Fabrication of p-n junction GaAs solar cells by a novel method

p⁺-n diffused junction GaAs solar cells have been successfully fabricated using a novel method in which the diffusion source, anti-reflective coating and protective cover layer are all formed in a single chemical vapor deposition run. The advantage of this process lies in its simple, low cost fabrication procedure and in the fact that the GaAs surface is protected throughout the fabrication procedure.     

Avalanche diode structures suitable for microwave-optical interactions

The r.f. performance of avalanche diode structures with an etched optical window at the top contact has been evaluated. Diode Q and r.f. oscillator tests in X-band IMPATT and S-band TRAPATT silicon diodes show that the optical window does not introduce appreciable series resistance nor degrade oscillator performance.     

Coliphages as an indicator of faecal pollution in water. Its relationship with indicator and pathogenic microorganisms

The study was designed to test the proposal that Escherichia coli specific bacteriophages might serve as universal faecal pollution indicators in water. A highly specific, sensitive and rapid technique for the detection and quantification of these virus particles was developed. The numerical relationship between E. coli and its parasitic phages was investigated in three different aqueous ecosystems such as sea water in the vicinity of sewage outfalls, river water contaminated by domestic and industrial sewage discharges, and estuarine waters, and found to be very close. In addition, the results obtained indicate that the coliphages are good indicators of the presence of the pathogenic microorganisms studied. In nearly all the water samples tested, the results suggest that coliphages are better indicators of faecal pollution than the classical indicator systems currently employed.     

Integrity of the pericardium. Its beneficial effects on the protection of the right ventricle in the presence of acute pulmonary hypertension

After cardiac transplant (CT), the right ventricle can be subject to an acute pressure overload, especially in cases where there is a pre-existing severe pulmonary hypertension. Objectives: To determine the maximum tolerance of the right ventricle (MxTRV) when faced with acute pressure overload. To study the function of both ventricles of the healthy heart (donor) when faced with different degrees of pulmonary hypertension. To detect possible interactions between the ventricles in the absence of the pericardium to approximate the experimental model to the clinical model of CT. Methods: The pulmonary artery is progressively constrained in an experimental model until biventricular failure is detected. This experiment is performed in two different situations: with and without pericardial integrity. Results: When pericardial integrity is maintained the MxTRV faced with a pressure overload is 73.2+/-8.56 mmHg. When this pressure is exceeded there is a circulatory collapse with a sharp fall in the cardiac output and in the aortic pressure. However, when pericardectomy is performed (model similar to CT), only 52+/-6.71 mmHg is tolerated (p< 0.001). Conclusions: With the pericardium open, as in CT, the maximum pressure that the right ventricle can support is significantly less than with the pericardium closed. The pericardium has a positive effect in protecting the systolic ventricular interaction.     

Genotyping of Portuguese Chlamydia trachomatis urogenital isolates

OBJECTIVE: To determine the prevalence of the different Chlamydia trachomatis genotypes in Portuguese patients. METHODS: Urogenital isolates (n = 240) derived from attenders of various clinics in the Lisbon area were differentiated into genovars by genotyping with restriction fragment length polymorphism (RFLP) analysis of the PCR amplified omp1 gene. RESULTS: Genotype E was the most common for both men (47.9%) and women (43.8%). Genotypes D and F were the second most prevalent for men (11.3%) and genotype H was the second most prevalent for women (19.5%). Genotypes F, G, D, in women and H, G, I, in men, were found in a lower percentage of cases. Genotypes B, Ba, J, K, L1 and L2 were very rarely detected. CONCLUSIONS: With one exception, the overall distribution of Chlamydia trachomatis genotypes in our study is similar to what has been observed in other western countries. The only exception is the unusual prevalence of genotype H among women. The clinical manifestations associated with this and other genotypes were similar.     

Frequency domain (1 kHz-40 GHz) characterisation of thin films for multichip module packaging technology

Parallel plate capacitors for the broadband dielectric characterisation of both high (amorphous BaTiO/sub 3/ and amorphous TaO/sub x/) and low (parylene) dielectric constant thin films were fabricated at low temperature (<200 degrees C). The dielectric constant and loss tangent were determined through the measurement of C, G and the S parameters of the capacitors. These thin film dielectrics exhibit no dispersion in the frequency range 1 kHz-40 GHz.<>