bluuebunny/crossref_metadata_2025 huggingface dataset:
Développement vocationnel de l’adulte : vers un modèle en « escalier »
Authors: Riverin-Simard Danielle
Published: July 2012

Le présent article décrit un essai de modèle de développement vocationnel qui pourrait illustrer son processus, graphiquement, par un escalier. Pour décrire ce modèle, on indique tout d’abord sa situation « théorique » ainsi que ses postulats généraux; en un deuxième temps, on explique le choix de la durée de chaque stade, la nature de ces stades alternatifs, les conditions facilitant le passage d’un stade à un autre, ainsi que divers concepts connexes.
Recherche d’une explication aux abandons de cours en mathématiques au Cégep
Authors: Ste-Marie Monique , Winsberg Suzanne
Published: July 2012

L’objectif de cette recherche était de voir si une des raisons au « drop out » en mathématiques pouvait se trouver dans l’attitude des étudiants face aux cours de mathématiques et face aux études collégiales en général. Nous avons comparé un groupe de persévérants et un groupe de décrocheurs en mathématiques quant à l’importance qu’ils accordaient à ces cours et aux études, l’intérêt qu’ils y portaient et le degré de difficulté qu’ils en percevaient. Ces facteurs furent mesurés à l’aide d’une adaptation française du différenciateur sématique de Geis. Les résultats ont montré qu’il n’y a pas eu de différence entre les deux groupes au niveau de l’attitude face aux cours de mathématiques, mais qu’il y a eu une différence quant à l’attitude face aux études en général.
Les motivations exprimées dans les manuels scolaires du Québec
Authors: Salamé Ramzi F. , Désilets-Cayer Louise
Published: July 2012

Cette recherche consiste en l’analyse du contenu motivationnel des textes de six manuels de lecture parmi les plus communément utilisés au Québec par les enfants francophones de 2e et 4e années du niveau primaire. Elle s’inspire de la tradition de recherches en motivation humaine commencées il y a trente ans par D.C. McClelland et ses collaborteurs. L’objectif en est de recenser la fréquence d’apparition des thèmes motivationnels pour les besoins d’auto-préservation tels que les besoins primaires et de sécurité, et les besoins psycho-sociaux, tels que l’affiliation, la réalisation et le pouvoir. Les résultats démontrent un taux élevé de la motivation au pouvoir, suivi de la motivation à la sécurité, des motivations secondaires et de l’affiliation, au détriment de la motivation à la réalisation qui se retrouve en dernière place, exception faite d’un seul manuel de lecture. Par rapport à ceux de 2e année, les textes de 4e année sont moins denses en thèmes bien qu’ils soient plus élaborés, plus descriptifs ou plus répétitifs. La partie critique présente quelques explications pour les résultats et des indications pour des recherches futures.
Une banque d’objectifs et d’items pour l’apprentissage de la lecture à la maternelle et au premier cycle du cours primaire
Authors: Nézet-Séguin Claudine , Séguin Serge P.
Published: July 2012

Pendant huit ans, le Groupe de recherche en évaluation des curriculum (GREC) et la Commission des Mille-Îles (C.S.M.I.) ont poursuivi une recherche qui consistait principalement à élaborer et à expérimenter sur le terrain un curriculum pour l’apprentissage de la lecture au niveau primaire. Au compte des productions de cette recherche, une banque a été mise au point pour regrouper fonctionnellement les 84 objectifs d’apprentissage tracés dans ce curriculum pour la maternelle et pour le premier cycle du primaire, ainsi que 283 items validés pour mesurer ces objectifs. Cette banque, ici décrite, regroupe ces objectifs et ces items de façon à les rendre accessibles et utiles aux enseignants, aux responsables scolaires et aux chercheurs en éducation.
L’impact des facteurs scolaires sur la réussite des étudiants au niveau secondaire : perspectives d’analyse et avenues de recherche
Authors: Trottier Claude
Published: July 2012

L’objectif de cet article est de discuter des perspectives d’analyse et d’identifier certaines avenues de recherche relatives à l’impact des facteurs scolaires sur la réussite des étudiants. L’auteur estime que l’on a eu tendance au cours des années 1970 à tirer des conclusions hâtives et prématurées sur l’effet de ces facteurs, soit parce qu’on a proposé une interprétation de résultats de recherche qui allait parfois au-delà de ce que les données permettaient d’affirmer, soit parce qu’on n’a pas su identifier et conceptualiser de façon adéquate les processus scolaires internes susceptibles d’influencer le rendement scolaire des étudiants.
L’analyse des données axée sur les développements éducatifs
Authors: Dassa Clément
Published: July 2012

L’auteur présente une nouvelle méthode1 d’analyse des données longitudinales qui pallie les lacunes des techniques et des modèles existants. À partir des caractéristiques propres au changement dans le domaine éducatif et plus particulièrement à ses aspects cognitifs et affectifs, l’importance d’une information portant aussi bien sur la structure globale des données que sur les profils individuels est mise en évidence. La famille de modèles proposée répond à ce besoin en intégrant le domaine des courbes de développement au domaine de l’analyse factorielle.

