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72 result(s) for "Zeng, Yan-Bo"
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Self-interacting multistate boson stars
A bstract In this paper, we consider rotating multistate boson stars with quartic self-interactions. In contrast to the nodeless quartic-boson stars in [1], the self-interacting multistate boson stars (SIMBSs) have two types of nodes, including the 1 S 2 S and 1 S 2 P states. We show the mass M of SIMBSs as a function of the synchronized frequency ω , and the nonsynchronized frequency ω 2 for three different cases. Moreover, for the case of two coexisting states with self-interacting potential, we study the mass M of SIMBSs versus the angular momentum J for the synchronized frequency ω and the nonsynchronized frequency ω 2 . Furthermore, for three different cases, we analyze the coexisting phase with both the ground and first excited states for SIMBSs. We also calculate the maximum value of coupling parameter Λ, and find the coupling parameter Λ exists the finite range.
Rotating hybrid axion-miniboson stars
We construct rotating hybrid axion-miniboson stars (RHABSs), which are asymptotically flat, stationary, axially symmetric solutions of (3+1)-dimensional Einstein–Klein–Gordon theory. RHABSs consist of an axion field (ground state) and a free complex scalar field (first excited state). The solutions of RHABSs have two types of nodes, including 1 S 2 S state and 1 S 2 P state. For different axion decay constants f a , we present the mass M of RHABSs as a function of the synchronized frequency, as well as the nonsynchronized frequency, and explore the mass M versus the angular momentum J for the synchronized frequency and the nonsynchronized frequency, respectively. Furthermore, we study the effect of axion decay constant f a and free scalar field mass μ f on the existence domain of the synchronized frequency ω .
Bioactive Steroids with Structural Diversity from the South China Sea Soft Coral Lobophytum sp. and Sponge Xestospongia sp
A chemical investigation of the soft coral Lobophytum sp. and the sponge Xestospongia sp. from the South China Sea led to the isolation of five steroids, including two new compounds (1 and 4) and one known natural product (3). Compounds 1–3 were derived from the soft coral Lobophytum sp., while 4 and 5 were obtained from the sponge Xestospongia sp. The structures of these compounds were determined by extensive spectroscopic analysis, the time-dependent density functional theory–electronic circular dichroism (TDDFT-ECD) calculation method, and comparison with the spectral data previously reported in the literature. The antibacterial and anti-inflammatory activities of isolated compounds were evaluated in vitro. Compounds 1–3, 4, and 5 exhibited weak antibacterial activity against vancomycin-resistant Enterococcus faecium G1, Streptococcus parauberis KSP28, Photobacterium damselae FP2244, Lactococcus garvieae FP5245, and Pseudomonas aeruginosa ZJ028. Moreover, compound 3 showed significant anti-inflammatory activity by inhibiting lipopolysaccharide (LPS)-induced NO production in RAW 264.7 cells, with an IC50 value of 13.48 μM.
Equatorial orbits of spinning test particles in rotating boson stars
In this paper, we study circular orbits of spinning test particles in the background of a rotating boson star. Using the pole-dipole approximation and neglecting the back-reaction of the spinning test particle on the spacetime, the equation of motion of the spinning test particle is described by the Mathisson–Papapetrou–Dixon equation. We solve this equation under the Tulczyjew spin-supplementary condition and obtain the four-momentum and four-velocity of the spinning test particle. Quite different from the spinless particle, the effective potential of the spinning particle with zero orbital angular momentum goes to infinite at the center of the rotating boson star. This will lead to the fact that the spinning particle can not pass through the center of the boson star. However, when the spin angular momentum and orbital angular momentum satisfy 2s¯+l¯=0, the effective potential is not divergent anymore and the spinning particle can pass through the center of the rotating boson star. We still investigate how the spin affects the structure of the circular orbits and we find that the spin will induce the larger or smaller regions of no circular orbits, unstable circular orbits, and stable circular orbits. Moreover, the radius and energy of the circular orbit will be decreased or increased by the particle spin. These results will have an important application in testing the gravitational waves in the boson star background.
