1,019 research outputs found

    The excitation of O2 in auroras

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    Newly measured electron impact cross sections for excitation of the a 1 Delta g and b 1 Sigma g+ electronic states of O2 were employed to predict the absolute volume emission rates from these states under auroral conditions. A secondary electron electron flux typical of an IBC II nighttime aurora was used and the most important quenching processes were included in the calculations. The new excitation cross sections for the a 1 Delta g and b 1 Sigma g+ states are more than an order of magnitude larger than previous estimates, and lead to correspondingly greater intensities in the atmospheric and IR-atmospheric band systems. The calculated intensity ratios of the volume emission rates of 7621 A and 1.27 microns to that for 3914 A are smaller than obtained from aircraft observations and recent rocket experiments

    Factors Affecting Annual Deer Harvest in Arkansas

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    An understanding of general forces affecting annual harvest is essential to the management of white-tailed deer (Odocoileus virginianus). A predictive model based on such factors would be valuable to managers. The relationship between 27 different variables and annual, legal deer harvest in Arkansas was evaluated for 1957-1986. Variables most affecting harvest were soybean acreage, hay acreage, number of days in the deer season, rain during the deer season, and total state timber production, total state pulpwood production, and deer harvest 2 years prior. Because significant autocorrelation and heteroscedasticity were present in the variables, log-linear, first differencing and non-linear quasi-Newton regression methods were used in addition to ordinary least squares. First differencing removed autocorrelation and heteroscedasticity, but fit was not acceptable (R2 = 0.710). Non-linear estimation of first differenced log transformed variables provided an acceptably high R2 (0.896) with high significance of the individual parameter estimators. Factors associated with habitat quality 2 years prior most affected present-year deer harvest

    Depositional constraints from detrital zircon geochronology of strata from multiple lithotectonic belts in south-central Maine, USA

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    The bedrock geology of south-central Maine is characterized by a series of fault-bounded lithotectonic terranes that were accreted onto the Laurentian margin during Silurian-Devonian orogenesis.  The multiple phases of deformation and metamorphism associated with this tectonism obscured most primary features in the protolith rocks, leading to uncertainties in their pre-accretionary history. Here we present the results of detrital zircon geochronology from five of these terranes and make interpretations on their depositional ages, sediment provenance, and tectonic setting of deposition.Detrital zircon from Silurian rocks of the Vassalboro Group in the eastern-most portion of the Central Maine basin indicate sediment input in an extensional setting from both Laurentian and Ordovician sources.  Results from Ordovician rocks of the Casco Bay Group of the Liberty-Orrington belt support earlier findings that these rocks have strong peri-Gondwanan affinities.  Detrital zircon from the Appleton Ridge Formation and Ghent phyllite of the Fredericton trough are consistent with a peri-Gondwanan sediment source with no evidence of Laurentian sediment input.  These findings are consistent with that of Dokken et al. (2018) for older Fredericton trough strata (i.e., Digdeguash Formation) east of the Fredericton fault in southern New Brunswick.  Two samples from the Jam Brook complex reveal extreme differences in depositional age (Ordovician vs. Mesoproterozoic) and tectonic affinity and support the hypothesis that this narrow belt represents a fault complex containing a wide variety of stratigraphic units.  Detrital zircon from Ordovician rocks of the Benner Hill Sequence indicate a peri-Gondwanan sediment source with no Laurentian input.Collectively, the pre-Silurian rocks of the Liberty-Orrington belt, Jam Brook complex, Benner Hill Sequence, and Late Ordovician-Early Silurian strata from the Appleton Ridge and Ghent phyllite in the Fredericton trough show peri-Gondwanan affinities with no evidence of Laurentian sediment input.  This suggests a barrier exisited between the Laurentian margin and these peri-Gondwanan terranes prior to about 435 Ma.  In contrast, Silurian strata from the eastern portion of the Central Maine basin do show evidence of a Laurentian sediment source, along with deposition in an extensional setting (lacking in all other samples), thus signaling a fundamental change in tectonic regime

    Changing Hydrozoan Bauplans by Silencing Hox-Like Genes

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    Regulatory genes of the Antp class have been a major factor for the invention and radiation of animal bauplans. One of the most diverse animal phyla are the Cnidaria, which are close to the root of metazoan life and which often appear in two distinct generations and a remarkable variety of body forms. Hox-like genes have been known to be involved in axial patterning in the Cnidaria and have been suspected to play roles in the genetic control of many of the observed bauplan changes. Unfortunately RNAi mediated gene silencing studies have not been satisfactory for marine invertebrate organisms thus far. No direct evidence supporting Hox-like gene induced bauplan changes in cnidarians have been documented as of yet. Herein, we report a protocol for RNAi transfection of marine invertebrates and demonstrate that knock downs of Hox-like genes in Cnidaria create substantial bauplan alterations, including the formation of multiple oral poles (“heads”) by Cnox-2 and Cnox-3 inhibition, deformation of the main body axis by Cnox-5 inhibition and duplication of tentacles by Cnox-1 inhibition. All phenotypes observed in the course of the RNAi studies were identical to those obtained by morpholino antisense oligo experiments and are reminiscent of macroevolutionary bauplan changes. The reported protocol will allow routine RNAi studies in marine invertebrates to be established

    Pion-Muon Asymmetry Revisited

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    Long ago an unexpected and unexplainable phenomena was observed. The distribution of muons from positive pion decay at rest was anisotropic with an excess in the backward direction relative to the direction of the proton beam from which the pions were created. Although this effect was observed by several different groups with pions produced by different means, the result was not accepted by the physics community, because it is in direct conflict with a large set of other experiments indicating that the pion is a pseudoscalar particle. It is possible to satisfy both sets of experiments if helicity-zero vector particles exist and the pion is such a particle. Helicity-zero vector particles have direction but no net spin. For the neutral pion to be a vector particle requires an additional modification to conventional theory as discussed herein. An experiment is proposed which can prove that the asymmetry in the distribution of muons from pion decay is a genuine physical effect because the asymmetry can be modified in a controllable manner. A positive result will also prove that the pion is NOT a pseudoscalar particle.Comment: 9 pages, 3 figure
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