60,003 research outputs found

    Localization of the number of photons of ground states in nonrelativistic QED

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    One electron system minimally coupled to a quantized radiation field is considered. It is assumed that the quantized radiation field is {\it massless}, and {\it no} infrared cutoff is imposed. The Hamiltonian, HH, of this system is defined as a self-adjoint operator acting on \LR\otimes\fff\cong L^2(\BR;\fff), where \fff is the Boson Fock space over L^2(\BR\times\{1,2\}). It is shown that the ground state, \gr, of HH belongs to ∩k=1∞D(1⊗Nk)\cap_{k=1}^\infty D(1\otimes N^k), where NN denotes the number operator of \fff. Moreover it is shown that, for almost every electron position variable x\in\BR and for arbitrary k≥0k\geq 0, \|(1\otimes \N)\gr (x) \|_\fff \leq D_ke^{-\delta |x|^{m+1}} with some constants m≥0m\geq 0, Dk>0D_k>0, and δ>0\delta>0 independent of kk. In particular \gr\in \cap_{k=1}^\infty D (e^{\beta |x|^{m+1}}\otimes N^k) for 0<β<δ/20<\beta<\delta/2 is obtained.Comment: 43page

    Free flux flow resistivity in strongly overdoped high-T_c cuprate; purely viscous motion of the vortices in semiclassical d-wave superconductor

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    We report the free flux flow (FFF) resistivity associated with a purely viscous motion of the vortices in moderately clean d-wave superconductor Bi:2201 in the strongly overdoped regime (T_c=16K) for a wide range of the magnetic field in the vortex state. The FFF resistivity is obtained by measuring the microwave surface impedance at different microwave frequencies. It is found that the FFF resistivity is remarkably different from that of conventional s-wave superconductors. At low fields (H<0.2H_c2) the FFF resistivity increases linearly with H with a coefficient which is far larger than that found in conventional s-wave superconductors. At higher fields, the FFF resistivity increases in proportion to \sqrt H up to H_c2. Based on these results, the energy dissipation mechanism associated with the viscous vortex motion in "semiclassical" d-wave superconductors with gap nodes is discussed. Two possible scenarios are put forth for these field dependence; the enhancement of the quasiparticle relaxation rate and the reduction of the number of the quasiparticles participating the energy dissipation in d-wave vortex state.Comment: 9 pages 7 figures, to appear in Phys. Rev.

    Clinically relevant investigation of flattening filter-free skin dose

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    As flattening filter-free (FFF) photon beams become readily available for treatment delivery in techniques such as SBRT, thorough investigation of skin dose from FFF photon beams is necessary under clinically relevant conditions. Using a parallel-plate PTW Markus chamber placed in a custom water-equivalent phantom, surface-dose measurements were taken at 2 × 2, 3 × 3, 4 × 4, 6 × 6, 8 × 8, 10 × 10, 20 × 20, and 30 × 30 cm2 field sizes, at 80, 90, and 100 cm source-to-surface distances (SSDs), and with fields defined by jaws and multileaf collimator (MLC) using multiple beam energies (6X, 6XFFF, 10X, and 10XFFF). The same set of measurements was repeated with the chamber at a reference depth of 10 cm. Each surface measurement was normalized by its corresponding reference depth measurement for analysis. The FFF surface doses at 100 cm SSD were higher than flattened surface doses by 45% at 2 × 2 cm2 to 13% at 20 × 20 cm2 for 6 MV energy. These surface dose differences varied to a greater degree as energy increased, ranging from +63% at 2 × 2 cm2 to -2% at 20 × 20 cm2 for 10 MV. At small field sizes, higher energy increased FFF surface dose relative to flattened surface dose; while at larger field sizes, relative FFF surface dose was higher for lower energies. At both energies investigated, decreasing SSD caused a decrease in the ratios of FFF-to-flattened surface dose. Variability with SSD of FFF-to flattened surface dose differences increased with field size and ranged from 0% to 6%. The field size at which FFF and flattened beams gave the same skin dose increased with decreasing beam energy. Surface dose was higher with MLC fields compared to jaw fields under most conditions, with the difference reaching its maximum at a field size between 4 × 4 cm2 and 6 × 6 cm2 for a given energy and SSD. This study conveyed the magnitude of surface dose in a clinically meaningful manner by reporting results normalized to 10 cm depth dose instead of depth of dose maximum

