783 research outputs found
How predation can slow, stop or reverse a prey invasion
How predation can slow, stop or reverse a prey invasio
The use of embolic signal detection in multicenter trials to evaluate antiplatelet efficacy: signal analysis and quality control mechanisms in the CARESS (Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic carotid Stenosis) trial
<p><b>Background and Purpose:</b> The CARESS (Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic carotid Stenosis) trial proved the effectiveness of the combination of clopidogrel and aspirin compared with aspirin alone in reducing presence and number of microembolic signals (MES) in patients with recently symptomatic carotid stenosis. The present study aimed at installing primary and secondary quality control measures in CARESS because MES evaluation relies on subjective judgment by human experts.</p>
<p><b>Methods:</b> As primary quality control, centers participating in CARESS evaluated a reference digital audio tape (DAT) before the study containing both MES and artifacts. Interobserver agreement of classifying signals as MES was expressed as proportions of specific agreement of positive ratings (ps±values). For all DATs included in CARESS (n=300), online number of MES and off-line number of MES read by the central reader were compared using correlation coefficients. As secondary control, a sample of 16 of 300 DATs was cross-validated by another independent reader (post-trial validator).</p>
<p><b>Results:</b> For the reference tape, the cumulative ps±value was 0.894 based on 12 of 14 observers. Two observers with very different results improved after a training procedure. Agreement between post-trial validator and central reader was ps+=0.805, indicating very good agreement. Correlation between online evaluation and off-line evaluation of DATs was very good overall (cumulative Ï=0.84; P<0.001).</p>
<p><b>Conclusion:</b> Multicenter studies using MES as outcome parameter are feasible. However, primary and secondary quality control procedures are important.</p>
Baryon masses at second order in large- chiral perturbation theory
We consider flavor breaking in the the octet and decuplet baryon masses at
second order in large- chiral perturbation theory, where is the number
of QCD colors. We assume that , where is the number of light quark
flavors, and are the parameters controlling
flavor breaking in chiral perturbation theory. We consistently include
non-analytic contributions to the baryon masses at orders , , and . The corrections are small for
the relations that follow from symmetry alone, but the corrections to
the large- relations are large and have the wrong sign. Chiral
power-counting and large- consistency allow a 2-loop contribution at order
, and a non-trivial explicit calculation is required to show
that this contribution vanishes. At second order in the expansion, there are
eight relations that are non-trivial consequences of the expansion, all
of which are well satisfied within the experimental errors. The average
deviation at this order is 7 \MeV for the \De I = 0 mass differences and
0.35 \MeV for the \De I \ne 0 mass differences, consistent with the
expectation that the error is of order .Comment: 19 pages, 2 uuencoded ps figs, uses revte
Strong Conformal Dynamics at the LHC and on the Lattice
Conformal technicolor is a paradigm for new physics at LHC that may solve the
problems of strong electroweak symmetry breaking for quark masses and precision
electroweak data. We give explicit examples of conformal technicolor theories
based on a QCD-like sector. We suggest a practical method to test the conformal
dynamics of these theories on the lattice.Comment: v2: Generalized discussion of lattice measurement of hadron masses,
references added, minor clarifications v3: references added, minor change
Epidemiological and pathological screening of suspected cases of contagious bovine pleuropneumonia in Yola Modern Abattoir, Adamawa State Nigeria
Contagious bovine pleuropneumonia is an important infectious disease of cattle caused by Mycoplasma mycoides subsp. mycoides and a major constraint to cattle production in sub-Saharan Africa. This study was aimed to identify pathological and histopathological lesions identified in cattle tentatively diagnosed with CBPP at Yola Modern Abattoir, Adamawa State. A total of 9,750 cattle were examined at post-mortem for a period of six months, 110 (1.13%) had lesions suggestive of CBPP out of which seventeen (17) were randomly selected and processed for histopathology based on standard laboratory protocols. Based on sex, CBPP lesion was observed more in female 63 (1.06%) than in the male 47 (1.24%). Whereas, CBPP lesions was observed highest in White Fulani breed 68 (1.14%) followed by Cross breeds 23 (91.16%) and Sokoto Gudali 19 (1.74%) and lowest in Red Bororo 10 (1.36%). There was insignificant statistical association (P>0.05) between CBPP lesions and sex and breed of cattle sampled. Age distribution of CBPP lesion was observed higher in cattle between ages of 4-7 years 79 (1.16%), followed by cattle of 1-3 years 28 (1.15%) and least in cattle less than 1 year 3 (0.60%) with significant statistical difference (P<0.05) between the age groups. Histopathology lesions observed include severe congestion of pulmonary blood vessel in all the lung tissues and fibrin exudation into inter-alveolar spaces with almost all the alveoli collapsed. The bronchiolar epithelium was observed to be thickened, hyperplastic and folded, with a considerable quantity of edematous fluid and numerous inflammatory cells seen in the lumen. In conclusion, this study had demonstrated the presence of CBPP lesions in cattle in the study area. Therefore, serological screening of all cattle, stamping out policies and aggressive annual vaccination campaigns are thus recommended in the study area
Effects of deer on woodland structure revealed through terrestrial laser scanning
1. Terrestrial laser scanning (TLS) captures the three-dimensional structure of habitats. Compared to traditional methods of forest mensuration, it allows quantification of structure at increased resolution, and the derivation of novel metrics with which to inform ecological studies and habitat management.
