4,752 research outputs found
A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A (I): model and the near-infrared and X-ray flares
Flares from the supermassive black hole in our Galaxy, Sagittarius~A
(Sgr A), are routinely observed over the last decade or so. Despite
numerous observational and theoretical efforts, the nature of such flares still
remains poorly understood, although a few phenomenological scenarios have been
proposed. In this work, we develop the Yuan et al. (2009) scenario into a
magnetohydrodynamic (MHD) model for Sgr A flares. This model is
analogous with the theory of solar flares and coronal mass ejection in solar
physics. In the model, magnetic field loops emerge from the accretion flow onto
Sgr A and are twisted to form flux ropes because of shear and
turbulence. The magnetic energy is also accumulated in this process until a
threshold is reached. This then results in a catastrophic evolution of a flux
rope with the help of magnetic reconnection in the current sheet. In this
catastrophic process, the magnetic energy is partially converted into the
energy of non-thermal electrons. We have quantitatively calculated the
dynamical evolution of the height, size, and velocity of the flux rope, as well
as the magnetic field in the flare regions, and the energy distribution of
relativistic electrons in this process. We further calculate the synchrotron
radiation from these electrons and compare the obtained light curves with the
observed ones. We find that the model can reasonably explain the main
observations of near-infrared (NIR) and X-ray flares including their light
curves and spectra. It can also potentially explain the frequency-dependent
time delay seen in radio flare light curves.Comment: 17 pages, 13 figures, accepted by MNRA
Dynamics of glass phases in the two-dimensional gauge glass model
Large-scale simulations have been performed on the current-driven
two-dimensional XY gauge glass model with resistively-shunted-junction
dynamics. It is observed that the linear resistivity at low temperatures tends
to zero, providing strong evidence of glass transition at finite temperature.
Dynamic scaling analysis demonstrates that perfect collapses of current-voltage
data can be achieved with the glass transition temperature , the
correlation length critical exponent , and the dynamic critical
exponent . A genuine continuous depinning transition is found at zero
temperature. For creeping at low temperatures, critical exponents are evaluated
and a non-Arrhenius creep motion is observed in the glass phase.Comment: 10 pages, 6 figure
Study on Salting Out-Steam Distillation Extraction Technology and Antibacterial Activities of Essential Oil From Cumin Seeds
The effects of different factors on the yield of essential oil from were discussed, and the extraction conditions of essential oil from cumin seeds by salting out-steam distillation technology based on single-factor test and orthogonal experiment, as well as its antibacterial activities on several common food spoilage bacteria were studied in this paper. The results showed that, the impact order of the influence factors was liquid/solid ratio > distilling time > NaCl concentration, and optimized extraction conditions were as follows, liquid to material ratio 15:1, soaking time 1 h, 4% NaCl, steam distilling time 3 h. The yield of essential oil was up to 4.48% under these conditions. The results of antibacterial activity assays showed that the essential oil from cumin seeds exhibited the different antibacterial activities against some food borne pathogens, especially it presented the best inhibitory effect against Bacillus subtilis with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 6.25 and 12.5 mg/mL respectively, followed by Staphylococcus albus and Staphylococcus aureus, the lowest for Pseudomonas aeruginosa and Shigella dysenteria
Editorial: Unravelling Copper-Regulatory Systems and Copper-Affected Pathways in Cancer Cells to Improve Current Therapies
Unravelling Copper-Regulatory Systems and Copper-Affected Pathways in Cancer Cells to Improve Current Therapie
Methods for preventing and treating cancer using N-thiolated β-lactam compounds and analogs thereof
The subject invention concerns N-thiolated β-lactam compounds of formula A, wherein R1 is a hydrocarbon group having 1–8 carbon atoms; R3 is an organothio group; and R4 is alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heterocycloalkyl, cycloalkenyl, or heterocycloalkenyl, and analogs and pharmaceutically acceptable salts, esters and amides thereof. The subject invention also concerns methods for inducing tumor cell death or inhibiting tumor cell proliferation, and methods for inducing DNA damage, inhibiting DNA replication, activating p38 MAP kinase, or activating caspase cascade activation, or releasing cytochrome C from mitochondria into the cytoplasm in a tumor cell. Methods for treating cancer using N-thiolated β-lactam compounds, as well as pharmaceutical compositions comprising the same are further disclosed
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