C720

F. Robert Henderson et al., Increasing Eastern Bluebirds in Kansas, Kansas State University, November 1990

Static dielectric response of icosahedral fullerenes from C60 to C2160 by an all electron density functional theory

The static dielectric response of C60, C180, C240, C540, C720, C960, C1500, and C2160 fullerenes is characterized by an all-electron density-functional method. First, the screened polarizabilities of C60, C180, C240, and C540, are determined by the finite-field method using Gaussian basis set containing 35 basis functions per atom. In the second set of calculations, the unscreened polarizabilities are calculated for fullerenes C60 through C2160 from the self-consistent Kohn-Sham orbitals and eigen-values using the sum-over-states method. The approximate screened polarizabilities, obtained by applying a correction determined within linear response theory show excellent agreement with the finite-field polarizabilities. The static dipole polarizability per atom in C2160 is (4 Angstrom^3) three times larger than that in C60 (1.344 Angstrom^3). Our results reduce the uncertainty in various theoretical models used previously to describe the dielectric response of fullerenes and show that quantum size effects in polarizability are significantly smaller than previously thought.Comment: RevTex, 3 figure

BGP-like TE Capabilities for SHIM6

In this paper we present a comprehensive set of mechanisms that restore to the site administrator the capacity of enforcing traffic engineering (TE) policies in a multiaddressed IPv6 scenario. The mechanisms rely on the ability of SHIM6 to securely perform locator changes in a transparent fashion to transport and application layers. Once an outgoing path has been selected for a communication by proper routing configuration in the site, the source prefix of SHIM6 data packets is rewritten by the site routers to avoid packet discarding due to ingress filtering. The SHIM6 locator preferences exchanged in the context establishment phase are modified by the site routers to influence in the path used for receiving traffic. Scalable deployment is ensured by the stateless nature of these mechanisms.Publicad

Pratiques phytosanitaires paysannes dans les savanes d'Afrique centrale

International audienceAvec une production de plus de 300 000 tonnes, la culture cotonnière joue un rôle moteur dans l'économie sous-régionale de l'Afrique centrale. Par ailleurs, les productions maraîchères destinées au marché local ou à l'exportation participent à la sécurité alimentaire de la région et à la diversification des sources de revenus des paysans. La protection de ces cultures, soumises à de fortes attaques parasitaires, a entraîné une consommation croissante de pesticides. Outre le problème d'un coût monétaire élevé, leur mauvaise utilisation a des effets négatifs sur la santé des utilisateurs et des consommateurs mais aussi sur l'environnement. Elle provoque de surcroît la sélection d'insectes résistants. La présente étude a pour but de caractériser les pratiques phytosanitaires paysannes dans les systèmes de cultures associant coton et niébé comme dans le maraîchage. L'inventaire des pesticides, celui des sources d'approvisionnement et le recensement des différents textes administratifs et réglementaires en matière de gestion des pesticides, ont été réalisés dans chaque pays. Une typologie des pratiques phytosanitaires des producteurs et des revendeurs a été établie. L'étude a permis de recenser les pesticides mis sur le marché, les types d'emballages, le reconditionnement, ainsi que les circuits d'approvisionnement, de distribution et de vente. Quatre principaux canaux de distribution des pesticides ont été identifiés : canal étatique et para-étatique, canal non étatique (sociétés de développement, projets), canal privé (circuit commercial) et agriculteurs. Les familles chimiques les plus utilisées sont celles des organophosphorés (29 %), des carbamates (21 %), des pyréthrinoïdes (18 %) et des organochlorés (9 %). Les produits destinés à la protection du coton, pour lesquels les paysans disposent d'un crédit, sont souvent détournés sur d'autres cultures. Pour la majorité des paysans interrogés, l'emploi de pesticides permet encore d'assurer un bon rendement et de réduire les pertes liées aux ravageurs. Cependant, ils n'ont pas une bonne connaissance des matières actives utilisées, des doses d'application, des fréquences de traitement et de leurs impacts sur la santé humaine. Cette étude confirme une utilisation non contrôlée des pesticides « coton » tout au long de l'année sur des cultures autres que le cotonnier, plus particulièrement sur le niébé et la tomate. Le manque de formation et d'information des producteurs ainsi que le non-respect des cadres légaux relatifs à la commercialisation et l'utilisation des pesticides sont des facteurs qui aggravent la situation sanitaire des populations de la sous-région

