535 research outputs found

    Neuronal Control of Swimming Behavior: Comparison of Vertebrate and Invertebrate Model Systems

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    Swimming movements in the leech and lamprey are highly analogous, and lack homology. Thus, similarities in mechanisms must arise from convergent evolution rather than from common ancestry. Despite over 40 years of parallel investigations into this annelid and primitive vertebrate, a close comparison of the approaches and results of this research is lacking. The present review evaluates the neural mechanisms underlying swimming in these two animals and describes the many similarities that provide intriguing examples of convergent evolution. Specifically, we discuss swim initiation, maintenance and termination, isolated nervous system preparations, neural-circuitry, central oscillators, intersegmental coupling, phase lags, cycle periods and sensory feedback. Comparative studies between species highlight mechanisms that optimize behavior and allow us a broader understanding of nervous system function

    EC94-852 Cash Flow Planning Form

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    This extension circular covers the following areas of a cash flow planning form: Beginning Cash Balance, Operating Sales (crop and hay, market livestock, livestock product, custom work); Capital Sales (breeding livestock, machinery and equipment); Personal Income (wages, interest); Operating Expenses (car/truck, chemicals, conservation, custom hire, feed purchased, fertilizers and lime, freight and trucking, gasoline, fuel and oil, insurance, labor hired, rents and leases, repairs and maintenance, seeds and plants, storage, warehousing, supplies, taxes, utilities, veterinary, breeding fees and medicine, feeder livestock); Capital Purchases (breeding livestock, machinery and equipment, family living withdrawals, personal investments, income and social security, term loan payments); Net Cash Available (operating loan borrowings, operating loan payments); and Ending Operating Loan Balance. Along with the Cash Flow Planning Form is a Projected Income Statement Form which covers Projected Business Income (operating sales, breeding livestock, estimated cash income adjustments, estimated gross revenues, estimated value of production); Project Business Expenses (cash operating, esimated operating, prepaid and supplies, cash investment in growing crops, accounts payable); Projected Net Income Summary (estimated net income from operations, estimated net business income, estimated net income after taxes, estimated earned net worth change); and a Physical Inventory Flows Worksheet

    Correlating Infall with Deuterium Fractionation in Dense Cores

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    We present a survey of HCO+ (3-2) observations pointed towards dense cores with previous measurements of N(N2D+)/N(N2H+). Of the 26 cores in this survey, five show the spectroscopic signature of outward motion, nine exhibit neither inward nor outward motion, eleven appear to be infalling, and one is not detected. We compare the degree of deuterium fractionation with infall velocities calculated from the HCO+ spectra and find that those cores with [D]/[H] > 0.1 are more likely to have the signature of inward motions than cores with smaller [D]/[H] ratios. Infall motions are also much more common in cores with masses exceeding their thermal Jeans masses. The fastest infall velocity measured belongs to one of the two protostellar cores in our survey, L1521F, and the observed motions are typically on the order of the sound speed.Comment: Accepted to Ap

    Comparison of Two-hinged and Hingeless Light Gage, Cold-formed Steel Frames

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    Agricultural Engineerin

    EC92-891, Farm Financial Records: Record-Keeping Alternatives For Nebraska Producers

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    A well organized and complete set of records is an important part of a successful farm business. Farm records are needed to prepare income tax reports, as a basis for credit, and to assist with management decisions including lease arrangements, insurance programs, cropping decisions, marketnig, and participation in government programs. Many options are available to Nebraska producers. They range from the simple hand-kept record books to fully computerized systems. A description of the major alternatives that are available to Nebraska producers follows in this publication

    Infall/Expansion Velocities in the Low-Mass Dense Cores L492, L694-2, and L1521F: Dependence on Position and Molecular Tracer

