8,943 research outputs found

    A Derivation of Moment Evolution Equations for Linear Open Quantum Systems

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    Given a linear open quantum system which is described by a Lindblad master equation, we detail the calculation of the moment evolution equations from this master equation. We stress that the moment evolution equations are well-known, but their explicit derivation from the master equation cannot be found in the literature to the best of our knowledge, and so we provide this derivation for the interested reader

    A dynamical model of the local cosmic expansion

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    We combine the equations of motion that govern the dynamics of galaxies in the local volume with Bayesian techniques in order to fit orbits to published distances and velocities of galaxies within ∼3\sim 3 Mpc. We find a Local Group (LG) mass 2.3±0.7×1012M⊙2.3\pm 0.7\times 10^{12}{\rm M}_\odot that is consistent with the combined dynamical masses of M31 and the Milky Way, and a mass ratio 0.54−0.17+0.230.54^{+0.23}_{-0.17} that rules out models where our Galaxy is more massive than M31 with ∼95%\sim 95\% confidence. The Milky Way's circular velocity at the solar radius is relatively high, 245±23245\pm 23 km/s, which helps to reconcile the mass derived from the local Hubble flow with the larger value suggested by the `timing argument'. Adopting {\it Planck}'s bounds on ΩΛ\Omega_\Lambda yields a (local) Hubble constant H0=67±5H_0=67\pm 5km/s/Mpc which is consistent with the value found on cosmological scales. Restricted N-body experiments show that substructures tend to fall onto the LG along the Milky Way-M31 axis, where the quadrupole attraction is maximum. Tests against mock data indicate that neglecting this effect slightly overestimates the LG mass without biasing the rest of model parameters. We also show that both the time-dependence of the LG potential and the cosmological constant have little impact on the observed local Hubble flow.Comment: 22 pages, 14 figures. Accepted to MNRAS. An error in the apex calculation (Appendix A) was found and has been fixed. The new constraints favour models where the Milky Way is less massive than M31. The rest of model parameters and conclusions remain unchange

    A Content Analysis of Interviewee Reports of Medical School Admissions Interviews

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    Introduction. Prospective medical school applicants use Internet websites to gain information about medical school interviews as well as to offer their experience in such interviews. This study examined applicants’ reported experiences of interviews and compared them to the purposes of the interview as purported by medical schools. Method. Content analysis of student feedback regarding medical school interviews at 161 medical schools was conducted for entries of over 4600 students applying to medical school who anonymously and voluntarily completed an online questionnaire. Results. Across all medical schools, nearly one half of all cited interview questions addressed non-cognitive characteristics of the applicants. Top ranked medical schools were reported to ask significantly more interpersonal and illegal questions and fewer academic/general knowledge questions than other medical schools. Lower ranked schools did not differ significantly in the types of questions reportedly asked applicants compared to other medical schools. Discussion. Medical school interviews are generally gathering types of information about applicants that admissions personnel identify as important in the admission decision. In addition to measuring interpersonal characteristics, medical school admissions interviews are assessing cognitive abilities and ethical decision-making. Sources on the Internet provide actual medical school interview questions to prospective students. This practice can help them gain an undue advantage in interviewing. Admissions committees and faculty who interview students may want to consider how best to obtain accurate and valid responses from applicants
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