2,985 research outputs found
The X-ray nature of the LINER nuclear sources
The analysis of the X-ray data for a sample of 51 LINER nuclei with available
X-ray Chandra imaging is reported. Our aim was to investigate the physical
mechanisms which power LINER nuclear activity. The use of multiwavelenght
information at radio, UV, optical HST and X-ray lead us to conclude that at
least 60% of the LINERs are hosting a low luminosity AGN in their nuclei. This
percentage may be even higher if the Compton-thickness of some nuclei (mostly
with SB-like hard X-ray morphology) is confirmed.Comment: Conference proceedings to appear in "The Central Engine of Active
Galactic Nuclei", ed. L.C. Ho and J.-M. Wang (San Francisco: ASP
The effect of calcitriol, paricalcitol, and a calcimimetic on extraosseous calcifications in uremic rats
Vitamin D derivatives and calcimimetics are used to treat secondary hyperparathyroidism in patients with chronic renal failure. We investigated the effect of calcitriol, paricalcitol, and the calcimimetic AMG 641 on soft-tissue calcification in uremic rats with secondary hyperparathyroidism. Control and uremic rats were treated with vehicle, calcitriol, paricalcitol, AMG 641, or a combination of AMG 641 plus calcitriol or paricalcitol. Parathyroid hormone levels were reduced by all treatments but were better controlled by the combination of paricalcitol and AMG 641. The calcimimetic alone did not induce extraosseous calcification but co-administration of AMG 641 reduced soft-tissue calcification and aortic mineralization in both calcitriol- and paricalcitol-treated rats. Survival was significantly reduced in rats treated with calcitriol and this mortality was attenuated by co-treatment with AMG 641. Our study shows that extraskeletal calcification was present in animals treated with calcitriol and paricalcitol but not with AMG 641. When used in combination with paricalcitol, AMG 641 provided excellent control of secondary hyperparathyroidism and prevented mortality associated with the use of vitamin D derivatives without causing tissue calcification
Slave-Boson Three-Band Model with O-O Hopping for High-Tc Superconductors
Slave boson mean-field approximation is carried out analytically for weakly
doped CuO_2 conduction planes, characterized by Cu-O charge transfer energy
\Delta_{pd}, Cu-O hopping t_0, O-O hopping t' and repulsion U_d between holes
on Cu site taken as infinite. At zero doping \delta, finite negative
t',|t'|<t_0/2, expands the range of stability of the covalent, conducting state
on the expense of the insulating state which, however, remains stable at larger
\Delta_{pd}. For sufficiently large \Delta_{pd} the renormalized charge
transfer energy saturates at 4|t'| instead of decreasing to zero, as at t'=0
case. In contrast to t', finite \delta suppresses the insulating state nearly
symmetrically with respect to the sign of \delta. The regime with charge
transfer energy renormalized close to 4|t'| fits remarkably well the ARPES
spectra of Bi2212 and LSCO, and, in the latter case, explains the observed
strong doping dependence of the Cu-O hopping.Comment: 4 pages, 2 figure
Confirmation of involvement of new variants at CDKN2A/B in pediatric acute lymphoblastic leukemia susceptibility in the Spanish population
The locus CDKN2A/B (9p21.3), which comprises the tumor suppressors genes CDKN2A and CDKN2B and the long noncoding RNA (lncRNA) known as ANRIL (or CDKN2B-AS), was associated with childhood acute lymphoblastic leukemia (ALL) susceptibility in several genome wide association studies (GWAS). However, the variants associated in the diverse studies were different. Recently, new and independent SNPs deregulating the locus function were also identified in association with ALL risk. This diversity in the results may be explained because different variants in each population could alter CDKN2A/B locus function through diverse mechanisms. Therefore, the aim of this study was to determine whether the annotated risk variants in the CDKN2A/B locus affect the susceptibility of B cell precursor ALL (B-ALL) in our Spanish population and explore if other SNPs altering additional regulatory mechanisms could be also involved. We analyzed the four SNPs proposed by GWAs and two additional SNPs in miRNA binding sites in 217 pediatric patients with B-ALL and 330 healthy controls. The SNPs rs2811712, rs3731249, rs3217992 and rs2811709 were associated with B-ALL susceptibility in our Spanish population. ALL subtypes analyses showed that rs2811712 was associated with B-hyperdiploid ALL. These results provide evidence for the influence of genetic variants at CDKN2A/B locus with the risk of developing B-ALL
Hot Interstellar Gas and Stellar Energy Feedback in the Antennae Galaxies
We have analyzed Chandra archival observations of the Antennae galaxies to
study the distribution and physical properties of its hot interstellar gas.
