6,790 research outputs found
Kinetic treatment of parallel gradient nonuniformity for the ICRF heatingâA fourier integral approach
We study the generally nonlocal VlasovâMaxwell wave propagation and absorption problem for an arbitrarily nonuniform plasma. The Fourier transform of the nonlocal dielectric response kernel, K(r,k), is constructed by integration along particle orbits in the nonuniform field. Although a finite Larmor radius expansion of the transverse particle motion still applies, the phase integrals which comprise the usual plasma dispersion function are altered, containing an additional parameter characterizing the parallel field gradient. The use of realistic phase decorrelation estimates over a single bounce orbit leads to a reduction of the phase integrals to a tractible form. We numerically solve a 1âD sheared field version of the resultant integral equation describing the mode conversion physics. Significant changes are found for small kâ„ values. In addition, local absorption in the resonance zone appears to be stratified in conjunction with the rfâparticle phase correlation which occurs for particles passing through the localized resonance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87459/2/350_1.pd
Laser Accelerated Plasma Propulsion System (LAPPS)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76736/1/AIAA-2001-3810-844.pd
The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems
We investigate the relationship between age and chromospheric activity for
139 M dwarf stars in wide binary systems with white dwarf companions. The age
of each system is determined from the cooling age of its white dwarf component.
The current limit for activity-age relations found for M dwarfs in open
clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for
the exploration of this relationship at ages older than 4 Gyr. The general
trend of stars remaining active for a longer time at later spectral type is
confirmed. However, our larger sample and greater age range reveals additional
complexity in assigning age based on activity alone. We find that M dwarfs in
wide binaries older than 4 Gyr depart from the log-linear relation for clusters
and are found to have activity at magnitudes, colors and masses which are
brighter, bluer and more massive than predicted by the cluster relation. In
addition to our activity-age results, we present the measured radial velocities
and complete space motions for 161 white dwarf stars in wide binaries.Comment: 22 pages including 9 figures and 5 tables. Accepted for publication
in The Astronomical Journa
An Improved 96-well Turbidity Assay for T4 Lysozyme Activity
T4 lysozyme (T4L) is an important model system for investigating the relationship between protein structure and function. Despite being extensively studied, a reliable, quantitative activity assay for T4L has not been developed. Here, we present an improved T4L turbidity assay as well as an affinity-based T4L expression and purification protocol. This assay is designed for 96-well format and utilizes conditions amenable for both T4L and other lysozymes. This protocol enables easy, efficient, and quantitative characterization of T4L variants and allows comparison between different lysozymes. Our method: âąIs applicable for all lysozymes, with enhanced sensitivity for T4 lysozyme compared to other 96-well plate turbidity assays;âąUtilizes standardized conditions for comparing T4 lysozyme variants and other lysozymes; andâąIncorporates a simplified expression and purification protocol for T4 lysozyme
Evidence for quantum confinement in the photoluminescence of porous Si and SiGe
We have used anodization techniques to process porous surface regions in p-type Czochralski Si and in p-type Si0.85Ge0.15 epitaxial layers grown by molecular beam epitaxy. The SiGe layers were unrelaxed before processing. We have observed strong near-infrared and visible light emission from both systems. Analysis of the radiative and nonradiative recombination processes indicate that the emission is consistent with the decay of excitons localized in structures of one or zero dimensions
Facilitating Transformation in Workforce Training: Using Clinical Theory to Understand Psychological Self-Sufficiency
Acknowledging the scarcity of a bottom up social work practice model in facilitating the development of success in workforce development programs, this study explores Psychological self-sufficiency (PSS) as an emerging social work practice theory. Phenomenological studies of low-income jobseekers in employment training along with the empirical validation of measures of the core constructs of PSS â employment hope scale (EHS) and perceived employment barrier scale (PEBS) â and testing of the theoretical model resulted in the emergence of a new theory of PSS. PSS was conceptually defined as a dynamic and internal drive that activates the process of transforming cognitively and affectively perceived barriers into hope driven action â the process that enables individuals to move forward toward goals. Based on the evidence of PSS, a participant-centered group intervention model called transforming impossible into possible (TIP) program was developed. This article delineates the trajectory of PSS theory development by critically reviewing various streams of practice theories influencing the PSS theory. Next, the conditions that necessitated the creation of the TIP program and its core principles underlying the functions of PSS are explained. By depicting the TIP program with direct quotes of clientsâ experiences, authors exemplify the successful self-discovery process through enhanced PSS skills as a result of participating in the TIP program
A relational quantum computer using only two-qubit total spin measurement and an initial supply of highly mixed single qubit states
We prove that universal quantum computation is possible using only (i) the
physically natural measurement on two qubits which distinguishes the singlet
from the triplet subspace, and (ii) qubits prepared in almost any three
different (potentially highly mixed) states. In some sense this measurement is
a `more universal' dynamical element than a universal 2-qubit unitary gate,
since the latter must be supplemented by measurement. Because of the rotational
invariance of the measurement used, our scheme is robust to collective
decoherence in a manner very different to previous proposals - in effect it is
only ever sensitive to the relational properties of the qubits.Comment: TR apologises for yet again finding a coauthor with a ridiculous
middle name [12
Magnetic Gaps related to Spin Glass Order in Fermionic Systems
We provide evidence for spin glass related magnetic gaps in the fermionic
density of states below the freezing temperature. Model calculations are
presented and proposed to be relevant for explaining resistivity measurements
which observe a crossover from variable-range- to activated behavior. The
magnetic field dependence of a hardgap and the low temperature decay of the
density of states are given. In models with fermion transport a new
metal-insulator transition is predicted to occur due to the spin-glass gap,
anteceding the spin glass to quantum paramagnet transition at smaller spin
density. Important fluctuation effects due to finite range frustrated
interactions are estimated and discussed.Comment: 4 pages, 1 Postscript figure, revised version accepted for
publication in Physical Review Letter
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