Three-dimensional flows in slowly-varying planar geometries

We consider laminar flow in channels constrained geometrically to remain between two parallel planes; this geometry is typical of microchannels obtained with a single step by current microfabrication techniques. For pressure-driven Stokes flow in this geometry and assuming that the channel dimensions change slowly in the streamwise direction, we show that the velocity component perpendicular to the constraint plane cannot be zero unless the channel has both constant curvature and constant cross-sectional width. This result implies that it is, in principle, possible to design "planar mixers", i.e. passive mixers for channels that are constrained to lie in a flat layer using only streamwise variations of their in-plane dimensions. Numerical results are presented for the case of a channel with sinusoidally varying width

A Strategic Approach to Agricultural Research Program Planning in Sub-Saharan Africa

Research and Development/Tech Change/Emerging Technologies, Downloads May 2008-July 2009: 13,

A Strategic Approach to Agricultural Research Program Planning in Sub-Saharan Africa

Recent studies have shown that agricultural research can have high payoffs in Africa, but impact depends on how well technology fits with evolving needs and capacity in the agricultural sector and the rest of the economy. Structural adjustment policies (e.g., market liberalization, currency devaluation) and political change are transforming user demands for new technology and the economic environment in which technology must perform. The challenge is how to design agricultural research as a strategic input to promote broad-based economic growth, structural transformation, and food security in the increasingly market-driven, but fragile, economies of Africa.Food Security, Food Policy, Agricultural Research, Research and Development/Tech Change/Emerging Technologies, Downloads May 2008-July 2009: 44, Q18,

A Global Photometric Analysis of 2MASS Calibration Data

We present results from the application of a global photometric calibration (GPC) procedure to calibration data from the first 2 years of The Two Micron All Sky Survey (2MASS). The GPC algorithm uses photometry of both primary standards and moderately bright `tracer' stars in 35 2MASS calibration fields. During the first two years of the Survey, each standard was observed on approximately 50 nights, with about 900 individual measurements. Based on the photometry of primary standard stars and secondary tracer stars and under the assumption that the nightly zeropoint drift is linear, GPC ties together all calibration fields and all survey nights simultaneously, producing a globally optimized solution. Calibration solutions for the Northern and Southern hemisphere observatories are found separately, and are tested for global consistency based on common fields near the celestial equator. Several results from the GPC are presented, including establishing candidate secondary standards, monitoring of near-infrared atmospheric extinction coefficients, and verification of global validity of the standards. The solution gives long-term averages of the atmospheric extinction coefficients, A_J=0.096, A_H=0.026, A_{K_s}=0.066 (North) and A_J=0.092, A_H=0.031, A_{K_s}=0.065 (South), with formal error of 0.001. The residuals show small seasonal variations, most likely due to changing atmospheric content of water vapor. Extension of the GPC to approximately 100 field stars in each of the 35 calibration fields yields a catalog of more than two thousand photometric standards ranging from 10th to 14th magnitude, with photometry that is globally consistent to $\sim 1$.Comment: 19 pages, 10 figures; Submitted to AJ. The table of secondary standards is available from ftp://nova.astro.umass.edu/pub/nikolaev/ or ftp://anon-ftp.ipac.caltech.edu/pub/2mass/globalcal

All Six Planets Known to Orbit Kepler-11 Have Low Densities

The Kepler-11 planetary system contains six transiting planets ranging in size from 1.8 to 4.2 times the radius of Earth. Five of these planets orbit in a tightly-packed configuration with periods between 10 and 47 days. We perform a dynamical analysis of the system based upon transit timing variations observed in more than three years of \ik photometric data. Stellar parameters are derived using a combination of spectral classification and constraints on the star's density derived from transit profiles together with planetary eccentricity vectors provided by our dynamical study. Combining masses of the planets relative to the star from our dynamical study and radii of the planets relative to the star from transit depths together with deduced stellar properties yields measurements of the radii of all six planets, masses of the five inner planets, and an upper bound to the mass of the outermost planet, whose orbital period is 118 days. We find mass-radius combinations for all six planets that imply that substantial fractions of their volumes are occupied by constituents that are less dense than rock. The Kepler-11 system contains the lowest mass exoplanets for which both mass and radius have been measured.Comment: 39 pages, 10 figure

Characterizing the gut microbiome in trauma: significant changes in microbial diversity occur early after severe injury.

