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Long-term Stability (long-term + stability)
Kinds of Long-term Stability Selected AbstractsPersonality Development: An Introduction Toward Process Approaches to Long-Term Stability and Change in PersonsJOURNAL OF PERSONALITY, Issue 6 2003William G. Graziano This special issue is concerned with the systematic transformation of persons and personalities as they move through their lives. The focus is on developmental processes early in the life course that influence both long-term stability and change. Contributors represent diverse topics and viewpoints, but offer new data on classical issues of personality, including trait structure, self-regulation and internalization, self-evaluation, and self-efficacy. In addition, the issue includes empirical contributions on newer approaches to bullying, developmental processes in psychopathology, the influence of racial and ethnic discrimination on subsequent adjustment, and cultural influences on personality development. The issue also includes a special contribution addressing methodological and statistical advances in dealing with prospective longitudinal data assessing personality over time. [source] Optimization of Enzymatic Gas-Phase Reactions by Increasing the Long-Term Stability of the CatalystBIOTECHNOLOGY PROGRESS, Issue 3 2004Clara Ferloni Enzymatic gas-phase reactions are usually performed in continuous reactors, and thus very stable and active catalysts are required to perform such transformations on cost-effective levels. The present work is concerned with the reduction of gaseous acetophenone to enantiomerically pure ( R)-1-phenylethanol catalyzed by solid alcohol dehydrogenase from Lactobacillus brevis (LBADH), immobilized onto glass beads. Initially, the catalyst preparation displayed a half-life of 1 day under reaction conditions at 40 °C and at a water activity of 0.5. It was shown that the observed decrease in activity is due to a degradation of the enzyme itself (LBADH) and not of the co-immobilized cofactor NADP. By the addition of sucrose to the cell extract before immobilization of the enzyme, the half-life of the catalyst preparation (at 40 °C) was increased 40 times. The stabilized catalyst preparation was employed in a continuous gas-phase reactor at different temperatures (25,60 °C). At 50 °C, a space-time yield of 107 g/L/d was achieved within the first 80 h of continuous reaction. [source] Long-term Stability of Endocardial Left Ventricular Pacing Leads Placed via the Coronary SinusPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2009GRACE LIN M.D. Background: Left ventricular endocardial pacing leads placed via the coronary sinus (CS) are increasingly implanted to achieve cardiac resynchronization therapy (CRT); however, the long-term stability of these leads is unknown. We sought to determine the implant success and long-term stability of CS leads in our single center experience. Methods: All consecutive patients who underwent CRT via implantation of the CS lead between January 1999 and December 2005 were included. Pacing thresholds at implant and during long-term follow-up were reviewed and the rate of acute (within 24 hours of implant) and chronic (>24 hours) lead failure was determined. Results: A total of 512 patients (mean age 68 ± 12 years; 409 [80%] male) underwent CRT device implantation and were included. The CS lead implantation was successful on the initial implantation in 487 patients (95%) and subsequently successful in six patients (24%) in whom initial attempts were unsuccessful. Acute lead failure occurred in 25 patients (5.1%) and was most commonly due to persistent extra-cardiac stimulation. The rate of chronic lead failure was 4% in the first year and remained stable during long-term follow-up. The CS lead pacing thresholds remained stable with only minimal increase (1.42 ± 0.85 V/0.42 ± 0.25 ms vs 1.51 ± 1.05 V/0.47 ± 0.29 ms; P = 0.04). Conclusions: Placement of a left ventricular pacing lead via the CS is feasible and safe in the vast majority of patients. Once placed, the CS leads remain stable with excellent pacing thresholds over the longer term. [source] Long-term stability of biological denitrification process for high strength nitrate removal from wastewater of uranium industryENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2008Prashant M. Biradar Abstract The aim of the present study was to biologically denitrify uranium nitrate raffinate (UNR) from nuclear industry, which is a principle source of high strength nitrate waste. To denitrify the high nitrate waste, a pilot-scale continuous stirred tank reactor was designed with two inbuilt settlers. Acclimatization of mixed culture with synthetic waste was carried out prior to the inoculation of the acclimatized sludge into the reactor. Initial concentration of nitrate in uranium raffinate was 77,000 