FACTORS AFFECTING THE PROFITABILITY OF GOLF COURSES IN GEORGIA

Land Economics/Use,

Phonon Band Structure and Thermal Transport Correlation in a Layered Diatomic Crystal

To elucidate the relationship between a crystal's structure, its thermal conductivity, and its phonon dispersion characteristics, an analysis is conducted on layered diatomic Lennard-Jones crystals with various mass ratios. Lattice dynamics theory and molecular dynamics simulations are used to predict the phonon dispersion curves and the thermal conductivity. The layered structure generates directionally dependent thermal conductivities lower than those predicted by density trends alone. The dispersion characteristics are quantified using a set of novel band diagram metrics, which are used to assess the contributions of acoustic phonons and optical phonons to the thermal conductivity. The thermal conductivity increases as the extent of the acoustic modes increases, and decreases as the extent of the stop bands increases. The sensitivity of the thermal conductivity to the band diagram metrics is highest at low temperatures, where there is less anharmonic scattering, indicating that dispersion plays a more prominent role in thermal transport in that regime. We propose that the dispersion metrics (i) provide an indirect measure of the relative contributions of dispersion and anharmonic scattering to the thermal transport, and (ii) uncouple the standard thermal conductivity structure-property relation to that of structure-dispersion and dispersion-property relations, providing opportunities for better understanding of the underlying physical mechanisms and a potential tool for material design.Comment: 30 pages, 10 figure

The achievement of good chemical status: an impossible mission for local water managers?

The European Water Framework Directive (2000) required to achieve good ecological and chemical status in surface waters of the EU Member States in 2015. For pesticides, this means ensuring that concentrations in rivers do not exceed 0.1 g/L per molecule and 0.5 g/L for the sum of the concentrations of the different molecules found. At national scale, EcoPhyto plan (2008) aimed to reduce pesticide use by 50% within 10. This plan has been revised and postponed to 2025 as observed pesticide use is varying between years and concentrations in river did not decrease as expected. Although vineyards cover a small percentage of agricultural land surfaces, they contribute to 20% of national pesticide use. The presence of pesticides in rivers surrounding wine territories is therefore a current environmental concern. Thus, the recovery of the water quality requires local action programs to reduce pesticide contamination in rivers. The Layon catchment comprises 13% of vineyard. It is therefore subject to an action program led by the local water committee: the SAGE Layon-Aubance-Louet. Its goal is to ensure pesticide concentrations are reduced to 1 g/L in 2018 and 0.5 g/L in 2027. In this context, one of the actions of the SAGE, with the assistance of the University of Angers, addresses the study of peaks in pesticide concentrations during runoff events in a small catchment covered by vineyards. Between 2009 and 2016, one of the two farmers has converted to organic farming with consequent decreases in pesticides input to the case study which thus complied with the EcoPhyto objectives. Results demonstrate first a peak intensity of pesticides in runoff waters in relation with the date of application with a decrease of concentrations during time after the treatment and second a relation between peaks of SPM and pesticides. Transfer of pesticides in this catchment is strongly linked to runoff. Thus, even if the increase of grass surface within vineyard improves the soil stability and decreases erosion sensitivity, it is not sufficient to stop all transfer of pesticides. Following the results of this study, neither the objectives of national policies to reduce by half the pesticide use nor the local objectives to decrease partially the un-weeded surface of vineyards would permit to achieve good chemical status, as confirmed by the current state of the water quality of the Layon river monitored by local water managers. Thus, in the continuation of all its efforts

A Detailed Examination of Astrophysical Constraints on the Symmetry Energy and the Neutron Skin of ²⁰⁸Pb with Minimal Modeling Assumptions

The symmetry energy and its density dependence are pivotal for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of $0.283\pm0.071$ fm for the neutron-skin thickness of $^{208}$Pb, $R_{\rm skin}^{^{208}\text{Pb}}$, implying a symmetry-energy slope parameter $L$ of $106\pm37$ MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy $S_0$, $L$, and $R_{\rm skin}^{^{208}\text{Pb}}$ directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER favor smaller values of the neutron skin and $L$, as well as negative symmetry incompressibilities. Combining astrophysical data with chiral effective field theory ($\chi$EFT) and PREX-II constraints yields $S_0 = 33.0^{+2.0}_{-1.8}$ MeV, $L=53^{+14}_{-15}$ MeV, and $R_{\rm skin}^{^{208}\text{Pb}} = 0.17^{+0.04}_{-0.04}$ fm. We also examine the consistency of several individual $\chi$EFT calculations with astrophysical observations and terrestrial experiments. We find that there is only mild tension between $\chi$EFT, astrophysical data, and PREX-II's $R_\mathrm{skin}^{^{208}\mathrm{Pb}}$ measurement ($p$-value $= 12.3\%$) and that there is excellent agreement between $\chi$EFT, astrophysical data, and other nuclear experiments

