14,011 research outputs found

    Weak Wave Turbulence Scaling Theory for Diffusion and Relative Diffusion in Turbulent Surface Waves

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    We examine the applicability of the weak wave turbulence theory in explaining experimental scaling results obtained for the diffusion and relative diffusion of particles moving on turbulent surface waves. For capillary waves our theoretical results are shown to be in good agreement with experimental results, where a distinct crossover in diffusive behavior is observed at the driving frequency. For gravity waves our results are discussed in the light of ocean wave studies.Comment: 5 pages; for related work visit http://www.imedea.uib.es/~victo

    Root to Kellerer

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    We revisit Kellerer's Theorem, that is, we show that for a family of real probability distributions (μt)t∈[0,1](\mu_t)_{t\in [0,1]} which increases in convex order there exists a Markov martingale (St)t∈[0,1](S_t)_{t\in[0,1]} s.t.\ St∼μtS_t\sim \mu_t. To establish the result, we observe that the set of martingale measures with given marginals carries a natural compact Polish topology. Based on a particular property of the martingale coupling associated to Root's embedding this allows for a relatively concise proof of Kellerer's theorem. We emphasize that many of our arguments are borrowed from Kellerer \cite{Ke72}, Lowther \cite{Lo07}, and Hirsch-Roynette-Profeta-Yor \cite{HiPr11,HiRo12}.Comment: 8 pages, 1 figur

    Stable States of Biological Organisms

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    A novel model of biological organisms is advanced, treating an organism as a self-consistent system subject to a pathogen flux. The principal novelty of the model is that it describes not some parts, but a biological organism as a whole. The organism is modeled by a five-dimensional dynamical system. The organism homeostasis is described by the evolution equations for five interacting components: healthy cells, ill cells, innate immune cells, specific immune cells, and pathogens. The stability analysis demonstrates that, in a wide domain of the parameter space, the system exhibits robust structural stability. There always exist four stable stationary solutions characterizing four qualitatively differing states of the organism: alive state, boundary state, critical state, and dead state.Comment: Latex file, 12 pages, 4 figure

    What are women's mode of birth preferences and why? A systematic scoping review.

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    BACKGROUND:The optimal caesarean section rate is estimated to be between 10-15%; however, it is much higher in high and many middle-income countries and continues to be lower in some middle and low-income countries. While a range of factors influence caesarean section rates, women's mode of birth preferences also play a role. The aim of this study was to map the literature in relation to women's mode of birth preferences, and identify underlying reasons for, and factors associated with, these preferences. METHOD:Using a scoping review methodology, quantitative and qualitative evidence was systematically considered. To identify studies, PubMed, Maternity and Infant Care, MEDLINE, and Web of Science were searched for the period from 2008 to 2018, and reference lists of included studies were examined. FINDINGS:A total of 65 studies were included. While the majority of women prefer a vaginal birth, between 5-20% in high-income countries and 1.4 to 50% in low-middle-income countries prefer a caesarean section. The six main reasons or factors associated with a mode of birth preference were: (1) perceptions of safety; (2) fear of pain; (3) previous birth experience; (4) encouragement and dissuasion from health professionals; (5) social and cultural influences; and (6) access to information and educational levels. CONCLUSION:To help ensure women receive the required care that is aligned with their preferences, processes of shared decision-making should be implemented. Shared decision-making has the potential to reduce the rate of unnecessary interventions, and also improve the willingness of women to accept a medically-indicated caesarean section in low-income countries

