Effect of frequency on the electrical characteristics of tin-antimony-oxide mixtures

The effect of frequency (100 Hz to 1 MHz) both on complex permittivity and on complex impedance data was used to study the conduction processes in Sn-Sb-O systems between 300 and 873 K. The conductance of tin oxide was increased by the addition of antimony oxide at all frequencies and a peak in conductivity was observed at 5 wt% Sb₂O₃. The effect of frequency on conductance was in agreement with the universal behaviour of solid dielectrics, whilst the atmosphere-dependent capacitance indicated surface dipole phenomena. The catalytic activity and selectivity patterns for the oxidation of propylene above 650 K may be correlated with the observed electrical behaviour, which is related to the mobility of lattice oxygen in the outer layers of the surface.On leave from Institutul de Chimie Fizica, Academia Româna, Bucuresti 77208 Romania     

Effect of rHuEpo therapy in dialysis patients on endogenous erythropoietin synthesis after renal transplantation

BACKGROUND: Pertussis is a highly contagious respiratory disease and the most serious effects occur in young infants. Recently it has been shown that rapid and highly specific PCR can be a useful diagnostic tool for detection of pertussis infection. To our knowledge there are no previous studies concerning the disappearance of Bordetella pertussis DNA from the nasopharynx during antimicrobial treatment. METHODS: We studied prospectively how rapidly live B. pertussis organisms and DNA of these bacteria disappear from the nasopharynx during erythromycin therapy in unvaccinated infants. Eighty-five nasopharyngeal swabs obtained from nine erythromycin-treated infants with pertussis on consecutive days during hospitalization were tested by PCR and culture. The PCR products were further analyzed by Southern hybridization. RESULTS: On the fourth day of treatment 56% of the samples were positive by culture and 89% by PCR, whereas after 7 days the rates were 0 and 56%, respectively. In seven of nine patients PCR remained positive for 1 to 7 days longer than culture. The follow-up study also showed the semiquantitative nature of the PCR assay. The intensity of the PCR products in agarose gel usually weakened with time during erythromycin therapy. CONCLUSIONS: The results of this study show that PCR assay can achieve the specific diagnosis of pertussis infection in a large proportion of infants even when antimicrobial treatment has killed the organisms and culture is no longer positive.     

Structure and Properties at the Ferroelectric/Electrode Interface between Lead Zirconate Titanate and Copper

In advanced actuator systems, ferroelectric ceramics are usually made into multilayered stacks to obtain optimum performance. This is done by interlacing noble metals (such as Pt/Pd) with ceramic green sheet and cofiring. The present study proposes an alternative, more economic electrode. Copper has been successfully diffusion bonded to several PZT-based ferroelectric ceramics in a multilayer configuration. The microstructure and the relevant physical properties of the interfaces have been investigated. This has been achieved by using microscopy, as well as by mechanical and electrical characterization. These studies indicate that no reaction product forms at the interface and, furthermore, that the interface exhibits good cohesion.     

Adiabatic shear localization in titanium and Ti-6 pct Al-4 pct V alloy

Ballistic impact experiments were conducted on 12.5 mm thick commercial purity titanium and Ti-6 pct Al-4 pct V alloy plates using steel “stepped” projectiles with 10.5 mm diameter. The impact velocities varied between 578 m per second and 846 m per second, and a flash X-ray technique was used to determine projectile velocity and to assure the normality of impact. The microstructural damage mechanisms associated with impact (shear band formation, shock wave propagation, and dynamic fracture) were analyzed by optical, and scanning and transmission electron microscopy. Elliptical and spherical cavities were observed along the bands. Microindentation hardness differences between the bands and adjacent regions were slight for the targets; for the projectiles, the hardness in the band was significantly lower than that of surrounding regions. Observation of the fractured regions along the bands showed unique features indicating possible melting. Transmission-electron microscopy of a shear band in titanium revealed microcrystalline features (∼0.3 μm diameter) with poorly defined grain boundaries. Formerly Graduate Student, Department of Metallurgical and Materials Engineering, New Mexico Institute of Mining and Technology, Socorro, NM 87801     

The use of various buffers in the preparation of human lymphocytes for SEM observation

A study is presented of various buffers utilized in the preparation of human lymphocytes for scanning electron microscopy. Of nineteen different buffers tested, Hanks' balanced salt solution +0·04 mol sucrose appeared most adequate for satisfactory preservation of lymphocyte surface architecture.     

Alterations of phospholipids in ischemic canine myocardium during acute arrhythmia

Myocardial ischemia was produced in the left ventricle of the canine heart by a Harris two-stage occlusion of the left anterior descending coronary artery. The lipid content in the ischemic myocardium was analyzed and compared with the control tissue. No significant change in total phospholipid and cholesterol was detected. A 2-fold elevation in the levels of the major lysophospholipids was observed during acute ventricular arrhythmias at 24hr after the onset of ischemia. Such increases were not caused by preferential hydrolysis of phospholipid plasmalogens from the parent phospholipids.     

DETECTION AND QUANTITATIVE DETERMINATION OF PAPAIN IN BEER

We have investigated an ultra-sensitive method for the quantitative determination of proteolytic enzymes in biological media by means of a chromogenic substrate (Hide Powder Azure), and adapted it to the determination of papain in beer. At pH 6 and in presence of EDTA and cysteine hydrochloride, the hydrolysis of this substrate at 37° C. by papain for 90 min. allows the rapid determination of an activity of less than I tyrosine unit/ml./min. This makes it possible to control the survival of papain in beer before, during and after pasteurization and during storage.