Determining the long living quasi-normal modes of relativistic stars

Methods of finding quasi-normal modes of non-rotating relativistic stars have been well established,however,none of the existing treatments which take spacetime and fluid oscillations fully into account can determine modes of long decay time,e.g.,the p and g mode series,or the f modes for stars with low compactness ratio (M/R). In this paper we show how the quasi-normal modes of long lifetime can be determined through refinements of a treatment originally due to Detweiler and Lindblom. The determination of the p mode series has been argued in the literature to have implication on the life time of gravitational wave sources and stellar stability. In this paper we 1) provide detailed steps in our treatment to facilitate future effort in this direction; 2) correct mistakes in the literature on the formulation; and 3) analyse the accuracy of the quasi-normal mode frequencies obtained and the limitations of the treatment.     

苯酚与钠反应的实验改进

介绍了一种苯酚与钠反应的实验方案,验证“酚羟基活泼性大于醇羟基”。实验操作简便,现象持续明显,适用于课堂演示,有利于教学。     

Antioxidant and α-glucosidase inhibitory ingredients identified from Jerusalem artichoke flowers

Jerusalem artichoke (JA, Helianthus tuberosus L.) has been researched extensively due to its wide range of uses, but there are limited studies on its flowers. In this study, we report the first detailed phytochemical study on JA flowers, which yielded 21 compounds. Compound 4 was identified as a major water-soluble yellow pigment of JA flowers. In addition, the methanol extract of JA flowers and the isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Among the tested compounds, compound 13 showed the strongest ABTS⁺ free radical scavenging activity with SC₅₀ value of 2.30 ± 0.13 μg/mL, and compound 6 showed most potent α-glucosidase inhibitory activity with inhibition rate of 60.0% ± 10.3% at a concentration of 250 μg/mL. Results showed that methanol extract of JA flowers exhibited antioxidant and α-glucosidase inhibitory activities which could be attributed to its phenolic ingredients including chlorogenic acid derivatives, flavonoids and phenols.     

Study on Molecular Recognition of Pinocembrin with Methylated-β-Cyclodextrin

The inclusion behavior, inclusion capacity and inclusion mode of pinocembrin (PIN) with dimethyl-β-cyclodextrin (DM-β-CD) and trimethyl-β-cyclodextrin (TM-β-CD) were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM), UV-visible spectral titration and molecular docking. The results showed that the packing ratio of PIN/DM-β-CD complex and PIN/TM-β-CD complex was 1:1. The water solubility of PIN increased by 817 times and 575 times in the inclusion complex with DM-β-CD and TM-β-CD, respectively. Molecular docking showed the PIN entered from the large end of the DM-β-CD molecule and penetrated through the cavity. The A and B rings of the PIN were respectively located at the big and small ends of the CD molecule. For the TM-β-CD, only A and C rings of the PIN entered the cavity of CD.     

Effects of temperature on the structure of neutron stars at high temperature

In Newtonian physics, higher temperature leads to higher thermal pressure, which provides stronger support against the gravitational contraction of stars. However, in the temperature range of tens of MeV involved in the evolution of a proto-neutron star or a higher massive neutron star, the effects of temperature are richer. We showed that, for a high temperature neutron star (HTNS) constructed with a realistic equation of state (EOS), the HTNS may expand or contract during cooling, the central density may increase or decrease, the quasi-normal mode oscillation frequencies may increase or decrease, and in particular, (i) independent of the EOS, for a HTNS of a given mass, there exists a maximum temperature \(T_{max}\) that it could ever attend at birth (with the value of \(T_{max}\) different for different EOS), and (ii) for the Hempel EOS and the Shen EOS, there is a range of mass that the HTNS may gravitationally collapse after a period of radiative cooling; however, for the Lattimer–Swesty EOS and Banik EOS, no delayed collapse is possible. Our study, which describes the cooling of HTNSs with simple quasi-stationary TOV sequences, provides an understanding of the effects of the thermal energy/pressure at high temperature, and a demonstration that different EOSs can lead to qualitatively different evolution paths.     

