Improved confidence limits for low-dose carcinogenic risk assessment from animal data

An improved procedure is presented for estimating low-dose risks from dichotomous animal data. Based on the multistage model of cancer, the procedure gives a maximum likelihood fit to the experimental data. Because the model is approximately linear in the low-dose range, the procedure may be considered to be a generalized method for linear extrapolation which uses all of the data. The extrapolation procedure is different from an earlier procedure based upon the multistage model in that two improved methods are put forward for calculating statistical confidence limits. (One is a linearized approximation of the other.) A further innovation is a recommendation for the integration of several data sets in the calculation of risk levels.     

Methodology issues in epidemiological assessment of health effects of low-dose ionising radiation

Epidemiological assessment of the health effects of exposure to low-dose ionising radiation is limited by the need for very large sample sizes and by various sources of bias that may generally affect epidemiological studies. Motivated by the present focus on low-dose effects, the following questions are examined: what are the strictly unavoidable limiting factors in the epidemiological methodology; what is its resolution limit in terms of effect size and what can be done to obtain further supportive evidence from the data?     

Exposure assessment: implications for epidemiological studies of ionizing radiation

Quantitative estimates of ionizing radiation exposure are often available for use in epidemiological studies. However, depending on the context, the quality of the exposure estimates can vary. For example, the estimates may be specific to individuals in the study or generic values averaged over populations; unavailable for some of the potential study subjects or vary in their form between individuals; based on contemporary measurements or assessed retrospectively; based on measurements alone, on surrogate measures of exposure, or on an exposure assessment model; or, as is often the case, cover one source of radiation exposure rather than all of them. Various ways in which ionizing radiation exposures have been assessed are illustrated through reference to some studies of childhood leukaemia, concerning environmental, medical, natural and parental occupational exposures. Based on this, implications for the interpretation of radiation epidemiological studies are discussed.     

Risk of road accident associated with the use of drugs: A systematic review and meta-analysis of evidence from epidemiological studies

This paper is a corrigendum to a previously published paper where errors were detected. The errors have been corrected in this paper. The paper is otherwise identical to the previously published paper. A systematic review and meta-analysis of studies that have assessed the risk of accident associated with the use of drugs when driving is presented. The meta-analysis included 66 studies containing a total of 264 estimates of the effects on accident risk of using illicit or prescribed drugs when driving. Summary estimates of the odds ratio of accident involvement are presented for amphetamines, analgesics, anti-asthmatics, anti-depressives, anti-histamines, benzodiazepines, cannabis, cocaine, opiates, penicillin and zopiclone (a sleeping pill). For most of the drugs, small or moderate increases in accident risk associated with the use of the drugs were found. Information about whether the drugs were actually used while driving and about the doses used was often imprecise. Most studies that have evaluated the presence of a dose-response relationship between the dose of drugs taken and the effects on accident risk confirm the existence of a dose-response relationship. Use of drugs while driving tends to have a larger effect on the risk of fatal and serious injury accidents than on the risk of less serious accidents (usually property-damage-only accidents). The quality of the studies that have assessed risk varied greatly. There was a tendency for the estimated effects of drug use on accident risk to be smaller in well-controlled studies than in poorly controlled studies. Evidence of publication bias was found for some drugs. The associations found cannot be interpreted as causal relationships, principally because most studies do not control very well for potentially confounding factors.     

Exposure assessment and other challenges in non-ionizing radiation studies of childhood leukaemia

Studies of electromagnetic fields (EMF) and the development of childhood leukaemia face unique difficulties. EMF are imperceptible, ubiquitous, have multiple sources, and can vary greatly over time and distances. Childhood leukaemia and high average exposures to magnetic fields are both quite rare. Thus, a major challenge in EMF epidemiology is the small number of highly exposed cases and the necessity for retrospective assessment of exposure. Only studies designed to minimize bias while maximizing our ability to detect an association, should one exist, would have a potential to contribute to our understanding. New approaches are needed; the most promising in the extremely low-frequency range involves a study of a highly exposed cohort of children who have lived in apartments next to built-in transformers or electrical equipment rooms. Another promising avenue is an investigation of possible joint effects of environmental exposures and genetic co-factors. An exposure assessment methodology for residential radiofrequency fields is still in its infancy. Rapid changes in technology and exponential increases in its use make exposure assessment more difficult and urgent.     

