5,869 research outputs found
Predicting morphotropic phase boundary locations and transition temperatures in Pb- and Bi-based perovskite solid solutions from crystal chemical data and first-principles calculations
Using data obtained from first-principles calculations, we show that the
position of the morphotropic phase boundary (MPB) and transition temperature at
MPB in ferroelectric perovskite solutions can be predicted with quantitative
accuracy from the properties of the constituent cations. We find that the mole
fraction of PbTiO at MPB in Pb(BB)O-PbTiO,
BiBO-PbTiO and Bi(BB)O-PbTiO exhibits a linear
dependence on the ionic size (tolerance factor) and the ionic displacements of
the B-cations as found by density functional theory calculations. This
dependence is due to competition between the local repulsion and A-cation
displacement alignment interactions. Inclusion of first-principles displacement
data also allows accurate prediction of transiton temperatures at the MPB. The
obtained structure-property correlations are used to predict morphotropic phase
boundaries and transition temperatures in as yet unsynthesized solid solutions.Comment: Accepted for publication in J. Appl. Phy
Review of the occupational health and safety of Britain’s ethnic minorities
This report sets out an evidence-based review on work-related health and safety issues relating to black and
minority ethnic groups. Data included available statistical materials and a systematic review of published research
and practice-based reports.
UK South Asians are generally under-represented within the most hazardous occupational groups. They have
lower accident rates overall, while Black Caribbean workers rates are similar to the general population;
Bangladeshi and Chinese workers report lowest workplace injury rates
UK South Asian people exhibit higher levels of limiting long-term illness (LLI) and self reported poor health than the
general population while Black Africans and Chinese report lower levels. Ethnic minority workers with LLI are more
likely than whites to withdraw from the workforce, or to experience lower wage rates.
Some of these findings conflict with evidence of differentials from USA, Europe and Australasia, but there is a
dearth of effective primary research or reliable monitoring data from UK sources.
There remains a need to improve monitoring and data collection relating to black and ethnic minority populations
and migrant workers. Suggestions are made relating to workshops on occupational health promotion programmes
for ethnic minorities, and ethnic minority health and safety 'Beacon' sites
Dynamical trapping and chaotic scattering of the harmonically driven barrier
A detailed analysis of the classical nonlinear dynamics of a single driven
square potential barrier with harmonically oscillating position is performed.
The system exhibits dynamical trapping which is associated with the existence
of a stable island in phase space. Due to the unstable periodic orbits of the
KAM-structure, the driven barrier is a chaotic scatterer and shows stickiness
of scattering trajectories in the vicinity of the stable island. The
transmission function of a suitably prepared ensemble yields results which are
very similar to tunneling resonances in the quantum mechanical regime. However,
the origin of these resonances is different in the classical regime.Comment: 14 page
Enhanced Tetragonality in (\u3cem\u3ex\u3c/em\u3e)PbTiO\u3csub\u3e3\u3c/sub\u3e-(1-x)Bi(\u3cem\u3eB′B″\u3c/em\u3e)O\u3csub\u3e3\u3c/sub\u3e systems: Bi(Zn\u3csub\u3e3/4\u3c/sub\u3eWN\u3csub\u3e1/4\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e
Solid solutions in the (x)PbTiO3–(1−x)Bi(Zn3/4W1/4)O3 system have been examined by x-ray diffraction, dielectric measurements, and thermal analysis. Bi(Zn3/4W1/4)O3increases the tetragonality and Curie temperature of PbTiO3 which reach a value of 1.08 and 530 °C, respectively, at the limit of the single-phase perovskite forming region (x~0.8). The observation of a sustained increase in the tetragonality in this system is similar to the behavior of the (x)PbTiO3–(1−x)Bi(Zn1/2Ti1/2)O3 system and highlights the unique properties of Bi-based systems when the B sites contain high concentrations of highly polarizable cations
AAS, growth hormone, and insulin abuse: psychological and neuroendocrine effects
The nontherapeutic use of prescription medicines by individuals involved in sport is increasing. Anabolic-androgenic steroids (AAS) are the most widely abused drug. Much of our knowledge of the psychological and physiological effects of human growth hormone (hGH) and insulin has been learned from deficiency states. As a consequence of the Internet revolution, previously unobtainable and expensive designer drugs, particularly recombinant human growth hormone (rhGH) and insulin, have become freely available at ridiculously discounted prices from countries such as China and are being abused. These drugs have various physiological and psychological effects and medical personnel must become aware that such prescription medicine abuse appears to be used not only for performance and cosmetic reasons, but as a consequence of psychological pre-morbidity
Arterial pulse wave velocity, inflammatory markers, pathological GH and IGF states, cardiovascular and cerebrovascular disease
Blood pressure (BP) measurements provide information regarding risk factors associated with cardiovascular disease, but only in a specific artery. Arterial stiffness (AS) can be determined by measurement of arterial pulse wave velocity (APWV). Separate from any role as a surrogate marker, AS is an important determinant of pulse pressure, left ventricular function and coronary artery perfusion pressure. Proximal elastic arteries and peripheral muscular arteries respond differently to aging and to medication. Endogenous human growth hormone (hGH), secreted by the anterior pituitary, peaks during early adulthood, declining at 14% per decade. Levels of insulin-like growth factor-I (IGF-I) are at their peak during late adolescence and decline throughout adulthood, mirror imaging GH. Arterial endothelial dysfunction, an accepted cause of increased APWV in GH deficiency (GHD) is reversed by recombinant human (rh) GH therapy, favorably influencing the risk for atherogenesis. APWV is a noninvasive method for measuring atherosclerotic and hypertensive vascular changes increases with age and atherosclerosis leading to increased systolic blood pressure and increased left ventricular hypertrophy. Aerobic exercise training increases arterial compliance and reduces systolic blood pressure. Whole body arterial compliance is lowered in strength-trained individuals. Homocysteine and C-reactive protein are two inflammatory markers directly linked with arterial endothelial dysfunction. Reviews of GH in the somatopause have not been favorable and side effects of treatment have marred its use except in classical GHD. Is it possible that we should be assessing the combined effects of therapy with rhGH and rhIGF-I? Only multiple intervention studies will provide the answer
A new tool in the toolbox for large-scale, high-throughput fisheries mark-recapture studies using genetic identification
Structure and dielectric response in the high ferroelectric Bi(Zn,Ti)O-PbTiO solid solutions
Theoretical {\em ab initio} and experimental methods were used to investigate
the Bi(Zn,Ti)O-(1-)PbTiO (BZT-PT) solid solution. We find that
hybridization between Zn 4 and O 2 orbitals allows the formation of
short, covalent Zn-O bonds, enabling favorable coupling between A-site and
B-site displacements. This leads to large polarization, strong tetragonality
and an elevated ferroelectric to paraelectric phase transition temperature.
nhomogeneities in local structure near the 90 domain boundaries can be
deduced from the asymetric peak broadening in the neutron and x-ray diffraction
spectra. These extrinsic effects make the ferroelectric to paraelectric phase
transition diffuse in BZT-PT solid solutions
- …