280 research outputs found

    Excluded Volume Effects in the Quark Meson Coupling Model

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    Excluded volume effects are incorporated in the quark meson coupling model to take into account in a phenomenological way the hard core repulsion of the nuclear force. The formalism employed is thermodynamically consistent and does not violate causality. The effects of the excluded volume on in-medium nucleon properties and the nuclear matter equation of state are investigated as a function of the size of the hard core. It is found that in-medium nucleon properties are not altered significantly by the excluded volume, even for large hard core radii, and the equation of state becomes stiffer as the size of the hard core increases.Comment: 14 pages, revtex, 6 figure

    Time--delay autosynchronization of the spatio-temporal dynamics in resonant tunneling diodes

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    The double barrier resonant tunneling diode exhibits complex spatio-temporal patterns including low-dimensional chaos when operated in an active external circuit. We demonstrate how autosynchronization by time--delayed feedback control can be used to select and stabilize specific current density patterns in a noninvasive way. We compare the efficiency of different control schemes involving feedback in either local spatial or global degrees of freedom. The numerically obtained Floquet exponents are explained by analytical results from linear stability analysis.Comment: 10 pages, 16 figure

    Specific Heat Study of the Magnetic Superconductor HoNi2B2C

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    The complex magnetic transitions and superconductivity of HoNi2B2C were studied via the dependence of the heat capacity on temperature and in-plane field angle. We provide an extended, comprehensive magnetic phase diagram for B // [100] and B // [110] based on the thermodynamic measurements. Three magnetic transitions and the superconducting transition were clearly observed. The 5.2 K transition (T_{N}) shows a hysteresis with temperature, indicating the first order nature of the transition at B=0 T. The 6 K transition (T_{M}), namely the onset of the long-range ordering, displays a dramatic in-plane anisotropy: T_{M} increases with increasing magnetic field for B // [100] while it decreases with increasing field for B // [110]. The anomalous anisotropy in T_{M} indicates that the transition is related to the a-axis spiral structure. The 5.5 K transition (T^{*}) shows similar behavior to the 5.2 K transition, i.e., a small in-plane anisotropy and scaling with Ising model. This last transition is ascribed to the change from a^{*} dominant phase to c^{*} dominant phase.Comment: 9 pages, 11 figure

    Family-based obesity prevention for infants: Design of the “Mothers & Others” randomized trial

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    Objective Our goal is to test the efficacy of a family-based, multi-component intervention focused on infants of African-American (AA) mothers and families, a minority population at elevated risk for pediatric obesity, versus a child safety attention-control group to promote healthy weight gain patterns during the first two years of life. Design, participants, and methods The design is a two-group randomized controlled trial among 468 AA pregnant women in central North Carolina. Mothers and study partners in the intervention group receive anticipatory guidance on breastfeeding, responsive feeding, use of non-food soothing techniques for infant crying, appropriate timing and quality of complementary feeding, age-appropriate infant sleep, and minimization of TV/media. The primary delivery channel is 6 home visits by a peer educator, 4 interim newsletters and twice-weekly text messaging. Intervention families also receive 2 home visits from an International Board Certified Lactation Consultant. Assessments occur at 28 and 37 weeks gestation and when infants are 1, 3, 6, 9, 12, and 15 months of age. Results The primary outcome is infant/toddler growth and likelihood of overweight at 15 months. Differences between groups are expected to be achieved through uptake of the targeted infant feeding and care behaviors (secondary outcomes) and change in caregivers' modifiable risk factors (mediators) underpinning the intervention. Conclusions If successful in promoting healthy infant growth and enhancing caregiver behaviors, “Mothers and Others” will have high public health relevance for future obesity-prevention efforts aimed at children younger than 2 years, including interventional research and federal, state, and community health programs. Trial Registration ClinicalTrials.gov, NCT01938118, August 9, 2013

    Improved Effective Potential in Curved Spacetime and Quantum Matter - Higher Derivative Gravity Theory

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    \noindent{\large\bf Abstract.} We develop a general formalism to study the renormalization group (RG) improved effective potential for renormalizable gauge theories ---including matter-R2R^2-gravity--- in curved spacetime. The result is given up to quadratic terms in curvature, and one-loop effective potentials may be easiliy obtained from it. As an example, we consider scalar QED, where dimensional transmutation in curved space and the phase structure of the potential (in particular, curvature-induced phase trnasitions), are discussed. For scalar QED with higher-derivative quantum gravity (QG), we examine the influence of QG on dimensional transmutation and calculate QG corrections to the scalar-to-vector mass ratio. The phase structure of the RG-improved effective potential is also studied in this case, and the values of the induced Newton and cosmological coupling constants at the critical point are estimated. Stability of the running scalar coupling in the Yukawa theory with conformally invariant higher-derivative QG, and in the Standard Model with the same addition, is numerically analyzed. We show that, in these models, QG tends to make the scalar sector less unstable.Comment: 23 pages, Oct 17 199

