963 resultados para Rischio finanziario, Value-at-Risk, Expected Shortfall


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Tamarin monkeys, of the genus Saguinus, spend over half their lives at arboreal sleeping sites. The decision as to which site to use is likely to have considerable fitness consequences. These decisions about sleeping sites by three troops of golden-handed tamarin Saguinus midas midas were examined over a 9-mo period at a rainforest site in French Guiana. Data are presented on the physical nature of sleeping sites, their number, position within home ranges, and pattern of use and reuse, aspects of behaviour at retirement and egress, and predation attempts on the study troops. Cumulative plot analysis indicated that a tamarin troop used 30-40 sleeping sites in a 100-day period, approximately half of which were used very infrequently, so that consecutive reuse was never greater than three nights. Sleeping trees were superior in architectural parameters and liana weight to non-sleeping trees. There were no more sleeping sites than expected within the home range boundary region of the tamarins or in areas of overlap with the home ranges of neighbouring troops. Tamarins selected sleeping sites nearest to the last feeding site of the day on 25% of occasions. The study troops engaged in a number of activities that may reduce predation risk; raptor attacks on the study troops over 9 mo were frequent but unsuccessful. Tamarins often visited a sleeping site several hours before arrival, and were more likely to visit a site before use if they had not used it recently. The decision to select a sleeping site therefore involved knowledge of the previous frequency of use of that site.

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Aims To determine whether children with infections in early life (recorded routinely in general practice) have a reduced risk of Type 1 diabetes, as would be expected from the hygiene hypothesis.

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This paper examines (i) whether value-growth characteristics have more power than past performance in predicting return reversals; and (ii) whether typical rational behaviour such as incentives to delay paying capital gain taxes can better explain long-term reversals than past performance. We find that value-growth characteristics generally provide better explanations for long-term stock returns than past performance. The evidence also shows that winners identified by capital gains dominate past performance winners in predicting reversals in the cross-sectional comparison. However, in the time-series analysis, when returns on capital gain winners are adjusted by the Fama and French (1996) risk factors, the predictive power of capital gain winners disappears. Our results show that capital gain winners are heavily featured as growth stocks. Return reversals in capital gain winners potentially reflect market price corrections for growth stocks. We conclude that investors’ incentives to delay paying capital gain taxes cannot fully rationalise long-term reversals in the UK market. Our results also imply that the long-term return pattern potentially reflects a mixture of investor rational and irrational behaviour.

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The valuation of environmental benefits has been well researched in the forestry sector. This is not generally the case in the agriculture sector although schemes to compensate farmers for provision of officially defined environmental benefits are already in place throughout the European Union. This paper draws on empirical findings from forestry and deductions from economic theory to challenge the notion of the universality of such benefits. Empirical findings from forestry suggest recreational use value is location specific rather than widely spread. Household utility theory predicts zero willingness to pay to maintain the status quo level of a previously unpaid for environmental benefit (when provision is not perceived as under risk) but a positive willingness to pay for an increase. Thus, non use values cannot be attributed to the major part of existing commercial forestry area but to spatially restricted schemes such as additional afforestation or preservation of ancient natural woodlands.