    What are women's mode of birth preferences and why? A systematic scoping review

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    Background: The optimal caesarean section rate is estimated to be between 10–15%; however, it is much higher in high and many middle-income countries and continues to be lower in some middle and low-income countries. While a range of factors influence caesarean section rates, women's mode of birth preferences also play a role. The aim of this study was to map the literature in relation to women's mode of birth preferences, and identify underlying reasons for, and factors associated with, these preferences. Method: Using a scoping review methodology, quantitative and qualitative evidence was systematically considered. To identify studies, PubMed, Maternity and Infant Care, MEDLINE, and Web of Science were searched for the period from 2008 to 2018, and reference lists of included studies were examined. Findings: A total of 65 studies were included. While the majority of women prefer a vaginal birth, between 5–20% in high-income countries and 1.4 to 50% in low-middle-income countries prefer a caesarean section. The six main reasons or factors associated with a mode of birth preference were: (1) perceptions of safety; (2) fear of pain; (3) previous birth experience; (4) encouragement and dissuasion from health professionals; (5) social and cultural influences; and (6) access to information and educational levels. Conclusion: To help ensure women receive the required care that is aligned with their preferences, processes of shared decision-making should be implemented. Shared decision-making has the potential to reduce the rate of unnecessary interventions, and also improve the willingness of women to accept a medically-indicated caesarean section in low-income countries

    Improved Orbital Parameters And Transit Monitoring For HD 156846b

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    HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer reduce the predicted transit time uncertainty to 20 minutes, an order of magnitude improvement over the ephemeris from the discovery paper. We photometrically monitored a predicted transit window under relatively poor photometric conditions, from which our non-detection does not rule out a transiting geometry. We also present photometry that demonstrates stability at the millimagnitude level over its rotational timescale

    The ground state of the Lithium atom in strong magnetic fields

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    The ground and some excited states of the Li atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 10^8 T. With increasing field strength the ground state undergoes two transitions involving three different electronic configurations: for weak fields the ground state configuration arises from the field-free 1s^22s configuration, for intermediate fields from the 1s^22p_{-1} configuration and in high fields the 1s2p_{-1}3d_{-2} electronic configuration is responsible for the properties of the atom. The transition field strengths are determined. Calculations on the ground state of the Li+ ion allow us to describe the field-dependent ionization energy of the Li atom. Some general arguments on the ground states of multi-electron atoms in strong magnetic fields are provided.Comment: 11 pages, 6 figures, submitted to Physical Review

    Fractional Superstrings with Space-Time Critical Dimensions Four and Six

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    We propose possible new string theories based on local world-sheet symmetries corresponding to extensions of the Virasoro algebra by fractional spin currents. They have critical central charges c=6(K+8)/(K+2)c=6(K+8)/(K+2) and Minkowski space-time dimensions D=2+16/KD=2+16/K for K≥2K\geq2 an integer. We present evidence for their existence by constructing modular invariant partition functions and the massless particle spectra. The dimension 44 and 66 strings have space-time supersymmetry.Comment: 9 page

    The ground state of the carbon atom in strong magnetic fields

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    The ground and a few excited states of the carbon atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 10^9 T. With increasing field strength the ground state undergoes six transitions involving seven different electronic configurations which belong to three groups with different spin projections S_z=-1,-2,-3. For weak fields the ground state configuration arises from the field-free 1s^2 2s^2 2p_0 2p_{-1}, S_z=-1 configuration. With increasing field strength the ground state involves the four S_z=-2 configurations 1s^22s2p_0 2p_{-1}2p_{+1}, 1s^22s2p_0 2p_{-1}3d_{-2}, 1s^22p_0 2p_{-1}3d_{-2}4f_{-3} and 1s^22p_{-1}3d_{-2}4f_{-3}5g_{-4}, followed by the two fully spin polarized S_z=-3 configurations 1s2p_02p_{-1}3d_{-2}4f_{-3}5g_{-4} and 1s2p_{-1}3d_{-2}4f_{-3}5g_{-4}6h_{-5}. The last configuration forms the ground state of the carbon atom in the high field regime \gamma>18.664. The above series of ground state configurations is extracted from the results of numerical calculations for more than twenty electronic configurations selected due to some general energetical arguments.Comment: 6 figures,acc. Phys.Rev.

    Electromagnetic dipole moments of charged baryons with bent crystals at the LHC

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    We propose a unique program of measurements of electric and magnetic dipole moments of charm, beauty and strange charged baryons at the LHC, based on the phenomenon of spin precession of channeled particles in bent crystals. Studies of crystal channeling and spin precession of positively- and negatively-charged particles are presented, along with feasibility studies and expected sensitivities for the proposed experiment using a layout based on the LHCb detector.Comment: 19 pages, 13 figure
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