benabbassi, A. [Centre Universitaire de Bechar (Algeria); Khatchian, A.S. [Institut d' automobiles et de routes de Moscow (Russian Federation)

    1999-07-01

    The experimental study of diesel turbo-compound engine performances are revealed a deterioration of performances when, it operates with heat loss restriction achieved by change of aluminium piston by an assembled piston. An adapted optimisation of the injection system has improved the engine performances. The improvement in the case of the assembled piston was more considerable. The measurements of wall temperatures and of heat fluxes accompanied by the computation of temperature distribution have permitted to make some important observations. The hypothesis concerning the intensification of the heat transfer during the heat loss restriction is not found a confirmation in this study. (authors)

  7. Synthesis of zirconium by zirconium tetrachloride reduction by magnesio-thermia. Experimental study and modelling; Elaboration de zirconium par reduction de tetrachlorure de zirconium par magnesothermie. Etude experimentale et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Basin, N

    2001-01-01

    This work deals with the synthesis of zirconium. The ore is carbo-chlorinated to obtain the tetrachloride which is then purified by selective condensation and extractive distillation. Zirconium tetrachloride is then reduced by magnesium and the pseudo-alloy is obtained according to the global following reaction (Kroll process): ZrCl{sub 4} + 2 Mg = 2 MgCl{sub 2}. By thermodynamics, it has been shown that the volatilization of magnesium chloride and the formation of zirconium sub-chlorides are minimized when the combined effects of temperature and of dilution with argon are limited. With these conditions, the products, essentially zirconium and magnesium chloride, are obtained in equivalence ratio in the magnesio-thermia reaction. The global kinetics of the reduction process has been studied by a thermal gravimetric method. A thermo-balance device has been developed specially for this kinetics study. It runs under a controlled atmosphere and is coupled to a vapor tetrachloride feed unit. The transformation is modelled supposing that the zirconium and magnesium chloride formation result: 1)of the evaporation of magnesium from its liquid phase 2)of the transfer of magnesium and zirconium tetrachloride vapors towards the front of the reaction located in the gaseous phase 3)of the chemical reaction. In the studied conditions, the diffusion is supposed to be the limiting process. The influence of the following parameters: geometry of the reactive zone, temperature, scanning rate of the argon-zirconium tetrachloride mixture, composition of the argon-zirconium tetrachloride mixture has been experimentally studied and confronted with success to the model. (O.M.)

  8. Experimental and numerical study of two-phase flows at the inlet of evaporators in vapour compression cycles; Etude experimentale et numerique d'ecoulements diphasiques a l'entree des evaporateurs de cycles thermodynamiques

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, M

    2007-09-15

    Maldistribution of liquid-vapour two phase flows causes a significant decrease of the thermal and hydraulic performance of evaporators in thermodynamic vapour compression cycles. A first experimental installation was used to visualize the two phase flow evolution between the expansion valve and the evaporator inlet. A second experimental set-up simulating a compact heat exchanger has been designed to identify the functional and geometrical parameters creating the best distribution of the two phases in the different channels. An analysis and a comprehension of the relation between the geometrical and functional parameters with the flow pattern inside the header and the two phase distribution, has been established. A numerical simulations of a stratified flow and a stratified jet flow have been carried out using two CFD codes: FLUENT and NEPTUNE. In the case of a fragmented jet configuration, a global definition of the interfacial area concentration for a separated phases and dispersed phases flow has been established and a model calculating the fragmented mass fraction has been developed. (author)

  9. Experimental study and simulation of fused silica damage initiation by laser pulse irradiation; Etude experimentale et modelisation de l'initiation de l'endommagement de la silice sous irradiation laser impulsionnelle

    Energy Technology Data Exchange (ETDEWEB)

    Bonneau, F.; Combis, J.L.; Vierne, J. [CEA Bruyeres-le-Chatel, Dept. de Physique Theorique et Appliquee, 91 (France)] [and others

    2002-07-01

    In order to resolve problems concerning the understanding and the control of laser-induced damage of silica optical elements, a collaboration between the CEA (CESTA/DLP, DIF/DPTA, and Grenoble/LETI) and different university laboratories has been undertaken. Ultra-pure silica 'model' samples, seeded with gold nano-particles whose diameter does not exceed 5 nm, were made at the LASIM in Lyon. The aim in using these samples is to observe the mechanism of damage initiation that can be attributed to inclusions of nano-metric site. This report presents the different steps encountered during this study: making the samples, the laser-induced damage tests performed at the CESTA, and the 'Nomarski' and 'atomic force' microscope observations of this damage carried out at the Fresnel Institute in Marseille. These samples were also used for a series of experiments using a time-of-flight mass spectrometer at ANL near Chicago. This installation is of great interest because it enables us to combine the laser irradiation of the sample with the chemical identification of material ejected by the sample. A precise evaluation of the quantity of gold atoms emitted during irradiation can thus be obtained from the experimental results. The experimental data is then interpreted, and in particular, compared to, numerical simulations obtained with the DELPOR program. A very encouraging result is the existence of a pre-damage phase at very low fluences that is not detectable by classical optical devices. The experimental means developed for such 'model' samples should be transposable to the analysis of industrial glasses. (authors)

  10. Experimental studies of ions and atoms interaction with insulating surface; Etude experimentale de l'interaction rasante d'atomes et d'ions sur des surfaces isolantes

    Energy Technology Data Exchange (ETDEWEB)

    Villette, J

    2000-10-15

    Grazing collisions (<3 deg.) of keV ions and atoms: H{sup +}, Ne{sup +}, Ne{sup 0}, Na{sup +} on LiF (001) single crystal, an ionic insulator, are investigated by a time of flight technique. The incident beam is chopped and the scattered particles are collected on a position sensitive detector providing differential cross section while the time of flight gives the energy loss. Deflection plates allow the charge state analysis. Secondary electrons are detected in coincidence allowing direct measurements of electron emission yield, angular and energetic distribution through time of flight measurements. The target electronic structure characterized by a large band gap, governs the collisional processes: charge exchange, electronic excitations and electron emission. In particular, these studies show that the population of local target excitations surface excitons is the major contribution to the kinetic energy transfer (stopping power). Auger neutralization of Ne{sup +} and He{sup +} ions reveals the population of quasi-molecular excitons, an exciton bound on two holes. Referenced in the literature as trion. A direct energy balance determines the binding energy associated with these excited states of the surface. Besides these electronic energy loss processes, two nuclear energy loss mechanisms are characterized. These processes imply momentum transfer to individual target atoms during close binary collisions or, if the projectile is charged, to collective mode of optical phonons induced by the projectile coulomb field. The effect of the temperature on the scattering profile, the contribution of topological surface defects to the energy loss profile and to skipping motion on the surface are analyzed in view of classical trajectory simulations. (author)

  11. Experimental and numerical study of the strong interaction between wakes of cylindrical obstacles; Etude experimentale et numerique de l'interaction forte entre sillages d'obstacles cylindriques

    Energy Technology Data Exchange (ETDEWEB)

    Brun, Ch

    1998-04-02

    In the context of thermal-hydraulics of nuclear reactors, strong interaction between wakes is encountered in the bottom of reactor vessels where control and measurement rods of variable size and disposition interact with the overall wakes generated in these flow zones. This study deals with the strong interaction between two wakes developed downstream of two parallel cylinders with a small spacing. The analysis focusses on the effect of the Reynolds regime which controls the equilibrium between the inertia and viscosity forces of the fluid and influences the large scale behaviour of the flow with the development of hydrodynamic instabilities and turbulence. The document is organized as follows: the characteristic phenomena of wakes formation downstream of cylindrical obstacles are recalled in the first chapter (single cylinder, interaction between two tubes, case of a bundle of tubes perpendicular to the flow). The experimental setup (hydraulic loop, velocity and pressure measurement instrumentation) and the statistical procedures applied to the signals measured are detailed in chapters 2 and 3. Chapter 4 is devoted to the experimental study of the strong interaction between two tubes. Laser Doppler velocity measurements in the wakes close to cylinders and pressure measurements performed on tube walls are reported in this chapter. In chapter 5, a 2-D numerical simulation of two typical cases of interaction (Re = 1000 and Re = 5000) is performed. In the last chapter, a more complex application of strong interactions inside and downstream of a bunch of staggered tubes is analyzed experimentally for equivalent Reynolds regimes. (J.S.)

  12. Experimental investigation of the effects of aqueous species on the dissolution kinetics of R7T7 glass; Etude experimentale de l`influence d`especes aqueuses sur la cinetique de dissolution du verre nucleaire R7T7

    Energy Technology Data Exchange (ETDEWEB)

    Gin, S.

    1994-10-01

    This contribution to the study of aqueous corrosion of the French ``R7T7`` reference nuclear containment glass includes a bibliographic survey of prior investigations, highlighting the problems encountered in interpreting the interactions in systems containing clay materials in contact with the glass. An experimental methodology is proposed to investigate the effects of inorganic aqueous species separately from those of a few organic acids on the dissolution mechanisms and kinetics of R7T7 glass at 90 deg. C. The experimental results discussed support the idea that several glass network forming elements may have a kinetically limiting role. The most likely hypothesis to account for the absence of saturation conditions with respect to the glass in certain clay media involves the formation of complexes with kinetically limiting metallic elements such as aluminum released by glass corrosion. This work contributes to a better understanding of the basic mechanisms of nuclear glass dissolution in a geological repository environment. It facilitates the interpretation of glass alteration studies in realistic or actual solutions and may contribute to specifying near field chemical barriers in the form of additives (amorphous silica, aluminum hydroxides or phosphates) around the glass disposal package to enhance the stability of the glass matrix. (author). 148 refs., 40 figs., 32 tabs., 1 append.

  13. Experimental study of the mechanisms of CO{sub 2} capture by calcium cycle under circulating fluidized bed conditions; Etude experimentale des mecanismes de capture du CO{sub 2} par cycle calcium en lit fluidise circulant

    Energy Technology Data Exchange (ETDEWEB)

    Hoteit, A

    2006-06-15

    The work undertaken in this Thesis in partnership with department R and D of ALSTOM Power Boilers, CEMEX and the ADEME, relates to the experimental study of various phenomena associated to CO{sub 2} capture under circulating fluidized bed conditions. The size of particles, temperature and the CO{sub 2} concentration have an influence on the limestone calcination reaction. The reaction of carbonation of lime is not total. During successive cycles of calcination/carbonation, the rate of carbonation obtained with hydrated lime is increasingly higher than that obtained with the lime. Under continuously reducing conditions, the decomposition of sulphates present in the bed ashes is not total. This decomposition is total under reduction/oxidation cycles. A modeling of calcination allowed to determine the intrinsic kinetic constants of calcination and carbonation. (author)

  14. Experimental thermal study and numerical simulation of a composite solar wall. Optimization of the energetic performances; Etude thermique experimentale et simulation numerique d`un mur solaire composite. Optimisation des performances energetiques

    Energy Technology Data Exchange (ETDEWEB)

    Zalewski, L.

    1996-11-27

    The objective of this work is the analysis of a passive solar component: the composite solar wall, a building component, which includes an insulating panel located behind the massive wall. This panel has two vents located at the top and at the bottom, which allow the air to circulate from the room to the layer in contact with the back of the massive wall, where it is heated, and then back to the room. The solar energy is transferred to the building by conduction through the massive wall, and then by convection using a thermosyphon phenomenon. The monitoring of 2 solar houses in Verdun-Thierville (Meuse, France) has clearly shown, control issues of the air layer. The wall must be operated as autonomously as possible, to not be a constraint for the occupants and to get an optimization of the energy gains. To solve these problems, a composite solar wall prototype was erected in a test cell at Cadarache and tested in real operating conditions. This allows to use a more complete instrumentation, to have access more easily to the sensors and to study various configurations. The first experiments revealed an inverse thermosyphon phenomenon. To avoid this effect, two systems were designed, tested at Cadarache and then implemented in the walls at Verdun. (author) 77 refs.

  15. An experimental study on mineral sequestration of CO{sub 2} in basics and ultra basics rocks; Etude experimentale des reactions de carbonatation minerale du CO{sub 2} dans les roches basiques et ultrabasiques

    Energy Technology Data Exchange (ETDEWEB)

    Dufaud, F

    2006-11-15

    The first part of the thesis is dedicated to dissolution data of siderite FeCO{sub 3} and magnetite Fe{sub 3}O{sub 4} which have been monitored in situ on the FAME beamline of the european synchrotron radiation facility in Grenoble. Iron in solution close to siderite single crystals is shown to be divalent hydrated. The small size of the experimentally investigated volume of solution (200 *400 micrometer and 3 mm height) allowed to work with single crystals in well defined geometries. No specific interaction was observed between iron (II) and dissolved inorganic carbon, suggesting that modelling siderite evolution under high CO{sub 2} pressures by using CO{sub 2}-less very acidic (pH 1-2) solutions is adequate. Using initial reaction rates, we get an activation energy for siderite dissolution of 62 kJ.mol{sup -1}, consistent with existing literature data. Such a value is suggestive of a mineral/solution interface mechanism.. Data from this study and from literature are consistent over a temperature range 25 C - 125 C and a pH range pH 1-7 with an empirical law: pk = pH + E{sub a}/(ln(10)*RT(K)) - log(S/V) - 10,5 where E{sub a} = 62 kJ.mol{sup -1} and S/V is the ratio between solid surface S and fluid volume V. A value of activation energy of 73.5 kJ.mol{sup -1} is obtained in the case of magnetite, also consistent with mineral/solution processes. The second and major part of the thesis work is the realization of analogical experiments for simulating carbonation of basic and ultra basic minerals. Experiments were carried out on consolidated rock cores at 90 C and 280 bar of CO{sub 2} (low temperature experiments) and on powders contained in metallic capsules at 400-500 C and 1000-1700 bars of CO{sub 2} (high temperature experiments). The rate of mineral storage of CO{sub 2} was defined as the molar ratio of solid carbonate formed over total CO{sub 2} injected. It is of about 1% in three months in low temperature experiments whereas it reaches several tens of percents per hour in high temperature experiments. In all cases, carbonation is shown to proceed according to dissolution/precipitation mechanisms. A quasi stoichiometric coupling is evidenced between carbonation and (proto) serpentinization in high-temperature experiments. Newly formed carbonates are mostly magnesite MgCO{sub 3} with Fe and Ca in solid solution. In low temperature samples, the silicates are covered with a thin silica layer and with carbonate spherules consisting of ankerite CaFe(CO{sub 3}){sub 2} - dolomite CaMg(CO{sub 3}){sub 2} - siderite cores surrounded by magnesite overgrowth. In CO{sub 2}-saturated water, peridotites are more reactive than serpentinite and basalts, in accordance with thermodynamic modelling whereas serpentinites are the most reactive in the supercritical CO{sub 2} phase, showing stronger reactivities in this latter phase than in CO{sub 2}-saturated water. In high temperature experiments, the rate of mineral storage is larger at 400 C than at 500 C, in agreement with thermodynamic modelling of the system. High water fugacities and high fluid salinities are shown to have a positive effect on mineral storage rates. Isotopic mass balance of carbon have evidenced that about 15% of the mineral storage consist of a reduced carbon phase, also identified by transmission electron microscopy as an ill-organized graphite phase. (author)

  16. Modelling and experimental study of the behavior of radon and radon decay products in an enclosure. Application to houses; Modelisation et etude experimentale du comportement du radon et de ses descendants dans une enceinte confinee. Application a une habitation

    Energy Technology Data Exchange (ETDEWEB)

    Gouronnec, A.M.

    1995-02-03

    Since the eighties, more and more studies were performed about radon and its decay products in houses with one of the aim being the estimation of the dose received by their inhabitants. Then, the principal objective of this work is to describe the behaviour of radon and its decay products within a dwelling. In the first part to the report, a few definitions are given and data from literature give an idea of indoor radon and radon decay products activities and/or size distribution. Aspects of dosimetry are presented too. In the second part of the work, a mathematical model, called `PRADDO` of Physic of Radon and radon Decay products in Domestic environment is developed on the basis of the classical model written by Jacobi in 1972. On the one hand, it has to predict radon decay products activities in systems consisting in one or more enclosure(s), from radon activity and from ambient aerosol concentration and size distribution. On the other hand, one part of the model is assigned to study the influence of the entry model parameters variation on the calculated quantities. Then, in the third part of the work, two experimental studies are realised in order to compare measurements to modelization. The first experimentation is a laboratory work, made on the test bench ICARE from IPSN, and the second one consists in describing the basement of an occupied house from Brittany. In the two cases, the comparison between experiments and modelling shows a good agreement if particles are present in the air, but any conclusion is made when is no aerosol in the enclosure. (author). 158 refs., 81 figs., 42 tabs.

  17. Proton scattering from unstable nuclei {sup 20}O, {sup 30}S, {sup 34}Ar: experimental study and models; Diffusion de protons sur les noyaux instables {sup 20}O, {sup 30}S, {sup 34}Ar: etude experimentale et developpement de modeles

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Elias [Institut de Physique Nucleaire, CNRS - IN2P3, Universite Paris - Sud, 91406 Orsay Cedex (France)

    2000-01-28

    Elastic and inelastic proton scattering from the unstable nuclei {sup 20}O, {sup 30}S and {sup 34}Ar were measured in inverse kinematics at the Grand Accelerateur National d'Ions Lourds. Secondary beams of {sup 20}O at 43 MeV/A, {sup 30}S at 53 MeV/A and {sup 34}Ar at 47 MeV/A impinged on a (CH{sub 2}){sub n} target. Recoiling protons were detected in the silicon strip array MUST. Energies and angular distributions of the first 2{sup +} and 3{sup -} states were measured. A phenomenological analysis yields values of the deformation parameters {beta}{sub 2} and {beta}{sub 3} of 0.55 (6) and 0.35 (5) for {sup 20}O, 0.32 (3) and 0.22 (4) for {sup 30}S, 0.27 (2) and 0.39 (3) for {sup 34}Ar, respectively, and allows the extraction of the ratio of neutron to proton transition matrix elements (M{sub n}/M{sub p})/(N/Z) for 2{sup +} states: 2.35 (37) for {sup 20}O, 0.93 (20) for {sup 30}S and 1.35 (28) for {sup 34}Ar. Therefore the proton rich nuclei {sup 30}S and {sup 34}Ar show a 2{sup +} excitation of isoscalar character whereas the excitation of {sup 20}O is of isovector character. In order to perform a microscopic analysis of the data, we have developed a QRPA model, using three Skyrme interaction: SIII, SG2, SLy4. This model reproduces measured B(EL) values for the oxygen, sulfur and argon isotopic chains, whereas RPA calculations, which do not take pairing into account, underestimate these values. In the case of the QRPA model the energies of the first 2{sup +} state are overestimated by about 1 MeV, but the evolution along the isotopic chains is well reproduced. (M{sub n}/M{sub p})/(N/Z) ratios for the first 2{sup +} state deduced from the microscopic analysis using QRPA are 1.98 for {sup 20}O, 1.05 for {sup 30}S and 1.00 for {sup 34}Ar, in agreement with the conclusions of the phenomenological analysis. However important discrepancies are observed between the two types of analysis for other isotopes, in particular neutron rich argon and sulfur nuclei. (author)

  18. Experimental study of a separated jets burner: application to the natural gas-pure oxygen combustion; Etude experimentale du comportement de bruleurs a jets separes: application a la combustion gaz naturel-oxygene pur

    Energy Technology Data Exchange (ETDEWEB)

    Salentey, L.

    2002-04-15

    The evolution of pollution standards and the optimisation of furnaces performances require a development of new burner generation and also the improvement of combustion techniques. Actually, the use of oxy-combustion in separated jets burners offers interesting prospects for NO{sub x} emission reduction and on the modularity of flames properties (lift off, flame front topology, flame length). The complex geometry of those burners leads to several problems like the three-dimensional character of the flow, which may sometimes disturb the flame stability as flames are lifted above the burner. This experimental study deals with a simplified version of that kind of burner constituted with a central natural gas jet surrounded by two oxygen jets. Primary, the study of non-reactive jet was planned in order to understand dynamic and mixture phenomena involved between jets and to provide a database useful for the computer code validation. The reactive flow developed in a furnace, which simulates the real conditions, had been characterised. The studies of the dynamic field using Laser Doppler Velocimetry (LDV) and of the turbulent mixture by conditional Laser tomography were supplemented in combustion by the visualisation of the spontaneous emission of radical OH, in the initial and final zone of the oxy-flames, like by the measurement of pollutants like NO{sub x} and soot. The measurements carried out while varying speeds of injection as well as the gap between the jets made possible the highlight of the influence of these parameters upon the stabilisation of the oxy-flames as well as the modification of the topology and the characteristics of the flows. The comparison of the measurements made in non-reactive and reactive flow shows the influence of oxy-combustion on the dynamic and scalar development of the flow for this type of burners. (author)

  19. Experimental and numerical study of heat transfer in an annular gap without axial flow with a rotating inner cylinder; Etude experimentale et numerique des transferts de chaleur en espace annulaire sans debit axial et avec cylindre interieur tournant

    Energy Technology Data Exchange (ETDEWEB)

    Bouafia, M. [Cemif, Centre d`Etudes mecanique d`ile-de-France, 91 - Evry (France); Ziouchi, A. [IAP de Boumerdes (Algeria); Bertin, Y.; Saulnier, J.B. [Centre National de la Recherche Scientifique (CNRS), 86 - Poitiers (France). Laboratoire d`etudes thermiques, UMR 6608

    1999-07-01

    The convective heat transfer between the walls of an annular gap with a rotating inner cylinder are studied experimentally and numerically. Two geometrical configurations are analysed: the surfaces of the cylinders are either smooth, or the moving wall is smooth and the other is axially grooved. The experimental study allowed us to appreciate the increase of heat transfer in the presence of grooves for values of Taylor number up to 2.10{sup 7}. The study of the flow and of the heat transfer has also been conducted by numerical simulation by means of three-dimensional laminar model for the grooved gap, and of an axisymmetric model for the smooth gap; the comparison of numerical and experimental data have shown a good agreement of the Nusselt number for values of Taylor number up to 4.10{sup 5}. (authors) 16 refs.

  20. Experimental study of an oxygen-hydrogen diffusion flame laden with solid alumina particles; Etude experimentale d'une flamme de diffusion oxygene-hydrogene ensemencee en particules solides d'alumine

    Energy Technology Data Exchange (ETDEWEB)

    Labor, S.

    2003-07-15

    Monocrystalline sapphire microspheres are generated through the melting of alumina (AL{sub 2}O{sub 3}) particles in a flame. The alumina particles are injected in a very peculiar O{sub 2}/H{sub 2} confined diffusion flame as it is a downwards vertical flame having fuel in periphery of a central powdered oxygen jet. Quantitative measurements were carried out (ADL, PIV) and supplemented by a numerical study (N3S-Natur). (1) The laminar behavior of the isothermal conditions is kept through reactive flow. Therefore, particles will mainly collide due to speed gradients. (2) It has been shown that an axial particle will have a transit time int the high temperature zone very different to that of an off-line one. (3) The PIV date proved that the particle density was not homogeneous. (4) The hydrogen jet hardly influences the flame aerodynamic structure. Conversely, the central oxygen jet is at premium due to its effect on both the flame speed and temperature distribution. (author)

  1. Etude experimentale de l'effet de rochet de traction-torsion d'un acier inoxydable 17-12 Mo-SPH, de 20 A 650° C

    Science.gov (United States)

    Delobelle, P.

    1989-08-01

    Le but du presént article est 1'étude expérimentale du phénomèna de rochet 2D de traction-torsion, essai non proportionnel particulièrement riche en informations et très peu étudié. La séquence expérimentale consiste en l'application d'une faible contrainte secondaire de traction et en la superposition d'une déformation cyclique, d'amplitude maximale constante, pour une vitesse et une isotherme fixées. Nous avons étudie 1'ensemble des caractéristiques de ce chargement, à savoir, l'effet de la contrainte axiale σ zz, de l'amplitude de la déformation {Δɛ zθT}/{2}, de la vitesse de déformation ge zθT et de la température T. On identifie des mécanismes d'interaction dislocations-défauts ponctuels pour le domaine des températures intermédiaires. En conclusion, ce type d'essai réalise une synthèse des difficultés que l'on peut rencontrer lors de la modélisation, presque tous les effets (en dehors de l'anisotropie initiate) étant présents et intimement liés: comportement viscoplastique, effet de normalité, de mémoire évanescente de l'histoire antérieure, du temps, de la température, de la configuration des défauts ponctuels, de contrainte moyenne et enfin, à plus haute température, de précipitation à longue distance.

  2. Experimental study of a two-phase flow inside a pyrex channel using R-11 as refrigerant; Etude experimentale d'un ecoulement diphasique dans un canal en pyrex en utilisant le R-11 comme refrigerant

    Energy Technology Data Exchange (ETDEWEB)

    Bouaichaoui, Y.; Semine, M.; Belalouache, F. [Centre de Recherche Nucleaire de Birine/Comena, Djelfa (Algeria); Hanini, S. [Universite Yahia Fares de Medea, LBMPT (Algeria)

    2006-07-01

    This work deals with the experimental study of a two-phase flow inside a test loop, using R-11 as refrigerant. The test-loop is made of pyrex, allowing the visualization of the fluid structure changes during joule heating. Preliminary results have permitted to observe the boiling initiation phenomenon, which corresponds to the occurrence of the very first steam bubbles inside the flow, and the boiling crisis phenomenon which coincides with the formation of a steam coating around the heating element. The parameters controlling these phenomena have been measured and compared to the data available in the literature. (J.S.)

  3. Experimental study of the vaporization of a droplets injection in a fluidized gas-solid media; Etude experimentale de la vaporisation d'un jet de goutelettes au contact d'un milieu gaz-solide fluidise

    Energy Technology Data Exchange (ETDEWEB)

    Leclere, K.

    2002-09-01

    The quality of feedstock injection in the Fluid Catalytic Process (FCC) is essential to ensure a good vaporization. The vaporization should be fast so that the cracking reaction in the gaseous phase can happen within the short residence time in the riser (a few seconds). Vaporization is helped by a uniform injection of droplets as small as possible as well as a good mixing with the catalyst particles that represent the main heat source. Several models were developed to predict the droplet vaporization in a gas-solid media. However, no experimental validation exists for these models, whose predictions vary (from 1 to several hundreds of milliseconds). The objective of this study was to get a better understanding of the physical phenomena taking place during droplet vaporization. This was done in two steps. First, operating limits had to be defined to ensure an optimal vaporization and to avoid local saturation and agglomerate formation. These limits were precisely determined under laboratory conditions to validate a model that showed that agglomeration does not occur under industrial conditions. Then, a kinematic study of vaporization under operating conditions without agglomerate formation was performed. An original measurement technique was developed to get samples at very short times (tens of milliseconds). Experiments showed that heat transfer was not limiting and that mass transfer was the limiting process during vaporization. The developed model was thus based on mass transfer through a boundary layer. The validation of this model in a dense fluidized bed justified its application to operating conditions were the bed voidance is higher. A detailed study of operating parameters will help determine how to improve vaporization. (author)

  4. Bacterial Adhesion & Blocking Bacterial Adhesion

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk

    2008-01-01

    tract to the microbial flocs in waste water treatment facilities. Microbial biofilms may however also cause a wide range of industrial and medical problems, and have been implicated in a wide range of persistent infectious diseases, including implantassociated microbial infections. Bacterial adhesion...... is the first committing step in biofilm formation, and has therefore been intensely scrutinized. Much however, still remains elusive. Bacterial adhesion is a highly complex process, which is influenced by a variety of factors. In this thesis, a range of physico-chemical, molecular and environmental parameters......, which influence the transition from a planktonic lifestyle to a sessile lifestyle, have been studied. Protein conditioning film formation was found to influence bacterial adhesion and subsequent biofilm formation considerable, and an aqueous extract of fish muscle tissue was shown to significantly...

  5. Bacterial lipases

    NARCIS (Netherlands)

    Jaeger, Karl-Erich; Ransac, Stéphane; Dijkstra, Bauke W.; Colson, Charles; Heuvel, Margreet van; Misset, Onno

    1994-01-01

    Many different bacterial species produce lipases which hydrolyze esters of glycerol with preferably long-chain fatty acids. They act at the interface generated by a hydrophobic lipid substrate in a hydrophilic aqueous medium. A characteristic property of lipases is called interfacial activation, mea

  6. COMPLIANCE OF KÖHLER OP:33 NO I-II-III ETUDE BOOKS THAT ARE USED IN HIGH SCHOOLS OF FINE ARTS WITH FLUTE CONCERTOS

    Directory of Open Access Journals (Sweden)

    Yucan EKE

    2015-09-01

    Full Text Available This research is done for attesting the compliance of the etudes in German composer Ernesto Köhler’s op:33 no I-II-III books that are used in high schools of fine arts, with ability to play the flute concertos in high schools of fine arts 12 grade program, in terms of the knowledge – skills and musical functions they cover and also for contributing to learning by matching the etudes and works which are relevant. Etudes and the chosen concertos are analyzed and separated into templates in terms of melody, rhythm and tone for this research. Opinions are taken from the flute lesson instructors of various universities of Turkey to define the melody, technique and rhythm patterns. As a result of the analysis, Köhler op: 33, Book I, Etudes: 2,3,6,7,8,9,10,11,12; Köhler op: 33, Book II, Etudes:1,3,4,5,8,9,10,11; Köhler op: 33, Book III, Etudes: 1, 2, 4, 5, 6, 8; It is determined that the etudes given above in Köhler books are qualified enough to be preparative and instructive for the ability of playing the flute concertos. Some suggestions are given about which etude(s is instructive for which concerto and what kind of benefits could be gained, by this study. Based on the observed results, various suggestions are made about defining and studying the etudes which meet the technical, rhythmic and melodic features of the target concerto.

  7. Estadísticos poblacionales de Triatoma sordida Stäl 1859 (Hemiptera : Reduviidae en condiciones experimentales

    Directory of Open Access Journals (Sweden)

    Oscherov Elena B.

    1996-01-01

    Full Text Available Se realizó el seguimiento longitudinal de cuatro cohortes de 100 huevos cada una. Los insectos fueron criados a 28°C ± 3°C y 63 % ± 10% de humedad relativa, y alimentados cada siete días sobre gallina (Gallus domesticus, durante 40 min. Las cohortes fueron controladas una vez por semana. Se observó un valor constante de supervivencia en las cuatro cohortes, sin picos importantes. La expectativa de vida de los machos, en promedio, fue de 37,4 semanas y la de las hembras 36,8. El tiempo generacional demandó 61,7 semanas. La tasa reproductiva neta indica que esta población se incrementará 143,3 veces con cada generación. La tasa intrínseca de crecimiento natural fue de 0,082 por semana. El máximo valor reproductivo se verificó, en promedio, a la tercer semana del ingreso al estado adulto. La distribución estable de edades de T. sordida sería de 32% huevos, 26% ninfas de primer estadio, 19% ninfas de segundo estadio, 13% ninfas de tercer estadio, 6% ninfas de cuarto estadio, 3% ninfas de quinto estadio y 1% de adultos. Es la primera cita para Argentina sobre la tabla de vida de T. sordida. El análisis de estos parámetros permite considerar que esta especie se comporta como "K estratega", en condiciones experimentales.

  8. Estadísticos poblacionales de Triatoma sordida Stäl 1859 (Hemiptera : Reduviidae en condiciones experimentales

    Directory of Open Access Journals (Sweden)

    Elena B. Oscherov

    1996-10-01

    Full Text Available Se realizó el seguimiento longitudinal de cuatro cohortes de 100 huevos cada una. Los insectos fueron criados a 28°C ± 3°C y 63 % ± 10% de humedad relativa, y alimentados cada siete días sobre gallina (Gallus domesticus, durante 40 min. Las cohortes fueron controladas una vez por semana. Se observó un valor constante de supervivencia en las cuatro cohortes, sin picos importantes. La expectativa de vida de los machos, en promedio, fue de 37,4 semanas y la de las hembras 36,8. El tiempo generacional demandó 61,7 semanas. La tasa reproductiva neta indica que esta población se incrementará 143,3 veces con cada generación. La tasa intrínseca de crecimiento natural fue de 0,082 por semana. El máximo valor reproductivo se verificó, en promedio, a la tercer semana del ingreso al estado adulto. La distribución estable de edades de T. sordida sería de 32% huevos, 26% ninfas de primer estadio, 19% ninfas de segundo estadio, 13% ninfas de tercer estadio, 6% ninfas de cuarto estadio, 3% ninfas de quinto estadio y 1% de adultos. Es la primera cita para Argentina sobre la tabla de vida de T. sordida. El análisis de estos parámetros permite considerar que esta especie se comporta como "K estratega", en condiciones experimentales.

  9. Bacterial Ecology

    DEFF Research Database (Denmark)

    Fenchel, Tom

    2011-01-01

    Bacterial ecology is concerned with the interactions between bacteria and their biological and nonbiological environments and with the role of bacteria in biogeochemical element cycling. Many fundamental properties of bacteria are consequences of their small size. Thus, they can efficiently exploit...... biogeochemical processes are carried exclusively by bacteria. * Bacteria play an important role in all types of habitats including some that cannot support eukaryotic life....

  10. [Bacterial vaginosis].

    Science.gov (United States)

    Romero Herrero, Daniel; Andreu Domingo, Antonia

    2016-07-01

    Bacterial vaginosis (BV) is the main cause of vaginal dysbacteriosis in the women during the reproductive age. It is an entity in which many studies have focused for years and which is still open for discussion topics. This is due to the diversity of microorganisms that cause it and therefore, its difficult treatment. Bacterial vaginosis is probably the result of vaginal colonization by complex bacterial communities, many of them non-cultivable and with interdependent metabolism where anaerobic populations most likely play an important role in its pathogenesis. The main symptoms are an increase of vaginal discharge and the unpleasant smell of it. It can lead to serious consequences for women, such as an increased risk of contracting sexually transmitted infections including human immunodeficiency virus and upper genital tract and pregnancy complications. Gram stain is the gold standard for microbiological diagnosis of BV, but can also be diagnosed using the Amsel clinical criteria. It should not be considered a sexually transmitted disease but it is highly related to sex. Recurrence is the main problem of medical treatment. Apart from BV, there are other dysbacteriosis less characterized like aerobic vaginitis of which further studies are coming slowly but are achieving more attention and consensus among specialists. PMID:27474242

  11. Etude sur les tendons en materiaux composites et leur application aux ancrages postcontraints

    Science.gov (United States)

    Chennouf, Adil

    L'objectif general de la presente these est d'evaluer le comportement a l'arrachement et au fluage d'ancrages injectes constitues de tendons en materiaux composites afin d'etablir des recommandations plus appropriees et realistes pour le dimensionnement et la conception. Quatre types de tendons en materiaux composites, deux a base de fibres d'aramide et deux a base de fibres de carbone, ont ete utilises dans l'etude. Les travaux de recherche de cette these ont porte notamment sur: (I) Une caracterisation physique et mecanique des tendons en materiaux composites utilises dans l'etude. (II) Une etude en laboratoire sur les coulis de scellement. La premiere etape de cette etude a concerne le developpement d'un coulis de scellement performant adapte aux tendons en materiaux composites et a differentes situations d'injection. La seconde etape a traite des essais de caracterisations physique et mecanique du coulis de scellement developpe comparativement a trois coulis de scellement usuels d'un meme rapport E/L de 0,4. (III) Une etude sur des modeles reduits d'ancrages injectes. (IV) Une etude sur des modeles d'ancrages a grande echelle. La synthese de ces etudes a permis d'enoncer les principales conclusions suivantes: (1) Les valeurs moyennes des charges de rupture des tendons en materiaux composites ont ete de 1% a 29% superieures a celles specifiees par les manufacturiers. (2) L'etude sur les coulis de scellement a permis le developpement de coulis de ciment repondant aux criteres fixes, soient une grande stabilite, une bonne fluidite, une legere expansion et de bonnes caracteristiques mecaniques. (3) Les tendons en materiaux composites ont montre des contraintes d'adherence maximum superieures a celles des tendons en acier. (4) Le type de fibre, la configuration et le fini de surface des tendons en materiaux composites gouvernent leur resistance a l'adherence. (5) L'introduction de sable et d'autres ajouts comme les fines de silice et la poudre d'aluminium au coulis

  12. Cómo trabajar las ciencias experimentales a través del método Doman y las inteligencias múltiples

    OpenAIRE

    Ontoria González, Laura

    2015-01-01

    El proyecto que se presenta a continuación consiste en una propuesta didáctica innovadora relacionada con las ciencias experimentales en el aula de Infantil a través del método Doman y las Inteligencias Múltiples. El empleo de estas metodologías de manera conjunta se apoya y justifica de manera teórica y práctica. La propuesta didáctica se llevó a cabo en un centro escolar en el nivel de cuatro años, concretamente con veinticinco alumnos, con resultados muy positivos.

  13. Eficiencia estadística de diseños experimentales de bloques incompletos para el análisis de variables espacialmente autocorrelacionadas

    OpenAIRE

    Mata Pombo, Raúl de la; Zas Arregui, Rafael; Merlo, Esther

    2008-01-01

    Gran parte de los experimentos en campo de carácter ecológico evalúan variables espacialmente autocorrelacionadas, lo que supone una posible violación de los requisitos del análisis de variancia convencional. Para absorber parte de esta variación espacial se recurre a la instalación de dichos ensayos bajo diseños experimentales, tal como los de bloques completos al azar, los más comunes y sencillos, o los de bloques incompletos, con bloques de menor tamaño, más eficaces pero con mayor c...

  14. Modelización del sistema de almacenamietno de energía y de su regulador de un vehículo solar de fines experimentales

    OpenAIRE

    Mendoza Zaplana, Sergio

    2015-01-01

    En este proyecto, se pretende modelizar con el programa ‘Matlab-Simulink’ un sistema de acumulación y regulación para un vehículo solar de fines experimentales. Compuesto este por un motor de corriente continua de imanes permanentes de características similares a las que presenta el prototipo del vehículo Aníbal, desarrollado por el Departamento de Ingeniería Eléctrica de la Universidad Politécnica de Cartagena. Con el objetivo de modelizar un sistema de acumulación y regulación además de ave...

  15. Caracterización comparativa a la faena de cinco híbridos experimentales de pollo campero con diferente genotipo materno

    OpenAIRE

    Dottavio, Ana María; Advínculo, S. A.; Librera, J. E.; Romera, Bernardo Martín; Canet, Zulma E.; Di Masso, Ricardo

    2014-01-01

    Se evaluaron la proporción de pechuga, pata muslo y grasa abdominal y el rendimiento a la faena de machos pertenecientes a cinco grupos genéticos experimentales de pollos camperos. Los grupos provenían del cruzamiento entre gallos de la población sintética paterna AH’, mejorada por tasa de crecimiento y eficiencia alimenticia y gallinas de cinco poblaciones sintéticas maternas. Como grupo testigo se utilizaron machos contemporáneos de la versión tradicional de Campero INTA. Las aves producto ...

  16. El puzzle de grupos: una alternativa a la exposición magistral para el aprendizaje activo de técnicas experimentales con herbicidas

    OpenAIRE

    Brusco, Marta I.; Miguel A. Fernández; Zingaretti, Osvaldo; Sosa, J; García, Fernando D.

    2012-01-01

    Se presenta la implementación y evaluación de una experiencia educativa basada en la técnica del “puzzle de grupos”, como una alternativa a la exposición magistral. La finalidad de la actividad fue favorecer el aprendizaje activo, mediante la aplicación de contenidos conceptuales a una situación concreta, en sustitución de la recepción pasiva por parte de los estudiantes de información trasmitida por el docente. El tema fue “Técnicas experimentales con herbicidas”, dentro de un curso de Terap...

  17. THE INVESTIGATION OF ETUDES AND PIECES USED IN BEGINNING FLUTE EDUCATION IN MUSIC TEACHER EDUCATION DEPARTMENTS

    OpenAIRE

    UYAN, Zeynep Deniz

    2014-01-01

    In this paper, the investigation of the most common etudes-pieces used in the first year flute education from the angle of target and target behaviours was purposed. Interview, questionairre and literature review techniques were used to gather the information needed. Classifications were done, qualitative and quantitative tables were made and statistical frequencies-percentages were used. As a result of these studies, it was determined that there is not a common flute education programme in a...

  18. 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

  19. Programa de viviendas experimentales en Móstoles, Comunidad de Madrid. España. (Preámbulo

    Directory of Open Access Journals (Sweden)

    Abad Carrascosa, Manuel

    1990-04-01

    Full Text Available This program consists of a total of 102 houses. They are situated in one of the housing estates in the General Urbanization Plan of the Móstoles Town Council (Town on outskirts of Madrid. The development of the prototypes of three different types of housing is to be studied with the aim of studying the experimental results of each one: — Progressive housing. — Housing with passive solar energy — Housing constructed on a basis of a special system in series. The three have the common aim of achieving finanical saving, but by different means: initial investment, saving in energy expenditure, the constructive system. The group of houses is about to be delivered into the hands of its users. We regret the incompleteness of the Information due to the lack of the most important results; the derivatives of its use and development, and Information of a social, economic, cultural, etc., character.

    Esta actuación consta de un total de 102 viviendas. Se encuentran localizadas en uno de los polígonos del Plan General de Urbanismo del Ayuntamiento de Móstoles (Población del extrarradio de Madrid. Se plantea el estudio y desarrollo, por separado, de tres prototipos diferentes de vivienda con el fin de poder estudiar los resultados experimentales de cada uno: — Viviendas progresivas. — Viviendas con energía solar pasiva. — Viviendas construidas a base de un sistema especial en serie. Los tres plantean el ahorro económico como fin común, pero desde distintas bases de partida: la inversión inicial; el ahorro energético, y el sistema constructivo. El conjunto se encuentra a punto de ser entregado a sus usuarios. Lamentamos lo incompleto de la información debido a la falta de sus resultados más importantes: los derivados de su uso y desarrollo; sociales, económicos, culturales, etcétera.

  20. El AMMI y cluster en la selección de los mejores híbridos experimentales de maíz

    Directory of Open Access Journals (Sweden)

    Guillermo Casta\\u00F1\\u00F3n

    2000-01-01

    Full Text Available El AMMI y Cluster en la selección de los mejores híbridos experimentales de maiz. En un experimento de maíz repetido en cuatro ambientes, se aplicó el análisis de efectos principales aditivos e interacción multiplicativa (AMMI y el de taxonomía numérica o cluster, para estudiar si la estabilidad del rendimiento de grano (RG de los híbridos ensayados se asociaba con el agrupamiento de los híbridos hecho por el cluster. Las variables que tuvieron más peso en el agrupamiento fueron el RG, altura de la planta (AP,altura de mazorca ( AM y mazorca por planta (PRO, principalmente. De lo encontrado en este trabajo se puede establecer que el AMMI es efectivo en la estimación de la estabilidad de los híbridos experimentales evaluados y que junto con el cluster, pueden ser dos herramientas útiles para hacer una buena selección de material experimental con mayores posibilidades de éxito

  1. Bacterial Hydrodynamics

    Science.gov (United States)

    Lauga, Eric

    2016-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells, yet they represent the bulk of the world's biomass and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micrometer scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically complex environments. Using hydrodynamics as an organizing framework, I review the biomechanics of bacterial motility and look ahead to future challenges.

  2. Bacterial hydrodynamics

    CERN Document Server

    Lauga, Eric

    2015-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.

  3. Experimental techniques; Techniques experimentales

    Energy Technology Data Exchange (ETDEWEB)

    Roussel-Chomaz, P. [GANIL CNRS/IN2P3, CEA/DSM, 14 - Caen (France)

    2007-07-01

    This lecture presents the experimental techniques, developed in the last 10 or 15 years, in order to perform a new class of experiments with exotic nuclei, where the reactions induced by these nuclei allow to get information on their structure. A brief review of the secondary beams production methods will be given, with some examples of facilities in operation or under project. The important developments performed recently on cryogenic targets will be presented. The different detection systems will be reviewed, both the beam detectors before the targets, and the many kind of detectors necessary to detect all outgoing particles after the reaction: magnetic spectrometer for the heavy fragment, detection systems for the target recoil nucleus, {gamma} detectors. Finally, several typical examples of experiments will be detailed, in order to illustrate the use of each detector either alone, or in coincidence with others. (author)

  4. ENFERMEDAD DE HUNTINGTON: MODELOS EXPERIMENTALES Y PERSPECTIVAS TERAPÉUTICAS Huntington'disease: Experimentals Models and Therapeutic Perspectives

    Directory of Open Access Journals (Sweden)

    TERESA SERRANO SÁNCHEZ

    Full Text Available La enfermedad de Huntington (EH es un trastorno degenerativo de Weiss de origen hereditario. Hasta el momento no existe un tratamiento efectivo para la enfermedad que inexorablemente después de transcurridos 15 a 20 años, evoluciona hacia incapacidad total o muerte. En este trabajo se revisan las características clínicas y morfológicas de la EH y los modelos experimentales más utilizados para su estudio tomando como fuente, artículos indexados en la base de datos Medline publicados en los últimos 20 años. Se valoran las ventajas y desventajas de estos modelos y su perspectiva para el desarrollo de ensayos clínicos. El consenso de lo reportado plantea que de los modelos tóxicos, los inducidos por neurotoxinas tales como ácido quinolínico parecen ser los más adecuados para reproducir las características neuropatológicas, y por otro lado los modelos genéticos contribuyen con más evidencias al conocimiento del origen etiológico de la enfermedad. Numerosos tratamientos han sido aplicados en el manejo de las manifestaciones clínicas que aparecen en EH, sin poder detener o disminuir las afectaciones que derivan de la pérdida neuronal. La sintomatología clínica ha sido posible reproducirla, al menos en parte, en animales de experimentación lo que ha permitido realizar ensayos terapéuticos. Desde el punto de vista de tratamiento, lo que más promisorio parece ser, la terapia celular con células provenientes de diferentes fuentes y dentro de ellas las no neurales, que implican menor censura ética y mayor factibilidad de obtención para la aplicación en los enfermos. Por otro lado el desarrollo de la tecnología del ARN de interferencia, emerge como una herramienta terapéutica potencial para el tratamiento de EH, así como para responder interrogantes básicas relacionadas con el desarrollo de la enfermedad.Huntington'disease (HD is a degenerative dysfunction of hereditary origin. Up to date there is not, an effective treatment

  5. Some experiments on the high-low transition of quartz; Recherches experimentales sur une transformation du quartz

    Energy Technology Data Exchange (ETDEWEB)

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

    1959-12-15

    , nous avons rassemble un grand nombre de resultats numeriques relatifs aux proprietes elastiques, piezoelectriques et optiques du quartz. Certains ont ete collectes dans la litterature; d'autres ont ete obtenus par nous a l'aide de methodes experimentales que nous decrivons, de facon a pouvoir presenter un tableau complet de l'evolution de ces constantes dans un domaine de temperature entourant largement le point de transformation {alpha} - {beta} situe a 574 deg. C. De nouveaux phenomenes ont ete observes au cours de ces mesures. Dans la troisieme partie, nous montrons qu'une meme fonction de la temperature decrit l'evolution de la constante piezoelectrique et de la constante elastique qui s'annulent en phase {beta}. Une seule autre fonction suffit a decrire correctement l'evolution de toutes les autres constantes etudiees, depuis leur valeur en phase {alpha} jusqu'a leur valeur en phase {beta}. A l'aide d'hypotheses sur la nature de l'entropie de transformation, nous essayons enfin d'expliquer la forme de ces fonctions. (auteur)

  6. Contribution to thermodynamics and kinetics of argon, krypton and xenon at very low temperatures; Contribution a l'etude thermodynamique et cinetique de l'argon, du krypton et du xenon aux tres basses temperatures

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-07-01

    A critical analysis of the main theories of condensation, which are due to Zwanzig, Cabrera, Mc Caroll and Ehrlich, Wanlass, Armand, and Yu and Soo, is made. A condensation coefficient equal to unity is expected from these theories, except Armand and Yu and Soo, when the temperature of the gas impinging on its own solid phase is equal or less than 300 K. Using a resonating quartz microbalance the sensitivity of which is 10{sup -9} g. cm{sup 2} the experimental data agree with these theories when the temperature of the solid is less than 20 K. However the agreement must be interpreted for the more sophisticated theories of Armand and Yu and Soo. Regarding the sublimation of the rare gases one is faced with the theories of Salter, Eyring, Goodman and Armand. Within an order of magnitude the experimental data given here agree with the expected values. Moreover Armand theory is able to give the physical meaning of the observed results for argon sublimation from a krypton or a xenon crystalline substrate: localized modes of surface vibration occur. The relaxation time for the thermalization of the argon deposit is found greater than twelve hours at 25 K. (author) [French] Ce travail inclut l'etude critique des principales theories de la condensation dues a Zwanzig, Cabrera, Mc Caroll et Ehrlich, Wanlass, Armand, et Yu et Soo. Ces theories, sauf les deux dernieres, prevoient un coefficient de condensation egal a 1 lorsque le gaz incident sur son propre solide a une temperature inferieure ou egale a 300 K. Les mesures effectuees a l'aide d'une microbalance a quarz resonnant sensible a 10{sup -9} g. cm{sup 2} ont confirme ces theories dans le cas ou la temperature du solide est inferieure a 20 K. Cet accord doit cependant etre interprete pour les theories plus completes d'Armand d'une part, Yu et Soo d'autre part. Pour la sublimation des gaz rares on se trouve en presence des theories de Salter, Eyring, Goodman et Armand. Leurs previsions sont

  7. Experimental study of the test module of the electromagnetic end-cap calorimeter for the ATLAS experiment. Study of the spin correlation in the production of pairs tt-bar; Etude experimentale des performances du module 0 du calorimetre electromagnetique bouchon d'ATLAS. Etude de la correlation de spin dans la production des paires tt-bar au LHC

    Energy Technology Data Exchange (ETDEWEB)

    Hinz, L

    2001-06-01

    LHC, the future CERN proton collider, will start in 2006. It will be devoted to a better understanding of the Standard Model and new physics research. With a 10 {integral}b{sup -1} per year at low luminosity during the first three years, then 100 {integral}b{sup -1} per year, and energy of 14 TeV in the center of mass, the LHC is designed to discover the Standard or SUSY Higgs boson, or probe signature of new physics. ATLAS, one of the four experiments at the LHC, can study a large physics range, as Higgs boson, top and bottom, gauge bosons and new particles expected by SUSY model or other models beyond the Standard Model. The CPPM laboratory is responsible of a part of the electromagnetic end-cap calorimeter for the ATLAS experiment. In 1999, an ATLAS-like prototype of module was stacked in Marseille and intensively tested at CERN. Description of the calorimeter and a part of test-beam results are presented in this PhD manuscript. In parallel, a study about potentiality of the tt-bar spin correlation measurement was done. The high tt-bar statistic produced at the LHC allows to explore the quark top properties in details and being sensitive to new physics phenomena. Signatures of such physics can be extracted from tt-bar decay product angular distributions which are sensitive to tt-bar spin correlation. (authors)

  8. Experimental study and computerized simulation of the elements fixation in trace on mineral oxides. Contribution to the study of natural solids adsorption properties; Etude experimentale et modelisation de la fixation d`elements en trace sur des oxydes mineraux. Contribution a l`etude des proprietes adsorbantes des solides naturels

    Energy Technology Data Exchange (ETDEWEB)

    Marmier, N.

    1994-12-01

    The aim of this work is to identify some natural or synthetical materials allowing the nuclear wastes confinement in underground geological sites by adsorption of radioelements. The materials composition variety which can be used is very large it is then necessary to make use of models able to predict solid complexes behaviour towards the adsorption from known properties of parent constituents. This type of model still does not exist and its focusing requires the demonstration of mineral complexes parent constituents intrinsic properties additivity. The oxides as aluminium or silicon oxides being parent constituents, the author has demonstrated their properties additivity in an aluminium-silicon oxides physical mixture and in an aluminium silicate : the kaolinite. These surface properties have been determined for different quantities of aluminium and silicon oxides in a 0,1 M sodium nitrate. This study has been realized following the steps below : choice of a theoretical concept describing the adsorption adapted to the studied solid-solution system : the surface complexation model at constant capacitance; the focusing of a surface chemical and physical parameters determination method; the verification of these properties additivity on the aluminium-silicon oxides mixture and on the kaolinite. The studied cation for the adsorption on these materials is the ytterbium trivalent ion because the behaviour of the trivalent ions towards the adsorption is not very well known and because the lanthanides are considered as compounds similar to some fission products present in radioactive wastes. The method used for this work is applicable to all the other ions. (O.L.). 73 refs., 91 figs., 14 tabs.

  9. Study of current instabilities in high resistivity gallium arsenide; Etude des instabilites de courant dans l'arseniure de gallium de haute resistivite

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-07-01

    'arseniure de gallium de haute resistivite. Nous montrons que ces oscillations sont associees a la progression lente d'un domaine de fort champ electrique a travers tout l'echantillon. L'etude experimentale des proprietes de ces instabilites nous a permis de differencier ce phenomene de l'effet Gunn, des effets acoustoelectriques et des effets de contacts. Nous proposons pour rendre compte de ce type d'instabilites un mecanisme de piegeage differentiel sur des impuretes repulsives, capable de depeupler la bande de conduction a champ electrique eleve et de donner naissance a un domaine de champ intense. Le developpement qualitatif de ce modele nous permet de rendre compte de toutes les proprietes des cristaux d'arseniure de gallium de haute resistivite soumis a un champ electrique eleve: augmentation de la constante de Hall, existence d'un seuil de tension pour ces oscillations, formation de domaines de champ intense, lenteur de la propagation de ces domaines, enfin possibilite de renverser le sens de la propagation du domaine sans detruire celui-ci. Le developpement quantitatif du modele permet de calculer les differentes grandeurs caracteristiques de ces instabilites. La comparaison avec l'experience montre une bonne concordance, les legeres divergences provenant surtout de la meconnaissance actuelle des proprietes de transport dans l'arseniure de gallium aux champs electriques eleves. A la lumiere de ce modele, il apparait que le phenomene d'instabilite etudie peut se produire pour une gamme etendue de concentrations en centres repulsifs, et pour toute une gamme de resistivites. Ceci explique qu'il apparaisse systematiquement dans l'arseniure de gallium de moyenne et haute resistivite. (auteurs)

  10. Actividades experimentales para la enseñanza de las ciencias naturales en educación básica

    OpenAIRE

    Mayra García Ruiz; Raúl Calixto Flores

    1999-01-01

    Este trabajo plantea algunos de los problemas y mitos detectados en la enseñanza de las ciencias naturales (CN) en la educación básica en México. Asimismo, desarrolla una propuesta de estrategia de enseñanza de las CN, basada en la reflexión sobre el uso de las actividades experimentales en clase. Por último, describe la experiencia de la aplicación de una actividad experimental en un grupo de niños de educación primaria entre los 10 y 12 años de edad. Dicha actividad se adoptó después para l...