Solvophobically-driven oligo(ethylene glycol) helical foldamers. Synthesis, characterization, and complexation with ethane-1,2-diaminium

Oligo(ethylene glycols) 1a-h, which are incorporated with one to eight 2,3-naphthylene units, respectively, have been synthesized and characterized. The conformational changes of the new oligomers have been investigated in chloroform-acetonitrile binary solvents by the UV-vis, (1)H NMR, and fluorescent spectroscopy. It has been revealed that the naphthalene units in hexamer 1f, heptamer 1g, and octamer 1h are driven by solvophobic interaction to stack in polar solvents. As a result, compact helical conformations are formed that give rise to a cavity similar to that of 18-crown-6. Shorter oligomers 1b-e exhibit weaker folding tendency. (1)H NMR studies reveal that 1f-h are able to complex ammonium or ethane-1,2-diaminium 19, but not secondary ammonium compounds. The association constants of complexes 1f.19, 1g.19, and 1h.19 in acetonitrile are determined to be 3.5(+/-0.4) x 10(3), 1.0(+/-0.12) x 10(4), and 2.5(+/-0.4) x 10(4) M(-1), respectively, with the (1)H NMR titration method. For comparison, hexamer 22, which incorporates six 1,5-naphthylene units, is also prepared. The UV-vis and fluorescent investigations show that 22 is also able to fold in polar solvents, but no helical structure can be produced due to mismatch of the stacking naphthalene units and consequently there is no obvious complexation between 22 with ethane-1,2-diaminium ion. The structures of the longest foldamer 1h and its complex with 19 have been studied with molecular mechanics calculations. This work represents a new approach to building folding conformations from flexible linear molecules.     

Syntheses,Characterizations and Crystal Structures of (E)-2-Methyl-1,3-diphenylisothiouronium Iodide and 1,3-Dibenzyl-2-methylisothiouronium Iodide

Two thiouronium iodide salts,(E)-2-methyl-1,3-diphenylisothiouronium iodide(1) and 1,3-dibenzyl-2-methylisothiouronium iodide(2),were synthesized and characterized by single-crystal X-ray diffraction,1H NMR,IR,UV-vis and luminescence spectra.Single-crystal X-ray diffraction reveals that compound 1 crystallizes in monoclinic system,P21/n space group with a = 11.273(2),b = 10.318(2),c = 12.962(3) ?,β = 99.03(3)°,V = 1489.0(5) ?3 and Z = 4;compound 2 crystallizes in monoclinic system,C2/c space group with a = 11.706(2),b = 14.119(3),c = 20.930(4) ?,β = 103.84(3)°,V = 3358.8(12) ?3 and Z = 8.The thiouroniums of both compounds are Y-shaped planar structures to form a cross-conjugated system.The averaged bond lengths of C-N and C-S indicate the presence of "Y" aromaticity.The researches on UV-vis and luminescence spectra of compounds 1 and 2 indicate that they can form inclusion complex with β-CD in the aqueous solution.     

A six-step synthetic approach to marine natural product (+)-aureol

A concise synthetic approach to the marine natural product (+)-aureol has been achieved from readily available starting materials using obviously fewer steps in comparison to the related report in literature (6 steps versus 12 steps from (+)-sclareolide). Key steps of this protocol include a boron trifluoride-catalyzed domino 1,2-H and 1,2-methyl shifts and a nickel(II)-catalyzed cross-coupling reaction between an alkyl iodide and an aryl Grignard reagent.     

2-(4-N-硝基，N-甲基氨基苯基)-(4-硝基苯基)-5-(2,4,6- 三硝基苯基)噻唑的 合成及其性能研究

为解决非线性光学活性有机分子透明性差及熔点低的问题,设计合成了2-(4-N-硝基,N-甲基氨基苯基)-(4-硝基苯基)-5-(2,4,6-三硝基苯基)噻唑化合物,并研究了其热性能及光学性质。根据实验结果得出由于杂环的引入,提高了化合物的裂解温度,并较好地改善了有机分子的透明性。     

2-对乙酰氨基苯基-4,5-二对硝基苯基咪唑的合成及性能

咪唑化合物;非线性光学活性有机化合物;2-对乙酰氨基苯基-4;5-二对硝基苯基咪唑的合成及性能