238 research outputs found
Functional characterizations of trace spaces in Lipschitz domains
Using a factorization theorem of Douglas, we prove functional
characterizations of trace spaces involving a family of
positive self-adjoint operators. Our method is based on the use of a suitable
operator by taking the trace on the boundary of a bounded
Lipschitz domain and applying Moore--Penrose
pseudo-inverse properties together with a special inner product on
. Moreover, generalized results of the Moore--Penrose
pseudo-inverse are also established.Comment: This is a preprint of a paper whose final and definite form is with
'Banach J. Math. Anal.', ISSN: 1735-8787, available at
[https://projecteuclid.org/info/euclid.bjma]. Submitted 21-Aug-2018; Article
accepted on 30-Nov-201
Spectral Energy Distributions of Be and Other Massive Stars
We present spectrophotometric data from 0.4 to 4.2 microns for bright,
northern sky, Be stars and several other types of massive stars. Our goal is to
use these data with ongoing, high angular resolution, interferometric
observations to model the density structure and sky orientation of the gas
surrounding these stars. We also present a montage of the H-alpha and
near-infrared emission lines that form in Be star disks. We find that a
simplified measurement of the IR excess flux appears to be correlated with the
strength of emission lines from high level transitions of hydrogen. This
suggests that the near-IR continuum and upper level line fluxes both form in
the inner part of the disk, close to the star.Comment: 2010, PASP, 122, 37
Amyloid ÎČ peptides modify the expression of antioxidant repair enzymes and a potassium channel in the septohippocampal system
Alzheimer\u27s disease (AD) is a progressive, neurodegenerative brain disorder characterized by extracellular accumulations of amyloid ÎČ (AÎČ) peptides, intracellular accumulation of abnormal proteins, and early loss of basal forebrain neurons. Recent studies have indicated that the conformation of AÎČ is crucial for neuronal toxicity, with intermediate misfolded forms such as oligomers being more toxic than the final fibrillar forms. Our previous work shows that AÎČ blocks the potassium (K(+)) currents IM and IA in septal neurons, increasing firing rates, diminishing rhythmicity and firing coherence. Evidence also suggests that oxidative stress (OS) plays a role in AD pathogenesis. Thus we wished to determine the effect of oligomeric and fibrillar forms of AÎČââââ on septohippocampal damage, oxidative damage, and dysfunction in AD. Oligomeric and fibrillar forms of AÎČââââ were injected into the CA1 region of the hippocampus in live rats. The rats were sacrificed 24 hours and 1 month after AÎČ or sham injection to additionally evaluate the temporal effects. The expression levels of the K(+) voltage-gated channel, KQT-like subfamily, member 2 (KCNQâ) and the OS-related genes superoxide dismutase 1, 8-oxoguanine DNA glycosylase, and monamine oxidase A, were analyzed in the hippocampus, medial, and lateral septum. Our results show that both forms of AÎČ exhibit time-dependent differential modulation of OS and K(+) channel genes in the analyzed regions. Importantly, we demonstrate that AÎČ injected into the hippocampus triggered changes in gene expression in anatomical regions distant from the injection site. Thus the AÎČ effect was transmitted to anatomically separate sites, because of the functional coupling of the brain structures
MOST detects corotating bright spots on the mid-O type giant {\xi} Persei
We have used the MOST (Microvariability and Oscillations of STars)
microsatellite to obtain four weeks of contiguous high-precision broadband
visual photometry of the O7.5III(n)((f)) star {\xi} Persei in November 2011.
This star is well known from previous work to show prominent DACs (Discrete
Absorption Components) on time-scales of about 2 d from UV spectroscopy and NRP
(Non Radial Pulsation) with one (l = 3) p-mode oscillation with a period of 3.5
h from optical spectroscopy. Our MOST-orbit (101.4 min) binned photometry fails
to reveal any periodic light variations above the 0.1 mmag 3-sigma noise level
for periods of hours, while several prominent Fourier peaks emerge at the 1
mmag level in the two-day period range. These longer-period variations are
unlikely due to pulsations, including gravity modes. From our simulations based
upon a simple spot model, we deduce that we are seeing the photometric
modulation of several co-rotating bright spots on the stellar surface. In our
model, the starting times (random) and lifetimes (up to several rotations) vary
from one spot to another yet all spots rotate at the same period of 4.18 d, the
best-estimated rotation period of the star. This is the first convincing
reported case of co-rotating bright spots on an O star, with important
implications for drivers of the DACs (resulting from CIRs - Corotating
Interaction Regions) with possible bright-spot generation via a breakout at the
surface of a global magnetic field generated by a subsurface convection zone.Comment: 9 pages, 4 figures, 2 tables, MNRAS in pres
Effects of a Composite Endomycorrhizal Inoculum on Olive Cuttings under the Greenhouse Conditions
This study was carried out in a nursery to evaluate the impact of mycorrhizal fungi on the cutting's root growth, and root colonization of a Moroccan olive variety âPicholine Marocaine' under greenhouse conditions during 2 years of cultivation. The results revealed that the inoculation with a composite inoculum of arbuscular mycorrhizal fungi (AMF) stimulated an early root formation and high development of vegetative shoots in inoculated cuttings respectively, 35 days (50 days in the control plots) and 40 days (60 days in the control plots) after their culture. The progressive establishment of mycorrhizal symbiosis in the roots of the inoculated plants showed that the root and vegetative masses were respectively 24 g and 19.5 g two years after inoculation. The average height and the leave's number of the inoculated plants relative to the control were respectively s 42/ 12 cm and 145/12.
