5,534 research outputs found

    Quantifying Long-Term Changes in Carbon Stocks and Forest Structure from Amazon Forest Degradation

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    Despite sustained declines in Amazon deforestation, forest degradation from logging and firecontinues to threaten carbon stocks, habitat, and biodiversity in frontier forests along the Amazon arcof deforestation. Limited data on the magnitude of carbon losses and rates of carbon recoveryfollowing forest degradation have hindered carbon accounting efforts and contributed to incompletenational reporting to reduce emissions from deforestation and forest degradation (REDD+). Wecombined annual time series of Landsat imagery and high-density airborne lidar data to characterizethe variability, magnitude, and persistence of Amazon forest degradation impacts on abovegroundcarbon density (ACD) and canopy structure. On average, degraded forests contained 45.1% of thecarbon stocks in intact forests, and differences persisted even after 15 years of regrowth. Incomparison to logging, understory fires resulted in the largest and longest-lasting differences in ACD.Heterogeneity in burned forest structure varied by fire severity and frequency. Forests with a historyof one, two, and three or more fires retained only 54.4%, 25.2%, and 7.6% of intact ACD,respectively, when measured after a year of regrowth. Unlike the additive impact of successive fires,selective logging before burning did not explain additional variability in modeled ACD loss andrecovery of burned forests. Airborne lidar also provides quantitative measures of habitat structure thatcan aid the estimation of co-benefits of avoided degradation. Notably, forest carbon stocks recoveredfaster than attributes of canopy structure that are critical for biodiversity in tropical forests, includingthe abundance of tall trees. We provide the first comprehensive look-up table of emissions factors forspecific degradation pathways at standard reporting intervals in the Amazon. Estimated carbon lossand recovery trajectories provide an important foundation for assessing the long-term contributionsfrom forest degradation to regional carbon cycling and advance our understanding of the currentstate of frontier forests

    MENTORING PRACTICES IN PNU PARTNER SCHOOLS : TOWARDS POLICY CREATION IN CAPACITY BUILDING OF COOPERATING TEACHERS FOR EFFECTIVE MENTORING

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    The practice of mentoring student teachers seeks the much needed intervention and reform in the preparation of future teacher professionals who will eventually implement the K-12 Curriculum in the Philippines. The present study investigated on the perception of student teachers on the way they were mentored during their practice teaching in the selected partner schools. Additionally, this paper presents the beliefs and practices of cooperating teachers which student teachers perceive to be effective in the mentoring process. Data gathered from surveys and interviews with student teachers and cooperating teachers for this study pointed the strengths of the mentoring program as well as pitfalls that need to be addressed. The cooperating teachers in the different partner schools identified elements which are believed to be areas of concern that make them feel the need to undergo capability building. The findings presented here are intended to inform the development of policies in building cooperating teachers‟ capability for effective mentoring

    A new matrix-free algorithm for the large-scale trust-region subproblem

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    We present a new method for the large-scale trust-region subproblem. The method is matrix-free in the sense that only matrix-vector products are required. We recast the trust-region subproblem as a parameterized eigenvalue problem and compute an optimal value for the parameter. We then nd the solution of the trust-region subproblem from the eigenvectors associated with two of the smallest eigenvalues of the parameterized eigenvalue problem corresponding to the optimal parameter. The new algorithm uses a different interpolating scheme than existing methods and introduces a uni ed iteration that naturally includes the so-called hard case. We show that the new iteration is well defined and convergent at a superlinear rate. We present computational results to illustrate convergence properties and robustness of the method.11361164

    Depletion of angiotensin-converting enzyme 2 reduces brain serotonin and impairs the running-induced neurogenic response

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    This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordPhysical exercise induces cell proliferation in the adult hippocampus in rodents. Serotonin (5-HT) and angiotensin (Ang) II are important mediators of the pro-mitotic effect of physical activity. Here, we examine precursor cells in the adult brain of mice lacking angiotensin-converting enzyme (ACE) 2, and explore the effect of an acute running stimulus on neurogenesis. ACE2 metabolizes Ang II to Ang-(1-7) and is essential for the intestinal uptake of tryptophan (Trp), the 5-HT precursor. In ACE2-deficient mice, we observed a decrease in brain 5-HT levels and no increase in the number of BrdU-positive cells following exercise. Targeting the Ang II/AT1 axis by blocking the receptor, or experimentally increasing Trp/5-HT levels in the brain of ACE2-deficient mice, did not rescue the running-induced effect. Furthermore, mice lacking the Ang-(1-7) receptor, Mas, presented a normal neurogenic response to exercise. Our results identify ACE2 as a novel factor required for exercise-dependent modulation of adult neurogenesis and essential for 5-HT metabolism

