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Selected AbstractsAdsorptive Stripping Voltammetric Detection of Single-Stranded DNA at Electrochemically Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 23 2002Huai-Sheng Wang Abstract Electrochemically modified glassy carbon electrode (GCE) was used to study the electrochemical oxidation and detection of denatured single-stranded (ss) DNA by means of adsorptive stripping voltammetry. The modification of GCE, by electrochemical oxidation at +1.75,V (vs.SCE) for 10,min and cyclic sweep between +0.3,V and ,1.3,V for 20,cycles in pH,5.0 phosphate buffer, results in 100-fold improvement in sensitivity for ssDNA detection. We speculated that the modified GCE has a high affinity to single-stranded DNA through hydrogen bond (specific static adsorption). Single-stranded DNA can accumulate at the GCE surface at open circuit and produce a well-defined oxidation peak corresponding to the guanine residues at about +0.80,V in pH,5.0 phosphate buffer, while the native DNA gives no signal under the same condition. The peak currents are proportional to the ssDNA concentration in the range of 0,18.0,,g,mL,1. The detection limit of denatured ssDNA is ca. 0.2,,g mL,1 when the accumulation time is 8,min at open circuit. The accumulation mechanism of ssDNA on the modified GCE was discussed. [source] External Features of the First Instar Larva of Damaster (Coptolabrus) jankowskii jankowskii (Coleoptera; Carabidae)ENTOMOLOGICAL RESEARCH, Issue 2 2002Jung Lark KIM ABSTRACT Larval features of the carabid beetle, Damaster (Coptolabrus) jankowskii jankowskii (Oberthür) were investigated for the first time. For accomplishing the purpose, the adult beetles were collected by pitfall traps in the deciduous forest of Mt. Palgongsan, southern Korea. They have been reared under the laboratory condition of 16L: 8D at 20°C. The first instar larvae were obtained by isolating eggs after oviposition and were kept at the same condition. In the present study, external morphology of the first instar larva of this subspecies are described and its important character states and comparisons with the kin species are also discussed. [source] Industry sponsorship and selection of comparators in randomized clinical trialsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2010D. N. Lathyris Eur J Clin Invest 2010; 40 (2): 172,182 Abstract Background, Most clinical trials on medical interventions are sponsored by the industry. The choice of comparators shapes the accumulated evidence. We aimed to assess how often major companies sponsor trials that involve only their own products. Methods, Studies were identified by searching ClinicalTrials.gov for trials registered in 2006. We focused on randomized trials involving the 15 companies that had sponsored the largest number of registered trials in ClinicalTrials.gov in that period. Results, Overall, 577 randomized trials were eligible for analysis and 82% had a single industry sponsor [89% (166/187) of the placebo-control trials, 87% (91/105) of trials comparing different doses or ways of administration of the same intervention, and 78% (221/285) of other active control trials]. The compared intervention(s) belonged to a single company in 67% of the trials (89%, 81% and 47% in the three categories respectively). All 15 companies strongly preferred to run trials where they were the only industry sponsor or even the only owner of the assessed interventions. Co-sponsorship typically reflected co-ownership of the same intervention by both companies. Head-to-head comparison of different active interventions developed by different companies occurred in only 18 trials with two or more industry sponsors. Conclusions, Each company generates a clinical research agenda that is strongly focused on its own products, while comparisons involving different interventions from different companies are uncommon. This diminishes the ability to understand the relative merits of different interventions for the same condition. [source] Constant vapour pressure evaporation from a fragrance emulsion,effect of solubility of surfactant in the fragrance compoundFLAVOUR AND FRAGRANCE JOURNAL, Issue 1 2009Lingling Ge Abstract The algebraic system to extract information from phase diagrams was used to establish some of the conditions for an emulsion to evaporate under constant vapour pressure. The model system for the calculations was an emulsion characterized by virtually no solubility in water by either the surfactant or the fragrance and the same condition for the water in the oil. The surfactant and the fragrance, on the other hand, were assumed to be mutually completely soluble and this solution was presupposed to be close to ideal. The results showed a surprisingly strong dependence of the times for evaporation under constant vapour pressure on the surfactant concentration in the oil phase, at which the two-phase equilibrium between the aqueous and the oil phases is replaced by a three-phase equilibrium: aqueous phase, oil phase and liquid crystal phase. The lower this concentration, the more extended the times for evaporation under constant vapour pressure. