bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarimetric measurements in prominences and “tornadoes” observed by THEMIS
Authors: Schmieder Brigitte , Ariste Arturo López , Levens Peter , Labrosse Nicolas , Dalmasse Kévin 
Published: July 2015

AbstractSince 2013, coordinated campaigns with the THEMIS spectropolarimeter in Tenerife and other instruments (space based: Hinode/SOT, IRIS or ground based: Sac Peak, Meudon) are organized to observe prominences. THEMIS records spectropolarimetry at the He I D3 and we use the PCA inversion technique to derive their field strength, inclination and azimuth.All of the observed prominences are quiescent, as they were stable as filaments for at least three days and not eruptive. They present similar characteristics, they are highly dynamic and present horizontal magnetic fields. Statistically, the inclination from the local vertical is around 90 degrees, with some points around 60 and 120 degrees. The field strength is between 5 and 15 Gauss. We tested the effects of adding a turbulent field component to the horizontal field. For those pixels showing inclinations around 60 and 120 degrees, we find that such a model is compatible with the polarimetric observations. In some of these prominences, identified as “tornadoes” the field strength may reach 50 Gauss, and in the top of the tornadoes some points exhibit an inclination which cannot correspond to any model in our grid of models. We investigate different solutions.
Atmospheres, magnetism, mass loss of red supergiant stars
Authors: Josselin E. , Lambert J. , Aurière M. , Petit P. , Ryde N. 
Published: July 2015

AbstractRed supergiant stars (RSGs) are not only a key evolutionary stage of massive stars participating in the chemical evolution of galaxies, they also represent a fantastic and challenging laboratory of (magneto-)hydrodynamics. We present recent results and on-going research on mass loss, atmospheres, and polarimetric studies of RSGs that reveal a magnetic field of unknown origin. We discuss the potential interplay between these different processes.
Linear spectropolarimetry: a new tool for the physical characterization of asteroids
Authors: Bagnulo S. , Cellino A. , Sterzik M. F. 
Published: July 2015

AbstractThe surfaces of the atmosphere-less objects of our solar system are traditionally probed via reflectance measurements and/or broadband linear polarimetry. Little attention has been paid so far to the wavelength dependence of the linear polarization of the scattered light. We decided to explore the potential of spectropolarimetry as a remote sensing tool for asteroids in addition to the more traditional reflectance measurements, and we carried out a spectropolarimetric survey of asteroids – to our best knolwedge, the first of its kind. We observed a sample of asteroids of different albedo and taxonomic classes, as well as a few regions at the limb of the Moon. We show that objects exhibiting similar reflectance spectra may display totally different polarization spectra, and we suggest that both intensity and polarization spectra should be used for asteroid classification. We also found that in some cases the Umov law is violated, that is, in contrast to what is expected from simple physical considerations, the fraction of linear polarization and the reflectance spectra may be correlated positively. We conclude that future modelling attempts of the surface structure of asteroids should be aimed at explaining both reflectance and polarization spectra.
Line Profile Variations of Solar Analog Stars: Chromospheric Indexes vs. Li Abundance. The Host Star Search.
Authors: Amazo-Gómez E. M. , Harutyunyan G. , Alvarado-Gómez J. D. , Strassmeier K. G. , Weber M. , Carroll T. A. 
Published: July 2015

AbstractPolarBase contains stellar spectropolarimetric data collected with the NARVAL & ESPaDOnS instruments (Petitet al. 2014). Their respective spectral resolutions are 65 000 and 68 000, in spectropolarimetric mode. As the first part of this work, we use the NARVAL spectropolarimetric repositories. We selected spectra from a sample of cool stars with effective Temperature (Teff) ranging between 4900 to 6000 K. This sample contains stellar systems with and without reported exoplanets. We exploit the full wavelength range from 380 to 900 nm in order to obtain chromospheric indexes such as the CaiiH&K S-Index, and a CaiiIRT and Hα index. We calibrated our measurements using the Mount Wilson S-Index values. Furthermore, we employ lithium (Li) abundance measurements from the literature (Gonzalezet al. 2010; Delgado Menaet al. 2014; Israelianet al. 2004), investigating in this way a possible correlation between the chromospheric activity measurements and the Li abundance in 32 selected cool stars.
On the importance of partial frequency redistribution in modeling the scattering polarization
Authors: Nagendra K. N. 
Published: July 2015