  11. Bio-metric study of pig karyotype; Etude biometrique du caryotype du porc

    Energy Technology Data Exchange (ETDEWEB)

    Haag, J.; Lacourly, N.; Nizza, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    This study has a twofold purpose, the former is to determine the swine karyotype as accurately as possible, the latter is to try and develop a method of automatic classification and to show its possibilities and limits. (authors) [French] Cette etude a un double objet: d'une part, de definir de la facon aussi precise que possible le caryotype du porc et d'autre part, de tenter une methode de classification automatique et d'en montrer les possibilites ainsi que les limites. (auteurs)

  12. Prevention of bacterial adhesion

    DEFF Research Database (Denmark)

    Klemm, Per; Vejborg, Rebecca Munk; Hancock, Viktoria

    2010-01-01

    Management of bacterial infections is becoming increasingly difficult due to the emergence and increasing prevalence of bacterial pathogens that are resistant to available antibiotics. Conventional antibiotics generally kill bacteria by interfering with vital cellular functions, an approach that ...

  13. ANÁLISIS DE ESTABILIDAD DE HÍBRIDOS EXPERIMENTALES DE MAÍZ CON ALTA CALIDAD DE PROTEÍNA EN COSTA RICA

    Directory of Open Access Journals (Sweden)

    Nevio Bonilla-Morales

    2012-01-01

    Full Text Available El objetivo de este trabajo fue determinar la adaptación de híbridos experimentales de maíz en Costa Rica. Se evaluaron veinticuatro híbridos experimentales de grano blanco en las condiciones agroecológicas de bosque tropical húmedo, durante el período 2009-2011, en las localidades de Concepción, Guagaral, Chánguena, El Águila, Veracruz, Los Chiles y Upala, con temperaturas entre 26 y 35°C y una precipitación entre los 2700-3200 mm, esto con el fin de obtener el rendimiento y respuesta a los principales factores abióticos y bióticos. Se empleó un diseño de alfa látice con tres repeticiones. Los híbridos fueron evaluados en dos ciclos de siembra por localidad y por año. Los resultados del análisis combinado indicaron diferencias significativas al 0,05 entre genotipos y el gráfico del AMMI-biplot evidenció que los materiales con mayor estabilidad fueron: CLQRCWQ121/CLQRCWQ122//CML491 (QPM; CML494/CML495 (Normal; (CLQRCWQ121/CLQRCWQ26//CML491 (QPM; (CLQRCWQ121/CML502//CML491 (QPM con rendimientos promedio de 9,3; 9,0; 8,7 y 8,8 t/ha, respectivamente. Las localidades donde se obtuvo mayor rendimiento fueron El Águila y Guagaral, 9,8 y 8,5 t/ha, respectivamente. En cuanto a la interacción de localidades y genotipos el AMMI biplot mostró que El Águila y Guagaral tuvieron condiciones agroclimáticas más favorables para la expresión del potencial de los híbridos evaluados. Por su parte, Veracruz y Concepción presentaron condiciones agroclimáticas menos favorables para el desempeño de los materiales. La interacción genotipo x ambiente tuvo un valor de 62,1% en la prueba de Gollob.

  14. Prevention of bacterial adhesion

    DEFF Research Database (Denmark)

    Klemm, Per; Vejborg, Rebecca Munk; Hancock, Viktoria

    2010-01-01

    that imposes selection pressure for resistant bacteria. New approaches are urgently needed. Targeting bacterial virulence functions directly is an attractive alternative. An obvious target is bacterial adhesion. Bacterial adhesion to surfaces is the first step in colonization, invasion, and biofilm formation....... As such, adhesion represents the Achilles heel of crucial pathogenic functions. It follows that interference with adhesion can reduce bacterial virulence. Here, we illustrate this important topic with examples of techniques being developed that can inhibit bacterial adhesion. Some of these will become...

  15. Nuevos datos experimentales sobre parámetros hidrogeológicos de la Cuenca de Madrid obtenidos a partir de muestras de sondeos

    Directory of Open Access Journals (Sweden)

    Villarroya Gil, F. I.

    1990-12-01

    Full Text Available A critical review of main hydrogeological parameters (porosity, permeability and specific storage coefficient of Madrid Basin Detrital Aquifer is done. For this study, data from the bibliography and new laboratory analysis of grain size distribution (26, dry density (26, specific weight (26, permeability (20 and consolidation test (6 samples from three boreholes are used. The results are quite similar to those than already exist in the literature, although the porosity obtained is higher.Se hace una revisión crítica de los principales parámetros hidrogeológicos (porosidad, permeabilidad y coeficiente de almacenamiento específico, del Terciario detrítico de la cuenca de Madrid. Para este estudio además de los datos existentes en la bibliografía, se han realizado una serie de análisis de laboratorio desarrollados en las instalaciones del SGOP obteniendo, de esta manera, nuevos valores experimentales de los citados parámetros, mediante ensayos granulométricos (26, de densidad seca (26, de peso específico (26, de permeabilidad (20 y ensayos edométricos (6. Las muestras proceden de tres sondeos realizados en el casco urbano de Madrid por el SGOP (MOPU. Los resultados obtenidos coinciden, en gran medida, con los existentes en la bibliografía, si bien, los valores de porosidad total son marcadamente más altos.

  16. Análisis conductual aplicado en neuropsicología: fundamentos teóricos, experimentales y empíricos.

    Directory of Open Access Journals (Sweden)

    José Alonso Aguilar-Valera

    2016-01-01

    Full Text Available El presente artículo presenta una revisión teórica donde se expone la importancia que tienen los principios y técnicas conductuales dentro del ámbito de la rehabilitación neuropsicológica. En la intervención clínica con pacientes víctimas de disfunción, daño o deterioro neurológico, donde las consecuencias directas sobre el comportamiento son significativas, el uso de las estrategias provenientes de las técnicas de modificación de conducta (conductuales y/o conductual-cognitivas son importantes para el tratamiento de los diversos síndromes neuroconductuales, estando dentro de las competencias del especialista en esta área aplicada de las neurociencias. Además de describirse tanto aspectos teóricos como experimentales de principal relevancia para estos fines, también se mencionarán algunos estudios empíricos llevados a cabo, bajo una metodología de caso único, para una mejor comprensión sobre la utilidad aplicativa de los principios conductuales en el ámbito de la neuropsicología clínica.

  17. Ensayo de abrasión de Darmstadt para tuberías de alcantarillado pluvial: revisión de condiciones experimentales

    Directory of Open Access Journals (Sweden)

    Andrés Eduardo Torres Abello

    2009-01-01

    Full Text Available El ensayo de abrasión de Darmstadt se ha utilizado principalmente para comparar la abrasión de diferentes tipos de tuberías. Sin embargo, no se han evidenciado claramente aún relaciones entre los resultados obtenidos mediante dicho ensayo y variables como la vida útil de los materiales o la composición del agua transportada. A partir de un montaje experimental, similar al de Darmstadt, se ensayaron tubos de concreto sin revestimiento, haciendo variar las condiciones experimentales. Se observó que el factor que más influencia tiene sobre los resultados obtenidos es la dureza del material abrasivo, seguido por la concentración en DBO5. Los resultados de abrasión obtenidos en laboratorio se compararon con estimaciones de abrasión sobre tubos de concreto en operación con el objetivo de observar una posible relación entre el tiempo del ensayo Darmstadt y el tiempo de servicio de las tuberías de alcantarillado.

  18. Patrones iniciales de sucesión en claros experimentales de plantaciones de Pinus patula en el Embalse de Chisacá, Usme, Cundinamarca (Colombia

    Directory of Open Access Journals (Sweden)

    Vargas Ríos Orlando

    2006-06-01

    Full Text Available Se presenta un estudio que determina el efecto de la creación de claros experimentales con diferentes densidades sobre los patrones iniciales de sucesión dentro de plantaciones de Pinus patula. Adicionalmente, se evaluó el efecto de la remoción de acículas del suelo. Antes del establecimiento de los claros ya se encontraban en las parcelas la mayoría de las especies (30, pero en muy baja proporción; luego del aclareo, se registraron
    25 especies determinadas entre plantas vasculares (20 y no vasculares (5; 13 de éstas resultaron de mayor relevancia debido a su mayor cobertura en las parcelas. Se pudo establecer que la apertura de claros, además de la mayor disponibilidad de luz solar, permite una mayor entrada de agua, con lo cual se estimula la germinación, crecimiento y establecimiento de individuos relativamente rápido. Se determinó que existe un banco de semillas dentro de las acículas del suelo. Es importante continuar con el monitoreo de las parcelas para un mejor entendimiento del fenómeno sucesional que ocurre.

  19. Loxoscelismo en Chile: estudios epidemiológicos, clínicos y experimentales Loxoscelism in Chile: epidemiological, clinical and experimental studies

    Directory of Open Access Journals (Sweden)

    Hugo Schenone

    1989-12-01

    Full Text Available Se presenta un enfoque panorámico de estudios epidemiológicos, clínicos y experimentales referentes a Loxosceles laeta y loxoscelismo efectuados en 1955-1988 en Santiago, Chile. Se estudiaron 216 casos de loxoscelismo. Los hechos más relevantes fueron: 52,8% correspondió a mujeres; edad entre 7 meses y 78 años; 84,3% fué loxoscelismo cutáneo (LO y 15,7% loxoscelismo cutáneo-visceral (LCV; 73,6% sucedió en época calurosa; en 86,6% el accidente ocurrió en la vivienda, especialmente en dormitorios, mientras la persona dormía o se vestía. La araña fué vista en 60,2% de los casos e identificada en laboratorio como L. laeta en 17,7% (10,6% de los 216 casos. Los sitios más frecuen temente afectados fueron las extremidades con 67,6%, lancetazo urente fué el síntoma inicial más frecuente. Dolor, edema y placa livedoide, la cual posteriormente se transformaría en escara necrótica, fueron las manifestaciones locales predominantes. En LCV hematuria y hemoglobinuria fueron constantes, ictericia, fiebre y compromiso de conciencia se presentaron en la mayoría de los casos. Tratamiento: LC con antihistamínicos o corticoides inyectables, LCV con corti-coides inyectables. La condición de los pacientes en el último control fué: curación completa en 75,5%, curación con secuela cicatrizal en 8,3%, muerte en 3,7% (todos con LCV y abandono en 12,5%. Adicionalmente, se ha efectuado una serie de estudios experimentales, tanto in vivo como in vitro para esclarecer aspectos básicos sobre el veneno de L. laeta y el tratamiento del loxoscelismo.A panoramic sight of epidemiological, clinical and experimental studies, referring to Loxosceles laeta and loxoscelism, carried out in 1955-1988, in Santiago, Chile is presented. Two-hundred and sixteen cases of loxosce lism were studied. The most relevant features were: 84.3% corresponded to cutaneous loxosce lism (CD and 15.7% to viscerocutaneous loxos celism (VCD; 73.6% ocurred in hot season; in 86

  20. Vimentin in Bacterial Infections

    Directory of Open Access Journals (Sweden)

    Tim N. Mak

    2016-04-01

    Full Text Available Despite well-studied bacterial strategies to target actin to subvert the host cell cytoskeleton, thus promoting bacterial survival, replication, and dissemination, relatively little is known about the bacterial interaction with other components of the host cell cytoskeleton, including intermediate filaments (IFs. IFs have not only roles in maintaining the structural integrity of the cell, but they are also involved in many cellular processes including cell adhesion, immune signaling, and autophagy, processes that are important in the context of bacterial infections. Here, we summarize the knowledge about the role of IFs in bacterial infections, focusing on the type III IF protein vimentin. Recent studies have revealed the involvement of vimentin in host cell defenses, acting as ligand for several pattern recognition receptors of the innate immune system. Two main aspects of bacteria-vimentin interactions are presented in this review: the role of vimentin in pathogen-binding on the cell surface and subsequent bacterial invasion and the interaction of cytosolic vimentin and intracellular pathogens with regards to innate immune signaling. Mechanistic insight is presented involving distinct bacterial virulence factors that target vimentin to subvert its function in order to change the host cell fate in the course of a bacterial infection.

  1. Investigation experimentale de l'ecoulement et des performances thermiques du nanofluide eau-oxyde de cuivre dans un Micro-Canal Chauffe

    Science.gov (United States)

    Rimbault, Benjamin

    Cette these de maitrise presentee par articles visait a etudier le comportement hydraulique et thermique d'un ecoulement de nanofluides en micro-canal chauffe. Nous avons etudie premierement de l'eau distillee, ensuite des melanges de particules d'oxyde de cuivre (taille 29nm) avec de l'eau distillee en concentrations particulaires volumiques 4.5%, 1.03%, et 0.24% (CuO-H2O). L'ecoulement force des differents fluides a ete realise au moyen de pompes a engrenages au sein d'un circuit ferme, comprenant un micro-canal a section rectangulaire (e=1.116mm,1=25.229mm) chauffe sur deux faces paralleles via des cartouches electriques, deux echangeurs de chaleurs en serie, ainsi qu'un debitmetre magnetique. A notre connaissance peu d'etudes sur l'ecoulement de nanofluides d'oxyde de cuivre-eau en micro-canal rectangulaire chauffe sont disponibles dans la litterature, cette recherche sert de contribution. Premierement, une validation avec la litterature a ete effectuee pour le cas d'un ecoulement d'eau entre plaques planes paralleles chauffees. Des essais hydrauliques ont ete realises pour une gamme du nombre de Reynolds allant jusqu'a Re=5000 a temperature constante. Par la suite des essais thermiques jusqu'a Re=2500 ont consiste en une elevation de temperature fixe (20.5°C a 30.5°C) a travers la longueur du micro-canal sous un regime stationnaire. Les resultats ont demontre une augmentation de la perte de pression et du coefficient de frottement des nanofluides sur l'eau pour un meme debit. Une telle augmentation de perte de pression etait de +70%, +25%, et +0 a 30% respectivement pour les concentrations 4.50%, 1.03%, et 0.24%. Concernant la transition laminaire a turbulent les comportements semblaient indiquer une valeur critique semblable entre l'eau et les differentes concentrations avec et sans chauffage a un nombre de Reynolds critique Rem 1000. Nous avons observe une legere augmentation du coefficient de convection thermique avec le debit massique pour les faibles

  2. La Actividad metacognitiva como desencadenante de procesos autorreguladores en las concepciones y prácticas de enseñanza de los profesores de ciencias experimentales una propuesta de formación del profesorado /

    OpenAIRE

    Lucio Gil, Rafael

    2004-01-01

    Consultable des del TDX Títol obtingut de la portada digitalitzada Las reformas educativas y los enfoques de la formación del profesorado de ciencias experimentales han mostrado tener poca eficacia en Nicaragua, por cuanto se traducen en cambios formales y no en cambios de concepciones y prácticas. Esta realidad se traduce en modelos de formación del profesorado con enfoque técnico que no favorecen la reflexión y autonomía docentes. Por esta razón el objetivo de este trabajo es elaborar...

  3. La actividad metacognitiva como desencadenante de procesos autorreguladores en las concepciones y prácticas de enseñanza de los profesores de ciencias experimentales. Una propuesta de Formación

    OpenAIRE

    Lucio Gil, Rafael

    2001-01-01

    Las reformas educativas y los enfoques de la formación del profesorado de ciencias experimentales han mostrado tener poca eficacia en Nicaragua, por cuanto se traducen en cambios formales y no en cambios de concepciones y prácticas. Esta realidad se traduce en modelos de formación del profesorado con enfoque técnico que no favorecen la reflexión y autonomía docentes.Por esta razón el objetivo de este trabajo es elaborar y poner a prueba una propuesta de formación docente con un grupo de cuatr...

  4. Interfering with bacterial gossip

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Tolker-Nielsen, Tim; Givskov, Michael

    2011-01-01

    defense. Antibiotics exhibit a rather limited effect on biofilms. Furthermore, antibiotics have an ‘inherent obsolescence’ because they select for development of resistance. Bacterial infections with origin in bacterial biofilms have become a serious threat in developed countries. Pseudomonas aeruginosa...... that appropriately target bacteria in their relevant habitat with the aim of mitigating their destructive impact on patients. In this review we describe molecular mechanisms involved in “bacterial gossip” (more scientifically referred to as quorum sensing (QS) and c-di-GMP signaling), virulence, biofilm formation...

  5. Pharmacological study of radioactive-gold colloid transport by blood and by serous exudate; Contribution a l'etude pharmacologique du transport des colloides d'or radioactif par le sang et les exsudats sereux

    Energy Technology Data Exchange (ETDEWEB)

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

    1966-06-01

    substances et particulierement dans le transport de l'or colloidal radioactif. Les fractions sanguines qui peuvent participer au transport de l'or colloidal sont les hematies, les leucocytes et elements histiocytaires, et le plasma. La repartition de la radioactivite dans ces elements est precisee en pratiquant des autoradiographies de coupes de culots de sang centrifuge et congele apres incubation avec de l'or colloidal. Cette etude montre l'importance du plasma dans le transport des particules radioactives. Nous avons alors recherche une fixation eventuelle de l'or colloidal 198 sur les diverses proteines seriques en appliquant certaines methodes de separation a savoir une filtration-exclusion sur colonne de gel de Sephadex G-200 et un fractionnement electrophoretique sur papier et sur acetate de cellulose gelatineux (cellogel). Nous avons etudie la liaison ''in vitro'' et ''in vivo'' des particules colloidales d'or 198 d'abord avec les proteines seriques de sujets sains puis avec les proteines des liquides d'epanchement d'origine pathologique, chez l'homme, ou du a une inflammation experimentale a la carragenine chez le rat. Les particules d'or colloidal 198 de 30 m{mu} (S-2) sont liees dans une certaine mesure aux {alpha}2 globulines sanguines ou ascitiques, celles de 5 m{mu} (S-6) sont liees aux {alpha}1 globulines de meme que les grains contenus dans l'or polydisperse. Cette liaison semble intervenir grace a la couche protectrice de macromolecules constituees par la gelatine. Seules les caracteristiques physicochimiques de grains colloidaux peuvent expliquer leur difference de localisation sur l'electrophoregramme. L'or sous forme ionique, par contre, est combine, aux seules albumines si la quantite de metal presente ne depasse pas une certaine limite. (auteur)

  6. Contribution to the study, by magnetic resonance, of the properties of heavily doped silicon at low temperature; Contribution a l'etude par resonance magnetique des proprietes a basse temperature du silicium fortement dope

    Energy Technology Data Exchange (ETDEWEB)

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

    1965-10-01

    nature dipolaire avec ces memes centres paramagnetiques. On propose un mecanisme base sur l'existence des paires ionisees pour la relaxation electronique des donneurs dependant de leur concentration qui est mise en evidence par une etude experimentale dans la gamme 10{sup 16}-10{sup 17} impuretes par cm{sup 3}. Pour des densites croissantes d'impuretes, la delocalisation des electrons s'accentue. Avec 2,5 X 10{sup 18} P/cm{sup 3} le couplage de nature hyperfine avec les electrons est responsable de la relaxation nucleaire {sup 29}Si. On obtient que la densite electronique presente encore dans le domaine metallique un maximum important au voisinage des impuretes. Une estimation de la largeur de la bande d'impuretes (19 deg. K) est obtenue d'apres la mesure de la susceptibilite paramagnetique electronique. (auteur)

  7. Bacterial Wound Culture

    Science.gov (United States)

    ... Home Visit Global Sites Search Help? Bacterial Wound Culture Share this page: Was this page helpful? Also known as: Aerobic Wound Culture; Anaerobic Wound Culture Formal name: Culture, wound Related ...

  8. Bacterial surface adaptation

    Science.gov (United States)

    Utada, Andrew

    2014-03-01

    Biofilms are structured multi-cellular communities that are fundamental to the biology and ecology of bacteria. Parasitic bacterial biofilms can cause lethal infections and biofouling, but commensal bacterial biofilms, such as those found in the gut, can break down otherwise indigestible plant polysaccharides and allow us to enjoy vegetables. The first step in biofilm formation, adaptation to life on a surface, requires a working knowledge of low Reynolds number fluid physics, and the coordination of biochemical signaling, polysaccharide production, and molecular motility motors. These crucial early stages of biofilm formation are at present poorly understood. By adapting methods from soft matter physics, we dissect bacterial social behavior at the single cell level for several prototypical bacterial species, including Pseudomonas aeruginosa and Vibrio cholerae.

  9. Bacterial intermediate filaments

    DEFF Research Database (Denmark)

    Charbon, Godefroid; Cabeen, M.; Jacobs-Wagner, C.

    2009-01-01

    Crescentin, which is the founding member of a rapidly growing family of bacterial cytoskeletal proteins, was previously proposed to resemble eukaryotic intermediate filament (IF) proteins based on structural prediction and in vitro polymerization properties. Here, we demonstrate that crescentin...

  10. Bacterial Meningitis in Infants

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2004-04-01

    Full Text Available A retrospective study of 80 infantile patients (ages 30-365 days; 47 male, 33 female with culture-proven bacterial meningitis seen over a 16 year period (1986-2001 is reported from Taiwan.

  11. ETUDE DE L’ETAT NUTRITIONNEL ET SANITAIRE DE QUELQUES VARIETES DU GENRE PRUNUS DANS LA WILAYA DE TLEMCEN

    OpenAIRE

    HADJ ABDELKADER, Fatima Zohra

    2014-01-01

    ETUDE DE L’ETAT NUTRITIONNEL ET SANITAIRE DE QUELQUES VARIETES DU GENRE PRUNUS DANS LA WILAYA DE TLEMCEN La présente expérimentation s'inscrit dans le cadre d'une recherche sur la nutrition minérale et l’état sanitaire de quelques espèces du genre Prunus en l’occurrence le merisier (Prunus avium) et Sainte Lucie (Prunus mahaleb) avec quelques cultivars tels que Gaouar et Bigarreau Noir. Ce travail est basé essentiellement sur l'analyse physicochimique de l’eau et du sol ainsi que l'anal...

  12. Coeficientes de digestibilidad total y de proteínas en alimentos experimentales para juveniles de Oplegnathus insignis (Kner, 1867 (Perciformes, Oplegnathidae

    Directory of Open Access Journals (Sweden)

    Avelino Muñoz

    2015-05-01

    Full Text Available Los alimentos para peces están formulados con diversos ingredientes, donde la harina de pescado es la principal fuente de proteína. Sin embargo, este insumo tiene un alto costo que lleva a la necesidad de evaluar nuevas fuentes de proteínas y probarlas en especies marinas. Oplegnathus insignis (San Pedro, Pacific beakfish es una especie omnívora en su etapa intermareal y carnívora en su etapa submareal, que ha sido cultivada de manera experimental, siendo necesario incorporar dietas formuladas. Este estudio reporta la experiencia en alimentación y nutrición, de juveniles de O. insignis alimentados con dietas formuladas con distintas fuentes de proteína. Se efectuó una experiencia con juveniles de O. insignis provenientes de un cultivo experimental. Se formularon cuatro alimentos, uno en base de harina de pescado (referencia y tres modificando la fuente de proteína del alimento de referencia, intercambiando un 30% de harina de pescado, por harina de soya, harina de moluscos y harina de quinoa. Se experimentó con 180 ind de 295,6 g y de 450 días post-eclosión, distribuidos en 12 estanques rectangulares de 1,6 m³. La alimentación fue a saciedad. Se efectuaron análisis próximales de los alimentos experimentales de las heces colectadas. Se determinó los coeficientes de digestibilidad total y proteína. El alimento con mayor contenido de proteína fue el que contenía harina de moluscos. El mayor coeficiente de digestibilidad total lo tienen los alimentos con harina de pescado (68,0% y harina de moluscos (67,1%, mientras que en los alimentos en base a harinas vegetales, la digestibilidad total para la harina de soya fue de 62,7% y para harina de quinoa de 64,1%. Estos resultados indican que es factible reemplazar un 30% de la harina de pescado por harinas de origen vegetal.

  13. Etude de l'affaiblissement du comportement mecanique du pergelisol du au rechauffement climatique

    Science.gov (United States)

    Buteau, Sylvie

    Le rechauffement climatique predit pour les prochaines decennies, aura des impacts majeurs sur le pergelisol qui sont tres peu documentes pour l'instant. La presente etude a pour but d'evaluer ces impacts sur les proprietes mecaniques du pergelisol et sa stabilite a long terme. Une nouvelle technique d'essai de penetration au cone a taux de deformation controle, a ete developpee pour caracteriser en place le pergelisol. Ces essais geotechniques et la mesure de differentes proprietes physiques ont ete effectues sur une butte de pergelisol au cours du printemps 2000. Le developpement et l'utilisation d'un modele geothermique 1D tenant compte de la thermodependance du comportement mecanique ont permis d'evaluer que les etendues de pergelisol chaud deviendraient instables a la suite d'un rechauffement de l'ordre de 5°C sur cent ans. En effet, la resistance mecanique du pergelisol diminuera alors rapidement jusqu'a 11,6 MPa, ce qui correspond a une perte relative de 98% de la resistance par rapport a un scenario sans rechauffement.

  14. Preparation and study of dialkyl nitroxide radicals; Preparation et etude de radicaux nitroxydes diacyles

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-07-01

    These radicals are obtained by oxidation of N-hydroxy-imides with lead tetracetate or p-nitro-perbenzoic acid. These imides are prepared by heating dicarboxylic acids anhydrides with benzyloxy-amine followed by catalytic hydrogenation of N-benzyloxy-imides so obtained. Two series of radicals have mainly been studied, the first concerning five-membered cyclic imides, the second six-membered cyclic imides, these molecules having methyls substituents or no on the carbon ring. N. M. R. spectra of some O-benzyl-imides have been analysed. These different results have made it possible to study the conformation and stereochemistry of these imides. (author) [French] Ces radicaux sont obtenus par oxydation d'imides N-hydroxyles par le tetracetate de plomb ou l'acide p-nitroperbenzoique; ces imides sont prepares par chauffage d'anhydrides de diacides en presence de benzyloxyamine suivie d'une hydrogenation catalytique des N-benzyloxyimides ainsi obtenus. Deux series de radicaux ont principalement ete etudies: la premiere relative a des imides cycliques a cinq chainons, la seconde a des imides cycliques a six chainons, ces molecules ayant des substituants methyles ou non sur la chaine carbonee. Les derives O-benzyles de quelques-uns de ces imides ont ete analyses en R. M. N. Ces differents resultats ont permis une etude de la conformation et de la stereochimie de ces imides. (auteur)

  15. The bacterial lipocalins.

    Science.gov (United States)

    Bishop, R E

    2000-10-18

    The lipocalins were once regarded as a eukaryotic protein family, but new members have been recently discovered in bacteria. The first bacterial lipocalin (Blc) was identified in Escherichia coli as an outer membrane lipoprotein expressed under conditions of environmental stress. Blc is distinguished from most lipocalins by the absence of intramolecular disulfide bonds, but the presence of a membrane anchor is shared with two of its closest homologues, apolipoprotein D and lazarillo. Several common features of the membrane-anchored lipocalins suggest that each may play an important role in membrane biogenesis and repair. Additionally, Blc proteins are implicated in the dissemination of antibiotic resistance genes and in the activation of immunity. Recent genome sequencing efforts reveal the existence of at least 20 bacterial lipocalins. The lipocalins appear to have originated in Gram-negative bacteria and were probably transferred horizontally to eukaryotes from the endosymbiotic alpha-proteobacterial ancestor of the mitochondrion. The genome sequences also reveal that some bacterial lipocalins exhibit disulfide bonds and alternative modes of subcellular localization, which include targeting to the periplasmic space, the cytoplasmic membrane, and the cytosol. The relationships between bacterial lipocalin structure and function further illuminate the common biochemistry of bacterial and eukaryotic cells.

  16. Diagnosis of bacterial vaginosis

    Directory of Open Access Journals (Sweden)

    Đukić Slobodanka

    2013-01-01

    Full Text Available Bacterial vaginosis is a common, complex clinical syndrome characterized by alterations in the normal vaginal flora. When symptomatic, it is associated with a malodorous vaginal discharge and on occasion vaginal burning or itching. Under normal conditions, lactobacilli constitute 95% of the bacteria in the vagina. Bacterial vaginosis is associated with severe reduction or absence of the normal H2O2­producing lactobacilli and overgrowth of anaerobic bacteria and Gardnerella vaginalis, Atopobium vaginae, Mycoplasma hominis and Mobiluncus species. Most types of infectious disease are diagnosed by culture, by isolating an antigen or RNA/DNA from the microbe, or by serodiagnosis to determine the presence of antibodies to the microbe. Therefore, demonstration of the presence of an infectious agent is often a necessary criterion for the diagnosis of the disease. This is not the case for bacterial vaginosis, since the ultimate cause of the disease is not yet known. There are a variety of methods for the diagnosis of bacterial vaginosis but no method can at present be regarded as the best. Diagnosing bacterial vaginosis has long been based on the clinical criteria of Amsel, whereby three of four defined criteria must be satisfied. Nugent’s scoring system has been further developed and includes validation of the categories of observable bacteria structures. Up­to­date molecular tests are introduced, and better understanding of vaginal microbiome, a clear definition for bacterial vaginosis, and short­term and long­term fluctuations in vaginal microflora will help to better define molecular tests within the broader clinical context.

  17. Bacterial glycosyltransferase toxins.

    Science.gov (United States)

    Jank, Thomas; Belyi, Yury; Aktories, Klaus

    2015-12-01

    Mono-glycosylation of host proteins is a common mechanism by which bacterial protein toxins manipulate cellular functions of eukaryotic target host cells. Prototypic for this group of glycosyltransferase toxins are Clostridium difficile toxins A and B, which modify guanine nucleotide-binding proteins of the Rho family. However, toxin-induced glycosylation is not restricted to the Clostridia. Various types of bacterial pathogens including Escherichia coli, Yersinia, Photorhabdus and Legionella species produce glycosyltransferase toxins. Recent studies discovered novel unexpected variations in host protein targets and amino acid acceptors of toxin-catalysed glycosylation. These findings open new perspectives in toxin as well as in carbohydrate research.

  18. Estrategias experimentales para el estudio de las propiedades de la proteína Core del virus de la hepatitis C

    Directory of Open Access Journals (Sweden)

    Gonzálo Correa Arango

    2004-03-01

    Full Text Available

    El modelo de infección por el Virus de la Hepatitis C (VHC se ha convertido en el tópico de interés de numerosos equipos de investigación, considerando el alto porcentaje de infección persistente asociada al VHC. En efecto, del 50 al 80% de los pacientes con infección por el VHC, desarrollan infección persistente, que puede evolucionar a cirrosis y carcinoma hepatocelular (HCC. Este modelo presenta dos obstáculos mayores para su estudio: la ausencia de un sistema eficiente de replicación viral in vitro y el limitado número de modelos animales.

    La proteína Core del VHC, además de ser la unidad estructural de la cápside viral, parece estar implicada en las estrategias virales de persistencia y oncogénesis; nuestro grupo ha planteado estrategias experimentales para estudiar algunas de sus propiedades, tales como su capacidad inmunonoduladora en cultivos de cálulas dendríticas humanas, su capacidad de modificar la expresión del ARNm en células HepG2 con expresión transitoria de Core y la presencia de esta proteína en tejido hepático proveniente de pacientes con diagnóstico de HCC; dichas estrategias experimentales han sido:

    Producción de la proteína Core del VHC en el sistema baculovirus y purificación en condiciones nativas para su evaluación en ensayos biológicos.

    Expresión transitoria de la proteína Core del VHC en la línea celular HepG2, mediante transducción con partículas recombinantes del Virus Semliki Forest (SFV.

    Estudio de la expresión de p53

  19. Seizures Complicating Bacterial Meningitis

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2004-09-01

    Full Text Available The clinical data of 116 patients, 1 month to <5 years of age, admitted for bacterial meningitis, and grouped according to those with and without seizures during hospitalization, were compared in a study at Buddhist Dalin Tzu Chi General Hospital, Chang Gung Memorial Hospital and other centers in Taiwan.

  20. Bacterial extracellular lignin peroxidase

    Science.gov (United States)

    Crawford, Donald L.; Ramachandra, Muralidhara

    1993-01-01

    A newly discovered lignin peroxidase enzyme is provided. The enzyme is obtained from a bacterial source and is capable of degrading the lignin portion of lignocellulose in the presence of hydrogen peroxide. The enzyme is extracellular, oxidative, inducible by lignin, larch wood xylan, or related substrates and capable of attacking certain lignin substructure chemical bonds that are not degradable by fungal lignin peroxidases.

  1. Bacterial Skin Infections

    Science.gov (United States)

    ... or scraped, the injury should be washed with soap and water and covered with a sterile bandage. Petrolatum may be applied to open areas to keep the tissue moist and to try to prevent bacterial invasion. Doctors recommend that people do not use ...

  2. Vimentin in Bacterial Infections

    DEFF Research Database (Denmark)

    Mak, Tim N; Brüggemann, Holger

    2016-01-01

    filaments (IFs). IFs have not only roles in maintaining the structural integrity of the cell, but they are also involved in many cellular processes including cell adhesion, immune signaling, and autophagy, processes that are important in the context of bacterial infections. Here, we summarize the knowledge...

  3. Bacterial microflora of nectarines

    Science.gov (United States)

    Microflora of fruit surfaces has been the best source of antagonists against fungi causing postharvest decays of fruit. However, there is little information on microflora colonizing surfaces of fruits other than grapes, apples, and citrus fruit. We characterized bacterial microflora on nectarine f...

  4. Modeling intraocular bacterial infections.

    Science.gov (United States)

    Astley, Roger A; Coburn, Phillip S; Parkunan, Salai Madhumathi; Callegan, Michelle C

    2016-09-01

    Bacterial endophthalmitis is an infection and inflammation of the posterior segment of the eye which can result in significant loss of visual acuity. Even with prompt antibiotic, anti-inflammatory and surgical intervention, vision and even the eye itself may be lost. For the past century, experimental animal models have been used to examine various aspects of the pathogenesis and pathophysiology of bacterial endophthalmitis, to further the development of anti-inflammatory treatment strategies, and to evaluate the pharmacokinetics and efficacies of antibiotics. Experimental models allow independent control of many parameters of infection and facilitate systematic examination of infection outcomes. While no single animal model perfectly reproduces the human pathology of bacterial endophthalmitis, investigators have successfully used these models to understand the infectious process and the host response, and have provided new information regarding therapeutic options for the treatment of bacterial endophthalmitis. This review highlights experimental animal models of endophthalmitis and correlates this information with the clinical setting. The goal is to identify knowledge gaps that may be addressed in future experimental and clinical studies focused on improvements in the therapeutic preservation of vision during and after this disease. PMID:27154427

  5. Contribution to the study of french pitchblendes; Contribution a l'etude des pechblendes francaises

    Energy Technology Data Exchange (ETDEWEB)

    Geffroy, J. [Commissariat a l' Energie Atomique, Lab. de Mineralogie, Centre de Chatillon (France). Centre d' Etudes Nucleaires; Sarcia, J.A. [Commissariat a l' Energie Atomique, Div. de la Crouzille, Haute Vienne (France). Centre d' Etudes Nucleaires

    1955-07-01

    The authors first review the characteristics of uraninite-pitchblende, as deduced of present literature. They set apart from typical pitchblende a black oxide aspect, which probably corresponds to neo-formations, and a 'para-pitchblende' aspect, which they relate to deep sur-oxidation of normal pitchblende. They insist on the easy replacement of pitchblende by silica. and give indications as to changes in vein stones (fluorite, quartz, etc...). A detailed study of paragenesis and successions in french uranium districts follows (including discussion of uranium of uranium-bearing coals). The authors attempt to classify french pitchblende veins. They are chiefly epithermal and poor in satellite ores. Three types of deposits are identified: massive - pitchblende type, silica type, fluorite type. These deposits, as those of Portugal, are included in granite, Central-European peri-batholitic types where uranium associates which Ni, Co, Bi and Ag, are in France both rare and poor. Finally, the authors attempt to bring out in the european Hercynian area a particular distribution of paragenetic types. (authors) [French] Les auteurs recapitulent d'abord les caracteres et les occurences de l'uraninite - pechblende, tels qu'ils peuvent etre degages de l'actuelle bibliographie. Ils exposent ensuite les faits qui du point de vue mineralogique seulement ressortent de l'etude mineralogique et chalcographique des pechblendes francaises et de leurs satellites. Ils distinguent de la pechblende-type un facies oxyde noir; correspondant probablement a une neoformation, et un facies parapechblende, qui est rapporte a une sur oxydation hypogene de la pechblende proprement dite. Ils insistent sur le facile remaniement de la pechblende par la slice; et donnent quelques precisions sur les modifications des gangues (fluorine, quartz, etc...). Suit l'etude detaillee des parageneses et des successions dans les districts uraniferes francais: Divisions du

  6. Heme uptake in bacterial pathogens

    OpenAIRE

    Contreras, Heidi; Chim, Nicholas; Credali, Alfredo; Goulding, Celia W.

    2014-01-01

    Iron is an essential nutrient for the survival of organisms. Bacterial pathogens possess specialized pathways to acquire heme from their human hosts. In this review, we present recent structural and biochemical data that provide mechanistic insights into several bacterial heme uptake pathways, encompassing the sequestration of heme from human hemoproteins to secreted or membrane-associated bacterial proteins, the transport of heme across bacterial membranes, and the degradation of heme within...

  7. Etude de la dynamique des porteurs dans des nanofils de silicium par spectroscopie terahertz

    Science.gov (United States)

    Beaudoin, Alexandre

    Ce memoire presente une etude des proprietes de conduction electrique et de la dynamique temporelle des porteurs de charges dans des nanofils de silicium sondes par rayonnement terahertz. Les cas de nanofils de silicium non intentionnellement dopes et dopes type n sont compares pour differentes configurations du montage experimental. Les mesures de spectroscopie terahertz en transmission montre qu'il est possible de detecter la presence de dopants dans les nanofils via leur absorption du rayonnement terahertz (˜ 1--12 meV). Les difficultes de modelisation de la transmission d'une impulsion electromagnetique dans un systeme de nanofils sont egalement discutees. La detection differentielle, une modification au systeme de spectroscopie terahertz, est testee et ses performances sont comparees au montage de caracterisation standard. Les instructions et des recommendations pour la mise en place de ce type de mesure sont incluses. Les resultats d'une experience de pompe optique-sonde terahertz sont egalement presentes. Dans cette experience, les porteurs de charge temporairement crees suite a l'absorption de la pompe optique (lambda ˜ 800 nm) dans les nanofils (les photoporteurs) s'ajoutent aux porteurs initialement presents et augmentent done l'absorption du rayonnement terahertz. Premierement, l'anisotropie de l'absorption terahertz et de la pompe optique par les nanofils est demontree. Deuxiemement, le temps de recombinaison des photoporteurs est etudie en fonction du nombre de photoporteurs injectes. Une hypothese expliquant les comportements observes pour les nanofils non-dopes et dopes-n est presentee. Troisiemement, la photoconductivite est extraite pour les nanofils non-dopes et dopes-n sur une plage de 0.5 a 2 THz. Un lissage sur la photoconductivite permet d'estimer le nombre de dopants dans les nanofils dopes-n. Mots-cles: nanofil, silicium, terahertz, conductivite, spectroscopie, photoconductivite.

  8. Modelos experimentales in vivo de enfermedad inflamatoria intestinal y cáncer colorrectal: Conceptos, modelos actuales y aplicabilidad In vivo experimental models of inflammatory bowel disease and colorectal cancer

    Directory of Open Access Journals (Sweden)

    J. Mañé Almero

    2007-04-01

    Full Text Available No existe un modelo animal ideal para el estudio de patologías humanas como la EII o el CCR. En la última década, a los modelos inducidos por agentes exógenos se han incorporado los animales manipulados genéticamente. Los modelos experimentales de EII reproducen procesos inflamatorios intestinales heterogéneos, al igual de sucede en el ser humano. Mientras que los modelos de CCR remedan las mutaciones halladas en el hombre aunque con repercusiones fenotípicas diferentes. En ambos casos, estos sistemas experimentales son influidos por la genética y el ambiente. Hoy por hoy, los modelos animales son unos valiosos bioensayos, complejos y completos, para el estudio de nuevas estrategias terapéuticas en la EII (IL-10, anti-IL-12, probióticos y agentes protectores de la CCR (ácidos grasos n3, AINES y inhibidores de COX-2.There is no ideal animal model for the study of human pathologies such as IBD or CRC. For the last decade, genetically engineered animal models have been incorporated to models induced by exogenous agents. Experimental models of IBD reproduce heterogeneous intestinal inflammatory conditions, as it occurs in the human being, whereas CRC models imitate those mutations found in man although with different phenotypic repercussions. In both cases, these experimental systems are influenced by genetics and the environment. Today, animal models represent valued, complex, and complete bioassays for the study of new therapeutic strategies in IBD (IL-10, anti-IL-12, probiotics and protective agents in CRC (n-3 fatty acids, NSAIDS, and COX-2 inhibitors.

  9. Bacterial chemoreceptors and chemoeffectors.

    Science.gov (United States)

    Bi, Shuangyu; Lai, Luhua

    2015-02-01

    Bacteria use chemotaxis signaling pathways to sense environmental changes. Escherichia coli chemotaxis system represents an ideal model that illustrates fundamental principles of biological signaling processes. Chemoreceptors are crucial signaling proteins that mediate taxis toward a wide range of chemoeffectors. Recently, in deep study of the biochemical and structural features of chemoreceptors, the organization of higher-order clusters in native cells, and the signal transduction mechanisms related to the on-off signal output provides us with general insights to understand how chemotaxis performs high sensitivity, precise adaptation, signal amplification, and wide dynamic range. Along with the increasing knowledge, bacterial chemoreceptors can be engineered to sense novel chemoeffectors, which has extensive applications in therapeutics and industry. Here we mainly review recent advances in the E. coli chemotaxis system involving structure and organization of chemoreceptors, discovery, design, and characterization of chemoeffectors, and signal recognition and transduction mechanisms. Possible strategies for changing the specificity of bacterial chemoreceptors to sense novel chemoeffectors are also discussed.

  10. Bacterial Colony Optimization

    Directory of Open Access Journals (Sweden)

    Ben Niu

    2012-01-01

    Full Text Available This paper investigates the behaviors at different developmental stages in Escherichia coli (E. coli lifecycle and developing a new biologically inspired optimization algorithm named bacterial colony optimization (BCO. BCO is based on a lifecycle model that simulates some typical behaviors of E. coli bacteria during their whole lifecycle, including chemotaxis, communication, elimination, reproduction, and migration. A newly created chemotaxis strategy combined with communication mechanism is developed to simplify the bacterial optimization, which is spread over the whole optimization process. However, the other behaviors such as elimination, reproduction, and migration are implemented only when the given conditions are satisfied. Two types of interactive communication schemas: individuals exchange schema and group exchange schema are designed to improve the optimization efficiency. In the simulation studies, a set of 12 benchmark functions belonging to three classes (unimodal, multimodal, and rotated problems are performed, and the performances of the proposed algorithms are compared with five recent evolutionary algorithms to demonstrate the superiority of BCO.

  11. [Bacterial diseases of rape].

    Science.gov (United States)

    Zakharova, O M; Mel'nychuk, M D; Dankevych, L A; Patyka, V P

    2012-01-01

    Bacterial destruction of the culture was described and its agents identified in the spring and winter rape crops. Typical symptoms are the following: browning of stem tissue and its mucilagization, chlorosis of leaves, yellowing and beginning of soft rot in the place of leaf stalks affixion to stems, loss of pigmentation (violet). Pathogenic properties of the collection strains and morphological, cultural, physiological, and biochemical properties of the agents of rape's bacterial diseases isolated by the authors have been investigated. It was found that all the isolates selected by the authors are highly or moderately aggressive towards different varieties of rape. According to the complex of phenotypic properties 44% of the total number of isolates selected by the authors are related to representatives of the genus Pseudomonas, 37% - to Xanthomonas and 19% - to Pectobacterium. PMID:23293826

  12. Bacterial transformation of terpenoids

    International Nuclear Information System (INIS)

    Data on the bacterial transformation of terpenoids published in the literature in the past decade are analyzed. Possible pathways for chemo-, regio- and stereoselective modifications of terpenoids are discussed. Considerable attention is given to new technological approaches to the synthesis of terpenoid derivatives suitable for the use in the perfume and food industry and promising as drugs and chiral intermediates for fine organic synthesis. The bibliography includes 246 references

  13. Supramolecular bacterial systems

    OpenAIRE

    Sankaran, Shrikrishnan

    2015-01-01

    For nearly over a decade, a wide variety of dynamic and responsive supramolecular architectures have been investigated and developed to address biological systems. Since the non-covalent interactions between individual molecular components in such architectures are similar to the interactions found in living systems, it was possible to integrate chemically-synthesized and naturally-occurring components to create platforms with interesting bioactive properties. Bacterial cells and recombinant ...

  14. Bacterial Colony Optimization

    OpenAIRE

    Ben Niu; Hong Wang

    2012-01-01

    This paper investigates the behaviors at different developmental stages in Escherichia coli (E. coli) lifecycle and developing a new biologically inspired optimization algorithm named bacterial colony optimization (BCO). BCO is based on a lifecycle model that simulates some typical behaviors of E. coli bacteria during their whole lifecycle, including chemotaxis, communication, elimination, reproduction, and migration. A newly created chemotaxis strategy combined with communication mechanism i...

  15. Experimental and theoretical study of bragg-Fresnel optics etched on multilayer structures. Application: lenses for X-Ray imaging; Etude experimentale et theorique d`optiques de bragg-Fresnel gravees sur miroirs interferentiels multicouches. Application: lentilles pour l`imagerie X

    Energy Technology Data Exchange (ETDEWEB)

    Soullie, G.

    1996-10-01

    This work concerns the study of a new type of X-ray focusing optics known as Bragg-Fresnel lenses developed for imaging in the X and X-UV range. These optics, etched on multilayer structure, combine the focusing properties of zone plate with the Bragg reflection of multilayer used like support. Using synchrotron sources and a plasma source produced by a laser, we tested the efficiency and the spatial resolution of these lenses. With a monochromatic beam, we first obtained the image of a object by using the first order diffraction of an elliptical off-axis Bragg-Fresnel lens. By using only one part of a lens, the superposition of different diffraction orders in focal plane can be avoided, thus improving the image contrast. In order to evaluate the chromatic aberrations of these lenses, we have summed on the same image, three exposures at different energies in the band pass of the multilayer. To reduce these kind of aberrations, we used a system composed of two off-axis lenses. To simplify the alignment, we tested an elliptical off-axis lens associated with a lamellar grating. Thus we are able to validate the theoretical approximation of an off-axis Bragg-Fresnel lens to a variable spaced grating. Finally, to show the perturbation brought by the zeroth order, we successively imaged a laser plasma source with a centred and an off-axis elliptical lenses. As with the synchrotron source, a set of images of a test object enabled us to improve the spatial resolution. (author).

  16. Laser shocks on helium, hydrogen and diamond: an experimental study of the warm dense matter zone; Chocs laser sur l'helium, l'hydrogene et le diamant: une etude experimentale de la 'Warm Dense Matter'

    Energy Technology Data Exchange (ETDEWEB)

    Brygoo, St

    2006-11-15

    The purpose of this work was to develop a new approach of laser shocks on pre-compressed targets in order to collect data concerning the equation of state in the warm dense matter zone of the phase diagram. The accuracy of the measurement has been increased by the use of a new metrology based on quartz. Quartz is considered as a standard for the measurement of both the pressure and the density, a model of an isentropic relaxation based on a Grueneisen type approximation has been developed. By combining laser shocks with diamond anvil cells and by using this new metrology, we have investigated the following systems: diamond, helium, hydrogen, deuterium and hydrogen-helium mixtures. The results for helium agree very well with the predictions of the Saumon-Chabrier model. The results for deuterium are consistent with the latest results found in literature. As for the results concerning hydrogen, they have showed the limits of the quartz-based metrology. In fact, by being so little dense we are at the limit of the application range of the quartz relaxation. A mixture of helium-hydrogen (50 %) has been investigated, no sign of phase separation has been found.

  17. Experimental and theoretical study of Bragg-Fresnel focalizing optical systems engraved on multi layers interferential mirrors adapted to X and X-UV fields; Etude experimentale et theorique d`optiques focalisantes de type Bragg-Fresnel gravees sur des miroirs interferentiels multicouches adaptes aux domaines X et X-UV

    Energy Technology Data Exchange (ETDEWEB)

    Idir, M.

    1995-02-01

    This work concerns the study of a particular type of X-ray focusing optics known as Bragg-Fresnel lenses, formed through ion-etching of multilayered structures. Using the Super-ACO (LURE/Orsay) synchrotron storage ring, we tested several Bragg-Fresnel lenses having either linear or elliptical geometries (producing a line or a point focus, respectively). Diffraction profiles were first obtained for the linear lenses ion-etched on W/Si multilayers of nano-metric period. The experimental results were compared with our theoretical predictions. We next proposed and tested a solution to the problem superposing the different diffraction orders in the focal plane, that of fabricating Bragg-Fresnel lenses with an off-axis configuration, first for the linear and then the elliptical geometry. An experimental application, for an off-axis elliptical lens produced a focused X-ray spot of 5 x 10 microns{sup 2} for the Super-ACO synchrotron source. The same lens also produced a 1/3-size X-ray image of a grid-like object at 1750 eV using the first and third diffraction orders. (author).

  18. A micro-mechanical analysis and an experimental characterisation of the behavior and the damaging processes of a 16MND5 pressure vessel steel at low temperature; Etude micromecanique et caracterisation experimentale du comportement et de l'endommagement de l'acier de cuve 16MND5 a basses temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Pesci, R

    2004-06-15

    As part of an important experimental and numerical research program launched by Electricite De France on the 16MND5 pressure vessel steel, sequenced and in-situ tensile tests are realized at low temperatures [-196 C;-60 C]. They enable to associate the observation of specimens, the complete cartography of which has been made with a scanning electron microscope (damaging processes, initiation and propagation of microcracks), with the stress states determined by X-ray diffraction, in order to establish relevant criteria. All these measurements enable to supply a two-scale polycrystalline modeling of behavior and damage (Mori-Tanaka/self-consistent) which is developed concurrently with the experimental characterization. This model proves to be a very efficient one, since it correctly reproduces the influence of temperature experimentally defined: the stress state in ferrite remains less important than in bainite (the difference never exceeds 150 MPa), whereas it is much higher in cementite. The heterogeneity of strains and stresses for each crystallographic orientation is well rendered; so is cleavage fracture normal to the {l_brace}100{r_brace} planes in ferrite (planes identified by electron back scattered diffraction during an in-situ tensile test at -150 C), which occurs sooner when temperature decreases, for a constant stress of about 700 MPa in this phase. (author)

  19. Characterization of domestic wastes incineration clinkers. Experimental study of the dioxines impact on the environment. Program ''industrial wastes'' DRC 01; Caracterisation des machefers d'incineration d'ordures menageres. Etude experimentale de l'impact des dioxines sur l'environnement. Programme ''dechets industriels'' DRC 01

    Energy Technology Data Exchange (ETDEWEB)

    Brazillet, C.; Badreddine, R

    2002-01-15

    Clinkers resulting from domestic wastes incineration are used in road construction since May 1994. A first study realized by the INERIS showed the poor dioxines content in clinkers and their weak transfer in the environment. In order to verify the hypothesis presented in this study, an experimental study controlled different structures using clinkers. It showed a difference between the clinkers used in old structures which reveal a higher dioxines content and the clinkers used in more recent structures which present weak dioxines content. The use of clinkers, even in the case of significant dioxines level, has not a negative impact on the environment taking into account the transfer modes of these substances. (A.L.B.)

  20. Experimental study and mechanical modelling of the effects of water-driving in an oil saturated chalk. Application to the petroleum industry; Etude experimentale et modelisation mecanique des effets du balayage a l'eau dans une craie saturee d'huile. Application a l'industrie petroliere

    Energy Technology Data Exchange (ETDEWEB)

    Mata, C.