The role of driver sleepiness in car crashes: a systematic review of epidemiological studies

To assess the available evidence for a causal role of driver sleepiness in car crashes or car crash injury, and to quantify the effect, a systematic review of the international literature was conducted. The review included all studies with a fatigue-related exposure measure, a crash or crash injury outcome measure and a comparison group, regardless of publication status, language or date of the study. Eighteen cross-sectional studies and one case-control study fulfilled the inclusion criteria. The fatigue-related exposures investigated in these studies were sleep disorders (n = 14), shift work (n = 2), sleep deprivation/fragmentation (n = 1), and excessive daytime sleepiness (n = 2). Only one study used an injury outcome measure. Studies were limited in their ability to establish a causal relationship by their design, by biases, and in many cases, by small sample sizes. The better quality cross-sectional studies were suggestive of a positive relationship between fatigue and crash risk, but could not provide reliable estimates of the strength of the association. The case-control study provided moderately strong evidence for an association between sleep apnoea and risk of driver injury, with an adjusted odds ratio of 7.2 (95% confidence interval 2.4-21.8). We conclude that the direct epidemiological evidence for a causal role of fatigue in car crashes is weak, but suggestive of an effect. To estimate the burden of injury due to fatigue-related crashes in the population, information is required from well-designed observational epidemiological studies about the prevalence of fatigue in the car driving population and the size of the risk this confers.     

The use of biologically based cancer risk models in radiation epidemiology

Biologically based risk projection models for radiation carcinogenesis seek to describe the fundamental biological processes involved in neoplastic transformation of somatic cells into malignant cancer cells. A validated biologically based model, whose parameters have a direct biological interpretation, can also be used to extrapolate cancer risks to different exposure conditions with some confidence. In this article biologically based models for radiation carcinogenesis, including the two-stage clonal expansion (TSCE) model and its extensions, are reviewed. The biological and mathematical bases for such models are described, and the implications of key model parameters for cancer risk assessment examined. Specific applications of versions of the TSCE model to important epidemiological datasets are discussed, including the Colorado uranium miners' cohort; a cohort of Chinese tin miners; the lifespan cohort of atomic bomb survivors in Hiroshima and Nagasaki; and a cohort of over 200,000 workers included in the National Dose Registry (NDR) of Canada.     

A review of the bystander effect and its implications for low-dose exposure

Current models for the interaction between ionising radiation and living cells or tissues are based on direct genetic damage produced by energy deposition in cellular DNA. An important observation which has questioned this basic assumption is the radiation-induced bystander response, in which cells which have not been directly targeted respond if their neighbours have been exposed. This response predominates at low doses of relevance to radiation risk analysis (<0.2 Gy) and therefore needs to be fully characterised. The development of microbeams, which allow individual cells within populations to be targeted with precise doses of radiation, has provided a useful tool for quantifying this response. The authors' studies have targeted individual human and mouse cells with counted protons and helium ions and monitored neighbouring cells for the production of bystander responses. Bystander responses have been measured after exposures as low as a single proton or helium ion delivered to an individual cell. An important aspect is that these responses saturate with increasing dose to the single target cell, thus the relative roles of direct and indirect (non-targeted) responses change with dose. Studies with multicellular, tissue-based models are providing evidence that bystander responses may have a complex phenotype involving multiple pathways and the overall response may be a balance between multiple signalling processes and responses to radiation exposure. Current models for radiation risk assume a linear non-threshold response and have generally been extrapolated from high-dose exposures. The involvement of competing processes at low doses may have important consequences for understanding the effects of low-dose exposure.     

