bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertebral Anomaly in Fossil Sea Cows (Mammalia, Sirenia)
Authors: Voss Manja , Asbach Patrick , Hilger André 
Published: April 2011

AbstractFour incompletely preserved caudal vertebrae lacking the neural arches of two fossil sirenian individuals of Halitherium schinzii (Oligocene) from the Rhine area in Germany and northern Belgium reveal osteological alterations. The caudal vertebrae possess a transverse process with growth retardation. This asymmetry indicates that the affected transverse processes are less developed than their counterparts and, consequently, deviate from the norm. Computed tomography (CT) scans reveal osteosclerotic patterns, a morphological feature that characterizes sea cows and supports the nonpathological state of the vertebrae. Additionally, no indications of vertebral fractures or any other occurrences due to external factors are present. This is the oldest documentation of such an anomaly in any sirenian and is interpreted here as hypoplasia, the underdevelopment of an organ or parts of it that might cause a functional deficiency. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.
Ground‐penetrating Radar in the Regio III (Pompeii, Italy): Archaeological Evidence
Authors: Barone P. M. , Bellomo T. , Mattei E. , Lauro S. E. , Pettinelli E. 
Published: April 2011

ABSTRACTGround‐penetrating radar (GPR) investigations were performed in Pompeii, in an area of the Regio III that is not yet fully excavated but is bounded by areas where much is known about the ancient Roman city. At the site studied, large areas containing preserved archaeological features are buried under as much as 8 m of volcanic deposits. The GPR survey was conducted using perpendicular reflection profiles in a grid adjacent to a scarp parallel to Nola Street, which allowed a direct correlation between the exposed ruins and the radar reflection features. An analysis of the GPR reflection profiles clearly shows the layering of the volcanic materials, with the underlying Roman architecture clearly differentiated. Amplitude analysis of all reflections within the grid produced spatial maps of the ruins containing a particular distribution of Roman elite buildings inside a Classic insula, including monumental fountains, apses and villas (domus); such architectural features were commonly incorporated into residences (villas) of wealthy people. Typically suburban districts of Roman cities contain non‐elite houses, whereas wealthy persons lived are in the city centre. However, in this case because these features are found away from the central district of Pompeii, it is possible to argue from the GPR analysis for the presence an elite off‐centre district possibly documenting suburban growth that reresents a newly wealthy society produced by the growing economy at the time of the eruption. The importance of collecting GPR reflection data in different directions was apparent in this study, as many of the architectural features of interest were visible in some profiles but not visible in others, depending on the orientation of the antenna dipolar field orientations. Copyright © 2011 John Wiley & Sons, Ltd.
Some properties of exact observability of linear stochastic systems and their applications
Authors: Hou Ting , Zhang Weihai , Ma Hongji 
Published: April 2011

AbstractA new criterion is proposed for exact observability of linear stochastic systems. As applications of this criterion, the effects of exact observability due to state/output feedback are investigated. In addition, under the conditions of stability and exact observability, we discuss the properties of a set defined by the generalized Lyapunov equations (GLEs).Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Black‐hole states in external galaxies
Authors: Belloni T.M. 
Published: April 2011

AbstractA large number of Ultra‐Luminous X‐ray Sources in external galaxies is now known, but the discussion about their nature is still unsettled: intermediate‐mass black holes or stellar‐mass black holes accreting above the Eddington limit? A promising path that can provide an answer is through comparison with “normal” stellar‐mass black holes. These display separate states, identified from both their energy spectra and their fast variability. Although the nature of these states and their transitions is not clear, such a comparison can be extremely useful. In this paper, I briefly outline our current phenomenological knowledge of these states and present a (partial) overview of the different approaches followed to make these comparisons (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Six years of XMM‐Newton observations of NGC 1313 X‐1 and X‐2
Authors: Pintore F. , Zampieri L. 
Published: April 2011

