6,046 research outputs found
Shaker slip-plate adapter
Magnesium adapter ties in all of the attachment bosses on a horizontal slip table and makes a rigid coupling which terminates in a single row of attachment bosses at the edge of the horizontal plate. This eliminates ineffective dissipation of the driving force in vibration tests
Ossification of ungular cartilages in front feet of cold-blooded trotters - a clinical radiographic evaluation of development over time
BACKGROUND: It has not yet been shown that ossification of ungular cartilages (OUC) is a pathological condition. Beside heredity, factors such as sex, age, repeated concussion, local trauma, hoof and body size have been suggested as contributing factors for OUC development. By comparing radiographs of front hooves from cold-blooded trotters with different age we wanted to evaluate when development of OUC in cold-blooded trotters occurs and if and when it stabilizes in relation to age and workload. Diagnosis and grading of OUC were based on radiological field examinations of 649 Swedish and Norwegian cold-blooded trottersâ front hooves. A hundred and forty-seven of the horses were re-examined 3-13 years (mean age 9, median 8 years) after the first occasion. All radiographs were evaluated blind, using two different grading systems for OUC. Work load, in form of number of races completed, and body size score were collected from official data. Four statistical ordinal regression models were used, compared and evaluated. RESULTS: We identified a breakpoint at 2.8â±â0.38 years of age when ossification ends and proposed a simpler grading system with more consistent results. There was no significant correlation between body size and grade of OUC. Comparison of different statistical methods for evaluation of ordinal data revealed a piecewise linear regression model as most suitable. CONCLUSIONS: Individuals with OUC developed this condition during the stage of life when their hooves develop in size. Results from this study can assist equine practitioners when examining and for understanding this condition in their clinical work and is also beneficial for the Scandinavian equine industry when devising breeding programs
Distinct nature of static and dynamic magnetic stripes in cuprate superconductors
We present detailed neutron scattering studies of the static and dynamic
stripes in an optimally doped high-temperature superconductor,
LaCuO. We find that the dynamic stripes do not disperse towards the
static stripes in the limit of vanishing energy transfer. We conclude that the
dynamic stripes observed in neutron scattering experiments are not the
Goldstone modes associated with the broken symmetry of the simultaneously
observed static stripes, but rather that the signals originate from different
domains in the sample. These domains may be related by structural twinning, or
may be entirely different phases, where the static stripes in one phase are
pinned versions of the dynamic stripes in the other. Our results explain
earlier observations of unusual dispersions in underdoped
LaSrCuO () and LaBaCuO ().
Our findings are relevant for all compounds exhibiting magnetic stripes, and
may thus be a vital part in unveiling the nature of high temperature
superconductivity
Ion pairing in model electrolytes: A study via three particle correlation functions
A novel integral equations approach is applied for studying ion pairing in
the restricted primitive model (RPM) electrolyte, i. e., the three point
extension (TPE) to the Ornstein-Zernike integral equations. In the TPE
approach, the three-particle correlation functions are obtained. The TPE results are compared to molecular
dynamics (MD) simulations and other theories. Good agreement between TPE and MD
is observed for a wide range of parameters, particularly where standard
integral equations theories fail, i. e., low salt concentration and high ionic
valence. Our results support the formation of ion pairs and aligned ion
complexes.Comment: 43 pages (including 18 EPS figs) - RevTeX 4 - J. Chem. Phys. (in
press
Mean-Field HP Model, Designability and Alpha-Helices in Protein Structures
Analysis of the geometric properties of a mean-field HP model on a square
lattice for protein structure shows that structures with large number of switch
backs between surface and core sites are chosen favorably by peptides as unique
ground states. Global comparison of model (binary) peptide sequences with
concatenated (binary) protein sequences listed in the Protein Data Bank and the
Dali Domain Dictionary indicates that the highest correlation occurs between
model peptides choosing the favored structures and those portions of protein
sequences containing alpha-helices.Comment: 4 pages, 2 figure
On the Clark-alpha model of turbulence: global regularity and long--time dynamics
In this paper we study a well-known three--dimensional turbulence model, the
filtered Clark model, or Clark-alpha model. This is Large Eddy Simulation (LES)
tensor-diffusivity model of turbulent flows with an additional spatial filter
of width alpha (). We show the global well-posedness of this model with
constant Navier-Stokes (eddy) viscosity. Moreover, we establish the existence
of a finite dimensional global attractor for this dissipative evolution system,
and we provide an anaytical estimate for its fractal and Hausdorff dimensions.