A review of experimental transverse Doppler studies

The possibility of detecting useful Doppler information when the ultrasound beam is transversely oriented to the flow, has so far been studied by several authors. A new theory, in particular, has demonstrated that the focusing properties of piezoelectric transducers involve a Doppler signal bandwidth proportional to the transverse velocity component. The key element to perform reliable “transverse” Doppler experimental studies is thus an efficient spectrum analyzer, capable of performing accurate and repeatable bandwidth measurements. The authors review here experimental tests of the new theory, independently done in several laboratories by means of a specially developed computerized spectrum analyzer. The results of these tests include the demonstration that the “transverse” Doppler bandwidth is invariant with the range of cell depth and dimensions. It is also discussed how the basic transverse Doppler technique can be conveniently extended to allow the two- and three-dimensional estimation of the flow vector. Experimental evidence about the possibility of using the new theory to give a correct interpretation of in vivo transverse spectrograms is also presented     

含氟聚合物涂料研究

综述了国内外近十年来含氟聚合物涂料研究方面的进展。     

A review of nanoindentation and related cathodoluminescence studies on semiconductor materials

Journal of Materials Science: Materials in Electronics - Nanoindentation studies on bulk and epitaxial semiconductor crystals have been reviewed in general. The common materials of technological...     

A note on evaluating the risk in continuous review inventory systems

This paper is an attempt to evaluate the long term risk of stock-out and obsolescence in continuous review inventory systems, typically of slow-moving but very critical items. Inventory decisions depend very much on the goodness of the estimates of the input parameters like the holding, ordering and stock-out costs. It is a well-known fact that stock-out cost is a very difficult parameter to estimate. The lower it is the lower the quality of service will be while the higher it is the higher the inventory cost would be and possibly higher obsolescence rate too. In this paper, we develop a framework to evaluate the risks, in the long term, of stock-out and obsolescence, especially for inventory of critical spares whose demand rate is not high. For this purpose, we propose the use of quasi-stationary distributions for continuous review (r, Q) inventory systems with the condition that the Laplace transforms of functions of interest are rational algebraic functions. We relate the quasi-stationary distribution to the conditional tail expectation which is a coherent risk measure used in finance and actuarial studies. Numerical illustration is also provided.     

Effects of radiation on thermal conductivity of some polymer resins

A study was made concerning the effect of radiation on the thermal conductivity of grade VK-9 adhesive (consisting of epoxy and polyamide resins) and of a Kriosil compound based on silicone resin.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 3, pp. 448–453, March, 1982.     

The influence of radon measurement errors on the uncertainties of epidemiological case-control studies

To analyse the influence of the parameters of case and control groups and uncertainties of radon concentration assessments on the dose-effect dependence, a special computer program was designed. The influence of measurement errors on the uncertainties of radon case-control analysis is demonstrated on examples of hypothetical case and control groups with sizes from 250-500 to 7000-14,000 members. The modelling was conducted using a Monte Carlo technique for different values of measurement uncertainties. The random errors of radon assessment affect both the numerical value of the slope coefficient β of the linear dependence of relative risk of lung cancer incidence on indoor radon concentration and the accuracy of this value. The extrapolation of the dependence of the slope coefficient β on the total (initial plus additional) random error of radon concentration assessment is suggested for the assessment of an unbiased value of the slope coefficient β.     

A review of risk factors and patterns of motorcycle injuries

Per vehicle mile traveled, motorcycle riders have a 34-fold higher risk of death in a crash than people driving other types of motor vehicles. While lower-extremity injuries most commonly occur in all motorcycle crashes, head injuries are most frequent in fatal crashes. Helmets and helmet use laws have been shown to be effective in reducing head injuries and deaths from motorcycle crashes. Alcohol is the major contributing factor to fatal crashes. Enforcement of legal limits on the blood alcohol concentration is effective in reducing motorcycle deaths, while some alcohol-related interventions such as a minimal legal drinking age, increased alcohol excise taxes, and responsible beverage service specifically for motorcycle riders have not been examined. Other modifiable protective or risk factors comprise inexperience and driver training, conspicuity and daytime headlight laws, motorcycle licensure and ownership, riding speed, and risk-taking behaviors. Features of motorcycle use and potentially effective prevention programs for motorcycle crash injuries in developing countries are discussed. Finally, recommendations for future motorcycle-injury research are made.     

