Malignant Tumors of the Central Nervous System

Malignant tumors of the central nervous system in adults comprise a heterogeneous group of malignancies, the largest subgroups comprising astrocytomas, ependymomas, and oligodendrogliomas. Glioblastomas are the most common tumor type, and they have dismal prognosis. Due to differences in cell type of origin, as well as pathogenesis, it is plausible that their etiology also differs between tumor types. The etiology of malignant CNS tumors is largely unknown and no occupational risk factors have been definitively identified. High doses of ionizing radiation increase the risk, but in occupational settings the dose levels appear too small to result in discernible excesses. Several studies have assessed possible effect of extremely low frequency and radiofrequency electromagnetic fields, but the results are inconsistent. Increased brain tumor risk has been reported in agricultural workers, but no specific exposure has been linked to them. Pesticides have been analyzed in several studies without showing a clear increase in risk.acceptedVersionPeer reviewe

Control of indexes of thermal-oxidative stability of mineral engine oil in severe service conditions

The power units of quarry machinery use hydraulic fluids having various bases. That increases the temperature range of the use of this equipment. The cornerstone affecting oil life is the boundary layer temperature on the friction surface while in operation. The catalysts of combustion are oxygen, destruction, and chemical reaction if the oil comes in contact with the metal

Achievement of required surface roughnesses in complex profile channels by dynamic combined processing

At present for processing of complex geometrical channels of workpieces electrochemical dimensional processing, vibro-impact machining and vibro-extruding are widely used. However combined electrochemical mechanical processing, that unites anodic dissolution and plastic flow of material in space and time, provides the required characteristics of surface layer. Local action anodic dissolution changes cold work amount and accelerates dissolution of micro- and macro-cusps, this causes annealing of physical and mechanical parameters in processed segments and accross the whole surface profile the required strengthening degree is attained. The authors examine annealing model for microsurface by grain displacement in channel where extrusion forcing is dictated by grains size and profile of narrow blade channel and also by actual processing conditions. Operating conditions that are recommended for implementation of combined electrochemical mechanical processing of impeller and turbine type workpieces are found by experiments. In consequence of field research they determined availability of standard microgeometry across the whole surface profile by combined processing with vibrations hashing with up to 2030 Hz frequency and low voltage current (in operation range from 1,2 till 1,8 V). Therein technological cycle decreases up to two fold, this reduces inadmissible jumping of blade edges and dimensional allowance

Achievement of required surface roughnesses in complex profile channels by dynamic combined processing

At present for processing of complex geometrical channels of workpieces electrochemical dimensional processing, vibro-impact machining and vibro-extruding are widely used. However combined electrochemical mechanical processing, that unites anodic dissolution and plastic flow of material in space and time, provides the required characteristics of surface layer. Local action anodic dissolution changes cold work amount and accelerates dissolution of micro- and macro-cusps, this causes annealing of physical and mechanical parameters in processed segments and accross the whole surface profile the required strengthening degree is attained. The authors examine annealing model for microsurface by grain displacement in channel where extrusion forcing is dictated by grains size and profile of narrow blade channel and also by actual processing conditions. Operating conditions that are recommended for implementation of combined electrochemical mechanical processing of impeller and turbine type workpieces are found by experiments. In consequence of field research they determined availability of standard microgeometry across the whole surface profile by combined processing with vibrations hashing with up to 2030 Hz frequency and low voltage current (in operation range from 1,2 till 1,8 V). Therein technological cycle decreases up to two fold, this reduces inadmissible jumping of blade edges and dimensional allowance

ICRP Publication 150: Cancer Risks from Plutonium and Uranium Exposure

International audienceThe objective of this publication is to provide a detailed review of results from recent epidemiological studies of cancer risk from exposure to plutonium and uranium, and how these results relate to the assumptions currently used for protection against alpha radiation. For plutonium, the two main studies are of the cohorts of workers employed at the nuclear installations at Mayak in the Russian Federation and at Sellafield in the United Kingdom. The analysis of the Mayak cohort provides an estimate of the slope of the dose-response for lung cancer risk, while at lower levels of plutonium exposure, the Sellafield cohort provides results that, within relatively large confidence intervals, are consistent with those for the Mayak cohort. Results from the Mayak cohort also show an association between plutonium exposure and risks of liver and bone cancers, but not of leukaemia. Lifetime excess risk of lung cancer mortality has been calculated for scenarios of acute and chronic inhalation of plutonium nitrate and plutonium oxide, similar to that done previously for radon and its decay products in Publication 115. Estimated lifetime excess risks of lung cancer mortality per unit absorbed dose are close to those derived from miner studies for exposure to radon and its progeny, and are compatible with the assumption of a radiation weighting factor of 20 for alpha particles. Epidemiological studies of cancer risk associated with uranium exposure have been conducted among cohorts of European and North American workers involved in the nuclear fuel cycle. Current results do not allow the reliable derivation of dose-risk models for uranium for any cancer type. Continuation of efforts to improve dose assessment associated with plutonium and uranium exposure is recommended for future researc