bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexibility in the N‐terminal actin‐binding domain: Clues from in silico mutations and molecular dynamics
Authors: Chakravarty Devlina , Chakraborti Soumyananda , Chakrabarti Pinak
Published: January 2015

Dystrophin is a long, rod‐shaped cytoskeleton protein implicated in muscular dystrophy (MDys). Utrophin is the closest autosomal homolog of dystrophin. Both proteins have N‐terminal actin‐binding domain (N‐ABD), a central rod domain and C‐terminal region. N‐ABD, composed of two calponin homology (CH) subdomains joined by a helical linker, harbors a few disease causing missense mutations. Although the two proteins share considerable homology (>72%) in N‐ABD, recent structural and biochemical studies have shown that there are significant differences (including stability, mode of actin‐binding) and their functions are not completely interchangeable. In this investigation, we have used extensive molecular dynamics simulations to understand the differences and the similarities of these two proteins, along with another actin‐binding protein, fimbrin. In silico mutations were performed to identify two key residues that might be responsible for the dynamical difference between the molecules. Simulation points to the inherent flexibility of the linker region, which adapts different conformations in the wild type dystrophin. Mutations T220V and G130D in dystrophin constrain the flexibility of the central helical region, while in the two known disease‐causing mutants, K18N and L54R, the helicity of the region is compromised. Phylogenetic tree and sequence analysis revealed that dystrophin and utrophin genes have probably originated from the same ancestor. The investigation would provide insight into the functional diversity of two closely related proteins and fimbrin, and contribute to our understanding of the mechanism of MDys. Proteins 2015; 83:696–710. © 2015 Wiley Periodicals, Inc.
Unusual phonon mode behaviour in zinc‐blende BN/GaN superlattices
Authors: Talwar Devki N. , Zhou Andrew F. , Yang Tzuen‐Rong
Published: January 2015

Comprehensive calculations of the long‐wavelength optical phonons are reported for zinc‐blende BN films by exploiting a linear response theory to simulate far‐infrared reflectivity and transmission spectra at oblique incidence. A rigid‐ion‐model is used to study the lattice dynamics of the unconventional BN/GaN short‐period superlattices (SLs). Besides empathizing, the anisotropic mode behaviour of optical phonons, the study has offered evidence of acoustic‐mode anti‐crossing, mini‐gap formation, confinement, as well as BN‐like modes falling between the gap regions separating the optical phonons of the two bulk (BN, GaN) semiconductor materials. A bond‐polarizability approach within the second‐nearest‐neighbour linear‐chain model is also employed to visualize the Raman intensity profiles of the short‐period BN/GaN SLs, revealing major trends of the phonon characteristics noted in many conventional SLs, while eliciting some interesting contrasts. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma‐assisted molecular beam epitaxy of strain‐compensated a‐plane InGaN/AlGaN superlattices
Authors: Enck Ryan W. , Woodward N. , Gallinat C. , Metcalfe G. , Sampath A. V. , Shen H. , Wraback M.
Published: January 2015

Strain‐compensated InGaN/AlGaN structures can enable the growth of thick layers of InGaN epitaxial films far beyond the critical thickness for InGaN grown pseudomorphically to GaN. In this paper, we demonstrate the epitaxial growth of high‐quality strain‐compensated a‐plane In0.12Ga0.88N/Al0.19Ga0.81N superlattices up to 5 times thicker than the critical thickness on free‐standing a‐plane GaN substrates by plasma‐assisted molecular beam epitaxy (PA‐MBE). The superlattices consist of 50 to 200 periods of 10 nm thick In0.12Ga0.88N and 6 nm thick Al0.19Ga0.81N layers. The structures are characterized using a double crystal X‐ray diffractometer, asymmetric reciprocal space mapping, and atomic force microscopy. We use X‐ray diffraction to determine the strain, composition, degree of relaxation, and superlattice period of our samples. The structural characteristics of periodic structures containing from 50 to 200 periods are compared to single layer, uncompensated In0.12Ga0.88N films. A 100 period structure exhibited only 15% relaxation compared to 69% relaxation for the bulk In0.12Ga0.88N film grown with the same total InGaN thickness but without strain‐compensating layers. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Encouraging Greater Student Inquiry Engagement in Science Through Motivational Support by Online Scientist‐Mentors
Authors: SCOGIN STEPHEN C. , STUESSY CAROL L.
Published: January 2015

Next Generation Science Standards (NGSS) call for integrating knowledge and practice in learning experiences in K‐12 science education. PlantingScience (PS), an ideal curriculum for use as an NGSS model, is a computer‐mediated collaborative learning environment intertwining scientific inquiry, classroom instruction, and online mentoring from scientists. With implementation in hundreds of classrooms across the United States, science teachers have noted PS as successful in motivating their students to engage in classroom inquiry investigations. To investigate the role of the online scientist‐mentors in motivating students in the PS learning environment, we used self‐determination theory (SDT) to guide a multiple case study of 10 student inquiry teams engaged in PS in a rural public school in a large Southwestern U.S. state. We used online dialogues between scientist‐mentors and their assigned student inquiry teams to answer research questions about the motivational support provided by scientist‐mentors and the association between this support and students' engagement in scientific inquiry. Analyses revealed a general relationship between scientist‐mentor motivational support and student inquiry engagement. Differences were observed in the specific ways in which scientists supported autonomy, competence, and relatedness. Student inquiry engagement corresponded to high support in relatedness, whereas correspondence with autonomy support was low.
An approach of security testing for third‐party component based on state mutation
Authors: Chen Jinfu , Chen Jiamei , Huang Rubing , Guo Yuchi , Zhan Yongzhao
Published: January 2015

