Importance of a thin cement mantle. Autopsy studies of eight hips

The question whether thin cement mantles around cemented femoral components led to an increased frequency of cracks in the cement was asked. Microscopically, multiple cross sections of eight femurs retrieved at autopsy from clinically successful total hip replacements after prolonged in vivo service containing well fixed Harris Design 2 cemented femoral components were studied. None of the components were loose by radiographic criteria. All were fixed solidly when loaded in vitro in simulated stair climbing and gait, as assessed by high resolution micromotion sensors. The specimens were sectioned transversely at 5-mm increments. The cross sections were examined under a dissecting microscope at x 100. A thin mantle arbitrarily was defined as a mantle of less than 1 mm in thickness. The analysis of the contact radiographs showed that the routine anteroposterior and lateral radiographs underestimated the prevalence of thin cement mantles and mantle defects. Although overall on all the cross sections 9% of the aggregated cement mantles was classified as having thin cement, 92 of the 101 cement cracks occurred in areas of the mantles that were less than 1 mm thick.     

Plastic embedding and surface erosion techniques in soft tissue scanning electron microscopy

The maintenance and true pictorial representation of the complex cyto-architecture of tissues is the aim of the preparatory methods for scanning electron microscopy. The procedure employed eliminates complications associated with and due to the vacuum technology necessarily employed in electron optic instruments using a scanning beam. Tissues are fixed by vascular perfusion after the administration of heparin eliminating clot formation. The infusion of Araldite in the tissues prevents the collapse and disorganization of cells due to the combined effects of dehydration, the vacuum of the scanning electron microscope and the scanning beam. The specimens are scoured with acetone and the blocks cured, this latter process ensures their permanence; the standard procedures of gold coating, stub mounting and painting the bases of specimens with a colloidal silver solution are then carried out. The method allows magnifications of the order of 10,000 diameters and an acceptable resolution of some 50 nm is obtained. Cytoarchitectural features demonstrated by the method described are borne out by transmission microscopy.     

Eddy currents in conducting magnetic recording media

Use of metallic magnetic recording media raises the possibility that medium eddy currents will influence the recording process. The mathematical analog to diffusion of heat allows exact solutions for cases approximating those of interest. Eddy current effects are shown to be negligible for usual thicknesses of longitudinal and perpendicular media.     

Acute clinical hypocalcemic myocardial depression during rapid blood transfusion and postoperative hemodialysis: a preventable complication

Cellular and humoral immunity, and lymphoid organ pathology, have been investigated in 10 institutionalized patients with tuberous sclerosis and 10 institutionalized matched controls without the disease. Type and incidence of infections and tumours were reviewed for each group, as was current medication. Elevated serum IgM levels were found in the patients with tuberous sclerosis, but no immunological deficiency of either cellular of humoral immunity was found, nor was there a difference in infection between the groups. Only patients with tuberous sclerosis had evidence of neoplasia. No morphological or histological abnormalities of lymph nodes, spleen or thymus were present. Explanations for the difference between tuberous sclerosis and ataxia telangiectasia are discussed, together with the effect of immuno-surveillance on the development of malignancy.     

Discharge pumping of dye vapors

We report the results of a study of discharge-excited dye vapors. For 20 dyes, fluorescence output was measured as a function of buffer gas, temperature, and discharge parameters. Although fluorescence efficiencies as high as 6 percent were obtained at low power levels, saturation effects limited the output fluorescence to values corresponding to gains of less than 0.2 cm^-1.     

Effectiveness of UV Advanced Oxidation for Destruction of Micro-Pollutants

UV light has become increasingly well-established as an effective primary disinfectant for Giardia and Cryptosporidium. Many utilities are now focusing attention on control of emerging contaminants, and looking at the effectiveness of UV advanced oxidation as part of a multiple-barrier treatment train for improving water quality. In research and a small number of full-scale applications, a UV advanced oxidation process (AOP) has been shown to be effective as part of a multiple-barrier water purification train. For the City of Aurora, Colorado, the Aurora Reservoir Water Purification Facility will include UV AOP as part of a multiple barrier approach to provide disinfection, nitrosamine destruction, and micro-pollutant removal. Bench-scale testing was performed to evaluate the effectiveness of UV AOP for the control of nitrosamines and other micro-pollutants. Compounds tested included N-nitrosodimethylamine (NDMA) and 8 other nitrosamines. The test results showed predictable and repeatable destruction of NDMA, and destruction of other tested nitrosamines exceeded NDMA destruction at the same collimated beam UV doses.     