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis, Structure and Electrical Properties of Mo-doped CeO2,Materials for SOFCsFUEL CELLS, Issue 5 2009Q. Li Abstract In this paper, we report the synthesis, structure and electrical conductivity of Mo-doped compounds with a nominal chemical formula of Ce1,xMoxO2+, (x,=,0.05, 0.07, 0.1) (CMO). The formation of fluorite-like structure with a small amount of Ce8Mo12O49 impurity (JCPDS Card No. 31-0330) was confirmed using a powder X-ray diffraction (PXRD). The fluoride-type structure was retained under wet H2 and CH4 atmospheres at 700 and 800,°C, while diffraction peaks due to metal Mo were observed in dry H2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce0.9Mo0.1O2+, exhibited the highest electrical conductivity with a value of 2.8,×,10,4 and 5.08,×,10,2 S cm,1 at 550,°C in air and wet H2, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O2 and N2. Chemical compatibility of Ce0.9Mo0.1O2+, with 10,mol-% Y2O3 stabilised ZrO2 (YSZ) and Ce0.9Gd0.1O1.95 (CGO) oxide ion electrolytes in wet H2 was evaluated at 800,1,000,°C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000,°C. The area specific polarisation resistance (ASPR) of Ce0.9Mo0.1O2+, on YSZ was found to be 8.58,ohm,cm2 at 800,°C in wet H2. [source] Resources and the Rule of Rescue1JOURNAL OF APPLIED PHILOSOPHY, Issue 4 2007MARK SHEEHAN abstract The central issue that I consider in this paper is the use of the so-called ,Rule of Rescue' in the context of resource allocation. This ,Rule' has played an important role in resource allocation decisions in various parts of the world. It was invoked in Ontario to overturn a decision not to fund treatment for Gaucher's Disease and it has also been used to justify resource decisions in Israel concerning the same condition. In the paper I consider the nature of the Rule of Rescue and its moral justification. The latter involves consideration of the distinction between agent-relative and agent-neutral obligations. If the Rule of Rescue is to be justified, it is plausible to think that it will be in the context of agent-relative obligations. Two problems with this suggestion are considered: the role of identifiability in the Rule of Rescue and the extent to which policy makers in a health care system can be taken to have such obligations. It is argued that in both cases these problems can be overcome and hence that there is a prima facie obligation to follow the Rule of Rescue. [source] Bisphosphonate-Associated Osteonecrosis of the Jaw: Report of a Task Force of the American Society for Bone and Mineral Research,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2007Sundeep Khosla (Chair) Abstract ONJ has been increasingly suspected to be a potential complication of bisphosphonate therapy in recent years. Thus, the ASBMR leadership appointed a multidisciplinary task force to address key questions related to case definition, epidemiology, risk factors, diagnostic imaging, clinical management, and future areas for research related to the disorder. This report summarizes the findings and recommendations of the task force. Introduction: The increasing recognition that use of bisphosphonates may be associated with osteonecrosis of the jaw (ONJ) led the leadership of the American Society for Bone and Mineral Research (ASBMR) to appoint a task force to address a number of key questions related to this disorder. Materials and Methods: A multidisciplinary expert group reviewed all pertinent published data on bisphosphonate-associated ONJ. Food and Drug Administration drug adverse event reports were also reviewed. Results and Conclusions: A case definition was developed so that subsequent studies could report on the same condition. The task force defined ONJ as the presence of exposed bone in the maxillofacial region that did not heal within 8 wk after identification by a health care provider. Based on review of both published and unpublished data, the risk of ONJ associated with oral bisphosphonate therapy for osteoporosis seems to be low, estimated between 1 in 10,000 and <1 in 100,000 patient-treatment years. However, the task force recognized that information on incidence of ONJ is rapidly evolving and that the true incidence may be higher. The risk of ONJ in patients with cancer treated with high doses of intravenous bisphosphonates is clearly higher, in the range of 1,10 per 100 patients (depending on duration of therapy). In the future, improved diagnostic imaging modalities, such as optical coherence tomography or MRI combined with contrast agents and the manipulation of image planes, may identify patients at preclinical or early stages of the disease. Management is largely supportive. A research agenda aimed at filling the considerable gaps in knowledge regarding this disorder was also outlined. [source] Studies on rheology and morphology of POE/PP thermoplastic elastomer dynamically crosslinked by peroxideJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2008Bo