4,395 research outputs found

    Studies in the use of cloud type statistics in mission simulation

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    A study to further improve NASA's global cloud statistics for mission simulation is reported. Regional homogeneity in cloud types was examined; most of the original region boundaries defined for cloud cover amount in previous studies were supported by the statistics on cloud types and the number of cloud layers. Conditionality in cloud statistics was also examined with special emphasis on temporal and spatial dependencies, and cloud type interdependence. Temporal conditionality was found up to 12 hours, and spatial conditionality up to 200 miles; the diurnal cycle in convective cloudiness was clearly evident. As expected, the joint occurrence of different cloud types reflected the dynamic processes which form the clouds. Other phases of the study improved the cloud type statistics for several region and proposed a mission simulation scheme combining the 4-dimensional atmospheric model, sponsored by MSFC, with the global cloud model

    Advances in startercultures and cultured foods

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    With 2005 retail sales close to $4.8 million, cultured dairy products are driving the growth of dairy foods consumption. Starter cultures are of great industrial significance in that they play a vital role in the manufacturing, flavor, and texture development of fermented dairy foods. Furthermore, additional interest in starter bacteria has been generated because of the data accumulating on the potential health benefits of these organisms. Today, starter cultures for fermented foods are developed mainly by design rather than by the traditional screening methods and trial and error. Advances in genetics and molecular biology have provided opportunities for genomic studies of these economically significant organisms and engineering of cultures that focuses on rational improvement of the industrially useful strain. Furthermore, much research has been published on the health benefits associated with ingesting cultured dairy foods and probiotics, particularly their role in modulating immune function. The aim of this review is to describe some of the major scientific advances made in starter and non-starter lactic acid bacteria during the past 10 yr, including genomic studies on dairy starter cultures, engineering of culture attributes, advances in phage control, developments in methods to enumerate lactic acid bacteria and probiotics in dairy foods, and the potential role of cultured dairy foods in modulation of immune function

    Young people and political action: who is taking responsibility for positive social change?

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    A human rights perspective suggests that we are all responsible for ensuring the human rights of others, which in turn ensures that our own human rights are respected and protected. A convenience sample of 108 young people (41 males and 67 females) aged between 16 and 25 completed a questionnaire which asked about (a) levels of involvement in political activity and (b) sense of personal responsibility for ensuring that the human rights of marginalised groups (e.g. ethnic minorities, immigrants, lesbians and gay men) are protected. Findings showed that most respondents supported (in principle) the notion of human rights for all, but tended to engage in low key political activity (e.g. signing petitions; donating money or goods to charity) rather than actively working towards positive social change. Qualitative data collected in the questionnaire suggested three main barriers to respondents viewing themselves as agents of positive social change: (1) "It’s not my problem", (2) "It’s not my responsibility", and (3) a sense of helplessness. Suggestions for how political action might best be mobilised among young people are also discussed.</p

    Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524

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    The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope commissioning phases, as well as observations with the full four-telescope array. \objectname{1ES 0806+524} is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly time scales is found. The photon spectrum for the period November 2007 to April 2008 can be characterized by a power law with photon index 3.6±1.0stat±0.3sys3.6 \pm 1.0_{\mathrm{stat}} \pm 0.3_{\mathrm{sys}} between ∼\sim300 GeV and ∼\sim700 GeV. The integral flux above 300 GeV is (2.2±0.5stat±0.4sys)×10−12 cm2 s−1(2.2\pm0.5_{\mathrm{stat}}\pm0.4_{\mathrm{sys}})\times10^{-12}\:\mathrm{cm}^{2}\:\mathrm{s}^{-1} which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous multiwavelength observations are combined with the VHE data to produce a broadband spectral energy distribution that can be reasonably described using a synchrotron-self Compton model.Comment: 14 pages, 4 figures, accepted to APJ