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    Although surveys of infall motions in dense cores have been carried out for years, few surveys have focused on mapping infall across cores using multiple spectral line observations. To fill this gap, we present IRAM 30-m Telescope maps of N2H+(1-0), DCO+(2-1), DCO+(3-2), and HCO+(3-2) emission towards two prestellar cores (L492 and L694-2) and one protostellar core (L1521F). We find that the measured infall velocity varies with position across each core and choice of molecular line, likely as a result of radial variations in core chemistry and dynamics. Line-of-sight infall speeds estimated from DCO+(2-1) line profiles can decrease by 40-50 m/s when observing at a radial offset >= 0.04 pc from the core's dust continuum emission peak. Median infall speeds calculated from all observed positions across a core can also vary by as much as 65 m/s depending on the transition. These results show that while single-pointing, single-transition surveys of core infall velocities may be good indicators of whether a core is either contracting or expanding, the magnitude of the velocities they measure are significantly impacted by the choice of molecular line, proximity to the core center, and core evolutionary state.Comment: Accepted for publication in Ap

    Concerted evolution of duplicated mitochondrial control regions in three related seabird species

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    <p>Abstract</p> <p>Background</p> <p>Many population genetic and phylogenetic analyses of mitochondrial DNA (mtDNA) assume that mitochondrial genomes do not undergo recombination. Recently, concerted evolution of duplicated mitochondrial control regions has been documented in a range of taxa. Although the molecular mechanism that facilitates concerted evolution is unknown, all proposed mechanisms involve mtDNA recombination.</p> <p>Results</p> <p>Here, we document a duplication of a large region (cytochrome <it>b</it>, tRNA<sup>Thr</sup>, tRNA<sup>Pro</sup>, ND6, tRNA<sup>Glu </sup>and the control region) in the mitochondrial genome of three related seabird species. To investigate the evolution of duplicate control regions, we sequenced both control region copies (CR1 and CR2) from 21 brown (<it>Sula leucogaster</it>), 21 red-footed (<it>S. sula</it>) and 21 blue-footed boobies (<it>S. nebouxii</it>). Phylogenetic analysis suggested that the duplicated control regions are predominantly evolving in concert; however, approximately 51 base pairs at the 5' end of CR1 and CR2 exhibited a discordant phylogenetic signal and appeared to be evolving independently.</p> <p>Conclusions</p> <p>Both the structure of the duplicated region and the conflicting phylogenetic signals are remarkably similar to a pattern found in <it>Thalassarche </it>albatrosses, which are united with boobies in a large clade that includes all procellariiform and most pelecaniform seabirds. Therefore we suggest that concerted evolution of duplicated control regions either is taxonomically widespread within seabirds, or that it has evolved many times.</p

    Cold temperature disinfestation of bagged flour

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    We conducted studies using a commercial freezer maintained at -17.8°C to determine the time needed to kill Tribolium castaneum eggs in a pallet of flour. Each bag weighed 22.7 kg, and there were 5 bags in each of 10 layers. The dimensions of the pallet were 109-cm wide by 132-cm long by 123-cm tall, and the weight of the stacked pallet was approximately 1152 kg. We conducted tests for nine internal goal temperatures of -12, -10, -8, -6, -4, -2, 0, 4 and 8°C. Internal temperatures in the most central location of the flour pallet reached: -11.0, -9.4, -6.9, -5.0, -3.5, -1.6, -0.1, 3.3, and 5.6°C and were achieved after 11.0, 9.1, 8.9, 7.2, 6.7, 5.8, 5.5, 5.2, and 4.2 days, respectively. For treatments where the goal temperature for the center bag ranged from -12 to 4°C, egg mortality was 100% in bags located in both the periphery and in the center of the pallet. When the temperature goal for the center bag was 8°C, 7 ± 2.5% of the eggs survived in bags located near the center of the pallet. Our data showed that temperatures that follow the dynamic temperature curve that takes place over 24.2 days (cool down and warm up for the 0°C temperature goal) resulted in 100% mortality of T. castaneum eggs. The reason for the difference in mortality for a static compared to a dynamic temperature treatment may be due to the fact that the dynamic temperature treatment occurs over a much longer duration. The fact that the treatment only required 5.5 days in the freezer before it could be shipped makes it a practical method to disinfest pallets of flour, especially because the bags do not need to be removed from the pallet and no chemicals are used
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