mg/L NO3. It was diluted and used as a feed to the reactor. Concentration of nitrate in feed was increased gradually from 10,000 mg/L NO3 to 40,000 mg/L NO3 with hydraulic retention time (HRT) maintained at 34.4 h. Complete denitrification of 40,000 mg/L NO3 was achieved in a specified HRT. To facilitate understanding of the treatablity and long-term stability of biological denitrification of UNR, study was carried out for 211 days by periodical perturbation of the system. Furthermore, to find the volume ratio of reactor to settler required for the full-scale design of the denitrification plant, settling of acclimatized sludge was carried out. © 2008 American Institute of Chemical Engineers Environ Prog, 2008 [source] Modelling Approach for Planar Self-Breathing PEMFC and Comparison with Experimental Results,FUEL CELLS, Issue 4 2004A. Schmitz Abstract This paper presents a model-based analysis of a proton exchange membrane fuel cell,(PEMFC) with a planar design as the power supply for portable applications. The cell is operated with hydrogen and consists of an open cathode side allowing for passive, self-breathing, operation. This planar fuel cell is fabricated using printed circuit board,(PCB) technology. Long-term stability of this type of fuel cell has been demonstrated. A stationary, two-dimensional, isothermal, mathematical model of the planar fuel cell is developed. Fickian diffusion of the gaseous components,(O2, H2, H2O) in the gas diffusion layers and the catalyst layers is accounted for. The transport of water is considered in the gaseous phase only. The electrochemical reactions are described by the Tafel equation. The potential and current balance equations are solved separately for protons and electrons. The resulting system of partial differential equations is solved by a finite element method using FEMLAB,(COMSOL Inc.) software. Three different cathode opening ratios are realized and the corresponding polarization curves are measured. The measurements are compared to numerical simulation results. The model reproduces the shape of the measured polarization curves and comparable limiting current density values, due to mass transport limitation, are obtained. The simulated distribution of gaseous water shows that an increase of the water concentration under the rib occurs. It is concluded that liquid water may condense under the rib leading to a reduction of the open pore space accessible for gas transport. Thus, a broad rib not only hinders the oxygen supply itself, but may also cause additional mass transport problems due to the condensation of water. [source] Long-term stability of eating disorder diagnosesINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue S3 2007Manfred M. Fichter MD Abstract Objective: Data on the stability of eating disorder (ED) diagnoses (DSM-IV) over 12 years are presented for a large sample (N = 311) of female eating disordered patients with anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Method: Assessments were made at the beginning of therapy and 2-, 6-, and 12-year follow-ups. Diagnoses were derived from the Structured Inventory for Anorexic and Bulimic Eating Disorders. Possible diagnostic outcome categories were AN, BN, BED, NOS, no ED, and deceased. Results: At all follow-ups, more patients changed from AN or BED to BN than vice versa. No diagnostic crossover from AN to BED or vice versa occurred. BED showed the greatest variability and AN had the greatest stability over time. While the long-term outcome of BN and BED is similar, AN had a considerably worse long-term outcome than either BN or BED. Conclusion: Of the ED diagnoses, AN was most stable and BED most variable. The considerable diagnostic flux between BN and BED and similarities in course and outcome of BN and BED point to common biological and psychological maintaining processes. AN and BED are nosologically quite distant. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 2007 [source] Long-term stability of periodontal conditions achieved following guided tissue regeneration with bioresorbable membranes: case series results after 6,7 yearsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 11 2004Andreas Stavropoulos Abstract Objectives: To evaluate the results of guided tissue regeneration (GTR) treatment of intrabony defects with bioresorbable membranes after 6,7 years, and to disclose factors that may influence the long-term outcome of the treatment. Methods: Twenty-five defects in 19 patients were treated by means of polylactic acid/citric acid ester copolymer bioresorbable membranes. At baseline and after 1 and 6,7 years, the following parameters were recorded: (1) probing pocket depth (PPD), (2) gingival recession (REC), (3) probing attachment level (PAL)=PPD+REC, (4) presence/absence of plaque (PI), (5) presence/absence of bleeding on probing (BOP). Smoking habits and