3,928 research outputs found
Interface superconductivity in LaNdSrCuO/LaSrCuO bilayers
We identify a distinct superconducting phase at the interface of a
LaNdSrCuO (LNSCO)/LaSrCuO
(LSCO) epitaxial bilayer system using ac screening measurements. A model based
on inter-diffusion of quasiparticles and condensate at the interface yields a
thickness of 25 nm for the interfacial layer. Two-dimensional
superconductivity of the interface layer appears to be governed by
Kosterlitz-Thouless-Berezinskii transition. A parallel magnetic field
suppresses the superconducting transition temperature of this layer with a pair
breaking parameter varying as
Expression pattern and regulation of genes differ between fibroblasts of adhesion and normal human peritoneum
BACKGROUND: Injury to the peritoneum during surgery is followed by a healing process that frequently results in the attachment of adjacent organs by a fibrous mass, referred commonly as adhesions. Because injuries to the peritoneum during surgery are inevitable, it is imperative that we understand the mechanisms of adhesion formation to prevent its occurrence. This requires thorough understanding of the molecular sequence that results in the attachment of injured peritoneum and the development of fibrous tissue. Recent data show that fibroblasts from the injured peritoneum may play a critical role in the formation of adhesion tissues. Therefore, identifying changes in gene expression pattern in the peritoneal fibroblasts during the process may provide clues to the mechanisms by which adhesion develop. METHODS: In this study, we compared expression patterns of larger number of genes in the fibroblasts isolated from adhesion and normal human peritoneum using gene filters. Contributions of TGF-beta1 and hypoxia in the altered expression of specific genes were also examined using a semiquantitative RT-PCR technique. RESULTS: Results show that several genes are differentially expressed between fibroblasts of normal and adhesion peritoneum and that the peritoneal fibroblast may acquire a different phenotype during adhesion formation. Genes that are differentially expressed between normal and adhesion fibroblasts encode molecules involved in cell adhesion, proliferation, differentiation, migration and factors regulating cytokines, transcription, translation and protein/vesicle trafficking. CONCLUSIONS: Our data substantiate that adhesion formation is a multigenic phenomenon and not all changes in gene expression pattern between normal and adhesion fibroblasts are the function of TGF-beta1 and hypoxia that are known to influence adhesion formation. Analysis of the gene expression data in the perspective of known functions of genes connote to additional targets that may be manipulated to inhibit adhesion development
Spectral and timing evolution of MAXI J1631-479 during the 2018-19 outburst with NICER
The X-ray transient MAXI J1631-479 went into outburst on 2018 December 21 and remained active for about seven months. Owing to various constraints it was monitored by NICER only during the decay phase of the outburst for about four months. The NICER observations were primarily in the soft state with a brief excursion to the hard intermediate state. While the soft state spectrum was dominated by thermal disc emission, the hard intermediate state spectrum had maximum contribution from the thermal Comptonization. Almost all intermediate-state power spectra had a Type-C low frequency quasi-periodic oscillation (within 4-10Hz), often accompanied by a harmonic component. The frequency of these oscillations increased and the fractional rms decreased with inner-disc temperature suggesting a geometric origin. The rms spectra during the intermediate state had a hard shape from above 1keV. Below 1keV the shape could not be constrained in most cases, while only a few observations showed a rise in amplitude
Solar cycle 24: an unusual polar field reversal
Aims: To investigate solar polar fields during cycle 24, using measurements
of solar magnetic fields in the latitude range 55 - 90 degree and 78 - 90
degree, to report a prolonged and unusual hemispheric asymmetry in the polar
field reversal pattern in solar cycle 24. Methods: This study was carried out
using medium resolution line-of-sight synoptic magnetograms from the magnetic
database of the National Solar Observatory at Kitt Peak (NSO/KP), USA for the
period between February 1975 and October 2017, covering solar cycles 21-24 and
high-resolution line-of-sight synoptic magnetograms from the Michaelson Doppler
Imager instrument onboard the Solar Heliospheric Observatory. Synoptic
magnetograms using radial measurements from the Heliospheric Magnetic Imager
instrument onboard the Solar Dynamics Observatory, covering solar cycle 23 and
24, were also used. Results: We show that the Southern solar hemisphere
unambiguously reversed polarity in mid-2013 while the reversal in the field in
the Northern solar hemisphere started as early as June 2012, was followed by a
sustained period of near-zero field strength lasting until the end of 2014,
after which the field began to show a clear rise from its near-zero value.
While this study compliments a similar study carried out using microwave
brightness measurements (Gopalswamy et al. 2016) which claimed that the field
reversal process in cycle 24 was completed by the end of 2015, our results show
that the field reversal in cycle 24 was completed earlier i.e. in late 2014.
Signatures of this unusual field reversal pattern were also clearly
identifiable in the solar wind, using our observations of interplanetary
scintillation at 327 MHz which supported our magnetic field observations and
confirmed that the field reversal process was completed at the end of 2014.Comment: 11 pages, 7 figures, Under review in A&
Kinetics & Mechanism of Oxidation of Benzoin & Its Derivatives by Tl(III) in Aqueous Acetic Acid
42-4
Bacterial Endophytes Enhance Competition by Invasive Plants
Premise of the study: Invasive plants can alter soil microbial communities and profoundly alter ecosystem processes. In the invasive grass Sorghum halepense, these disruptions are consequences of rhizome-associated bacterial endophytes. We describe the effects of N2-fixing bacterial strains from S. halepense (Rout and Chrzanowski, 2009) on plant growth and show that bacteria interact with the plant to alter soil nutrient cycles, enabling persistence of the invasive. Methods: We assessed fluxes in soil nutrients for ~4 yr across a site invaded by S. halepense. We assayed the N2-fixing bacteria in vitro for phosphate solubilization, iron chelation, and production of the plant-growth hormone indole-3-acetic acid (IAA). We assessed the plant’s ability to recruit bacterial partners from substrates and vertically transmit endophytes to seeds and used an antibiotic approach to inhibit bacterial activity in planta and assess microbial contributions to plant growth. Key results: We found persistent alterations to eight biogeochemical cycles (including nitrogen, phosphorus, and iron) in soils invaded by S. halepense. In this context, three bacterial isolates solubilized phosphate, and all produced iron siderophores and IAA in vitro. In growth chamber experiments, bacteria were transmitted vertically, and molecular analysis of bacterial community fingerprints from rhizomes indicated that endophytes are also horizontally recruited. Inhibiting bacterial activity with antibiotics resulted in significant declines in plant growth rate and biomass, with pronounced rhizome reductions. Conclusions: This work suggests a major role of endophytes on growth and resource allocation of an invasive plant. Indeed, bacterial isolate physiology is correlated with invader effects on biogeochemical cycles of nitrogen, phosphate, and iron
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