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Background: High plasma HDL cholesterol is associated with reduced risk of myocardial infarction, but whether this association is causal is unclear. Exploiting the fact that genotypes are randomly assigned at meiosis, are independent of non-genetic confounding, and are unmodified by disease processes, mendelian random isation can be used to test the hypothesis that the association of a plasma biomarker with disease is causal.
Methods: We performed two mendelian randomisation analyses. First, we used as an instrument a single nucleotide polymorphism (SNP) in the endothelial lipase gene (LIPG Asn396Ser) and tested this SNP in 20 studies (20 913 myocardial infarction cases, 95 407 controls). Second, we used as an instrument a genetic score consisting of 14 common SNPs that exclusively associate with HDL cholesterol and tested this score in up to 12 482 cases of myocardial infarction and 41 331 controls. As a positive control, we also tested a genetic score of 13 common SNPs exclusively associated with LDL cholesterol.
Findings: Carriers of the LIPG 396Ser allele (2·6% frequency) had higher HDL cholesterol (0·14 mmol/L higher p=8×10-13) but similar levels of other lipid and non-lipid risk factors for myocardial infarction compared with noncarriers. This difference in HDL cholesterol is expected to decrease risk of myocardial infarction by 13% (odds ratio [OR] 0·87, 95% CI 0·84-0·91). However, we noted that the 396Ser allele was not associated with risk of myocardial infarction (OR 0·99, 95% CI 0·88-1·11, p=0·85). From observational epidemiology, an increase of 1 SD in HDL cholesterol was associated with reduced risk of myocardial infarction (OR 0·62, 95% CI 0·58-0·66). However, a 1 SD increase in HDL cholesterol due to genetic score was not associated with risk of myocardial infarction (OR 0·93 95% CI 0·68-1·26, p=0·63). For LDL cholesterol, the estimate from observational epidemiology (a 1 SD increase in LDL cholesterol associated with OR 1·54, 95% CI 1·45-1·63) was concordant with that from genetic score (OR 2·13 95% CI 1·69-2·69, p=2×10 -10).
Interpretation: Some genetic mechanisms that raise plasma HDL cholesterol do not seem to lower risk of myocardial infarction. These data challenge the concept that raising of plasma HDL cholesterol will uniformly translate into reductions in risk of myocardial infarction.

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A key pathological feature of late-onset Alzheimer's disease (LOAD) is the abnormal extracellular accumulation of the amyloid-ß (Aß) peptide. Thus, altered Aß degradation could be a major contributor to the development of LOAD. Variants in the gene encoding the Aß-degrading enzyme, angiotensin-1 converting enzyme (ACE) therefore represent plausible candidates for association with LOAD pathology and risk. Following Alzgene meta-analyses of all published case-control studies, the ACE variants rs4291 and rs1800764 showed significant association with LOAD risk. Furthermore ACE haplotypes are associated with both plasma ACE levels and LOAD risk. We tested three ACE variants (rs4291, rs4343, and rs1800764) for association with LOAD in ten Caucasian case-control populations (n = 8,212). No association was found using multiple logistic models (all p > 0.09). We found no population heterogeneity (all p > 0.38) or evidence for association with LOAD risk following meta-analysis of the ten populations for rs4343 (OR = 1.00), rs4291 (OR = 0.97), or rs1800764 (OR = 0.99). Although we found no haplotypic association in our complete dataset (p = 0.51), a significant global haplotypic p-value was observed in one population (p = 0.007) due to an association of the H3 haplotype (OR = 0.72, p = 0.02) and a trend towards an association of H4 (OR = 1.38, p = 0.09) and H7 (OR = 2.07, p = 0.08) although these did not survive Bonferroni correction. Previously reported associations of ACE variants with LOAD will be diminished following this study. At best, ACE variants have modest effect sizes, which are likely part of a complex interaction between genetic, phenotypic and pharmacological effects that would be undetected in traditional case-control studies.

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Background

Endocrine disrupting chemicals and carcinogens, some of which may not yet have been classified as such, are present in many occupational environments and could increase breast cancer risk. Prior research has identified associations with breast cancer and work in agricultural and industrial settings. The purpose of this study was to further characterize possible links between breast cancer risk and occupation, particularly in farming and manufacturing, as well as to examine the impacts of early agricultural exposures, and exposure effects that are specific to the endocrine receptor status of tumours.

Methods

1005 breast cancer cases referred by a regional cancer center and 1147 randomly-selected community controls provided detailed data including occupational and reproductive histories. All reported jobs were industry- and occupation-coded for the construction of cumulative exposure metrics representing likely exposure to carcinogens and endocrine disruptors. In a frequency-matched case?control design, exposure effects were estimated using conditional logistic regression.

Results

Across all sectors, women in jobs with potentially high exposures to carcinogens and endocrine disruptors had elevated breast cancer risk (OR = 1.42; 95% CI, 1.18-1.73, for 10 years exposure duration). Specific sectors with elevated risk included: agriculture (OR = 1.36; 95% CI, 1.01-1.82); bars-gambling (OR = 2.28; 95% CI, 0.94-5.53); automotive plastics manufacturing (OR = 2.68; 95% CI, 1.47-4.88), food canning (OR = 2.35; 95% CI, 1.00-5.53), and metalworking (OR = 1.73; 95% CI, 1.02-2.92). Estrogen receptor status of tumors with elevated risk differed by occupational grouping. Premenopausal breast cancer risk was highest for automotive plastics (OR = 4.76; 95% CI, 1.58-14.4) and food canning (OR = 5.70; 95% CI, 1.03-31.5).

