Technical Study of a Standalone Photovoltaic–Wind Energy Based Hybrid Power Supply Systems for Island Electrification in Malaysia

Energy is one of the most important factors in the socioeconomic development of a country. In a developing country like Malaysia, the development of islands is mostly related to the availability of electric power. Power generated by renewable energy sources has recently become one of the most promising solutions for the electrification of islands and remote rural areas. But high dependency on weather conditions and the unpredictable nature of these renewable energy sources are the main drawbacks. To overcome this weakness, different green energy sources and power electronic converters need to be integrated with each other. This study presents a battery storage hybrid standalone photovoltaic-wind energy power supply system. In the proposed standalone hybrid system, a DC-DC buck-boost bidirectional converter controller is used to accumulates the surplus hybrid power in the battery bank and supplies this power to the load during the hybrid power shortage by maintaining the constant dc-link voltage. A three-phase voltage source inverter complex vector control scheme is used to control the load side voltage in terms of the voltage amplitude and frequency. Based on the simulation results obtained from MATLAB/Simulink, it has been found that the overall hybrid framework is capable of working under variable weather and load conditions.     

Studies on Crocker sarcoma 180 under the effect of alkylating agents. IV. Morphological studies of sarcoma 180 during treatment with the antitumour drug cytoxan

The effect of one massive dose of cytoxan (150 mg/kg), as an alkylating agent, on the morphology of sarcoma 180 cells was followed after 1, 3, 6, 12, 24, 48, 96, 120, and 168 h. After 1 h the cells of treated tumour showed clumping and a decrease in their size. In addition, statistical analysis manifested significant decrease in all phases of mitotic figures. All mitotic figures were completely stopped after 3 h from cytoxan treatment. After 6 and 12 h from cytoxan treatment the hyaline degenerations became more marked in the treated tumour tissue. Chromosomal bridge formation, nuclei aberrations and polynuclear cells were more prominent in 24, 48, and 96 h from cytoxan treatment. Increase in the nuclear size and hyaline degeneration were observed in treated section of 120 and 168 h.     

A clonal derivative of mammary epithelial cell line COMMA-D retains stem cell characteristics of unique morphological and functional heterogeneity

The COMMA-D cell line derived from mammary epithelial cells of midpregnant mice was shown previously to be heterogeneous as determined by phase-contrast microscopy, immunocytochemical staining, DNA content, and oncogenic potential (K.D. Danielson et al. (1984) Proc. Natl. Acad. Sci. USA 81, 3756; D. Medina et al. (1986) J. Natl. Cancer Inst. 76, 1143). Clonal subpopulations of COMMA-D cells have now been isolated by both transfection and selection using a dominant-selectable gene transfer vector and by limiting dilution. Despite their clonal origin, these subpopulations in many cases retained the heterogeneity of the parental COMMA-D line. Of 18 clonal lines assayed, only 5 were able to express beta-casein mRNA. Pooled populations of G418-resistant cells expressed substantially higher levels of beta-casein mRNA than the clonal lines. One of the expressing clonal lines, BNW-7, was characterized further, using immunocytochemical techniques. Approximately 10% of BNW-7 cells expressed casein under the appropriate hormonal and cell-substratum conditions by indirect immunofluorescent staining. Casein immunoperoxidase staining of BNW-7 cells on floating collagen gels revealed that casein-producing cells were localized in small alveolar structures, which were formed in a non-hormone-dependent fashion. The cells in these alveolar structures were cuboidal with basally located nuclei, expressed keratin intermediate filament proteins preferentially, and comprised approximately 18% of the total cells. Cells elsewhere on the surface of the gel displayed a flattened morphology, and expressed vimentin intermediate filament proteins preferentially. A proportion of COMMA-D cells, therefore, appeared to have some of the characteristics of mammary stem cells, and retained the ability to differentiate and form phenotypically heterogeneous cell populations in vitro.     

The relationship between polyploidy and organogenetic potential in embryo- and root-derived tissue cultures of Vicia faba L.

The cell cycle was examined in embryo and root explants of Vicia faba in culture to test whether or not polyploidy and aneuploidy affected organogenetic potential. Nuclear DNA contents and the mitotic index were measured in the 0–1 mm apical segment of primary roots of 5-day old seedlings and at various times following transfer to modified MS in darkness or Chu's N6 medium in an 8 h light/16h dark cycle (N6-MS programme) at 20°C. Mature embryos were dissected and cut longitudinally. Each half was cultured on the N6-MS programme. Root explants grown on MS in darkness developed into callus but there was no subsequent organogenesis. Only on the N6-MS programme were new roots initiated from root-derived callus. Using the N6-MS programme, embryo-derived callus became green and after 3 to 4 months, produced roots and shoots. Approximately 40% of these cultures regenerated plantlets. Polyploidy occurred within 24 h of culture irrespective of both tissue source and culture protocol. Variations in chromosome number from 2n=2x=12 were also routinely observed. Thus, calluses had the ability to initiate roots and shoots regardless of persistent polyploidy and aneuploidy. Compared with the baseline of cell cycle data for roots in vivo, the proportions of cells in the different cell cycle phases remained constant. Thus, in V. faba induction of organogenesis seems more related to culture protocols than to specific changes to the cell cycle. The mitotic index was significantly lower in vitro compared with meristems of intact roots.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Synthesis of New Bis(pyrazolo[1,5-a]pyrimidines) Linked to Different Spacers as Potential MurB Inhibitors

An efficient protocol was adopted to efficiently prepare three new series of bis(pyrazolo[1,5-a]pyrimidines) linked to different spacers. The new bis(pyrazolo[1,5-a]pyrimidines) were prepared in 80–90 % yields by reacting the respective bis(enaminones) and 4-(4-substituted benzyl)-1H-pyrazole-3,5-diamines in pyridine at reflux temperature for 5–7 h. The new products showed a wide spectrum of antibacterial activity against six different bacterial strains. In general, propane- and butane-linked bis(pyrazolo[1,5-a]pyrimidines), which are attached to 3-(4-methyl- or 4-methoxybenzyl) units, had the best antibacterial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values up to 2.5 and 5.1 μM, respectively. Additionally, the previous products demonstrated promising MurB inhibitory activity with IC₅₀ values up to 7.2 μM.     

Intraspecific diversity in the fungal speciesChaunopycnis alba: Implications for microbial screening programs

Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics.