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The concentrations of organochlorine insecticides (DDT and heptachlor) were investigated to estimate the effect of various washing and boiling/cooking to elucidate the concentration level we intake actually. For this study five most popular dry fish samples namely bombay duck (loittya), ribbon fish (chhuri), shrimp (chingri), chinese pomfret (rupchanda) and Indian salmon (lakhua) were analyzed. The highest concentrations of DDT and heptachlor were found 737.2 ppb (Indian salmon, normal) and 44.8 ppb (shrimp, normal) respectively; after boiling treatment a big amount was washed out and remained only 135.5 and 16.9 ppb respectively. Boiling treatment was found more effective than the others.

The concentrations of organochlorine insecticides DDT (Dichloro diphenyl trichloro ethane) and Heptachlor were investigated to estimate the current status of insecticides used in dry fish in different seasons and different species. Six most popular species of dry fishes namely Bombay duck (Loittya), Ribbon fish (Chhuri), Shrimp (Chingri), Hilsha shed (Ilish), Chinese pomfret (Rupchanda) and Indian salmon (Lakhua) were collected from Asadgonj (whole sell market for dry fish) of Chittagong, Bangladesh at different seasons, six samples at winter season (December) and six same samples at rainy season (July). The range of DDT concentration at winter was found 3.6 ug kg-1 to 250.8 ug kg-1 and at rainy season the range of concentration was found 11.1 ug kg-1 to 1107.4 ug kg-1. The range of Heptachlor concentration at winter was found 0.4 ug kg-1 to 2.5 ug kg-1 and at rainy season was found 1.1 ug kg-1 to 37.8 ug kg-1. The concentrations of DDT and Heptachlor were much higher in the samples of rainy season than the same samples of the winter.

To determine hazardous antibiotics/chemicals and pesticides residues in Good Aquaculture Practice(GAP) and non-GAP farms and exploring the post-harvest management techniques of shrimp/ prawn forensuring its food safety issues, a study was conducted from July 2016 to June 2019 in three upazilas viz.Bagerhat Sadar, Rampal and Kachua of Bagerhat district. A total of 550 shrimp/prawn farms were randomlysurveyed considering GAP criteria. The farms were categorized as Category A- the farms which comply 90-100% GAP criteria; Category B- farms which comply 70-< 90% GAP criteria and Category C- farms whichcomply 50-<70% GAP criteria. From the study it was found that only 1.67±0.58 % farms were underCategory-A, 37.67±6.81 % farms were under Category-B and 53±6.08 % farms were under Category-C. Atotal of 108 shrimp/prawn samples were collected in which 30% samples were from GAP farms and 70%samples were from non-GAP farms. Collected samples were analyzed for hazardous antibiotics/chemicals andpesticides residues (Heptachlor, Endrin, Dieldrin and DDT) using LC-MS and GC-MS machine. Nohazardous Nitrofuran and Chloramphenicol metabolites were found from the collected samples and noresidual concentrations of Heptachlor, Endrin, Dieldrin and DDT were found from GAP samples. In non-GAP samples, 14.8% samples contained some residues of Heptachlor, Endrin and Dieldrin in which 10.2%samples residues were lower than the Maximum Residual Limit (MRL) which is not harmful for humanhealth. Only 4.6% samples had residues which were slightly higher than the MRL. Exploration of postharvestmanagement techniques of shrimp and prawn were done by observing the icing system quality andtransportation system from farms to market/depot. It was found that 5.67±2.08% farmer used proper icingand transportation system as well, 16.33±3.21% farmers used moderate icing and transportation system and78±2% farmers used poor icing and transportation system. It was also observed that pathogenic bacterialload was higher in poor icing and transportation system as well than the proper icing and transportationsystem. From the study it can be concluded that, if farmers follow at least 50% of the GAP criteria then thefoods (shrimp/prawn) will be safer for human consumption.

IntroductionAmong the solid materials, metals are of great interest. For example iron is used in automobiles, copper in electric wiring, where as gold and silver are used in jewelry. These and other metals have played a very important role in the development of our technological world from early historical time to the present and will continue to do so in the future. The explanation of characteristic metallic properties is important to a metallurgist or an engineer who wishes to use metals for practical purposes and to a physicist who is interested in understanding the microscopic structure of materials.The tight-binding or screened version of the linearized muffin-tin-orbitals method (TB-LMTO) has provided an excellent starting point for first principles electronic structure determination of disordered alloys. The resulting Hamiltonian is short-ranged and therefore ideally provides the extension from the traditional adhoc tight-binding ideas into a fully-self-consistent first principles theory. The basis of the method has been described in detail (Andersen et al., 1994) and relevant details necessary for disordered alloys are given in (Anderson and Japsen et al.,1984).The study of electronic structure of disordered alloys is of great scientific and technological importance. Theoretical approaches have achieved considerable success through the development of mean-field approximations, the most successful of which is the coherent potential approximation (CPA) (Pinski, et al., 1991). Other techniques include super-cell approaches, attempted generalizations of the CPA and an alternative order-N Green's function technique (Abrikosov et al., 1996). The former is based on the self-consistent determination of a uniform medium to represent the substitutional alloy. The corresponding effective Hamiltonian is lattice transitionally symmetric and its Green function is a good approximation of the configurational averaged Green function. Of the later, the super-cell method is based on the study of different selected ordered structures at various concentrations. In these calculations a large unit cell is constructed which contains different possible configurations and is repeated to generate the entire lattice. The result of such a method contains the artifact of imposed lattice symmetry, which is OK provided we concentrate on the local properties at the centre of the supercell whose size is rather large. There is no straight-forward rule for constructing a super-cell and in realistic calculations it becomes computationally expensive. A large number of generalizations of the CPA are beset with analytical difficulties and their effective medium is often not translationally symmetric. The only really successful generalization with analytical and translational properties is the traveling cluster approximation of (Kaplan et al., 1981 AbstractWe have studied here the electronic structure of pure random disordered alloys formed by Ni with Cu and Au at different ratios by using the linearized tight-binding muffin-tin Orbital (TB-...