2,851 research outputs found
HI 21 cm Emission Line Study of Southern Galactic Supernova Remnants
We have searched for HI 21 cm line emission from shocked atomic gas
associated with southern supernova remnants (SNRs) using data from the Southern
Galactic Plane Survey. Among the 97 sources studied, we have detected 10 SNRs
with high-velocity HI emission confined to the SNR. The large velocity and the
spatial confinement suggest that the emission is likely from the gas
accelerated by the SN blast wave. We also detected 22 SNRs which show HI
emission significantly brighter than the surrounding regions over a wide
(\kms) velocity interval. The association with these SNRs is less certain.
We present the parameters and maps of the excess emission in these SNRs. We
discuss in some detail the ten individual SNRs with associated high-velocity HI
emission.Comment: 17 pages, 8 figures, accepted for publication in JKAS (Journal of the
Korean Astronomical Society
Properties of Central Caustics in Planetary Microlensing
To maximize the number of planet detections, current microlensing follow-up
observations are focusing on high-magnification events which have a higher
chance of being perturbed by central caustics. In this paper, we investigate
the properties of central caustics and the perturbations induced by them. We
derive analytic expressions of the location, size, and shape of the central
caustic as a function of the star-planet separation, , and the planet/star
mass ratio, , under the planetary perturbative approximation and compare the
results with those based on numerical computations. While it has been known
that the size of the planetary caustic is \propto \sqrt{q}, we find from this
work that the dependence of the size of the central caustic on is linear,
i.e., \propto q, implying that the central caustic shrinks much more rapidly
with the decrease of compared to the planetary caustic. The central-caustic
size depends also on the star-planet separation. If the size of the caustic is
defined as the separation between the two cusps on the star-planet axis
(horizontal width), we find that the dependence of the central-caustic size on
the separation is \propto (s+1/s). While the size of the central caustic
depends both on and q, its shape defined as the vertical/horizontal width
ratio, R_c, is solely dependent on the planetary separation and we derive an
analytic relation between R_c and s. Due to the smaller size of the central
caustic combined with much more rapid decrease of its size with the decrease of
q, the effect of finite source size on the perturbation induced by the central
caustic is much more severe than the effect on the perturbation induced by the
planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte
Optimization of glutathione production in batch and fed-batch cultures by the wild-type and recombinant strains of the methylotrophic yeast Hansenula polymorpha DL-1
<p>Abstract</p> <p>Background</p> <p>Tripeptide glutathione (gamma-glutamyl-L-cysteinyl-glycine) is the most abundant non-protein thiol that protects cells from metabolic and oxidative stresses and is widely used as medicine, food additives and in cosmetic industry. The methylotrophic yeast <it>Hansenula polymorpha </it>is regarded as a rich source of glutathione due to the role of this thiol in detoxifications of key intermediates of methanol metabolism. Cellular and extracellular glutathione production of <it>H. polymorpha </it>DL-1 in the wild type and recombinant strains which overexpress genes of glutathione biosynthesis (<it>GSH2</it>) and its precursor cysteine (<it>MET4</it>) was studied.</p> <p>Results</p> <p>Glutathione producing capacity of <it>H. polymorpha </it>DL-1 depending on parameters of cultivation (dissolved oxygen tension, pH, stirrer speed), carbon substrate (glucose, methanol) and type of overexpressed genes of glutathione and its precursor biosynthesis during batch and fed-batch fermentations were studied. Under optimized conditions of glucose fed-batch cultivation, the glutathione productivity of the engineered strains was increased from ~900 up to ~ 2300 mg of Total Intracellular Glutathione (TIG) or GSH+GSSG<sub>in</sub>, per liter of culture medium. Meantime, methanol fed-batch cultivation of one of the recombinant strains allowed achieving the extracellular glutathione productivity up to 250 mg of Total Extracellular Glutathione (TEG) or GSH+GSSG<sub>ex</sub>, per liter of the culture medium.</p> <p>Conclusions</p> <p><it>H. polymorpha </it>is an competitive glutathione producer as compared to other known yeast and bacteria strains (<it>Saccharomyces cerevisiae, Candida utilis, Escherichia coli, Lactococcus lactis </it>etc.) with good perspectives for further improvement especially for production of extracellular form of glutathione.</p
CVD-grown monolayer MoS2 in bioabsorbable electronics and biosensors
Transient electronics entails the capability of electronic components to dissolve or reabsorb in a controlled manner when used in biomedical implants. Here, the authors perform a systematic study of the processes of hydrolysis, bioabsorption, cytotoxicity and immunological biocompatibility of monolayer MoS2
