922 research outputs found
Age and Growth of Whale Sharks (Rhincodon typus) near the South Ari Atoll, Maldives
The whale shark (Rhincodon typus) has a global distribution in warm to warm temperate oceans, and is a species of high conservation concern currently categorized as Endangered on the International Union for Conservation of Nature (IUCN) Red List. Despite its dire conservation status and concerns about the growing number of ecotourism interactions with this species worldwide, relatively little information is available on key aspects of whale shark biology such as growth rates, reproductive rates, survival rates and breeding habitats. In particular, critical information such as age and growth of whale sharks is needed to improve the management and conservation of this species. Robust knowledge of life history parameters is needed to improve demographic models for whale sharks and enable better evaluation of their vulnerability to fishing pressures and recovery from population declines.
Whale sharks are well known to form aggregations in specific locations, with one such site being the South Ari Atoll in the Maldives. My study aimed to expand knowledge of the population dynamics, including age and growth, of whale sharks at the South Ari Atoll by calculating growth parameters and rates from encounters with free-swimming sharks over a decade (April 2006 to May 2016). A total of 1545 encounters with 125 individual sharks were recorded during this time period. To obtain the most accurate information on the sizes of whale sharks, total lengths were estimated by three different measurement methods (visual, laser photogrammetry, and tape), and linear regression was utilized to investigate how these different methods compared to one another. The results showed that visual estimates tended to underestimate sizes of the larger sharks, and laser and tape measurements yielded similar results to one another (R2 = 0.824). New sharks observed at the South Ari Atoll during the study period were significantly smaller than returning sharks, suggesting that young sharks may be recruited to the South Ari Atoll, where they stay and grow until reaching maturity before leaving the area.
To the best of my knowledge, my study is the first to infer growth parameters and rates from measurements of free-swimming whale sharks. Estimates of von Bertalanffy growth parameters for combined sexes, calculated from 180 encounters with 44 individual sharks (Males (n=40), Females (n=4), TL=3.16 m – 8.00 m), yielded an L¥ of 19.56 and a k value of 0.021. Analyzing 177 encounters with 40 male sharks (TL=3.16 m - 8.00 m) exclusively provided an L¥ of 18.08 and a k value of 0.023. These values correspond to a male age at maturity of ~25 years and a longevity of ~140 years, exceeding those estimated for whale sharks captured off Taiwan based on analysis of biannual vertebral rings (male maturity =17 years; longevity (combined sexes) = 80.4 years). There have been few growth studies, mainly from vertebral analysis, that have produced wide ranges in L¥ (14 – 20.5) and k values (0.017 – 0.037). These differences underscore the need for additional regional studies to obtain population specific estimates of these key life history parameters
Biventricular pacemaker therapy improves exercise capacity in patients with non‐obstructive hypertrophic cardiomyopathy via augmented diastolic filling on exercise
Aims Treatment options for patients with non‐obstructive hypertrophic cardiomyopathy (HCM) are limited. We sought to determine whether biventricular (BiV) pacing improves exercise capacity in HCM patients, and whether this is via augmented diastolic filling. Methods and results Thirty‐one patients with symptomatic non‐obstructive HCM were enrolled. Following device implantation, patients underwent detailed assessment of exercise diastolic filling using radionuclide ventriculography in BiV and sham pacing modes. Patients then entered an 8‐month crossover study of BiV and sham pacing in random order, to assess the effect on exercise capacity [peak oxygen consumption (VO2)]. Patients were grouped on pre‐specified analysis according to whether left ventricular end‐diastolic volume increased (+LVEDV) or was unchanged/decreased (–LVEDV) with exercise at baseline. Twenty‐nine patients (20 male, mean age 55 years) completed the study. There were 14 +LVEDV patients and 15 –LVEDV patients. Baseline peak VO2 was lower in –LVEDV patients vs. +LVEDV patients (16.2 ± 0.9 vs. 19.9 ± 1.1 mL/kg/min, P = 0.04). BiV pacing significantly increased exercise ΔLVEDV (P = 0.004) and Δstroke volume (P = 0.008) in –LVEDV patients, but not in +LVEDV patients. Left ventricular ejection fraction and end‐systolic elastance did not increase with BiV pacing in either group. This translated into significantly greater improvements in exercise capacity (peak VO2 + 1.4 mL/kg/min, P = 0.03) and quality of life scores (P = 0.02) in –LVEDV patients during the crossover study. There was no effect on left ventricular mechanical dyssynchrony in either group. Conclusion Symptomatic patients with non‐obstructive HCM may benefit from BiV pacing via augmentation of diastolic filling on exercise rather than contractile improvement. This may be due to relief of diastolic ventricular interaction. Clinical Trial Registration: ClinicalTrials.gov NCT00504647
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Attribution-based motivation treatment efficacy in an online learning environment for students who differ in cognitive elaboration