Yuan An ethylene-octene copolymer (POE)/polypropylene (PP) thermoplastic elastomer was prepared through dynamically crosslinking by 2,5-dimethyl-2,5-dilbuty (Peroxy) hexane (DHBP). The effects of DHBP concentration, POE/PP ratio, melt flow index (MFI) of PP, and mixer rotation on rheology and morphology of the thermoplastic elastomer were studied. The results showed that with increasing DHBP concentration or POE content, the size of crosslinked particles as well as the melt viscosity increased. Furthermore, agglomerates or a network structure formed as the size of crosslinked particles increased. The melt viscosity also increased as MFI of PP decreased, while the size of crosslinked particles decreased under the same condition. Research on the morphology of dynamically crosslinked POE/PP thermoplastic elastomer flowing through a capillary rheometer at different shear rates show that the reprocessing had little effect on the morphology of dynamically crosslinked elastomer. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source] Cultural Variations in the Placebo Effect: Ulcers, Anxiety, and Blood PressureMEDICAL ANTHROPOLOGY QUARTERLY, Issue 1 2000Daniel E. Moerman An analysis of the control groups in double-blind trials of medicines demonstrates broad variation,from 0 to 100 percent,in placebo effectiveness rates for the same treatment for the same condition. In two cases considered here, drug healing rates covary with placebo healing rates; placebo healing is the ultimate and inescapable "complementary medicine. " Several factors can account for the dramatic variation in placebo healing rates, including cultural ones. But because variation differs by illness, large placebo effects for one condition do not necessarily anticipate large placebo effects for other conditions as well. Deeper understanding of the intimate relationship between cultural and biological processes will require close ethnographic scrutiny of the meaningfulness of medical treatment in different societies, [placebo effect, ulcer disease, anxiety, hypertension, cross-cultural variation] [source] Lunar dust and lunar simulant activation and monitoringMETEORITICS & PLANETARY SCIENCE, Issue 7 2009William T. WALLACE One of the pressing concerns is the effect that lunar dust (the fraction of the lunar regolith <20 ,m in diameter) will have on systems, both human and mechanical, due to the fact that various problems were caused by dust during the Apollo missions. The loss of vacuum integrity in the lunar sample containers during the Apollo era ensured that the present lunar samples are not in the same condition as they were on the Moon; they have been passivated by oxygen and water vapor. To mitigate the harmful effects of lunar dust on humans, methods of "reactivating" the dust must be developed for experimentation, and, ideally, it should be possible to monitor the level of activity to determine methods of deactivating the dust in future lunar habitats. Here we present results demonstrating that simple grinding, as a simple analog to micrometeorite crushing, is apable of substantially activating lunar dust and lunar simulant, and it is possible to determine the level of chemical activity by monitoring the ability of the dust to produce hydroxyl radicals in aqueous solution. Comparisons between ground samples of lunar dust, lunar simulant, and quartz reveal that ground lunar dust is capable of producing over three times the amount of hydroxyl radicals as lunar simulant and an order of magnitude more than ground quartz. [source] Pleiotropic effects of environment-specific adaptation in Arabidopsis thalianaNEW PHYTOLOGIST, Issue 3 2009P. X. Kover Summary ,,Local adaptation may be important for the preservation of genetic diversity and the promotion of speciation. However, local adaptation may also constrain establishment in different environments. The consequences of local adaptation depend strongly on the pleiotropic effects of the genes involved in adaptation. ,,Here, we investigated the pleiotropic effects of the genetic response to selection in outbred lines of Arabidopsis artificially selected to flower earlier under both winter- and spring-annual simulated conditions. The consequences of adaptation were evaluated by reciprocally transplanting selected and control lines between the two conditions. ,,Selected lines always flower earlier than their controls, independent of growing conditions. However, selected lines, growing in the same condition in which they were selected, flower earlier than plants selected in the alternative environment. Plants selected to flower earlier in spring produce more fruits than controls when growing in the spring, and less fruits when growing in the winter; indicating that local adaptation has negative pleiotropic effects in another environment. ,,Our results indicate that local adaptation can arise even when selection targets the same trait in the same direction. Furthermore, it suggests that adaptation under the two different environments can generate fitness trade-offs