1,617 research outputs found
Energy Loss from a Moving Vortex in Superfluid Helium
We present measurements on both energy loss and pinning for a vortex
terminating on the curved surface of a cylindrical container. We vary surface
roughness, cell diameter, fluid velocity, and temperature. Although energy loss
and pinning both arise from interactions between the vortex and the surface,
their dependences on the experimental parameters differ, suggesting that
different mechanisms govern the two effects. We propose that the energy loss
stems from reconnections with a mesh of microscopic vortices that covers the
cell wall, while pinning is dominated by other influences such as the local
fluid velocity.Comment: 8 pages, 6 figure
Dynamics of perpendicular recording heads
3D modeling and inductance measurements were used to design an ultra-high frequency perpendicular system. Kerr microscopy and spin-stand experiments with focused ion beam (FI-B) trimmed perpendicular heads and perpendicular media directly verified the high frequency concepts
Amino acid losses during hemodialysis with infusion of amino acids and glucose
Amino acid losses during hemodialysis with infusion of amino acids and glucose. This study evaluated the effects during hemodialysis of intravenous infusion of amino acids and glucose on plasma amino acid and glucose concentrations and amino acid losses. Eight men undergoing maintenance hemodialysis were each studied during two dialyses using glucose-free dialysate. During one hemodialysis, they were infused with 800ml of normal saline. During the other hemodialysis, they were infused with an equal volume of water which contained 39.5g of essential and non-essential free L-amino acids and 200g of d-glucose. The solutions were infused throughout the dialysis procedure into the drip chamber of the venous outflow from the dialyzer. Subjects were fasted from the night before until the end of hemodialysis, and the order of administration of the two solutions was determined randomly. Plasma essential, non-essential, and total amino acids fell significantly during the infusion of normal saline and rose during the administration of amino acids and glucose. Dialysate total-free amino acid losses averaged 8.2 ± 3.1SDg during the infusion of normal saline and 12.6 ± 3.6g with the administration of amino acids and glucose. These findings indicate that the intravenous infusion of amino acids and glucose during hemodialysis prevents a fall in plasma amino acid and glucose concentrations and leads to only a slight increase in the losses of free amino acids into dialysate. Because most of the infused amino acids are retained, this technique may be used during hemodialysis to avoid a net outflow of amino acids, minimize disruption of amino acid and glucose pools, and provide a nutritional supplement.Pertes en amino-acides au cours de l'hĂ©modialyse avec perfusion d'acides aminĂ©s et de glucose. Cette Ă©tude a permis d'Ă©valuer les effets de la perfusion intraveineuse d'acides aminĂ©s et de glucose pendant l'hĂ©modialyse sur les concentrations plasmatiques d'acides aminĂ©s et de glucose, et les pertes d'acides aminĂ©s. Huit hommes en hĂ©modialyse chronique ont chacun Ă©tĂ© Ă©tudiĂ©s pendant deux dialyses avec un dialysat sans glucose. Pendant une des dialyses ils Ă©taient perfusĂ©s avec 800ml de solutĂ© physiologique. Pendant l'hemodialyse autre ils ont infusĂ© avec un Ă©gal volume d'eau contenant 39,5g de L-acides aminĂ©s libres essentiels ou non, et 200g de d-glucose. Les solutions Ă©taient perfusĂ©es pendant la dialyse dans la tubulure veineuse venant du dialyseur. Les malades Ă©taient Ă jeĂ»n la nuit prĂ©cĂ©dante et jusqu'Ă la fin de la dialyse, et l'ordre d'administration des deux solutions Ă©tait dĂ©terminĂ© au hasard. Les acides aminĂ©s plasmatiques totaux, essentiels et non essentiels ont significativement diminuĂ© pendant la perfusion de solutĂ© physiologique, et se sont Ă©levĂ©s pendant l'administration d'acides aminĂ©s et de glucose. Dans le dialysat, les pertes totales d'acides aminĂ©s libres Ă©taient en moyenne de 8,2 ± 3,1g (ds) pendant la perfusion de solutĂ© physiologique, et de 12,6 ± 3,6g lors de l'administration d'acides aminĂ©s et de glucose. Ces rĂ©sultats indiquent que la perfusion intraveineuse d'acides aminĂ©s et de glucose au cours de la dialyse empĂȘche la chute des acides aminĂ©s et du glucose plasmatiques et n'occasionne qu'une diminution minime des pertes en acides aminĂ©s libres dans le dialysat. Puisque la plupart des acides aminĂ©s perfusĂ©s est retenue, cette technique pourrait ĂȘtre utilisĂ©e pendant l'hĂ©modialyse pour Ă©viter une fuite nette d'acides aminĂ©s, pour minimiser la dissipation des rĂ©serves d'acides aminĂ©s et de glucose et pour apporter un supplĂ©ment nutritif
Temperature and Emission-Measure Profiles Along Long-Lived Solar Coronal Loops Observed with TRACE
We report an initial study of temperature and emission measure distributions
along four steady loops observed with the Transition Region and Coronal
Explorer (TRACE) at the limb of the Sun. The temperature diagnostic is the
filter ratio of the extreme-ultraviolet 171-angstrom and 195-angstrom
passbands. The emission measure diagnostic is the count rate in the
171-angstrom passband. We find essentially no temperature variation along the
loops. We compare the observed loop structure with theoretical isothermal and
nonisothermal static loop structure.Comment: 10 pages, 3 postscript figures (LaTeX, uses aaspp4.sty). Accepted by
ApJ Letter
Transversality of Electromagnetic Waves in the Calculus-Based Introductory Physics Course
Introductory calculus-based physics textbooks state that electromagnetic
