bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoscale Effects on the Stability of the λ‐Ti3O5 Polymorph
Authors: Makiura Rie , Takabayashi Yasuhiro , Fitch Andrew N. , Tokoro Hiroko , Ohkoshi Shin‐ichi , Prassides Kosmas 
Published: April 2011

AbstractThe nanocrystalline valency‐delocalized λ‐phase of the binary oxide Ti3O5 has recently emerged as a promising phase‐change material that exhibits rapid photo‐reversible optical and resistance changes at ambient temperature. Nanoscaling caused the monoclinic‐λ to monoclinic charge‐ordered β‐phase structural instability to shift to considerably lower temperatures compared to the bulk material, and led to a broad thermal hysteresis. The structural transformation was accompanied by a large change in volume and large lattice relaxations, which imply the presence of strong electron–phonon coupling. We attribute the suppression of the phase transition to the enhanced surface energy on the nanoscale.
UV Photolysis of ClOOCl and the Ozone Hole
Authors: Lin Jim J. , Chen Andrew F , Lee Yuan T. 
Published: April 2011

AbstractThe photochemistry of the ClO dimer (ClOOCl) plays a central role in the catalytic destruction of polar stratospheric ozone. In spite of decades of intense investigations, some of its laboratory photochemical data had not reached the desired accuracy to allow a reliable simulation of the stratospheric ozone loss until recently. Inevitable impurities in ClOOCl samples have obstructed conventional measurements. In particular, an absorption measurement of ClOOCl in 2007, which gave much lower cross sections than previous studies, implied that the formation of the ozone hole cannot be explained with current chemical models. Scientists have wondered whether the model is insufficient or the data is erroneous. Efforts aiming to resolve this controversy are reviewed in this paper, which emphasizes newly developed experiments to determine two critical photochemical properties of ClOOCl—its absorption cross section and product branching ratio—including the first reported product branching ratio at 351.8 nm photolysis.
Hard and soft spectral states of ULXs
Authors: Soria R. 
Published: April 2011

AbstractI discuss some differences between the observed spectral states of ultraluminous X‐ray sources (ULXs) and the canonical scheme of spectral states defined in Galactic black holes. The standard interpretation of ULXs with a curved spectrum, or a moderately steep power‐law with soft excess and high‐energy downturn, is that they are an extension of the very high state, up to luminosities ≈1–3LEdd. Two competing models are Comptonization in a warm corona, and slim disk; I suggest bulk motion Comptonization in the radiatively‐driven outflow as another possibility. The interpretation of ULXs with a hard power‐law spectrum is more problematic. Some of them remain in that state over a large range of luminosities; others switch directly to a curved state without going through a canonical high/soft state. I suggest that those ULXs are in a high/hard state not seen in Galactic black holes; that state may overlap with the low/hard state at lower accretion rates, and extend all the way to Eddington accretion rates. If some black holes can reach Eddington accretion rates without switching to a standard‐disk‐dominated state, it is also possible that they never quench their steady jets (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A large catalogue of ultraluminous X‐ray source candidates in nearby galaxies
Authors: Walton Dj. , Gladstone J.C. , Roberts T.P. , Fabian A.C. 
Published: April 2011

AbstractSince their discovery, Ultraluminous X‐ray sources (ULXs) have attracted attention due to their combination of extreme luminosities and extra‐nuclear locations. However, they are a fairly rare phenomenon, and attempts to investigate the general properties of the population have been hindered by a relative lack of known sources. Here, we present a large catalogue of ULX candidates including 655 detections of 475 discrete sources, based on the 2XMM Serendipitous Survey. To demonstrate the potential of such a resource, we present some scientific analysis of this population, focusing on the spectral turnover seen, often at ∼6 keV, in the highest quality ULX data. We also demonstrate how the recent reflection and Comptonisation interpretations of this feature may be distinguished observationally in the future, specifically using NGC 4517 ULX1, a previously unanalysed source with high quality data, as an example case (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The population of ULXs in the spiral galaxy NGC 2276
Authors: Wolter A. , Pizzolato F. , Rota S. , Mapelli M. , Ripamonti E. 
Published: April 2011

