bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term magnetic resonance imaging of stem cells in neonatal ischemic injury
Authors: Obenaus Andre , Dilmac Nejmi , Tone Beatriz , Tian Hou Rou , Hartman Richard , Digicaylioglu Murat , Snyder Evan Y. , Ashwal Stephen 
Published: November 2010

AbstractObjectiveQuantitative magnetic resonance imaging (MRI) can serially and noninvasively assess the degree of injury in rat pup models of hypoxic ischemic injury (HII). It can also noninvasively monitor stem cell migration following iron oxide prelabeling. Reports have shown that neural stem cells (NSCs) may help mediate neuroprotection or stimulate neuroreparative responses in adult and neonatal models of ischemic injury. We investigated the ability of high‐field MRI to monitor and noninvasively quantify the migration, proliferation, and location of iron oxide–labeled NSCs over very long time periods (58 weeks) in real time while contemporaneously correlating this activity with the evolving severity and extent of neural damage.MethodsLabeled clonal murine NSCs (mNSCs) were implanted 3 days after unilateral HII in 10‐day‐old rat pups into the contralateral striatum or ventricle. We developed methods for objectively quantifying key aspects of dynamic NSC behavior (eg, viability; extent, and speed of migration; degree of proliferation; extent of integration into host parenchyma). MRI images were validated with histological and immunohistochemical assessments.ResultsmNSCs rapidly migrated (100 μm/day) to the lesion site. Chains of migrating NSCs were observed in the corpus callosum. In pups subjected to HII, though not in intact control animals, we observed a 273% increase in the MR‐derived volume of mNSCs 4 weeks after implantation (correlating with the known proliferative behavior of endogenous and exogenous NSCs) that slowly declined over the 58‐week time course, with no adverse consequences. Large numbers of now quiescent mNSCs remained at the site of injury, many retaining their iron oxide label.InterpretationOur studies demonstrate that MRI can simultaneously monitor evolving neonatal cerebral injury as well as NSC migration and location. Most importantly, it can noninvasively monitor proliferation dynamically for prolonged time periods. To be able to pursue clinical trials in newborns using stem cell therapies it is axiomatic that safety be insured through the long‐term real time monitoring of cell fate and activity, particularly with regard to observing unanticipated risks to the developing brain. This study supports the feasibility of reliably using MRI for this purpose.Ann Neurol 2011
γ‐Secretase component presenilin is important for microglia β‐amyloid clearance
Authors: Farfara Dorit , Trudler Dorit , Segev‐Amzaleg Niva , Galron Ronit , Stein Reuven , Frenkel Dan 
Published: November 2010

AbstractObjectiveThe cleavage of amyloid precursor protein by γ‐secretase is an important aspect of the pathogenesis of Alzheimer's disease. γ‐Secretase also cleaves other membrane proteins (eg, Notch), which control cell development and homeostasis. Presenilin 1 and 2 are considered important determinants of the γ‐secretase catalytic site. Our aim was to investigate whether γ‐secretase can be important for microglial phagocytosis of Alzheimer's disease β‐amyloid.MethodsWe investigated the role of γ‐secretase in microglia activity toward β‐amyloid phagocytosis in cell culture using γ‐secretase inhibitors and small hairpin RNA and presenilin‐deficient mice.ResultsWe found that γ‐secretase inhibitors impair microglial activity as measured in gene expression, protein levels, and migration ability, which resulted in a reduction of soluble β‐amyloid phagocytosis. Moreover, microglia deficient in presenilin 1 and 2 showed impairment in phagocytosis of soluble β‐amyloid. Dysfunction in the γ‐secretase catalytic site led to an impairment in clearing insoluble β‐amyloid from brain sections taken from an Alzheimer's disease mouse model when compared to microglia from wild‐type mice.InterpretationWe suggest for the first time, a dual role for γ‐secretase in Alzheimer's disease. One role is the cleavage of the amyloid precursor protein for pathologic β‐amyloid production and the other is to regulate microglia activity that is important for clearing neurotoxic β‐amyloid deposits. Further studies of γ‐secretase‐mediated cellular pathways in microglia may provide useful insights into the development of Alzheimer's disease and other neurodegenerative diseases, providing future avenues for therapeutic intervention. ANN NEUROL 2010
JH biosynthesis by reproductive tissues and corpora allata in adult longhorned beetles, Apriona germari
Authors: Tian Ling , Ji Bao‐Zhong , Liu Shu‐Wen , He Chun‐Ling , Jin, Feng , Gao Jie , Stanley David , Li Sheng 
Published: November 2010