It is essential to study an effective approach of security testing for third‐party component. In this paper, to effectively trigger implicit vulnerabilities of third‐party components, an approach of security testing for third‐party component is proposed based on state mutation. To start with, executable method sequences of components are transformed into extended finite state machine. Then, according to characteristics of condition conflict and behavior conflict, two test case generation algorithms are addressed, that is, Operations Conflict Sequences Generation Algorithm and Conditions Conflict Sequences Generation Algorithm, which are designed to generate inaccessible sequences of behavior and condition conflicts. These conflict sequences are run. Furthermore, the security detecting algorithms are addressed to detect implicit vulnerabilities of third‐party components, and then, testing report of component security is obtained. In the end, some experiments are conducted on the basis of the proposed approach, and the experimental results show that the proposed approach can effectively detect security exceptions of third‐party components. Copyright © 2015 John Wiley & Sons, Ltd.
Surgical Management of Traumatic Penile Amputation: A Case Report and Review of the World Literature
Authors: Raheem Omer A. , Mirheydar Hossein S. , Patel Nishant D. , Patel Sunil H. , Suliman Ahmed , Buckley Jill C.
Published: January 2015

Introduction

There is paucity of case reports that describe the successful reimplantation of a penis after amputation. We sought to report on self-inflicted penile amputation and comment on its surgical management and review current literature.

Aim

To report on self-inflicted penile amputation and comment on its surgical management and review current literature.

Methods

A 19-year-old male with no prior medical history presented to our university-affiliated trauma center following sustaining a self-inflicted amputation of shaft penis secondary to severe methamphetamine-induced psychosis. He immediately underwent extensive reconstructive reimplantation of the penis performed jointly by plastics and urology teams reattaching all visible neurovascular bundles, urethra, and corporal and fascial layers. The patient was discharged with a suprapubic tube in place and a Foley catheter in place with well-healing tissue.

Main Outcome Measures

To review the current published literature and case reports on the management of penile amputation with particular emphasis its etiology, surgical repairs, potential complications and functional outcomes.

Results

We report herein a case of a traumatic penile amputation and successful outcome of microscopic reimplantation and review of the published literature with particular comments on surgical managements.

Conclusion

We review the literature and case reports on penile amputation and its etiology, surgical management, variables effecting outcomes, and its complications.
Identity Dilemmas: Toward a More Situated Understanding
Authors: Dunn Jennifer Leigh , Creek S. J.
Published: January 2015

When are identity dilemmas—when people possess identities that conflict with one another and both are potentially stigmatizing—most likely to occur? Are they the result of generic social processes? A review of some of the extant research on “identity work” suggests that historical “misalignments” of culture and stratification, which we refer to as “lag,” create the greatest potential for stigma and the reproduction of inequalities. Lag is exacerbated by complex, intersecting axes of hierarchy, and amplified as symbolic environments globalize and subcultures multiply. Articulating culture and structure reveals how power plays out in interaction, and highlights the omnipresence of struggles for treatment as “fully human.” We consider whether “alignment” is even possible when multiple dimensions of social location intertwine, compete, and collide. Following Schwalbe and Mason‐Schrock (1996), we argue that “subcultural” or collective identity work that brings new meanings into dominant cultural narratives may offer the greatest hope, but in the interim all coping strategies are costly.
The evolutionary diagnosis of mental disorder
Authors: Troisi Alfonso
Published: January 2015

Medicalization of human behavioral diversity is a recurrent theme in the history of psychiatry, and the problem of defining what is a genuine mental disorder is an unresolved question since the origins of clinical psychopathology. Darwinian psychiatry can formulate a definition of mental disorder that is value free and based on factual criteria. From an evolutionary perspective, genuine mental disorders are maladaptive conditions. The ultimate function of an adaptation is gene propagation via maximization of survival and reproduction. It follows that a distressing and/or disabling psychological or behavioral syndrome is a psychiatric disorder only if it impacts negatively on the individual's inclusive fitness. However, in many cases, an evolutionary definition of disorder cannot be reconciled with current social values. Thus, clinicians adopting the evolutionary approach should conform to the prevailing trend of contemporary medicine and accept that their task is to be healers of the distressed, not watchdogs of biological adaptation. These pragmatic considerations do not minimize the scientific validity of the Darwinian definition of mental disorders. Probably, its major contribution to psychiatric theory is the elimination of the necessity to find a brain lesion or dysfunctional mechanism to validate the distinction between disorders and non‐disorders. WIREs Cogn Sci 2015, 6:323–331. doi: 10.1002/wcs.1339

This article is categorized under:

Neuroscience > Clinical Neuroscience
Ligand‐Directed Assembly of Manganese and Zinc Complexes: Syntheses, Crystal Structures, and Bioactivities
Authors: Wang Cui‐Juan , Mao Kai‐Li , Qiu Guang‐Mei , Huang Shuai , Shan Lian‐Hai , Zhou Xian‐Li , Zhang Zhi‐Bin , Wang Yao‐Yu
Published: January 2015