waves are transverse and list many of their properties, but most such textbooks
do not bring forth arguments why this is so. Both physical and theoretical
arguments are at a level appropriate for students of courses based on such
books, and could be readily used by instructors of such courses. Here, we
discuss two physical arguments (based on polarization experiments and on lack
of monopole electromagnetic radiation), and the full argument for the
transversality of (plane) electromagnetic waves based on the integral Maxwell
equations. We also show, at a level appropriate for the introductory course,
why the electric and magnetic fields in a wave are in phase and the relation of
their magnitudes.Comment: 10 pages, 6 figure
Functional features defining the efficacy of cholesterol-conjugated, self-deliverable, chemically modified siRNAs
Progress in oligonucleotide chemistry has produced a shift in the nature of siRNA used, from formulated, minimally modified siRNAs, to unformulated, heavily modified siRNA conjugates. The introduction of extensive chemical modifications is essential for conjugate-mediated delivery. Modifications have a significant impact on siRNA efficacy through interference with recognition and processing by RNAi enzymatic machinery, severely restricting the sequence space available for siRNA design. Many algorithms available publicly can successfully predict the activity of non-modified siRNAs, but the efficiency of the algorithms for designing heavily modified siRNAs has never been systematically evaluated experimentally. Here we screened 356 cholesterol-conjugated siRNAs with extensive modifications and developed a linear regression-based algorithm that effectively predicts siRNA activity using two independent datasets. We further demonstrate that predictive determinants for modified and non-modified siRNAs differ substantially. The algorithm developed from the non-modified siRNAs dataset has no predictive power for modified siRNAs and vice versa. In the context of heavily modified siRNAs, the introduction of chemical asymmetry fully eliminates the requirement for thermodynamic bias, the major determinant for non-modified siRNA efficacy. Finally, we demonstrate that in addition to the sequence of the target site, the accessibility of the neighboring 3\u27 region significantly contributes to siRNA efficacy
Topological Field Theory and Rational Curves
We analyze the superstring propagating on a Calabi-Yau threefold. This theory
naturally leads to the consideration of Witten's topological non-linear
sigma-model and the structure of rational curves on the Calabi-Yau manifold. We
study in detail the case of the world-sheet of the string being mapped to a
multiple cover of an isolated rational curve and we show that a natural
compactification of the moduli space of such a multiple cover leads to a
formula in agreement with a conjecture by Candelas, de la Ossa, Green and
Parkes.Comment: 20 page
Reliability of self-report of health in juvenile offenders
The aim of the present study was to investigate the accuracy of self-reports of juvenile offenders on physical factors (e.g., sleep difficulties, weight related behaviors and weight perceptions), health risk behaviors (e.g., alcohol use), trauma history (e.g., physical and sexual abuse) and psychological factors (e.g., anxiety, suicidal and self-harm behaviors). Self-reports obtained via a Health Questionnaire from 242 incarcerated juvenile offenders were compared with standardized measures (Body Mass Index, Adolescent Psychopathology Scale and Child Trauma Questionnaire) to investigate the reliability (via construct validity) and veracity of their self-report. Using kappa estimates and receiver operating characteristic curves, results generally showed high agreement across measures, suggesting that self-report questions from the health survey could all be used reliably. The degree of accuracy indicated that young offenders are as reliable as clinical and community samples of adolescents in their self-report. These findings have implications for routine assessments and practice evaluations that rely on self-report as the method of data collection and as the basis for clinical formulation and treatment planning
Stop Making Sense(s) : Some late medieval and very late medieval views on faculty psychology
Peer reviewe
Active/Passive, âDiminishedâ/âBeautifulâ, âLightâ from Above and Below: Rereading Shekhinahâs Sexual Desire in Zohar al Shir ha-Shirim (Song of Songs)
In Zohar al Shir ha-Shirim, the Zoharâs reading of Song of Songs, Shekhinah, echoing themes associated with the Shulamite of the biblical text, consistently initiates cosmic union. Sexual desire in the zoharic texts is a form of capital necessary to facilitate sefirotic intercourse, although scholarly readings of the zoharic corpus often identify Shekhinah as a passive receptacle. This, however, is only true if the endemic contradictions within the texts are glossed over. In Song of Songs, the Shulamiteâs sexual âinitiativeâ is core. This was not lost on the author(s) of Zohar al Shir ha-Shirim, who, in struggling to explain Shekhinahâs sefirotic role in line with the erotics of Song of Songs, inescapably echoed the âdepatriarchalizingâ themes of the biblical text. As this article demonstrates, in Zohar al Shir ha-Shirim, Shekhinah is active and repeatedly encourages and frustrates cosmic sexual intercourse. Zohar al Shir ha-Shirim shows that it is possible to reread Shekhinahâs role beyond the androcentrism of the authors as well as scholarly assumptions about her passivity
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