AbstractWe report on juvenile hormone (JH) biosynthesis from long‐chain intermediates by specific reproductive tissues and the corpora allata (CA) prepared from adult longhorned beetles, Apriona germari. The testes, male accessory glands (MAGs), ovaries, and CA contained the long‐chain intermediates in the JH biosynthetic pathway, farnesoic acid (FA), methyl farnesoate (MF), and JH III. The testes and ovaries, but not CA, produced radioactive JH III after the addition of 3H‐methionine and, separately, unlabeled methionine, to the incubation medium. We inferred that endogenous FA is methylated to MF in the testes and ovaries. Addition of farnesol led to increased amounts of FA in the testes, MAGs, ovaries, and CA, indicating oxidation of farnesol to FA. Addition of FA to incubation medium yielded increased JH III, again indicating methylation of FA to MF in the testes, MAGs, ovaries, but not CA. Addition of MF to incubation medium also led to JH III, from which we inferred the epoxidation of MF to JH III. JH biosynthesis from farnesol in the testes, MAGs, and ovaries of A. germari proceeds via oxidation to FA, methylation to MF, and epoxidation to JH III. This is a well‐known pathway to JH III, described here for the first time in reproductive tissues of longhorned beetles. © 2010 Wiley Periodicals, Inc.
Seismological challenges for stellar structure
Authors: Christensen‐Dalsgaard J. 
Published: November 2010

AbstractHelioseismology has provided very detailed information about the solar interior, and extensive data on a large number of stars, although at less detail, are promised by the ongoing and upcoming asteroseismic projects. In the solar case there remain serious challenges in understanding the inferred solar structure, particularly in the light of the revised determinations of the solar surface composition. Also, a secure understanding of the origins of solar rotation as inferred from helioseismology, both in the radiative interior and in the convection zone, is still missing. In the stellar case challenges are certain to appear as the data allow more detailed inferences of the properties of stellar cores. Large remaining uncertainties in modelling concern the properties of convective cores and other processes that may cause mixing. As a result of developing asteroseismic signatures addressing these and other issues, we can look forward to a highly challenging, and hence exciting, era of stellar astrophysics (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The acoustic and magnetic solar cycle
Authors: Komm R. 
Published: November 2010

AbstractThe frequency variation of global modes provides information about the solar structure and the rotation rate of the solar interior. The solar‐cycle variation of the rotation rate, the so‐called torsional oscillation, extends throughout the convection zone. Alternating bands of faster‐ and slower‐than‐average rotation move from mid‐latitudes toward the equator during the solar cycle. The variation of the meridional flow, measured with local helioseismic techniques, is of similar amplitude. The zonal‐ and the meridional‐flow variation related to a new cycle are noticeable years before magnetic activity of the new cycle is present at the surface. The sound‐speed variations show a small, but significant variation with the solar cycle near the base of the convection zone, which might be interpreted as a change in magnetic field strength. The mode characteristics, such as acoustic radius and frequency shifts, provide information about changes in the near‐surface layers, where acoustic modes are excited (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Internal magnetic fields inferred from helioseismic data
Authors: Baldner C.S. , Antia H.M. , Basu S. , Larson T.P. 
Published: November 2010

AbstractMeasuring the internal solar magnetic fields and how they change over the course of a solar cycle is one of the key aims of helioseismology. We present the results of attempts to model the global mode splitting coefficients over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large‐scale magnetic field. The first results using only the a2 coefficients show that the data are best fit by a combination of a poloidal field and a double‐peaked near‐surface toroidal field. The toroidal fields are centered at r0 = 0.999 R⊙ and r0 = 0.996 R⊙ and are confined to the near‐surface layers. The poloidal field is a dipole field. The peak strength of the poloidal field is 124 ± 17 G. The toroidal field peaks at 380 ± 30 G and 1.4 ± 0.2 kG for the shallower and deeper fields, respectively. The field strengths are highly correlated with surface activity. We also examine the differences between the minima at the beginning and the end of solar cycle 23 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The interior of the Sun in 3‐D: Beyond the spherical Sun picture
Authors: Mathis S. 
Published: November 2010

