6,604 research outputs found
Coriolis effects during pitch and roll maneuvers in a piloted flight simulator
Effect of suprathreshold value of Coriolis acceleration on pilot of flight simulator - reference to perception of illusory motion and position in spac
Urban grasslands support threatened water voles
Urbanisation is often linked with habitat loss and a reduction in species richness but some species may be able to adapt to urban environments. Water voles Arvicola amphibius, a rapidly declining species in the UK, have recently been recorded in isolated grassland habitats in Glasgow, Scotland’s largest city (human population 1.2 million). The aim of this study was to determine the distribution and habitat characteristics of water vole populations occupying these dry grasslands. Field work was undertaken from March to October 2014 in a 34 km2 study area located 3 km east of the city centre. Field sign transects recorded water vole presence in 21/65 (32%) and 19/62 (31%) surveyed sites in spring and autumn, respectively. Vole occupancy increased with distance from water and was greatest in parkland, followed by sites with rank vegetation and roadside habitats. Occupancy was lower where signs of predators were recorded but surprisingly occupancy was found to be greater in the most disturbed sites, perhaps linked to the fact that many of these sites were public parks containing suitable grassland. Sites occupied by water voles were classed as neutral grasslands with species composition dominated by two main species. The number of grassland sites occupied by water voles, especially within public areas suggests that careful management of these urban grassland habitats will benefit the conservation of this highly threatened species in the UK
Generation of slow intense optical solitons in a resonance photonic crystal
We demonstrate interesting and previously unforeseen properties of a pair of
gap solitons in a resonant photonic crystal which are predicted and explained
in a physically transparent form using both analytical and numerical methods.
The most important result is the fact that an oscillating gap soliton created
by the presence of a localized population inversion inside the crystal can be
manipulated by means of a proper choice of bit rate, phase and amplitude
modulation. Developing this idea, we are able to obtain qualitatively different
regimes of a resonant photonic crystal operation. In particular, a noteworthy
observation is that both the delay time and amplitude difference must exceed a
certain level to ensure effective control over the soliton dynamics
The effects of screening length in the non-local screened-exchange functional
The screened exchange (sX) hybrid functional can give good band structures for simple sp bonded semiconductors and insulators, charge transfer insulators, Mott–Hubbard insulators, two dimensional systems and defect systems. This is particularly attributed to the sX hybrid scheme fixing the self-interaction problem associated with local functionals. We investigate the effect of varying the screening parameter of the exchange potential on various material properties such as the band gap. The Thomas Fermi screening scheme in which the screening parameter varies with an average valence electron density leads to a weak dependence of the band gap on valence electron density, so that a fixed screening parameter could be applied to heterogeneous systems like surfaces, interfaces and defects
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Consumer attitudes towards production diseases in intensive production systems
Many members of the public and important stakeholders operating at the upper end of the
food chain, may be unfamiliar with how food is produced, including within modern animal
production systems. The intensification of production is becoming increasingly common in
modern farming. However, intensive systems are particularly susceptible to production diseases,
with potentially negative consequences for farm animal welfare (FAW). Previous
research has demonstrated that the public are concerned about FAW, yet there has been little
research into attitudes towards production diseases, and their approval of interventions
to reduce these. This research explores the public’s attitudes towards, and preferences for,
FAW interventions in five European countries (Finland, Germany, Poland, Spain and the
UK). An online survey was conducted for broilers (n = 789), layers (n = 790) and pigs (n =
751). Data were analysed by means of Kruskal-Wallis ANOVA, exploratory factor analysis
and structural equation modelling. The results suggest that the public have concerns regarding
intensive production systems, in relation to FAW, naturalness and the use of antibiotics.
The most preferred interventions were the most “proactive” interventions, namely improved
housing and hygiene measures. The least preferred interventions were medicine-based,
which raised humane animal care and food safety concerns amongst respondents. The
results highlighted the influence of the identified concerns, perceived risks and benefits on
attitudes and subsequent behavioural intention, and the importance of supply chain stakeholders
addressing these concerns in the subsequent communications with the public
Classical turning surfaces in solids: When do they occur, and what do they mean?
Classical turning surfaces of Kohn-Sham potentials, separating
classically-allowed regions (CARs) from classically-forbidden regions (CFRs),
provide a useful and rigorous approach to understanding many chemical
properties of molecules. Here we calculate such surfaces for several
paradigmatic solids. Our study of perfect crystals at equilibrium geometries
suggests that CFRs are absent in metals, rare in covalent semiconductors, but
common in ionic and molecular crystals. A CFR can appear at a monovacancy in a
metal. In all materials, CFRs appear or grow as the internuclear distances are
uniformly expanded. Calculations with several approximate density functionals
and codes confirm these behaviors. A classical picture of conduction suggests
that CARs should be connected in metals, and disconnected in wide-gap
insulators. This classical picture is confirmed in the limits of extreme
uniform compression of the internuclear distances, where all materials become
metals without CFRs, and extreme expansion, where all materials become
insulators with disconnected and widely-separated CARs around the atoms.Comment: Added supplemental information (63 pages), was missing in original
submission. Minor typo corrections in Tables I and III for Eps_HO - vs(r)
column (and CFR % volume for Pt monovacancy) for PBE data onl
Hypertension in mice lacking 11beta-hydroxysteroid dehydrogenase type 2
Deficiency of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) in humans leads to the syndrome of apparent mineralocorticoid excess (SAME), in which cortisol illicitly occupies mineralocorticoid receptors, causing sodium retention, hypokalemia, and hypertension. However, the disorder is usually incompletely corrected by suppression of cortisol, suggesting additional and irreversible changes, perhaps in the kidney. To examine this further, we produced mice with targeted disruption of the 11β-HSD2 gene. Homozygous mutant mice (11β-HSD2(–/–)) appear normal at birth, but ∼50% show motor weakness and die within 48 hours. Both male and female survivors are fertile but exhibit hypokalemia, hypotonic polyuria, and apparent mineralocorticoid activity of corticosterone. Young adult 11β-HSD2(–/–) mice are markedly hypertensive, with a mean arterial blood pressure of 146 ± 2 mmHg, compared with 121 ± 2 mmHg in wild-type controls and 114 ± 4 mmHg in heterozygotes. The epithelium of the distal tubule of the nephron shows striking hypertrophy and hyperplasia. These histological changes do not readily reverse with mineralocorticoid receptor antagonism in adulthood. Thus, 11β-HSD2(–/–) mice demonstrate the major features of SAME, providing a unique rodent model to study the molecular mechanisms of kidney resetting leading to hypertension. J. Clin. Invest. 103:683–689 (1999
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