The compatibilityof tellurium with austenitic stainless steels

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

Analysis of Cosmogenic Impurities in Tellurium and Development of Tellurium Loading for the SNO+ Experiment

For the SNO+ neutrinoless double beta decay search, various backgrounds, ranging from impurities present naturally to those produced cosmogenically, must be understood and reduced. Cosmogenic backgrounds are particularly difficult to reduce as they are continually regenerated while exposed to high energy cosmic rays. To reduce these cosmogenics as much as possible the tellurium used for the neutrinoless double beta decay search will be purified underground. An analysis of the purification factors achievable for insoluble cosmogenic impurities found a reduction factor of $>$20.4 at 50\% C.L.. During the purification process the tellurium will come into contact with ultra pure water and nitric acid. These liquids both carry some cosmogenic impurities with them that could be potentially transferred to the tellurium. A conservative limit is set at $<$18 events in the SNO+ region of interest (ROI) per year as a result of contaminants from these liquids. In addition to cosmogenics brought underground, muons can produce radioactive isotopes while the tellurium is stored underground. A study on the rate at which muons produce these backgrounds finds an additional 1 event per year. In order to load the tellurium into the detector, it will be combined with 1,2-butanediol to form an organometallic complex. The complex was found to have minimal effect on the SNO+ acrylic vessel for 154 years.

Energy level decay and excited state absorption processes in erbium-doped tellurium glass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of Tellurium oxide glasses for photonic applications

Tellurite glasses are photonic materials of special interest to the branch of optoelectronic and communication, due to its important optical properties such as high refractive index, broad IR transmittance, low phonon energy etc. Tellurite glasses are solutions to the search of potential candidates for nonlinear optical devices. Low phonon energy makes it an efficient host for dopant ions like rare earths, allowing a better environment for radiative transitions. The dopant ions maintain majority of their individual properties in the glass matrix. Tellurites are less toxic than chalcogenides, more chemically and thermally stable which makes them a highly suitable fiber material for nonlinear applications in the midinfrared and they are of increased research interest in applications like laser, amplifier, sensor etc. Low melting point and glass transition temperature helps tellurite glass preparation easier than other glass families.In order to probe into the versatility of tellurite glasses in optoelectronic industry; we have synthesized and undertaken various optical studies on tellurite glasses. We have proved that the highly nonlinear tellurite glasses are suitable candidates in optical limiting, with comparatively lower optical limiting threshold. Tuning the optical properties of glasses is an important factor in the optoelectronic research. We have found that thermal poling is an efficient mechanism in tuning the optical properties of these materials. Another important nonlinear phenomenon found in zinc tellurite glasses is their ability to switch from reverse saturable absorption to saturable absorption in the presence of lanthanide ions. The proposed thesis to be submitted will have seven chapters.

Bis[(4-methylphenyl)ethynyl] telluride

The tellurium atom in the title bis-ethynyl telluride, Te(C(9)H(7))(2) or C(18)H(14)Te, is located on a crystallographic twofold axis, the C-Te-C angle being 92.23 (15)degrees. The dihedral angle between the rings is 87.27 (7)degrees. In the crystal structure, molecules are connected in chains parallel to the b axis and mediated by C-H center dot center dot center dot pi interactions.

A Novel Organotellurium Compound (RT-01) as a New Antileishmanial Agent

Leishmaniasis is a neglected disease and endemic in developing countries. A lack of adequate and definitive chemotherapeutic agents to fight against this infection has led to the investigation of numerous compounds. The aim of this study was to investigate the effect of RT-01, an organotellurane compound presenting biological activities, in 2 experimental systems against Leishmania amazonensis. The in vitro system consisted of promastigotes and amastigotes forms of the parasite, and the in vivo system consisted of L. amazonensis infected BALB/c mice, an extremely susceptible mouse strain. The compound proved to be toxic against promastigotes and amastigotes. The study also showed that treatment with RT-01 produces an effect similar to that treatment with the reference antimonial drug, Glucantime, in L. amazonensis infected mice. The best results were obtained following RT-01 intralesional administration (720 mu g/kg/day); mice showed significant delay in the development of cutaneous lesions and decreased numbers of parasites obtained from the lesions. Significant differences in tissue pathology consisted mainly of no expressive accumulation of inflammatory cells and well-preserved structures in the skin tissue of RT-01-treated mice compared with expressive infiltration of infected cells replacing the skin tissue in lesions of untreated mice. These findings highlight the fact that the apparent potency of organotellurane compounds, together with their relatively simple structure, may represent a new avenue for the development of novel drugs to combat parasitic diseases.

Theory of near-gap second harmonic generation in centrosymmetric magnetic semiconductors: Europium chalcogenides

Second harmonic generation is strictly forbidden in centrosymmetric materials, within the electric dipole approximation. Recently, it was found that the centrosymmetric magnetic semiconductors EuTe and EuSe can generate near-gap second harmonics, if the system is submitted to an external magnetic field. Here, a theoretical model is presented, which well describes the observed phenomena. The model shows that second harmonic generation becomes efficient when the magnetic dipole oscillations between the band-edge excited states of the system, induced by the excitation light, enter the in-phase regime, which can be achieved by applying a magnetic field to the material.

Sharp vibronic spectra of Cu(II) doped Cs2ZrCl6

The low temperature electronic spectrum of Cu(II) doped Cs2ZrCl6 is reported. It is found that Cu(II) is incorporated as the square planar copper tetrachloride ion, CuCl42-, which substitutes at the Zr(IV) site in the Cs2ZrCl6 lattice. There is a complete absence of axial coordination. The optical spectrum shows vibronic structure with peak widths as small as 8 cm(-1), far narrower than previously seen for this ion. The energy of the observed transitions and the Franck-Condon intensity pattern suggest that there is a substantial relaxation of the host lattice about the impurity ion. The relative intensity of the magnetic dipole component of the bands appears to be considerably greater than for pure copper(II) compounds containing the CuCl42- ion. (C) 1998 Elsevier Science B.V. All rights reserved.

VOC removal: Comparison of MCM-41 with hydrophobic zeolites and activated carbon

The recently discovered mesoporous molecular sieve MCM-41 was tested as an adsorbent for VOC removal. Its adsorption/desorption properties were evaluated and compared with other hydrophobic zeolites (silicalite-1 and zeolite Y) and a commercial activated carbon, BPL. The adsorption isotherms of some typical VOCs (benzene, carbon tetrachloride, and n-hexane) on MCM-41 are of type IV according to the IUPAC classification, drastically different from the other microporous adsorbents, indicating that VOCs, in the gas phase, have to be at high partial pressures in order to make the most of the new mesoporous material as an adsorbent for VOC removal. However, a proper modification of the pore openings of MCM-41 can change the isotherm types from type IV to type I without remarkable loss of the accessible pare volumes and, therefore, significantly enhance the adsorption performance at low partial pressures. Adsorption isotherms of water on these adsorbents are all of type V, demonstrating that they possess a similar hydrophobicity. Desorption of VOCs from MCM-41 could be achieved at lower temperatures (50-60 degrees C), while this had to be conducted at higher temperatures (100-120 degrees C) for microporous adsorbents, zeolites, and activated carbons.

Single-spin measurement using single-electron transistors to probe two-electron systems

We present a method for measuring single spins embedded in a solid by probing two-electron systems with a single-electron transistor (SET). Restrictions imposed by the Pauli principle on allowed two-electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well suited to measure. We focus on a particular system capable of being fabricated with current technology: a Te double donor in Si adjacent to a Si/SiO2, interface and lying directly beneath the SET island electrode, and we outline a measurement strategy capable of resolving single-electron and nuclear spins in this system. We discuss the limitations of the measurement imposed by spin scattering arising from fluctuations emanating from the SET and from lattice phonons. We conclude that measurement of single spins, a necessary requirement for several proposed quantum computer architectures, is feasible in Si using this strategy.

One-pot synthesis of mixed (Z)-1,2-bis(organylchalcogene)-1-alkenes precursors of the novel beta-organylthio vinyllithium intermediates

One-pot hydrochalcogenation of 1-phenylthioacetylenes using organylselenolate and organyltellurolate anions generated by the insertions of selenium and tellurium in n-organyl lithium produced (Z)-1,2-bis(organylchalcogene)-1-alkenes. The chemical reactivity of these mixed 1,2-bis(organylchalcogene)-1-alkenes was studied by Te/Li and Se/Li stereoretentive exchanges carried out with n-butyl lithium, furnishing the new intermediate species (Z)-beta-organylthio vinyllithium anions, which were trapped with aldehydes, to give the (Z)-3-hydroxy vinyl thioethers with total control of the regio- and stereochemistry. (c) 2010 Elsevier Ltd. All rights reserved.

Dose-dependent hepatic response to subchronic administration of nandrolone decanoate

Background: Androgenic anabolic steroids (AAS) are synthetic hormone derivatives of testosterone and are mainly used to enhance athletic performance and muscle mass, but medical applications also have been described. Short- and long-term side effects have been demonstrated in many organs, but the liver adverse effects are the most common and serious ones associated with AAS use. However, these effects have been supported by few clinical and experimental studies. Objective: To evaluate the hepatic function and structure after 5 wk of nandrolone decanoate administration at three different doses. Methods: Twenty-seven adult male Wistar rats were randomly assigned to the following groups: control, clinical, intermediate, and suprapharmacological doses of nandrolone decanoate during 5 wk. Results: The biochemical studies showed that nandrolone decanoate administration leads to a dose-dependent increase in serum levels of the aspartate aminotransferase (AST) (P < 0.05), alanine aminotransferase (ALT) (P < 0.01), and alkaline phosphatase (ALP) (P < 0.001), as well as a significant decrease in total proteins (P < 0.01), bilirubin (P < 0.05), total cholesterol and fractions (P < 0.05), and triglycerides (P < 0.05). Although a significant statistical difference was found for AST, ALT, and ALP when compared with the control group, their values remained within the normal range. The number of Kupffer cells was increased in the liver parenchyma (P < 0.05), and the content of collagen was increased in the central lobular vein wall, in the hepatic parenchyma, and in the portal space (P < 0.05). Conclusions: These results suggest that subchronic treatment with nandrolone decanoate, mainly administered at higher-than-clinical doses, are potentially deleterious to the liver, leading to incipient fibrosis.