23 research outputs found

    Novel approach to the study of quantum effects in the early universe

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    We develop a theoretical frame for the study of classical and quantum gravitational waves based on the properties of a nonlinear ordinary differential equation for a function σ(η)\sigma(\eta) of the conformal time η\eta, called the auxiliary field equation. At the classical level, σ(η)\sigma(\eta) can be expressed by means of two independent solutions of the ''master equation'' to which the perturbed Einstein equations for the gravitational waves can be reduced. At the quantum level, all the significant physical quantities can be formulated using Bogolubov transformations and the operator quadratic Hamiltonian corresponding to the classical version of a damped parametrically excited oscillator where the varying mass is replaced by the square cosmological scale factor a2(η)a^{2}(\eta). A quantum approach to the generation of gravitational waves is proposed on the grounds of the previous η−\eta-dependent Hamiltonian. An estimate in terms of σ(η)\sigma(\eta) and a(η)a(\eta) of the destruction of quantum coherence due to the gravitational evolution and an exact expression for the phase of a gravitational wave corresponding to any value of η\eta are also obtained. We conclude by discussing a few applications to quasi-de Sitter and standard de Sitter scenarios.Comment: 20 pages, to appear on PRD. Already published background material has been either settled up in a more compact form or eliminate

    Shell evolution approaching the N=20 island of inversion : Structure of 26Na

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    The levels in 26Na with single particle character have been observed for the first time using the d(25Na, pÎł) reaction at 5 MeV/nucleon. The measured excitation energies and the deduced spectroscopic factors are in good overall agreement with (0+1)hω shell model calculations performed in a complete spsdfp basis and incorporating a reduction in the N=20 gap. Notably, the 1p3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26Na, compared to the isotone 28Al. Thus, the lowering of the 1p3/2 orbital relative to the 0f7/2 occurring in the neighbouring Z=10 and 12 nuclei - 25,27Ne and 27,29Mg - is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion

    Reorientation-effect measurement of the first 2+ state in 12C : Confirmation of oblate deformation

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    A Coulomb-excitation reorientation-effect measurement using the TIGRESS γ−ray spectrometer at the TRIUMF/ISAC II facility has permitted the determination of the 〈21 +‖E2ˆ‖21 +〉 diagonal matrix element in 12C from particle−γ coincidence data and state-of-the-art no-core shell model calculations of the nuclear polarizability. The nuclear polarizability for the ground and first-excited (21 +) states in 12C have been calculated using chiral NN N4LO500 and NN+3NF350 interactions, which show convergence and agreement with photo-absorption cross-section data. Predictions show a change in the nuclear polarizability with a substantial increase between the ground state and first excited 21 + state at 4.439 MeV. The polarizability of the 21 + state is introduced into the current and previous Coulomb-excitation reorientation-effect analyses of 12C. Spectroscopic quadrupole moments of QS(21 +)=+0.053(44) eb and QS(21 +)=+0.08(3) eb are determined, respectively, yielding a weighted average of QS(21 +)=+0.071(25) eb, in agreement with recent ab initio calculations. The present measurement confirms that the 21 + state of 12C is oblate and emphasizes the important role played by the nuclear polarizability in Coulomb-excitation studies of light nuclei

    Labeling Preschoolers as Learning Disabled: A Cautionary Position

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    The purpose of this article is to explore the issues concerning the adaptation of school-based service delivery concepts for use in early childhood special education programs. The use of categorical labels for determining eligibility for preschool children is not required by law—and may be detrimental. The following concerns are discussed: (a) definitional issues in learning disabilities versus low achievement, (b) the dangers of labeling and low expectation sets, (c) repeated failure to demonstrate movement through a continuum of services (particularly to least restrictive environments), and (d) the efficacy of early intervention and school-based special services for those with mild or suspected developmental disabilities. Research is reviewed concerning definitional and assessment issues utilizing learning disabilities as a construct. Alternatives for describing the characteristics of young children who are significantly at risk or developmentally delayed are provided.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    Far-Field Analysis of Coupled Bulk and Boundary Layer Diffusion Toward an Ion Channel Entrance

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    We present a far-field analysis of ion diffusion toward a channel embedded in a membrane with a fixed charge density. The Smoluchowski equation, which represents the 3D problem, is approximated by a system of coupled three- and two-dimensional diffusions. The 2D diffusion models the quasi-two-dimensional diffusion of ions in a boundary layer in which the electrical potential interaction with the membrane surface charge is important. The 3D diffusion models ion transport in the bulk region outside the boundary layer. Analytical expressions for concentration and flux are developed that are accurate far from the channel entrance. These provide boundary conditions for a numerical solution of the problem. Our results are used to calculate far-field ion flows corresponding to experiments of Bell and Miller (Biophys. J. 45:279, 1984)

    Measuring outrage through a quantitative study of Iraqi immigrants in Michigan

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    Objectives: To measure the outrage towards five top hazards in Michigan of Iraqi immigrants from Sterling Heights and Dearborn, Michigan to enhance communication efforts. Methods: We recruited 84 Iraqi immigrants from two ACCESS community health and research facilities for this study. We utilized the Risk = Hazard + Outrage equation to measure outrage and total risk. Outrage was measured through a new survey instrument based off a list of nine outrage factors per hazard. We also used ANOVA to compare the hazards with each other and hazard and outrage levels. Results: Snowstorms were measured to be the highest outrage and power outages measured the lowest. Total risk was highest for snowstorms and lowest for pandemic influenza. Conclusions: The results measured outrage for each of the five Michigan hazards, showing what hazards Iraqi immigrants were most worried about. Because snowstorms were measured to have the highest outrage and overall measured risk, emergency preparedness and response professionals need to spend more time educating this group about snowstorms and learn from this group on resilience during power outages
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