frequency of dental-control visits were also recorded. Significance of differences between categorical variables was evaluated with McNemar's test, and between numerical variables with the t -test for paired observations. Generalized linear models were constructed to evaluate the influence of various factors on PAL gain and PPD changes from 1 to 6,7 years. Association of smoking, frequency of dental controls, oral hygiene, and BOP with sites losing 2 mm in PAL was evaluated with Fisher's exact test. Results: At baseline, a mean PPD of 8.7±1.1 mm and a mean PAL of 9.8±1.5 mm was recorded. Statistically significant clinical improvements were observed at 1 and 6,7 years after GTR treatment. An average residual PPD of 3.8±1.1 mm and a mean PAL gain of 3.8±1.4 mm were observed after 1 year. After 6,7 years the corresponding values were 4.7±1.3 and 3.6±1.4 mm, respectively. There were no statistically significant differences between the 1- and the 6,7-year values. At the 6,7-year control, only 16% of the sites had lost 2 mm (maximum 3 mm), of the PAL gain obtained 1 year after GTR treatment. None of the sites had lost all of the attachment gained 1 year after treatment. Smoking, frequency of dental controls, oral hygiene, and BOP did not seem to influence the change of PPD and PAL gain, or the stability of PAL gain (i.e. losing PAL or not) from 1 to 6,7 years from treatment. Conclusion: Clinical improvements achieved by GTR treatment of intrabony defects by means of bioresorbable membranes can be maintained on a long-term basis. [source] Childhood Personality Predicts Long-Term Trajectories of Shyness and Aggressiveness in the Context of Demographic Transitions in Emerging AdulthoodJOURNAL OF PERSONALITY, Issue 1 2008Jaap J. A. Dennissen ABSTRACT In a 19-year longitudinal study, childhood personality characteristics (assessed by teachers at ages 4 to 6) were significantly related to both initial levels and changes in parental judgments of shyness and aggressiveness. Long-term stability was demonstrated by the fact that overcontrollers had consistently higher scores in shyness and undercontrollers in aggressiveness. However, undercontrollers' shyness and overcontrollers' aggressiveness changed over time from a low to a high level. Also, both types assumed adult social roles, such as leaving the parental home, establishing a first romantic relationship, and getting a part-time job, at a later time than the resilient participants. A mediation analysis indicated that under- and overcontrollers' increasing aggressiveness between age 17 and 23 was due to their longer latency of getting a part-time job. Together, results demonstrate the importance of considering person-environment transactions in explaining both change and stability in personality between childhood and adulthood. [source] Long-term stability of an ambient self-curable latex based on colloidal dispersions in water of two reactive polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2005Xiaonong Chen Abstract An ambient self-curable latex (ASCL) was prepared via the blending of colloidal dispersions in water of a chloromethylstyrene-functionalized copolymer and a tertiary-amine-functionalized copolymer. Upon casting and drying under ambient conditions, the ASCL could generate crosslinked continuous polymer films. The crosslinking occurred via the Menschutkin reaction (quaternization) between the two types of functional groups. Because this reaction was reversible at high temperatures, the films could be decrosslinked and hence were self-curable. The prepared ASCL exhibited excellent colloidal and chemical stability during long-term storage: no significant changes in the colloidal properties, such as the particle size, electrophoretic mobility, and crosslinking reactivity, were observed after 48 months of storage. The electrophoretic measurements indicated that the electrostatic repulsion between the negatively charged particles of the ASCL was responsible for the excellent stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2598,2605, 2005 [source] The resonant structure of Jupiter's Trojan asteroids , I. Long-term stability and diffusionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006P. Robutel ABSTRACT We study the global dynamics of the jovian Trojan asteroids by means of the frequency map analysis. We find and classify the main resonant structures that serve as skeleton of the phase space near the Lagrangian points. These resonances organize and control the long-term dynamics of the Trojans. Besides the secondary and secular resonances, that have already been found in other asteroid sets in mean motion resonance (e.g. main belt, Kuiper belt), we identify a new type of resonance that involves secular frequencies and the frequency of the great inequality, but not the libration frequency. Moreover, this new family of resonances plays an important