2,300 research outputs found

    A Selected Bibliography of Topics on Employment Practices

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    Cornell University is currently funded by the U.S. Department of Education National Institute on Disability and Rehabilitation Research for a four-year Research and Demonstration entitled Improving Employment Practices Covered by Title I of the ADA (Grant # H133A70005). As a part of these efforts, we have done an extensive literature review on topics related to employer practices and the employment provisions of the Americans with Disabilities Act (ADA). This bibliography is the result of these eighteen months of efforts. This publication is available as a print product, and is accessible online at http://www.ilr.cornell.edu. We hope that these resources will be of assistance in helping human resource professionals, employers, providers of vocational rehabilitation services, advocacy organizations, and persons with disabilities and their family members to better employ the ADA in effectively implementing the accommodation process

    On the Determination of the Polarized Sea Distributions of the Nucleon

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    The possibilities to determine the flavor structure of the polarized sea (antiquark) distributions of the nucleon via vector boson (γ,W±,Z0)(\gamma^*, W^{\pm}, Z^0) production at high energy polarized hadron--hadron colliders, such as the Relativistic Heavy--Ion Collider (RHIC), are studied in detail. In particular the perturbative stability of the expected asymmetries in two representative models for the (un)broken flavor structure are investigated by confronting perturbative QCD leading order predictions of the expected asymmetries with their next--to--leading order counterparts.Comment: 28 pages, LaTe

    Spin-Dependent Structure Functions of Real and Virtual Photons

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    The implications of the positivity constraint, g1γ(P2)(x,Q2)F1γ(P2)(x,Q2)|g_1^{\gamma(P^2)}(x,Q^2)| \leq F_1^{\gamma(P^2)}(x,Q^2), on the presently unknown spin--dependent structure function g1γ(P2)(x,Q2)g_1^{\gamma(P^2)}(x,Q^2) of real and virtual photons are studied at scales Q2P2Q^2\gg P^2 where longitudinally polarized photons dominate physically relevant cross sections. In particular it is shown how to implement the physical constraints of positivity and continuity at P2=0P^2=0 in NLO calculations which afford a nontrivial choice of suitable (DIS) factorization schemes related to g1γg_1^{\gamma} and F1γF_1^{\gamma} and appropriate boundary conditions for the polarized parton distributions of real and virtual photons. The predictions of two extreme `maximal' and `minimal' saturation scenarios are presented and compared with results obtained within the framework of a simple quark `box' calculation expected to yield reasonable estimates in the not too small regions of xx and P2P^2.Comment: 33 pages, LaTeX, 12 figure

    The jet quenching in high energy nuclear collisions and quark-gluon plasma

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    e investigate the energy loss of quark and gluon jets in quark-gluon plasma produced in central Au+Au collisions at RHIC energy. We use the physical characteristic of initial and mixed phases, which were found in effective quasiparticle model for SPS and RHIC energy. At investigation of energy loss we take into account also the production of hot glue at first stage. The energy loss in expanding plasma is calculated in dominant first order of radiation intensity with accounting of finite kinematic bounds. We calculate the suppression of π0\pi^0 - spectra with moderate high pp_{\perp}, which is caused by energy loss of quark and gluon jets. The comparison with suppression of π0\pi^0 reported by PHENIX show, that correct quantitative description of suppression we have only in model of phase transition with decrease of thermal gluon mass and effective coupling G(T)G(T) in region of phase transition plasma into hadrons (at TTcT \simeq T_c). However quasiparticle model with increase of these values at TTcT \to T_c in accordance with perturbative QCD lead to too great energy loss of gluon and quark jets, which disagrees with data on suppression of π0\pi^0. Thus it is possible with help of hard processes to investigate the structure of phase transition. We show also, that energy losses at SPS energy are too small in order to be observable. This is caused in fact by sufficiently short plasma phase at this energy.Comment: 17 pages, 3 figures, 2 table

    Semi-Contained Neutrino Events in MACRO

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    Updated results are presented of low-energy (Eνˉ5GeV\bar{E_\nu} \sim 5 GeV) neutrino interactions observed by the MACRO detector. Two analyses (of different topologies) are presented; individually, and especially in their ratio, they are inconsistent with no oscillations and consistent with maximal mixing at Δm2\Delta m^2 of a few times 10310^{-3}.Comment: Paper presented at DPF2000, the American Physical Society's Division of Particles and Fields conferenc