The newly formed roots were mycorrhizal and present different structures characteristic of AMF: arbuscules, vesicles, hyphae and spores, whose frequency and intensity reached 90% and 75% two years after cuttings cultivation. The arbuscular and vesicular contents and the number of spores were 67%, 96% and 212 spores/ 100 g of soil respectively. The fourteen species of mycorrhizal fungi isolated from the rhizosphere belong to 4 genera (Glomus, Acaulospora, Gigaspora, and Scutellospora) and three families (Glomaceae, Acaulosporaceae and Gigasporacea).The Glomus genus was the most dominant (65%) followed by the Gigaspora genus (22%). Glomus intraradices, Gigaspora sp.2, Glomus versiformes are the most abundant species, their frequency of occurrence are respectively 30%, 21% and 16%
Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073
This is the author accepted manuscript. The final version is available from American Astronomical Society / IOP Publishing via the DOI in this record.The physical processes occurring within the inner few astronomical units of proto-planetary disks surrounding Herbig Ae stars are crucial to setting the environment in which the outer planet-forming disk evolves and put critical constraints on the processes of accretion and planet migration. We present the most complete published sample of high angular resolution H- and K-band observations of the stars HD 163296 and HD 190073, including 30 previously unpublished nights of observations of the former and 45 nights of the latter with the CHARA long-baseline interferometer, in addition to archival VLTI data. We confirm previous observations suggesting significant near-infrared emission originates within the putative dust evaporation front of HD 163296 and show this is the case for HD 190073 as well. The H- and K-band sizes are the same within (3±3)% for HD 163296 and within (6±10)% for HD 190073. The radial surface brightness profiles for both disks are remarkably Gaussian-like with little or no sign of the sharp edge expected for a dust evaporation front. Coupled with spectral energy distribution analysis, our direct measurements of the stellar flux component at H and K bands suggest that HD 190073 is much younger (<400 kyr) and more massive (~5.6 Mâ) than previously thought, mainly as a consequence of the new Gaia distance (891 pc).JDM and BRS acknowledge support from NSF-AST 1506540 and AA acknowledges support from NSF-AST 1311698.
CLD, AK, and SK acknowledge support from the ERC Starting Grant âImagePlanetFormDiscsâ (Grant Agreement
No. 639889), STFC Rutherford fellowship/grant (ST/J004030/1, ST/K003445/1) and Philip Leverhulme Prize (PLP2013-110).
