On the interconversion pathway of HBO<-->BOH

The potential energy surfaces have been constructed for the 1A', 3A', and 3A" states of HBO by using the multireference perturbation theory with the basis set cc-pVTZ (6d,10f). Two stationary points and a transition state have been characterized on all the three surfaces, which are in good agreement with available experiments and previous calculations. The interconversion pathways from metastable boron hydroxide BOH to the considerably more stable HBO are expounded based on the nature of the surfaces.     

白花夏枯草对高原家兔骨髓各级幼红细胞Feret直径的研究

本文应用透射电镜技术对平原移居高原（海拔３９００米）实验家兔骨髓内各级红系细胞电镜照片的费莱特直径（Ｆeret)进行了研究，实验分平原对照组，高原给药及高原对照三个组，实验结果：高原给药组骨髓原红，早、中，晚幼红细胞Ｆeret直径均低于高原对照组，差别有显著性，结果提示白花夏枯草可降低由低氧引起的各级幼红细胞胸体增大，从而降低血液的粘滞性，改善血循环。     

A Novel Way to Prepareγ-A1_2O_3 Supported SO_4~(2-)/ZrO_2 Solid Superacid Catalysts for n-Butane Isomerization

The isomerization of n-butane to isobutane, which is a valuable precursor for theproduction of MTBE and alkylated gasoline, on strong acid catalysts is an importantprocess in refining industry. Solid superacid, especially sulfated zirconia, has highcatalytic activity in n-butane isomerization at comparatively low temperatures andtherefore has attracted more attention of researchers in the past twenty years.' However,from the view point of practice, the activity of SZ needs to be improved fur…     

Complete assignments of 1H and 13C NMR spectroscopic data for three new stigmastane glycosides from Vernonia cumingiana

Three new steroidal saponins, Vernoniosides S1 ( 1 ), Vernoniosides S2 ( 2 ) and Vernoniosides S3 ( 3 ) were isolated from the stem of Vernonia cumingian. Their chemical structures were elucidated on the basis of MS, NMR spectroscopic and chemical analysis. Complete assignment of ¹H and ¹³C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HMQC, HMBC, ROESY). Copyright © 2008 John Wiley & Sons, Ltd.     

抗磨可靠性寿命的加速试验与预测

在工程实际中，对新机器零件的抗磨可靠性寿命进行评估或预测非常重要，但是，由于磨损是一种受多因素制约的随机过程，目前在实验室广泛采用的模拟磨损试验，不仅周期较长，而且预测误差也比较大。因此，提出了一种在保持磨损机相似的前提下合理选用高ＰＶ值的抗磨可靠性寿命加速试验的新方法。     

Two new eudesmane derivatives from Verbesina virginica

<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods.     

Dual-sensitive probe 1-imidazole-2-(5-benzoacridine)-ethanone for the determination of amines in environmental water using HPLC with fluorescence detection and online atmospheric chemical ionization-mass spectrometry identification

Dual-sensitive probe of 1-imidazole-2-(5-benzoacridine)-ethanone (IBAE) for the determination of free amines with fluorescence detection and online highly sensitive atmospheric chemical ionization-mass spectrometry identification (APCI-MS) has been developed. 2-(Benzoacridine)-5-acetic acid (BAAA) reacts with coupling agent N,N′-carbonyldiimidazole (CDI) to form a highly activated amide intermediate 1-imidazole-2-(5-benzoacridine)-ethanone (IBAE), which is dual-sensitive probe. The amide intermediate (IBAE) reacts preferably with amines in dimethylformamide (DMF) solvent to give the high yields of derivatives. IBAE-amine derivatives are not only sensitive to fluorescence but also to MS ionizable efficiency. The percent ionization δ values change from 0 to 57.32% in aqueous acetonitrile and from 0 to 62.14% in aqueous methanol. The relative standard deviations of the peak areas with fluorescence detection for each amine are <1.24% (40 ng/ml, n = 6). The fluorescence detection limits (at a signal-to-noise ratio of 3) are in the range of 0.15-0.50 ng/ml. The online APCI-MS detection limits are in the range of 2.07-8.51 ng/ml (at a signal-to-noise ratio of 3). Therefore, the facile IBAE intermediate derivatization allowed the development of a highly sensitive and specific method for the quantitative analysis of trace levels of amines in environmental water.     

2-(5-Benzoacridine)ethyl-p-toluenesulfonate as sensitive reagent for the determination of bile acids by HPLC with fluorescence detection and online atmospheric chemical ionization-mass spectrometric identification

2-(5-Benzoacridine)ethyl-p-toluenesulfonate (BAETS), a dual-sensitive probe, was reacted with bile acids in the presence of K₂CO₃ catalyst in dimethyl sulfoxide (DMSO) solvent to give BAETS–bile acid derivatives. Derivatives exhibited intense fluorescence (FL) with an excitation maximum at λ _ex 270 nm and an emission maximum at λ _em 510 nm. MS analysis using APCI-MS indicated that derivatives had excellent APCI-MS ionizability with percentage ionization δ values changing from 0 to 88.83% in aqueous acetonitrile and from 0 to 89.15% in aqueous methanol. The collision induced dissociation spectra of m/z [M + H]⁺ contained specific fragment ions at m/z [M + H−H₂O]⁺, [M + H−2H₂O]⁺, [M + H−3H₂O]⁺, 347.3, and 290.1. Repeatability was good for LC separation of BAETS–bile acid derivatives with aqueous acetonitrile as mobile phase. The relative standard deviations (RSDs) of retention time and peak area at 6.6 nmol mL⁻¹ levels with fluorescence detection (FL) were from 0.045 to 0.072% and from 2.16 to 2.73%, respectively. Excellent linear responses were observed, with regression coefficients >0.9995. The FL detection limits (S/N = 3) were in the range of 18.0–36.1 fmol. The online APCI-MS detection limits are in the range of 500–790 fmol (at a signal-to-noise ratio of 3).     

Synthesis and Characterizations of Ferrocenyl Carbonyl Chromium and Cobalt Clusters

Two novel bimetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅)–C≡C–C₆H₄–Fc] (Fc = C₅H₅FeC₅H₄] (1) and [Cr(CO)₃(η ⁶-C₆H₅)–C ≡ C–Fc–C(CH₃)₂–Fc] (3), were synthesized by the Sonogashira coupling reaction. By using of (1) and (3) as ligands to react with Co₂(CO)₈, two others novel polymetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}–C₆H₄–Fc] (2) and [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}Fc–C(CH₃)₂–Fc] (4) were obtained. Four carbonyl complexes were characterized by elemental analysis, FT-IR, NMR and MS. The molecular structures of complexes (1), (2) and (4) were determined by single crystal X-ray diffraction. The interactions among the ferrocenyl, Cr(CO)₃ and Co₂(CO)₆-η ²-μ ²-C≡C– units were investigated by cyclic voltammetry.     

New implementations of MRCI in semiempirical frameworks

Multireference configuration interaction with single and double excitations (MRCISD) as well as its analytic CI gradients has been implemented in the semiempirical framework. The hole‐particle symmetry and a mixed driven model for computing coupling coefficients have been used in the new code that allows us to perform MRCI and gradient calculations with higher efficiency and less storage requirements. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010