2. Lowland woodlands in the UK have altered in structure over the last century due to increased abundance of deer and a decline in management. We compared whole-canopy profiles between woodlands with high (>10 deer kmâ2) and low deer density (c. 1 deer kmâ2), and in stands with and without records of management interventions in the last 20 years, providing a test case for the application of TLS in habitat assessment for conservation and management.
3. Forty closed-canopy lowland woodlands (height range 16·5â29·4 m) were surveyed using TLS in two regions of the UK, divided into areas of high- and low-deer abundance, and between plots which had been recently managed or were unmanaged. Three-dimensional reconstructions of the woodlands were created to document the density of foliage and stem material across the entire vertical span of the canopy.
4. There was a 68% lower density of understorey foliage (0·5â2 m above-ground) in high-deer woodlands, consistent in both regions. Despite this, total amounts of foliage detected across the full canopy did not differ between deer density levels. High-deer sites were 5 m taller overall and differed in the distribution of foliage across their vertical profile. Managed woodlands, in contrast, exhibited relatively minor differences from controls, including a lower quantity of stem material at heights from 2 to 5 m, but no difference in foliage density. All main effects were replicated equally in both regions despite notable differences in stand structures between them.
5. Synthesis and applications. Terrestrial laser scanning allows ecologists to move beyond two-dimensional measures of vegetation structure and quantify patterns across complex, heterogeneous, three-dimensional habitats. Our findings suggest that reduction of deer populations is likely to have a strong impact on woodland structures and aid in restoring the complex understorey habitats required by many birds, whereas management interventions as currently practiced have limited and inconsistent effects
Dynamics of Gravity in a Higgs Phase
We investigate the universal low-energy dynamics of the simplest Higgs phase
for gravity, `ghost condensation.' We show that the nonlinear dynamics of the
`ghostone' field dominate for all interesting gravitational sources. Away from
caustic singularities, the dynamics is equivalent to the irrotational flow of a
perfect fluid with equation of state p \propto \rho^2, where the fluid
particles can have negative mass. We argue that this theory is free from
catastrophic instabilities due to growing modes, even though the null energy
condition is violated. Numerical simulations show that solutions generally have
singularities in which negative energy regions shrink to zero size. We exhibit
partial UV completions of the theory in which these singularities are smoothly
resolved, so this does not signal any inconsistency in the effective theory. We
also consider the bounds on the symmetry breaking scale M in this theory. We
argue that the nonlinear dynamics cuts off the Jeans instability of the linear
theory, and allows M \lsim 100MeV.Comment: 54 pages, 15 figures; postscript figures downloadable from
http://schwinger.harvard.edu/~wiseman/Ghost/ghostepsfigs.tar.gz ; v2:
substantial revision to section 5 on bound
Cellular Automata Simulating Experimental Properties of Traffic Flows
A model for 1D traffic flow is developed, which is discrete in space and
time. Like the cellular automaton model by Nagel and Schreckenberg [J. Phys. I
France 2, 2221 (1992)], it is simple, fast, and can describe stop-and-go
traffic. Due to its relation to the optimal velocity model by Bando et al.
[Phys. Rev. E 51, 1035 (1995)], its instability mechanism is of deterministic
nature. The model can be easily calibrated to empirical data and displays the
experimental features of traffic data recently reported by Kerner and Rehborn
[Phys. Rev. E 53, R1297 (1996)].Comment: For related work see
http://www.theo2.physik.uni-stuttgart.de/helbing.html and
http://traffic.comphys.uni-duisburg.de/member/home_schreck.htm
The <SPP> Green function and SU(3) breaking in Kl3 decays
Using the 1=/N-C expansion scheme and truncating the hadronic spectrum to the lowest-lying resonances, we match a meromorphic approximation to the Green function onto QCD by imposing the correct large-momentum falloff, both off- shell and on the relevant hadron mass shells. In this way we determine a number of chiral low-energy constants of O(p(6)), in particular the ones governing SU(3) breaking in the K-l3 vector form factor at zero momentum transfer. The main result of our matching procedure is that the known loop contributions largely dominate the corrections of O(p(6)) to f(+)(0). We discuss the implications of our final value f(+)(K0 pi-) (0) = 0.984 +/- 0.012 for the extraction of V-us from K-l3 decays
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