    2001-01-01

    The production of hydrocarbons may sometimes lead to compaction of the oil-reservoir layers with substantial collapse of the soil surface; this mechanism is usually mentioned as Subsidence. Classical remedy to this problem is to sustain the fluid pressure with the help of water injection. However, in presence of high porosity chalk (porosity > 30%), this technique does not give effective results: the subsidence rate at North Sea reservoirs (Ekofisk field), after injection, has remained unchanged. Some justify the subsistence in the chalk as caused by phenomena of dissolution of the carbonates; others think it is connected to the destruction of capillary menisci. In this research, we follow this second approach. This study is finalized to a better understanding of the compaction mechanisms in pure carbonates when water is injected. This is done by proposing -in micro-scale first and in macro-scale after- a physical model that agrees with empirical observations. In order to meet this target, IFP skills and experience in physical and chemical measurements (taken before, after and during mechanical tests) have proficiently joined ENPC laboratory (CERMMO) knowledge of micro and macro modelling. The soft rock studied is a Paris basin's white chalk (Craie de Guerville). Its physical and chemical characterisation (i.e.: silica content, porosity, permeability) is very similar to North Sea chalk, but Guerville chalk has never been in contact with oil and generally it crops out of the ground surface. Strength parameters of this rock have been first determined by standard triaxial tests. Three different saturation configurations have been examined: dry, fully oil-saturated and fully water-saturated. As literature clearly state, dry chalk is stronger than oil saturated chalk and the first two are largely stronger than water saturated chalk. Therefore uniaxial strain water injection tests have been performed on oil saturated samples. Results, coupled with previous physical measurements and SEM observation, let us highlight two different contributions to mechanical strength of chalk-: 1) The cohesion due to solid micro-bridges between calcite grains (always present in intact samples); 2) The cohesion due to water capillary menisci (which decreases when the degree of water saturation increases). On these grounds, an elasto-plastic model is proposed is order to explain how contributions are coupled. In this modelling, plastic strain is an hardening parameter while water saturation ratio is a softening one. Applications are developed in order to relate water-driving, stress state and subsidence rate in an oil reservoir configuration. (author)

  1. Theoretical and experimental study of high strain, high strain rate materials viscoplastic behaviour. Application to Mars 190 steel and tantalum; Etude theorique et experimentale du comportement viscoplastique des materiaux aux grandes deformations et grandes vitesses de deformations. Application a l'acier mars 190 et au tantale

    Energy Technology Data Exchange (ETDEWEB)

    Juanicotena, A

    1998-07-01

    This work enters in the general framework of the study and modelling of metallic materials viscoplastic behaviour in the area of high strain and high strain rate, from 10{sup 4} to 10{sup 5} s{sup -1}. We define a methodology allowing to describe the behaviour of armor steel Mars 190 and tantalum in the initial area. In a first time, the study of visco-plasticity physical mechanisms shows the necessity to take into account some fundamental processes of the plastic deformation. Then, the examination of various constitutive relations allows to select the Preston-Tonks-Wallace model, that notably reproduce the physical phenomenon of the flow stress saturation. In a second part, a mechanical characterization integrating loading direction, strain rate and temperature effects is conducted on the two materials. Moreover, these experimental results allow to calculate associated constants to Preston-Tonks-Wallace, Zerilli-Armstrong and Johnson-Cook models for each material. In a third time, in order to evaluate and to validate these constitutive laws, we conceive and develop an experimental device open to reach the area of study: the expanding spherical shell test. It concerns to impose a free radial expanding to a thin spherical shell by means a shock wave generated by an explosive. By the radial expanding velocity measure, we can determine stress, strain rate and strain applied on the spherical shell at each time. In a four and last part, we evaluate constitutive models out of their optimization area's. This validation is undertaken by comparisons 'experimental results/calculations' with the help of global experiences like expanding spherical shell test and Taylor test. (author)

  2. Experimental studies of X-UV rays by a laser plasma: X-UV strioscopy by means of multilayer mirrors; Etude experimentale de la refraction X-UV par un plasma laser: strioscopie X-UV a l`aide de miroirs multicouches

    Energy Technology Data Exchange (ETDEWEB)

    Lutrin, F

    1996-05-20

    This thesis studies a new instrument -from its conception to the measures interpretation- that analyses electronic density gradient in the super critical transportation area of a laser plasma (0,35 {mu}m). This device, so-called of X-UV Schlieren, is based on the refraction property of a probe beam by an index gradient. Its specificity is the use of the X-UV emission at 13 nm (92 eV) of another laser plasma as X-UV probe. The conception and characterization of this instrument are defined thanks to both the emissivity and reflectivity properties of laser plasmas and the reflectivity properties of multilayers. Within this report are presented strioscopy images, spatially and spectrally resolved of an aluminium plasma from a 3.10{sup 12} W/cm{sup 2} laser flux, probed by a 13 nm wavelength. The device has to be closely aligned so as to obtain good contrast and good spatial resolution. For the first time, the refraction of a X-UV probe beam by a laser plasma is displayed. The experiments show that this refraction is all the more obvious for a gold probe plasma of energy 105 J and an aluminium probed plasma of energy 1 J. According to our plasma hydrodynamic simulation, the detected refraction corresponds to an electronic density gradient of 6,5.10{sup 25} electrons/cm{sup 4} in the two first microns of the sur-critical area. To study the parameters dependence of this gradient in the sur-critical area, several solutions for improving the instrument are produced. (author) 168 refs.

  3. Theoretical and experimental study of an ytterbium-doped laser system for generating high energy impulses at high rate; Etude theorique et experimentale de l'architecture d'un laser a solide monocristallin ou ceramique dope ytterbium pour la generation d'impulsions de grande energie a haute cadence

    Energy Technology Data Exchange (ETDEWEB)

    Casagrande, O

    2007-03-15

    This work is dedicated to the study of ytterbium-doped laser systems that are developed for generating high mean power impulses in the context of inertial fusion. We show that rare earth sesquioxides appear as the most adequate matrix material for high mean power. As for the architecture of amplifiers, we show that amplifiers with thin disks longitudinally pumped by laser diodes and cooled through their back side are an adequate solution in order to handle thermal effects. The development of a mathematical model describing an ytterbium-doped laser amplifier has enabled us to optimize various parameters of the laser architecture and to compare different ytterbium-doped matrices. It was shown that ytterbium-doped rare earth sesquioxides have excellent amplification properties for the design of high mean power lasers. Furthermore, it was also shown that low temperatures favour both the thermo-mechanical features of laser amplifiers and the spectroscopic properties of ytterbium ions. (A.C.)

  4. Experimental and theoretical studies of the VUV emission and absorption spectra of H{sub 2}, HD and D{sub 2} molecules; Etude experimentale et theorique des spectres d'emission et d'absorption VUV des molecules H{sub 2}, D{sub 2} et HD

    Energy Technology Data Exchange (ETDEWEB)

    Roudjane, M

    2007-12-15

    The aim of this thesis is to carry out an experimental study of the absorption and emission spectra of the D{sub 2} and HD isotopes, with high resolution, in the VUV domain and to supplement it by a theoretical study of the excited electronic states involved in the observed transitions. The emission spectra of HD and D{sub 2} are produced by Penning discharge source operating under low pressure and are recorded in the spectral range 78 - 170 nm. The recorded spectra contains more than 20.000 lines. The analysis of the spectrum consists in identifying and assigning the lines to the electronic transitions between energy levels of the molecule. The present analysis is based on our theoretical calculations of the ro-vibrational energy levels of the excited electronic states and the transition probabilities from these states towards the energy levels of the fundamental state. The theoretical results are obtained by resolving the coupled equations between the excited electronic states B{sup 1}{sigma}{sub u}{sup 1}, B'{sup 1}{sigma}{sub u}{sup 1}, C{sup 1}{pi}{sub u}{sup 1} and D{sup 1}{pi}{sub u}{sup 1}, taking into account the nonadiabatic couplings between these states, and they are obtained in the adiabatic approximation for the excited electronic states B''B-bar{sup 1}{sigma}{sub u}{sup +}, D'{sup 1}{pi}{sub u}{sup 1} and D''{sup 1}{pi}{sub u}{sup 1}. The equations are resolved using a modern method based on the discretization variables representation method. In addition, we have carried out a study of the absorption spectra of the HD and D{sub 2} molecules.

  5. Temperature effect on the poro-mechanical or hydraulic behaviour of a carbonated rock and a mortar: experimental studies; Influence de la temperature sur le comportement poromecanique ou hydraulique d'une roche carbonatee et d'un mortier: etudes experimentales

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    Lion, M

    2004-07-15

    The main objective of this study is to evaluate the temperature effect on the hydraulic and poro-mechanical behaviour of a limestone. Many experimental tests (porosity and permeability measurements, uniaxial and hydrostatic compressions tests) were carried out in order to study the thermal treatments effect and so the thermal microcracking effect on rock behaviour. Moreover, an experimental device for permeability measurements under high temperatures (until 200 C) was realized. This experimental device permitted to study the permeability variation of the limestone under thermal stresses. Finally, the behaviour of cementitious materials was studied; the temperature effect on the permeability of a mortar was examined. (author)

  6. Experimental studies and modeling of X-Rays multilayer mirrors damages under high X-Ray flux generated by a laser-plasma experiment; Etude experimentale et modelisation de l`endommagement des miroirs multicouches X soumis a de hauts flux de rayonnement X dans le cadre de l`experience plasma-laser

    Energy Technology Data Exchange (ETDEWEB)

    Le Guern, F

    1996-05-24

    We have been able with this work to point out characterize X-Rays multilayers mirrors damages. We have designed two experimental set-up which have been installed in the HELIOTROPE experimental chamber of the OCTAL facility located at the CEA in Limeil-Valenton. We have demonstrated that X-Rays multilayer mirrors properties were drastically modified by X-Rays emitted by a golden laser plasma. We have, more precisely, introduced the damage speed concept to quantify the expansion of the multilayer mirror period. We have been able to classify different multilayer mirrors in function of their resistance to damage and we have demonstrated that a silicate layer deposited on a mirror allowed to increase his resistance to damage. In a second part we have developed a simulation tool in order to simulate the X-Rays multilayer mirrors optical properties modifications. We have therefore coupled a thermo-mechanic code with an optical program. The results of the simulations are in a rather good agreement with the experiments and can be used to predict, before experiments, the multilayer mirror behavior under X-Rays irradiation. (author) 55 refs.

  7. Study of secondary electron emission from thin carbon targets with swift charged particles: heavy ions, hydrogen ions; Etude experimentale de l`emission electronique secondaire de cibles minces de carbone sous l`impact de projectiles rapides: ions lourds, ions hydrogene (atomiques, moleculaires ou sous forme d`agregats)

    Energy Technology Data Exchange (ETDEWEB)

    Billebaud, A.

    1995-07-12

    The main subject of this work is the study of electron emission from the two surfaces of thin solid targets bombarded with swift charged particles. The slowing down of swift ions in matter is mainly due to inelastic interaction with target electrons (ionization, excitation): the energy transfer to target electrons is responsible for the secondary electron emission process. The phenomenological and theoretical descriptions of this phenomena are the subject of the first chapter. We focused on secondary electron emission induced by different kind of projectiles on thin carbon foils. In chapter two we describe hydrogen cluster induced electron emission measurement between 40 and 120 keV/proton. These projectiles, composed of several atoms, allowed us to study and highlight collective effects of the electron emission process. We extended our study of electron emission to molecular (H{sub 2}{sup +}, H{sub 3}{sup +}) and composite (H{sup -}, H{sup 0}) projectiles at higher energies (<= 2 MeV): we have designed an experimental set-up devoted to electron emission statistics measurements which allowed us to study, among others things, the role of projectile electrons in secondary electron emission. This experiment is described in the third chapter. Finally, the fourth chapter describes new measurements of electron emission induced by energetic (13 MeV/u) and highly charged argon ion provided by the medium energy beam line (SME) of GANIL (Caen), which have been analyzed in the framework of a semi-empirical model of secondary electron emission. This set of experiments brings new results on composite projectile interaction with matter, and on the consequences of high energy deposition in solids. (author).

  8. Methodological study of the diffusion of interacting cations through clays. Application: experimental tests and simulation of coupled chemistry-diffusion transport of alkaline ions through a synthetical bentonite; Etude methodologique de la diffusion de cations interagissants dans les argiles. Application: mise en oeuvre experimentale et modelisation du couplage chimie-diffusion d'alcalins dans une bentonite synthetique

    Energy Technology Data Exchange (ETDEWEB)

    Melkior, Th

    2000-07-01

    The subject of this work deals with the project of underground disposal of radioactive wastes in deep geological formations. It concerns the study of the migration of radionuclides through clays. In these materials, the main transport mechanism is assumed to be diffusion under natural conditions. Therefore, some diffusion experiments are conducted. With interacting solutes which present a strong affinity for the material, the duration of these tests will be too long, for the range of concentrations of interest. An alternative is to determine on one hand the geochemical retention properties using batch tests and crushed rock samples and, on the other hand, to deduce the transport parameters from diffusion tests realised with a non-interacting tracer, tritiated water. These data are then used to simulate the migration of the reactive elements with a numerical code which can deal with coupled chemistry-diffusion equations. The validity of this approach is tested by comparing the numerical simulations with the results of diffusion experiments of cations through a clay. The subject is investigated in the case of the diffusion of cesium, lithium and sodium through a compacted sodium bentonite. The diffusion tests are realised with the through-diffusion method. The comparison between the experimental results and the simulations shows that the latter tends to under estimate the propagation of the considered species. The differences could be attributed to surface diffusion and to a decrease of the accessibility to the sites of fixation of the bentonite, from the conditions of clay suspensions in batch tests to the situation of compacted samples. The influence of the experimental apparatus used during the diffusion tests on the results of the measurement has also been tested. It showed that these apparatus have to be taken into consideration when the experimental data are interpreted. A specific model has been therefore developed with the numerical code CASTEM 2000. (author)

  9. Adsorption of Cs{sup +}, Ni{sup 2+} and lanthanides onto a kaolinite and Na-montmorillonite up to 150{sup 0}C: an experimental and modeling study; Adsorption de Cs{sup +}, Ni{sup 2+} et des lanthanides sur une kaolinite et une smectite jusqu'a 150{sup 0}C: etude experimentale et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Tertre, E

    2005-10-15

    The motivation for this study is to assess the temperature effect on the clay minerals sorption properties. Sorption and desorption of Cs{sup +}, Ni{sup 2+} et Ln{sup 3+} onto a montmorillonite and a kaolinite were performed by batch experiments between 25 and 150 C, and in different pH and ionic strengths conditions. Sorption enthalpies varying between 0 and 80 kJ/mol were then calculated. For europium, surface spectroscopic analyses confirmed that the mechanism involved is adsorption, including at 150 C. Moreover, this method allowed us to obtain qualitatively the different adsorption equilibrium occurring during the reaction. An acid/base study of the clay surfaces was performed in order to assess the temperature effect on the surface charge of these minerals. Then, a surface complexation model including edge sites and structural sites was proposed to interpret the acid/base data and the europium sorption data. (author)

  10. New experimental method to study the collective modes in exotic nuclei; influence of the superfluidity on the cooling time of a neutron star; Nouvelle methode experimentale dediee a l'etude des modes collectifs dans les noyaux exotiques; influence de la superfluidite sur le temps de refroidissement d'une etoile a neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Monrozeau, Ch

    2007-07-15

    Giant monopole (GMR) and quadrupole (GQR) resonances have been measured in the {sup 56}Ni using inelastic scattering of 50 A.MeV deuteron at the Grand Accelerateur National d'Ions Lourds facility. This is the first experimental observation of isoscalar collective modes in a short-lived nucleus. The secondary beam was impinged on the active target Maya filled with a pure deuterium gas. Recoiling deuterons were detected in Maya and in a wall of nine silicon detectors. The GMR and GQR are centered at 19.3(0.5) and 16.2(0.5) MeV, respectively. Corresponding angular distributions were extracted from 3 to 7 degrees in the centre of mass frame. DWBA analysis based on RPA transition densities yields the percentage of the energy weighted sum rule exhausted: 136(27) % for the GMR et 76(13) % for the GQR. A finite temperature Hartree-Fock-Bogoliubov model was implemented to describe the 10 Wigner-Seitz cells which compose the inner crust of neutron stars and to microscopically calculate their specific heat. Calculations are performed with two contact pairing forces chosen to simulate the pairing properties of uniform neutron matter corresponding to the BCS approximation and to polarisation effects. Under the assumption of a rapid cooling of the core and an initial temperature of 100 keV in the inner crust, the cooling time of the star was estimated at 9 and 34 years, respectively. (author)

  11. Development and validation of an experimental procedure for studying the biaxial stress corrosion. Application to the systems: alloy-600/air and 316L/MgCl{sub 2}; Developpement et validation d'une procedure experimentale pour l'etude de la corrosion sous contrainte biaxiale. Application aux couples alliage 600 / air et 316L / MgCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Farre, M.Th

    1998-07-15

    One of the main preoccupation for maintaining EdF's nuclear pressurised water reactors is intergranular stress corrosion cracking of steam generator tubing (alloy 600: NC 15Fe). The most affected areas (first row U-bend and roll transition zone) are in biaxial stress state. The crack propagation is often axial and sometimes circumferential. The actual life prediction criterion for these structures depends on the maximal principal stress. The purpose of this study is to determine whether it is safe to use such a criterion in a case of biaxial stress state. A procedure is proposed and experimentally validated for designing specimen in a controlled biaxial stress state when submitted to traction. Quadrants I an IV of the stress space are the only ones explored. The aim is to use these specimens in order to realize stress corrosion tests in primary water with alloy 600. The procedure involves studying the biaxial behavior of the material. This shows the effect of hardening on the shape of the yield stress surface. The hardening of alloy 600 is mainly kinematic. The yield stress surface becomes concave in the hardening stress direction and flat in the opposite direction. The geometry of the specimen stems from parameterized shape optimisation. An elasto-viscoplastic behavior law is identified for alloy 600. Use of the law for calculating the strain state of one specimen is experimentally validated. This entire procedure has been successfully validated with biaxial stress corrosion cracking tests, using 316L and MgCl{sub 2} boiling at 154 deg C. In this case it is difficult to determine a life time criterion. It is shown that the criterion of the maximal principal stress is invalid in case of a biaxial stress state. (author)

  12. Numerical and experimental study of the influence of the operational parameters on the formation mechanisms of oxides of nitrogen during the combustion of mixtures of cellulosic and plastic materials; Etude experimentale et numerique de l'influence des parametres operatoires sur les mecanismes de formation des oxydes d'azote lors de la combustion de melanges de materiaux cellulosiques et plastiques

    Energy Technology Data Exchange (ETDEWEB)

    Andzi Barhe, T.

    2004-10-15

    The current thesis was performed within a collaboration between the Laboratoire de Combustion et de Detonique (LCD of the University of Poitiers) and the Laboratoire de Physique et de Chimie d'Environnement (LPCE) of the University of Ouagadougou. It was financed by Agency for Environment and Energy Management (ADEME). The principle object of this study is the optimisation of the combustion process during the incineration of waste. This optimisation is aimed at the reduction of the polluting emissions, principally CO and NO, during the incineration of cellulosic and plastic materials. It involves the analysis of the influence of the operational parameters on the polluting emissions and the control of reaction mechanisms of formation and reduction of these pollutants during the combustion process. Consequently, the study was performed in two parts: an experimental part and a numerical part. The experimental part was realised using a fixed bed counterflow reactor. This setup simulates the combustion within an industrial waste incinerator. The reactor allows the combustion of a vertical layer of waste mixture (wood, cardboard, PET, polyamide) to be followed. Three model mixtures representative of the makeup of household waste were studied in order to determine the influence of the composition of the waste on the emission of pollutants (CO and NO). The obtained results show that this parameter has a practically negligible influence within the tested parameter range. Consequently the formation of pollutants depends on the operating parameters - the equivalence ratio and the temperature. A numerical study of the influence of these parameters in order to show their impact on the mechanisms of pollutant formation and to determine the chemical mechanisms involved in the formation of oxides of nitrogen. The numerical study was performed with software developed at the LCD. This programme based on a detailed chemical model coupled to a simple physical model. It uses the calculation code CHEMKIN. It permits the simulation of combustion process within the gaseous zone of the fixed bed reactor. The programme is initialized with the results of the analysis of the pyrolysis which had previously been performed at the LCD on the materials which make up the model waste mixture. The pyrolysis products identified during this study are: HCN, NH{sub 3}, NO, NO{sub 2}, CO and light hydrocarbons. The results show that the simulation enables the determination of reactional mechanisms of the formation and reduction of oxides of nitrogen in the three combustion regimes identified during the experimental study. For each of the three regimes, a study of the impact of the combustion parameters on the yield of NO was performed. It can be seen that the response to the parameters is itself heavily dependent on the combustion regime. (author)

  13. Experimental study of the performance of bio-filtration systems for the treatment of a mixture of volatile organic compounds; Etude experimentale sur la performance de systemes de biofiltration pour le traitement d'un melange de composes organiques volatils

    Energy Technology Data Exchange (ETDEWEB)

    Gidas, M.B.

    2004-02-01

    The objective of this essentially experimental work was to study the treatment of a gaseous tributary containing a mixture of three VOCs (acetone, toluene and trichloroethylene) by bio-filtration with four bio-filters (B1, B2, B3 and B4), and to compare their performance in degrading pollutants. The filtering material for bio-filters B1 and B2 was an organic support (pig manure) and, for bio-filter B3, a mineral support (pozzolana). Bio-filter B4 consisted of a mixture of two supports, one organic and the other mineral, in correct proportions (pozzolana and pig manure). The feature of this study is the combination of the three VOCs with the two entirely different filtering materials used. A study on the state of knowledge allowed us to define the nature and sources of VOCs, the existing rules, the physico-chemical proprieties and the impact of the three VOCs used, the existing treatment procedures and in particularly bio-filtration: details on the principal operational parameters of the bio-filtration system and those influencing the performance of the bio-filter are detailed in the study. The methodology used, the complete installation set up in the laboratory and the characteristics of the material supports used are described, as well as the operational conditions for all the bio-filters studied. The experimental results for bio-filters B1, B2, B3 and B4 allowed us to follow the evolution of the parameters revealing the effectiveness (effectiveness and elimination capacity, mass load) and that of the operational parameters (pH, load losses, temperature, humidity, TOC, TEE, biomass, the flow rate of polluted gas and the bio-filter inlet VOS concentration).The elimination effectiveness attained by bio-filters B1 and B2 was 100% for acetone and 90% for toluene. For bio-filter B3, the maximum values were 100% for acetone and 50% for toluene, respectively after the third inoculation. Bio-filter B4 rapidly attained an elimination effectiveness of 100% for acetone and 90% for toluene, after complete re-watering of the porous media. TCE elimination effectiveness remained very limited for the four bio-filters studied (B 1-B2-B3-B4). The performance of the four bio-filters depended on the main parameters (humidity rate, load losses, and temperature) through the support. The acclimation period was longer for bio-filter B2 compared with bio-filters Bl and B4, and even longer for bio-filter B3. The pig manure was an excellent material for bio-filtration, with excellent microbial flora for speedy decomposition of VOCs, but with a shorter life than that of pozzolana. However, in spite of its structural stability and high porosity, the pozzolana required a meticulous inoculation and a long acclimatization period. The main advantage of the heterogeneous porous media (compost/pozzolana) was the satisfying performance of bio-filtration reached over long period (the operating limits were not reached). (author)

  14. Self-ignition and oxidation of various hydrocarbons between 600 and 1000 K at high pressure: experimental study with fast compression machine and modeling; Autoinflammation et oxydation de divers hydrocarbures entre 600 et 1000 K a haute pression: etude experimentale en machine a compression rapide et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Ribaucour, M.

    2002-12-01

    Low- and intermediate-temperature oxidation and self-ignition of hydrocarbons play a major role in spark ignition, diesel and HCCI (homogenous charge compression ignition) engines. A deep understanding of the chemistry linked with both phenomena is necessary to improve the engines efficiency and to reduce the formation of pollutants. This document treats of works about the self-ignition and oxidation at high pressure of various hydrocarbons between 600 and 1000 deg. K. The experimental tool used is a fast compression machine fitted with a fast sampling system for the measurement of self-ignition delays and of the concentrations of intermediate oxidation products. The advantages and limitations of this tool are discussed. The self-ignition of various hydrocarbons is compared using pre-defined data which characterize the phenomenologies like cold flames, negative temperature coefficients and self-ignition limits. The hydrocarbons considered are pure or binary mixtures of alkanes, pent-1-ene and n-butyl-benzene. The development of high pressure oxidation reaction schemes of alkanes between 600 and 1000 deg. K is described. It is directly based on the analysis of intermediate oxidation products. This methodology is also applied to pent-1-ene and n-butyl-benzene. The construction of detailed thermo-kinetic models of oxidation and the modeling of phenomena are made for n-butane, n-heptane, for the 3 pentane isomers, for pent-1-ene and n-butyl-benzene. Finally, the perspectives of future works are evoked. They concern new modeling and new methodologies to be applied in more predictive thermo-kinetic models and the reduction of detailed models in order to include them inside fluid dynamics codes. (J.S.)

  15. Experimental study of the saturation of parametric instabilities in the conditions of an inertial fusion plasma; Etude experimentale du developpement et de la saturation des instabilites parametriques dans des conditions representatives d'un plasma de fusion par confinement inertiel

    Energy Technology Data Exchange (ETDEWEB)

    Michel, D.T.

    2010-09-15

    This work presents the results of 3 series of experiments carried on the 2 French nanosecond multi-kilo-joule laser facilities: LULI 2000 and LIL (Laser Integration Line - that is a prototype of the future LMJ quadruplets). 2 issues have been tackled: first, the influence of the wavelength (second or third harmonic) on the saturation levels of Brillouin and Raman reflectivities and secondly, the laser smoothing and the imprint reduction through the use of a low-density foam layer. The first series of experiments has enabled us to get Brillouin backscattering rates in identical saturation regimes for the 2 frequencies: 2{omega} and 3{omega}. Hydrodynamic simulations and the interpretation of experimental results have shown that for both frequencies the laser-plasma conditions in which the instability develops are quite similar. In the second series of experiments we have shown that the saturation process that most limits the amplitude of the Electron Plasma Wave is the Langmuir decay instability (LDI). A low-density foam is efficient to reduce the imprint and if the foam ionization is supersonic, there is no risk to create a shock that could pre-heat the target core. A foam thickness of 500 {mu}m for a density of 10 mg/cm{sup 3} is efficient for a laser power of 10{sup 14} W/cm{sup 2}. (A.C.)

  16. Thermal stability of the aromatic fraction of Safaniya crude oil (Middle East): experimental study, kinetic scheme by molecular classes and geochemical implications; Stabilite thermique de la fraction aromatique de l'huile brute safaniya (Moyen-Orient): etude experimentale, schema cinetique par classes moleculaires et implications geochimiques

    Energy Technology Data Exchange (ETDEWEB)

    Al Darouich, T.

    2005-07-15

    The thermal evolution of reservoir oils is controlled by the kinetics of cracking reactions. The present work is concerned with the study of the thermal stability of the light aromatic components (C{sub 6}-C{sub 14}) of crude oils under geological conditions. The aim is to predict this stability through a mode l derived from laboratory pyrolyses. The light cut < 250 deg. C of Safaniya crude oil, corresponding to the C{sub 15} components, was obtained by fractionated distillation; pure aromatic fraction was then separated by liquid chromatography. Detailed molecular characterisation of the aromatic fraction was acquired using HPLC, GC and GC/MS. Then, quantified individual aromatic compounds were lumped into six molecular classes: BTXN, methyl-aromatics, alkyl-aromatics, naphthenic-aromatics, indene and sulphur - containing aromatics. Pyrolyses of the aromatic fraction were performed in gold tubes at 100 bars and different temperature/time conditions in a wide range (1 to 93%) of global conversion. Pyrolysis effluents were analysed and lumped into classes. The pyrolysis data were used to elaborate a semi - empirical kinetic scheme of 13 stoichiometric reactions for the primary and secondary cracking of the unstable classes. The scheme kinetic parameters were first estimated, and then numerically optimised, with the constraints of mass balance and hydrogen conservation. A set of pyrolysis experiments was performed at 375 deg.C under high pressures: 400, 800 and 1200 bars. Increasing slowing down in conversion rate with increasing pressure was thus observed compared to experiments at 100 bars. A slight selective effect of pressure on the different aromatic classes of the charge and on the product distribution was evidenced. The extrapolation of the kinetic model to the conditions of Elgin Field (North Sea) showed that pressure effect should shift the thermal cracking of light aromatics to higher temperatures by almost 8 deg. C. (author)

  17. Experimental study of Americium-241 biokinetics in Homarus Gammarus lobster. Analysis of the accumulation and detoxication mechanisms at the sub-cellular level; Etude experimentale des biocinetiques de l`americium-241 chez le homard homarus gammarus. Analyse des mecanismes d`accumulation et de detoxication au niveau subcellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Paquet, F.

    1991-12-01

    The Americium 241 radioelement accumulation and elimination rate and mechanisms in the lobster organism have been experimentally studied; incorporation and detoxification capacities of each organ are evaluated. The existence of various biological compartments is shown; the major role of the digestive gland in accumulation of the radioelement, its distribution towards the various organs, and its resorption is comprehensively described, with an analysis at the subcellular and molecular levels. 401 p., 65 fig., 43 tab., 428 ref.

  18. An experimental study of americium-241 biokinetics in the Lobster Homarus Gammarus. Analysis of the accumulation/storage and detoxification processes at the subcellular level; Etude experimentale des biocinetiques de l`americium-241 chez le homard homarus gammarus. Analyse des mecanismes d`accumulation et de detoxication au niveau subcellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Paquet, F.

    1993-01-01

    An experimental study of americium-241 kinetics has been conducted in the lobster Homarus gammmarus. The investigations were conducted at all the levels from the whole body to the subcellular and molecular levels. The animals were contaminated by a single or chronic ingestion of {sup 241} Am labelled mussels. Assessments of accumulation, elimination and distribution of the radionuclide were established on organisms kept in the laboratory; they made it possible to demonstrate the importance of the digestive gland in the radionuclide transfer pathways. The preliminary results led to structural then ultrastructural investigations of the digestive gland in association with radioautographic studies and cellular extractions methods. Four cellular types were demonstrated, only two of them being implied in the radionuclide retention, the former being responsible for americium intake and the latter for its long-term retention. By means of biochemical techniques, subcellular accumulation was studied and the organelles implied in the nuclide retention were specified. Finally, a method of cellular nuclei dissociation was developed; it made it possible to analyse the molecular nature of americium ligands and to demonstrate the function of the protein nuclear matrix in the nuclide retention.

  19. Experimental study on the influence of charge exchange on the stopping power in the interaction of chlorine with a gas and a deuterium plasma; Etude experimentale de l`influence des echanges de charges sur le pouvoir d`arret dans l`interaction d`ions chlore avec un gaz et un plasma de deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Nectoux, Marie [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1998-01-06

    This thesis is placed in the context of the physics of energy deposition of a multicharged heavy ion beam in matter at intermediate energies. The experiment gave measurements of energy loss as a function of final charge state for chlorine ions at 1.7 MeV/u in deuterium gas or plasma. In this way, we explore the influence of charge state evolution, depending on experimentally measured capture and ionization cross sections and the electron density of the target, on energy loss. The target is cylindrical and enclosed by two fast valves. The plasma is created in the gas by a discharge, which induces a magnetic perturbation of the beam (lens effect). This effect induces a divergent and misaligned outgoing beam. A simulation including charge state and velocity evolution of the projectile in flight in the magnetic field has been made in order to optimize beam analysis, to reach a precision better than 10{sup -3} in energy measurement. This study led to removal of the target to the `Split Pole`, a refocusing magnetic spectrometer. The first results obtained clearly show the dependence of energy loss on exit charge and especially on its evolution in the target. This is explained in terms of the lengths covered by the projectile in its successive charge states in the target, which depends on target electron density and the medium considered. In plasma, we observed an energy distribution with exit charge twice that observed in gas, because of a strong decrease of charge exchange. A comparison of data obtained in gas with stopping power calculated from Bethe-Bloch-Barkas theory leads to the necessity of including spatial extension of the projectile charge in the theory. (author) 81 refs., 62 figs., 5tabs.

  20. Experimental study of the spin structure of the neutron ({sup 3}He) with low Q{sup 2}: a relationship between the Bjorken and Gerasimov-Drell-Hearn sum rules; Etude experimentale de la structure en spin du neutron ({sup 3}He) a bas Q{sup 2}: une connexion entre les regles de somme de Bjorken et Gerasimov-Drell-Hearn

    Energy Technology Data Exchange (ETDEWEB)

    Deur, A

    2000-10-01

    This thesis presents an experimental study of the neutron (and {sup 3}He) spin structure with a particular emphasis in the resonance domain (experiment E94010 that took place in 1997 at Jefferson Lab (TJNAF or formerly CEBAF) in Virginia). A polarized {sup 3}He target was built in order to achieve this study since polarized {sup 3}He nuclei can be seen as polarized neutrons. This target allowed the measurement of the polarized absolute cross sections {sigma}{sub 1/2}(Q{sup 2}, {nu}) and {sigma}{sub 3/2}(Q{sup 2}, {nu}) from the inclusive reaction {sup {sup {yields}}{sup 3}He}({sup {yields}}e, e')X for incident beam energies ranging from 0.86 GeV to 5.07 GeV at a scattering angle of 15.5 deg. The Q{sup 2} evolution of the generalized Gerasimov-Drell-Hearn (GDH) integral on {sup 3}He and on neutron was measured from 0.1 GeV{sup 2} to 1.0 GeV{sup 2} in order to understand the transition between perturbative QCD and non-perturbative QCD. The integration domain in {nu} (the energy loss of the scattered electron) is from the pion threshold to about 2.5 GeV which covers both the resonance region and the Deep Inelastic Scattering. The high precision of our data constrains the models giving the Q{sup 2} evolution of the generalized GDH integral. The polarized quasi-elastic scattering was also measured. The cross section {sigma}{sup TT}(Q{sup 2}, {nu}) on {sup 3}He and the spin structure functions g{sub 1}{sup {sup 3}He}(Q{sup 2}, {nu}) and g{sub 2}{sup {sup 3}He}(Q{sup 2}, {nu}) are presented. These data are an indication that the higher-twists are small in our kinematics domain and that the Bloom-Gilman duality seems to hold for the polarized spin structure functions. (author)

  1. Realisation and experimental testing of silicon-point cathodes for field emission and field photoemission in a continuous and pulsed regime; Realisation et etude experimentale des cathodes a reseaux de pointes en silicium pour emission de champ et photoemission de champ en regime continu et pulse

    Energy Technology Data Exchange (ETDEWEB)

    Aboubacar, A.

    1993-03-26

    Acceleration technique and free electron laser improvements require the production of intense, bunched electron beams with small emittance. Photocathodes with arrays of tips have been prepared using microlithographic technique. Si(P) and Si(N) with (100) and (111) crystallographic orientation are used. Current emission due to field effect has been measured. Study of band bending at the surface with strong applied electric field is outline. Its interest is proved in field photoemission. Fowler-Nordheim` theory is used to determine the field reinforcement and emissive area. Experience in high vacuum chamber (pressure of few 10{sup -10} torr) yields satisfactory results from low P type silicon, instantaneous photocurrent is observed during a short exposure of light. Photocurrent of about a hundred times dark-current, at the threshold of field emission, from heavy density of tips is measured. An acousto-optic cell allows producing, with a continuous Argon laser, some pulsed beams of light. Optical excitation and photocurrent pulses follow with the same time. Quantum efficiency around 1% has been measured with low energy pulsed laser of a few nJ during few tens of ns at frequency of few MHz. (orig.).

  2. Experimental study of high current negative ion sources D{sup -} / H{sup -}. Analysis based on the simulation of the negative ion transport in the plasma source; Etude experimentale de sources a fort courant d`ions negatifs D{sup -} / H{sup -}. Analyse fondee sur la simulation du transport des ions dans le plasma de la source

    Energy Technology Data Exchange (ETDEWEB)

    Riz, D.

    1996-10-30

    In the frame of the development of a neutral beam injection system able to work the ITER tokamak (International Thermonuclear Experimental Reactor), two negative ion sources, Dragon and Kamaboko, have been installed on the MANTIS test bed in Cadarache, and studies in order to extract 20 mA/cm{sup 2} of D{sup -}. The two production modes of negative ions have been investigated: volume production; surface production after cesium injection in the discharge. Experiments have shown that cesium seeding is necessary in order to reach the requested performances for ITER. 20 mA/cm{sup 2} have been extracted from the Kamaboko source for an arc power density of 2.5 kW/liter. Simultaneously, a code called NIETZSCHE has been developed to simulate the negative ions transport in the source plasma, from their birth place to the extraction holes. The ion trajectory is calculated by numerically solving the 3D motion equation, while the atomic processes of destruction, of elastic collisions H{sup -}/H{sup +} and of charge exchange H{sup -}/H{sup 0} are handled at each time step by a Monte Carlo procedure. The code allows to obtain the extraction probability of a negative ion produced at a given location. The calculations performed with NIETZSCHE have allowed to explain several phenomena observed on negative ion sources, such as the isotopic effect H{sup -}/D{sup -} and the influence of the polarisation of the plasma grid and of the magnetic filter on the negative ions current. The code has also shown that, in the type of sources contemplated for ITER, working with large arc power densities (> 1 kW/liter), only negative ions produced in volume at a distance lower that 2 cm from the plasma grid and those produced at the grid surface have a chance of being extracted. (author). 122 refs.

  3. Experimental study and modelling of competitive adsorption equilibria of aromatics in liquid phase on X and Y faujasites; Etude experimentale et modelisation des equilibres d'adsorption competitive d'aromatiques en phase liquide sur des faujasites X et Y

    Energy Technology Data Exchange (ETDEWEB)

    Tournier, H.

    2000-10-13

    The separation of p-xylene from C{sub 8} aromatics is performed industrially by selective adsorption on zeolitic molecular sieves. The aim of this work is to study and model adsorption equilibria of C{sub 8} and C{sub 10} aromatics on X and Y zeolites. The experimental data are obtained by an entirely automated equipment allowing to work in a large range of temperature (50 deg. C - 250 deg. C). With this equipment, we can follow the evolution of the composition of the liquid phase and determine the composition of the adsorbed phase at equilibrium by a mass balance calculation and with an inert component. Two analytical techniques are used to determine the composition of the liquid phase: (1) a classical method using a gas chromatograph (GC) allowed to measure selectivities in the concentration range (3%-97%) in a component; (2) an original method based on the use and on the measure of {sup 13}C labelled xylenes was developed to investigate the ranges of strongly contrasting concentrations [0-3%] and [97%-100%] in a component, which are representative of high purity domains. Lastly, three thermodynamic models are used to describe the adsorption equilibria: the Langmuir-Freundlich model, the quasi-chemical model and the statistical model. The last model is the more interesting, because it is based on physical considerations. A new statistical model has been developed with taking into account some observations coming from adsorption phenomenon in zeolites. (author)

  4. Experimental and numerical studies of the effect of plasticity mechanisms on the brittle rupture by cleavage in low alloy steels; Etudes experimentale et numerique de l'effet des mecanismes de plasticite sur la rupture fragile par clivage dans les aciers faiblement allies

    Energy Technology Data Exchange (ETDEWEB)

    Libert, M

    2007-09-15

    It is indispensable to guarantee the integrity of PWR reactor vessels during an accidental running: in this context, the understanding and the modelling of the mechanisms of brittle rupture of steels are decisive elements of the complicated estimation of the service life of reactor vessels. The models of local approach of rupture by cleavage are one of the main tools of anticipation of the tensile strength of low alloy steels. In this work, the effect of the stresses heterogeneities in a local criteria of initiation of cleavage has been taken into account. The results of the microstructure calculations are used for proposing a statistical description of the local stresses distribution evolution. This statistical approach allows to propose a local approach model of the rupture depending both of the mechanical heterogeneities and of the sizes distributions of the defects. The behaviour of the material and its evolution are characterized at the microscopic and macroscopic scales in the temperature range [25 C, -196 C]. Simple tensile tests, velocity and temperature rises tests and toughness tests have been carried out. A micro-mechanical behaviour model describing the plastic behaviour below the transition temperature T{sub a} has been proposed. The behaviour law is based on the deformation mechanisms described in bibliography and identified by an inverse method from mechanical tests. The TEM observations and the characterization of the behaviour thermally activated allow to determine several parameters of the model. Simulations are carried out in order to model the main stress distributions {sigma}{sub 1} in two bainite microstructures corresponding to the elementary volume of the local approach of the rupture. The temperature and the triaxiality effects on the evolutions of the heterogeneities is characterized. A distribution function describing the distribution of the local values of {sigma}{sub 1} in terms of the main and equivalent mean stresses {sigma}{sub 1} and {sigma}{sub m} in the microstructure is proposed. This function is used for formulating a model of rupture local approach integrating the distribution of the critical defects sizes and the distributions of {sigma}{sub 1}. It is shown that in some cases, the dispersion of the local stresses is sufficient to explain the dispersions of the rupture stresses at the scale of the elementary volume. The dispersions of the rupture stresses are in agreement with those given by the Beremin model. The taken into account of the mechanical heterogeneities allows to introduce a dependency of the rupture probability in terms of temperature, of deformation and of triaxiality. (O.M.)

  5. Experimental and modeling study of the impact of vertical transport processes from the boundary-layer on the variability and the budget of tropospheric ozone; Etude experimentale et numerique de l'influence des processus de transport depuis la couche-limite sur la variabilite et le bilan d'ozone tropospherique

    Energy Technology Data Exchange (ETDEWEB)

    Colette, A

    2005-12-15

    Closing the tropospheric ozone budget requires a better understanding of the role of transport processes from the major reservoirs: the planetary boundary layer and the stratosphere. Case studies lead to the identification of mechanisms involved as well as their efficiency. However, their global impact on the budget must be addressed on a climatological basis. This manuscript is thus divided in two parts. First, we present case studies based on ozone LIDAR measurements performed during the ESCOMPTE campaign. This work consists in a data analysis investigation by means of a hybrid - Lagrangian study involving: global meteorological analyses, Lagrangian particle dispersion computation, and mesoscale, chemistry - transport, and Lagrangian photochemistry modeling. Our aim is to document the amount of observed ozone variability related to transport processes and, when appropriate, to infer the role of tropospheric photochemical production. Second, we propose a climatological analysis of the respective impact of transport from the boundary-layer and from the tropopause region on the tropospheric ozone budget. A multivariate analysis is presented and compared to a trajectography approach. Once validated, this algorithm is applied to the whole database of ozone profiles collected above Europe during the past 30 years in order to discuss the seasonal, geographical and temporal variability of transport processes as well as their impact on the tropospheric ozone budget. The variability of turbulent mixing and its impact on the persistence of tropospheric layers will also be discussed. (author)

  6. Experimental study and kinetic modeling of the thermal degradation of aromatic volatile organic compounds (benzene, toluene and xylene-para) in methane flames; Etude experimentale et modelisation cinetique de la degradation thermique des composes organiques volatils aromatiques benzenes, toluene et para-xylene dans des flammes de methane

    Energy Technology Data Exchange (ETDEWEB)

    Dupont, L.

    2001-02-01

    This study treats of the thermal degradation of a family of aromatic volatile organic compounds (VOCs) in laminar premixed methane flames at low pressure. The experimental influence of benzene, toluene and xylene-para on the structure of a reference methane flame has been studied. The molar fraction profiles of the stable and reactive, aliphatic, aromatic and cyclic species have been established by the coupling of the molecular beam sampling/mass spectroscopy technique with the gas chromatography/mass spectroscopy technique. Temperature profiles have been measured using a covered thermocouple. A detailed kinetic mechanism of oxidation of these compounds in flame conditions has been developed. Different available sub-mechanisms have been used as references: the GDF-Kin 1.0 model for the oxidation of methane and the models of Tan and Franck (1996) and of Lindstedt and Maurice (1996) in the case of benzene and toluene. In the case of para-xylene, a model has been developed because no mechanisms was available in the literature. These different mechanisms have been refined, completed or adjusted by comparing the experimental results with those obtained by kinetic modeling. The complete kinetic mechanism, comprising 156 chemical species involved in 1072 reactions allows to reproduce all the experimental observations in a satisfactory manner. The kinetic analysis of reactions velocity has permitted to determine oxidation kinetic schemes for benzene, toluene, xylene-para and for the cyclopentadienyl radical, main species at the origin of the rupture of the aromatic cycle. Reactions of recombination with the methyl radicals formed during methane oxidation, of the different aromatic or aliphatic radicals created during the oxidation of aromatics, play an important role and lead to the formation of several aromatic pollutants (ethyl-benzene for instance) or aliphatic pollutants (butadiene or penta-diene for instance) in flames. (J.S.)

  7. Experimental study of kinetic and mechanism of dissolution of apatite structured minerals. Application to the prediction of the long term behavior of an actinides storage host matrix; Etude experimentale de la cinetique et des mecanismes d'alteration de mineraux apatitiques. Application au comportement d'une ceramique de confinement d'actinides mineurs

    Energy Technology Data Exchange (ETDEWEB)

    Chairat, C

    2005-11-15

    The motivation for this study is to assess the potential of using apatite structured ceramics as long-lived actinide storage hosts. To assess their ability to resist aqueous corrosion, the dissolution of natural fluoro-apatite and synthetic Nd-britholite (neodymium is a proxy for the trivalent actinides) was studied. Mineral surfaces were characterized using a combined spectrometric, electrokinetic and potentiometric approach and dissolution rates were measured in closed and open system reactors as a function of solution composition. Experimental results suggest apatitic minerals dissolve via distinct step sequence: 1) fluoride release, 2) release of the calcium situated in the M1, and 3) the simultaneous removal of phosphate and calcium II via the breaking of only Ca-O bonds. TST based rate equations based in this mechanism accurately describe fluoro-apatite and synthetic britholite dissolution rates as a function of solution composition. Nd release rates are limited by precipitation of Nd-rhabdophane. (author)

  8. Experimental study of hot electrons propagation and energy deposition in solid or laser-shock compressed targets: applications to fast igniter; Etude experimentale de la propagation et du depot d'energie d'electrons rapides dans une cible solide ou comprimee par choc laser: application a l'allumeur rapide

    Energy Technology Data Exchange (ETDEWEB)

    Pisani, F

    2000-02-15

    In the fast igniter scheme, a recent approach proposed for the inertial confinement fusion, the idea is to dissociate the fuel ignition phase from its compression. The ignition phase would be then achieved by means of an external energy source: a fast electron beam generated by the interaction with an ultra-intense laser. The main goal of this work is to study the mechanisms of the hot electron energy transfer to the compressed fuel. We intent in particular to study the role of the electric and collisional effects involved in the hot electron propagation in a medium with properties similar to the compressed fuel. We carried out two experiments, one at the Vulcan laser facility (England) and the second one at the new LULI 100 TW laser (France). During the first experiment, we obtained the first results on the hot electron propagation in a dense and hot plasma. The innovating aspect of this work was in particular the use of the laser-shock technique to generate high pressures, allowing the strongly correlated and degenerated plasma to be created. The role of the electric and magnetic effects due to the space charge associated with the fast electron beam has been investigated in the second experiment. Here we studied the propagation in materials with different electrical characteristics: an insulator and a conductor. The analysis of the results showed that only by taking into account simultaneously the two propagation mechanisms (collisions and electric effects) a correct treatment of the energy deposition is possible. We also showed the importance of taking into account the induced modifications due to the electrons beam crossing the target, especially the induced heating. (author)

  9. Experimental study of chemical-mechanical coupling during percolation of reactive fluid through rocks under stress, in the context of the CO{sub 2} geological sequestration; Etude experimentale du couplage chimie-mecanique lors de la percolation d'un fluide reactif dans des roches sous contrainte, dans le contexte de la sequestration geologique du CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Le Guen, Y

    2006-10-15

    CO{sub 2} injection into geological repositories will induce chemical and mechanical instabilities. The study of these instabilities is based on experimental deformation of natural rock samples under stress, in the presence of fluids containing, or not, dissolved CO{sub 2}. Triaxial cells used for the experiments permitted an independent control and measurement of stress, temperature, fluid pressure and composition. Vertical strains were measured during several months, with a resolution of 1.10{sup -12} s{sup -1} on the strain rate. Simultaneously, fluids were analysed in order to quantify fluid-rock interactions. For limestone samples, percolation of CO{sub 2}-rich fluids increases strain rate by a factor 1.7 up to 5; on the other hand, sandstone deformation remained almost the same. Increase in strain rate with limestone samples was explained by injected water acidification by the CO{sub 2} which increases rock solubility and reaction kinetics. On the opposite, small effect of CO{sub 2} on quartz explains the absence of deformation. X-ray observations confirmed the importance of rock composition and structure on the porosity evolution. Numerical simulations of rock elastic properties showed increasing shear stress into the sample. Measured deformation showed an evolution of reservoir rocks mechanical properties. It was interpreted as the consequence of pressure solution mechanisms both at grains contacts and on grain free surfaces. (author)

  10. Contribution to the study of copper and copper-arsenic archaeo-metallurgy using light element analysis and experimental fusion; Contribution a l`etude de la paleometallurgie du cuivre et du cuivre-arsenic a partir de l`analyse des elements legers et de fusions experimentales

    Energy Technology Data Exchange (ETDEWEB)

    Papillon, F

    1997-12-31

    The objective of this study is to try a direct reconstruction from ancient artefacts of the elaboration technology used in the dawning copper metallurgy. This word is based on both the light elements analysis and the carry out of the principles of physical metallurgy. However the study of an archaeological artefact necessitates the use of non destructive methods. A main aspect of this work consists in developing the most adequate metallographic technique and the methods for the determination of oxygen and carbon by ion beam analysis. Additionally experimental melting of copper and copper arsenic alloys were carried out in laboratory, under various temperature and atmosphere conditions, and `on the field` in Archeodrome de Beaune, in order to reconstruct part of the prehistorical craftsmanship. The results of measurement are consistent with our general knowledge of oxido-reduction phenomena and the behaviour of copper and copper arsenic alloys s in agreement with the prediction of thermodynamics. The nuclear analysis of three ancient artefacts showed that the oxygen and carbon contents were closer to those of the Archeodrome than those of the laboratory. Further studies of the field should consider all parameters controlling the physical-chemistry of charcoal fire. (author) 96 refs.

  11. Low temperature oxidation, co-oxidation and auto-ignition of olefinic and aromatic blending compounds: Experimental study of interactions during the oxidation of a surrogate fuel; Oxydation, co-oxydation et auto-inflammation a basses temperatures d'alcenes et aromatiques types: etude experimentale des interactions au sein d'un carburant-modele

    Energy Technology Data Exchange (ETDEWEB)

    Vanhove, G.

    2004-12-15

    The low-temperature (600-900 K) and high-pressure (5-25 bar) oxidation and auto-ignition of the three position isomers of hexene, of binary mixtures of 1-hexene, toluene and iso-octane, and of a surrogate fuel composed of these three compounds were studied in motor conditions using a rapid compression machine. Auto-ignition delay times were measured as long as intermediate products concentrations during the delay. The results show that the oxidation chemistry of the hexenes is very dependent on the position of the double bond inside the molecule, and that strong interactions between the oxidation mechanisms of hydrocarbons in mixtures can occur. The data obtained concerning the surrogate fuel give a good insight into the behaviour of a practical gasoline after an homogeneous charge compression. (author)

  12. Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments; Etude experimentale et modelisation, du comportement, de l'endommagement et de la rupture en fluage a haute temperature de joint soudes en acier 9Cr1Mo-NbV

    Energy Technology Data Exchange (ETDEWEB)

    Gaffard, V

    2004-12-15

    Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also experimentally confirmed in the present study. The evaluation of creep flow and damage behaviour of the weldment requires two types of investigations, namely, the determination of the effect of welding on creep strength of the material especially in the heat affected zone (HAZ), and the investigation of the effect of the mismatch in creep properties between the weld metal, the base metal and the HAZ. To do so, the microstructure of the weakest HAZ was first reproduced on bulk specimens. These specimens were used to experimentally investigate the creep flow and damage behaviour of the weakest HAZ microstructure. The results of experiments allowed to fit a creep model for the simulated HAZ derived from the one designed for the base metal. The integration of constitutive equations of base metal, weld metal and simulated HAZ in finite element calculations of the heterogeneous weldment allows to study the effect of mismatch on creep properties and finally to predict creep lifetime of 9Cr1Mo-NbV welded components. (author)

  13. Theoretical and experimental study of the double ionization by electron impact involving the Auger effect: processes and exchanges interferences; Etude theorique et experimentale de la double ionisation par impact electronique incluant l'effet auger: interferences d'echanges et de processus

    Energy Technology Data Exchange (ETDEWEB)

    Catoire, F

    2006-09-15

    In this work, double ionisation mechanisms of argon by electron impact in which the Auger effect is included have been studied as a function of the incident electron energy. Five and six fold differential cross sections in angle and in energy have been measured and analysed in a coplanar geometry. The efficiency of the apparatus has been improved by the use of a new toroidal analyser. For the first time, the six fold differential cross section in which the Auger electron and the ejected electron with identical kinetic energies (205 eV) are involved, was measured at an incident energy of 956 eV in the case of argon. In the theoretical models developed during this work, the triple continuum is represented by a manifold of coulomb waves describing the interaction of all electrons with the residual ion. Exchange effects between electrons were also included in the models. Comparison between experimental and theoretical results allows to study the relative contribution of the Auger process and the direct double ionisation on the angular dependence five fold differential cross section. In particular, the Auger process contribution seems to become increasingly important as the incident energy is increased.

  14. L’Etude détaillée des accidents (EDA ): Un outil pour la recherche

    OpenAIRE

    Girard, Yves

    1995-01-01

    L’accès aux données est généralement une difficulté de la recherche. En matière de sécurité routière, une solution possible est le recours aux études approfondies d’accidents. Cette note expose I’Etude Détaillée des Accidents (EDA) de I’INRETS. L’objectif initial de I’EDA est d’enrichir la connaissance sur le déroulement des accidents en vue de leur prévention. La méthode de I’EDA repose sur une conception de l’accident comme symptôme de dysfonctionnement du système de circulation, sur une...