AbstractWe present results for X‐ray point sources in the Sc galaxy NGC 2276, obtained by analyzing Chandra data. The galaxy is known to be very active in many wavelengths, possibly due to gravitational interaction with the central elliptical of the group, NGC 2300. However, previous XMM‐Newton observations resulted in the detection of only one bright ULX and extended hot gas emission. We present here the X‐ray population in NGC 2276 which comprises 17 sources. We found that 6 of them are new ULX sources in this spiral galaxy resolved for the first time by Chandra. We constructed the luminosity function that can be interpreted as mainly due of high mass X‐ray binaries, and estimate the star formation rate (SFR) to be SFR ∼5–10 M⊙ yr–1 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The supergiant optical counterpart of ULX P13 in NGC 7793
Authors: Motch C. , Pakull M.W. , Grisé F. , Soria R. 
Published: April 2011

AbstractWe have identified the optical counterpart of the ULX source P13 in the nearby spiral galaxy NGC 7793. The object is a V ∼ 20.5 mag star, ten times brighter than any other established counterpart of a ULX in nearby galaxies. Medium resolution optical spectroscopy carried out in 2008 and 2009 with the ESO‐VLT reveals the presence of narrow high order Balmer, He I and Mg II absorption lines indicating a late B‐type supergiant companion star with mass between 10 and 20 M⊙. Stellar Hβ and He II λ 4686 Å emission lines are also seen superposed on the photospheric spectrum. We detect different patterns of radial velocity variations from the emission and absorption lines over a time interval of one month. The velocity of the high order Balmer absorption lines changes by ∼100 km s–1 while the Hβ and He II λ 4686 Å emission components vary by about the same amount but with a different phasing. Assuming that the observed velocity changes trace the motion of the mass‐donor star and of the X‐ray source implies a mass of the accreting black hole in the range of 3 to 100 M⊙ with a most probable value of ∼10 to 20 M⊙. We expect an orbital period in the range of 20 to 40 days based on the low density of the supergiant star. P13 is likely in a short‐lived, and thus rare high X‐ray luminosity evolutionary state associated with the ascension of the donor star onto the supergiant stage (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New observations of ULX supershells, and their implications
Authors: Russell D.M. , Yang Y.‐J. , Gladstone J.C. , Wiersema K. , Roberts T.P. 
Published: April 2011

AbstractNew optical narrowband imaging observations of the fields of several ultra‐luminous X‐ray sources (ULXs) are presented. Known supershell nebulae are associated with a number of these ULXs, which we detect in emission lines filters such as [S II], He II, [O II] and [O III]. New nebulae are discovered, which are candidate ULX‐powered supershells. The morphologies and emission line fluxes of these nebulae could then be used to infer the properties of the emitting gas, which gives clues to the energizing source (photoionization and/or shock‐excitation, both possibly from the ULX). Studies of supershells powered by ULXs can help to constrain the nature of ULXs themselves, such as the isotropy of the X‐ray emission and the strength of their outflows (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Does NGC 5408 X‐1 really contain an intermediate‐mass black hole?
Authors: Middleton M.J. , Roberts T.P. , Done C. , Jackson F.E. 
Published: April 2011

AbstractNGC,5408 X‐1 is one of only a handful of ultraluminous X‐ray sources (ULXs) to demonstrate a strong quasi‐periodic oscillation (QPO) in its lightcurve. This has been interpreted as being analogous to the type C low‐frequency QPO seen in black hole binaries (BHBs) when accreting at sub‐Eddington rates, implying an intermediate‐mass black hole (IMBH). However, in BHBs this QPO has a centroid frequency that scales tightly with the position of the low‐frequency break in the broad band power spectrum. In recent work we re‐assessed the data and found that the position of the break does not comply with the observed relationship in either of the available, archival XMM‐Newton observations. Thus the broad band power spectral shape does not support this identification of the QPO. We also found that the X‐ray spectra do not support a sub‐Eddington identification, instead favouring a two component model of soft thermal emission at low energies, together with low‐temperature, optically thick Comptonisation producing a tail which dominates above 2 keV. The energy dependent variability supports this deconvolution and indicates a large amount of variability present in the hard component. Such variability is only met by the BHB, GRS 1915+105, and some extreme NLS1s. This suggests that NGC 5408 X‐1 is in a similar super‐Eddington state, placing a natural limit on the mass of ≤100 M⊙. Here we compare in greater detail our analysis to that of previous work on this source's variability characteristics (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploring the nature of the brightest hyper‐luminous X‐ray source
Authors: Farrell S.A. , Servillat M. , Wiersema K. , Barret D. , Godet O. , Heywood I. , Maccarone T.J. , Oates S.R. , Plazolles B. , Webb N.A. 
Published: April 2011

AbstractThe small subset of hyper‐luminous X‐ray sources with luminosities in excess of ∼1041 erg s–1 are hard to explain without the presence of an intermediate mass black hole, as significantly super‐Eddington accretion and/or very small beaming angles are required. The recent discovery of HLX‐1, the most luminous object in this class with a record breaking luminosity of ∼1042 erg s–1 in the galaxy ESO 243‐49, therefore currently provides some of the strongest evidence for the existence of intermediate mass black holes. HLX‐1 is almost an order of magnitude brighter than the other hyperluminous sources, and appears to exhibit X‐ray spectral and flux variability similar to Galactic stellar mass black hole X‐ray binaries. In this paper we review the current state of knowledge on this intriguing source and outline the results of multi‐wavelength studies from radio to ultra‐violet wavelengths, including imaging and spectroscopy of the recently identified optical counterpart obtained with the Very Large Telescope. These results continue to support an intermediate mass black hole in excess of 500 M⊙ (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Remnants of massive metal‐poor stars: Viable engines for ultra‐luminous X‐ray sources
Authors: Mapelli M. , Ripamonti E. , Zampieri L. , Colpi M. 
Published: April 2011

AbstractMassive metal‐poor stars might end their life by directly collapsing into massive (≈25–80 M⊙) black holes (BHs). We derive the number of massive BHs (N BH) that are expected to form per galaxy via this mechanism. We select a sample of 66 galaxies with X‐ray coverage, measurements of the star formation rate (SFR) and of the metallicity. We find that NBH correlates with the number of observed ultra‐luminous X‐ray sources (ULXs) per galaxy in this sample. We discuss the dependence of NULX and of NBH on the SFR and on the metallicity (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The metallicity of the nebula surrounding the ultra‐luminous X‐ray source NGC 1313 X‐2
Authors: Ripamonti E. , Mapelli M. , Zampieri L. , Colpi M. 
Published: April 2011

AbstractRecent models of the formation of ultra‐luminous X‐ray sources (ULXs) predict that they preferentially form in low‐metallicity environments. We look at the metallicity of the nebula surrounding NGC 1313 X‐2, one of the best‐studied ULXs. Simple estimates, based on the extrapolation of the metallicity gradient within NGC 1313, or on empirical calibrations (relating metallicity to strong oxygen lines) suggest a quite low metal content (Z ∼ 0.1Z⊙). But such estimates do not account for the remarkably strong X‐ray flux irradiating the nebula. Then, we build photoionization models of the nebula using CLOUDY; using such models, the constraints on the metallicity weaken substantially, as we find 0.15Z⊙ ≤ Z ≤ 0.5Z⊙ (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular and developmental mechanisms of congenital heart valve disease
Authors: Lincoln Joy , Yutzey Katherine E. 
Published: April 2011

AbstractCongenital heart disease occurs in approximately 1% of all live births and includes structural abnormalities of the heart valves. However, this statistic underestimates congenital valve lesions, such as bicuspic aortic valve (BAV) and mitral valve prolapse (MVP), that typically become apparent later in life as progressive valve dysfunction and disease. At present, the standard treatment for valve disease is replacement, and approximately 95,000 surgical procedures are performed each year in the United States. The most common forms of congenital valve disease include abnormal valve cusp morphogenesis, as in the case of BAV, or defects in extracellular matrix (ECM) organization and homeostasis, as occurs in MVP. The etiology of these common valve diseases is largely unknown. However, the study of murine and avian model systems, along with human genetic linkage studies, have led to the identification of genes and regulatory processes that contribute to valve structural malformations and disease. This review focuses on the current understanding and therapeutic implications of molecular regulatory pathways that control valve development and contribute to valve disease. Birth Defects Research (Part A), 2011. © 2011 WileyA‐Liss, Inc.
Wnt signaling regulates atrioventricular canal formation upstream of BMP and Tbx2
Authors: Verhoeven Manon C. , Haase Christa , Christoffels Vincent M. , Weidinger Gilbert , Bakkers Jeroen 
Published: April 2011

