The present system of quantities and units for radiation protection

The International Commission on Radiation Units and Measurements has over the last decade developed operational quantities, the ambient, directional and personal dose equivalent, suitable for the measurement of radiation fields in a variety of circumstances. Experience with the use of these quantities to represent the dose limitation quantities defined by the International Commission on Radiological Protection in 1977 has been an important part of recent radiation protection metrology. The definition by International Commission on Radiological Protection in 1991 of new limitation quantities, the equivalent dose and the effective dose has necessitated a redirection of this work. The metrology field has made good progress, however. It has found that for photons, at least above 50 keV, the effective dose can be measured by the ambient dose equivalent about as well as the former effective dose equivalent. Unfortunately, for neutrons the existing and already quite severe complications have been made somewhat worse by the new quantities although not any worse in the important region between 0.1 and 1 MeV. Neutron measurements over a broad energy range are the subject of extensive evaluation and some new suggestions as the metrology field wrestles with these problems. Values of wR constitute an important part of the International Commission on Radiological Protection recommendations. A brief history of the development of higher relative biological effectiveness values for fission neutrons and alpha particles leading to the selection of 20 for wR in each case, is provided.     

降低钢轨脱碳层深度的研究

通过分析加热炉钢坯加热时间，加热温度和炉内气氛等工艺参数对钢轨脱碳层深度的影响，制定了降低钢轨脱碳层深度的技术措施，经现场实施应用，钢轨脱碳层深度保持在0．2－0．5mm的范围内，满足了钢轨对脱碳层浓度≤0.5mm的要求。     

A 12-year study (1975-1986) of mortality in methadone-maintenance patients: selected demographic characteristics and drug-use patterns of AIDS and non-AIDS-related deaths

This paper describes changes in demographic characteristics and drug use patterns of persons who died while enrolled in a New York City methadone-maintenance program during the years preceding and subsequent to the AIDS epidemic. Persons dying from AIDS were more likely to be younger, Hispanic, and male than those dying from other causes. Drug use increased during the 12-year study period, and the spread of the HIV infection among drug users may be reflected in an increased use of injectable drugs.     

Chromosomal instability is correlated with telomere erosion and inactivation of G2 checkpoint function in human fibroblasts expressing human papillomavirus type 16 E6 oncoprotein

Cell cycle checkpoints and tumor suppressor gene functions appear to be required for the maintenance of a stable genome in proliferating cells. In this study chromosomal destabilization was monitored in relation to telomere structure, lifespan control and G2 checkpoint function. Replicative senescence was inactivated in secondary cultures of human skin fibroblasts by expressing the human papillomavirus type 16 (HPV-16) E6 oncoprotein to inactivate p53. Chromosome aberrations were enumerated during in vitro aging of isogenic control (F5neo) and HPV-16E6-expressing (F5E6) fibroblasts. We found that structural and numerical aberrations in chromosomes were significantly increased in F5E6 cells during aging in vitro and fluorescence in situ hybridization (FISH) analysis using chromosome-specific probes demonstrated the occurrence of rearrangements involving chromosome 4 and 6 in genetically unstable F5E6 cells. Flow cytometry and karyotypic analyses revealed increased polyploidy and aneuploidy in F5E6 cells only at passages > 16, although these cells displayed defective mitotic spindle checkpoint function associated with inactivation of p53 at passages 5 and 16. G2 checkpoint function was confirmed to be gradually but progressively inactivated during in vitro aging of E6-expressing cells. Aging of F5neo fibroblasts was documented during in vitro passaging by induction of a senescence-associated marker, pH 6.0 lysosomal beta-galactosidase. F5E6 cells displayed extension of in vitro lifespan and did not induce beta-galactosidase at high passage. Erosion of telomeres during in vitro aging of telomerase-negative F5neo cells was demonstrated by Southern hybridization and by quantitative FISH analysis on an individual cell level. Telomeric signals diminished continuously as F5neo cells aged in vitro being reduced by 80% near the time of replicative senescence. Telomeric signals detected by FISH also decreased continuously during aging of telomerase-negative F5E6 cells, but telomeres appeared to be stabilized at passage 34 when telomerase was expressed. Chromosomal instability in E6-expressing cells was correlated (P < 0.05) with both loss of telomeric signals and inactivation of G2 checkpoint function. The results suggest that chromosomal stability depends upon a complex interaction among the systems of telomere length maintenance and cell cycle checkpoints.     

Amelioration of virulent Babesia bovis infection in calves by administration of the nitric oxide synthase inhibitor aminoguanidine

The expression of synaptosomal-associated protein (SNAP-25), neural growth-associated protein (GAP-43) and neural cell adhesion molecule (NCAM) were studied in mouse olfactory cells and axons for 2 weeks following unilateral bulbectomy. The olfactory cells and axons in the control olfactory epithelium were positive for SNAP-25 but levels decreased in the atrophic olfactory epithelium 3 days after bulbectomy. There was no expression of SNAP-25 in the olfactory epithelium on the bulbectomy side 7 days after bulbectomy, indicating that this protein may be a good marker for the degeneration of olfactory cells. The expression of NCAM was still found in the atrophic olfactory epithelium at 7 days after bulbectomy, while the expression of NCAM in the olfactory epithelium of the bulbectomy side was stronger than that on the control side at 14 days after bulbectomy. The expression of GAP-43 in the olfactory axonal bundles of the bulbectomy side at 3 and 4 days after bulbectomy was stronger than that on the control side. These results suggest that upregulation of NCAM may be related to the regeneration of the olfactory cells, with upregulation of GAP-43 probably playing a role in axonal regeneration after bulbectomy.     

Prognosis in malignant melanoma

A uniform and practical classification and staging system for melanoma must exist and be widely adopted if useful comparisons between different treatment centers and databases are to be made. This article reviews the 1992 American Joint Committee on Cancer pTNM staging system. In this classification, localized disease without regional nodal involvement is defined as stage I or II, depending on the tumor thickness of the primary melanoma. Regional lymph node involvement and/or in-transit metastasis is defined as stage III, and systemic metastatic disease is defined as stage IV.