A review of common stress measurement techniques as related to CVD diamond is presented. A correction to the commonly applied Stoney thin film equation for the substrate curvature technique is presented for coatings with a large stiffness mismatch with the substrate. The difficulties associated with the sin2ψ and peak width broadening X-ray diffraction techniques in highly oriented, X-ray transparent diamond are highlighted. Stress measurement by Raman spectroscopy is complicated by factors such as domain size, temperature, non-hydrostatic stress, degeneracy lifting and the presence of multiple peaks. Substrate curvature and Raman spectroscopy stress measurement results can be reconciled through consideration of these complicating factors and application of the appropriate corrections.

OBJECTIVES:To enumerate and characterize extended-spectrum beta-lactamases (ESBLs) amongst ceftriaxone-resistant coliforms in Blantyre, Malawi, where third-generation cephalosporin use is currently highly restricted.METHODS:Over the period April 2004-March 2005 all ceftriaxone-resistant isolates from blood cultures were examined for the presence of ESBLs. Isoelectric focusing was performed on enzyme extracts. PCR and DNA sequencing of amplicons were used to identify the underlying genetic determinants responsible for the ESBL phenotypes. Transferability of the ESBL phenotypes was tested by conjugation to a susceptible Escherichia coli J53.RESULTS:Enterobacteriaceae were isolated from 1191 blood cultures, of which 19 (1.6%) were ceftriaxone resistant. Ten isolates (0.7% of all isolates) demonstrated an ESBL phenotype but only eight were characterized as three isolates were from the same patient. Genotypes SHV-11 (n = 1), SHV-12 (n = 3), SHV-27 (n = 1), TEM-63 (n = 2) and CTX-M-15 (n = 1) were detected. Plasmid transfer of the ESBL resistance phenotype was successful for all the isolates.CONCLUSIONS:In a clinical setting of minimal cephalosporin usage there is already a diversity of ESBL genotypes. Increased use of cephalosporins in this setting is likely to result in a rapid expansion of ESBLs and their prevalence will need to be carefully monitored.

HIV-infected individuals are predisposed to infection with bacteria, in particular Streptococcus pneumoniae and non-typhi Salmonella. Other bacteria also complicate HIV disease, either because they are inherently pathogenic - Staphylococcus aureus, Enterobacteraciae, bacterial agents of enteritis - or they take advantage of advanced immunosuppression - Rhodococcus spp, Nocardia spp. An understanding of the role of bacteria is essential to the care of HIV-infected patients.

OBJECTIVES:To describe three cases of Rhodococcus equi infection in a cohort of HIV-1 infected adults in Entebbe, Uganda and to compare this to the rates and presentation of tuberculosis in this cohort.METHODS:Consecutive HIV-1 infected adults registering with a community HIV/AIDS clinic in Entebbe were enrolled in a cohort between October 1995 and June 1998 as part of an intervention trial of pneumococcal polysaccharide vaccine. Participants were routinely reviewed every 6 months and had open access to the clinic when unwell. Standard protocols were followed for investigation and management of illness. Microbiological investigations followed standard procedures.RESULTS:1372 (71% female) study participants were followed for 2141 person years of observation (pyo). Rhodococcus equi was isolated from three study participants from blood, a lymph node aspirate and stool. The individuals were undergoing investigation of acute pneumonia, acute cough with cervical lymphadenopathy and chronic fever with wasting, respectively. The clinical features of these cases are described. All had a CD4 T-cell count of <300/ml. The rate of R. equi infection in the cohort was 1.4/1000 pyo. There were 132 cases of pulmonary and extrapulmonary tuberculosis in the cohort which were diagnosed either microbiologically or clinically. The rate of laboratory confirmed mycobacterial disease was 50.1/1000 pyo. The ratio of mycobacterial disease to R. equi disease was 36:1 (95% CI 11-113:1).CONCLUSIONS:Rhodococcus equi infection occurs in HIV-1 infected adults in Africa. The infection is clinically indistinguishable from pulmonary and extra-pulmonary tuberculosis in the cohort described here. Although the rate of R. equi disease is much less than that of tuberculosis, it is important to consider it in the differential diagnosis of tuberculous infection in cases which are smear negative. Rhodococcus equi infection is probably underdiagnosed in Africa due to a lack of microbiological facilities and its resemblance to common commensal organisms.

