192 research outputs found
Impacts of alternative grassland management regimes on the population ecology of grassland birds
We investigated the impacts of rangeland management practices on the diversity, density, and nest survival of grassland songbirds and on the demography, habitat selection, and population viability of Greater Prairie-Chickens (Tympanuchus cupido). Our study site was located in eastcentral Kansas and included portions of Chase, Greenwood, Lyon, and Morris Counties. We had access to ~1,100 km2 of private and public lands. Over 95% of the land was privately owned (~1040 km2), and the remaining ~5% was the Tallgrass Prairie National Preserve. Our final project report is based on data collected during a 3-year period from Feb. 2011 through Feb. 2014. Our study focused on grassland songbirds and Greater Prairie-Chickens as indicators of ecosystem response. Our analyses are based on direct comparisons between monitoring efforts in pastures managed with patch-burn grazing (PBG) and pastures managed with traditional intensive early stocking and annual burning (IESB).Citation: Sandercock, B.K., V.L. Winder, A.E. Erickson, and L.B. McNew. 2014. Impacts of alternative grassland management regimes on the population ecology of grassland birds. Kansas Department of Wildlife, Parks and Tourism, Final Project Report for Award No. KDWP-W-67-R. (technical report)
Pooled Analysis of Individually Fed Finishing Trials
A pooled analysis of 21 finishing trials (2002–2016; 1530 animals) with cattle individually fed in Calan gate barns was conducted. Mixed model regression analysis following random coefficient methodology was used to evaluate relationships between performance variables and carcass characteristics. Gain had a greater effect on efficiency (R2 = 0.72) compared to intake (R2 = 0.02). The relationship between gain and efficiency was cubic, while intake had a quadratic relationship. The cubic response of gain relative to efficiency was continually increasing with relatively slight curves in the line heavily influenced by points that lay on the ends of the data. Efficiency also had cubic relationships with fat thickness and marbling of carcasses; however, the regressions had low R2 values of 0.01. There was a significant relationship between efficiency and fat thickness and marbling, but the variation around the trend line was high. Efficiency alone is a poor predictor of fat thickness and marbling
Impact of Shade in Beef Feedyards on Performance, Body Temperature, and Heat Stress Measures
A study using crossbred steers was conducted at a commercial feedyard to determine the effects of pen shades on cattle performance, body temperature, and cattle activity. Two heat events (Event 1 and Event 2) and one cool event were defined for the feeding period. No significant differences were observed for average daily gain, dry matter intake, feed to gain, or carcass characteristics at the end of the trial. During Event 1, cattle in pens with shade had lower panting scores than cattle in open pens. During Event 2, cattle in shade pens had greater dry matter intake, lower panting scores, and lower ear temperature. Throughout the entire feeding period, cattle in open pens had greater ear temperature and panting scores than cattle in shaded pens while movement was not different between treatments. Using shades for feedyard cattle did not impact performance, but did improve some measures of heat stress
Inflation, Large Branes, and the Shape of Space
Linde has recently argued that compact flat or negatively curved spatial
sections should, in many circumstances, be considered typical in Inflationary
cosmologies. We suggest that the "large brane instability" of Seiberg and
Witten eliminates the negative candidates in the context of string theory. That
leaves the flat, compact, three-dimensional manifolds -- Conway's *platycosms*.
We show that deep theorems of Schoen, Yau, Gromov and Lawson imply that, even
in this case, Seiberg-Witten instability can be avoided only with difficulty.
Using a specific cosmological model of the Maldacena-Maoz type, we explain how
to do this, and we also show how the list of platycosmic candidates can be
reduced to three. This leads to an extension of the basic idea: the conformal
compactification of the entire Euclidean spacetime also has the topology of a
flat, compact, four-dimensional space.Comment: 29 pages, clarifications, typos fixed, references adde
Quintessential Maldacena-Maoz Cosmologies
Maldacena and Maoz have proposed a new approach to holographic cosmology
based on Euclidean manifolds with disconnected boundaries. This approach
appears, however, to be in conflict with the known geometric results [the
Witten-Yau theorem and its extensions] on spaces with boundaries of
non-negative scalar curvature. We show precisely how the Maldacena-Maoz
approach evades these theorems. We also exhibit Maldacena-Maoz cosmologies with
[cosmologically] more natural matter content, namely quintessence instead of
Yang-Mills fields, thereby demonstrating that these cosmologies do not depend
on a special choice of matter to split the Euclidean boundary. We conclude that
if our Universe is fundamentally anti-de Sitter-like [with the current
acceleration being only temporary], then this may force us to confront the
holography of spaces with a connected bulk but a disconnected boundary.Comment: Much improved exposition, exponent in Cai-Galloway theorem fixed,
axionic interpretation of scalar explained, JHEP version. 33 pages, 3 eps
figure
Yersinia pseudotuberculosis BarA-UvrY Two-Component Regulatory System Represses Biofilms via CsrB