Three coordination networks with the 1, 2,4‐triazole linking units 3‐(4′‐imidazole phenyl)‐5‐(pyrid‐2′′‐yl)‐1, 2,4‐triazole (HIppyt) and 3‐(pyrazin‐2′‐yl)‐5‐(4′‐(pyrid‐4′′‐yl)‐phenyl)‐1, 2,4‐triazole (Hpypypt), respectively, were synthesized and structurally characterized. The structures of [Mn(Ippyt)2·2H2O] (1) and [Zn(Ippyt)2·2H2O] (2) were found to be similar despite the presence of different metal ions. When Ippyt was replaced by pypypt to react with Zn(OAc)2·2H2O, the 2D coordination polymer, {[Zn(pypypt)2]·2DMF}n (3) formed. The adjacent zinc(II) atoms with similar octahedral coordination environment are interlinked by four separate pypypt ligands to construct a 2D network structure. The biological activities of 1 and 3 were studied. The results indicate that 1 and 3 exhibit certain antimicrobial activities. Furthermore, solid‐state properties of thermal stability and photoluminescence properties at room temperature for these crystalline materials were also investigated.
Synthesis, Crystal Structure, and Properties of Mn(PO3F)(H2O)2
Authors: Weil Matthias , Baran Enrique J. , Kremer Reinhard K. , Libowitzky Eugen
Published: January 2015

Single crystals of manganese(II) fluorophosphate dihydrate, Mn(PO3F)(H2O)2, were grown in a metathesis reaction from aqueous solutions of MnCl2 and (NH4)2(PO3F). The crystal structure [P$\bar{1}$, Z = 2, a = 5.5280(7), b = 5.6357(7), c = 8.2570(10) Å, α = 81.279(2), β = 75.156(2), γ = 71.722(2)°, 1345 structure factors, 86 parameter, R[F2 > 2σ(F2)] = 0.0322, wR(F2 all) = 0.0771] consists of [MnO4(H2O)2] octahedra that share a common edge to form isolated double octahedra of the type [Mn2O2/2O4/1(H2O)4/1]. Each double octahedron is bridged by the oxygen atoms of six (PO3F) tetrahedra to six neighboring double octahedra into a layered arrangement parallel to (001). Adjacent layers are held together through weak O–H···O hydrogen bonds, and no significant hydrogen bonding interactions of the type O–H···F are observed. Vibrational spectra are discussed in terms of a site‐symmetry approximation for the (PO3F)2– anion. The thermal decomposition of Mn(PO3F)(H2O)2 starts above 130 °C. In a multi‐stage mechanism the end‐product Mn2P2O7 is formed at temperatures above 500 °C. Magnetic measurements suggest an antiferromagnetic ordering of Mn(PO3F)(H2O)2 at 3.4 K.
Role of Gadoxetic Acid‐Enhanced Magnetic Resonance Imaging in the Preoperative Evaluation of Small Hepatic Lesions in Patients with Colorectal Cancer
Authors: Cho Jai Young , Lee Yoon Jin , Han Ho‐Seong , Yoon Yoo‐Seok , Kim Jihoon , Choi YoungRok , Shin Hong Kyung , Lee Woohyung
Published: January 2015

Background

The initial abdominal computed tomography (CT) scans of patients with colorectal cancer (CRC) sometimes reveal equivocal hepatic lesions. In this study, we evaluated the outcomes of equivocal hepatic lesions found by abdominal CT and the diagnostic accuracy of subsequent liver magnetic resonance imaging (MRI).

Methods

We evaluated data of patients who underwent CRC resection between January 1, 2009 and December 31, 2009. Equivocal hepatic lesions of <1 cm in size on preoperative staging CT scans were included in this study. Gadoxetic acid‐enhanced liver MRI was subsequently performed in all patients. Hepatic lesions that grew during the follow‐up period (≥3 years) were considered potential metastases.

Results

Overall, 121 equivocal hepatic lesions were detected on preoperative staging CT in 65 out of 494 patients (13.2 %) who underwent colorectal surgery. Based on subsequent MRI, 11 lesions were classified as definitive metastatic lesions and 100 were classified as definitive benign lesions, including simple cysts or hemangiomas. Findings in the other 10 lesions were still inconclusive even after examining CT and MRI. Of the 11 lesions that were classified as metastatic by MRI and were resected, 10 were pathologically confirmed as metastases and one lesion was a pathologically benign nodule. All 100 benign lesions were stable on follow‐up imaging and were classified as benign. Of the 10 equivocal lesions, 6 increased in size during the follow up, suggesting they were early metastases, while 4 were stable. The sensitivity and specificity for detecting liver metastases by gadoxetic acid‐enhanced MRI of small equivocal hepatic lesions found by CT were 100 % (16/16) and 95.2 % (100/105), respectively, if MRI was equivocal or indicated definite metastasis. The negative predictive value was 100 % (100/100).

