bluuebunny/crossref_metadata_2025_split huggingface dataset:
Instabilities in the Gamma Ray Burst central engine. What makes the jet variable?
Authors: Janiuk Agnieszka , Yuan Ye-Fei , Perna Rosalba , Di Matteo Tiziana 
Published: February 2011

AbstractBoth types of long and short gamma ray bursts involve a stage of a hyper-Eddington accretion of hot and dense plasma torus onto a newly born black hole. The prompt gamma ray emission originates in jets at some distance from this ‘central engine’ and in most events is rapidly variable, having a form of sipkes and subpulses. This indicates at the variable nature of the engine itself, for which a plausible mechanism is an internal instability in the accreting flow. We solve numerically the structure and evolution of the neutrino-cooled torus. We take into account the detailed treatment of the microphysics in the nuclear equation of state that includes the neutrino trapping effect. The models are calculated for both Schwarzschild and Kerr black holes. We find that for sufficiently large accretion rates (>~10M⊙ s−1 for non-rotating black hole, and >~1M⊙ s−1 for rotating black hole, depending on its spin), the inner regions of the disk become opaque, while the helium nuclei are being photodissociated. The sudden change of pressure in this region leads to the development of a viscous and thermal instability, and the neutrino pressure acts similarly to the radiation pressure in sub-Eddington disks. In the case of rapidly rotating black holes, the instability is enhanced and appears for much lower accretion rates. We also find the important and possibly further destabilizing role of the energy transfer from the rotating black hole to the torus via the magnetic coupling.
Simulation of relativistic shocks and associated radiation from turbulent magnetic fields
Authors: Nishikawa K.-I. , Niemiec J. , Medvedev M. , Zhang B. , Hardee P. , Mizuno Y. , Nordlund A. , Frederiksen J. , Sol H. , Pohl M. , Hartmann D. H. , Fishman G. J. 
Published: February 2011

AbstractRecent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The “jitter” radiation from deflected electrons in turbulent magnetic fields has different properties from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We will present detailed spectra for conditions relevant to various astrophysical sites of collisionless shock formation. In particular we will discuss application to GRBs and SNRs.
Radio observations of jets from massive young stars
Authors: Rodríguez Luis F. 
Published: February 2011

AbstractThe formation of low mass stars takes place with the assistance of an accretion disk that transports gas and dust from the envelope of the system to the star, and a jet that removes angular momentum and allows accretion to proceed. In the radio, these ionized jets can be studied very close to the star via the thermal (free-free) emission they produce and at larger scales by the molecular outflows that result from their interaction with the surrounding medium. Is the same disk-jet process responsible for the formation of massive stars? I will review recent evidence for the presence of collimated jets and accretion disks in association with forming massive stars. The jets in massive protostars have large velocities that could produce a synchrotron component and I discuss the evidence for the presence of this non-thermal process in the jet associated with the HH 80-81 system.
Complete-fosmid and fosmid-end sequences reveal frequent horizontal gene transfers in marine uncultured planktonic archaea
Authors: Brochier-Armanet Céline , Deschamps Philippe , López-García Purificación , Zivanovic Yvan , Rodríguez-Valera Francisco , Moreira David 
Published: February 2011

Abstract
The extent of horizontal gene transfer (HGT) among marine pelagic prokaryotes and the role that HGT may have played in their adaptation to this particular environment remain open questions. This is partly due to the paucity of cultured species and genomic information for many widespread groups of marine bacteria and archaea. Molecular studies have revealed a large diversity and relative abundance of marine planktonic archaea, in particular of Thaumarchaeota (also known as group I Crenarchaeota) and Euryarchaeota of groups II and III, but only one species (the thaumarchaeote Candidatus Nitrosopumilus maritimus) has been isolated in pure culture so far. Therefore, metagenomics remains the most powerful approach to study these environmental groups. To investigate the impact of HGT in marine archaea, we carried out detailed phylogenetic analyses of all open reading frames of 21 archaeal 16S rRNA gene-containing fosmids and, to extend our analysis to other genomic regions, also of fosmid-end sequences of 12 774 fosmids from three different deep-sea locations (South Atlantic and Adriatic Sea at 1000 m depth, and Ionian Sea at 3000 m depth). We found high HGT rates in both marine planktonic Thaumarchaeota and Euryarchaeota, with remarkable converging values estimated from complete-fosmid and fosmid-end sequence analysis (25 and 21% of the genes, respectively). Most HGTs came from bacterial donors (mainly from Proteobacteria, Firmicutes and Chloroflexi) but also from other archaea and eukaryotes. Phylogenetic analyses showed that in most cases HGTs are shared by several representatives of the studied groups, implying that they are ancient and have been conserved over relatively long evolutionary periods. This, together with the functions carried out by these acquired genes (mostly related to energy metabolism and transport of metabolites across membranes), suggests that HGT has played an important role in the adaptation of these archaea to the cold and nutrient-depleted deep marine environment.
Quantitative optical extinction-based parametric method for sizing a single core–shell Ag–Ag2O nanoparticle
Authors: Santillán J M J , Scaffardi L B , Schinca D C 
Published: February 2011

This paper develops a parametric method for determining the core radius and shell thickness in small silver–silver-oxide core–shell nanoparticles (Nps) based on single particle optical extinction spectroscopy.
The method is based on the study of the relationship between plasmon peak wavelength, full width at half maximum (FWHM) and contrast of the extinction spectra as a function of core radius and shell thickness. This study reveals that plasmon peak wavelength is strongly dependent on shell thickness, whereas FWHM and contrast depend on both variables. These characteristics may be used for establishing an easy and fast stepwise procedure to size core–shell NPs from single particle absorption spectrum. The importance of the method lies in the possibility of monitoring the growth of the silver-oxide layer around small spherical silver Nps in real time.
Using the electrostatic approximation of Mie theory, core–shell single particle extinction spectra were calculated for a silver particle's core size smaller than about 20 nm and different thicknesses of silver oxide around it. Analysis of the obtained curves shows a very particular characteristic of the plasmon peak of small silver–silver-oxide Nps, expressed in the fact that its position is strongly dependent on oxide thickness and weakly dependent on the core radius. Even a very thin oxide layer shifts the plasmon peak noticeably, enabling plasmon tuning with appropriate shell thickness.
This characteristic, together with the behaviour of FWHM and contrast of the extinction spectra can be combined into a parametric method for sizing both core and shell of single silver Nps in a medium using only optical information. In turn, shell thickness can be related to oxygen content in the Np's surrounding media.
The method proposed is applied to size silver Nps from single particle extinction spectrum. The results are compared with full optical spectrum fitting using the electrostatic approximation in Mie theory. The method may be the basis for developing a plasmonic sensor for O2 concentration based on Ag single NP spectroscopy.
Enzymatic Activity of the Soybean Ecto-Apyrase GS52 Is Essential for Stimulation of Nodulation
Authors: Tanaka Kiwamu , Nguyen Cuong T. , Libault Marc , Cheng Jianlin , Stacey Gary 
Published: February 2011

Abstract
Nitrogen is an essential nutrient for plant growth. In the Rhizobium-legume symbiosis, root nodules are the sites of bacterial nitrogen fixation, in which atmospheric nitrogen is converted into a form that plants can utilize. While recent studies suggested an important role for the soybean (Glycine max) ecto-apyrase GS52 in rhizobial root hair infection and root nodule formation, precisely how this protein impacts the nodulation process remains undetermined. In this study, the biochemical characteristics of the GS52 enzyme were investigated. Computer modeling of the GS52 apyrase structure identified key amino acid residues important for catalytic activity, which were subsequently mutagenized. Although the GS52 enzyme exhibited broad substrate specificity, its activity on pyrimidine nucleotides and diphosphate nucleotides was significantly higher than on ATP. This result was corroborated by structural modeling of GS52, which predicted a low specificity for the adenine base within the substrate-binding pocket of the enzyme. The wild-type enzyme and its inactive mutant forms were expressed in soybean roots in order to evaluate the importance of GS52 enzymatic activity for nodulation. The results indicated a clear correlation between GS52 enzymatic activity and nodule number. Altogether, our study indicates that the catalytic activity of the GS52 apyrase, likely acting on extracellular nucleotides, is critical for rhizobial infection and nodulation.
Genetic and Genomic Evidence That Sucrose Is a Global Regulator of Plant Responses to Phosphate Starvation in Arabidopsis
Authors: Lei Mingguang , Liu Yidan , Zhang Baocai , Zhao Yingtao , Wang Xiujie , Zhou Yihua , Raghothama Kashchandra G. , Liu Dong 
Published: February 2011

Abstract
Plants respond to phosphate (Pi) starvation by exhibiting a suite of developmental, biochemical, and physiological changes to cope with this nutritional stress. To understand the molecular mechanism underlying these responses, we isolated an Arabidopsis (Arabidopsis thaliana) mutant, hypersensitive to phosphate starvation1 (hps1), which has enhanced sensitivity in almost all aspects of plant responses to Pi starvation. Molecular and genetic analyses indicated that the mutant phenotype is caused by overexpression of the SUCROSE TRANSPORTER2 (SUC2) gene. As a consequence, hps1 has a high level of sucrose (Suc) in both its shoot and root tissues. Overexpression of SUC2 or its closely related family members SUC1 and SUC5 in wild-type plants recapitulates the phenotype of hps1. In contrast, the disruption of SUC2 functions greatly inhibits plant responses to Pi starvation. Microarray analysis further indicated that 73% of the genes that are induced by Pi starvation in wild-type plants can be induced by elevated levels of Suc in hps1 mutants, even when they are grown under Pi-sufficient conditions. These genes include several important Pi signaling components and those that are directly involved in Pi transport, mobilization, and distribution between shoot and root. Interestingly, Suc and low-Pi signals appear to interact with each other both synergistically and antagonistically in regulating gene expression. Our genetic and genomic studies provide compelling evidence that Suc is a global regulator of plant responses to Pi starvation. This finding will help to further elucidate the signaling mechanism that controls plant responses to this particular nutritional stress.
Ageing hospital nurses’ well‐being at work: psychometric testing of the Dignity and Respect in Ageing Nurses’ Work Scale
Authors: Utriainen Kati , Kyngäs Helvi 
Published: February 2011

Scand J Caring Sci; 2011; 25; 617–624

Ageing hospital nurses’ well‐being at work: psychometric testing of the Dignity and Respect in Ageing Nurses’ Work Scale Valid and reliable methods to measure nurses’ well‐being at work as a positive phenomenon are needed. Factors promoting well‐being at work need to be identified, which would enable targeting interventions and development in nursing work in an appropriate manner. Due to dissimilarity of many areas of nursing work and unique features of every age group, specialized and aligned scales are needed. The aim of this article is to describe a study to develop and test the psychometric properties of the Dignity and Respect in Ageing Nurses’ Work Scale (DRANWS). A sample of 328 ageing Finnish hospital nurses in the first phase (response rate 55%) and 285 nurses in the second phase (response rate 48%) responded to the scale. Content validity was assessed by expert evaluation. Exploratory factor analysis was used to assess construct validity. Reliability (internal consistency) was assessed by Cronbach’s alpha coefficient. The DRANWS consists of 72 items and three dimensions: (1) nurse–nurse interaction (cohesion, feeling of freedom in work community, giving and receiving assistance and support, nurses’ status at work, perceiving one’s work as meaningful, being together with other nurses, nurses working in pairs), (2) nurse–patient interaction (patient satisfaction, well‐conducted nursing, encountering patients and helping them) and (3) nursing‐centredness (provision of good care to patients, putting the patient first, appreciation of nursing). Cronbach’s alphas ranged from 0.74 to 0.96 in the first phase and from 0.79 to 0.98 in the second phase, demonstrating the internal consistency of scale to be high. Content validity was good based on expert evaluations. Construct validity of the scale was also very good based on factor analysis. In conclusion, the DRANWS is a reliable and valid scale to measure well‐being at work of ageing hospital nurses focusing on dignity and respect.
Formal Infrastructure and Ethical Decision Making: An Empirical Investigation and Implications for Supply Management
Authors: Rottig Daniel , Koufteros Xenophon , Umphress Elizabeth 
Published: February 2011

