Inducible tolerance to Bacillus thuringiensis (Bt) endotoxins based on cell-free immune reactions.

The use of Bacillus thuringiensis (Bt) endotoxins to control insect vectors of human diseases and agricultural pests is threatened by the possible evolution of resistance in major pest species. Despite the use of Bt-endotoxins in transgenic crops covering about 80 million hectares, the precise details of how endotoxins bind to gut cells to kill insects are poorly understood. This limitation impedes our understanding of potential mechanisms of insect resistance to Bt-endotoxins other than the loss or modification of receptors. We explored a novel mechanism, where tolerance to Bt-endotoxins is correlated with an elevated immune status involving cell-free immune reactions in the gut lumen. The thesis project is based on investigations of a laboratory culture of the flour moth Ephestia kuehniella, which showed induction of hemolymph melanization a sign of immune induction, after feeding sub-lethal concentrations of a Bt-formulation. Since the elevated immune status was transmitted to subsequent generations by a maternal effect, an increase of toxin in the food by increments was possible every generation. Investigations of strains exposed to various toxin levels revealed a correlation between systemic immune induction and Bt-tolerance. Molecular analysis revealed a possible mechanism of immune mediated inactivation of Bt-endotoxins in the gut lumen. To gain more specific information about the effector pathways involved in the protection against the toxin, we studied the effects of Bt-toxin formulations in susceptible (non-induced) and tolerant (immune-induced) larvae after natural (parasitism-mediated) and chemical (tropolone-mediated) suppression of defence reactions. Although melanization in hemolymph was significantly reduced, there was no significant effect on susceptibility to the toxin in parasitised or tropolone-treated larvae. This suggests that melanization of hemolymph is correlated with an elevated immune status but not responsible for the observed tolerance to Bt-toxin. This leaves coagulation as a likely mechanism for Bt-tolerance in the gut lumen. To examine whether hemolymph proteins exist in the gut lumen were they could function as pro-coagulants to inactivate the toxin; we compared gut and plasma proteins of immune-induced larvae with those of non-induced larvae. This analysis revealed that the lipid carrier lipophorin represents a major component in the gut lumen and interacts with mature Bt-toxin like an oligomeric lectin that may inactivate the toxin in a cell free coagulation reaction in the gut lumen before it can reach the brush border membrane. Further analysis showed that lipophorin particles are the regulatory and effector components in innate immune defence reactions, which are involved in the recognition and inactivation of lipopolysaccharides (LPS) and bacteria even in the absence of hemocytes. Examination of proteins from lipophorin particles separated by low-density gradient centrifugation have shown that in immuneinduced insects sub-populations of lipophorin particles are associated with pattern recognition proteins, phenoloxidase and regulatory proteins that activate prophenoloxidase. Moreover, interactions with lectins resulted in the assembly of lipophorin particles into cage-like coagulation products, effectively protecting the surrounding tissues and cells from the potentially damaging effects of pathogens and phenoloxidase products. This cell-free immune reaction mediated by lipophorin particles may potentially involve in detoxification of poreforming toxins (Bt-endotoxins) in the gut lumen.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 200

Central limit theorem for some classes of dynamical systems

We consider a transformation T of the unit interval (0, 1) into itself which is piecewise C\sp2 and expanding. Using the spectral decomposition of the Frobenius-Perron operator of T, we give a proof of the Central Limit Theorem for\left({1\over n}\right)\sum\sbsp{i=0}{n-1}f\circ T\sp{i},where f is a function of bounded variation. It is also shown that the speed of covergence in the Central Limit Theorem is of the order ${1\over\sqrt n}.

Perceptions of Public University Students Towards Online Classes During COVID-19 Pandemic in Bangladesh

The disease outbreak COVID-19 pandemic impacted public health and safety and the educational systems worldwide. For fear of the further spread of diseases, most educational institutions, including Bangladesh, have postponed their face-to-face teaching. Therefore, this study explores public university student’s perceptions towards online classes during the COVID-19 pandemic in Bangladesh. Data had collected among students of Islamic University, Kushtia, Bangladesh, through an online survey. The study followed a quantitative approach, where the survey technique was used as an instrument of data collection. Results showed that most students faced difficulty participating in virtual classes and could not communicate with their friends correctly during online classes. Thus, they faced challenges in online schooling, and the majority of the students preferred conventional types of learning to virtual classes and did not understand the content of virtual classes easily. The study also explored that most students did not feel comfortable in online classes. Still, considering the present pandemic situation, they decided to participate in online classes to continue schooling. Besides, the study discovered that female students showed a better view than male students regarding online classes, and urban students have more positive appreciation than rural students. Furthermore, laptop or personal computer users showed more positive perceptions towards online education than mobile users. Moreover, Broadband/Wi-Fi users have more positive perceptions than mobile network users. These findings would be an essential guideline for governments, policymakers, technology developers, and university authorities for making better policy choices in the future

