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GC
Kinds of GC Terms modified by GC Selected AbstractsDifferential Pulse Voltammetric Determination of Selenocystine Using Selenium-gold Film Modified ElectrodeELECTROANALYSIS, Issue 17 2005Yan Bai Abstract Differential pulse voltammetric determination of selenocystine (SeC) using selenium-gold film modified glassy carbon electrode ((Se-Au)/GC) is presented. In 0.10,mol,L,1 KNO3 (pH,3.20) solution, SeC yields a sensitive reduction peak at ,740,mV on (Se-Au)/GC electrode. The peak current has a linear relationship with the concentration of SeC in the range of 5.0×10,8,7.0×10,4,mol,L,1, and a 3, detection limit of SeC is 3.0×10,8,mol,L,1. The relative standard deviation of the reduction current at SeC concentration of 10,6,mol,L,1 is 3.88% (n=8) using the same electrode, and 4.19% when using three modified electrodes prepared at different times. The content of SeC in the selenium-enriched yeast and selenium-enriched tea is determined. The total selenium in ordinary or selenium-enriched tea is determined by DAN fluorescence method. The results indicate that in selenium-enriched yeast about 20% of total selenium is present as SeC and in selenium-enriched tea SeC is the major form of selenoamino acids. The total selenium content in selenium-enriched tea soup is 0.09,,gSe/g accounting by 7% compared with that in selenium-enriched tea. Hence, only a little amount of selenium is utilized by drinking tea, and most selenium still stay in tealeaf. Uncertainty are 22.4% and 16.1% for determination of SeC in selenium-enriched yeast and selenium-enriched tea by differential pulse voltammetry (DPV) on (Se-Au)/GC electrode, respectively. [source] Sequence-dependent proton-transfer reaction in stacked GC pair III: The influence of proton transfer to conductivityINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 12 2010Yasuyuki Nakanishi Abstract We have computed current,voltage character of natural DNA and its proton-transferred structure by scattering theory based on density functional theory. The current is not observed if the electron path contains only hydrogen bonding such as one base pair. The current becomes larger if the electron path contains ,,, stacking molecule such as two base pairs. We also found that the conductivity of pseudo-ion pair (C+G,/G,C+), which is derived from proton-transfer reaction in CG/GC, differs from that of the original structure. On the other hand, the current changes dramatically if the electrode connects to guanine or cytosine, which can be explained by the difference of electron affinities. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Differential Pulse Voltammetric Determination of Uric Acid on Carbon-Coated Iron Nanoparticle Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 10 2008Shengfu Wang Abstract A carbon-coated iron nanoparticles (CIN, a new style fullerence related nanomaterial) modified glassy carbon electrode (CIN/GCE) has been developed for the determination of uric acid (UA). Electrochemical behaviors of UA on CIN/GCE were explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the voltammetric response of UA on CIN/GC was enhanced dramatically because of the strong accumulation effect of CIN and the large working area of the CIN/GC electrode. The parameters including the pH of supporting electrolyte, accumulation potential and time, that govern the analytical performance of UA have been studied and optimized. The DPV signal of UA on CIN/GCE increased linearly with its concentration in the range from 5.0×10,7 to 2.0×10,5 M, with a detection limit of 1.5×10,7 M (S/N=3). The CIN/GCE was used for the determination of UA in samples with satisfactory results. The proposed CIN/GCE electrochemical sensing platform holds great promise for simple, rapid, and accurate detection of UA. [source] Sapphire: copying garbage collection without stopping the worldCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 3-5 2003Richard L. Hudson Abstract The growing use in concurrent systems of languages that require garbage collection (GC), such as Java, is raising practical interest in concurrent GC. Sapphire is a new algorithm for concurrent copying GC for Java. It stresses minimizing the amount of time any given application thread may need to block to support the collector. In particular, Sapphire is intended to work well in the presence of a large number of application threads, on small- to medium-scale shared memory multiprocessors. Sapphire extends previous concurrent copying algorithms, and is most closely related to replicating copying collection, a GC technique in which application threads observe and update primarily