ABSTRACTBuilding on Rest's (1986) conceptual model of ethical decision making, we derive and empirically test a model that links an organization's formal ethical infrastructure to individuals’ moral awareness of ethical situations, moral judgment, and moral intention. We contribute to the literature by shedding light on the importance of a multifaceted formal ethical infrastructure—consisting of formal communication, recurrent communication, formal surveillance, and formal sanctions—as a crucial antecedent of moral awareness. In so doing, we discern how these four elements of a formal ethical infrastructure combine to collectively influence moral awareness based on a second‐order factor structure using structural equation modeling. We test our model based on survey data from 805 respondents with significant work experience across three separate ethical scenarios. Our results across the three scenarios provide overall support for our model. We found that a second‐order factor structure for the formal ethical infrastructure explains the variance among the four infrastructure elements and that a multifaceted formal ethical infrastructure significantly increases moral awareness. Our results further suggest a strong positive effect of moral awareness on moral judgment, which in turn was found to have a positive impact on moral intention. These results were substantiated when taking several individual and contextual control variables into account, such as gender, age, religiosity, work satisfaction, and a de facto ethical climate. Implications for theory, practice, and supply management are discussed.
Segmentation Opportunities for a Social Planner: Impact of Limited Resources
Authors: Yayla‐Küllü H. Müge , Parlaktürk Ali K. , Swaminathan Jayashankar M. 
Published: February 2011

ABSTRACTIn this research note, we investigate segmentation opportunities for social planners such as government agencies, nonprofits, and public organizations. These opportunities arise when the potential products are vertically (quality) differentiated and the consumers are heterogeneous in their preferences toward quality. In these cases, whether to offer quality differentiated products and what quality level to choose are important decisions for a social planner. In this research note, we identify the conditions where it is socially optimal to offer either one homogenous or two quality differentiated products. We find that the resource limitations may result in a single product offering and that the quality of the product depends on the maximum surplus per unit resource consumed by the products. We also compare our findings to a profit‐maximizing firm. We find that the resource limitations may cause a profit‐maximizing firm to provide a better service to some consumers than the social planner. Contrary to common wisdom, we also show that the capacity limitations may force the social planner to act like a profit‐maximizing firm in terms of its pricing and product mix choice.
Evaluation of Widely Used Diagnostic Tests To Detect West Nile Virus Infections in Horses Previously Infected with St. Louis Encephalitis Virus or Dengue Virus Type 2
Authors: Ledermann Jeremy P. , Lorono-Pino Maria A. , Ellis Christine , Saxton-Shaw Kali D. , Blitvich Bradley J. , Beaty Barry J. , Bowen Richard A. , Powers Ann M. 
Published: February 2011

ABSTRACT
Primary West Nile virus (WNV) infections can be diagnosed using a number of tests that detect infectious particles, nucleic acid, and specific IgM and/or IgG antibodies. However, serological identification of the infecting agent in secondary or subsequent flavivirus infections is problematic due to the extensive cross-reactivity of flavivirus antibodies. This is particularly difficult in the tropical Americas where multiple flaviviruses cocirculate. A study of sequential flavivirus infection in horses was undertaken using three medically important flaviviruses and five widely utilized diagnostic assays to determine if WNV infection in horses that had a previous St. Louis encephalitis virus (SLEV) or dengue virus type 2 (DENV-2) infection could be diagnosed. Following the primary inoculation, 25% (3/12) and 75% (3/4) of the horses mounted antibody responses against SLEV and DENV-2, respectively. Eighty-eight percent of horses subsequently inoculated with WNV had a WNV-specific antibody response that could be detected with one of these assays. The plaque reduction neutralization test (PRNT) was sensitive in detection but lacked specificity, especially following repeated flavivirus exposure. The WNV-specific IgM enzyme-linked immunosorbent assay (IgM ELISA) was able to detect an IgM antibody response and was not cross-reactive in a primary SLEV or DENV response. The WNV-specific blocking ELISA was specific, showing positives only following a WNV injection. Of great importance, we demonstrated that timing of sample collection and the need for multiple samples are important, as the infecting etiology could be misdiagnosed if only a single sample is tested.
Seroprevalence of Pandemic 2009 (H1N1) Influenza A Virus among Schoolchildren and Their Parents in Tokyo, Japan
Authors: Iwatsuki-Horimoto Kiyoko , Horimoto Taisuke , Tamura Daisuke , Kiso Maki , Kawakami Eiryo , Hatakeyama Shuji , Ebihara Yasuhiro , Koibuchi Tomohiko , Fujii Takeshi , Takahashi Kazuo , Shimojima Masayuki , Sakai-Tagawa Yuko , Ito Mutsumi , Sakabe Saori , Iwasa Ayaka , Takahashi Kei , Ishii Takashi , Gorai Takeo , Tsuji Koichiro , Iwamoto Aikichi , Kawaoka Yoshihiro 
Published: February 2011

