THE EFFECT OF DOPING WITH TANTALUM ON THE PROPERTIES OF YBA2CU3O7-Y

YBa2Cu3-xTaxO7-y (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared, X-ray diffraction shows that the system remains orthorhombic for all compositions studied but. for x > 0.2, Ta2O5 was detected as an impurity phase. Substitution of Ta5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)O planes. The introduction of the high-valence element tantalum produces extra free electrons. These electrons recombine with the positive carrier of the system, which causes the mobility and the Hall number of YBa2Cu3-xTaxO7-y to decrease and also results in a depression in T(c).

DOPING EFFECTS ON THE POLYMER-CHAIN STRUCTURE OF POLY(3-METHYLTHIOPHENE)

The C=C stretching Raman shifts and photoluminescence (PL) for poly(3-methylthiophene) (P3MT) are measured at various doping levels by in situ electrochemical Raman and PL spectroscopic techniques. It is found that the doping for P3MT induces the nonlinear excitations (soliton, Polaron, bipolaron), but also affects the polymer-chain structure, including the conjugated length and the interchain distance.

LIGHT-ASSISTED OXIDATIVE DOPING OF POLYANILINES

A novel doping phenomenon of fully reduced polyaniline and poly-o-methyl-aniline, "light-assisted oxidative doping", was found for the first time. The doping reaction was followed by FTIR, UV-VIS, ESR and electrical conductivity measurements. It was shown that the fully reduced polyanilines in the form of HCl-salts undergo a spontaneous transition from an insulator or semiconductor to a conductor when exposed to air and light, and their final molecular chain structures are analogous to those found in HCl-doped common polyanilines.

ON THE IODINE-DOPING OF POLYANILINE AND POLY-ORTHO-METHYLANILINE

The reactions of polyaniline and poly-omicron-methylaniline of different oxidation degrees with I2 were followed by FTIR and electrical conductivity measurements. The results showed that the reaction of common polyanilines with I2 was oxidation in nature whereas that of the fully reduced ones was doping. The latter took place in two steps: oxidation of benzene-diamine units into quinone-diimine units (redox between I2 and the polymer chain) and formation of a conjugated system consisting of four aromatic rings (intramolecular chain redox).

Post-grafting preparation of large-pore mesoporous materials with localized high content titanium doping

A new post-grafting process, consisting of two steps of substrate preparation and sol - gel post-grafting, has been developed to prepare titanium-doped mesoporous SBA-15 material with a double-layered structure and locally concentrated titanium content at the inner pore surface. With this novel technique, the single phased and originally ordered mesostructures can be well conserved; in the conventional direct synthesis they can be partially damaged when the frameworks are doped with high content heteroatoms. Titanium species exist in an isolated, tetrahedral structure and are localized at the pore surface; this is beneficial to both reactant access and product release. Characterization with XRD, N-2 adsorption/desorption isotherms, HREM/ EDS, ICP, UV - Vis, and the newly developed UV - Raman spectroscopy confirm these results. Preliminary catalytic tests with the selective epoxidation of cyclohexene show good catalytic activity. Among them, sample TiSBA-15-10 with a Si : Ti molar ratio of 10 shows a TON value of 75 and a highest product ( epoxide) yield of 55%.

Tailoring the morphology of WO₃films with substitutional cation doping: Effect on the photoelectrochemical properties

With the aim of improving the performance and extending the range of applications of mesoporous WO₃films, which were initially developed for the photoelectrochemical oxidation of water, we investigated the effect of a number of dopants (lithium, silicon, ruthenium, molybdenum and tin) upon the transparency, crystallinity, porosity and conductivity of the modified films. Tin, molybdenum and silicon were shown to improve the electrochromic behaviour of the layers whereas ruthenium enhanced considerably the electronic conductivity of the WO₃films. Interestingly, most of the dopants also affected the film morphology and the size of WO₃nanocrystals. X-ray photoelectron spectra revealed absence of significant segregation of doping elements within the film. Raman analyses confirmed that the monoclinic structure of WO₃films does not change upon substitutional cation doping; thus, the crystallinity of WO₃films is maintained.

Mid-infrared a-b plane response of YBa2Cu3O7-delta as a function of doping and temperature determined by attenuated total reflection

The mid-infrared optical response of c-axis thin films of YBa2Cu3O7-delta has been studied using Otto-configuration attenuated total reflectance. The measured reflectance-angle characteristics are dominated by a strong absorption feature due to the excitation of surface plasmons, and can be modeled to determine the a-b plane dielectric function. The results show that while epsilon(i,) and therefore sigma(r), are temperature independent, \epsilon(r)\ exhibits a moderate decrease with generalized Drude analysis shows that the plasma frequency is independent of temperature, but decreases with decreasing doping. The scattering rate increases with temperature, and also increases with decreasing doping, consistent with stronger coupling in the underdoped regime. The mass-enhancement is small but increases to 30-40% at delta = 0.6. Difficulties in reconciling the results with some current theories of high-T-c materials are discussed. Finally, the surface plasmon propagation lengths and penetration depths are shown to vary systematically with doping. (C) 2003 Elsevier B.V. All rights reserved.

Doping, sport and the law: time for repeal of prohibition?

This article concerns the legal issues that surround the prohibition of doping in sport. The current policy on the use of performance enhancing drugs (PEDs) in sport is underpinned by both a paternalistic desire to protect athletes’ health and the long-term integrity or ‘spirit’ of sport. The policy is put into administrative effect globally by the World Anti-Doping Agency (WADA), which provides the regulatory and legal framework through which the vast majority of international sports federations harmonise their anti-doping programmes. On outlining briefly both the broad administrative structures of international sport’s various anti-doping mechanisms, and specific legal issues that arise in disciplinary hearings involving athletes accused of doping, this article questions the sustainability of the current ‘zero tolerance’ approach, arguing, by way of analogy to the wider societal debate on the criminalisation of drugs, and as informed by Sunstein and Thaler’s theory of libertarian paternalism, that current policy on anti-doping has failed. Moreover, rather than the extant moral and punitive panic regarding doping in sport, this article, drawing respectively on Seddon’s and Simon’s work on the history of drugs and crime control mentality, contends that, as an alternative, harm reductionist measures should be promoted, including consideration of the medically supervised use of certain PEDs.

LC- HRMS based metabolomics in food safety and doping control – DeTECH21

Issues surrounding the misuse of prohibited and licensed substances in animals destined for food production and performance sport competition continue to be an enormous challenge to regulatory authorities charged with enforcing their control. Efficient analytical strategies are implemented to screen and confirm the presence of a wide range of exogenous substances in various biological matrices. However, such methods rely on the direct measurement of drugs and/or their metabolites in a targeted mode, allowing the detection of restricted number of compounds. As a consequence, emerging practices, in particular the use of natural hormones, designer drugs and low-dose cocktails, remain difficult to handle from a control point of view. A new SME-led FP7 funded project, DeTECH21, aims to overcome current limitations by applying an untargeted metabolomics approach based on liquid chromatography coupled to high resolution mass spectrometry and bioinformatic data analysis to identify bovine and equine animals which have been exposed to exogenous substances and assist in the identification of administered compounds. Markerbased strategies, dealing with the comprehensive analysis of metabolites present in a biological sample (urine/plasma/tissue), offer a reliable solution in the areas of food safety and animal sport doping control by effective, high-throughput and sensitive detection of exogenously administered agents. Therefore, the development of the first commercially available forensic test service based on metabolomics profiling will meet 21st century demands in animal forensics.