  15. Dosimeter calibration facilities and methods at the Radiation Measurement Laboratory of the Centre d'etudes nucleaires, Grenoble

    International Nuclear Information System (INIS)

    At the Centre d'etudes nucleaires, Grenoble, the Radiation Measurement Laboratory, which forms part of the Environmental Protection and Research Department, serves the entire Centre for purposes of dosimetry and the calibration of dose meters. The needs of radiation protection are such that one must have facilities for checking periodically the calibration of radiation-monitoring instruments and developing special dosimetry techniques. It was thought a good idea to arrange for the dosimetry and radiation protection team to assist other groups working at the Centre - in particular, the staff of the biology and radiobiology laboratories - and also bodies outside the framework of the French Commissariat a l'energie atomique. Thus, technical collaboration has been established with, for example, Grenoble's Centre hospitalier universitaire (university clinic), which makes use of the facilities and skills available at the Radiation Measurement Laboratory for solving special dosimetry problems. With the Laboratory's facilities it is possible to calibrate dose meters for gamma, beta and neutron measurements

  16. Etude des defauts microscopiques et des proprietes optiques, electroniques et magnetiques du compose neodyme cerium oxyde de cuivre

    Science.gov (United States)

    Richard, Pierre

    La presente these, qui combine des mesures de diffusion Raman, de transmission infrarouge, de conductivite hyperfrequence et d'interferometrie ultrasonore sur les composes Nd 2-xCexCuO 4, traite des defauts d'oxygene, ainsi que des proprietes optiques, electroniques et magnetiques de ces materiaux. Les resultats experimentaux obtenus sont correles avec plusieurs donnees experimentales disponibles dans la litterature. D'abord, la caracterisation des modes Raman et des niveaux d'energie de champ cristallin de l'ion Nd3+ au moyen de techniques optiques, en fonction du dopage en cerium et du contenu en oxygene, permettent de conclure a la presence de defauts lies a une non-stoechiometrie en oxygene dans ces composes. En effet, des excitations de champ cristallin assignees a des ions Nd3+ en sites irreguliers sont observees, en plus des bandes d'absorption associees aux ions Nd3+ en site regulier, dans les spectres correspondant aux multiplets 4I11/2, 4I13/2 et 4I 15/2 de l'ion Nd3+. Les resultats experimentaux indiquent que, contrairement a la croyance largement repandue, les oxygenes apicaux, bien que presents dans les echantillons dopes, ne sont pas enleves lors du processus de reduction des echantillons necessaire pour faire apparaitre la supraconductivite dans cette famille de cuprates. Au contraire, des lacunes d'oxygene, dont le type varie en fonction du dopage, sont creees lors de ce processus. En particulier, il est montre dans ce travail que la reduction des echantillons dopes de maniere optimale conduit a la creation de lacunes d'oxygene dans les plans CuO2. Les consequences de telles lacunes sont largement discutees. En outre, il est suggere que de telles lacunes sont responsables de la perte de l'ordre antiferromagnetique a longue portee des ions Cu2+. Finalement, l'interaction d'echange anisotrope Nd3+-Cu 2+ dans le compose nondope est caracterisee au moyen de la transmission infrarouge sous champ magnetique. L'eclatement des doublets de Kramers mesure

  17. Experimental contamination of margaritana margaritifera (L) (a Fresh water bivalve) by caesium 137; Contamination experimentale de margaritana margaritifera (L) (bivalve d'eau douce) par le cesium 137

    Energy Technology Data Exchange (ETDEWEB)

    Foulquier, L.; Bovard, P.; Grauby, A. [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

    1966-07-01

    The hydro biological research carried out in the Radio-Ecology Section has led the authors to study some Margaritana sampling stations situated down-stream from the Monts d'Arree nuclear power station. They describe the preservation and contamination methods used for fixing the {sup 137}Cs concentration factors in the case of Margaritana Margaritifera (L). The results of experiments carried out over a period of one hundred days show that the specific activity of the various organs is stabilized after thirty to thirty-five days. The authors have noticed a relatively low adsorption on the shell through the intermediary of micro-organisms, and a strong and rapid absorption in the soft parts. The concentration factors have values, at equilibrium, of around: 9 for the shell, 300 for all the organs, and 38 for the whole animal. A comparison of these results with work published by other authors makes it possible to draw general conclusions concerning the mechanism of {sup 137}Cs fixation by lamellibranch, as well as their capacity of fixation. (author) [French] Les etudes hydrobiologiques effectuees au sein de la Section de Radio-Ecologie ont amene les auteurs a etudier des stations de prelevement de Margaritana en aval de la Centrale Nucleaire des Monts d'Arree. Ils decrivent les methodes de conservation et de contamination utilisees pour l'etablissement des facteurs de concentration du {sup 137}Cs par Margaritana margaritifera (L). Les resultats des experimentations menees pendant cent jours montrent que les activites specifiques de la coquille et des differents organes se stabilisent au bout de trente a trente-cinq jours. Les auteurs constatent une adsorption relativement faible sur la coquille par l'intermediaire des micro-organismes et une absorption forte et rapide dans les parties molles. Les facteurs de concentration se situent, a l'equilibre, autour de: 9 pour la coquille, 300 pour l'ensemble des organes et 38 si l'on considere

  18. Spontaneous bacterial peritonitis

    Institute of Scientific and Technical Information of China (English)

    Anastasios Koulaouzidis; Shivaram Bhat; Athar A Saeed

    2009-01-01

    Since its initial description in 1964, research has transformed spontaneous bacterial peritonitis (SBP) from a feared disease (with reported mortality of 90%) to a treatable complication of decompensated cirrhosis,albeit with steady prevalence and a high recurrence rate. Bacterial translocation, the key mechanism in the pathogenesis of SBP, is only possible because of the concurrent failure of defensive mechanisms in cirrhosis.Variants of SBP should be treated. Leucocyte esterase reagent strips have managed to shorten the 'tap-toshot' time, while future studies should look into their combined use with ascitic fluid pH. Third generation cephalosporins are the antibiotic of choice because they have a number of advantages. Renal dysfunction has been shown to be an independent predictor of mortality in patients with SBP. Albumin is felt to reduce the risk of renal impairment by improving effective intravascular volume, and by helping to bind proinflammatory molecules. Following a single episode of SBP, patients should have long-term antibiotic prophylaxis and be considered for liver transplantation.

  19. Antimicrobials for bacterial bioterrorism agents.

    Science.gov (United States)

    Sarkar-Tyson, Mitali; Atkins, Helen S

    2011-06-01

    The limitations of current antimicrobials for highly virulent pathogens considered as potential bioterrorism agents drives the requirement for new antimicrobials that are suitable for use in populations in the event of a deliberate release. Strategies targeting bacterial virulence offer the potential for new countermeasures to combat bacterial bioterrorism agents, including those active against a broad spectrum of pathogens. Although early in the development of antivirulence approaches, inhibitors of bacterial type III secretion systems and cell division mechanisms show promise for the future.

  20. Ajuste de un Modelo Hidrodinámico para una Columna con Empaques Estructurados usando Valores Experimentales Fit of an Hydrodynamic Model for a Structured Packing Column using Experimental Data

    Directory of Open Access Journals (Sweden)

    R.H. Chávez

    2004-01-01

    Full Text Available El objetivo del presente trabajo es ajustar un modelo hidrodinámico para columna empacada con empaque estructurado, partiendo de valores experimentales. Se comparan dos empaques, uno construido en el Instituto Nacional de Investigaciones Nucleares (ININ, de gasa de alambre de latón, y otro de la empresa Sulzer Ltda., de gasa de alambre de acero inoxidable. El modelo hidrodinámico se ajustó mediante la técnica de mínimos cuadrados con el método Levenberg-Marquardt para ecuaciones no lineales. Se obtuvieron las caídas de presión experimentales y teóricas determinadas por el modelo, así como los parámetros de ajuste del modelo tanto para el empaque ININ, como para el Sulzer BX. El empaque ININ mostró mayor caída de presión que el empaque Sulzer BX, debido a sus características geométricas. Se concluye que con la determinación de los parámetros de ajuste del modelo, se puede definir los regímenes del flujo de columnas que empleen empaque estructurado ININ y Sulzer BX.The objective of the present study is to fit a hydrodynamic model for a packed column with structured packing, based on experimental values. Two packing materials were used, one was made by the Instituto Nacional de Investigaciones Nucleares (ININ of the gauze type made of brass and the other by Sulzer Ltda., also of the gauze type but made of stainless steel. The hydrodynamic model was fit using the method of least squares using the Levenberg and Marquardt methodology for non-linear equations. Experimental and theoretical pressure drops were determined using the model, as well as the fitted parameters of the model both for ININ and Sulzer BX packings. The ININ packing has a higher pressure drop than the Sulzer BX, due to its geometric characteristics. It is concluded that by using the fitted parameters of the model, flow regimes in the column may be defined when using ININ or Sulzer BX structured packing

  1. [Small intestine bacterial overgrowth].

    Science.gov (United States)

    Leung Ki, E L; Roduit, J; Delarive, J; Guyot, J; Michetti, P; Dorta, G

    2010-01-27

    Small intestine bacterial overgrowth (SIBO) is a condition characterised by nutrient malabsorption and excessive bacteria in the small intestine. It typically presents with diarrhea, flatulence and a syndrome of malabsorption (steatorrhea, macrocytic anemia). However, it may be asymptomatic in the eldery. A high index of suspicion is necessary in order to differentiate SIBO from other similar presenting disorders such as coeliac disease, lactose intolerance or the irritable bowel syndrome. A search for predisposing factor is thus necessary. These factors may be anatomical (stenosis, blind loop), or functional (intestinal hypomotility, achlorydria). The hydrogen breath test is the most frequently used diagnostic test although it lacks standardisation. The treatment of SIBO consists of eliminating predisposing factors and broad-spectrum antibiotic therapy. PMID:20214190

  2. Studying bacterial multispecies biofilms

    DEFF Research Database (Denmark)

    Røder, Henriette Lyng; Sørensen, Søren Johannes; Burmølle, Mette

    2016-01-01

    The high prevalence and significance of multispecies biofilms have now been demonstrated in various bacterial habitats with medical, industrial, and ecological relevance. It is highly evident that several species of bacteria coexist and interact in biofilms, which highlights the need for evaluating...... the approaches used to study these complex communities. This review focuses on the establishment of multispecies biofilms in vitro, interspecies interactions in microhabitats, and how to select communities for evaluation. Studies have used different experimental approaches; here we evaluate the benefits...... and drawbacks of varying the degree of complexity. This review aims to facilitate multispecies biofilm research in order to expand the current limited knowledge on interspecies interactions. Recent technological advances have enabled total diversity analysis of highly complex and diverse microbial communities...

  3. Bacterial proteases and virulence

    DEFF Research Database (Denmark)

    Frees, Dorte; Brøndsted, Lone; Ingmer, Hanne

    2013-01-01

    Bacterial pathogens rely on proteolysis for variety of purposes during the infection process. In the cytosol, the main proteolytic players are the conserved Clp and Lon proteases that directly contribute to virulence through the timely degradation of virulence regulators and indirectly by providing...... tolerance to adverse conditions such as those experienced in the host. In the membrane, HtrA performs similar functions whereas the extracellular proteases, in close contact with host components, pave the way for spreading infections by degrading host matrix components or interfering with host cell...... signalling to short-circuit host cell processes. Common to both intra- and extracellular proteases is the tight control of their proteolytic activities. In general, substrate recognition by the intracellular proteases is highly selective which is, in part, attributed to the chaperone activity associated...

  4. Bacterial Protein-Tyrosine Kinases

    DEFF Research Database (Denmark)

    Shi, Lei; Kobir, Ahasanul; Jers, Carsten;

    2010-01-01

    in exopolysaccharide production, virulence, DNA metabolism, stress response and other key functions of the bacterial cell. BY-kinases act through autophosphorylation (mainly in exopolysaccharide production) and phosphorylation of other proteins, which have in most cases been shown to be activated by tyrosine......Bacteria and Eukarya share essentially the same family of protein-serine/threonine kinases, also known as the Hanks-type kinases. However, when it comes to protein-tyrosine phosphorylation, bacteria seem to have gone their own way. Bacterial protein-tyrosine kinases (BY-kinases) are bacterial...... and highlighted their importance in bacterial physiology. Having no orthologues in Eukarya, BY-kinases are receiving a growing attention from the biomedical field, since they represent a particularly promising target for anti-bacterial drug design....

  5. Molecular approaches for bacterial azoreductases

    Directory of Open Access Journals (Sweden)

    Montira Leelakriangsak

    2013-12-01

    Full Text Available Azo dyes are the dominant types of synthetic dyes, widely used in textiles, foods, leather, printing, tattooing, cosmetics, and pharmaceutical industries. Many microorganisms are able to decolorize azo dyes, and there is increasing interest in biological waste treatment methods. Bacterial azoreductases can cleave azo linkages (-N=N- in azo dyes, forming aromatic amines. This review mainly focuses on employing molecular approaches, including gene manipulation and recombinant strains, to study bacterial azoreductases. The construction of the recombinant protein by cloning and the overexpression of azoreductase is described. The mechanisms and function of bacterial azoreductases can be studied by other molecular techniques discussed in this review, such as RT-PCR, southern blot analysis, western blot analysis, zymography, and muta-genesis in order to understand bacterial azoreductase properties, function and application. In addition, understanding the regulation of azoreductase gene expression will lead to the systematic use of gene manipulation in bacterial strains for new strategies in future waste remediation technologies.

  6. Métodos Experimentales de Estudio de la Percepción Temprana del Habla/ Experimental Study Techniques for the Early Speech Perception/ Métodos Experimentais de Estudo da Percepção Precoce da Fala

    Directory of Open Access Journals (Sweden)

    Leonardo Francisco Barón Birchenall

    2014-07-01

    Full Text Available El estudio de la percepción temprana del habla surgió a comienzos de la década de los setenta, pero solo se desarrolló plenamente diez años después, debido a la aparición y adaptación de nuevos métodos empíricos y herramientas tecnológicas. En este artículo se presenta una revisión de los métodos experimentales que pueden ser utilizados para el estudio de la percepción del habla en niños menores de un año. También se refieren algunas de las conclusiones teóricas más relevantes que se han alcanzado gracias a su aplicación. Se pretende brindar un panorama del estado metodológico y teórico del estudio de la percepción del lenguaje hablado durante el primer año de vida.

  7. Positioning of bacterial chemoreceptors.

    Science.gov (United States)

    Jones, Christopher W; Armitage, Judith P

    2015-05-01

    For optimum growth, bacteria must adapt to their environment, and one way that many species do this is by moving towards favourable conditions. To do so requires mechanisms to both physically drive movement and provide directionality to this movement. The pathways that control this directionality comprise chemoreceptors, which, along with an adaptor protein (CheW) and kinase (CheA), form large hexagonal arrays. These arrays can be formed around transmembrane receptors, resulting in arrays embedded in the inner membrane, or they can comprise soluble receptors, forming arrays in the cytoplasm. Across bacterial species, chemoreceptor arrays (both transmembrane and soluble) are localised to a variety of positions within the cell; some species with multiple arrays demonstrate this variety within individual cells. In many cases, the positioning pattern of the arrays is linked to the need for segregation of arrays between daughter cells on division, ensuring the production of chemotactically competent progeny. Multiple mechanisms have evolved to drive this segregation, including stochastic self-assembly, cellular landmarks, and the utilisation of ParA homologues. The variety of mechanisms highlights the importance of chemotaxis to motile species.

  8. Evolution of Bacterial Suicide

    Science.gov (United States)

    Tchernookov, Martin; Nemenman, Ilya

    2013-03-01

    While active, controlled cellular suicide (autolysis) in bacteria is commonly observed, it has been hard to argue that autolysis can be beneficial to an individual who commits it. We propose a theoretical model that predicts that bacterial autolysis is evolutionarily advantageous to an individualand would fixate in physically structured environments for stationary phase colonies. We perform spatially resolved agent-based simulations of the model, which predict that lower mixing in the environment results in fixation of a higher autolysis rate from a single mutated cell, regardless of the colony's genetic diversity. We argue that quorum sensing will fixate as well, even if initially rare, if it is coupled to controlling the autolysis rate. The model does not predict a strong additional competitive advantage for cells where autolysis is controlled by quorum sensing systems that distinguish self from nonself. These predictions are broadly supported by recent experimental results in B. subtilisand S. pneumoniae. Research partially supported by the James S McDonnell Foundation grant No. 220020321 and by HFSP grant No. RGY0084/2011.

  9. Electromagnetism of Bacterial Growth

    Science.gov (United States)

    Ainiwaer, Ailiyasi

    2011-10-01

    There has been increasing concern from the public about personal health due to the significant rise in the daily use of electrical devices such as cell phones, radios, computers, GPS, video games and television. All of these devices create electromagnetic (EM) fields, which are simply magnetic and electric fields surrounding the appliances that simultaneously affect the human bio-system. Although these can affect the human system, obstacles can easily shield or weaken the electrical fields; however, magnetic fields cannot be weakened and can pass through walls, human bodies and most other objects. The present study was conducted to examine the possible effects of bacteria when exposed to magnetic fields. The results indicate that a strong causal relationship is not clear, since different magnetic fields affect the bacteria differently, with some causing an increase in bacterial cells, and others causing a decrease in the same cells. This phenomenon has yet to be explained, but the current study attempts to offer a mathematical explanation for this occurrence. The researchers added cultures to the magnetic fields to examine any effects to ion transportation. Researchers discovered ions such as potassium and sodium are affected by the magnetic field. A formula is presented in the analysis section to explain this effect.

  10. Etude du stockage de l'hydrogene sur des nanostructures de carbone microporeuses

    Science.gov (United States)

    Poirier, Eric

    2007-12-01

    Le stockage de l'hydrogene par adsorption sur des adsorbants nano-structures a ete etudie sous differentes conditions de pression et de temperature. Les adsorbants etudies sont principalement des nanotubes de carbone a simple paroi ainsi que des structures metallo-organiques. Les mesures ont ete realisees a l'aide de systemes gravimetriques et volumetriques tres sensibles specialement mis au point pour de petits echantillons necessitant un degazage in situ. Les appareils developpes, au nombre de quatre, comprennent deux systemes gravimetriques et deux systemes volumetriques. Ensemble, ces systemes couvrent la plage de pressions (0-100) bars ainsi que la plage de temperatures (77-295) K. Les differentes analyses montrent que l'adsorption d'hydrogene sur les adsorbants nano-structures etudies est maximale a 77 K et varie entre environ (1.5 et 4) % masse. A temperature ambiante, l'adsorption croit lineairement avec la pression et demeure sous les 1% masse pour des pressions inferieures a 100 bars. L'adsorption d'hydrogene sur ces materiaux dans ces conditions se compare notamment a celle obtenue sur des charbons actives. La modelisation de l'adsorption a egalement ete realisee dans des conditions cryogeniques a l'aide du modele de Dubinin-Astakhov sous une forme adaptee pour l'adsorption supercritique. Les enthalpies d'adsorption calculees a partir de ce modele varient sous les 6 kJ/mole et sont donc consistantes avec des processus de physisorption. L'applicabilite du modele de Dubinin-Astakhov suggere que l'adsorption d'hydrogene puisse etre representee par un processus de remplissage des pores par un pseudo-liquide. Ces travaux s'inscrivent dans un contexte ou la capacite d'adsorption reelle des nanostructures de carbone est sujette a la controverse. En consequence, l'approche experimentale adoptee se distingue par les differentes demarches mises de l'avant pour l'obtention de mesures fiables sur des echantillons de faibles masses ainsi que par son caractere

  11. Bacterial Communities: Interactions to Scale

    Science.gov (United States)

    Stubbendieck, Reed M.; Vargas-Bautista, Carol; Straight, Paul D.

    2016-01-01

    In the environment, bacteria live in complex multispecies communities. These communities span in scale from small, multicellular aggregates to billions or trillions of cells within the gastrointestinal tract of animals. The dynamics of bacterial communities are determined by pairwise interactions that occur between different species in the community. Though interactions occur between a few cells at a time, the outcomes of these interchanges have ramifications that ripple through many orders of magnitude, and ultimately affect the macroscopic world including the health of host organisms. In this review we cover how bacterial competition influences the structures of bacterial communities. We also emphasize methods and insights garnered from culture-dependent pairwise interaction studies, metagenomic analyses, and modeling experiments. Finally, we argue that the integration of multiple approaches will be instrumental to future understanding of the underlying dynamics of bacterial communities. PMID:27551280

  12. Bacterial Communities: Interactions to Scale

    Directory of Open Access Journals (Sweden)

    Reed M. Stubbendieck

    2016-08-01

    Full Text Available In the environment, bacteria live in complex multispecies communities. These communities span in scale from small, multicellular aggregates to billions or trillions of cells within the gastrointestinal tract of animals. The dynamics of bacterial communities are determined by pairwise interactions that occur between different species in the community. Though interactions occur between a few cells at a time, the outcomes of these interchanges have ramifications that ripple through many orders of magnitude, and ultimately affect the macroscopic world including the health of host organisms. In this review we cover how bacterial competition influences the structures of bacterial communities. We also emphasize methods and insights garnered from culture-dependent pairwise interaction studies, metagenomic analyses, and modeling experiments. Finally, we argue that the integration of multiple approaches will be instrumental to future understanding of the underlying dynamics of bacterial communities.

  13. Meningitis bacteriana Bacterial meningitis

    Directory of Open Access Journals (Sweden)

    Ana Teresa Alvarado Guevara

    2006-03-01

    causales son virales lo cual conlleva a las diferentes sub-clasificaciones. También en ciertos casos puede ser ocasionada por hongos, bacterias atípicas, micobacterias y parásitos.In Costa Rica the bacterial meningitis had turn into a high-priority subject in which to monitoring epidemiologist. It had been talked about in the last months, to dice an increase in the attention is published of this subject, due to this phenomenon it becomes necessary to make a revision of topic. Meningitis is an inflammation of leptomeninges and colonization of the subarachnoid cerebrospinal fluid (LCR due to different agents, which produces meningeal symptoms (ex. migraine, neck rigidity, and photophobia and pleocytosis in LCR. De pending on the variables to take into account is possible to group it in different classifications, taking into account the time of evolution are possible to be divided in acute or chronic, to first with few hours or days of beginning of the symptoms, whereas the chronicle also presents a silence course but of the disease of approximately 4 weeks of instauration. There is a difference according to its etiologic agent; they can be infectious and non-infectious. Examples of common non-infectious causes include medications (ex, nonsteroidal anti-inflammatory drugs, and antibiotics and carcinomatosis. A classification exists as well according to the causal agent. The acute bacterial meningitis remarks a bacterial origin of the syndrome, which characterizes by the by an acute onset of meningeal symptoms and neutrophilic pleocytosis. Each one of the bacteriological agents, parasitic or fungus finishes by characterizing the different presentations of the clinical features (ex, meningocóccica meningitis, Cryptococcus meningitis. Finally, there is also the aseptic meningitis, denominated in this form because it’s nonpyogenic cellular response caused by many types of agents. The patients show an acute beginning of symptoms, fever and lymphocytic pleocytosis. After

  14. Bacterial Culture of Neonatal Sepsis

    OpenAIRE

    AH Movahedian; R Moniri; Z Mosayebi

    2006-01-01

    Neonatal bacterial sepsis is one of the major cause of morbidity and mortality in neonates. This retrospective study was performed to determine the incidence of bacterial sepsis with focus on Gram negative organisms in neonates admitted at Beheshti Hospital in Kashan, during a 3-yr period, from September 2002 to September 2005. Blood culture was performed on all neonates with risk factors or signs of suggestive sepsis. Blood samples were cultured using brain heart infusion (BHI) broth accordi...

  15. Mast cells in bacterial infections

    OpenAIRE

    Rönnberg, Elin

    2014-01-01

    Mast cells are implicated in immunity towards bacterial infection, but the molecular mechanisms by which mast cells contribute to the host response are only partially understood. Previous studies have examined how mast cells react to purified bacterial cell wall components, such as peptidoglycan and lipopolysaccharide. To investigate how mast cells react to live bacteria we co-cultured mast cells and the gram-positive bacteria Streptococcus equi (S. equi) and Staphylococcus aureus (S. aureus)...

  16. Bacterial Alkaloids Prevent Amoebal Predation.

    Science.gov (United States)

    Klapper, Martin; Götze, Sebastian; Barnett, Robert; Willing, Karsten; Stallforth, Pierre

    2016-07-25

    Bacterial defense mechanisms have evolved to protect bacteria against predation by nematodes, predatory bacteria, or amoebae. We identified novel bacterial alkaloids (pyreudiones A-D) that protect the producer, Pseudomonas fluorescens HKI0770, against amoebal predation. Isolation, structure elucidation, total synthesis, and a proposed biosynthetic pathway for these structures are presented. The generation of P. fluorescens gene-deletion mutants unable to produce pyreudiones rendered the bacterium edible to a variety of soil-dwelling amoebae. PMID:27294402

  17. Bacterial cellulose/boehmite composites

    International Nuclear Information System (INIS)

    Composites based on bacterial cellulose membranes and boehmite were obtained. SEM results indicate that the bacterial cellulose (BC) membranes are totally covered by boehmite and obtained XRD patterns suggest structural changes due to this boehmite addition. Thermal stability is accessed through TG curves and is dependent on boehmite content. Transparency is high comparing to pure BC as can be seen through UV-vis absorption spectroscopy. (author)

  18. For a return to the Etudes sur les sciences sociales. Local autonomy and territorial wealth according to Sismondi

    Directory of Open Access Journals (Sweden)

    Giuseppe Pioletti

    2015-12-01

    Full Text Available The article aims to analyse the Etudes sur les sciences sociales, published by Sismondi between 1836 and 1838, conducted in the light of the theses not only of the historians of Italian thinking who have determined the revival of interest in the Genevan’s doctrine, but also of very relevant works on issues of the growth and degrowth of the world economy. In particular, Pioletti focuses attention on the question of the territories: for the social scientist Sismondi at the end of the 1830s, they are functional and ideally constitutional units, where rules and customs apply that alone can deal with the risks of haphazard economic growth. Small localities, small estates: from these elements Sismondi also draws inspiration for an original theory of government – and for the national and local relations in the modern States – which, albeit presenting itself in 1836, was clearly affected by an interest that had been manifested in the historiographic field from 1807.

  19. Research trends in radiobiology since 40 years. a new approach: the enzymatic repair function of DNA, internal factor in evolution of biological systems under irradiation; Etude des tendances des recherches en radiologie depuis 40 ans. Une nouvelle voie de recherche: la fonction de reparation enzymatique de l'ADN, facteur interne d'evolution des systemes biologiques sous rayonnement

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-07-01

    . Il y a moins d'une generation, l'on croyait encore que les effets des rayonnements sur les systemes vivants etaient des effets directs, immediats, irreparables et definitifs. Depuis lors, on s'est rendu compte que les radiolesions pouvaient resulter d'effets indirects, etre tardives, reparables, et le plus souvent modifiables par des traitements chimiques ou biochimiques ad hoc. Cependant, la percee decisive en radiobiologie se situe entre 1962 et 1964, avec la decouverte que la cellule possede un mecanisme de defense active vis-a-vis de tout ce qui peut porter atteinte a l'integrite du patrimoine genetique inscrit dans la structure meme de l'ADN. L'existence d'une quatrieme fonction de l'ADN, celle d'auto-reparation, par voie enzymatique sous controle genetique, apporte enfin a la radiobiologie la base biologique moleculaire qui lui manquait pour sortir de la nuit 'phenomenologique' ou elle s'etait enfoncee apres l'abandon de la generalisation de la theorie de Lea, faute de preuve experimentale. Dans la seconde partie, cette fois prospective, de l'etude l'auteur tente une synthese elargie en considerant le role que peut jouer cette fonction de reparation de l'ADN non seulement du point de vue de la survie des systemes biologiques irradies en presence ou non d'agents modificateurs de dose ou mutagenes, mais aussi de celui de l'evolution naturelle ou artificielle de ces systemes sous rayonnement. Les donnees les plus recentes de la litterature sont en accord avec ce qui ne constitue encore qu'une hypothese generale de recherche. Des travaux portant sur les caracteres phenotypiques et genotypiques lies a l'acquisition de radioresistance gamma et UV, chez 'Escherichia coli K12', ont ete entrepris par l'auteur, en collaboration avec O. Tremeau en vue d'apporter une contribution experimentale nouvelle a cet egard. (auteur)

  20. Etude de l'influence de la temperature et de l'humidite sur les proprietes mecaniques en traction des fibres de chanvre et de coco

    Science.gov (United States)

    Ho Thi, Thu Nga

    L'objectif de cette etude fut d'etablir l'effet de l'humidite et de la temperature sur la resistance en traction et le module elastique des fibres de chanvre et de coco. Deux etudes ont ete realisees afin d'atteindre cet objectif. La premiere vise l'absorption de l'humidite dans ces fibres en exposition dans l'air (de 0%RH a 80%RH) ainsi que l'absorption de l'eau dans ces fibres immergees dans l'eau aux differentes temperatures. La deuxieme consiste a mesurer la resistance en traction et le module elastique de ces fibres sous differentes conditions d'humidite et de temperature. En basant sur les resultats experimentaux obtenus, les methodes semi empiriques et de reseaux de neurones ont ete utilisees pour but de predire les proprietes en traction (resistance et module d'elasticite) des fibres de chanvre et de coco sous l'influence de l'humidite et de la temperature.

  1. The Human Vaginal Bacterial Biota and Bacterial Vaginosis

    Directory of Open Access Journals (Sweden)

    Sujatha Srinivasan

    2008-01-01

    Full Text Available The bacterial biota of the human vagina can have a profound impact on the health of women and their neonates. Changes in the vaginal microbiota have been associated with several adverse health outcomes including premature birth, pelvic inflammatory disease, and acquisition of HIV infection. Cultivation-independent molecular methods have provided new insights regarding bacterial diversity in this important niche, particularly in women with the common condition bacterial vaginosis (BV. PCR methods have shown that women with BV have complex communities of vaginal bacteria that include many fastidious species, particularly from the phyla Bacteroidetes and Actinobacteria. Healthy women are mostly colonized with lactobacilli such as Lactobacillus crispatus, Lactobacillus jensenii, and Lactobacillus iners, though a variety of other bacteria may be present. The microbiology of BV is heterogeneous. The presence of Gardnerella vaginalis and Atopobium vaginae coating the vaginal epithelium in some subjects with BV suggests that biofilms may contribute to this condition.

  2. Contribution to the study of hydrogenated and oxygenated impurities in liquid sodium; Contribution a l'etude des impuretees hydrogenees et oxygenees dans le sodium liquide

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-07-15

    This study is made up essentially of two parts. The first is devoted to the development of dosage methods for selectively determining the oxygenated and hydrogenated impurities present in sodium, that is the oxide, the hydride and the hydroxide. The second makes use of these methods for a study of the Na-H{sub 2}-O{sub 2} system, as well as of the related problem of the attack of pyrex glass by molten sodium. The conventional method for dosing oxygen by amalgamation was first adapted to the simultaneous measurement of the hydride. We then developed a method for dosing the total hydrogen by measuring successively the concentrations of gas present in the hydride and hydroxide form. This method is based on the thermal decomposition of the hydride and the reaction between sodium and the hydroxide. Our contribution to the study of the Na-H{sub 2}-O{sub 2} System consists first of all in the study of the reaction between hydrogen and sodium in the temperature range from 150 to 250 deg C and at a pressure of about 150 mm of mercury. The study of the thermal decomposition of the hydride in sodium was then studied. It was possible to make some qualitative observations concerning the reaction between sodium and sodium hydroxide. Finally some complementary tests made it possible to define the nature of the phenomena occurring during the attack of pyrex glass by sodium. (author) [French] Cette etude comporte essentiellement deux parties. La premiere est consacree a la mise au point de methodes de dosages permettant de determiner selectivement les impuretes oxygenees et hydrogenees presentes dans le sodium, a savoir l'oxyde, l'hydrure et l'hydroxyde. La seconde met a profit ces methodes en vue de l'etude du systeme Na-H{sub 2}-O{sub 2}. ainsi que du phenomene connexe d'attaque du verre pyrex par le sodium fondu. La methode classique de dosage de l'oxygene par amalgamation a d'abord ete adaptee au dosage simultane de l'hydrure. Nous avons

  3. Bacterial tactic responses.

    Science.gov (United States)

    Armitage, J P

    1999-01-01

    Many, if not most, bacterial species swim. The synthesis and operation of the flagellum, the most complex organelle of a bacterium, takes a significant percentage of cellular energy, particularly in the nutrient limited environments in which many motile species are found. It is obvious that motility accords cells a survival advantage over non-motile mutants under normal, poorly mixed conditions and is an important determinant in the development of many associations between bacteria and other organisms, whether as pathogens or symbionts and in colonization of niches and the development of biofilms. This survival advantage is the result of sensory control of swimming behaviour. Although too small to sense a gradient along the length of the cell, and unable to swim great distances because of buffetting by Brownian motion and the curvature resulting from a rotating flagellum, bacteria can bias their random swimming direction towards a more favourable environment. The favourable environment will vary from species to species and there is now evidence that in many species this can change depending on the current physiological growth state of the cell. In general, bacteria sense changes in a range of nutrients and toxins, compounds altering electron transport, acceptors or donors into the electron transport chain, pH, temperature and even the magnetic field of the Earth. The sensory signals are balanced, and may be balanced with other sensory pathways such as quorum sensing, to identify the optimum current environment. The central sensory pathway in this process is common to most bacteria and most effectors. The environmental change is sensed by a sensory protein. In most species examined this is a transmembrane protein, sensing the external environment, but there is increasing evidence for additional cytoplasmic receptors in many species. All receptors, whether sensing sugars, amino acids or oxygen, share a cytoplasmic signalling domain that controls the activity of a

  4. New Treatments for Bacterial Keratitis

    Directory of Open Access Journals (Sweden)

    Raymond L. M. Wong

    2012-01-01

    Full Text Available Purpose. To review the newer treatments for bacterial keratitis. Data Sources. PubMed literature search up to April 2012. Study Selection. Key words used for literature search: “infectious keratitis”, “microbial keratitis”, “infective keratitis”, “new treatments for infectious keratitis”, “fourth generation fluoroquinolones”, “moxifloxacin”, “gatifloxacin”, “collagen cross-linking”, and “photodynamic therapy”. Data Extraction. Over 2400 articles were retrieved. Large scale studies or publications at more recent dates were selected. Data Synthesis. Broad spectrum antibiotics have been the main stay of treatment for bacterial keratitis but with the emergence of bacterial resistance; there is a need for newer antimicrobial agents and treatment methods. Fourth-generation fluoroquinolones and corneal collagen cross-linking are amongst the new treatments. In vitro studies and prospective clinical trials have shown that fourth-generation fluoroquinolones are better than the older generation fluoroquinolones and are as potent as combined fortified antibiotics against common pathogens that cause bacterial keratitis. Collagen cross-linking was shown to improve healing of infectious corneal ulcer in treatment-resistant cases or as an adjunct to antibiotics treatment. Conclusion. Fourth-generation fluoroquinolones are good alternatives to standard treatment of bacterial keratitis using combined fortified topical antibiotics. Collagen cross-linking may be considered in treatment-resistant infectious keratitis or as an adjunct to antibiotics therapy.

  5. Behaviour of an irradiated photomultiplier; Etude du comportement d'un photomultiplicateur sous rayonnements nucleaires

    Energy Technology Data Exchange (ETDEWEB)

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

    1967-04-15

    With the aim of using scintillation detectors for the starting-up, the study of transient phenomena, the control or the safety of a nuclear reactor or of a critical assembly, the behaviour of 8 photomultipliers (Radiotechnique 51 AVP and UVP, and EMI 9524 B) has been studied in the gamma flux of 1 to 10{sup 3} Rh{sup -1} in a storage well, and in an EL 2 reactor channel where the exposures varied between 1 to 2 x 10{sup 3} Rh{sup -1} and 6 x 10{sup 5} to 5 x 10{sup 7} n.cm{sup -2}.s{sup -1}. Spurious pulses are produced by this radiation at the photomultiplier anode. By comparing the amplitudes of these pulses to those produced by a NaI scintillator, it was observed that their maximum energy level was about 100 keV at 10{sup 3} Rh{sup -1} in the gamma flow of the storage well and from 200 to 400 keV at 10{sup 3} Rh{sup -1} and 10{sup 7} n.cm{sup -2}.s{sup -1} in the reactor channel. Furthermore, the detection of a luminous reference pulse corresponding to 200 keV (NaI) is only perturbed at values Of above a few hundred Rh{sup -1} the {gamma} radiation alone, and above 5 x 10{sup 6} n.cm{sup -2}.s{sup -1} and {approx} 500 Rh{sup -1} in the reactor channel. The dispersion of these results is of the order of 2 for the 8 tubes tested. The main part of the {gamma} radiation effect is attributed to the Cerenkov effect in the window of the photomultiplier. The possibility of separating the respective effects of neutrons and of {gamma} radiation is considered. No marked evolution in the photomultiplier parameters during exposure was noticed. Their characteristics were not modified by the doses received, the largest of which attained 4 x 10{sup 12} neutrons.cm{sup -2} and {approx_equal} 3 x 10{sup 4} roentgens. The advantages of using photomultipliers and fast circuits for widening the field of use of photomultipliers under irradiation is stressed. (author) [French] En vue de l'utilisation de detecteurs a scintillations pour le demarrage, l'etude des phenomenes

  6. Etude des phenomenes dynamiques ultrarapides et des caracteristiques impulsionnelles d'emission terahertz du supraconducteur YBCO

    Science.gov (United States)

    Savard, Stephane

    Les premieres etudes d'antennes a base de supraconducteurs a haute temperature critique emettant une impulsion electromagnetique dont le contenu en frequence se situe dans le domaine terahertz remontent a 1996. Une antenne supraconductrice est formee d'un micro-pont d'une couche mince supraconductrice sur lequel un courant continu est applique. Un faisceau laser dans le visible est focalise sur le micro-pont et place le supraconducteur dans un etat hors-equilibre ou des paires sont brisees. Grace a la relaxation des quasiparticules en surplus et eventuellement de la reformation des paires supraconductrices, nous pouvons etudier la nature de la supraconductivite. L'analyse de la cinetique temporelle du champ electromagnetique emis par une telle antenne terahertz supraconductrice s'est averee utile pour decrire qualitativement les caracteristiques de celle-ci en fonction des parametres d'operation tels que le courant applique, la temperature et la puissance d'excitation. La comprehension de l'etat hors-equilibre est la cle pour comprendre le fonctionnement des antennes terahertz supraconductrices a haute temperature critique. Dans le but de comprendre ultimement cet etat hors-equilibre, nous avions besoin d'une methode et d'un modele pour extraire de facon plus systematique les proprietes intrinseques du materiau qui compose l'antenne terahertz a partir des caracteristiques d'emission de celle-ci. Nous avons developpe une procedure pour calibrer le spectrometre dans le domaine temporel en utilisant des antennes terahertz de GaAs bombarde aux protons H+ comme emetteur et detecteur. Une fois le montage calibre, nous y avons insere une antenne emettrice dipolaire de YBa 2Cu3O7-delta . Un modele avec des fonctions exponentielles de montee et de descente du signal est utilise pour lisser le spectre du champ electromagnetique de l'antenne de YBa 2Cu3O7-delta, ce qui nous permet d'extraire les proprietes intrinseques de ce dernier. Pour confirmer la validite du modele

  7. Antibiotic resistance of bacterial biofilms

    DEFF Research Database (Denmark)

    Hoiby, N.; Bjarnsholt, T.; Givskov, M.;

    2010-01-01

    A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and DNA. Bacterial biofilms cause chronic infections because they show increased tolerance to antibiotics and disinfectant chemicals as well as resisting phagocytosis...... and other components of the body's defence system. The persistence of, for example, staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infection in cystic fibrosis patients is caused by biofilm-growing mucoid strains....... Characteristically, gradients of nutrients and oxygen exist from the top to the bottom of biofilms and these gradients are associated with decreased bacterial metabolic activity and increased doubling times of the bacterial cells; it is these more or less dormant cells that are responsible for some of the tolerance...

  8. Phylogenetic organization of bacterial activity.

    Science.gov (United States)

    Morrissey, Ember M; Mau, Rebecca L; Schwartz, Egbert; Caporaso, J Gregory; Dijkstra, Paul; van Gestel, Natasja; Koch, Benjamin J; Liu, Cindy M; Hayer, Michaela; McHugh, Theresa A; Marks, Jane C; Price, Lance B; Hungate, Bruce A

    2016-09-01

    Phylogeny is an ecologically meaningful way to classify plants and animals, as closely related taxa frequently have similar ecological characteristics, functional traits and effects on ecosystem processes. For bacteria, however, phylogeny has been argued to be an unreliable indicator of an organism's ecology owing to evolutionary processes more common to microbes such as gene loss and lateral gene transfer, as well as convergent evolution. Here we use advanced stable isotope probing with (13)C and (18)O to show that evolutionary history has ecological significance for in situ bacterial activity. Phylogenetic organization in the activity of bacteria sets the stage for characterizing the functional attributes of bacterial taxonomic groups. Connecting identity with function in this way will allow scientists to begin building a mechanistic understanding of how bacterial community composition regulates critical ecosystem functions. PMID:26943624

  9. Bacterial Degradation of Aromatic Compounds

    Directory of Open Access Journals (Sweden)

    Qing X. Li

    2009-01-01

    Full Text Available Aromatic compounds are among the most prevalent and persistent pollutants in the environment. Petroleum-contaminated soil and sediment commonly contain a mixture of polycyclic aromatic hydrocarbons (PAHs and heterocyclic aromatics. Aromatics derived from industrial activities often have functional groups such as alkyls, halogens and nitro groups. Biodegradation is a major mechanism of removal of organic pollutants from a contaminated site. This review focuses on bacterial degradation pathways of selected aromatic compounds. Catabolic pathways of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene are described in detail. Bacterial catabolism of the heterocycles dibenzofuran, carbazole, dibenzothiophene, and dibenzodioxin is discussed. Bacterial catabolism of alkylated PAHs is summarized, followed by a brief discussion of proteomics and metabolomics as powerful tools for elucidation of biodegradation mechanisms.

  10. Clinical applications of bacterial glycoproteins.

    Science.gov (United States)

    Fulton, Kelly M; Smith, Jeffrey C; Twine, Susan M

    2016-01-01

    There is an ongoing race between bacterial evolution and medical advances. Pathogens have the advantages of short generation times and horizontal gene transfer that enable rapid adaptation to new host environments and therapeutics that currently outpaces clinical research. Antibiotic resistance, the growing impact of nosocomial infections, cancer-causing bacteria, the risk of zoonosis, and the possibility of biowarfare all emphasize the increasingly urgent need for medical research focussed on bacterial pathogens. Bacterial glycoproteins are promising targets for alternative therapeutic intervention since they are often surface exposed, involved in host-pathogen interactions, required for virulence, and contain distinctive glycan structures. The potential exists to exploit these unique structures to improve clinical prevention, diagnosis, and treatment strategies. Translation of the potential in this field to actual clinical impact is an exciting prospect for fighting infectious diseases. PMID:26971465

  11. Composes inter-halogenes sous pression: etude des transformations structurales dans le monobromure d'iode sous forme dense

    Science.gov (United States)

    Bouchard, Alexandre

    La famille des composes halogenes et inter-halogenes representent des solides moleculaires adoptant des phases denses communes avec des solides moleculaires diatomiques comme l'azote et l'hydrogene. Parmi les transformations structurales et electroniques induites sous haute pression et observees dans ces solides, on note, entre autres, la dissociation moleculaire et la metallisation. De plus, l'etude des phases denses de l'iode a permis recemment l'observation d'une structure cristalline possedant une modulation dite incommensurable, c'est-a-dire une modulation possedant une periodicite differente de celle de la structure cristalline, jetant ainsi une lumiere nouvelle sur le processus de dissociation moleculaire dans les solides halogenes. Dans ce memoire, on propose d'etudier les changements structuraux dans monobromure d'iode (IBr), un compose inter-halogene possedant des proprietes structurales semblables a celles de deux composes halogenes, soit l'iode (I 2) et le brome (Br2) sous leur forme solide. Des experiences de diffraction des rayons X de poudres en utilisant un rayonnement synchrotron ont ete realisees a temperature ambiante sur l'IBr en variant la pression jusqu'aux environs de 60 GPa. La nature chimique particuliere du compose IBr a necessite la mise au point de techniques de chargement d'echantillon destinees a preserver l'integrite chimique de la substance utilisee. On rapporte egalement l'observation d'une phase de l'IBr presentant une modulation incommensurable. Les phases observees dans l'IBr permettent d'etablir des paralleles avec les phases denses rapportees dans I2 et Br2 par le biais d'un modele phenomenologique decrivant la sequence structurale des solides halogenes sous forme condensee.

  12. Disease notes - Bacterial root rot

    Science.gov (United States)

    Bacterial root rot initiated by lactic acid bacteria, particularly Leuconostoc, occurs every year in Idaho sugarbeet fields. Hot fall weather seems to make the problem worse. Although Leuconostoc initiates the rot, other bacteria and yeast frequently invade the tissue as well. The acetic acid bac...

  13. Biotechnological applications of bacterial cellulases

    Directory of Open Access Journals (Sweden)

    Esther Menendez

    2015-08-01

    Full Text Available Cellulases have numerous applications in several industries, including biofuel production, food and feed industry, brewing, pulp and paper, textile, laundry, and agriculture.Cellulose-degrading bacteria are widely spread in nature, being isolated from quite different environments. Cellulose degradation is the result of a synergic process between an endoglucanase, an exoglucanase and a,β-glucosidase. Bacterial endoglucanases degrade ß-1,4-glucan linkages of cellulose amorphous zones, meanwhile exoglucanases cleave the remaining oligosaccharide chains, originating cellobiose, which is hydrolyzed by ß-glucanases. Bacterial cellulases (EC 3.2.1.4 are comprised in fourteen Glycosil Hydrolase families. Several advantages, such as higher growth rates and genetic versatility, emphasize the suitability and advantages of bacterial cellulases over other sources for this group of enzymes. This review summarizes the main known cellulolytic bacteria and the best strategies to optimize their cellulase production, focusing on endoglucanases, as well as it reviews the main biotechnological applications of bacterial cellulases in several industries, medicine and agriculture.

  14. A Program Against Bacterial Bioterrorism

    DEFF Research Database (Denmark)

    Kemp, Michael; Dargis, Rimtas; Andresen, Keld;

    2012-01-01

    In 2002 it was decided to establish laboratory facilities in Denmark for diagnosing agents associated with bioterrorism in order to make an immediate appropriate response to the release of such agents possible. Molecular assays for detection of specific agents and molecular and proteomic techniques...... for bacterial infections not associated with bioterrorism that are difficult to culture or identify....

  15. Molecular Mechanisms Underlying Bacterial Persisters

    DEFF Research Database (Denmark)

    Maisonneuve, Etienne; Gerdes, Kenn

    2014-01-01

    technological advances in microfluidics and reporter genes have improved this scenario. Here, we summarize recent progress in the field, revealing the ubiquitous bacterial stress alarmone ppGpp as an emerging central regulator of multidrug tolerance and persistence, both in stochastically and environmentally...

  16. Reconstruction de la surface de Fermi dans l'etat normal d'un supraconducteur a haute Tc: Une etude du transport electrique en champ magnetique intense

    Science.gov (United States)

    Le Boeuf, David

    Des mesures de resistance longitudinale et de resistance de Hall en champ magnetique intense transverse (perpendiculaire aux plans CuO2) ont ete effectuees au sein de monocristaux de YBa2Cu3Oy (YBCO) demacles, ordonnes et de grande purete, afin d'etudier l'etat fondamental des supraconducteurs a haute Tc dans le regime sous-dope. Cette etude a ete realisee en fonction du dopage et de l'orientation du courant d'excitation J par rapport a l'axe orthorhombique b de la structure cristalline. Les mesures en champ magnetique intense revelent par suppression de la supraconductivite des oscillations magnetiques des resistances longitudinale et de Hall dans YBa2Cu 3O6.51 et YBa2Cu4O8. La conformite du comportement de ces oscillations quantiques au formalisme de Lifshitz-Kosevich, apporte la preuve de l'existence d'une surface de Fermi fermee a caractere quasi-2D, abritant des quasiparticules coherentes respectant la statistique de Fermi-Dirac, dans la phase pseudogap d'YBCO. La faible frequence des oscillations quantiques, combinee avec l'etude de la partie monotone de la resistance de Hall en fonction de la temperature indique que la surface de Fermi d'YBCO sous-dope comprend une petite poche de Fermi occupee par des porteurs de charge negative. Cette particularite de la surface de Fermi dans le regime sous-dope incompatible avec les calculs de structure de bande est en fort contraste avec la structure electronique presente dans le regime surdope. Cette observation implique ainsi l'existence d'un point critique quantique dans le diagramme de phase d'YBCO, au voisinage duquel la surface de Fermi doit subir une reconstruction induite par l'etablissement d'une brisure de la symetrie de translation du reseau cristallin sous-jacent. Enfin, l'etude en fonction du dopage de la resistance de Hall et de la resistance longitudinale en champ magnetique intense suggere qu'un ordre du type onde de densite (DW) est responsable de la reconstruction de la surface de Fermi. L'analogie de

  17. ESTUDIO DE SECUENCIAS DE TALLA LÍTICA A TRAVÉS DE MODELOS EXPERIMENTALES EN ROCAS SILÍCEAS DEL CENTRO DE ARGENTINA (Study of lithic carving sequences through experimental models in siliceous rocks of central Argentina

    Directory of Open Access Journals (Sweden)

    Eduardo Pautassi

    2012-10-01

    Full Text Available La evidencia arqueológica dejada por los grupos humanos que habitaron el centro de Argentina (provincias de Córdoba y San Luis, desde las primeras ocupaciones hasta momentos previos a la conquista española, pone de manifiesto que estas poblaciones desarrollaron diversas estrategias y adaptaciones a lo largo del tiempo. Una de estas estrategias es la producción de artefactos líticos. En este trabajo, se aborda el estudio de las secuencias de reducción de clastos y de manufactura de bifaces experimentales aplicando la metodología de análisis «no tipológico» para el estudio de los desechos de talla. Estas experiencias fueron realizadas como resultado del análisis de la tecnología lítica de sitios arqueológicos ubicados en la localidad arqueológica de Estancia La Suiza, San Luis. La finalidad de este trabajo es comparar ciertos atributos de las lascas producto de la experimentación para diferenciar tipos de actividades de talla. Realizar esta propuesta nos permite presentar en otra oportunidad la comparación con el registro arqueológico, e intentar dilucidar cómo fueron los diferentes momentos en el proceso de talla. ENGLISH: The archaeological evidence left by the humans who occupied the center of Argentina (comprising the present territory of the provinces of Cordoba and San Luis, Argentina, from the earliest settlements until the moments before the Spanish conquest, shows that these populations developed different strategies and adaptations to the environment over time. One such strategy is the production of lithic artifacts. This contribution specifically addresses the study of sequence of cores and reducing manufacturing bifaces by applying the methodology of the “non-typological” analysis to the study of debitage. These experiments were conducted as a result of the analysis of the lithic technology of archaeological sites located at the archaeological locality of Estancia La Suiza, in San Luis province. The purpose of

  18. Cognitive outcome in adults after bacterial meningitis.

    NARCIS (Netherlands)

    Hoogman, M.; Beek, D. van de; Weisfelt, M.; Gans, J. de; Schmand, B.

    2007-01-01

    OBJECTIVE: To evaluate cognitive outcome in adult survivors of bacterial meningitis. METHODS: Data from three prospective multicentre studies were pooled and reanalysed, involving 155 adults surviving bacterial meningitis (79 after pneumococcal and 76 after meningococcal meningitis) and 72 healthy c

  19. Contribution to the study of the stability of water-cooled reactors; Contribution a l'etude de la stabilite des reacteurs refroidis par de l'eau

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-06-01

    This work is devoted to the study of the stability of reactors cooled by water subjected only to natural convection. It is made up of two parts, a theoretical study and experimental work, each of these parts being devoted to a consideration of linear and non-linear conditions: - calculation of the transfer function of the reactor using neutronic and hydrodynamic linear equations with the determination of the instability threshold; - demonstration of the existence of the limiting oscillation cycle in the case of a linear feedback using MALKIN'S method; - measurement and interpretation of the reactor's transfer functions and of the hydrodynamic transfer functions; and - analysis of the noise due to boiling. (author) [French] Dans ce travail on etudie la stabilite des piles refroidies par de l'eau circulant en convection naturelle. Cette etude se divise en deux parties: un travail theorique et un travail experimental, chacune de ces parties comportant une etude lineaire et une etude non-lineaire: - calcul de la fonction de transfert du reacteur a partir des equations lineaires de la neutronique et de l'hydrodynamique avec determination du seuil d'instabilite; - demonstration de l'existence du cycle limite des oscillations dans le cas d'une retroaction lineaire en utilisant la methode de MALKIN; - mesure et interpretation de la fonction de transfert du reacteur et des fonctions de transfert hydrodynamiques; et - analyse du bruit d'ebullition. (auteur)

  20. Filtration properties of bacterial cellulose membranes

    OpenAIRE

    Lehtonen, Janika

    2015-01-01

    Bacterial cellulose has the same molecular formula as cellulose from plant origin, but it is characterized by several unique properties including high purity, crystallinity and mechanical strength. These properties are dependent on parameters such as the bacterial strain used, the cultivation conditions and post-growth processing. The possibility to achieve bacterial cellulose membranes with different properties by varying these parameters could make bacterial cellulose an interesting materi...

  1. Distribution of Triplet Separators in Bacterial Genomes

    Institute of Scientific and Technical Information of China (English)

    HU Rui; ZHENG Wei-Mou

    2001-01-01

    Distributions of triplet separator lengths for two bacterial complete genomes are analyzed. The theoretical distributions for the independent random sequence and the first-order Markov chain are derived and compared with the distributions of the bacterial genomes. A prominent double band structure, which does not exist in the theoretical distributions, is observed in the bacterial distributions for most triplets.``

  2. Effets Seebeck et Nernst dans les cuprates: Etude de la reconstruction de la surface de Fermi sous champ magnetique intense

    Science.gov (United States)

    Laliberte, Francis

    2010-06-01

    Ce memoire presente des mesures de transport thermoelectrique, les effets Seebeck et Nernst, dans une serie d'echantillons de supraconducteurs a haute temperature critique. Des resultats obtenus recemment au Laboratoire National des Champs Magnetiques Intenses a Grenoble sur La1.7Eu0.2Sr0.1 CuO4, La1.675Eu0.2Sr0.125CuO 4, La1.64Eu0.2Sr0.16CuO4, La1.74Eu0.1Sr0.16CuO4 et La 1.4Nd0.4Sr0.2CuO4 sont analyses. Une attention particuliere est accordee aux equations de la theorie semi-classique du transport et leur validite est verifiee. La procedure experimentale et les materiaux utilises pour concevoir les montages de mesures sont expliques en detail. Enfin, un chapitre est dedie a l'explication et l'interpretation des resultats de transport thermoelectrique sur YBa2Cu3O6+delta publies au cours de l'hiver 2010 dans les revues Nature et Physical Review Letters. Les donnees d'effet Seebeck dans les echantillons de La 1.8-x,Eu0.2SrxCuO 4, ou un changement de signe est observe, permettent de conclure a la presence d'une poche d'electrons dans la surface de Fermi qui domine le transport a basse temperature dans la region sous-dopee du diagramme de phase. Cette conclusion est similaire a celle obtenue par des mesures d'effet Hall dans YBa 2Cu3O6+delta et elle cadre bien dans un scenario de reconstruction de la surface de Fermi. Les donnees d'effet Nernst recueillies indiquent que la contribution des fluctuations supraconductrices est limitee a un modeste intervalle de temperature au-dessus de la temperature critique.

