A study of structure, electrical and optical properties of some Vanadate glasses

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Studies of semiconducting glasses have become of great interest in recent years because of their importance in the theory of solid state physics and in their applicability to electronic devices. Of these classes of materials the transition metal oxide glasses are much the most thoroughly studied. In these glasses the transition metal oxide e. g. V205-TiO2-MoO39 WO3, Cu0 is a major constituent i.e > 50 mol%. We start this work with a discussion about a critical review of the history, formation and modern theory of non-crystalline semiconductors in general and glassy state in particular. The aim of the experimental work in present study is to check the validity of the theories and models proposed so far to explain the origin and the nature of the charge carriers, structure, electrical and optical properties of some transition metal oxide glasses based on vanadium pentoxide. For this purpose series of binary V205-P205 glass samples containing 50 to 90 mol% V205 as well as ternary V2015-P205-Te02 glasses containing 60 mol% V2051 (40-x) mol% P205 and x mol% Te02 in which x varies from 5 to 35 were prepared by normal cooling from the melt. It was found that the glass forming region of the system under consideration is fairly large and in binary V205-P205 systems, glass with up to 95 moll V205 could be prepared. Density measurements indicate that in binary V205 - P205 glasses the density increases linearly with increasing V205 content and in ternary V205 - P205 - TeO2 systems density increases with increasing Te02 content. It was also found that the density of both systems are affected by annealing temperature. Electron spin resonance (E.S.R.) studies show that in vanadate glasses, the vanadium exists in more than one valency state mainly V5+ and V4+ of which V4+ is paramagnetic and detectable by E. S. R. This could be taken as some evidence of a hopping conduction mechanism in vanadate glasses and conduction is due to transfer of charge form V4+ to V5+ ions and this is discussed in the terms of small polaron. It is found that the conduction in these glasses is Ohmic up to a field of the order of 4x 105 Vcm-1 with an activation energy range from 0.31 to 0.48 e.V depending on composition and independent of temperatures in our range of temperature (above room temperature). Above this field conduction becomes non-Ohmic which is found to be due to lowering the potential barrier of the carriers at high electric field as was predicted by Poole and Frenkel. Memory switching is observed in thin blown film samples of both binary and ternary glass systems, which is associated with field-induced crystallization of a localized region and formation of conductive channel in the switched area due to self heating effect. In other words the conducting zone consists of VO2 crystals which possess more metal-like conductivity. Infra-red absorption spectra of these glasses revealed that some of the absorption bands of glasses and crystalline V205 are similar which is some evidence that the vanadium ions exists in six-fold co-ordination in disordered glassy systems as well as ordered crystalline V205. The fundamental absorption edge of these glasses occurs in the short wave length region of the visible and is dependent on composition, and the fundamental absorption arises form direct forbidden transitions and occurs at a photon energy of about 1.9-2.6 e.V depending on composition. The absorption edge in these glasses is found to be of the same order of magnitude as that in crystalline V205

Optimisation of inspection policy for multi-line production systems

This paper develops a simulation model to determine the cost-optimum inspection policy for a multi-line production system taking account of simultaneous downtime. The machines in the multi-line system are subject to a two stage failure process that is modelled using the delay-time concept. Our study indicates that: consecutive inspection of lines with priority for failure repair is cost-optimal, with a cost reduction of 61% compared to a ‘run-to-failure’ policy; and maintainers need to be responsive to operational requirements. Our ideas are developed in the context of a case study of a plant with three parallel lines, one of which is on cold-standby. Keywords: maintenance; delay-time model; simulation; production; parallel lines; manufacturing; preventive maintenance

Performance enhancement of a thermoelectric harvester with a PCM/metal foam composite

