NOPR Collection:

Transport properties of SnTe_xSe_1-x thin films

2014-02-19T16:42:36Z

Title: Transport properties of SnTe_xSe_1-x thin films Authors: Zayed, H A; Soliman, L I; Farag, B S; Shehata, F M Abstract: The ternary semiconductors SnTe_xSe_1-x, (where 0≤ x ≤1), were prepared by fusion method. The SnTe_xSe_1-x thin films were prepared by thermal evaporation under vacuum of about 10^-5 Torr. The structure and the composition analysis of SnTe_xSe_1-x in powder and this films form were investigated by X-ray diffraction and microprobe analysis technique respectively. It was found that the electrical conductivity σ increases, while the activation energy decreased with increasing composition (x). The thermoelectric power and Hall voltage measurements indicated that the SnTe_xSe_1-x thin films were P-type conduction. The SnTe_xSe_1-x thin films were non-degenerate semiconductor for all values of x from zero to 0.8 while for SnTe (x=1) the films were degenerate and had a metallic behaviour. Moreover the carrier density P was changed from~10¹⁷ to 10²¹cm^-3 as changed from zero to one. It was found that the mobility of SnTe_xSe_1-x thin films increased as x increased, which indicated the presence of two types of scattering mechanisms, namely ionized impurity scattering as well as grain boundary potential barrier scattering. The effective mass m of SnTe_xSe_1-x thin films were found to increase with composition x. Page(s): 654-660

Application of magnetic fluids in medicine and biotechnology

2014-02-28T16:47:11Z

Title: Application of magnetic fluids in medicine and biotechnology Authors: Ramchand, C N; Pande, Priyadarshini; Kopcansky, Peter; Mehta, R V Abstract: Several advancements have been made in the last two decades for targeting drugs to a specific area in the human body. Liposomes, resealed erythrocyte ghost preparations, antibody mediated drug targeting to specific cancer cells have become popular means of drug targeting. However all these methods are associated with several practical problems and involve tedious development stages. In the past few years, this group has been involved in developing the usage of magnetic particles as suitable carriers for delivering drugs. This method of drug delivery ensures site-specific action as well as easy to develop and use technology. Clot lytic agents like streptokinase, urokinase or tissue plasminogen activator are traditionally used for treating thrombosis. One of the major problems associated with this treatment is its nonspecific and undirected thrombolytic activity. Using magnetic fluids, as carriers for above enzymes would ensure specificity of action, reduction in amount and time of action of the drug with no side effects. This line of action could be used in treating peripheral and coronary occlusive diseases. The process of hysteresis can be utilized to develop heat in magnetic fluids and this can be used to induce hyperthermia to treat tissues/cells, especially in oncology. This, in addition to delivering anticancer drugs via magnetic particles could prove to be an excellent line of treatment for cancer chemotherapy. Phase I clinical trials using reversibly bound anticancer drug epirubicin were done, and it was found that the ferrofluid could be successfully directed to the tumors in about one-half of the patients. Present studies have shown that proteins can be bound to magnetic particles without losing their biological properties. Some of the enzymes immobilized by us have been found to retain almost 90% of their activity. The same principle could be used to deliver anti cancer and thrombolytic drugs, which have been entrapped in protein microspheres. These can be targeted to tumor cells by an external magnetic field so that it an deliver the drug slowly and in the required amount at the same time avoiding side effects associated with these drugs. The applications of magnetic fluids in other fields are also manifold. Magnetic for isolating mRNA are quicker and more efficient, and they avoid organic solvents and the need for a precipitation step. Magnetic beads linked to high affinity capture antibodies have been widely accepted as separation techniques of specific target ligands or particles such as bacteria or leukocytes from complex mixtures, such as bone marrow, blood and other body fluids. Detection of contaminating microorganisms like, staphylococcus sp. In milk using a magnetic based ELISA (Enzyme Linked Immunosorbent Assay) has been developed. It is also proposed to use this technology to immobilize polymixin B antibiotic for the treatment of endotoxic shock. The extreme toxicity of this antibiotic could be avoided using dialysis to remove the magneti cally bound antibiotic, from systematic circulation, after its action. Similarly using magnetically immobilized antifungal agent amphoterecin, for systemic application., could reduce toxicity of this antifungal agent. Investigating the use of magnetically immobilized Horseshoe crab protein for combating endotoxic shock could also prove to be an effective line of treatment. Using magnetic particles as such or erythrocyte ghost preparations of the same could be used as an opaque medium in angiography and radiography techniques. In addition to this, using magnetically immobilized microorganisms for wastewater treatment is an extremely cost effective technology. Page(s): 683-686

Computer controlled femtosecond optical delay line for ultrafast optics and spectroscopy

2014-02-23T16:40:49Z

Title: Computer controlled femtosecond optical delay line for ultrafast optics and spectroscopy Authors: Rajesh, R Justin; Natarajan, T S; Bisht, Prem B Abstract: Computer controlled optical delay line for experiments in ultrafast laser optics and spectroscopy has been fabricated. Spatial resolution of 0.5μm and an optical resolution of 16 fs have been obtained from the set up. An ultrafast decay of 50 ps for the relaxation of an organic dye has been recorded using this set up as an example. Fabrication details of this economical and indigenous PC-controlled optical delay line along with the so ft ware requirement are presented here. Page(s): 636-639

Optimal efficiency of an irreversible heat engine with thermal reservoir of finite heat capacitance using method of Lagrangian multiplier

2014-02-19T16:41:52Z

Title: Optimal efficiency of an irreversible heat engine with thermal reservoir of finite heat capacitance using method of Lagrangian multiplier Authors: Kaushik, S C; Kumar, P Abstract: The finite time thermodynamic optimization of an irreversible heat engine having thermal reservoirs of finite heat capacitance has been presented. A general expression for the optimum efficiency of heat engine is derived at maximum work output and given heat input flow rate condition. External irreversibility is due to finite temperature difference between system working fluid and thermal reservoirs (source/sink) while internal irreversibility is due to non-isentropic expansion and compression within the system which is represented by an irreversibility parameter indicating the deviation from endoreversible case. It is found that the direct of internal irreversibility is more pronounced than the external irreversibility associated with the heat engine. The effect of various operating parameters on the efficiency of the heat engine is studied and numerical results are presented in the end. Page(s): 628-635

NOPR Collection:

Transport properties of SnTexSe1-x thin films

Application of magnetic fluids in medicine and biotechnology

Computer controlled femtosecond optical delay line for ultrafast optics and spectroscopy

Optimal efficiency of an irreversible heat engine with thermal reservoir of finite heat capacitance using method of Lagrangian multiplier

Transport properties of SnTe_xSe_1-x thin films