Conclusions

These observations support hypotheses linking breast cancer risk and exposures likely to include carcinogens and endocrine disruptors, and demonstrate the value of detailed work histories in environmental and occupational epidemiology.

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We use conjoint choice questions to investigate people's tastes for cancer risk reductions and income in the context of public programs that would provide for remediation at abandoned industrial contaminated sites. Our survey was self-administered using the computer by persons living in the vicinity of an important contaminated site on the Italian National Priority List. The value of a prevented case of cancer is €2.6 million, but this figure does vary with income, perceived exposure to contaminants, and respondent opinions about priorities that should be pursued by cleanup programs. © 2011 Society for Risk Analysis.

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Objective: Establish maternal preferences for a third-trimester ultrasound scan in a healthy, low-risk pregnant population.

Design: Cross-sectional study incorporating a discrete choice experiment.

Setting: A large, urban maternity hospital in Northern Ireland.

Participants: One hundred and forty-six women in their second trimester of pregnancy.

Methods: A discrete choice experiment was designed to elicit preferences for four attributes of a third-trimester ultrasound scan: health-care professional conducting the scan, detection rate for abnormal foetal growth, provision of non-medical information, cost. Additional data collected included age, marital status, socio-economic status, obstetric history, pregnancy-specific stress levels, perceived health and whether pregnancy was planned. Analysis was undertaken using a mixed logit model with interaction effects.

Main outcome measures: Women's preferences for, and trade-offs between, the attributes of a hypothetical scan and indirect willingness-to-pay estimates.

Results: Women had significant positive preference for higher rate of detection, lower cost and provision of non-medical information, with no significant value placed on scan operator. Interaction effects revealed subgroups that valued the scan most: women experiencing their first pregnancy, women reporting higher levels of stress, an adverse obstetric history and older women.

Conclusions: Women were able to trade on aspects of care and place relative importance on clinical, non-clinical outcomes and processes of service delivery, thus highlighting the potential of using health utilities in the development of services from a clinical, economic and social perspective. Specifically, maternal preferences exhibited provide valuable information for designing a randomized trial of effectiveness and insight for clinical and policy decision makers to inform woman-centred care.

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Health professionals are expected to support family caregivers of patients requiring palliative care. However, there is a dearth of empirical evidence to help clinicians identify caregivers who might be at risk of poor psychosocial functioning.

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Toasting friends and family with realgar wines and painting children's foreheads and limbs with the leftover realgar/alcohol slurries is an important customary ritual during the Dragon Boat Festival (DBF); a Chinese national holiday and ancient feast day celebrated throughout Asia. Realgar is an arsenic sulfide mineral, and source of highly toxic inorganic arsenic. Despite the long history of realgar use during the DBF, associated risk to human health by arsenic ingestion or percutaneous adsorption is unknown. To address this urine samples were collected from a cohort of volunteers who were partaking in the DBF festivities. The total concentration of arsenic in the wine consumed was 70 mg L(-1) with all the arsenic found to be inorganic. Total arsenic concentrations in adult urine reached a maximum of ca. 550 mu g L(-1) (mean 220.2 mu g L(-1)) after 16 h post-ingestion of realgar wine, while face painting caused arsenic levels in children's urine to soar to 100 mu g L(-1) (mean 85.3 mu g L(-1)) 40 h after the initial paint application. The average concentration of inorganic arsenic in the urine of realgar wine drinkers on average doubled 16 h after drinking, although this was not permanent and levels subsided after 28 h. As would be expected in young children, the proportions of organic arsenic in the urine remained high throughout the 88-h monitoring period. However, even when arsenic concentrations in the urine peaked at 40 h after paint application, concentrations in the urine only declined slightly thereafter, suggesting pronounced longer term dermal accumulation and penetration of arsenic. Drinking wines blended with realgar or using realgar based paints on children does result in the significant absorption of arsenic and therefore presents a potentially serious and currently unquantified health risk. (C) 2011 Elsevier Ltd. All rights reserved.