Detoxification of Synthetic Pyrethroid Insecticides by Thermophilic Microorganisms

Microbially-mediated detoxification of five synthetic pyrethroid insecticides was achieved by a mixed culture growing anaerobically at 75°C. These pyrethroids were hydrolysed to non-insecticidal products after a period of 4–8 weeks' incubation. Of these five permethrin was the most readily transformed and Fastac the most recalcitrant. The mixed culture consisted of a facultative anaerobe and two other obligate anaerobes including a methanogen. This culture was derived from terrestrial sediments from hot-springs in New Zealand. This is the first reported microbial biotransformation of these xenobiotics at a temperature of 75°C. © 1997 SCI.     

Distributed ESD protection for high-speed integrated circuits

Conventional ESD guidelines dictate a large protection device close to the pad. The resulting capacitive load causes a severe impedance mismatch and bandwidth degradation. A distributed ESD protection scheme is proposed to enable a low-loss impedance-matched transition from the package to the chip. A simple resistive model adequately predicts the ESD behavior under stress according to the charged device and human body models. The large area of the distributed ESD scheme could limit its application to designs such as distributed amplifiers, rf transceivers, A/D converters, and serial links with only a few dedicated high-speed interfaces. The distributed ESD protection is compatible with high-speed layout guidelines, requiring only low-loss transmission lines in addition to a conventional ESD device     

The effect of rhBMP-2 and PRP delivery by biodegradable β-tricalcium phosphate scaffolds on new bone formation in a non-through rabbit cranial defect model

This study evaluated whether the combination of biodegradable β-tricalcium phosphate (β-TCP) scaffolds with recombinant human bone morphogenetic protein-2 (rhBMP-2) or platelet-rich plasma (PRP) could accelerate bone formation and increase bone height using a rabbit non-through cranial bone defect model. Four non-through cylindrical bone defects with a diameter of 8-mm were surgically created on the cranium of rabbits. β-TCP scaffolds in the presence and absence of impregnated rhBMP-2 or PRP were placed into the defects. At 8 and 16 weeks after implantation, samples were dissected and fixed for analysis by microcomputed tomography and histology. Only defects with rhBMP-2 impregnated β-TCP scaffolds showed significantly enhanced bone formation compared to non-impregnated β-TCP scaffolds (P < 0.05). Although new bone was higher than adjacent bone at 8 weeks after implantation, vertical bone augmentation was not observed at 16 weeks after implantation, probably due to scaffold resorption occurring concurrently with new bone formation.     

Screening natural products for inhibitors of quinone reductase-2 using ultrafiltration LC-MS

Inhibitors of quinone reductase-2 (NQO2; QR-2) can have antimalarial activity and antitumor activities or can function as chemoprevention agents by preventing the metabolic activation of toxic quinones such as menadione. To expedite the search for new natural product inhibitors of QR-2, we developed a screening assay based on ultrafiltration liquid chromatography-mass spectrometry that is compatible with complex samples such as bacterial or botanical extracts. Human QR-2 was prepared recombinantly, and the known QR-2 inhibitor, resveratrol, was used as a positive control and as a competitive ligand to eliminate false positives. Ultrafiltration LC-MS screening of extracts of marine sediment bacteria resulted in the discovery of tetrangulol methyl ether as an inhibitor of QR-2. When applied to the screening of hop extracts from the botanical, Humulus lupulus L., xanthohumol and xanthohumol D were identified as ligands of QR-2. Inhibition of QR-2 by these ligands was confirmed using a functional enzyme assay. Furthermore, binding of xanthohumol and xanthohumol D to the active site of QR-2 was confirmed using X-ray crystallography. Ultrafiltration LC-MS was shown to be a useful assay for the discovery of inhibitors of QR-2 in complex matrixes such as extracts of bacteria and botanicals.