role in the slow transport mechanism that drives Trojans from the inner stable region to eventual ejections. Finally, we relate this global view of the dynamics with the observed Trojans, identify the asteroids that are close to these resonances and study their long-term behaviour. [source] Original Article: Long-term stability of thyroid hormones and DNA in blood spots kept under varying storage conditionsPEDIATRICS INTERNATIONAL, Issue 4 2010Asmahan A. EL Ezzi Abstract Background:, Congenital hypothyroidism is screened using blood spotted on filter paper that may be transported from remote areas to central testing facilities. However, storage conditions and transportation may affect sample quality. Methods:, We examined long-term stability of thyroid-stimulating hormone (TSH) and thyroxin (TT4) in blood spotted on filter paper, which was stored at room temperature (RT), 4°C and ,20°C under continuous or intermittent power supply (six hours on and six hours off around the clock.) Hormone levels in the discs were measured periodically for up to ten years. Extraction of DNA from blood spots and polymerase chain reaction were performed. Results:, Our results showed that TT4 was stable for up to 6.1, 5.34 and 5.16 years when stored at ,20°C, 4°C and RT, respectively. TSH was stable for up to 2.7 years at RT, and for up to 6.5 and 4.1 years when stored at ,20°C and 4°C, respectively, under continuous power supply. However, under intermittent power supply, TSH was stable for up to 3.8 and 2.5 years when stored at 4°C and ,20°C, respectively. Mitochondrial cytochrome oxidase and sex-determining region of Y chromosome genes were successfully amplified from DNA extracted from the blood spots. Conclusion:, Our data indicate that TT4 and TSH are most stable in blood spots stored at ,20°C under continuous power supply. However, they can be stored at RT or at 4°C and ,20°C under interrupted power supply for at least 2.5 years. Moreover, the DNA extracted from the blood spots was intact and suitable for genetic studies. [source] Long-term stability of dye-sensitised solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2001A. Hinsch Accelerated ageing tests on large numbers of nanocrystalline dye-sensitised solar cells (nc-DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye-sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd. [source] Novel multi-peptide vaccination in Hla-A2+ hormone sensitive patients with biochemical relapse of prostate cancerTHE PROSTATE, Issue 9 2009Susan Feyerabend Abstract BACKGROUND A phase I/II trial was conducted to assess feasibility and tolerability of tumor associated antigen peptide vaccination in hormone sensitive prostate carcinoma (PC) patients with biochemical recurrence after primary surgical treatment. METHODS Nineteen HLA-A2 positive patients with rising PSA without detectable metastatic disease or local recurrence received 11 HLA-A*0201-restricted and two HLA class II synthetic peptides derived from PC tumor antigens subcutaneously for 18 months or until PSA progression. The vaccine was emulgated in montanide ISA51 and combined with imiquimod, GM-CSF, mucin-1-mRNA/protamine complex, local hyperthermia or no adjuvant. PSA was assessed, geometric mean doubling times (DT) calculated and clinical performance monitored. RESULTS PSA DT of 4 out of 19 patients (21%) increased from 4.9 to 25.8 months during vaccination. Out of these, two patients (11%) exhibited PSA stability for 28 and 31 months which were still continuing at data cut-off. One patient showed no change of PSA DT during vaccination but decline after the therapy. Three patients had an interim PSA decline or DT increase followed by DT decrease compared to baseline PSA DT. Three of the responding patients received imiquimod and one the mucin-1-mRNA/protamine complex as adjuvant; both are Toll-like receptor-7 agonists. Eleven (58%) patients had progressive PSA values. The vaccine was well tolerated, and no grade III or IV toxicity occurred. CONCLUSION Multi-peptide vaccination stabilized or slowed down PSA progress in four of 19 cases. The vaccination approach is promising with moderate adverse events. Long-term stability delayed androgen deprivation up to 31 months. TLR-7 co-activation seems to be beneficial. Prostate 69: 917,927, 2009. © 2009 Wiley-Liss, Inc. [source] Long-term stability of edible preferences in individuals with developmental disabilitiesBEHAVIORAL INTERVENTIONS, Issue 3 2007Francis J. Ciccone Multiple stimulus without replacement (MSWO) preference assessments were used to examine the stability of preference hierarchies in eight individuals with developmental disabilities. In Study 1, preference assessments using edible items were conducted 6 months apart; in Study 2, assessments were conducted 12 months apart. As in previous studies analyzing preference stability, individual differences in