分类: 天文学 >> 天文学 提交时间: 2023-08-04
摘要: The inner boundary of a black hole accretion disk is often set to the marginally stable circular orbit (or the innermost stable circular orbit, ISCO) around the black hole. It is important for the theories of black hole accretion disks and their applications to astrophysical black hole systems. Traditionally, the marginally stable circular orbit is obtained by considering the equatorial motion of a test particle around a black hole. However, in reality the accretion flow around black holes consists of fluid, in which the pressure often plays an important role. Here we consider the influence of fluid pressure on the location of marginally stable circular orbit around black holes. It is found that when the temperature of the fluid is so low that the thermal energy of a particle is much smaller than its rest energy, the location of marginally stable circular orbit is almost the same as that in the test particle case. However, we demonstrate that in some special cases the marginally stable circular orbit can be different when the fluid pressure is large and the thermal energy becomes non-negligible comparing with the rest energy. We present our results for both the cases of non-spinning and spinning black holes. The influences of our results on the black hole spin parameter measurement in X-ray binaries and the energy release efficiency of accretion flows around black holes are discussed.
分类: 医学、药学 >> 基础医学 提交时间: 2017-12-07 合作期刊: 《分子影像学杂志》
摘要: Objective Cabrol procedure was introduced by Professor Cabrol C in 1981, but little information existed regardingthe results of Cabrol technique in aortic dissection(AD). This study explored a 7-year period results of aortic root replacementsin type A aortic dissection employing this procedure. Methods From January 2009 to December 2016, 47 patients with type Aaortic dissection received Cabrol procedure in our hospital. All patients received echocardiography and CT scan of whole aortabefore operation. Cabrol procedure was performed to repair the aortic root. The replacement of right hemi aortic arch or totalaortic arch and a stented frozen elephant trunk implantation might be performed based on the extent of the dissection in theaortic arch. A retrospective analysis was performed to evaluate the effectiveness of this procedure in type A aortic dissection.Results Forty-seven cases were admitted, including 6 cases of simple Cabrol procedure, 13 cases with concomitantreplacement of right hemi aortic arch and 28 cases with concomitant total aortic arch replacement and frozen elephant trunktechnique.The 30-day mortality was 10.6%(5/47). 25.5%(12/47) of patients developed acute renal failure, and 12.8%(6/47)needed continuous renal replacement therapy (CRRT) during hospital time. The median hospital time were 25.5 d, rangingfrom 15 to 128 d.It followed-up from 6 to 36 months. Conclusion The Cabrol procedure is feasible and safe for patients withtype A aortic dissection. The artificial blood vessels are unobstructed.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-15
摘要: As discussed recently by Hooper and Tait, the singlino-like dark matter in the Minimal Supersymmetric Standard Model (MSSM) extended by a singlet Higgs superfield can give a perfect explanation for both the relic density and the Pamela result through the Sommerfeld-enhanced annihilation into singlet Higgs bosons (a or h followed by h -> aa) with a being light enough to decay dominantly to muons or electrons. In this work we analyze the parameter space required by such a dark matter explanation and also consider the constraints from the LEP experiments. We find that although the light singlet Higgs bosons have small mixings with the Higgs doublets in the allowed parameter space, their couplings with the SM-like Higgs boson h(SM) (the lightest doublet-dominant Higgs boson) can be enhanced by the soft parameter A(kappa) and, in order to meet the stringent LEP constraints, the h(SM) tends to decay into the singlet Higgs pairs a a or hh instead of b (b) over bar. So the h(SM) produced at the LHC will give a multi-muon signal, h(SM) -> aa -> 4 mu or h(SM) -> hh -> 4a -> 8 mu.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-15
摘要: We perform a comparative study of the neutralino dark matter scattering on nucleon in three popular supersymmetric models: the minimal (MSSM), the next-to-minimal (NMSSM) and the nearly minimal (nMSSM). First, we give the predictions of the elastic cross section by scanning over the parameter space allowed by various direct and indirect constraints, which are from the measurement of the cosmic dark matter relic density, the collider search for Higgs boson and sparticles, the precision electroweak measurements and the muon anomalous magnetic moment. Then we demonstrate the property of the allowed parameter space with/without the new limits from CDMS II. We obtain the following observations: (i) For each model the new CDMS limits can exclude a large part of the parameter space allowed by current collider constraints; (ii) The property of the allowed parameter space is similar for MSSM and NMSSM, but quite different for nMSSM; (iii) For each model the future SuperCDMS can cover most of the allowed parameter space given that all soft breaking parameters are below 1 TeV.