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Doping Agent (doping + agent)
Selected AbstractsImproved Hydrogen Storage Properties of Ti-Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents,ADVANCED MATERIALS, Issue 12 2003B. Bogdanovi By using nanosized doping agents, the properties of Ti-catalyzed NaAlH4 storage systems are considerably improved. Hydrogenation,dehydrogenation cyclic testing shows that with nanosized TiN dopants, storage capacities of 5 wt.-% H2 could be achieved. Doping with nanosized Ti brought hydrogenation times close to those required for practical applications, combined with high capacity (4.5 wt.-% H2, see Figure). [source] Determination of 13C/12C ratios of urinary excreted boldenone and its main metabolite 5,-androst-1-en-17,-ol-3-oneDRUG TESTING AND ANALYSIS, Issue 5 2010Thomas Piper Abstract Boldenone (androsta,1,4,dien,17,,ol,3,one, Bo) is an anabolic steroid known to have been used in cattle breeding or equine sport as a doping agent for many years. Although not clinically approved for human application, Bo or its main metabolite 5,-androst-1-en-17,-ol-3-one (BM1) were detected in several doping control samples. For more than 15 years the possibility of endogenous Bo production in human beings has been discussed. This is a challenging issue for doping control laboratories as Bo belongs to the list of prohibited substances of the World Anti-Doping Agency and therefore the chance for false positive testing is significant. By GC/C/IRMS (gas chromatography/combustion/isotope ratio mass spectrometry) it should be possible to analyze the 13C/12C ratio of either Bo or BM1 and to distinguish whether their source is endogenous or exogenous. Therefore a method was developed to determine the 13C/12C ratios of Bo, BM1, pregnanediol, androsterone, etiocholanolone, and testosterone from a single urine specimen. The validity of the method was ensured by repeated processing of urine fortified with 2,50 ng/mL Bo and BM1. The specificity of the method was ensured by gas chromatography/mass spectrometry determinations. Out of 23 samples investigated throughout the last four years, 11 showed 13C/12C ratios of Bo or BM1 inconsistent with an exogenous origin. Two of these samples were collected from the same athlete within a one-month interval, strongly indicating the chance of endogenous Bo production by this athlete. Copyright © 2010 John Wiley & Sons, Ltd. [source] Enhanced Electrical Switching and Electrochromic Properties of Poly(p-phenylenebenzobisthiazole) Thin Films Embedded with Nano-WO3ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Jiahua Zhu Abstract The electrical switching and electrochromic phenomena of a novel nanocomposite comprising poly(p-phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO3) nanoparticles are investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfonic acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%). The electrical conductivity of 5% WO3/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as-received PBZT and PBZT/CSA thin films. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow an ohmic conduction mechanism. Stable electrical conductivity switching is observed before and after applying a bias on the pristine PBZT and WO3/PBZT nanocomposite thin films. Electrochromic phenomena of both PBZT and WO3/PBZT nanocomposite thin films with high contrast ratio are observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed. [source] Synthesis and characterization of imine-coupled polyphenols containing carbazole unitsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009smet Kaya Abstract Imine coupled phenolic monomers containing carbazole unit were synthesized in four steps. The monomers were polymerized via oxidative polycondensation by air as oxidant in an aqueous alkaline medium at 50°C. The structures of compounds were confirmed by ultraviolet,visible (UV,vis), Fourier transform infrared, and 1H- and 13C-NMR techniques. The conductivity measurements of these polymers were made by the four-point probe technique and iodine was used as doping agent. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electrochemical and optical band gap values were calculated by the results of the UV,vis and the cyclic voltammetry measurement, respectively. The number-average molecular weight, weight-average molecular weight, and polydispersity index values were determined by the size exclusion chromatography technique. Also, thermal behavior of these polymers was determined by thermogravimetric/differential thermal analysis measurements in a N2 atmosphere between 20 and 1000°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Dual functionality of PTSA as electrolyte and dopant in the electrochemical synthesis of polyaniline, and its effect on electrical propertiesPOLYMER INTERNATIONAL, Issue 7 2007Sambhu Bhadra Abstract The electrochemical synthesis of polyaniline (PAni) powder was carried out from an aqueous solution of 0.15 mol L,1 aniline with varying concentrations of p -toluenesulphonic acid (PTSA) at room temperature. The PAni samples thus obtained were characterized using DC and AC conductivity, dielectric properties, infrared spectroscopy, thermogravimetric analysis, X-ray analysis, scanning electron microscopy and ultraviolet spectroscopy. Results showed that PTSA is acting both as electrolyte and doping agent. With an increase in the PTSA concentration, there is more polaron formation, and this means an increase in charge carrier concentration and mobility. This accounts for the increase in conductivity and improved dielectric properties of the resultant PAni. The polymer was subjected to a heating and cooling cycle. The change in conductivity during the heating cycle is quite different from that during the cooling cycle, indicating some kind of hysteresis phenomenon occurring in the system. Moreover there is a net decrease in room temperature conductivity of PAni when subjected to the heating,cooling cycle. This may be due to the oxidation of PAni and generation of some kind of disorder in the structure of PAni during the heating,cooling process. Copyright © 2007 Society of Chemical Industry [source] Improved Hydrogen Storage Properties of Ti-Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents,ADVANCED MATERIALS, Issue 12 2003B. Bogdanovi By using nanosized doping agents, the properties of Ti-catalyzed NaAlH4 storage systems are considerably improved. Hydrogenation,dehydrogenation cyclic testing shows that with nanosized TiN dopants, storage capacities of 5 wt.-% H2 could be achieved. Doping with nanosized Ti brought hydrogenation times close to those required for practical applications, combined with high capacity (4.5 wt.-% H2, see Figure). [source] Emerging drugs: mechanism of action, mass spectrometry and doping control analysisJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2009Mario Thevis Abstract The number of compounds and doping methods in sports is in a state of constant flux. In addition to ,traditional' doping agents, such as anabolic androgenic steroids or erythropoietin, new therapeutics and emerging drugs have considerable potential for misuse in elite sport. Such compounds are commonly based on new chemical structures, and the mechanisms underlying their modes of action represent new therapeutic approaches arising from recent advances in medical research; therefore, sports drug testing procedures need to be continuously modified and complementary methods developed, preferably based on mass spectrometry, to enable comprehensive doping controls. This tutorial not only discusses emerging drugs that can be categorized as anabolic agents (selective androgen receptor modulators, SARMs), gene doping [hypoxia-inducible factor stabilizers, peroxisome-proliferator-activated receptor (PPAR),-agonists] and erythropoietin-mimetics (Hematide) but also compounds with potentially performance-enhancing properties that are not classified in the current list of the World Anti-Doping Agency. Compounds such as ryanodine-calstabin-complex modulators (benzothiazepines) are included, their mass spectrometric properties discussed, and current approaches in sports drug testing outlined. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||