that can maintain genetic variation for flowering time. [source] Light controls shoot meristem organogenic activity and leaf primordia growth during bud burst in Rosa sp.PLANT CELL & ENVIRONMENT, Issue 11 2008TIFFANIE GIRAULT ABSTRACT Light controls bud burst in many plants, which subsequently affects their architecture. Nevertheless, very little is known about this photomorphogenic process. This study ascertains the effects of light on bud burst and on two of its components, i.e. growth of preformed leaves and meristem organogenesis in six cultivars from three Rosa species (R. hybrida L., R. chinensis L., R. wichurana L.). Defoliated plants were severed above the third basal bud and exposed, either to darkness or to different intensities of white light, to blue, red or to FR, at constant temperature. Bud bursting was inhibited in darkness in the six cultivars of Rosa, but not in Arabidopsis, tomato and poplar plants under the same condition. In all Rosa cultivars, bud burst, growth of preformed leaves and meristem organogenesis were triggered by blue and red lights, and extended by increasing light intensities. FR was inhibitory of bud burst. Partial shading experiments demonstrated that bud and not stem was the active site for light perception in bud burst. [source] Physicochemical responses of Pythium porphyrae (Oomycota), the causative organism of red rot disease in Porphyra to acidificationAQUACULTURE RESEARCH, Issue 15 2009Eun Kyoung Hwang Abstract Physicochemical responses to acidification in Pythium porphyrae, the causative organism of red rot disease in Porphyra, were investigated. The acid tolerance of P. porphyrae mycelia under pH 4 (acidic condition) condition increased significantly compared with that of the mycelia under pH 8 (condition equivalent to seawater) condition. Free amino acid levels in the mycelia decreased 1.3,8.8-fold under pH 4 condition. However, some free amino acids such as the d -cysteinolic acid-like component, phosphoethanolamine, glutamic acid, aminoadipic acid and methionine increased 2.6,21.7-fold under the same condition. Proton flux on the mycelia exposed to pH 8 increased significantly compared with the mycelia exposed to pH 4. The patterns of proteins present (examined by two-dimensional polyacrylamide gel electrophoresis) differed among the pH conditions. These results suggest that P. porphyrae acquires acid tolerance and is able to adapt to the changing pH conditions. This has significant implications for the use of acidic fungicide treatment for prevention of red rot disease on Porphyra farms. [source] Working criteria of mild cognitive impairment in community: findings from Gwangju Dementia and Mild Cognitive Impairment Study (GDEMCIS)ASIA-PACIFIC PSYCHIATRY, Issue 1 2009Kang Soo Lee MD Abstract Introduction: The clinical determination of relative severity of impairment along the spectrum of mild cognitive impairment (MCI) may be valuable for the prediction of dementia. The purpose of the present study is to suggest the working criteria of MCI based on severity in the community sample. Methods: The MCI group was divided into three groups by severity according to cognitive and functional status. The grade I MCI group was based on the original concept of Petersen's MCI. The grade II MCI group was in the same condition as grade I MCI, except that the general cognitive function was not intact. The grade III MCI group was defined as the condition not essentially preserved instrumental to the activity of daily living, but not definite in dementia regardless of general cognitive and functional state. Results: A total of 38.5% of the subjects were classified as not cognitively impaired (NCI), 41.4% as MCI, and 10.3% as having dementia. Preliminary results showed that the grades I, II, and III MCI groups had a tendency to lie between the NCI and dementia groups. Discussion: Prospective cohort studies with clinical correlations are needed to determine whether our working criteria of MCI considering characteristics of the rural elderly, such as low education and less comprehensive activities of daily living (ADL), would be useful. [source] Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of the collagen-binding region of RspB from Erysipelothrix rhusiopathiaeACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Aribam Swarmistha Devi RspB is a surface adhesin of Erysipelothrix rhusiopathiae. A recombinant form of the collagen-binding region of this protein, RspB(31,348), has been overexpressed in Escherichia coli in native and selenomethionine-derivative forms and purified using affinity and gel-permeation chromatography. Thin plate-like crystals were obtained by the hanging-drop vapour-diffusion method using the same condition for both forms. The native crystals diffracted to a resolution of 2.5,Å using an in-house X-ray source, while the selenomethionine-derivative crystals diffracted to a resolution of 2.2,Å using synchrotron radiation. The crystals belonged to the monoclinic space group P21, with unit-cell parameters a = 46.19, b = 66.65, c = 101.72,Å, , = 