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As-grown and chemically reduced Rh-doped (1500 p.p.m.) KnbO3 single crystals grown by the Czochralski method have been characterized. Reduction of the grown crystals at different levels was carried out under a mixture of CO and CO2 gases as the crystals were grown with excess oxygen. The effect of reduction and poling on crystalline perfection was studied by high-resolution X-ray diffraction (HRXRD) using a multi-crystal X-ray diffractometer developed in-house. The diffraction curves of the as-grown, electrically poled, moderately reduced and heavily reduced single-crystal specimens show remarkable differences. The studies by HRXRD reveal that poling has some influence on the improvement of crystalline perfection, while chemical reduction has a great influence on crystalline perfection; at moderate reduction the crystal becomes nearly perfect, but when the reduction is very heavy the crystal quality decreases slightly, although it is still better than for unreduced samples. Asymmetry of the diffraction curves with respect to the peak position reveals that the as-grown specimens contain a high concentration of both vacancies and self-interstitials. After poling, the concentration of self-interstitial defects is lowered to some extent. When the specimen is moderately chemically reduced, the scattered intensity on both sides of the peak is greatly reduced, showing that the concentrations of both vacancies and interstitials are reduced to a great extent owing to chemical reduction. This clearly indicates that, as a result of the chemical reduction of oxygen in the crystal, crystalline perfection is enhanced significantly. However, under heavy chemical reduction, the number of vacancy defects is increased to a significant extent. Raman scattering, dielectric and photoluminescence studies also show interesting features, with excellent correlation with the degree of crystalline perfection influenced by the processes of reduction and poling. [ABSTRACT FROM AUTHOR]

Comparisons were made of the immunity conferred by five different fowl pox virus vaccines namely IVRI, BM, Srini, HP1 and local, using the I/M, F/F, oral and I/N routes of immunization in chicks of different age group. All the vaccine virus strains were adapted on the CAM of 12-day-old embryonated eggs. The age at first and second vaccination by the I/M and F/F routes was the 8th and 14th week, while the age was the 3rd and 7th week for the oral and I/N routes. Immunity was determined by challenge with a field strain of fowl pox virus 4 weeks after each vaccination. The vaccines appeared to be safe for immunization by all 4 routes. HP1 and BM vaccine strains gave the greatest (80%) protection by the I/M route. The Srini, HP1 and BM vaccines provided 100% immunity by the F/F route after the second vaccination. The Srini vaccine by the oral route gave 62.5% immunity followed by HP1 and local vaccine (50%). Local vaccine by I/N route provided 80% after the first vaccination. Zusammenfassung Vergleichende Untersuchungen über die Immunogenität von Geflügelpockenvirus-Vaccinen In vergleichenden Untersuchungen über den Infektionsschutz durch verschiedene Geflügelpokken-Vakzinen wurden IVRI, BM, Srini, HP1 sowie ein lokaler Impfstamm getestet. Dabei wurden die Immunisierungswege intramuskulär, oral, intranasal sowie die Federfollikelmethode bei Küken verschiedener Altersgruppen angewendet. Alle Impfvirusstämme waren an die CAM 12tägig embryonierter Eier adaptiert. Die erste und zweite Impfung erfolgte i.m. und F.F. in der 8. und 14., oral und intranasal in der 3. und 7. Lebenswoche der Tiere. Der Impfschutz wurde jeweils 4 Wochen p. vacc. in einem Belastungsversuch mit einem Geflügelpocken-Feldstamm überprüft. Die Impfstämme zeigten bei allen 4 Immunisierungswegen eine gute Wirksamkeit. Bei i.m. Applikation bewirkten HP1 und BM den größten Schutz (80%). Nach der zweiten Impfung mittels F.F.-Methode wurde mit HP1 und BM 100% Immunität erreicht. Srini führte bei oraler Applikation zu 62,5% Infektionsschutz, gefolgt von HP1 und der lokalen Vakzine (50%). Nach intranasaler Applikation der lokalen Vakzine betrug die Immunität 80% nach der ersten Impfung. [ABSTRACT FROM AUTHOR]