ABSTRACTSince its emergence, the 2009 pandemic H1N1 virus has spread rapidly throughout the world. Previously, we reported that most individuals born after 1920 do not have cross-reactive virus-neutralizing antibodies against pandemic (H1N1) 2009 virus, indicating that they were immunologically naïve to the pandemic virus prior to its emergence. This finding provided us with an excellent opportunity for a seroepidemiological investigation of the transmission mode of the pandemic virus in the community. To gain insight into its transmission within communities, we performed a serosurvey for pandemic virus infection with schoolchildren at an elementary school in Tokyo, Japan, and their parents. We observed a high prevalence of neutralizing antibodies to the pandemic virus in the children at this school, although the percentage of children positive for the neutralizing antibodies varied among classrooms. While a much lower prevalence was observed among parents, seropositivity of the parents correlated with that of their schoolchildren. Moreover, many adults appeared to have experienced asymptomatic infection with the pandemic virus. These data suggest that the pandemic virus was readily transmitted among schoolchildren in elementary schools and that it was also transmitted from schoolchildren to their parents.
Antigen-Specific Memory B-Cell Responses in Bangladeshi Adults after One- or Two-Dose Oral Killed Cholera Vaccination and Comparison with Responses in Patients with Naturally Acquired Cholera
Authors: Alam Mohammad Murshid , Riyadh M. Asrafuzzaman , Fatema Kaniz , Rahman Mohammad Arif , Akhtar Nayeema , Ahmed Tanvir , Chowdhury Mohiul Islam , Chowdhury Fahima , Calderwood Stephen B. , Harris Jason B. , Ryan Edward T. , Qadri Firdausi 
Published: February 2011

ABSTRACTThe mediators of protective immunity against cholera are currently unknown, but memory B-cell responses may play a central role in facilitating long-term and anamnestic responses againstVibrio cholerae, the cause of cholera. We compared memory B-cell responses in adults with natural cholera in Bangladesh (n= 70) to responses in Bangladeshi adults after one-dose (n= 30) or two-dose (n= 30) administration of an oral killed cholera vaccine, WC-rBS (Dukoral; Crucell), assessing the responses at the acute stage of disease or prevaccination and then on days 3, 30, 90, 180, 270, and 360. Individuals with natural cholera developed prominent vibriocidal and plasma anti-cholera toxin B subunit (CtxB) and lipopolysaccharide (LPS) IgG and IgA responses, but these responses returned to baseline by 1 year of follow-up. Vaccinees developed plasma anti-CtxB and anti-LPS IgG and IgA responses that were generally comparable to those in individuals recovering from natural disease, but vibriocidal responses were lower in vaccinees than in infected patients. Individuals recovering from natural disease developed memory B-cell IgG and IgA anti-CtxB and anti-LPS responses by day 30, and these responses were detectable through at least days 180 to 360. In contrast, we detected no IgA or IgG memory B-cell responses to LPS in vaccinees; anti-CtxB IgA responses were only detectable on day 30, and anti-CtxB IgG responses were detectable until days 90 to 180, compared to days 270 to 360 in patients. These findings may explain in part the relatively short-term protection afforded by oral cholera vaccination compared to natural disease.