3,824 research outputs found

    A Modest Proposal: Toward Improved Access to Biotechnology Research Tools by Implementing a Broad Experimental Use Exception

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    Economic Analysis of Base Acre and Payment Yield Designations Under the 2002 U.S. Farm Act

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    The 2002 Farm Act provided farmland owners the opportunity to update commodity program base acres and payment yields used for calculating selected program benefits. Findings in this report suggest that farmland owners responded to economic incentives in these decisions, selecting those options for designating base acres that resulted in the greatest expected flow of program payments. Decisions of farmland owners in South Dakota, in upland cotton area, and in the Heartland region support the payment-maximization argument. In general, landowners favored maximizing payments over aligning base acres to current or recent plantings. Farmland owners with high-payment base acres, such as rice and cotton, held on to these base acres and, whenever possible, expanded them. Analogously, landowners with low-payment commodity base acres, such as oats and barley, switched to higher payment commodities whenever possible.base, 2002 Farm Act, direct payments, counter-cyclical payments, production flexibility contract payments, base acres, program yields, Agricultural and Food Policy, Farm Management,

    The synoptic regulation of dryline intensity

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    To investigate the role of synoptic-scale processes in regulating the strength of the dryline, a dataset is constructed of all drylines occurring within the West Texas Mesonet (WTM) during April, May, and June of 2004 and 2005. In addition, dewpoint and wind data were collected from stations on the western (Morton; MORT) and eastern (Paducah; PADU) periphery of the WTM domain (230 km across), generally oriented east–west across the typical location of the dryline in west Texas. Drylines were characterized by two variables: the difference in dewpoint between MORT and PADU (hereafter, dryline intensity) and the difference in the eastward component of the wind between MORT and PADU (hereafter, dryline conflu-ence). A high degree of correlation existed between the two variables, consistent with a strong role for dryline confluence in determining dryline intensity. Some cases departing from the strong correlation between these variables represent synoptically quiescent drylines whose strength is likely dominated by boundary layer mixing processes. Composite synoptic analyses were constructed of the upper and lower quartiles of dryline intensity, termed STRONG and WEAK, respectively. STRONG drylines were associated with a short-wave trough in the upper-level westerlies approaching west Texas, an accompanying surface cyclone over eastern Ne

    Specificity and Actions of an Arylaspartate Inhibitor of Glutamate Transport at the Schaffer Collateral-CA1 Pyramidal Cell Synapse

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    In this study we characterized the pharmacological selectivity and physiological actions of a new arylaspartate glutamate transporter blocker, L-threo-ß-benzylaspartate (L-TBA). At concentrations up to 100 µM, L-TBA did not act as an AMPA receptor (AMPAR) or NMDA receptor (NMDAR) agonist or antagonist when applied to outside-out patches from mouse hippocampal CA1 pyramidal neurons. L-TBA had no effect on the amplitude of field excitatory postsynaptic potentials (fEPSPs) recorded at the Schaffer collateral-CA1 pyramidal cell synapse. Excitatory postsynaptic currents (EPSCs) in CA1 pyramidal neurons were unaffected by L-TBA in the presence of physiological extracellular Mg2+ concentrations, but in Mg2+-free solution, EPSCs were significantly prolonged as a consequence of increased NMDAR activity. Although L-TBA exhibited approximately four-fold selectivity for neuronal EAAT3 over glial EAAT1/EAAT2 transporter subtypes expressed in Xenopus oocytes, the L-TBA concentration-dependence of the EPSC charge transfer increase in the absence of Mg2+ was the same in hippocampal slices from EAAT3 +/+ and EAAT3 −/− mice, suggesting that TBA effects were primarily due to block of glial transporters. Consistent with this, L-TBA blocked synaptically evoked transporter currents in CA1 astrocytes with a potency in accord with its block of heterologously expressed glial transporters. Extracellular recording in the presence of physiological Mg2+ revealed that L-TBA prolonged fEPSPs in a frequency-dependent manner by selectively increasing the NMDAR-mediated component of the fEPSP during short bursts of activity. The data indicate that glial glutamate transporters play a dominant role in limiting extrasynaptic transmitter diffusion and binding to NMDARs. Furthermore, NMDAR signaling is primarily limited by voltage-dependent Mg2+ block during low-frequency activity, while the relative contribution of transport increases during short bursts of higher frequency signaling