Anomalous microwave conductivity coherence peak in c-axis MgB2 thin film
The temperature dependence of the real part of the microwave complex
conductivity at 17.9 GHz obtained from surface impedance measurements of two
c-axis oriented MgB2 thin films reveals a pronounced maximum at a temperature
around 0.6 times the critical temperature. Calculations in the frame of a
two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that
this maximum corresponds to an anomalous coherence peak resembling the two-gap
nature of MgB2. Our model assumes there is no interband impurity scattering and
a weak interband pairing interaction, as suggested by bandstructure
calculations. In addition, the observation of a coherence peak indicates that
the pi-band is in the dirty limit and dominates the total conductivity of our
filmsComment: 10 pages, 4 figures, to be published in Phys. Rev. Let
The Effects of Fermentation and Split Application of Liquid Swine Manure on Dry Matter Yield of Italian Ryegrass and Subsequent Soil Quality
Regulation of tissue-dependent differences in CD8+ T cell apoptosis during viral infection
Virus-specific CD8+ T cells in the lymphoid organs contract at the resolution of virus infections by apoptosis or by dissemination into peripheral tissues, and those residing in nonlymphoid organs, including the peritoneal cavity and fat pads, are more resistant to apoptosis than those in the spleen and lymph nodes. This stability of memory T cells in the nonlymphoid tissues may enhance protection to secondary challenges. Here, we show that lymphocytic choriomeningitis virus (LCMV)-specific CD8+ T cells in nonlymphoid tissues were enriched for memory precursors (expressing high levels of interleukin-7 receptor and low levels of killer cell lectin-like receptor G1 [IL-7Rhi KLRG1lo]) and had higher expression of CD27, CXCR3, and T cell factor-1 (TCF-1), each a marker that is individually correlated with decreased apoptosis. CD8+ T cells in the peritoneal cavity of TCF-1-deficient mice had decreased survival, suggesting a role for TCF-1 in promoting survival in the nonlymphoid tissues. CXCR3+ CD8+ T cells resisted apoptosis and accumulated in the lymph nodes of mice treated with FTY720, which blocks the export of lymph node cells into peripheral tissue. The peritoneal exudate cells (PEC) expressed increased amounts of CXCR3 ligands, CXCL9 and CXCL10, which may normally recruit these nonapoptotic cells from the lymph nodes. In addition, adoptive transfer of splenic CD8+ T cells into PEC or spleen environments showed that the peritoneal environment promoted survival of CD8+ T cells. Thus, intrinsic stability of T cells which are present in the nonlymphoid tissues along with preferential migration of apoptosis-resistant CD8+ T cells into peripheral sites and the availability of tissue-specific factors that enhance memory cell survival may collectively account for the tissue-dependent apoptotic differences.
IMPORTANCE: Most infections are initiated at nonlymphoid tissue sites, and the presence of memory T cells in nonlymphoid tissues is critical for protective immunity in various viral infection models. Virus-specific CD8+ T cells in the nonlymphoid tissues are more resistant to apoptosis than those in lymphoid organs during the resolution and memory phase of the immune response to acute LCMV infection. Here, we investigated the mechanisms promoting stability of T cells in the nonlymphoid tissues. This increased resistance to apoptosis of virus-specific CD8+ T cells in nonlymphoid tissues was due to several factors. Nonlymphoid tissues were enriched in memory phenotype CD8+ T cells, which were intrinsically resistant to apoptosis irrespective of the tissue environment. Furthermore, apoptosis-resistant CD8+ T cells preferentially migrated into the nonlymphoid tissues, where the availability of tissue-specific factors may enhance memory cell survival. Our findings are relevant for the generation of long-lasting vaccines providing protection at peripheral infection sites
High thermoelectric performance in (Bi_(0.25)Sb_(0.75)_2 Te_3 due to band convergence and improved by carrier concentration control
Bi_2Te_3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by optimizing the converging valence bands of Bi_2Te_3 and Sb_2Te_3 in the (Bi_(1âx)Sb_x)_2Te_3 system when x = 0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi0.25Sb0.75)2Te3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT = 1.05 (at 300 K) without nanostructuring
Coherence lengths and anisotropy in MgB2 superconductor
Field and temperature microwave measurements have been carried out on MgB2
thin film grown on Al2O3 substrate. The analysis reveals the mean field
coherence length xi_{MF} in the mixed state and a temperature independent
anisotropy ratio gamma_{MF} = xi_{MF}^{ab} / xi_{MF}^c approximately 2. At the
superconducting transition, the scaling of the fluctuation conductivity yields
the Ginzburg-Landau coherence length with a different anisotropy ratio
gamma_{GL} = 2.8, also temperature independent.Comment: submitted to PR
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