Young Radio Pulsars in Galactic Globular Clusters

Currently three isolated radio pulsars and one binary radio pulsar with no evidence of any previous recycling are known in 97 surveyed Galactic globular clusters. As pointed out by Lyne et al., the presence of these pulsars cannot be explained by core-collapse supernovae, as is commonly assumed for their counterparts in the Galactic disk. We apply a Bayesian analysis to the results from surveys for radio pulsars in globular clusters and find the number of potentially observable non-recycled radio pulsars present in all clusters to be < 3600. Accounting for beaming and retention considerations, the implied birth rate for any formation scenario for all 97 clusters is < 0.25 pulsars per century assuming a Maxwellian distribution of velocities with a dispersion of 10 km s^{-1}. The implied birth rates for higher velocity dispersions are substantially higher than inferred for such pulsars in the Galactic disk. This suggests that the velocity dispersion of young pulsars in globular clusters is significantly lower than those of disk pulsars. These numbers may be substantial overestimates due to the fact that the currently known sample of young pulsars is observed only in metal-rich clusters. We propose that young pulsars may only be formed in globular clusters with metallicities with log[Fe/H] > -0.6. In this case, the potentially observable population of such young pulsars is 447^{+1420}_{-399} (the error bars give the 95% confidence interval) and their birth rate is 0.012^{+0.037}_{-0.010} pulsars per century. The mostly likely creation scenario to explain these pulsars is the electron capture supernova of a OMgNe white dwarf.Comment: 13 Pages, 6 Figures, 4 Tables, to appear in Ap

Effects of metal-on-metal wear on the host immune system and infection in hip arthroplasty

Methods We reviewed the available literature on the influence of degradation products of MOM bearings in total hip arthroplasties on infection risk. Results Wear products were found to influence the risk of infection by hampering the immune system, by inhibiting or accelerating bacterial growth, and by a possible antibiotic resistance and heavy metal co-selection mechanism. Interpretation Whether or not the combined effects of MOM wear products make MOM bearings less or more prone to infection requires investigation in the near future

Approximations of copulas via transformed moments

We study the problem of approximating the copula and copula density function from a sequence of transformed moments. In particular, when frequency moments of an underlying bivariate distribution are available, the uniform convergence of the reconstructed copula and the rate of approximation of the copula density function are obtained. Finally, the accuracies of the approximation and estimation are illustrated in a simulation study

Resource testing of modified plain bearings for the aviation industry

The resource tests of plain bearings with metal-polymer tribo-systems developed for the aviation industry are presented. The purpose of the work is to determine the wear resistance of modern anti-friction polymer materials in plain bearings in comparison with metal fluoroplastic tape. The uniqueness of the tests lies in the use of a combination of high-performance polymer materials in a pair with chromium and molybdenum coating during the reversible movements of plain bearings. Since the use of such bearings is mass in nature, the use of titanium materials in the manufacture of bearing cages will allow to significantly reduce the weight of the aircraft and increase its efficiency. It was determined that a plain bearing with a polymer material of carbon and polyamide fibers and PTFE with functional additives shows a wear resistance 1.8-2 times greater on the segment of 40-100 thousand cycles than bearings with other materials during laboratory resource tests. Also, industrial tests have established that after 2 million cycles, a hinged bearing with a metal-polymer tape shows a result that is 1.2-1.5 times lower in wear resistance than polymer materials, but all these results are within the tolerances of normal bearing operation. Industrial tests have proven that at replacing the inner ring of a plain sliding bearing with a titanium alloy with a molybdenum coating, the wear resistance is almost the same or slightly lower than when the polymer rubs against steel. Technological recommendations have been developed and a new design and materials of plain sliding bearings with polymer anti-friction coatings for the aviation industry have been proposed. The implementation of technological recommendations in the production of bearings will allow to move away from the universality of the use of plain bearings and extend their wear resistance and durability in general due to the use of the full thickness of the polymer material and the development of bearings with predicted characteristics for a specific task