Narrow Results

The energies of cosmic rays, fully ionized charged nuclei, extend over a wide range up to 10²⁰ eV. A particularly interesting energy region spans from 10¹⁴ to 10¹⁸ eV, where the all-particle energy spectrum exhibits two interesting structures, the ‘knee’ and the ‘second knee’. An explanation of these features is thought to be an important step in understanding of the origin of the high-energy particles. Recent results of air shower experiments in this region are discussed. Special attention is drawn to explain the principle of air shower measurements — a simple Heitler model of (hadronic) air showers is developed.

There are no gold standard experimental models for osteoarthritis (OA). In recent years, around 25 different OA models have been reported, including surgically induced, enzymatically or chemically induced, spontaneous, genetically modified, and drug- or supplement-induced models using different animal species. Each model has its advantages and disadvantages. This chapter introduces an anterior cruciate ligament transection (ACLT)-induced OA model in rats, and the relevant histological evaluation methods for confirmation of the successful establishment of this model.

Attrition and eventual loss of articular cartilage are crucial elements in the pathophysiology of osteoarthritis. Preventing the breakdown of cartilage is believed to be critical in order to preserve the functional integrity of a joint. Magnetic resonance imaging (MRI) and advanced digital postprocessing techniques have opened novel possibilities for in vivo quantitative analysis of cartilage morphology, structure, and function in health and disease. Techniques of semiquantitative scoring of human knee cartilage pathology and quantitative assessment of human cartilage have recently been developed. Though cartilage represents a thin layer of material relative to the size of voxels typically used for MRI, cartilage thickness and volume have been quantified in human and in small animals. MRI-detected cartilage loss has been shown to be more sensitive than radiography-detected joint space narrowing. Progress made in MRI technology in the last few years allows longitudinal studies of knee cartilage with an accuracy good enough to follow disease-caused changes and to evaluate the therapeutic effects of chondroprotective drugs.

Ceramic bearing surfaces have been used over the last 25 years as a clinical solution to the polyethylene wear debris which has been attributed as the major cause of aseptic loosening in total hip arthroplasties. Research has continued over the last 15 years to transpose the technology from the hip to the knee. Monolithic ceramic knee devices have been implanted, mainly in Japan, but the problem of the femoral fixation has remained. The improvement in the polyethylene materials, coupled with the more congruent knee designs, has focused the major issue to wear particle generation as opposed to fatigue or delamination.

The focus of the Brite EuRam project “Advanced Metal to Ceramic Joining Techniques To Optimise low-friction knee prostheses” was to address the issue of fixation in conjunction with the optimum ceramic bearing surface. This was achieved by the development of a biocompatible active alloy braze for joining medical grade Y-TZP zirconia to titanium alloy. Through optimised chemistry and processing conditions a high strength active alloy braze joint was obtained that satisfied all biological and mechanical requirements.

Extensive Finite Element analysis, mechanical, fatigue, wear and compression strength testing were performed to validate the new concept.

Implants (hemitrochlea) were prepared from nacre (mother of pearl) and implanted in the knees of sheep. Cartilage formed at the endoarticular surfaces of the implant, and new endochondral bone was also formed at the interface between the host cancellous bone and nacre. These phenomena resulted in the total integration of the implant.

The composition of the cosmic rays in the knee region (≈ 10⁴ TeV/nucleus) of all particle spectrum is considered to be the result of the particle acceleration and propagation from the astrophysical sources. The steeply falling cosmic ray spectrum makes a direct measurement of the composition difficult, but it can be inferred from the measurements of the showers generated by the interaction of the primary cosmic ray with the Earth atmosphere. In particular the characteristics of the muon bundles produced in the showers depend on the primary cosmic ray nature. The ANTARES telescope is situated 2.5 km under the Mediterranean Sea off the coast of Toulon, France. It is taking data in its complete configuration since 2008 with nearly 900 photomultipliers installed on 12 lines. The trigger rate is a few Hz dominated by atmospheric muons. A method using a multiple layered neural network as a classifier was developed to estimate the relative contribution of proton and iron showers from the energy and multiplicity distribution of the muon tracks reaching the detector. The performance of the method estimated from simulation will be discussed.