AbstractIt is well-known that partial frequency redistribution (PRD) is the basic physical mechanism to correctly describe radiative transfer in spectral lines. In the case of polarized line scattering, the PRD becomes particularly important to describe the line-wing polarization, instead of the well-known mechanism of complete redistribution (CRD). Historically, the two-level atom PRD scattering matrices for polarized line scattering were first derived in the 1970's, and later generalized to the case of arbitrary fields in 1997. The latter formulation of the PRD matrices have subsequently been used in the solution of the line transfer equation to successfully model the non-magnetic (resonance scattering) and the magnetic (Hanle scattering) polarization observations. In recent years, using the Kramers-Heisenberg approach, we formulated PRD matrices for various physical mechanisms like quantum interference involving fine- and hyperfine-structure states in a two-term atom. The effect of collisions is included in an approximate way. We have used these PRD matrices to model the observed linear polarization in several interesting lines of the Second Solar Spectrum. In this paper I present a few results which highlight the importance of PRD in the interpretation of the polarized Stokes profiles.
The impact of surface dynamo magnetic fields on the chemical abundance determination
Authors: Shchukina Nataliya G. , Sukhorukov Andrii V. , Bueno Javier Trujillo 
Published: July 2015

AbstractThe solar abundances of Fe and of the CNO elements play an important role in addressing a number of important issues such as the formation, structure, and evolution of the Sun and the solar system, the origin of the chemical elements, and the evolution of stars and galaxies. Despite the large number of papers published on this issue, debates about the solar abundances of these elements continue. The aim of the present investigation is to quantify the impact of photospheric magnetic fields on the determination of the solar chemical abundances. To this end, we used two 3D snapshot models of the quiet solar photosphere with a different magnetization taken from recent magneto-convection simulations with small-scale dynamo action. Using such 3D models we have carried out spectral synthesis for a large set of Fei, Ci, Ni, and Oi lines, in order to derive abundance corrections caused by the magnetic, Zeeman broadening of the intensity profiles and the magnetically induced changes of the photospheric temperature structure. We find that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the abundances of iron, carbon, nitrogen and oxygen is negligible.
Modeling the center-to-limb variation of the Ca i 4227 Å line using FCHHT models
Authors: Supriya H. D. , Smitha H. N. , Nagendra K. N. , Stenflo J. O. , Bianda M. , Ravindra B. , Ramelli R. , Anusha L. S. 
Published: July 2015

AbstractThe Ca i 4227 Å is a chromospheric line exhibiting the largest degree of linear polarization near the limb, in the visible spectrum of the Sun. Modeling the observations of the center-to-limb variations (CLV) of different lines in the Second Solar Spectrum helps to sample the height dependence of the magnetic field, as the observations made at different lines of sight sample different heights in the solar atmosphere. Supriya et al. (2014) attempted to simultaneously model the CLV of the (I, Q/I) spectra of the Ca i 4227 Å line using the standard 1-D FAL model atmospheres. They found that the standard FAL model atmospheres and also any appropriate combination of them, fail to simultaneously fit the observed Stokes (I, Q/I) profiles at all the limb distances (μ) satisfying at the same time all the observational constraints. This failure of 1-D modeling approach can probably be overcome by using multi-dimensional modeling which is computationally expensive. To eliminate an even wider choice of 1-D models, we attempt here to simultaneously model the CLV of the (I, Q/I) spectra using the FCHHT solar model atmospheres which are updated and recent versions of the FAL models. The details of our modeling efforts and the results are presented.
Formation of polarized spectral lines in atmospheres with horizontal inhomogeneities
Authors: Tichý A. , Štěpán J. , Bueno J. Trujillo , Kubát J. 
Published: July 2015

AbstractWe study the problem of the generation and transfer of spectral line intensity and polarization in models of stellar atmospheres with horizontal plasma inhomogeneities. We solve the non-LTE radiative transfer problem in full 3D geometry taking into account resonant scattering polarization and its modification by magnetic fields via the Hanle effect. We show that horizontal fluctuations of the thermodynamical conditions of stellar atmospheres can have a significant impact on the linear polarization of the emergent spectral line radiation and its center-to-limb variation.
Histone deacetylase inhibition protects hearing against acute ototoxicity by activating the Nf-κB pathway
Authors: Layman W S , Williams D M , Dearman J A , Sauceda M A , Zuo J 
Published: July 2015