Conclusion

Gadoxetic acid‐enhanced MRI is a useful diagnostic tool for assessing equivocal hepatic lesions on preoperative CT of CRC patients that allows increased diagnostic accuracy and detection of additional colorectal liver metastasis lesions.
International note: Teen users' problematic online behavior: Using panel data from South Korea
Authors: Kim Jung Eun , Kim Jinhee
Published: January 2015

The purpose of this study was to identify factors of teen users' problematic online behaviors using data from the Korea Youth Panel Survey (KYPS) collected over a four‐year period. Problematic online behaviors included unauthorized ID use, disguising one's age or gender while chatting online, and cursing/insulting someone in a chat room or on a bulletin board. Results from the panel data analyses showed that many adolescents explored and discontinued engaging in online delinquency as they got older. Respondents' offline behaviors and self‐control were significantly associated with problematic online behaviors, supporting the importance of internal traits. Peer effects were consistently more important than parental effects on teen's online delinquency. Increases in time spent using a computer also contributed to the likelihood of problematic online behaviors.
Characteristic molecular vibrations of adenosine receptor ligands
Authors: Chee Hyun Keun , Yang Jin-San , Joung Je-Gun , Zhang Byoung-Tak , Oh S. June
Published: January 2015

Although the regulation of membrane receptor activation is known to be crucial for molecular signal transduction, the molecular mechanism underlying receptor activation is not fully elucidated. Here we study the physicochemical nature of membrane receptor behavior by investigating the characteristic molecular vibrations of receptor ligands using computational chemistry and informatics methods. By using information gain, t‐tests, and support vector machines, we have identified highly informative features of adenosine receptor (AdoR) ligand and corresponding functional amino acid residues such as Asn (6.55) of AdoR that has informative significance and is indispensable for ligand recognition of AdoRs. These findings may provide new perspectives and insights into the fundamental mechanism of class A G protein‐coupled receptor activation.
Validation of an Analytical Method for the Determination of the Activity of Protease in Animal Feed Additives and in Animal Feedingstuffs
Authors: Dillon G.P. , Filer K. , Moran C.A.
Published: January 2015

The nutrient availability in animal feeds can be improved by including exogenous enzymes to the feed, either by helping breakdown anti-nutritional factors or by increasing digestibility of complex ingredients thereby releasing more nutrients for utilisation. This process can improve the efficiency of meat and egg production, increase animal health, decrease feeding costs and reduce nutrients in animal waste. Proteases are protein-digesting enzymes that are used in animal nutrition to break down storage proteins in various plant materials and proteinaceous anti-nutrients in vegetable proteins. The analysis of exogenous proteases in feed additives and after they have been added to feed has proven technically challenging. Accordingly, the purpose of this work was to validate a method for the determination of the activity of protease in animal feed additives and supplemented animal feed. The approach used for the assay was to adapt an assay based on the hydrolysis of haemoglobin. The method validations examined a range of parameters including; linearity & range; uncertainty, sensitivity, accuracy and studies designed to highlight any possible matrix effects on various types of supplemented feed. The assay method described herein is convenient and inexpensive and could be applied to the analysis of proteases in animal feeds during quality control and in investigating fraudulent adulteration of feed to ensure the authenticity and traceability of the product.
Unsteady Flow between Two Orthogonally Moving Porous Disks
Authors: Ghaffar M. , Ali K. , Yasmin A. , Ashraf M.
Published: January 2015

The unsteady laminar incompressible flow of a fluid between two orthogonally moving porous coaxial disks is considered numerically. A transformation is used to reduce the governing partial differential equations (PDEs) to a set of nonlinear coupled ordinary differential equations. The effects of physical parameters of interest such as the wall expansion ratio and the permeability Reynolds number on the velocity are discussed in detail.
Solution for a Crack Embedded in Multiply Confocally Elliptical Layers in Antiplane Elasticity
Authors: Chen Y.-Z.
Published: January 2015

This paper provides a general solution for a crack embedded in multiply confocally elliptical layers in antiplane elasticity. In the problem, the elastic medium is composed of an inclusion, many confocally elliptical layers and the infinite matrix with different elastic properties. In addition, the remote loading is applied at infinity. The complex variable method and the conformal mapping technique are used. On the mapping plane, the complex potentials for the inclusion and many layers are assumed in a particular form with two undetermined coefficients. The continuity conditions for the displacement and traction along the interface between two adjacent layers are formulated and studied. By enforcing those conditions along the interface, the exact relation between two sets of two undetermined coefficients in the complex potentials forj-th layer andj+ 1-th layer can be evaluated. From the traction free condition along the crack faces, the correct form of the complex potential for the cracked inclusion is obtained. Finally, many numerical results are provided.
La structure du temps est-elle indécidable? Sous-détermination et structure du temps chez Newton-Smith
Authors: ARDOUREL VINCENT
Published: January 2015

Dans La structure du temps, William H. Newton-Smith avance la thèse selon laquelle il est impossible de décider si la structure du temps est continue ou simplement dense. L’objectif de cet article est d’examiner dans quelle mesure la thèse de Newton-Smith est justifiée. D’un côté, je soutiens que l’argumentation qu’il propose est insuffisamment convaincante. D’un autre côté, je montre comment pallier cette critique et, dans ce nouveau contexte, je propose une révision des conséquences de sa thèse de l’indécidabilité.
Age, growth and longevity of the grey triggerfish, Balistes capriscus Gmelin, 1789 (Teleostei, Balistidae) in the Gulf of Gabès, southern Tunisia, Mediterranean Sea
Authors: Kacem Hichem , Boudaya Lobna , Neifar Lassâd
Published: January 2015

The age and growth parameters of grey triggerfish, Balistes capriscus from the Gulf of Gabès, southern Tunisia, Mediterranean Sea, were estimated from the first dorsal spine sections of 463 specimens (206 males and 257 females), whose fork length was between 139 and 427 mm and the total weight ranged from 90.04 to 1967.41 g. The monthly percentage of specimens having a terminal translucent zone has indicated that the growth zone is formed once a year, during the cold season (February). The von Bertalanffy growth equations were: FL = 420.7 [1 − e−0.233(t + 0.123)] and FL = 417.0 [1 − e−0.238(t + 0.074)], for males and females, respectively. The longevity estimated was 13 years old for both sexes. The instantaneous mortality rates were estimated to 0.23 for males and 0.24 for females. The weight–length relationships of the grey triggerfish were Wt = 21.510−3 LF3.046 and Wt = 41.010−3 LF2.835, for males and females, respectively.
Bernard Stonehouse
Authors: Burton Robert
Published: January 2015

Bernard Stonehouse (Fig. 1) died on 12 November 2014 at the age of 88. Best known for his pioneering studies of penguins, Stonehouse's proud claim was that he had been pecked by all the world's 17 species except one (the Galapagos penguin Spheniscus mendiculus). He was one of the few people to have spent three consecutive years in the Antarctic and was latterly involved with the Antarctic tourist industry both as a lecturer aboard cruise ships and as leader of a long-term study on its ecological impact.
Cross-sectional survey of antibiotic resistance in Escherichia coli isolated from diseased farm livestock in England and Wales
Authors: CHENEY T. E. A. , SMITH R. P. , HUTCHINSON J. P. , BRUNTON L. A. , PRITCHARD G. , TEALE C. J.
Published: January 2015

Between 2005 and 2007, E. coli obtained from clinical diagnostic submissions from cattle, goats, pigs and sheep to government laboratories in England and Wales were tested for sensitivity to 16 antimicrobials. Resistance was most commonly observed against ampicillin, streptomycin, sulphonamides and tetracyclines. Resistance levels varied significantly between species, with isolates from cattle frequently showing the highest levels. Verocytotoxigenic E. coli (VTEC) expressed less resistance than non-VTEC. Only 19·3% of non-VTEC and 43·5% of VTEC were susceptible to all antimicrobials, while 47·1% and 30·4%, respectively, were resistant to ⩾5 antimicrobials. The resistance phenotype SSuT was commonly observed, and isolates resistant to third-generation cephalosporins were also identified. We recommend judicious antimicrobial usage in the livestock industry in order to preserve efficacy.
A rare complication of radiofrequency ablation: skin burn
Authors: Ertuğrul İlker , Karagöz Tevfik , Aykan Hayrettin H.
Published: January 2015

Radiofrequency ablation is the first-line treatment for arrhythmias with high success and low complication rates. Skin burns have been reported rarely after electrophysiological procedures, especially procedures in which higher-power energy is used and multiple ablations are performed. Here, we report a case of skin burn that developed after radiofrequency ablation for ventricular tachycardia originating from the right ventricular outflow tract.
Winds of metal-poor OB stars: Updates from HST-COS UV spectroscopy
Authors: García M. , Herrero A. , Najarro F. , Lennon D. J. , Urbaneja M. A.
Published: January 2015

In the race to break the SMC frontier and reach metallicity conditions closer to the First Stars the information from UV spectroscopy is usually overlooked. New HST-COS observations of OB stars in the metal-poor galaxy IC1613, with oxygen content ~1/10 solar, have proved the important role of UV spectroscopy to characterize blue massive stars and their winds. The terminal velocities (υ∞) and abundances derived from the dataset have shed new light on the problem of metal-poor massive stars with strong winds. Furthermore, our results question the υ∞-υesc and υ∞-Z scaling relations whose use in optical-only studies may introduce large uncertainties in the derived mass loss rates and wind-momenta. Finally, our results indicate that the detailed abundance pattern of each star may have a non-negligible impact on its wind properties, and scaling these as a function of one single metallicity parameter is probably too coarse an approximation. Considering, for instance, that the [α/Fe] ratio evolves with the star formation history of each galaxy, we may be in need of updating all our wind recipes.
New prescriptions of turbulent transport from local numerical simulations
Authors: Prat V. , Lignières F. , Lesur G.
Published: January 2015

Massive stars often experience fast rotation, which is known to induce turbulent mixing with a strong impact on the evolution of these stars. Local direct numerical simulations of turbulent transport in stellar radiative zones are a promising way to constrain phenomenological transport models currently used in many stellar evolution codes. We present here the results of such simulations of stably-stratified sheared turbulence taking notably into account the effects of thermal diffusion and chemical stratification. We also discuss the impact of theses results on stellar evolution theory.
Rotational velocities of single and binary O-type stars in the Tarantula Nebula
Authors: Ramírez-Agudelo O. H. , Sana H. , de Koter A. , Simón-Díaz S. , de Mink S. E. , Tramper F. , Dufton P. L. , Evans C. J. , Gräfener G. , Herrero A. , Langer N. , Lennon D. J. , Maíz Apellániz J. , Markova N. , Najarro F. , Puls J. , Taylor W.D. , Vink J.S.
Published: January 2015

Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, υe sin i, of ~330 O-type objects, i.e. ~210 spectroscopic single stars and ~110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30 Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the υe sin i distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100 km s−1. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tail of stars rotating more rapidly than 300 km s−1, the sample of primaries does not feature such a high-velocity tail. The tail of the presumed-single star distribution is attributed for the most part – and could potentially be completely due – to spun-up binary products that appear as single stars or that have merged. This would be consistent with the lack of such post-interaction products in the binary sample, that is expected to be dominated by pre-interaction systems. The peak in this distribution is broader and is shifted toward somewhat higher spin rates compared to the distribution of presumed-single stars. Systems displaying large radial velocity variations, typical for short period systems, appear mostly responsible for these differences.
Luminous Infrared Sources in the Local Group: Identifying the Missing Links in Massive Star Evolution
Authors: Britavskiy N. , Bonanos A. Z. , Mehner A.
Published: January 2015

We present the first systematic survey of dusty massive stars (RSGs, LBVs, sgB[e]) in nearby galaxies, with the goal of understanding their importance in massive star evolution. Using the fact that these stars are bright in mid-infrared colors due to dust, we provide a technique for selecting and identifying dusty evolved stars based on the results of Bonanos et al. (2009, 2010), Britavskiy et al. (2014), and archival Spitzer/IRAC photometry. We present the results of our spectroscopic follow-up of luminous infrared sources in the Local Group dwarf irregular galaxies: Pegasus, Phoenix, Sextans A and WLM. The survey aims to complete the census of dusty massive stars in the Local Group.
First Results of the Analysis of the Wolf-Rayet Star WR6
Authors: Gormaz-Matamala Alex C. , Hervé Anthony , Chené André-Nicolas , Curé Michel , Mennickent Ronald
Published: January 2015

We present the first results of our analysis of the famous variable star, WR6 (HD50896). Using IUE ultraviolet data and an ESPaDOnS spectropolarimetric survey of this star, we plan to determine possible variation of the stellar and wind parameters during the different phases using the radiative transfer code CMFGEN. After the detection of parameter's modifications as a function of the phase, we will analyse deeper the origin of these variability (for example, CIRs?). In the present poster we show the first results of our analysis of the variability and the first step of the stellar parameter determination of the average spectrum of this star.
Massive stars: flare activity due to infalls of comet-like bodies
Authors: Ibadov Subhon , Ibodov Firuz S.
Published: January 2015

Passages of comet-like bodies through the atmosphere/chromosphere of massive stars at velocities more than 600 km/s will be accompanied, due to aerodynamic effects as crushing and flattening, by impulse generation of hot plasma within a relatively very thin layer near the stellar surface/photosphere as well as “blast” shock wave, i.e., impact-generated photospheric stellar/solar flares. Observational manifestations of such high-temperature phenomena will be eruption of the explosive layer's hot plasma, on materials of the star and “exploding” comet nuclei, into the circumstellar environment and variable anomalies in chemical abundances of metal atoms/ions like Fe, Si etc. Interferometric and spectroscopic observations/monitoring of young massive stars with dense protoplanetary discs are of interest for massive stars physics/evolution, including identification of mechanisms for massive stars variability.
Line profile variability in spectra of hot massive stars
Authors: Kholtygin Alexander , Sudnik Natallia , Dushin Viacheslav
Published: January 2015

We report the results of our study of the fast line profile variability (LPV) (hours – few days) in the spectra of bright OB and WR stars. All spectra were obtained with 6-m and 1-m telescope of Russian Special Astrophysical Observatory (SAO) and 1.8-m telescope of Bohyunsan Optical Astronomy Observatory, Korea (BOAO). We detected both the stochastic LPV, connected with the formation of small-scale structures in the stellar wind and the regular LPV induced by the large-scale structures in the wind.
Investigation of the brightest stars in the Cyg OB2 association
Authors: Maryeva Olga , Parfenov Sergey
Published: January 2015

We present the results of investigation of most luminous stars belonging to the Cyg OB2 association using quantitative analysis of high-resolution spectra. Physical parameters derived using the cmfgen and tlusty atmospheric codes allow us to estimate the mass and age of these stars.
Markov Chain Monte-Carlo Models of Starburst Clusters
Authors: Melnick Jorge
Published: January 2015

There are a number of stochastic effects that must be considered when comparing models to observations of starburst clusters: the IMF is never fully populated; the stars can never be strictly coeval; stars rotate and their photometric properties depend on orientation; a significant fraction of massive stars are in interacting binaries; and the extinction varies from star to star. The probability distributions of each of these effects are nota prioriknown, but must be extracted from the observations. Markov Chain Monte-Carlo methods appear to provide the best statistical approach. Here I present an example of stochastic age effects upon the upper mass limit of the IMF of the Arches cluster as derived from near-IR photometry.
A spectroscopic and photometric study of the interacting binary and double period variable HD 170582
Authors: Mennickent R. E. , Djurašević G. , Cabezas M. , Cséki A. , Rosales J. , Niemczura E. , Araya I. , Curé M.
Published: January 2015

