bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic Adsorptive Stripping Voltammetry of Molybdenum: Redox Kinetic Measurements
Authors: Quentel François , Mirčeski Valentin
Published: September 2004

The electrode mechanism of Mo(VI) reduction was studied under catalytic adsorptive stripping mode by means of square‐wave voltammetry (SWV). Mo(VI) creates a stable surface active complex with mandelic acid. The electrode reaction of Mo(VI)‐mandelic acid system undergoes as one‐electron reduction, exhibiting properties of a surface electrode process. In the presence of chlorate, bromate, and hydrogen peroxide, the electrode reaction is transposed into a catalytic mechanism. The experimental results are compared with the recent theory for surface catalytic reaction, enabling qualitative characterization of the electrode mechanism in the presence of different catalytic agents. Utilizing both the method of “split SW peaks” and “quasireversible maximum” the standard redox rate constant of Mo(VI)‐mandelic acid system was estimates as ks=150±5 s−1. By fitting the experimental and theoretical results, the following catalytic rate constants have been estimated: (8.0±0.5)×104 mol−1 dm3 s−1, (1.0±0.1)×105 mol−1 dm3 s−1, and (3.2±0.1)×106 mol−1 dm3 s−1, for hydrogen peroxide, chlorate, and bromate, respectively.
A Selective Voltammetric Method for Uric Acid Detection at a Glassy Carbon Electrode Modified with Electrodeposited Film Containing DNA and Pt‐Fe(III) Nanocomposites
Authors: Wang Shuqing , Lu Liping , Lin Xiangqin
Published: September 2004

A novel biosensor by electrochemical codeposited Pt‐Fe(III) nanocomposites and DNA film was constructed and applied to the detection of uric acid (UA) in the presence of high concentration of ascorbic acid (AA). Based on its strong catalytic activity toward the oxidation of UA and AA, the modified electrode resolved the overlapping voltammetric response of UA and AA into two well‐defined peaks with a large anodic peak difference (ΔEpa) of about 380mV. The catalytic peak current obtained from differential pulse voltammetry (DPV) was linearly dependent on the UA concentration from 3.8×10−6 to 1.6×10−4 M (r=0.9967) with coexistence of 5.0×10−4 M AA. The detection limit was 1.8×10−6 M (S/N=3) and the presence of 20 times higher concentration of AA did not interfere with the determination. The modified electrode shows good sensitivity, selectivity and stability.
Adsorptive Stripping Voltammetry of Rifamycins at Unmodified and Surfactant‐Modified Carbon Paste Electrodes
Authors: Gutiérrez‐Fernández Sonia , Blanco‐López M. C. , Lobo‐Castañón M. Jesús , Miranda‐Ordieres Arturo J. , Tuñón‐Blanco Paulino
Published: September 2004

The electrochemical behavior of the antibiotics rifampicin and rifamycin SV is investigated by cyclic voltammetry at carbon paste and in situ surfactant modified carbon paste electrodes. Both antibiotics adsorb on the unmodified electrodes and show a reversible redox process due to the oxidation of the 6,9‐dihydroxynaphthalene moiety to the corresponding naphthoquinone. This process is used as analytical signal for developing adsorptive voltammetric methods for the determination of the antibiotics. Experimental parameters, such as pH of the supporting electrolyte, accumulation potential and time are optimized. After accumulation from acidic solutions (0.1 M KCl pH 2 or HCl 0.2 M) at −0.1 or 0 V for 3 min, the differential pulse oxidation peak current changes linearly with the antibiotic concentration in the range 3.5×10−10 M −5.4×10−9 M or 5×10−11 M −1.0×10−9 M for rifampicin and rifamycin SV, respectively. Rifamycin SV is not accumulated on carbon paste electrodes modified in situ with the anionic surfactant sodium dodecyl sulfate, whereas rifampicin is readily accumulated on this modified electrodes resulting in a signal enhancement and allowing rifampicin determinations without interference from rifamycin SV. On the other hand, selective determination of rifamycin SV in the presence of rifampicin is achieved by using carbon paste electrodes in situ modified with the cationic surfactant cetyltrimethylammonium chloride.
Speciation of Arsenic by Potentiometric Stripping Analysis Using Gold(III) Solution as Chemical Reoxidant and a Wall‐Jet Flow Cell
Authors: Muñoz Emma , Palmero Susana
Published: September 2004

A simple procedure is described for the potentiometric stripping of arsenic with a wall‐jet cell by means of potentiostatic co‐deposition of gold and arsenic at a glassy‐carbon electrode and subsequent chemical stripping with Au(III). Optimum medium containing 160 mg L−1 of Au(III) in HCl 0.1 M, where it is possible to speciate As(III) and As(V). As(V) was electrodeposited directly without prior chemical reduction at working electrode. As(III) was first determined at an electrodeposition potential of −0.1 V. Afterwards, total arsenic was determined by an electrodeposition potential of −0.7 V, from the area of peak obtained of the differential stripping potentiogram by using the standard addition method. The original As(V) concentration in the sample was calculated by difference. The possibilities of the optimized method were demonstrated by determinations of As(III), As(V) and total arsenic in samples of polluted water.
Comparison of prospective and retrospective methods for haplotype inference in case‐control studies
Authors: Satten Glen A. , Epstein Michael P.
Published: September 2004