AbstractWith all the results now obtained by global helioseismology, it is clear that we have to go beyond the classical spherical modelling of the Sun. In this way, it is now necessary to draw a picture that takes into account internal dynamical processes such as rotation, magnetic field, and waves from the core to the surface. This is a challenging task since such mechanisms involve length and time‐scales that differ from several orders of magnitude and impact on the solar behaviour both on dynamical and secular times. In this review, I will thus describe the present state of the art in the modelling of the internal dynamics of the Sun (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
What does the Sun suggest about global oscillation amplitudes in solar‐like stars
Authors: Severino G. , Straus Th. , Oliviero M. , Steffen M. 
Published: November 2010

AbstractMotivated by the results of CoRoT and based on the solar experience, we develop a new stellar scaling law for the intensity‐velocity amplitude ratio (gain) of resonant oscillations, which is a quantity independent of the excitation model. The comparison of our approach with observations gives new interesting results for the Sun as a star. Moreover, for a sample of three solar‐like stars observed by CoRoT, we found that our scaling law provides an explanation of the low observed luminosity amplitudes which is an alternative to non‐adiabatic effects (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local helioseismology and the active Sun
Authors: Schunker H. 
Published: November 2010

AbstractThe goal of local helioseismology is to elicit three‐dimensional information about the sub‐surface (or far‐side) structure and dynamics of the Sun from observations of the helioseismic wave field at the surface. The physical quantities of interest include flows, sound‐speed deviations and magnetic fields. However, strong surface magnetic fields induce large perturbations to the waves making inversions difficult to interpret. The purpose of this paper is to outline the methods of analysis used in local helioseismology, review discoveries associated with the magnetic Sun made using local helioseismology from the past three years, and highlight the efforts towards imaging the interior in the presence of strong magnetic fields (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new code for Fourier‐Legendre analysis of large datasets: First results and a comparison with ring‐diagram analysis
Authors: Doerr H.‐P. , Roth M. , Zaatri A. , Krieger L. , Thompson M. J. 
Published: November 2010

AbstractFourier‐Legendre decomposition (FLD) of solar Doppler imaging data is a promising method to estimate the sub‐surface solar meridional flow. FLD is sensible to low‐degree oscillation modes and thus has the potential to probe the deep meridional flow. We present a newly developed code to be used for large scale FLD analysis of helioseismic data as provided by the Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI) instrument, and the upcoming Helioseismic and Magnetic Imager (HMI) instrument. First results obtained with the new code are qualitatively comparable to those obtained from ring‐diagram analyis of the same time series (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observational results from active region seismology
Authors: Gonzälez Hernández I. 
Published: November 2010

AbstractActive regions are one of the most observed features in the solar surface. High‐resolution solar telescopes on ground and space have revealed the fine configuration of umbra and penumbra of sunspots with amazing detail. However, the subsurface structure of sunspots and active regions remains, for the most part, unknown. Thanks to the development of local helioseismology methods, the properties of active regions under the solar surface are starting to unravel. This paper reviews some of the main results obtained from the application of local helioseismology techniques to the study of the subsurface dynamics and magnetic properties of active regions (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on the core µ ‐gradient of the solar‐like star HD 49385 via low‐degree mixed modes
Authors: Deheuvels S. , Michel E. 
Published: November 2010

AbstractThe existence of an ℓ = 1 avoided crossing in the spectrum of the solar‐like pulsator CoRoT*‐target HD 49385 (*The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES with participation of the Science Programs of ESA; ESA's RSSD, Austria, Belgium, Brazil, Germany, and Spain.) was established by Deheuvels & Michel (2009). It is the first confirmed detection of such a phenomenon. The authors showed in a preliminary modeling of the star that it was in a post main sequence status. Being a 1.3 M⊙ ‐star, HD 49385 has had a convective core during its main sequence phase. The µ ‐gradient left by the withdrawal of this core bears information about the processes of transport at the boundary of the core. We here investigate the constraints that the observed avoided crossing brings on the µ ‐gradient in the core of the star (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An alternative to mode fitting
Authors: Mosser B. 
Published: November 2010

