Effective Debye temperature for a 2-dimensional crystal

Various studies have shown that the mean square amplitude of atoms on the surface of a crystal is almost twice that in the bulk. We believe that the results obtained by Kothari, using simple physical arguments for surface vibrations, were in error. We have also shown that the results could be explained by taking the contribution of bending waves in addition to surface vibrations for a 2-dimensional crystal.     

Magnetoacoustic open-orbit antiresonance in silver

Antiresonance (sharp attenuation minima) predicted theoretically by Sievert in 1967 and the rich harmonics observed experimentally by Khatri and Peverly in 1973 in copper have remained unexplained to a great extend. In this letter, we report our preliminary results on this novel effect (antiresonance) for shear waves propagated along the [111] crystallographic direction in silver.     

Review on asymmetric synthetic methodologies for chiral isoquinuclidines; 2008 to date

Isoquinuclidines constitute the central structural nucleus of numerous biologically active natural products, for example, iboga alkaloids such as ibogamine and catharanthine as well as non-indole-containing alkaloids such as the dioscorine and the cannivonines. Furthermore, in medicinal and pharmaceutical chemistry, the isoquinuclidine core is commonly employed as a rigid azabicyclic scaffold, thus providing significant precursors in the synthesis of numerous valuable alkaloids. Summarizing well-organized approaches to access the chiral isoquinuclidine structural centerpiece signifies a significant endeavor not only for developing biologically active natural products but also enhancing biological researches that can lead to possible drug discovery. Over time, the values and methodologies for the asymmetric synthesis of chiral isoquinuclidines are increasing; hence to advance asymmetric synthesis, this review combines and discusses the pros and cons of each synthesis techniques from 2008. This review should be helpful for promoting further developments of asymmetric synthetic methodologies and for medicinal chemistry.     

Screening for oxidative damage by engineered nanomaterials: a comparative evaluation of FRAS and DCFH

Several acellular assays are routinely used to measure oxidative stress elicited by engineered nanomaterials (ENMs), yet little comparative evaluations of such methods exist. This study compares for the first time the performance of the dichlorofluorescein (DCFH) assay which measures reactive oxygen species (ROS) generation, to that of the ferric-reducing ability of serum (FRAS) assay, which measures biological oxidant damage in serum. A diverse set of 28 commercially important and extensively characterized ENMs were tested on both the assays. Intracellular oxidative stress was also assessed on a representative subset of seven ENMs in THP-1 (phorbol 12-myristate 13-acetate matured human monocytes) cells. Associations between assay responses and ENM physicochemical properties were assessed via correlation and regression analysis. DCFH correlated strongly with FRAS after dose normalization for mass (R ² = 0.78) and surface area (R ² = 0.68). Only 10/28 ENMs were positive in DCFH versus 21/28 in FRAS. Both assays were strongly associated with specific surface area and transition metal content. Qualitatively, a similar response ranking was observed for acellular FRAS and intracellular reduced:oxidized glutathione ratio (GSH:GSSG) in cells. Quantitatively, weak correlation was found between intracellular GSSG and FRAS or DCFH (R ² < 0.25) even after calculating effective dose to cells. The FRAS assay was more sensitive than DCFH, especially for ENMs with low to moderate oxidative damage potential, and may serve as a more biologically relevant substitute for acellular ROS measurements of ENMs. Further in vitro and in vivo validations of FRAS against other toxicological endpoints with larger datasets are recommended.     

Multiple active motifs grafted on cyclotriphosphazene core: a novel catalyst for the chemical activation of carbon dioxide

A novel catalyst having multiple triphenylphosphonium chloride motifs on a single cyclotriphosphazene molecule has been developed for the chemical activation of carbon dioxide for the production of propylene carbonate from carbon dioxide and propylene oxide. The unique structure and multiple catalytic sites on a single framework are the prime factors, resulted in the enhanced catalytic activity and afforded high product yield.     

Synthesis and Crystal Structure of 3,5-Dichloro-N-(2-methoxyphenyl)benzamide

<正>The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously confirmed by the single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the monoclinic space group P2_1/c with unit cell dimensions of a = 4.9369(16), b = 13.351(5), c = 20.168(7), β = 96.755(8)°, V = 1320.1(8)~3 and Z = 4.     

Synthesis of Some New 2-(4-Methoxybenzothiazol-2′-yl amino)-4-(2-chloro-4-trifluoromethylanilino)-6-(substituted thioureido)-1,3,5-triazine as Antifungal Agents

2,4,6-Trichloro 1,3,5-triazine was selectively reacted with new nucleophilic reagents such as 4-methoxy-2-aminobenzothiazole, 2-chloro-4-trifluoromethyl-aniline, and phenylsubstituted thiourea in alkaline medium to give 2-(4-methoxybenzothiazol-2′-ylamino)-4-(phenylthioureido)-6-(substitutedthioureido)-1,3,5-triazines. The structures of these compounds were confirmed by IR, ¹H NMR, ¹⁹F NMR, mass spectral data, and elemental analysis. The compounds show fungicidal activity against Alternaria alternata, Aspergillus niger, and Macrofomina.

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