Eleven distinct diffuse X-ray emission regions are selected according to their
underlying interstellar structures and star formation activity. The X-ray
spectra of these regions are used to determine their thermal energy contents
and cooling timescales. Young star clusters in these regions are also
identified and their photometric measurements are compared to evolutionary
stellar population synthesis models to assess their masses and ages. The
cluster properties are then used to determine the stellar wind and supernova
energies injected into the ISM. Comparisons between the thermal energy in the
hot ISM and the expected stellar energy input show that young star clusters are
sufficient to power the X-ray-emitting gas in some, but not all, active star
formation regions. Super-star clusters, with masses >= 1x10^5 M_sol, heat the
ISM, but the yield of hot interstellar gas is not directly proportional to the
cluster mass. Finally, there exist diffuse X-ray emission regions which do not
show active star formation or massive young star clusters. These regions may be
powered by field stars or low-mass clusters formed within the last ~100 Myr.Comment: 36 pages, 6 figures, 8 tables, 2 appendices, to appear in the
Astrophysical Journal, April 20 issu
Involvement of SNPs in miR-3117 and miR-3689d2 in childhood acute lymphoblastic leukemia risk
Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Numerous studies have shown that microRNAs (miRNAs) could play a role in this disease. Nowadays, more than 2500 miRNAs have been described, that regulate more than 50% of genes, including those involved in B-cell maturation, differentiation and proliferation. Genetic variants in miRNAs can alter their own levels or function, affecting their target gene expression, and then, may affect ALL risk. Therefore, the aim of this study was to determine the role of miRNA genetic variants in B-ALL susceptibility. We analyzed all variants in pre-miRNAs (MAF > 1%) in two independent cohorts from Spain and Slovenia and inferred their functional effect by in silico analysis. SNPs rs12402181 in miR-3117 and rs62571442 in miR-3689d2 were associated with ALL risk in both cohorts, possibly through their effect on MAPK signalling pathway. These SNPs could be novel markers for ALL susceptibility
Development and RF-Performance of AlGaN/GaN and InAlN/GaN HEMTs on Large-Diameter High-Resistivity Silicon Substrates
A CMOS-compatible industrial processing and RF analysis of 150 mm GaN-on-HR-Si substrates with AlGaN and InAlN barrier is presented. Process development along with transfer to large-wafer scale is shown and some HEMT calibration devices produced on AlGaN/GaN following the aforementioned procedure are characterized in terms of RF-performance by using a set of measured multi-bias S-parameters. An automatic small-signal equivalent circuit extraction strategy for these AlGaN/GaN DUTs is validated and some de-embedded figures of merit are drawn out in order to initially evaluate this promising technology.This work is supported by the I Plan Propio de la Univ. de MĂĄlaga (PhD Grant-401), and the European Microwave Associationâą by the EuMA Internship Award 2021 edition. Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tech
ROSAT observations of X-ray emission from planetary nebulae
We have searched the entire ROSAT archive for useful observations to study
X-ray emission from Galactic planetary nebulae (PNs). The search yields a
sample of 63 PNs, which we call the ROSAT PN sample. About 20-25% of this
sample show X-ray emission; these include 13 definite detections and three
possible detections (at a 2-sigma level). All X-ray sources in these PNs are
concentrated near the central stars. Only A 30, BD+30 3639, and NGC 6543 are
marginally resolved by the ROSAT instruments. Three types of X-ray spectra are
seen in PNs. Type 1 consists of only soft X-ray emission (<0.5 keV), peaks at
0.1-0.2 keV, and can be fitted by blackbody models at temperatures 1-2 10^5 K.
Type 2 consists of harder X-ray emission, peaks at >0.5 keV, and can be fitted
by thin plasma emission models at temperatures of a few 10^6 K. Type 3 is a
composite of a bright Type 1 component and a fainter Type 2 component.
Unresolved soft sources with Type 1 spectra or the soft component of Type 3
spectra are most likely photospheric emission from the hot central stars.
Absorption cross sections are large for these soft-energy photons; therefore,
only large, tenuous, evolved PNs with hot central stars and small absorption
column densities have been detected. The origin of hard X-ray emission from PNs
is uncertain. PNs with Type 2 spectra are small, dense, young nebulae with
relatively cool (<<10^5 K) central stars, while PNs with Type 3 X-ray spectra
are large, tenuous, evolved nebulae with hot central stars. The hard X-ray
luminosities are also different between these two types of PNs, indicating
perhaps different origins of their hard X-ray emission. Future Chandra and XMM
observations with high spatial and spectral resolution will help to understand
the origin of hard X-ray emission from PNs.Comment: To be published in The Astrophysical Journal Supplement Series. 21
pages, 7 figures, 5 table
High Energy Theorems at Large-N
Sum rules for products of two, three and four QCD currents are derived using
chiral symmetry at infinite momentum in the large-N limit. These exact
relations among meson decay constants, axialvector couplings and masses
determine the asymptotic behavior of an infinite number of QCD correlators. The
familiar spectral function sum rules for products of two QCD currents are among
the relations derived. With this precise knowledge of asymptotic behavior, an
infinite number of large-N QCD correlators can be constructed using dispersion
relations. A detailed derivation is given of the exact large-N pion vector form
factor and forward pion-pion scattering amplitudes.Comment: 34 pages TeX and mtexsis.tex, 10 figures (uses epsf
Gene therapy with mesenchymal stem cells expressing IFN-Ă ameliorates neuroinflammation in experimental models of multiple sclerosis
[Background and Purpose]: Recombinant IFNâĂ is one of the firstâline treatments in multiple sclerosis (MS), despite its lack of efficacy in some patients. In this context, mesenchymal stem cells (MSCs) represent a promising therapeutic alternative due to their immunomodulatory properties and multipotency. Moreover, by taking advantage of their pathotropism, these cells can be genetically modified to be used as carriers for delivering or secreting therapeutic drugs into injured tissues. Here, we report the therapeutic effect of systemic delivery of adiposeâderived MSCs (AdMSCs), transduced with the IFNâÎČ gene, into mice with experimental autoimmune encephalomyelitis (EAE).[Experimental Approach]: Relapsingâremitting and chronic progressive EAE were induced in mice. Cells were injected i.v. Disease severity, inflammation and tissue damage were assessed clinically, by flow cytometry of spleens and histopathological evaluation of the CNS respectively.[Key Results]: Genetic engineering did not modify the biological characteristics of these AdMSCs (morphology, growth rate, immunophenotype and multipotency). Furthermore, the transduction of IFNâĂ to AdMSCs maintained and, in some cases, enhanced the functional properties of AdMSCs by ameliorating the symptoms of MS in EAE models and by decreasing indications of peripheral and central neuroâinflammation.[Conclusion and Implications]: Gene therapy was found to be more effective than cell therapy in ameliorating several clinical parameters in both EAE models, presumably due to the continuous expression of IFNâÎČ. Furthermore, it has significant advantages over AdMSC therapy, and also over systemic IFNâĂ treatment, by providing longâterm expression of the cytokine at therapeutic concentrations and reducing the frequency of injections, while minimizing doseâlimiting side effects.This work was supported by Fondo de Investigaciones Sanitarias ISCIII (Spain) and Fondo Europeo de Desarrollo Regional (FEDER) from the European Union through the research grants PI12/01097 and PI15/00963 and ISCIII Red de Terapia Celular TerCel RD12/0019/0006 to F.M., by the ConsejerĂa de EconomĂa, InnovaciĂłn, Ciencia y Empleo, Junta de AndalucĂaâFEDER/Fondo de Cohesion Europeo (FSE) de AndalucĂa through the research grants P09âCTSâ04532, PIâ57069 and PAIDIâBioâ326 to F.M. and PIâ0160/2012 to K.B. M.J.P.âM. has been supported by grants from Red TemĂĄtica de InvestigaciĂłn Cooperativa Red Española de Esclerosis MĂșltiple REEM (RD07/0060 and RD12/0032). B.O. is financed by a contract from Excelent Project CTSâ7670/11 from ConsejerĂa de EconomĂa, InnovaciĂłn, Ciencia y Empleo (Junta de AndalucĂa)
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