  3. Beach sediments drift study by means of radioactive tracers; L'etude du transport littoral par la methode des traceurs radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Hours, R. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Jaffry, P. [Electricite de France (EDF), 78 - Chatou (France). Lab. National d' Hydraulique

    1959-07-01

    The present state of the sediments drift studies by means of radioactive tracers is exposed. Various processes of labelling, immersion and detection, used in France and other countries, are reviewed. A more extended analysis of some aspects of the problem by the same authors can be found in 'La Houille Blanche', number 3, may-june 1959 (Rapport C.E.A. number 1269). (author) [French] L'etude du transport littoral des sediments et galets par la methode des traceurs radioactifs est en plein developpement. Le present rapport precise l'etat actuel de la question. Les techniques de marquage, d'immersion et de detection utilisees en France et a l'etranger sont decrites; une analyse plus detaillee de certains aspects de la question est presentee par les memes auteurs dans 'La Houille Blanche', numero 3, mai-juin 1959 (Rapport C.E.A. numero 1269). (auteur)

  4. Etudes écologique, floristique, phytosociologique et ethnobotanique de la forêt marécageuse de Lokoli, Zogbodomey - Bénin

    OpenAIRE

    Dan, Céline

    2009-01-01

    Etudes écologique, floristique, phytosociologique et ethnobotanique de la forêt marécageuse de Lokoli (Zogbodomey – Bénin)La forêt marécageuse de Lokoli, située dans le sud du Bénin est une formation non protégée, bien qu’elle soit la seule forêt marécageuse avec un cours d’eau permanent connue en Afrique de l’Ouest. Pour envisager une prise de décision de conservation et de protection de cet écosystème forestier, il est important de disposer d’une meilleure connaissance de sa flore, de sa vé...

  5. Bacterial chromosome organization and segregation.

    Science.gov (United States)

    Badrinarayanan, Anjana; Le, Tung B K; Laub, Michael T

    2015-01-01

    If fully stretched out, a typical bacterial chromosome would be nearly 1 mm long, approximately 1,000 times the length of a cell. Not only must cells massively compact their genetic material, but they must also organize their DNA in a manner that is compatible with a range of cellular processes, including DNA replication, DNA repair, homologous recombination, and horizontal gene transfer. Recent work, driven in part by technological advances, has begun to reveal the general principles of chromosome organization in bacteria. Here, drawing on studies of many different organisms, we review the emerging picture of how bacterial chromosomes are structured at multiple length scales, highlighting the functions of various DNA-binding proteins and the impact of physical forces. Additionally, we discuss the spatial dynamics of chromosomes, particularly during their segregation to daughter cells. Although there has been tremendous progress, we also highlight gaps that remain in understanding chromosome organization and segregation. PMID:26566111

  6. Bacterial streamers in curved microchannels

    Science.gov (United States)

    Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

    2009-11-01

    Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.

  7. Bacterial survival in Martian conditions

    CERN Document Server

    D'Alessandro, Giuseppe Galletta; Giulio Bertoloni; Maurizio

    2010-01-01

    We shortly discuss the observable consequences of the two hypotheses about the origin of life on Earth and Mars: the Lithopanspermia (Mars to Earth or viceversa) and the origin from a unique progenitor, that for Earth is called LUCA (the LUCA hypothesis). To test the possibility that some lifeforms similar to the terrestrial ones may survive on Mars, we designed and built two simulators of Martian environments where to perform experiments with different bacterial strains: LISA and mini-LISA. Our LISA environmental chambers can reproduce the conditions of many Martian locations near the surface trough changes of temperature, pressure, UV fluence and atmospheric composition. Both simulators are open to collaboration with other laboratories interested in performing experiments on many kind of samples (biological, minerals, electronic) in situations similar to that of the red planet. Inside LISA we have studied the survival of several bacterial strains and endospores. We verified that the UV light is the major re...

  8. Collective Functionality through Bacterial Individuality

    Science.gov (United States)

    Ackermann, Martin

    According to the conventional view, the properties of an organism are a product of nature and nurture - of its genes and the environment it lives in. Recent experiments with unicellular organisms have challenged this view: several molecular mechanisms generate phenotypic variation independently of environmental signals, leading to variation in clonal groups. My presentation will focus on the causes and consequences of this microbial individuality. Using examples from bacterial genetic model systems, I will first discuss different molecular and cellular mechanisms that give rise to bacterial individuality. Then, I will discuss the consequences of individuality, and focus on how phenotypic variation in clonal populations of bacteria can promote interactions between individuals, lead to the division of labor, and allow clonal groups of bacteria to cope with environmental uncertainty. Variation between individuals thus provides clonal groups with collective functionality.

  9. Bacterial communication and group behavior

    OpenAIRE

    Greenberg, E. Peter

    2003-01-01

    The existence of species-specific and interspecies bacterial cell-cell communication and group organization was only recently accepted. Researchers are now realizing that the ability of these microbial teams to communicate and form structures, known as biofilms, at key times during the establishment of infection significantly increases their ability to evade both host defenses and antibiotics. This Perspective series discusses the known signaling mechanisms, the roles they play in both chroni...

  10. The problem of bacterial diarrhoea.

    Science.gov (United States)

    Harries, J T

    1976-01-01

    The reported incidence of "pathogenic" bacteria, as judged by serotype, in the stools of children with acute diarrhoea has varied from 4 to 33% over the last twenty years. Techniques such as tissue culture provide a means for detecting enterotoxin-producing strains of bacteria, strains which often do not possess "pathogenic" serotypes. "Pathogenicity" requires redefinition, and the aetiological importance of bacteria in diarrhoea is probably considerably greater than previous reports have indicated. Colonization of the bowel by a pathogen will result in structural and/or mucosal abnormalities, and will depend on a series of complex interactions between the external environment, the pathogen, and the host and its resident bacterial flora. Enteropathogenic bacteria may be broadly classified as (i) invasive (e.g. Shigella, Salmonella and some Escherichia coli) which predominantly affect the distal bowel, or (ii) non-invasive (e.g. Vibrio cholerae and E. coli) which affect the proximal bowel. V. cholerae and E. coli elaborate heat-labile enterotoxins which activate adenylate cyclase and induce small intestinal secretion; the secretory effects of heat-stable E. coli and heat-labile Shigella dysenteriae enterotoxins are not accompanied by cyclase activation. The two major complications of acute diarrhoea are (i) hypernatraemic dehydration with its attendant neurological, renal and vascular lesions, and (ii) protracted diarrhoea which may lead to severe malnutrition. Deconjugation of bile salts and colonization of the small bowel with toxigenic strains of E. coli may be important in the pathophysiology of the protracted diarrhoea syndrome. The control of bacterial diarrhoea requires a corrdinated political, educational, social, public health and scientific attack. Bacterial diarrhoea is a major health problem throughout the world, and carries an appreciable morbidity and mortality. This is particularly the case during infancy, and in those developing parts of the world

  11. Bacterial survival in Martian conditions

    OpenAIRE

    Galletta, Giuseppe; Bertoloni, Giulio; D'Alessandro, Maurizio

    2010-01-01

    We shortly discuss the observable consequences of the two hypotheses about the origin of life on Earth and Mars: the Lithopanspermia (Mars to Earth or viceversa) and the origin from a unique progenitor, that for Earth is called LUCA (the LUCA hypothesis). To test the possibility that some lifeforms similar to the terrestrial ones may survive on Mars, we designed and built two simulators of Martian environments where to perform experiments with different bacterial strains: LISA and mini-LISA. ...

  12. Small intestinal bacterial overgrowth syndrome

    Institute of Scientific and Technical Information of China (English)

    Jan; Bures; Jiri; Cyrany; Darina; Kohoutova; Miroslav; Frstl; Stanislav; Rejchrt; Jaroslav; Kvetina; Viktor; Vorisek; Marcela; Kopacova

    2010-01-01

    Human intestinal microbiota create a complex polymi-crobial ecology. This is characterised by its high population density, wide diversity and complexity of interaction. Any dysbalance of this complex intestinal microbiome, both qualitative and quantitative, might have serious health consequence for a macro-organism, including small intestinal bacterial overgrowth syndrome (SIBO).SIBO is defined as an increase in the number and/or alteration in the type of bacteria in the upper gastro-intestinal tract. There...

  13. Population dynamics of bacterial persistence

    OpenAIRE

    Patra, Pintu

    2014-01-01

    The life of microorganisms is characterized by two main tasks, rapid growth under conditions permitting growth and survival under stressful conditions. The environments, in which microorganisms dwell, vary in space and time. The microorganisms innovate diverse strategies to readily adapt to the regularly fluctuating environments. Phenotypic heterogeneity is one such strategy, where an isogenic population splits into subpopulations that respond differently under identical environments. Bacteri...

  14. Immunization by a bacterial aerosol

    OpenAIRE

    Garcia-Contreras, Lucila; Wong, Yun-Ling; Muttil, Pavan; Padilla, Danielle; Sadoff, Jerry; DeRousse, Jessica; Germishuizen, Willem Andreas; Goonesekera, Sunali; Elbert, Katharina; Bloom, Barry R.; Miller, Rich; Fourie, P. Bernard; Hickey, Anthony; Edwards, David

    2008-01-01

    By manufacturing a single-particle system in two particulate forms (i.e., micrometer size and nanometer size), we have designed a bacterial vaccine form that exhibits improved efficacy of immunization. Microstructural properties are adapted to alter dispersive and aerosol properties independently. Dried “nanomicroparticle” vaccines possess two axes of nanoscale dimensions and a third axis of micrometer dimension; the last one permits effective micrometer-like physical dispersion, and the form...

  15. Rheumatoid arthritis and bacterial infections

    OpenAIRE

    N L Prokopjeva; N N Vesikova; I M Marusenko; V A Ryabkov

    2008-01-01

    To study features of bacterial infections course in pts with rheumatoid arthritis (RA) and changes of laboratory measures after focus of infection sanation. Material and methods. 46 pts with definite rheumatoid arthritis were examined at the time of comorbid infection (Cl) detection and after infection focus sanation. Bacteriological test with evaluation of flora sensitivity to antibiotics by disco-diffusion method was performed at baseline and after the course of antibacterial therapy to ass...

  16. Molecular approaches for bacterial azoreductases

    OpenAIRE

    Montira Leelakriangsak

    2013-01-01

    Azo dyes are the dominant types of synthetic dyes, widely used in textiles, foods, leather, printing, tattooing, cosmetics, and pharmaceutical industries. Many microorganisms are able to decolorize azo dyes, and there is increasing interest in biological waste treatment methods. Bacterial azoreductases can cleave azo linkages (-N=N-) in azo dyes, forming aromatic amines. This review mainly focuses on employing molecular approaches, including gene manipulation and recombinant strains, to study...

  17. Bacterial meningitis by streptococcus agalactiae

    OpenAIRE

    Villarreal-Velásquez Tatiana Paola; Cortés-Daza César Camilo

    2012-01-01

    Introduction: bacterial meningitis is an infectious disease considered a medicalemergency. The timely management has an important impact on the evolution of thedisease. Streptococcus agalactiae, a major causative agent of severe infections innewborns can colonize different tissues, including the central nervous system.Case report: Male patient 47 years old from rural areas, with work activity as amilker of cattle, referred to tertiary care, with disorientation, neck stiffness, and grandmal se...

  18. INVESTIGATION EXPERIMENTALE DE JOINT EN T SOUDE

    OpenAIRE

    SAIDANI, Messaoud

    2011-01-01

    Cet article présente les résultats d'une recherche expérimentale sur le comportement des connexions T-end soudées à profil creux circulaire (CHS) des éléments soumis à une traction axiale. Un total de 22 échantillons ont été testés jusqu'à défaillance. Paramètres pris en compte pour l'enquête ont été la taille du tube et l'épaisseur de la couronne. L'épaisseur de la plaque cale a été maintenue constante pour tous les tests. L'orientation de la plaque cale par rapport au tube a été étudiée et ...

  19. Bacterial sex in dental plaque

    Directory of Open Access Journals (Sweden)

    Ingar Olsen

    2013-06-01

    Full Text Available Genes are transferred between bacteria in dental plaque by transduction, conjugation, and transformation. Membrane vesicles can also provide a mechanism for horizontal gene transfer. DNA transfer is considered bacterial sex, but the transfer is not parallel to processes that we associate with sex in higher organisms. Several examples of bacterial gene transfer in the oral cavity are given in this review. How frequently this occurs in dental plaque is not clear, but evidence suggests that it affects a number of the major genera present. It has been estimated that new sequences in genomes established through horizontal gene transfer can constitute up to 30% of bacterial genomes. Gene transfer can be both inter- and intrageneric, and it can also affect transient organisms. The transferred DNA can be integrated or recombined in the recipient's chromosome or remain as an extrachromosomal inheritable element. This can make dental plaque a reservoir for antimicrobial resistance genes. The ability to transfer DNA is important for bacteria, making them better adapted to the harsh environment of the human mouth, and promoting their survival, virulence, and pathogenicity.

  20. Cytochemical Differences in Bacterial Glycocalyx

    Science.gov (United States)

    Krautgartner, Wolf Dietrich; Vitkov, Ljubomir; Hannig, Matthias; Pelz, Klaus; Stoiber, Walter

    2005-02-01

    To examine new cytochemical aspects of the bacterial adhesion, a strain 41452/01 of the oral commensal Streptococcus sanguis and a wild strain of Staphylococcus aureus were grown with and without sucrose supplementation for 6 days. Osmiumtetraoxyde (OsO4), uranyl acetate (UA), ruthenium red (RR), cupromeronic blue (CB) staining with critical electrolytic concentrations (CECs), and the tannic acid-metal salt technique (TAMST) were applied for electron microscopy. Cytochemically, only RR-positive fimbriae in S. sanguis were visualized. By contrast, some types of fimbriae staining were observed in S. aureus glycocalyx: RR-positive, OsO4-positive, tannophilic and CB-positive with ceasing point at 0.3 M MgCl2. The CB staining with CEC, used for the first time for visualization of glycoproteins of bacterial glycocalyx, also reveals intacellular CB-positive substances-probably the monomeric molecules, that is, subunits forming the fimbriae via extracellular assembly. Thus, glycosylated components of the biofilm matrix can be reliably related to single cells. The visualization of intracellular components by CB with CEC enables clear distinction between S. aureus and other bacteria, which do not produce CB-positive substances. The small quantities of tannophilic substances found in S. aureus makes the use of TAMST for the same purpose difficult. The present work protocol enables, for the first time, a partial cytochemical differentiation of the bacterial glycocalyx.

  1. Contribution to the study of deformed heavy nuclei by means of nuclear reactions; Contribution a l'etude des noyaux lourds deformes au moyen de reactions nucleaires

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-06-01

    The experimental results obtained in the study of the (d,p) reactions, at E{sub d} = 12 MeV, on the three even-even deformed nuclei {sup 170}Yb, {sup 172}Yb and {sup 174}Yb have been analysed in terms of DWBA calculations. The spectroscopic information relative to the odd final nuclei have been compared with the predictions of the collective model and of the Nilsson's model. The effect of various parameters used in the DWBA analysis (form factors, optical wave functions) has been carefully studied. The observed differences between the three final nuclei are qualitatively reproduced in the experimental study of resonances, seen in excitation functions of elastically and inelastically scattered protons on the same target nuclei, and corresponding to analogue states in the three nuclei {sup 171}Lu, {sup 173}Lu and {sup 175}Lu. (author) [French] Les resultats experimentaux de l'etude des reactions (d.p) a E{sub d} = 12 MeV, sur les noyaux deformes pairs-pairs {sup 170}Yb, {sup 172}Yb et {sup 174}Yb ont ete interpretes dans le cadre de l'approximation de Born des ondes deformees. Les informations spectroscopiques relatives aux noyaux impairs finals ont ete comparees aux predictions du modele collectif et du modele de Nilsson, apres avoir examine avec soin l'influence des differents parametres (facteurs de forme, fonctions d'onde 'optiques') utilises lors de l'analyse. Les differences observees entre les trois noyaux finals sont qualitativement reproduites par les resultats experimentaux de l'etude de resonances dans les fonctions d'excitation de diffusion elastique et inelastique de protons sur les memes noyaux-cibles, lors de la recherche d'etats analogues dans les noyaux {sup 171}Lu, {sup 173}Lu et {sup 175}Lu. (auteur)

  2. Kinetic study of the reaction of nitrogen with uranium monocarbide; Etude cinetique de la reaction de l'azote sur le monocarbure d'uranium

    Energy Technology Data Exchange (ETDEWEB)

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

    1968-07-01

    The nitridation of uranium monocarbide pieces, microspheres and powder as well, is investigated in the temperature range 700 - 1200 deg. C and the kinetics of this reaction specified, using a thermogravimetric experimental procedure. In every case; the kinetics appears to be linear, except for massive monocarbide at temperatures above 950 deg. C which obeys following the rate law: {delta} m{sup x} = Kt, with x = 1.5 {+-} 0.1 Accordingly, the activation energy varies from 15 to 30 Kcal/mole. Furthermore, as evidenced by the curves K = F(P), the rate of nitridation increases proportionally to the square root of nitrogen pressure. The particular behaviour of the powders can be accounted for through a study of their 'over-temperature'. On the basis of all experimental results, the author suggests a reactional mechanism. (author) [French] L'etude thermogravimetrique de nitruration du monocarbure d'uranium sous differentes formes: massif, billes, poudre, entre 700 et 1200 deg. C, permet de connaitre la cinetique de cette reaction. Dans tous les cas la loi est lineaire sauf pour le monocarbure massif aux temperatures superieures a 950 deg. C, ou elle peut s'exprimer sous la forme: {delta} m{sup x} = Kt avec x = 1,5 {+-} 0,1 L'energie d'activation varie de 15 a 30 Kcal/mole suivant le type de loi rencontre. Les courbes K = F(P) montrent que la vitesse de nitruration croit avec la racine carree de la pression d'azote. L'etude de surtemperature des poudres permet d'expliquer leur comportement particulier. L'auteur propose un mecanisme reactionnel regroupant l'ensemble des resultats experimentaux. (auteur)

  3. Bacterial adhesion and biofilms on surfaces

    Institute of Scientific and Technical Information of China (English)

    Trevor Roger Garrett; Manmohan Bhakoo; Zhibing Zhang

    2008-01-01

    Bacterial adhesion has become a significant problem in industry and in the domicile,and much research has been done for deeper understanding of the processes involved.A generic biological model of bacterial adhesion and population growth called the bacterial biofilm growth cycle,has been described and modified many times.The biofilm growth cycle encompasses bacterial adhesion at all levels,starting with the initial physical attraction of bacteria to a substrate,and ending with the eventual liberation of cell dusters from the biofilm matrix.When describing bacterial adhesion one is simply describing one or more stages of biofilm development,neglecting the fact that the population may not reach maturity.This article provides an overview of bacterial adhesion.cites examples of how bac-terial adhesion affects industry and summarises methods and instrumentation used to improve our understanding of the adhesive prop-erties of bacteria.

  4. CÁNCER Y TERAPÉUTICA CON PRODUCTOS DE LA COLMENA. REVISIÓN SISTEMÁTICA DE LOS ESTUDIOS EXPERIMENTALES Cancer therapy with bee products. Systematic review of experimental studies

    Directory of Open Access Journals (Sweden)

    Andrés Jagua-Gualdrón

    2012-04-01

    Full Text Available Antecedentes. Los productos de la colmena se han utilizados desde hace más de dos milenios con fines terapéuticos. Conceptos teóricos basados en la composición de los productos hacen pensar que podrían ser de utilidad en el manejo del cáncer. Objetivo. Resumir la evidencia experimental disponible en la actualidad sobre el uso de los productos de la colmena en el manejo del cáncer. Material y métodos. Se realizó una revisión sistemática de los estudios experimentales publicados a través de las bibliotecas digitales PUBMED, LiLACS y OVID en los cuales se evaluara la utilidad del uso de los distintos productos de la colmena sobre cultivos de células tumorales o sobre modelos animales de cáncer. Se realizó un análisis cualitativo de la información y se construyeron tablas de resumen. Resultados. La búsqueda arrojó un total de 391 resultados de los cuales únicamente 55 cumplieron los criterios de inclusión. El veneno de abejas, la miel y el propóleo son los productos con un mayor número de publicaciones. La mayoría son estudios in vitro y son pocos los modelos en animales realizado. Se describen los mecanismos de acción a través de los cuales estos podrían llegar a ejercer acciones farmacológicas útiles en el manejo del cáncer. Conclusión. La aplicación de los productos de la colmena en el cáncer es un campo incipiente pero prometedor de investigación. Existe evidencia experimental que documenta la plausibilidad biológica de este uso. Es necesario realizar modelos animales que permitan describir el comportamiento de los productos y documentar su seguridad y utilidad terapéutica en el cáncer.Background. The beehive products have been used for more than two millennia with therapeutic purposes. Theoretical models based on the composition of products suggest that might be useful in cancer management. Objective. To summarize experimental evidence available to date on the use of beehive products in cancer management

  5. Experimental investigation of smectite hydration from the simulation of 001 X-ray diffraction lines. Implications for the characterization of mineralogical modifications of the 'argilite' from the Meuse - Haute Marne site as a result of a thermal perturbation; Etude experimentale de l'hydratation des smectites par simulation des raies OOl de diffraction des rayons X. Implications pour l'etude d'une perturbation thermique sur la mineralogie de l'argilite du site Meuse-Haute Marne

    Energy Technology Data Exchange (ETDEWEB)

    Ferrage, E

    2004-10-15

    The structural modifications affecting the reactive mineral constituents of the clay barriers (smectite) and possibly resulting from the thermal pulse related to nuclear waste storage are essentially limited to the amount and location of the layer charge deficit. These modifications likely impact the hydration properties of these minerals, and a specific methodology has thus been developed to describe, using simulation of X-ray diffraction profiles (001 reflections), these hydration properties and specifically the heterogeneity resulting from the inter-stratification of different layer types, each exhibiting a specific hydration state. The detailed study of the hydration properties of a low-charge montmorillonite (octahedral charge) has shown that the affinity of the interlayer cation for water rules the hydration state and the thickness of hydrated smectite layers. If the layer charge is increased, the transition between the different hydration states is shifted, following a water desorption isotherm, towards lower relative humidities. In addition, the hydration of studied beidellites (tetrahedral charge) was shown to be more heterogeneous than that of montmorillonites. The developed methodology also allowed describing the structural modifications resulting from a chemical perturbation (chlorinated anionic background, pH). Finally, the link between the thickness of elementary layers and the amount of interlayer water molecules has been evidenced. A new structure model has also been determined for these interlayer species allowing an improved description of their positional distribution in bi-hydrated interlayers. (author)

  6. Influence of age on radioinduced cognitive disorders: Experimental studies with cerebral irradiation of 30 Gy in 10 sessions and 12 days in the Wistar rat at 1.5, 4 and 18 months; Influence de l'age sur les troubles cognitifs radioinduits : etudes experimentales avec irradiation cerebrale de 30 Gy en 10 seances et 12 jours chez le rat Wistar de 1 1/2, 4 et 18 mois

    Energy Technology Data Exchange (ETDEWEB)

    Lamproglou, I. [Lab. de Chimie et Biophysique des Traceurs, Faculte de Medecine Xavier Bichat, Paris (France); Baillet, F.; Boisserie, G.; Mazeron, J.J. [Service de Radiotherapie, Hopital de la Pitie-Salpetriere, Paris (France); Delattre, J.Y. [Dept. of Neurology and Inst. National de la Sante et de la Recherche Medicale, INSERM, Hopital de la Pitie-Salpetriere, Paris (France)

    2002-07-01

    The objective of this study was to determine the influence of age on the learning and memory dysfunction induced by cranial radiation in the male Wistar rat. Ninety-six 45-day-old, 70 4-month-old, and 78 18-month-old male rats were divided in two equal groups: (i) irradiated and (ii) control. A course of whole-brain radiation therapy (30 Gy in 10 fractions over 12 days) was administered to the irradiated group, while the control group received sham irradiation. Sequential behavioral studies including one and two-way avoidance tests were undertaken before and after the 7 months following radiation. The results suggest that radiation induced progressive and irreversible memory dysfunction in elderly (18-month-old) rats, but this effect was partial or almost reversible in the 4-month-old and 45-day-old rats, respectively. In return, the learning dysfunction was age non-dependent despite the fact that is occurs more rapidly in the young (45 days, 4 months) rats. (author)

  7. Experimental study and modelling of the U(VI)-NaCl-H{sub 2}O ternary system with respect to pH and NaCl concentration at T=155 degrees C and Psat; Etude experimentale et modelisation du systeme ternaire U(VI)-NaCl-H{sub 2}O en fonction du pH et de la concentration en NaCl, a T = 155C et Psat

    Energy Technology Data Exchange (ETDEWEB)

    Rozsypal, Ch.; Chinh, Nguyen-Trung [CREGU, 54 - Vandoeuvre les Nancy (France); Cuney, M. [Universite Henri Poincare - Nancy 1, UMR 7566 G2R, 54 - Vandoeuvre-les-Nancy (France)

    2009-07-01

    The authors report an experimental investigation of the solubility of U(VI) in the UO{sub 3}-NaCl-H{sub 2}O ternary system with respect to the pH (between 2.9 and 13.4) at a temperature of 155 C. The average experiment duration has been 4 months in an acid medium and 6 months in a basic medium. At the end of these experiments, solid phases have been analysed by X-ray diffraction, transmission and scanning electronic microscopy, and Raman spectroscopy. The content in dissolved uranium has been determined. The obtained results show that the initial UO{sub 3} transformed into three types of solid phases: uranium oxides in acid medium, uranates, and sodium chloro-uranates

  8. Experimental study and modeling of the propagation of an alkaline concentration wave coming from a cement matrix an passing through the argilite of the Meuse / Haute-Marne laboratory; Etude experimentale et modelisation de la propagation d'une onde de concentration alcaline issue d'une matrice cimentiere a travers l'argilite du site du laboratoire Meuse / Haute-Marne

    Energy Technology Data Exchange (ETDEWEB)

    Roussel, Th

    2001-12-01

    The propagation of an alkaline wave through a clay rock has been investigated- The wave is generated by a cementitious matrix through the Callovo-Oxfordian argillite of the Meuse Haute-Marne Laboratory (-480 m depth). The argillite itself is composed of quartz, micas, calcite and an interstratified l/S. In order to characterise the interactions between the alkaline fluid and the argillaceous medium, dynamic column experiments have been carried out. The originality of the investigation methodology consists in exploiting the data generated from the breakthrough curves as well as from the characterisation of the solids extracted from the columns. Two types of processes having totally different reaction times have hence been thoroughly studied: - Fast surface adsorption and condensation reactions: On the one hand cation adsorption reactions by site ionisation have been characterised. They are responsible of the buffering effect of the clays. On the other hand an original reaction of calcium compound condensation in the interlayer space of the swelling clays has been revealed. These processes have been modelled and their simulations with the IMPACT calculation code showed that the models elaborated were very satisfying. - Strongly kinetically limited dissolution/precipitation reactions: The main primary phases dissolved are quartz and interstratified l/S. The precipitation of secondary phases are mainly C(A)SH and zeolites. After the injection of an alkaline fluid for 6 months at 60 deg C, the argillite is strongly amorphized but only 20 to 30% of the quartz and the interstratified I/S are dissolved. Therefore, dissolution kinetics of the primary phases and the solubility products of the main secondary phases have been determined. (author)

  9. Incineration of oxygenated volatile organic compounds. Experimental study and kinetic modeling of the oxidation of methyl ethyl ketone, ethyl acetate and butan-2-ol in methane flames; Incineration de composes organiques volatils oxygenes. Etude experimentale et modelisation cinetique de l'oxydation de la methyl ethyl cetone, de l'acetate d'ethyle et du butan-2-ol dans des flammes de methane

    Energy Technology Data Exchange (ETDEWEB)

    Decottignies, V.

    2000-12-01

    This work deals with the low pressure (0.05 atm) degradation of three volatile organic compounds (VOCs): methyl-ethyl-ketone, ethyl acetate and butan-2-ol, in premixed stoichiometric laminar methane flames seeded with 1 to 3% of each VOC. Molar fraction profiles of species have been obtained using microprobe sampling coupled with a gas chromatography and a mass spectroscopy analysis. Temperature profiles have been obtained using the covered thermocouple technique in the presence of the microprobe. The addition of a VOC in the initial reagents mixture leads to an increase of the quantity of intermediate hydrocarbon compounds and in particular of some soot precursor species. The degradation of VOCs leads to the formation of oxygenated intermediates like methanol, dimethyl-ether, acetaldehyde, propanal, acetone and vinyl acetate, the type of VOC having an effect on the quantities produced. The degradation of a VOC can lead to the formation of more toxic or polluting compounds (methyl vinyl ketone, acetic acid and acrolein) than the VOC itself. In the conditions of the study, the intermediate compounds are totally destructed inside the reactional area of the flame front and are no more present in the burnt gases. Sub-mechanisms of VOC oxidation have been developed using experimental observations and the most recent recommendations of the literature. These sub-mechanisms comprise 49 species involved in 241 elementary reactions. Their validation has been performed by comparing the experiment with the kinetic modeling on the molar fraction profiles of the detected species. Experimental data are well reproduced by the model for most species. The addition of a VOC inside the initial reagents mixture creates an important reactivity increase, in particular in the case of butan-2-ol seeded flames. The analysis of reactional ways has permitted to draw out the main reactions responsible for the degradation of the 3 VOCs and the ways of formation and consumption of the intermediate compounds specific of these VOCs. (J.S.)

  10. Periodontal diseases as bacterial infection

    Directory of Open Access Journals (Sweden)

    A. Bascones Martínez

    2005-12-01

    Full Text Available The periodontal disease is conformed by a group of illnesses affecting the gums and dental support structures. They are caused by certain bacteria found in the bacterial plaque. These bacteria are essential to the onset of illness; however, there are predisposing factors in both the host and the microorganisms that will have an effect on the pathogenesis of the illness. Periodontopathogenic bacterial microbiota is needed, but by itself, it is not enough to cause the illness, requiring the presence of a susceptible host. These diseases have been classified as gingivitis, when limited to the gums, and periodontitis, when they spread to deeper tissues. Classification of periodontal disease has varied over the years.The one used in this work was approved at the International Workshop for a Classification of Periodontal Diseases and Conditions, held in 1999. This study is an overview of the different periodontal disease syndromes. Later, the systematic use of antibiotic treatment consisting of amoxicillin, amoxicillinclavulanic acid, and metronidazole as first line coadjuvant treatment of these illnesses will be reviewed.

  11. Bacterial mutagenicity assays: test methods.

    Science.gov (United States)

    Gatehouse, David

    2012-01-01

    The most widely used assays for detecting chemically induced gene mutations are those employing bacteria. The plate incorporation assay using various Salmonella typhimurium LT2 and E. coli WP2 strains is a short-term bacterial reverse mutation assay specifically designed to detect a wide range of chemical substances capable of causing DNA damage leading to gene mutations. The test is used worldwide as an initial screen to determine the mutagenic potential of new chemicals and drugs.The test uses several strains of S. typhimurium which carry different mutations in various genes of the histidine operon, and E. coli which carry the same AT base pair at the critical mutation site within the trpE gene. These mutations act as hot spots for mutagens that cause DNA damage via different mechanisms. When these auxotrophic bacterial strains are grown on a minimal media agar plates containing a trace of the required amino-acid (histidine or tryptophan), only those bacteria that revert to amino-acid independence (His(+) or Tryp(+)) will grow to form visible colonies. The number of spontaneously induced revertant colonies per plate is relatively constant. However, when a mutagen is added to the plate, the number of revertant colonies per plate is increased, usually in a dose-related manner.This chapter provides detailed procedures for performing the test in the presence and absence of a metabolic activation system (S9-mix), including advice on specific assay variations and any technical problems. PMID:22147566

  12. BACTERIAL DESEASES IN SEA FISH

    Directory of Open Access Journals (Sweden)

    Ivančica Strunjak-Perović

    1997-10-01

    Full Text Available With development of the fish culturing in the sea, the interest in their health also increased. The reason for this are diseases or rather mortality that occur in such controlled cultures and cause great economic losses. By growing large quantities of fish in rather small species, natural conditions are changed, so fish is more sensitive and prone to infection agents (viruses, bacteria, parasites. Besides, a large fish density in the cultural process accelerates spreading if the diseases, but also enables a better perception of them. In wild populations sick specimen very quickly become predator’s prey, witch makes it difficult to note any pathological changes in such fish. There are lots of articles on viral, bacterial and parasitic diseases nowdays, but this work deals exclusively with bacterial deseases that occur in the controlled sea cultures (vibriosis, furunculosis, pastherelosis, nocardiosis, mycobaceriosis, edwardsielosis, yersiniosis, deseases caused by bacteria of genera Flexibacter, Pseudomonas, Aeromonas, Streptococus and bacteria nephryithis. Yet, the knowledge of these deseases vary, depending on wether a fish species is being cultured for a longer period of time or is only being introduced in the controlled culture.

  13. Bioinformatic Comparison of Bacterial Secretomes

    Institute of Scientific and Technical Information of China (English)

    Catharine Song; Aseem Kumar; Mazen Saleh

    2009-01-01

    The rapid increasing number of completed bacterial genomes provides a good op-portunity to compare their proteomes. This study was undertaken to specifically compare and contrast their secretomes-the fraction of the proteome with pre-dicted N-terminal signal sequences, both type Ⅰ and type Ⅱ. A total of 176 theoreti-cal bacterial proteomes were examined using the ExProt program. Compared with the Gram-positives, the Gram-negative bacteria were found, on average, to con-tain a larger number of potential Sec-dependent sequences. In the Gram-negative bacteria but not in the others, there was a positive correlation between proteome size and secretome size, while there was no correlation between secretome size and pathogenicity. Within the Gram-negative bacteria, intracellular pathogens were found to have the smallest secretomes. However, the secretomes of certain bacte-ria did not fit into the observed pattern. Specifically, the secretome of Borrelia burgdoferi has an unusually large number of putative lipoproteins, and the signal peptides of mycoplasmas show closer sequence similarity to those of the Gram-negative bacteria. Our analysis also suggests that even for a theoretical minimal genome of 300 open reading frames, a fraction of this gene pool (up to a maximum of 20%) may code for proteins with Sec-dependent signal sequences.

  14. Bacterial Culture of Neonatal Sepsis

    Directory of Open Access Journals (Sweden)

    AH Movahedian

    2006-08-01

    Full Text Available Neonatal bacterial sepsis is one of the major cause of morbidity and mortality in neonates. This retrospective study was performed to determine the incidence of bacterial sepsis with focus on Gram negative organisms in neonates admitted at Beheshti Hospital in Kashan, during a 3-yr period, from September 2002 to September 2005. Blood culture was performed on all neonates with risk factors or signs of suggestive sepsis. Blood samples were cultured using brain heart infusion (BHI broth according to standard method. From the 1680 neonates 36% had positive blood culture for Pseudomans aeruginosa, 20.7% for Coagulase negative Staphylococci, and 17% for Klebsiella spp. Gram-negative organisms accounted for 72.1% of all positive cultures. The overall mortality rate was 19.8% (22 /111 of whom 63.6% (14 /22 were preterm. Pseudomona aeruginosa and Klebsiella spp. showed a high degree of resistance to commonly used antibiotics (ampicillin, gentamicin as well as third generation cephalosporins. Continued local surveillance studies are urged to monitor emerging antimicrobial resistance and to guide interventions to minimize its occurrence.

  15. Immunization by a bacterial aerosol.

    Science.gov (United States)

    Garcia-Contreras, Lucila; Wong, Yun-Ling; Muttil, Pavan; Padilla, Danielle; Sadoff, Jerry; Derousse, Jessica; Germishuizen, Willem Andreas; Goonesekera, Sunali; Elbert, Katharina; Bloom, Barry R; Miller, Rich; Fourie, P Bernard; Hickey, Anthony; Edwards, David

    2008-03-25

    By manufacturing a single-particle system in two particulate forms (i.e., micrometer size and nanometer size), we have designed a bacterial vaccine form that exhibits improved efficacy of immunization. Microstructural properties are adapted to alter dispersive and aerosol properties independently. Dried "nanomicroparticle" vaccines possess two axes of nanoscale dimensions and a third axis of micrometer dimension; the last one permits effective micrometer-like physical dispersion, and the former provides alignment of the principal nanodimension particle axes with the direction of airflow. Particles formed with this combination of nano- and micrometer-scale dimensions possess a greater ability to aerosolize than particles of standard spherical isotropic shape and of similar geometric diameter. Here, we demonstrate effective application of this biomaterial by using the live attenuated tuberculosis vaccine bacille Calmette-Guérin (BCG). Prepared as a spray-dried nanomicroparticle aerosol, BCG vaccine exhibited high-efficiency delivery and peripheral lung targeting capacity from a low-cost and technically simple delivery system. Aerosol delivery of the BCG nanomicroparticle to normal guinea pigs subsequently challenged with virulent Mycobacterium tuberculosis significantly reduced bacterial burden and lung pathology both relative to untreated animals and to control animals immunized with the standard parenteral BCG. PMID:18344320

  16. Remodeling bacterial polysaccharides by metabolic pathway engineering

    OpenAIRE

    Yi, Wen; Liu, Xianwei; Li, Yanhong; Li, Jianjun; Xia, Chengfeng; Zhou, Guangyan; Zhang, Wenpeng; Zhao, Wei; Chen, Xi; Wang, Peng George

    2009-01-01

    Introducing structural modifications into biomolecules represents a powerful approach to dissect their functions and roles in biological processes. Bacterial polysaccharides, despite their rich structural information and essential roles in bacterium-host interactions and bacterial virulence, have largely been unexplored for in vivo structural modifications. In this study, we demonstrate the incorporation of a panel of monosaccharide analogs into bacterial polysaccharides in a highly homogenou...

  17. Effect of aerosolization on subsequent bacterial survival.

    OpenAIRE

    Walter, M V; Marthi, B; Fieland, V P; Ganio, L M

    1990-01-01

    To determine whether aerosolization could impair bacterial survival, Pseudomonas syringae and Erwinia herbicola were aerosolized in a greenhouse, the aerosol was sampled at various distances from the site of release by using all-glass impingers, and bacterial survival was followed in the impingers for 6 h. Bacterial survival subsequent to aerosolization of P. syringae and E. herbicola was not impaired 1 m from the site of release. P. syringae aerosolized at 3 to 15 m from the site of release ...

  18. Drag Reduction of Bacterial Cellulose Suspensions

    OpenAIRE

    Ogata, Satoshi; Numakawa, Tetsuya; Kubo, Takuya

    2010-01-01

    Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were carried out by measuring the pressure drop in pipe flow. It was found that bacterial cellulose suspensions give rise to drag reduction in the turbulent flow range. We observed a maximum drag reduction ratio of 11% and found that it increased with the concentration of the bacterial cellulose suspension. However, the drag reduction effect decreased in the presence of mechani...

  19. Drag Reduction of Bacterial Cellulose Suspensions

    OpenAIRE

    Satoshi Ogata; Tetsuya Numakawa; Takuya Kubo

    2011-01-01

    Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were carried out by measuring the pressure drop in pipe flow. It was found that bacterial cellulose suspensions give rise to drag reduction in the turbulent flow range. We observed a maximum drag reduction ratio of 11% and found that it increased with the concentration of the bacterial cellulose suspension. However, the drag reduction effect decreased in the presence of mechani...

  20. Bacterial successions in the Broiler Gastrointestinal tract

    DEFF Research Database (Denmark)

    Ranjitkar, Samir; Lawley, Blair; Tannock, Gerald;

    2016-01-01

    of crop, gizzard, ileum and ceca in relation to the feeding strategy and age (8, 15, 22, 25, 29 and 36 days). Of the four dietary treatments, bacterial diversity was analyzed for MBF and CKMS-30 by 454-pyrosequencing of 16S rRNA gene. Since there was no significant influence of diets on bacterial...... diversity, data were pooled for downstream analysis. With increasing age, a clear succession of bacterial communities and an increased bacterial diversity was observed. Lactobacillaceae (mainly Lactobacillus) represented most of the Firmicutes at all ages and in all segments of the gut except the ceca...

  1. Application De Methodes Nucleaires Et Physico-chimiques D'analyse A L'etude, Apres Implantation, D'un Depot De Bioverre Sur Un Alliage De Titane, En Vue D'une Optimisation De La Biocompatibilite Et De La Fonctionnalite A Long Terme

    CERN Document Server

    Brun, V

    1999-01-01

    Application De Methodes Nucleaires Et Physico-chimiques D'analyse A L'etude, Apres Implantation, D'un Depot De Bioverre Sur Un Alliage De Titane, En Vue D'une Optimisation De La Biocompatibilite Et De La Fonctionnalite A Long Terme

  2. Etude des mécanismes des réactions induites par les noyaux à halo de neutrons $^{11}Be$ (49,2 MeV/nucléon) et $ ^{6}He$ (41,5 MeéV/nucléon) sur le plomb en fonction de l'inélasticité des collisions

    CERN Document Server

    Patois, Y

    2001-01-01

    Etude des mécanismes des réactions induites par les noyaux à halo de neutrons $^{11}Be$ (49,2 MeV/nucléon) et $ ^{6}He$ (41,5 MeéV/nucléon) sur le plomb en fonction de l'inélasticité des collisions

  3. Contribution a l'etude de l'inactivation de micro-organismes par plasma

    Science.gov (United States)

    Benhacene-Boudam, Mustafa-Karim

    intensity, the inactivation rate was also found to obey a fluence law and its dependence on temperature could be modeled by the Arrhenius relation. Keywords: sterilization, atmospheric-pressure plasma, low-pressure plasma, UV photons, bacterial spores, survival curves, UV and heating synergy.

  4. Effect of heavy metals on bacterial transport

    Science.gov (United States)

    Zhang, H.; Olson, M. S.

    2010-12-01

    Adsorption of metals onto bacteria and soil takes place as stormwater runoff infiltrates into the subsurface. Changes in both bacterial surfaces and soil elemental content have been observed, and may alter the attachment of bacteria to soil surfaces. In this study, scanning electron microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) analyses were performed on soil samples equilibrated with synthetic stormwater amended with copper, lead and zinc. The results demonstrate the presence of copper and zinc on soil surfaces. To investigate bacterial attachment behavior, sets of batch sorption experiments were conducted on Escherichia Coli (E. coli) under different chemical conditions by varying solution compositions (nutrient solution vs synthetic stormwater). The adsorption data is best described using theoretical linear isotherms. The equilibrium coefficient (Kd) of E. coli is higher in synthetic stormwater than in nutrient solution without heavy metals. The adsorption of heavy metals onto bacterial surfaces significantly decreases their negative surface charge as determined via zeta potential measurements (-17.0±5.96mv for E. coli equilibrated with synthetic stormwater vs -21.6±5.45mv for E. coli equilibrated with nutrient solution), indicating that bacterial attachment may increase due to the attachment of metals onto bacterial surfaces and their subsequent change in surface charge. The attachment efficiency (α) of bacteria was also calculated and compared for both solution chemistries. Bacterial attachment efficiency (α) in synthetic stormwater is 0.997, which is twice as high as that in nutrient solution(α 0.465). The ratio of bacterial diameter : collector diameter suggests minimal soil straining during bacterial transport. Results suggest that the presence of metals in synthetic stormwater leads to an increase in bacterial attachment to soil surfaces. In terms of designing stormwater infiltration basins, the presence of heavy metals seems to

  5. Autoproteolytic Activation of Bacterial Toxins

    Directory of Open Access Journals (Sweden)

    Aimee Shen

    2010-05-01

    Full Text Available Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD in Multifunctional Autoprocessing RTX-like (MARTX and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6, which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins.

  6. Cooperative Model of Bacterial Sensing

    CERN Document Server

    Shi, Y; Shi, Yu; Duke, Thomas

    1998-01-01

    Bacterial chemotaxis is controlled by the signalling of a cluster of receptors. A cooperative model is presented, in which coupling between neighbouring receptor dimers enhances the sensitivity with which stimuli can be detected, without diminishing the range of chemoeffector concentration over which chemotaxis can operate. Individual receptor dimers have two stable conformational states: one active, one inactive. Noise gives rise to a distribution between these states, with the probability influenced by ligand binding, and also by the conformational states of adjacent receptor dimers. The two-state model is solved, based on an equivalence with the Ising model in a randomly distributed magnetic field. The model has only two effective parameters, and unifies a number of experimental findings. According to the value of the parameter comparing coupling and noise, the signal can be arbitrarily sensitive to changes in the fraction of receptor dimers to which ligand is bound. The counteracting effect of a change of...

  7. Bacterial ice crystal controlling proteins.

    Science.gov (United States)

    Lorv, Janet S H; Rose, David R; Glick, Bernard R

    2014-01-01

    Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions. PMID:24579057

  8. Unexpected versatility in bacterial riboswitches.

    Science.gov (United States)

    Mellin, J R; Cossart, Pascale

    2015-03-01

    Bacterial riboswitches are elements present in the 5'-untranslated regions (UTRs) of mRNA molecules that bind to ligands and regulate the expression of downstream genes. Riboswitches typically regulate the expression of protein-coding genes. However, mechanisms of riboswitch-mediated regulation have recently been shown to be more diverse than originally thought, with reports showing that riboswitches can regulate the expression of noncoding RNAs and control the access of proteins, such as transcription termination factor Rho and RNase E, to a nascent RNA. Riboswitches are also increasingly used in biotechnology, with advances in the engineering of synthetic riboswitches and the development of riboswitch-based sensors. In this review we address the emerging roles and mechanisms of riboswitch-mediated regulation in natura and recent progress in the development of riboswitch-based technology. PMID:25708284

  9. Contribution to the study of {pi}{sup -} + p {yields} {pi}{sup 0} + n and {pi}{sup -} + p {yields} {pi}{sup 0} + {pi} + n reactions at the energies of the maxima of the {pi}-nucleon interaction in the T = 1/2 state total cross section; Contribution a l'etude des reactions {pi}{sup -} + p {yields} {pi}{sup 0} + n et {pi}{sup -} + p {yields} {pi}{sup 0} + n aux energies des maxima de la section efficace totale de l'interaction {pi}{sup -} nucleon dans l'etat de spin isobarique T = 1/2

    Energy Technology Data Exchange (ETDEWEB)

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

    1962-07-01

    avec et sans plomb. La transmission experimentale ainsi definie est fonction du nombre moyen de photons presents, donc du rapport entre les voies neutres {pi}{sup 0} n et {pi}{sup 0} {pi}{sup 0} n. Dans le dernier chapitre de ce travail, nous avons discute les resultats experimentaux, en les comparant a ceux obtenus par d'autres auteurs dans l'etude de la photoproduction et de l'interaction {pi}-nucleon. (auteur)

  10. A study of the conformation and stability of nitroxide free radicals; Etude de la conformation et de la stabilite de radicaux libres nitroxydes

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-03-01

    les constantes de couplage des protons situes en {gamma} de l'azote ont une dependance spatiale tres marquee au meme titre que les protons situes en {beta}, ce que les etudes anterieures n'avaient pu preciser. Une analyse conformationnelle est effectuee par RMN a 310 MHz, en temperature variable. La synthese du di-t-butyl nitroxyde marque au carbone 13 en position {alpha} du groupement nitroxyde a permis de determiner avec certitude la constante d'interaction hyperfine electron carbone 13 quaternaire, grandeur qui n'avait pas ete mesuree jusqu'alors. Les constantes de couplage mesurees dans les radicaux piperidiniques tetramethyles en 2,2,6,6 ont pu etre ensuite attribuees a des carbones 13 situes en {beta} de l'azote, et leur variation a pu etre reliee a la conformation des cycles. C'est l'objet de la seconde partie. Dans un dernier chapitre, l'etude cinetique d'un radical nitroxyde instable, ayant un hydrogene en {beta}, met en evidence une decomposition bimoleculaire qui met en jeu la rupture de la liaison C-H; ceci est demontre par effet isotopique primaire. On peut conclure de cette etude qu'un nitroxyde est stable lorsque les differents groupes attaches a l'atome d'azote ne peuvent provoquer une decomposition du radical, soit intramoleculairement, si la geometrie de la molecule le permet, soit intermoleculairement par dimerisation sur un autre centre d'une molecule voisine, conduisant ainsi a une fragmentation ou a une disproportionation. (auteur)

  11. Use of Bacteriophages to control bacterial pathogens

    Science.gov (United States)

    Lytic bacteriophages can provide a natural method and an effective alternative to antibiotics to reduce bacterial pathogens in animals, foods, and other environments. Bacteriophages (phages) are viruses which infect bacterial cells and eventually kill them through lysis, and represent the most abun...

  12. Plant Natural Products Targeting Bacterial Virulence Factors.

    Science.gov (United States)

    Silva, Laura Nunes; Zimmer, Karine Rigon; Macedo, Alexandre José; Trentin, Danielle Silva

    2016-08-24

    Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas. PMID:27437994

  13. Bacterial cell division proteins as antibiotic targets

    NARCIS (Netherlands)

    T. den Blaauwen; J.M. Andreu; O. Monasterio

    2014-01-01

    Proteins involved in bacterial cell division often do not have a counterpart in eukaryotic cells and they are essential for the survival of the bacteria. The genetic accessibility of many bacterial species in combination with the Green Fluorescence Protein revolution to study localization of protein

  14. Recent advances in bacterial heme protein biochemistry

    OpenAIRE

    Mayfield, Jeffery A.; Dehner, Carolyn A.; Dubois, Jennifer L.

    2011-01-01

    Recent progress in genetics, fed by the burst in genome sequence data, has led to the identification of a host of novel bacterial heme proteins that are now being characterized in structural and mechanistic terms. The following short review highlights very recent work with bacterial heme proteins involved in the uptake, biosynthesis, degradation, and use of heme in respiration and sensing.

  15. Multiple bacterial species reside in chronic wounds

    DEFF Research Database (Denmark)

    Gjødsbøl, Kristine; Christensen, Jens Jørgen; Karlsmark, Tonny;

    2006-01-01

    The aim of the study was to investigate the bacterial profile of chronic venous leg ulcers and the importance of the profile to ulcer development. Patients with persisting venous leg ulcers were included and followed for 8 weeks. Every second week, ulcer samples were collected and the bacterial s...

  16. Bacterial biofilms: prokaryotic adventures in multicellularity

    DEFF Research Database (Denmark)

    Webb, J.S.; Givskov, Michael Christian; Kjelleberg, S.

    2003-01-01

    The development of bacterial biofilms includes both the initial social behavior of undifferentiated cells, as well as cell death and differentiation in the mature biofilm, and displays several striking similarities with higher organisms. Recent advances in the field provide new insight...... into differentiation and cell death events in bacterial biofilm development and propose that biofilms have an unexpected level of multicellularity....

  17. Barriers to bacterial motility on unsaturated surfaces

    DEFF Research Database (Denmark)

    Dechesne, Arnaud; Smets, Barth F.

    2013-01-01

    and their isogenic mutants unable to express various type of motility we aimed to quantify the physical limits of bacterial motility. Our results demonstrate how hydration controls bacterial motility under unsaturated conditions. They can form the base of improved biodegradation models that include microbial...

  18. Sustainable strategies for treatment of bacterial infections

    DEFF Research Database (Denmark)

    Molin, Søren

    2014-01-01

    not in a foreseeable future develop novel approaches and strategies to combat bacterial infections, many people will be at risk of dying from even trivial infections for which we until recently had highly effective antibiotics. We have for a number of years investigated chronic bacterial lung infections in patients...

  19. Clinical and symptomatological study of pigs subjected to a lethal dose of integral gamma irradiation; Etude clinique et symptomatologique chez le porc soumis a une irradiation gamma totale a dose letale

    Energy Technology Data Exchange (ETDEWEB)

    Vaiman, M.; Guenet, J.-L.; Maas, J.; Nizza, P

    1966-05-01

    Results are reported from a clinical and haematological study on a Corsican species of pigs wholly exposed to an approximately lethal dose of {gamma} radiation. The aim of this work was to examine the changes in the irradiation syndrome of irradiation for pigs to make it thus possible to devise further experiments, in particular in the therapeutic field. The dose received was 285 rads (measured as the absorption in the vertical antero-posterior medial plane). Data are presented on cyto-haematological changes in the blood circulating immediately after irradiation, and followed up to death, and changes in the medullary cytology after irradiation. The clinical picture of lethal radiation injury in swine is described. (authors) [French] Les auteurs rapportent les resultats d'une etude clinique et hematologique chez des porcs de race corse irradies in toto a dose sensiblement letale. Le but de cette etude etait de connaitre l'evolution du syndrome aigu d'irradiation chez le porc et de permettre ainsi le developpement d'experimentations ulterieures, en particulier dans le domaine therapeutique. La dose delivree etait de 285 rad (en dose absorbee au niveau du plan median vertical anteroposterieur. L'etude a porte essentiellement: 1. Sur les modifications cyclo-hematologiques du sang circulant immediatement apres l'irradiation, pour les differentes lignees cellulaires; l'evolution de ces modifications a ete notee jusqu'a la mort; 2. Sur les modifications de la cytologie medullaire apres irradiation (evolution du myelogramme et essai d'evaluation de la cellularite de la moelle osseuse);: 3. Sur les signes cliniques, d'ailleurs tres discrets, observes chez les porcs apres irradiation. (auteurs)

  20. A Replisome's journey through the bacterial chromosome.

    Science.gov (United States)

    Beattie, Thomas R; Reyes-Lamothe, Rodrigo

    2015-01-01

    Genome duplication requires the coordinated activity of a multi-component machine, the replisome. In contrast to the background of metabolic diversity across the bacterial domain, the composition and architecture of the bacterial replisome seem to have suffered few changes during evolution. This immutability underlines the replisome's efficiency in copying the genome. It also highlights the success of various strategies inherent to the replisome for responding to stress and avoiding problems during critical stages of DNA synthesis. Here we summarize current understanding of bacterial replisome architecture and highlight the known variations in different bacterial taxa. We then look at the mechanisms in place to ensure that the bacterial replisome is assembled appropriately on DNA, kept together during elongation, and disassembled upon termination. We put forward the idea that the architecture of the replisome may be more flexible that previously thought and speculate on elements of the replisome that maintain its stability to ensure a safe journey from origin to terminus. PMID:26097470

  1. Structural biology of bacterial RNA polymerase.

    Science.gov (United States)

    Murakami, Katsuhiko S

    2015-05-11

    Since its discovery and characterization in the early 1960s (Hurwitz, J. The discovery of RNA polymerase. J. Biol. Chem. 2005, 280, 42477-42485), an enormous amount of biochemical, biophysical and genetic data has been collected on bacterial RNA polymerase (RNAP). In the late 1990s, structural information pertaining to bacterial RNAP has emerged that provided unprecedented insights into the function and mechanism of RNA transcription. In this review, I list all structures related to bacterial RNAP (as determined by X-ray crystallography and NMR methods available from the Protein Data Bank), describe their contributions to bacterial transcription research and discuss the role that small molecules play in inhibiting bacterial RNA transcription.