AbstractThe space mission CoRoT provides us with a large amount of high‐duty cycle long‐duration observations. Mode fitting has proven to be efficient for the complete and detailed analysis of the oscillation pattern, but remains time consuming. Furthermore, the photometric background due to granulation severely complicates the analysis. Therefore, we attempt to provide an alternative to mode fitting, for the determination of large separations. With the envelope autocorrelation function and a dedicated filter, it is possible to measure the variation of the large separation independently for the ridges with even and odd degrees. The method appears to be as accurate as the mode fitting. It can be very easily implemented and is very rapid (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectrum analysis and seismic interpretation of a solar‐like pulsator (HD 49933) observed by CoRoT
Authors: Benomar O. , Baudin F. , Marques J.P. , Goupil M.J. , Lebreton Y. , Deheuvels S. 
Published: November 2010

AbstractThe star HD 49933 has been observed by the mission CoRoT two times (for 60 and 137 days). Its spectrum shows a wealth of oscillation modes but was found difficult to analyse. In the following, we summarize why it was so, and then present a modeling of the star using seismic constraints and show the effect of the microscopic diffusion and of the overshoot in the modeling. We conclude that some convective overshoot from the core is needed while it is difficult to give a definitive conclusion concerning the effect of the microscopic diffusion on the modeling of HD 49933 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Can asteroseismology solve the solar abundance problem? The test case of HD 43587
Authors: Mazumdar A. , Singhal L. , Prabhu S. 
Published: November 2010

AbstractThe recent downward revision of solar abundances has serious implications not only for the Sun, but for distant stars as well. The effects of altering the mixture of elements inside a star and lowering the overall metallicity on stellar oscillation frequencies are tested on theoretical models of a CoRoT primary target star, HD 43587. It is found that although frequency separations are significantly affected by changes in the chemical makeup, it might still be difficult to distinguish between the two cases of solar abundances because of the ambiguity in the fundamental parameters, such as effective temperature, luminosity, and [Fe/H] of the target star (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Kepler Asteroseismic Investigation: Scientific goals and first results
Authors: Kjeldsen H. , Christensen‐Dalsgaard J. , Handberg R. , Brown T.M. , Gilliland R.L. , Borucki W.J. , Koch D. 
Published: November 2010

AbstractKepler is a NASA mission designed to detect exoplanets and characterize the properties of exoplanetary systems. Kepler also includes an asteroseismic programme which is being conducted through the Kepler Asteroseismic Science Consortium (KASC), whose 400 members are organized into 13 working groups by type of variable star. So far data have been available from the first 7 month of the mission containing a total of 2937 targets observed at a 1‐min cadence for periods between 10 days and 7 months. The goals of the asteroseismic part of the Kepler project is to perform detailed studies of stellar interiors. The first results of the asteroseismic analysis are orders of magnitude better than seen before, and this bodes well for how the future analysis of Kepler data for many types of stars will impact our general understanding of stellar structure and evolution (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asteroseismology of solar‐type stars with Kepler I: Data analysis
Authors: Karoff C. , Chaplin W.J. , Appourchaux T. , Elsworth Y. , Garcia R.A. , Houdek G. , Metcalfe T.S. , Molenda‐Żakowicz J. , Monteiro M.J.P.F.G. , Thompson M.J. , Christensen‐Dalsgaard J. , Gilliland R.L. , Kjeldsen H. , Basu S. , Bedding T.R. , Campante T.L. , Eggenberger P. , Fletcher S.T. , Gaulme P. , Handberg R. , Hekker S. , Martic M. , Mathur S. , Mosser B. , Regulo C. , Roxburgh I.W. , Salabert D. , Stello D. , Verner G.A , Belkacem K. , Biazzo K. , Cunha M.S. , Gruberbauer M. , Guzik J.A. , Kupka F. , Leroy B. , Ludwig H.‐G. , Mathis S. , Noels A. , Noyes R.W. , Roca Cortes T. , Roth M. , Sato K.H. , Schmitt J. , Suran M.D. , Trampedach R. , Uytterhoeven K. , Ventura R. , Wilson P.A. 
Published: November 2010

AbstractWe report on the first asteroseismic analysis of solar‐type stars observed by Kepler. Observations of three G‐type stars, made at one‐minute cadence during the first 33.5 days of science operations, reveal high signal‐to‐noise solar‐like oscillation spectra in all three stars: About 20 modes of oscillation can clearly be distinguished in each star. We discuss the appearance of the oscillation spectra, including the presence of a possible signature of faculae, and the presence of mixed modes in one of the three stars (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solar‐like oscillations in cluster stars
Authors: Stello D. , Basu S. , Bedding T.R. , Brogaard K. , Bruntt H. , Chaplin W.J. , Christensen‐Dalsgaard J. , Demarque P. , Elsworth Y.P. , García R.A. , Gilliland R.L. , Hekker S. , Huber D. , Karoff C. , Kjeldsen H. , Lebreton Y. , Mathur S. , Meibom S. , Molenda‐Żakowicz J. , Noels A. , Roxburgh I.W. , Aguirre V.S. , Sterken C. , Szabö R. 
Published: November 2010

