1,738 research outputs found
Experimental joint immobilization in guinea pigs. Effects on the knee joint
In young and adult guinea pigs, the aftermath experimentally induced by the immobilization of the knee joint in hyperextended forced position was studied. Joint immobilization which varied from one to nine weeks was attained by plaster. Eighty knee joints were examined macro and microscopically. Findings included: (1) muscular hypotrophy and joint stiffness in all animals, directly proportional to the length of immobilization; (2) haemoarthrosis in the first week; (3) intra-articular fibrous tissue proliferation ending up with fibrous ankylosis; (4) hyaline articular cartilage erosions; (5) various degrees of destructive menisci changes. A tentative explanation of the fibrous tissue proliferation and of the cartilage changes is offered
Merger Transitions in Brane--Black-Hole Systems: Criticality, Scaling, and Self-Similarity
We propose a toy model for study merger transitions in a curved spaceime with
an arbitrary number of dimensions. This model includes a bulk N-dimensional
static spherically symmetric black hole and a test D-dimensional brane
interacting with the black hole. The brane is asymptotically flat and allows
O(D-1) group of symmetry. Such a brane--black-hole (BBH) system has two
different phases. The first one is formed by solutions describing a brane
crossing the horizon of the bulk black hole. In this case the internal induced
geometry of the brane describes D-dimensional black hole. The other phase
consists of solutions for branes which do not intersect the horizon and the
induced geometry does not have a horizon. We study a critical solution at the
threshold of the brane-black-hole formation, and the solutions which are close
to it. In particular, we demonstrate, that there exists a striking similarity
of the merger transition, during which the phase of the BBH-system is changed,
both with the Choptuik critical collapse and with the merger transitions in the
higher dimensional caged black-hole--black-string system.Comment: 9 pages 2 figures; additional remarks and references are added at
Section IX "Discussion
Theory of Anisotropic Hopping Transport due to Spiral Correlations in the Spin-Glass Phase of Underdoped Cuprates
We study the in-plane resistivity anisotropy in the spin-glass phase of the
high- cuprates, on the basis of holes moving in a spiral spin
background. This picture follows from analysis of the extended model with
Coulomb impurities. In the variable-range hopping regime the resistivity
anisotropy is found to have a maximum value of around 90%, and it decreases
with temperature, in excellent agreement with experiments in
LaSrCuO. In our approach the transport anisotropy is due to the
non-collinearity of the spiral spin state, rather than an intrinsic tendency of
the charges to self-organize.Comment: 5 pages, 4 figures; expanded versio
Stability of the spiral phase in the 2D extended t-J model
We analyze the t-t'-t''-J model at low doping by chiral perturbation theory
and show that the (1,0) spiral state is stabilized by the presence of t',t''
above critical values around 0.2J, assuming t/J=3.1. We find that the (magnon
mediated) hole-hole interactions have an important effect on the region of
charge stability in the space of parameters t',t'', generally increasing
stability, while the stability in the magnetic sector is guaranteed by the
presence of spin quantum fluctuations (order from disorder effect). These
conclusions are based on perturbative analysis performed up to two loops, with
very good convergence.Comment: 7 pages, 6 figure
Multi-waveband Emission Maps of Blazars
We are leading a comprehensive multi-waveband monitoring program of 34
gamma-ray bright blazars designed to locate the emission regions of blazars
from radio to gamma-ray frequencies. The "maps" are anchored by sequences of
images in both total and polarized intensity obtained with the VLBA at an
angular resolution of ~ 0.1 milliarcseconds. The time-variable linear
polarization at radio to optical wavelengths and radio to gamma-ray light
curves allow us to specify the locations of flares relative to bright
stationary features seen in the images and to infer the geometry of the
magnetic field in different regions of the jet. Our data reveal that some
flares occur simultaneously at different wavebands and others are only seen at
some of the frequencies. The flares are often triggered by a superluminal knot
passing through the stationary "core" on the VLBA images. Other flares occur
upstream or even parsecs downstream of the core.Comment: 5 pages, including 2 figures; to be published in Journal of
Astrophysics and Astronomy, as part of proceedings of the meeting
"Multiwavelength Variability of Blazars" held in Guangzhou, China, in
September 201
Structural and energetic properties of nickel clusters:
The four most stable structures of Ni clusters with from 2 to 150
have been determined using a combination of the embedded-atom method in the
version of Daw, Baskes and Foiles, the {\it variable metric/quasi-Newton}
method, and our own {\it Aufbau/Abbau} method. A systematic study of
energetics, structure, growth, and stability of also larger clusters has been
carried through without more or less severe assumptions on the initial
geometries in the structure optimization, on the symmetry, or on bond lengths.
It is shown that cluster growth is predominantly icosahedral with of
{\it fcc}, {\it tetrahedral} and {\it decahedral} growth. For the first time in
unbiased computations it is found that Ni is the multilayer (third
Mackay) icosahedron. Further, we point to an enhanced ability of {\it fcc}
clusters to compete with the icosahedral and decahedral structures in the
vicinity of N=79. In addition, it is shown that conversion from the {\it
hcp}/anti-Mackay kind of icosahedral growth to the {\it fcc}/Mackay one occurs
within a transition layer including several cluster sizes. Moreover, we present
and apply different analytical tools in studying structural and energetic
properties of such a large class of clusters. These include means for
identifying the overall shape, the occurrence of atomic shells, the similarity
of the clusters with, e.g., fragments of the {\it fcc} crystal or of a large
icosahedral cluster, and a way of analysing whether the -atom cluster can be
considered constructed from the -atom one by adding an extra atom. In
addition, we compare in detail with results from chemical-probe experiment.
Maybe the most central result is that first for clusters with above 80
general trends can be identified.Comment: 37 pages, 11 figure
Parallel-propagated frame along null geodesics in higher-dimensional black hole spacetimes
In [arXiv:0803.3259] the equations describing the parallel transport of
orthonormal frames along timelike (spacelike) geodesics in a spacetime
admitting a non-degenerate principal conformal Killing-Yano 2-form h were
solved. The construction employed is based on studying the Darboux subspaces of
the 2-form F obtained as a projection of h along the geodesic trajectory. In
this paper we demonstrate that, although slightly modified, a similar
construction is possible also in the case of null geodesics. In particular, we
explicitly construct the parallel-transported frames along null geodesics in
D=4,5,6 Kerr-NUT-(A)dS spacetimes. We further discuss the parallel transport
along principal null directions in these spacetimes. Such directions coincide
with the eigenvectors of the principal conformal Killing-Yano tensor. Finally,
we show how to obtain a parallel-transported frame along null geodesics in the
background of the 4D Plebanski-Demianski metric which admits only a conformal
generalization of the Killing-Yano tensor.Comment: 17 pages, no figure
Simulation of the Impact on the Workload of the Enlargement of the Clinical Staff of a Specialistic Reference Center
Quality of care and patient satisfaction are important aspects of high standard care. If clinical staff is subject to an elevated workload there is a possible decrease of both. This justifies the development of tools to quantify the workload and to find organizational changes that will normalize it. We have previously developed a simulation system to quantify the workload of the staff working in a regional reference center for the treatment of bleeding and hemorrhagic disorders. The goal of this new work is to simulate, through an agent-based model, the impact of adding a physician to the staff. Ten sets of initial parameters were defined to simulate ten typical weeks. Results show that the introduction of the new physician together with a second ambulatory room can reduce the workload of all the staff to the expected 8-hour. In this situation, in which the staff workload does not exceed the daily capacity, we may suppose that an increase in the quality of care and patient satisfaction will be possible
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