  2. Structural Biology of Bacterial RNA Polymerase

    Directory of Open Access Journals (Sweden)

    Katsuhiko S. Murakami

    2015-05-01

    Full Text Available Since its discovery and characterization in the early 1960s (Hurwitz, J. The discovery of RNA polymerase. J. Biol. Chem. 2005, 280, 42477–42485, an enormous amount of biochemical, biophysical and genetic data has been collected on bacterial RNA polymerase (RNAP. In the late 1990s, structural information pertaining to bacterial RNAP has emerged that provided unprecedented insights into the function and mechanism of RNA transcription. In this review, I list all structures related to bacterial RNAP (as determined by X-ray crystallography and NMR methods available from the Protein Data Bank, describe their contributions to bacterial transcription research and discuss the role that small molecules play in inhibiting bacterial RNA transcription.

  3. Etude exploratoire des conceptions de la circulation sanguine aupres d'eleves de l'ordre collegial

    Science.gov (United States)

    Robitaille, Jean-Marc

    Il existe peu d'etudes sur les conceptions touchant les domaines de la biologie, notamment sur les conceptions de la circulation sanguine Nous avons observe egalement l'absence de recherche menee aupres d'eleves de l'ordre collegial sur cette question. Nous avons voulu combler une lacune en menant une recherche sur les conceptions de la circulation sanguine aupres d'eleves de l'ordre collegial. Pour mener cette recherche nous nous sommes inspires d'une methode developpee par Treagust (1988). Le premier niveau de formulation didactique etablit l'architecture du systeme et la fonction nutritive de la circulation. Le second niveau de formulation didactique decrit et relie les parametres de la dynamique de la circulation et leur relation: Pression, Debit et Resistance. Le troisieme niveau de formulation didactique s'interesse au controle de la circulation du sang dans un contexte d'homeostasie qui implique la regulation de la pression arterielle. Nous avons construit un questionnaire en nous guidant sur les niveaux de formulation didactique et l'analyse des entrevues menees aupres de dix-huit eleves, representatifs de la population cible. Ce questionnaire fut administre a un echantillon de 2300 eleves disperses dans six colleges de la region de Montreal. Notre echantillon comprend des eleves inscrits a des programmes de l'ordre collegial en Sciences de la nature et en Techniques de la sante et qui n'ont pas suivi le cours sur la circulation sanguine. Notre analyse des reponses des eleves de notre echantillon aux questions sur le premier niveau de formulation didactique revele que la majorite des eleves considerent que le systeme circulatoire relie les organes les uns aux autres dans un circuit en serie. Notre analyse revele egalement que la majorite des eleves estiment que les nutriments sont extraits du sang par les organes selon un processus de selection base sur les besoins determines par la fonction de l'organe. Ces besoins sont differents selon les organes qui ne

  4. Etude des phenomenes de penetration des especes chimiques dans les revetements cathodiques des cuves d'electrolyse de l'aluminium

    Science.gov (United States)

    Brisson, Pierre-Yves

    Cette these decrit l'etude effectuee sur les phenomenes d'insertion du sodium et de penetration du bain electrolytique dans les revetements cathodiques des cuves d'electrolyse de l'aluminium. L'etude fut effectuee a l'aide d'un montage permettant d'effectuer l'electrolyse en laboratoire. Trois types de revetement cathodiques furent etudies : des blocs semi-graphitique, des blocs graphitiques et des blocs graphitises. L'insertion du sodium dans les trois differents types de blocs fut etudiee a l'aide de la spectrometrie des photoelectrons X (XPS). L'analyse a permis de mettre en evidence deux formes de sodium dans l'anthracite et la phase liante des materiaux semi-graphitiques et graphitiques, indiquant qu'une fraction du sodium se retrouve sous forme adsorbee dans les micropores des materiaux alors que l'autre fraction est inseree dans la structure cristalline du carbone. Dans les phases graphitiques (materiaux graphitises et graphitiques), seuls les micropores sont occupes par le sodium Ce resultat explique la tendance observee selon laquelle l'ajout de graphite dans les blocs permet d'abaisser le gonflement sodique. Les mecanismes de penetration du bain dans le reseau poreux des materiaux furent etudies en microscopie electronique et en diffraction des rayons X sur des echantillons apres differents temps d'electrolyses et en variant l'atmosphere (soit sous argon ou sous azote). Ces analyses ont permis d'identifier le mecanisme conduisant a la mouillabilite du bain sur le carbone en fonction de l'atmosphere entourant l'electrolyse. Ainsi, sous azote, la formation de NaCN dans les pores des materiaux par reactions entre le sodium et l'azote permet une mouillabilite accrue du bain alors qu'en absence d'azote (sous argon), le carbure d'aluminium, formes a la surface des pores, joue un role similaire. Dans ce dernier cas, la penetration du bain est moins rapide etant donnee la necessite de toujours amener des especes contenant de l'aluminium en tete du front de

  5. Contribution to the micrographic study of uranium and its alloys; Contribution a l'etude micrographique de l'uranium et de ses alliages

    Energy Technology Data Exchange (ETDEWEB)

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

    1956-06-15

    The present report is the result of research carried out by the radio metallurgy section, to perfect micrographic techniques applicable to the study of samples of irradiated uranium. In the first part of this work, two polishing baths are developed, having the qualities with a minimum of disadvantages inherent in their respective compositions: they are, on the one hand perchloric acid-ethanol mixtures, and on the other hand a phospho-chromic-ethanol bath. In the chapter following, the micrographic attack of uranium is studied. The only satisfactory process is oxidation by cathode bombardment forming epitaxic layers. In the third chapter, an attempt is made to characterise the different surface states of the uranium by dissolution potential measurements and electronic diffraction. In the fourth chapter are given some examples of the application of these techniques to the micrographic study of various uranium alloys. In an appendix, it is shown how the chemical oxidation after phospho-chromic-alcohol polishing allows the different inclusions present in the molten uranium to be distinguished. By X-ray diffraction, uranium monocarbide and mononitride inclusions in particular are characterised. (author) [French] Le present rapport est le resultat de recherches effectuees au service de radiometallurgie pour la mise au point de techniques micrographiques applicables a l'etude d'echantillons d'uranium irradie. Dans la premiere partie de ce travail, nous mettons au point deux bains de polissage qui presentent les qualites inherentes a leur composition respective, avec le minimum d'inconvenients: ce sont d'une part des melanges acide perchlorique-ethanol, et d'autre part un bain phospho-chromique-ethanol. Dans le chapitre suivant, nous etudions l'attaque micrographique de l'uranium. Seul le procede d'oxydation par bombardement cathodique formant des couches epitaxiques, est satisfaisant. Dans le troisieme chapitre, nous essayons

  6. Estadísticos poblacionales de Triatoma sordida Stäl 1859 (Hemiptera : Reduviidae en condiciones experimentales Population statistics of Triatoma sordida Stäl 1859 (Hemiptera: Reduviidae in experimental conditions

    Directory of Open Access Journals (Sweden)

    Elena B. Oscherov

    1996-10-01

    Full Text Available Se realizó el seguimiento longitudinal de cuatro cohortes de 100 huevos cada una. Los insectos fueron criados a 28°C ± 3°C y 63 % ± 10% de humedad relativa, y alimentados cada siete días sobre gallina (Gallus domesticus, durante 40 min. Las cohortes fueron controladas una vez por semana. Se observó un valor constante de supervivencia en las cuatro cohortes, sin picos importantes. La expectativa de vida de los machos, en promedio, fue de 37,4 semanas y la de las hembras 36,8. El tiempo generacional demandó 61,7 semanas. La tasa reproductiva neta indica que esta población se incrementará 143,3 veces con cada generación. La tasa intrínseca de crecimiento natural fue de 0,082 por semana. El máximo valor reproductivo se verificó, en promedio, a la tercer semana del ingreso al estado adulto. La distribución estable de edades de T. sordida sería de 32% huevos, 26% ninfas de primer estadio, 19% ninfas de segundo estadio, 13% ninfas de tercer estadio, 6% ninfas de cuarto estadio, 3% ninfas de quinto estadio y 1% de adultos. Es la primera cita para Argentina sobre la tabla de vida de T. sordida. El análisis de estos parámetros permite considerar que esta especie se comporta como "K estratega", en condiciones experimentales.Foram estudados diferentes parâmetros populacionais de Triatoma sordida em condições de laboratório. Realizou-se um seguimento longitudinal de quatro coortes de 100 ovos cada uma; os insetos foram criados a 28°C ± 3°C e 63% ± 10% de umidade relativa, e alimentados cada sete dias sobre galinha (Gallus domesticus durante 40'. As coortes foram controladas uma vez por semana. A expectativa de vida média dos machos foi de 37,4 semanas e a das fêmeas de 36,8.O tempo médio de desenvolvimento foi de 61,7 semanas. A taxa reprodutiva líquida indica que esta população aumentará 143,2 vezes durante cada geração. A taxa intrínseca do crecimento natural foi de 0,082 por semana. A média do valor máximo reprodutivo

  7. Study and installation of concrete shielding in the civil engineering of nuclear construction (1960); Etude et mise en place des betons de protection dans le genie civil des ouvrages nucleaires (1960)

    Energy Technology Data Exchange (ETDEWEB)

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

    1960-07-01

    The object of this report is to give technical information about high density concretes which have become very important for radiation biological shielding. The most generally used heavy aggregates (barytes, ilmenite, ferrophosphorus, limonite, magnetite and iron punching) to make these concretes are investigated from the point of view prospecting and physical and chemical characteristics. At first, a general survey of shielding concretes is made involving the study of components, mixing and placing methods, then, a detailed investigation of some high density concretes: barytes concrete, with incorporation of iron punching or iron shot, ferrophosphorus concrete, ilmenite concrete and magnetite concrete, more particularly with regard to grading and mix proportions and testing process. To put this survey in concrete form, two practical designs are described such as they have been carried out at the Saclay Nuclear Station. Specifications are given for diverse concretes and for making the proton-synchrotron 'Saturne' shielding blocks. (author) [French] Ce rapport a pour objet de donner des precisions techniques au sujet des betons a haute densite qui ont pris une grande importance pour la protection biologique contre les rayonnements. Les agregats lourds les plus couramment utilises (barytine, ilmenite, ferrophosphore, limonite, magnetite et riblons) pour la fabrication de ces betons, sont examines du point de vue prospection et caracteristiques physiques et chimiques. On procede d'abord a une etude generale des betons de protection comprenant l'etude des constituants, de la confection et de la mise en place, ensuite, a un examen detaille de quelques betons a haute densite: betons a base de barytine, avec incorporation de riblons ou de grenaille de fonte, betons au ferrophosphore, a base d'ilmenite ou de magnetite, notamment en ce qui concerne la granulometrie, la composition, le dosage et les processus d'essais. Pour concretiser ces

  8. Microfluidic Approaches to Bacterial Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Hee-Deung Park

    2012-08-01

    Full Text Available Bacterial biofilms—aggregations of bacterial cells and extracellular polymeric substrates (EPS—are an important subject of research in the fields of biology and medical science. Under aquatic conditions, bacterial cells form biofilms as a mechanism for improving survival and dispersion. In this review, we discuss bacterial biofilm development as a structurally and dynamically complex biological system and propose microfluidic approaches for the study of bacterial biofilms. Biofilms develop through a series of steps as bacteria interact with their environment. Gene expression and environmental conditions, including surface properties, hydrodynamic conditions, quorum sensing signals, and the characteristics of the medium, can have positive or negative influences on bacterial biofilm formation. The influences of each factor and the combined effects of multiple factors may be addressed using microfluidic approaches, which provide a promising means for controlling the hydrodynamic conditions, establishing stable chemical gradients, performing measurement in a high-throughput manner, providing real-time monitoring, and providing in vivo-like in vitro culture devices. An increased understanding of biofilms derived from microfluidic approaches may be relevant to improving our understanding of the contributions of determinants to bacterial biofilm development.

  9. EFFECTS OF BACTERIAL VAGINOSIS ON PERINATAL OUTCOME

    Directory of Open Access Journals (Sweden)

    Rajshree

    2014-02-01

    Full Text Available NTRODUCTION: Bacterial vaginosis is a condition in which the normal lactobacillus ( predominant vaginal flora is replaced with anaerobic bacteria , gardnerella vaginalis and mycoplasma hominis . Our study was designed to find out the effects of bacterial vaginosis on fetomaternal outcome in pregnant women . MATERIAL & METHODS: A prospective study was conducted in MGMCH , Jaipur from S eptember’12 to February ’13 . 100 women attending the antenatal clinic were recruited during their antenatal visit after 20 weeks of gestation and obs erved for presence of bacterial vaginosis and followed till pregnancy outcome . Prevalence of bacterial vaginosis was determined by Nugent and Amsel criteria . Maternal and neonatal morbidity were studied accordingly . RESULT: Prevalence of bacterial vagino sis by Nugent criteria was 19% . There was a significant association between the period of gestation at which the patient delivers and Nugent scoring of her gram stain picture (p=0 . 01 . Relationship between nursery admissions of baby and bacterial vaginosi s was found to be highly significant (p=0 . 01 . Out of the 100 babies delivered , 20% had low birth weight , 2% had birth asphyxia & Apgar score < 5 , 7% delivered prematurely & 14% babies had to be transferred to neonatal care units for various causes . CONCL USION: Bacterial vaginosis was found to be significantly associated with adverse pregnancy outcome in the form of increased risk of preterm delivery , low birth weight , birth asphyxia in neonate . It was also concluded that there was a definite role of trea tment because it can prevent a considerable number of preterm deliveries .

  10. Bacterial microleakage of aged adhesive restorations

    Directory of Open Access Journals (Sweden)

    Nevin Cobanoglu

    2015-01-01

    Full Text Available Objective: The aim of this study was to investigate the marginal bacterial leakage of two self-etch adhesive systems after long-term water storage. Materials and Methods: Class V cavities were prepared on the buccal and lingual surfaces of extracted premolar teeth. After the sterilization of the teeth, four cavities were not restored for control purposes, whereas the other teeth were divided into two groups (n = 16 cavities each: Clearfil Protect Bond (CPB, Clearfil SE Bond (CSE. After the application of the bonding agent, cavities were restored with a composite resin. Then, the teeth were thermo cycled, stored in saline solution for 6 months and put into a broth culture of Streptococcus mutans. The teeth were fixed, sectioned and stained using the Gram-Colour modified method. The stained sections were then evaluated under a light microscope. The bacterial leakage was scored as: 0 - absence of stained bacteria, 1 - bacterial staining along the cavity walls, 2 - bacterial staining within the cut dentinal tubules. The data were analysed using the Kruskal-Wallis and Mann-Whitney U-test (P = 0.05. Results: The bacterial staining was detected within the cut dentinal tubules in all control cavities, in three cavities in the CSE group and one cavity in the CPB group. There were no observed statistically significant differences between the bacterial penetrations of the two bonding systems (P > 0.05. Conclusion: Both bonding systems provided acceptable prevention of marginal bacterial leakage after long-term water storage.

  11. BACTERIAL FLORA IN DIABETIC ULCER

    Directory of Open Access Journals (Sweden)

    Anitha Lavanya

    2015-04-01

    Full Text Available BACKGROUND : Diabetic foot infections are one of the most feared complications of diabetes. This study was undertaken to determine the common etiological agents of diabetic foot infections and their in vitro antibiotic susceptibility. METHODS : A prospective study was p erformed over a period of two years in a tertiary care hospital. The aerobic and anaerobic bacterial agents were isolated and their antibiotic susceptibility pattern was determined . RESULTS : One hundred patients with Diabetic ulcer were studied, of which 6 5 were males and 35 were females. Majority of patients were in the age group of 51 to 60 years (37% and polymicrobial etiology was 64 % and monomicrobial etiology was 36%. A total of 187 organisms were isolated of which 165 were aerobic and 22 were anaero bic. Most frequently isolated aerobic organisms were Pseudomonas Sp., Klebsiella Sp., E coli Sp., and Staphylococcus aureus. The common anaerobic organisms isolated were Peptostreptococcus Sp. And Bacterioids Sp. CONCLUSION : High prevalence of multi - drug r esistant pathogens was observed. Amikacin, Imipenem were active against gram - negative bacilli, while vancomycin was found to be active against gram - positive bacteria.

  12. Phenotypic plasticity in bacterial plasmids.

    Science.gov (United States)

    Turner, Paul E

    2004-01-01

    Plasmid pB15 was previously shown to evolve increased horizontal (infectious) transfer at the expense of reduced vertical (intergenerational) transfer and vice versa, a key trade-off assumed in theories of parasite virulence. Whereas the models predict that susceptible host abundance should determine which mode of transfer is selectively favored, host density failed to mediate the trade-off in pB15. One possibility is that the plasmid's transfer deviates from the assumption that horizontal spread (conjugation) occurs in direct proportion to cell density. I tested this hypothesis using Escherichia coli/pB15 associations in laboratory serial culture. Contrary to most models of plasmid transfer kinetics, my data show that pB15 invades static (nonshaking) bacterial cultures only at intermediate densities. The results can be explained by phenotypic plasticity in traits governing plasmid transfer. As cells become more numerous, the plasmid's conjugative transfer unexpectedly declines, while the trade-off between transmission routes causes vertical transfer to increase. Thus, at intermediate densities the plasmid's horizontal transfer can offset selection against plasmid-bearing cells, but at high densities pB15 conjugates so poorly that it cannot invade. I discuss adaptive vs. nonadaptive causes for the phenotypic plasticity, as well as potential mechanisms that may lead to complex transfer dynamics of plasmids in liquid environments. PMID:15166133

  13. Rheumatoid arthritis and bacterial infections

    Directory of Open Access Journals (Sweden)

    N L Prokopjeva

    2008-01-01

    Full Text Available To study features of bacterial infections course in pts with rheumatoid arthritis (RA and changes of laboratory measures after focus of infection sanation. Material and methods. 46 pts with definite rheumatoid arthritis were examined at the time of comorbid infection (Cl detection and after infection focus sanation. Bacteriological test with evaluation of flora sensitivity to antibiotics by disco-diffusion method was performed at baseline and after the course of antibacterial therapy to assess its efficacy. Hemogram, serum fibrinogen, rheumatoid factor, circulating immune complexes (CIC, C-reactive protein levels were assessed. Serum interleukin (IL 1(3, IL6 and neopterin concentrations were examined by immune-enzyme assay in a part of pts. Typical clinical features of Cl were present in only 28 (60,9% pts. 13 (28,3% pts had fever, 12 (26,0% — leukocytosis, 15 (32,6% — changes of leucocyte populations. Some laboratory measures (thrombocytes, fibrinogen, CIC, neopterin levels significantly decreased (p<0,05 after infection focus sanation without correction of disease modifying therapy. Cl quite often develop as asymptomatic processes most often in pts with high activity and can induce disturbances promoting appearance of endothelial dysfunction, atherothrombosis and reduction of life duration. So timely detection and proper sanation of infection focuses should be performed in pts with RA

  14. Bacterial binding to extracellular proteins - in vitro adhesion

    DEFF Research Database (Denmark)

    Schou, C.; Fiehn, N.-E.

    1999-01-01

    Viridans streptococci, bacterial adherence, extracellular matrix proteins, surface receptors, endocarditis......Viridans streptococci, bacterial adherence, extracellular matrix proteins, surface receptors, endocarditis...

  15. Efecto de la densidad de siembra sobre las interacciones biológicas entre las leguminosas Lupinus bogotensis y Vicia benghalensis con las nativas Solanum oblongifolium y Viburnum tinoides en parcelas experimentales de restauración ecológica del bosque altoandino / Effect of plant density on the biological interactions between the legume Lupinus bogotensis and Vicia benghalensis with natives Solanum oblongifolium and Viburnum tinoides in experimental plots of ecological restoration of the high Andean forest

    OpenAIRE

    Gómez Ruiz, Pilar Angélica

    2011-01-01

    Durante nueve meses, se evaluó la interacción entre las especies leguminosas Lupinus bogotensis y Vicia benghalensis, con las especies arbóreas nativas Solanum oblongifolium y Viburnum tinoides, en parcelas experimentales de restauración ecológica ubicadas en los alrededores del embalse de Chisacá (vereda El Hato, Usme, Bogotá). Las variables evaluadas en las especies nativas fueron: altura, diámetro, número de hojas o ramas y supervivencia. Los tratamientos corresponden a las especies le...

  16. Biochemistry of Bacterial Multidrug Efflux Pumps

    Directory of Open Access Journals (Sweden)

    Sanath Kumar

    2012-04-01

    Full Text Available Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in bacterial pathogens, these active multi-drug efflux mechanisms remain a major area of intense study, so that ultimately measures may be discovered to inhibit these active multi-drug efflux pumps.

  17. Tobacco use increases susceptibility to bacterial infection

    Directory of Open Access Journals (Sweden)

    Demuth Donald R

    2008-12-01

    Full Text Available Abstract Active smokers and those exposed to secondhand smoke are at increased risk of bacterial infection. Tobacco smoke exposure increases susceptibility to respiratory tract infections, including tuberculosis, pneumonia and Legionnaires disease; bacterial vaginosis and sexually transmitted diseases, such as chlamydia and gonorrhoea; Helicobacter pylori infection; periodontitis; meningitis; otitis media; and post-surgical and nosocomial infections. Tobacco smoke compromises the anti-bacterial function of leukocytes, including neutrophils, monocytes, T cells and B cells, providing a mechanistic explanation for increased infection risk. Further epidemiological, clinical and mechanistic research into this important area is warranted.

  18. Bacterial gasotransmitters: an innate defense against antibiotics.

    Science.gov (United States)

    Luhachack, Lyly; Nudler, Evgeny

    2014-10-01

    In recent decades, there has been growing interest in the field of gasotransmitters, endogenous gaseous signaling molecules (NO, H2S, and CO), as regulators of a multitude of biochemical pathways and physiological processes. Most of the concerted effort has been on eukaryotic gasotransmitters until the subsequent discovery of bacterial counterparts. While the fundamental aspects of bacterial gasotransmitters remain undefined and necessitate further research, we will discuss a known specific role they play in defense against antibiotics. Considering the current dilemma of multidrug-resistant bacteria we consider it particularly prudent to exploring novel targets and approaches, of which the bacterial gasotransmitters, nitric oxide and hydrogen sulfide represent.

  19. Spontaneous Bacterial Peritonitis in Subclinical Hypothyroidism

    Directory of Open Access Journals (Sweden)

    Dalip Gupta

    2013-11-01

    Full Text Available Hypothyroidism is an uncommon cause of ascites. Here we describe a case of a 75 year-old female patient with spontaneous bacterial peritonitis and subclinical hypothyroidism that resolved with thyroid replacement and antibiotic therapy respectively. Ascitic fluid analysis revealed a gram-positive bacterium on gram staining. A review of the literature revealed just one other reported case of myxoedema ascites with concomitant spontaneous bacterial peritonitis and no case has till been reported of spontaneous bacterial peritonitis in subclinical hypothyroidism.

  20. Early oesophageal cancer: results of a European multicentre survey. Group Européen pour l'Etude des Maladies de l'Oesophage.

    Science.gov (United States)

    Bonavina, L

    1995-01-01

    Early oesophageal cancer has been extensively studied in Far-Eastern countries, where its prevalence is high. A multicentre survey was conducted within the Groupe Européen pour l'Etude des Maladies de l'Oesophage to analyse results of surgical treatment in patients with disease staged as pTis-T1 N0 M0 according to the tumour node metastasis classification. Of 9743 patients with squamous cell oesophageal carcinoma observed since 1980, 4663 underwent resection; 253 (5.4 per cent) of these fulfilled the criteria for inclusion in the study. The overall mortality rate was 9.1 per cent (23 patients), and was higher after transthoracic than transhiatal oesophagectomy (10.7 versus 6 per cent, P not significant). Pathological examination showed an intraepithelial tumour in 46 patients (18.2 per cent), intramucosal carcinoma in 64 (25.3 per cent) and a submucosal lesion in 143 (56.5 per cent). The overall 5-year survival rate for patients with intraepithelial, intramucosal and submucosal tumours was 92.8, 72.8 and 44.3 per cent respectively. The 5-year survival rate was higher after transthoracic than transhiatal oesophagectomy (66 versus 52 per cent). No survival advantage was observed after either operation in patients with mucosal tumours. Of 21 patients with recurrent disease, 20 had a submucosal lesion. The 5-year survival rate in patients with submucosal tumour was higher after transthoracic than transhiatal oesophagectomy (54.2 versus 25.5 per cent).

  1. Electronic temperature measurement on the deca II plasma using the Bremsstrahlung; Mesure de la temperature electronique du plasma de deca II par etude du rayonnement de freinage

    Energy Technology Data Exchange (ETDEWEB)

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

    1967-06-01

    The electronic temperature of the DECA II machine's plasma is determined by studying the Bremsstrahlung. Two types of detectors are used for this measurement, a set scintillator-photo-multiplicator and a photoelectric effect detector with a massive silver target. The method used is the classical 'absorbent method', The absorbents used are thin formvar foils whose thickness is between 600 and 12 500 angstrom. The measurements done in two different working conditions of the DECA II machine have given: Te {approx_equal} 200 eV in the first case and Te {approx_equal} 70 eV in the second case. (author) [French] Nous avons determine la temperature electronique du plasma de la machine DECA II par l'etude du rayonnement de freinage. Pour cette mesure nous avons utilise deux types de detecteurs: des ensembles scintillateur-photomultiplicateur et un detecteur a effet photoelectrique a cible massive en argent. La methode utilisee pour cette mesure est la classique methode des absorbants. Nous avons utilise des feuilles de format tres mince (de 600 a 12 500 angstrom) comme absorbant. Les mesures faites dans deux regimes de travail differents de la machine DECA II nous ont conduit a: Te {approx_equal} 200 eV dans un cas et Te {approx_equal} eV dans l'autre cas. (auteur)

  2. Positively regulated bacterial expression systems.

    Science.gov (United States)

    Brautaset, Trygve; Lale, Rahmi; Valla, Svein

    2009-01-01

    Regulated promoters are useful tools for many aspects related to recombinant gene expression in bacteria, including for high-level expression of heterologous proteins and for expression at physiological levels in metabolic engineering applications. In general, it is common to express the genes of interest from an inducible promoter controlled either by a positive regulator or by a repressor protein. In this review, we discuss established and potentially useful positively regulated bacterial promoter systems, with a particular emphasis on those that are controlled by the AraC-XylS family of transcriptional activators. The systems function in a wide range of microorganisms, including enterobacteria, soil bacteria, lactic bacteria and streptomycetes. The available systems that have been applied to express heterologous genes are regulated either by sugars (L-arabinose, L-rhamnose, xylose and sucrose), substituted benzenes, cyclohexanone-related compounds, ε-caprolactam, propionate, thiostrepton, alkanes or peptides. It is of applied interest that some of the inducers require the presence of transport systems, some are more prone than others to become metabolized by the host and some have been applied mainly in one or a limited number of species. Based on bioinformatics analyses, the AraC-XylS family of regulators contains a large number of different members (currently over 300), but only a small fraction of these, the XylS/Pm, AraC/P(BAD), RhaR-RhaS/rhaBAD, NitR/PnitA and ChnR/Pb regulator/promoter systems, have so far been explored for biotechnological applications.

  3. Bacterial diversity associated with freshwater zooplankton

    DEFF Research Database (Denmark)

    Grossart, Hans-Peter; Dziallas, Claudia; Tang, Kam W.

    2009-01-01

    Bacterial community compositions (BCC) associated with the cladoceran Bosmina coregoni and the cyclopoid copepod Thermocyclops oithonoides in oligotrophic Lake Stechlin versus eutrophic Lake Dagow (northeastern Germany) were compared using molecular techniques. We also transplanted the zooplankton...

  4. Bacterial bioluminescence in marine pollution assessment

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, N.; Chandramohan, D.

    Warm water marine luminous bacterial species, particularly Vibrio harveyi, V. fischeri and Photobacterium leiognathi, are easy to isolate, maintain and handle in the laboratories without strict temperature requirements, which is an important...

  5. The Bacterial Microbiota in Inflammatory Lung Diseases

    Science.gov (United States)

    Huffnagle, Gary B.; Dickson, Robert P.

    2016-01-01

    Numerous lines of evidence, ranging from recent studies back to those in the 1920's, have demonstrated that the lungs are NOT bacteria-free during health. We have recently proposed that the entire respiratory tract should be considered a single ecosystem extending from the nasal and oral cavities to the alveoli, which includes gradients and niches that modulate microbiome dispersion, retention, survival and proliferation. Bacterial exposure and colonization of the lungs during health is most likely constant and transient, respectively. Host microanatomy, cell biology and innate defenses are altered during chronic lung disease, which in turn, alters the dynamics of bacterial turnover in the lungs and can lead to longer term bacterial colonization, as well as blooms of well-recognized respiratory bacterial pathogens. A few new respiratory colonizers have been identified by culture-independent methods, such as Pseudomonas fluorescens; however, the role of these bacteria in respiratory disease remains to be determined. PMID:26122174

  6. Bacterie oorzaak van woekerziekte in lelie

    NARCIS (Netherlands)

    Doorn, van J.; Pham, K.T.K.; Hollinger, T.C.

    2003-01-01

    PPO heeft onderzoek gedaan naar achtergronden en het optreden van bacterie in lelies. Onderzoek heeft vastgesteld dat Rhodococcus fascians verantwoordelijk is voor deze ziekte. Toetsen zijn ontwikkeld die de woekerziekte snel kunnen aantonen

  7. Rho-modifying bacterial protein toxins.

    Science.gov (United States)

    Aktories, Klaus

    2015-12-01

    Rho proteins are targets of numerous bacterial protein toxins, which manipulate the GTP-binding proteins by covalent modifications, including ADP ribosylation, glycosylation, adenylylation, proteolytic cleavage and deamidation. Bacterial toxins are important virulence factors but are also potent and efficient pharmacological tools to study the physiological functions of their eukaryotic targets. Recent studies indicate that amazing variations exist in the molecular mechanisms by which toxins attack Rho proteins, which are discussed here.

  8. Bacterial volatiles promote growth in Arabidopsis

    OpenAIRE

    Ryu, Choong-Min; Mohamed A. Farag; Hu, Chia-Hui; Reddy, Munagala S.; Wei, Han-Xun; Paré, Paul W.; Kloepper, Joseph W.

    2003-01-01

    Several chemical changes in soil are associated with plant growth-promoting rhizobacteria (PGPR). Some bacterial strains directly regulate plant physiology by mimicking synthesis of plant hormones, whereas others increase mineral and nitrogen availability in the soil as a way to augment growth. Identification of bacterial chemical messengers that trigger growth promotion has been limited in part by the understanding of how plants respond to external stimuli. With an increasing appreciation of...

  9. Biochemistry of Bacterial Multidrug Efflux Pumps

    OpenAIRE

    Sanath Kumar; Varela, Manuel F.

    2012-01-01

    Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in ...

  10. Bacterial Evolution and Bak-Sneppen Model

    OpenAIRE

    Bose, Indrani; Chaudhuri, Indranath

    2002-01-01

    Recently, Lenski et al [Elena,Lenski,Travisano] have carried out several experiments on bacterial evolution. Their findings support the theory of punctuated equilibrium in biological evolution. They have further quantified the relative contributions of adaptation, chance and history to bacterial evolution. In this paper, we show that a modified $M$-trait Bak-Sneppen model can explain many of the experimental results in a qualitative manner.

  11. Enteral nutrient solutions. Limiting bacterial growth.

    Science.gov (United States)

    Paauw, J D; Fagerman, K E; McCamish, M A; Dean, R E

    1984-06-01

    Bacterial contamination of enteral nutrient solutions ( ENS ) in FFcess of food product standards is known to occur in the hospital setting. The large amounts of bacteria often given with ENS have been shown to create a reservoir for nosocomial infections, and nonpathogenic bacteria have been implicated. Patient tolerance is dependent on immune status and the bacterial load delivered to the gut. The purpose of this study was to evaluate the bacterial growth-sustaining properties of various ENS and to devise methods to limit bacterial growth. Five commercial products were prepared under sterile conditions. After inoculation with approximately 5 X 10(3) organisms/cm3 of Enterobacter cloacae, each solution was hung at room temperature for 24 hours with samples drawn at fixed intervals and plated for bacterial counts. Bacterial growth rates in Ensure, Travasorb , and Vital were markedly higher than those in Precision and Vivonex. Vivonex was noted to contain potassium sorbate (KS) used as a fungistatic agent. Recent studies have identified KS as a broad-spectrum bacteriostatic food preservative that is federally approved for this use. KS (0.03%) was added to Travasorb inoculated with 5 X 10(3) organisms/cm(3) of E. cloacae. The bacterial growth rate was reduced by 75 per cent, and the final count of 2-3 X 10(4) organisms/ml was within the federally regulated limit for milk. This study suggests that initial inoculum, growth rate, and hang time can be altered to provide a significant reduction in final bacterial counts in ENS . PMID:6428286

  12. Asynchronous exponential growth of a bacterial population

    Directory of Open Access Journals (Sweden)

    Mohamed Boulanouar

    2014-01-01

    Full Text Available In this work, we complete a study started earlier in [1,2] wherein a model of growing bacterial population has been the matter of a mathematical analysis. We show that the full model is governed by a strongly continuous semigroup. Beside the positivity and the irreducibility of the generated semigroup, we describe its asymptotic behavior in the uniform topology which leads to the asynchronous exponential growth of the bacterial population.

  13. Pattern Formation in a Bacterial Colony Model

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2014-01-01

    Full Text Available We investigate the spatiotemporal dynamics of a bacterial colony model. Based on the stability analysis, we derive the conditions for Hopf and Turing bifurcations. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by parameters in the model and find that the model dynamics exhibit a diffusion controlled formation growth to spots, holes and stripes pattern replication, which show that the bacterial colony model is useful in revealing the spatial predation dynamics in the real world.

  14. Jellyfish modulate bacterial dynamic and community structure.

    Directory of Open Access Journals (Sweden)

    Tinkara Tinta

    Full Text Available Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into

  15. Bacterial Probiotic Modulation of Dendritic Cells

    OpenAIRE

    Drakes, Maureen; Blanchard, Thomas; Czinn, Steven

    2004-01-01

    Intestinal dendritic cells are continually exposed to ingested microorganisms and high concentrations of endogenous bacterial flora. These cells can be activated by infectious agents and other stimuli to induce T-cell responses and to produce chemokines which recruit other cells to the local environment. Bacterial probiotics are of increasing use against intestinal disorders such as inflammatory bowel disease. They act as nonpathogenic stimuli within the gut to regain immunologic quiescence. ...

  16. Syntheses and study of pyrrolidinic nitroxide free radicals. Preparation of a nitroxide-type stable bi-radical; Synthese et etudes de radicaux libres nitroxydes pyrrolidiniques. Preparation d'un biradical stable du type nitroxyde

    Energy Technology Data Exchange (ETDEWEB)

    Dupeyre, R.M. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires, Laboratoire de chimie organique physique

    1967-12-01

    Syntheses and study of pyrrolidinic nitroxide free radicals: These radicals are obtained by oxidation, with hydrogen peroxide, of pyrrolidinic amines prepared from triacetonamine by ring contraction. The U. V,, I. R, and E.P.R. spectral characteristics have been determined. The oxidation of these amines with hydrogen peroxide has led also to rupture of the pentagonal ring; some of the decomposition products have been identified. The high chemical stability of the nitroxide group has made it possible to synthesize and study a stable bi-radical. (author) [French] Syntheses et etudes de radicaux libres nitroxydes pyrrolidiniques: Ces radicaux sont obtenus par oxydation l'eau oxygenee d'amines pyrrolidiniques preparees a partir de la triacetonamine par contraction de cycle. Les caracteristiques spectroscopiques ultra-violettes, infra-rouge et resonance paramagnetique sont determinees. Cependant, 1'oxydation de ces amines a l'eau oxygenee a entraine la coupure du cycle pentagonal et identification de certaines substances de decomposition obtenues. La grande stabilite chimique de groupement nitroxyde a permis la synthese et l'etude d'un biradical stable. (auteur)

  17. 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)

  18. The intrinsic resistome of bacterial pathogens

    Directory of Open Access Journals (Sweden)

    Jorge Andrés Olivares Pacheco

    2013-04-01

    Full Text Available Intrinsically resistant bacteria have emerged as a relevant health problem in the last years. Those bacterial species, several of them with an environmental origin, present naturally a low-level susceptibility to several drugs. It has been proposed that intrinsic resistance is mainly the consequence of the impermeability of cellular envelopes, the activity of multidrug efflux pumps or the lack of appropriate targets for a given family of drugs. However, recently published articles indicate that the characteristic phenotype of susceptibility to antibiotics of a given bacterial species depends on the concerted activity of several elements, what has been named as intrinsic resistome. These determinants comprise not just classical resistance genes. Other elements, several of them involved in basic bacterial metabolic processes, are of relevance for the intrinsic resistance of bacterial pathogens. In the present review we analyse recent publications on the intrinsic resistomes of Escherichia coli and Pseudomonas aeruginosa. We present as well information on the role that global regulators of bacterial metabolism, as Crc from P. aeruginosa, may have on modulating bacterial susceptibility to antibiotics. Finally, we discuss the possibility of searching inhibitors of the intrinsic resistome in the aim of improving the activity of drugs currently in use for clinical practice.

  19. Bacterial carbon cycling in a subarctic fjord

    DEFF Research Database (Denmark)

    Middelboe, Mathias; Glud, Ronnie Nøhr; Sejr, M.K.

    2012-01-01

    and BGE were positively correlated with BDOC concentration, suggesting that organic carbon availability was limiting bacterial activity and carbon conversion efficiency. Viral production was low (0.8–1.8 × 104 viruses mL−1 h−1) as compared to low-latitude environments, suggesting a relatively small effect......In this seasonal study, we examined the environmental controls and quantitative importance of bacterial carbon consumption in the water column and the sediment in the subarctic Kobbefjord, Greenland. Depth-integrated bacterial production in the photic zone varied from 5.0 ± 2.7 mg C m−2 d−1...... in February to 42 ± 28 mg C m−2 d−1 in May and 34 ± 7 mg C m−2 d−1 in September, corresponding to a bacterial production to primary production ratio of 0.34 ± 0.14, 0.07 ± 0.04, and 0.08 ± 0.06, respectively. Based on measured bacterial growth efficiencies (BGEs) of 0.09–0.10, pelagic bacterial carbon...

  20. Small molecule control of bacterial biofilms.

    Science.gov (United States)

    Worthington, Roberta J; Richards, Justin J; Melander, Christian

    2012-10-01

    Bacterial biofilms are defined as a surface attached community of bacteria embedded in a matrix of extracellular polymeric substances that they have produced. When in the biofilm state, bacteria are more resistant to antibiotics and the host immune response than are their planktonic counterparts. Biofilms are increasingly recognized as being significant in human disease, accounting for 80% of bacterial infections in the body and diseases associated with bacterial biofilms include: lung infections of cystic fibrosis patients, colitis, urethritis, conjunctivitis, otitis, endocarditis and periodontitis. Additionally, biofilm infections of indwelling medical devices are of particular concern, as once the device is colonized infection is virtually impossible to eradicate. Given the prominence of biofilms in infectious diseases, there has been an increased effort toward the development of small molecules that will modulate bacterial biofilm development and maintenance. In this review, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms through non-microbicidal mechanisms. The review discuses the numerous approaches that have been applied to the discovery of lead small molecules that mediate biofilm development. These approaches are grouped into: (1) the identification and development of small molecules that target one of the bacterial signaling pathways involved in biofilm regulation, (2) chemical library screening for compounds with anti-biofilm activity, and (3) the identification of natural products that possess anti-biofilm activity, and the chemical manipulation of these natural products to obtain analogues with increased activity. PMID:22733439

  1. Proteomics in the Study of Bacterial Keratitis

    Directory of Open Access Journals (Sweden)

    Rachida Bouhenni

    2015-12-01

    Full Text Available Bacterial keratitis is a serious ocular infection that can cause severe visual loss if treatment is not initiated at an early stage. It is most commonly caused by Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, or Serratia species. Depending on the invading organism, bacterial keratitis can progress rapidly, leading to corneal destruction and potential blindness. Common risk factors for bacterial keratitis include contact lens wear, ocular trauma, ocular surface disease, ocular surgery, lid deformity, chronic use of topical steroids, contaminated ocular medications or solutions, and systemic immunosuppression. The pathogenesis of bacterial keratitis, which depends on the bacterium-host interaction and the virulence of the invading bacterium, is complicated and not completely understood. This review highlights some of the proteomic technologies that have been used to identify virulence factors and the host response to infections of bacterial keratitis in order to understand the disease process and develop improved methods of diagnosis and treatment. Although work in this field is not abundant, proteomic technologies have provided valuable information toward our current knowledge of bacterial keratitis. More studies using global proteomic approaches are warranted because it is an important tool to identify novel targets for intervention and prevention of corneal damage caused by these virulent microorganisms.

  2. Comprehensive phylogenetic analysis of bacterial reverse transcriptases.

    Directory of Open Access Journals (Sweden)

    Nicolás Toro

    Full Text Available Much less is known about reverse transcriptases (RTs in prokaryotes than in eukaryotes, with most prokaryotic enzymes still uncharacterized. Two surveys involving BLAST searches for RT genes in prokaryotic genomes revealed the presence of large numbers of diverse, uncharacterized RTs and RT-like sequences. Here, using consistent annotation across all sequenced bacterial species from GenBank and other sources via RAST, available from the PATRIC (Pathogenic Resource Integration Center platform, we have compiled the data for currently annotated reverse transcriptases from completely sequenced bacterial genomes. RT sequences are broadly distributed across bacterial phyla, but green sulfur bacteria and cyanobacteria have the highest levels of RT sequence diversity (≤85% identity per genome. By contrast, phylum Actinobacteria, for which a large number of genomes have been sequenced, was found to have a low RT sequence diversity. Phylogenetic analyses revealed that bacterial RTs could be classified into 17 main groups: group II introns, retrons/retron-like RTs, diversity-generating retroelements (DGRs, Abi-like RTs, CRISPR-Cas-associated RTs, group II-like RTs (G2L, and 11 other groups of RTs of unknown function. Proteobacteria had the highest potential functional diversity, as they possessed most of the RT groups. Group II introns and DGRs were the most widely distributed RTs in bacterial phyla. Our results provide insights into bacterial RT phylogeny and the basis for an update of annotation systems based on sequence/domain homology.

  3. ETUDES CHIMIQUE ET BIOLOGIQUE DES HUILES ESSENTIELLES DE QUATRE PLANTES AROMATIQUES MEDICINALES DE CÔTE D'IVOIRE

    OpenAIRE

    Toure , Daouda

    2015-01-01

    Bacterial resistance to antibiotics has become a real concern. Faced with this, research antimicrobialcompounds is more relevant than ever. The plants are a potentiel source of these compounds. The present studydescribes the chemical composition, antibacterial and antioxidant activity of Chromoleana odorata (Asteracea)Ageratum conyzoïdes (Asteracea), Croton hirtus (Euphorbiaceae) and Cardiospermum grandiflorum (Sapindaceae)essential oils of four aromatics and medicinal provide from Ivory Coas...

  4. Datos experimentales de la cinética del secado y del modelo matemático para pulpa de cupuaçu (Theobroma grandiflorum en rodajas Kinetic drying experimental data and mathematical model for cupuaçu pulp (Theobroma grandiflora slices

    Directory of Open Access Journals (Sweden)

    Abraham Damian Giraldo-Zuniga

    2010-03-01

    Full Text Available En este trabajo fueron obtenidos experimentalmente la cinética del secado de la pulpa de cupuaçu en forma de rodajas con espesor de 0,5 cm. El secado fue realizado utilizándose un secador laboratorial de bandejas, a las temperaturas de 50, 60 y 70 ºC y a la velocidad del aire de secado de 1,5 m/s. De acuerdo con los datos de la cinética del secado se puede observar que cuanto mayor es la temperatura del secado mayor es la velocidad del secado. El tiempo requerido para secar el producto hasta una humedad del 20%, fueron 9,2, 8,1 y 7,3 horas para las temperaturas de secado de 50, 60 y 70 ºC respectivamente. Las curvas experimentales del secado fueron ajustados al modelo difusional de Fick considerándose la muestra como una lámina infinita y al modelo de Page. Los dos modelos se ajustaron bien a los datos experimentales. Los coeficientes de difusión del modelo de Fick variaron de 1.171 a 1.561 m/s².This work examined experimentally the kinetics of drying cupuaçu pulp (Theobroma grandiflorum slices. The experimental runs were driven in a laboratory dryer, at temperatures of 50, 60 and 70 ºC and an air drying velocity of 1.5 m/s. According to the kinetics study, increasing the temperature led to a decrease in drying time. The required drying times were 9.2, 8.1 and 7.3 hours for drying temperatures of 50, 60 and 70 ºC respectively. The experimental drying curves were adjusted to Fick's diffusional model for an infinite lamina with shrinkage and Page model. The diffusion coefficients of the Fick model varied between 1.171 and 1.561 m/s².

  5. Nest Material Shapes Eggs Bacterial Environment

    Science.gov (United States)

    Ruiz-Castellano, Cristina; Tomás, Gustavo; Ruiz-Rodríguez, Magdalena; Martín-Gálvez, David; Soler, Juan José

    2016-01-01

    Selective pressures imposed by pathogenic microorganisms to embryos have selected in hosts for a battery of antimicrobial lines of defenses that includes physical and chemical barriers. Due to the antimicrobial properties of volatile compounds of green plants and of chemicals of feather degrading bacteria, the use of aromatic plants and feathers for nest building has been suggested as one of these barriers. However, experimental evidence suggesting such effects is scarce in the literature. During two consecutive years, we explored experimentally the effects of these nest materials on loads of different groups of bacteria (mesophilic bacteria, Enterobacteriaceae, Staphylococcus and Enterococcus) of eggshells in nests of spotless starlings (Sturnus unicolor) at the beginning and at the end of the incubation period. This was also explored in artificial nests without incubation activity. We also experimentally increased bacterial density of eggs in natural and artificial nests and explored the effects of nest lining treatments on eggshell bacterial load. Support for the hypothetical antimicrobial function of nest materials was mainly detected for the year and location with larger average values of eggshell bacterial density. The beneficial effects of feathers and plants were more easily detected in artificial nests with no incubation activity, suggesting an active role of incubation against bacterial colonization of eggshells. Pigmented and unpigmented feathers reduced eggshell bacterial load in starling nests and artificial nest boxes. Results from artificial nests allowed us to discuss and discard alternative scenarios explaining the detected association, particularly those related to the possible sexual role of feathers and aromatic plants in starling nests. All these results considered together confirm the antimicrobial functionality mainly of feathers but also of plants used as nest materials, and highlight the importance of temporally and geographically

  6. Acute Bacterial Prostatitis: Diagnosis and Management.

    Science.gov (United States)

    Coker, Timothy J; Dierfeldt, Daniel M

    2016-01-15

    Acute bacterial prostatitis is an acute infection of the prostate gland that causes pelvic pain and urinary tract symptoms, such as dysuria, urinary frequency, and urinary retention, and may lead to systemic symptoms, such as fevers, chills, nausea, emesis, and malaise. Although the true incidence is unknown, acute bacterial prostatitis is estimated to comprise approximately 10% of all cases of prostatitis. Most acute bacterial prostatitis infections are community acquired, but some occur after transurethral manipulation procedures, such as urethral catheterization and cystoscopy, or after transrectal prostate biopsy. The physical examination should include abdominal, genital, and digital rectal examination to assess for a tender, enlarged, or boggy prostate. Diagnosis is predominantly made based on history and physical examination, but may be aided by urinalysis. Urine cultures should be obtained in all patients who are suspected of having acute bacterial prostatitis to determine the responsible bacteria and its antibiotic sensitivity pattern. Additional laboratory studies can be obtained based on risk factors and severity of illness. Radiography is typically unnecessary. Most patients can be treated as outpatients with oral antibiotics and supportive measures. Hospitalization and broad-spectrum intravenous antibiotics should be considered in patients who are systemically ill, unable to voluntarily urinate, unable to tolerate oral intake, or have risk factors for antibiotic resistance. Typical antibiotic regimens include ceftriaxone and doxycycline, ciprofloxacin, and piperacillin/tazobactam. The risk of nosocomial bacterial prostatitis can be reduced by using antibiotics, such as ciprofloxacin, before transrectal prostate biopsy. PMID:26926407

  7. Microbial Degradation of Aniline by Bacterial Consortium

    Institute of Scientific and Technical Information of China (English)

    JIAN-LONG WANG; ZE-YU MAO; WEI-ZHONG WU

    2003-01-01

    Objective To investigate the characteristics of microbial degradation of aniline by a stable bacterial consortium. Methods The bacterial consortium was isolated from activated sludge treating chemical wastewater using aniline as the sole source of carbon and nitrogen by enrichment and isolation technique. The biomass was measured as optical density (OD) at 510 nm using a spectrophotometer. Aniline concentrations were determined by spectrophotometer. The intermediates of aniline degradation were identified by GC/MS method. Results The bacterial consortium could grow at a range of aniline concentrations between 50 and 500 mg/L. The optimal pH and temperature for aniline degradation were determined to be 7.0 and 30, respectively. The presence of NH4NO3 as an additional nitrogen source (100-500 mg/L) had no adverse effect on bacterial growth and aniline degradation. The presence of heavy metal ions, such as Co2+, Zn2+, Ni2+, Mn2+ and Cu2+ had an inhibitory effect on aniline degradation. Conclusions The isolated bacterial consortium candegrade aniline up to 500 mg/L effectively and tolerate some heavy metal ions that commonly exist in chemical wastewater. It has a potential to be applied in the practical treatment of aniline-containingwastewater.

  8. Bacterial coinfections in children with viral wheezing.

    Science.gov (United States)

    Lehtinen, P; Jartti, T; Virkki, R; Vuorinen, T; Leinonen, M; Peltola, V; Ruohola, A; Ruuskanen, O

    2006-07-01

    Bacterial coinfections occur in respiratory viral infections, but the attack rates and the clinical profile are not clear. The aim of this study was to determine bacterial coinfections in children hospitalized for acute expiratory wheezing with defined viral etiology. A total of 220 children aged 3 months to 16 years were investigated. The viral etiology of wheezing was confirmed by viral culture, antigen detection, serologic investigation, and/or PCR. Specific antibodies to common respiratory bacteria were measured from acute and convalescent serum samples. All children were examined clinically for acute otitis media, and subgroups of children were examined radiologically for sinusitis and pneumonia. Rhinovirus (32%), respiratory syncytial virus (31%), and enteroviruses (31%) were the most common causative viruses. Serologic evidence of bacterial coinfection was found in 18% of the children. Streptococcus pneumoniae (8%) and Mycoplasma pneumoniae (5%) were the most common causative bacteria. Acute otitis media was diagnosed in 44% of the children. Chest radiographs showed alveolar infiltrates in 10%, and paranasal radiographs and clinical signs showed sinusitis in 17% of the older children studied. Leukocyte counts and serum C-reactive protein levels were low in a great majority of patients. Viral lower respiratory tract infection in children is often associated with bacterial-type upper respiratory tract infections. However, coexisting bacterial lower respiratory tract infections that induce systemic inflammatory response are seldom detected.

  9. Emerging bacterial pathogens: the past and beyond.

    Science.gov (United States)

    Vouga, M; Greub, G

    2016-01-01

    Since the 1950s, medical communities have been facing with emerging and reemerging infectious diseases, and emerging pathogens are now considered to be a major microbiologic public health threat. In this review, we focus on bacterial emerging diseases and explore factors involved in their emergence as well as future challenges. We identified 26 major emerging and reemerging infectious diseases of bacterial origin; most of them originated either from an animal and are considered to be zoonoses or from water sources. Major contributing factors in the emergence of these bacterial infections are: (1) development of new diagnostic tools, such as improvements in culture methods, development of molecular techniques and implementation of mass spectrometry in microbiology; (2) increase in human exposure to bacterial pathogens as a result of sociodemographic and environmental changes; and (3) emergence of more virulent bacterial strains and opportunistic infections, especially affecting immunocompromised populations. A precise definition of their implications in human disease is challenging and requires the comprehensive integration of microbiological, clinical and epidemiologic aspects as well as the use of experimental models. It is now urgent to allocate financial resources to gather international data to provide a better understanding of the clinical relevance of these waterborne and zoonotic emerging diseases.

