4,588 research outputs found
Constructing an Ecology of Foster Care: An Analysis of the Entry and Exit Patterns of Foster Homes
This paper aims to illustrate the viability of using concepts and theoretical arguments from organization ecology to analyze dynamic change processes in foster care. The general topic is the relationship between foster homes and their environments. The specific focus is the effects of the environment on the entry and exit patterns of new foster homes. Drawing on our earlier studies of the 23 year history of a population of foster homes, various hypotheses shown to have validity in accounting for the processes underlying the founding and disbanding offormal organizations, also apply in the case of the entry and exit processes offoster homes. One important contribution of this paper is in re-asserting the role of theory in studying foster care, and in helping organize existing knowledge. A second contribution is in reminding us that foster homes should be conceptualized and studied as existing in relation to their social context. They are embedded in social and organizational communities, and the nature of this embeddedness has important implications not only for understanding their behavior but also for how they should be approached in policy terms
Magnetic excitations in underdoped Ba(Fe1-xCox)2As2 with x=0.047
The magnetic excitations in the paramagnetic-tetragonal phase of underdoped
Ba(Fe0.953Co0.047)2As2, as measured by inelastic neutron scattering, can be
well described by a phenomenological model with purely diffusive spin dynamics.
At low energies, the spectrum around the magnetic ordering vector Q_AFM
consists of a single peak with elliptical shape in momentum space. At high
energies, this inelastic peak is split into two peaks across the direction
perpendicular to Q_AFM. We use our fittings to argue that such a splitting is
not due to incommensurability or propagating spin-wave excitations, but is
rather a consequence of the anisotropies in the Landau damping and in the
magnetic correlation length, both of which are allowed by the tetragonal
symmetry of the system. We also measure the magnetic spectrum deep inside the
magnetically-ordered phase, and find that it is remarkably similar to the
spectrum of the paramagnetic phase, revealing the strongly overdamped character
of the magnetic excitations.Comment: 12 pages, 7 figure
Recommended from our members
Sequence Stratigraphy, Depositional Systems, and Production Trends in the Atoka Series and Mid-Pennsylvanian Cleveland and Marmaton Formations, Western Anadarko Basin
Slides from Sequence Stratigraphy, Depositional Systems, and Production Trends in the Atoka Series and Mid-Pennsylvanian Cleveland and Marmaton Formations, Western Anadarko Basin Workshop Presented by the Bureau of Economic Geology State of Texas Advanced Resource Recovery (STARR) Program and PTTC Texas and SE New Mexico Region November 10, 2009 Ellison Miles Geotechnology Institute, DallasBureau of Economic Geolog
Neutrino Mass, Sneutrino Dark Matter and Signals of Lepton Flavor Violation in the MRSSM
We study the phenomenology of mixed-sneutrino dark matter in the Minimal
R-Symmetric Supersymmetric Standard Model (MRSSM). Mixed sneutrinos fit
naturally within the MRSSM, as the smallness (or absence) of neutrino Yukawa
couplings singles out sneutrino A-terms as the only ones not automatically
forbidden by R-symmetry. We perform a study of randomly generated sneutrino
mass matrices and find that (i) the measured value of is well
within the range of typical values obtained for the relic abundance of the
lightest sneutrino, (ii) with small lepton-number-violating mass terms
for the right-handed sneutrinos, random
matrices satisfying the constraint have a decent probability of
satisfying direct detection constraints, and much of the remaining parameter
space will be probed by upcoming experiments, (iii) the terms radiatively generate appropriately small Majorana neutrino
masses, with neutrino oscillation data favoring a mostly sterile lightest
sneutrino with a dominantly mu/tau-flavored active component, and (iv) a
sneutrino LSP with a significant mu component can lead to striking signals of
e-mu flavor violation in dilepton invariant-mass distributions at the LHC.Comment: Revised collider analysis in Sec. 5 after fixing error in particle
spectrum, References adde
The Factor Analysis of Ipsative Measures
This article deals with the problem of analyzing sets of ipsative variables using the common factor model. We demonstrate that the usual assumptions of the common factor model, especially the assumption of uncorrelated disturbances, are not appropriate for sets of ipsative variables. We develop a common factor model that takes into account the ipsative properties of such data and show how this model can be applied to any set of ipsative measures using the methods of confirmatory factor analysis. We then suggest that the application of this model may be useful in modeling the latent content of sets ofrankings and other measures that have the ipsative property as a result of the measurement procedure. Finally, we apply the model to Kohn's measures of parental values, using sample data from the General Social Surveys.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68736/2/10.1177_004912418000900206.pd
Quantification of DNA-associated proteins inside eukaryotic cells using single-molecule localization microscopy
