275 research outputs found

    The Topographic Signature of Ecosystem Climate Sensitivity in the Western United States

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    It has been suggested that hillslope topography can produce hydrologic refugia, sites where ecosystem productivity is relatively insensitive to climate variation. However, the ecological impacts and spatial distribution of these sites are poorly resolved across gradients in climate. We quantified the response of ecosystem net primary productivity to changes in the annual climatic water balance for 30 years using pixel‐specific linear regression (30‐m resolution) across the western United States. The standardized slopes of these models represent ecosystem climate sensitivity and provide a means to identify drought‐resistant ecosystems. Productive and resistant ecosystems were most frequent in convergent hillslope positions, especially in semiarid climates. Ecosystems in divergent positions were moderately resistant to climate variability, but less productive relative to convergent positions. This topographic effect was significantly dampened in hygric and xeric climates. In aggregate, spatial patterns of ecosystem sensitivity can be implemented for regional planning to maximize conservation in landscapes more resistant to perturbations

    Declining Lung Function and Cardiovascular Risk: The ARIC Study

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    Background: Pulmonary dysfunction predicts incident cardiovascular disease (CVD). Objectives: The purpose of this study was to evaluate whether longitudinal decline in lung function is associated with incident heart failure (HF), coronary heart disease (CHD), and stroke. Methods: Among 10,351 participants in the ARIC (Atherosclerosis Risk In Communities) study free of CVD, rapid lung function decline was defined as the greatest quartile (n = 2,585) of decline in either forced expiratory volume in 1 s (FEV1) (>1.9% decline/year) or forced vital capacity (FVC) (>2.1% decline/year) over 2.9 ± 0.2 years. The relationship between rapid decline in FEV1 or FVC and subsequent incident HF, CHD, stroke, or a composite of these was assessed using multivariable Cox regression adjusting for the baseline spirometry value, demographics, height, body mass index, heart rate, diabetes, hypertension, low-density lipoprotein, use of lipid-lowering medication, N-terminal fragment of prohormone for B-type natriuretic peptide, and smoking. Results: The mean age was 54 ± 6 years, 56% were women, and 81% were white. At 17 ± 6 years of follow-up, HF occurred in 14%, CHD 11%, stroke 6%, and the composite in 24%. Rapid decline in FEV1 and in FVC were both associated with a heightened risk of incident HF (hazard ratio [HR]: 1.17; 95% confidence interval [CI]: 1.04 to 1.33; p = 0.010; and HR: 1.27; 95% CI: 1.12 to 1.44; p < 0.001; respectively), with rapid decline in FEV1 most prognostic in the first year of follow-up (HR: 4.22; 95% CI: 1.34 to 13.26; p = 0.01). Rapid decline in FEV1 was also associated with incident stroke (HR: 1.25; 95% CI: 1.04 to 1.50; p = 0.015). Conclusions: A rapid decline in lung function, assessed by serial spirometry, is associated with a higher incidence of subsequent CVD, particularly incident HF

    New York: the animated city

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    The urban landscape of New York City is one that is familiar to many, but, through the medium of animation, this familiarity has been consistently challenged. Often metamorphic, and always meticulously constructed, animated imagery encourages reflective thinking. Focusing on the themes of construction, destruction, and interactivity, this article seeks to cast critical light upon the animated double life that New York City has lived through the following moving image texts: Disney’s Fantasia 2000 (1999), Patrick Jean’s computer-generated short Pixels (2009), and Rockstar Games’ open-world blockbuster Grand Theft Auto IV (2008)