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: The luminescent properties of two Eu3+ compounds based on quinoline-2-carboxylic acid (Hqc), [Na2Eu2(qc)6(CH3COO)2(H2O)4].2DMF (1) and [Eu2(qc)6(H2O)6].3H2O (2), as well as their syntheses and structures are reported. Both compounds are formed by slow evaporation at room temperature and exhibit zero dimensional dinuclear structures. It is worth mentioning that a 4.5-fold enhancement in luminescent quantum yield is achieved by reducing the nonradiative deactivation, through which the quantum yield increases remarkably to 67.62% for 1 compared with 12.18% for 2.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two new inorganic-organic hybrid vanadogermanates H[Cd(en)(phen)(H2O)][Cd(en)(phen)]{[Cd(phen)]2[Ge8V12O41(OH)7]}�H2O (1) and [Cd(dien)2][Cd(dien)]2{[Cd(phen)]2Ge8V12O42(H2O)(OH)6}�.5H2O (2) (en = ethylenediamine, dien = diethylenetriamine, phen = 1,10-phenanthroline) have been synthesized by hydrothermal method. Their structures were measured by single-crystal X-ray diffractions, thermogravimetric analysis, powder X-ray diffractions and infrared spectra. Structural analysis reveals that compound 1 is an infrequent dimeric structure based on di-Cd-substituted Ge-V-O cluster and transition-metal complex bridges, while compound 2 is an infinite 1-D chain constructed from di-Cd-substituted Ge-V-O clusters and dinuclear bridging complexes. Magnetic measurement indicated that both 1 and 2 exhibit antiferromagnetic behaviors.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Aiming at the subband division of ultra-wide bandwidth low-frequency (UWL) signal (frequency coverage range: 704–4032 MHz) of the Xinjiang 110 m QiTai radio Telescope (QTT), a scheme of ultra-wide bandwidth signal is designed. First, we analyze the effect of different window functions such as the Hanning window, Hamming window, and Kaiser window on the performance of finite impulse response (FIR) digital filters, and implement a critical sampling polyphase filter bank (CS-PFB) based on the Hamming window FIR digital filter. Second, we generate 3328 MHz simulation data of ultra-wideband pulsar baseband in the frequency range of 704–4032 MHz using the ultra-wide bandwidth pulsar baseband data generation algorithm based on the 400 MHz bandwidth pulsar baseband data obtained from Parkes CASPSR observations. Third, we obtain 26 subbands of 128 MHz based on CS-PFB and the simulation data, and the pulse profile of each subband by coherent dispersion, integration, and folding. Finally, the phase of each subband pulse profile is aligned by non-coherent dedispersion, and to generate a broadband pulse profile, which is basically the same as the pulse profile obtained from the original data using DSPSR. The experimental results show that the scheme for the QTT UWL receiving system is feasible, and the proposed channel algorithm in this paper is effective.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: External micro-PIXE measurements were done to investigate the accumulation of Nd3+ on green algae species euglena gracilis. According to the Nd distribution patterns in the gracilis cells, the biosorption of Nd3+ to the cells compartments can be observed. Comparing elemental mappings of the cell treated with different doses of the 1 mg/mL Nd3+ solution, the Nd uptake of euglena gracilis cells do no relate with the doses. From distributions of Ca and Mg, it is found that the Ca is complementary to Nd partly, and the Nd and Mg distributions are alike to each other, showing that Nd may be mainly in the chlorophyll molecules. The biochemistry related is discussed.
分类: 生物学 >> 生物医药 提交时间: 2017-03-30
摘要: Fungi have emerged as the fourth most common pathogens isolated in nosocomial bloodstream infections, and Candida albicans is the most common human fungal pathogen. Only a few antibiotics are effective in the treatment of fungal infections. In addition, the repetition and lengthy duration of fluconazole therapy has led to an increased incidence of azole resistance and treatment failure associated with C. albicans. To investigate the mechanism of drug resistance and explore new targets to treat clinically resistant fungal pathogens, we examined the large-scale gene expression profile of two sets of matched fluconazole-susceptible and -resistant bloodstream C. albicans isolates from bone marrow transplanted (BMT) patients for the first time by microarray analysis. More than 198 differentially expressed genes were identified and they were confirmed and validated by RT-PCR independently. Not surprisingly, the resistant phenotype is associated with increased expression of CDR mRNA, as well as some common genes involved in drug resistance such as CaIFU5, CaRTA2 and CaIFD6. Meanwhile, some special functional groups of genes, including ATP binding cassette (ABC) transporter genes (IPF7530, CaYOR1, CaPXA1), oxidative stress response genes (CaALD5, CaGRP1, CaSOD2, IPF10565), copper transport and iron mobilization-related genes (CaCRD1/2, CaCTR1/2, CaCCC2, CaFET3) were found to be differentially expressed in the resistant isolates. Furthermore, among these differentially expressed genes, some co-regulated with CaCDR1, CaCDR2 and CaIFU5, such as CaPDR16 and CaIFD6, have a DRE-like element and may interact with TAC1 in the promoter region. These findings may shed light on mechanisms of azole resistance in C. albicans and clinical antifungal therapy.
提交时间: 2017-05-02
摘要: Indium-zinc-oxide [IZO]-based electric double layer [EDL] transistors gated by solution-processed chitosan electrolyte films are fabricated on glass substrates and used for mimicking synaptic plasticity. The conductance of the self-assembled IZO channel t