151 research outputs found
Contribution to the knowledge of the Cu–Sn–Zn system for compositions close to brass alloys
The effect of tin content in the equilibrium phases of the Cu–Zn-based alloys, within the range of chemical compositions with interest
to brass producers is described. For this purpose, ternary alloys with copper contents between 55.4 and 67.5 wt.% and tin contents up to 5.30 wt.% have been studied. The chemical composition of each alloy has been determined by X-ray fluorescence spectrometry (XRF).
Isothermal homogenization, followed by rapid cooling, has been employed to determine the equilibrium phases at different temperatures.
The homogenized alloys have been observed by scanning electron microscopy and the respective chemical analysis of the phases determined by electron probe microanalysis (EPMA). The statistical analysis of the obtained results enable to correlate the chemical composition of equilibrium phases with temperature. The chemical composition of the three-phase field, for the studied temperatures, has also been determined
Energy cost and return for hunting in African wild dogs and Cheetahs
African wild dogs (Lycaon pictus) are reported to hunt with energetically costly long chase distances. We used high-resolution GPS and inertial technology to record 1,119 high-speed chases of all members of a pack of six adult African wild dogs in northern Botswana. Dogs performed multiple short, high-speed, mostly unsuccessful chases to capture prey, while cheetahs (Acinonyx jubatus) undertook even shorter, higher-speed hunts. We used an energy balance model to show that the energy return from group hunting and feeding substantially outweighs the cost of multiple short chases, which indicates that African wild dogs are more energetically robust than previously believed. Comparison with cheetah illustrates the trade-off between sheer athleticism and high individual kill rate characteristic of cheetahs, and the energetic robustness of frequent opportunistic group hunting and feeding by African wild dogs
Patterns of Risk of Depressive Symptoms Among HIV-Positive Women in the Southeastern United States
Depressive symptoms are a common response to HIV disease, and women appear to be at particularly high risk. The authors report results from a crosssectional analysis of data collected from 280 rural women with HIV/AIDS in the Southeastern United States aimed at identifying risk factors of depressive symptoms. Stress theory provided a framework for identification of potential risk factors. Descriptive statistics, measures of association, and regression analyses were used to systematically identify patterns of risk. The final regression model included 22 factors that accounted for 69% of the variance in depressive symptoms. The majority of variance in depressive symptoms was accounted for by only six variables: the frequency of HIV symptoms, recent experiences of sadness/hopelessness, the availability of social support, and the use of three coping strategies: living positively with HIV, isolation/withdrawal, and denial/avoidance. The results suggest a number of intervention strategies for use with rural women with HIV/AIDS
A homogeneous database of sunspot areas covering more than 130 years
The historical record of sunspot areas is a valuable and widely used proxy of
solar activity and variability. The Royal Greenwich Observatory (RGO) regularly
measured this and other parameters between 1874 and 1976. After that time
records from a number of different observatories are available. These, however,
show systematic differences and often have significants gaps. Our goal is to
obtain a uniform and complete sunspot area time series by combining different
data sets. A homogeneus composite of sunspot areas is essential for different
applications in solar physics, among others for irradiance reconstructions.
Data recorded simultaneously at different observatories are statistically
compared in order to determine the intercalibration factors. Using these data
we compile a complete and cross-calibrated time series. The Greenwich data set
is used as a basis until 1976, the Russian data (a compilation of observations
made at stations in the former USSR) between 1977 and 1985 and data compiled by
the USAF network since 1986. Other data sets (Rome, Yunnan, Catania) are used
to fill up the remaining gaps. Using the final sunspot areas record the
Photometric Sunspot Index is calculated. We also show that the use of
uncalibrated sunspot areas data sets can seriously affect the estimate of
irradiance variations. Our analysis implies that there is no basis for the
claim that UV irradiance variations have a much smaller influence on climate
than total solar irradiance variations.Comment: 40 pages, 8 figures; JGR - Space Physics, publishe
Coronary-Heart-Disease-Associated Genetic Variant at the COL4A1/COL4A2 Locus Affects COL4A1/COL4A2 Expression, Vascular Cell Survival, Atherosclerotic Plaque Stability and Risk of Myocardial Infarction.
