Finite element Soret Dufour effects on an unsteady MHD heat and mass transfer flow past an accelerated inclined vertical plate

The present study is focused on the Soret and Dufour effects on magnetohydrodynamics unsteady fluid flow over an accelerated inclined vertical plate with thermal radiation and heat source. Solution of the nondimensional governing differential equations are worked out by the efficient Galerkin finite element method. The influence of several relevant flow parameters on velocity, temperature, and concentration distributions, as well as the numerical results, are studied and graphically displayed. The nondimensional skin friction and the rate of heat and mass transfer parameters are presented in the Tables 1-3 below. Raising the Soret number results in growing concentrations, but the converse is true for the Schmidt number. Skin friction reduces when Soret and Dufour numbers increase. The present simulations apply to the processing of magnetic materials in the chemical and metallurgical industries.     

Predominance of Bacilli and Clostridia in microbial community of biohydrogen producing biofilm sustained under diverse acidogenic operating conditions

Microbial community structure of acidogenic biofilm from long-term operated sequencing batch bioreactor producing biohydrogen was analyzed through culture independent technique. Bioreactor was operated under variable operation and substrate conditions for a period of 1435 days. Phylogenetic distribution showed a significant diversity and illustrated the presence of four dominant operational taxonomic units (OTUs) viz., Bacteroidia, Bacilli, Clostridia, Flavobacteria and Aquificae. Dominance of Clostridia and Bacilli classes were observed each with four OTUs. Majority of OTUs were found to produce fermentative H₂. Even at higher load and under diverse operating conditions bioreactor functioned without any process inhibition which indicates the robustness of sustained microbial community. Community structure of bioreactor was comparatively evaluated with other bioreactor producing H₂, operated with same parent culture and conditions but with different substrates, established the dynamics and shift of microbial diversity which corresponded to diverse substrates used for the bioreactor operation.     

ARNO3, a Sec7-domain guanine nucleotide exchange factor for ADP ribosylation factor 1, is involved in the control of Golgi structure and function

Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat proteins and is regulated by ADP ribosylation factor (ARF) 1. ARF1 activation is promoted by guanine nucleotide exchange factors (GEFs), which catalyze the transition to GTP-bound ARF1. We recently have identified a human protein, ARNO (ARF nucleotide-binding-site opener), as an ARF1-GEF that shares a conserved domain with the yeast Sec7 protein. We now describe a human Sec7 domain-containing GEF referred to as ARNO3. ARNO and ARNO3, as well as a third GEF called cytohesin-1, form a family of highly related proteins with identical structural organization that consists of a central Sec7 domain and a carboxy-terminal pleckstrin homology domain. We show that all three proteins act as ARF1 GEF in vitro, whereas they have no effect on ARF6, an ARF protein implicated in the early endocytic pathway. Substrate specificity of ARNO-like GEFs for ARF1 depends solely on the Sec7 domain. Overexpression of ARNO3 in mammalian cells results in (i) fragmentation of the Golgi apparatus, (ii) redistribution of Golgi resident proteins as well as the coat component beta-COP, and (iii) inhibition of SEAP transport (secreted form of alkaline phosphatase). In contrast, the distribution of endocytic markers is not affected. This study indicates that Sec7 domain-containing GEFs control intracellular membrane compartment structure and function through the regulation of specific ARF proteins in mammalian cells.     

Sweet Potato Starch Microparticles as Controlled Drug Release Carriers: Preparation and In Vitro Drug Release