We compare bias and power of three methods for haplotype inference on disease risk using unphased genotype data from a case‐control study. We examine the prospective score test of Schaid et al. ([2002] Am. J. Hum. Genet 70:425–434), a novel modification of the prospective estimating equations of Zhao et al. ([2003] Am. J. Hum. Genet. 72:1231–1250) and the retrospective likelihood of Epstein and Satten ([2003] Am. J. Hum. Genet. 73:1316–1329). We find that all three approaches are roughly comparable when the haplotype effect on disease odds follows a multiplicative model. However, for dominant and recessive models of haplotype effect, the retrospective‐likelihood method has increased efficiency with respect to the prospective methods. As all three methods assume haplotype frequencies are in Hardy‐Weinberg Equilibrium (HWE), we compare the robustness of each procedure to departures from HWE. We find the prospective methods are robust to departure from HWE, while the retrospective‐likelihood method is biased for dominant and recessive models of haplotype effect. To remedy this limitation of the retrospective‐likelihood method, we propose a modification that allows for a non‐negative fixation index (common to all haplotype pairs) and show it dramatically reduces the bias of the retrospective likelihood when HWE is violated. Published 2004 Wiley‐Liss, Inc.
Algorithms for inferring haplotypes
Authors: Niu Tianhua
Published: September 2004

Haplotype phase information in diploid organisms provides valuable information on human evolutionary history and may lead to the development of more efficient strategies to identify genetic variants that increase susceptibility to human diseases. Molecular haplotyping methods are labor‐intensive, low‐throughput, and very costly. Therefore, algorithms based on formal statistical theories were shown to be very effective and cost‐efficient for haplotype reconstruction. This review covers 1) population‐based haplotype inference methods: Clark's algorithm, expectation‐maximization (EM) algorithm, coalescence‐based algorithms (pseudo‐Gibbs sampler and perfect/imperfect phylogeny), and partition‐ligation algorithm implemented by a fully Bayesian model (Haplotyper) or by EM (PLEM); 2) family‐based haplotype inference methods; 3) the handling of genotype scoring uncertainties (i.e., genotyping errors and raw two‐dimensional genotype scatterplots) in inferring haplotypes; and 4) haplotype inference methods for pooled DNA samples. The advantages and limitations of each algorithm are discussed. By using simulations based on empirical data on the G6PD gene and TNFRSF5 gene, I demonstrate that different algorithms have different degrees of sensitivity to various extents of population diversities and genotyping error rates. Future development of statistical algorithms for addressing haplotype reconstruction will resort more and more to ideas based on combinatorial mathematics, graphical models, and machine learning, and they will have profound impacts on population genetics and genetic epidemiology with the advent of the human HapMap. © 2004 Wiley‐Liss, Inc.
The role of haplotypes in candidate gene studies
Authors: Clark Andrew G.
Published: September 2004

Human geneticists working on systems for which it is possible to make a strong case for a set of candidate genes face the problem of whether it is necessary to consider the variation in those genes as phased haplotypes, or whether the one‐SNP‐at‐a‐time approach might perform as well. There are three reasons why the phased haplotype route should be an improvement. First, the protein products of the candidate genes occur in polypeptide chains whose folding and other properties may depend on particular combinations of amino acids. Second, population genetic principles show us that variation in populations is inherently structured into haplotypes. Third, the statistical power of association tests with phased data is likely to be improved because of the reduction in dimension. However, in reality it takes a great deal of extra work to obtain valid haplotype phase information, and inferred phase information may simply compound the errors. In addition, if the causal connection between SNPs and a phenotype is truly driven by just a single SNP, then the haplotype‐based approach may perform worse than the one‐SNP‐at‐a‐time approach. Here we examine some of the factors that affect haplotype patterns in genes, how haplotypes may be inferred, and how haplotypes have been useful in the context of testing association between candidate genes and complex traits. © 2004 Wiley‐Liss, Inc.
Tag SNP selection for association studies
Authors: Stram Daniel O.
Published: September 2004

This report describes current methods for selection of informative single nucleotide polymorphisms (SNPs) using data from a dense network of SNPs that have been genotyped in a relatively small panel of subjects. We discuss the following issues: (1) Optimal selection of SNPs based upon maximizing either the predictability of unmeasured SNPs or the predictability of SNP haplotypes as selection criteria. (2) The dependence of the performance of tag SNP selection methods upon the density of SNP markers genotyped for the purpose of haplotype discovery and tag SNP selection. (3) The likely power of case‐control studies to detect the influence upon disease risk of common disease‐causing variants in candidate genes in a haplotype‐based analysis. We propose a quasi‐empirical approach towards evaluating the power of large studies with this calculation based upon the SNP genotype and haplotype frequencies estimated in a haplotype discovery panel. In this calculation, each common SNP in turn is treated as a potential unmeasured causal variant and subjected to a correlation analysis using the remaining SNPs. We use a small portion of the HapMap ENCODE data (488 common SNPs genotyped over approximately a 500 kb region of chromosome 2) as an illustrative example of this approach towards power evaluation. © 2004 Wiley‐Liss, Inc.
The influence of novel bioactive glasses on in vitro osteoblast behavior
Authors: Foppiano Silvia , Marshall Sally J. , Marshall Grayson W. , Saiz Eduardo , Tomsia Antoni P.
Published: September 2004

