Stryker Osteonics: Prosthetic Knee Joint

We examine, within a simple bearing model of a knee joint that only consideres pure sliding, the effect of the presence of a small vertical hole in the load area on the fluid film properties. The calculations indicate that fluid is entrapped in such a hole, which, for constant load, causes a smaller minimal film separation of the two surfaces. This will lower the horizontal friction, but may also bring about surface contact in high load situations

The foraging ecology of greyheaded mollymawks at Marion Island: in relation to known longline fishing activity

Incidental mortality due to longline fishing has been implicated as the main cause for the global population decline in grey-headed mollymawks (Thalassarche chrysostoma). Two of these fisheries, within the potential foraging range of grey-headed mollymawks breeding on Marion Island, have increased drastically over the past 5–10 years. In order to understand the impacts of these fisheries on the grey-headed mollymawk population breeding on Marion Island, we studied their foraging ecology by tracking their foraging trips and sampling their diets. During the incubation stage, birds made long foraging trips, mostly towards the subtropical convergence and sub-Antarctic zones, bringing them into contact with areas of intense southern blue-fin tuna (Thunnus maccoyii) longline fishing. Females spent a higher proportion of their time within these areas than males, thus exposing themselves to a higher risk of incidental mortality from this fishery. During the early chick-rearing stage, foraging trips were shorter and to the southwest of the island in the Polar frontal and Antarctic zones, thus avoiding any contact with the southern blue-fin tuna industry. However, short foraging trips (<2 days) were made within the boundary of known Patagonian toothfish (Dissostichus eleginoides) longline sets around Marion Island. Males made a higher proportion of short foraging trips and spent more time within the boundaries of the toothfish fishery than females. These differences may account for the male-biased mortality of grey-headed mollymawks observed in the toothfish fishery around Marion Island. Although a decrease in the annual breeding population has not been detected on Marion Island as yet, we warn that the methods used to detect these changes are inaccurate in measuring short term population changes (<10 years) and that the impacts of these fisheries may already have altered the demographic structure of this population

P- and T-violating πNN\pi N N form factor

The form factor of the parity and time-reversal violating (PTV) pion-nucleon interaction is calculated from one-loop vertex diagrams. The degrees of freedom included in the effective lagrangian are nucleons, pions, $\eta$, $\rho$ and $\omega$ mesons. We show that by studying the form factor one can constrain the PTV meson-nucleon coupling constants. We evaluate the mean square radius associated with the PTV $\pi N N$ vertex. Using the mean square radius, we estimate the effect of the PTV $\pi N N$ vertex on the neutron electric dipole moment, and find a very small correction. We also extract the renormalisation group $\beta$ function and use it to discuss evolution of the PTV $\pi N N$ coupling constant beyond the hadronic mass scale.Comment: 14 pages, 2 figures. Added discussion of neutron EDM; to be published in Nucl.Phys.

Updated tests of scaling and universality for the spin-spin correlations in the 2D and 3D spin-S Ising models using high-temperature expansions

We have extended, from order 12 through order 25, the high-temperature series expansions (in zero magnetic field) for the spin-spin correlations of the spin-S Ising models on the square, simple-cubic and body-centered-cubic lattices. On the basis of this large set of data, we confirm accurately the validity of the scaling and universality hypotheses by resuming several tests which involve the correlation function, its moments and the exponential or the second-moment correlation-lengths.Comment: 21 pages, 8 figure

SS Ari: a shallow-contact close binary system

Two CCD epochs of light minimum and a complete R light curve of SS Ari are presented. The light curve obtained in 2007 was analyzed with the 2003 version of the W-D code. It is shown that SS Ari is a shallow contact binary system with a mass ratio $q=3.25$ and a degree of contact factor f=9.4(\pm0.8%). A period investigation based on all available data shows that there may exist two distinct solutions about the assumed third body. One, assuming eccentric orbit of the third body and constant orbital period of the eclipsing pair results in a massive third body with $M_3=1.73M_{\odot}$ and P_3=87.0$yr. On the contrary, assuming continuous period changes of the eclipsing pair the orbital period of tertiary is 37.75yr and its mass is about$0.278M_{\odot}$. Both of the cases suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table

Algebraic Self-Similar Renormalization in Theory of Critical Phenomena

We consider the method of self-similar renormalization for calculating critical temperatures and critical indices. A new optimized variant of the method for an effective summation of asymptotic series is suggested and illustrated by several different examples. The advantage of the method is in combining simplicity with high accuracy.Comment: 1 file, 44 pages, RevTe

The branched-chain aminotransferase proteins: Novel redox chaperones for protein disulfide isomerase-implications in Alzheimer's disease

Aims: The human branched-chain aminotransferase proteins (hBCATm and hBCATc) are regulated through oxidation and S-nitrosation. However, it remains unknown whether they share common redox characteristics to enzymes such as protein disulfide isomerase (PDI) in terms of regulating cellular repair and protein misfolding. Results: Here, similar to PDI, the hBCAT proteins showed dithiol-disulfide isomerase activity that was mediated through an S-glutathionylated mechanism. Site-directed mutagenesis of the active thiols of the CXXC motif demonstrates that they are fundamental to optimal protein folding. Far Western analysis indicated that both hBCAT proteins can associate with PDI. Co-immunoprecipitation studies demonstrated that hBCATm directly binds to PDI in IMR-32 cells and the human brain. Electron and confocal microscopy validated the expression of PDI in mitochondria (using Mia40 as a mitochondrial control), where both PDI and Mia40 were found to be co-localized with hBCATm. Under conditions of oxidative stress, this interaction is decreased, suggesting that the proposed chaperone role for hBCATm may be perturbed. Moreover, immunohistochemistry studies show that PDI and hBCAT are expressed in the same neuronal and endothelial cells of the vasculature of the human brain, supporting a physiological role for this binding. Innovation: This study identifies a novel redox role for hBCAT and confirms that hBCATm differentially binds to PDI under cellular stress. Conclusion: These studies indicate that hBCAT may play a role in the stress response of the cell as a novel redox chaperone, which, if compromised, may result in protein misfolding, creating aggregates as a key feature in neurodegenerative conditions such as Alzheimer's disease. © 2014 Mary Ann Liebert, Inc

The Saffman-Taylor problem on a sphere

The Saffman-Taylor problem addresses the morphological instability of an interface separating two immiscible, viscous fluids when they move in a narrow gap between two flat parallel plates (Hele-Shaw cell). In this work, we extend the classic Saffman-Taylor situation, by considering the flow between two curved, closely spaced, concentric spheres (spherical Hele-Shaw cell). We derive the mode-coupling differential equation for the interface perturbation amplitudes and study both linear and nonlinear flow regimes. The effect of the spherical cell (positive) spatial curvature on the shape of the interfacial patterns is investigated. We show that stability properties of the fluid-fluid interface are sensitive to the curvature of the surface. In particular, it is found that positive spatial curvature inhibits finger tip-splitting. Hele-Shaw flow on weakly negative, curved surfaces is briefly discussed.Comment: 26 pages, 4 figures, RevTex, accepted for publication in Phys. Rev.