6,325 research outputs found

    Allometry and growth of eight tree taxa in United Kingdom woodlands.

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    This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0As part of a project to develop predictive ecosystem models of United Kingdom woodlands we have collated data from two United Kingdom woodlands - Wytham Woods and Alice Holt. Here we present data from 582 individual trees of eight taxa in the form of summary variables relating to the allometric relationships between trunk diameter, height, crown height, crown radius and trunk radial growth rate to the tree's light environment and diameter at breast height. In addition the raw data files containing the variables from which the summary data were obtained. Large sample sizes with longitudinal data spanning 22 years make these datasets useful for future studies concerned with the way trees change in size and shape over their life-span

    Bulletin No. 169 - The Use of Alkali Water for Irrigation

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    Because of the scanty rainfall of arid regions, the soluble materials in the rocks and soil are not leached out as they are where the rainfall is high. As a result, the accumulation of excessive quantities of soluble salts is likely to be a menace to arid soils. Farm practices must be directed toward preventing this condition

    Leading quantum gravitational corrections to QED

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    We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged spin-1/2 fermions in the combined theory of general relativity and QED. The coupled Dirac-Einstein system is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracted from the action, and the non-analytic contributions to the 1-loop scattering matrix are calculated in the non-relativistic limit. The non-analytical parts of the scattering amplitude are known to give the long range, low energy, leading quantum corrections, are used to construct the leading post-Newtonian and quantum corrections to the two-particle non-relativistic scattering matrix potential for two massive fermions with electric charge.Comment: 14 pages, 29 figures, format RevTex

    An Empirical Investigation on Perception of Organizational Politics, Job Stress & Job Satisfaction Among Academicians in Pakistan Using Second-Order Construct

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    Level of job satisfactions among academicians has remained enriched area of research for the academic’s institutions. Therefore, the rationale behind conducting research was to investigate the influence of Perception of Organizational Politics (POP) and Job Stress (JSt) on Job satisfaction (JS) academicians. Research framework has been formed based on Social Exchange Theory (SET) to create logical relationships among variable which explained that employees behave accordingly as per response they received from management’s behavior. For the execution of analysis data was collected from 300 teachers of public sector universities of Punjab, Pakistan through psychometric defined instruments. Software SmartPLS was used for assessment of measurement and structural model. Results from the analysis demonstrates that POP has significant and negative effect on JS and significant positive effect on JSt while significant negative effect was observed between JSt and JS. The results revealed useful information for the stakeholders and policy makers to focus and develop and organizational structure to eliminate the influence of POP in academic institutions

    Sensing the heat: Climate change vulnerability and foreign direct investment inflows

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    We investigate whether climate change vulnerability determines foreign direct investment (FDI) inflows. We reason that multinational firms foresee a higher climate change vulnerability of host-country a locational disadvantage while making FDI allocation decisions. Utilizing annual data from 152 countries spanning the period 1996–2019 and employing the panel pooled ordinary least square regressions, we evidence that FDI inflows are lower in countries more vulnerable to climate change. We also observe that FDI inflows are only sensitive to climate-related risks in high- and middle-income countries, but not in low-income countries where the market size is a primary driver of FDI inflows. Moreover, we also find that host countries may weaken the adverse effects of climate change vulnerability on FDI inflows by strengthening the economic, institutional, and social environment

    Performance of a C4F8O Gas Radiator Ring Imaging Cherenkov Detector Using Multi-anode Photomultiplier Tubes

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    We report on test results of a novel ring imaging Cherenkov (RICH) detection system consisting of a 3 meter long gaseous C4F8O radiator, a focusing mirror, and a photon detector array based on Hamamatsu multi-anode photomultiplier tubes. This system was developed to identify charged particles in the momentum range from 3-70 GeV/c for the BTeV experiment.Comment: 28 pages, 23 figures, submitted to Nuclear Instruments and Method

    Surface van der Waals Forces in a Nutshell

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    Most often in chemical physics, long range van der Waals surface interactions are approximated by the exact asymptotic result at vanishing distance, the well known additive approximation of London dispersion forces due to Hamaker. However, the description of retardation effects that is known since the time of Casimir is completely neglected for lack of a tractable expression. Here we show that it is possible to describe surface van der Waals forces at arbitrary distances in one single simple equation. The result captures the long sought crossover from non-retarded (London) to retarded (Casimir) interactions, the effect of polarization in condensed media and the full suppression of retarded interactions at large distance. This is achieved with similar accuracy and the same material properties that are used to approximate the Hamaker constant in conventional applications. The results show that at ambient temperature, retardation effects significantly change the power law exponent of the conventional Hamaker result for distances of just a few nanometers.Comment: 6 pages + 4 figures + supplementary materia

    Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula

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    We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star Eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.Comment: 17 pages, 5 figures, accepted by Ap
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