stability were found in both studies. However, mean rank order coefficients across participants revealed interesting findings in both comparisons. Generally, preference for edible items, particularly the most and least preferred stimuli, was more stable across time than has been found in other research conducted with leisure items. Stability was greater when only 6 months lapsed between assessments. Moreover, for three of the eight participants, rank order coefficients were significant across both studies indicating the possibility that some individuals may tend toward more stable preferences. Copyright © 2007 John Wiley & Sons, Ltd. [source] Long-term stability of hornet cuticular hydrocarbons facilitates chemotaxonomy using museum specimensBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009STEPHEN J. MARTIN Cuticular hydrocarbons are key compounds used for insect chemical communication and their species-specificity makes them of great utility to chemotaxonomists. However, very little is known about their long-term stability in relation to their use as reliable taxonomic tools. We compared the cuticular hydrocarbon profiles of fresh extracts from four hornet (Vespa) species with extracts from specimens that were frozen for 1 year and of those stored in insect display boxes for 20 years. Cuticular hydrocarbon profiles were qualitatively very stable, maintaining their species-specific profiles even after 20 years. The long-term stability of cuticular hydrocarbons in hymenopterans opens up the possibility of using museum collections for chemotaxonomy studies and helping with the delineation of species in difficult groups. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 732,737. [source] Synthesis and Characterization of a New Class of Energetic Compounds , Ammonium NitriminotetrazolatesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2008Thomas Abstract 1-Methyl-5-nitriminotetrazole (1) and 2-methyl-5-nitraminotetrazole (2) obtained by nitration of 1-methyl-5-aminotetrazole (3) and 2-methyl-5-aminotetrazole (4) were deprotonated using aqueous ammonia solution yielding the energetic compounds, ammonium 1-methyl-5-nitriminotetrazolate (5) and ammonium 2-methyl-5-nitriminotetrazolate (6). The nitrogen-rich salts were tested and characterized comprehensively using vibrational spectroscopy (Infrared (IR) and Raman), multinuclear (1H, 13C, 14N, and 15N) NMR spectroscopy, and elemental analysis. The molecular structures in the crystalline state were determined using low temperature single crystal X-ray diffraction. The thermal behavior and the decompositions were investigated using differential scanning calorimetry (DSC) and gas IR spectroscopy. The heats of formation were calculated using bomb calorimetric measurements. In addition, the relevant detonation parameters, like the detonation pressure and velocity of detonation were calculated using the software EXPLO5 outperforming the values of TNT. Last but not least the sensitivities were determined using BAM methods showing moderate values against impact and friction (drophammer and friction tester) and the long-term stabilities were tested using Flexy Thermal safety calorimetry (TSC). X-ray crystallography: 5: monoclinic, P21/c, a=370.06(2),pm, b=2079.06(9),pm, c=859.69(5),pm, ,=99.120(5)°, V=65306(6),pm3, Z=4, ,calc=1.639,g cm,3; 6: monoclinic, P21, a=365.39(2),pm, b=,788.82(5),pm, c=1124.95(7),pm, ,=91.818(6), V=32408(3),pm3, Z=2, ,calc=1.651,g cm,3. [source] Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion BiocompositeELECTROANALYSIS, Issue 3 2010Kangfu Zhou Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source] Flow-Through Assay of Quinine Using Solid Contact Potentiometric Sensors Based on Molecularly Imprinted PolymersELECTROANALYSIS, Issue 24 2009Ayman Abstract Miniaturized potentiometric membrane sensors for quinine incorporated with molecular imprinted polymer (MIP) were synthesized and implemented. Planar PVC based polymeric membrane sensors containing quinine-methacrylic and/or acrylic acid-ethylene glycol methacrylate were dispensed into anisotropically etched wells on polyimide wafers. The determination of quinine was carried out in acidic solution at pH,6, where positively charged species predominated prevalently. The suggested miniaturized planner sensors exhibited marked selectivity, sensitivity, long-term stability and reproducibility. At their optimum conditions, the sensors displayed wide concentration ranges of 4.0×10,6,1.0×10,2mol L,1 and 1.0×10,5,1.0×10,2 mol L,1 with slopes of about 61.3,55.7,mV decade,1; respectively. Sensors exhibit detection limits of 1.2×10,6 and 8.2×10,6 mol L,1 upon the use of methacrylic and acrylic acid monomers in the imprinted polymer, respectively. Validation of the assay method according to the quality assurance standards (range, within-day repeatability, between-day variability, standard