1. Cette étude a fait l’objet d’une communication au Congrès International de l’A.S.U. à Nancy (France), le 3 juin 1981.
Les facteurs associés à l’intervention des enseignants en activité physique
Authors: Desrosiers Pauline
Published: July 2012

Le but de l’étude est d’examiner le degré de relation entre l’intensité d’intervention des enseignants ayant acquis une formation de base en activité physique au primaire et des facteurs ayant trait aux caractéristiques personnelles des enseignants et à leur contexte de travail. L’étude a été effectuée auprès de 79 sujets. Les facteurs examinés, considérés de façon isolée, se sont avérés en faible relation avec la fréquence et la durée d’intervention. Une plus grande part de l’intervention peut être expliquée en considérant de façon simultanée plusieurs facteurs.
L’administrateur scolaire par rapport à ses homonymes des secteurs public et privé
Authors: Brunet Luc , Bordeleau Yvan
Published: July 2012

Le but de cet article est de présenter les résultats obtenus sur le style de gestion du personnel auprès de trois groupes de gestionnaires des milieux scolaire, privé et de la fonction publique. Les résultats démontrent que ces gestionnaires présentent des styles de leadership qui diffèrent. Les gestionnaires scolaires et ceux de la fonction publique présentent des profils de leadership qui peuvent s’apparenter, tandis que les gestionnaires du secteur privé présentent un profil complètement à part.
Une école de verre : transparence spatiale et distance sociale
Authors: Saint-Jacques Marcel
Published: July 2012

Le présent article veut mettre en évidence le changement dans les relations quand une école s’ouvre à son milieu. L’utilisation et l’application du cadre théorique de Bateson et de Watzlawick et al., concernant les modèles de relations, permettent de faire une analyse culturelle qualitative de la dynamique d’une école primaire et d’apporter une contribution concrète à l’école communautaire et responsable des années 1980.
Le rapport de la Commission d’étude sur la formation des adultes et son intérêt pour les sciences de l’éducation
Authors: Haramein Ali , Thérien Michel , Tremblay Nicole
Published: July 2012

Cette étude critique du Rapport de la Commission d’étude sur la formation des adultes est divisée en trois parties. Elle présente des pistes d’analyse possibles du Rapport, développe quelques points importants qui irriguent l’argumentation du Rapport et constituent les fondements majeurs d’un grand nombre de ses analyses et, enfin, souligne les points qui intéressent les sciences de l’éducation. À cette étude s’ajoutent quelques commentaires de la présidente de la Commission d’étude sur la formation des adultes.
Quelques précisions sur l’entrevue clinique pour fin de diagnostic
Authors: Ska Bernadette
Published: July 2012

Dans cet article, l’auteure soumet aux lecteurs quelques réflexions sur l’entrevue clinique. Un rappel de l’origine de la méthode est suivi de la présentation de quelques unes de ses caractéristiques. L’auteure y souligne la situation particulière des partenaires, les objectifs et le cheminement d’une telle entrevue. Elle aborde ensuite quelques problèmes méthodologiques concernant les questions de l’interviewer et les réponses de l’interviewé. Enfin, l’auteure présente quelques suggestions plus pratiques sur la façon de mener une entrevue diagnostique.
Changements morphologiques de la clientèle estudiantine de l’Université de Montréal au cours de la période 1950-1980
Authors: Van Dromme Léon
Published: July 2012

L’auteur étudie, à partir de données quantitatives que fournissent cinq enquêtes effectuées au cours de la période 1950-1980, les transformations morphologiques qu’a connues la population estudiantine de l’Université de Montréal ces trente dernières années. Les variables retenues sont : les effectifs (temps plein, temps partiel), l’origine sociale, le statut civil, le sexe et l’âge. Il est fait état de comparaisons sous chacune de ces variables, en partant de ces enquêtes, et de comparaisons avec les données que fournissent d’autres recherches ou enquêtes. Les changements morphologiques mis en évidence par ces comparaisons sont discutés puis rapportés au contexte d’évolution du système d’éducation d’ensemble.
Changing household consumption to address climate change: social scientific insights and challenges
Authors: Shwom Rachael , Lorenzen Janet A.
Published: July 2012

Reducing greenhouse gas (GHG)‐intensive consumption can be an important route to reducing the GHG emissions that cause climate change. To effectively mitigate climate change by reforming human consumption patterns we must have a comprehensive understanding of the linkages between consumption and climate change and how consumption may be altered. This article begins by reviewing the empirical research that links consumption and GHG emissions and identifies GHG‐intensive actions and systems. We then identify four social science understandings of consumption: the consumer as homo economicus, the predictably irrational consumer, the locked‐in consumer, and the socially organized consumer. These understandings of consumption that emerge from economics, psychology, anthropology, and sociology lead us to different conclusions on what can be done to change consumption patterns to mitigate climate change. To effectively transform consumption, we advocate the implementation of a range of policy solutions and explore several levers for managing change. WIREs Clim Change 2012 doi: 10.1002/wcc.182

This article is categorized under:

Perceptions, Behavior, and Communication of Climate Change > Behavior Change and Responses
Intronic features that determine the selection of the 3′ splice site
Authors: Pérez‐Valle Jorge , Vilardell Josep
Published: July 2012