FB acknowledges support from NSF-AST 1210972 and 1445935. MS acknowledges support by the NASA
Origins of Solar Systems grant NAG5-9475, and NASA Astrophysics Data Program contract NNH05CD30C. The CHARA Array is supported by the National Science Foundation under Grant No. AST-1211929, AST-1636624,
and AST-1715788. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU
Office of the Vice President for Research and Economic Development
The H-band Emitting Region of the Luminous Blue Variable P Cygni: Spectrophotometry and Interferometry of the Wind
This is the final version of the article. Available from American Astronomical Society / IOP Publishing via the DOI in this record.We present the first high angular resolution observations in the near-infrared H band (1.6 Όm) of the luminous blue variable star P Cygni. We obtained six-telescope interferometric observations with the CHARA Array and the MIRC beam combiner. These show that the spatial flux distribution is larger than expected for the stellar photosphere. A two-component model for the star (uniform disk) plus a halo (two-dimensional Gaussian) yields an excellent fit of the observations, and we suggest that the halo corresponds to flux emitted from the base of the stellar wind. This wind component contributes about 45% of the H-band flux and has an angular FWHM = 0.96 mas, compared to the predicted stellar diameter of 0.41 mas. We show several images reconstructed from the interferometric visibilities and closure phases, and they indicate a generally spherical geometry for the wind. We also obtained near-infrared spectrophotometry of P Cygni from which we derive the flux excess compared to a purely photospheric spectral energy distribution. The H-band flux excess matches that from the wind flux fraction derived from the two-component fits to the interferometry. We find evidence of significant near-infrared flux variability over the period from 2006 to 2010 that appears similar to the variations in the Hα emission flux from the wind.We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. Support for Ritter Astrophysical Research Center during the time of the observations was provided by the National Science Foundation Program for Research and Education with Small Telescopes (NSF-PREST) under grant AST-0440784 (N.D.M.). This work was also supported by the National Science Foundation under grants AST-0606861 and AST-1009080 (D.R.G.). N.D.R. gratefully acknowledges his current CRAQ postdoctoral fellowship. We are grateful for the insightful comments of A. F. J. Moffat that improved portions of the paper, discussions with Paco Najarro and Luc Dessart about spectroscopic modeling of P Cygni, and support of the MIRC 6 telescope beam combiner by Ettore Pedretti. Institutional support has been provided by the GSU College of Arts and Sciences and by the Research Program Enhancement fund of the Board of Regents of the University System of Georgia, administered through the GSU Office of the Vice President for Research. Operational funding for the CHARA Array is provided by the GSU College of Arts and Sciences, by the National Science Foundation through grants AST-0606958 and AST-0908253, by the W. M. Keck Foundation, and by the NASA Exoplanet Science Institute. We thank the Mount Wilson Institute for providing infrastructure support at Mount Wilson Observatory. The CHARA Array, operated by Georgia State University, was built with funding provided by the National Science Foundation, Georgia State University, the W. M. Keck Foundation, and the David and Lucile Packard Foundation. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W. M. Keck Foundation. J.D.M. acknowledges University of Michigan and NSF AST-0707927 for support of MIRC construction and observations. D.P.C. acknowledges support under NSF AST-0907790 to Boston University. We gratefully acknowledge all of this support. This research has made use of the SIMBAD database operated at CDS, Strasbourg, France
Protein Pattern Formation
Protein pattern formation is essential for the spatial organization of many
intracellular processes like cell division, flagellum positioning, and
chemotaxis. A prominent example of intracellular patterns are the oscillatory
pole-to-pole oscillations of Min proteins in \textit{E. coli} whose biological
function is to ensure precise cell division. Cell polarization, a prerequisite
for processes such as stem cell differentiation and cell polarity in yeast, is
also mediated by a diffusion-reaction process. More generally, these functional
modules of cells serve as model systems for self-organization, one of the core
principles of life. Under which conditions spatio-temporal patterns emerge, and
how these patterns are regulated by biochemical and geometrical factors are
major aspects of current research. Here we review recent theoretical and
experimental advances in the field of intracellular pattern formation, focusing
on general design principles and fundamental physical mechanisms.Comment: 17 pages, 14 figures, review articl
Optoelectronic characterization of CuInGa(S)2 thin films grown by spray pyrolysis for photovoltaic application
[EN] Copper-indium gallium disulfide (CIGS) is a good absorber for photovoltaic application. Thin films of CIGS were prepared by spray pyrolysis on glass substrates in the ambient atmosphere. The films were characterized by different techniques, such as structural, morphological, optical and electrical properties of CIGS films were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), spectrophotometer and Hall effect, respectively. After optimization, the deposited films structure, grain size, and crystallinity became more important with an increase of annealing time at 370 degrees C for 20 min. Transmission electron microscopy (TEM) analysis shows that the interface sheets are well crystallized and the inter planer distance are 0.25 nm, 0.28 nm, and 0.36 nm. The atomic force microscopy (AFM) observation shows that the grain size and roughness can be tolerated by optimizing the annealing time. The strong absorbance and low transmittance were observed for the prepared films with a suitable energy bandgap about 1.46 eV. The Hall effect measurement system examined that CIGS films exhibited optimal electrical properties, resistivity, carrier mobility, and carrier concentration which were determined to be 4.22 x 10(6) omega cm, 6.18 x 10(2) cm(2) V-1 S-1 and 4.22 x 10(6) cm(-3), respectively. The optoelectronic properties of CIGS material recommended being used for the photovoltaic application.Prof. Bouchaib HARTITI, The Senior Associate at ICTP, is very grateful to ICTP for permanent support. Prof. Mohamed Ebn Touhami, Director of the University Center for Analysis, Expertise, Transfer of Technology and Incubation, Kenitra, Morocco, is very grateful to CUA2TI for financial support. Thanks to Doctor Diogo M.F. Santos for the supervision of Amal Bouich's work during her research in CeFEMA research center. 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Optik 183, 137â147 (2019
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