Geometries of the Halocarbene anions HCF- and CF2-: ab initio calculation and Franck-Condon analysis

A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectra of HCF- and CF2- radicals. Geometry optimization and harmonic vibrational frequency calculations have been performed on the (X) over tilde (1)A' state of HCF and (X) over tilde (2)A" state of HCF-, and (X) over tilde (1)A(1) state of CF2 and (X) over tilde B-2(1) state of CF2-. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of HCF- and CF2- respectively. The theoretical spectra obtained by employing B3LYP/6-311 + G(2d,p) values are in excellent agreement with the observed ones. In addition, the equilibrium geometry parameters, R(CF) = 0.1475 +/- 0.0005 nm, of the (X) over tilde (2)A" state of HCF-, and r(FC) = 0.1425 +/- 0.0005 nm and angle(FCF) = 100.5 +/- 0.5degrees, of the (X) over tilde B-2(i) state of CF2-, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. (C) 2003 Elsevier B.V. All rights reserved.

Low temperature heat capacity and thermal stability of nanocrystalline nickel

The heat capacity (C-p) of nanocrystalline nickel (nc-Ni, 40 mn crystallite size) has been measured over the temperature range of 78-370 K with a high-resolution automated adiabatic calorimeter. The measured results are compared with the C-p values of the corresponding coarse-grained crystal, and an enhancement of heat capacity of the nanocrystalline nickel was observed to be 2-4% in the temperature range between 100 and 370 K. The thermal stability of the nanocrystalline nickel sample was determined by a differential scanning calorimeter and a thermogravimetric system. The melting point of nc-Ni is the same as that of the corresponding coarse-grained crystalline nickel and the sample is stable at temperature lower than 500 K. (C) 2002 Elsevier Science B.V. All rights reserved.

Electrochemical, quantum chemical and SEM investigation of the inhibiting effect and mechanism of ciprofloxacin, norfloxacin and ofloxacin on the corrosion for mild steel in hydrochloric acid

The inhibiting effect and mechanism of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylicacid(ciprofloxacin), 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid (norfloxacin) and (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7 H-pyrido(1,2,3-de)-1,4-benzoxazine-6 carboxylic acid (ofloxacin) on the corrosion of mild steel in 1 mol/L HCl have been studied using electrochemical method, quantum chemical method and SEM at 303 K. The potentiodynamic results showed that these compounds suppressed both cathodic and anodic processes of mild steel corrosion in 1 mol/L HCl. The impedance spectroscopy showed that R-p values increased, and C-dl values decreased with the rising of the working concentration. Quantum chemical calculation showed that there was a positive correlation between some inhibitors structure properties and the inhibitory efficiency. The inhibitors function through adsorption followed Langmuir isotherm, and chemisorption made more contribution to the adsorption of the inhibitors on the steel surface compared with physical adsorption. SEM analysis suggested that the metal had been protected from aggressive corrosion because of the addition of the inhibitors.

中国黄土的磁组构特征及其古风向指示意义

The transportation and deposition of eolian materials of Chinese loess is correlated and effected by the monsoon from the mid-high latitude. Therefore study of the winter monsoon evolution can help us to understand the dynamic mechanism to climate changes in the east-Asian areas. The anisotropy of magnetic susceptibility (AMS) measurements have been carried out on the samples from the last 250ka wind -blown loess-paleosol sequences at Baicaoyuan and Luochuan. And the main conclusions are following:The magnetic foliation is almost horizontal of the two sections. AMS canthus be represented by an oblate ellipsoid with average K3 perpendicular to thebedding plane and Ki within the bedding plane. It has also shown that the ^-factor isless than 0.5 of the majority of samples. So the two sections are normal magneticfabric for sediments.The degree of anisotropy always shows a strong correlation with the foliationrather than with lineation, therefore the anisotropy is controlled by the foliation.Furthermore the foliation is nearly less than 1.02 and shows the typical wind-blownsediments anisotropy.The intensity of winter monsoon, grain size of the eolian inputs, the foliationand the degree of anisotropy are somewhat inter-related. Generally, the higherintensity of the winter monsoon will carry coarser-grained eolian material, therebyresulting in a larger foliation during deposition. Also the post-depositional compactioncontributes to the anisotropy.The AMS features between loess and paleosol are somewhat different. Wefound that the F, P values of paleosol are lower than that of its parent loess respectively. Moreover, the difference does also exists between the two sections. The anisotropy of Baicaoyuan is more significant than Luochuan section, which maybe related with the location and the intensity of the post-deposition reworks.5. We note that the declination of the long axis is NWW in Baicaoyuan section and the observed NWW direction of the winter monsoon winds based on AMS is consistent with the view that the winter monsoons prevail along the NW-SE direction. But at the Luochuan section, because of the strong affection of the post-deposition reworks, the direction of the long axis is nearly random in the foliation and hardly recognizes the paleowind direction since the last two interglacials.Correlation between the two loess-paleosol sequences implies that it is available in arid or semi-arid areas to take AMS to recognize the paleowind directions on the Loess Plateau.