Astrophysical Constraints on the Symmetry Energy and the Neutron Skin of ²⁰⁸Pb with Minimal Modeling Assumptions

The symmetry energy and its density dependence are crucial inputs for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of $0.283 \pm 0.071$ fm for the neutron-skin thickness of $^{208}$Pb, implying a slope parameter $L = 106 \pm 37$ MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy $S_0$, $L$, and $R_\mathrm{skin}^{^{208}\mathrm{Pb}}$ directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER clearly favor smaller values of the neutron skin and $L$, as well as negative symmetry incompressibilities. Combining astrophysical data with PREX-II and chiral effective field theory constraints yields $S_0 = 33.0^{+2.0}_{-1.8}$ MeV, $L=53^{+14}_{-15}$ MeV, and $R_\mathrm{skin}^{^{208}\mathrm{Pb}}=0.17^{+0.04}_{-0.04}$ fm

Evolution des pratiques de traction animale et conséquences sur la durabilité des systèmes de culture

Dans les systèmes de culture des zones de savane de l'Afrique de l'Ouest et du Centre, la traction animale occupe une place déterminante pour renforcer la capacité d'intervention des producteurs lors des étapes clés du calendrier agricole: préparation des terres, semis, désherbage, transport. Ces dix dernières années, trois facteurs ont déterminé les évolutions des pratiques: i) le démantèlement des services d'appui publics a rendu plus difficile l'acquisition et l'entretien des attelages, ii) l'augmentation de la pression foncière en zone rurale a renforcé les synergies agriculture élevage et induit des pratiques d'intensification par le travail (mécanisation des désherbages...), iii) la diffusion des herbicides a provoqué un repli du labour. Les conséquences agronomiques de ces évolutions sur la durabilité des systèmes de production sont parfois positives (amélioration de la flexibilité du travail, de la production et des revenus financiers des ménages), parfois négatives (marginalisation du rôle de l'élevage dans les transferts de fertilité, dégradation du semis mécanique, dégradation des itinéraires techniques, déforestation...). Des propositions d'amélioration de la technique sont suggérées. (Résumé d'auteur

Non-perturbative effects and the resummed Higgs transverse momentum distribution at the LHC

We investigate the form of the non-perturbative parameterization in both the impact parameter (b) space and transverse momentum (p_T) space resummation formalisms for the transverse momentum distribution of single massive bosons produced at hadron colliders. We propose to analyse data on Upsilon hadroproduction as a means of studying the non-perturbative contribution in processes with two gluons in the initial state. We also discuss the theoretical errors on the resummed Higgs transverse momentum distribution at the LHC arising from the non-perturbative contribution.Comment: 22 pages, 10 figure

Hydrogen and Deuterium Loss from the Terrestrial Atmosphere: A Quantitative Assessment of Nonthermal Escape Fluxes

A comprehensive one-dimensional photochemical model extending from the middle atmosphere (50 km) to the exobase (432 km) has been used to study the escape of hydrogen and deuterium from the Earth's atmosphere. The model incorporates recent advances in chemical kinetics as well as atmospheric observations by satellites, especially the Atmosphere Explorer C satellite. The results suggest: (1) the escape fluxes of both H and D are limited by the upward transport of total hydrogen and total deuterium at the homopause (this result is known as Hunten's limiting flux theorem); (2) about one fourth of total hydrogen escape is thermal, the rest being nonthermal; (3) escape of D is nonthermal; and (4) charge exchange and polar wind are important mechanisms for the nonthermal escape of H and D, but other nonthermal mechanisms may be required. The efficiency to escape from the terrestrial atmosphere for D is 0.74 of the efficiency for H. If the difference between the D/H ratio measured in deep-sea tholeiite glass and that of standard sea water, δD = −77‰, were caused by the escape of H and D, we estimate that as much water as the equivalent of 36% of the present ocean might have been lost in the past