Electrical switching studies on Ge-​Te-​Tl chalcogenide glasses: Effect of thallium on the composition dependence of switching voltages

Bulk Ge17Te83-​xTlx glasses (0 ≤ x ≤ 13)​, have been found to exhibit memory type elec. switching. The switching voltages (also known as threshold voltage - Vth) of Ge17Te83-​xTlx glasses decrease with increasing Tl content. The rate of decrease of Vth is greater at lower concns. and Vth falls at a slower rate for higher Tl concns. (x ≥ 6)​. The addn. of Tl to the Ge-​Te network fragments the covalent network and introduces ionic nature to it; the redn. in network connectivity decreases switching voltages with Tl content. The decrease in the glass transition temps. of Ge17Te83-​xTlx glasses with increasing Tl concn. supports the idea of decrease in network connectivity with Tl addn. The more metallic nature of Tl also contributes to the obsd. redn. in the switching voltages of Ge17Te83-​xTlx glasses with Tl content. Further, there is an interesting correlation seen between the threshold voltage Vth and the av. bond energy, as a function of Tl content. The switching voltages of Ge17Te83-​xTlx glasses have been found to decrease with sample thickness almost linearly. The set-​reset studies indicate that the Ge17Te81Tl2 sample can be switched for >10 cycles, whereas other glasses could not be reset beyond 2 switching cycles

Towards Urban City with Sustainable Buildings: A Model for Dhaka City, Bangladesh

Dhaka has experienced high economic growth escorted by rapid urbanization. Physical infrastructures of Dhaka city growing day by day with the swiftness of rapid urbanization. It revealed that most of the physical infrastructures i.e. buildings of Dhaka city did not follow the characteristics of sustainability resulting significant threats to well beings.  In this perspective, ensuring sustainability in building is time worthy issue in Bangladesh. This paper tried to address the issues of sustainable building as well as propose a sustainable and smart design which will swathe criteria of environment, social and economic sustainability for Dhaka city. If the majority of the objects of proposed design are met, the building will be more probable to meet the changing requirements of the settlers, as well as make it a more sustainable, protected, secure, efficient and environmentally friendly place in which to stay. Keywords: Dhaka city, Smart materials, Sustainable design, Sustainable building

A Small Macroeconometric Model of the Bangladesh Economy

Abstract This paper describes a macroeconometric model of the Bangladesh economy using annual time series data from FY-1980 to FY-2006. The model is constructed with seven macroeconomic blocks, consumption, investment, production, government, trade, money, and price, capturing transmission among blocks. Structural equations under each block are estimated using short-run error correction model, where long-run equations into error correction terms represent economic theory. Hendry's general to a specific procedure is followed to get final short-run error correction equations. Validity of the model is checked both within the sample and out of sample cases. Results from validity study mark that the model is reasonably useful for forecasting and policy analysis. JEL Classification: C51, E1

Analysis of Social Vulnerability to Earthquake Hazards in Dhaka South City, Bangladesh Using a Modified PAR Model

The study aims at investigating the root causes, dynamic pressures, and unsafe conditions to the progression of the vulnerability of earthquake hazards among the people residing in the 22nd ward of Hazaribagh Thana of Dhaka South City (DSC) in Bangladesh. Following a purposive sampling procedure, the study selected the 22nd Ward of Dhaka South city. As part of qualitative methods, a total of 20 Key Informants Interviews (KII) were carried out and six focus group discussions (FGDs) were conducted. By adopting a modified Pressure and Release (PAR) model, the study revealed that the low-income status of the family, lack of proper health services, single-headed family, gender, differently able person, and the interpersonal good relation members, the availability of urban emergency center has found root causes for the progression of the vulnerability of earthquake hazards. Lack of appropriate skills, unplanned residences, and industry contribute to the production of dynamic pressures of the vulnerability of earthquake hazards. The unsafe conditions involve poor housing materials, dangerous locations for residents, and a lack of first aid documents associated with the production of the vulnerability of earthquake hazards