Franck-Condon simulation of the photoelectron spectrum of SO2- including Duschinsky effects

A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectrum of the anion SO. Geometry optimizations and harmonic vibrational frequency calculations have been performed on the XA(1) state of SO2 and (XB1)-B-2 state of SO2. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of SO2. The theoretical spectra obtained by employing CCSD(T)/6-31 I+G(2d,p) values are in excellent agreement with the experiment. In addition, the equilibrium geometric parameters, r(c)(OS) = 0.1508 +/- 0.0005 nm and theta(e)(O-S-0) = 113.5 +/- 0.5 degrees, of the (XB1)-B-2 state of SO2, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. (c) 2005 Elsevier B.V. All rights reserved.

Low Spring Constant Regulates P-Selectin-Psgl-1 Bond Rupture

Forced dissociation of selectin-ligand bonds is crucial to such biological processes as leukocyte recruitment, thrombosis formation, and tumor metastasis. Although the bond rupture has been well known at high loading rate r(f) (>= 10(2) pN/s), defined as the product of spring constant k and retract velocity v, how the low r(f) (< 10(2) pN/s) or the low k regulates the bond dissociation remains unclear. Here an optical trap assay was used to quantify the bond rupture at r(f) <= 20 pN/s with low k (similar to 10(-3)-10(-2) pN/nm) when P-selectin and P-selectin glycoprotein ligand 1 (PSGL-1) were respectively coupled onto two glass microbeads. Our data indicated that the bond rupture force f retained the similar values when r(f) increased up to 20 pN/s. It was also found that f varied with different combinations of k and v even at the same r(f). The most probable force, f

Anti Human Immunodeficiency Virus Type 1 (HIV-1) Agents 4. Discovery of 5,5 '-(p-Phenylenebisazo)-8-hydroxyquinoline Sulfonates as New HIV-1 Inhibitors in Vitro

To search for compounds with superior anti-human immunodeficiency virus type 1 (HIV-1) activity, ten 5,5'-(p-phenylenebisazo)-8-hydroxyquinoline sulfonates (4a-j) were synthesized and preliminarily evaluated as HIV-1 inhibitors in vitro for the first time. Some compounds demonstrated anti-HIV-1 activity, especially 5,5'-(p-phenylenebisazo)-8-hydroxyquinoline p-ethylbenzenesulfonate (4g) and 5,5'-(p-phenylenebisazo)-8-hydroxyquinoline p-chlorobenzenesulfonate (41) showed the more potent anti-HIV-1 activity with 50% effective concentration (EC50) values of 2.59 and 4.01 mu g/ml, and therapeutic index (TI) values of 31.77 and 24.51, respectively.

Body loadings and health risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans at an intensive electronic waste recycling site in China

This study is one of the very few investigating the dioxin body burden of a group of child-bearing-aged women at an electronic waste (e-waste) recycling site (Taizhou, Zhejiang Province) (24 +/- 2.83 years of age, 40% were primiparae) and a reference site (Lin'an city, Zhejiang Province, about 245 km away from Taizhou) (24 +/- 2.35 years of age, 100% were primiparae) in China. Five sets of samples (each set consisted of human milk, placenta, and hair) were collected from each site. Body burdens of people from the e-waste processing site (human milk, 21.02 +/- 13.81 pg WHO-TEQ(1998/g) fat (World Health Organization toxic equivalency 1998); placenta, 31.15 +/- 15.67 pg WHO-TEQ(1998/g) fat; hair, 33.82 +/- 17.74 pg WHO-TEQ(1998/g) dry wt) showed significantly higher levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurnas (PCDD/Fs) than those from the reference site (human milk, 9.35 +/- 7.39 pg WHO-TEQ(1998/g) fat, placenta, 11.91 +/- 7.05 pg WHO-TEQ(1998/g) fat; hair, 5.59 +/- 4.36 pg WHO-TEQ(1998/g) dry wt) and were comparatively higher than other studies. The difference between the two sites was due to e-waste recycling operations, for example, open burning, which led to high background levels. Moreover, mothers from the e-waste recycling site consumed more foods of animal origin. The estimated daily intake of PCDD/Fs within 6 months by breast-fed infants from the e-waste processing site was 2 times higher than that from the reference site. Both values exceeded the WHO tolerable daily intake for adults by at least 25 and 11 times, respectively. Our results implicated that e-waste recycling operations cause prominent PCDD/F levels in the environment and in humans. The elevated body burden may have health implications for the next generation.

