Creation of progressive technology for production of lubricating oils

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 17–20, May, 1990.     

Controlling the U −-center density in Se-As chalcogenide-glass semiconductors by doping with metals and halogens

Temperature dependences of the drift mobilities of electrons and holes are investigated in chalcogenide-glass semiconductors with composition Se₉₅As₅, both without impurities and with the impurities Ag and Br. The data obtained indicate that the localized states that control the transport of charge carriers are U ⁻-centers, and that the change in the magnitude of the drift mobility after doping is caused by a change in the concentration of these centers. Estimates of the concentrations of positive and negatively charged intrinsic defects show that their values are similar, equalling ∼10¹⁶ cm⁻³ in impurity-free glasses with the composition Se₉₅As₅ and lying in the range 10¹³–10¹⁷ cm⁻³ when these glasses are doped with Ag, Br, and Cl. It is established that halogen impurities change the concentration of U ⁻-centers most strongly (by two to three orders of magnitude). Analysis of the data obtained shows that the percentage of electrically active Br and Cl impurity atoms is 1%, while for Ag atoms it is 10⁻²%. Fiz. Tekh. Poluprovodn. 33, 866–869 (July 1999)     

Study of the Spatial and Current Dynamics of Optical Loss in Semiconductor Laser Heterostructures by Optical Probing

Semiconductors - The spatial and temporal dynamics of the optical loss and carrier density in the heterostructure of a semiconductor laser with a segmented contact are studied using an optical...     

Transient current in amorphous, porous semiconductor-crystalline semiconductor structures

The time-of-flight technique in the weak signal mode (i.e., under conditions of small charge drift in the sample) is used to study the transient photocurrent in amorphous (porous) semiconductor-crystalline semiconductor structures. Amorphous Se-As materials, porous Si, and crystalline Si and CdSe were incorporated in the structures. The carrier drift mobilities in the amorphous and porous layers of the structures were determined. The appearance of a cusp on the curves of the transient current is shown to be caused by acceleration of carriers passing through the interface between the amorphous (porous) layer and the crystal. It is established that the carrier acceleration influences the drift mobility and the dispersion parameters. Fiz. Tekh. Poluprovodn. 32, 187–191 (February 1998)     

Multilevel Recording in Ge2Sb2Te5 Thin Films

Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...     

Properties of porous cast charges based on mixtures of ammonium nitrate and carbamide

The explosive and physicochemical properties of porous mixtures based on ammonium nitrate, carbamide, and aluminum powder are considered. A melting curve for the ammonium nitrate/carbamide system is plotted using differential scanning calorimetry. The critical detonation diameter is obtained for a charge density of 0.6–0.7 g/cm³. The dependence of the charge density on the degree of filling of the mold with the melt is determined. Detonation velocity is measured for various densities. An explanation of the difference between the experimental and calculated values is proposed.     

Cytotoxic Potential of a-Azepano- and 3-Amino-3,4-SeCo-Triterpenoids

Semi-synthetic triterpenoids, holding an amino substituted seven-membered A-ring (azepano-ring), which could be synthesized from triterpenic oximes through a Beckmann type rearrangement followed by a reduction of lactame fragment, are considered to be novel promising agents exhibiting anti-microbial, alpha-glucosidase, and butyrylcholinesterase inhibitory activities. In this study, in an attempt to develop new antitumor candidates, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives of betulin, oleanolic, ursolic, and glycyrrhetinic acids were evaluated for their cytotoxic activity against five human cancer cell lines and non-malignant mouse fibroblasts by means of a colorimetric sulforhodamine assay. Azepanoallobetulinic acid amide derivative 11 was the most cytotoxic compound of this series but showed little selectivity between the different human tumor cell lines. Flow cytometry experiments showed compound 11 to act mainly by apoptosis (44.3%) and late apoptosis (21.4%). The compounds were further screened at the National Cancer Institute towards a panel of 60 cancer cell lines. It was found that compounds 3, 4, 7, 8, 9, 11, 15, 16, 19, and 20 showed growth inhibitory (GI₅₀) against the most sensitive cell lines at submicromolar concentrations (0.20–0.94 μM), and their cytotoxic activity (LC₅₀) was also high (1–6 μM). Derivatives 3, 8, 11, 15, and 16 demonstrated a certain selectivity profile at GI₅₀ level from 5.16 to 9.56 towards K-562, CCRF-CEM, HL-60(TB), and RPMI-8226 (Leukemia), HT29 (Colon cancer), and OVCAR-4 (Ovarian cancer) cell lines. Selectivity indexes of azepanoerythrodiol 3 at TGI level ranged from 5.93 (CNS cancer cell lines SF-539, SNB-19 and SNB-75) to 14.89 for HCT-116 (colon cancer) with SI 9.56 at GI₅₀ level for the leukemia cell line K-562. The present study highlighted the importance of A-azepano-ring in the triterpenic core for the development of novel antitumor agents, and a future aim to increase the selectivity profile will thus lie in the area of modifications of azepano-triterpenic acids at their carboxyl group.