1,409 research outputs found
A Framework for Analyzing Knowledge Utilization in Social Work Practice
Methodological and conceptual limitations have resulted in knowledge being defined so narrowly that we accept the inaccurate conclusion that social workers fail to utilize knowledge. This article seeks to rectify this problem by clarifying the concept of knowledge utilization in social work practice. Toward this end a framework is proposed that makes explicit the philosophy of science and practice assumptions germane to the use of knowledge in practice
The Diffusion of Humans and Cultures in the Course of the Spread of Farming
The most profound change in the relationship between humans and their
environment was the introduction of agriculture and pastoralism. [....] For an
understanding of the expansion process, it appears appropriate to apply a
diffusive model. Broadly, these numerical modeling approaches can be catego-
rized in correlative, continuous and discrete. Common to all approaches is the
comparison to collections of radiocarbon data that show the apparent wave of
advance of the transition to farming. However, these data sets differ in entry
density and data quality. Often they disregard local and regional specifics and
research gaps, or dating uncertainties. Thus, most of these data bases may only
be used on a very general, broad scale. One of the pitfalls of using
irregularly spaced or irregularly documented radiocarbon data becomes evident
from the map generated by Fort (this volume, Chapter 16): while the general
east-west and south-north trends become evident, some areas appear as having
undergone anomalously early transitions to farming. This may be due to faulty
entries into the data base or regional problems with radiocarbon dating, if not
unnoticed or undocumented laboratory mistakes.Comment: 20 pages, 5 figures, submitted to Diffusive Spreading in Nature,
Technology and Society, edited by Armin Bunde, J\"urgen Caro, J\"org
K\"arger, Gero Vogl, Chapter 1
Relationship between dielectric properties and critical behavior of the electric birefringence in binary liquid mixtures
We present experimental results on the critical exponent ψEKE describing the divergence of the Kerr constant of binary liquid mixtures near the critical consolute point. We show that the measured value of ψEKE agrees with the theoretical prediction only if the measurement is performed with a mixture of two liquids presenting a small mismatch in the dielectric constant, and that the measured ψEKE grows as the dielectric constant mismatch increases. Such findings are consistent with a recent model which assumes that the elongation of critical fluctations along the direction of the electric field can become so strong that fluctuations in the direction perpendicular to the electric field may cross over from Ising to mean-field behavior
Negative length orbits in normal-superconductor billiard systems
The Path-Length Spectra of mesoscopic systems including diffractive
scatterers and connected to superconductor is studied theoretically. We show
that the spectra differs fundamentally from that of normal systems due to the
presence of Andreev reflection. It is shown that negative path-lengths should
arise in the spectra as opposed to normal system. To highlight this effect we
carried out both quantum mechanical and semiclassical calculations for the
simplest possible diffractive scatterer. The most pronounced peaks in the
Path-Length Spectra of the reflection amplitude are identified by the routes
that the electron and/or hole travels.Comment: 4 pages, 4 figures include
An amphitropic cAMP-binding protein in yeast mitochondria
ABSTRACT: We describe the first example of a mitochondrial protein with a covalently attached phos-phatidylinositol moiety acting as a membrane anchor. The protein can be metabolically labeled with both stearic acid and inositol. The stearic acid label is removed by phospholipase D whereupon the protein with the retained inositol label is released from the membrane. This protein is a cAMP receptor of the yeast Saccharomyces cereuisiae and tightly associated with the inner mitochondrial membrane. However, it is converted into a soluble form during incubation of isolated mitochondria with Ca2+ and phospholipid (or lipid derivatives). This transition requires the action of a proteinaceous, N-ethylmaleimide-sensitive component of the intermembrane space and is accompanied by a decrease in the lipophilicity of the cAMP receptor. We propose that the component of the intermembrane space triggers the amphitropic behavior of the mitochondrial lipid-modified CAMP-binding protein through a phospholipase activity. Only in recent years specific fatty acids have been recog-nized to play important roles in the association of proteins with membranes. Both noncovalent and covalent interactions be-tween fatty acids and proteins have been reported. Among the latter are GTP-binding proteins (Molenaar et al., 1988)
Precise Measurement of the Pi+ -> Pi0 e+ nu Branching Ratio
Using a large acceptance calorimeter and a stopped pion beam we have made a
precise measurement of the rare Pi+ -> Pi0 e+ Nu,(pi_beta) decay branching
ratio. We have evaluated the branching ratio by normalizing the number of
observed pi_beta decays to the number of observed Pi+ -> e+ Nu, (pi_{e2})
decays. We find the value of Gamma(Pi+ -> Pi0 e+ Nu)/Gamma(total) = [1.036 +/-
0.004(stat.) +/- 0.004(syst.) +/- 0.003(pi_{e2})] x 10^{-8}$, where the first
uncertainty is statistical, the second systematic, and the third is the pi_{e2}
branching ratio uncertainty. Our result agrees well with the Standard Model
prediction.Comment: 4 pages, 5 figures, 1 table, revtex4; changed content; updated
analysi
The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies
We review a sample of the early literature in which the reality of the
expansion is discussed, explain Hubble's reticence to accept the expansion as
real, and contrast the Tolman surface brightness test with three other modern
tests. We search for the Tolman surface brightness depression with redshift
using the Hubble Space Telescope (HST) data from Paper III for 34 early-type
galaxies from the three clusters Cl 1324+3011 (z=0.76), Cl 1604+4304 (z=0.90),
and Cl 1604+4321 (z=0.92). Depressions of the surface brightness relative to
the zero-redshift fiducial lines in the mean surface brightness, log linear
radius diagrams of Paper I are found for all three clusters. Expressed as the
exponent, n, in 2.5 log (1 + z)^n mag, the value of n for all three clusters is
n = 2.59 +/- 0.17 in the R band and 3.37 +/- 0.13 in the I band for a q_o = 1/2
model. The sensitivity of the result to the assumed value of q_o is shown to be
less than 23% between q_o = 0 and +1. For a true Tolman signal with n = 4, the
luminosity evolution in the look-back time, expressed as the exponent in 2.5
log (1+z)^(4-n) mag, must then be between 1.72 to 1.19 in the R band and 0.94
to 0.45 in the I band. We show that this is precisely the range expected from
the evolutionary models of Bruzual & Charlot. We conclude that the Tolman
surface brightness test is consistent with the reality of the expansion. We
have also used the high-redshift HST data to test the ``tired light''
speculation for a non-expansion model for the redshift. The HST data rule out
the ``tired light'' model at a significance level of better than 10 sigma.Comment: 36 pages, 6 figures; accepted for publication in the Astronomical
Journa
Time-resolved dynamics of electron wave packets in chaotic and regular quantum billiards with leads
We perform numerical studies of the wave packet propagation through open
quantum billiards whose classical counterparts exhibit regular and chaotic
dynamics. We show that for t less or similar to tau (tau being the Heisenberg
time), the features in the transmitted and reflected currents are directly
related to specific classical trajectories connecting the billiard leads. In
contrast, the long-time asymptotics of the wave packet dynamics is
qualitatively different for classical and quantum billiards. In particularly,
the decay of the quantum system obeys a power law that depends on the number of
decay channels, and is not sensitive to the nature of classical dynamics
(chaotic or regular).Comment: 5 pages, 4 figure
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