Most eukaryotic primary transcripts include segments, or introns, that will be accurately removed during RNA biogenesis. This process, known as pre‐messenger RNA splicing, is catalyzed by the spliceosome, accurately selecting a set of intronic marks from others apparently equivalent. This identification is critical, as incorrectly spliced RNAs can be toxic for the organism. One of these marks, the dinucleotide AG, signals the intronic 3′ end, or 3′ splice site (ss). In this review we will focus on those intronic features that have an impact on 3′ ss selection. These include the location and type of neighboring sequences, and their distance to the 3′ end. We will see that their interplay is needed to select the right intronic end, and that this can be modulated by additional intronic elements that contribute to alternative splicing, whereby diverse RNAs can be generated from identical precursors. This complexity, still poorly understood, is fundamental for the accuracy of gene expression. In addition, a clear knowledge of 3′ ss selection is needed to fully decipher the coding potential of genomes. WIREs RNA 2012 doi: 10.1002/wrna.1131

This article is categorized under:

RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems

RNA Processing > Splicing Regulation/Alternative Splicing

Regulatory RNAs/RNAi/Riboswitches > Riboswitches
Examination of aluminium and zinc plasmas from an inductive furnace by spectroscopy
Authors: BURM K. T. A. L.
Published: July 2012

The production of aluminium and zinc plasmas for the deposition of coatings upon steel strip is monitored by optical emission spectroscopy measurements. The plasma is created from an inductive source. The atom and the ion densities as well as the electron temperature are obtained such that the plasma can be characterized. It will be shown that the obtained plasmas are typically highly ionized and deviate from thermal equilibrium.
SOME SECOND THOUGHTS ON PROGRESSIVISM AND RIGHTS
Authors: Eisenach Eldon J.
Published: July 2012

After summarizing the ways in which Progressive intellectuals attacked individualist understandings of rights and mechanistic understandings of constitutional government, a series of second thoughts on this argument are pursued. The first centers on the ways in which progressivism differed from New Deal liberalism, especially regarding “big government.” Progressive understandings of politics rest on a distinction between “government(s)” and “state,” derived from Tocqueville and Lincoln’s understandings of popular sovereignty. Secondly, this distinction is reinforced by their stress on an articulate and coherent public opinion that would provide democratic legitimacy to all forms of governing institutions, both “public” and “private,” that serve the common good. The Civil War experience was their model, one which they first thought would be reincarnated in the preparation for World War I. Given both private and public assaults on free speech, Progressives in the 1920s often led the movement for protections of civil liberties and for a new respect paid to the First Amendment. The conclusion examines the continuities and discontinuities of Progressive political thought in contemporary political discourse.
Night-time Lookout Duty: The Role of Ambient Light Levels and Dark Adaptation
Authors: Wynn Tony , Howarth Peter A. , Kunze Bert R.
Published: July 2012

The aim of this research was to clarify and quantify the demands of the working environment and watch-keeping regime for large commercial ships in relation to dark adaptation. The night lookout task requires the identification of the relatively bright navigational lights of other ships against the dark background of the sky and sea. The probability of detection is determined by the ambient lighting conditions on the bridge and the dark adapted state of vision. Light levels were such that threshold sensitivity (after 15 minutes) was reduced by around 2 log units in comparison to complete darkness. This has implications for the effective range of navigational lights at sea as defined in regulations. The intensity and position of navigation lights on larger vessels is such that the sensitivity of the eye under typical bridge conditions is likely to be sufficient for their visibility to be acceptable. This may not be the case for less well lit small craft.
The neurobiology of oppositional defiant disorder and conduct disorder: Altered functioning in three mental domains
Authors: Matthys Walter , Vanderschuren Louk J. M. J. , Schutter Dennis J. L. G.
Published: July 2012

This review discusses neurobiological studies of oppositional defiant disorder and conduct disorder within the conceptual framework of three interrelated mental domains: punishment processing, reward processing, and cognitive control. First, impaired fear conditioning, reduced cortisol reactivity to stress, amygdala hyporeactivity to negative stimuli, and altered serotonin and noradrenaline neurotransmission suggest low punishment sensitivity, which may compromise the ability of children and adolescents to make associations between inappropriate behaviors and forthcoming punishments. Second, sympathetic nervous system hyporeactivity to incentives, low basal heart rate associated with sensation seeking, orbitofrontal cortex hyporeactiviy to reward, and altered dopamine functioning suggest a hyposensitivity to reward. The associated unpleasant emotional state may make children and adolescents prone to sensation-seeking behavior such as rule breaking, delinquency, and substance abuse. Third, impairments in executive functions, especially when motivational factors are involved, as well as structural deficits and impaired functioning of the paralimbic system encompassing the orbitofrontal and cingulate cortex, suggest impaired cognitive control over emotional behavior. In the discussion we argue that more insight into the neurobiology of oppositional defiance disorder and conduct disorder may be obtained by studying these disorders separately and by paying attention to the heterogeneity of symptoms within each disorder.
Photo-Opera:La fanciulla del Westand the staging souvenir
Authors: LOCKHART ELLEN
Published: July 2012

Giacomo Puccini'sLa fanciulla del West, premièred in New York, 1910, represents what we might call a photographic turn in the later Puccini. For one, itsmise-en-scènewas given textual status equivalent to that of libreto and music. The opera's first costumes and sets were crafted for the Metropolitan Opera House from stills of the source play,The Girl of the Golden Westby David Belasco. What is more, the circulation of photographs and eventually a staginglivretensured thatLa fanciullalooked the same in every iteration. In this model, authorship and performance become acts of remediation between layers of machine-generated souvenirs. BothThe GirlandLa fanciullabear the marks of their mediated nature:The Girlsuggests a fragile third dimension through the use of panoramas and scrims; during its famous Act I sunsetLa fanciullamoves from a realist sound-world towards a fantasy one, the latter marked by disembodied humming from a tenor chorus and even a new instrument, thefonica, designed by Puccini to be sounded by electricity. This essay suggests that the purported resistance of Puccinian opera to revisionist staging has its roots in critiques of realism's ‘statistical’ universe, and the perceptual modes held to be available to mass-consumed art.
Puccini, in the distance
Authors: SCHWARTZ ARMAN
Published: July 2012