AbstractAuditory hair cells have repeatedly been shown to be susceptible to ototoxicity from a multitude of drugs including aminoglycoside antibiotics. Here, we found that systemic HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) on adult mice offers almost complete protection against hair cell loss and hearing threshold shifts from acute ototoxic insult from kanamycin potentiated with furosemide. We also found that the apparent lack of hair cell loss was completely independent of spontaneous or facilitated (ectopic Atoh1 induction) hair cell regeneration. Rather, SAHA treatment correlated with RelA acetylation (K310) and subsequent activation of the Nf-κB pro-survival pathway leading to expression of pro-survival genes such as Cflar (cFLIP) and Bcl2l1 (Bcl-xL). In addition, we also detected increased expression of pro-survival genes Cdkn1a (p21) and Hspa1a (Hsp70), and decreased expression of the pro-apoptosis gene Bcl2l11 (Bim). These data combined provide evidence that class I HDACs control the transcriptional activation of pro-survival pathways in response to ototoxic insult by regulating the acetylation status of transcription factors found at the crossroads of cell death and survival in the mammalian inner ear.
Stereospecific induction of apoptosis in tumor cells via endogenous C16-ceramide and distinct transcripts
Authors: Blaess M , Le HP , Claus RA , Kohl M , Deigner H-P 
Published: July 2015

AbstractConcentration and distribution of individual endogenous ceramide species is crucial for apoptosis induction in response to various stimuli. Exogenous ceramide analogs induce apoptosis and can in turn modify the composition/concentrations of endogenous ceramide species and associated signaling. In this study, we show here that the elevation of endogenous C16-ceramide levels is a common feature of several known apoptosis-inducing triggers like mmLDL, TNF-alpha, H2O2and exogenous C6-ceramide.Vice versaapoptosis requires elevation of endogenous C16-ceramide levels in cells. Enantiomers of a synthetic ceramide analog HPL-1RS36N have been developed as probes and vary in their capacity to inducing apoptosis in macrophages and HT-29 cells. Apoptosis induction by the two synthetic ceramide analogs HPL-39N and HPL-1R36N correlates with generation of cellular C16-ceramide concentration. In contrast to the S-enantiomer HPL-1S36N, the R-enantiomer HPL-1R36N shows significant effects on the expression of distinct genes known to be involved in cell cycle, cell growth and cell death (CXCL10, CCL5 and TNF-alpha), similarly on apoptosis induction. Enantioselective effects on transcription induced by metabolically stable synthetic probes provide clues on molecular mechanisms of ceramide-induced signaling, as well as leads for future anti-cancer agents.
Mechanism of potassium ion uptake by the Na+/K+-ATPase
Authors: Castillo Juan P. , Rui Huan , Basilio Daniel , Das Avisek , Roux Benoît , Latorre Ramon , Bezanilla Francisco , Holmgren Miguel 
Published: July 2015

AbstractThe Na+/K+-ATPase restores sodium (Na+) and potassium (K+) electrochemical gradients dissipated by action potentials and ion-coupled transport processes. As ions are transported, they become transiently trapped between intracellular and extracellular gates. Once the external gate opens, three Na+ ions are released, followed by the binding and occlusion of two K+ ions. While the mechanisms of Na+ release have been well characterized by the study of transient Na+ currents, smaller and faster transient currents mediated by external K+ have been more difficult to study. Here we show that external K+ ions travelling to their binding sites sense only a small fraction of the electric field as they rapidly and simultaneously become occluded. Consistent with these results, molecular dynamics simulations of a pump model show a wide water-filled access channel connecting the binding site to the external solution. These results suggest a mechanism of K+ gating different from that of Na+ occlusion.
Plasmodium falciparum full life cycle and Plasmodium ovale liver stages in humanized mice
Authors: Soulard Valérie , Bosson-Vanga Henriette , Lorthiois Audrey , Roucher Clémentine , Franetich Jean- François , Zanghi Gigliola , Bordessoulles Mallaury , Tefit Maurel , Thellier Marc , Morosan Serban , Le Naour Gilles , Capron Frédérique , Suemizu Hiroshi , Snounou Georges , Moreno-Sabater Alicia , Mazier Dominique 
Published: July 2015

