155,763 research outputs found

    Helium window for shock-tube monochromators

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    Technique for coupling vacuum ultraviolet monochromator to shock tube to avoid loss of high energy ultraviolet light during quantitative measurements is described. System consists of helium gas window pumping through small aperture in entrance pupil of monochromator. Diagram of equipment and principles of operation are presented

    Anomalous Hall effect in the Co-based Heusler compounds Co2_{2}FeSi and Co2_{2}FeAl

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    The anomalous Hall effect (AHE) in the Heusler compounds Co2_{2}FeSi and Co2_{2}FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity ρxx\rho_{xx} as well as the anomalous Hall resistivity ρahe\rho_{ahe}. Analyzing the scaling behavior of ρahe\rho_{ahe} in terms of ρxx\rho_{xx} points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds

    Genealogical constructions of population models

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    Representations of population models in terms of countable systems of particles are constructed, in which each particle has a `type', typically recording both spatial position and genetic type, and a level. For finite intensity models, the levels are distributed on [0,λ][0,\lambda ], whereas in the infinite intensity limit λ\lambda\rightarrow\infty, at each time tt, the joint distribution of types and levels is conditionally Poisson, with mean measure Ξ(t)×\Xi (t)\times \ell where \ell denotes Lebesgue measure and Ξ(t)\Xi (t) is a measure-valued population process. The time-evolution of the levels captures the genealogies of the particles in the population. Key forces of ecology and genetics can be captured within this common framework. Models covered incorporate both individual and event based births and deaths, one-for-one replacement, immigration, independent `thinning' and independent or exchangeable spatial motion and mutation of individuals. Since birth and death probabilities can depend on type, they also include natural selection. The primary goal of the paper is to present particle-with-level or lookdown constructions for each of these elements of a population model. Then the elements can be combined to specify the desired model. In particular, a non-trivial extension of the spatial Λ\Lambda-Fleming-Viot process is constructed

    Signatures of Spherical Compactification at the LHC

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    TeV-scale extra dimensions may play an important role in electroweak or supersymmetry breaking. We examine the phenomenology of such dimensions, compactified on a sphere SnS^n, n2n \geq 2, and show that they possess distinct features and signatures. For example, unlike flat toroidal manifolds, spheres do not trivially allow fermion massless modes. Acceptable phenomenology then generically leads to "non-universal" extra dimensions with "pole-localized" 4-dd fermions; the bosonic fields can be in the bulk. Due to spherical symmetry, some Kaluza-Klein (KK) modes of bulk gauge fields are either stable or extremely long-lived, depending on the graviton KK spectrum. Using precision electroweak data, we constrain the lightest gauge field KK modes to lie above 4\simeq 4 TeV. We show that some of these KK resonances are within the reach of the LHC in several different production channels. The models we study can be uniquely identified by their collider signatures.Comment: 21 pages, 5 fig

    Similarity parameters for radiative energy transfer in isothermal and non-isothermal gas mixtures

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    The similarity groups for multicomponent, reacting gas mixtures with radiative energy transport are derived (Section I). The resulting relations are used to consider the feasibility if scaling for flow processes with radiative energy transport under highly simplified conditions (Sections 2 and 3). Next the scaling parameters are derived for radiant energy emission from isobaric and isothermal gases for arbitrary opacities and various spectral line and molecular band models (Section 4). Scaling parameters for radiant energy emission from isobaric but non-isothermal systems are discussed for arbitrary opacities and various spectral line and molecular band models under the restrictions imposed on the allowed temperature profiles for dispersion and Doppler lines by the Eddington-Barbier approximation (Section 5). Finally, we consider the radiative scaling properties for representative temperature profiles for both collision-broadened and Doppler-broadened line profiles on the basis if exact numerical calculations that we have performed for a rotational spectral line belonging to a molecular vibration-rotation band. (Section 6). It appears that simple scaling rules generally constitute a fair approximation for dispersion lines in non-isothermal systems but that corresponding relations apply to lines with Doppler contour only in the transparent gas regime

    An SO(3)-monopole cobordism formula relating Donaldson and Seiberg-Witten invariants

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    We prove an analogue of the Kotschick-Morgan conjecture in the context of SO(3) monopoles, obtaining a formula relating the Donaldson and Seiberg-Witten invariants of smooth four-manifolds using the SO(3)-monopole cobordism. The main technical difficulty in the SO(3)-monopole program relating the Seiberg-Witten and Donaldson invariants has been to compute intersection pairings on links of strata of reducible SO(3) monopoles, namely the moduli spaces of Seiberg-Witten monopoles lying in lower-level strata of the Uhlenbeck compactification of the moduli space of SO(3) monopoles [arXiv:dg-ga/9710032]. In this monograph, we prove --- modulo a gluing theorem which is an extension of our earlier work in [arXiv:math/9907107] --- that these intersection pairings can be expressed in terms of topological data and Seiberg-Witten invariants of the four-manifold. This conclusion is analogous to the Kotschick-Morgan conjecture concerning the wall-crossing formula for Donaldson invariants of a four-manifold with b2+=1b_2^+=1; that wall-crossing formula and the resulting structure of Donaldson invariants for four-manifolds with b2+=1b_2^+=1 were established, assuming the Kotschick-Morgan conjecture, by Goettsche [arXiv:alg-geom/9506018] and Goettsche and Zagier [arXiv:alg-geom/9612020]. In this monograph, we reduce the proof of the Kotschick-Morgan conjecture to an extension of previously established gluing theorems for anti-self-dual SO(3) connections (see [arXiv:math/9812060] and references therein). Since the first version of our monograph was circulated, applications of our results have appeared in the proof of Property P for knots by Kronheimer and Mrowka [arXiv:math/0311489] and work of Sivek on Donaldson invariants for symplectic four-manifolds [arXiv:1301.0377].Comment: x + 229 page

    Daubert\u27s Significance

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    The authors review and note the limited reach of Daubert v. Merrell Dow Pharmaceuticals. They also address its implications for concerned non-lawyers
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