9,798 research outputs found

    Pressure and protein denaturation

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    Kinetic analyses have indicated that moderate hydrostatic pressures, up to some 700 atmospheres, oppose reversible and irreversible denaturations of certain enzyme systems, apparent at temperatures above the normal optimum of the enzyme reaction, as well as at lower temperatures in the presence of denaturants such as alcohol (1-4). Qualitative observations have shown that such pressures also retard the precipitation of highly purified human serum globulin and egg albumin at 65° (5) and slow the destruction of specific antitoxic activity at the same temperature (6). In this study we have obtained quantitative data with regard to the influence of various pressures, up to 10,000 pounds per sq. in., and of low concentrations of ethyl alcohol on the time course of precipitation of human serum globulin (1) at 65° and pH 6.0

    Acoustic Space Movement Planning in a Neural Model of Motor Equivalent Vowel Production

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    Recent evidence suggests that speakers utilize an acoustic-like reference frame for the planning of speech movements. DIVA, a computational model of speech acquisition and motor equivalent speech production, has previously been shown to provide explanations for a wide range of speech production data using a constriction-based reference frame for movement planning. This paper extends the previous work by investigating an acoustic-like planning frame in the DIVA modeling framework. During a babbling phase, the model self-organizes targets in the planning space for each of ten vowels and learns a mapping from desired movement directions in this planning space into appropriate articulator velocities. Simulation results verify that after babbling the model is capable of producing easily recognizable vowel sounds using an acoustic planning space consisting of the formants F1 and F2. The model successfully reaches all vowel targets from any initial vocal tract configuration, even in the presence of constraints such as a blocked jaw.Office of Naval Research (N00014-91-J-4100, N00014-92-J-4015); Air Force Office of Scientific Research (F49620-92-J-0499

    A STOCHASTIC DOMINANCE ANALYSIS OF CONTRACT GRAZING FEEDER CATTLE

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    Contract grazing feeder cattle is an arrangement where cattle owned by one party graze forage produced on land owned by another party. The forage producer is paid a fixed price per pound gained. Stochastic dominance analysis is used to compare contract grazing and the more traditional system in which the same individual owns both the cattle and land.Livestock Production/Industries,

    Recipients of electric-powered indoor/outdoor wheelchairs provided by a National Health Service: A cross-sectional study

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    This is the post-print version of the final paper published in Archives of Physical Medicine and Rehabilitation. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 by the American Congress of Rehabilitation Medicine.OBJECTIVE: To describe the characteristics, across all ages, of powered wheelchair users and the assistive technology prescribed by a regional specialist wheelchair service DESIGN: Cross-sectional study SETTING: Regional wheelchair service provided to those fulfilling strict eligibility criteria by a National Health Service serving a population of 3 million. PARTICIPANTS: 544 Electric Powered Indoor/outdoor wheelchair (EPIOC) users. INTERVENTIONS: Not applicable MAIN OUTCOME MEASURES: Demographic, clinical/diagnostic details of EPIOC recipients including pain, (kypho)scoliosis and ventilators. Technical features including specialised (adaptive) seating (SS), tilt in space (TIS), and modified control systems. Factors were related to age groups: 1 (0-15), 2 (16-24), 3 (25-54), 4 (55-74) and 5 (75+). RESULTS: 262 men mean age 41.7 (range 8-82, sd 20.7) and 282 women mean age 47.2 (range 7-92, sd 19.7) years were studied. Neurological/neuromuscular conditions predominated (81%) with cerebral palsy (CP) (18.9%) and multiple sclerosis (16.4%). Conditions presenting at birth or during childhood constituted 39%. 99 had problematic pain, 83 a (kypho)scoliosis and 11 used ventilators. SS was provided to 169 users (31%), the majority had CP or muscular dystrophy. TIS was used by 258 (53%). Younger people were more likely to receive TIS than older ones. Only 92 had SS and TIS, mean age 29 (range 8-72, sd 17.8) years. 52 used modified control systems. CONCLUSIONS: The diversity of EPIOC users across age and diagnostic groups is shown. Their complex interrelationships with these technical features of EPIOC prescription are explored. Younger users were more complex due to age-related changes. This study provides outcomes of the EPIOC prescription for this heterogeneous group of very severely disabled people

    Zonal Flows and Long-Lived Axisymmetric Pressure Bumps in Magnetorotational Turbulence

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    We study the behavior of magnetorotational turbulence in shearing box simulations with a radial and azimuthal extent up to ten scale heights. Maxwell and Reynolds stresses are found to increase by more than a factor two when increasing the box size beyond two scale heights in the radial direction. Further increase of the box size has little or no effect on the statistical properties of the turbulence. An inverse cascade excites magnetic field structures at the largest scales of the box. The corresponding 10% variation in the Maxwell stress launches a zonal flow of alternating sub- and super-Keplerian velocity. This in turn generates a banded density structure in geostrophic balance between pressure and Coriolis forces. We present a simplified model for the appearance of zonal flows, in which stochastic forcing by the magnetic tension on short time-scales creates zonal flow structures with life-times of several tens of orbits. We experiment with various improved shearing box algorithms to reduce the numerical diffusivity introduced by the supersonic shear flow. While a standard finite difference advection scheme shows signs of a suppression of turbulent activity near the edges of the box, this problem is eliminated by a new method where the Keplerian shear advection is advanced in time by interpolation in Fourier space.Comment: Accepted for publication in Ap