Thin diamond coatings are often suggested to enhance thermal conductivity of some substrate. We measured the effective thermal conductivity of varying thicknesses of diamond on tape cast, polycrystalline silicon carbide. The effective thermal conductivity of 30 μm diamond on tape cast silicon carbide is 1.7 W/(cm K). The effective thermal conductivity can be increased to 2.2 W/(cm K) by increasing the diamond thickness to approximately 70 μm. With the measured effective thermal conductivity, the thicknesses of the diamond film and substrate, and knowledge of the thermal conductivity of the substrate material, the thermal conductivity of the diamond layer can be calculated from a simple formula. The thermal conductivity of the 30-μm and 69-μm diamond layers were found to be 3.9 W/(cm K) and 5.8 W/(cm K), respectively.

Because of the unfavorable mechanical properties of diamond. the source and type of stresses present must be identified and controlled at every stage of the CVD diamond deposition process in order to develop a high-yield, large-wafer-scale fabrication process. In this paper, we report on the types of defect and stress encountered in free-standing CVD diamond films deposited by d.c. are jet deposition. Substrate materials and designs, temperature non-uniformity, and process conditions all contribute to the type and magnitude of stresses present in a film. Results of mechanical strength testing by biaxial flexure are presented. Strength sample sets consisted of 20 disks from each diamond wafer. Results from over 50 wafers are summarized. Weibull analysis of strength data is presented, with a description of the effects of thickness and sample orientation. It is shown that by implementing tight process control and through judicious selection of a substrate material, d.c. are jet technology is capable of producing 175 mm diameter wafers at high yield with uniform properties. (C) 1999 Elsevier Science S.A. All rights reserved.

The results of a round robin series of measurements of the thermal conductivity and thermal diffusivity of chemical-vapor-deposited (CVD) diamond are reported. The present round robin (RR2) is an outgrowth of an earlier series (RR1) aimed at understanding which measurement techniques are best suited to measuring the high conductivity of CVD diamond. RR2 includes diamond specimens of higher homogeneity, non-diamond specimens of lower conductivity as controls, and measurements by 14 laboratories using five techniques, with all techniques but one used by more than one laboratory. The data are converted to thermal conductivity at 25°C to facilitate comparisons among specimens and laboratories. The statistical analysis excludes outliers using Chauvenet's criterion, resulting in data from typically two or three laboratories being excluded for each specimen. The analysis arrives at mean values in the range 1300–2000Wm−1K−1 for the diamond samples, as expected because of the conditions of preparation, with uncertainties in the range 1.5–4%. For the non-diamond materials, SiC and AlN, the results are 268Wm−1K−1±2.2% and 178Wm−1K−1±2.5%, respectively. Comparing techniques, the d.c.-heated bar is found to be the most accurate, typically ±5% or better. Under favorable conditions, Ångström's thermal wave method can apparently yield relative uncertainties of ±5–10%, and the mirage effect ±5–15%. Too few laboratories used the transient thermal grating and laser flash methods to make general comments on their accuracy, but one expects a comparable accuracy if used on specimens that are fine-grained and thermally isotropic. Deviations, sometimes large, from these optimal accuracies are examined, and it is suggested that certain experimental details are important for achieving accuracy. It is also found that the estimates of experimental uncertainty provided by most laboratories seriously underestimate the actual deviations of their data from the mean conductivity.

Market forecasts which predict hundreds of millions of dollars or more in CVD diamond sales in the near future almost universally assume insertion of CVD diamond into a broad range of electronic packages. Most also assume development of smaller, more specialized markets such as radiation detectors. As with the introduction of any new material, design issues arise which usually require the compatibility of the new material with some existing design. Implementation of the new design into prototypes and products also presents challenges. We present two case studies involving the development of products utilizing CVD diamond: an r.f./microwave package component and a radiation detector. In both cases, materials and processes are chosen to maximize the benefits of diamond, minimize manufacturing costs, and ensure product reliability. Both the intrinsic and processed properties of the bulk and surface regions of the diamond affect the performance of the package or device. Material properties specific to each application are considered. Production issues are addressed through conceptual models including processing and material compatibility issues, prototype design and fabrication, environmental test results, design refinement and optimization, and actual “in-service” performance.