Mediciones de potencial zeta de microesferas de vidrio en glicol de etileno y en soluciones tampón de fosfato

Este artículo cubre el procedimiento y los resultados obtenidos midiendo potencial zeta (¿) de microesferas de vidrio en glicol de etileno y en soluciones tampón (soluciones buffer) de fosfato. El potencial zeta fue medido usando el dispositivo NICOMP ZLS 388 el cual emplea el principio de dispersión electroforética de la luz. El potencial zeta de las microesferas en soluciones de agua y glicol de etileno fue medido entre -63 y -68 mV y en las soluciones tampón de fosfato varia entre -60 y -110 mV. Los resultados que fueron obtenidos son comparados con resultados publicados para las soluciones mencionadas. Finalmente son discutidas las dificultades asociadas con la medición del potencial zeta.This report covers the procedure and results obtained by measuring zeta potential (¿) of glass microspheres in phosphate buffers and ethylene glycol. Zeta potential was measured using the NICOMP ZLS 388 which employs electrophoretic light scattering. Zeta potential in ethylene glycol-water solutions was measured between -63 and -68 mV. The measured zeta potential of glass microspheres in phosphate buffer solutions varied between -60 and -110 mV. The obtained results are compared with similar published results for ethylene glycol and buffer solutions. Also discussed are the difficulties associated with measuring the zeta potential

Regionally and climatically restricted patterns of distribution of genetic diversity in a migratory bat species, Miniopterus schreibersii (Chiroptera: Vespertilionidae)

<p>Abstract</p> <p>Background</p> <p>Various mechanisms such as geographic barriers and glacial episodes have been proposed as determinants of intra-specific and inter-specific differentiation of populations, and the distribution of their genetic diversity. More recently, habitat and climate differences, and corresponding adaptations have been shown to be forces influencing the phylogeographic evolution of some vertebrates. In this study, we examined the contribution of these various factors on the genetic differentiation of the bent-winged bat, <it>Miniopterus schreibersii</it>, in southeastern Europe and Anatolia.</p> <p>Results and conclusion</p> <p>Our results showed differentiation in mitochondrial DNA coupled with weaker nuclear differentiation. We found evidence for restriction of lineages to geographical areas for hundreds of generations. The results showed that the most likely ancestral haplotype was restricted to the same geographic area (the Balkans) for at least 6,000 years. We were able to delineate the migration routes during the population expansion process, which followed the coasts and the inland for different nested mitochondrial clades. Hence, we were able to describe a scenario showing how multiple biotic and abiotic events including glacial periods, climate and historical dispersal patterns complemented each other in causing regional and local differentiation within a species.</p

High yielding large-scale transient expression of Biotherapeutics in CHO: Beyond preclinical development

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Experimental Evaluation of Power Bus Decoupling on a 4-Layer Printed Circuit Board

The switching of active devices on printed circuit boards (PCBs) can cause a momentary surge or drop in the power bus voltage. Decoupling capacitors are often utilized to alleviate this problem. They help to stabilize the power bus voltage by supplying transient current to active devices. The decoupling strategy, including where to place the high-frequency decoupling capacitors, is often a topic of debate. This paper examines the effect of decoupling capacitor placement on a 4-layer printed circuit board. Some design guidelines are provided

Mitigating Power Bus Noise with Embedded Capacitance in PCB Designs

This paper investigates the power bus noise and power bus impedance of printed circuit boards with four different kinds of embedded capacitance. These boards have power-ground plane pairs separated by a very thin layer of material with high dielectric permittivity. It is shown that embedded capacitance effectively reduces power bus noise over the entire frequency range evaluated (up to 5 GHz)

Power-Bus Decoupling with Embedded Capacitance in Printed Circuit Board Design

This paper experimentally investigates the effectiveness of embedded capacitance for reducing power-bus noise in high-speed printed circuit board designs. Boards with embedded capacitance employ closely spaced power-return plane pairs separated by a thin layer of dielectric material. In this paper, test boards with four embedded capacitance materials are evaluated. Power-bus input impedance measurements and power-bus noise measurements are presented for boards with various dimensions and layer stack ups. Unlike discrete decoupling capacitors, whose effective frequency range is generally limited to a few hundred megahertz due to interconnect inductance, embedded capacitance was found to efficiently reduce power-bus noise over the entire frequency range evaluated (up to 5 GHz)

A multi-organ transcriptome resource for the Burmese Python (Python molurus bivittatus)

<p>Abstract</p> <p>Background</p> <p>Snakes provide a unique vertebrate system for studying a diversity of extreme adaptations, including those related to development, metabolism, physiology, and venom. Despite their importance as research models, genomic resources for snakes are few. Among snakes, the Burmese python is the premier model for studying extremes of metabolic fluctuation and physiological remodelling. In this species, the consumption of large infrequent meals can induce a 40-fold increase in metabolic rate and more than a doubling in size of some organs. To provide a foundation for research utilizing the python, our aim was to assemble and annotate a transcriptome reference from the heart and liver. To accomplish this aim, we used the 454-FLX sequencing platform to collect sequence data from multiple cDNA libraries.</p> <p>Results</p> <p>We collected nearly 1 million 454 sequence reads, and assembled these into 37,245 contigs with a combined length of 13,409,006 bp. To identify known genes, these contigs were compared to chicken and lizard gene sets, and to all Genbank sequences. A total of 13,286 of these contigs were annotated based on similarity to known genes or Genbank sequences. We used gene ontology (GO) assignments to characterize the types of genes in this transcriptome resource. The raw data, transcript contig assembly, and transcript annotations are made available online for use by the broader research community.</p> <p>Conclusion</p> <p>These data should facilitate future studies using pythons and snakes in general, helping to further contribute to the utilization of snakes as a model evolutionary and physiological system. This sequence collection represents a major genomic resource for the Burmese python, and the large number of transcript sequences characterized should contribute to future research in this and other snake species.</p

Joint Genome-Wide Profiling of miRNA and mRNA Expression in Alzheimer's Disease Cortex Reveals Altered miRNA Regulation

Although microRNAs are being extensively studied for their involvement in cancer and development, little is known about their roles in Alzheimer's disease (AD). In this study, we used microarrays for the first joint profiling and analysis of miRNAs and mRNAs expression in brain cortex from AD and age-matched control subjects. These data provided the unique opportunity to study the relationship between miRNA and mRNA expression in normal and AD brains. Using a non-parametric analysis, we showed that the levels of many miRNAs can be either positively or negatively correlated with those of their target mRNAs. Comparative analysis with independent cancer datasets showed that such miRNA-mRNA expression correlations are not static, but rather context-dependent. Subsequently, we identified a large set of miRNA-mRNA associations that are changed in AD versus control, highlighting AD-specific changes in the miRNA regulatory system. Our results demonstrate a robust relationship between the levels of miRNAs and those of their targets in the brain. This has implications in the study of the molecular pathology of AD, as well as miRNA biology in general

Power Bus Noise Reduction using Power Islands in Printed Circuit Board Designs

Power islands are often used to isolate devices that put noise on a power bus from devices that may be susceptible to power bus noise. At high frequencies however, the effectiveness of these islands depends on the implementation. This paper experimentally investigates the effectiveness of different power island structures at frequencies up to 3 GHz