    Using CO2 to Determine Inhaled Contaminant Volumes and Blower Effectiveness in Several Types of Respirators

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    This experiment was conducted to determine how much contaminant could be expected to be inhaled when overbreathing several different types of respirators. These included several tight-fitting and loose-fitting powered air-purifying respirators (PAPRs) and one air-purifying respirator (APR). CO2 was used as a tracer gas in the ambient air, and several loose-and tight-fitting respirators were tested on the head form of a breathing machine. CO2 concentration in the exhaled breath was monitored as well as CO2 concentration in the ambient air. This concentration ratio was able to give a measurement of protection factor, not for the respirator necessarily, but for the wearer. Flow rates in the filter/blower inlet and breathing machine outlet were also monitored, so blower effectiveness (defined as the blower contribution to inhaled air) could also be determined. Wearer protection factors were found to range from 1.1 for the Racal AirMate loose-fitting PAPR to infinity for the 3M Hood, 3M Breath-Easy PAPR, and SE 400 breath-responsive PAPR. Inhaled contaminant volumes depended on tidal volume but ranged from 2.02 L to 0 L for the same respirators, respectively. Blower effectiveness was about 1.0 for tight-fitting APRs, 0.18 for the Racal, and greater than 1.0 for two of the loose-fitting PAPRs. With blower effectiveness greater than 1.0, some blower flow during the exhalation phase contributes to the subsequent inhalation. Results from this experiment point to different ways to measure respirator efficacy

    A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372

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    Aims: We present the first in-depth study of the kinematic properties and derive the structural parameters of NGC 4372 based on the fit of a Plummer profile and a rotating, physical model. We explore the link between internal rotation to different cluster properties and together with similar studies of more GCs, we put these in the context of globular cluster formation and evolution. Methods: We present radial velocities for 131 cluster member stars measured from high-resolution FLAMES/GIRAFFE observations. Their membership to the GC is additionally confirmed from precise metallicity estimates. Using this kinematic data set we build a velocity dispersion profile and a systemic rotation curve. Additionally, we obtain an elliptical number density profile of NGC 4372 based on optical images using a MCMC fitting algorithm. From this we derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and e=0.08+/-0.01. Finally, we give a physical interpretation of the observed morphological and kinematic properties of this GC by fitting an axisymmetric, differentially rotating, dynamical model. Results: Our results show that NGC 4372 has an unusually high ratio of rotation amplitude to velocity dispersion (1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild flattening of NGC 4372 in the direction of its rotation. Given its old age, this suggests that the flattening is indeed caused by the systemic rotation rather than tidal interactions with the Galaxy. Additionally, we estimate the dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3 M_Sun/L_Sun, representative of an old, purely stellar population.Comment: Accepted for publication in A&A, 12 pages, 14 figures, 2 table

    Efficient Triangle Counting in Large Graphs via Degree-based Vertex Partitioning

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    The number of triangles is a computationally expensive graph statistic which is frequently used in complex network analysis (e.g., transitivity ratio), in various random graph models (e.g., exponential random graph model) and in important real world applications such as spam detection, uncovering of the hidden thematic structure of the Web and link recommendation. Counting triangles in graphs with millions and billions of edges requires algorithms which run fast, use small amount of space, provide accurate estimates of the number of triangles and preferably are parallelizable. In this paper we present an efficient triangle counting algorithm which can be adapted to the semistreaming model. The key idea of our algorithm is to combine the sampling algorithm of Tsourakakis et al. and the partitioning of the set of vertices into a high degree and a low degree subset respectively as in the Alon, Yuster and Zwick work treating each set appropriately. We obtain a running time O(m+m3/2Δlogntϵ2)O \left(m + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right) and an ϵ\epsilon approximation (multiplicative error), where nn is the number of vertices, mm the number of edges and Δ\Delta the maximum number of triangles an edge is contained. Furthermore, we show how this algorithm can be adapted to the semistreaming model with space usage O(m1/2logn+m3/2Δlogntϵ2)O\left(m^{1/2}\log{n} + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right) and a constant number of passes (three) over the graph stream. We apply our methods in various networks with several millions of edges and we obtain excellent results. Finally, we propose a random projection based method for triangle counting and provide a sufficient condition to obtain an estimate with low variance.Comment: 1) 12 pages 2) To appear in the 7th Workshop on Algorithms and Models for the Web Graph (WAW 2010
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