4,395 research outputs found

    Chiral QCD, General QCD Parameterization and Constituent Quark Models

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    Several recent papers -using effective QCD chiral Lagrangians- reproduced results obtained with the general QCD parameterization (GP). These include the baryon 8+10 mass formula, the octet magnetic moments and the coincidental nature of the "perfect" -3/2 ratio between the magnetic moments of p and n. Although we anticipated that the GP covers the case of chiral treatments, the above results explicitly exemplify this fact. Also we show by the GP that -in any model or theory (chiral or non chiral) reproducing the results of exact QCD- the Franklin (Coleman Glashow) sum rule for the octet magnetic moments must be violated.Comment: 10 pages, Latex; abridged version (same results), removed some reference

    Comparison of Decision Rules for Subsurface Drip Irrigation Practices Using a Nonlinear Mathematical Programming Model

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    A comparison of decision rules has been made for case studies of corn production using subsurface drip irrigation under three agricultural management practices (no irrigation, uniform irrigation, and variable rate irrigation). The uniform irrigation strategy appeared to perform the best than the other two management practices under different risk scenarios.corn production, mathematical programming, profitability, risk management, subsurface drip irrigation, variable rate irrigation, Farm Management,

    A guide to nature immersion: psychological and physiological benefits

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    Nature exposure has been renowned for its positive physiological and psychological benefits. Recent years have seen a rise in nature immersion programs that make use of Guided Forest Therapy walks in a standard sequence of sensory awareness activities to expose participants to natural environments in a safe but effective manner. The study aimed to compare the efficacy of guided versus unguided nature immersion, upon three dependent variables of mood, nature connectedness and heartrate. 51 participants were assigned to either guided or unguided nature immersion. Nature connectedness (Connectedness to Nature Scale, CNS), Environmental Identity Scale, EID short form) and mood (Positive and Negative Affect Scale, PANAS) were assessed before and after nature immersion, while heart rate was tracked continuously by a wristwatch heart rate tracker throughout the 2-h experience. Demographics and general health practice (GHP) information were also collected. A mixed model ANOVA revealed that nature connectedness and mood (but not heart rate) improved post-immersion for all participants. Comparing the guided/unguided conditions, there were no significant differences in the change in nature connectedness, mood or heart rate. Comparing within the five segments within the standard sequence in the guided condition, the third and fifth segments revealed a significantly lower heart rate compared to the baseline heart rate

    High-severity wildfire leads to multi-decadal impacts on soil biogeochemistry in mixed-conifer forests.

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    During the past century, systematic wildfire suppression has decreased fire frequency and increased fire severity in the western United States of America. While this has resulted in large ecological changes aboveground such as altered tree species composition and increased forest density, little is known about the long-term, belowground implications of altered, ecologically novel, fire regimes, especially on soil biological processes. To better understand the long-term implications of ecologically novel, high-severity fire, we used a 44-yr high-severity fire chronosequence in the Sierra Nevada where forests were historically adapted to frequent, low-severity fire, but were fire suppressed for at least 70 yr. High-severity fire in the Sierra Nevada resulted in a long-term (44 +yr) decrease (>50%, P < 0.05) in soil extracellular enzyme activities, basal microbial respiration (56-72%, P < 0.05), and organic carbon (>50%, P < 0.05) in the upper 5 cm compared to sites that had not been burned for at least 115 yr. However, nitrogen (N) processes were only affected in the most recent fire site (4 yr post-fire). Net nitrification increased by over 600% in the most recent fire site (P < 0.001), but returned to similar levels as the unburned control in the 13-yr site. Contrary to previous studies, we did not find a consistent effect of plant cover type on soil biogeochemical processes in mid-successional (10-50 yr) forest soils. Rather, the 44-yr reduction in soil organic carbon (C) quantity correlated positively with dampened C cycling processes. Our results show the drastic and long-term implication of ecologically novel, high-severity fire on soil biogeochemistry and underscore the need for long-term fire ecological experiments

    Quark-quark correlations and baryon electroweak observables

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    The simple independent quark models have difficulties explaining simultaneously the totality of the known hyperon magnetic moments and hyperon semi-leptonic decay rates. We show that both the Goldstone boson loop contributions and the two-quark effective exchange currents are essential in explaining these observables.Comment: 7 pages, 1 figur

    Review of methods applicable to the assessment of mold exposure to children.

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    This article presents discussion of the assessment of the exposure of children to fungi, substances derived from fungi, and the environmental conditions that may lead to exposure. The principles driving investigations of fungal contamination and subsequent exposure are presented as well as guidelines for conducting these investigations. A comprehensive description of available research sampling and analysis techniques is also presented

    The effect of age and font size on reading text on handheld computers

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    Though there have been many studies of computer based text reading, only a few have considered the small screens of handheld computers. This paper presents an investigation into the effect of varying font size between 2 and 16 point on reading text on a handheld computer. By using both older and younger participants the possible effects of age were examined. Reading speed and accuracy were measured and subjective views of participants recorded. Objective results showed that there was little difference in reading performance above 6 point, but subjective comments from participants showed a preference for sizes in the middle range. We therefore suggest, for reading tasks, that designers of interfaces for mobile computers provide fonts in the range of 8-12 point to maximize readability for the widest range of users

    Handling uncertainties in modelling manufacturing processes with hybrid swarm intelligence

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    Seldom has research regarding manufacturing process modelling considered the two common types ofuncertainties which are caused by randomness as in material properties and by fuzziness as in the inexact knowledge in manufacturing processes. Accuracies of process models can be downgraded if these uncertainties are ignored in the development of process models. In this paper, a hybrid swarm intelligence algorithm for developing process models which intends to achieve significant accuracies for manufacturing process modelling by addressing these two uncertainties is proposed. The hybrid swarm intelligence algorithm first applies the mechanism of particle swarm optimisation to generate structures of process models in polynomial forms, and then it applies the mechanism of fuzzy least square regression algorithm to determine fuzzy coefficients on polynomials so as to address the two uncertainties, fuzziness and randomness. Apart from addressing the two uncertainties, the common feature in manufacturing processes, nonlinearities between process parameters, which are not inevitable in manufacturing processes, can also be addressed. The effectiveness of the hybrid swarm algorithm is demonstrated by modelling of the solder paste dispensing process
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