Implant success requires a direct bond between bone and implant surface. Bioinert implants, such as titanium alloys, are commonly plasma‐spray–coated with a bone‐bonding, bioactive material such as hydroxyapatite. Such coatings tend to be chemically and topographically inhomogeneous without reproducible properties. A family of bioactive glasses that can be enameled and reliably adheres to titanium alloy has been developed. In this study the cytocompatibility of two of these glass compositions was tested in the as‐cast condition. The effects of these glasses on the early and late events of osseous tissue formation in vitro were determined with MC3T3‐E1.4 mouse osteoblast‐like cells. MC3T3‐E1.4 cells were cultured on glasses containing 55 and 50 wt % SiO2, with titanium alloy (Ti6Al4V) and tissue culture polystyrene as controls. Cellular adhesion and proliferation, and alkaline phosphatase activity were studied over 5 to 15 days in culture. Qualitative and quantitative assays of mineralization were conducted. The osteoblast‐like cells showed increased proliferation when grown on a bioactive glass containing 50 wt % silica. However, the adhesion, differentiation and mineralization behavior were similar on both glass compositions used in this study. These bioactive glasses proved to be cytocompatible substrata for osteoblast‐like cell culture, and yielded higher cellular proliferation than titanium alloy. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 242–249, 2004
Efficacy and cytotoxicity of cationic‐agent–mediated nonviral gene transfer into osteoblasts
Authors: Kim Soo‐Woo , Ogawa Takahiro , Tabata Yasuhiko , Nishimura Ichiro
Published: September 2004

Ex vivo gene transfer into osteoblastic cells is an advantageous strategy for bone tissue engineering. This study investigated the efficacy and cytotoxicity of in vitro cationic‐agent–mediated nonviral gene transfer into osteoblasts. Various cationic agents, lipid, gelatin, and polyethylenimine (PEI) were tested. Each was formulated in various concentrations to form a complex with plasmid DNA encoding red fluorescent protein. The cationic agent/DNA complexes were transfected into human fetal osteoblastic cell line and rat bone‐marrow–derived primary osteoblasts, as well as NIH 3T3 fibroblast controls. Rat primary osteoblasts were transfected more with cationic lipid and PEI agents than with gelatin carrier, yielding transfection efficacy up to 18.1% and 12.7 %, respectively. In contrast, human fetal osteoblastic cell line was transfected more with cationic lipid and gelatin than with PEI. There was a positive correlation between the lipid and PEI doses and cytotoxicity. When the lipid and PEI were used to transfect the rat primary osteoblasts in a dose that yielded the highest transfection efficacy, cell survival rates decreased as low as 40%. When their transfection efficacies into primary osteoblasts were compromised at two thirds of the highest value, that is, 12.6% and 8.3% for the lipid and PEI, respectively, the cell survival rate was nearly 80%. Cationic gelatin was associated with cell survival rates over 60 % in any cell type, regardless of the doses tested. These results suggest that different types of osteoblastic cells may possess different ability to the uptake and expression of cationic‐agent–bound DNA. There seemed to be agent‐specific threshold doses that dropped the cell survival rate. Cationic‐agent–mediated nonviral gene transfer into osteoblastic cells may be successful when the agent‐ and dose‐dependent transfection efficacy and cytotoxicity are optimized. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 308–315, 2004
Biodegradability and cell‐mediated contraction of porous collagen scaffolds: The effect of lysine as a novel crosslinking bridge
Authors: Ma Lie , Gao Changyou , Mao Zhengwei , Zhou Jie , Shen Jiacong
Published: September 2004

A novel crosslinking method was adopted to modify the porous collagen scaffolds by using a water‐soluble carbodiimide, 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDAC) and N‐hydroxysuccinimide (NHS) in the presence of lysine, which functions as a crosslinking bridge. In vitro biodegradation tests proved that in the presence of lysine the biostability of the EDAC crosslinked scaffolds was greatly enhanced. The biostability of the resultant scaffolds was also elucidated as a function of the concentrations of lysine and EDAC/NHS. Compared to the Col‐DHT, the ability of the Col‐EDAC and the Col/Lys to resist cell‐mediated contraction (CMC) was greatly enhanced. Yet no obvious difference between the Col‐EDAC and the Col/Lys was found with respect to CMC. SEM observations showed that the microstructure of the crosslinked scaffolds could be largely preserved after fibroblast seeding. As a result, MTT assays proved that the fibroblasts in the Col/Lys scaffolds proliferated faster compared to the DHT‐treated one on the assumption that the cell viability was preserved to a similar level. Histological section results indicated that the Col/Lys scaffolds had the ability to accelerate the cell infiltration and proliferation. All these results demonstrated that this novel crosslinking method is an effective way to achieve a collagen scaffold with improved biostability and a more stable structure, which can resist cell‐mediated contraction. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 334–342, 2004
Biocompatible Mn2+‐doped carbonated hydroxyapatite thin films grown by pulsed laser deposition
Authors: György E. , Toricelli P. , Socol G. , Iliescu M. , Mayer I. , Mihailescu I. N. , Bigi A. , Werckman J.
Published: September 2004

Mn2+‐doped carbonated hydroxyapatite (Mn‐CHA) thin films were obtained by pulsed laser deposition on Ti substrates. The results of the performed complementary diagnostic techniques, X‐ray diffraction, infrared spectroscopy, X‐ray photoelectron spectroscopy, and energy dispersive X‐ray spectroscopy investigations indicate that the films are crystalline with a Ca/P ratio of about 1.64–1.66. The optimum conditions, when nearly stoichiometric crystalline thin films were deposited, were found to be 10 Pa oxygen pressure, 400°C substrate temperature, and postdeposition heat treatment in water vapors at the same substrate temperature. The films were seeded with L929 fibroblast and hFOB1.19 osteoblast cells and subjected to in vitro tests. Both fibroblast and osteoblast cells have a good adherence on the Mn‐CHA film and on the Ti or polystyrene references. Proliferation and viability tests showed that osteoblast cells growth on Mn‐CHA–coated Ti was enhanced as compared to uncoated pure Ti surfaces. Caspase‐1 activity was not affected significantly by the material, showing that Mn‐CHA does not induce apoptosis of cultured cells. These results demonstrate that Mn‐CHA films on Ti should provoke a faster osteointegration of the coated implants as compared to pure Ti. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 353–358, 2004
On partitions of {1,…,2m+ 1}\{k} into differencesd,…,d+m− 1: Extended Langford sequences of large defect
Authors: Linek Vaclav , Mor Shai
Published: September 2004