Direct Metal Laser Fabrication of Cu Slabs from Powder Precursor: Surface Depth of Melt and Furnace Temperature Issues

A DMLF processing unit based on a raster-scanned 80 W CO2 laser beam has been developed to process single layers of metallic powder precursor. The process chamber provides atmosphere control (high vacuum and inert gas refill) besides temperature elevation up to 700 o C. In this work, copper powder precursor is confined inside a refractory steel mask surrounded by an aluminum oxide jacket that acts as insulator. The powder layers can have thicknesses of 0,5 and 1 mm. An infrared pyrometer measures in real time the temperature at one location in the surface of the powder bed. Scan speed, scan step, and furnace temperature have been varied to find combinations of such parameters that render surface melting and maximum densification. Partially melted samples were produced and their mass density was measured. Micro-hardness and surface roughness were also measured along the resolidified surface, the first rendering an average of 80,6 HV compared to the 90-105 HV of oxygen free copper, while the second resulting in an 8 μm Ra value. Maximum melt of depth achieved is ~0,15 mm followed by a sintered layer.Mechanical Engineerin

Surgical anatomy of the uncinate process and transverse foramen determined by computer tomography

Study Design Computed tomography–based cohort study. Objective Although there are publications concerning the relationship between the vertebral artery and uncinate process, there is no practical guide detailing the dimensions of this region to use during decompression of the intervertebral foramen. The purpose of this study is to determine the anatomic parameters that can be used as a guide for thorough decompression of the intervertebral foramen. Methods Fifty-one patients with three-dimensional computed tomography scans of the cervical spine from 2003 to 2012 were included. On axial views, we measured the distance from the midline to the medial and lateral cortices of the pedicle bilaterally from C3 to C7. On coronal reconstructed views, we measured the minimum height of the uncinate process from the cranial cortex of the pedicle adjacent to the posterior cortex of vertebral body and the maximal height of the uncinate process from the cranial cortex of the pedicle at the midportion of the vertebral body bilaterally from C3 to C7. Results The mean distances from midline to the medial and lateral cortices of the pedicle were 10.1 ± 1.3 mm and 13.9 ± 1.5 mm, respectively. The mean minimum height of the uncinate process from the cranial cortex of the pedicle was 4.6 ± 1.6 mm and the mean maximal height was 6.1 ± 1.7 mm. Conclusions Our results suggest that in most cases, one can thoroughly decompress the intervertebral foramen by removing the uncinate out to 13 mm laterally from the midline and 4 mm above the pedicle without violating the transverse foramen

Virtual Population Units: A New Institutional Approach to Fisheries Management

This paper describes an alternative, rights-based approach to the economic problems of fisheries management and governance. The approach is based on the concept of a Virtual Population (VP), which provides an alternative way to define use rights in a fishery management system. Included is a comparison of harvest rates under the VP regime, “sole-owner,†and open-access regimes. In comparison, a VP solution is more efficient than open access and can approach that of a sole owner. More importantly, in our opinion, the approach contains a higher degree of local control over issues such as concentration of ownership and, unlike some community-based systems, provides an explicit, decentralized incentive for conservation. It also contains a built-in incentive mechanism for end-of-year conservation that is absent from individual transferable quotas (ITQs).Virtual populations, virtual population units, ITQs, marginal valuation, Resource /Energy Economics and Policy, Q220, Q590, C720, D830,