    Reproductive Biology of Common Small Pelagic Fishes in Manila Bay, Philippines

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    Reproductive biology of the three dominant species (Sardinella gibbosa, Sardinella fimbriata, and Rastrelliger kanagurta) were studied in Manila Bay from January 2014 to December 2015. The data were collected from landed catch (coming from gillnet, lift net, purse seine, ringnet, and trawl) and during the actual trawl fishing survey. A total of 2,383 Sardinella gibbosa, 2,334 Sardinella fimbriata, and 549 Rastrelliger kanagurta were analyzed by pooling the two years data. The overall female to male ratio conformed to the expected 1:1 sex ratio. These species spawn throughout the year with major peak in March and April and minor peak in October to December for Sardinella gibbosa; with major peak in February to May and minor peak in October to December for Sardinella fimbriata; and for Rastrelliger kanagurta, with major peak in October to December and minor peak in May and June. The GSI values correlate with the maturation of the gonads of these species. The length at maturity (Lm50) was calculated at 12.75 cm in males and 13.25 cm in females for S. gibbosa; 12.25 cm in males and 12.75 cm in females for S. fimbriata; and 25.5 cm in males and 24.5 cm in females for R. kanagurta

    A Three-Site Mechanism for Agonist/Antagonist Selective Binding to Vasopressin Receptors

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    Molecular-dynamics simulations with metadynamics enhanced sampling reveal three distinct binding sites for arginine vasopressin (AVP) within its V2 -receptor (V2 R). Two of these, the vestibule and intermediate sites, block (antagonize) the receptor, and the third is the orthosteric activation (agonist) site. The contacts found for the orthosteric site satisfy all the requirements deduced from mutagenesis experiments. Metadynamics simulations for V2 R and its V1a R-analog give an excellent correlation with experimental binding free energies by assuming that the most stable binding site in the simulations corresponds to the experimental binding free energy in each case. The resulting three-site mechanism separates agonists from antagonists and explains subtype selectivity

    Association Between Alcohol Intake and Cardiac Remodeling

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    Background: Alcohol-induced cardiotoxicity is incompletely understood. Specifically, the long-term impact of alcohol use on ventricular remodeling or dysfunction, its modulators, and effect thresholds among young adults remain controversial. Objectives: The authors sought to evaluate a potential relationship between alcohol intake and cardiac remodeling, assessed by echocardiography, over 20 years of follow-up. Methods: Among the CARDIA (Coronary Artery Risk Development in Young Adults) study cohort, the authors studied all subjects without baseline heart disorders who provided adequate information on their drinking habits and underwent echocardiographic evaluation at years 5 and 25 of the study. The echocardiographic outcomes were left ventricular (LV) ejection fraction, indexed LV end-diastolic volume and LV mass, and left atrial diameter. Participants were grouped according to their weighted-average weekly drinking habits. An additional analysis used the estimated cumulative alcohol consumption. Regression models and multivariable fractional polynomials were used to evaluate the association between alcohol consumption and the outcomes. Results: Among the 2,368 participants, alcohol consumption was an independent predictor of higher indexed LV mass (p = 0.014) and indexed LV end-diastolic volume (p = 0.037), regardless of sex. No significant relationship between alcohol intake and LV ejection fraction was found. Drinking predominantly wine was associated with less cardiac remodeling and there was a nonsignificant trend for a harmful effect of binge drinking. Conclusions: After 20 years of follow-up, alcohol intake was associated with adverse cardiac remodeling, although it was not related with LV systolic dysfunction in this initially healthy young cohort. Our results also suggest that drinking predominantly wine associates with less deleterious findings in cardiac structure.info:eu-repo/semantics/publishedVersio

    Gender differences in the association between adverse events in childhood or adolescence and the risk of premature mortality

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    To examine, by gender, the relationship between adverse events in childhood or adolescence and the increased risk of early mortality (before 80 years). The study sample included 941 participants of the English Longitudinal Study of Aging who died between 2007 and 2018. Data on socioeconomic status, infectious diseases, and parental stress in childhood or adolescence were collected at baseline (2006). Logistic regression models were adjusted by socioeconomic, behavioral and clinical variables. Having lived with only one parent (OR 3.79; p = 0.01), overprotection from the father (OR 1.12; p = 0.04) and having had an infectious disease in childhood or adolescence (OR 2.05; p = 0.01) were risk factors for mortality before the age of 80 in men. In women, overprotection from the father (OR 1.22; p < 0.01) was the only risk factor for mortality before the age of 80, whereas a low occupation of the head of the family (OR 0.58; p = 0.04) and greater care from the mother in childhood or adolescence (OR 0.86; p = 0.03) were protective factors. Independently of one’s current characteristics, having worse socioeconomic status and health in childhood or adolescence increased the risk of early mortality in men. Parental overprotection increased the risk of early mortality in both sexes, whereas maternal care favored longevity in women
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