It is shown that form= 2d− 1, 2d, 2d+ 1, andd≥ 1, the set {1, 2,…, 2m+ 2}, − {2,k} can be partitioned into differencesd,d+ 1,…,d+m− 1 whenever (m,k) ≡ (0,0), (1,d+ 1), (2, 1), (3,d) (mod (4,2)) and (d,m,k) ≠ (1,1,3), (2,3,7) (where (x,y) ≡ (u,ν) mod (m,n) iffx≡u(modm) andy≡ν(modn)). It is also shown that ifm≥ 2d− 1 andm∉ [2d+ 2, 8d− 5], then the set {1, 2, …, 2m+ 1} − {k} can be partitioned into differencesd,d+ 1,…,d+m− 1 whenever (m,k) ≡ (0, 1), (1,d), (2,0), (3,d+ 1) mod (4,2). Finally, ford= 4 we obtain a complete result for when {1,…,2m+ 1} − {k} can be partitioned into differences 4,5,…,m+ 3. © 2004 Wiley Periodicals, Inc.
There exist non‐isomorphic STS(19) with equivalent point codes
Authors: Kaski Petteri , Östergård Patric R. J.
Published: September 2004

The rows of a point by block incidence matrix of a design can be used to generate a code, the point code of the design. It is known that binary point codes of non‐isomorphic Steiner triple systems of order hr STS(v), are inequivalent whenv ≤ 15, but whether this also holds for higher orders has been open. In the current paper, an example of two non‐isomorphic STS(19) with equivalent point codes is presented. © 2004 Wiley Periodicals, Inc.
Hormonal regulation of the Grb14 signal modulator and its role in cell cycle progression of MCF‐7 human breast cancer cells
Authors: Kairouz Rania , Parmar Jayamala , Lyons Ruth J. , Swarbrick Alexander , Musgrove Elizabeth A. , Daly Roger J.
Published: September 2004

Growth factor receptor bound (Grb)14 is a member of the Grb7 family of src homology (SH)2 domain‐containing proteins. These proteins perform both adaptor and modulatory roles in receptor tyrosine kinase (RTK) signaling, although their regulation is poorly understood. In this study, a positive correlation between Grb14 protein expression and ERα status in breast cancer cell lines led us to investigate regulation of Grb14 by estradiol and insulin, which synergize in the regulation of breast cancer cell proliferation. In MCF‐7 cells maintained in charcoal‐stripped serum, Grb14 expression was downregulated by estradiol and increased by the pure anti‐estrogen ICI 182780. Under serum‐free conditions, insulin enhanced Grb14 expression but this effect was repressed by estradiol when both hormones were used in combination. Using a system in which c‐Myc induction drives cell cycle progression independently of estradiol, we demonstrated that Grb14 regulation was specific to estradiol treatment. Finally, we demonstrated a novel functional role for Grb14 whereby its overexpression inhibited not only insulin‐ but also estrogen‐induced cell cycle progression. This was associated with decreased extracellular signal‐regulated kinase (Erk)1/2 activation in insulin‐stimulated Grb14‐overexpressing cells. These data represent the first demonstration of regulation of Grb14 expression levels in response to hormonal stimuli, and are consistent with its role as a repressor of insulin signaling where it is induced as a negative feedback mechanism. A role for Grb14 is also shown in estrogen/insulin crosstalk since estradiol blocks the insulin‐induced induction of this protein. © 2004 Wiley‐Liss, Inc.
Gene therapy for malignant glioma using Sindbis vectors expressing a fusogenic membrane glycoprotein
Authors: Zhang Jie , Frolov Ilya , Russell Stephen J.
Published: September 2004

Background

Malignant glioma has a dismal prognosis. It was previously shown that glioma cells are efficiently killed when they express a gene coding for a hyperfusogenic mutant of the gibbon ape leukemia virus envelope glycoprotein (GALV.fus). However, production of viral vectors expressing GALV.fus has proven problematic because the transgene is toxic to vector‐producing cells of human origin. We reasoned that Sindbis‐virus‐based vectors might be ideal for GALV.fus gene transfer because high‐titer stocks can easily be generated in hamster cells and Sindbis virus efficiently infects human tumor cells through the high‐affinity 67 kDa laminin receptor. In addition, Sindbis virus nonstructural proteins are potent inducers of apoptosis, and Sindbis vector RNAs expressing fusogenic viral proteins have been shown to spread from cell‐to‐cell in membrane‐formed infectious particles.

Methods

Sindbis virus replicon‐containing particles were generated by co‐transfecting vector and helper RNAs into baby hamster kidney (BHK‐21) cells. Packaged beta‐galactosidase and GALV.fus expressing Sindbis vectors were used to infect glioma cell lines, which were then compared for syncytial cytopathic effect, cell killing, and release of infectious virus‐like particles containing the vector genome. Finally, the efficacy of GALV.fus and beta‐galactosidase Sindbis vectors was compared in an orthotopic intracerebral U87 glioma xenograft model in nude mice.

