The cement mantle in the Exeter impaction allografting technique. A cause for concern

The postoperative radiographs of 35 patients who underwent impaction allografting of the proximal femur were reviewed. Of Gruen zones that could be clearly visualized, 39.9% contained areas where cement was absent. Even when an adequate mantle was present, cement voids were commonly seen. These cement mantle deficiencies were confirmed in a series of cadaveric impaction allografting procedures. They appear to be a consequence, at least in part, of an inadequate differential between trial and actual component sizes. Additionally, 4 patients were identified with significant component migration secondary to radiographically visible cement mantle fractures within the first 6 months of surgery. It is concluded that the surgical technique requires modification to ensure a more consistent cement mantle and clinical result.     

The role of small bowel follow-through examination in the diagnosis of coeliac disease

A retrospective study of 105 barium follow-through examinations on 102 patients suspected of having malabsorption syndrome has been carried out to assess the usefulness of this technique in the diagnosis of coeliac disease. Comparison with histological and biochemical data has been made. Of the 34 examinations on 31 patients with a proven diagnosis of coeliac disease, 30 examinations showed both abnormal X-ray and biopsy findings, two examinations showed normal X-ray appearance but abnormal jejunal biopsy and two showed normal jejunal histology but abnormal X-ray findings. There were two cases with sensitivity, non-invasive nature, ease and cheapness of the technique, barium follow-through examination is suggested as the initial investigation in patients suspected of coeliac disease.     

Accumulation of atmospheric and sedimentary PCBs and toxaphene in a Lake Michigan food web

Seston, sediment, settling organic matter, and food web members were collected from Grand Traverse Bay, Lake Michigan, between April 1997 and September 1998 to examine PCB and toxaphene biomagnification. Stable isotopes of nitrogen and carbon were analyzed in samples and used to establish trophic structure of the food web and to determine the importance of atmospheric versus sedimentary sources in delivering PCBs to the food web. Nitrogen isotopes were confounded by multiple variables in this system, particularly seasonal variation, and did not display a simple pattern of enrichment among trophic levels. However, delta13C displayed little seasonal variation and was positively correlated with PCB concentrations among food web members (r2 = 0.69). Plots of delta13C vs PCBs separate food web members into three distinct groupings comprised of invertebrates, primary forage fish, and predatory fish. Stable isotope values of the primary organic sources indicate that the atmosphere, and not the sediment, is the most likely source of PCBs to the food web of Lake Michigan. Additionally, we suggest that seston may be important in delivering PCBs to pelagic food web members and species that receive a majority of their nutrition through pelagic sources. In contrast, settling particles are implicated in delivering PCBs to benthic organisms and Mysis relicta.     

High temperature; stable,spectrally selective solar absorbers for thermochemical hydrogen production

The thermochemical reduction of water by reactions similar to the Mark I process requires a processing temperature of 730°C. The efficient utilization of solar photothermal energy conversion, in distributed collector systems, to attain this temperature will require the use of suitable spectrally selective surfaces which are stable at the operating temperature.A coating system with demonstrated high temperature capability has been developed at the Optical Sciences Center under NSF/RANN sponsorship. A silicon thin film absorber is deposited by chemical vapor deposition (CVD) on a silver thin film reflector. This optical stack is fabricated at temperatures in excess of 800°C, and the CVD technology is amenable to large scale production in a flow-through system.At 500°C the present Si-Ag system has typical solar absorptance and total normal emittance values of 0.75 and 0.06, respectively. Samples were fabricated which maintained their high spectral selectivity after 2000 thermal cycles between 150°C and 450°C, and after 100 h at 600°C. Further process studies now underway indicate that the solar absorptance can be improved to better than 0.85 by employing a Si-Ge multilayer absorber and that the operating range of the stacks can potentially be raised to the 800–900°C range by employing a refractory metal thin film reflector.     

The carbon dioxide laser in cervical intraepithelial neoplasia: a five-year experience in treating 230 patients

Two hundred and thirty patients with cervical intraepithelial neoplasia were treated over a 5-year period with the carbon dioxide laser at the University of Kansas. Analysis of cytologic findings, biopsy results, location of the lesion, treatment factors, and recurrence rates are reported. Ninety percent of the patients were cytologically free of intraepithelial neoplasia at the end of the study.     

Al-Ag alloy films for solar reflectors

Films of Al-Ag alloys were formed using triode sputtering. Films with a wide variety of composition were produced and evaluated. Films deposited at low substrate temperatures have a high specular reflectance. At higher temperatures, two-phase alloys form which have rough low reflecting surfaces.     

Optically sensed EM-field probes for pulsed fields

The characteristics of photonic probes that give them the potential to measure pulsed electromagnetic fields more accurately than has been possible in the past are discussed. An overview of system design is presented with particular emphasis on the transfer functions of appropriate antennas and electrooptic modulators. Noise sources which limit the sensitivity to low signals are discussed and used to determine the noise equivalent field (NEF). The characteristics of some probes developed by the US National Institute of Standards and Technology (NIST) are presented. The NEFs of these probes are about 0.1 V-m^-1 -Hz^-1/2 and are about 10³ times the theoretical limits. For a 1-Hz bandwidth their dynamic ranges are on the order of 70 dB. Optical guided wave technology holds considerable promise for fabricating modulators with a wide variety of operating parameters that can improve probe performance and extend their applications to a wider region of the electromagnetic spectrum