Head-on Collision of Ion-Acoustic Solitary Waves with Two Negative Ion Species in Electron–Positron–Ion Plasmas and Production of Rogue Waves

Plasma Physics Reports - The interactions between ion acoustic solitary waves (IASWs) are investigated considering completely ionized electron–positron–ion (e–p–i) plasmas...     

Functional Gene Hybridization Patterns of Terrestrial Ammonia-Oxidizing Bacteria

Abstract The biochemical pathway and genetics of autotrophic ammonia oxidation have been studied almost exclusively in Nitrosomonas europaea. Terrestrial autotrophic ammonia-oxidizing bacteria (AAOs), however, comprise two distinct phylogenetic groups in the beta-Proteobacteria, the Nitrosomonas and Nitrosospira groups. Hybridization patterns were used to assess the potential of functional probes in non-PCR-based molecular analysis of natural AAO populations and their activity. The objective of this study was to obtain an overview of functional gene homologies by hybridizing probes derived from N. europaea gene sequences ranging in size from 0.45 to 4.5 kb, and labeled with 32P to Southern blots containing genomic DNA from four Nitrosospira representatives. Probes were specific for genes encoding ammonia monooxygenase (amoA and amoB), hydroxylamine oxidoreductase (hao), and cytochrome c-554 (hcy). These probes produced hybridization signals, at low stringency (30 degreesC), with DNA from each of the four representatives; signals at higher stringency (42 degreesC) were greatly reduced or absent. The hybridization signals at low stringency ranged from 20 to 76% of the total signal obtained with N. europaea DNA. These results indicate that all four functional genes in the ammonia oxidation pathway have diverged between the Nitrosomonas and Nitrosospira groups. The hao probe produced the most consistent hybridization intensities among the Nitrosospira representatives, suggesting that hao sequences would provide the best probes for non-PCR-based molecular analysis of terrestrial AAOs. Since N. europaea can also denitrify, an additional objective was to hybridize genomic DNA from AAOs with probes for Pseudomonas genes involved in denitrification. These probes were specific for genes encoding heme-type dissimilatory nitrite reductase (dNir), Cu-type dNir, and nitrous oxide reductase (nosz). No hybridization signals were observed from probes for the heme-type dNir or nosz, but Nitrosospira sp. NpAV and Nitrosolobus sp. 24-C hybridized, under low-stringency conditions, with the Cu-type dNir probe. These results indicate that AAOs may also differ in their mechanisms and capacities for denitrification.     

Clastogenic effects of copper sulphate on the bone marrow chromosomes of mice in vivo

Copper sulphate administered intraperitoneally to Swiss albino mice in vivo induced a significant increase in the frequency of chromosomal aberrations in bone marrow cells as all concentrations used (1.1-6.6 mg/kg b.w.), when compared to the negative control. Statistical analysis indicates that the degree of clastogenicity was directly related to the concentrations used and indirectly to the period of exposure. The effect was maximal at 6 h after treatment as compared with 12 and 24 h.     

Effects of stannic chloride on human leucocytes in vitro

Single dose treatment with stannic chloride (4 micrograms/ml) on human lymphocytes in vitro revealed a significant increase of chromosomal aberrations. These showed a distinct relationship with the donor's age. Single and isochromatid breaks including gaps, premature chromosome condensation, irregular staining, stretching of the centromere and interchange, i.e. quadriradial exchange of chromosome arms, and also aneuploidy, were observed.     

Lipase-catalyzed methanolysis of palm oil in presence and absence of organic solvent for production of biodiesel

Enzymatic production of methyl esters (biodiesel) by methanolysis of palm oil in presence and absence of organic solvent was investigated using Candida antarctica lipase immobilized on acrylic resin as a biocatalyst. Although, at least molar equivalent of methanol (methanol-palm oil ratio 3:1) is required for the complete conversion of palm oil to methyl esters, lipase catalyzed methanolysis of palm oil in absence of organic solvent was poisoned by adding more than 1/3 molar equivalent of methanol. The use of polar organic solvents prevented the lipase to be poisoned in methanolysis with a molar equivalent of methanol, and tetrahydrofuran (THF) was found to be the most effective. The presence of water in methanolysis of palm oil both in presence and absence of THF inhibited the reaction rate but this inhibition was considerably low in THF containing system. The palm oil-lipase (w/w) ratio significantly influenced the activity of lipase and the optimal ratio in presence and absence of THF was 100 and 50, respectively.     

Deciphering Parameter Sensitivity in the BvgAS Signal Transduction

To understand the switching of different phenotypic phases of Bordetella pertussis, we propose an optimized mathematical framework for signal transduction through BvgAS two-component system. The response of the network output to the sensory input has been demonstrated in steady state. An analysis in terms of local sensitivity amplification characterizes the nature of the molecular switch. The sensitivity analysis of the model parameters within the framework of various correlation coefficients helps to decipher the contribution of the modular structure in signal propagation. Once classified, the model parameters are tuned to generate the behavior of some novel strains using simulated annealing, a stochastic optimization technique.     

State and management of wetlands in Bangladesh

Wetlands are a vital link between land and water in Bangladesh. A majority of the people of Bangladesh are critically dependent on wetlands. In this paper, the values of wetlands, causes and effects of wetlands degradation, as well as the present wetlands management approach, are analyzed and recommendations for wetlands management are suggested based on participatory rural appraisal (PRA), field visit, personal experience, and existing literature and information. Wetlands play a crucial role in maintaining the ecological balance of ecosystems, but wetlands habitat of Bangladesh is under constant threat due to increase of population, intensive agriculture, overfishing, siltation, pollution, ill-planned infrastructures, lack of institutional coordination, lack of awareness, etc. As a result biodiversity is reducing, many species of flora and fauna are threatened, wetlands-based ecosystem is degenerating, and the living conditions of local people are deteriorating as livelihoods, socioeconomic institutions, and cultural values are affected. Wetlands management is not addressed separately in water management activities of Bangladesh. In order to balance human needs and wetlands conservation, a mainly community-based wetlands management approach has been taken in Bangladesh, but this is not enough to prevent the degradation of wetlands. Therefore, Bangladesh now needs a comprehensive strategy combining political, economic, social, and technological approaches to stop further degradation of wetlands. Therefore, wetlands management should be incorporated into a system of integrated land and water use and, indeed, into the socioeconomic system of the country. Policies, strategies, and management plans for sustainable use and conservation of wetlands of Bangladesh must be based on solid knowledge and understanding of their ecological and socioeconomic functions and processes.