    Random walks and polymers in the presence of quenched disorder

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    After a general introduction to the field, we describe some recent results concerning disorder effects on both `random walk models', where the random walk is a dynamical process generated by local transition rules, and on `polymer models', where each random walk trajectory representing the configuration of a polymer chain is associated to a global Boltzmann weight. For random walk models, we explain, on the specific examples of the Sinai model and of the trap model, how disorder induces anomalous diffusion, aging behaviours and Golosov localization, and how these properties can be understood via a strong disorder renormalization approach. For polymer models, we discuss the critical properties of various delocalization transitions involving random polymers. We first summarize some recent progresses in the general theory of random critical points : thermodynamic observables are not self-averaging at criticality whenever disorder is relevant, and this lack of self-averaging is directly related to the probability distribution of pseudo-critical temperatures Tc(i,L)T_c(i,L) over the ensemble of samples (i)(i) of size LL. We describe the results of this analysis for the bidimensional wetting and for the Poland-Scheraga model of DNA denaturation.Comment: 17 pages, Conference Proceedings "Mathematics and Physics", I.H.E.S., France, November 200

    Heart failure risk across the spectrum of ankle-brachial index: The ARIC study (Atherosclerosis RiskIn Communities)

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    The aim of this study was to describe the relationship between ankle brachial index (ABI) and the risk for heart failure (HF). Background: The ABI is a simple, noninvasive measure associated with atherosclerotic cardiovascular disease and death; however, the relationship between ABI and risk for HF is less well characterized. Methods: Between 1987 and 1989 in the ARIC (Atherosclerosis Risk In Communities) study, an oscillometric device was used to measure blood pressure in a single upper and randomly chosen lower extremity to determine the ABI. Incident HF events were defined by the first hospitalization with an International Classification of Diseases, Ninth Revision, code of 428.x through 2008. The risk for HF was assessed across the ABI range using restricted cubic splines and Cox proportional hazards models. Results: ABI was available in 13,150 participants free from prevalent HF. Over a mean 17.7 years of follow-up, 1,809 incident HF events occurred. After adjustment for traditional HF risk factors, prevalent coronary heart disease, subclinical carotid atherosclerosis, and interim myocardial infarction, compared with an ABI of 1.01 to 1.40, participants with ABIs≀0.90 were at increased risk for HF (hazard ratio: 1.40; 95% confidence interval: 1.12 to 1.74), as were participants with ABIs of 0.91 to 1.00 (hazard ratio: 1.36; 95% confidence interval: 1.17 to 1.59). Conclusions: In a middle-age community cohort, an ABI≀1.00 was significantly associated with an increased risk for HF, independent of traditional HF risk factors, prevalent coronary heart disease, carotid atherosclerosis, and interim myocardial infarction. Low ABI may reflect not only overt atherosclerosis but also pathologic processes in the development of HF beyond epicardial atherosclerotic disease and myocardial infarction alone. A low ABI, as a simple, noninvasive measure, may be a risk marker for HF

    Heart Failure Stages among Older Adults in the Community: The Atherosclerosis Risk in Communities Study

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    Background: Although heart failure (HF) disproportionately affects older adults, little data exist regarding the prevalence of American College of Cardiology/American Heart Association HF stages among older individuals in the community. Additionally, the role of contemporary measures of longitudinal strain and diastolic dysfunction in defining HF stages is unclear. Methods: HF stages were classified in 6118 participants in the Atherosclerosis Risk in Communities study (67-91 years of age) at the fifth study visit as follows: A (asymptomatic with HF risk factors but no cardiac structural or functional abnormalities), B (asymptomatic with structural abnormalities, defined as left ventricular hypertrophy, dilation or dysfunction, or significant valvular disease), C1 (clinical HF without prior hospitalization), and C2 (clinical HF with earlier hospitalization). Results: Using the traditional definitions of HF stages, only 5% of examined participants were free of HF risk factors or structural heart disease (Stage 0), 52% were categorized as Stage A, 30% Stage B, 7% Stage C1, and 6% Stage C2. Worse HF stage was associated with a greater risk of incident HF hospitalization or death at a median follow-up of 608 days. Left ventricular (LV) ejection fraction was preserved in 77% and 65% in Stages C1 and C2, respectively. Incorporation of longitudinal strain and diastolic dysfunction into the Stage B definition reclassified 14% of the sample from Stage A to B and improved the net reclassification index (P=0.028) and integrated discrimination index (P=0.016). Abnormal LV structure, systolic function (based on LV ejection fraction and longitudinal strain), and diastolic function (based on e', E/e', and left atrial volume index) were each independently and additively associated with risk of incident HF hospitalization or death in Stage A and B participants. Conclusions: The majority of older adults in the community are at risk for HF (Stages A or B), appreciably more compared with previous reports in younger community-based samples. LV ejection fraction is robustly preserved in at least two-thirds of older adults with prevalent HF (Stage C), highlighting the burden of HF with preserved LV ejection fraction in the elderly. LV diastolic function and longitudinal strain provide incremental prognostic value beyond conventional measures of LV structure and LV ejection fraction in identifying persons at risk for HF hospitalization or death