deviation, accuracy, and good performance characteristics) which could assure good reliable novel sensors for quinine estimation was justified. Application of the proposed flow-through assay method for routine determination of quinine in soft drinks was assayed and the results compared favorably with data obtained by the standard fluorimetric method. [source] A Contactless Impedance Probe for Simple and Rapid Determination of the Ratio of Liquids with Different Permittivities in Binary MixturesELECTROANALYSIS, Issue 1 2009Franti, ek Opekar Abstract Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long-term stability and the possibility of powering them from a battery make them suitable for hand-held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol. [source] Direct Electrochemistry and Electrocatalysis of Myoglobin Immobilized on Gold Nanoparticles/Carbon Nanotubes Nanohybrid FilmELECTROANALYSIS, Issue 17 2008Wei Cao Abstract A novel nanohybrid material, constructed by gold nanoparticles (GNPs) and multiwalled carbon nanotubes (MWNTs), was designed for immobilization and biosensing of myoglobin (Mb). Morphology of the nanohybrid film was characterized by SEM. UV-vis spectroscopy demonstrated that Mb on the composite film could retain its native structure. Direct electrochemistry of Mb immobilized on the GNPs/MWNTs film was investigated. The immobilized Mb showed a couple of quasireversible and well-defined cyclic voltammetry peaks with a formal potential of about ,0.35,V (vs. Ag/AgCl) in pH,6.0 phosphate buffer solution (PBS) solution. Furthermore, the modified electrode also displayed good sensitivity, wide linear range and long-term stability to the detection of hydrogen peroxide. The experiment results demonstrated that the hybrid matrix provided a biocompatible microenvironment for protein and supplied a necessary pathway for its direct electron transfer. [source] Renewable Copper and Silver Amalgam Film Electrodes of Prolonged Application for the Determination of Elemental Sulfur Using Stripping VoltammetryELECTROANALYSIS, Issue 7 2008Robert Piech Abstract New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12,mm2, both electrodes are characterized by very good surface reproducibility (,2%) and long-term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1,2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16,ng L,1 to 4.8,,g L,1 for Hg(Cu)FE, and up to 6.4,,g L,1 for Hg(Ag)FE (tacc=15,s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60,s are as low as 14,ng L,1 for Hg(Cu)FE and 4,ng L,1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. [source] Nitrate-Selective Solid Contact Electrodes with Poly(3-octylthiophene) and Poly(aniline) as Ion-to-Electron Transducers Buffered with Electron-Ion-Exchanging ResinELECTROANALYSIS, Issue 13-14 2006Galina Abstract The study of nitrate selective solid contact electrodes containing poly(3-octyl)thiophene and poly(aniline) demonstrated the advantage of buffering the transducing layer with electron-ion-exchanging resin. The buffering, in particular in the case of poly(aniline) doped with nitrate anions ensured significant improvement of the long-term stability and piece-to-piece reproducibility of the electrode potentials. It is shown that the redox species causes potential drift after a long time delay, probably because of slow diffusion in the membrane bulk. [source] Direct and Rapid Detection of Diphtherotoxin via Potentiometric Immunosensor Based on Nanoparticles Mixture and Polyvinyl Butyral as MatrixesELECTROANALYSIS, Issue 24 2005Dianping Tang Abstract In this paper a novel potentiometric immunosensor for direct and rapid detection of diphtherotoxin (D-Ag) has been developed by means of self-assembly of monoclonal diphtheria antibody (D-Ab) onto a platinum electrode based on nanoparticles mixture (containing gold nanoparticles and silica nanoparticles) and polyvinyl butyral (PVB) as matrixes. At first, D-Ab was absorbed onto the surface of nanoparticles mixture, and then they were entrapped into polyvinyl butyral sol-gel network on a platinum electrode. The detection is based on the change in the potentiometric response before and after the antigen-antibody reaction in a phosphate buffer solution (pH,7.0). The immobilized D-Ab exhibited direct potentiometric response toward D-Ag. In comparison to the conventional applied methods, this strategy could allow antibodies immobilized with higher loading amount and better retained immunoactivity, as demonstrated by potentiometric response, cyclic voltammetry and electrochemical impedance spectroscopy of the immunosensor. The immunosensor with nanoparticles mixture exhibited much higher sensitivity, better reproducibility, and long-term stability than that with gold nanoparticles or silica nanoparticles alone. The linear range was from 5.0×10,3 to 1.2,,g,mL,1 with a detection limit of 