AbstractWe present a brief overview of the history of attempts to obtain a clear detection of solar‐like oscillations in cluster stars, and discuss the results on the first clear detection, which was made by the Kepler Asteroseismic Science Consortium (KASC) Working Group 2 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kepler observations: Light shed on the hybridγDoradus –δScuti pulsation phenomenon
Authors: Grigahcène A. , Uytterhoeven K. , Antoci V. , Balona L. , Catanzaro G. , Daszyńska‐Daszkiewicz J. , Guzik J.A. , Handler G. , Houdek G. , Kurtz D.W. , Marconi M. , Monteiro M.J.P.F.G. , Moya A. , Ripepi V. , Suárez J.‐C. , Borucki W.J. , Brown T.M. , Christensen‐Dalsgaard J. , Gilliland R.L. , Jenkins J.M. , Kjeldsen H. , Koch D. , Bernabei S. , Bradley P. , Breger M. , Di Criscienzo M. , Dupret M.‐A. , García R.A. , García Hernández A. , Jackiewicz J. , Kaiser A. , Lehmann H. , Martín‐Ruiz S. , Mathias P. , Molenda‐Żakowicz J. , Nemec J.M. , Nuspl J. , Paparó M. , Roth M. , Szabó R. , Suran M.D. , Ventura R. 
Published: November 2010

AbstractThrough the observational study of stellar pulsations, the internal structure of stars can be probed and theoretical models can be tested. The main sequence ‐γDoradus (Dor) andδScuti (Sct) stars with masses 1.2–2.5 M⊙are particularly interesting for asteroseismic study. The ‐γDor stars pulsate in high‐order gravity (g) modes, with pulsational periods of order of one day. TheδSct stars, on the other hand, show low‐order g and pressure (p) modes with periods of order of 2 hours. Theory predicts the existence of ‘hybrid’ stars, i.e. stars pulsating in both types of modes, in an overlap region between the instability strips of ‐γDor andδSct stars in the Hertzsprung‐Russell diagram. Hybrid stars are particularly interesting as the two types of modes probe different regions of the stellar interior and hence provide complementary model constraints. Before the advent of Kepler, only a few hybrid stars had been confirmed. The Kepler satellite is providing a true revolution in the study of and search for hybrid stars. Analysis of the first 50 days of Kepler data of hundreds of ‐γDor andδSct candidates reveals extremely rich frequency spectra, with most stars showing frequencies in both theδSct and ‐γDor frequency range. As these results show that there are practically no pureδSct or ‐γDor pulsators, a new observational classification scheme is proposed by Grigahcène et al. (2010). We present their results and characterize 234 stars in terms ofδSct, ‐γDor,δSct/‐γDor or ‐γDor/δSct hybrids (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ground‐based follow‐up in relation to Kepler asteroseismic investigation
Authors: Uytterhoeven K. , Briquet M. , Bruntt H. , De Cat P. , Frandsen S. , Gutiérrez‐Soto J. , Kiss L. , Kurtz D.W. , Marconi M. , Molenda‐Żakowicz J. , Østensen R. , Randall S. , Southworth J. , Szabó R. , KASC Working Groups on ground‐based observations  
Published: November 2010

AbstractThe Kepler space mission, successfully launched in March 2009, is providing continuous and high‐precision photometry of thousands of stars simultaneously. The uninterrupted time‐series of stars of all known pulsation types are a precious source for asteroseismic studies. The Kepler data do not provide information on the physical parameters, such as log g, metallicity, and v sin i, which are crucial for successful asteroseismic modelling. Additional ground‐based time‐series data are needed to characterize mode parameters in several types of pulsating stars. Therefore, ground‐based multi‐colour photometry and mid/high‐resolution spectroscopy are needed to complement the space data. We present ground‐based activities within KASC on selected asteroseismic Kepler targets of several pulsation types (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)