4,083 research outputs found
Disabled people’s experiences of anti-social behaviour and harassment in social housing: a critical review
Closed-form expressions for correlated density matrices: application to dispersive interactions and example of (He)2
Empirically correlated density matrices of N-electron systems are
investigated. Exact closed-form expressions are derived for the one- and
two-electron reduced density matrices from a general pairwise correlated wave
function. Approximate expressions are proposed which reflect dispersive
interactions between closed-shell centro-symmetric subsystems. Said expressions
clearly illustrate the consequences of second-order correlation effects on the
reduced density matrices. Application is made to a simple example: the (He)2
system. Reduced density matrices are explicitly calculated, correct to second
order in correlation, and compared with approximations of independent electrons
and independent electron pairs. The models proposed allow for variational
calculations of interaction energies and equilibrium distance as well as a
clear interpretation of dispersive effects on electron distributions. Both
exchange and second order correlation effects are shown to play a critical role
on the quality of the results.Comment: 22 page
Effect of a gluteal activation warm-up on explosive exercise performance
Objectives To evaluate the effect of a gluteal
activation warm-up on the performance of an explosive
exercise (the high hang pull (HHP)).
Methods Seventeen professional rugby union players
performed one set of three HHPs (with 80% of their
one repetition maximum load) following both a control
and activation warm-up. Peak electrical activity of the
gluteus maximus and medius was quantified using
electromyography (EMG). In addition, the kinematics
and kinetics of nine players was also recorded using
force plate and motion capture technology. These data
were analysed using a previously described
musculoskeletal model of the right lower limb in order
to provide estimates of the muscular force expressed
during the movement.
Results The mean peak EMG activity of the gluteus
maximus was significantly lower following the
activation warm-up as compared with the control
(p<0.05, effect size d=0.30). There were no significant
differences in the mean peak estimated forces in
gluteus maximus and medius, the quadriceps or
hamstrings (p=0.053), although there was a trend
towards increased force in gluteus maximus and
hamstrings following the activation warm-up. There
were no differences between the ground reaction
forces following the two warm-ups.
Conclusion This study suggests that a gluteal
activation warm-up may facilitate recruitment of the
gluteal musculature by potentiating the glutes in such
a way that a smaller neural drive evokes the same or
greater force production during movement. This could
in turn potentially improve movement quality
Development of a stratospheric and mesospheric microwave temperature sounder experiment
A passive microwave spectrometer system for measuring global atmospheric temperature profiles from 0-75 km altitude was developed and analyzed. The system utilizes 12 channels near the 5 mm wavelength oxygen absorption band and is designed to provide global coverage by scanning perpendicular to the orbital track of a polar orbiting satellite. A significant improvement in the accuracy of theoretical atmospheric microwave transmittance functions was achieved through the development of a first-order approximation to overlapping line theory for the oxygen molecule. This approximation is particularly important in the troposphere and lower stratosphere where pressure-broadening blends nearby lines. Ground-based and aircraft observations of several resonances of stratospheric oxygen generally support the theory. The 23, 25, 29, and 31 atmospheric oxygen lines were measured and the frequencies of several such oxygen lines were measured with improved precision. The polarization and Zeeman splitting of the atmospheric 27 line was also observed
Screened hybrid functional applied to 3d^0-->3d^8 transition-metal perovskites LaMO3 (M=Sc-Cu): influence of the exchange mixing parameter on the structural, electronic and magnetic properties
We assess the performance of the Heyd-Scuseria-Ernzerhof (HSE) screened
hybrid density functional scheme applied to the perovskite family LaMO3
(M=Sc-Cu) and discuss the role of the mixing parameter alpha (which determines
the fraction of exact Hartree-Fock exchange included in the density functional
theory (DFT) exchange-correlation functional) on the structural, electronic,
and magnetic properties. The physical complexity of this class of compounds,
manifested by the largely varying electronic characters
(band/Mott-Hubbard/charge-transfer insulators and metals), magnetic orderings,
structural distortions (cooperative Jahn-Teller like instabilities), as well as
by the strong competition between localization/delocalization effects
associated with the gradual filling of the t_2g and e_g orbitals, symbolize a
critical and challenging case for theory. Our results indicates that HSE is
able to provide a consistent picture of the complex physical scenario
encountered across the LaMO3 series and significantly improve the standard DFT
description. The only exceptions are the correlated paramagnetic metals LaNiO3
and LaCuO3, which are found to be treated better within DFT. By fitting the
ground state properties with respect to alpha we have constructed a set of
'optimum' values of alpha from LaScO3 to LaCuO3: it is found that the 'optimum'
mixing parameter decreases with increasing filling of the d manifold (LaScO3:
0.25; LaTiO3 & LaVO3: 0.10-0.15; LaCrO3, LaMnO3, and LaFeO3: 0.15; LaCoO3:
0.05; LaNiO3 & LaCuO3: 0). This trend can be nicely correlated with the
modulation of the screening and dielectric properties across the LaMO3 series,
thus providing a physical justification to the empirical fitting procedure.Comment: 32 pages, 29 figure
The organization of conspecific face space in nonhuman primates
Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but comparative studies with monkeys suggest that these may be the result of recent evolutionary adaptations. The present study utilized the novel approach of face space, a powerful theoretical framework used to understand the representation of face identity in humans, to further explore species differences in face processing. According to the theory, faces are represented by vectors in a multidimensional space, the centre of which is defined by an average face. Each dimension codes features important for describing a face's identity, and vector length codes the feature's distinctiveness. Chimpanzees and rhesus monkeys discriminated male and female conspecifics' faces, rated by humans for their distinctiveness, using a computerized task. Multidimensional scaling analyses showed that the organization of face space was similar between humans and chimpanzees. Distinctive faces had the longest vectors and were the easiest for chimpanzees to discriminate. In contrast, distinctiveness did not correlate with the performance of rhesus monkeys. The feature dimensions for each species' face space were visualized and described using morphing techniques. These results confirm species differences in the perceptual representation of conspecific faces, which are discussed within an evolutionary framework
On the effect of Ti on Oxidation Behaviour of a Polycrystalline Nickel-based Superalloy
Titanium is commonly added to nickel superalloys but has a well-documented
detrimental effect on oxidation resistance. The present work constitutes the
first atomistic-scale quantitative measurements of grain boundary and bulk
compositions in the oxide scale of a current generation polycrystalline nickel
superalloy performed through atom probe tomography. Titanium was found to be
particularly detrimental to oxide scale growth through grain boundary
diffusion
Emergence and evolution of Plasmodium falciparum histidine-rich protein 2 and 3 deletion mutant parasites in Ethiopia [preprint]
Malaria diagnostic testing in Africa is threatened by Plasmodium falciparum parasites lacking histidine-rich protein 2 (pfhrp2) and 3 (pfhrp3) genes. Among 12,572 subjects enrolled along Ethiopia’s borders with Eritrea, Sudan, and South Sudan and using multiple assays, we estimate HRP2-based rapid diagnostic tests would miss 9.7% (95% CI 8.5-11.1) of falciparum malaria cases due to pfhrp2 deletion. Established and novel genomic tools reveal distinct subtelomeric deletion patterns, well-established pfhrp3 deletions, and recent expansion of pfhrp2 deletion. Current diagnostic strategies need to be urgently reconsidered in Ethiopia, and expanded surveillance is needed throughout the Horn of Africa
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