558 research outputs found
Utility of (11)C-methionine and (11)C-donepezil for imaging of Staphylococcus aureus induced osteomyelitis in a juvenile porcine model:comparison to autologous (111)In-labelled leukocytes, (99m) Tc-DPD, and (18)F-FDG
The aim of this study was to compare (11)C-methionine and (11)C-donepezil positron emission tomography (PET) with (111)In-labeled leukocyte and (99m)Tc-DPD (Tc-99m 3,3-diphosphono-1,2-propanedicarboxylic acid) single-photon emission computed tomography (SPECT), and (18)F-fluorodeoxyglucose ((18)F-FDG) PET to improve detection of osteomyelitis. The tracersâ diagnostic utility where tested in a juvenile porcine hematogenously induced osteomyelitis model comparable to osteomyelitis in children. Five 8-9 weeks old female domestic pigs were scanned seven days after intra-arterial inoculation in the right femoral artery with a porcine strain of Staphylococcus aureus. The sequential scan protocol included Computed Tomography, (11)C-methionine and (11)C-donepezil PET, (99m)Tc-DPD and (111)In-labelled leukocytes scintigraphy, and (18)F-FDG PET. This was followed by necropsy of the pigs and gross pathology, histopathology, and microbial examination. The pigs developed a total of 24 osteomyelitic lesions, 4 lesions characterized as contiguous abscesses and pulmonary abscesses (in two pigs). By comparing the 24 osteomyelitic lesions, (18)F-FDG accumulated in 100%, (111)In-leukocytes in 79%, (11)C-methionine in 79%, (11)C-donepezil in 58%, and (99m)Tc-DPD in none. Overall, (18)F-FDG PET was superior to (111)In-leukocyte SPECT and (11)C-methionine in marking infectious lesions
Evidence for tidal interaction and merger as the origin of galaxy morphology evolution in compact groups
We present the results of a morphological study based on NIR images of 25
galaxies, with different levels of nuclear activity, in 8 Compact Groups of
Galaxies (CGs). We perform independently two different analysis: a isophotal
study and a study of morphological asymmetries. The results yielded by the two
analysis are highly consistent. For the first time, it is possible to show that
deviations from pure ellipses are produced by inhomogeneous stellar mass
distributions related to galaxy interactions and mergers. We find evidence of
mass asymmetries in 74% of the galaxies in our sample. In 59% of these cases,
the asymmetries come in pairs, and are consistent with tidal effects produced
by the proximity of companion galaxies. The symmetric galaxies are generally
small in size or mass, inactive, and have an early-type morphology. In 20% of
the galaxies we find evidence for cannibalism. In 36% of the early-type
galaxies the color gradient is positive (blue nucleus) or flat. Summing up
these results, as much as 52% of the galaxies in our sample could show evidence
of an on going or past mergers. Our observations suggest that galaxies in CGs
merge more frequently under ``dry'' conditions. The high frequency of
interacting and merging galaxies observed in our study is consistent with the
bias of our sample towards CGs of type B, which represents the most active
phase in the evolution of the groups. In these groups we also find a strong
correlation between asymmetries and nuclear activity in early-type galaxies.
This correlation allows us to identify tidal interactions and mergers as the
cause of galaxy morphology transformation in CGs.[abridge]Comment: 64 pages, 35 figures. Accepted for publication in Ap
Mott effect at the chiral phase transition and anomalous J/Psi suppression
We investigate the in-medium modification of the charmonium break-up
processes due to the Mott effect for light (pi) and open-charm (D, D*) mesons
at the chiral/deconfinement phase transition. A model calculation for the
process J/Psi + pi -> D + \bar D* + h.c. is presented which demonstrates that
the Mott effect for the D-mesons leads to a threshold effect in the thermal
averaged break-up cross section. This effect is suggested as an explanation of
the phenomenon of anomalous J/Psi suppression in the CERN NA50 experiment.Comment: 9 pages, 3 figures; final version to appear in Phys. Lett.
Guiding structures with multiply connected cross-sections: evolution of propagation in external fields at complex Robin parameters
Properties of the two-dimensional ring and three-dimensional infinitely long
straight hollow waveguide with unit width and inner radius in the
superposition of the longitudinal uniform magnetic field and
Aharonov-Bohm flux are analyzed within the framework of the scalar Helmholtz
equation under the assumption that the Robin boundary conditions at the inner
and outer confining walls contain extrapolation lengths and
, respectively, with nonzero imaginary parts. It is shown that,
compared to the disk geometry, the annulus opens up additional possibilities of
varying magnetization and currents by tuning imaginary components of the Robin
parameters on each confining circumference; in particular, the possibility of
restoring a lossless longitudinal flux by zeroing imaginary part of the
total transverse energy is discussed. The energy turns real under
special correlation between the imaginary parts of and
with the opposite signs what physically corresponds to the
equal transverse fluxes through the inner and outer interfaces of the annulus.