A review of some damage tolerance design approaches for aircraft structures

Damage tolerance design is becoming a necessity in the design of modern aircraft although its importance was recognized as long as four centuries ago by Leonardo da Vinci. Two decades ago structural design engineers and research workers felt the need of incorporating damage tolerance in the design of aircraft structure. Due to a lack of comprehensive damage tolerance methodology large scale component test results were used to develop empirical damage tolerance methods. Recently, linear elastic fracture mechanics has been used in predicting residual strength and crack growth rates in damaged structure. As a result of these efforts significant developments in cracked structure analytical methodology have been achieved. The recent Air Force requirement to apply linear elastic fracture mechanics approach in damage tolerance design of aircraft structures, warrants and critical review of various approaches. In this paper an attempt has been made to critically review some damage tolerance design approaches and their application to aircraft structures.

The paper consists of three main sections: The first section reviews the residual strength analysis methodology, assumptions and limitations of each method are discussed through a simple example. The second part surveys the various crack propagation laws, including linear and non-linear ranges and spectrum loading effects. In the third and last section, fracture mechanics methodology is applied to several types of built-up structural components under spectrum loading conditions. The comparison of test results and analysis of complex structures indicate that simple methods of fracture mechanics can be applied to find the damage tolerant strength and rate of crack growth.

The review presented in this paper indicates that the majority of work done in development of fracture mechanics analytical methodology has been based on data obtained from small scale laboratory specimens tested under closely controlled conditions of damage and environment. The validity of the methodology for complex structure under complex loading conditions has not been established. Before the results of a fracture mechanics analytical methodology can be accepted with a high degree of confidence many realism factors must be properly accounted for in the analysis.     

A review of the scientific basis for radiation protection of the patient

The use of ionising radiation in medicine is the single largest man-made source of population exposure. Individual and collective doses to patients arising from the medical use of ionising radiations continue to rise significantly year on year. This is due to the increasing use of medical imaging procedures in modern healthcare systems as well as the continued development of new high dose techniques. This paper reviews the scientific basis for the principles of radiation protection as defined by the International Commission on Radiological Protection. These principles attempt to include exposures arising from both medical and non-medical applications within a common framework and have evolved over many years and changing socio-economic considerations. In particular, the concepts of justification and ALARA (doses should be as low as reasonably achievable), which underpin the principles for medical exposures are assessed in terms of their applicability to the scientific process and relevance to a rapidly changing technologically-led healthcare system. Radiation protection is an integral component of patient safety in medical practices and needs to be evidence based and amenable to the scientific process. The limitations imposed by the existing philosophy of radiation protection to the development of a quantitative framework for adequately assessing the performance of medical imaging systems are highlighted. In particular, medical practitioners will require quantitative guidance as to the risk-benefits arising from modern X-ray imaging methods if they are to make rational judgements as to the applicability of modern high-dose techniques to particular diagnostic and therapeutic tasks. At present such guidance is variable due to the lack of a rational framework for assessing the clinical impact of medical imaging techniques. The possible integration of radiation protection concepts into fundamental bio-medical imaging research activities is discussed.     

A general review of synchrotron radiation,its uses and special technologies

Synchrotron radiation is increasingly being used for research in many branches of science. This article provides a general introduction to the field, describing why it is important and discussing how the radiation is generated and utilized from a technological point of view. Attention is paid to current key points and problems involved in this and their solutions particularly those with respect to present generation machines. The usefulness of the radiation as a research tool embracing a wide range of disciplines is discussed at length. Examples of all the major experimental programs are given and described in some detail.