Microstructure and phase constitution near the interface of Cu/Al vacuum brazing using Al-Si filler metal

Brazing of Cu to Al using Al-Si filler metal has been carried out by vacuum brazing technology. The microstructure and the phase constitution in Cu/Al joint were studied by means of metallography, electron probe microanalyser (EPMA) and X-ray diffraction (XRD). Experimental results obtained showed that two kinds of intermetallic compounds (IMCs) are formed near the interface of copper and brazing seam region and those are Cu₃Al₂ and CuAl₂ phases. Moreover, ε-Cu₁₅Si₄, Al-Si and CuZn₂ are formed on the α-Al solid solution in the brazing seam region. Technology parameters of vacuum brazing were: brazing temperature T=590-610 °C, vacuum level 10⁻³ Pa, holding time t=5-10 min.     

Single yeast cell vacuolar milieu viscosity assessment by fluorescence polarization microscopy with computer image analysis

This study was undertaken to evaluate the apparent viscosity within the vacuoles of single Saccharomyces cerevisiae cells by steady‐state fluorescence anisotropy measurements of quinacrine, using wide‐field fluorescence polarization microscopy combined with computer image analysis. Quinacrine was shown to be rather specifically accumulated within the vacuoles of the cells. This accumulation was effectively reversed by ATP depletion of the cells, with no detectable binding of the dye within the vacuoles. Quinacrine fluorescence anisotropy in the sucrose solutions of various viscosities obeyed the Perrin equation. The fluorescence anisotropy of quinacrine was measured in the vacuoles of 39 cells. From cell to cell, this parameter changed in the range 0.032–0.086. Using the Perrin plot as a calibration curve, apparent viscosity values of the vacuolar milieu were calculated for each cell. The population of the cells studied was heterogeneous with regard to vacuolar viscosity, which was in the range 3.5 ± 0.4–14.06 ± 0.64 cP. There was a characteristic distribution of the frequencies of cells with apparent viscosities within certain limits, and cells with viscosity values in the range 5–6 cP were the most frequent. No relationship was found between the sizes of the vacuoles and their apparent viscosities. Copyright © 2012 John Wiley & Sons, Ltd.     

Quench Factor Analysis for Predicting Precipitation Hardening of Sheets from Aluminum Alloy V-1341 of the Al – Mg – Si System

Metal Science and Heat Treatment - Prediction of precipitation hardening of sheets from aluminum alloy V-1341 of the Al – Mg – Si system with the help of mathematical modeling is...     

Renal cell tumours in mice: electron microscopy versus immunohistochemistry

15 renal cell tumours induced in CBA male mice by 1,2-dimethylhydrazine were studied electronmicroscopically (EM). All these tumours earlier were investigated histochemically and immunohistochemically with the use of gamma-glutamyltranspeptidase (GGT) as a marker of the proximal tubules and antigen A6 as a marker of distal tubules and/or collecting ducts. One of the tumours was GGT-positive and antigen A6-negative and ultrastructurally well developed brush border was found. This correlation between immunohistochemistry and EM data allowed to conclude that the site of origin of this tumour were the cells of the proximal tubules. All other tumours were GGT-negative and antigen A6-positive, i.e. the development of these tumours from the distal tubules (and not from the proximal tubules) could be suspected. However in 5 of these neoplasms reduced brush border was found. Microvilli were of a smaller size than in normal proximal tubules and were frequently located not on the apical cell surface but in the narrow spaces between two cells. Invaginations and apical vesicles typical for the normal proximal tubules were also found in some tumour cells. EM and immunohistochemical data combined allow to suggest the origin of these tumours from the common precursor cell capable of differentiation, in the course of tumour progression, into the cells with properties of proximal and/or distal tubules.