18,419 research outputs found
SPACEBAR: Kinematic design by computer graphics
The interactive graphics computer program SPACEBAR, conceived to reduce the time and complexity associated with the development of kinematic mechanisms on the design board, was described. This program allows the direct design and analysis of mechanisms right at the terminal screen. All input variables, including linkage geometry, stiffness, and applied loading conditions, can be fed into or changed at the terminal and may be displayed in three dimensions. All mechanism configurations can be cycled through their range of travel and viewed in their various geometric positions. Output data includes geometric positioning in orthogonal coordinates of each node point in the mechanism, velocity and acceleration of the node points, and internal loads and displacements of the node points and linkages. All analysis calculations take at most a few seconds to complete. Output data can be viewed at the scope and also printed at the discretion of the user
Universality in the off-equilibrium critical dynamics of the diluted Ising model
We study the off-equilibrium critical dynamics of the three dimensional
diluted Ising model. We compute the dynamical critical exponent and we show
that it is independent of the dilution only when we take into account the
scaling-corrections to the dynamics. Finally we will compare our results with
the experimental data.Comment: Final Version, 5 Latex pages (RevTeX) plus 3 eps figure
Patient Satisfaction and Ultrasound Use During Pregnancy
Use, number, and frequency of ultrasounds women receive during pregnancy vary widely in practice. Current evidence suggests that women presenting with pregnancy complications benefit from additional ultrasounds, although excessive ultrasound use in low risk pregnancies may be unnecessary, costly and potentially harmful. However, evidence also finds that the use of ultrasound technology is associated with mothers’ feelings of security and satisfaction with care; health care organizations are incentivized to promote these feelings of patient satisfaction, especially when clinical risk is considered low. Here, we examine the impact of ultrasound use on satisfaction during pregnancy among women in the Northeast who have recently given birth through an online retrospective survey. Contrary to expectations, findings suggest that ultrasound use is not a significant driver of satisfaction with pregnancyrelated care. Efforts to enhance patient satisfaction during pregnancy using ultrasounds may increase resource use and cost, but do little to enhance patient experience overal
A gyrokinetic model for the plasma periphery of tokamak devices
A gyrokinetic model is presented that can properly describe strong flows,
large and small amplitude electromagnetic fluctuations occurring on scale
lengths ranging from the electron Larmor radius to the equilibrium
perpendicular pressure gradient scale length, and large deviations from thermal
equilibrium. The formulation of the gyrokinetic model is based on a second
order description of the single charged particle dynamics, derived from Lie
perturbation theory, where the fast particle gyromotion is decoupled from the
slow drifts, assuming that the ratio of the ion sound Larmor radius to the
perpendicular equilibrium pressure scale length is small. The collective
behavior of the plasma is obtained by a gyrokinetic Boltzmann equation that
describes the evolution of the gyroaveraged distribution function and includes
a non-linear gyrokinetic Dougherty collision operator. The gyrokinetic model is
then developed into a set of coupled fluid equations referred to as the
gyrokinetic moment hierarchy. To obtain this hierarchy, the gyroaveraged
distribution function is expanded onto a velocity-space Hermite-Laguerre
polynomial basis and the gyrokinetic equation is projected onto the same basis,
obtaining the spatial and temporal evolution of the Hermite-Laguerre expansion
coefficients. The Hermite-Laguerre projection is performed accurately at
arbitrary perpendicular wavenumber values. Finally, the self-consistent
evolution of the electromagnetic fields is described by a set of gyrokinetic
Maxwell's equations derived from a variational principle, with the velocity
integrals of the gyroaveraged distribution function explicitly evaluated
Metastable SUSY Breaking and Supergravity at Finite Temperature
We study how coupling to supergravity affects the phase structure of a system
exhibiting dynamical supersymmetry breaking in a metastable vacuum. More
precisely, we consider the Seiberg dual of SQCD coupled to supergravity at
finite temperature. We show that the gravitational interactions decrease the
critical temperature for the second order phase transition in the quark
direction, that is also present in the global case. Furthermore, we find that,
due to supergravity, a new second order phase transition occurs in the meson
direction, whenever there is a nonvanishing constant term in the
superpotential. Notably, this phase transition is a necessary condition for the
fields to roll, as the system cools down, towards the metastable susy breaking
vacuum, because of the supergravity-induced shift of the metastable minimum
away from zero meson vevs. Finally, we comment on the phase structure of the
KKLT model with uplifting sector given by the Seiberg dual of SQCD.Comment: 38 pages; Section 6 amended and expanded, references adde
A hot bubble at the centre of M81
Context. Messier 81 has the nearest active nucleus with broad H
emission. A detailed study of this galaxy's centre is important for
understanding the innermost structure of the AGN phenomenon.
Aims. Our goal is to seek previously undetected structures using additional
techniques to reanalyse a data cube obtained with the GMOS-IFU installed on the
Gemini North telescope (Schnorr M\"uller et al. 2011).
Method. We analysed the data cube using techniques of noise reduction,
spatial deconvolution, starlight subtraction, PCA tomography, and comparison
with HST images.
Results. We identified a hot bubble with T 43500 K that is associated
with strong emission of [N II]5755\AA\ and a high [O
I]6300/H ratio; the bubble displays a bluish continuum,
surrounded by a thin shell of H + [N II] emission. We also reinterpret
the outflow found by Schnorr M\"uller et al. (2011) showing that the
blueshifted cone nearly coincides with the radio jet, as expected.
Conclusions. We interpret the hot bubble as having been caused by post
starburst events that left one or more clusters of young stars, similar to the
ones found at the centre of the Milky Way, such as the Arches and the IRS 16
clusters. Shocked structures from combined young stellar winds or supernova
remnants are probably the cause of this hot gas and the low ionization
emission.Comment: 5 pages, 4 figures, accepted for publication in A&
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