Pre and post fire carbon dynamics in a Florida Scrub oak

Scrub oak is a xeromorphic shrub ecosystem discontinuously distributed in coastal and inland Florida. It supports a high biodiversity which includes a large number of endangered and threatened species. Its structural features are maintained by a fire return cycle of 7 to 10 years which maintains the biodiversity. Management of fire prone ecosystems such as this raises the question of whether the management strategy contributes to the system being a carbon sink or carbon source over the long-term. We used eddy covariance and biometric approaches to measure carbon dynamics in a Florida scrub oak ecosystem located at Kennedy Space Center in east Central Florida from April 2004 to December 2007. The study site was controlled burned in February 2006. Two years previous to fire, the site experienced average precipitation but drought conditions during the two years after fire. Net ecosystem production (NEP) was 419 g C m-2 yr-1 during the first year of measurements, and the ecosystem incorporated 823 g C m-2 during the 22 months before the fire. Aboveground net primary production (NPP) represented 50% of annual NEP. Carbon released by fire reached 316 g C m-2. Ecosystem respiration (Re) dominated the carbon balance during the first six months after fire, and the ecosystem released an extra 119 g C m-2. However, gross ecosystem production (GEP) increased with leaf area index (LAI) after fire, dominating the carbon balance during the following six months. The ecosystem was a carbon sink of 88 g C m-2 yr-1 during the first year after the fire. Leaf area index (LAI) reached 1.54 m2 m-2 by October 2007 (80% of pre-burn value for the same time period). The scrub oak ecosystem was a continuous carbon sink six months after the fire despite the dominant drought conditions during 2006 – 2007. The ecosystem offset 80% (251 g C m-2) of the carbon released in the fire during the following twenty two months after the fire. Considering the fire return cycle of 7 to 10 years and the fact that the study site and a similar site nearby incorporated more than 400 g C m-2 yr-1 during the two years before fire, this scrub oak is a net carbon sink in the landscape under current management strategies

The Global R-linear Convergence of Nesterov's Accelerated Gradient Method with Unknown Strongly Convex Parameter

The Nesterov accelerated gradient (NAG) method is an important extrapolation-based numerical algorithm that accelerates the convergence of the gradient descent method in convex optimization. When dealing with an objective function that is $\mu$-strongly convex, selecting extrapolation coefficients dependent on $\mu$ enables global R-linear convergence. In cases where $\mu$ is unknown, a commonly adopted approach is to set the extrapolation coefficient using the original NAG method. This choice allows for achieving the optimal iteration complexity among first-order methods for general convex problems. However, it remains unknown whether the NAG method with an unknown strongly convex parameter exhibits global R-linear convergence for strongly convex problems. In this work, we answer this question positively by establishing the Q-linear convergence of certain constructed Lyapunov sequences. Furthermore, we extend our result to the global R-linear convergence of the accelerated proximal gradient method, which is employed for solving strongly convex composite optimization problems. Interestingly, these results contradict the findings of the continuous counterpart of the NAG method in [Su, Boyd, and Cand\'es, J. Mach. Learn. Res., 2016, 17(153), 1-43], where the convergence rate by the suggested ordinary differential equation cannot exceed the $O(1/{\tt poly}(k))$ for strongly convex functions

Why don't most mutual funds short sell?

An intriguing observation in the US mutual fund industry is that most equity funds do not short sell, even though virtually all regulatory restrictions on short selling had been lifted by 1997. We shed light on this puzzle by conducting the first systematic analysis of long-short equity funds' portfolio compositions, fund performance, and capital flows. Our results reveal that: 1) long-short mutual funds hold substantially more cash than their long-only peers and have a market beta significantly below one; 2) long-short funds generate a large positive alpha of 5% a year in risky holdings but slightly underperform their long-only peers in total returns; and 3) long-short funds face much higher flow-performance sensitivities and are more prone to use cash to absorb capital flows. We discuss several possible explanations for these findings

Off-hour admission and mortality risk for 28 specific diseases: A systematic review and meta-analysis of 251 cohorts

Background: A considerable amount of studies have examined the relationship between off-hours (weekends and nights) admission and mortality risk for various diseases, but the results remain equivocal. Methods and Results: Through a search of EMBASE, PUBMED, Web of Science, and Cochrane Database of Systematic Reviews, we identified cohort studies that evaluated the association between off-hour admission and mortality risk for disease. In a random effects meta-analysis of 140 identified articles (251 cohorts), off-hour admission was strongly associated with increased mortality for aortic aneurysm (odds ratio [OR], 1.52; 95% confidence interval, 1.30-1.77), breast cancer (1.50, 1.21-1.86), leukemia (1.45, 1.17-1.79), respiratory neoplasm (1.32, 1.20-1.26), pancreatic cancer (1.32, 1.12-1.56), malignant neoplasm of genitourinary organs (1.27, 1.08-1.49), colorectal cancer (1.26, 1.07-1.49), pulmonary embolism (1.20, 1.13-1.28), arrhythmia and cardiac arrest (1.19, 1.09-1.29), and lymphoma (1.19, 1.06-1.34). Weaker (OR<1.19) but statistically significant association was noted for renal failure, traumatic brain injury, heart failure, intracerebral hemorrhage, subarachnoid hemorrhage, stroke, gastrointestinal bleeding, myocardial infarction, chronic obstructive pulmonary disease, and bloodstream infections. No association was found for hip fracture, pneumonia, intestinal obstruction, aspiration pneumonia, peptic ulcer, trauma, diverticulitis, and neonatal mortality. Overall, Off-hour admission was associated with increased mortality for 28 diseases combined (OR, 1.11; 95% confidence interval, 1.10-1.13).Conclusions: Off-hour admission is associated with increased mortality risk, and the associations varied substantially for different diseases. Specialists, nurses, as well as hospital administrators and health policy makers can take these findings into consideration to improve the quality and continuity of medical services

Genome-wide identification and functional analysis of lincRNAs acting as miRNA targets or decoys in maize

LincRNA information derived from three articles. (XLS 20 kb