Mode-medium instability in an unstable resonator

The mode-medium instability of an active medium in an unstable resonator is investigated. The asymptotic solution due to Horwitz, valid for large Fresnel numbers in an empty cavity, is modified by introducing gain/ phase sheets in front of the resonator mirrors. The effect of medium coupling to the mode in the cavity is obtained by introducing a general time-independent Green's function in the Fox-Li formulation. The time evolution is then obtained by repeated integration of the beam propagation in the cavity. The diffractive terms are shown to grow rapidly at the expense of the geometric term. This instability responsible for the deterioration of the beam quality is studied numerically for a CO(2) lasing system as an example.

Differing patterns of human protooncogene expression in peripheral blood and bone marrow acute leukemia cells

The levels of protooncogene RNA in matched bone marrow and peripheral blood cells obtained from patients with newly diagnosed acute myelogenous leukemia were compared. While the absolute amounts of c-myc RNA in the matched specimens are similar, the levels are not correlated. In contrast, while the levels of c-fos RNA in the matched bone marrow and peripheral blood cells are correlated, the absolute levels of c-fos RNA differ substantially. The level of histone H3 RNA is higher in bone marrow cells than in peripheral blood cells. These substantial differences in protooncogene RNA levels between leukemic cells found in the bone marrow and in the peripheral blood make it impossible to accurately "characterize" gene expression in leukemic cells if studies are restricted to the cells in either compartment. Additionally, there appears to be a significant relationship between the levels of c-fos RNA and triose phosphate isomerase RNA and the height of the white blood cell count and between the level of c-fos RNA in marrow cells and the proportion of monocytic cells present.

Analysis of mutagenic nitroarenes in carbon black by high-performance liquid chromatography

A method was developed for the analysis of mutagenic nitroarenes in carbon black. The procedure included extraction, pre-separation column chromatography on silica gel, and determination by high-performance liquid chromatography (HPLC) using a diode-array detector. Different solvents, such as dichloromethane, benzene, toluene, and chlorobenzene were used for the extraction of carbon black. It was found that chlorobenzene yielded the highest amount of extracted material. The pre-separation, the optimization of the HPLC separation, the selection of detection wavelengths, and the calibration curve are discussed. 3-Nitro-9-fluorenone was detected in a treated carbon black, which is used for making carbon ink. The identification of peaks in the sample chromatograms was confirmed by comparing the retention time and the UV spectra with those of standards.

Wall-bound proteins of pollen tubes after self- and cross-pollination in Lilium longiflorum

Wall-bound proteins of Lilium longiflorum pollen tubes grown in vivo constitute 20-27% of the dry matter. Twenty-two-twenty-six percent of these proteins are NaCl soluble. Wall-bound proteins of in vivo pollen tubes are present in amounts 5-7 times that found in tubes grown in vitro. The protein pattern of wall-bound proteins is different between in vitro and in vivo grown pollen tubes. There are two kinds of pollen tube wall proteins: loosely bound and tightly bound. The latter are NaCl insoluble, contain hydroxyproline and are assumed to be covalently bound. No significant differences have been found in the amount of wall-bound proteins present between pollen tubes resulting after self-pollination and those resulting from cross-pollination. However, some band differences between self- and cross pollen tubes have been observed after gel electrophoresis. It can be supposed that some wall-bound proteins of pollen tubes are associated with the incompatibility reaction.

Induction of gastric adenocarcinoma in rats by N-methyl-N-nitro-N-nitroso-guanidine and ultrastructural changes of epithelial cells of the pyloric gland region

Rats of non-pure strain were allowed to drink N-Methyl-N-Nitro-N-Nitroso-guanidine (MNNG) solution (200-250 micrograms per milliliter) ad libitum. After 14 months, in addition to MNNG, each of them was fed with 1 ml of saturated NaCl solution once a week. During a period of 18 months, there were 5 cases of gastric adenocarcinoma and 2 cases of adenocarcinoma of the duodenum among 18 experimental rats. Besides, there were a few cases of papilloma of the fore-stomach and carcinoma of the lung. In 17 control rats, no tumors of the gastro-intestinal tract were seen. Microscopic examination of the mucosa of the pyloric gland region of the stomach in the experimental rats showed that the deep epithelial cells of the gastric pit exhibited a marked degree of proliferation and a malignant change had started in these cells. Electron microscopic observation of these epithelial cells revealed that the the proliferating cells showed only increased nucleocytoplasmic ratio, while those with atypical hyperplasia showed that the form of the nucleus and the changes in the basement membrane and intercellular junctions were somewhat similar to those of malignant cells. It is believed that increase in concentration of the carcinogens and prolongation of the time of contact with them may induce malignant tumors in the insensitive animal.