Josephson junction with an amorphous silicon barrier

A Josephson junction Nb/Si/Nb with a 10 nm thick amorphous silicon barrier is studied. The upper electrode contains a 2 nm thick sublayer of amorphous phase adjacent to the barrier, as revealed by cross-sectional TEM. Thus, the junction can be considered as a S-I-N-S system with the N layer represented by amorphous niobium. Peculiarities in the I–V and Δ(T) dependencies are observed and explained as a consequence of a proximity effect present in the upper electrode.     

Study of the optical and structural properties of multi quantum well structures grown on high-index surfaces

The MOVPE overgrowth of high [0 1¯ 1]-oriented ridges confined at sides by facets related to {n 1 1} crystallographic planes is reported. We studied the influence of the side tilt on the thickness of the AlGaAs and GaAs epitaxial layers grown under the condition of the kinetic growth mode. The multi quantum well (MQW) structures were prepared on the sides of ridges tilted at 54.7°, 45° and 30° to (1 0 0). The sidewall surface morphologies before and after epitaxial growth were evaluated and compared. We observed no tendency towards planarization towards a neighbouring high-index crystallographic plane, such as (2 1 1) and (3 1 1). We also showed that the quantum wells of the MQW structure make a smooth transition over the edge between the top surface and the facet as both AlGaAs and GaAs grew at similar rates on the surfaces.     

Study of the growth and structural properties of InMnAs dots grown on high-index surfaces by MOVPE

The growth of InMnAs quantum dots by low pressure MOVPE technique on patterned (1 0 0) GaAs substrates was studied. The patterning in the form of ridges with sidewalls having (2 1 1) and (3 1 1) facets was prepared by wet chemical etching via a GaAs/AlAs sacrificial etching mask structure. AFM studies showed that the dots formation and distribution were very similar for both types of facets under study. InMnAs dot density on the (3 1 1) plane is about 5–7 times lower in comparison to that on the (1 0 0) planar substrate. The dots on sidewalls are larger in comparison to average dots formatted on planar GaAs (1 0 0) substrate. The lateral dimensions of these dots are in the interval 100–180 nm. In addition, dot distribution along the sidewall (from top to bottom) is not uniform. A higher dot concentration was observed close to the intersection of (3 1 1) facets with concave bottom part of the valleys between ridges. Finally, no dots were grown on the (1 0 0) plane created by self-faceting on the top of the triangular ridges. This is probably a consequence of the high quality of the (1 0 0) facet formed by lateral overgrowth.     

Resistivity and structure of evaporated polycrystalline molybdenum films

Molybdenum films of thickness 20–2600 nm were evaporated at a substrate temperature of 650°C and were then vacuum annealed at 900°C. The mean grain size of films increased with increasing thickness and it became saturated at about 130 nm for films thicker than 1000 nm. Using this result, the Mayadas-Shatzkes model of grain boundary scattering was used for the interpretation of the observed thickness dependence of the resistivity of the films. Values of the grain boundary electron reflection coefficient, which increase with decreasing film thickness, were used to fit the experimental data to theoretical curves.     

Mo/SiO2 nanocomposite films for optical coatings prepared by vacuum magnetron sputtering

The embedding of metallic nanoparticles in the traditional optical materials (e.g. SiO₂) gives us the possibility to create new optical materials. Metallic particles of nanometric dimensions can be transparent in wide spectral ranges of light. The incorporation of nanocrystal inclusions in such nanocomposites provides the benefit of targeted manipulations of their macroscopic optical response. In this paper we present the possibility to create, using vacuum deposition methods, the nanocomposite coatings with fairly small refractivity.     

Laparoscopic gastrostomy: report on 20 cases

At the surgical clinic of the Faculty Hospital in Ostrava-Poruba since November 1993 till June 1998 20 laparoscopic gastrostomies were performed. The main indication was to ensure enteral nutrition in patients where, due to obstruction of the oesophagus, it was impossible to implement percutaneous puncture gastrostomy. The surgical procedure lasted on average 37 minutes and was completed successfully in all patients. Three patients died within thirty days. This procedure made it possible that eighty percent of the patients could be discharged from hospital and go home.     