the old copies of objects. The key innovations of Sapphire are: (1) the ability to ,flip' one thread at a time (changing the thread's view from the old copies of objects to the new copies), as opposed to needing to stop all threads and flip them at the same time; (2) exploiting Java semantics and assuming any data races occur on volatile fields, to avoid a barrier on reads of non-volatile fields; and (3) working in concert with virtually any underlying (non-concurrent) copying collection algorithm. Copyright © 2003 John Wiley & Sons, Ltd. [source] Modulation of antigen expression in B-cell precursor acute lymphoblastic leukemia during induction therapy is partly transient: Evidence for a drug-induced regulatory phenomenon.CYTOMETRY, Issue 3 2010Results of the AIEOP-BFM-ALL-FLOW-MRD-Study Group Abstract Background: Changes of antigen expression on residual blast cells of acute lymphoblastic leukemia (ALL) occur during induction treatment. Many markers used for phenotyping and minimal residual disease (MRD) monitoring are affected. Glucocorticoid (GC)-induced expression modulation has been causally suspected, however, subclone selection may also cause the phenomenon. Methods: We investigated this by following the phenotypic evolution of leukemic cells with flow cytometry from diagnosis to four time points during and after GC containing chemotherapy in the 20 (of 360 consecutive) B-cell precursor patients with ALL who had persistent MRD throughout. Results: The early expression changes of CD10 and CD34 were reversible after stop of GC containing chemotherapy. Modulation of CD20 and CD45 occurred mostly during the GC phase, whereas CD11a also changed later on. Blast cells at diagnosis falling into gates designed according to "shifted" phenotypes from follow-up did not form clusters and were frequently less numerous than later on. Conclusions: Our data support the idea that drug-induced modulation rather than selection causes the phenomenon. The good message for MRD assessment is that modulation is transient in at least two (CD10 and CD34) of the five prominent antigens investigated and reverts to initial aberrant patterns after stop of GC therapy, whereas CD20 expression gains new aberrations exploitable for MRD detection. © 2010 Clinical Cytometry Society [source] Evaluation of malignant and benign gastric biopsy specimens by mRNA expression profile and multivariate statistical methodsCYTOMETRY, Issue 5 2007Orsolya Galamb Abstract Background: mRNA expression array and multivariate statistical analysis of gastric biopsies can yield insight into the molecular biology basis of local alterations, supporting expression-based identification of morphological alterations. Methods: From 11 patients with erosive gastritis(EG), 5 with adenocarcinoma (GC), 11 with atrophic gastritis (AG) gastric biopsies were collected, total RNA isolated, T7 amplification and expression analysis of 1047 mRNAs was performed using commercial glass arrays (Clontech, USA). After microarray quality control, applicable data were available from 7 EG, 4 GC, and 5 AG. Multivariate statistical and cell functional analysis were performed. Real-time RT-PCR and immunohistochemistry were used for validation. Results: GC was characterized by overregulated v-raf, v-erb-a, BCL2-associated- athanogene, immediate-early-response-3, Polo-like kinase, CDK-2, cyclin-C, Pin1 genes, and downregulated ADP-ribosyltransferase, sialophorin and DCC. AG cases had increased PDGF-receptor, TGF-,-receptor-3, and decreased death-associated-protein-3, ,-1-catenin, topoisomerase-1 levels. In EG upregulation of IGF-receptor-1, CD9, transferrin receptor, integrins, and underexpression of keratin-5, caspase-4 was found. Discriminant analysis could reclassify all samples correctly using four parameters. Conclusions: mRNA expression array analysis of gastric biopsies yields previously known and new data in the evaluation of local gastric alterations. © 2007 Clinical Cytometry Society [source] Safety of sertindole versus risperidone in schizophrenia: principal results of the sertindole cohort prospective study (SCoP)ACTA PSYCHIATRICA SCANDINAVICA, Issue 5 2010S. H. L. Thomas Thomas SHL, Drici MD, Hall GC, Crocq MA, Everitt B, Lader MH, Le Jeunne C, Naber D, Priori S, Sturkenboom M, Thibaut F, Peuskens J, Mittoux A, Tanghøj P, Toumi M, Moore ND, Mann RD. Safety of sertindole versus risperidone in schizophrenia: principal results of the sertindole cohort prospective study (SCoP) Objective:, To explore whether sertindole increases all-cause mortality or cardiac events requiring hospitalization, compared with risperidone. Method:, Multinational randomized, open-label, parallel-group