  10. Etude du processus de changement vecu par des familles ayant decide d'adopter volontairement des comportements d'attenuation des changements climatiques

    Science.gov (United States)

    Leger, Michel T.

    recension des ecrits sur le changement de comportement en environnement. Nous explorons egalement la famille comme systeme fonctionnel de sorte a mieux comprendre ce contexte d'action environnementale qui est, a notre connaissance, peu etudie. Dans le deuxieme article, nous presentons nos resultats de recherche concernant les facteurs d'influence observes ainsi que les competences manifestees au cours du processus d'adoption de nouveaux comportements environnementaux dans trois familles. Enfin, le troisieme article presente les resultats du cas d'une quatrieme famille ou les membres vivent depuis longtemps des modes de vie ecologique. Dans le cadre d'une demarche d'analyse par theorisation ancree, l'etude de ce cas modele nous a permis d'approfondir les categories conceptuelles identifiees dans le deuxieme article de sorte a produire une modelisation de l'integration de comportements environnementaux dans le contexte de la famille. Les conclusions degagees grace a la recension des ecrits nous ont permis d'identifier les elements qui pourraient influencer l'adoption de comportements environnementaux dans des familles. La recension a aussi permis une meilleure comprehension des divers facteurs qui peuvent affecter l'adoption de comportements environnementaux et, enfin, elle a permis de mieux cerner le phenomene de changement de comportement dans le contexte de la famille consideree comme un systeme. En appliquant un processus d'analyse inductif, a partir de nos donnees qualitatives, les resultats de notre etude multi-cas nous ont indique que deux construits conceptuels semblent influencer l'adoption de comportements environnementaux en famille : 1) les valeurs biospheriques communes au sein de la famille et 2) les competences collectivement mises a profit collectivement durant l'essai de nouveaux comportements environnementaux. Notre modelisation du processus de changement dans des familles indique aussi qu'une dynamique familiale collaborative et la presence d'un groupe de

  11. Possibilities and limitations of analogue methods for studying the dynamics of nuclear power stations; Possibilites et limitations du calcul analogique pour les etudes dynamiques de centrales nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Caillet, C.; Deat, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    speciaux que l'on decrit en discutant la validite des approximations choisies. 4. Les simulateurs de machines tournantes: on souligne le caractere particulier que presentent les calculs des machines tournantes en raison de la necessite ou l'on est de passer par l'intermediaire d'abaques. On propose l'utilisation d'une memoire a acces aleatoire permettant un traitement analogique de ces problemes. 5. Etude d'une centrale nucleaire: on etudie, sur un exemple, les problemes poses par l'interconnexion d'elements du type precedent pour la simulation de grands ensembles (centrales nucleaires) et on souligne le role des elements ordinaires de calcul. 6. Conclusion: on souligne la necessite pour toutes ces etudes, de disposer d'un materiel de qualite et on discute la signification des resultats ainsi obtenus. (auteur)

  12. Mesoscopic modeling of bacterial flagellar microhydrodynamics.

    Science.gov (United States)

    Gebremichael, Yeshitila; Ayton, Gary S; Voth, Gregory A

    2006-11-15

    A particle-based hybrid method of elastic network model and smooth-particle hydrodynamics has been employed to describe the propulsion of bacterial flagella in a viscous hydrodynamic environment. The method explicitly models the two aspects of bacterial propulsion that involve flagellar flexibility and long-range hydrodynamic interaction of low-Reynolds-number flow. The model further incorporates the molecular organization of the flagellar filament at a coarse-grained level in terms of the 11 protofilaments. Each of these protofilaments is represented by a collection of material points that represent the flagellin proteins. A computational model of a single flexible helical segment representing the filament of a bacterial flagellum is presented. The propulsive dynamics and the flow fields generated by the motion of the model filament are examined. The nature of flagellar deformation and the influence of hydrodynamics in determining the shape of deformations are examined based on the helical filament.

  13. Counterimmunoelectrophoresis in the diagnosis of bacterial meningitis

    DEFF Research Database (Denmark)

    Colding, H; Lind, I

    1977-01-01

    The aim of the present study was to investigate whether counterimmunoelectrophoresis (CIE) would facilitate the rapid, etiological diagnosis of bacterial meningitis when used in parallel with other routine methods in a medical bacteriological laboratory. Of 3,674 consecutive specimens of cerebros......The aim of the present study was to investigate whether counterimmunoelectrophoresis (CIE) would facilitate the rapid, etiological diagnosis of bacterial meningitis when used in parallel with other routine methods in a medical bacteriological laboratory. Of 3,674 consecutive specimens....../139) of the culture-negative specimens. CSF specimens from 21 patients with bacterial meningitis caused by other species were all negative in CIE, except four, three of which contained Escherichia coli antigen reacting with antiserum to N. meningitidis group B and one E. coli antigen reacting with antiserum to H...

  14. Endolymphatic sac involvement in bacterial meningitis

    DEFF Research Database (Denmark)

    Møller, Martin Nue; Brandt, Christian; Østergaard, Christian;

    2015-01-01

    The commonest sequelae of bacterial meningitis are related to the inner ear. Little is known about the inner ear immune defense. Evidence suggests that the endolymphatic sac provides some protection against infection. A potential involvement of the endolymphatic sac in bacterial meningitis...... is largely unaccounted for, and thus the object of the present study. A well-established adult rat model of Streptococcus pneumoniae meningitis was employed. Thirty adult rats were inoculated intrathecally with Streptococcus pneumoniae and received no additional treatment. Six rats were sham...... days. Bacteria invaded the inner ear through the cochlear aquaduct. On days 5-6, the bacteria invaded the endolymphatic sac through the endolymphatic duct subsequent to invasion of the vestibular endolymphatic compartment. No evidence of direct bacterial invasion of the sac through the meninges...

  15. Evaluation of silicon oil on bacterial growth

    Directory of Open Access Journals (Sweden)

    Fabio Adams

    2012-04-01

    Full Text Available PURPOSE: To analyze the antimicrobial properties of silicon oil (Óleo de Silicone®, Ophthalmos, Brazil on in vitro bacterial growth of different microorganisms related to endophthalmitis. METHODS: The following microorganisms were analyzed: (1 Pseudomonas aeruginosa (ATCC 27583; (2 Escherichia coli (ATCC 25922; (3 Staphylococcus aureus (ATCC 25923; (4 Staphylococcus epidermidis (ATCC 12228; (5 Candida albicans (ATCC 10231; (6 Klebsiella pneumoniae (ATCC 13883; and (7 Streptococcus pneumoniae (ATCC 49619. The plates were incubated at 35 ± 2ºC and its growth examined after 24 hours. An empty disk was placed in the center of each plate as a control. RESULTS: No inhibition halos were verified in any of the plates containing the four different concentrations of the bacterial inocula. CONCLUSIONS: The silicon oil 1000 cps does not have any effect on bacterial growth of any of the studied microrganisms.

  16. Citrobacter rodentium mouse model of bacterial infection.

    Science.gov (United States)

    Crepin, Valerie F; Collins, James W; Habibzay, Maryam; Frankel, Gad

    2016-10-01

    Infection of mice with Citrobacter rodentium is a robust model to study bacterial pathogenesis, mucosal immunology, the health benefits of probiotics and the role of the microbiota during infection. C. rodentium was first isolated by Barthold from an outbreak of mouse diarrhea in Yale University in 1972 and was 'rediscovered' by Falkow and Schauer in 1993. Since then the use of the model has proliferated, and it is now the gold standard for studying virulence of the closely related human pathogens enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively). Here we provide a detailed protocol for various applications of the model, including bacterial growth, site-directed mutagenesis, mouse inoculation (from cultured cells and after cohabitation), monitoring of bacterial colonization, tissue extraction and analysis, immune responses, probiotic treatment and microbiota analysis. The main protocol, from mouse infection to clearance and analysis of tissues and host responses, takes ∼5 weeks to complete. PMID:27606775

  17. Comprehensive characterization of indoor airborne bacterial profile

    Institute of Scientific and Technical Information of China (English)

    P.L.Chan; P.H.F.Yu; Y.W.Cheng; C.Y.Chan; P.K.Wong

    2009-01-01

    This is the first detailed characterization of the air-borne bacterial profiles in indoor environments and two restaurants were selected for this study.Fifteen genera of bacteria were isolated from each restaurant and identified by three different bacterial identification systems including MIDI, Biolog and Riboprinter?.The dominant bacteria of both restaurants were Gram-positive bacteria in which Micrococcus and Bacillus species were the most abundant species.Most bacteria identified were representative species of skin and respiratory tract of human, and soil.Although the bacterial levels in these restaurants were below the limit of the Hong Kong Indoor Air Quality Objective (HKIAQO) Level 1 standard (i.e., < 500 cfu/m3), the majority of these bacteria were opportunistic pathogens.These results suggested that the identity of airborne bacteria should also be included in the IAQ to ensure there is a safety guideline for the public.

  18. Liver Cirrhosis and Intestinal Bacterial Translocation

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    Intestinal barrier dysfunction, facilitating translocation of bacteria and bacterial products, plays an important role in the pathophysiology of liver cirrhosis and its complications. Intestinal defense system including microbial barrier, immunologic barrier, mechanical barrier, chemical barrier, plays an important role in the maintenance of intestinal function. Under normal circumstances, the intestinal barrier can prevent intestinal bacteria through the intestinal wall from spreading to the body. Severe infection, trauma, shock, cirrhosis, malnutrition, immune suppression conditions, intestinal bacteria and endotoxin translocation, can lead to multiple organ dysfunction. The intestinal microlfora is not only involved in the digestion of nutrients, but also in local immunity, forming a barrier against pathogenic microorganisms. The derangement of the gut microlfora may lead to microbial translocation, deifned as the passage of viable microorganisms or bacterial products from the intestinal lumen to the mesenteric lymph nodes and other extraintestinal sites. In patients with cirrhosis, primary and intestinal lfora imbalance, intestinal bacterial overgrowth, intestinal mucosal barrier dysfunction, endotoxemia is associated with weakened immunity.

  19. Strategy of control for bacterial biofilm processes

    Directory of Open Access Journals (Sweden)

    A. N. Mayansky

    2012-01-01

    Full Text Available Main directions of the modern search of the antibiofilm preparations aimed at adhesive bacterial reactions, control of QS-systems, influence over bis-(3’-5’-cyclic dimeric guanosine monophosphate (cdi-GMP, and secretory bacterial processes are analysed. Approaches for biofilm dispersal and increasing the sensitivity of biofilm bacteria to antimicrobial drugs are discussed. It is underlined that the majority of inhibitor molecules were studied in vitro or in infected mice experiments. It is prognosed that in future there will appear medical preparations which will help for fighting bacterial biofilms preventing their development and spreading in the host organism.

  20. Biofilms: an emergent form of bacterial life.

    Science.gov (United States)

    Flemming, Hans-Curt; Wingender, Jost; Szewzyk, Ulrich; Steinberg, Peter; Rice, Scott A; Kjelleberg, Staffan

    2016-08-11

    Bacterial biofilms are formed by communities that are embedded in a self-produced matrix of extracellular polymeric substances (EPS). Importantly, bacteria in biofilms exhibit a set of 'emergent properties' that differ substantially from free-living bacterial cells. In this Review, we consider the fundamental role of the biofilm matrix in establishing the emergent properties of biofilms, describing how the characteristic features of biofilms - such as social cooperation, resource capture and enhanced survival of exposure to antimicrobials - all rely on the structural and functional properties of the matrix. Finally, we highlight the value of an ecological perspective in the study of the emergent properties of biofilms, which enables an appreciation of the ecological success of biofilms as habitat formers and, more generally, as a bacterial lifestyle. PMID:27510863

  1. Bacterial responses to reactive chlorine species.

    Science.gov (United States)

    Gray, Michael J; Wholey, Wei-Yun; Jakob, Ursula

    2013-01-01

    Hypochlorous acid (HOCl), the active ingredient of household bleach, is the most common disinfectant in medical, industrial, and domestic use and plays an important role in microbial killing in the innate immune system. Given the critical importance of the antimicrobial properties of chlorine to public health, it is surprising how little is known about the ways in which bacteria sense and respond to reactive chlorine species (RCS). Although the literature on bacterial responses to reactive oxygen species (ROS) is enormous, work addressing bacterial responses to RCS has begun only recently. Transcriptomic and proteomic studies now provide new insights into how bacteria mount defenses against this important class of antimicrobial compounds. In this review, we summarize the current knowledge, emphasizing the overlaps between RCS stress responses and other more well-characterized bacterial defense systems, and identify outstanding questions that represent productive avenues for future research. PMID:23768204

  2. Bacterial degradation of monocyclic aromatic amines

    Directory of Open Access Journals (Sweden)

    Pankaj Kumar Arora

    2015-08-01

    Full Text Available Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic compounds has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines.

  3. [Chemotherapy of severe bacterial infections in pediatrics].

    Science.gov (United States)

    Guggenbichler, J P

    1983-01-01

    Bacterial infections are frequent events in premature and newborn infants. The reason is a defective specific and nonspecific defence of bacterial organisms. Some immunoglobulins like IgM and IgA including secretory IgA are absent. Premature infants also show a decreased level of IgG. Cellular immunity is anatomically intact but functionally defective. A number of complement factors are lacking, the activation of the alternative pathway is impaired. Newborn infants with perinatal problems like asphyxia or difficult delivery, show defects of leucocyte function like decreased deformability, defective chemotaxis and defective killing of ingested bacteria. Certain diseases, like hypoxia and malformations of immature organ functions in this age group (decreased acid production in the stomach), facilitate bacterial colonization of surface epithelia and the invasion of tissues. Consequences of these pathogenetic mechanisms are an unimpaired propagation of bacterial organisms into the blood and meninges without localization of the infecting organisms at the entry site. Bacterial meningitis is not considered a separate disease entity but a complication of bacteremia and sepsis. Clinical symptoms are nonspecific at the onset of the infection. Fever is frequently absent; decreased appetite, vomiting, a bloated abdomen, diarrhea, tachycardia, tachypnea are early signs of a bacterial infection, a grey mottled appearance, cyanosis, jaundice, petechiae, apneic spells, seizure activity and a metabolic acidosis are symptoms of advanced infection. Successful treatment at this stage is often not possible. Every sign of a decreased well being of a newborn of premature infant warrants laboratory and bacteriologic work up for septicemia.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6316669

  4. Contribution to the study of the uranium-hydrogen system; Contribution a l'etude du systeme uranium-hydrogene

    Energy Technology Data Exchange (ETDEWEB)

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

    1965-01-01

    Previous work on uranium-hydrogen system is reviewed. The U-H{sub 2}-UH{sub n} equilibrium is then investigated at pressures below one atmosphere, i.e. at temperatures lower than 430 deg. C. The hydride obtained at equilibrium is deficient in hydrogen (UH{sub n<3}), the hydrogen deficit increasing as the temperature rises. Thermodynamic functions for the formation of non-stoichiometric hydride and of one hydrogen vacancy are derived from pressure composition isotherms, in U-H phase diagram is proposed. The hydrogenation of U-UC alloys is also examined at pressures below one atmosphere with regard to the equilibrium: (free U + UC) - H{sub 2}-UH{sub n}. The equilibrium conditions are found different from that observed for pure uranium. (author) [French] Une etude bibliographique du systeme uranium-hydrogene est exposee. L'equilibre U-H{sub 2}-UH{sub n} est ensuite etudie sous des pressions inferieures a une atmosphere, soit aux temperatures inferieures a environ 430 degs. C. L'hydrure obtenu a l'equilibre est deficitaire en hydrogene - UH{sub n<3} - et d'autant plus que la temperature s'eleve. Les grandeurs thermodynamiques relatives a la formation et a la saturation de l'hydrure, ainsi qu'a la formation d'une lacune d'hydrogene sont deduites des pressions d'equilibre. Un modele de diagramme de phases U-H est propose. L'hyduration des alliages U-UC est etudiee egalement sous des pressions inferieures a l'atmosphere, au point de vue de l'equilibre (U libre + UC) - H{sub 2}-UH{sub n}. Les conditions d'equilibre sont trouvees differentes de celles observees sur l'uranium pur. (auteur)

  5. Concerning the study of the irreversible magnetic behaviour of superconductivity; Contribution a l'etude du comportement magnetique irreversible des supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

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

    1965-03-01

    The influence of the presence of extended lattice defects on the magnetic behaviour has been studied for the case of type I superconductors, such as Re and Ta, and in a more quantitative manner for the type II superconductor niobium. In this case, measurements of the thermal conductivity have given an estimate of the relative concentration of lattice defects in each specimen. These measurements show that the larger the number of lattice defects, the more irreversible becomes the magnetization curve, and the larger becomes the values of the critical current, which is related by a simple model to the magnetization values. Finally, a study by transmission electron microscopy has confirmed on the one hand the diversity of the extended lattice defects and on the other hand has allowed the formulation of several hypothesis on their respective influence. [French] L'influence de la presence de defauts etendus sur le comportement magnetique a ete etudie pour des supraconducteurs de premiere espece, tels que le rhenium et le tantale, et plus quantitativement pour un supraconducteur de deuxieme espece, le niobium. Dans ce cas, des mesures de conductibilite thermique ont permis d'estimer la concentration relative des defauts du reseau dans chaque echantillon. Ces mesures montrent que plus les defauts du reseau sont nombreux, plus la courbe d'aimantation est irreversible, et plus les valeurs du courant critique, reliees par un modele simple aux valeurs de l'aimantation, sont elevees. Enfin une etude par microscopie electronique en transmission - a permis d'une part de constater la diversite des defauts etendus et d'autre part de formuler quelques hypotheses sur leurs influences respectives.

  6. Some investigations on the pitting attack of magnesium and its alloys; Contribution a l'etude de la corrosion par piqures du magnesium et de ses alliages

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-03-01

    The pitting attack of magnesium and its alloys has been studied by means of potentio-kinetic polarisation curves; the following parameters have been considered: structural state and composition of the metal, chloride concentration and pH of the medium. The electrochemical data obtained demonstrate that when pH = 12, a localized corrosion might appear as soon as a 10{sup -3} M NaCl concentration is reached; on the other hand, when pH = 13, a much higher concentration (five times) has no effect. In the same conditions, the coupling of magnesium with various noble materials (graphite, platinum, 18/10 stainless steel) also dramatically increases its susceptibility to pitting, but only when chloride ions are present in the solution. Usual corrosion tests have confirmed these electrochemical results. A micrographic study of the pits has shown that their morphology is connected with the metallurgical state of the specimens. (author) [French] La corrosion par piqures du magnesium est etudiee a l'aide des courbes de polarisation potentiocinetiques en fonction des parametres suivants etat structural et composition du metal, concentration en chlorure et pH de la solution. De ces mesures electrochimiques on deduit qu'a pH 12, des la concentration 10{sup -3} M en NaCl, il existe un risque de corrosion localisee, tandis qu'a pH 13 une concentration cinq fois plus forte doit etre sans effet. Dans les memes conditions on montre que le couplage du magnesium avec differents elements nobles (graphite, platine, acier inoxydable 18/10) accroit fortement sa susceptibilite a l'attaque par piqures, excepte dans les solutions exemptes d'ions chlorures. Des essais classiques de corrosion dans les differentes solutions envisagees precedemment confirment les resultats de cette etude electrochimique. L'examen micrographique des piqures montre que leur morphologie est liee a l'etat metallurgique des echantillons. (auteur)

  7. Inhibiting bacterial toxins by channel blockage.

    Science.gov (United States)

    Bezrukov, Sergey M; Nestorovich, Ekaterina M

    2016-03-01

    Emergent rational drug design techniques explore individual properties of target biomolecules, small and macromolecule drug candidates, and the physical forces governing their interactions. In this minireview, we focus on the single-molecule biophysical studies of channel-forming bacterial toxins that suggest new approaches for their inhibition. We discuss several examples of blockage of bacterial pore-forming and AB-type toxins by the tailor-made compounds. In the concluding remarks, the most effective rationally designed pore-blocking antitoxins are compared with the small-molecule inhibitors of ion-selective channels of neurophysiology.

  8. Glucocorticosteroids: as Adjuvant Therapy for Bacterial Infections

    Directory of Open Access Journals (Sweden)

    WONDIM MELKAM

    2015-01-01

    Full Text Available Glucocorticoids (GCs, synthetic analogues of the natural steroid hormones, are well known for their antiinflammatory and immunosuppressive properties in the periphery. They are widely and successfully used in the treatment of autoimmune diseases, chronic inflammation, and transplant rejection. Nowadays, GCs are claimed to have a beneficial role being as adjunct therapy in various infections. Different studies have been conducted to investigate their use as adjuvant therapy for different bacterial infection. This review, therefore, summarizes various bacterial infections for which glucocorticoids are reported to be used as adjuvant therapy, strategies for administration of glucocorticoids, and challenges of using glucocorticoids as adjuvant therapy.

  9. Bacterial Association with Particles: Aggregation to Dissolution

    Digital Repository Service at National Institute of Oceanography (India)

    DeSouza, M.J.B.D.

    , G.H., Hamilton, I.R., 1989. Competition between Streptococcus mutans and Lactobacillus caseii in mixed continuous culture. Oral Microbiol. Immunol. 4, 57-64. Bowen, J.D., Stolzenbach, D., Chisholm, S.W., 1993. Simulating bacterial clustering around... stream_size 68898 stream_content_type text/plain stream_name Judith_chap06.pdf.txt stream_source_info Judith_chap06.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 6. Bacterial Association...

  10. Production of bacterial cellulose from alternate feedstocks

    Energy Technology Data Exchange (ETDEWEB)

    D. N. Thompson; M. A. Hamilton

    2000-05-07

    Production of bacterial cellulose by Acetobacter xylinum ATCC 10821 and 23770 in static cultures was tested from unamended food process effluents. Effluents included low- and high-solids potato effluents (LS and HS), cheese whey permeate (CW), and sugar beet raffinate (CSB). Strain 23770 produced 10% less cellulose from glucose than did 10821, and diverted more glucose to gluconate. Unamended HS, CW, and CSB were unsuitable for cellulose production by either strain, while LS was unsuitable for production by 10821. However, 23770 produced 17% more cellulose from LS than from glucose, indicating unamended LS could serve as a feedstock for bacterial cellulose.

  11. Production of Bacterial Cellulose from Alternate Feedstocks

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, David Neil; Hamilton, Melinda Ann

    2000-05-01

    Production of bacterial cellulose by Acetobacter xylinum ATCC 10821 and 23770 in static cultures was tested from unamended food process effluents. Effluents included low- and high-solids potato effluents (LS & HS), cheese whey permeate (CW), and sugar beet raffinate (CSB). Strain 23770 produced 10% less cellulose from glucose than did 10821, and diverted more glucose to gluconate. Unamended HS, CW, and CSB were unsuitable for cellulose production by either strain, while LS was unsuitable for production by 10821. However, 23770 produced 17% more cellulose from LS than from glucose, indicating unamended LS could serve as a feedstock for bacterial cellulose.

  12. Horizontal gene transfer and bacterial diversity

    Indian Academy of Sciences (India)

    Chitra Dutta; Archana Pan

    2002-02-01

    Bacterial genomes are extremely dynamic and mosaic in nature. A substantial amount of genetic information is inserted into or deleted from such genomes through the process of horizontal transfer. Through the introduction of novel physiological traits from distantly related organisms, horizontal gene transfer often causes drastic changes in the ecological and pathogenic character of bacterial species and thereby promotes microbial diversification and speciation. This review discusses how the recent influx of complete chromosomal sequences of various microorganisms has allowed for a quantitative assessment of the scope, rate and impact of horizontally transmitted information on microbial evolution.

  13. Neurosonographic findings of bacterial meningitis in Infants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Moon Chul; Lee, Sung Sik; Lee, Hong Kue; Lee, Soon Il [Sowa Children' s Hospital, Seoul (Korea, Republic of)

    1989-02-15

    44 infants under 1 year were studied retrospectively during these illness and follow up after 1 week intervals. The spectrum of sonographic features of bacterial meningitis in acute stage included normal scan (20 patients), echogenic sulci (10 patients), echogenic lining of epandymas (8 patients), Abnormal parenchymal echogenecity (6 patients). On follow up examination with 1 week intervals, variety of complications was found in 14 patients (32%) of the infants. There were ventriculomegaly in 7 patients, extraaxial fluid collection in 4 patients, brain abscess in 2 patients and poor encephalic cyst in 1 patient. We conclude that ultrasound was an effective method for evaluation of progression and complications of bacterial meningitis.

  14. CT scan of bacterial and aseptic meningitis

    Energy Technology Data Exchange (ETDEWEB)

    Takemoto, Kazumasa; Saiwai, Shigeo; Tamaoka, Koichi (Kobe Central Municipal Hospital (Japan))

    1983-01-01

    CT scans of the patients with aseptic and bacterial meningitis were reviewed and compared to previous reports. In aseptic meningitis, no abnormal CT findings were observed. In bacterial meningitis, CT findings were ventricular dilatation, subdural fluid collection, parenchymal low density, intracerebral hematoma and meningeal enhancement after contrast injection. Three patients among 48 suffered from status epileptics during the course of the illness. All of the 3 patients developed parenchymal inhomogeneous low density and progressive ventricular dilatation which did not improve after ventricular peritoneal shunt surgery. We believe that these changes are most likely due to hypoxic hypoxemia during epileptic seizure and meningitis itself seems to play a little role.

  15. Le transfert de connaissances entre les mathematiques et les sciences. Une etude exploratoire aupres d'eleves de 4e secondaire

    Science.gov (United States)

    Samson, Ghislain

    2003-06-01

    Au moment ou dans plusieurs pays on travaille a refondre les programmes d'etudes, tant au primaire qu'au secondaire, l'interet pour le transfert renait. Un des concepts fondamentaux en apprentissage consiste en l'habilete a reutiliser de facon consciente et efficace un acquis d'une situation a une autre situation. Cette recherche emane de preoccupations professionnelles au moment ou le chercheur etait enseignant au secondaire. Au cours de ces annees, il lui a ete possible de constater que plusieurs eleves percevaient difficilement les liens presents entre les disciplines mathematiques et scientifiques. Des travaux en psychologie cognitive et plus particulierement selon une perspective du traitement de l'information ont servi de cadre de reference pour evaluer et analyser les capacites de transfert aupres d'eleves de 4e secondaire. Ce cadre de reference permet de formuler le principal objectif qui est de mieux comprendre le processus de transfert chez des eleves en situation de resolution de problemes scientifiques. Cette these s'interesse donc au transfert en tant que phenomene important du processus d'apprentissage au sens de l'integration. La methode de recherche choisie, de nature qualitative, est principalement axee sur l'evaluation de la capacite a transferer des connaissances lors d'une epreuve et d'un entretien. Pour evaluer ce potentiel de transfert, nous avons elabore deux outils: une epreuve en mathematiques et en sciences et un guide d'entretien. Pour la passation de l'epreuve, le chercheur a pu compter sur la collaboration de 130 sujets provenant de deux ecoles. L'entretien complete la prise de donnees avec 13 sujets ayant accepte de poursuivre l'etude. Les donnees recueillies par ces instruments font ensuite l'objet d'une analyse de contenu. En premier lieu, les verbatims de l'epreuve et de l'entretien ont ete transcrits, puis codifies. La correction des reponses fournies pour les problemes resolus s'est faite a partir d'une grille d

  16. Some bio-morphological particularities of hop (Humulus lupulus L. cultivated near Cluj

    Directory of Open Access Journals (Sweden)

    Alexandru SALONTAI

    1977-08-01

    Full Text Available Le houblon est l' une des plantes avec une grande plasticite biologique presentant, en fonction de l'acclimatation, differentes particularites morphologiques, anatomiques et fonctionnelles (1, 2, 3, 6. Bien que le houblon soit cultive depuis tres longtemps dans notre pays les etudes scientifiques portant sur la morpho-biologie sont peu nombreuses (4, 5. Dans cette etude sont presentes les resultats de certaines recherches portant sur la structure morpho - biologique des sortes de houblon, comparativement aux sortes plus valeureuses en culture a la Station experimentale de l'Institut Agronomique de Cluj-Napoca.

  17. Blowing loop in the EL-4 reactor: CO{sub 2} flow control analogue study; Boucle de soufflage de la centrale EL-4 - regulation du debit CO{sub 2} - etude analogique

    Energy Technology Data Exchange (ETDEWEB)

    Chazal, G.; Merle, J.P.; Guillemard, B. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Leroy, C.; Robin, L.; Jacquin, J.C.; Cornudet, A. [Societe INDATOM, France (France)

    1966-07-01

    This report describes one study which contributed to the construction of the Monts d'Arree nuclear power station: EL-4. The reactor is cooled by a CO{sub 2} current provided by 3 turbo-blower groups. The priming vapour for the turbines is taken at the exit of the main CO{sub 2} - H{sub 2}O exchangers. The operation of EL 4 is based on a high degree of centralization of the controls which attributes an important role to the general regulation circuits. This general regulation includes in particular an internal blowing loop which controls the CO{sub 2} flow. The study of the control of this CO{sub 2} flow is made up of 3 parts: - analogue representation of the reactors cooling circuit and of the turbo blower unit. - first test campaign using the analogue computer describing the natural behaviour of the system in the absence of control. theoretical determination of the regulation factors; definition of the regulation using an analogue computer and second test campaign for recording the performances of the blowing loop. The 4. part of the report deals with the analogue study: analogue equations - development. (authors) [French] Ce rapport prend place parmi les etudes de realisation de la Centrale des Monts d'Arree EL-4. Le reacteur est refroidi par une circulation de CO{sub 2} assuree par 3 groupes turbosoufflantes. La vapeur d'entrainement des turbines est prelevee a la sortie des echangeurs principaux CO{sub 2} - H{sub 2}O. L'exploitation de EL-4 repose sur une centralisation poussee des moyens de controle-commande qui attribue un role essentiel aux circuits de regulation generale. Cette regulation generale comporte en particulier une boucle interne de soufflage qui realise un asservissement du debit de CO{sub 2}. L'etude de cette regulation du debit CO{sub 2} comprend 3 parties: - representation analogique du circuit de refroidissement du reacteur et de l'ensemble turbine-soufflante. - premiere campagne d'essais sur calculateur

  18. Effect of isolate of ruminal fibrolytic bacterial culture supplementation on fibrolytic bacterial population and survivability of inoculated bacterial strain in lactating Murrah buffaloes

    Directory of Open Access Journals (Sweden)

    Brishketu Kumar

    2013-02-01

    Full Text Available Aim: The present study was conducted to evaluate the effect of bacterial culture supplementation on ruminal fibrolytic bacterial population as well as on survivability of inoculated bacterial strain in lactating Murrah buffaloes kept on high fibre diet. Materials and Methods: Fibrolytic bacterial strains were isolated from rumen liquor of fistulated Murrah buffaloes and live bacterial culture were supplemented orally in treatment group of lactating Murrah buffaloes fed on high fibre diet to see it's effect on ruminal fibrolytic bacterial population as well as to see the effect of survivability of the inoculated bacterial strain at three different time interval in comparison to control group. Results: It has been shown by real time quantification study that supplementation of bacterial culture orally increases the population of major fibre degrading bacteria i.e. Ruminococcus flavefaciens, Ruminococcus albus as well as Fibrobacter succinogenes whereas there was decrease in secondary fibre degrading bacterial population i.e. Butyrivibrio fibrisolvens over the different time periods. However, the inoculated strain of Ruminococcus flavefaciens survived significantly over the period of time, which was shown in stability of increased inoculated bacterial population. Conclusion: The isolates of fibrolytic bacterial strains are found to be useful in increasing the number of major ruminal fibre degrading bacteria in lactating buffaloes and may act as probiotic in large ruminants on fibre-based diets. [Vet World 2013; 6(1.000: 14-17

  19. The 'Swiss cheese' instability of bacterial biofilms

    CERN Document Server

    Jang, Hongchul; Stocker, Roman

    2012-01-01

    We demonstrate a novel pattern that results in bacterial biofilms as a result of the competition between hydrodynamic forces and adhesion forces. After the passage of an air plug, the break up of the residual thin liquid film scrapes and rearranges bacteria on the surface, such that a Swiss cheese pattern of holes is left in the residual biofilm.

  20. Bacterial proteases: targets for diagnostics and therapy

    NARCIS (Netherlands)

    W.E. Kaman; J.P. Hays; H.P. Endtz; F.J. Bikker

    2014-01-01

    Proteases are essential for the proliferation and growth of bacteria, and are also known to contribute to bacterial virulence. This makes them interesting candidates as diagnostic and therapeutic targets for infectious diseases. In this review, the authors discuss the most recent developments and po

  1. Bacterial community reconstruction using compressed sensing.

    Science.gov (United States)

    Amir, Amnon; Zuk, Or

    2011-11-01

    Bacteria are the unseen majority on our planet, with millions of species and comprising most of the living protoplasm. We propose a novel approach for reconstruction of the composition of an unknown mixture of bacteria using a single Sanger-sequencing reaction of the mixture. Our method is based on compressive sensing theory, which deals with reconstruction of a sparse signal using a small number of measurements. Utilizing the fact that in many cases each bacterial community is comprised of a small subset of all known bacterial species, we show the feasibility of this approach for determining the composition of a bacterial mixture. Using simulations, we show that sequencing a few hundred base-pairs of the 16S rRNA gene sequence may provide enough information for reconstruction of mixtures containing tens of species, out of tens of thousands, even in the presence of realistic measurement noise. Finally, we show initial promising results when applying our method for the reconstruction of a toy experimental mixture with five species. Our approach may have a potential for a simple and efficient way for identifying bacterial species compositions in biological samples. All supplementary data and the MATLAB code are available at www.broadinstitute.org/?orzuk/publications/BCS/.

  2. Multiple bacterial species reside in chronic wounds

    DEFF Research Database (Denmark)

    Gjødsbøl, Kristine; Christensen, Jens Jørgen; Karlsmark, Tonny;

    2006-01-01

    species present were identified. More than one bacterial species were detected in all the ulcers. The most common bacteria found were Staphylococcus aureus (found in 93.5% of the ulcers), Enterococcus faecalis (71.7%), Pseudomonas aeruginosa (52.2%), coagulase-negative staphylococci (45.7%), Proteus...

  3. Respiratory bacterial infections in cystic fibrosis

    DEFF Research Database (Denmark)

    Ciofu, Oana; Hansen, Christine R; Høiby, Niels

    2013-01-01

    PURPOSE OF REVIEW: Bacterial respiratory infections are the main cause of morbidity and mortality in patients with cystic fibrosis (CF). Pseudomonas aeruginosa remains the main pathogen in adults, but other Gram-negative bacteria such as Achromobacter xylosoxidans and Stenotrophomonas maltophilia...... respiratory tract (nasal sampling) should be investigated and both infection sites should be treated....

  4. Model for Mutation in Bacterial Populations

    Science.gov (United States)

    Donangelo, R.; Fort, H.

    2002-07-01

    We describe the evolution of E. coli populations through a Bak-Sneppen-type model which incorporates random mutations. We show that, for a value of the mutation level which coincides with the one estimated from experiments, this model reproduces the measures of mean fitness relative to that of a common ancestor, performed for over 10 000 bacterial generations.

  5. A model for mutation in bacterial populations

    OpenAIRE

    Donangelo, R.; Fort, H.

    2002-01-01

    We describe the evolution of $E.coli$ populations through a Bak-Sneppen type model which incorporates random mutations. We show that, for a value of the mutation level which coincides with the one estimated from experiments, this model reproduces the measures of mean fitness relative to that of a common ancestor, performed for over 10,000 bacterial generations.

  6. Punctuated equilibrium in an evolving bacterial population

    OpenAIRE

    Chaudhuri, Indranath; Bose, Indrani

    1999-01-01

    Recently, Lenski et al have carried out an experiment on bacterial evolution. Their findings support the theory of punctuated equilibrium in biological evolution. We show that the M=2 Bak-Sneppen model can explain some of the experimental results in a qualitative manner.

  7. Bacterial cell biology outside the streetlight.

    Science.gov (United States)

    Bulgheresi, Silvia

    2016-09-01

    As much as vertical transmission of microbial symbionts requires their deep integration into the host reproductive and developmental biology, symbiotic lifestyle might profoundly affect bacterial growth and proliferation. This review describes the reproductive oddities displayed by bacteria associated - more or less intimately - with multicellular eukaryotes.

  8. A study of bacterial gene regulatory mechanisms

    DEFF Research Database (Denmark)

    Hansen, Sabine

    of GRNs this thesis also provided the first evidence of the sensor histidine kinase VC1831 being an additional player in the Vibrio cholerae quorum sensing (QS) GRN. Bacteria use a process of cell-cell communication called QS which enable the bacterial cells to collectively control their gene expression...

  9. Removal of triphenylmethane dyes by bacterial consortium.

    Science.gov (United States)

    Cheriaa, Jihane; Khaireddine, Monia; Rouabhia, Mahmoud; Bakhrouf, Amina

    2012-01-01

    A new consortium of four bacterial isolates (Agrobacterium radiobacter; Bacillus spp.; Sphingomonas paucimobilis, and Aeromonas hydrophila)-(CM-4) was used to degrade and to decolorize triphenylmethane dyes. All bacteria were isolated from activated sludge extracted from a wastewater treatment station of a dyeing industry plant. Individual bacterial isolates exhibited a remarkable color-removal capability against crystal violet (50 mg/L) and malachite green (50 mg/L) dyes within 24 h. Interestingly, the microbial consortium CM-4 shows a high decolorizing percentage for crystal violet and malachite green, respectively, 91% and 99% within 2 h. The rate of chemical oxygen demand (COD) removal increases after 24 h, reaching 61.5% and 84.2% for crystal violet and malachite green, respectively. UV-Visible absorption spectra, FTIR analysis and the inspection of bacterial cells growth indicated that color removal by the CM-4 was due to biodegradation. Evaluation of mutagenicity by using Salmonella typhimurium test strains, TA98 and TA100 studies revealed that the degradation of crystal violet and malachite green by CM-4 did not lead to mutagenic products. Altogether, these results demonstrated the usefulness of the bacterial consortium in the treatment of the textile dyes.

  10. Bacterial enzymes involved in lignin degradation.

    Science.gov (United States)

    de Gonzalo, Gonzalo; Colpa, Dana I; Habib, Mohamed H M; Fraaije, Marco W

    2016-10-20

    Lignin forms a large part of plant biomass. It is a highly heterogeneous polymer of 4-hydroxyphenylpropanoid units and is embedded within polysaccharide polymers forming lignocellulose. Lignin provides strength and rigidity to plants and is rather resilient towards degradation. To improve the (bio)processing of lignocellulosic feedstocks, more effective degradation methods of lignin are in demand. Nature has found ways to fully degrade lignin through the production of dedicated ligninolytic enzyme systems. While such enzymes have been well thoroughly studied for ligninolytic fungi, only in recent years biochemical studies on bacterial enzymes capable of lignin modification have intensified. This has revealed several types of enzymes available to bacteria that enable them to act on lignin. Two major classes of bacterial lignin-modifying enzymes are DyP-type peroxidases and laccases. Yet, recently also several other bacterial enzymes have been discovered that seem to play a role in lignin modifications. In the present review, we provide an overview of recent advances in the identification and use of bacterial enzymes acting on lignin or lignin-derived products. PMID:27544286

  11. Meningococcal Disease (Bacterial Meningitis) Vaccine and Pregnancy

    Science.gov (United States)

    Meningococcal Disease (Bacterial meningitis) Vaccine and Pregnancy In every pregnancy, a woman starts out with a 3-5% chance of having a baby ... advice from your health care provider. What is meningitis? Meningitis is an infection of the lining that ...

  12. Bacterial flora of the sigmoid neovagina

    NARCIS (Netherlands)

    T.A. Toolenaar; I. Freundt (Ingrid); J.H. Wagenvoort; F.J. Huikeshoven (Frans); M. Vogel; J. Jeekel (Hans); A.C. Drogendijk

    1993-01-01

    textabstractThe bacterial microbiota of 15 sigmoid neovaginas, created in patients with congenital vaginal aplasia or male transsexualism, was studied. No specimen was sterile, and only normal inhabitants of the colon were cultured. The total counts of bacteria were low

  13. Bacterial vaginosis with special reference to anaerobes

    Directory of Open Access Journals (Sweden)

    Sumati A

    2009-01-01

    Full Text Available Aims: This study was undertaken to assess the prevalence of bacterial vaginosis (BV and to estimate the prevalence of anaerobic organisms in vaginal discharge of women suffering from bacterial vaginosis. Settings and Design: Patients attending the Obstetrics and Gynecology Department of a Medical College Hospital. A one year cross-sectional study. Methods and Materials: High vaginal swabs taken from 174 female patients complaining of abnormal vaginal discharge. BV was diagnosed by clinical composite criteria and by gram stain. Anaerobes were isolated and identified from the discharge. Statistical Analysis Used: Chi square test, with level of significance set at a value of P< 0.05. Results: BV was diagnosed in 68.39% of the cases by using clinical composite criteria and in 58.4% of the cases by gram stain. Anaerobic culture isolation of vaginal swabs revealed that out of 174 cases 143 (82.65% were culture positive for anaerobes. Bacteroides were significantly raised in BV as compared with non bacterial vaginosis (NBV; < 0.05%. Conclusions: Anaerobic bacteria are important pathogens in the causation of bacterial vaginosis along with other aerobic organisms. Bacteroides and peptostreptococci are significantly raised in BV.

  14. Bacterial ice nucleation: significance and molecular basis.

    Science.gov (United States)

    Gurian-Sherman, D; Lindow, S E

    1993-11-01

    Several bacterial species are able to catalyze ice formation at temperatures as warm as -2 degrees C. These microorganisms efficiently catalyze ice formation at temperatures much higher than most organic or inorganic substances. Because of their ubiquity on the surfaces of frost-sensitive plants, they are responsible for initiating ice formation, which results in frost injury. The high temperature of ice catalysis conferred by bacterial ice nuclei makes them useful in ice nucleation-limited processes such as artificial snow production, the freezing of some food products, and possibly in future whether modification schemes. The rarity of other ice nuclei active at high subfreezing temperature, and the ease and sensitivity with which ice nuclei can be quantified, have made the use of a promoterless bacterial ice nucleation gene valuable as a reporter of transcription. Target genes to which this promoter is fused can be used in cells in natural habitats. Warm-temperature ice nucleation sites have also been extensively studied at a molecular level. Nucleation sites active at high temperatures (above -5 degrees C) are probably composed of bacterial ice nucleation protein molecules that form functionally aligned aggregates. Models of ice nucleation proteins predict that they form a planar array of hydrogen binding groups that closely complement that of an ice crystal face. Moreover, interdigitation of these molecules may produce a large contiguous template for ice formation.

  15. Bacterial cell biology outside the streetlight.

    Science.gov (United States)

    Bulgheresi, Silvia

    2016-09-01

    As much as vertical transmission of microbial symbionts requires their deep integration into the host reproductive and developmental biology, symbiotic lifestyle might profoundly affect bacterial growth and proliferation. This review describes the reproductive oddities displayed by bacteria associated - more or less intimately - with multicellular eukaryotes. PMID:27306428

  16. Corticosteroids for acute adult bacterial meningitis

    NARCIS (Netherlands)

    D. van de Beek

    2009-01-01

    Bacterial meningitis in adults is a severe disease, with high fatality and morbidity rates. Experimental studies showed that the inflammatory response in the subarachnoid space is associated with unfavorable outcome. In these experiments, corticosteroids, and in particular dexamethasone, were able t

  17. Bacterial meningitis: Mechanisms of disease and therapy

    NARCIS (Netherlands)

    R.F. Kornelisse (René); R. de Groot (Ronald); H.J. Neijens (Herman)

    1995-01-01

    textabstractBacterial meningitis continues to be a serious infectious disease with a high morbidity and mortality in young children. Early recognition and initiation of adequate treatment are the major determinants for a good outcome. Recent advances in our understanding of the host inflammatory res

  18. Field determination of bacterial disappearance in seawater

    DEFF Research Database (Denmark)

    Harremoës, Poul

    1970-01-01

    The article presents two approaches to field determination of disappearance of viable, fecal bacteria after discharge with sewage into a marine environment. The first approach is based on simultaneous sampling for bacterial counting and monitoring of dilution using a conservative tracer, which...

  19. Bacterial ice nucleation: significance and molecular basis.

    Science.gov (United States)

    Gurian-Sherman, D; Lindow, S E

    1993-11-01

    Several bacterial species are able to catalyze ice formation at temperatures as warm as -2 degrees C. These microorganisms efficiently catalyze ice formation at temperatures much higher than most organic or inorganic substances. Because of their ubiquity on the surfaces of frost-sensitive plants, they are responsible for initiating ice formation, which results in frost injury. The high temperature of ice catalysis conferred by bacterial ice nuclei makes them useful in ice nucleation-limited processes such as artificial snow production, the freezing of some food products, and possibly in future whether modification schemes. The rarity of other ice nuclei active at high subfreezing temperature, and the ease and sensitivity with which ice nuclei can be quantified, have made the use of a promoterless bacterial ice nucleation gene valuable as a reporter of transcription. Target genes to which this promoter is fused can be used in cells in natural habitats. Warm-temperature ice nucleation sites have also been extensively studied at a molecular level. Nucleation sites active at high temperatures (above -5 degrees C) are probably composed of bacterial ice nucleation protein molecules that form functionally aligned aggregates. Models of ice nucleation proteins predict that they form a planar array of hydrogen binding groups that closely complement that of an ice crystal face. Moreover, interdigitation of these molecules may produce a large contiguous template for ice formation. PMID:8224607

  20. Enzymatic removal and disinfection of bacterial biofilms

    DEFF Research Database (Denmark)

    Johansen, Charlotte; Falholt, Per; Gram, Lone

    1997-01-01

    -coated hydroxyapatite. The activity of enzymes against bacterial cells in biofilm was measured by fluorescence microscopy and an indirect conductance test in which evolution of carbon dioxide was measured. Glucose oxidase combined with lactoperoxidase was bactericidal against biofilm bacteria but did not remove...

  1. Bacterial Acclimation Inside an Aqueous Battery.

    Directory of Open Access Journals (Sweden)

    Dexian Dong

    Full Text Available Specific environmental stresses may lead to induced genomic instability in bacteria, generating beneficial mutants and potentially accelerating the breeding of industrial microorganisms. The environmental stresses inside the aqueous battery may be derived from such conditions as ion shuttle, pH gradient, free radical reaction and electric field. In most industrial and medical applications, electric fields and direct currents are used to kill bacteria and yeast. However, the present study focused on increasing bacterial survival inside an operating battery. Using a bacterial acclimation strategy, both Escherichia coli and Bacillus subtilis were acclimated for 10 battery operation cycles and survived in the battery for over 3 days. The acclimated bacteria changed in cell shape, growth rate and colony color. Further analysis indicated that electrolyte concentration could be one of the major factors determining bacterial survival inside an aqueous battery. The acclimation process significantly improved the viability of both bacteria E. coli and B. subtilis. The viability of acclimated strains was not affected under battery cycle conditions of 0.18-0.80 mA cm(-2 and 1.4-2.1 V. Bacterial addition within 1.0×10(10 cells mL(-1 did not significantly affect battery performance. Because the environmental stress inside the aqueous battery is specific, the use of this battery acclimation strategy may be of great potential for the breeding of industrial microorganisms.

  2. Removal of Triphenylmethane Dyes by Bacterial Consortium

    Directory of Open Access Journals (Sweden)

    Jihane Cheriaa

    2012-01-01

    Full Text Available A new consortium of four bacterial isolates (Agrobacterium radiobacter; Bacillus spp.; Sphingomonas paucimobilis, and Aeromonas hydrophila-(CM-4 was used to degrade and to decolorize triphenylmethane dyes. All bacteria were isolated from activated sludge extracted from a wastewater treatment station of a dyeing industry plant. Individual bacterial isolates exhibited a remarkable color-removal capability against crystal violet (50 mg/L and malachite green (50 mg/L dyes within 24 h. Interestingly, the microbial consortium CM-4 shows a high decolorizing percentage for crystal violet and malachite green, respectively, 91% and 99% within 2 h. The rate of chemical oxygen demand (COD removal increases after 24 h, reaching 61.5% and 84.2% for crystal violet and malachite green, respectively. UV-Visible absorption spectra, FTIR analysis and the inspection of bacterial cells growth indicated that color removal by the CM-4 was due to biodegradation. Evaluation of mutagenicity by using Salmonella typhimurium test strains, TA98 and TA100 studies revealed that the degradation of crystal violet and malachite green by CM-4 did not lead to mutagenic products. Altogether, these results demonstrated the usefulness of the bacterial consortium in the treatment of the textile dyes.

  3. Discovery of inhibitors of bacterial histidine kinases

    NARCIS (Netherlands)

    Velikova, N.R.

    2014-01-01

    Discovery of Inhibitors of Bacterial Histidine Kinases

    Summary

    The thesis is on novel antibacterial drug discovery (http://youtu.be/NRMWOGgeysM). Using structure-based and fragment-based dru

  4. Bacterial Sphingomyelinases and Phospholipases as Virulence Factors.

    Science.gov (United States)

    Flores-Díaz, Marietta; Monturiol-Gross, Laura; Naylor, Claire; Alape-Girón, Alberto; Flieger, Antje

    2016-09-01

    Bacterial sphingomyelinases and phospholipases are a heterogeneous group of esterases which are usually surface associated or secreted by a wide variety of Gram-positive and Gram-negative bacteria. These enzymes hydrolyze sphingomyelin and glycerophospholipids, respectively, generating products identical to the ones produced by eukaryotic enzymes which play crucial roles in distinct physiological processes, including membrane dynamics, cellular signaling, migration, growth, and death. Several bacterial sphingomyelinases and phospholipases are essential for virulence of extracellular, facultative, or obligate intracellular pathogens, as these enzymes contribute to phagosomal escape or phagosomal maturation avoidance, favoring tissue colonization, infection establishment and progression, or immune response evasion. This work presents a classification proposal for bacterial sphingomyelinases and phospholipases that considers not only their enzymatic activities but also their structural aspects. An overview of the main physiopathological activities is provided for each enzyme type, as are examples in which inactivation of a sphingomyelinase- or a phospholipase-encoding gene impairs the virulence of a pathogen. The identification of sphingomyelinases and phospholipases important for bacterial pathogenesis and the development of inhibitors for these enzymes could generate candidate vaccines and therapeutic agents, which will diminish the impacts of the associated human and animal diseases. PMID:27307578

  5. Bacterial DNA delays human eosinophil apoptosis

    OpenAIRE

    Ilmarinen, Pinja; Hasala, Hannele; Sareila, Outi; Moilanen, Eeva; Kankaanranta, Hannu

    2009-01-01

    Bacterial DNA delays human eosinophil apoptosis correspondance: Corresponding author. Tel.: +358 3 3551 6687; fax: +358 3 3551 8082. (Ilmarinen, Pinja) (Ilmarinen, Pinja) The Immunopharmacology Research Group--> , Medical School--> , University of Tampere and Research Unit--> , Tampere University Hospital--> , Tampere--> - FINLAND (Ilmarinen, Pinja) The Immunopharmacology ...

  6. Vancomycin prophylaxis of experimental Streptococcus sanguis. Inhibition of bacterial adherence rather than bacterial killing.

    OpenAIRE

    Bernard, J. P.; Francioli, P.; Glauser, M P

    1981-01-01

    Using a strain of Streptococcus sanguis tolerant to vancomycin to infect aortic vegetations in rats, we found that prophylactic intravenous vancomycin given 30 min before bacterial challenge decreased the incidence of endocarditis from 88 to 8% (P less than 10(-5)). Because peak vancomycin serum levels were below the minimal bactericidal concentration, mechanisms of protection other than bacterial killing were investigated. S. sanguis were incubated with inhibitory concentration of vancomycin...

  7. Biomechanics of bacterial walls: studies of bacterial thread made from Bacillus subtilis.

    OpenAIRE

    Thwaites, J J; Mendelson, N H

    1985-01-01

    Bacterial threads of up to 1 m in length have been produced from filaments of separation-suppressed mutants of Bacillus subtilis. Individual threads may contain 20,000 cellular filaments in parallel alignment. The tensile properties of bacterial threads have been examined by using conventional textile engineering techniques. The kinetics of elongation at constant load are indicative of a viscoelastic material. Both Young's modulus and breaking stress are highly dependent upon relative humidit...

  8. A study of bacterial contamination of rattlesnake venom

    Directory of Open Access Journals (Sweden)

    E. Garcia-Lima

    1987-03-01

    Full Text Available The authors studied the bacterial contamination of rattlesnake venom isolated from snakes in captivity and wild snakes caught recently. The captive snakes showed a relatively high incidence of bacterial contamination of their venom.

  9. Bacterial adhesion of porphyromonas gingivalis on provisional fixed prosthetic materials

    Directory of Open Access Journals (Sweden)

    Mustafa Zortuk

    2010-01-01

    Conclusion : The quantity of bacterial adhesion and surface roughness differed among the assessed provisional fixed prosthodontic materials. The light-polymerized provisional material Revotek LC had rougher surface and more bacterial adhesion compared with the others.

  10. A simple technique to assess bacterial attachment to metal surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    Sonak, S.; Bhosle, N.B.

    There are several methods to assess bacterial adhesion to metal surfaces. Although these methods are sensitive, they are time consuming and need expensive chemicals and instruments. Hence, their use in assessing bacterial adhesion is limited...

  11. Cholinesterase modulations in patients with acute bacterial meningitis

    DEFF Research Database (Denmark)

    Berg, Ronan M G; Ofek, Keren; Qvist, Tavs;

    2011-01-01

    The circulating cholinesterases acetyl- and butyrylcholinesterase may be suppressed and subsequently released from the brain in acute bacterial meningitis.......The circulating cholinesterases acetyl- and butyrylcholinesterase may be suppressed and subsequently released from the brain in acute bacterial meningitis....

  12. Risk of Bacterial Meningitis in Children with Cochlear Implants

    Science.gov (United States)

    ... Information For... Media Policy Makers Risk of Bacterial Meningitis in Children with Cochlear Implants Language: English Español ( ... Compartir 2002 Study of the Risk of Bacterial Meningitis in Children with Cochlear Implants Many people have ...