Results

High‐titer stocks (>109 infectious units (iu)/ml) of the GALV.fus and beta‐galactosidase vectors were obtained. Glioma cells infected with the GALV.fus vector formed large syncytia which died rapidly by apoptosis and released infectious membrane‐formed particles that could transfer vector genomes to uninfected cells. The GALV.fus vector had significantly greater antitumor therapeutic potency than the β‐galactosidase vector in the U87 glioma xenograft model.

Conclusions

Sindbis vectors expressing GALV.fus can be packaged into infectious viral particles to high titer, they exhibit potent bystander cytopathic potential and are active against U87 glioma xenografts. Sindbis‐virus‐based replicons appear to be efficient vector systems for delivery and expression of fusogenic membrane glycoproteins. Copyright © 2004 John Wiley & Sons, Ltd.
Inhibitory effects of Hibiscus sabdariffa L extract on low‐density lipoprotein oxidation and anti‐hyperlipidemia in fructose‐fed and cholesterol‐fed rats
Authors: Chen Chang‐Che , Chou Fen‐Pi , Ho Yung‐Chyan , Lin Wea‐Lung , Wang Chin‐Pin , Kao Erl‐Shyh , Huang An‐Chung , Wang Chau‐Jong
Published: September 2004

Hibiscus sabdariffa L extract (HSE) is an aqueous extract of Hibiscus sabdariffa L flowers that is used as a local soft drink and medical herb in Taiwan. Oxidation of low‐density lipoprotein (LDL) has been shown to increase the incidence of atherosclerosis. In this study, we determined the antioxidative activity of HSE on LDL oxidation by examining relative electrophoretic mobilities (REM) and thiobarbituric acid‐reactive substances (TBARS). The data revealed an inhibitory effect of HSE on Cu2+‐mediated REM and TBARS. HSE exhibited a remarkable ability to reduce cholesterol degradation and ApoB fragmentation. Overall, HSE showed a high potency to inhibit the production of oxidized LDL induced by copper and, specifically, to reduce serum triglycerides in high‐fructose diet (HFD) fed rats and serum cholesterol in high‐cholesterol diet (HCD) fed animals. The levels of LDL and the ratio of LDL‐cholesterol (LDL‐C) to HDL‐cholesterol (HDL‐C) were reduced by HSE in both hyperlipidaemia models. Based on these findings, we suggest that HSE may be used to inhibit LDL oxidation and to prevent various types of hyperlipidaemia in HFD‐ or HCD‐fed rats. Copyright © 2004 Society of Chemical Industry
Synthesis and complete NMR spectral assignment of thiophene‐substituted sulfinyl monomers
Authors: Henckens Anja , Adriaensens Peter , Gelan Jan , Lutsen Laurence , Vanderzande Dirk
Published: September 2004

This paper describes the synthesis of thiophene‐substituted sulfinyl monomers. It comprises a four‐step reaction by which the thiophene unit is built in via Suzuki coupling. These monomers could be used as building blocks for the preparation of conducting polymers via a new concept: the sulfinyl precursor route i.e. via thiophene substituted poly(p‐phenylenevinylene) precursors. Furthermore, the complete 1H and 13C NMR signal assignment is presented. In addition to being essential for the characterization of the polymers concerned, it offers useful input information for further improvement of chemical shift prediction software. Furthermore, the T1C relaxation decay times are demonstrated to have the potential of being a fast and robust criterion for the spectral assignment of analogous monomers. Copyright © 2004 John Wiley & Sons, Ltd.
33S NMR spectra of sulfonium salts: calculated and experimental
Authors: Dickinson L. Charles , Chesnut Donald B. , Quin Louis D.
Published: September 2004

33S NMR chemical shifts were calculated by the scaled DFT and EMPI approaches for the fluoride, chloride and bromide of trimethylsulfonium ion (1) and S‐methyltetrahydrothiophenium ion (2), in addition to the free cations. Experimental values were obtained for the iodides of 1 (δ +48, CS2 = 0 ppm) and 2 (δ +95), and were found to agree with the calculated values well within the standard deviation of 35 ppm (3.5% of the shielding range) established in earlier work for a great variety of sulfur compounds. An earlier literature value of δ +750 for the iodide of 2 is therefore to be replaced. Calculations provide a shift of δ +68 for S‐methylthianium ion with equatorial methyl, indicating that the reported value of δ +670 for the iodide is also incorrect. Copyright © 2004 John Wiley & Sons, Ltd.
A continuum‐discrete hydromechanical analysis of granular deposit liquefaction
Authors: Zeghal M. , El Shamy U.
Published: September 2004

A coupled continuum‐discrete hydromechanical model was employed to analyse the liquefaction of a saturated loose deposit of cohesionless particles when subjected to a dynamic base excitation. The pore fluid flow was idealized using averaged Navier–Stokes equations and the discrete element method was employed to model the solid phase particles. A well established semi‐empirical relationship was utilized to quantify the fluid–particle interactions. The conducted simulations revealed a number of salient micro‐mechanical mechanisms and response patterns associated with the deposit liquefaction. Space and time variation of porosity was a major factor which affected the coupled response of the solid and fluid phases. Pore fluid flow was within Darcy's regime. The predicted response exhibited macroscopic patterns consistent with experimental results and case histories of the liquefaction of granular soil deposits. Copyright © 2004 John Wiley & Sons, Ltd.
K0 estimation in level granular soil from anisotropic wave velocities on the basis of micromechanics
Authors: Pan Y.‐W. , Liou J.‐C.
Published: September 2004