study, with blinded classification of outcomes, in 9858 patients with schizophrenia. Results:, After 14147 person-years, there was no effect of treatment on overall mortality (sertindole 64, risperidone 61 deaths, Hazard Ratio (HR) = 1.12 (90% CI: 0.83, 1.50)) or cardiac events requiring hospitalization [sertindole 10, risperidone 6, HR = 1.73 (95% CI: 0.63, 4.78)]: Of these, four were considered arrhythmia-related (three sertindole, one risperidone). Cardiac mortality was higher with sertindole (Independent Safety Committee (ISC): 31 vs. 12, HR=2.84 (95% CI: 1.45, 5.55), P = 0.0022; Investigators 17 vs. 8, HR=2.13 (95% CI: 0.91, 4.98), P = 0.081). There was no significant difference in completed suicide, but fewer sertindole recipients attempted suicide (ISC: 68 vs. 78, HR=0.93 (95% CI: 0.66, 1.29), P = 0.65; Investigators: 43 vs. 65, HR=0.67 (95% CI: 0.45, 0.99), P = 0.044). Conclusion:, Sertindole did not increase all-cause mortality, but cardiac mortality was higher and suicide attempts may be lower with sertindole. [source] Predictors of glycaemic control in indigent patients presenting with diabetic ketoacidosisDIABETES OBESITY & METABOLISM, Issue 3 2005M. Maldonado Aim:, To derive predictors of good glycaemic control in patients presenting with diabetic ketoacidosis (DKA) followed prospectively in a specialized clinic. Methods:, One hundred and sixty-one adult patients were admitted during a 31-month period and followed for at least 12 months. After 1 year, the patients were classified into three groups: good control (GC) (HbA1c , 7%), intermediate control (IC) (HbA1c 7,9%) and poor control (PC) (HbA1c > 9%). Characteristics of patients in the three groups were compared both at baseline and during follow-up. Results:, At 12 months, 36% of the patients were classified as GC, 27% as IC and 37% as PC. GC patients had higher fasting serum C-peptide levels 0.7 ± 0.54 compared to 0.38 ± 0.29 and 0.16 ± 0.21 nmol/l, respectively, for the IC and PC patients (p < 0.0001). A higher proportion GC patient had a C-peptide level greater than 0.33 nmol/l than that for IC and PC patients (86, 61 and 19%, respectively; p < 0.0001). Exogenous insulin was safely discontinued in 50, 30 and 3% of patients, respectively, in the GC, IC and PC groups (p < 0.0001). Compliance with life-style interventions was higher in the GC than that in IC and PC patients (87, 41 and 5%, respectively; p < 0.0001). In the logistic regression analysis, predictors of good glycaemic control were having baseline fasting serum C-peptide value ,0.33 mmol/l, OR: 3.01 (95% CI 1.07,8.55, p = 0.03) and compliance with life-style interventions OR 12.66 (95% CI 3.73,51.57, p = 0.0001). Conclusion:, Among adult patients with DKA, significant predictors of good glycaemic control are preserved ,-cell function and compliance with life-style modifications. [source] Differences in endoscopic views during biopsy through the right and left lower biopsy channels of the upper gastrointestinal endoscopeDIGESTIVE ENDOSCOPY, Issue 3 2004Naoki Mantani Background:, It has not been established as to which side the biopsy (instrument) channel should be placed in the tip of a front-viewing upper gastrointestinal (GI) endoscope to allow an en-face approach to lesions on various aspects of the stomach wall. Methods:, Using a front-viewing two-channel endoscope, we identi,ed a difference in endoscopic views during biopsy between lower-right and lower-left channels. Colored marks were distributed on the lesser curvature (LC), greater curvature (GC), anterior wall (AW), and posterior wall (PW) in the ,stomach' of a dummy for mock-performance of upper GI endoscopy. When biopsy forceps through the different channels touched the marks, an endoscopic photograph was taken. Furthermore, when biopsy specimens were obtained from PW lesions in several patients, endoscopic views were compared between the two biopsy channels. Results:, In the dummy study, no remarkable difference was detected in targeting the marks on AW, LC, or GC of the stomach. The dummy and the patient study showed that the lower-right approach could target PW lesions with a more adequate endoscopic view than from the lower left. The lower-left approach targeted PW lesions on the higher body with a nearly blinded endoscopic view. Specimens from PW of the upper body, which could be precisely obtained under direct visual control through the lower-right channel, were no smaller than those obtained using the channel on the lower left. Conclusion:, The present study suggests that the lower-right channel may be preferable to the lower-left channel in the tip of a front-viewing upper GI endoscope. [source] A Novel Polycatechol/Ordered Mesoporous Carbon Composite Film Modified Electrode and Its Electrocatalytic ApplicationELECTROANALYSIS, Issue 15 2010Jing Bai Abstract Polycatechol (PCC) was prepared by electropolymerizing catechol (CC) on the surface of an ordered mesoporous carbon (OMC) modified electrode for the first time. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to characterize the structure and electrochemical behaviors of PCC/OMC nanocomposite film. Compared with the bare GC and OMC/GC electrodes, the PCC/OMC/GC electrode exhibits a good electrocatalysis toward the oxidation of NADH at 0.0,V with a high sensitivity (8.7 mA/mM). These make PCC/OMC/GC electrode a promising candidate for stable and efficient electrochemical sensors for the detection of NADH. [source] Influence of Metal Nanoparticles on the Electrocatalytic Oxidation of Glucose by Poly(NiIIteta) Modified ElectrodesELECTROANALYSIS, Issue 5 2010Pratap Azad Abstract Conductive polymeric [NiII(teta)]2+ (teta=C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane) films (poly(Ni)) have been deposited on the surface of glassy carbon (GC), Nafion (Nf) modified GC (GC/Nf) and Nf stabilized Ag and Au nanoparticles (NPs) modified GC (GC/Ag-Nf and GC/Au-Nf) electrodes. The cyclic voltammogram of the resulting electrodes, show a well defined redox peak due to oxidation and reduction of poly(Ni) system in 0.1,M NaOH. They show electrocatalytic activity towards the oxidation of glucose. AFM studies reveal the formation of poly(Ni) film on the modified electrodes. Presence of metal NPs increases electron transfer rate and electrocatalytic oxidation current by improving the communication within the Nf and poly(Ni) films. In the presence of metal NPs, 4 fold increase in current for glucose oxidation was observed. [source] Bismuth/Polyaniline/Glassy Carbon Electrodes Prepared with Different Protocols for Stripping Voltammetric Determination of Trace Cd and Pb in Solutions Having SurfactantsELECTROANALYSIS, Issue 2 2010M. Wang Abstract To improve reproducibility, stability and sensitivity, a bismuth (Bi) thin film was coated on glassy carbon (GC) substrates which surfaces were modified with a porous thin layer of polyaniline (PANI) via multipulse potentiostatic electropolymerization to form Bi/PANI/GC electrodes (Bi/PANI/GCEs). The Bi/PANI/GCEs were used successfully for simultaneous detection and determination of Cd2+ and Pb2+ ions, and various parameters were studied with reference to square wave anodic stripping voltammetric (SWASV) signals. The experimental results depicted that the environment-friendly Bi/PANI/GCEs had the ability to rapidly monitor trace heavy metals even in the presence of surface-active compounds. [source] A New Indirect Electroanalytical Method to Monitor the Contamination of Natural Waters with 4-Nitrophenol Using Multiwall Carbon NanotubesELECTROANALYSIS, Issue 9 2009Cruz Moraes, Fernando Abstract The electrochemical detection of the hazardous pollutant 4-nitrophenol (4-NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4-NP in natural water. Electrochemical impedance spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4-NP on the GC/MWNCT surface) in a potential region which is approximately 700,mV less positive than that needed to oxidize 4-NP, thus minimizing the interference of matrix components. The limit of detection for 4-NP obtained using square-wave voltammetry (0.12,,mol L,1) was lower than the value advised by EPA. A natural water sample from a dam located in São Carlos (Brazil) was spiked with 4-NP and analyzed by the standard addition method using the GC/MWCNT electrode, without any further purification step. The recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4-NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV-vis detection. [source] Direct Electron Transfer and Electrocatalysis of Hemoglobin on Chitosan-TiO2 Nanorods-Glass Carbon ElectrodeELECTROANALYSIS, Issue 20 2008Xiaoling Xiao Abstract The direct electron transfer between hemoglobin (Hb) and the glassy carbon electrode (GC) can be readily achieved via a high biocompatible composite system based on biopolymer chitosan (CHT) and TiO2 nanorods (TiO2 -NRs). TiO2 -NRs greatly promote the electron transfer between Hb and GC, which contribute to the higher redox peaks. UV-vis spectra result indicated the Hb entrapped in the composite film well keep its native structure. The immobilized Hb remains its bioelectrocatalytical activity to the reduction of H2O2 with a lower detection limit. A novel, sensitive, reproducible and stable electrochemical biosensing platform of H2O2 based on Hb-TiO2 -CHT electrode is explored. [source] Properties of Poly(sodium 