This essay charts the contours of a ‘second practice’ in Puccini's corpus. Whereas his operas from the 1890s are fuelled by a longing for unmediated access to empirical reality, his later works unleash a variety of distant sounds that unsettle the aesthetics ofverismoopera. These sounds, which draw on the ontology of wireless transmission just as surely as his earlier works do on that of phonographic transcription, find their fullest expression inSuor Angelica. The notorious Marian apparition that concludes that opera has long been mocked and explained away, and no wonder: for, if we attempt to take the miracle seriously, we may (like Puccini himself, in the years followingMadama Butterfly) begin to doubt whether modernism ever was an art of confidence and disenchantment.
Evaluation of Active Mortality Surveillance System Data for Monitoring Hurricane-Related Deaths—Texas, 2008
Authors: Choudhary Ekta , Zane David F. , Beasley Crystal , Jones Russell , Rey Araceli , Noe Rebecca S. , Martin Colleen , Wolkin Amy F. , Bayleyegn Tesfaye M.
Published: July 2012

Introduction

The Texas Department of State Health Services (DSHS) implemented an active mortality surveillance system to enumerate and characterize hurricane-related deaths during Hurricane Ike in 2008. This surveillance system used established guidelines and case definitions to categorize deaths as directly, indirectly, and possibly related to Hurricane Ike.

Objective

The objective of this study was to evaluate Texas DSHS' active mortality surveillance system using US Centers for Disease Control and Prevention's (CDC) surveillance system evaluation guidelines.

Methods

Using CDC's Updated Guidelines for Surveillance System Evaluation, the active mortality surveillance system of the Texas DSHS was evaluated. Data from the active mortality surveillance system were compared with Texas vital statistics data for the same time period to estimate the completeness of reported disaster-related deaths.

Results

From September 8 through October 13, 2008, medical examiners (MEs) and Justices of the Peace (JPs) in 44 affected counties reported deaths daily by using a one-page, standardized mortality form. The active mortality surveillance system identified 74 hurricane-related deaths, whereas a review of vital statistics data revealed only four deaths that were hurricane-related. The average time of reporting a death by active mortality surveillance and vital statistics was 14 days and 16 days, respectively.

Conclusions

Texas's active mortality surveillance system successfully identified hurricane-related deaths. Evaluation of the active mortality surveillance system suggested that it is necessary to collect detailed and representative mortality data during a hurricane because vital statistics do not capture sufficient information to identify whether deaths are hurricane-related. The results from this evaluation will help improve active mortality surveillance during hurricanes which, in turn, will enhance preparedness and response plans and identify public health interventions to reduce future hurricane-related mortality rates.

Choudhary E, Zane DF, Beasley C, Jones R, Rey A, Noe RS, Martin C, Wolkin AF, Bayleyegn TM. Evaluation of active mortality surveillance system data for monitoring hurricane-related deaths, Texas, 2008. Prehosp Disaster Med. 2012;27(4):1-6.
Correlates of Perceived Care Comfort with an EMS Professional Having a Legal Conviction
Authors: Blau Gary , Gibson Gregory
Published: July 2012

Objectives

The first objective was to examine the outcome of how comfortable a potential EMS-caller would be receiving care from an out-of-hospital-care EMS professional who might have a legal conviction. A second objective was to test for correlates that would explain this outcome.

Methods

In the autumn of 2010, a structured phone survey was conducted. To maximize geographical representation across the contiguous United States, a clustered, stratified sampling strategy was used based upon US Postal Service zip codes.

Results

Of the 2,443 phone calls made, 1,051 (43%) full survey responses were obtained. Data cleaning efforts reduced the total to 929 in the final model regression analysis. Results revealed significant public discomfort in receiving care from EMS professionals who may have such a conviction. In addition, respondents who are less educated and older more strongly (1) agree that EMS professionals should have their licenses revoked for wrongdoing; (2) agree EMS professionals should be screened before being hired; (3) perceive EMS credentials to be important; (4) support a lawsuit for improper care; and (5) are collectively less comfortable with being cared for by an EMS professional who may have a legal conviction. Reliable scales were found for future research use.

Conclusion

There is significant public discomfort in receiving care from EMS professionals who may have a legal conviction. The results of this study provide increased impetus for the careful screening of EMS professionals before they are hired or allowed to be volunteers. Beyond this due diligence, the results serve as a reminder for increased EMS provider awareness of the importance of exhibiting professionalism when dealing with the public.

