Spectrophotometric method for precision determination of elements of the nuclear fuel cycle

Published data on precision spectorphotometric determination of U, Th, Pu, and other elements of the nuclear fuel cycle in solutions on a two-channel analyzer with the relative random uncertainty S _r = 0.1?C0.2% are summarized. The method was used for certification and fabrication of Pu and U total weight fraction standards for mass spectrometer calibration. New data on precision determination of U, Ru, Er, Gd, Sm, Re, and Tc on serial Shimadzu UV devices in the photometric mode with the relative random uncertainty S _r = 0.02?C0.04% are presented. The relative total uncertainty that can be attained with the spectrophotometric method is as low as 0.03?C0.05%, which makes this method competitive with other precision methods used.     

Acidic urine pH is associated with elevated levels of free urinary benzidine and N-acetylbenzidine and urothelial cell DNA adducts in exposed workers

We evaluated the influence of urine pH on the proportion of urinary benzidine (BZ) and N-acetylbenzidine present in the free, unconjugated state and on exfoliated urothelial cell DNA adduct levels in 32 workers exposed to BZ in India. Postworkshift urine pH was inversely correlated with the proportions of BZ (r = -0.78; P < 0.0001) and N-acetylbenzidine (r = -0.67; P < 0.0001) present as free compounds. Furthermore, the average of each subject's pre- and postworkshift urine pH was negatively associated with the predominant urothelial DNA adduct (P = 0.0037, adjusted for urinary BZ and metabolites), which has been shown to cochromatograph with a N-(3'-phosphodeoxyguanosin-8-yl)-N'-acetylbenzidine adduct standard. Controlling for internal dose, individuals with urine pH < 6 had 10-fold higher DNA adduct levels compared to subjects with urine pH > or = 7. As reported previously, polymorphisms in NAT1, NAT2, and GSTM1 had no impact on DNA adduct levels. This is the first study to demonstrate that urine pH has a strong influence on the presence of free urinary aromatic amine compounds and on urothelial cell DNA adduct levels in exposed humans. Because there is evidence that acidic urine has a similar influence on aromatic amines derived from cigarette smoke, urine pH, which is influenced by diet, may be an important susceptibility factor for bladder cancer caused by tobacco in the general population.     

Antibody responses of cows during an outbreak of neosporosis evaluated by indirect fluorescent antibody test and different enzyme-linked immunosorbent assays

Hairpin ribozymes with high cleavage activities were designed. An extra sequence was introduced at the 3'-end of the hairpin ribozyme to increase the binding to the substrate RNA, as compared to the wild-type hairpin ribozyme. A three-way junction (TWJ) was formed between the newly designed ribozyme and the substrate RNA. The complex with a solid TWJ showed less RNA cleavage activity than the wild-type hairpin ribozyme. However, the ribozyme with a TWJ with five unpaired bases or propandiol phosphate linkers had higher cleavage activity than the parent ribozyme without the TWJ. When a cis-cleavage system, in which the 5'-end of the substrate RNA was conjugated to the 3'-end of the ribozyme, was employed, the complex with the TWJ containing unpaired bases was also cleaved faster than the complex with the solid TWJ. This suggested that these differences in the cleavage activities were derived from the confirmation, and this was proven by nondenaturing gel electrophoresis. The TWJ hairpin ribozyme containing unpaired bases is able to bind strongly with substrate RNAs and to cleave them efficiently. Since the three-way ribozyme presented here is more active than the wild-type ribozyme, this type of ribozyme can serve as a more efficient tool to control RNA activities in vitro and in vivo.     

Relation between the space flight-induced frequency of dominant lethal mutations and the level of allozyme heterozygosity in Drosophila melanogaster populations

Currently, the treatment of falciparum malaria is seriously compromised by spreading drug resistance. We studied the effects of camptothecin, a potent and specific topoisomerase I inhibitor, on erythrocytic malaria parasites in vitro. In Plasmodium falciparum, camptothecin trapped protein-DNA complexes, inhibited nucleic acid biosynthesis, and was cytotoxic. These results provide proof for the concept that topoisomerase I is a vulnerable target for new antimalarial drug development.     

The French SF-36 Health Survey: translation, cultural adaptation and preliminary psychometric evaluation

This article reports on the main developmental stages and on the preliminary psychometric assessment of the final French version of the SF-36. A standard forward/backward translation procedure was followed. When translating survey items, the emphasis was placed on conceptual equivalence. When translating response choices, we attempted to select a set of response choices that replicate the U.S. version. The distance between the response choices was checked using visual analogue scales (N = 30). The adaptation procedure also included formal ratings of the difficulty of the translation, of the quality of the translation, and of the equivalence between the American source version and the French target version. The face validity was checked during lay panel sessions at which the translated questionnaire was administered to subjects from the general public, hospital employees, and subjects with a low level of education. Standard psychometric techniques were used to evaluate the cultural adaptation of the SF-36, using data from a general population survey. The main objective of this analysis was to determine how well the scaling assumptions (summated rating or Likert-type scaling construction) of the SF-36 were satisfied. The results support the claim that the scaling properties of the French version of the SF-36 are adequate and that health outcomes may be reliably assessed using this version of the instrument.     

Lasing at 1.5 µm in quantum dot structures on GaAs substrates

Lasing at 1488–1515 nm in the temperature range 20–83°C was obtained in structures with an active region based on multiply stacked arrays of self-organized quantum dots grown on GaAs substrates. The threshold current density of a laser with four cleaved facets was 800 A/cm2 at room temperature. The method of wavelength extension is based on the use of a metamorphic buffer layer with an In content of about 20% intended for relieving the lattice mismatch stress.