103 research outputs found

    Herbicide Control of Broom Snakeweed (Gutierrezia sarothrae)

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    Broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) is a native invasive species that is widely distributed across western North America. It is very competitive with other vegetation and can reduce or displace desirable grasses and forbs. Removal of snakeweed from rangelands can result in increased forage production of desirable plant species. The evaluation of new herbicides to determine their efficacy in controlling broom snakeweed assists in providing land managers with alternatives to control broom snakeweed. The objective of this study was to evaluate herbicides applied in the spring to determine efficacy of control of broom snakeweed. 2,4-D + triclopyr had the greatest reduction in snakeweed density at 97 ± 14.6 % (P \u3c 0.0001). Aminopyralid and 2,4-D were also effective at reducing snakeweed density at 73 ± 14.6 % control. Our results demonstrate that 2,4-D + triclopyr, a new herbicide, can be used in controlling broom snakeweed in the spring

    X-Ray Timing of the Young Pulsar in 3C 58

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    PSR J0205+6449 is a young pulsar in the Crab-like pulsar wind nebula 3C 58 which is thought to be a result of the historical supernova SN1181 CE. The 65.7-ms pulsar is the second most energetic of the known Galactic pulsars and has been shown to be remarkably cool for its age, implying non-standard cooling processes in the neutron star core. We report on RXTE timing observations taken during AO7 and supplemented by monthly radio observations of the pulsar made with the Green Bank Telescope (GBT). The total duration covered with the timing solutions is 450 days. We measure very high levels of timing noise from the source and find evidence for a ``giant'' glitch of magnitude Delta nu/nu ~ 1x10^-6 that occurred in 2002 October. We have also measured the phase-resolved spectra of the pulsations and find them to be surprisingly hard, with photon indices Gamma = 0.84 +0.06/-0.15 for the main pulse and Gamma = 1.0 +0.4/-0.3 for the interpulse assuming an absorbed power-law model.Comment: 4 pages, 6 figures. To appear in the proceedings of X-ray Timing 2003: Rossi and Beyond, ed. P. Kaaret, F.K. Lamb, & J.H. Swank (Melville, NY: American Institute of Physics

    Comparative genomics of borderline oxacillin-resistant Staphylococcus aureus detected during a pseudo-outbreak of methicillin-resistant S. aureus in a neonatal intensive care unit

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    Active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) is a component of our neonatal intensive care unit (NICU) infection prevention efforts. Recent atypical trends prompted review of 42 suspected MRSA isolates. Species identification was confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and methicillin resistance was reevaluated by PBP2a lateral flow assay, cefoxitin/oxacillin susceptibility testing

    Consumption of endophyte-infected fescue seed during the dry period does not decrease milk production in the following lactation.

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    Ergot alkaloids in endophyte-infected grasses inhibit prolactin (PRL) secretion and may reduce milk production of cows consuming these grasses. We investigated the effects of consuming endophyte-infected fescue seed during late lactation and the dry period on mammary growth, differentiation, and milk production. Twenty-four multiparous Holstein cows were randomly assigned to 3 treatment groups. Starting at 90±4 d prepartum, cows were fed endophyte-free fescue seed (control; CON), endophyte-free fescue seed plus 3×/wk subcutaneous injections of bromocriptine (0.1mg/kg of body weight, positive control; BROMO), or endophyte-infected fescue seed (INF) as 10% of the diet on an as fed basis. Although milk yield of groups did not differ before treatment, at dry off (-60 d prepartum) INF and BROMO cows produced less milk than CON. Throughout the treatment period, basal concentrations of PRL and the prepartum increase in plasma PRL were reduced in INF and BROMO cows compared with CON cows. Three weeks after the end of treatment, circulating concentrations of PRL were equivalent across groups. In the subsequent lactation milk yield was not decreased; in fact, BROMO cows exhibited a 9% increase in milk yield relative to CON. Evaluation of mammary tissue during the dry period and the subsequent lactation, by quantitative histology and immunohistochemical analysis of proliferation markers and putative mammary stem or progenitor cell markers, indicated that feeding endophyte-infected fescue seed did not significantly affect mammary growth and development. Feeding endophyte-infected grasses during the dry period may permit effective utilization of feed resources without compromising milk production in the next lactation

    Functional Identification of Valerena-1,10-diene Synthase, a Terpene Synthase Catalyzing a Unique Chemical Cascade in the Biosynthesis of Biologically Active Sesquiterpenes in Valeriana officinalis