Blau G, Gibson G. Correlates of perceived care comfort with an EMS professional having a legal conviction. Prehosp Disaster Med. 2012;27(4):1-6.
Treating molecules in arbitrary spin states using the parametric two-electron reduced-density-matrix method
Authors: Schwerdtfeger Christine A. , Mazziotti David A.
Published: July 2012

Minimizing the electronic energy with respect to a parameterized two-electron reduced density matrix (2-RDM) is known as a parametric variational 2-RDM method. The parametric 2-RDM method with the M 2-RDM parametrization [D. A. Mazziotti, Phys. Rev. Lett. 101, 253002 (2008)]10.1103/PhysRevLett.101.253002 is extended to treat molecules in arbitrary spin states. Like its singlet counterpart, the M parametric 2-RDM method for arbitrary spin states is derived using approximate N-representability conditions, which allow it to capture more correlation energy than coupled cluster with single and double excitations at a lower computational cost. We present energies, optimized bond lengths, potential energy curves, and occupation numbers for a set of molecules in a variety of spin states using the M and K parametric 2-RDM methods as well as several wavefunction methods. We show that the M parametric 2-RDM method can describe bond breaking of open-shell molecules like triplet \documentclass[12pt]{minimal}\begin{document}$\rm {B_2}$\end{document}B2 and singlet and triplet \documentclass[12pt]{minimal}\begin{document}$\rm {OH^+}$\end{document} OH + even in the presence of strong correlation. Finally, the computed 2-RDMs are shown to be nearly N-representable at both equilibrium and non-equilibrium geometries.
Branching ratio measurements of the predissociation of 12C16O by time-slice velocity-map ion imaging in the energy region from 108 000 to 110 500 cm−1
Authors: Gao Hong , Song Yu , Yang Lei , Shi Xiaoyu , Yin Qing-Zhu , Ng C. Y. , Jackson William M.
Published: July 2012

Direct branching ratio measurements of the three lowest dissociation channels of 12C16O that produce C(3P) + O(3P), C(1D) + O(3P), and C(3P) + O(1D) are reported in the vacuum ultraviolet region from 108 000 cm−1 (92.59 nm) to 110 500 cm−1 (90.50 nm) using the time-slice velocity-map ion imaging and nonlinear resonant four-wave mixing techniques. Rotationally, resolved carbon ion yield spectra for both 1Σ+ and 1Π bands of CO in this region have been obtained. Our measurements using this technique show that the branching ratio in this energy region, especially the relative percentages of the two spin-forbidden channels, is strongly dependent on the particular electronic and vibrational energy levels of CO that are excited.
The role of the magnetic orbitals in the calculation of the magnetic coupling constants from multireference perturbation theory methods
Authors: Angeli Celestino , Calzado Carmen J.
Published: July 2012

The use of multireference perturbation theory (MRPT) for the calculation of the magnetic coupling in binuclear complexes has shown to give poor results if applied on a minimal active space complete active space self-consistent field (CASSCF) wavefunction. In this work, we identify the origin of this problem in the starting CASSCF orbitals, which are exceedingly localized on the metal atoms. Focusing on the case of antiferromagnetic systems, it is shown that the form of the active orbitals has a dramatic effect on the relative description of the neutral and ionic structures. Finally, a simple and computational inexpensive strategy is proposed for the calculation of a set of magnetic orbitals describing in a more balanced way the neutral and ionic structures. The use of these orbitals, instead the CASSCF ones, in minimal active space MRPT2 calculations leads to a marked improvement of the J values, which become in reasonable agreement with those obtained with the expensive high level difference dedicated configuration interaction approach and with the experimental values.
Plasma screening effects on the energies of hydrogen atom
Authors: Soylu A.
Published: July 2012

A more general exponential cosine screened Coulomb potential is used for the first time to investigate the screening effects on the hydrogen atom in plasmas. This potential is examined for four different cases that correspond to four different type potentials when the different parameters are used in the potential within the framework of the well-known asymptotic iteration method. By solving the corresponding the radial Schrödinger equation with the screened and exponential cosine screened Coulomb potentials and comparing the obtained energy eigenvalues with the results of other studies, the applicability of the method to this kind of plasma physics problem is shown. The energy values of more general exponential cosine screened Coulomb potential are presented for various parameters in the potential. One of the advantages of the present potential is that it exhibits stronger screening effect than that of the exponential cosine screened Coulomb potential and it is also reduced to screened Coulomb and exponential cosine screened Coulomb as well as Coulomb potentials for special values of parameters. The parameters in the potential would be useful to model screening effects which cause an increase or decrease in the energy values of hydrogen atom in both Debye and quantum plasmas and in this manner this potential would be useful for the investigations of the atomic structure and collisions in plasmas.
Growth direction dependence of the electron spin dynamics in {111} GaAs quantum wells
Authors: Ye H. Q. , Wang G. , Liu B. L. , Shi Z. W. , Wang W. X. , Fontaine C. , Balocchi A. , Amand T. , Lagarde D. , Renucci P. , Marie X.
Published: July 2012

The electron spin dynamics is studied by time-resolved Kerr rotation in GaAs/AlGaAs quantum wells embedded in NIP structures grown on (111)A or (111)B-oriented substrates. In both cases the spin lifetimes are significantly increased by applying an external electric field, but this field has to point along the growth direction for structures grown on (111)A and opposite to it for the ones grown on (111)B. This extended electron spin lifetime is the result of the suppression of the D’yakonov-Perel spin relaxation mechanism [Sov. Phys. Solid State 13, 3023 (1972)] due to the cancellation effect of the internal Dresselhaus term [Phys. Rev. 100, 580 (1955)] with the external electric field induced Rashba one [J. Phys. C 17, 6039 (1984)], both governing the conduction band spin-orbit splitting. These results demonstrate the key role played by the growth direction in the design of spintronic devices.
Numerical simulation of thin-shell direct drive DHe3-filled capsules fielded at OMEGA
Authors: Miles A. R. , Chung H.-K. , Heeter R. , Hsing W. , Koch J. A. , Park H.-S. , Robey H. F. , Scott H. A. , Tommasini R. , Frenje J. , Li C. K. , Petrasso R. , Glebov V. , Lee R. W.
Published: July 2012