The formation of biofilms by Yersinia pseudotuberculosis (Yptb) and Y. pestis requires the hmsHFRS genes, which direct production of a polysaccharide extracellular matrix (Hms-ECM). Despite possessing identical hmsHFRS sequences, Yptb produces much less Hms-ECM than Y. pestis. The regulatory influences that control Yptb Hms-ECM production and biofilm formation are not fully understood. In this study, negative regulators of biofilm production in Yptb were identified. Inactivation of the BarA/UvrY two-component system or the CsrB regulatory RNA increased binding of Congo Red dye, which correlates with extracellular polysaccharide production. These mutants also produced biofilms that were substantially more cohesive than the wild type strain. Disruption of uvrY was not sufficient for Yptb to cause proventricular blockage during infection of Xenopsylla cheopis fleas. However, this strain was less acutely toxic toward fleas than wild type Yptb. Flow cytometry measurements of lectin binding indicated that Yptb BarA/UvrY/CsrB mutants may produce higher levels of other carbohydrates in addition to poly-GlcNAc Hms-ECM. In an effort to characterize the relevant downstream targets of the BarA/UvrY system, we conducted a proteomic analysis to identify proteins with lower abundance in the csrB::Tn5 mutant strain. Urease subunit proteins were less abundant and urease enzymatic activity was lower, which likely reduced toxicity toward fleas. Loss of CsrB impacted expression of several potential regulatory proteins that may influence biofilms, including the RcsB regulator. Overexpression of CsrB did not alter the Congo-red binding phenotype of an rcsB::Tn5 mutant, suggesting that the effect of CsrB on biofilms may require RcsB. These results underscore the regulatory and compositional differences between Yptb and Y. pestis biofilms. By activating CsrB expression, the Yptb BarA/UvrY two-component system has pleiotropic effects that impact biofilm production and stability
The Phantom Divide in String Gas Cosmology
One of the main virtues of string gas cosmology is that it resolves
cosmological singularities. Since the Universe can be approximated by a locally
asymptotically de Sitter spacetime by the end of the inflationary era, a
singularity theorem implies that these cosmologies effectively violate the Null
Energy Condition [not just the Strong Energy Condition]. We stress that this is
an extremely robust result, which does not depend on assuming that the spatial
sections remain precisely flat in the early Universe. This means, however, that
it must be possible for string cosmologies to cross the recently much-discussed
"phantom divide" [from w -1, where w is the equation-of-state
parameter]. This naturally raises the question as to whether the phantom divide
can be crossed again, to account for recent observations suggesting that w < -1
at the present time. We argue that non-perturbative string effects rule out
this possibility, even if the NEC violation in question is only "effective".Comment: 29 pages, 5 eps figures, references adde
Answering a Basic Objection to Bang/Crunch Holography
The current cosmic acceleration does not imply that our Universe is basically
de Sitter-like: in the first part of this work we argue that, by introducing
matter into *anti-de Sitter* spacetime in a natural way, one may be able to
account for the acceleration just as well. However, this leads to a Big Crunch,
and the Euclidean versions of Bang/Crunch cosmologies have [apparently]
disconnected conformal boundaries. As Maldacena and Maoz have recently
stressed, this seems to contradict the holographic principle. In the second
part we argue that this "double boundary problem" is a matter not of geometry
but rather of how one chooses a conformal compactification: if one chooses to
compactify in an unorthodox way, then the appearance of disconnectedness can be
regarded as a *coordinate effect*. With the kind of matter we have introduced
here, namely a Euclidean axion, the underlying compact Euclidean manifold has
an unexpectedly non-trivial topology: it is in fact one of the 75 possible
underlying manifolds of flat compact four-dimensional Euclidean spaces.Comment: 29 pages, 3 figures, added references and comparison with "cyclic"
cosmology, JHEP versio
Pre-Inflationary Spacetime in String Cosmology
Seiberg and Witten have shown that the non-perturbative stability of string
physics on conformally compactified spacetimes is related to the behaviour of
the areas and volumes of certain branes as the brane is moved towards infinity.
If, as is particularly natural in quantum cosmology, the spatial sections of an
accelerating cosmological model are flat and compact, then the spacetime is on
the brink of disaster: it turns out that the version of inflationary spacetime
geometry with toral spatial sections is marginally stable in the Seiberg-Witten
sense. The question is whether the system remains stable before and after
Inflation, when the spacetime geometry is distorted away from the inflationary
form but still has flat spatial sections. We show that it is indeed possible to
avoid disaster, but that requiring stability at all times imposes non-trivial
conditions on the spacetime geometry of the early Universe in string cosmology.
This in turn allows us to suggest a candidate for the structure which, in the
earliest Universe, forbids cosmological singularities.Comment: Final version to appear in NPB, 27 pages including 1 eps figur
An Assay to Monitor HIV-1 Protease Activity for the Identification of Novel Inhibitors in T-Cells
The emergence of resistant HIV strains, together with the severe side-effects of existing drugs and lack of development of effective anti-HIV vaccines highlight the need for novel antivirals, as well as innovative methods to facilitate their discovery. Here, we have developed an assay in T-cells to monitor the proteolytic activity of the HIV-1 protease (PR). The assay is based on the inducible expression of HIV-1 PR fused within the Gal4 DNA-binding and transactivation domains. The fusion protein binds to the Gal4 responsive element and activates the downstream reporter, enhanced green fluorescent protein (eGFP) gene only in the presence of an effective PR Inhibitor (PI). Thus, in this assay, eGFP acts as a biosensor of PR activity, making it ideal for flow cytometry based screening. Furthermore, the assay was developed using retroviral technology in T-cells, thus providing an ideal environment for the screening of potential novel PIs in a cell-type that represents the natural milieu of HIV infection. Clones with the highest sensitivity, and robust, reliable and reproducible reporter activity, were selected. The assay is easily adaptable to other PR variants, a multiplex platform, as well as to high-throughput plate reader based assays and will greatly facilitate the search for novel peptide and chemical compound based PIs in T-cells
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