This study aims to explore the possibility for estimating K0 in a level ground of granular soil by seismic methods on the basis of micromechanics theory. The idea was to simulate in situ cross‐hole seismic method for the measurement of wave velocities along various directions of wave‐propagation. This work made use of a field simulator to control a K0 condition (zero lateral strain condition) in specimens. A series of vertical loading containing subsequent loading and unloading were applied to the specimen prepared by pluviation. In general, the K0 values determined experimentally in this work agreed with the exiting empirical relations. K0 value was also calibrated from measured anisotropic wave velocities using an optimization procedure. From the comparison of the back‐calculated and measured results of K0, it revealed the feasibility for the determination of the in situ lateral stress in granular soil by seismic methods and on the basis of micromechanics theory as long as enough wave‐velocity measurements along various directions of wave‐propagation were available. The potential for the usage of the presented methodology for the determination of the in situ lateral stress in level‐ground of granular soil by seismic methods seems encouraging. Copyright © 2004 John Wiley & Sons, Ltd.
Methanolysis of 1‐aryl‐1,2‐epoxycyclohexanes in the condensed and in the gas phase: importance of the substituent for the reaction mechanism
Authors: Crotti Paolo , Di Bussolo Valeria , Macchia Franco , Favero Lucilla , Pineschi Mauro , Lucarelli Laura , Roselli Graziella , Renzi Gabriele
Published: September 2004

The stereoselectivity of a series of 1‐aryl‐1,2‐epoxycyclohexanes substituted on the phenyl group was determined in acid methanolysis in the condensed phase (0.2 N H2SO4–MeOH) and in the reaction with MeOH in the gas phase under catalysis by a gaseous Brønsted acid (D3+). The results obtained show the presence of a clear Hammett‐type dependence of the syn/anti adduct ratio on the Brown σ+ of the substituent on the phenyl group, thus confirming the validity of the ion–dipole pair mechanism in order to rationalize the stereochemical behavior of 2‐aryloxiranes in opening reactions under acidic conditions. Only in the cases of the p‐OMe‐ and p‐NO2‐substituted epoxides, does an SN1 and an SN2 process, respectively, appear to be involved. Copyright © 2004 John Wiley & Sons, Ltd.
Rheological and mechanical properties of epoxy/polyurethane blends initiated by N‐benzylpyrazinium hexafluoroantimonate salt
Authors: Park Soo‐Jin , Kang Jun‐Gil , Kwon Soo‐Han
Published: September 2004

In this work the cure behavior and rheological and mechanical interfacial properties of the diglycidylether of bisphenol A (DGEBA)/polyurethane (PU) blend system, initiated by 1 wt % N‐benzylpyrazinium hexafluoroantimonate as a latent thermal catalyst, were investigated. To characterize the mechanical interfacial properties of the system, the critical stress intensity factor (KIC) was calculated with a single‐edge‐notched beam (SEN) beam fracture toughness test. And an impact test was performed at room and cryogenic temperatures to determine the performance of PU at room and low‐temperatures, respectively. As a result, the Ec of the blend system was increased with increasing PU content, showing a maximum value at 30 wt % PU, which was in good agreement with the mechanical properties of the blend system. Consequently, these results could be explained by the improvement that occurred in intermolecular hydrogen bonding between the hydroxyl group in EP and the isocyanate group in PU, resulting in increased compatibility of the components within the interpenetrating polymer networks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3841–3848, 2004
Principles of carbopeptoid folding: a molecular dynamics simulation study
Authors: Baron Riccardo , Bakowies Dirk , van Gunsteren Wilfred F.
Published: September 2004

The conformational spaces of five oligomers of tetrahydrofuran‐based carbopeptoids in chloroform and dimethyl sulfoxide were investigated through nine molecular dynamics simulations. Prompted by nuclear magnetic resonance experiments that indicated various stable folds for some but not all of these carbopeptoids, their folding behaviour was investigated as a function of stereochemistry, chain length and solvent. The conformational distributions of these molecules were analysed in terms of occurrence of hydrogen bonds, backbone torsional‐angle distributions, conformational clustering and solute configurational entropy. While a cis‐linkage across the tetrahydrofuran ring favours right‐handed helical structures, a trans‐linkage results in a larger conformational variability. Intra‐solute hydrogen bonding is reduced with increasing chain length and with increasing solvent polarity. Solute configurational entropies confirm the picture obtained: they are smaller for cis‐ than for trans‐linked peptides, for chloroform than for dimethyl sulfoxide as solvent and for shorter peptide chains. The simulations provide an atomic picture of molecular conformational variability that is consistent with the available experimental data. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Structure‐activity relationship study of anoplin
Authors: Ifrah Dan , Doisy Xavier , Ryge Trine S. , Hansen Paul R.
Published: September 2004