Thin-shell deuterium-helium-3 (DHe3) filled glass capsules on the Omega laser provide a fast-implosion experimental platform for developing separate time-resolved measurements of ion, electron, and radiation temperatures in nonequilibrium plasmas. Dynamically significant non-local thermodynamic equilibrium (NLTE) conditions are created by the addition of xenon dopant to the DHe3 gas fill, in quantities sufficient to have an impact on yields, compression, and cooling rates. The high-Z dopant dramatically increases the radiative cooling rate in the plasma, allowing it to collapse in compressions that can be an order of magnitude higher than in undoped capsules. A baseline LASNEX simulation model using detailed configuration accounting NLTE atomic physics shows very good agreement with the data for doped as well as undoped capsules, while other models either underpredict or overpredict the radiative cooling enhancement. The baseline model captures the behavior of the capsule when the D:He3 ratio is varied well away from equimolar, suggesting no yield anomaly with either nearly pure deuterium or He3 fills. Variation of the electron-ion coupling in the baseline simulation model shows agreement with the data for a coupling multiplier that is within 20% of unity. Reliably inferring electron-ion coupling strength from the data is complicated by uncertainties in the hydrodynamic mix and other parameters, but many of these can be mitigated in follow-on experiments at the National Ignition Facility.
Impact ignition of aluminum-teflon based energetic materials impregnated with nano-structured carbon additives
Authors: Kappagantula Keerti , Pantoya Michelle L. , Hunt Emily M.
Published: July 2012

The inclusion of graphene into composite energetic materials to enhance their performance is a new area of interest. Studies have shown that the addition of graphene significantly enhances the thermal transport properties of an energetic composite, but how graphene influences the composite’s ignition sensitivity has not been studied. The objective of this study is to examine the influence of carbon additives in composite energetic material composed of aluminum and polytetrafluoroethylene (Teflon™) on ignition sensitivity due to low velocity, drop weight impact. Specifically, three forms of carbon additives were investigated and selected based on different physical and structural properties: spherically shaped amorphous nano particles of carbon, cylindrically shaped multi walled carbon nanotubes, and sheet like graphene flakes. Results show an interesting trend: composites consisting of carbon nanotubes are significantly more sensitive to impact ignition and require the lowest ignition energy. In contrast, graphene is least sensitive to ignition exhibiting negligible reduction in ignition energy with low concentrations of graphene additive. While graphene does not significantly sensitize the energetic composite to ignition, graphene does, however, result in greater overall reactivity as observed through images of the reaction. The enhanced thermal transport properties of graphene containing composites may promote greater energy transport once ignited, but those properties do not also increase ignition sensitivity. These results and the understanding of the structural arrangement of particles within a composite as a key parameter affecting impact ignition sensitivity will have an impact on the safe handling and use of composite energetic materials.
Terahertz wavefront measurement with a Hartmann sensor
Authors: Richter H. , Greiner-Bär M. , Deßmann N. , Pfund J. , Wienold M. , Schrottke L. , Hey R. , Grahn H. T. , Hübers H.-W.
Published: July 2012

The measurement of the wavefront of a terahertz (THz) beam is essential for the development of any optical instrument operating at THz frequencies. We have realized a Hartmann wavefront sensor for the THz frequency range. The sensor is based on an aperture plate consisting of a regular square pattern of holes and a microbolometer camera. The performance of the sensor is demonstrated by characterizing the wavefront of a THz beam emitted by a quantum-cascade laser. The wavefront determined by the sensor agrees well with that expected from a Gaussian-shaped beam. The spatial resolution is 1 mm, and a single-wavefront measurement takes less than 1 s.
Hysteresis mechanism in low-voltage and high mobility pentacene thin-film transistors with polyvinyl alcohol dielectric
Authors: Wang Wei , Ma Dongge , Pan Su , Yang Yudan
Published: July 2012

In this letter, the hysteresis mechanism of organic thin-film transistors (OTFTs) with polyvinyl alcohol (PVA) as gate dielectric is studied. By examining OTFTs with a blocking polymer layer between gate and PVA or between channel and PVA, we confirm that the origin of the hysteresis is caused by the holes injected from the gate and/or from the channel and trapped in the interface of pentacene/PVA and the PVA bulk. A method is proposed to reduce the hysteresis. As a result, a pentacene OTFT with free-hysteresis and high mobility of 1.8 cm2/Vs is achieved by a triple-layer polymer dielectric at low-operating voltages.
Communication: On the origin of the non-Arrhenius behavior in water reorientation dynamics
Authors: Stirnemann Guillaume , Laage Damien
Published: July 2012