The aim of this study was to investigate the in vitro drug release behavior of sweet potato starch (SPS) microparticles intended for controlled drug delivery applications. Diclofenac sodium (DS) was used as a model drug candidate in the present study. SPS microparticles were prepared using a spray-drying technique by varying the polymer concentration and drug loading. The mean particles size of drug-loaded spray-dried SPS microparticles was between 10.3 and 13.1 µm. The mean particle size increased slightly with increase in the concentration of SPS. The mean particle size of spray-dried SPS microparticles increased from 10.3 to 13.1 µm when the concentration of SPS increased from 2 to 4% w/v. Under the current spray-drying conditions, the percentage yield of spray-dried SPS microparticles did not vary much among the various formulations and it was between 65.2 and 70.1%. The encapsulation efficiencies of SPS microparticles formulations was between 95.1–98.2%, suggesting good encapsulating ability of the SPS polymer by spary drying. Drug release from all the formulations of spray-dried SPS microparticles was controlled over period of 6 h. The cumulative amount of drug release from the spray-dried SPS microparticles decreased with an increase in the concentration of SPS, while it increases as the drug loading is increased. Release of the drug from spray-dried SPS microparticles followed Fick's law of diffusion since a good correlation coefficient (R²) was observed with the Higuchi plots (R² = 0.9928 to 0.9979).     

Chromatin decondensation, pronucleus formation, metaphase entry and chromosome complements of human spermatozoa after intracytoplasmic sperm injection into hamster oocytes

Obtaining karyotypes from human spermatozoa after microinjection into Syrian golden hamster oocytes is difficult and the hitherto reported results are unsatisfactory. This may be related to the injection and culture technique or to the high susceptibility of the hamster oocytes to undergo parthenogenetic activation or both. Therefore, we investigated the hamster oocyte-human sperm microinjection model using the following two approaches: (i) application of contemporary techniques for injection (touching the sperm tail) and culture (hamster embryo culture medium, HECM-3, 10% CO2) and (ii) omission of Ca2+ from the injection medium. Thus, in the first series of experiments, 252 hamster oocytes were injected with human spermatozoa. Among the 219 (87%) oocytes that survived the injection procedure, the mean percentages of male pronucleus formation [two pronuclei (2PN), two polar bodies (PB)], mitotic metaphase entry and sperm chromosome spreads were 41.4, 27.8 and 18.2% respectively. Analysis of the oocytes which failed to develop the male pronucleus following injection revealed that most of them had developed only the hamster female PN while the sperm nuclei were either intact or swollen (partially decondensed), indicating that failure of oocyte activation was not the likely reason for the failure of male PN formation in these oocytes. In the next series of experiments, sibling oocytes were alternately injected with spermatozoa suspended either in the regular (1.9 mM Ca2+) or Ca2+-free injection medium (experiment set 2, n=278). A significant improvement was noted in the mean percentages of oocytes with 2PN, 2PB, metaphase entry and sperm chromosome spreads in the Ca2+-free group versus the regular group (2PN, 2PB: 51 versus 36.6%, metaphase entry: 36.3 versus 26.9% and sperm chromosome spreads: 28 versus 20.4%; all P < 0.04). Thus, parthenogenetic activation appears to be one of the contributing factors for the failure of male PN formation after heterospecific hamster ICSI. From these experiments it can be concluded that application of the advanced injection and culture techniques and omission of Ca2+ from the injection medium are promising for the routine application of the hamster oocyte microinjection for karyotyping of human spermatozoa with poor fertilizing capacity.     

Analysis and optimal design of semi-insulator passivatedhigh-voltage field plate structures and comparison with dielectricpassivated structures

The influences of the field oxide thickness and the junction depth on the breakdown voltage of semi-insulator passivated planar junctions with the field plate are investigated using a 2D simulator. This is done by analyzing the two extreme situations: the planar junction with an infinitely long field plate, and the deep-depleted MOS structure having a finite size. This rather unconventional approach has offered a new physical insight into the role of the metal field plate and has revealed that the severe field crowding associated with a shallow planar junction can be greatly suppressed by using a thin field oxide. The breakdown voltage and the optimal field oxide thickness of the semi-insulator passivated field plate structures remain nearly constant over a wide variation in the junction depth, and therefore such structures are attractive for realizing high-voltages in vertical devices fabricated by low-voltage IC technology. The influences of the field plate width and the inter-electrode spacing are studied by the conventional approach, and a simple and widely applicable design guideline is given for both the nonpunchthrough and the punchthrough type structures. The influence of the surface charge in the range 0 to 10¹² cm^-2 is found to be negligible. The semi-insulator passivated and the dielectric passivated field plate structures are compared under optimal conditions. This suggests that the semi-insulator passivated structures are attractive when thin field oxide and a shallow planar junction are needed and that the dielectric passivated structures are better when compactness is desired     