We present a spectroscopic and photometric study of the interacting binary and Double Period Variable HD 170582 based on the analysis of the ASAS V-band light curve and our high-resolution spectra mostly obtained with CHIRON spectrograph at the 1.5m CTIO telescope.
The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31 and M33
Authors: Neugent Kathryn F. , Massey Philip
Published: January 2015

Here we investigate whether the inability of the Geneva evolutionary models to predict a large enough WC/WN ratio at high metallicities (while succeeding at lower metallicities) is due to their single star nature. We hypothesize that Roche-lobe overflow in close binary systems may produce a greater number of WC stars at higher metallicities. But, this would suggest that the frequency of close massive binaries is metallicity dependent. We now present our results based on observations of ~100 Wolf-Rayet binaries in the varying metallicity environments of M31 and M33.
Westerlund 1 is a Galactic Treasure Chest: The Wolf-Rayet Stars
Authors: Rosslowe C. K. , Crowther P. A.
Published: January 2015

The Westerlund 1 Galactic cluster hosts an eclectic mix of coeval massive stars. At a modest distance of 4–5 kpc, it offers a unique opportunity to study the resolved stellar content of a young (~5 Myr) high mass (5·104M⊙) star cluster. With the aim of testing single-star evolutionary predictions, and revealing any signatures of binary evolution, we discuss on-going analyses of NTT/SOFI near-IR spectroscopy of Wolf-Rayet stars in Westerlund 1. We find that late WN stars are H-poor compared to their counterparts in the Milky Way field, and nearly all are less luminous than predicted by single-star Geneva isochrones at the age of Westerlund 1.
Herschel/PACS: Constraining clumping in the intermediate wind region of OB stars
Authors: Rubio-Díez M. M. , Najarro F. , Sundqvist J. O. , Traficante A. , Puls J. , Calzoletti L. , Herrero A. , Figer D. , Martin-Pintado J.
Published: January 2015

At present, it is well established that previously accepted mass-loss rates (Ṁ) of luminous OB stars may be overestimated when clumping is neglected. Our Herschel/PACS Far-Infrared (Far-IR) observations of a set of OB stars allow us to improve our knowledge of clumping stratification, constraining clumping properties in intermediate wind regions. In this work, better sampled clumping structure estimates are provided for ι Ori, ε Ori and ξ Per as well as an initial estimate of the clumping properties of the wind from τ Sco. These observations will allow us to obtain reliable mass-loss rates and improve our understanding of the wind physics.
Spectral analysis of LBV stars in M31: AF And and Var 15
Authors: Valeev A. F. , Sholukhova O. , Fabrika S.
Published: January 2015

We study spectra of two bona fide LBV stars in M31: AF And and Var 15. The spectra were obtained with the 6-m telescope (Russia) from 2005 to 2012. The model spectra were calculated with the CMFGEN code. We have not found strong changes in the spectra of the LBV stars in that time interval, however a certain variability has been detected. We estimate the star and wind parameters, such as luminosity, temperature, raduis, mass loss rate, escape velocity, hydrogen content, and reddening. We study the stars on the Hertzsprung-Russell diagram and find their initial masses using evolutionary tracks by Meynet et al. (1994).
Variational approach for rotating-stellar evolution in Lagrange scheme
Authors: Yasutake Nobutoshi , Yamada Shoichi
Published: January 2015

We have developed an entirely new formulation to obtain self-gravitating, axisymmetric configurations in permanent rotation. It is based on the Lagrangian variational principle and, as a consequence, will allow us to apply it to stellar evolution calculations rather easily. We adopt a Monte Carlo technique, which is analogous to those employed in other fields, e.g. nuclear physics, in minimizing the energy functional. We also present the analogies between the study on rotating stellar configurations and the one on deformed nuclei. Possible applications are not limited to main sequence stars but will be extended to e.g. compact stars, proto-stars and planets. We believe that our formulation will be a major break-through then.
Behaviour of Pulsations in Hydrodynamic Models of Massive Stars
Authors: Lovekin C. C. , Guzik J. A.
Published: January 2015

We have calculated the pulsations of massive stars using a nonlinear hydrodynamic code including time-dependent convection. The basic structure models are based on a standard grid published by Meynet et al. (1994). Using the basic structure, we calculated envelope models, which include the outer few percent of the star. These models go down to depths of at least 2 million K. These models, which range from 40 to 85 solar masses, show a range of pulsation behaviours. We find models with very long period pulsations (> 100 d), resulting in high amplitude changes in the surface properties. We also find a few models that show outburst-like behaviour. The details of this behaviour are discussed, including calculations of the resulting wind mass-loss rates.
Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution
Authors: Neilson Hilding R. , Bisol Alexandra C. , Guinan Ed , Engle Scott
Published: January 2015

Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 M⊙ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip.
Pulsations of massive stars beyond TAMS: effects of mass loss, diffusion, overshooting
Authors: Ostrowski Jakub , Daszyńska-Daszkiewicz Jadwiga
Published: January 2015

We present an influence of mass loss, element diffusion and convective overshooting on instability areas of SPBsg stars with masses of 13 - 18 M⊙. Evolutionary phases before and after helium core ignition are considered. We discuss how these effects affect the structure of the blue loops and hence a coverage of instability areas.
Asteroseismology of the SPB star HD 21071
Authors: Szewczuk Wojciech , Daszyńska-Daszkiewicz Jadwiga
Published: January 2015

