1,720 research outputs found

    Leaf Size and Leaf Area Index in Fagus sylvatica Forests: Competing Effects of Precipitation, Temperature, and Nitrogen Availability

    Get PDF
    Plants across diverse biomes tend to produce smaller leaves and a reduced total leaf area when exposed to drought. For mature trees of a single species, however, the leaf area-water supply relationship is not well understood. We tested the paradigm of leaf area reduction upon drought by a transect study with 14 mature Fagus sylvatica forests along a steep precipitation gradient (970-520 mm y(-1)) by applying two independent methods of leaf size determination. Contrary to expectation, average leaf size in dry stands (520-550 mm y(-1)) was about 40% larger and SLA was higher than in moist stands (910-970 mm y(-1)). As a result of increased leaf sizes, leaf area index significantly increased from the high- to the low-precipitation stands. Multiple regression analyses suggested that average leaf size was primarily controlled by temperature, whereas the influence of soil moisture and soil C/N ratio was low. Summer rainfall of the preceding year was the most significant predictor of total leaf number. We assume that leaf expansion of beech was independent of water supply, because it takes place in May with ample soil water reserves along the entire transect. In contrast, bud formation, which determines total leaf number, occurs in mid-summer, when droughts are severest. We conclude that leaf expansion and stand leaf area of beech along this precipitation gradient are not a simple function of water availability, but are controlled by several abiotic factors including spring temperature and possibly also nitrogen supply, which both tend to increase toward drier sites, thus overlaying any negative effect of water shortage on leaf development.Deutsche Bundesstiftung Umwel

    Neutron Drops and Skyrme Energy-Density Functionals

    Full text link
    The Jπ^{\pi}=0+^+ ground state of a drop of 8 neutrons and the lowest 1/2^- and 3/2^- states of 7-neutron drops, all in an external well, are computed accurately with variational and Green's function Monte Carlo methods for a Hamiltonian containing the Argonne v18v_{18} two-nucleon and Urbana IX three-nucleon potentials. These states are also calculated using Skyrme-type energy-density functionals. Commonly used functionals overestimate the central density of these drops and the spin-orbit splitting of 7-neutron drops. Improvements in the functionals are suggested

    Many-body effects in 16O(e,e'p)

    Get PDF
    Effects of nucleon-nucleon correlations on exclusive (e,ep)(e,e'p) reactions on closed-shell nuclei leading to single-hole states are studied using 16O(e,ep)15N^{16}O(e,e'p)^{15}N (6.326.32 MeV, 3/23/2^-) as an example. The quasi-hole wave function, calculated from the overlap of translationally invariant many-body variational wave functions containing realistic spatial, spin and isospin correlations, seems to describe the initial state of the struck proton accurately inside the nucleus, however it is too large at the surface. The effect of short-range correlations on the final state is found to be largely cancelled by the increase in the transparency for the struck proton. It is estimated that the values of the spectroscopic factors obtained with the DWIA may increase by a few percent due to correlation effects in the final state.Comment: 21 Pages, PHY-7849-TH-9

    Systematic study of Coulomb distortion effects in exclusive (e,e'p) reactions

    Get PDF
    A technique to deal with Coulomb electron distortions in the analysis of (e,e'p) reactions is presented. Thereby, no approximations are made. The suggested technique relies on a partial-wave expansion of the electron wave functions and a multipole decomposition of the electron and nuclear current in momentum space. In that way, we succeed in keeping the computational times within reasonable limits. This theoretical framework is used to calculate the quasielastic (e,e'p) reduced cross sections for proton knockout from the valence shells in 16^{16}O, 40^{40}Ca, 90^{90}Zr and 208^{208}Pb. The final-state interaction of the ejected proton with the residual nucleus is treated within an optical potential model. The role of electron distortion on the extracted spectroscopic factors is discussed.Comment: 45 pages, 10 encapsulated postscript figures, Revtex, uses epsfig.sty and fancybox.sty, to be published in Physical Review

    Screening of Dementia in Portuguese Primary Care: Methodology, Assessment Tools, and Main Results

    Get PDF
    The objectives of this article are as follows: (1) to describe the assessment protocol used to outline people with probable dementia in Primary Health Care; (2) to show the methodological design and procedure to obtain a representative sample of patients with probable dementia; and (3) to report the main characteristics of the sample collected in the context of the study “Characteristics and needs of people with probable dementia.” The study protocol was based on the “Community Assessment of Risk and Treatment Strategies (CARTS) Program” and is composed by a set of instruments that allow the assessment of older adults with probable dementia in several areas (health, psychological, functionality, and other). Descriptive analysis was used to characterize the final sample (n = 436). The study protocol as well as the methodological procedure to obtain the referral of research participants and data collection on the condition of people with probable dementia in Primary Health Care proved to be a valuable tool to obtain a sample of patients distributed by the full range of probable dementia in a large geographical area. Results may allocate the design of care pathways for old people with cognitive disorders to prevent, delay impairment, and/or optimize quality of life of patients

