749 research outputs found

    RF System Upgrades to the Advanced Photon Source Linear Accelerator in Support of the Fel Operation

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    The S-band linear accelerator, which was built to be the source of particles and the front end of the Advanced Photon Source injector, is now also being used to support a low-energy undulator test line (LEUTL) and to drive a free-electron laser (FEL). The more severe rf stability requirements of the FEL have resulted in an effort to identify sources of phase and amplitude instability and implement corresponding upgrades to the rf generation chain and the measurement system. Test data and improvements implemented and planned are describedComment: LC 2000 (3 pages, 6 figures

    The politics of in/visibility: carving out queer space in Ul'yanovsk

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    <p>In spite of a growing interest within sexualities studies in the concept of queer space (Oswin 2008), existing literature focuses almost exclusively on its most visible and territorialised forms, such as the gay scene, thus privileging Western metropolitan areas as hubs of queer consumer culture (Binnie 2004). While the literature has emphasised the political significance of queer space as a site of resistance to hegemonic gender and sexual norms, it has again predominantly focused on overt claims to public space embodied in Pride events, neglecting other less open forms of resistance.</p><p> This article contributes new insights to current debates about the construction and meaning of queer space by considering how city space is appropriated by an informal queer network in Ul’ianovsk. The group routinely occupied very public locations meeting and socialising on the street or in mainstream cafĂ©s in central Ul’ianovsk, although claims to these spaces as queer were mostly contingent, precarious or invisible to outsiders. The article considers how provincial location affects tactics used to carve out communal space, foregrounding the importance of local context and collective agency in shaping specific forms of resistance, and questioning ethnocentric assumptions about the empowering potential of visibility.</p&gt

    Geometrically induced modification of surface plasmons in the optical and telecom regimes

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    We demonstrate that the introduction of a subwavelength periodic modulation into a metallic structure strongly modifies the guiding characteristics of the surface plasmon modes supported by the system. Moreover, it is also shown how a new type of a tightly confined surface plasmon polariton mode can be created by just milling a periodic corrugation into a metallic ridge placed on top of a metal surface

    Double Spin Asymmetries A_NN and A_SS at sqrt{s}=200 GeV in Polarized Proton-Proton Elastic Scattering at RHIC

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    We present the first measurements of the double spin asymmetries A_NN and A_SS at sqrt{s}=200 GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). The data were collected in the four momentum transfer t range 0.01<|t|<0.03 (GeV/c)^2. The measured asymmetries, which are consistent with zero, allow us to estimate upper limits on the double helicity-flip amplitudes phi_2 and phi_4 at small t as well as on the difference Delta(sigma_T) between the total cross sections for transversely polarized protons with antiparallel or parallel spin orientations.Comment: 13 pages with 3 figures. Final version accepted by Phys. Lett.

    Two approximate formulae for the binding energies in Lambda hypernuclei and light nuclei

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    Two approximate formulae are given for the binding energies in Lambda-hypernuclei and light nuclei by means of the (reduced) Poeschl-Teller and the Gaussian central potentials. Those easily programmable formulae combine the eigenvalues of the transformed Jacobi eigenequation and an application of the hypervirial theorems.Comment: Accepted for publication in Europhysics Letter

    AA--Dependence of ΛΛ\Lambda\Lambda Bond Energies in Double---Λ\Lambda Hypernuclei

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    The AA-dependence of the bond energy ΔBΛΛ\Delta B_{\Lambda\Lambda} of the ΛΛ{\Lambda\Lambda} hypernuclear ground states is calculated in a three-body Λ+Λ+AZ{\Lambda + \Lambda + {^{A}Z}} model and in the Skyrme-Hartree-Fock approach. Various ΛΛ{\Lambda\Lambda} and Λ\Lambda-nucleus or ΛN{\Lambda N} potentials are used and the sensitivity of ΔBΛΛ\Delta B_{\Lambda\Lambda} to the interactions is discussed. It is shown that in medium and heavy ΛΛ{\Lambda\Lambda} hypernuclei, ΔBΛΛ\Delta B_{\Lambda\Lambda} is a linear function of rΛ−3r_{\Lambda}^{-3}, where rΛr_\Lambda is rms radius of the hyperon orbital. It looks unlikely that it will be possible to extract ΛΛ{\Lambda\Lambda} interaction from the double-Λ\Lambda hypernuclear energies only, the additional information about the Λ\Lambda-core interaction, in particular, on rΛr_{\Lambda} is needed.Comment: 11 pages, LaTex, 3 figure

    Gamma-Ray Spectroscopy of Λ16^{16}_\LambdaO and Λ15^{15}_\LambdaN Hypernuclei via the 16^{16}O(K−,π−)(K^-, \pi^-) reaction

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    he bound-state level structures of the Λ16^{16}_{\Lambda}O and Λ15^{15}_{\Lambda}N hypernuclei were studied by Îł\gamma-ray spectroscopy using a germanium detector array (Hyperball) via the 16^{16}O (K−,Ï€âˆ’ÎłK^-, \pi^- \gamma) reaction. A level scheme for Λ16^{16}_{\Lambda}O was determined from the observation of three Îł\gamma-ray transitions from the doublet of states (2−2^-,1−1^-) at ∌6.7\sim 6.7 MeV to the ground-state doublet (1−1^-,0−0^-). The Λ15^{15}_{\Lambda}N hypernuclei were produced via proton emission from unbound states in Λ16^{16}_{\Lambda}O . Three Îł\gamma -rays were observed and the lifetime of the 1/2+;11/2^+;1 state in Λ15^{15}_{\Lambda}N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin-dependence of the ΛN\Lambda N interaction is discussed. In particular, the measured Λ16^{16}_{\Lambda}O ground-state doublet spacing of 26.4 ±\pm 1.6 ±\pm 0.5 keV determines a small but nonzero strength of the ΛN\Lambda N tensor interaction.Comment: 22 pages, 17 figure

    Inseminação artificial em tempo fixo em caprinos leiteiros com sĂȘmen resfriado por 24 ou 48 horas.

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    Resumo: Avaliou-se a capacidade fertilizante do sĂȘmen caprino resfriado a 5ÂșC por 24 (T24) ou 48 h (T48). Foram utilizados como doadores de sĂȘmen trĂȘs bodes da raça CanĂĄrias. Conclui-se que o sĂȘmen caprino, resfriado por 48 horas a 5ÂșC, tem o mesmo potencial de fertilização do sĂȘmen resfriado por 24 horas a 5ÂșC e que as inseminaçÔes foram realizadas precocemente, para o protocolo sugerido
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