175 research outputs found
Critical Ignition Temperature of Fuel-air Explosive
The charge of fuel-air explosive (FAE) warhead usually is solid-liquid mixed fuel. The solid component is aluminium powder. To meet the demand of FAE weapon usage and storage safety, in the mixed-fuel medium, there must be gaps where adiabatic compression occurs during launchin-e overloading- of warhead. Adiabatic compression makes the temperature of the mediumin the gaps to rise. High temperature can cause dxplosion of the mixed fuel during launching acceleration of the warhead, which is very dangerous. Because the fuel is a multicomponentmixture, the critical ignitioh temperature can't be determined only by one component. Through experiment, the critical ignition temperature of the mixed fuel is attained, and the changingregularity of the pressure following the temperature is shown in this paper
Quantum theory of electronic double-slit diffraction
The phenomena of electron, neutron, atomic and molecular diffraction have
been studied by many experiments, and these experiments are explained by some
theoretical works. In this paper, we study electronic double-slit diffraction
with quantum mechanical approach. We can obtain the results: (1) When the slit
width is in the range of we can obtain the obvious
diffraction patterns. (2) when the ratio of , order are missing in
diffraction pattern. (3)When the ratio of , there isn't missing order in diffraction pattern. (4) We
also find a new quantum mechanics effect that the slit thickness has a
large affect to the electronic diffraction patterns. We think all the
predictions in our work can be tested by the electronic double-slit diffraction
experiment.Comment: 9pages, 14figure
A predator-prey interaction between a marine Pseudoalteromonas sp. and Gram-positive bacteria
Predator-prey interactions play important roles in the cycling of marine organic matter. Here we show that a Gram-negative bacterium isolated from marine sediments (Pseudoalteromonas sp. strain CF6-2) can kill Gram-positive bacteria of diverse peptidoglycan (PG) chemotypes by secreting the metalloprotease pseudoalterin. Secretion of the enzyme requires a Type II secretion system. Pseudoalterin binds to the glycan strands of Gram positive bacterial PG and degrades the PG peptide chains, leading to cell death. The released nutrients, including PG-derived D-amino acids, can then be utilized by strain CF6-2 for growth. Pseudoalterin synthesis is induced by PG degradation products such as glycine and glycine-rich oligopeptides. Genes encoding putative pseudoalterin-like proteins are found in many other marine bacteria. This study reveals a new microbial interaction in the ocean
KIC 10417986: Spectroscopic confirmation of the nature of the binary system with a {\delta} Scuti component
KIC 10417986 is a short orbital period (0.0737 d) ellipsoidal variable star
with a {\delta} Scuti and {\gamma} Doradus hybrid pulsations component
discovered by Kepler. The ground-based spectroscopic observations were carried
out in the winters of 2020 and 2021 to investigate the binary nature of this
star. We derive the orbital parameters using the rvfit code with a result of K1
= 29.7 1.5 km/s, {\gamma} = -18.7 1.7 km/s, and confirm an orbital
period of 0.84495 d instead of the result given by Kepler. The atmospheric
parameters of the primary are determined by the synthetic spectra fitting
technique with the estimated values of Teff = 7411 187 K, log g = 4.2
0.3 dex, [M/H] = 0.08 0.09 dex and vsini = 52 11 km/s. KIC
10417986 is a circular orbit binary system. From the single-lined nature and
mass function of the star, the derived orbital inclination is 26 6{\deg},
and the mass of the secondary is from 0.43 to 0.7 M_sun, which should be a
late-K to early-M type star. Fourteen frequencies are extracted from Kepler
light curves, of which six independent frequencies in the high-frequency region
are identified as the p-mode pulsations of {\delta} Scuti star, and one
independent frequency in the low-frequency region (f2 = 1.3033 c/d) is probably
the rotational frequency due to the starspots rather than the ellipsoidal
effect or g-mode of {\gamma} Doradus.Comment: 18 pages, 8 figure
Yin-Cold
Traditional Chinese Medicine (TCM) therapies should be tailored according to the different syndrome types. In order to identify the relationship between the TCM Yin-cold (YC) or Yang-heat (YH) syndrome types and the EGFR gene status, we prospectively studied 310 NSCLC patients. TCM YH or YC was diagnosed by three TCM experts. TCM symptoms and signs were entered into a binary cluster analysis. The relationships between the EGFR gene status, YH or YC syndrome types, and classification by cluster analysis were analyzed using the chi-square test and multivariate logistic regression. In the 299 patients who had their EGFR gene tested, 45.24% YC (76/168) and 25.95% YH (34/131) patients had EGFR mutations (p=0.001). Among the 292 patients entered into the cluster analysis, 132 were classified into group A, with signs and symptoms similar to YC, whereas 160 group B patients were similar to YH. In the 281 patients with EGFR tested, 45.67% group A (58/127) and 28.57% group B patients (44/154) had EGFR mutations (p=0.003). The EGFR status was independently correlated with TCM syndrome type and classification by cluster analysis on multivariate logistic regression. NSCLC patients with YC were more likely to have EGFR gene mutations
Structural mechanism for bacterial oxidation of oceanic trimethylamine into trimethylamine N -oxide
Trimethylamine (TMA) and trimethylamine N-oxide (TMAO) are widespread in the ocean and are important nitrogen source for bacteria. TMA monooxygenase (Tmm), a bacterial flavin-containing monooxygenase (FMO), is found widespread in marine bacteria and is responsible for converting TMA to TMAO. However, the molecular mechanism of TMA oxygenation by Tmm has not been explained. Here, we determined the crystal structures of two reaction intermediates of a marine bacterial Tmm (RnTmm) and elucidated the catalytic mechanism of TMA oxidation by RnTmm. The catalytic process of Tmm consists of a reductive half-reaction and an oxidative half-reaction. In the reductive half-reaction, FAD is reduced and a C4a-hydroperoxyflavin intermediate forms. In the oxidative half-reaction, this intermediate attracts TMA through electronic interactions. After TMA binding, NADP+ bends and interacts with D317, shutting off the entrance to create a protected micro-environment for catalysis and exposing C4a-hydroperoxyflavin to TMA for oxidation. Sequence analysis suggests that the proposed catalytic mechanism is common for bacterial Tmms. These findings reveal the catalytic process of TMA oxidation by marine bacterial Tmm and first show that NADP+ undergoes a conformational change in the oxidative half-reaction of FMOs
Automatic Determination of Stellar Atmospheric Parameters and Construction of Stellar Spectral Templates of the Guoshoujing Telescope (LAMOST)
A number of spectroscopic surveys have been carried out or are planned to
study the origin of the Milky Way. Their exploitation requires reliable
automated methods and softwares to measure the fundamental parameters of the
stars. Adopting the ULySS package, we have tested the effect of different
resolutions and signal-to-noise ratios (SNR) on the measurement of the stellar
atmospheric parameters (effective temperature Teff, surface gravity log g, and
metallicity [Fe/H]). We show that ULySS is reliable to determine these
parameters with medium-resolution spectra (R~2000). Then, we applied the method
to measure the parameters of 771 stars selected in the commissioning database
of the Guoshoujing Telescope (GSJT). The results were compared with the
SDSS/SEGUE Stellar Parameter Pipeline (SSPP), and we derived precisions of 167
K, 0.34 dex, and 0.16 dex for Teff, log g and [Fe/H] respectively. Furthermore,
120 of these stars are selected to construct the primary stellar spectra
template library (Version 1.0) of GSJT, and will be deployed as basic
ingredients for the GSJT automated parametrization pipeline.Comment: 23 pages, 15 figures, accepted by RA
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