4-styrenesulfonate)-Ionic Liquid Composite Film and Its Application in the Determination of Trace Metals Combined with Bismuth Film ElectrodeELECTROANALYSIS, Issue 5 2008Jianbo Jia Abstract A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF6) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4-styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)64,/Fe(CN)63, can be effectively improved at the PSS-BMIMPF6 modified GC. The bismuth modified PSS-BMIMPF6 composite film electrodes (GC/PSS-BMIMPF6/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS-BMIMPF6/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50,,g L,1. And the detection limits were 0.07,,g L,1 for Cd(II) and 0.09,,g L,1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120,s, respectively. Finally, the GC/PSS-BMIMPF6/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy. [source] Amperometric Glucose Biosensors Based on Glassy Carbon and SWCNT-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 1 2008Irene Carpani Abstract Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochemical activation at +1.80,V (vs. SCE) for 900,s, have been used with the aim of comparing their performances in the development of enzyme electrodes. Commercial SWCNTs have been pretreated with 2.2,M HNO3 for 20,h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors has been confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solutions of 0.1,M phosphate buffer (pH,5.5), containing dissolved oxygen, at a potential of ,0.40,V vs. SCE. Although the performances of the two carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addition, the preparation procedure of such biosensors was more simple, rapid and reproducible. [source] Chitosan Incorporating Cetyltrimethylammonium Bromide Modified Glassy Carbon Electrode for Simultaneous Determination of Ascorbic Acid and DopamineELECTROANALYSIS, Issue 17 2007Xuelian Zou Abstract Simultaneous determination of a neurotransmitter, dopamine (DA), and ascorbic acid (AA) is achieved at neutral pH on a chitosan incorporating cetyltrimethylammonium bromide (CTAB) modified glassy carbon (GC) electrode. Differential pulse voltammetry (DPV) technique was used to investigate the electrochemical response of DA and AA at a glassy carbon electrode modified with chitosan incorporating CTAB. An optimum 6.0,mmol L,1 of CTAB together with 0.5 wt% of chitosan was used to improve the resolution and the determination sensitivity. In 0.1,mol L,1 aqueous phosphate buffer solution of pH,6.8, the chitosan-CTAB modified electrode showed a good electrocatalytic response towards DA and AA. The anodic peak potential of DA shifted positively, while that of AA shifted negatively. Thus, the difference of the anodic peaks of DA and AA reached 0.23,V, which was enough to separate the two anodic peaks very well. The presented method herein could be applied to the direct simultaneous determination of DA and AA without prior treatment. The anodic peak currents (Ipa) of DPV are proportional to DA in the concentration range of 8,,M to 1000,,M, to that of AA 10,,M to 2000,,M, with correlation coefficients of 0.9930 and 0.9945, respectively. The linear range is much wider than previously reported. [source] Preparation, Characterization and Analytical Applications of a New and Novel Electrically Conducting PolymerELECTROANALYSIS, Issue 15 2006F. D'Eramo Abstract In this study, a glassy carbon electrode (GC) was modified with an electropolymerized film of 1-naphthylamine (1-NAP) with a subsequent overoxidation treatment in 0.2,M sodium hydroxide solution. This polymer p-1-NAPox film coated GC electrode was used for the selective determination of dopamine (DA) in the presence of a triple concentration of ascorbic acid (AA). These studies were performed using cyclic voltammetry and square-wave voltammetry at physiological pH. p-1-NAPox shows an attractive permselectivity, a marked enhancement of the current response and antifouling properties when compared to a bare GC electrode activated in basic media. With a preconcentration time of 3,minutes at open circuit, linear calibration plots were obtained for DA in buffer solution (pH,7.4) over the concentration range from 1×10,6,1×10,4 M with a detection limit of 1.59×10,7 M. [source] Amperometric Sensor for Heparin: Sensing Mechanism and Application in Human Blood Plasma AnalysisELECTROANALYSIS, Issue 13-14 2006Jan Langmaier Abstract Voltammetric measurements of heparin at a rotating glassy carbon (GC) electrode coated with a polyvinylchloride membrane are reported. A spin-coating technique is used to prepare thin membranes (20,40,,m) with a composition of 25% (w/w) PVC, 1,1,-dimethylferrocene as a