In the asymptotic case of the very large radius, simple expressions are derived
and applied to the analysis of the dependence of the real energy on
and . New features also emerge in the magnetic
field influence; for example, if, for the quantum disk, the imaginary energy
is quenched by the strong intensities , then for the annulus this
takes place only when the inner Robin distance is real;
otherwise, it almost quadratically depends on with the corresponding
enhancement of the reactive scattering. Closely related problem of the hole in
the otherwise uniform medium is also addressed for real and complex
extrapolation lengths with the emphasis on the comparative analysis with its
dot counterpart.Comment: 37 pages, 9 figure
Effect of tensor couplings in a relativistic Hartree approach for finite nuclei
The relativistic Hartree approach describing the bound states of both
nucleons and anti-nucleons in finite nuclei has been extended to include tensor
couplings for the - and -meson. After readjusting the parameters
of the model to the properties of spherical nuclei, the effect of
tensor-coupling terms rises the spin-orbit force by a factor of 2, while a
large effective nucleon mass sustains. The overall
nucleon spectra of shell-model states are improved evidently. The predicted
anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.Comment: 31 pages, 4 postscript figures include
Dynamic capabilities and knowledge management: an integrative role for learning?
Modern strategic management theories try to explain why firms differ, because new sources of competitive advantage are keenly sought in the dynamic and complex environment of global competition. Two areas in particular have attracted the attention of researchers: the role of dynamic capabilities, and the firm's abilities for knowledge management. In this paper, we argue that there is a link between these two concepts, which has not been fully articulated in the literature. The aim of the paper is therefore to ascertain the conceptual connection between them as a basis for future research. Our proposed framework acknowledges and critiques the distinct roots of each field, identifies boundaries, and proposes relationships between the constructs and firm performance
Toward a More Comprehensive Understanding of organizational influences On Implementation: the organization theory For Implementation Science Framework
INTRODUCTION: Implementation is influenced by factors beyond individual clinical settings. Nevertheless, implementation research often focuses on factors related to individual providers and practices, potentially due to limitations of available frameworks. Extant frameworks do not adequately capture the myriad organizational influences on implementation. Organization theories capture diverse organizational influences but remain underused in implementation science. to advance their use among implementation scientists, we distilled 70 constructs from nine organization theories identified in our previous work into theoretical domains in the Organization Theory for Implementation Science (OTIS) framework.
METHODS: The process of distilling organization theory constructs into domains involved concept mapping and iterative consensus-building. First, we recruited organization and implementation scientists to participate in an online concept mapping exercise in which they sorted organization theory constructs into domains representing similar theoretical concepts. Multidimensional scaling and hierarchical cluster analyses were used to produce visual representations (clusters) of the relationships among constructs in concept maps. Second, to interpret concept maps, we engaged members of the Cancer Prevention and Control Research Network (CPCRN) OTIS workgroup in consensus-building discussions.
RESULTS: Twenty-four experts participated in concept mapping. Based on resulting construct groupings\u27 coherence, OTIS workgroup members selected the 10-cluster solution (from options of 7-13 clusters) and then reorganized clusters in consensus-building discussions to increase coherence. This process yielded six final OTIS domains: organizational characteristics (e.g., size; age); governance and operations (e.g., organizational and social subsystems); tasks and processes (e.g., technology cycles; excess capacity); knowledge and learning (e.g., tacit knowledge; sense making); characteristics of a population of organizations (e.g., isomorphism; selection pressure); and interorganizational relationships (e.g., dominance; interdependence).