We combine molecular dynamics simulations and analytic modeling to determine the origin of the non-Arrhenius temperature dependence of liquid water's reorientation and hydrogen-bond dynamics between 235 K and 350 K. We present a quantitative model connecting hydrogen-bond exchange dynamics to local structural fluctuations, measured by the asphericity of Voronoi cells associated with each water molecule. For a fixed local structure the regular Arrhenius behavior is recovered, and the global anomalous temperature dependence is demonstrated to essentially result from a continuous shift in the unimodal structure distribution upon cooling. The non-Arrhenius behavior can thus be explained without invoking an equilibrium between distinct structures. In addition, the large width of the homogeneous structural distribution is shown to cause a growing dynamical heterogeneity and a non-exponential relaxation at low temperature.
Nitrogen-polar core-shell GaN light-emitting diodes grown by selective area metalorganic vapor phase epitaxy
Authors: Li Shunfeng , Wang Xue , Fündling Sönke , Erenburg Milena , Ledig Johannes , Wei Jiandong , Wehmann Hergo H. , Waag Andreas , Bergbauer Werner , Mandl Martin , Strassburg Martin , Trampert Achim , Jahn Uwe , Riechert Henning , Jönen Holger , Hangleiter Andreas
Published: July 2012

Homogeneous nitrogen-polar GaN core-shell light emitting diode (LED) arrays were fabricated by selective area growth on patterned substrates. Transmission electron microscopy measurements prove the core-shell structure of the rod LEDs. Depending on the growth facets, the InGaN/GaN multi-quantum wells (MQWs) show different dimensions and morphology. Cathodoluminescence (CL) measurements reveal a MQWs emission centered at about 415 nm on sidewalls and another emission at 460 nm from top surfaces. CL line scans on cleaved rod also indicate the core-shell morphology. Finally, an internal quantum efficiency of about 28% at room temperature was determined by an all-optical method on a LED array.
Organic-free suspension of large-area graphene
Authors: Ledwosinska E. , Gaskell P. , Guermoune A. , Siaj M. , Szkopek T.
Published: July 2012

We report an entirely organic-free method to suspend monolayer graphene grown by chemical vapour deposition over 10–20 μm apertures in a Cu substrate. Auger electron spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope measurements confirm high quality graphene with no measurable contamination beyond that resulting from air exposure. This method can be used to prepare graphene for fundamental studies and applications where the utmost cleanliness and structural integrity are required.
Predicting effective permittivity of composites containing conductive inclusions at microwave frequencies
Authors: Garner Allen L. , Parker Gregory J. , Simone Davide L.
Published: July 2012

We predict the effective dielectric properties at microwave frequencies of composites containing various volume loadings of high conductivity (stainless steel or iron) spheres or flakes by adapting the semi-empirical method developed by McLachlan. Rather than the typical approach of fixing A (A = 1/vc – 1, where vc is percolation threshold) for a given inclusion shape, we consider it as an unknown and fix one of the geometric exponents. We observe that A varies linearly with the inverse of volume loading with a higher slope for flakes than spheres. The exponent is consistently higher for spheres than flakes and for iron than stainless steel. We achieve good agreement between measured and calculated permittivity over a wide range of volume loadings, inclusion shapes, and materials from 3 to 20 GHz.
Epigenetic stability, adaptability, and reversibility in human embryonic stem cells
Authors: Tompkins Joshua D. , Hall Christine , Chen Vincent Chang-yi , Li Arthur Xuejun , Wu Xiwei , Hsu David , Couture Larry A. , Riggs Arthur D.
Published: July 2012

The stability of human embryonic stem cells (hESCs) is of critical importance for both experimental and clinical applications. We find that as an initial response to altered culture conditions, hESCs change their transcription profile for hundreds of genes and their DNA methylation profiles for several genes outside the core pluripotency network. After adaption to conditions of feeder-free defined and/or xeno-free culture systems, expression and DNA methylation profiles are quite stable for additional passaging. However, upon reversion to the original feeder-based culture conditions, numerous transcription changes are not reversible. Similarly, although the majority of DNA methylation changes are reversible, highlighting the plasticity of DNA methylation, a few are persistent. Collectively, this indicates these cells harbor a memory of culture history. For culture-induced DNA methylation changes, we also note an intriguing correlation: hypomethylation of regions 500–2440 bp upstream of promoters correlates with decreased expression, opposite to that commonly seen at promoter-proximal regions. Lastly, changes in regulation of G-coupled protein receptor pathways provide a partial explanation for many of the unique transcriptional changes observed during hESC adaptation and reverse adaptation.
Stupeur et tremblements: configuration de la faille dans
Le Sang d'un poète
de Jean Cocteau
Authors: Andréo Benjamin
Published: July 2012