Development of single-molecule localization microscopy techniques has allowed nanometre scale localization accuracy inside cells, permitting the resolution of ultra-fine cell structure and the elucidation of crucial molecular mechanisms. Application of these methodologies to understanding processes underlying DNA replication and repair has been limited to defined in vitro biochemical analysis and prokaryotic cells. In order to expand these techniques to eukaryotic systems, we have further developed a photo-activated localization microscopy-based method to directly visualize DNA-associated proteins in unfixed eukaryotic cells. We demonstrate that motion blurring of fluorescence due to protein diffusivity can be used to selectively image the DNA-bound population of proteins. We designed and tested a simple methodology and show that it can be used to detect changes in DNA binding of a replicative helicase subunit, Mcm4, and the replication sliding clamp, PCNA, between different stages of the cell cycle and between distinct genetic backgrounds
Complete Genome Sequence and Comparative Metabolic Profiling of the Prototypical Enteroaggregative Escherichia coli Strain 042
Background \ud
Escherichia coli can experience a multifaceted life, in some cases acting as a commensal while in other cases causing intestinal and/or extraintestinal disease. Several studies suggest enteroaggregative E. coli are the predominant cause of E. coli-mediated diarrhea in the developed world and are second only to Campylobacter sp. as a cause of bacterial-mediated diarrhea. Furthermore, enteroaggregative E. coli are a predominant cause of persistent diarrhea in the developing world where infection has been associated with malnourishment and growth retardation. \ud
\ud
Methods \ud
In this study we determined the complete genomic sequence of E. coli 042, the prototypical member of the enteroaggregative E. coli, which has been shown to cause disease in volunteer studies. We performed genomic and phylogenetic comparisons with other E. coli strains revealing previously uncharacterised virulence factors including a variety of secreted proteins and a capsular polysaccharide biosynthetic locus. In addition, by using Biologâ„¢ Phenotype Microarrays we have provided a full metabolic profiling of E. coli 042 and the non-pathogenic lab strain E. coli K-12. We have highlighted the genetic basis for many of the metabolic differences between E. coli 042 and E. coli K-12. \ud
\ud
Conclusion \ud
This study provides a genetic context for the vast amount of experimental and epidemiological data published thus far and provides a template for future diagnostic and intervention strategies
The intracluster magnetic field power spectrum in A2199
We investigate the magnetic field power spectrum in the cool core galaxy
cluster A2199 by analyzing the polarized emission of the central radio source
3C338. The polarized radiation from the radio emitting plasma is modified by
the Faraday rotation as it passes through the magneto-ionic intracluster
medium. We use Very Large Array observations between 1665 and 8415 MHz to
produce detailed Faraday rotation measure and fractional polarization images of
the radio galaxy. We simulate Gaussian random three-dimensional magnetic field
models with different power-law power spectra and we assume that the field
strength decreases radially with the thermal gas density as n_e^{\eta}. By
comparing the synthetic and the observed images with a Bayesian approach, we
constrain the strength and structure of the magnetic field associated with the
intracluster medium. We find that the Faraday rotation toward 3C338 in A2199 is
consistent with a magnetic field power law power spectrum characterized by an
index n=(2.8 \pm 1.3) between a maximum and a minimum scale of fluctuation of
\Lambda_{max}=(35 \pm 28) kpc and \Lambda_{min}=(0.7 \pm 0.1) kpc,
respectively. By including in the modeling X-ray cavities coincident with the
radio galaxy lobes, we find a magnetic field strength of =(11.7 \pm 9.0)
\mu G at the cluster center. Further out, the field decreases with the radius
following the gas density to the power of \eta=(0.9 \pm 0.5).Comment: 17 pages, 12 figures, A&A accepte
Higgs friends and counterfeits at hadron colliders
We consider the possibility of "Higgs counterfeits" - scalars that can be
produced with cross sections comparable to the SM Higgs, and which decay with
identical relative observable branching ratios, but which are nonetheless not
responsible for electroweak symmetry breaking. We also consider a related
scenario involving "Higgs friends," fields similarly produced through gg fusion
processes, which would be discovered through diboson channels WW, ZZ, gamma
gamma, or even gamma Z, potentially with larger cross sections times branching
ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs
counterfeit, rather than directly pointing towards the origin of the weak
scale, would indicate the presence of new colored fields necessary for the
sizable production cross section (and possibly new colorless but electroweakly
charged states as well, in the case of the diboson decays of a Higgs friend).
These particles could easily be confused for an ordinary Higgs, perhaps with an
additional generation to explain the different cross section, and we emphasize
the importance of vector boson fusion as a channel to distinguish a Higgs
counterfeit from a true Higgs. Such fields would naturally be expected in
scenarios with "effective Z's," where heavy states charged under the SM produce
effective charges for SM fields under a new gauge force. We discuss the
prospects for discovery of Higgs counterfeits, Higgs friends, and associated
charged fields at the LHC.Comment: 27 pages, 5 figures. References added and typos fixe
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