Trellis-coded CPFSK and soft-decision feedback equalization for micro-cellular wireless applications

In this paper, trellis-codedM-ary CPFSK with noncoherent envelope detection and adaptive channel equalization are investigated to improve the bit error rate (BER) performance of microcellular digital wireless communications systems. For the same spectral efficiency, the trellis-coded modulation (TCM) schemes studied outperform minimum shift keying (MSK) with noncoherent or differentially coherent detection in Rayleigh fading channels. For the case of frequency-selective fading channels, adaptive channel equalization is applied to mitigate the time-variant intersymbol interference (ISI). A new equalizer structure is proposed which, in its feedback path, makes use of fractionally spaced signal samples instead of symbol-spaced hard decisions on transmitted symbols. Computer simulation results indicate that the soft-decision feedback equalizer (SDFE) can significantly improve the system's performance.     

Isolement de bacteries pathogenes contaminant une eau a l'aide d'immunoadsorbants

The potability of water is indicated by the presence or the absence of bacteria from faecal origin. According to the World Health Organization, water is not considered dangerous in the absence of such bacteria. However, only a water free of true pathogenic bacteria is clearly drinkable. In our laboratory, we have elaborated a method allowing direct isolation from water of the main pathogenic bacteria which are common faecal contaminants. These bacteria include Salmonella typhi-murium, Escherichia coli K 88 and K 99 and Vibrio cholerae of the El Tor biotype. Our method consists of filtering contaminated water through small immunoabsorbant columns packed with polyacrylamide-agarose beads coupled to specific antibodies against bacterial antigenic structures.Antisera were obtained from rabbits immunized with antigenic fractions of the bacterial walls, known as Ch 1 + 2 (V. cholerae) Tm 1 + 2 (S. typhi-murium), Ec 1 + 2 K 88 and K 99 (E. coli K 88 and K 99). Antibodies were then isolated and coupled to glutaraldehyde-activated 3% polyacrylamide 4% agarose beads (AcA 34). 500 ml of contaminated water was filtered through the columns. The water consisted either of artificially contaminated samples from the Oise river (France) or of similarly contaminated saline. After filtration, the beads were recovered from the columns, diluted in hypersaline peptone water (V. cholerae) or saline (S. typhi-murium, E. coli K 88 and K 99) and incubated overnight at 37°C. The growth from the hypersaline peptone or saline broth was then removed, placed onto Petri dishes and the colonies were counted.Water samples containing a mixture of 10³ of each of the four bacteria were filtered through beads coated with the different antibodies. Bacteria retained on the beads were only those against which antibodies were directed (Table 1). On the other hand, we have analysed column effluent waters after passing 10³ bacteria through the relevant columns. No bacteria were detected after filtration, which suggest that most of the bacteria were retained on the beads. Bacteria were found in column effluent waters when the water samples contained more than 10⁵ bacteria.This technique is highly specific and allows the filtration of relatively large quantities of water. We believe the method may prove useful for collecting pathogenic bacteria from water directly, without the need for the usual isolation steps.     

Improvement of intermodulation distortion in microwave m.e.s.f.e.t. amplifiers using gate-bias compensation

A simple technique is described for improving the intermodulation distortion performance of microwave m.e.s.f.e.t. amplifiers. The technique utilises transistor gate-bias compensation controlled by the input signal level of the amplifier. For a constant output power of 0 dBm, an improvement in third-order intermodulation distortion product of up to 10 dB has been observed. The advantages and limitations of the technique are discussed.