    Parent BMI Increase 2 to 5 Years Post-study Related to Change in Age but Independent of Other Sociodemographics, Health Behavior, and Study Engagement (P16-001-19)

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    Objectives Characterize parent (P) weight change 2-5 y post participation in Fuel for Fun (FFF) a controlled trial of a school and family intervention focused on culinary and physical activity experiences for 4th grade youth. Methods P who had participated with their 4th grader in FFF were recruited via email to enroll in a follow-up (FFFFU) assessment. FFF-FU survey set included measures from the original study and new items pertinent to P of adolescents. Physical activity was measured with the IPAQ; low income was denoted as using an income-based program or worry about money for food. Height, weight, age in FFF and FFF-FU were self reported. Perimenopausal age included 47 y within BL and FFF-FU. Youth in FFF cohorts 1 and 4 were controls and cohorts 2 and 3 included the multi-component intervention. P were enrolled in 1 of 4 treatments varying in type and intensity. FFF and FFF-FU data were collected online using the Qualtrics platform. FFF P completed surveys at baseline (BL), post-intervention, and 4 months post-study. FFF-FU data were collected spring 2018, about 2 to 5 years years post-BL. Data were analyzed with repeated measures controlling for BL or FFF-FU sociodemographics, engagement, health behaviors. Results; Of the 418 FFF P, 127 completed FFF-FU surveys (mean age 42.5 6.0 y) with 115 providing weight and height. FFF-FU sample was female (88%), white (84%), active (44% high activity), educated (69% college degree or higher), but had lower BMI and fewer with low income than FFF P. Of FFF-FU providing heights/weights at the 4 assessments, mean (SE) BMIs were 24.2 (0.5), 24.4 (0.5), 24.6 (0.6) and 25.7 (0.6) respectively. Change in BMI was significant after controlling for age, stress, ethnicity, sex, physical activity level, P treatment and engagement, but not when BL to FFU-FU change in age or perimenopausal age were controlled. The significantly greater increase in BMI for P of intervention youth than controls persisted when controlling for sociodemographic and health behavior findings, but not when BL to FFFFU age change, perimenopausal age or activity level were controlled. Conclusions; Significant weight gain by P of youth in a nutrition intervention 2 to 5 years post-study was unrelated to stress, ethnicity, activity level, income, but was related to the FFF-FU age change from BL and perimenopausal age

    Accurate solutions of Colebrook-White’s friction factor formulae

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    Estimations of friction factor (Ff) in pipeline systems and fluid transport are essential ingredients in engineering fields and processes. In this paper explicit friction factor formulae (Fff) were proposed and evaluated with an aim of developing error free Fff. General Fff that relate Ff, Reynolds number (Re) and relative roughness (Rr) were proposed. Colebrook – White’s formula was used to compute different Ff for Re between 4 x 103 and 1.704 x 108, and Rr between 1.0 x 10-7 and 0.052 using Microsoft Excel Solver to fix the Fff. The fixed Fff were used to compute Ff for Re between 4 x 103 and 1.704 x 108 and Rr between 1.0 x 10-7 and 0.052. Accuracy of the fixed Fff was evaluated using relative error; model of selection (MSC) and Akaike Information Criterion (AIC) and compared with the previous Fff using Colebrook–White’s Ff as the reference. The study revealed that Ff estimated using the fixed Fff were the same as Ff estimated using Colebrook – White’s Fff. The fixed Fff provided the lowest relative error of (0.02 %; 0.06 % and 0.04 % ), the highest MSC (14.03; 12.42 and 13.07); and the lowest AIC (-73006; -64580 and -67982). The study concluded that modeling of Fff using numerical methods and Microsoft Excel Solver are better tools for estimating Ff in pipeline flow problems.Keywords: Friction factor, MSC; AIC; Reynolds number; Engineering Field; pipe flow, statistical method

    On filling families of finite subsets of the Cantor set

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    Let \ee>0 and \fff be a family of finite subsets of the Cantor set \ccc. Following D. H. Fremlin, we say that \fff is \ee-filling over \ccc if \fff is hereditary and for every F\subseteq\ccc finite there exists G⊆FG\subseteq F such that G\in\fff and |G|\geq\ee |F|. We show that if \fff is \ee-filling over \ccc and CC-measurable in [\ccc]^{<\omega}, then for every P\subseteq\ccc perfect there exists Q⊆PQ\subseteq P perfect with [Q]^{<\omega}\subseteq\fff. A similar result for weaker versions of density is also obtained.Comment: 14 pages, no figures. Mathematical Proceedings of the Cambridge Philosophical Society (to appear

    From flood science to flood policy: The Foresight Future Flooding Project, seven years on.

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    Purpose: The Foresight Future Flooding (FFF) project researched flood risk in the UK to the year 2100 for central government, using scenarios and a national risk assessment model backed by qualitative analysis from panels of some 45 senior scientists. The purpose of this paper is to assess the impact of the project, both nationally and internationally. Design/methodology/approach: This paper assesses the impact of the FFF project, both nationally and internationally, using web searches, document analysis, and a questionnaire survey of key actors in the flood risk management policy field. Findings: It was found that the penetration of the project into professionals' consciousness was high in relation to other comparable projects and publications, and its impact on policy - both immediately and continuing - was profound. The FFF initiative did not create policy change, however, but facilitated its legitimation, adding impetus to what was already there, as one element of a part-catalytic and part-incremental process of policy evolution. Research limitations/implications: Special circumstances, internal and external to the project, mean that this cannot be a simple model for matching research to policymakers' needs in the future. Practical implications: Important lessons may be learnt from this project about both the methods of forward-looking foresight-type research, and the way that its results are disseminated to its target audiences. Originality/value: This is an innovative attempt to assess the impact of a new type of foresight project. © Emerald Group Publishing Limited

    Low motivation and unawareness in small farmers as an obstacle for implementation of the EU pig welfare rules

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    Using semi-structured interviews, Croatian pig farmers and institutional stakeholders were asked about their intentions to improve pig welfare, future perspectives, opinions and communication efforts on the EU pig welfare directives. While full-time family farmers (FFF) and employees at farm enterprises (EFE) expressed interest in improving pig welfare on their farms as a prerequisite for increasing competitiveness in the future, part-time family farmers (PFF) were not interested in pig welfare because they did not want to increase productivity and feared for their existence. Communication between institutional stakeholders and FFF with more than ten sows is best stablished, whereas communication with EFE is more via private consultants and communication with PFF is lacking. As Croatia is today counting over 85% farms as production units with up to 10 sows covering 75% of whole pig production, these results represent considerably important indicators of necessity to approach this population of farmers

    Reproducing Quantum Probability Distributions at the Speed of Classical Dynamics: A New Approach for Developing Force-Field Functors

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    Modeling nuclear quantum effects is required for accurate molecular dynamics (MD) simulations of molecules. The community has paid special attention to water and other biomolecules that show hydrogen bonding. Standard methods of modeling nuclear quantum effects like Ring Polymer Molecular Dynamics (RPMD) are computationally costlier than running classical trajectories. A force-field functor (FFF) is an alternative method that computes an effective force field which replicates quantum properties of the original force field. In this work, we propose an efficient method of computing FFF using the Wigner-Kirkwood expansion. As a test case, we calculate a range of thermodynamic properties of Neon, obtaining the same level of accuracy as RPMD, but with the shorter runtime of classical simulations. By modifying existing MD programs, the proposed method could be used in the future to increase the efficiency and accuracy of MD simulations involving water and proteins

    From bench to bedside - current clinical and translational challenges in fibula free flap reconstruction.

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    Fibula free flaps (FFF) represent a working horse for different reconstructive scenarios in facial surgery. While FFF were initially established for mandible reconstruction, advancements in planning for microsurgical techniques have paved the way toward a broader spectrum of indications, including maxillary defects. Essential factors to improve patient outcomes following FFF include minimal donor site morbidity, adequate bone length, and dual blood supply. Yet, persisting clinical and translational challenges hamper the effectiveness of FFF. In the preoperative phase, virtual surgical planning and artificial intelligence tools carry untapped potential, while the intraoperative role of individualized surgical templates and bioprinted prostheses remains to be summarized. Further, the integration of novel flap monitoring technologies into postoperative patient management has been subject to translational and clinical research efforts. Overall, there is a paucity of studies condensing the body of knowledge on emerging technologies and techniques in FFF surgery. Herein, we aim to review current challenges and solution possibilities in FFF. This line of research may serve as a pocket guide on cutting-edge developments and facilitate future targeted research in FFF
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