Attribution-based motivation treatments can boost performance in competitive achievement settings (Perry and Hamm 2017), yet their efficacy relative to mediating processes and affect-based treatments remains largely unexamined. In a two-semester, pre-post, randomized treatment study (n = 806), attributional retraining (AR) and stress-reduction (SR) treatments were administered in an online learning environment to first-year college students who differed in cognitive elaboration (low, high). Low elaborators who received AR outperformed their SR peers by nearly a letter grade on a class test assessed 5 months post-treatment. Path analysis revealed this AR-performance linkage was mediated by causal attributions, perceived control, and positive and negative achievement emotions in a hypothesized causal sequence. Results advance the literature by showing AR (vs. SR) improved performance indirectly via cognitive and affective process variables specified by Weiner’s (1985a, 2012) attribution theory of motivation and emotion
Different paths to the modern state in Europe: the interaction between domestic political economy and interstate competition
Theoretical work on state formation and capacity has focused mostly on early modern Europe and on the experience of western European states during this period. While a number of European states monopolized domestic tax collection and achieved gains in state capacity during the early modern era, for others revenues stagnated or even declined, and these variations motivated alternative hypotheses for determinants of fiscal and state capacity. In this study we test the basic hypotheses in the existing literature making use of the large date set we have compiled for all of the leading states across the continent. We find strong empirical support for two prevailing threads in the literature, arguing respectively that interstate wars and changes in economic structure towards an urbanized economy had positive fiscal impact. Regarding the main point of contention in the theoretical literature, whether it was representative or authoritarian political regimes that facilitated the gains in fiscal capacity, we do not find conclusive evidence that one performed better than the other. Instead, the empirical evidence we have gathered lends supports to the hypothesis that when under pressure of war, the fiscal performance of representative regimes was better in the more urbanized-commercial economies and the fiscal performance of authoritarian regimes was better in rural-agrarian economie
CCL2 Is Associated with a Faster Rate of Cognitive Decline during Early Stages of Alzheimer's Disease
Chemokine (C-C motif) receptor 2 (CCR2)-signaling can mediate accumulation of microglia at sites affected by neuroinflammation. CCR2 and its main ligand CCL2 (MCP-1) might also be involved in the altered metabolism of beta-amyloid (Aβ) underlying Alzheimer's disease (AD). We therefore measured the levels of CCL2 and three other CCR2 ligands, i.e. CCL11 (eotaxin), CCL13 (MCP-4) and CCL26 (eotaxin-3), in the cerebrospinal fluid (CSF) and plasma of 30 controls and 119 patients with mild cognitive impairment (MCI) at baseline. During clinical follow-up 52 MCI patients were clinically stable for five years, 47 developed AD (i.e. cases with prodromal AD at baseline) and 20 developed other dementias. Only CSF CCL26 was statistically significantly elevated in patients with prodromal AD when compared to controls (p = 0.002). However, in patients with prodromal AD, the CCL2 levels in CSF at baseline correlated with a faster cognitive decline during follow-up (rs = 0.42, p = 0.004). Furthermore, prodromal AD patients in the highest tertile of CSF CCL2 exhibited a significantly faster cognitive decline (p<0.001) and developed AD dementia within a shorter time period (p<0.003) compared to those in the lowest tertile. Finally, in the entire MCI cohort, CSF CCL2 could be combined with CSF Tau, P-tau and Aβ42 to predict both future conversion to AD and the rate of cognitive decline. If these results are corroborated in future studies, CCL2 in CSF could be a candidate biomarker for prediction of future disease progression rate in prodromal AD. Moreover, CCR2-related signaling pathways might be new therapeutic targets for therapies aiming at slowing down the disease progression rate of AD
Public health insurance and entry into self-employment
We estimate the impact of a differential treatment of paid employees versus
self-employed workers in a public health insurance system on the entry rate
into entrepreneurship. In Germany, the public health insurance system is
mandatory for most paid employees, but not for the selfemployed, who usually
buy private health insurance. Private health insurance contributions are
relatively low for the young and healthy, and until 2013 also for males, but
less attractive at the other ends of these dimensions and if membership in the
public health insurance allows other family members to be covered by
contribution-free family insurance. Therefore, the health insurance system can
create incentives or disincentives to starting up a business depending on the
family’s situation and health. We estimate a discrete time hazard rate model
of entrepreneurial entry based on representative household panel data for
Germany, which include personal health information, and we account for non-
random sample selection. We estimate that an increase in the health insurance
cost differential between self-employed workers and paid employees by 100 euro
per month decreases the annual probability of entry into selfemployment by
0.38 percentage points, i.e. about a third of the average annual entry rate.