Our estimate is proportional to , where is the integral spatial
scale and is the viscous dissipation length scale. This explicit bound is
consistent with the physical estimate for the number of degrees of freedom
based on heuristic arguments. Using semi-rigorous physical arguments we show
that the inertial range of the energy spectrum for the Clark- model has
the usual Kolmogorov power law for wave numbers and
decay power law for This is evidence that the
Clark model parameterizes efficiently the large wave numbers within
the inertial range, , so that they contain much less translational
kinetic energy than their counterparts in the Navier-Stokes equations.Comment: 11 pages, no figures, submitted to J of Turbulenc
Geometric Integration of Hamiltonian Systems Perturbed by Rayleigh Damping
Explicit and semi-explicit geometric integration schemes for dissipative
perturbations of Hamiltonian systems are analyzed. The dissipation is
characterized by a small parameter , and the schemes under study
preserve the symplectic structure in the case . In the case
the energy dissipation rate is shown to be asymptotically
correct by backward error analysis. Theoretical results on monotone decrease of
the modified Hamiltonian function for small enough step sizes are given.
Further, an analysis proving near conservation of relative equilibria for small
enough step sizes is conducted.
Numerical examples, verifying the analyses, are given for a planar pendulum
and an elastic 3--D pendulum. The results are superior in comparison with a
conventional explicit Runge-Kutta method of the same order
Origin of Native Driving Force in Protein Folding
We derive an expression with four adjustable parameters that reproduces well
the 20x20 Miyazawa-Jernigan potential matrix extracted from known protein
structures. The numerical values of the parameters can be approximately
computed from the surface tension of water, water-screened dipole interactions
between residues and water and among residues, and average exposures of
residues in folded proteins.Comment: LaTeX file, Postscript file; 4 pages, 1 figure (mij.eps), 2 table
Natural iron enrichment around the Antarctic Peninsula in the Southern Ocean
As part of the US-AMLR program in January-February of 2006, 99 stations in
the South Shetland Islands-Antarctic Peninsula region were sampled to
understand the variability in hydrographic and biological properties related
to the abundance and distribution of krill in this area. Concentrations of
dissolved iron (DFe) and total acid-leachable iron (TaLFe) were measured in
the upper 150 m at 16 of these stations (both coastal and pelagic waters) to
better resolve the factors limiting primary production in this area and in
downstream waters of the Scotia Sea. The concentrations of DFe and TaLFe in
the upper mixed layer (UML) were relatively high in Weddell Sea Shelf Waters
(~0.6 nM and 15 nM, respectively) and low in Drake Passage waters
(~0.2 nM and 0.9 nM, respectively). In the Bransfield
Strait, representing a mixture of waters from the Weddell Sea and the
Antarctic Circumpolar Current (ACC), concentrations of DFe were ~0.4 nM
and of TaLFe ~1.7 nM. The highest concentrations of DFe and TaLFe
in the UML were found at shallow coastal stations close to Livingston Island
(~1.6 nM and 100 nM, respectively). The ratio of TaLFe:DFe varied
with the distance to land: ~45 at the shallow coastal stations, ~15
in the high-salinity waters of Bransfield Strait, and ~4 in ACC
waters. Concentrations of DFe increased slightly with depth in the water
column, while that of TaLFe did not show any consistent trend with depth.
Our Fe data are discussed in regard to the hydrography and water circulation
patterns in the study area, and with the hypothesis that the relatively high
rates of primary production in the central regions of the Scotia Sea are
partially sustained by natural iron enrichment resulting
from a northeasterly flow of iron-rich coastal waters originating in
the South Shetland Islands-Antarctic Peninsula region
Many-body GW calculations of ground-state properties: Quasi-2D electron systems and van der Waals forces
We present GW many-body results for ground-state properties of two simple but very distinct families of inhomogeneous systems in which traditional implementations of density-functional theory (DFT) fail drastically. The GW approach gives notably better results than the well-known random-phase approximation, at a similar computational cost. These results establish GW as a superior alternative to standard DFT schemes without the expensive numerical effort required by quantum Monte Carlo simulations
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