Thermophysical Properties of Electrically Conductive SiC–(Nb,Ti–C)<Subscript>ss</Subscript>-Based Cermets

Multifunctional cermets are being developed for a range of novel applications. The present paper deals with thermophysical properties of electrically conductive SiC-based cermets. The cermets were prepared by in situ reaction using a two-step sintering process. The thermophysical properties, namely, thermal conductivity, thermal diffusivity, and heat capacity, were measured using the pulse transient technique. The microstructure and chemical composition of the samples were characterized by SEM (scanning electron microscopy), TEM (transmission electron microscopy), STEM (scanning transmission electron microscopy), and EDX (energy dispersive X-ray analysis) techniques. The observed thermophysical data were correlated with the observed microstructures and chemical nature of the SiC-based cermets.     

Stacked Josephson junction based on Nb/Si superlattice

We report on the technology and basic electrical properties of ten-fold stacked Nb/Si/Nb Josephson junction (JJ). The problem of making a large number of stacked JJs with identical properties was solved by metallic superlattice preparation technology. The uniformity of Si barriers thickness was examined by low angle X-ray diffraction and cross-sectional transmission electron microscopy. To prevent pinholes in the Si barriers the Nb/Si superlattice was sputtered at the regime at which smoothing of interfacial roughness occurs. The stacked junction exhibit both ac and dc Josephson effects. In the I_c(B) diffraction pattern there is an extra periodicity of about 2–3 G in addition to a larger period of about 21 G.     

Microsporidia of the genus Trachipleistophora--causative agents of human microsporidiosis: description of Trachipleistophora anthropophthera n. sp. (Protozoa: Microsporidia)

Only limited data are available on chromosomes specifically involved in prostatic tumour progression. This study has evaluated the cytogenetic status of primary prostatic carcinomas, local tumour recurrences, and distant metastases, representing different time points in prostatic tumour progression. Interphase in situ hybridization (ISH) was applied with a set of (peri) centromeric DNA probes, specific for chromosomes 1, 7, 8 and Y, to routinely processed tissue sections of 73 tumour specimens from 32 patients. Longitudinal evaluation was possible in 11 cases with local recurrence and nine cases with distant metastases. The remaining 12 patients showed no evidence of local recurrence or distant metastasis after radical prostatectomy on follow-up (mean 60.5 months) and served as a reference. Numerical aberrations of at least one chromosome were found in 27 per cent of the local recurrences and 56 per cent of the distant metastases. In decreasing order of frequency, +8, +7, and -Y were observed in the recurrences and +8, +7, -Y, and +1 in the distant metastases. Evaluation of the corresponding primary tumour tissue of the recurrence group showed numerical aberrations in 45 per cent of cases. The aberrations found were, in decreasing order of frequency, -Y, +7, and +8. In the concomitant primary tumour tissue of the distant metastasis group, numerical aberrations were detected in 67 per cent of cases. The aberrations most frequently encountered were +8, -Y, followed by +7. In four cases, a concordance was found between the primary tumour and its recurrence or distant metastasis. Discrepancies might have been caused by cytogenetic heterogeneity. Comparison of the primary tumour tissue of the reference, the recurrence, and the distant metastasis groups showed a significant increase for the percentage of cases with numerical aberrations (Ptrend = 0.02). Likewise, a trend was seen for gain of chromosome 7 and/or 8 (Ptrend < 0.05). The number of DNA aneuploid tumours also increased in these different groups (Ptrend = 0.03). These data suggest that cancers which recur in time display an intermediate position between tumours of disease-free patients and metastatic cancers.     

Prolonged exercise in prepubertal boys. I. Cardiovascular and metabolic adjustment

The pharmacokinetics of lofepramine, an imipramine analogue, have been studied by administering single oral doses to volunteers, determination of plasma levels of lofepramine and desemthylimipramine after ten days of oral administration to patients, and by relating plasma levels to the effect on uptake of noradrenaline by isolated rats irides and brain slices of plasma samples collected during treatment. The results indicate that lofepramine undergoes pronounced first pass elimination and that desmethylimipramine is a major metabolite of it. During steady-state conditions the plasma level of lofepramine fluctuates considerably between doses. A linear relation was found between inhibition of neuronal uptake of noradrenaline and the plasma concentration of desmethylimipramine. No effect was seen on the uptake of 5-hydroxytryptamine in brain slices incubated in patients' plasma which suggests that neither lofepramine nor its metabolites formed in vivo in man affect neuronal uptake is this amine. Lofepramine belongs to the group of tricyclic antidepressants which preferentially inhibit noradrenaline uptake.