1.1×10,3,,g,mL,1. Up to 16 successive assay cycles with retentive sensitivity were achieved for the probes regenerated with in 0.2,mol,L,1 glycine-hydrochloric acid (Gly-HCl) buffer solution and 0.25,mol,L,1 NaCl. Moreover, the immunosensor with nanoparticles mixture was applied to evaluate a number of practical specimens with potentiometric results in acceptable agreement with those given by the ELISA method, implying a promising alternative approach for detecting diphtherotoxin in the clinical diagnosis. [source] Chitosan-Glutamate Oxidase Gels: Synthesis, Characterization, and Glutamate DeterminationELECTROANALYSIS, Issue 23 2005Maogen Zhang Abstract The biopolymer chitosan (CHIT) was chemically modified with glutaric dialdehyde (GDI) and used for the covalent immobilization of enzyme glutamate oxidase (GmOx). The relationships between the loaded, retained, and active units of GmOx in the CHIT-GDI-GmOx gels were determined by electrochemical assays. The latter indicated that on average ca. 95% of the GmOx was retained in the CHIT-GDI matrix that was loaded with 0.10,3.0 units of the enzyme. The maximum activity of the GmOx immobilized in the gels corresponded to ca. 5% of the activity of the free enzyme. Platinum electrodes coated with CHIT-GDI-GmOx gels (films) were used as amperometric biosensors for glutamate. Such biosensors displayed good operational and long-term stability (at least 11,h and 100 days, respectively) in conjunction with low detection limit of 0.10,,M glutamate (S/N=3), linear range up to 0.5,mM (R2=0.991), sensitivity of 100 mA M,1 cm,2, and short response time (t90%=2,s). This demonstrated an efficient signal transduction in the Pt/CHIT-GDI-GmOx+glutamate system. The CHIT-GDI-GmOx gels constitute a new biosensing element for the development of glutamate biosensors. [source] Carbon nanotube/poly(methyl methacrylate) composite electrode for capillary electrophoretic measurement of honokiol and magnolol in Cortex Magnoliae OfficinalisELECTROPHORESIS, Issue 16 2006Xiao Yao Abstract This paper describes the development and the application of a novel carbon nanotube/poly(methyl methacrylate) (CNT/PMMA) composite electrode as a sensitive amperometric detector of CE. The composite electrode was fabricated on the basis of the in,situ polymerization of a mixture of CNT and prepolymerized methylmethacrylate in the microchannel of a piece of fused-silica capillary under heat. The performance of this unique system has been demonstrated by separating and detecting honokiol and magnolol in traditional Chinese medicine, Cortex Magnoliae Officinalis. Factors influencing their separation and detection processes were examined and optimized. Honokiol and magnolol were well separated within 7,min in a 40 cm long capillary at a separation voltage of 15,kV using a 50 mM borate buffer (pH,9.2). The new CNT-based CE detector offered significantly lower operating potentials, yielded substantially enhanced S/N characteristics, and exhibited resistance to surface fouling and hence enhanced stability. It demonstrated long-term stability and reproducibility with RSDs of less than 5% for the peak current (n = 9) and should also find a wide range of applications in microchip CE, flowing injection analysis, and other microfluidic analysis systems. [source] Long-term stability of biological denitrification process for high strength nitrate removal from wastewater of uranium industryENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2008Prashant M. Biradar Abstract The aim of the present study was to biologically denitrify uranium nitrate raffinate (UNR) from nuclear industry, which is a principle source of high strength nitrate waste. To denitrify the high nitrate waste, a pilot-scale continuous stirred tank reactor was designed with two inbuilt settlers. Acclimatization of mixed culture with synthetic waste was carried out prior to the inoculation of the acclimatized sludge into the reactor. Initial concentration of nitrate in uranium raffinate was 77,000 mg/L NO3. It was diluted and used as a feed to the reactor. Concentration of nitrate in feed was increased gradually from 10,000 mg/L NO3 to 40,000 mg/L NO3 with hydraulic retention time (HRT) maintained at 34.4 h. Complete denitrification of 40,000 mg/L NO3 was achieved in a specified HRT. To facilitate understanding of the treatablity and long-term stability of biological denitrification of UNR, study was carried out for 211 days by periodical perturbation of the system. Furthermore, to find the volume ratio of reactor to settler required for the full-scale design of the denitrification plant, settling of acclimatized sludge was carried out. © 2008 American Institute of Chemical Engineers Environ Prog, 2008 [source] Four-year water degradation of a resin-modified glass-ionomer adhesive bonded to dentinEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2004Jan De