Genome-wide association studies have revealed an association between coronary heart disease (CHD) and genetic variation on chromosome 13q34, with the lead single nucleotide polymorphism rs4773144 residing in the COL4A2 gene in this genomic region. We investigated the functional effects of this genetic variant. Analyses of primary cultures of vascular smooth muscle cells (SMCs) and endothelial cells (ECs) from different individuals showed a difference between rs4773144 genotypes in COL4A2 and COL4A1 expression levels, being lowest in the G/G genotype, intermediate in A/G and highest in A/A. Chromatin immunoprecipitation followed by allelic imbalance assays of primary cultures of SMCs and ECs that were of the A/G genotype revealed that the G allele had lower transcriptional activity than the A allele. Electrophoretic mobility shift assays and luciferase reporter gene assays showed that a short DNA sequence encompassing the rs4773144 site interacted with a nuclear protein, with lower efficiency for the G allele, and that the G allele sequence had lower activity in driving reporter gene expression. Analyses of cultured SMCs from different individuals demonstrated that cells of the G/G genotype had higher apoptosis rates. Immunohistochemical and histological examinations of ex vivo atherosclerotic coronary arteries from different individuals disclosed that atherosclerotic plaques with the G/G genotype had lower collagen IV abundance and thinner fibrous cap, a hallmark of unstable, rupture-prone plaques. A study of a cohort of patients with angiographically documented coronary artery disease showed that patients of the G/G genotype had higher rates of myocardial infarction, a phenotype often caused by plaque rupture. These results indicate that the CHD-related genetic variant at the COL4A2 locus affects COL4A2/COL4A1 expression, SMC survival, and atherosclerotic plaque stability, providing a mechanistic explanation for the association between the genetic variant and CHD risk
Multi-system neurological disease is common in patients with OPA1 mutations
Additional neurological features have recently been described in seven families transmitting pathogenic mutations in OPA1, the most common cause of autosomal dominant optic atrophy. However, the frequency of these syndromal ‘dominant optic atrophy plus’ variants and the extent of neurological involvement have not been established. In this large multi-centre study of 104 patients from 45 independent families, including 60 new cases, we show that extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers. Bilateral sensorineural deafness beginning in late childhood and early adulthood was a prominent manifestation, followed by a combination of ataxia, myopathy, peripheral neuropathy and progressive external ophthalmoplegia from the third decade of life onwards. We also identified novel clinical presentations with spastic paraparesis mimicking hereditary spastic paraplegia, and a multiple sclerosis-like illness. In contrast to initial reports, multi-system neurological disease was associated with all mutational subtypes, although there was an increased risk with missense mutations [odds ratio = 3.06, 95% confidence interval = 1.44–6.49; P = 0.0027], and mutations located within the guanosine triphosphate-ase region (odds ratio = 2.29, 95% confidence interval = 1.08–4.82; P = 0.0271). Histochemical and molecular characterization of skeletal muscle biopsies revealed the presence of cytochrome c oxidase-deficient fibres and multiple mitochondrial DNA deletions in the majority of patients harbouring OPA1 mutations, even in those with isolated optic nerve involvement. However, the cytochrome c oxidase-deficient load was over four times higher in the dominant optic atrophy + group compared to the pure optic neuropathy group, implicating a causal role for these secondary mitochondrial DNA defects in disease pathophysiology. Individuals with dominant optic atrophy plus phenotypes also had significantly worse visual outcomes, and careful surveillance is therefore mandatory to optimize the detection and management of neurological disability in a group of patients who already have significant visual impairment
It is Not All About the Benjamins: Understanding Preferences for Mates with Resources
We contend that preferences for mates with resources or money might be calibrated on where a potential mate gets her/his money. In three studies (N= 668) we examined the nature of individuals' preferences for mates who have resources or money. Both sexes preferred a long-term mate who has earned her/his money over other sources. In particular, women preferred mates who earned their money over other potential means of getting resources (i.e., inheritance, embezzlement, and windfall). Women maintained a high level of interest in mates who earned their money regardless of duration of the mateship whereas men became less interested in a mate who earned her money in the context of short-term relationships. Overall, the sexes preferred a mate who earned their money more strongly in the long-term than the short-term context. Results are discussed from evolutionary and sociocultural models of mate preferences
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Foreign policy and globalization theory: The case of Israel
Since the early 1990s, international relations has witnessed a stimulating debate on globalization. This debate laid the foundations for globalization theory (GT), providing the tools for an empirical examination of the globalization of multiple activities: from politics and organized violence, to finance, trade and production, through culture and environmental degradation. However, examination of what appear to be the best-known works on globalization reveals that foreign policy has been virtually excluded from GT. In this context, based on what is described here as a synergistic transformationalist approach (STA) to globalization, I provide a critique of GT. The critique is geared towards examining why foreign policy hitherto has been overlooked by contemporary GT. I expose the problems this generates and address them by exploring how STA enables GT to incorporate foreign policy. I use the case of Israel heuristically to elicit how incorporating foreign policy into GT may provide a better understanding of the relationship between foreign policy and globalization. Three themes are highlighted: the role of foreign policy in inducing and reproducing globalization; determining the mutually constitutive relationship between globalization and the state; and shaping the interfacing between international politics and globalization
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