The present numerical investigation examines the performance improvement of thermoelectric generators (TEGs) by using phase change materials (PCM) and porous medium. Due to the high latent heat of PCMs, both sides of the TEG were filled with paraffin RT35 (on the cold-side) and paraffin RT69 (on the hot-side). The PCM in the cold-side of the TEG was used as a heat-sink whereas the PCM in hot-side of the TEG was used to reduce the output voltage fluctuations. Since the system was periodically subjected to heat flux from an external heat source, the paraffin in the hot-side of the TEG was also used to generate a continuous thermal heat when the heat source was cut-off. To increase the thermal conductivity of the phase change material, this investigation studied the effect of using the copper porous medium with different porosities (0.80, 0.90, and 0.95) and three different pores per inches (PPI) as 10, 20, and 40. The results show that the use of porous on the cold-side of the TEG produces more electrical energy and output voltage compared to (i) having porous medium on the hot-side and (ii) using PCM without porous medium on both sides of the thermoelectric generator. Furthermore, the results indicated that the TEG performance enhanced by increasing PPI and reducing porosity. As a result, by increasing the PPI from 10 to 40 (at 0.80 porosity) and by reducing porosity from 0.95 to 0.80 (at PPI 20), the electricity generated increases by 13.57 and 5.36%, respectively

A biophysical study on the mechanism of interactions of DOX or PTX with α-lactalbumin as a delivery carrier

© 2018, The Author(s). Doxorubicin and paclitaxel, two hydrophobic chemotherapeutic agents, are used in cancer therapies. Presence of hydrophobic patches and a flexible fold could probably make α-Lactalbumin a suitable carrier for hydrophobic drugs. In the present study, a variety of thermodynamic, spectroscopic, computational, and cellular techniques were applied to assess α-lactalbumin potential as a carrier for doxorubicin and paclitaxel. According to isothermal titration calorimetry data, the interaction between α-lactalbumin and doxorubicin or paclitaxel is spontaneous and the K (M−1) value for the interaction of α-lactalbumin and paclitaxel is higher than that for doxorubicin. Differential scanning calorimetry and anisotropy results indicated formation of α-lactalbumin complexes with doxorubicin or paclitaxel. Furthermore, molecular docking and dynamic studies revealed that TRPs are not involved in α-Lac’s interaction with Doxorubicin while TRP 60 interacts with paclitaxel. Based on Pace analysis to determine protein thermal stability, doxorubicin and paclitaxel induced higher and lower thermal stability in α-lactalbumin, respectively. Besides, fluorescence lifetime measurements reflected that the interaction between α-lactalbumin with doxorubicin or paclitaxel was of static nature. Therefore, the authors hypothesized that α-lactalbumin could serve as a carrier for doxorubicin and paclitaxel by reducing cytotoxicity and apoptosis which was demonstrated during our in vitro cell studies

The effect of hydro-alcoholic extract of Kelussia odoratissma Mozaffarian (KOM) seed on histopathology & joints diameter in experimental model of Incomplete Freund,s adjuvant induced arthritis in rat

BACKGROUND AND OBJECTIVE: Arthritis is one of the inflammatory diseases that can cause debilitating problems. Existing drugs have numerous side effects that limit their use. KOM has anti-inflammatory properties due to its flavonoid compounds. Therefore, this study was performed to investigate the anti-inflammatory effects of hydroalcoholic extract of KOM in an experimental model of arthritis. METHODS: In this experimental study, 46 male Wistar rats were randomly divided into 7 groups: healthy and patient control groups, normal saline recipient , hydrocortisone recipient and 3 groups treated with hydroalcoholic extract at doses of 300, 500 and 700 mg/kg. First, KOM was extracted then arthritis induced by injection of 0.1 cc of Incomplete Freund's adjuvant, and from 15th day KOM extract was injected intraperitoneally. On the last day (31st), their ankle joint was prepared for histological examination and the groups were compared. FINDINGS: The results showed that doses of 300, 500 and 700 mg/kg of hydroalcoholic extract did not significantly reduce joint diameter. Histologic studies of positive control group showed subcutaneous inflammation, destruction and fibrosis of cartilage and panus formation which subcutaneous inflammation was reduced in the low and high doses of the extract (p<0.05). CONCLUSION: The results of this study showed that hydroalcoholic extract of KOM reduced subcutaneous inflammation but had no significant effect on joint diameter and other histopathologic and immunological changes in IFA induced arthritis

Geostatistical modeling and spatial distribution analysis of porosity and permeability in the Shurijeh-B reservoir of Khangiran gas field in Iran