AbstractIn the developing heart, the atrioventricular canal (AVC) is essential for separation and alignment of the cardiac chambers, for valve formation, and serves to delay the electrical impulse from the atria to the ventricles. Defects in various aspects of its formation are the most common form of congenital heart defects. Using mutant and transgenic approaches in zebrafish, this study demonstrates that Wnt/β‐catenin signaling is both sufficient and required for the induction of BMP4 and Tbx2b expression in the AVC and consequently the proper patterning of the myocardium. Furthermore, genetic analysis shows that Wnt/β‐catenin signaling is upstream and in a linear pathway with BMP and Tbx2 during AVC specification. Birth Defects Research(Part A), 2011. ©2011 Wiley‐Liss, Inc.
What chick and mouse models have taught us about the role of the endocardium in congenital heart disease
Authors: DeLaughter Daniel M. , Saint‐Jean Leshana , Baldwin H. Scott , Barnett Joey V. 
Published: April 2011

AbstractSpecific cell and tissue interactions drive the formation and function of the vertebrate cardiovascular system. Although much attention has been focused on the muscular components of the developing heart, the endocardium plays a key role in the formation of a functioning heart. Endocardial cells exhibit heterogeneity that allows them to participate in events such as the formation of the valves, septation of the outflow tract, and trabeculation. Here we review, the contributions of the endocardium to cardiovascular development and outline useful approaches developed in the chick and mouse that have revealed endocardial cell heterogeneity, the signaling molecules that direct endocardial cell behavior, and how these insights have contributed to our understanding of cardiovascular development and disease. Birth Defects Research (Part A), 2011. © 2011 Wiley‐Liss, Inc.
Genome‐wide approaches to the study of adaptive gene expression evolution
Authors: Fraser Hunter B. 
Published: April 2011

AbstractThe role of gene expression in evolutionary adaptation has been a subject of debate for over 40 years.cis‐regulation of transcription has been proposed to be the primary source of morphological novelty in evolution, though this is based on only a handful of examples. Recently the first genome‐wide studies of gene expression adaptation have been published, giving us an initial global view of this process. Systematic studies such as these will allow a number of key questions currently facing the field of gene expression evolution to be addressed.
Pairing phosphoinositides with calcium ions in endolysosomal dynamics
Authors: Shen Dongbiao , Wang Xiang , Xu Haoxing 
Published: April 2011

AbstractThe direction and specificity of endolysosomal membrane trafficking is tightly regulated by various cytosolic and membrane‐bound factors, including soluble NSF attachment protein receptors (SNAREs), Rab GTPases, and phosphoinositides. Another trafficking regulatory factor is juxta‐organellar Ca2+, which is hypothesized to be released from the lumen of endolysosomes and to be present at higher concentrations near fusion/fission sites. The recent identification and characterization of several Ca2+ channel proteins from endolysosomal membranes has provided a unique opportunity to examine the roles of Ca2+ and Ca2+ channels in the membrane trafficking of endolysosomes. SNAREs, Rab GTPases, and phosphoinositides have been reported to regulate plasma membrane ion channels, thereby suggesting that these trafficking regulators may also modulate endolysosomal dynamics by controlling Ca2+ flux across endolysosomal membranes. In this paper, we discuss the roles of phosphoinositides, Ca2+, and potential interactions between endolysosomal Ca2+ channels and phosphoinositides in endolysosomal dynamics.
Evaluation of microwave‐assisted extraction for aristolochic acid from Aristolochiae Fructus by chromatographic analysis coupled with nephrotoxicity studies
Authors: Zhou Ting , Xiao Xiao‐Hua , Wang Jia‐Yue , Chen Jin‐Ling , Xu Xian‐Fang , He Zhi‐Feng , Li Gong‐Ke 
Published: April 2011

ABSTRACTIn this paper, a microwave‐assisted extraction (MAE) method was established for aristolochic acid‐I from Aristolochiae Fructus, and the advantage of MAE was evaluated by chromatographic analysis coupled with nephrotoxicity studies. The experimental parameters of MAE for aristolochic acid‐I in Aristolochiae Fructus were investigated and MAE was compared with Soxhlet extraction and ultrasound‐assisted extraction in terms of extraction yields and extraction conditions. Under the optimum conditions, MAE could provide higher extraction yields of aristolochic acid‐I (1.10 mg/g) than ultrasound‐assisted extraction (0.82 mg/g) and Soxhlet extraction (0.95 mg/g), in addition to using less solvent and having a shorter extraction time. Furthermore, the nephrotoxicities of the extracts of Aristolochiae Fructus from different extraction procedures were investigated in Sprague–Dawley rats. The results of nephrotoxicity studies of, for example, general conditions, biochemistry parameters and histopathology examination showed no significantly differences in the nephrotoxicity levels of the extracts from MAE and that from Soxhlet extraction. These results indicated that MAE technique is a simple, rapid and effective extraction method, and the microwave irradiation during MAE procedure did not have any influence on the nephrotoxicity of Aristolochiae Fructus compared with Soxhlet extraction. Copyright © 2011 John Wiley & Sons, Ltd.
HIVE: Helping interdisciplinary vocabulary engineering
Authors: Greenberg Jane , Losee Robert , Agüera José Ramón Pérez , Scherle Ryan , White Hollie , Willis Craig 
Published: April 2011