We perform mode identification for the frequency peaks detected in the light variation of HD 21071 including the effects of rotation via the traditional approximation. We find the angular numbers (ℓ, m) for all observed frequencies and limit the range of the rotational velocity. In the next step, we make an attempt towards seismic modelling of the star in order to constrain its global parameters.
Amplitude Modulation of Cepheid Radial Velocity Curves as a Systematic Source of Uncertainty for Baade-Wesselink Distances
Authors: Anderson Richard I.
Published: January 2015

I report on the recent discovery of modulation in the radial velocity curves in four classical Cepheids. This discovery may enable significant improvements in the accuracy of Baade-Wesselink distances by revealing a not previously considered systematic source of uncertainty.
Unraveling the variability of σ Ori E
Authors: Oksala M. E. , Kochukhov O. , Krtička J. , Prvák M. , Mikulášek Z.
Published: January 2015

σ Ori E (HD 37479) is the prototypical helium-strong star shown to harbor a strong magnetic field, as well as a magnetosphere consisting of two clouds of plasma. The observed optical (ubvy) light curve of σ Ori E is dominated by eclipse features due to circumstellar material, however, there remain additional features unexplained by the Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki (2005). Using the technique of magnetic Doppler imaging (MDI), spectropolarimetric observations of σ Ori E are used to produce maps of both the magnetic field topology and various elemental abundance distributions. We also present an analysis utilizing these computed MDI maps in conjunction with non-local thermodynamical equilibrium TLUSTY models to study the optical brightness variability of this star arising from surface inhomogeneities. It has been suggested that this physical phenomena may be responsible for the light curve inconsistencies between the model and observations.
The magnetic field of ζ Ori A
Authors: Blazère A. , Neiner C. , Bouret J-C. , Tkachenko A. ,   the MiMeS collaboration
Published: January 2015

Magnetic fields play a significant role in the evolution of massive stars. About 7% of massive stars are found to be magnetic at a level detectable with current instrumentation (Wade et al. 2013) and only a few magnetic O stars are known. Detecting magnetic field in O stars is particularly challenging because they only have few, often broad, lines to measure the field, which leads to a deficit in the knowledge of the basic magnetic properties of O stars. We present new spectropolarimetric Narval observations of ζ Ori A. We also provide a new analysis of both the new and older data taking binarity into account. The aim of this study was to confirm the presence of a magnetic field in ζ Ori A. We identify that it belongs to ζ Ori Aa and characterize it.
Abundance analysis of HD 22920 spectra
Authors: Khalack Viktor , Poitras Patrick
Published: January 2015

The new spectropolarimetric observations of HD 22920 with ESPaDOnS at CFHT reveal a strong variability of its spectral line profiles with the phase of stellar rotation. We have obtained Teff = 13640 K, logg=3.72 for this star from the best fit of its nine Balmer line profiles. The respective model of stellar atmosphere was calculated to perform abundance analysis of HD 22920 using the spectra obtained for three different phases of stellar rotation. We have found that silicon and chromium abundances appear to be vertically stratified in the atmosphere of HD 22920. Meanwhile, silicon shows hints for a possible variability of vertical abundance stratification with rotational phase.
Fundamental properties of single O stars in the MiMeS survey
Authors: Martins F. , Hervé A. , Bouret J.-C. , Marcolino W. L. F. , Wade G. A. , Neiner C. , Alecian E. ,   the MiMeS collaboration
Published: January 2015

We present preliminary results of the determination of fundamental parameters of single O-type stars in the MiMeS survey. We present the sample and we focus on surface CNO abundances, showing how they change as stars evolve off the zero-age main sequence.
The UVMag space project: UV and visible spectropolarimetry of massive stars
Authors: Neiner Coralie ,   the UVMag consortium
Published: January 2015

UVMag is a medium-size space telescope equipped with a high-resolution spectropolarimetrer working in the UV and visible domains. It will be proposed to ESA for a future M mission. It will allow scientists to study all types of stars as well as e.g. exoplanets and the interstellar medium. It will be particularly useful for massive stars, since their spectral energy distribution peaks in the UV. UVMag will allow us to study massive stars and their circumstellar environment (in particular the stellar wind) spectroscopically in great details. Moreover, with UVMag's polarimetric capabilities we will be able, for the first time, to measure the magnetic field of massive stars simultaneously at the stellar surface and in the wind lines, i.e. to completely map their magnetosphere.
Stellar magnetic fields from four Stokes parameter observations
Authors: Rusomarov N. , Kochukhov O. , Piskunov N.
Published: January 2015

Magnetic Doppler imaging (MDI) from observations of four Stokes parameters can uncover new information that is of interest to the evolution and structure of magnetic fields of intermediate and high-mass stars. Our MDI study of the chemically peculiar star HD 24712 from four Stokes parameter observations, obtained with the HARPSpol instrument at the 3.6-m ESO telescope, revealed a magnetic field with strong dipolar component and weak small-scale contributions. This finding gives evidence for the hypothesis that old Ap stars have predominantly dipolar magnetic fields.