The main objectives of this study are analysis of spatial behavior of the porosity and permeability, presenting direction of anisotropy for each variable and describing variation of these parameters in Shurijeh B gas reservoir in Khangiran gas field. Porosity well log data of 32 wells are available for performing this geostatistical analysis. A univariate statistical analysis is done on both porosity and permeability to provide a framework for geostatistical analysis and modeling. For spatial analysis of these parameters, the experimental semivariogram of each variable in different direction as well as their variogram map plotted to find out the direction of anisotropy and their geostatistical parameters such as range, sill, and nugget effect for later geostatistical work and finally for geostatistical modeling, two approaches kriging and Sequential Gaussian Simulation are used to get porosity and permeability maps through the entire reservoir. All of statistical and geostatistical analysis has been done using GSLIB and PETREL software. Maximum and minimum direction of continuity are found to be N75W and N15E, respectively. Geostatistical parameters of calculated semivariogram in this direction like range of 7000 m and nugget of 0.2 are used for modeling. Both kriging and SGS method used for modeling but kriging tends to smooth out estimates but on the other hand SGS method tends to show up details. Cross-validation also used to validate the generated modeling

Global burden of human brucellosis : a systematic review of disease frequency

BACKGROUND: This report presents a systematic review of scientific literature published between 1990-2010 relating to the frequency of human brucellosis, commissioned by WHO. The objectives were to identify high quality disease incidence data to complement existing knowledge of the global disease burden and, ultimately, to contribute towards the calculation of a Disability-Adjusted Life Years (DALY) estimate for brucellosis.METHODS/PRINCIPAL FINDINGS: Thirty three databases were searched, identifying 2,385 articles relating to human brucellosis. Based on strict screening criteria, 60 studies were selected for quality assessment, of which only 29 were of sufficient quality for data analysis. Data were only available from 15 countries in the regions of Northern Africa and Middle East, Western Europe, Central and South America, Sub-Saharan Africa, and Central Asia. Half of the studies presented incidence data, six of which were longitudinal prospective studies, and half presented seroprevalence data which were converted to incidence rates. Brucellosis incidence varied widely between, and within, countries. Although study biases cannot be ruled out, demographic, occupational, and socioeconomic factors likely play a role. Aggregated data at national or regional levels do not capture these complexities of disease dynamics and, consequently, at-risk populations or areas may be overlooked. In many brucellosis-endemic countries, health systems are weak and passively-acquired official data underestimate the true disease burden.CONCLUSIONS: High quality research is essential for an accurate assessment of disease burden, particularly in Eastern Europe, the Asia-Pacific, Central and South America and Africa where data are lacking. Providing formal epidemiological and statistical training to researchers is essential for improving study quality. An integrated approach to disease surveillance involving both human health and veterinary services would allow a better understand of disease dynamics at the animal-human interface, as well as a more cost-effective utilisation of resources

Prevalence and Correlates of Hepatitis C Infection among Male Injection Drug Users in Detention, Tehran, Iran

For the benefit of planning for the future care and treatment of people infected with hepatitis C virus (HCV) and to help guide prevention and control programs, data are needed on HCV seroprevalence and associated risk factors. We conducted a cross-sectional sero-behavioral survey of injection drug users (IDU) detained for mandatory rehabilitation during a police sweep of Tehran, Iran, in early 2006. During the study period, a consecutive sample comprising 454 of 499 (91.0%) men arrested and determined to be IDU by urine test and physical examination consented to a face-to-face interview and blood collection for HCV antibody testing. Overall, HCV prevalence was 80.0% (95% confidence interval (CI) 76.2–83.6). Factors independently associated with HCV infection included history of incarceration (adjusted OR 4.35, 95% CI 1.88–10.08), age of first injection ≤25 years (OR 2.72, 95% CI 1.09–6.82), and history of tattooing (OR 2.33, 95% CI 1.05–5.17). HCV prevalence in this population of IDU upon intake to jail was extremely high and possibly approaching saturation. Findings support that incarceration is contributing to the increased spread of HCV infection in Iran and calls for urgent increased availability of HCV treatment, long-term preparation for the care of complications of chronic infection, and rapid scale-up of programs for the primary prevention of parenterally transmitted infections among drug users