    Detection of Extended VHE Gamma Ray Emission from G106.3+2.7 with VERITAS

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    We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3 sigma (pre-trials) detection has a full angular extent of roughly 0.6deg by 0.4deg. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 0.4deg away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. The VHE energy spectrum measured with VERITAS is well characterized by a power law dN/dE = N_0(E/3 TeV)^{-G} with a differential index of G = 2.29 +/- 0.33stat +/- 0.30sys and a flux of N_0 = (1.15 +/- 0.27stat +/- 0.35sys)x 10^{-13} cm^{-2} s^{-1} TeV^{-1}. The integral flux above 1 TeV corresponds to ~5 percent of the steady Crab Nebula emission above the same energy. We describe the observations and analysis of the object and briefly discuss the implications of the detection in a multiwavelength context.Comment: 5 pages, 2 figure

    Network development in biological gels: role in lymphatic vessel development

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    In this paper, we present a model that explains the prepatterning of lymphatic vessel morphology in collagen gels. This model is derived using the theory of two phase rubber material due to Flory and coworkers and it consists of two coupled fourth order partial differential equations describing the evolution of the collagen volume fraction, and the evolution of the proton concentration in a collagen implant; as described in experiments of Boardman and Swartz (Circ. Res. 92, 801–808, 2003). Using linear stability analysis, we find that above a critical level of proton concentration, spatial patterns form due to small perturbations in the initially uniform steady state. Using a long wavelength reduction, we can reduce the two coupled partial differential equations to one fourth order equation that is very similar to the Cahn–Hilliard equation; however, it has more complex nonlinearities and degeneracies. We present the results of numerical simulations and discuss the biological implications of our model

    Evaluation of Genetic Diversity in White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.) Through Measurement of Simple Sequence Repeat (SSR) Polymorphism

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    White clover (Trifolium repens L.) is a key important temperate pasture legume. Due to the obligate outbreeding nature of white clover, individual genotypes within cultivars are highly genetically heterogeneous. Genetic diversity has been assessed within and between 16 elite cultivars derived from Europe, North and South America, New Zealand and Australia

    VERITAS Upper Limit on the VHE Emission from the Radio Galaxy NGC 1275

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    The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E > 100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei (AGN) with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hours. No VHE gamma-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope (LAT) result.Comment: Accepted for publication in ApJ Letter

    Quantitative Trait Locus Analysis of Morphogenetic and Developmental Traits in an SSR and AFLP-Based Genetic Map of White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.)

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    Molecular marker-assisted plant breeding is a key target for the temperate legume pasture crop white clover (Trifolium repens L.). The first genetic linkage map of white clover has been constructed using self-fertile mutants to derive an intercross based fourth and fifth generation inbred parental genotypes (F2[I.4R x I.5J]). The framework map was constructed using simple sequence repeat (TRSSR) and amplified fragment length polymorphism (AFLP) markers. Eighteen linkage groups (LG) corresponding to the anticipated 16 chromosomes of white clover (2n = 4x = 32), with a total map length of 825 cM were derived from a total of 135 markers (78 TRSSR loci and 57 AFLP loci). The F2(I.4R x I.5J) family has been subjected to intensive phenotypic analysis for a range of morphogenetic and developmental traits over several years at IGER, Aberystwyth, Wales and East Craigs, near Edinburgh, Scotland. The resulting phenotypic data were analysed independently to identify QTL (quantitative trait loci) for the various traits, using single marker regression (SMR), interval mapping (IM) and composite interval mapping (CIM) techniques. Multiple coincident QTL regions were identified from the different years and different sites for the same or related traits. The data were reanalysed using a meta-analysis across years and sites and Best Linear Unbiased Estimates (BLUEs) were derived for the plant spread, petiole length, leaf width, leaf length, leaf area, internode length, plant height and flowering date traits. A total of 24 QTLs were identified on 10 of the linkage groups. Three regions on LGs 2, 7 and 12 all demonstrated overlapping QTLs for multiple traits (Figure 1). A meta-analysis approach can quickly identify regions of the genome that control the trait in a robust predictable manner across multiple spatial and temporal replication for rapid targeted genetic enhancement via marker-assisted breeding. This first genetic dissection of agronomic traits in white clover provides the basis for comparative trait-mapping studies and the enhanced development and implementation of marker-assisted breeding strategies
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