AbstractWe present a systematic analysis of the X‐ray spectra of NGC 1313 X‐1 and NGC 1313 X‐2, using six years of XMM‐Newton observations (17 observations). We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the effects of an accretion disc plus an optically thick corona. We checked the consistency of this spectral model on the basis of the variability patterns of its spectral parameters. We found that the two sources show different spectral states. We tentatively interpret the observed behaviour of NGC 1313 X‐1 within the framework of super‐Eddington accretion and that of NGC 1313 X‐2 within the framework of near Eddington accretion. We also attempted to determine the chemical abundances in the local environment of NGC 1313 X‐1 and X‐2, analyzing the RGS spectra of the longest observation available (122 ks). The results appear to indicate solar metallicity for the local environment of NGC 1313 X‐1 and sub‐solar metallicity for NGC 1313 X‐2 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The demographics of ultraluminous X‐ray sources
Authors: Swartz D.A. 
Published: April 2011

AbstractResults of recent statistical studies of the population of ultraluminous X‐ray sources are presented. Special emphasis is placed on the outcome of a complete survey of 140 nearby galaxies hosting 114 ULXs. It is shown that ULXs are preferentially associated with young star‐forming regions but not necessarily with massive young clusters, that ULXs occur at a higher rate (per unit mass) in dwarf galaxies compared to giant galaxies and that ULXs rarely occur in galactic halos. If an upper limit to the luminosity of ULXs exists, then it must be above several times 1040 erg s–1 in the X‐ray band. The luminosity function is still too sparsely sampled above this luminosity for a more definitive statement to be made (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unlocking the nature of ultraluminous X‐ray sources using their X‐ray spectra
Authors: Gladstone J.C. , Roberts T.P. , Done C. 
Published: April 2011

AbstractWe explore the nature of ultraluminous X‐ray sources through detailed investigations of their spectral shape using some of the highest quality data available in the XMM‐Newton public archives. Phenomenological models allow us to characterise their spectra, while more ‘physically‐motivated’ models enable us to explore the physical processes underlying these characteristics. These physical models imply the presence of extreme (probably super‐Eddington) accretion on to stellar mass black holes (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The collective X‐ray luminosity of HMXB as a SFR indicator
Authors: Mineo S. , Gilfanov M. , Sunyaev R. 
Published: April 2011

AbstractWe study the relation between the X‐ray luminosity of compact sources and the SFR of the host galaxy. Our sample includes 38 galaxies for which a uniform set of X‐ray, infra‐red and ultraviolet data from Chandra, Spitzer and GALEX has been collected. Our primary goals are (i) to obtain a more accurate calibration of the Lx–SFR relation and (ii) to understand the origin of the dispersion in the Lx–SFR relation observed in previous studies. Preliminary results of this project are reported below (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Key results from an XMM‐Newton and Chandra study of a new sample of extreme ULXs from the 2XMM catalogue
Authors: Sutton A.D. , Roberts T.P. , Walton D.J. 
Published: April 2011

AbstractWe present highlights from a study of a sample of 10 extreme‐luminosity candidate ultraluminous X‐ray sources (Lx > 5 × 1040 erg s–1), all at distances <100 Mpc, identified from a cross‐correlation of the RC3 catalogue of galaxies with the 2XMM catalogue. Five of the sample have also been observed by Chandra. Of the 10 sources, seven reside in the disc or arms of spiral galaxies, and the remaining three are close to large elliptical galaxies. Unlike many less luminous ultraluminous X‐ray sources, temporal variability is observed on short (ks) and long (yr) timescales for most sources in our sample. Long term spectral variability is also evident in some sources. In one case, we use archival Chandra data to demonstrate that a hyperluminous X‐ray source candidate identified by XMM‐Newton is actually resolved into multiple point sources at high spatial resolution, but note that the other candidates remain unresolved under Chandra's intense scrutiny (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical variability of the ultraluminous X‐ray source NGC 1313 X‐2
Authors: Impiombato D. , Zampieri L. , Falomo R. , Grisé F. , Soria R. 
Published: April 2011

AbstractWe analyzed the longest phase‐connected photometric dataset available for NGC 1313 X‐2, looking for the ∼6 day modulation reported by Liu et al. (2009). The folded B ‐band light curve shows a 6 days periodicity with a significance slightly larger than 3σ. The low statistical significance of this modulation, along with the lack of detection in the V band, make its identification uncertain (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compact radio emission in Ultraluminous X‐ray sources
Authors: Mezcua M. , Lobanov A.P. 
Published: April 2011

