Zoonotic potential of Salmonella enterica carried by pet tortoises

The prevalence of Salmonella in chelonians is not known in the UK and it is not clear whether such Salmonella strains would be pathogenic for human beings. Some strains, such as members of the Arizonae subgroup, may be unable to cause anything more than very mild disease. To determine the carriage of Salmonella in pet tortoises, cloacal swabs were taken for culture. Salmonella enterica Group D was isolated from 5 of the 89 samples. All five were from the same household of seven tortoises. Salmonella isolates were shown by PCR to carry the invA and spiC genes associated with pathogenicity islands 1 and 2. Each isolate carried both genes indicating they had the genetic basis for disease and enterocyte invasion in human beings. The study indicates a low rate of asymptomatic carriage among the general population of pet tortoises. However, it does suggest that those Salmonella strains colonising the tortoise can carry Salmonella pathogenicity island (SPI)-1 and SPI-2 conferring the potential to cause disease in human beings and other animals

Do Elementary Science Methods Textbooks Promote Understanding of Shadows?

Elementary science methods textbooks can be an important resource for future elementary teachers of science. Since shadows are a common topic in elementary school and Next Generation Science Standards (NGSS Lead States, 2013). A series of ten shadows concepts were formed into a learning progression by Wizman and Fortus (2007). For this research, ten science methods textbook were read and analyzed about how each of the shadow concepts were addressed. These methods textbooks focused on a limited number of shadow concepts. Consequently, as a future reference, they are very limited in addressing all ten shadow concepts

Verbal-Spatial Cue Conflict: Implications for the Design of Collision-Avoidance Warning Systems

A spatial auditory Stroop paradigm was used to examine the effects of verbal-spatial cue conflict on response accuracy, reaction time, and driving performance. Participants responded to either the semantic meaning or the spatial location of a directional word, which were either congruent (i.e. the word “right” being presented from the right) or incongruent (i.e. the word “right” being presented from the left), while following a lead car in a simulated driving scenario. Accuracy was worse when participants were responding to the spatial location of a word in an incongruent trial, indicating that participants experienced significant interference when trying to ignore the semantic meaning of the word when it conflicted with the presentation location. Implications for the design of collision-avoidance warning systems are discussed

Von Bezold assimilation effect reverses in stereoscopic conditions

Lightness contrast and lightness assimilation are opposite phenomena: in contrast, grey targets appear darker when bordering bright surfaces (inducers) rather than dark ones; in assimilation, the opposite occurs. The question is: which visual process favours the occurrence of one phenomenon over the other? Researchers provided three answers to this question. The first asserts that both phenomena are caused by peripheral processes; the second attributes their occurrence to central processes; and the third claims that contrast involves central processes, whilst assimilation involves peripheral ones. To test these hypotheses, an experiment on an IT system equipped with goggles for stereo vision was run. Observers were asked to evaluate the lightness of a grey target, and two variables were systematically manipulated: (i) the apparent distance of the inducers; and (ii) brightness of the inducers. The retinal stimulation was kept constant throughout, so that the peripheral processes remained the same. The results show that the lightness of the target depends on both variables. As the retinal stimulation was kept constant, we conclude that central mechanisms are involved in both lightness contrast and lightness assimilation

Cosmology in three dimensions: steps towards the general solution

We use covariant and first-order formalism techniques to study the properties of general relativistic cosmology in three dimensions. The covariant approach provides an irreducible decomposition of the relativistic equations, which allows for a mathematically compact and physically transparent description of the 3-dimensional spacetimes. Using this information we review the features of homogeneous and isotropic 3-d cosmologies, provide a number of new solutions and study gauge invariant perturbations around them. The first-order formalism is then used to provide a detailed study of the most general 3-d spacetimes containing perfect-fluid matter. Assuming the material content to be dust with comoving spatial 2-velocities, we find the general solution of the Einstein equations with non-zero (and zero) cosmological constant and generalise known solutions of Kriele and the 3-d counterparts of the Szekeres solutions. In the case of a non-comoving dust fluid we find the general solution in the case of one non-zero fluid velocity component. We consider the asymptotic behaviour of the families of 3-d cosmologies with rotation and shear and analyse their singular structure. We also provide the general solution for cosmologies with one spacelike Killing vector, find solutions for cosmologies containing scalar fields and identify all the PP-wave 2+1 spacetimes.Comment: 35 pages, 2 figure

Varying c cosmology and Planck value constraints

It has been suggested that by increasing the speed of light during the early universe various cosmological problems of standard big bang cosmology can be overcome, without requiring an inflationary phase. However, we find that as the Planck length and Planck time are then made correspondingly smaller, and together with the need that the universe should not re-enter a Planck epoch, the higher $c$ models have very limited ability to resolve such problems. For a constantly decreasing $c$ the universe will quickly becomes quantum gravitationally dominated as time increases: the opposite to standard cosmology where quantum behaviour is only ascribed to early times.Comment: extended versio

Present Acceleration of Universe, Holographic Dark Energy and Brans-Dicke Theory

The present day accelerated expansion of the universe is naturally addressed within the Brans-Dicke theory just by using holographic dark energy model with inverse of Hubble scale as IR cutoff. It is also concluded that if the universe continues to expand, then one day it might be completely filled with dark energy.Comment: 10 page

Gravitational memory of natural wormholes

A traversable wormhole solution of general scalar-tensor field equations is presented. We have shown, after a numerical analysis for the behavior of the scalar field of Brans-Dicke theory, that the solution is completely singularity--free. Furthermore, the analysis of more general scalar field dependent coupling constants indicates that the gravitational memory phenomenon may play an important role in the fate of natural wormholes.Comment: 14 pages revtex, 1 ps figur

Structure and stability of the Lukash plane-wave spacetime

We study the vacuum, plane-wave Bianchi $VII{}_{h}$ spacetimes described by the Lukash metric. Combining covariant with orthonormal frame techniques, we describe these models in terms of their irreducible kinematical and geometrical quantities. This covariant description is used to study analytically the response of the Lukash spacetime to linear perturbations. We find that the stability of the vacuum solution depends crucially on the background shear anisotropy. The stronger the deviation from the Hubble expansion, the more likely the overall linear instability of the model. Our analysis addresses rotational, shear and Weyl curvature perturbations and identifies conditions sufficient for the linear growth of these distortions.Comment: Revised version, references added. To appear in Class. Quantum Gra