    Ground state correlations and mean-field in 16^{16}O

    Get PDF
    We use the coupled cluster expansion (exp(S)\exp(S) method) to generate the complete ground state correlations due to the NN interaction. Part of this procedure is the calculation of the two-body G matrix inside the nucleus in which it is being used. This formalism is being applied to 16O^{16}O in a configuration space of 50 ω\hbar\omega. The resulting ground state wave function is used to calculate the binding energy and one- and two-body densities for the ground state of 16O^{16}O.Comment: 9 pages, 9 figures, LaTe

    Avaliação da satisfação e importância atribuída aos serviços prestados na área da saúde mental

    Get PDF
    Com o objectivo de avaliar o grau de satisfação e importância atribuída aos serviços prestados na consulta na área da saúde mental e identificar as relações entre as variáveis demográficas e o grau de satisfação do utente foi realizado um estudo descritivo transversal, numa amostra de 305 utentes. Com a aplicação do questionário verificamos que a satisfação conjugada com a importância fornece-nos informação valiosa permitindo identificar pontos fortes, oportunidades ou necessidades de melhoria dos serviços. Neste estudo verificamos que os utentes encontram-se satisfeitos com os serviços prestados e consideram-nos importantes. Na análise bivariada, encontramos relação entre a satisfação e escolaridade.In order to evaluate the degree of satisfaction and importance attached to services provided in the consultation on mental health and identify relationships between demographic variables and the degree of user satisfaction was conducted a cross-sectional survey in a sample of 305 users. With the application of the questionnaire we found that satisfaction coupled with the importance provides us with valuable information allowing identifying strengths, opportunities or needs for improved services. In this study we found that users are satisfied with the services provided and consider them important. In bivariate analysis, we found the relationship between satisfaction and education level

    Kandungan, Resorpsi N dan P Serta Specifi C Leaf Area Daun Kakao (Theobroma Cacao L.) pada Cekaman Kekeringan

    Full text link
    Plant nutrient absorptions depend on their environment and plants' stage of development. Beside from soil, nutrient absorption also proceed through resorption in leaves. The resorption efficiency varies based on types of habitat. Drought stress also influences the efficiency of nutrient resorption, growth rate, and plant development. The purpose of this research was to study the change of nitrogen (N) and phosphorus (P) content and leaf resorption value of N and P, and specific leaf area of 6-years old cacao grown under drought stress. Research was carried out in a cacao plantation with 7-years old Gliricidia sepium Jacq. as shading trees. The results showed that drought stress with Troughfall Displacement Experiment (TDE) system did not affect the content and resorption level of N and P of cacao leaves. However, N resorption of cacao leaves tended to increase while P resorption decreased. Cacao plants experienced drought stress have the ability to resorp leaf N for 46.64-50.63%, leaf P for 47.98-58.40%, whereas, the control plants had the leaf N resorption of 45.05-52.97%, and leaf P resorption of 36.64-44.10%. Drought stress for 13 months on 6-years old cacao did not affect specifi c leaf area

    Wavelet Based Fractal Analysis of Airborne Pollen

    Full text link
    The most abundant biological particles in the atmosphere are pollen grains and spores. Self protection of pollen allergy is possible through the information of future pollen contents in the air. In spite of the importance of airborne pol len concentration forecasting, it has not been possible to predict the pollen concentrations with great accuracy, and about 25% of the daily pollen forecasts have resulted in failures. Previous analysis of the dynamic characteristics of atmospheric pollen time series indicate that the system can be described by a low dimensional chaotic map. We apply the wavelet transform to study the multifractal characteristics of an a irborne pollen time series. We find the persistence behaviour associated to low pollen concentration values and to the most rare events of highest pollen co ncentration values. The information and the correlation dimensions correspond to a chaotic system showing loss of information with time evolution.Comment: 11 pages, 7 figure

    A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements

    Full text link
    We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires a high cold neutron flux, control of systematic errors at the ppb level, and the use of current mode gamma-ray detection with vacuum photo diodes and low-noise solid-state preamplifiers. The average detector photoelectron yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in the measurement is therefore dominated by the fluctuations in the number of gamma rays absorbed in the detector (counting statistics) rather than the intrinsic detector noise. The detectors were tested for noise performance, sensitivity to magnetic fields, pedestal stability and cosmic background. False asymmetries due to gain changes and electronic pickup in the detector system were measured to be consistent with zero to an accuracy of 10910^{-9} in a few hours. We report on the design, operating criteria, and the results of measurements performed to test the detector array.Comment: 33 pages, 20 figures, 2 table
    corecore