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  • Articles  (1,064,956)
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  • Physics  (807,233)
  • Energy, Environment Protection, Nuclear Power Engineering  (285,632)
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  • 1
    ISSN: 1539-6924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 2
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    Risk analysis 18 (1998), S. 563-573 
    ISSN: 1539-6924
    Keywords: Risk assessment ; mourning doves ; hunting ; radionuclides ; heavy metals ; lead shot ; cesium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Recreational and subsistence hunters and anglers consume a wide range of species, including birds, mammals, fish and shellfish, some of which represent significant exposure pathways for environmental toxic agents. This study focuses on the Department of Energy's (DOE's) Savannah River Site (SRS), a former nuclear weapons production facility in South Carolina. The potential risk of contaminant intake from consuming mourning doves (Zenaida macroura), the most popular United States game bird, was examined under various risk scenarios. For all of these scenarios we used the mean tissue concentration of six metals (lead, mercury, cadmium, selenium, chromium, manganese) and radiocesium, in doves collected on and near SRS. We also estimated risk to a child consuming doves that had the maximum contaminant level. We used the cancer slope factor for radiocesium, the Environmental Protection Agencies Uptake/Biokinetic model for lead, and published reference doses for the other metals. As a result of our risk assessments we recommend management of water levels in contaminated reservoirs so that lake bed sediments are not exposed to use by gamebirds and other terrestrial wildlife. Particularly, measures should be taken to insure that the hunting public does not have access to such a site. Our data also indicate that doves on popular hunting areas are exposed to excess lead, suggesting that banning lead shot for doves, as has been done for waterfowl, is desirable.
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  • 3
    ISSN: 1539-6924
    Keywords: Exposure duration ; survey data ; longevity bias ; angler populations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Exposure duration is an important component in determining long-term dose rates associated with exposure to environmental contaminants. Surveys of exposed populations collect information on individuals' past behaviors, including the durations of a behavior up to the time of the survey. This paper presents an empirical approach for determining the distribution of total durations that is consistent with the distribution past durations obtained from surveys. This approach is appropriate where the rates of beginning and ending a behavior are relatively constant over time. The approach allows the incorporation of information on the distribution of age in a population into the determination of the distribution of durations. The paper also explores the impact of “longevity” bias on survey data. A case study of the application of this approach to two angler populations is also provided. The results of the case study have characteristics similar to the results reported by Israeli and Nelson (Risk Anal. 12, 65–72 (1992)) from their analytical model of residential duration. Specifically, the average period of time for the total duration in the entire population is shorter than the average period of time reported for historical duration in the surveyed individuals.
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  • 4
    ISSN: 1539-6924
    Keywords: Risk perceptions ; cultural theory ; psychometric paradigm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper seeks to compare two frameworks which have been proposed to explain risk perceptions, namely, cultural theory and the psychometric paradigm. A structured questionnaire which incorporated elements from both approaches was administered to 129 residents of Norwich, England. The qualitative risk characteristics generated by the psychometric paradigm explained a far greater proportion of the variance in risk perceptions than cultural biases, though it should be borne in mind that the qualitative characteristics refer directly to risks whereas cultural biases are much more distant variables. Correlations between cultural biases and risk perceptions were very low, but the key point was that each cultural bias was associated with concern about distinct types of risks and that the pattern of responses was compatible with that predicted by cultural theory. The cultural approach also provided indicators for underlying beliefs regarding trust and the environment; beliefs which were consistent within each world view but divergent between them. An important drawback, however, was that the psychometric questionnaire could only allocate 32% of the respondents unequivocally to one of the four cultural types. The rest of the sample expressed several cultural biases simultaneously, or none at all. Cultural biases are therefore probably best interpreted as four extreme world views, and a mixture of qualitative and quantitative research methodologies would generate better insights into who might defend these views in what circumstances, whether there are only four mutually exclusive world views or not, and how these views are related to patterns of social solidarity, and judgments on institutional trust.