    Predictors of mortality by sex and race in heart failure with preserved ejection fraction: Aric community surveillance study

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    BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) accounts for half of heart failure hospitalizations, with limited data on predictors of mortality by sex and race. We evaluated for differences in predictors of all-cause mortality by sex and race among hospitalized patients with HFpEF in the ARIC (Atherosclerosis Risk in Communities) Community Surveillance Study. METHODS AND RESULTS: Adjudicated HFpEF hospitalization events from 2005 to 2013 were analyzed from the ARIC Community Surveillance Study, comprising 4 US communities. Comparisons between clinical characteristics and mortality at 1 year were made by sex and race. Of 4335 adjudicated acute decompensated heart failure cases, 1892 cases (weighted n=8987) were categorized as HFpEF. Men had an increased risk of 1-year mortality compared with women in adjusted analysis (hazard ratio [HR], 1.27; 95% CI, 1.06–1.52 [P=0.01]). Black participants had lower mortality compared with White participants in unadjusted and adjusted analyses (HR, 0.79; 95% CI, 0.64–0.97 [P=0.02]). Age, heart rate, worsening renal function, and low hemoglobin were associated with increased mortality in all subgroups. Higher body mass index was associated with improved survival in men, with borderline interaction by sex. Higher blood pressure was associated with improved survival among all groups, with significant interaction by race. CONCLUSIONS: In a diverse HFpEF population, men had worse survival compared with women, and Black participants had improved survival compared with White participants. Age, heart rate, and worsening renal function were associated with increased mortality across all subgroups; high blood pressure was associated with decreased mortality with interaction by race. These insights into sex-and race-based differences in predictors of mortality may help strategize targeted management of HFpEF

    Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies

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    Background: Epidemiologic studies examining the relations between dairy product and calcium intakes and breast cancer have been inconclusive, especially for tumor subtypes. Objective: To evaluate the associations between intakes of specific dairy products and calcium and risk of breast cancer overall and for subtypes defined by estrogen receptor (ER) status. Method: We pooled the individual-level data of over 1 million women who were followed for a maximum of 8-20 years across studies. Associations were evaluated for dairy product and calcium intakes and risk of incident invasive breast cancer overall (n = 37,861 cases) and by subtypes defined by ER status. Study-specific multivariable hazard ratios (HRs) were estimated and then combined using random-effects models. Results: Overall, no clear association was observed between the consumption of specific dairy foods, dietary (from foods only) calcium, and total (from foods and supplements) calcium, and risk of overall breast cancer. Although each dairy product showed a null or very weak inverse association with risk of overall breast cancer (P, test for trend >0.05 for all), differences by ER status were suggested for yogurt and cottage/ricotta cheese with associations observed for ER-negative tumors only (pooled HR = 0.90, 95% CI: 0.83, 0.98 comparing >= 60 g/d with = 25 g/d with Conclusion: Our study shows that adult dairy or calcium consumption is unlikely to associate with a higher risk of breast cancer and that higher yogurt and cottage/ricotta cheese intakes were inversely associated with the risk of ER-negative breast cancer, a less hormonally dependent subtype with poor prognosis. Future studies on fermented dairy products, earlier life exposures, ER-negative breast cancer, and different racial/ethnic populations may further elucidate the relation
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