L'objet de cet article est de dégager, à l'aide du premier volet de la trilogie orphique (
Le Sang d'un poète
), les différents ‘jeux’ de la poétique coctalienne: à l'image du reste de sa production poétique, les poésies filmées que sont chacun de ses films sont en effet traversées de lignes de rupture, de failles et de faillites. Il s'agit ici à la fois de repérer ces ruptures — où j'opposerai ‘tremblement’ à ‘stupeur’, comprise comme un engourdissement abêtissant des facultés sensibles —, mais encore d'identifier la pratique à dessein par le poète du séisme poétique. Pour Cocteau, il fut toujours question de s'éloigner des ‘bêtes effets de poésie’ afin de toucher à la poésie véritable, et il se donna dans le cinématographe les moyens d'attester le pouvoir de dérangement de la poésie: tremblement des valeurs établies (raison, opinion bien pensante), de l'identité (psychologique ou sexuelle), du réel et de l'‘irréel’ mais aussi, à terme, du langage poétique et cinématographique.
Le Sang d'un poète
sert donc ici d'introduction à une lecture de la configuration de la faille chez Jean Cocteau, lecture éclairée par le propre métadiscours du poète sur sa création poétique, et qui légitimerait de voir en Jean Cocteau un épicentre poétique et voyageur qui propagerait ses ondes destructrices dans le but de revivifier nos sens et de nous initier au mystère poétique.
Molecular Basis for Different Levels of
tet
(M) Expression in Streptococcus pneumoniae Clinical Isolates
Authors: Grohs Patrick , Trieu-Cuot Patrick , Podglajen Isabelle , Grondin Sophie , Firon Arnaud , Poyart Claire , Varon Emmanuelle , Gutmann Laurent
Published: July 2012

Seventy-four unrelated clinical isolates of
Streptococcus pneumoniae
harboring the
tet
(M) gene were studied. Seven strains with low tetracycline (Tc) MICs (0.25 to 0.5 μg/ml) were found to harbor truncated
tet
(M) alleles that were inactivated by different frameshift mutations. In contrast, five strains bore deletions in the
tet
(M) promoter region, among which four displayed increased Tc MICs (16 to 64 μg/ml). The same promoter mutations were detected in Tc-resistant mutants selected
in vitro
from various susceptible strains. Sequence analysis revealed that these deletions might impede the formation of the transcriptional attenuator located immediately upstream of
tet
(M). Expression in
Enterococcus faecalis
of a
tet
(M) reporter gene transcribed from these promoter mutants conferred a level of Tc resistance similar to that observed in the parental
S. pneumoniae
strains. These results show that different levels of Tc susceptibility found in clinical isolates of
S. pneumoniae
can be explained by frameshift mutations within
tet
(M) and by alterations of the upstream transcriptional attenuator.
Effects of 14-Alpha-Lipoyl Andrographolide on Quorum Sensing in Pseudomonas aeruginosa
Authors: Ma Li , Liu Xiangyang , Liang Haihua , Che Yizhou , Chen Caixia , Dai Huanqin , Yu Ke , Liu Mei , Ma Luyan , Yang Ching-Hong , Song Fuhang , Wang Yuqiang , Zhang Lixin
Published: July 2012

InPseudomonas aeruginosa, the quorum-sensing (QS) system is closely related to biofilm formation. We previously demonstrated that 14-alpha-lipoyl andrographolide (AL-1) has synergistic effects on antibiofilm and antivirulence factors (pyocyanin and exopolysaccharide) ofP. aeruginosawhen combined with conventional antibiotics, while it has little inhibitory effect on its growth. However, its molecular mechanism remains elusive. Here we investigated the effect of AL-1 on QS systems, especially the Las and Rhl systems. This investigation showed that AL-1 can inhibit LasR–3-oxo-C12-homoserine lactone (HSL) interactions and repress the transcriptional level of QS-regulated genes. Reverse transcription (RT)-PCR data showed that AL-1 significantly reduced the expression levels oflasR,lasI,rhlR, andrhlIin a dose-dependent manner. AL-1 not only decreased the expression level of Psl, which is positively regulated by the Las system, but also increased the level of secretion of ExoS, which is negatively regulated by the Rhl system, indicating that AL-1 has multiple effects on both the Las and Rhl systems. It is no wonder that AL-1 showed synergistic effects with other antimicrobial agents in the treatment ofP. aeruginosainfections.
Characterization of a Rifampin-Inactivating Glycosyltransferase from a Screen of Environmental Actinomycetes
Authors: Spanogiannopoulos Peter , Thaker Maulik , Koteva Kalinka , Waglechner Nicholas , Wright Gerard D.
Published: July 2012

Identifying and understanding the collection of all antibiotic resistance determinants presented in the global microbiota, the antibiotic resistome, provides insight into the evolution of antibiotic resistance and critical information for the development of future antimicrobials. The rifamycins are broad-spectrum antibiotics that target bacterial transcription by inhibition of RNA polymerase. Although mutational alteration of the drug target is the predominant mechanism of resistance to this family of antibiotics in the clinic, a number of diverse inactivation mechanisms have also been reported. In this report, we investigate a subset of environmental rifampin-resistant actinomycete isolates and identify a diverse collection of rifampin inactivation mechanisms. We describe a single isolate, WAC1438, capable of inactivating rifampin by glycosylation. A draft genome sequence of WAC1438 (most closely related to
Streptomyces speibonae
, according to a 16S rRNA gene comparison) was assembled, and the associated rifampin glycosyltransferase open reading frame,
rgt1438
, was identified. The role of
rgt1438
in rifampin resistance was confirmed by its disruption in the bacterial chromosome, resulting in a loss of antibiotic inactivation and a 4-fold decrease in MIC. Interestingly, examination of the RNA polymerase β-subunit sequence of WAC1438 suggests that it harbors a resistant target and thus possesses dual mechanisms of rifamycin resistance. Using an
in vitro
assay with purified enzyme, Rgt1438 could inactivate a variety of rifamycin antibiotics with comparable steady-state kinetics constants. Our results identify
rgt1438
as a rifampin resistance determinant from WAC1438 capable of inactivating an assortment of rifamycins, adding a new element to the rifampin resistome.