  13. Targeted imaging of bacterial infections : advances, hurdles and hopes

    NARCIS (Netherlands)

    van Oosten, Marleen; Hahn, Markus; Crane, Lucia M. A.; Pleijhuis, Rick G.; Francis, Kevin P.; van Dijl, Jan Maarten; van Dam, Gooitzen M.

    2015-01-01

    Bacterial infections represent an increasing problem in modern health care, in particular due to ageing populations and accumulating bacterial resistance to antibiotics. Diagnosis is rarely straightforward and consequently treatment is often delayed or indefinite. Therefore, novel tools that can be

  14. Hyperglycemia in bacterial meningitis: a prospective cohort study

    NARCIS (Netherlands)

    E.S. Schut; W.F. Westendorp; J. de Gans; N.D. Kruyt; L. Spanjaard; J.B. Reitsma; D. van de Beek

    2009-01-01

    ABSTRACT: BACKGROUND: Hyperglycemia has been associated with unfavorable outcome in several disorders, but few data are available in bacterial meningitis. We assessed the incidence and significance of hyperglycemia in adults with bacterial meningitis. METHODS: We collected data prospectively between

  15. New methods to assess bacterial injury in water.

    OpenAIRE

    Zaske, S K; Dockins, W S; Schillinger, J. E.; McFeters, G A

    1980-01-01

    Two methods are described for measurement of bacterial injury in water. Laboratory time preceding cell division measured with slide cultures and spheroplast formation after lysozyme treatment were accurate and rapid measurements of bacterial damage.

  16. Comparative Research on the Drum Music Playing Techniques of Etude and Gu Bian Dance Music%《练习曲》与《鼓边舞曲》鼓乐演奏技法比较研究

    Institute of Scientific and Technical Information of China (English)

    王军

    2016-01-01

    文章描述了中国大堂鼓独奏曲《鼓边舞曲》的移植过程,并将其与原曲——俄罗斯小军鼓独奏作品《练习曲》进行比较,重点阐释了中西两种鼓乐器在乐曲演奏中的技法特色。%This paper described the process of adapting a Russia snare drum solo piece Etude to the Chinese Datang drum solo work Gu Bian Dance Music, and com-pared both of them, explained with the focus on the features playing techniques of Chinese and Western drum in the music.

  17. Contribution to the study of plasmatic fibrinogen and serum albumin: effects of irradiation; Contribution a l'etude du fibrinogene et de la serum-albumine plasmatiques - effets de l'irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Suscillon, M. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Grenoble, 38 (France)

    1967-07-01

    The author studies the modifications of properties and structure of serum albumin and fibrinogen solution when subjected to radiation of low energy (X rays). On the other hand, two original techniques are exposed: 1. Amperometric determination of fibrin stabilizing factor or factor XIII of hemostasis. 2. Spectrophotometric study of fibrin formation kinetics. Then showing off and quantitative determination of platelets fibrinogen is exposed. (author) [French] L'auteur etudie les modifications des proprietes et de la structure des molecules de serum-albumine et de fibrinogene en solution soumise a un flux de RX de basse energie. D'autre part deux techniques originales sont exposees : 1. Dosage amperometrique du facteur stabilisant de la fibrine. 2. Etude spectrophotometrique de la cinetique de la fibro-formation. Enfin une mise en evidence et un dosage du fibrinogene plaquettaire sont presentes. (auteur)

  18. Study of the age of uranium-containing mineral deposits in the Limouzat, the bois-noir mountains (12963); Etude des ages des mineralisations uraniferes du gisement du Limouzat, Massif des bois-noirs (1963)

    Energy Technology Data Exchange (ETDEWEB)

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

    1963-07-01

    The present work is concerned with 7 different samples taken at various levels in the Limouzat mine in the Bois-Noirs mountains. It has been possible to show that the uranium dates from 265 M.Y. and that a rearrangement occurred 65 M.Y. ago. A {gamma}-spectrometer study which was originally intended to show the existence of the lack of balance in the radon circulation, has made it possible to show that the {gamma} spectra recorded on various samples could be erroneous. We observed in effect that the presence of lead, iron, etc., had a strong influence on the {gamma} spectrum of the radium family, whereas all research workers have considered that concentrations in the uranium ore were negligible and had no significant effect on the study of the {gamma} spectra of the samples. It is obvious that an interesting study has to be undertaken on the screen effects of the different cations existing in the ores. We believe that it is possible to show the presence of certain elements directly by {gamma}-spectrometry. The ages measured with the mass spectrometer present two types of disagreement but these have been explained by considering that there occurred a first arrival of lead followed by a rearrangement and, at certain points, a second arrival at this date. Finally, the deposit studied undergoes a circulation of uranium and of radon. (author) [French] La presente etude a porte sur 7 prelevements differents effectues a divers niveaux de la mine du Limouzat, massif des Bois-Noirs. Elle a permis de mettre en evidence une premiere venue d'uranium il y a 265 M.A., suivie d'un remaniements il y a 65 M.A. Une etude au spectrometre {gamma} destinee, a l'origine, a prouver les desequilibres dus aux circulations de radon a permis de montrer que les spectres {gamma} enregistres sur divers echantillons pouvaient etre entaches d'erreurs. Nous nous sommes apercus en effet que la presence de plomb, de fer..., avait une forte influence sur le spectre {gamma} de la

  19. (E)TUDE DE ENC(E)PHALE ATLAS DANS PR(E) - TRAITEMENT ET POST- TRAITEMENT DE MALADIE C(E)R(E)BROVASCULAIRE ISCH(E)MIQUE PAR "PIAN TAN NING"

    Institute of Scientific and Technical Information of China (English)

    LIU Mingshun; WU Xinman; HAN Ying; GU Langjie; LIU Qingrui

    2003-01-01

    Objectif: De explorer valeure appliquée de encéphale atlas dans évaluation de effet curatif de maladie cérébrovasculaire ischémique. Méthode: Etude comparative de encéphale atlas de 300 malades avec maladie cérébrovasculaire ischémique avant et après traitement est réalisé. Résultat:Encéphale atlas est changé manifestement avant et après traitement. Conclusion: Encéplale atlas est un index valable de jugement de effet curatif dans maladie cérébrovasculaire ischémique.

  20. La praxéologie comme modèle didactique pour la problématique EIAH. Etude de cas : la modélisation des connaissances des élèves.

    OpenAIRE

    Chaachoua, Hamid

    2011-01-01

    Présentation au séminaire national de didactique des mathématiques.Chaachoua H. (2011) La praxéologie comme modèle didactique pour la problématique EIAH. Etude de cas : la modélisation des connaissances des élèves. In Abboud-Blanchard M., Flückiger A. (eds). Séminaire national de didactique des mathématiques. 81-102. Paris. http://www.irem.univ-paris-diderot.fr/up/publications/AAR12001.pdf Notre recherche porte sur la modélisation didactique et informatique des connaissances des élèves et ...

  1. Bacterial melanin promotes recovery after sciatic nerve injury in rats

    OpenAIRE

    Gevorkyan, Olga. V.; Meliksetyan, Irina B.; Petrosyan, Tigran R.; Hovsepyan, Anichka S.

    2015-01-01

    Bacterial melanin, obtained from the mutant strain of Bacillus Thuringiensis, has been shown to promote recovery after central nervous system injury. It is hypothesized, in this study, that bacterial melanin can promote structural and functional recovery after peripheral nerve injury. Rats subjected to sciatic nerve transection were intramuscularly administered bacterial melanin. The sciatic nerve transected rats that did not receive intramuscular administration of bacterial melanin served as...

  2. Estimating Bacterial Loadings to Surface Waters from Agricultural Watersheds

    OpenAIRE

    Panhorst, Kimberly A.

    2002-01-01

    Fecal bacteria and pathogens are a major source of surface water impairment. In Virginia alone, approximately 73% of impaired waters are impaired due to fecal coliforms (FC). Because bacteria are a significant cause of water body impairment and existing bacterial models are predominantly based upon laboratory-derived information, bacterial models are needed that describe bacterial die-off and transport processes under field conditions. Before these bacterial models can be developed, more f...

  3. New Class of Competitive Inhibitor of Bacterial Histidine Kinases

    OpenAIRE

    Gilmour, Raymond; Foster, J. Estelle; Sheng, Qin; McClain, Jonathan R.; Riley, Anna; Sun, Pei-Ming; Ng, Wai-Leung; Yan, Dalai; Nicas, Thalia I.; Henry, Kenneth; Winkler, Malcolm E.

    2005-01-01

    Bacterial histidine kinases have been proposed as targets for the discovery of new antibiotics, yet few specific inhibitors of bacterial histidine kinases have been reported. We report here a novel thienopyridine (TEP) compound that inhibits bacterial histidine kinases competitively with respect to ATP but does not comparably inhibit mammalian serine/threonine kinases. Although it partitions into membranes and does not inhibit the growth of bacterial or mammalian cells, TEP could serve as a s...

  4. Detection and analysis of neutral and charged particles. Application to the study of hot plasmas; Detection et analyse des particules chargees et neutres appliquees a l'etude des plasmas chauds

    Energy Technology Data Exchange (ETDEWEB)

    Renaud, C. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires. Groupe de recherches de l' association EURATOM-CEA sur la fusion controlee

    1966-12-01

    To measure the energy spectrum of ions in a plasma, one must extract the ions without altering the spectrum. For a dense plasma this presents difficulties, one method is the measurement of the energy spectrum of atoms produced by charge-exchange reactions of ions with residual gas. The measurements of both the energy spectrum and the flux of atoms leaving the magnetic configuration of the device DECA II (Dispositif d'Etude de Compression Adiabatique) are made by: an ion detector which permits the measurement of ion currents {>=} 10{sup -16} A, an electrostatic analyser of energy range 10 eV - 10 keV, a magnetic analyser for ion momentum {<=} 10{sup 5} gauss-cm, and a gas cell to convert fast atoms into ions. (author) [French] Pour mesurer le spectre en energie des ions dans un plasma on doit extraire des ions sans en modifier l'energie. Dans le cas de plasmas denses cela presente certaines difficultes. Une mesure du spectre en energie des ions est alors possible a partir du spectre en energie des atomes produits par collision d'echange de charge entre les ions du plasma et le gaz residuel. Pour effectuer la mesure du spectre en energie et du flux d'atomes s'echappant de la configuration magnetique du Dispositif d'Etude de Compression Adiabatique (DECA II) nous avons mis au point: un detecteur d'ions permettant la mesure de courant {>=} 10{sup -16} A, d'un analyseur electrostatique dont la gamme d'analyse en energie est comprise entre 10 eV et 10 keV, d'un analyseur magnetique capable d'analyser des ions d'une quantite de mouvement {<=} 10{sup 5} gauss cm, ainsi qu'une cellule a gaz permettant l'ionisation des atomes rapides. (auteur)

  5. Discovery of New Substrates for LuxAB Bacterial Bioluminescence.

    Science.gov (United States)

    Jiang, Tianyu; Wang, Weishan; Wu, Xingkang; Wu, Wenxiao; Bai, Haixiu; Ma, Zhao; Shen, Yuemao; Yang, Keqian; Li, Minyong

    2016-08-01

    In this article, four novel substrates with long halftime have been designed and synthesized successfully for luxAB bacterial bioluminescence. After in vitro and in vivo biological evaluation, these molecules can emit obvious bioluminescence emission with known bacterial luciferase, thus indicating a new promising approach to developing the bacterial bioluminescent system. PMID:26896339

  6. Discovery of New Substrates for LuxAB Bacterial Bioluminescence.

    Science.gov (United States)

    Jiang, Tianyu; Wang, Weishan; Wu, Xingkang; Wu, Wenxiao; Bai, Haixiu; Ma, Zhao; Shen, Yuemao; Yang, Keqian; Li, Minyong

    2016-08-01

    In this article, four novel substrates with long halftime have been designed and synthesized successfully for luxAB bacterial bioluminescence. After in vitro and in vivo biological evaluation, these molecules can emit obvious bioluminescence emission with known bacterial luciferase, thus indicating a new promising approach to developing the bacterial bioluminescent system.

  7. Bacterial pathogens modulate an apoptosis differentiation program in human neutrophils

    OpenAIRE

    Kobayashi, Scott D.; Braughton, Kevin R.; Whitney, Adeline R.; Voyich, Jovanka M.; Schwan, Tom G.; Musser, James M.; DeLeo, Frank R.

    2003-01-01

    Human polymorphonuclear leukocytes (PMNs or neutrophils) are essential to the innate immune response against bacterial pathogens. Recent evidence suggests that PMN apoptosis facilitates resolution of inflammation during bacterial infection. Although progress has been made toward understanding apoptosis in neutrophils, very little is known about transcriptional regulation of this process during bacterial infection. To gain insight into the molecular processes that facilitate resolution of infe...

  8. Bacterial protein toxins : tools to study mammalian molecular cell biology

    NARCIS (Netherlands)

    Wüthrich, I.W.

    2014-01-01

    Bacterial protein toxins are genetically encoded proteinaceous macromolecules that upon exposure causes perturbation of cellular metabolism in a susceptible host. A bacterial toxin can work at a distance from the site of infection, and has direct and quantifiable actions. Bacterial protein toxins ca

  9. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    Science.gov (United States)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2015-12-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

  10. 21 CFR 1210.16 - Method of bacterial count.

    Science.gov (United States)

    2010-04-01

    ... FEDERAL IMPORT MILK ACT Inspection and Testing § 1210.16 Method of bacterial count. The bacterial count of milk and cream refers to the number of viable bacteria as determined by the standard plate method of... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Method of bacterial count. 1210.16 Section...

  11. Caracterización del borde de un relicto de bosque altoandino dominado por Chusquea scandens (Kunth y evaluación del efecto de disturbios experimentales sobre la regeneración natural en la Reserva forestal municipal de Cogua (Cundinamarca, Colombia

    Directory of Open Access Journals (Sweden)

    Vargas Ríos Orlando

    2004-12-01

    Full Text Available El presente estudio se realizó en la Reserva Forestal Municipal de Cogua (Cundinamarca, Colombia, como parte del proyecto “Hacia un modelo de restauración del bosque”. Tiene como objetivos caracterizar el borde de avance del bosque, dominado por la especie Chusquea scandens y evaluar la regeneración de especies luego de disturbios experimentales a lo largo del borde de bosque. Con el primero se generó información preliminar del estado del borde de avance y del potencial que puede existir allí para la regeneración natural de la vegetación, el muestreo se realizó entre los meses de julio y octubre de 2003, en el cual se evaluaron algunas condiciones bióticas, abióticas y edáficas por medio del método línea intercepto a lo largo del gradiente pastizal-chuscal-bosque. El segundo estableció que tipo de disturbios son favorables para activar y potencializar la regeneración en los bordes de avance dominados por el chusque, los disturbios se basaron en reducir la competencia que hace el chusque por luz, así como también aumentar la disponibilidad de espacio para el establecimiento de otras especies. Para la caracterización del borde de avance se obtuvo que hacia el pastizal el chusque presenta una
    alta densidad que genera una zona de difícil acceso, lo cual puede funcionar como una barrera natural que reduce la influencia de especies de áreas abiertas en el interior del borde de avance, en donde se presentan peque��os claros donde el chuscal se reduce y se muestra una regeneración natural de especies. Además se estableció que a altas densidades del chusque se reducen las posibilidades de regeneración natural y la implantación de especies arbóreas, así como también, que la regeneración presentada hacia el interior del borde de avance está dominada por especies de borde y de bosque, siendo las herbáceas, enredaderas y arbustos las formas de crecimiento más importantes. Luego de los disturbios experimentales se

  12. The study of the extreme radiation tolerance mechanisms of the bacterium Deinococcus deserti by a functional genomics approach; Etude des mecanismes de l'extreme tolerance aux radiations de la bacterie Deinococcus deserti par une approche de genomique fonctionnelle

    Energy Technology Data Exchange (ETDEWEB)

    Dulermo, R.

    2009-12-15

    The genome of Deinococcus deserti, a highly radiation-tolerant bacterium, was analyzed and compared to those of D. radiodurans and D. geothermalis. About 230 proteins are specifically conserved in these 3 species, including IrrE, a regulator protein essential for radio tolerance. D.deserti has several supplementary DNA repair genes, like imuY and dnaE2 (trans-lesion DNA polymerases). Moreover, D. deserti has 3 recA that code for 2 different RecA proteins (RecAC et RecAP). To study these genes, genetic tools were developed for D. deserti. Different results suggest that IrrE, required for the induction of several genes after irradiation, has peptidase activity. The 2 RecA proteins are functional for DNA repair. D. deserti is mutable by UV, which requires ImuY, DnaE2 and RecAC, but not RecAP. (author)

  13. Bacterial protein toxins in human cancers.

    Science.gov (United States)

    Rosadi, Francesca; Fiorentini, Carla; Fabbri, Alessia

    2016-02-01

    Many bacteria causing persistent infections produce toxins whose mechanisms of action indicate that they could have a role in carcinogenesis. Some toxins, like CDT and colibactin, directly attack the genome by damaging DNA whereas others, as for example CNF1, CagA and BFT, impinge on key eukaryotic processes, such as cellular signalling and cell death. These bacterial toxins, together with other less known toxins, mimic carcinogens and tumour promoters. The aim of this review is to fulfil an up-to-date analysis of toxins with carcinogenic potential that have been already correlated to human cancers. Bacterial toxins-induced carcinogenesis represents an emerging aspect in bacteriology, and its significance is increasingly recognized.

  14. Discrete modelling of bacterial conjugation dynamics

    CERN Document Server

    Goni-Moreno, Angel

    2012-01-01

    In bacterial populations, cells are able to cooperate in order to yield complex collective functionalities. Interest in population-level cellular behaviour is increasing, due to both our expanding knowledge of the underlying biological principles, and the growing range of possible applications for engineered microbial consortia. Researchers in the field of synthetic biology - the application of engineering principles to living systems - have, for example, recently shown how useful decision-making circuits may be distributed across a bacterial population. The ability of cells to interact through small signalling molecules (a mechanism known as it quorum sensing) is the basis for the majority of existing engineered systems. However, horizontal gene transfer (or conjugation) offers the possibility of cells exchanging messages (using DNA) that are much more information-rich. The potential of engineering this conjugation mechanism to suit specific goals will guide future developments in this area. Motivated by a l...

  15. Bacterial Zoonoses Transmitted by Household Pets

    DEFF Research Database (Denmark)

    Damborg, Peter Panduro; Broens, E.M.; Chomel, B.B.;

    2016-01-01

    The close contact between household pets and people offers favourable conditions for bacterial transmission. In this article, the aetiology, prevalence, transmission, impact on human health and preventative measures are summarized for selected bacterial zoonoses transmissible by household pets. Six...... zoonoses representing distinct transmission routes were selected arbitrarily based on the available information on incidence and severity of pet-associated disease caused by zoonotic bacteria: bite infections and cat scratch disease (physical injuries), psittacosis (inhalation), leptospirosis (contact...... with urine), and campylobacteriosis and salmonellosis (faecal–oral ingestion). Antimicrobial resistance was also included due to the recent emergence of multidrug-resistant bacteria of zoonotic potential in dogs and cats. There is a general lack of data on pathogen prevalence in the relevant pet population...

  16. Bursting the bubble on bacterial biofilms

    DEFF Research Database (Denmark)

    Crusz, Shanika A; Popat, Roman; Rybtke, Morten Theil;

    2012-01-01

    The flow cell biofilm system is an important and widely used tool for the in vitro cultivation and evaluation of bacterial biofilms under hydrodynamic conditions of flow. This paper provides an introduction to the background and use of such systems, accompanied by a detailed guide to the assembly...... of the apparatus including the description of new modifications which enhance its performance. As such, this is an essential guide for the novice biofilm researcher as well as providing valuable trouble-shooting techniques for even the most experienced laboratories. The adoption of a common and reliable...... methodology amongst researchers would enable findings to be shared and replicated amongst the biofilm research community, with the overall aim of advancing understanding and management of these complex and widespread bacterial communities....

  17. Metabolism links bacterial biofilms and colon carcinogenesis.

    Science.gov (United States)

    Johnson, Caroline H; Dejea, Christine M; Edler, David; Hoang, Linh T; Santidrian, Antonio F; Felding, Brunhilde H; Ivanisevic, Julijana; Cho, Kevin; Wick, Elizabeth C; Hechenbleikner, Elizabeth M; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A; Pardoll, Drew M; White, James R; Patti, Gary J; Sears, Cynthia L; Siuzdak, Gary

    2015-06-01

    Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N(1), N(12)-diacetylspermine in both biofilm-positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N(1), N(12)-diacetylspermine levels to those seen in biofilm-negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression.

  18. The clinical impact of bacterial biofilms

    DEFF Research Database (Denmark)

    Høiby, Niels; Ciofu, Oana; Johansen, Helle Krogh;

    2011-01-01

    Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria (and fungi) are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA....... Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation....... Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity...

  19. Procalcitonin in sepsis and bacterial infections

    Directory of Open Access Journals (Sweden)

    Abhijit Chaudhury

    2013-10-01

    Full Text Available The differentiation of sepsis and systemic bacterial infections from other causes of systemic inflammatory response is crucial from the therapeutic point of view. The clinical signs and symptoms are non-specific and traditional biomarkers like white cell count, erythrocyte sedimentation rate and C-reactive protein are not sufficiently sensitive or specific to guide therapeutic decisions. Procalcitonin (PCT is considered a reliable marker for the diagnosis and prognosis of moderate to severe bacterial infections, and it has also been evaluated to guide the clinicians in the rational usage of antibiotics. This review describes the diagnostic and prognostic role of PCT as a biomarker in various clinical settings along with the laboratory aspects and its usefulness in risk stratification and antibiotic stewardship.

  20. Effects of hydrodynamic interactions in bacterial swimming.

    Science.gov (United States)

    Chattopadhyay, Suddhashil; Lun Wu, Xiao

    2008-03-01

    The lack of precise experimental data has prevented the investigation of the effects of long range hydrodynamic interactions in bacterial swimming. We perform measurements on various strains of bacteria with the aid of optical tweezers to shed light on this aspect of bacterial motility. Geometrical parameters recorded by fluorescence microscopy are used with theories which model flagella propulsion (Resistive force theory & Lighthill's formulation which includes long range interactions). Comparison of the predictions of these theories with experimental data, observed directly from swimming bacterium, led to the conclusion that while long range inetractions were important for single polar flagellated strains (Vibrio Alginolyticus & Caulobacter Crescentus), local force theory was adequate to describe the swimming of multi-flagellated Esherichia Coli. We performed additional measurements on E. Coli minicells (miniature cells with single polar flagellum) to try and determine the cause of this apparent effect of shielding of long range interactions in multiple flagellated bacteria.

  1. Bacterial Toxins as Pathogen Weapons Against Phagocytes.

    Science.gov (United States)

    do Vale, Ana; Cabanes, Didier; Sousa, Sandra

    2016-01-01

    Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.

  2. ANTIMICROBIAL ACTIVITY OF LACTIC ACID BACTERIAL ISOLATES

    Directory of Open Access Journals (Sweden)

    Utkarsha S. Shivsharan

    2013-08-01

    Full Text Available Micro-organisms have tendency to produce antimicrobial substances which show biological activity against other kind of micro-organisms. This phenomenon of bacterial antagonism is observed in lactic acid bacteria with competitive advantages. The lactic acid bacteria are commonly present in many fermented products, fruits and milk products. The variety of antimicrobial substances produced by lactic acid bacteria showing good inhibition capacity include production of lactic acid, acetic acid, hydrogen peroxide, carbon dioxide, diacetyl and bacteriocin. Bacteriocins produced by lactic acid bacteria are the subject of intense research because of their antimicrobial activity against food born bacteria such as Listeria monocytogenes, staphylococcus aureus, Bacillus cereus, Clostridium botulinum and several others .Bacteriocins may be bacteriostatic or bactericidal with narrow or broad range of activity. The main of the study was to study the antimicrobial activity of such lactic acid bacterial isolates.

  3. Bacterial microbiome of lungs in COPD.

    Science.gov (United States)

    Sze, Marc A; Hogg, James C; Sin, Don D

    2014-01-01

    Chronic obstructive pulmonary disease (COPD) is currently the third leading cause of death in the world. Although smoking is the main risk factor for this disease, only a minority of smokers develop COPD. Why this happens is largely unknown. Recent discoveries by the human microbiome project have shed new light on the importance and richness of the bacterial microbiota at different body sites in human beings. The microbiota plays a particularly important role in the development and functional integrity of the immune system. Shifts or perturbations in the microbiota can lead to disease. COPD is in part mediated by dysregulated immune responses to cigarette smoke and other environmental insults. Although traditionally the lung has been viewed as a sterile organ, by using highly sensitive genomic techniques, recent reports have identified diverse bacterial communities in the human lung that may change in COPD. This review summarizes the current knowledge concerning the lung microbiota in COPD and its potential implications for pathogenesis of the disease.

  4. Bacterial toxins as pathogen weapons against phagocytes

    Directory of Open Access Journals (Sweden)

    Ana edo Vale

    2016-02-01

    Full Text Available Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favour microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signalling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.

  5. Future of Bacterial Therapy of Cancer.

    Science.gov (United States)

    Hoffman, Robert M

    2016-01-01

    Bacterial therapy of cancer has a centuries-long history and was first-line therapy at the hospital in New York City that would become Memorial Sloan-Kettering Cancer Center, under Dr. William B. Coley. However, after Coley's death in 1936, bacterial therapy of cancer ceased in the clinic until the present century. Clinical trials have been recently carried out for strains of the obligate anaerobe Clostridium novyi with the toxin gene deleted, and on an attenuated strain of Salmonella typhimurium (S. typhimurium), which is a facultative anaerobe that can grow in viable, as well as necrotic, areas of tumors, unlike Clostridium, which can only grow in the hypoxic areas. Our laboratory has developed the novel strain S. typhimurium A1-R that is effective against all tumor types in clinically-relevant mouse models, including patient-derived orthotopic xenograft (PDOX) mouse models. This chapter suggests future clinical applications for S. typhimurium A1-R.

  6. Within-host evolution of bacterial pathogens

    Science.gov (United States)

    Didelot, Xavier; Walker, A. Sarah; Peto, Tim E.; Crook, Derrick W.; Wilson, Daniel J.

    2016-01-01

    Whole genome sequencing has opened the way to investigating the dynamics and genomic evolution of bacterial pathogens during colonization and infection of humans. The application of this technology to the longitudinal study of adaptation in the infected host — in particular, the evolution of drug resistance and host adaptation in patients chronically infected with opportunistic pathogens — has revealed remarkable patterns of convergent evolution, pointing to an inherent repeatability of evolution. In this Review, we describe how these studies have advanced our understanding of the mechanisms and principles of within-host genome evolution, and we consider the consequences of findings such as a potent adaptive potential for pathogenicity. Finally, we discuss the possibility that genomics may be used in the future to predict the clinical progression of bacterial infections, and to suggest the best treatment option. PMID:26806595

  7. Structure and operation of bacterial tripartite pumps.

    Science.gov (United States)

    Hinchliffe, Philip; Symmons, Martyn F; Hughes, Colin; Koronakis, Vassilis

    2013-01-01

    In bacteria such as Pseudomonas aeruginosa and Escherichia coli, tripartite membrane machineries, or pumps, determine the efflux of small noxious molecules, such as detergents, heavy metals, and antibiotics, and the export of large proteins including toxins. They are therefore influential in bacterial survival, particularly during infections caused by multidrug-resistant pathogens. In these tripartite pumps an inner membrane transporter, typically an ATPase or proton antiporter, binds and translocates export or efflux substrates. In cooperation with a periplasmic adaptor protein it recruits and opens a TolC family cell exit duct, which is anchored in the outer membrane and projects across the periplasmic space between inner and outer membranes. Assembled tripartite pumps thus span the entire bacterial cell envelope. We review the atomic structures of each of the three pump components and discuss how these have allowed high-resolution views of tripartite pump assembly, operation, and possible inhibition. PMID:23808339

  8. Formaldehyde stress responses in bacterial pathogens

    Directory of Open Access Journals (Sweden)

    Nathan Houqian Chen

    2016-03-01

    Full Text Available Formaldehyde is the simplest of all aldehydes and is highly cytotoxic. Its use and associated dangers from environmental exposure have been well documented. Detoxification systems for formaldehyde are found throughout the biological world and they are especially important in methylotrophic bacteria, which generate this compound as part of their metabolism of methanol. Formaldehyde metabolizing systems can be divided into those dependent upon pterin cofactors, sugar phosphates and those dependent upon glutathione. The more prevalent thiol-dependent formaldehyde detoxification system is found in many bacterial pathogens, almost all of which do not metabolize methane or methanol. This review describes the endogenous and exogenous sources of formaldehyde, its toxic effects and mechanisms of detoxification. The methods of formaldehyde sensing are also described with a focus on the formaldehyde responsive transcription factors HxlR, FrmR and NmlR. Finally, the physiological relevance of detoxification systems for formaldehyde in bacterial pathogens is discussed.

  9. Novel Nitrocellulose Made from Bacterial Cellulose

    Science.gov (United States)

    Sun, Dong-Ping; Ma, Bo; Zhu, Chun-Lin; Liu, Chang-Sheng; Yang, Jia-Zhi

    2010-04-01

    Nitrocellulose (NC) is useful in several industrial segments, especially in the production of gun, rocket, and missile propellants. The conventional way to prepare NC is done through the nitration of plant cellulose with nitric acid. In this work, bacterial cellulose nitrate (NBC) is synthesized by bacterial cellulose (BC) and nitro-sulfric acid under heterogeneous conditions. NBC with the degree of substitution (DS) of 1-2.85 was obtained, and the effects of sulfuric to nitric ratio, reaction temperature, and reaction time on the value of DS of NBC are discussed. The samples are also characterized by elemental analysis, thermal analysis, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction.

  10. Immunization of newborns with bacterial conjugate vaccines.

    Science.gov (United States)

    van den Biggelaar, Anita H J; Pomat, William S

    2013-05-17

    Bacterial conjugate vaccines are based on the principle of coupling immunogenic bacterial capsular polysaccharides to a carrier protein to facilitate the induction of memory T-cell responses. Following the success of Haemophilus influenzae type b conjugate vaccines in the 1980s, conjugate vaccines for Streptococcus pneumoniae and Neisseria meningitidis infections were developed and proven to be effective in protecting children against invasive disease. In this review, the use of conjugate vaccines in human newborns is discussed. Neonatal Haemophilus influenzae type b and pneumococcal conjugate vaccination schedules have been trialed and proven to be safe, with the majority of studies demonstrating no evidence for the induction of immune tolerance. Whether their neonatal administration also results in an earlier induction of clinical protection in the first 2-3 critical months of life is still to be demonstrated. PMID:22728221

  11. Bacterial consortia for crude oil spill remediation

    International Nuclear Information System (INIS)

    Oil spills generate enormous public concern and highlight the need for cost effective ad environmentally acceptable mitigation technologies. Physico-chemical methods are not completely effective after a spill. Hence, there is a need for improved and alternative technologies. Bioremediation is the most environmentally sound technology for clean up. This report intends to determine the potential of a bacterial consortium for degradation of Gulf and Bombay High crude oil. A four membered consortium was designed that could degrade 70% of the crude oil. A member of consortium produced a biosurfactant, rhamnolipid, that emulsified crude oil efficiently for effective degradation by the other members of consortium. The wide range of hydrocarbonoclastic capabilities of the selected members of bacterial consortium leads to the degradation of both aromatic and aliphatic fractions of crude oil in 72 hours. (Author)

  12. The Bacterial Microflora of Fish, Revised

    Directory of Open Access Journals (Sweden)

    B. Austin

    2006-01-01

    Full Text Available The results of numerous studies indicate that fish possess bacterial populations on or in their skin, gills, digestive tract, and light-emitting organs. In addition, the internal organs (kidney, liver, and spleen of healthy fish may contain bacteria, but there is debate about whether or not muscle is actually sterile. Using traditional culture-dependent techniques, the numbers and taxonomic composition of the bacterial populations generally reflect those of the surrounding water. More modern culture-independent approaches have permitted the recognition of previously uncultured bacteria. The role of the organisms includes the ability to degrade complex molecules (therefore exercising a potential benefit in nutrition, to produce vitamins and polymers, and to be responsible for the emission of light by the light-emitting organs of deep-sea fish. Taxa, including Pseudomonas, may contribute to spoilage by the production of histamines in fish tissue.

  13. Bacterial Modulation of Plant Ethylene Levels.

    Science.gov (United States)

    Gamalero, Elisa; Glick, Bernard R

    2015-09-01

    A focus on the mechanisms by which ACC deaminase-containing bacteria facilitate plant growth.Bacteria that produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, when present either on the surface of plant roots (rhizospheric) or within plant tissues (endophytic), play an active role in modulating ethylene levels in plants. This enzyme activity facilitates plant growth especially in the presence of various environmental stresses. Thus, plant growth-promoting bacteria that express ACC deaminase activity protect plants from growth inhibition by flooding and anoxia, drought, high salt, the presence of fungal and bacterial pathogens, nematodes, and the presence of metals and organic contaminants. Bacteria that express ACC deaminase activity also decrease the rate of flower wilting, promote the rooting of cuttings, and facilitate the nodulation of legumes. Here, the mechanisms behind bacterial ACC deaminase facilitation of plant growth and development are discussed, and numerous examples of the use of bacteria with this activity are summarized. PMID:25897004

  14. Formaldehyde Stress Responses in Bacterial Pathogens.

    Science.gov (United States)

    Chen, Nathan H; Djoko, Karrera Y; Veyrier, Frédéric J; McEwan, Alastair G

    2016-01-01

    Formaldehyde is the simplest of all aldehydes and is highly cytotoxic. Its use and associated dangers from environmental exposure have been well documented. Detoxification systems for formaldehyde are found throughout the biological world and they are especially important in methylotrophic bacteria, which generate this compound as part of their metabolism of methanol. Formaldehyde metabolizing systems can be divided into those dependent upon pterin cofactors, sugar phosphates and those dependent upon glutathione. The more prevalent thiol-dependent formaldehyde detoxification system is found in many bacterial pathogens, almost all of which do not metabolize methane or methanol. This review describes the endogenous and exogenous sources of formaldehyde, its toxic effects and mechanisms of detoxification. The methods of formaldehyde sensing are also described with a focus on the formaldehyde responsive transcription factors HxlR, FrmR, and NmlR. Finally, the physiological relevance of detoxification systems for formaldehyde in bacterial pathogens is discussed. PMID:26973631

  15. Influenza and bacterial pneumonia - constant companions

    OpenAIRE

    Wunderink, Richard G.

    2010-01-01

    Sequential or concomitant influenza and bacterial pneumonia are two common syndromes seen in community-acquired pneumonia. Inadequacies of diagnostic testing make separating simple pneumonia with either bacteria or influenza from concomitant or sequential influenza with both microorganisms difficult, although the novel 2009 H1N1 epidemic may improve the availability of molecular testing for viruses. Given the frequency of viral pneumonia and diagnostic limitations, empirical antivirals may be...

  16. Diffusion of an ellipsoid in bacterial suspensions

    OpenAIRE

    Peng, Yi; Lai, Lipeng; Tai, Yi-Shu; Zhang, Kechun; Xu, Xinliang; Cheng, Xiang

    2015-01-01

    Active matter such as swarming bacteria and motile colloids exhibits exotic properties different from conventional equilibrium materials. Among these properties, the enhanced diffusion of tracer particles is generally deemed as a hallmark of active matter. Here, rather than spherical tracers, we investigate the diffusion of isolated ellipsoids in quasi-two-dimensional bacterial bath. Our study reveals a nonlinear enhancement of both translational and rotational diffusions. More importantly, w...

  17. Bacterial Plasmids in Antarctic Natural Microbial Assemblages

    OpenAIRE

    Kobori, Hiromi; Sullivan, Cornelius W.; Shizuya, Hiroaki

    1984-01-01

    Samples of psychrophilic and psychrotrophic bacteria were collected from sea ice, seawater, sediments, and benthic or ice-associated animals in McMurdo Sound, Antarctica. A total of 155 strains were isolated and tested for the presence of plasmids by DNA agarose gel electrophoresis. Thirty-one percent of the isolates carried at least one kind of plasmid. Bacterial isolates taken from sediments showed the highest plasmid incidence (42%), and isolates from seawater showed the lowest plasmid inc...

  18. Bacterial small RNAs in the Genus Rickettsia

    OpenAIRE

    Schroeder, Casey L. C.; Narra, Hema P.; Rojas, Mark; Sahni, Abha; Patel, Jignesh; Khanipov, Kamil; Wood, Thomas G.; Fofanov, Yuriy; Sahni, Sanjeev K.

    2015-01-01

    Background Rickettsia species are obligate intracellular Gram-negative pathogenic bacteria and the etiologic agents of diseases such as Rocky Mountain spotted fever (RMSF), Mediterranean spotted fever, epidemic typhus, and murine typhus. Genome sequencing revealed that R. prowazekii has ~25 % non-coding DNA, the majority of which is thought to be either “junk DNA” or pseudogenes resulting from genomic reduction. These characteristics also define other Rickettsia genomes. Bacterial small RNAs,...

  19. Spontaneous bacterial peritonitis: Few additional points

    Institute of Scientific and Technical Information of China (English)

    Pankaj Jain

    2009-01-01

    Spontaneous bacterial peritonitis (SBP) is a treatable complication of decompensated cirrhosis. Coagulopathy with evidence of hyperfibrinolysis or clinically evident disseminated intravascular coagulation precludes paracentesis. Alcoholic hepatitis with fever, leucocytosis and abdominal pain should be evaluated for SBP. Oral ofloxacin is as effective as parenteral cefotaxime in treatment of SBP except for inpatients with vomiting,encephalopathy, or renal failure. Albumin is superior to hydroxyethyl starch in treatment of SBP.

  20. Intermittency measurement in two dimensional bacterial turbulence

    CERN Document Server

    Qiu, Xiang; Huang, Yongxiang; Chen, Ming; Lu, Zhiming; Liu, Yulu; Zhou, Quan

    2016-01-01

    In this paper, an experimental velocity database of a bacterial collective motion , e.g., \\textit{B. subtilis}, in turbulent phase with volume filling fraction $84\\%$ provided by Professor Goldstein at the Cambridge University UK, was analyzed to emphasize the scaling behavior of this active turbulence system. This was accomplished by performing a Hilbert-based methodology analysis to retrieve the scaling property without the $\\beta-$limitation. A dual-power-law behavior separated by the viscosity scale $\\ell_{\

  1. Factors influencing bacterial adhesion to contact lenses

    OpenAIRE

    Dutta, Debarun; Cole, Nerida; Willcox, Mark

    2012-01-01

    The process of any contact lens related keratitis generally starts with the adhesion of opportunistic pathogens to contact lens surface. This article focuses on identifying the factors which have been reported to affect bacterial adhesion to contact lenses. Adhesion to lenses differs between various genera/species/strains of bacteria. Pseudomonas aeruginosa, which is the predominant causative organism, adheres in the highest numbers to both hydrogel and silicone hydrogel lenses in vitro. The ...

  2. Dielectrophoretic assay of bacterial resistance to antibiotics

    Energy Technology Data Exchange (ETDEWEB)

    Johari, Juliana [School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK (United Kingdom); Huebner, Yvonne [School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK (United Kingdom); Hull, Judith C [School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK (United Kingdom); Dale, Jeremy W [School of Biomedical and Life Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK (United Kingdom); Hughes, Michael P [School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK (United Kingdom)

    2003-07-21

    The dielectrophoretic collection spectra of antibiotic-sensitive and antibiotic-resistant strains of Staphylococcus epidermidis have been determined. These indicate that in the absence of antibiotic treatment there is a strong similarity between the dielectric properties of sensitive and resistant strains, and that there is a significant difference between the sensitive strains before and after treatment with the antibiotic streptomycin after 24 h exposure. This method offers possibilities for the assessment of bacterial resistance to antibiotics. (note)

  3. Mathematical description of bacterial traveling pulses

    OpenAIRE

    Bournaveas, Nikolaos; Buguin, Axel; Calvez, Vincent; Perthame, Benoît; Saragosti, Jonathan; Silberzan, Pascal

    2009-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on {\\em E. coli} have shown precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at a macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic run-and-t...

  4. Mathematical Description of Bacterial Traveling Pulses

    OpenAIRE

    Saragosti, Jonathan; Calvez, Vincent; Bournaveas, Nikolaos; Buguin, Axel; Silberzan, Pascal; Perthame, Benoît

    2010-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on Escherichia coli have shown the precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at the macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic ...

  5. Mathematical description of bacterial traveling pulses

    OpenAIRE

    Bournaveas, Nikolaos; Buguin, Axel; Calvez, Vincent; Perthame, Benoît; Saragosti, Jonathan; Silberzan, Pascal

    2010-01-01

    The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on E. coli have shown precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at a macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic run-and-tumble ...

  6. Xylella Genomics and Bacterial Pathogenicity to Plants

    OpenAIRE

    Dow, J. M.; Daniels, M J

    2000-01-01

    Xylella fastidiosa, a pathogen of citrus, is the first plant pathogenic bacterium for which the complete genome sequence has been published. Inspection of the sequence reveals high relatedness to many genes of other pathogens, notably Xanthomonas campestris. Based on this, we suggest that Xylella possesses certain easily testable properties that contribute to pathogenicity. We also present some general considerations for deriving information on pathogenicity from bacterial genomics.

  7. Biomineralization and magnetism of bacterial magnetosomes

    Institute of Scientific and Technical Information of China (English)

    PAN Yongxin; DENG Chenglong; LIU Qingsong; Nikolai Petersen; ZHU Rixiang

    2004-01-01

    Magnetosomes of magnetotactic bacteria are of great interest in understanding biomineralization and possible links between organisms and geomagnetic field. Fossil magnetosomes are ubiquitous in marine and lake sediments and may significantly contribute to magnetic signals. In this review, we firstly introduce some characteristics of magnetotactic bacteria, followed by considering recent progress in magnetosome formation, magnetic measurements, and identification of bacterial magnetites in bulk sediments as well as their paleoenvironmental implications. Finally, we briefly discuss potential future breakthroughs in magnetosome studies and its applications.

  8. Small Intestinal Bacterial Overgrowth: A Comprehensive Review

    OpenAIRE

    Dukowicz, Andrew C.; Lacy, Brian E.; Levine, Gary M

    2007-01-01

    Small intestinal bacterial overgrowth (SIBO), defined as excessive bacteria in the small intestine, remains a poorly understood disease. Initially thought to occur in only a small number of patients, it is now apparent that this disorder is more prevalent than previously thought. Patients with SIBO vary in presentation, from being only mildly symptomatic to suffering from chronic diarrhea, weight loss, and malabsorption. A number of diagnostic tests are currently available, although the optim...

  9. BACTERIAL INFECTIONS IN RECIPIENTS OF RENAL ALLOGRAFT

    Directory of Open Access Journals (Sweden)

    A. V. Vatazin

    2012-01-01

    Full Text Available The study is devoted to analysis of microflora spectrum in various biological materials in patients after renal transplantation. The character of the flora is strongly dependent on the infectious process localization. Gram- positive and gram-negative bacteria are found in approximately equal proportions with a slight predominance of gram-positive flora. Isolated bacteria in most cases had pronounced polyvalent antibiotic resistance. The performed analysis substantiated recommendations for rational antibiotic therapy of various bacterial infections. 

  10. Bacterial Enhancement of Vinyl Fouling by Algae

    OpenAIRE

    Holmes, Paul E.

    1986-01-01

    The role of bacteria in the development of algae on low-density vinyl was investigated. Unidentified bacterial contaminants in unialgal stock cultures of Phormidium faveolarum and Pleurochloris pyrenoidosa enhanced, by 1 to 2 orders of magnitude, colonization of vinyl by these algae, as determined by epifluorescence microscopy counts and chlorophyll a in extracts of colonized vinyl. Colonization by bacteria always preceded that by algae. Scanning electron microscopy of the colonized Phormidiu...

  11. Bacterial Community Development in Experimental Gingivitis

    OpenAIRE

    Kistler, James O; Veronica Booth; Bradshaw, David J.; Wade, William G.

    2013-01-01

    Current knowledge of the microbial composition of dental plaque in early gingivitis is based largely on microscopy and cultural methods, which do not provide a comprehensive description of oral microbial communities. This study used 454-pyrosequencing of the V1-V3 region of 16S rRNA genes (approximately 500 bp), and bacterial culture, to characterize the composition of plaque during the transition from periodontal health to gingivitis. A total of 20 healthy volunteers abstained from oral hygi...

  12. Biocompatibility of Bacterial Cellulose Based Biomaterials

    OpenAIRE

    Omar P. Troncoso; Solene Commeaux; Torres, Fernando G.

    2012-01-01

    Some bacteria can synthesize cellulose when they are cultivated under adequate conditions. These bacteria produce a mat of cellulose on the top of the culture medium, which is formed by a three-dimensional coherent network of pure cellulose nanofibers. Bacterial cellulose (BC) has been widely used in different fields, such as the paper industry, electronics and tissue engineering due to its remarkable mechanical properties, conformability and porosity. Nanocomposites based on BC have received...

  13. PRODUCTION AND CHARACTERIZATION OF ECONOMICAL BACTERIAL CELLULOSE

    OpenAIRE

    Houssni El-Saied; Ahmed I. El-Diwany; Altaf H. Bast; Nagwa A. Atwa; Dina E. El-Ghwas

    2008-01-01

    The present study investigates the economical production of bacterial cellulose (BC) by Gluconacetobacter subsp. Xylinus (ATCC 10245) in 250 ml Erlenmeyer flasks cultivated under static conditions. The fermentation media used contained food industrial by-product liquors, such as black strap molasses solution and corn steep liquor (CSL), which represents some of the most economical carbon and nitrogen sources. However, because of the presence of undesirable components in molasses (such as colo...

  14. Diagnosis of bacterial hepatic abscess by CT

    Institute of Scientific and Technical Information of China (English)

    Cheng-Lin Wang; Xue-Jun Guo; Shui-Bo Qiu; Yi Lei; Zhi-Dong Yuan; Han-Bin Dong; Hui-An Liu

    2007-01-01

    BACKGROUND: Bacterial hepatic abscess usually is acute and progressive, often resulting in sepsis, impairment of liver function and disseminated intravascular coagulation. The mortality rate was as high as 80%in the past. For the purpose of early diagnosis and differential diagnosis of this disease, we probed the imaging manifestations and their characteristics in bacterial hepatic abscesses by CT scan. METHODS:Twenty-four lesions from 21 patients with bacterial hepatic abscesses that were conifrmed by clinical features, puncture and culture were reviewed for CT manifestations. Fourteen patients were male and 7 were female, with an average age of 56.2 years. All lesions underwent CT plain scan and three-phase enhanced scan and 15 patients underwent delayed-phase imaging. Three senior radiologists read the iflms in accordance with a standard. RESULTS: Among 24 lesions, 18 (75%) were situated in the right liver with diameters of 1.4-9.3 cm (average 4.5 cm). Nineteen (79.2%) lesions were round or sub-round in shape, and 22 (91.7%) had smooth, uninterrupted and sharp edges. All lesions showed low attenuation of less than 20 Hu. Twenty-two enhanced lesions (91.7%) had rim-shaped enhancement in the abscess wall, and 13 (54.2%) showed single or double-ring signs. Eighteen (75%) displayed honeycomb-like, grid-like or strip-like enhancement. Eighteen (75%) were regionally enhanced in the surroundings or upper or lower layers. Only 2 (8.3%) displayed a gas-liquid surface sign. CONCLUSIONS:  The CT ifndings of bacterial hepatic abscess are usually typical, and the diagnosis of the abscess is not dififcult. To precisely diagnose atypical cases, it is necessary to combine CT with clinical observations and follow-up.

  15. Bacterial Artificial Chromosome Mutagenesis Using Recombineering

    OpenAIRE

    Kumaran Narayanan; Qingwen Chen

    2011-01-01

    Gene expression from bacterial artificial chromosome (BAC) clones has been demonstrated to facilitate physiologically relevant levels compared to viral and nonviral cDNA vectors. BACs are large enough to transfer intact genes in their native chromosomal setting together with flanking regulatory elements to provide all the signals for correct spatiotemporal gene expression. Until recently, the use of BACs for functional studies has been limited because their large size has inherently presented...

  16. Collective decision making in bacterial viruses.

    Science.gov (United States)

    Weitz, Joshua S; Mileyko, Yuriy; Joh, Richard I; Voit, Eberhard O

    2008-09-15

    For many bacterial viruses, the choice of whether to kill host cells or enter a latent state depends on the multiplicity of coinfection. Here, we present a mathematical theory of how bacterial viruses can make collective decisions concerning the fate of infected cells. We base our theory on mechanistic models of gene regulatory dynamics. Unlike most previous work, we treat the copy number of viral genes as variable. Increasing the viral copy number increases the rate of transcription of viral mRNAs. When viral regulation of cell fate includes nonlinear feedback loops, very small changes in transcriptional rates can lead to dramatic changes in steady-state gene expression. Hence, we prove that deterministic decisions can be reached, e.g., lysis or latency, depending on the cellular multiplicity of infection within a broad class of gene regulatory models of viral decision-making. Comparisons of a parameterized version of the model with molecular studies of the decision structure in the temperate bacteriophage lambda are consistent with our conclusions. Because the model is general, it suggests that bacterial viruses can respond adaptively to changes in population dynamics, and that features of collective decision-making in viruses are evolvable life history traits.

  17. Patterning bacterial communities on epithelial cells.

    Directory of Open Access Journals (Sweden)

    Mohammed Dwidar

    Full Text Available Micropatterning of bacteria using aqueous two phase system (ATPS enables the localized culture and formation of physically separated bacterial communities on human epithelial cell sheets. This method was used to compare the effects of Escherichia coli strain MG1655 and an isogenic invasive counterpart that expresses the invasin (inv gene from Yersinia pseudotuberculosis on the underlying epithelial cell layer. Large portions of the cell layer beneath the invasive strain were killed or detached while the non-invasive E. coli had no apparent effect on the epithelial cell layer over a 24 h observation period. In addition, simultaneous testing of the localized effects of three different bacterial species; E. coli MG1655, Shigella boydii KACC 10792 and Pseudomonas sp DSM 50906 on an epithelial cell layer is also demonstrated. The paper further shows the ability to use a bacterial predator, Bdellovibriobacteriovorus HD 100, to selectively remove the E. coli, S. boydii and P. sp communities from this bacteria-patterned epithelial cell layer. Importantly, predation and removal of the P. Sp was critical for maintaining viability of the underlying epithelial cells. Although this paper focuses on a few specific cell types, the technique should be broadly applicable to understand a variety of bacteria-epithelial cell interactions.

  18. Acute otitis media and acute bacterial sinusitis.

    Science.gov (United States)

    Wald, Ellen R

    2011-05-01

    Acute otitis media and acute bacterial sinusitis are 2 of the most common indications for antimicrobial agents in children. Together, they are responsible for billions of dollars of health care expenditures. The pathogenesis of the 2 conditions is identical. In the majority of children with each condition, a preceding viral upper respiratory tract infection predisposes to the development of the acute bacterial complication. It has been shown that viral upper respiratory tract infection predisposes to the development of acute otitis media in 37% of cases. Currently, precise microbiologic diagnosis of acute otitis media and acute bacterial sinusitis requires performance of tympanocentesis in the former and sinus aspiration in the latter. The identification of a virus from the nasopharynx in either case does not obviate the need for antimicrobial therapy. Furthermore, nasal and nasopharyngeal swabs are not useful in predicting the results of culture of the middle ear or paranasal sinus. However, it is possible that a combination of information regarding nasopharyngeal colonization with bacteria and infection with specific viruses may inform treatment decisions in the future.

  19. Carbon nanotubes as in vivo bacterial probes

    Science.gov (United States)

    Bardhan, Neelkanth M.; Ghosh, Debadyuti; Belcher, Angela M.

    2014-09-01

    With the rise in antibiotic-resistant infections, non-invasive sensing of infectious diseases is increasingly important. Optical imaging, although safer and simpler, is less developed than other modalities such as radioimaging, due to low availability of target-specific molecular probes. Here we report carbon nanotubes (SWNTs) as bacterial probes for fluorescence imaging of pathogenic infections. We demonstrate that SWNTs functionalized using M13 bacteriophage (M13-SWNT) can distinguish between F‧-positive and F‧-negative bacterial strains. Moreover, through one-step modification, we attach an anti-bacterial antibody on M13-SWNT, making it easily tunable for sensing specific F‧-negative bacteria. We illustrate detection of Staphylococcus aureus intramuscular infections, with ~3.4 × enhancement in fluorescence intensity over background. SWNT imaging presents lower signal spread ~0.08 × and higher signal amplification ~1.4 × , compared with conventional dyes. We show the probe offers greater ~5.7 × enhancement in imaging of S. aureus infective endocarditis. These biologically functionalized, aqueous-dispersed, actively targeted, modularly tunable SWNT probes offer new avenues for exploration of deeply buried infections.

  20. Bacterial Chemotaxis with a Moving Target

    Science.gov (United States)

    Dominick, Corey

    2015-03-01

    Most chemotaxis studies so far have been conducted in a quiescent fluid with a well-defined chemical gradient. Such experiments may be appropriate for studying enteric bacteria, such as Escherichia coli, but the environment it provides is very different from that typically encountered by marine bacteria. Herein we describe an experiment in which marine bacterium Vibrio alginolyticusis subject to stimulation by a small moving target. A micropipette of the tip size <1 ?m is used to slowly release a chemoattractant, serine, at different concentrations. The pipette is made to move with different patterns and speeds, ranging from 0 to 100 ?m/s; the latter is about twice the bacterial swimming speed. We found that if the pipette is moved slowly, with 1/4 of bacterial swimming speed, cells accumulate near the tip region but when it is moved with speed greater than 1/2 the bacterial swimming speed, cells trail behind the pipette over a large distance. The behaviors observed in V. alginolyticusare significantly different from E. coli, suggesting that the former is a better chemotaxer in a changing environment.