DISCUSSION: Organizational influences on implementation are poorly understood, in part due to the limitations of extant frameworks. to improve understanding of organizational influences on implementation, we distilled 70 constructs from nine organization theories into six domains. Applications of the OTIS framework will enhance understanding of organizational influences on implementation, promote theory-driven strategies for organizational change, improve understanding of mechanisms underlying relationships between OTIS constructs and implementation, and allow for framework refinement. Next steps include testing the OTIS framework in implementation research and adapting it for use among policymakers and practitioners
Rotation Curves of Spiral Galaxies
Rotation curves of spiral galaxies are the major tool for determining the
distribution of mass in spiral galaxies. They provide fundamental information
for understanding the dynamics, evolution and formation of spiral galaxies. We
describe various methods to derive rotation curves, and review the results
obtained. We discuss the basic characteristics of observed rotation curves in
relation to various galaxy properties, such as Hubble type, structure,
activity, and environment.Comment: 40 pages, 6 gif figures; Ann. Rev. Astron. Astrophys. Vol. 39, p.137,
200
Increasing Access to Organization Theories for Implementation Science
Background Organization theories offer numerous existing, highly relevant, yet largely untapped explanations of the organizational dynamics underlying evidence-based intervention (EBI) implementation. Rooted in ideas regarding power, autonomy, and control, organization theories can explain how and why organizations adopt, implement, and sustain EBI use. Although they have gained visibility, organization theories remain underused in implementation research, perhaps due to their inaccessibility to implementation scientists. To improve access to organization theory among implementation scientists, we summarized organization theories with relevance to implementation science. Methods Led by the Cancer Prevention and Control Research Network (CPCRN) Organization Theory for Implementation Science workgroup, we employed a modified Delphi process to reach a consensus among 18 experts at the intersection of organization and implementation science regarding organization theories with relevance to implementation science. From texts that described the organization theories, using standardized abstraction forms, two investigators independently abstracted information regarding constructs, propositions regarding how or why constructs might influence implementation, the potential relevance of organization theories' propositions for implementation, and overviews of each theory. The investigators then reconciled discrepancies until reaching consensus. A third investigator reviewed reconciled abstraction forms for accuracy, coherence, and completeness. Findings We identified nine organization theories with relevance to implementation science: contingency, complexity, institutional, network, organizational learning, resource dependence, sociotechnical, and transaction cost economics. From the theories, we abstracted 70 constructs and 65 propositions. An example proposition from institutional theory is: âCoercive, mimetic, and normative pressures contribute to organizationsâŠwithin an organizational field [becoming increasingly similar].â These propositions can be operationalized as levers to facilitate EBI implementation. Conclusions To increase use in the field, organization theories must be made more accessible to implementation scientists. The abstraction forms developed in this study are now publicly available on the CPCRN website with the goal of increasing access to organization theories among an interdisciplinary audience of implementation scientists through the CPCRN Scholars program and other venues. Next steps include consolidating organization theory constructs into domains and translating the resulting framework for use among researchers, policymakers and practitioners, aiding them in accounting for a comprehensive set of organization theory constructs thought to influence EBI implementation
Symmetry Energy II: Isobaric Analog States
Using excitation energies to isobaric analog states (IAS) and charge
invariance, we extract nuclear symmetry coefficients, from a mass formula, on a
nucleus-by-nucleus basis. Consistently with charge invariance, the coefficients
vary weakly across an isobaric chain. However, they change strongly with
nuclear mass and range from a_a~10 MeV at mass A~10 to a_a~22 MeV at A~240.
Following the considerations of a Hohenberg-Kohn functional for nuclear
systems, we determine how to find in practice the symmetry coefficient using
neutron and proton densities, even when those densities are simultaneously
affected by significant symmetry-energy and Coulomb effects. These results
facilitate extracting the symmetry coefficients from Skyrme-Hartree-Fock (SHF)
calculations, that we carry out using a variety of Skyrme parametrizations in
the literature. For the parametrizations, we catalog novel short-wavelength
instabilities. In comparing the SHF and IAS results for the symmetry
coefficients, we arrive at narrow (+-2.4 MeV) constraints on the symmetry
energy values S(rho) at 0.04<rho<0.13 fm^-3. Towards normal density the
constraints significantly widen, but the normal value of energy a_a^V and the
slope parameter L are found to be strongly correlated. To narrow the
constraints, we reach for the measurements of asymmetry skins and arrive at
a_a^V=(30.2-33.7) MeV and L=(35-70) MeV, with those values being again strongly
positively correlated along the diagonal of their combined region. Inclusion of
the skin constraints allows to narrow the constraints on S(rho), at
0.04<rho<0.13 fm^-3, down to +-1.1 MeV. Several microscopic calculations,
including variational, Bruckner-Hartree-Fock and Dirac-Bruckner-Hartree-Fock,
are consistent with our constraint region on S(rho).Comment: 101 pages, 27 figures, 2 tables; submitted to Nuclear Physics
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