AbstractWe present results from our studies of radio emission from selected Ultraluminous X‐ray (ULX) sources, using archival Giant Metrewave Radio Telescope (GMRT) data and new European VLBI Network (EVN) observations. The GMRT data are used to find possible faint radio emission from ULX sources located in late‐type galaxies in the Chandra Deep Fields. No detections are found at 235, 325, and 610 MHz, and upper limits on the radio flux densities at these frequencies are given. The EVN observations target milliarcsecond‐scale structures in three ULXs with known radio counterparts (N4449‐X1, N4088‐X1, and N4861‐X2). We confirm an earlier identification of the ULX N4449‐X1 with a supernova remnant and obtain the most accurate estimates of its size and age. We detect compact radio emission for the ULX N4088‐X1, which could harbour an intermediate mass black hole (IMBH) of 105 M⊙ accreting at a sub‐Eddington rate. We detect a compact radio component in the ULX N4861‐X2, with a brightness temperature >106 K and an indication for possible extended emission. If the extended structure is confirmed, this ULX could be an H II region with a diameter of 8.6 pc and surface brightness temperature ≥105 K. The compact radio emission may be coming from a ∼105 M⊙ black hole accreting at 0.1 MEdd (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A search for radio counterparts to Chandra ULX candidates
Authors: Pérez‐Ramírez D. , Mezcua M. , Leon S. , Caballero‐García M.D. 
Published: April 2011

AbstractWe present a systematic search for radio counterparts to Ultraluminous X‐ray (ULX) source candidates based on a cross‐correlation of the Swartz et al. (2004) ULX catalogue based on Chandra data and the FIRST radio survey. We find seven cases of conspicuous peaks of radio emission that could be associated to ULX sources. Among these seven ULX radio candidates, three X‐ray sources are located within 5″of the FIRST radio peaks. These three cases are shown and discussed individually (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
(No) dynamical constraints on the mass of the black hole in two ULXs
Authors: Roberts T.P. , Gladstone J.C. , Goulding A.D. , Swinbank A.M. , Ward M.J. , Goad M.R. , Levan A.J. 
Published: April 2011

AbstractWe present the preliminary results of two Gemini campaigns to constrain the mass of the black hole in an ultraluminous X‐ray source (ULX) via optical spectroscopy. Pilot studies of the optical counterparts of a number of ULXs revealed two candidates for further detailed study, based on the presence of a broad He II 4686 Å emission line. A sequence of 10 long‐slit spectra were obtained for each object, and the velocity shift of the ULX counterpart measured. Although radial velocity variations are observed, they are not sinusoidal, and no mass function is obtained. However, the broad He II line is highly variable on timescales shorter than a day. If associated with the reprocessing of X‐rays in the accretion disc, its breadth implies that the disc must be close to face‐on (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Supercritical accretion and ULXs
Authors: Mineshige S. , Ohsuga K. 
Published: April 2011

AbstractSupercritical (or super‐Eddington) accretion seems to occur in various black hole objects, including microquasars and ultra‐luminous X‐ray sources. We, here, elucidate the theory of supercritical accretion flow based on our two‐dimensional (2‐D) global radiation‐hydrodynamic (RHD) and radiation‐magnetohydrodynamic (RMHD) simulations. We first confirm that there is practically no limit to the accretion rate onto black holes. We then discuss several noteworthy observable features of the supercritical flow; that is, mild beaming, relativistic, collimated outflow, and inverse‐Compton scattering spectra by optically thick outflow. For face‐on observers the maximum apparent (isotropic) luminosities of ∼22LE (with L E being the Eddington luminosity) can be achieved for the mass supply rate of ∼50LE/c2. Even larger isotropic luminosities are possible for higher mass supply rates. For edge‐on observers, conversely, the apparent luminosity will be much less. It will be even lower, if the the innermost bright part of the disk is obscured by the outer part. High velocity (>0.5c) jet accelerated by radiation‐pressure force and collimated by Lorentz force is also expected. We expect large kinetic luminosity, ∼0.1LE, and high mass outflow rate, ∼10LE/c2. This may account for large ionizing nebulae around ULXs (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Forming massive black holes through stellar collapse: Observational diagnostics
Authors: Fryer C.L. , Heger A. 
Published: April 2011