Quantitative structure-property relationships for octanol-air partition coefficients of polychlorinated naphthalenes, chlorobenzenes and p,p '-DDT

The octanol-air partition coefficient (K-OA) is a key descriptor of chemicals partitioning between the atmosphere and environmental organic phases. Quantitative structure-property relationships (QSPR) are necessary to model and predict KOA from molecular structures. Based on 12 quantum chemical descriptors computed by the PM3 Hamiltonian, using partial least squares (PLS) analysis, a QSPR model for logarithms of K-OA to base 10 (log K-OA) for polychlorinated naphthalenes (PCNs), chlorobenzenes and p,p'-DDT was obtained. The cross-validated Q(cum)(2) value of the model is 0.973, indicating a good predictive ability of the model. The main factors governing log K-OA of the PCNs, chlorobenzenes, and p,p'-DDT are, in order of decreasing importance, molecular size and molecular ability of donating/accepting electrons to participate in intermolecular interactions. The intermolecular dispersive interactions play a leading role in governing log K-OA. The more chlorines in PCN and chlorobenzene molecules, the greater the log K-OA values. Increasing E-LUMO (the energy of the lowest unoccupied molecular orbital) of the molecules leads to decreasing log K-OA values, implying possible intermolecular interactions between the molecules under study and octanol molecules. (C) 2002 Elsevier Science Ltd. All rights reserved.

Vertical variations in kinetics of alkaline phosphatase and P species in sediments of a shallow Chinese eutrophic lake (Lake Donghu)

The vertical distribution of the variables relevant to P forms in sediments were studied in a shallow Chinese freshwater lake (Lake Donghu) in 1997, 1998, 1999 and 2000, to assess the contribution of enzyme to P availability in sediment cores. Sediment P was fractionationd into iron-bound P, calcium-bound P, acid soluble organic P (ASOP) and hot NaOH extractable residual organic P. The former two species made the largest contribution to the sediment P pool. All P species exhibited significantly higher concentrations in different depths at Station I, compared with those found at Station II, except for ASOP. Coupled with these lower ASOP concentrations, the V-max data of alkaline phosphatase, measured on the same samples, were significantly higher at station I. Taken together, ASOP were probably important in supplying the enzymatic substrate (Phosphatase Hydrolyzable Phosphorus, PHP) into interstitial water. Dissolved orthophosphate and PHP concentrations were highly heterogeneous , but peaked in subsurface, paralleled by higher V-max and lower K-m values of alkaline phosphatase, throughout the sediment core. Sediment in the eutrophic lake is not only enriched in available P (iron-bound P), or stores residual P, but also tends to release PHP, thereby inducing the production of alkaline phosphatase and releasing o-P into water column by enzymatic hydrolysis. The latter process may also occur in relatively deep sediment layers.

Persistence of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in Ya-Er Lake area, China

The concentrations of polychlorinayed dibenzo-p-dioxins and dibenzofurans (PCDD/F) in surface sediment, soil, human hair, acid fish muscle from Ya-Er Lake area, China, were analyzed. The results showed that there were very high concentrations of PCDD/F existing in these samples. The results also indicated that Ya-Er Lake, which received a large amount of waste water from a nearby chloroalkali plant, was heavily polluted by PCDD:F. The present study demonstrated that those congeners, which possess at least three chlorine atoms in the lateral position with a fourth chlorine atom in the neighborhood bond of the third single chlorine atom, such as 1,2,7,8-TCDF and 2,3.6,7-TCDF, were very resistant to biodegradation due to the "neighbor effect" of every two chlorine atoms. The present study suggested that human hair may be a suitable alternative bioindicator for detecting PCDD/F exposure. (C) 2001 Elsevier Science Ltd. All rights reserved.

Prediction of the retentions of polybrominated dibenzo-p-dioxins (PBDDs) by using the retentions of polychlorinated dibenzo-p-dioxins (PCDDs)

The retention equations ln k' = A + B/T of 49 polychlorinated dibenzo-p-dioxins (PCDDs) and 4 polybrominated dibenzo-p-dioxins (PBDDs) in gas chromatography (GC) have been investigated to evaluate the properties of regression coefficients A and B. The quantitative relationships between A and B values of PCDDs and those of PBDDs are found. The regression equations derived have correlation coefficients greater than 0.997. The A, B values of any PBDD can be predicted by using the A, B values of the PCDD according to these relationships. Using these predicted A and B values, the retention times of all PBDDs can be predicted at any temperature program. It is very useful to identify the peak position of any PBDD because at present there are only a few standards of PBDDs available. (C) 2000 Elsevier Science Ltd. All rights reserved.

Quantitative relationship between chromatographic retentions and molecular structures of polychlorinated dibenzo-p-dioxins (PCDDs)

A new approach to study the quantitative relationships between chromatographic retentions and molecular structures of polychlorinated dibenzo-p-dioxins (PCDDs) is described. The retention equations of PCDDs log k' = A + B/T in gas chromatography (GC) are used to evaluate the properties of the regression coefficients A and B, which have been widely accepted as highly reliable chromatographic retentions. The quantitative relationships between the A, B values and the molecular structures are found. The molecular descriptors given for the first time in this article are very effective. As a result, the regression equations are derived with correlation coefficients greater than 0.9995. The A, B values of PCDDs with no standards available have been predicted according to these relationships. They are very useful in chromatographic identification. The retention times of all PCDDs can be conveniently predicted at any temperature program. Compared with the data obtained from the relevant experiments, the results of prediction are very accurate. (C) 2000 Elsevier Science Ltd. All rights reserved.