    The induction of behavioural sensitization is associated with cocaine-induced structural plasticity in the core (but not shell) of the nucleus accumbens

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    Repeated exposure to cocaine increases the density of dendritic spines on medium spiny neurons in the nucleus accumbens (Acb) and pyramidal cells in the medial prefrontal cortex (mPFC). To determine if this is associated with the development of psychomotor sensitization, rats were given daily i.p. injections of 15 mg/kg of cocaine (or saline) for 8 days, either in their home cage (which failed to induce significant psychomotor sensitization) or in a distinct and relatively novel test cage (which induced robust psychomotor sensitization). Their brains were obtained 2 weeks after the last injection and processed for Golgi–Cox staining. In the Acb core (AcbC) cocaine treatment increased spine density only in the group that developed psychomotor sensitization (i.e. in the Novel but not Home group), and there was a significant positive correlation between the degree of psychomotor sensitization and spine density. In the Acb shell (AcbS) cocaine increased spine density to the same extent in both groups; i.e. independent of psychomotor sensitization. In the mPFC cocaine increased spine density in both groups, but to a significantly greater extent in the Novel group. Furthermore, when rats were treated at Home with a higher dose of cocaine (30 mg/kg), cocaine now induced psychomotor sensitization in this context, and also increased spine density in the AcbC. Thus, the context in which cocaine is experienced influences its ability to reorganize patterns of synaptic connectivity in the Acb and mPFC, and the induction of psychomotor sensitization is associated with structural plasticity in the AcbC and mPFC, but not the AcbS.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73532/1/j.1460-9568.2004.03612.x.pd

    Empathetic Understanding and Deliberative Democracy

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    Epistemic democracy is standardly characterized in terms of “aiming at truth”. This presupposes a veritistic conception of epistemic value, according to which truth is the fundamental epistemic goal. I will raise an objection to the standard (veritistic) account of epistemic democracy, focusing specifically on deliberative democracy. I then propose a version of deliberative democracy that is grounded in non‐veritistic epistemic goals. In particular, I argue that deliberation is valuable because it facilitates empathetic understanding. I claim that empathetic understanding is an epistemic good that doesn't have truth as its primary goal

    SJS/TEN 2019: From Science to Translation

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    Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are potentially life-threatening, immune-mediated adverse reactions characterized by widespread erythema, epidermal necrosis, and detachment of skin and mucosa. Efforts to grow and develop functional international collaborations and a multidisciplinary interactive network focusing on SJS/TEN as an uncommon but high burden disease will be necessary to improve efforts in prevention, early diagnosis and improved acute and long-term management. SJS/TEN 2019: From Science to Translation was a 1.5-day scientific program held April 26-27, 2019, in Vancouver, Canada. The meeting successfully engaged clinicians, researchers, and patients and conducted many productive discussions on research and patient care needs

    A Theoretical Model of a Molecular-Motor-Powered Pump

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    The motion of a cylindrical bead in a fluid contained within a two-dimensional channel is investigated using the boundary element method as a model of a biomolecular-motor-powered microfluidics pump. The novelty of the pump lies in the use of motor proteins (kinesin) to power the bead motion and the few moving parts comprising the pump. The performance and feasibility of this pump design is investigated using two model geometries: a straight channel, and a curved channel with two concentric circular walls. In the straight channel geometry, it is shown that increasing the bead radius relative to the channel width, increases the flow rate at the expense of increasing the force the kinesins must generate in order to move the bead. Pump efficiency is generally higher for larger bead radii, and larger beads can support higher imposed loads. In the circular channel geometry, it is shown that bead rotation modifies the force required to move the bead and that shifting the bead inward slightly reduces the required force. Bead rotation has a minimal effect on flow rate. Recirculation regions, which can develop between the bead and the channel walls, influence the stresses and force on the bead. These results suggest this pump design is feasible, and the kinesin molecules provide sufficient force to deliver pico- to atto- l/s flows.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44478/1/10544_2005_Article_6168.pd

    The L 98-59 System: Three Transiting, Terrestrial-Size Planets Orbiting A Nearby M Dwarf

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    We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)—a bright M dwarf at a distance of 10.6 pc. Using the Gaia-measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 R⊕ to 1.6 R⊕. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false-positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system
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