743 research outputs found

    Multiple-scattering Modelling of Scattering by Biological Cells

    Get PDF
    Past work on scattering by biological cells has been restricted to unrealistic oversimplified models of cells, or uses slow methods unsuited for calculations involving large numbers of cells or varying illumination. We consider the systematic use of fast, accurate methods for modelling light scattering in realistic complex biological cells. This will allow, for example, the study of light scattering by realistic ensembles of cells, which is immediately applicable to optical cancer detection, and remote sensing of microorganisms. It will also be possible to study light scattering by cells under constantly varying illumination, such as encountered in applications like flow cytometry

    Possible ΔΔ\Delta\Delta dibaryons in the quark cluster model

    Full text link
    In the framework of RGM, the binding energy of one channel ΔΔ(3,0)\Delta\Delta_{(3,0)}(d∗d^*) and ΔΔ(0,3)\Delta\Delta_{(0,3)} are studied in the chiral SU(3) quark cluster model. It is shown that the binding energies of the systems are a few tens of MeV. The behavior of the chiral field is also investigated by comparing the results with those in the SU(2) and the extended SU(2) chiral quark models. It is found that the symmetry property of the ΔΔ\Delta\Delta system makes the contribution of the relative kinetic energy operator between two clusters attractive. This is very beneficial for forming the bound dibaryon. Meanwhile the chiral-quark field coupling also plays a very important role on binding. The S-wave phase shifts and the corresponding scattering lengths of the systems are also given.Comment: LeTex with 2 ps figure

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

    Full text link
    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

    Variational calculations of the Λ\Lambda-seperation energy of the Λ17_{\Lambda}^{17}O hypernucleus

    Full text link
    Variational Monte Carlo calculations have been made for the Λ17_{ \Lambda}^{17}O hypernucleus using realistic two- and three-baryon interactions. A two pion exchange potential with spin- and space-exchange components is used for the Λ\LambdaN potential. Three-body two-pion exchange and strongly repulsive dispersive Λ\LambdaNN interactions are also included. The trial wave function is constructed from pair- and triplet-correlation operators acting on a single particle determinant. These operators consist of central, spin, isospin, tensor and three- baryon potential components. A cluster Monte Carlo method is developed for noncentral correlations and is used with up to four-baryon clusters in our calculations. The three-baryon Λ\LambdaNN force is discussed.Comment: 24 pages, 2 figs available by fax., for publication in Phys. Rev.

    Density dependent hadron field theory for hypernuclei

    Get PDF
    The Density Dependent Relativistic Hadron Field (DDRH) theory, previously introduced and applied to isospin nuclei, is extended to hypernuclei by including the octet hyperons. Infinite matter Dirac-Brueckner theory for octet baryons and the derivation of in-medium DDRH baryon-meson vertices is discussed. From the properties of Dirac-Brueckner interactions it is found that hyperon and nucleon self-energies and vertices are related by the ratios of free space coupling constants. This leads to simple scaling laws for the in-medium hyperon and nucleon vertices. The model is applied in relativistic DDRH mean-field calculations to singl$\Lambda nuclei. Free space N-Lambda T-matrix results are used for the scalar vertex. As the only free parameter the hyperon vector vertex scaling factor is adjusted to a selected set of hypernuclear data. Spectroscopic data of single Lambda hypernuclei over the full mass range are well described. The reduced Lambda spin-orbit splitting is reproduced and found to be related closely the medium dependence of scalar and vector interactions.Comment: 38 pages, 9 figure

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

    Get PDF
    <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

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

    Get PDF
    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

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

    Get PDF
    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.
    • 

    corecore