Munck Glass-ionomers are auto-adhesive to tooth tissue through combined micro-mechanical and chemical bonding. How much each of the two bonding components contributes to the actual bonding effectiveness is, however, not known and there is not much information available on long-term stability. The objective of this study was to assess the bonding effectiveness of a resin-modified glass-ionomer adhesive to dentin after 4 yr of water storage. Fuji Bond LC (GC) was applied without (i) and with pretreatment using (ii) a polyalkenoic acid conditioner and (iii) a 37.5% phosphoric acid etchant. The etchant was used to exclude any chemical interaction with hydroxyapatite. The micro-tensile bond strength (µTBS) to dentin decreased significantly over the 4 yr period in all three experimental groups. After 24 h and 4 yr, the lowest µTBS was recorded when dentin was not pretreated. The highest µTBS was obtained following polyalkenoic acid pretreatment, although this was not significantly different from specimens that were pretreated using phosphoric acid. Pretreating dentin with phosphoric acid intensified micromechanical interlocking at the expense of chemical bonding potential to hydroxyapatite. Nevertheless, correlating the µTBS data with failure analysis through scanning electron microscopy and transmission electron microscopy indicated that combined micro-mechanical and chemical bonding involving pretreatment with the polyalkenoic acid conditioner yielded the most durable bond. [source] Organic Electronics: High Tg Cyclic Olefin Copolymer Gate Dielectrics for N,N,-Ditridecyl Perylene Diimide Based Field-Effect Transistors: Improving Performance and Stability with Thermal Treatment (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Mater. Abstract A novel application of ethylene-norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field-effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally-treated N,N, -ditridecyl perylene diimide (PTCDI-C13)-based n-type FETs using a COC/SiO2 gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95° ± 1°) and high thermal stability (glass transition temperature = 181 °C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI-C13 domains grown on the COC/SiO2 gate dielectric increases significantly. The resulting n-type FETs exhibit high atmospheric field-effect mobilities, up to 0.90 cm2 V,1 s,1 in the 20 V saturation regime and long-term stability with respect to H2O/O2 degradation, hysteresis, or sweep-stress over 110 days. By integrating the n-type FETs with p-type pentacene-based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized. [source] High Tg Cyclic Olefin Copolymer Gate Dielectrics for N,N,-Ditridecyl Perylene Diimide Based Field-Effect Transistors: Improving Performance and Stability with Thermal TreatmentADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Jaeyoung Jang Abstract A novel application of ethylene-norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field-effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally-treated N,N, -ditridecyl perylene diimide (PTCDI-C13)-based n-type FETs using a COC/SiO2 gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95° ± 1°) and high thermal stability (glass transition temperature = 181 °C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI-C13 domains grown on the COC/SiO2 gate dielectric increases significantly. The resulting n-type FETs exhibit high atmospheric field-effect mobilities, up to 0.90 cm2 V,1 s,1 in the 20 V saturation regime and long-term stability with respect to H2O/O2 degradation, hysteresis, or sweep-stress over 110 days. By integrating the n-type FETs with p-type pentacene-based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized. [source] Stable Inverted Polymer/Fullerene Solar Cells Using a Cationic Polythiophene Modified PEDOT:PSS Cathodic InterfaceADVANCED FUNCTIONAL MATERIALS, Issue 15 2010David A. Rider Abstract A cationic and water-soluble polythiophene [poly[3-(6-pyridiniumylhexyl)thiophene bromide] (P3PHT+Br,)] is synthesized and used in combination with anionic poly(3,4-ethylenedioxythiophene):poly(p -styrenesulfonate) (PEDOT:PSS), to produce hybrid coatings on indium tin oxide (ITO). Two coating strategies are established: i) electrostatic layer-by-layer assembly with colloidal suspensions of (PEDOT:PSS),, and ii) modification of an electrochemically prepared (PEDOT:PSS), film on ITO. The coatings are found to modify the work function of ITO such that it could act as a cathode in inverted 2,5-diyl-poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) polymer photovoltaic cells. The interfacial modifier created from the layer-by-layer assembly route is used to produce efficient inverted organic photovoltaic devices (power conversion efficiency ,2%) with significant long-term stability in excess of 500,h. 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