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    Valerian is an herbal preparation from the roots of Valeriana officinalis used as an anxiolytic and sedative and in the treatment of insomnia. The biological activities of valerian are attributed to valerenic acid and its putative biosynthetic precursor valerenadiene, sesquiterpenes, found in V. officinalis roots. These sesquiterpenes retain an isobutenyl side chain whose origin has been long recognized as enigmatic because a chemical rationalization for their biosynthesis has not been obvious. Using recently developed metabolomic and transcriptomic resources, we identified seven V. officinalis terpene synthase genes (VoTPSs), two that were functionally characterized as monoterpene synthases and three that preferred farnesyl diphosphate, the substrate for sesquiterpene synthases. The reaction products for two of the sesquiterpene synthases exhibiting root-specific expression were characterized by a combination of GC-MS and NMR in comparison to the terpenes accumulating in planta. VoTPS7 encodes for a synthase that biosynthesizes predominately germacrene C, whereas VoTPS1 catalyzes the conversion of farnesyl diphosphate to valerena-1,10-diene. Using a yeast expression system, specific labeled [13C]acetate, and NMR, we investigated the catalytic mechanism for VoTPS1 and provide evidence for the involvement of a caryophyllenyl carbocation, a cyclobutyl intermediate, in the biosynthesis of valerena-1,10-diene. We suggest a similar mechanism for the biosynthesis of several other biologically related isobutenyl-containing sesquiterpenes

    Properties and Evolution of the Redback Millisecond Pulsar Binary PSR J2129-0429

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    PSR J2129−0429 is a "redback" eclipsing millisecond pulsar binary with an unusually long 15.2 hr orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean m_R = 16.6 mag), allowing us to construct the longest baseline photometric data set available for such a system. We present 10 years of archival and new photometry of the companion from the Lincoln Near-Earth Asteroid Research Survey, the Catalina Real-time Transient Survey, the Palomar Transient Factory, the Palomar 60 inch, and the Las Cumbres Observatory Global Telescope. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200 inch indicates that the pulsar is massive: 1.74 ± 0.18 M_☉. The G-type pulsar companion has mass 0.44 ± 0.04 M_☉, one of the heaviest known redback companions. It is currently 95 ± 1% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr^(−1) secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical light curve shape. This behavior may indicate that the companion is cooling. Binary evolution calculations indicate that PSR J2129−0429 has an orbital period almost exactly at the bifurcation period between systems that converge into tighter orbits as black widows and redbacks and those that diverge into wider pulsar–white dwarf binaries. Its eventual fate may depend on whether it undergoes future episodes of mass transfer and increased irradiation

    Functional Diffusion Tensor Imaging: Measuring Task-Related Fractional Anisotropy Changes in the Human Brain along White Matter Tracts

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    Functional neural networks in the human brain can be studied from correlations between activated gray matter regions measured with fMRI. However, while providing important information on gray matter activation, no information is gathered on the co-activity along white matter tracts in neural networks.We report on a functional diffusion tensor imaging (fDTI) method that measures task-related changes in fractional anisotropy (FA) along white matter tracts. We hypothesize that these fractional anisotropy changes relate to morphological changes of glial cells induced by axonal activity although the exact physiological underpinnings of the measured FA changes remain to be elucidated. As expected, these changes are very small as compared to the physiological noise and a reliable detection of the signal change would require a large number of measurements. However, a substantial increase in signal-to-noise ratio was achieved by pooling the signal over the complete fiber tract. Adopting such a tract-based statistics enabled us to measure the signal within a practically feasible time period. Activation in the sensory thalamocortical tract and optic radiation in eight healthy human subjects was found during tactile and visual stimulation, respectively.The results of our experiments indicate that these FA changes may serve as a functional contrast mechanism for white matter. This noninvasive fDTI method may provide a new approach to study functional neural networks in the human brain

    Freedom, Servitude and Voluntary Labor

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    We present an economic framework to revisit and reframe some important debates over the nature of free versus unfree labor and the economic consequences of emancipation. We use a simple general equilibrium model in which labor can be either free or coerced and where land and labor will be exchanged on markets that can be competitive or manipulated or via other non-market collusive arrangements. By working with variants of the same basic model under different assumptions about initial economy-wide factor endowments and asset ownership we can compare equilibrium distributional outcomes under different institutional and contractual arrangements including markets with free labor and free tenancy, slavery, and tenancy arrangements with tied labor-service obligations. Analysis of these different contractual and organizational forms yields insights that accord with common sense, but that are often overlooked or downplayed in academic debates, particularly amongst economists

    Gamma-ray and radio properties of six pulsars detected by the fermi large area telescope

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    We report the detection of pulsed γ-rays for PSRs J0631+1036, J0659+1414, J0742-2822, J1420-6048, J1509-5850, and J1718-3825 using the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (formerly known as GLAST). Although these six pulsars are diverse in terms of their spin parameters, they share an important feature: their γ-ray light curves are (at least given the current count statistics) single peaked. For two pulsars, there are hints for a double-peaked structure in the light curves. The shapes of the observed light curves of this group of pulsars are discussed in the light of models for which the emission originates from high up in the magnetosphere. The observed phases of the γ-ray light curves are, in general, consistent with those predicted by high-altitude models, although we speculate that the γ-ray emission of PSR J0659+1414, possibly featuring the softest spectrum of all Fermi pulsars coupled with a very low efficiency, arises from relatively low down in the magnetosphere. High-quality radio polarization data are available showing that all but one have a high degree of linear polarization. This allows us to place some constraints on the viewing geometry and aids the comparison of the γ-ray light curves with high-energy beam models
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