reference electron donor for the GC|membrane interface, nitrophenyl octyl ether (o -NPOE) or bis(2-ethylhexyl) sebacate (DOS) as a plasticizer, and hexadecyltrimethylammonium tetrakis(4-chlorophenyl) borate (HTMATPBCl) or tridodecylmethylammonium tetrakis(4-chlorophenyl) borate (TDMATPBCl) as a background electrolyte. It is shown that the electrodes coated with either the HTMA+/o -NPOE (DOS) or TDMA+/o -NPOE (DOS) membrane provide a comparable amperometric response towards heparin (1,10,U mL,1) in the aqueous solution of 0.1,M LiCl. However, only the membranes formulated with TDMATPBCl can be used for an amperometric assay of heparin in human blood plasma with a detection limit of 0.2,U mL,1. Effects of membrane composition, heparin concentration, rotation speed and sweep rate on the voltammetric behavior of heparin provide some insight into the sensing mechanism. Theoretical analysis of the amperometric response is outlined, and the numeric simulation of the voltammetric behavior is presented. [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] Amperometry of Heparin Polyion Using a Rotating Disk Electrode Coated with a Plasticized PVC MembraneELECTROANALYSIS, Issue 2 2006Jan Langmaier Abstract Electrochemical method of detection of heparin polyion was developed based on voltammetry of heparin on a rotating glassy carbon (GC) electrode coated with a plasticized PVC membrane. The membrane was deposited on the GC disk by spin-coating technique using a mixture of solutions of PVC in tetrahydrofuran, and 1,1,-dimethylferrocene (DMFc) and hexadecyltrimethylammonium tetrakis(4-chlorophenyl)borate (HTMATPBCl) in o -nitrophenyl octyl ether. UV/vis reflection spectrometry was used to evaluate the membrane thickness, which exhibits a linear correlation with the membrane resistance measured by impedance spectroscopy. It is shown that this electrode can be used for amperometric or coulometric detection of heparin in aqueous samples of medically relevant concentrations (1,10,U mL,1), with a detection limit of 1.4,U mL,1. Evidence is provided indicating that the current determining step is the reversible adsorption of the ion-pair of heparin polyion with HTMA+ cation at the membrane/aqueous electrolyte interface, which is driven by oxidation of DMFc at the GC/membrane interface. [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] Spectroelectrochemical and Voltammetric Studies of L -DOPAELECTROANALYSIS, Issue 2 2003Xiaoqiang Liu Abstract The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E0=228,mV, the apparent electron-transfer number of the electrooxidation reaction ,n=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k0=(3.93±0.12)×10,4,cm s,1 (SD=1.02×10,2), and the formation equilibrium constant of the following chemical reaction kc=(5.38±0.34)×10,1,s,1 (SD=1.02×10,2) were also obtained. [source] Characteristics of strawberry plants propagated by in vitro bioreactor culture and ex vitro propagation methodENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2009Samir C. Debnath Abstract Reproducible protocol for regeneration of complete plantlets from ,Bounty' strawberry (Fragaria ananassa Duch.), using a combination of gelled medium and bioreactor system, has been standardized. Sepals, leaf discs, and petiole halves produced multiple buds and shoots when cultured on semi solid-gelled medium containing 4 ,M thidiazuron (TDZ) for 4 wk followed by transferring in liquid medium containing 2,,M TDZ in a bioreactor system and cultured for another 4 wk. TDZ induced shoot proliferation at 0.1,,M in the bioreactor system but inhibited shoot elongation. TDZ-induced shoots were elongated and rooted in vitro on gelled medium containing 2,,M zeatin. Such bioreactor-derived tissue culture (BC) plantlets obtained from sepal explants were grown ex vitro and compared with those propagated by tissue culture on gelled medium (GC) and by conventional runner cuttings (RC), for growth, morphology, anthocyanin content, and antioxidant activity after three growth seasons. The BC and GC plants produced more crowns, runners, leaves, and berries than the RC plants although berry weight per plant did not differ significantly. BC and GC plants produced berries with more anthocyanin contents and antioxidant activities than those produced by the RC plants. However, intersimple sequence repeat (ISSR) marker assay produced a homogenous amplification profile in the tissue culture and donor control plants confirming the clonal fidelity of micropropagated plants. In vitro culture on TDZ and zeatin-containing nutrient media apparently induced the juvenile branching characteristics that favored enhanced vegetative growth with more