    Information preserving structures: A general framework for quantum zero-error information

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    Quantum systems carry information. Quantum theory supports at least two distinct kinds of information (classical and quantum), and a variety of different ways to encode and preserve information in physical systems. A system's ability to carry information is constrained and defined by the noise in its dynamics. This paper introduces an operational framework, using information-preserving structures to classify all the kinds of information that can be perfectly (i.e., with zero error) preserved by quantum dynamics. We prove that every perfectly preserved code has the same structure as a matrix algebra, and that preserved information can always be corrected. We also classify distinct operational criteria for preservation (e.g., "noiseless", "unitarily correctible", etc.) and introduce two new and natural criteria for measurement-stabilized and unconditionally preserved codes. Finally, for several of these operational critera, we present efficient (polynomial in the state-space dimension) algorithms to find all of a channel's information-preserving structures.Comment: 29 pages, 19 examples. Contains complete proofs for all the theorems in arXiv:0705.428

    Triacylglycerol synthesis by PDAT1 in the absence of DGAT1 activity is dependent on re-acylation of LPC by LPCAT2

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    <p>Abstract</p> <p>Background</p> <p>The <it>Arabidopsis thaliana dgat1 </it>mutant, <it>AS11</it>, has an oil content which is decreased by 30%, and a strongly increased ratio of 18:3/20:1, compared to wild type. Despite lacking a functional DGAT1, <it>AS11 </it>still manages to make 70% of WT seed oil levels. Recently, it was demonstrated that in the absence of <it>DGAT1</it>, <it>PDAT1 </it>was essential for normal seed development, and is a dominant determinant in <it>Arabidopsis </it>TAG biosynthesis.</p> <p>Methods</p> <p>Biochemical, metabolic and gene expression studies combined with genetic crossing of selected <it>Arabidopsis </it>mutants have been carried out to demonstrate the contribution of <it>Arabidopsis </it>PDAT1 and LPCAT2 in the absence of DGAT1 activity.</p> <p>Results</p> <p>Through microarray and RT-PCR gene expression analyses of <it>AS11 </it>vs. WT mid-developing siliques, we observed consistent trends between the two methods. <it>FAD2 </it>and <it>FAD3 </it>were up-regulated and <it>FAE1 </it>down-regulated, consistent with the <it>AS11 </it>acyl phenotype. <it>PDAT1 </it>expression was up-regulated by <it>ca </it>65% while <it>PDAT2 </it>expression was up-regulated only 15%, reinforcing the dominant role of <it>PDAT1 </it>in <it>AS11 </it>TAG biosynthesis. The expression of <it>LPCAT2 </it>was up-regulated by 50-75%, while <it>LPCAT1 </it>expression was not significantly affected. <it>In vitro </it>LPCAT activity was enhanced by 75-125% in microsomal protein preparations from mid-developing <it>AS11 </it>seed <it>vs </it>WT. Co-incident homozygous knockout lines of <it>dgat1</it>/<it>lpcat2 </it>exhibited severe penalties on TAG biosynthesis, delayed plant development and seed set, even with a functional PDAT1; the double mutant <it>dgat1/lpcat1 </it>showed only marginally lower oil content than <it>AS11</it>.</p> <p>Conclusions</p> <p>Collectively, the data strongly support that in <it>AS11 </it>it is <it>LPCAT2 </it>up-regulation which is primarily responsible for assisting in PDAT1-catalyzed TAG biosynthesis, maintaining a supply of PC as co-substrate to transfer <it>sn</it>-2 moieties to the <it>sn</it>-3 position of the enlarged <it>AS11 </it>DAG pool.</p

    O/IR Polarimetry for the 2010 Decade (GAN): Science at the Edge, Sharp Tools for All

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    Science opportunities and recommendations concerning optical/infrared polarimetry for the upcoming decade in the field of Galactic science. Community-based White Paper to Astro2010 in response to the call for such papers.Comment: White Paper to the Galactic Neighborhood (GAN) Science Frontiers Panel of the Astro2010 Decadal Surve
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