94.11°. [source] The Oxidative Damage of Plasmid DNA by Ascorbic Acid Derivatives in vitro: The First Research on the Relationship between the Structure of Ascorbic Acid and the Oxidative Damage of Plasmid DNACHEMISTRY & BIODIVERSITY, Issue 9 2006Pei-Yan Liu Abstract To study the structure,function relationship of the oxidative-damage effect of ascorbic acid, we have focused on the interaction between plasmid DNA pUC19 and a series of ascorbic acid derivatives modified on different OH groups in the presence of transition metal ions. Some ascorbic acid derivatives can selectively cleave plasmid DNA from Form I to Form II in the presence of low concentration of Cu2+ just like ascorbic acid itself, while other derivatives oxidatively damage plasmid DNA slightly. We found that those derivatives with unattached 2-OH and 3-OH groups retain the ability to cleave the plasmid DNA. The derivatives that have been methylated on 2-OH or 3-OH can only cleave plasmid DNA softly, and those derivatives that have been protected on both 2-OH and 3-OH can hardly exert an oxidative damage on plasmid DNA under the same condition. Form these results, we can draw the conclusion that 2-OH and 3-OH groups of the ascorbic acid molecule contribute most to this biological activity. [source] Detection of glaucomatous damage using multifocal ERGCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 6 2005Henry Ho-Lung Chan PhD FAAO The first-order kernel analysis in multifocal electroretinogram (mfERG) using low contrast stimulation is suggested as a way to detect the inner retinal responses in animal studies. In this case report, this protocol is applied to human patients with glaucoma to demonstrate the possibility of using mfERG as a tool to detect glaucomatous damage. Two patients with glaucoma were recruited and had mfERG measurements with the 103-scaled hexagonal stimulus pattern at low (50 per cent) contrast. Their responses were analysed and compared with those from normal subjects with the mfERG measured under the same condition. In the normal subjects, there were obvious oscillatory components on the ascending and descending limbs of the first-order kernel response to 50 per cent contrast. In the glaucomatous patients, the oscillatory component on the descending limb was obviously diminished. In addition, this component was significantly diminished in the quadrant with a glaucomatous visual field defect. This suggests that the low-contrast stimulation condition in mERG measurement may provide a good way to detect glaucomatous damage and this may help in clinical diagnosis of glaucoma. [source] The Readability of Path-Preserving Clusterings of GraphsCOMPUTER GRAPHICS FORUM, Issue 3 2010Daniel Archambault Abstract Graph visualization systems often exploit opaque metanodes to reduce visual clutter and improve the readability of large graphs. This filtering can be done in a path-preserving way based on attribute values associated with the nodes of the graph. Despite extensive use of these representations, as far as we know, no formal experimentation exists to evaluate if they improve the readability of graphs. In this paper, we present the results of a user study that formally evaluates how such representations affect the readability of graphs. We also explore the effect of graph size and connectivity in terms of this primary research question. Overall, for our tasks, we did not find a significant difference when this clustering is used. However, if the graph is highly connected, these clusterings can improve performance. Also, if the graph is large enough and can be simplified into a few metanodes, benefits in performance on global tasks are realized. Under these same conditions, however, performance of local attribute tasks may be reduced. [source] Particle size of powders under hydrothermal conditionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2003Wen-Jun Li Abstract Various non-oxide (CuI, AgI, AgCl, PbS, CuS and ZnS) and oxide (ZnO, TiO2, SnO2, CeO2 and ZrO2) powders were prepared under hydrothermal conditions to investigate the effects of temperature, pH and precursors on the particle size of powders. It was found that the particle sizes of PbS, CuS and ZnS powders were much smaller than that of CuI, AgI and AgCl powders prepared under the same conditions. The particle sizes of TiO2, SnO2, CeO2 and ZrO2 powders are much smaller than that of ZnO powders prepared under the same conditions. It is concluded that the solution conditions have a certain effect on the particle size of powders under the hydrothermal conditions. The particle size of powders increased with the rising of temperature. Additional factors affecting the particle size were uncovered through studying the nucleation mechanism. The particle size was mainly related to the Madelung constant and the electric charge number of ions. Powders with smaller particle size resulted from systems that possessed the larger Madelung constant and ionic charge number. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Noninvasive Assessment of Coronary Flow Reserve in the Left Anterior Descending Artery by Transthoracic Echocardiography before and after StentingECHOCARDIOGRAPHY, Issue 8 2007Elie Chammas M.D., F.E.S.C. Background: Noninvasive assessment of coronary flow reserve in the left anterior descending artery (LAD) by transthoracic Doppler echocardiography (TTDE) has been already validated as a new method for determining the degree of stenosis over the proximal flow. Objectives: The aim of the study is to determine, by TTDE, the feasibility and the value of the coronary flow reserve (CFR) (defined as the maximal increase in coronary blood flow above its basal pressure for a given perfusion pressure when coronary circulation is maximally dilated) in the mid-to-distal LAD before and after percutaneous angioplasty and to demonstrate the early recovery of microvascular tone immediately after stenting. Methods: The study population consisted of 36 patients with significant isolated LAD stenosis (70,90%) identified by coronary angiography. CFR was recorded in the mid-to-distal LAD at rest and during hyperemia obtained after adenosine intravenous infusion before and after stenting. Results: Adequate visualization of the LAD was obtained in 25 out of 36 patients (70%). At rest the mean CFR was 1.5132 ± 0.33 (1.1,2.58). However, after stenting the mean CFR was significantly higher: 2.18 ± 0.55 (1.3,3.8), with P <0.01. Conclusions: CFR can be easily determined by TTE in approximately 70% of patients. Noninvasive Doppler echocardiography shows impaired CFR in patients with LAD disease. After stenting CFR is restored, demonstrating early recovery of microvascular tone. These results are comparable to those published in the same conditions. Larger series with a long-term follow-up may allow identifying patients at high risk for restenosis after stenting. [source] Working Electrodes from Amalgam Paste for Electrochemical MeasurementsELECTROANALYSIS, Issue 4 2008Bogdan Yosypchuk Abstract Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA-PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA-PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA-PE is high, and the electrode allows measurements at highly negative potentials. AgA-PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2,-bipyridine) can be performed on AgA-PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes. [source] Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly-Gly-His Modified Glassy Carbon and Gold ElectrodesELECTROANALYSIS, Issue 12 2006Guozhen Liu Abstract This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly-Gly-His for the detection of copper ions. Gly-Gly-His is attached to a glassy carbon (GC) surface modified with 4-carboxyphenyl moieties or a gold surface modified with 3-mercaptopropionic acid by the reaction of the N-terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X-ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly-Gly-His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7,9. Interference studies and investigations of stability of the Gly-Gly-His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self-assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure. [source] Voltammetric Assay of Naproxen in Pharmaceutical Formulations Using Boron-Doped Diamond ElectrodeELECTROANALYSIS, Issue 11 2005V. Suryanarayanan Abstract The electrooxidation of naproxen was studied, for the first time, using boron-doped diamond (BDD) electrode by cyclic and differential pulse voltammetry (CV and DPV) in nonaqueous solvent supporting electrolyte system. The results were also compared with glassy carbon electrode (GC) under the same conditions. Naproxen undergoes one electron transfer resulting in the formation of cation radical for the first electrooxidation step, which follows other chemical and electrochemical steps such as deprotonation, removal of another electron and the attack of nucleophile (ECEC mechanism). BDD electrode provided higher signal to background ratio, well resolved and highly reproducible cyclic voltammograms than the GC electrode. With a scan rate of 50,mV s,1 and pulse height of 50,ms, respectively, the DPV technique was able to determine the naproxen concentrations in the range of 0.5 to 50,,M with a detection limit of 30,nM. The influence of interference compounds namely 2-acetyl-6-methoxy naphthalene (AMN) on naproxen oxidation can also be followed successfully. Moreover, the percentage of AMN present in the standard chemical form of a mixture containing naproxen can be found accurately. Rapidity, precise and good selectivity were also found for the determination of naproxen in pharmaceutical formulations. [source] Analysis of flavonoids by CE using capacitively coupled contactless conductivity detectionELECTROPHORESIS, Issue 5 2007Stefan Bachmann Abstract A CE method employing capacitively coupled contactless conductivity (C4D) compared to indirect UV-detection was developed for the analysis of phytochemically relevant flavonoids, such as 6-hydroxyflavone, biochanin A, hesperetin and naringenin. To ensure fast separation