Search

Ceramic bearings have several desirable properties, such as resistance to wear, hardness, and biocompatibility, that favour it as an articulating surface in hip arthroplasty. However, ceramic fracture remains a concern. We have reviewed the contemporary literature, addressing the factors that can influence the incidence of ceramic bearing surface fracture.Cite this article: Bone Joint J2019;101-B:897–901.

Neutron generation from deuterated polystylene and deuterium cluster targets by using femto- second high intensity lasers have been studied, as well as an analysis by the 1D PIC computer simulation to study the dynamics of the laser matter interaction.

Experimental investigations on soft x-ray lasers based on optical field ionization of gases with an ultrashort-pulse terawatt laser system are presented. The x-ray laser active medium was created using an elongated gas puff target formed by pulsed injection of a small amount of gas from a high-pressure electromagnetic valve through a nozzle in the form of a slit. The target was irradiated with a laser pulses from a 20-fs. 50-mJ Ti:Sapphire (Ti:S) laser system Both recombination and collisional soft x-ray laser scheme have been studied. Soft x-ray spectra from nitrogen, oxygen, and xenon targets are presented and discussed.

The wavelength tunability of high harmonic generation is presented. By applying intense femtosecond laser pulse to gaseous medium, the wavelengths of high-order harmonics could be tuned. The wavelength shift large enough to cover the interval between adjacent orders was obtained in harmonics from Ar and Ne atoms driven by 25 fs pulses, opening a way to realize a tunable coherent x-ray source.

We report the first observation of X-ray emission (4 - 18 nm) from small-sized Ne clusters heated by high-intensity, 25-100 fs laser pulses. The Ne spectrum started to drastically change in emitting ions from Ne5+to Ne7+below the pre-expansion temperature of -120 °C. The significant change in the spectrum is attributed to the collisional heating of small-sized Ne clusters formed in the cryogenically cooled gas jet. Though the size of Ne clusters in our experiment is estimated to be quite small, i.e. a few tens of atoms per cluster, and thus they were undetectable by the standard Rayleigh scattering technique, the appearance of spectral lines of Ne7+ions presented clear evidence of collisional heating that occurred in near-solid-density cluster. By extending the laser pulse length from 25 fs to 100 fs, considerably higher X-ray yield from the highest charge state Ne7+was observed in the covered spectral region, showing more efficient absorption of 100 fs laser pulse.

We have developed a silver-mirror-based multipass preamplifier for a broadband amplification in a terawatt Ti:sapphire laser. With the extremely broad bandwidth of the silver mirrors, a very broad amplified spectrum can be generated at an amplified energy of 4 mJ; the amplified spectral width is 65 nm at half maximum and 160 nm at −25 dB without any spectral shaping technique. Such a broad amplification can be explained well by the simulation that includes gain narrowing and gain saturation. Even after a further amplification to an energy of 600 mJ, the amplified spectrum is broad enough to support an ~20 fs transform-limited pulse duration.

Irradiation of the N−D stretching band in crystalline deuterium-doped ammonium copper Tutton salt rotates the ammonium ion and changes the conformation of molecules about the copper. The crystal salt exists in at least two different crystal forms, each form containing a particular Jahn−Teller distorted copper conformation. We consider only the “A” form crystal. In this crystal, the minority conformation (B) appears with the majority conformation (A) as the temperature is raised. The spectral holes and antiholes produced by the changes in conformation occur in patterns that depend on the exact frequency of irradiation. Each pattern appears and eventually decays with different kinetics over a range of times. The variation of the hole widths, measured at different temperatures, reveals the presence of various conformations in the crystal lattice. This inhomogeneity is related to the statistical distribution of conformations A and B weighted by their thermal populations. The kinetics of the decay of the holes yields the rate constants of transformation from one conformation to the other. The numerical values and the kinetic model agree well with the experimental data.

The title compound doped with a small amount of deuterium shows infrared bands due to the N−D and O−D stretching vibrations. When one of the N−D bands is irradiated with an infrared laser, holes and anti-holes are produced. The pattern of these holes/anti-holes depends on the irradiation time. A ten-minute irradiation produces holes/anti-holes in the N−D bands only. A ten-second irradiation produces holes/anti-holes in the O−D bands as well. The features produced by the ten-second irradiation decay during the longer irradiation. Thus, the burning and decay kinetics of the Tutton salts involve processes that occur on at least two time scales.

A simplified model is presented to predict the strength variations of brittle matrix composites, reinforced by steel fibres, with the variations of fibre parameters—length, diameter and volume fraction. This model predicts that its tensile and flexural strength increase non‐linearly with the fibre volume fraction. It also predicts that similar non‐linear behaviour should be observed with the reduction of the fibre diameter when other parameters are kept constant. The experimental results support both these theoretical predictions. It is also explained why an increase in the fibre length does not always significantly increase the fracture toughness. The objective of this paper is not to explain and understand in great detail the science of all phenomena responsible for the strength increase of fibre reinforced brittle matrix composites, but to provide a simple engineering explanation as to why its strength increases with the fibre addition, and how this increase can be quantitatively related to the variations in fibre parameters—fibre volume fraction, fibre length and diameter. These simplifying steps are needed to provide a tool that the practicing engineers can use to predict the brittle matrix strength variation with the fibre parameters. In the area of geomechanics, the results presented here can be used to assess and predict the behaviour of fibre‐reinforced earth. Copyright © 2000 John Wiley & Sons, Ltd.

We studied a family with nonprogressive congenital ataxia (NPCA) previously reported in 1985. Follow-up evaluation documented a nonprogressive course. Older family members developed ataxic spells and vertical oscillopsia triggered by stress and exercise. Linkage analysis using a 10K single-nucleotide polymorphism array found suggestive linkage to four loci on chromosomes 1q44, 5q35.1-35.3, 7q36.2-36.3, and 9q31.2-32 and ruled out linkage to the NPCA locus on 3p, proving genetic heterogeneity for autosomal dominant NPCA.