AbstractEditor's SummaryHIVE (Helping Interdisciplinary Vocabulary Engineering) is an effort to automatically generate metadata for content, drawing descriptor terms from multiple vocabularies encoded as Simple Knowledge Organization Systems (SKOS). The effort is a response to the challenges of interoperability, cost and usability of multiple terminology sets often needed to adequately describe digital resources. By offering access to more than one vocabulary with useful descriptors for a broad domain, HIVE enables aggregating the best terms to describe resources and automatically apply metadata. HIVE offers knowledge management value for multidisciplinary digital collections while demonstrating the expanded potential use of SKOS. The initiative is headed by the Metadata Research Center at the University of North Carolina's School of Information and Library Science working with several institutional partners. Conferences and workshops are scheduled to inform interested developers and users, who are invited to try out, contribute to and evaluate the system.
Activity‐Based Profiling of Retaining β‐Glucosidases: A Comparative Study
Authors: Witte Martin D. , Walvoort Marthe T. C. , Li Kah‐Yee , Kallemeijn Wouter W. , Donker‐Koopman Wilma E. , Boot Rolf G. , Aerts Johannes M. F. G. , Codée Jeroen D. C. , van der Marel Gijsbert A. , Overkleeft Herman S. 
Published: April 2011

AbstractActivity‐based protein profiling (ABPP) is a versatile strategy to report on enzyme activity in vitro, in situ, and in vivo. The development and use of ABPP tools and techniques has met with considerable success in monitoring physiological processes involving esterases and proteases. Activity‐based profiling of glycosidases, on the other hand, has proven more difficult, and to date no broad‐spectrum glycosidase activity‐based probes (ABPs) have been reported. In a comparative study, we investigated both 2‐deoxy‐2‐fluoroglycosides and cyclitol epoxides for their utility as a starting point towards retaining β‐glucosidase ABP. We also investigated the merits of direct labeling and two‐step bio‐orthogonal labeling in reporting on glucosidase activity under various conditions. Our results demonstrate that 1) in general cyclitol epoxides are the superior glucosidase ABPs, 2) that direct labeling is the more efficient approach but it hinges on the ability of the glucosidase to be accommodated in the active site of the reporter (BODIPY) entity, and 3) that two‐step bio‐orthogonal labeling can be achieved on isolated enzymes but translating this protocol to cell extracts requires more investigation.
Click Peptide Concept: O‐Acyl Isopeptide of Islet Amyloid Polypeptide as a Nonaggregative Precursor Molecule
Authors: Yoshiya Taku , Higa Ayano , Abe Naoko , Fukao Fukue , Kuruma Tomomi , Toda Yuki , Sohma Youhei , Kiso Yoshiaki 
Published: April 2011

AbstractThe O‐acyl isopeptide (1) of islet amyloid polypeptide (IAPP), which contains an ester moiety at both Ala8‐Thr9 and Ser19‐Ser20, was prepared by sequential segment condensation based on the O‐acyl isopeptide method. Isopeptide 1 possessed nonaggregative properties, retaining its random coil structure under the acidic conditions; this suggests that the insertion of the O‐acyl isopeptide structures in IAPP suppressed aggregation of the molecule. As a result of the rapid O‐to‐N acyl shift of 1 under neutral pH, in situ‐formed IAPP adopted a random‐coil structure at the start of the experiment, and then underwent conformational change to α‐helix/β‐sheet mixed structures as well as aggregation. The click peptide strategy with the nonaggregative precursor molecule 1 could be a useful experimental tool to identify the functions of IAPP, by overcoming the handling difficulties that arise from IAPP's intense and uncontrollable self‐assembling nature.