5,077 research outputs found

    HD 4915: A Maunder Minimum Candidate

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    We study the magnetic activity cycle of HD 4915 using the \ion{Ca}{2} H \& K emission line strengths measured by Keck I/HIRES spectrograph. The star has been observed as a part of California Planet Search Program from 2006 to present. We note decreasing amplitude in the magnetic activity cycle, a pattern suggesting the star's entry into a Magnetic Grand Minimum (MGM) state, reminiscent of the Sun's Maunder and Dalton Minima. We recommend further monitoring of the star to confirm the grand minimum nature of the dynamo, which would provide insight into the state of the Sun's chromosphere and the global magnetic field during its grand minima. We also recommend continued observations of H \& K emission lines, and ground or space based photometric observations to estimate the sunspot coverage.Comment: To be submitted to AAS Journals; comments welcom

    The effect of within-crop habitat manipulations on the conservation biological control of aphids in field-grown lettuce

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    Within-crop habitat manipulations have the potential to increase the biological control of pests in horticultural field crops. Wildflower strips have been shown to increase the abundance of natural enemies, but there is little evidence to date of an impact on pest populations. The aim of this study was to determine whether withincrop wildflower strips can increase the natural regulation of pests in horticultural field crops. Aphid numbers in plots of lettuce grown adjacent to wildflower strips were compared with those in plots grown in the absence of wildflowers. The presence of wildflower strips led to a decrease in aphid numbers on adjacent lettuce plants during June and July, but had less impact in August and September. The decrease in aphid numbers was greatest close to the wildflower strips and, the decrease in aphid numbers declined with increasing distance from the wildflower strips, with little effect at a distance of ten metres. The main natural enemies found in the crop were those that dispersed aerially, which is consistent with data from previous studies on cereal crops. Analysis and interpretation of natural enemy numbers was difficult due to low recovery of natural enemies, and the numbers appeared to follow changes in aphid abundance rather than being directly linked to the presence of wildflower strips. Cutting the wildflower strips, to remove floral resources, had no impact on the reduction in aphid numbers achieved during June and July, but decreased the effect of the wildflower strips during August and September. The results suggest that wildflower strips can lead to increased natural regulation of pest aphids in outdoor lettuce crops, but more research is required to determine how this is mediated by natural enemies and how the impact of wildflower strips on natural pest regulation changes during the growing season

    Can Computers Motivate? The Association Between End User Computing Levels, Job Motivation, And Job Core Characteristics: A Field Study

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    While end user computing (EUC) has been studied from the standpoint of classification and management, less attention has been placed on how the utilization of the technology impacts on users jobs.  This study proposes that differing levels of EUC activity will be associated with differing levels of job characteristics and computer related job outcomes.  The study focused on the jobs of 121 middle managers and professional workers enrolled in an MBA program at a southeastern university.  The study finds that with successive levels of complexity in EUC utilization, there are corresponding increases in the levels of users' experiencing of job core characteristics

    Early CRT monitoring using time-domain optical coherence tomography does not add to visual acuity for predicting visual loss in patients with central retinal vein occlusion treated with intravitreal ranibizumab:A secondary analysis of trial data

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    Our primary purpose was to assess the clinical (predictive) validity of central retinal thickness (CRT) and best corrected visual acuity (BCVA) at 1 week and 1 month after starting treatment with ranibizumab for central retinal vein occlusion. The authors also assessed detectability of response to treatment

    The Economic Value of Irrigation in the Texas Panhandle

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    The Texas Panhandle relies largely on the Ogallala Aquifer for access to water for irrigated agricultural production. With current pumping rates and slow recharge rates, the aquifer will at some point in the future no longer be an economically viable source of water for agriculture. The objective of this study is to estimate the value of irrigated agriculture to the region. A hypothetical policy restriction is imposed which assumes a one hundred percent conversion to dryland agriculture. The study estimates the economic impact of such a change on producer income and the resulting socioeconomic impacts on communities in the region.economic impacts, IMPLAN, irrigated production, Ogallala Aquifer, water policy, Community/Rural/Urban Development, Environmental Economics and Policy, Q18, Q32, Q38,

    Understanding Soybean Plant Population Recommendations for Iowa

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    Concerns over rapidly escalating seed prices have caused farmers, agronomists, and seed suppliers to revisit soybean planting rates. This publication discusses optimum soybean planting rates in Iowa and surrounding states. This is a must read for those who want to reduce their seed input costshttps://lib.dr.iastate.edu/extension_ag_pubs/1179/thumbnail.jp

    Promyelocytic leukemia protein isoform II inhibits infection by human adenovirus type 5 through effects on HSP70 and the interferon response

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    Promyelocytic leukemia (PML) proteins have been implicated in antiviral responses but PML and associated proteins are also suggested to support virus replication. One isoform, PML-II, is required for efficient transcription of interferon and interferon-responsive genes. . We therefore investigated the PML-II contribution to human adenovirus 5 (Ad5) infection, using shRNA-mediated knock-down. HelaΔII cells showed a 2 - 3 fold elevation in Ad5 yield, reflecting an increase in late gene expression. This increase was found to be due in part to the reduced innate immune response consequent upon PML-II depletion. However the effect was minor because the viral E4 Orf3 protein targets and inactivates this PML-II function. The major benefit to Ad5 in HelaΔII cells was exerted via an increase in HSP70; depletion of HSP70 completely reversed this replicative advantage. Increased Ad5 late gene expression was not due either to the previously described inhibition of inflammatory responses by HSP70 or to effects of HSP70 on major late promoter or L4 promoter activity but might be linked to an observed increase in E1B 55K, as this protein is known to be required for efficient late gene expression. The induction of HSP70 by PML-II removal was specific for the HSPA1B gene among the HSP70 gene family and thus was not the consequence of a general stress response. Taken together, these data show that PML-II, through its various actions, has an overall negative effect on the Ad5 life-cycle

    K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147

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    We identify a sub-Neptune exoplanet (Rp=2.5±0.2R_p = 2.5 \pm 0.2 R⊕_\oplus) transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H] = +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2 Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%, and a duration of ~4 hours. Based on our analysis of high-resolution MIKE spectra, broadband optical and NIR photometry, the cluster parallax and interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST, we estimate the following properties for the host star: M⋆=1.01±0.03M_\star = 1.01 \pm 0.03 M⊙_\odot, R⋆=0.95±0.03R_\star= 0.95 \pm 0.03 R⊙_\odot, and Teff=5695±50T_{\rm eff} = 5695 \pm 50 K. This star appears to be single, based on our modeling of the photometry, the low radial velocity variability measured over nearly ten years, and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry. Applying a probabilistic mass-radius relation, we estimate that the mass of this planet is Mp=7+5−3M_p = 7 +5 -3 M⊕_\oplus, which would cause a RV semi-amplitude of K=2±1K = 2 \pm 1 m s−1^{-1} that may be measurable with existing precise RV facilities. After statistically validating this planet with BLENDER, we now designate it K2-231 b, making it the second sub-stellar object to be discovered in Ruprecht 147 and the first planet; it joins the small but growing ranks of 23 other planets found in open clusters.Comment: 24 pages, 7 figures, light curve included as separate fil
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