AbstractExperimental studies of Plasmodium parasites that infect humans are restricted by their host specificity. Humanized mice offer a means to overcome this and further provide the opportunity to observe the parasites in vivo. Here we improve on previous protocols to achieve efficient double engraftment of TK-NOG mice by human primary hepatocytes and red blood cells. Thus, we obtain the complete hepatic development of P. falciparum, the transition to the erythrocytic stages, their subsequent multiplication, and the appearance of mature gametocytes over an extended period of observation. Furthermore, using sporozoites derived from two P. ovale-infected patients, we show that human hepatocytes engrafted in TK-NOG mice sustain maturation of the liver stages, and the presence of late-developing schizonts indicate the eventual activation of quiescent parasites. Thus, TK-NOG mice are highly suited for in vivo observations on the Plasmodium species of humans.
MEG3 long noncoding RNA regulates the TGF-β pathway genes through formation of RNA–DNA triplex structures
Authors: Mondal Tanmoy , Subhash Santhilal , Vaid Roshan , Enroth Stefan , Uday Sireesha , Reinius Björn , Mitra Sanhita , Mohammed Arif , James Alva Rani , Hoberg Emily , Moustakas Aristidis , Gyllensten Ulf , Jones Steven J.M. , Gustafsson Claes M , Sims Andrew H , Westerlund Fredrik , Gorab Eduardo , Kanduri Chandrasekhar 
Published: July 2015

AbstractLong noncoding RNAs (lncRNAs) regulate gene expression by association with chromatin, but how they target chromatin remains poorly understood. We have used chromatin RNA immunoprecipitation-coupled high-throughput sequencing to identify 276 lncRNAs enriched in repressive chromatin from breast cancer cells. Using one of the chromatin-interacting lncRNAs, MEG3, we explore the mechanisms by which lncRNAs target chromatin. Here we show that MEG3 and EZH2 share common target genes, including the TGF-β pathway genes. Genome-wide mapping of MEG3 binding sites reveals that MEG3 modulates the activity of TGF-β genes by binding to distal regulatory elements. MEG3 binding sites have GA-rich sequences, which guide MEG3 to the chromatin through RNA–DNA triplex formation. We have found that RNA–DNA triplex structures are widespread and are present over the MEG3 binding sites associated with the TGF-β pathway genes. Our findings suggest that RNA–DNA triplex formation could be a general characteristic of target gene recognition by the chromatin-interacting lncRNAs.
Fgf and Esrrb integrate epigenetic and transcriptional networks that regulate self-renewal of trophoblast stem cells
Authors: Latos Paulina A. , Goncalves Angela , Oxley David , Mohammed Hisham , Turro Ernest , Hemberger Myriam 
Published: July 2015

AbstractEsrrb (oestrogen-related receptor beta) is a transcription factor implicated in embryonic stem (ES) cell self-renewal, yet its knockout causes intrauterine lethality due to defects in trophoblast development. Here we show that in trophoblast stem (TS) cells, Esrrb is a downstream target of fibroblast growth factor (Fgf) signalling and is critical to drive TS cell self-renewal. In contrast to its occupancy of pluripotency-associated loci in ES cells, Esrrb sustains the stemness of TS cells by direct binding and regulation of TS cell-specific transcription factors including Elf5 and Eomes. To elucidate the mechanisms whereby Esrrb controls the expression of its targets, we characterized its TS cell-specific interactome using mass spectrometry. Unlike in ES cells, Esrrb interacts in TS cells with the histone demethylase Lsd1 and with the RNA Polymerase II-associated Integrator complex. Our findings provide new insights into both the general and context-dependent wiring of transcription factor networks in stem cells by master transcription factors.
Engineering a dirhodium artificial metalloenzyme for selective olefin cyclopropanation
Authors: Srivastava Poonam , Yang Hao , Ellis-Guardiola Ken , Lewis Jared C. 
Published: July 2015

AbstractArtificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium catalyst to a prolyl oligopeptidase containing a genetically encoded L-4-azidophenylalanine residue to create an ArM that catalyses olefin cyclopropanation. Scaffold mutagenesis is then used to improve the enantioselectivity of this reaction, and cyclopropanation of a range of styrenes and donor–acceptor carbene precursors were accepted. The ArM reduces the formation of byproducts, including those resulting from the reaction of dirhodium–carbene intermediates with water. This shows that an ArM can improve the substrate specificity of a catalyst and, for the first time, the water tolerance of a metal-catalysed reaction. Given the diversity of reactions catalysed by dirhodium complexes, we anticipate that dirhodium ArMs will provide many unique opportunities for selective catalysis.
Developmental disruptions underlying brain abnormalities in ciliopathies
Authors: Guo Jiami , Higginbotham Holden , Li Jingjun , Nichols Jackie , Hirt Josua , Ghukasyan Vladimir , Anton E.S. 
Published: July 2015

AbstractPrimary cilia are essential conveyors of signals underlying major cell functions. Cerebral cortical progenitors and neurons have a primary cilium. The significance of cilia function for brain development and function is evident in the plethora of developmental brain disorders associated with human ciliopathies. Nevertheless, the role of primary cilia function in corticogenesis remains largely unknown. Here we delineate the functions of primary cilia in the construction of cerebral cortex and their relevance to ciliopathies, using an shRNA library targeting ciliopathy genes known to cause brain disorders, but whose roles in brain development are unclear. We used the library to query how ciliopathy genes affect distinct stages of mouse cortical development, in particular neural progenitor development, neuronal migration, neuronal differentiation and early neuronal connectivity. Our results define the developmental functions of ciliopathy genes and delineate disrupted developmental events that are integrally related to the emergence of brain abnormalities in ciliopathies.
Unusual fast secondary relaxation in metallic glass
Authors: Wang Q. , Zhang S.T. , Yang Y. , Dong Y.D. , Liu C.T. , Lu J. 
Published: July 2015

AbstractThe relaxation spectrum of glassy solids has long been used to probe their dynamic structural features and the fundamental deformation mechanisms. Structurally complicated glasses, such as molecular glasses, often exhibit multiple relaxation processes. By comparison, metallic glasses have a simple atomic structure with dense atomic packing, and their relaxation spectra were commonly found to be simpler than those of molecular glasses. Here we show the compelling evidence obtained across a wide range of temperatures and frequencies from a La-based metallic glass, which clearly shows two peaks of secondary relaxations (fast versus slow) in addition to the primary relaxation peak. The discovery of the unusual fast secondary relaxation unveils the complicated relaxation dynamics in metallic glasses and, more importantly, provides us the clues which help decode the structural features serving as the ‘trigger’ of inelasticity on mechanical agitations.
CCR2 inhibition sequesters multiple subsets of leukocytes in the bone marrow
Authors: Fujimura Naoki , Xu Baohui , Dalman Jackson , Deng Hongping , Aoyama Kohji , Dalman Ronald L 
Published: July 2015

AbstractChemokine receptor CCR2 mediates monocyte mobilization from the bone marrow (BM) and subsequent migration into target tissues. The degree to which CCR2 is differentially expressed in leukocyte subsets and the contribution of CCR2 to these leukocyte mobilization from the BM are poorly understood. Using red fluorescence protein CCR2 reporter mice, we found heterogeneity in CCR2 expression among leukocyte subsets in varying tissues. CCR2 was highly expressed by inflammatory monocytes, dendritic cells, plasmacytoid dendritic cells and NK cells in all tissues. Unexpectedly, more than 60% of neutrophils expressed CCR2, albeit at low levels. CCR2 expression in T cells, B cells and NK T cells was greatest in the BM compared to other tissues. Genetic CCR2 deficiency markedly sequestered all leukocyte subsets in the BM, with reciprocal reduction noted in the peripheral blood and spleen. CCR2 inhibition via treatment with CCR2 signaling inhibitor propagermanium produced similar effects. Propagermanium also mitigated lipopolysaccharide-induced BM leukocyte egress. Consistent with its functional significance, CCR2 antibody staining revealed surface CCR2 expression within a subset of BM neutrophils. These results demonstrate the central role CCR2 plays in mediating leukocyte mobilization from the BM and suggest a role for CCR2 inhibition in managing monocytes/macrophages-mediated chronic inflammatory conditions.