    The Kinetic Interpretation of the DGLAP Equation, its Kramers-Moyal Expansion and Positivity of Helicity Distributions

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    According to a rederivation - due to Collins and Qiu - the DGLAP equation can be reinterpreted (in leading order) in a probabilistic way. This form of the equation has been used indirectly to prove the bound Δf(x,Q)<f(x,Q)|\Delta f(x,Q)| < f(x,Q) between polarized and unpolarized distributions, or positivity of the helicity distributions, for any QQ. We reanalize this issue by performing a detailed numerical study of the positivity bounds of the helicity distributions. To obtain the numerical solution we implement an x-space based algorithm for polarized and unpolarized distributions to next-to-leading order in αs\alpha_s, which we illustrate. We also elaborate on some of the formal properties of the Collins-Qiu form and comment on the underlying regularization, introduce a Kramers-Moyal expansion of the equation and briefly analize its Fokker-Planck approximation. These follow quite naturally once the master version is given. We illustrate this expansion both for the valence quark distribution qVq_V and for the transverse spin distribution h1h_1.Comment: 38 pages, 27 figures, Dedicated to Prof. Pierre Ramond for his 60th birthda

    Uncertainties of the CJK 5 Flavour LO Parton Distributions in the Real Photon

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    Radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real, unpolarized photon, calculated in the CJK model being an improved realization of the CJKL approach, have been recently presented. The results were obtained through a global fit to the experimental F2^gamma data. In this paper we present, obtained for the very first time in the photon case, an estimate of the uncertainties of the CJK parton distributions due to the experimental errors. The analysis is based on the Hessian method which was recently applied in the proton parton structure analysis. Sets of test parametrizations are given for the CJK model. They allow for calculation of its best fit parton distributions along with F2^gamma and for computation of uncertainties of any physical value depending on the real photon parton densities. We test the applicability of the approach by comparing uncertainties of example cross-sections calculated in the Hessian and Lagrange methods. Moreover, we present a detailed analysis of the chi^2 of the CJK fit and its relation to the data. We show that large chi^2/DOF of the fit is due to only a few of the experimental measurements. By excluding them chi^2/DOF approx 1 can be obtained.Comment: 28 pages, 8 eps figures, 2 Latex figures; FORTRAN programs available at http://www.fuw.edu.pl/~pjank/param.html; table 10, figure 10 and section 6 correcte

    Full Carbon Account for Russia.

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    The Forestry Project (FOR) at IIASA has produced a full carbon account (FCA) for Russia for 1990, together with scenarios for 2010. Currently, there are rather big question marks regarding the existing carbon accounts for Russia, and Russia is critical to the global carbon balance due to its size. IIASA is in a position to perform solid analysis of Russia because of the databases that the Institute has built over the years. FOR based this work on a comprehensive geographic information system comprising georeferenced descriptions of the environment and land of Russia, which in turn are based on a number of thematic, digitized maps and databases. For the Russian energy sector and other industrial sectors (except the forest industry), the project used emissions estimates from the recent IIASA study "Global Energy Perspectives" (1998). The project carried out a separate substudy for the Russian forest industry sector. According to FOR's estimate, the total fluxes (including energy and industry sectors) in Russia were a net source of 527 teragrams of carbon (Tg C) in 1990. To illustrate the possible development of the carbon pools and fluxes over the next 10 years, FOR developed three different scenarios for the period 1990-2010, reflecting different assumptions regarding Russia's GDP growth. According to these scenarios, Russia will continue to be a net source of carbon to the atmosphere with 156-385 Tg C in 2010, including the emissions from energy and other industrial sectors. However, analysis of the FCA also shows considerable uncertainties involved in the carbon accounting. These uncertainties exceed the calculated changes in the full flux balance for the period 1990-2010. At present, this raises grave questions regarding the reliability of any accounting system used to measure terrestrial ecosystems for compliance with the Kyoto Protocol.
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