Anoplin is a decapeptide amide, GLLKRIKTLL‐NH2 derived from the venom sac of the solitary spider wasp, Anoplius samariensis. It is active against Gram‐positive and Gram‐negative bacteria and is not hemolytic towards human erythrocytes. The present paper reports a structure‐activity study of anoplin based on 37 analogues including an Ala‐scan, C‐ and N‐truncations, and single and multiple residue substitutions with various amino acids. The analogues were tested for antibacterial activity against both S. aureus ATCC 25923 and E. coli ATCC 25922, and several potent antibacterial analogues were identified. The cytotoxicity of the analogues against human erythrocytes was assessed in a hemolytic activity assay. The antibacterial activity and selectivity of the analogues against S. aureus and E. coli varied considerably, depending on the hydrophobicity and position of the various substituted amino acids. In certain cases the selectivity for Gram‐positive and Gram‐negative bacteria was either reversed or altogether eliminated. In addition, it was generally found that antibacterial activity coincided with hemolytic activity. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Nonadiabatic sudden increase of the cooperative kinetic effect at lattice energy stabilization—Microscopic mechanism of superconducting state transition: Model study of MgB2
Authors: Baňacký Pavol
Published: September 2004

The theory of the nonadiabatic electron–vibration interactions has been applied to the study of MgB2 superconducting state transition. It has been shown that at nonadiabatic conditions in which the Born–Oppenheimer approximation is not valid and electronic motion is dependent not only on the nuclear coordinates but also on the nuclear momenta, the fermionic ground‐state energy of the studied system can be stabilized by nonadiabatic electron–phonon interactions at broken translation symmetry. Moreover, the new arising state is geometrically degenerate; i.e., there are an infinite number of different nuclear configurations with the same fermionic ground‐state energy. The model study of MgB2 yields results that are in a good agreement with the experimental data. For distorted lattice, with 0.016 Å/atom of in‐plane out‐of‐phase BB atoms displacements out of the equilibrium (E2g phonon mode) when the nonadiabatic interactions are most effective, it has been calculated that the new arising state is 87 meV/unit cell more stable than the equilibrium–high symmetry clumped nuclear structure at the level of the Born–Oppenheimer approximation. The calculated Tc is 39.5 K. The resulting density of states exhibits two‐peak character, in full agreement with the tunneling spectra. The peaks are at ±4 meV, corresponding to the change of the π band density of states, and at ±7.6 meV, corresponding to the σ band. The superconducting state transition can be characterized as a nonadiabatic sudden increase of the cooperative kinetic effect at lattice energy stabilization (NASICKELES). © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Nonadiabatic photodissociation dynamics
Authors: Zhao Mei‐Yu , Meng Qing‐Tian , Xie Ting‐Xian , Han Ke‐Li , He Guo‐Zhong
Published: September 2004

The photodissociation dynamics of the triatomic (or pseudo‐triatomic) system in the nonadiabatic multiple electronic states is investigated by employing a time‐dependent quantum wave packet method, while the time propagation of the wave packet is carried out using the split‐operator scheme. As a numerical example, the photodissociation dynamics of CH3I in three electronic states 1Q1(A′), 1Q1(A″), and 3Q0+ is studied and CH3I is treated as a pseudotriatomic model. The absorption spectra and product vibrational state distributions are calculated and compared with previous theoretical work. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Correlation between sensitivity and approximated heats of detonation of several nitroamines using quantum mechanical methods
Authors: Edwards Jesse , Eybl Claudia , Johnson Brian
Published: September 2004

Storage, synthesis, and application of energetic materials is significantly impacted by the fundamental property of sensitivity. The method of storage and handling is affected by the sensitive nature of the explosive. Possessing the ability to predict the sensitivity of energetic material candidates before expensive synthesis is begun would be an asset. Also, predicting the applications of various energetic compounds before synthesis and testing can be made possible with the aid of sensitivity predictions. Quantum mechanical methods are applied to approximating the heat of detonation. Correlation between heat of detonation and impact sensitivity is examined. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
More QR‐SCMEH‐MO calculations on group VIB transition metal molecules, M2 (M = Cr, Mo, W, Sg): Valence and valence‐core effects
Authors: Boudreaux E. A. , Baxter E.
Published: September 2004

At the 2001 Sanibel Symposium a presentation of MO calculations derived from the QR‐SCMEH‐MO method applied to Cr2 and Mo2 was made and subsequently published in the proceedings 22. This was followed by similar unpublished calculations on W2 and Sg2 presented at the 43rd Sanibel Symposium in 2003. Unfortunately, in neither of these instances were specific evaluations regarding magnitudes of spin‐pairing energies versus MO eigenvalues taken into account. However, when these factors were subsequently examined in detail, we found that the pattern of MO occupancies and overall bonding features were significantly altered from that reported previously. Among these M2 molecules (Cr2 and Mo2) are found to have open‐shell, triplet delta HOMOs, in which the spins are antiferromagnetically coupled to produce spin singlet ground states. It has been observed that the electronic structures of these molecules must be ascribed apparently to correlation effects confined not only to the valence electrons, but to valence/valence‐core electrons as well. Within a transition metal series the atomic configurations are: ns2np6nda(n + 1)sb; 1 ≤ a ≤ 10; 1 ≤ b ≤ 2. The nda(n + 1)sb portion is naturally the valence component, and the ns2np6 portion is the valence‐core component. All levels below the latter are the inner core, which are frozen in these calculations. Consequently, in molecular bonding there is not only valence correlation, but the likelihood of valence/valence‐core correlation as well; particularly since these are no longer necessarily correlated as they were in the separated atoms. There apparently are no influences from the inner core. Of course, these features apply specifically to the SCMEH‐MO method. Because the SCMEH‐MO method, in general, is not an ab initio type of routine, wherein all electron correlation is explicitly accounted for, it is essential to limit correlation only to those AOs specifically affected by bonding. Furthermore, these effects seem to be uniquely associated with the abnormally short bond distances in these particular molecules. All of the features of this study will be presented and contrasted. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
A portable automated system for trace gas sampling in the field and stable isotope analysis in the laboratory
Authors: Theis Daniel E. , Saurer Matthias , Blum Herbert , Frossard Emmanuel , Siegwolf Rolf T. W.
Published: September 2004

A computer‐controllable mobile system is presented which enables the automatic collection of 33 air samples in the field and the subsequent analysis for δ13C and δ18O stable isotope ratios of a carbon‐containing trace gas in the laboratory, e.g. CO2, CO or CH4. The system includes a manifold gas source input for profile sampling and an infrared gas analyzer for in situ CO2 concentration measurements. Measurements of δ13C and δ18O of all 33 samples can run unattended and take less than six hours for CO2. Laboratory tests with three gases (compressed air with different pCO2 and stable isotope compositions) showed a measurement precision of 0.03‰ for δ13C and 0.02‰ for δ18O of CO2 (standard error (SE), n = 11). A field test of our system, in which 66 air samples were collected within a 24‐hour period above grassland, showed a correlation of 0.99 (r2) between the inverse of pCO2 and δ13C of CO2. Storage of samples until analysis is possible for about 1 week; this can be an important factor for sampling in remote areas. A wider range of applications in the field is open with our system, since sampling and analysis of CO and CH4 for stable isotope composition is also possible. Samples of compressed air had a measurement precision (SE, n = 33) of 0.03‰ for δ13C and of 0.04‰ for δ18O on CO and of 0.07‰ for δ13C on CH4. Our system should therefore further facilitate research of trace gases in the context of the carbon cycle in the field, and opens many other possible applications with carbon‐ and possibly non‐carbon‐containing trace gases. Copyright © 2004 John Wiley & Sons, Ltd.
Vicinal hydroxylation of unsaturated fatty acids for structural characterization of intact neutral phospholipids by negative electrospray ionization tandem quadrupole mass spectrometry
Authors: Moe Morten K. , Anderssen Trude , Strøm Morten B. , Jensen Einar
Published: September 2004

We report a novel method allowing the complete structural characterization of intact species of the phospholipid classes phosphatidylcholine and phosphatidylethanolamine by utilizing negative electrospray ionization quadrupole tandem mass spectrometry (MS/MS). Information on the molecular weight of the intact phospholipid species, the class to which it belongs, the molecular mass of the fatty acid substituents and their regioisomerism, is easily revealed by MS/MS. Throughout our investigations the R2COO− ions were more abundant than the R1COO− ions, and this observation is used for regioisomeric assignment of the two fatty acids. However, for phospholipid species containing an unsaturated fatty acid, information on the position of the double bond is not achieved in this way. By converting the olefinic sites to their 1,2‐dihydroxylated derivatives, information on the position of the hydroxyl groups (and hence of the double bond) is obtained by performing a second MS/MS experiment. Thus, a complete structural characterization of intact phosphatidylcholine and phosphatidylethanolamine species is obtained by performing these two MS/MS experiments. In order to ensure structural distinction of isobaric species, a number of phosphatidylethanolamine and phosphatidylcholine species were synthesized from lyso‐phosphatidylcholine and analyzed by the present method. The applicability of the method to real samples is also demonstrated by the complete structural elucidation of the two phosphatidylcholine species 16:0/18:1Δ9 and 16:0/18:1Δ11 from egg yolk. Copyright © 2004 John Wiley & Sons, Ltd.
Toward a systematic approach for selection of NASA technology portfolios
Authors: Weisbin Charles R. , Rodriguez Guillermo , Elfes Alberto , Smith Jeffrey H.
Published: September 2004

There is an important need for a consistent analytical foundation supporting the selection and monitoring of R&D tasks that support new system concepts that enable future NASA missions. This capability should be applicable at various degrees of abstraction, depending upon whether one is interested in formulation, development, or operations. It should also be applicable to a single project, a program comprised of a group of projects, an enterprise typically including multiple programs, and the overall agency itself. Emphasis here is on technology selection and new initiatives, but the same approach can be generalized to other applications, dealing, for example, with new system architectures, risk reduction, and task allocation among humans and machines. The purpose of this paper is to describe one such approach, which is in its early stages of implementation within NASA programs, and to discuss several illustrative examples. © 2004 Wiley Periodicals, Inc. Syst Eng 7: 285–302, 2004
A Longitudinal Study on Social Development as an Impetus for School Reform Toward an Integrated School Day
Authors: Pulkkinen Lea
Published: September 2004

The Jyväskylä Longitudinal Study of Personality and Social Development, in which the same individuals have been studied from the age of 8 to age 42, has warranted the conclusion that children should be encouraged toward prosocial development at an early age, because it helps them to integrate into the school environment and saves them from the cycle of maladaptation. A project was designed at the invitation of a Finnish parliamentary group for the enhancement of children's socioemotional development at school. The project comprises seven subprojects including interventions at three levels: the child's behavior, school as a learning environment, and the school's relationships with the surrounding world. The core of the project is the subproject for the Integrated School Day. It refers to a new learning culture with different learning, care, and leisure activities organized in cooperation between several professions. Finnish children spend long afternoons alone while both parents are working full-time. The project aims at decreasing the amount of time pupils are without adult supervision, facilitating socioemotional development by creating a firm basis for leisure activities, and strengthening the social capital of the school and initial social capital of children. The project began in 2002 in seven schools within four communities, with about 2000 students from grades 1 to 9. Beginning in the fall of 2004, the law will mandate that supervision of children's activities in the morning and afternoon should be available throughout the country for all first- and second-grade children and for special needs children at any grade.