Background:Recent studies have demonstrated the vital influence of commensal microbial communities on human health. The central role of the gut in the response to injury is well described; however, no prior studies have used culture-independent profiling techniques to characterize the gut microbiome after severe trauma. We hypothesized that in critically injured patients, the gut microbiome would undergo significant compositional changes in the first 72 hours after injury. Methods:Trauma stool samples were prospectively collected via digital rectal examination at the time of presentation (0 hour). Patients admitted to the intensive care unit (n=12) had additional stool samples collected at 24 hours and/or 72 hours. Uninjured patients served as controls (n=10). DNA was extracted from stool samples and 16S rRNA-targeted PCR amplification was performed; amplicons were sequenced and binned into operational taxonomic units (OTUs; 97% sequence similarity). Diversity was analyzed using principle coordinates analyses, and negative binomial regression was used to determine significantly enriched OTUs. Results:Critically injured patients had a median Injury Severity Score of 27 and suffered polytrauma. At baseline (0 hour), there were no detectable differences in gut microbial community diversity between injured and uninjured patients. Injured patients developed changes in gut microbiome composition within 72 hours, characterized by significant alterations in phylogenetic composition and taxon relative abundance. Members of the bacterial orders Bacteroidales, Fusobacteriales and Verrucomicrobiales were depleted during 72 hours, whereas Clostridiales and Enterococcus members enriched significantly. Discussion:In this initial study of the gut microbiome after trauma, we demonstrate that significant changes in phylogenetic composition and relative abundance occur in the first 72 hours after injury. This rapid change in intestinal microbiota represents a critical phenomenon that may influence outcomes after severe trauma. A better understanding of the nature of these postinjury changes may lead to the ability to intervene in otherwise pathological clinical trajectories. Level of evidence:III. Study type:Prognostic/epidemiological

Carriers of a novel frame-shift insertion in WNT16a possess elevated pancreatic expression of TCF7L2

BACKGROUND: The discovery of TCF7L2 as a global type 2 diabetes (T2D) gene has sparked investigations to explore the clinical utility of its variants for guiding the development of new diagnostic and therapeutic strategies. However, interpreting the resulting associations into function still remains unclear. Canonical Wnt signaling regulates β-catenin and its binding with TCF7L2, which in turn is critical for the production of glucagon-like peptide-1 (GLP-1). This study examines the role of a novel frame-shift insertion discovered in a conserved region of WNT16a, and it is proposed that this mutation affects T2D susceptibility in conjunction with gene variants in TCF7L2. RESULTS: Our results predicted that the insertion would convert the upstream open reading frame in the Wnt16a mRNA to an alternative, in-frame translation initiation site, resulting in the prevention of nonsense-mediated decay, leading to a consequent stabilization of the mutated WNT16a message. To examine the role of Wnt16a in the Wnt signaling pathway, DNA and serum samples from 2,034 individuals (48% with T2D) from the Sikh Diabetes Study were used in this investigation. Prevalence of Wnt16a insertion did not differ among T2D cases (33%) and controls (32%). However, there was a 3.2 fold increase in Wnt16a mRNA levels in pancreatic tissues from the insertion carriers and a significant increase (70%, p < 0.0001) in luciferase activity in the constructs carrying the insertion. The expression of TCF7L2 mRNA in pancreas was also elevated (~23-fold) among the insertion carriers (p=0.003). CONCLUSIONS: Our results suggest synergistic effects of WNT16a insertion and the at-risk ‘T’ allele of TCF7L2 (rs7903146) for elevating the expression of TCF7L2 in human pancreas which may affect the regulation of downstream target genes involved in the development of T2D through Wnt/β-catenin/TCF7L2 signaling pathway. However, further studies would be needed to mechanistically link the two definitively

Uma Abordagem Estratégica Sobre e Planificação de Programas de Pesquisa Agrícola na África Sub-Sahariana

Crop Production/Industries, Downloads July 2008-June 2009: 5,

Une approche stratégique pour la planification du programme de recherche agricole en Afrique sub-saharienne

Des études récentes ont montré que la recherche agricole en Afrique peut avoir une rentabilité élevée, mais son impact dépend de l'adaptabilité des nouvelles technologies aux capacités et aux besoins changeants du secteur agricole et du reste de l'économie. Les politiques d'ajustement structurel (ex : la libéralisation des marchés et la dévaluation monétaire) et les changements politiques sont en train de transformer la demande de nouvelles technologies et l'environnement économique au sein duquel ces technologies doivent opérer. Le défi est de concevoir la recherche agricole comme un intrant stratégique qui encourage une croissance économique à base élargie, la transformation structurelle de l'économie et la sécurité alimentaire dans des économies africaines de plus de plus orientées vers la production pour la commercialisation mais qui restent encore fragiles.food security, food policy, agricultural research, Research and Development/Tech Change/Emerging Technologies, Downloads June 2008-June 2009: 11, Q18,