at highest selectivity, sensitivity and peak symmetry, the pH value and the concentration of the running BGE had to be optimized regarding both co- and counter-EOF mode. Optimum conditions were found to be 1.0 and 5.0,mM chromate BGE (pH,9.50) in the counter- and co-EOF mode, respectively. Validation of the established CE-C4D method pointed out to be approximately seven times more sensitive compared to indirect UV-detection applying the same conditions. The lower LOD defined at an S/N of 3:1 was found between 0.12 and 0.21,µg/mL for the analytes of interest using C4D and between 0.77 and 1.20,µg/mL using indirect UV-detection. Compared to an earlier published CE method employing direct UV-detection, C4D was found to be approximately two times more sensitive. Due to the lower baseline noise, C4D showed an excellent regression coefficient >0.99 compared to 0.93 when using indirect UV detection calibrating within a concentration range between 1 and 10,µg/mL. The influence of the sugar moiety on the conductivity of a flavonoid was studied upon the analysis of the aglycon hesperetin and the rutinosid hesperidin. The sugar moiety in hesperedin shows a higher conductivity compared to hesperetin. Finally, the optimized established CE-C4D method was applied to the determination and quantification of naringenin in Sinupret®. [source] Expression of caspase and apoptotic signal pathway induced by sulfur dioxideENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2010Juli Bai Abstract Sulfur dioxide (SO2) is a common air pollutant that is released in low concentrations into the atmosphere and in higher concentrations in some work places. In the present study, male Wistar rats were housed in exposure chambers and treated with 14.00 ± 1.01, 28.00 ± 1.77, and 56.00 ± 3.44 mg/m3 SO2 for 7 days (6 hr/day), while control rats were exposed to filtered air under the same conditions. The mRNA and protein levels of caspase-3, caspase-8, and caspase-9 were analyzed using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and an immunohistochemistry method. Activities of caspases were detected using colorimetric and fluorescent assays. Chromatin degradation and cell morphological changes were investigated by TUNEL assay and H&E staining in livers and lungs, respectively. The results showed that mRNA levels, protein levels and activities of caspase-3, caspase-8, and caspase-9 were increased in a dose-dependent manner in livers and lungs of rats after SO2 inhalation. In addition, livers were infiltrated with lymphocytes, congestion and inflammation occurred in lungs, and eosinophil cells and apoptotic cells increased in both livers and lungs after SO2 inhalation. These results suggest that SO2 exposure increases the expression and activity of both initiator and and effector caspases, and may induce apoptosis in liver and lung of rats through both death receptor and mitochondrial pathways. Environ. Mol. Mutagen. 2010. © 2009 Wiley-Liss, Inc. [source] Comparative mechanisms of zearalenone and ochratoxin A toxicities on cultured HepG2 cells: Is oxidative stress a common process?ENVIRONMENTAL TOXICOLOGY, Issue 6 2009Emna El Golli Bennour Abstract Zearalenone (ZEN) and Ochratoxin A (OTA) are structurally diverse fungal metabolites that can contaminate feed and foodstuff and can cause serious health problems for animals as well as for humans. In this study, we get further insight of the molecular aspects of ZEN and OTA toxicities in cultured human HepG2 hepatocytes. In this context, we have monitored the effects of ZEN and OTA on (i) cell viability, (ii) heat shock protein (Hsp) 70 and Hsp 27 gene expressions as a parameter of protective and adaptive response, (iii) oxidative damage, and (iv) cell death pathways. Our results clearly showed that both ZEN and OTA inhibit cell proliferation. For ZEN, a significant induction of Hsp 70 and Hsp 27 was observed. In the same conditions, ZEN generated an important amount of reactive oxygen species (ROS). Antioxidant supplements restored the major part of cell mortality induced by ZEN. However, OTA treatment downregulated Hsp 70 and Hsp 27 protein and mRNA levels and did not induce ROS generation. Antioxidant supplements did not have a significant effect on OTA-induced cell mortality. Using another cell system (Vero monkey kidney cells), we demonstrated that OTA downregulates three members of HSP 70 family: Hsp 70, Hsp 75, and Hsp 78. Our findings showed that oxidative damage seemed to be the predominant toxic effect for ZEN, while OTA toxicity seemed to be rather because of the absence of Hsps protective response. Furthermore, the two mycotoxins induced an apoptotic cell death. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009. [source] Mutagenicity of nitroaromatic degradation compoundsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Ranjit S. Padda Abstract The mutagenicity of 2,4-dinitrotoluene (24DNT), and 2,6-dinitrotoluene (26DNT), and their related transformation products such as hydroxylamine and amine derivatives, which are formed by Clostridium acetobutylicum, were tested in crude cell extracts using Salmonella typhimurium TA100. A previous publication already reported the mutagenic activities of 2,4,6-trinitrotoluene (TNT) and its related hydroxylamine derivatives in this test system. A time course of the mutagenicity during the anaerobic transformation of TNT, 24DNT, and 26DNT was also investigated under the same conditions to compare with the results from the pure compounds. The monohydroxylamino intermediates 2-hydroxylamino-4-nitrotoluene (2HA4NT), 4-hydroxylamino-2-nitrotoluene (4HA2NT) and 2-hydroxylamino-6-nitrotoluene (2HA6NT) formed during anaerobic transformation of dinitrotoluenes were proven to be mutagenic in the Ames test using Salmonella typhimurium TA100. This study reports that 4HA2NT is the most stable derivative, whereas 2HA4NT and 2HA6NT are less stable and these intermediates are mutagenic in the Ames test. Both 24DNT and 26DNT and their final metabolites 2,4-diaminotoluene (24DAT) and 2,6-aminotoluene (26DAT) appeared nonmutagenic. In a time-course study of TNT degradation, the temporal sample containing 85% of 2,4-dihydroxylamino-6-nitrotoluene (24HA6NT) is most mutagenic. These observations suggest that the bioremediation approach for treatment of 24DNT and 26DNT should be carried past the hydroxylamino intermediate. [source] O -Acylated 2-Phosphanylphenol Derivatives , Useful Ligands in the Nickel-Catalyzed Polymerization of EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2009Dmitry G. Yakhvarov Abstract The title ligands were prepared by O -acylation of 2-diphenylphosphanyl-4-methylphenol (1) or directly by double lithiation of 2-bromo-4-methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O)Cl (R = Me, tBu, Ph, 4-MeOC6H4) to afford diphenylphosphinate 2 and carboxylic esters 3a,d. X-ray crystal structure analyses of 3b,d show conformations in which the P -phenyl substituents are rotated away from the ester group and the C(O)O , planes are nearly perpendicular to the phenol ring , plane. O -Acylated phosphanylphenols 2 and 3a,d form highly active catalysts with Ni(1,5-cod)2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O -acyl bond upon heating with nickel(0) precursor compounds in the presence of ethylene. The precursors are P-coordinated Ni0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 (in a 2:1 molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the precatalysts are activated. Catalysts 2Ni and 3a,dNi convert ethylene nearly quantitatively, 2Ni slowly, and 3a,dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0 into the O,C(O)R bond of 3a,d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by ,-hydride elimination changes the mechanism to the phosphanylphenolate,NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a,dNi catalysts relative to that observed for 1Ni and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Dinuclear Titanium(IV) Complexes Bearing Phenoxide-Tethered N-Heterocyclic Carbene Ligands with cisoid Conformation through Control of HydrolysisEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2007Dao Zhang Abstract In situ generated N-heterocyclic carbene salt derivative Na2(L) of 1,3-bis(4,6-di- tert -butyl-2-hydroxybenzyl)imidazolium bromide, [H3(L)]Br, reacted with 1 equiv. of TiBr4 at ,78 °C to give a titanium complex of the composition [(L)TiBr2(thf)] (1), while the reaction in a 2:1 ratio under the same conditions afforded bisligand titanium complex [(L)2Ti] (2). Two oxygen-bridged titanium dimers, {[(L)TiBr]2(,-O)} (4) and {[(L)Ti(,-O)]2} (5), were obtained by control of hydrolysis of 1 and [(L)Ti(CH2Ph)2] (3) in tetrahydrofuran and diethyl ether. The molecular structures of 2, 4, and 5 have been confirmed by X-ray single-crystal analysis. The phenoxide-functionalized NHC ligand adopts transoid conformation in mononuclear complex 2 but rare cisoid conformation in dinuclear complexes 4 and 5. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] The Role of [,2 -Bis(tert -butylsulfonyl)acetylene](carbonyl)(,5 -cyclopentadienyl)cobalt(I) as an Intermediate in the Alkyne Dimerisation,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2005Tobias H. Staeb Abstract Dicarbonyl(,5 -cyclopentadienyl)cobalt(I) (1) reacts with the electron-poor alkyne bis(tert -butylsulfonyl)acetylene to give the corresponding cyclobutadiene complex 6, whereas the reaction of [CpCo(CO)2] with dimethyl acetylenedicarboxylate yields the cyclopentadienone complex 7 under the same conditions. The cyclobutadiene complex 6 could not be obtained by the treatment of [,2 -bis(tert -butylsulfonyl)acetylene](carbonyl)(,5 -cyclopentadienyl)cobalt(I) [3(H)] with an excess of bis(tert -butylsulfonyl)acetylene. The same holds for the treatment of 3(H) with dimethyl acetylenedicarboxylate and bis(catecholatoboryl)acetylene. With these results we assume that the monoalkyne complex 3(H) is not an intermediate in the alkyne oligomerisation of electron-poor alkynes, as was shown for electron-rich ones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] | |||||||||||||||||||||||||||||||||||||||||||||||||