AbstractMassive black holes are believed to reside in the centers of many galaxies. Their seeds, 1000–100 000 solar mass black holes are believed to have formed during the first epoch of star formation. Observations of X‐ray binaries suggest that at least some intermediate mass black holes form at lower redshifts. If so, we may be able to observe these massive collapses. These collapses are very different than normal core‐collapse supernovae, however, and observing the collapse of massive stars will require different observing strategies than those used for normal stellar collapse. Unlike supernovae, the collapse of massive stars may not produce any burst of photons and we must be more creative in observing the occurrence of such exotic “outbursts”. Here we briefly review the observational prospects of massive star collapse, focusing on the ever‐present neutrino signal (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The black hole in NGC 1313 X‐2
Authors: Zampieri L. , Patruno A. 
Published: April 2011

AbstractThe amount of data available for NGC 1313 X‐2 make it a cornerstone for the study of ultraluminous X‐ray sources (ULXs). We modelled the optical and X‐ray data of this ULX with a binary evolution code that takes into account X‐ray irradiation. We restricted the candidate binary system to be either a 50–100 M⊙ black hole (BH) accreting from a 12–15 M⊙ main sequence star or a 20 M⊙ BH with a 12–15 M⊙ giant donor. If the orbital period of the system is ∼6 days, a 20 M⊙ BH model becomes unlikely and we are left with the only possibility that the compact accretor in NGC 1313 X‐2 is a massive BH of 50–100 M⊙. We briefly discuss these results within the framework of an alternative scenario for the formation ofULXs, in which a portion ofthem may contain BHs of ≳30–40 M⊙ formed from very massive stars in a low metallicity environment (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The use of demand correlation in the modeling of air carrier departure delays as first‐order autoregressive random processes
Authors: Mott John H. 
Published: April 2011

SUMMARYA method for modeling air carrier departure delays at commercial‐service airports as autoregressive random processes is presented. This method employs the correlation of a priori demand data to significantly reduce prediction error in the optimal least‐squares estimator for additive white noise. The reduction factor of the prediction error is demonstrated to be on the order of 102 over that of the unbiased estimator. Copyright © 2011 John Wiley & Sons, Ltd.
Getting to the heart of planar cell polarity signaling
Authors: Henderson Deborah J. , Chaudhry Bill 
Published: April 2011

AbstractThe genes that underpin normal heart development, and which can be disrupted to result in congenital structural malformations, are rapidly being uncovered. However, the specific cellular processes that lie downstream of these genetic cascades, accurately shaping tissues and complex structures within the heart, remain relatively unclear. The noncanonical Wnt planar cell polarity (PCP) signaling pathway is known to have a role in embryonic morphogenesis and as such is an important candidate pathway to carry out these roles in heart development. The pathway regulates the polarization of cells in a variety of contexts, allowing cells to change shape and position and to “know” their orientation within a mass of tissue. PCP signaling has also been shown recently to regulate the cellular position of the primary cilium. This organelle is known to be crucial for the establishment of left‐right patterning in the early embryo and may also act as a signaling antenna for other developmental and regulatory pathways. It is not surprising that recent studies have also linked PCP to left‐right patterning. In this review, we will examine the current evidence suggesting that PCP signaling has a central role in cardiac development and malformation. Birth Defects Research (Part A) 2011. © 2011 Wiley‐Liss, Inc.
Xenopus: An emerging model for studying congenital heart disease
Authors: Kaltenbrun Erin , Tandon Panna , Amin Nirav M. , Waldron Lauren , Showell Chris , Conlon Frank L. 
Published: April 2011

AbstractCongenital heart defects affect nearly 1% of all newborns and are a significant cause of infant death. Clinical studies have identified a number of congenital heart syndromes associated with mutations in genes that are involved in the complex process of cardiogenesis. The African clawed frog, Xenopus, has been instrumental in studies of vertebrate heart development and provides a valuable tool to investigate the molecular mechanisms underlying human congenital heart diseases. In this review, we discuss the methodologies that make Xenopus an ideal model system to investigate heart development and disease. We also outline congenital heart conditions linked to cardiac genes that have been well studied in Xenopus and describe some emerging technologies that will further aid in the study of these complex syndromes. Birth Defects Research (Part A), 2011. © 2011 Wiley‐Liss, Inc.
TGFβ signaling and congenital heart disease: Insights from mouse studies
Authors: Arthur Helen M. , Bamforth Simon D. 
Published: April 2011

AbstractTransforming growth factor β (TGFβ) regulates one of the major signaling pathways that control tissue morphogenesis. In vitro experiments using heart explants indicated the importance of this signaling pathway for the generation of cushion mesenchymal cells, which ultimately contribute to the valves and septa of the mature heart. Recent advances in mouse genetics have enabled in vivo investigation into the roles of individual ligands, receptors, and coreceptors of this pathway, including investigation of the tissue specificity of these roles in heart development. This work has revealed that (1) cushion mesenchyme can form in the absence of TGFβ signaling, although mesenchymal cell numbers may be misregulated; (2) TGFβ signaling is essential for correct remodeling of the cushions, particularly those of the outflow tract; (3) TGFβ signaling also has a role in ensuring accurate remodeling of the pharyngeal arch arteries to form the mature aortic arch; and (4) mesenchymal cells derived from the epicardium require TGFβ signaling to promote their differentiation to vascular smooth muscle cells to support the coronary arteries. In addition, a mouse genetics approach has also been used to investigate the disease pathogenesis of Loeys‐Dietz syndrome, a familial autosomal dominant human disorder characterized by a dilated aortic root, and associated with mutations in the two TGFβ signaling receptor genes,TGFBR1andTGFBR2. Further important insights are likely as this exciting work progresses. Birth Defects Research (Part A), 2011.© 2011 Wiley‐Liss, Inc.
The emerging genetic landscape underlying cardiac conduction system function
Authors: Arnolds David E. , Chu Alison , McNally Elizabeth M. , Nobrega Marcelo A. , Moskowitz Ivan P. 
Published: April 2011

AbstractProper function of an organized Cardiac Conduction System (CCS) is vital to the survival of metazoans ranging from fly to man. The routine use of non‐invasive electrocardiogram measures in the diagnosis and monitoring of cardiovascular health has established a trove of reliable CCS functional data in both normal and diseased cardiac states. Recent combination of echocardiogram (ECG) data with genome‐wide association studies has identified genomic regions implicated in ECG variability which impact CCS function. In this study, we review the substantial recent progress in this area, highlighting the identification of novel loci, confirming the importance of previously implicated loci in CCS function, and exploring potential links between genes with important roles in developmental processes and variation in function of the CCS. Birth Defects Research (Part A), 2011. © 2011 Wiley‐Liss, Inc.
Metabolic self‐organization of bioluminescent Escherichia coli
Authors: Šimkus Remigijus , Baronas Romas 
Published: April 2011

ABSTRACTA possible reason for the complexity of the signals produced by bioluminescent biosensors might be self‐organization of the cells. In order to verify this possibility, bioluminescence images of cultures of lux gene reporter Escherichia coli were recorded for several hours after being placed into 8–10 mm diameter cylindrical containers. It was found that luminous cells distribute near the three‐phase contact line, forming irregular azimuthal waves. As we show, space–time plots of quasi‐one‐dimensional bioluminescence measured along the contact line can be simulated by reaction–diffusion–chemotaxis equations, in which the reaction term for the cells is a logistic (autocatalytic) growth function. It was found that the growth rate of the luminous cells (~0.02 s−1) is >100 times higher than the growth rate of E. coli. We provide an explanation for this result by assuming that E. coli exhibits considerable respiratory flexibility (the ability of oxygen‐induced switching from one metabolic pathway to another). According to the simple two‐state model presented here, the number of oxic (luminous) cells grows at the expense of anoxic (dark) cells, whereas the total number of (oxic and anoxic) cells remains unchanged. It is conjectured that the corresponding reaction–diffusion–chemotaxis model for bioluminescence pattern formation can be considered as a model for the energy‐taxis and metabolic self‐organization in the population of the metabolically flexible bacteria under hypoxic conditions. Copyright © 2011 John Wiley & Sons, Ltd.