crown, runners, leaf, and berry production. [source] A survey on two years of medication regulation in horse races in IranEQUINE VETERINARY JOURNAL, Issue 2 2010S. LOTFOLLAHZADEH Summary Reasons for performing study: The present survey evaluated the use of prohibited substances cases in the first 2 years of medication regulation in horseracing in Iran so that the impact of these regulations on the level of positive cases over the period could be assessed. Objectives: To determine the prevalence of positive tests for prohibited substances in horse races during 2 years of a drugs testing programme in Iran. Methods: A total of 656 horses that were winners or second in races were tested during the 2 year study. In the first year 354 horses (209 males and 145 females) and in the second year 302 horses (155 males and 147 females) were tested. In the 2 years, 306 were found to be positive. Urine samples were taken from candidate horses and sent to the Central Doping Laboratory. Blood samples were taken from those horses where a urine sample could not be taken within one hour. Detection and measurement of prohibited substances were carried out by ELISA, GC and HPLC using standard methods. Results: Thirty-two percent of males were positive for prohibited substances, which was not significantly different from the percentage of females (25.5%). In the second year, of the 302 horses tested for prohibited substances, 33.5% of males were positive, again similar to females (33.3%). Almost 83% of horses tested positive for prohibited substances once in the first year, 15% tested positive twice and 2% tested positive 3 times. In the second year 78% tested positive once, 15% tested positive twice and 7% tested positive 3 times. Morphine was the most used prohibited substance and was detected 42 times during the survey, followed by caffeine and phenylbutazone. Morphine was also the most used drug in combination with other drugs in both years. Conclusions: Morphine and caffeine were the most popular prohibited substances found in the measurements. As these substances were found in the environment and food stuffs, their presence in the samples may be due to unintentional feeding of contaminated materials (bread, hay and chocolate). [source] Fas and Fas ligand expression on germinal center type-diffuse large B-cell lymphoma is associated with the clinical outcomeEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 6 2006Yasushi Kojima Abstract:, In recent years, diffuse large B-cell lymphoma (DLBCL) has been classified by DNA microarray analysis into the germinal center B-cell-like (GC) type, the activated B-cell-like (ABC) type and type 3. The latter two types can be collectively categorized as the non-GC (NGC) type. From the prognostic perspective, the GC type has a favorable clinical outcome when compared with the NGC type. The protein Fas induces apoptosis of lymphocytes by binding with the Fas ligand (FasL), and escape from such apoptosis is considered to lead to malignant transformation of the cells and unrestricted growth of lymphoma. We proposed a hypothesis that Fas/FasL expression could be possibly related with a better survival of GC type DLBCL and evaluated 69 DLBCL cases immunohistochemically with CD10, Bcl-6, MUM1, Fas and FasL. These lymphomas were classified as GC type (positive for CD10 or Bcl-6 and negative for MUM1) or NGC type. The GC type had a better overall survival rate than the NGC type (P = 0.0723). Among markers as given above, positive CD10 was the most significant prognostic factor for overall survival in total DLBCL (P < 0.05). In the GC type, Fas and FasL expressions were significantly associated with a favorable overall survival (Fas: P < 0.005; FasL: P < 0.05). Hence, Fas or FasL expression might contribute to a better prognosis of this type of DLBCL. [source] Indirect study of thrombopoiesis(TPO, reticulated platelets, glycocalicin)in patients with hereditary macrothrombocytopeniaEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2000F. Fabris To better understand the pathogenesis of thrombopoiesis in this hereditary thrombocytopenic disorder, we determined the percentage of reticulated platelets (RP), plasma glycocalicin (GC) and thrombopoietin (TPO) levels in 29 patients with CHMT, 23 patients with immune thrombocytopenic purpura (ITP), and 17 patients with thrombocytopenia secondary to decreased bone marrow megakaryocytes (hypoplasia). The % RP was similar in CHMT (2.27±1.33) and hypoplasia (1.98±1.35) patients and markedly lower than that in ITP patients (8.80±7.97; p<0.001), suggesting that the production of new platelets is reduced in CHMT. Plasma GC was within the normal range (0.84±0.16 ,g/mL) both in patients with CHMT (0.63±0.20 ,g/mL) and ITP (0.82±0.90 ,g/mL), while it was significantly decreased in patients with hypoplasia (0.16±0.04 ,g/mL; p<0.001). When the GC value was normalized for platelet count, the GC index was normal in CHMT patients (2.05±1.1) and in patients with hypoplasia (0.85±0.10) while it was significantly increased in ITP patients (10.88±18.00; p<0.001); thus, patients with CHMT seem to have a normal platelet turnover. TPO was significantly increased in CHMT (195±72 pg/ml) as compared with normal (80±53 pg/ml; p<0.002); however, the mean level was not as high as in ITP patients (345±167 pg/mL; p<0.001). This finding suggests that CHMT syndrome is not secondary to a defective production of TPO and that megakaryocyte mass is nearly normal. [source] Glycolipid-activated NKT cells support the induction of persistent plasma cell responses and antibody titersEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2008Scott Devera Abstract NKT cell activation with CD1d-binding glycolipid ,-galactosylceramide (,-GC) enhances antibody responses to co-administered T-dependent antigen. The efficacy of ,-GC relative to other CD1d-binding glycolipids and adjuvants is not known. There is little information on how NKT cells affect antibody production beyond initial booster-stimulated recall responses. We therefore tested the hypothesis that ,-GC stimulates induction of plasma cells and antibody responses as effectively as Th1- and Th2-skewing variants of ,-GC and several other adjuvants. C57BL/6 and CD1d,/, mice were immunized with nitrophenol-conjugated keyhole limpet hemocyanin (NP-KLH) plus ,-GC or NP-KLH plus adjuvants before administration of an NP-KLH booster and assessing antibody responses and plasma cell frequency. ,-GC boosted long-term antibody responses as efficiently as all other agents tested and induced plasma cells that were detected in bone marrow 13,weeks after immunization. We then determined whether NKT cells were required in the presence of other adjuvants. CD1d,/, mice had a reduced induction of plasma cells in response to NP-KLH/Alum as compared to C57BL/6 mice. However, NKT cells were not required for the continued presence of those cells that were induced. Although NKT cells are capable of inducing persistent plasma cell responses, they may not play a major role in supporting longevity post-induction. [source] Fc,RII expression on follicular dendritic cells and immunoreceptor tyrosine-based inhibition motif signaling in B,cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2004Yüksel Aydar Abstract Immune complexes (IC) initiate immunoreceptor tyrosine-based inhibition motif (ITIM) signaling and inhibit B,cell activation by coligating B,cell receptor for antigen (BCR) and Fc,RII. Nevertheless, IC on follicular dendritic cells (FDC) stimulate rapid germinal center (GC) B,cell proliferation suggesting that interactions between IC and FDC render IC capable of B,cell activation. Tounderstand this, we studied the kinetics of FDC Fc,RII and complement receptors,1 and,2 (CR1&2) expressions during the GC reaction and determined whether FDC Fc,RII could bind Fc in IC and block ITIM signaling. Mice were immunized with sheep red blood cells (SRBC), and CR1&2 and Fc,RII levels in FDC reticula were monitored. The role of FDC Fc,RII was studied using anti-BCR-stimulated A20 cells. Levels of FDC Fc,RII in spleens of SRBC-injected mice increased within 24,h and were dramatically increased (,50-fold) on days,3 and,5. In contrast, CR1&2 levels increased less than twofold. Addition of normal FDC, but not FDC lacking Fc,RII, reduced and reversed anti-BCR-induced SH2 domain-containing inositol phosphatase (SHIP)-1 phosphorylation in A20 cells. FDC wereable to induce normal recall responses even after overnight incubation of the lymphocytes with IC to stimulate ITIM signaling. Engagement of Ig Fc with numerous Fc,RII on FDC appears to minimize IC-induced ITIM signaling. Thus, rapid up-regulation of FDC Fc,RII may explain why poorly immunogenic IC are rendered highly immunogenic when presented by FDC in GC. [source] Synthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Alberto Albinati Abstract Transition-metal N,N -dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic,organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl-functionalised copper carbamato complex. During the synthesis of the N,N -diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X-ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC,MS) experiments were carried out, which allowed us to identify 3,4-dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] | |||||||||||||||||||||||||||||||||||||||||||