20,529 research outputs found
Presence of Salmonella and Campylobacter spp. in Wild Small Mammals on Organic Farms
The presence of Salmonella and Campylobacter spp. in rodents and insectivores (n 282) was investigated
on organic farms. Infections were encountered in house mice (8 of 83 Campylobacter positive and 1 of 83
Salmonella sp. strain Livingstone positive) and brown rats (1 of 8 Campylobacter positive) but not in other
species. No shared Campylobacter genotypes were found between rodent and pig manure isolates. Effective
on-farm rodent management is recommended
Normal Pursuit-System Limitations— First Discovered in Infantile Nystagmus Syndrome
Infantile nystagmus syndrome (INS) patients occasionally have impaired pursuit. Model and patient data identified relative timing between target motion initiation and INS-waveform saccades as the cause. We used a new stimulus, the “step-pause-ramp” (SPR), to induce saccades proximal to target-velocity onset and test their effect on normal pursuit. Our OMS model predicted that proximal saccades impaired normal ramp responses, as in INS. Eye movements of subjects were calibrated monocularly and recorded binocularly; data were analyzed using OMtools software. Proximal saccades caused lengthened target acquisition times and steady-state position errors, confirming the model’s predictions. Spontaneous pursuit oscillation supported the hypothesis that INS is caused by loss of smooth-pursuit damping. Snooth pursuit may be impaired by saccades overlapping targetmotion onset
Causal inference via string diagram surgery
Extracting causal relationships from observed correlations is a growing area in probabilistic reasoning, originating with the seminal work of Pearl and others from the early 1990s. This paper develops a new, categorically oriented view based on a clear distinction between syntax (string diagrams) and semantics (stochastic matrices), connected via interpretations as structure-preserving functors. A key notion in the identification of causal effects is that of an intervention, whereby a variable is forcefully set to a particular value independent of any prior propensities. We represent the effect of such an intervention as an endo-functor which performs 'string diagram surgery' within the syntactic category of string diagrams. This diagram surgery in turn yields a new, interventional distribution via the interpretation functor. While in general there is no way to compute interventional distributions purely from observed data, we show that this is possible in certain special cases using a calculational tool called comb disintegration. We demonstrate the use of this technique on two well-known toy examples: one where we predict the causal effect of smoking on cancer in the presence of a confounding common cause and where we show that this technique provides simple sufficient conditions for computing interventions which apply to a wide variety of situations considered in the causal inference literature; the other one is an illustration of counterfactual reasoning where the same interventional techniques are used, but now in a 'twinned' set-up, with two version of the world - one factual and one counterfactual - joined together via exogenous variables that capture the uncertainties at hand
Deductive Verification of Unmodified Linux Kernel Library Functions
This paper presents results from the development and evaluation of a
deductive verification benchmark consisting of 26 unmodified Linux kernel
library functions implementing conventional memory and string operations. The
formal contract of the functions was extracted from their source code and was
represented in the form of preconditions and postconditions. The correctness of
23 functions was completely proved using AstraVer toolset, although success for
11 functions was achieved using 2 new specification language constructs.
Another 2 functions were proved after a minor modification of their source
code, while the final one cannot be completely proved using the existing memory
model. The benchmark can be used for the testing and evaluation of deductive
verification tools and as a starting point for verifying other parts of the
Linux kernel.Comment: 18 pages, 2 tables, 6 listings. Accepted to ISoLA 2018 conference.
Evaluating Tools for Software Verification trac
Longitudinal aerodynamic characteristics of a subsonic, energy-efficient transport configuration in the National Transonic Facility
The Reynolds number, aeroelasticity, boundary layer transition, and nonadiabatic wall temperature effects, and data repeatability was determined in the National Transonic Facility (NTF) for a subsonic, energy efficient transport model. The model was tested over a Mach number range of 0.50 to 0.86 and a Reynolds number range of 1.9 million to approximately 23.0 million (based on mean geometric chord). The majority of the data was taken using cryogenic nitrogen (data at 1.9 million Reynolds number was taken in air). Force and moment, wing pressure, and wing thermocouple data are presented. The data indicate that increasing Reynolds number resulted in greater effective camber of the supercritical wing and horizontal tail, resulting in greater lift and pitching moment coefficients at nearly all angles of attack for M = 0.82. As Reynolds number was increased, untrimmed L/D increased, the angle of attack for maximum L/D decreased, drag creep was reduced significantly, and drag divergence Mach number increased slightly. Data repeatability for both modes of operation of the NTF (air and cryogenic nitrogen) was generally very good, and nonadiabatic wall effects were estimated to be small. Transition-free and transition-fixed configurations had significantly different force and moment data at M = 0.82 for low Reynolds number, and very small differences were noted at high Reynolds numbers
Involutive Categories and Monoids, with a GNS-correspondence
This paper develops the basics of the theory of involutive categories and
shows that such categories provide the natural setting in which to describe
involutive monoids. It is shown how categories of Eilenberg-Moore algebras of
involutive monads are involutive, with conjugation for modules and vector
spaces as special case. The core of the so-called Gelfand-Naimark-Segal (GNS)
construction is identified as a bijective correspondence between states on
involutive monoids and inner products. This correspondence exists in arbritrary
involutive categories
Enhancement of p-GaN conductivity using PECVD SiOx
A technique to enhance the hole concentration in activated Mg-doped p-type GaN epitaxial layers is described. The method consists of depositing a porous plasma-nhancedchemical vapor deposited SiOx layer on top of p-GaN after which the sample is heated to 950°C in nitrogen ambient for 1 min followed by the removal of the SiOx layer in a buffered HF solution. A significant improvement of the conductivity of the p-GaN layer has been obtained
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