The results show that the phenomenon of entrepreneurship lock, which an
emerging literature describes for the system of employer provided health
insurance in the USA, can also occur in a public health insurance system.
Therefore, entrepreneurial activity should be taken into account when
discussing potential health care reforms, not only in the USA and in Germany
Validation of the Ottawa Ankle Rules in Iran: A prospective survey
BACKGROUND: Acute ankle injuries are one of the most common reasons for presenting to emergency departments, but only a small percentage of patients – approximately 15% – have clinically significant fractures. However, these patients are almost always referred for radiography. The Ottawa Ankle Rules (OARs) have been designed to reduce the number of unnecessary radiographs ordered for these patients. The objective of this study was to validate the OARs in the Iranian population. METHODS: This prospective survey was done among 200 patients with acute ankle injury from January 2004 to April 2004 in the Akhtar Orthopedics Hospital Emergency Department. Main outcome measures of this survey were: sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratios (positive and negative) of the OARs. RESULTS: Sensitivity of the OARs for detecting 37 ankle fractures (23 in the malleolar zone and 14 in the midfoot zone) was 100% for each of the two zones, and 100% for both zones. Specificity of the OARs for detecting fractures was 40.50% for both zones, 40.50% for the malleolar zone, and 56.00% for the midfoot zone. Implementation of the OARs had the potential for reducing radiographs by 33%. CONCLUSION: OARs are very accurate and highly sensitive tools for detecting ankle fractures. Implementation of these rules would lead to significant reduction in the number of radiographs, costs, radiation exposure and waiting times in emergency departments
Adherence with isoniazid for prevention of tuberculosis among HIV-infected adults in South Africa
BACKGROUND: Tuberculosis (TB) is the most common opportunistic infection in HIV-infected adults in developing countries. Isoniazid (INH) is recommended for treatment of latent TB infection, however non-adherence is common. The purpose of this study was to apply in-house prepared isoniazid (INH) urine test strips in a clinical setting, and identify predictors of positive test results in an adherence questionnaire in HIV-infected adults taking INH for prevention of TB. METHODS: Cross-sectional study of adherence using a questionnaire and urine test strips for detection of INH metabolites at two hospitals in Pietermaritzburg, South Africa. Participants were aged at least 18 years, HIV positive, and receiving INH for prevention of tuberculosis disease. Univariate and multivariate analyses are used to identify factors relevant to adherence. RESULTS: 301 consecutive patients were recruited. 28% of participants had negative urine tests. 32 (37.2%, 95% CI25.4, 45.0) of the 86 patients who received INH from peripheral pharmacies said the pharmacy had run out of INH at some time, compared with central hospital pharmacies (p = 0.0001). In univariate analysis, a negative test was associated with self-reported missed INH doses (p = 0.043). Each 12-hour increment since last reported dose increased the likelihood of a negative test by 34% (p = 0.0007). Belief in INH safety was associated with a positive test (p = 0.021). In multivariate analysis, patients who believed INH is important for prevention of TB disease were more likely to be negative (p = 0.0086). CONCLUSION: Adequate drug availability at peripheral pharmacies remains an important intervention for TB prevention. Key questions may identify potentially non-adherent patients. In-house prepared urine tests strips are an effective and cheap method of objectively assessing INH adherence, and could be used an important tool in TB control programs
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