Characterization and Determination of 2-(2-Phenylethyl)chromones in Agarwood by GC-MS
Agarwood is the fragrant resinous heartwood obtained from certain trees in the genus Aquilaria belonging to the family Thymelaeaceae. 2-(2-Phenylethyl)chromones and characteristic sesquiterpenes are the main classes of aromatic compounds isolated from agarwood. Although there are many sesquiterpenes, relatively few 2-(2-phenylethyl)chromones have been determined in agarwood by GC-MS. After analysis of the MS spectra of eighteen 2-(2-phenylethyl)chromone derivatives isolated from agarwood and identified by NMR spectroscopy, together with the reported MS data and characteristic of structures of 2-(2-phenylethyl)chromones, the MS characterization, fragmentation patterns and characteristic fragment peaks for the compounds were deduced and a table summarizing MS characterization of 2-(2-phenylethyl)chromones in agarwood is presented. All the 2-(2-phenylethyl)chromones previously reported in agarwood are substituted by methoxy or/and hydroxy groups, except for one compound. Due to the fact they all possess the same basic skeleton (molecular weight: 250) and similar substituent groups (methoxy or hydroxy groups), a formula (30m + 16n = MW − 250) is provided to calculate the number of methoxy (m) or hydroxy (n) groups according to molecular ion peak or molecular weight (MW). We deduced that the characteristic fragmentation behaviors of the 2-(2-phenylethyl)chromones are the cleavages of the CH2-CH2 bond between chromone moiety and phenyl moiety. Thus, characteristic fragment ions, such as m/z 91 [C7H7], 107 [C7H6+OH], 121 [C7H6+OCH3], 137 [C7H5+OH+OCH3] are formed by different substituted benzyl moieties, while characteristic fragment ions such as m/z 160 [C10H8O2], 176 [C10H7O2+OH], 190 [C10H7O2+OCH3], 220 [C10H6O2+OCH3×2] are formed by different substituted chromone moieties. Furthermore, rules regarding to the relationship between the positions of hydroxy or methoxy groups and the relative abundances of benzyl and chromone fragment ions have been deduced. Elucidation of how the positions of hydroxy or methoxy groups affect the relative abundances of benzyl and chromone fragment peaks is also provided. Fifteen unidentified compounds of an artificial agarwood sample analyzed by GC-MS, were preliminary determined as 2-(2-phenylethyl)chromones by analysis of their MS characterization and by comparison of their MS spectra with those of 18 standard compounds or 2-(2-phenylethyl)chromones reported in literature according to the above-mentioned methods and rules. This report will be helpful for the analysis and structural elucidation of 2-(2-phenylethyl)chromones in agarwood by GC-MS, and provides fast and reliable characterization of the quality of agarwood.
A New 2-(2-Phenylethyl)Chromone from Chinese Eaglewood
A new 2-(2-phenylethyl)chromone, 5,6,7,8-tetrahydroxy-2-(3-hydroxy-4-methoxyphenethyl)-5,6,7,8-tetrahydro-4H-chromen-4-one (1) was isolated from the Chinese eaglewood [Aquilaria sinensis (Lour.) Gilg]. Its structure was established by detailed MS and NMR spectroscopic analysis, as well as comparison with literature data.
A Fatty Acid Glycoside from a Marine-Derived Fungus Isolated from Mangrove Plant Scyphiphora hydrophyllacea
To study the antimicrobial components from the endophytic fungus A1 of mangrove plant Scyphiphora hydrophyllacea Gaertn. F., a new fatty acid glucoside was isolated by column chromatography from the broth of A1, and its structure was identified as R-3-hydroxyundecanoic acid methylester-3-O-α-l-rhamnopyranoside (1) by spectroscopic methods including 1D and 2D NMR (HMQC, 1H-1H COSY and HMBC) and chemical methods. Antimicrobial assay showed compound 1 possessed modest inhibitory effect on Saphylococcus aureus and methicillin-resistant S. aureus (MRSA) using the filter paper disc agar diffusion method.
Distance-stratified sociodemographic differences in telemedicine use in surgical oncology clinics at an academic medical center
We examined telemedicine use across 38,883 surgical oncology visits (2021-2023) at a Northern California cancer center. At ≥20 miles from clinics, Hispanic (OR = 0.76, 95% CI [0.68,0.85]), Asian/Pacific Islander (OR = 0.75, 95% CI [0.66,0.84]), interpreter-needing (OR = 0.67, 95% CI [0.59,0.77]), and Medicaid patients (OR = 0.85, 95% CI [0.76,0.96]) had lower telemedicine use, while low-income patients showed higher utilization (OR = 1.67, 95% CI [1.46,1.91]). At <20 miles, no differences were observed for Hispanic, interpreter-needing, Medicaid, or low-income patients, but Asian/Pacific Islanders showed higher use (OR = 1.16, 95% CI [1.04-1.30]). Geographic distance modifies telemedicine access patterns.
Caloxanthones O and P: Two New Prenylated Xanthones from Calophyllum inophyllum
Chemical investigation of the EtOH extract of the twigs of Calophyllum inophyllum collected in Hainan Province of China resulted in the isolation of two new prenylated xanthones, caloxanthone O (1) and caloxanthone P (2). Their structures were elucidated by a study of their physical and spectral data. Compound 1 exhibited cytotoxicity against human gastric cancer cell line (SGC-7901),with an IC50 value of 22.4 μg mL-1.
Scyphiphin C, a New Iridoid from Scyphiphora hydrophyllacea
Chemical investigation of the ethanol extract of the aerial parts of Scyphiphora hydrophyllacea Gaertn.collected in Hainan Province of China resulted in the isolation of a new iridoid, scyphiphin C (1) and a known iridoid glycoside, shanzhiside methyl ester (2). Their structures were elucidated by a study of their physical and spectral data.