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  • 5
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    Risk analysis 19 (1999), S. 283-294 
    ISSN: 1539-6924
    Keywords: Risk perception ; pesticides ; pest management ; health effects ; agricultural pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Water pollution from agricultural pesticides continues to be a public concern. Given that the use of such pesticides on the farm is largely governed by voluntary behavior, it is important to understand what drives farmer behavior. Health belief models in public health and social psychology argue that persons who have adverse health experiences are likely to undertake preventive behavior. An analogous hypothesis set was tested here: farmers who believe they have had adverse health experiences from pesticides are likely to have heightened concerns about pesticides and are more likely to take greater precautions in dealing with pesticides. This work is based on an original survey of a population of 2700 corn and soybean growers in Maryland, New York, and Pennsylvania using the U.S. Department of Agriculture data base. It was designed as a mail survey with telephone follow-up, and resulted in a 60 percent response rate. Farm operators report experiencing adverse health problems they believe are associated with pesticides that is equivalent to an incidence rate that is higher than the reported incidence of occupational pesticide poisonings, but similar to the reported incidence of all pesticide poisonings. Farmers who report experiencing such problems have more heightened concerns about water pollution from fertilizers and pesticides, and illness and injury from mixing, loading, and applying pesticides than farmers who have not experienced such problems. Farmers who report experiencing such problems also are more likely to report using alternative pest management practices than farmers who do not report having such problems. This implies that farmers who have had such experiences do care about the effects of application and do engage in alternative means of pest management, which at least involve the reduction in pesticide use.
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  • 6
    ISSN: 1539-6924
    Keywords: Ethnicity ; fish consumption ; advisories ; Savannah River ; methylmercury ; risk perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract South Carolina has issued fish consumption advisories for the Savannah River based on mercury and radionuclide levels. We examine differences in fishing rates and fish consumption of 258 people interviewed while fishing along the Savannah River, as a function of age, education, ethnicity, employment history, and income, and test the assumption that the average consumption of fish is less than the recreational value of 19 kg/year assumed by risk assessors. Ethnicity and education contributed significantly to explaining variations in number of fish meals per month, serving size, and total quantity of fish consumed per year. Blacks fished more often, ate more fish meals of slightly larger serving sizes, and consumed more fish per year than did Whites. Although education and income were correlated, education contributed most significantly to behavior; people who did not graduate from high school ate fish more often, ate more fish per year, and ate more whole fish than people who graduated from high school. Computing consumption of fish for each person individually indicates that (1) people who eat fish more often also eat larger portions, (2) a substantial number of people consume more than the amount of fish used to compute risk to recreational fishermen, (3) some people consume more than the subsistence level default assumption (50 kg/year) and (4) Blacks consume more fish per year than Whites, putting them at greater risk from contaminants in fish. Overall, ethnicity, age, and education contributed to variations in fishing behavior and consumption.
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  • 7
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    Risk analysis 19 (1999), S. 453-459 
    ISSN: 1539-6924
    Keywords: Efficiency ; nonquantal ; probit ; quantal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Methods of quantitative risk assessment for toxic responses that are measured on a continuous scale are not well established. Although risk-assessment procedures that attempt to utilize the quantitative information in such data have been proposed, there is no general agreement that these procedures are appreciably more efficient than common quantal dose–response procedures that operate on dichotomized continuous data. This paper points out an equivalence between the dose–response models of the nonquantal approach of Kodell and West(1) and a quantal probit procedure, and provides results from a Monte Carlo simulation study to compare coverage probabilities of statistical lower confidence limits on dose corresponding to specified additional risk based on applying the two procedures to continuous data from a dose–response experiment. The nonquantal approach is shown to be superior, in terms of both statistical validity and statistical efficiency.
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  • 8
    ISSN: 1539-6924
    Keywords: Threshold ; measurement error ; mortality ; air pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The association between daily fluctuations in ambient particulate matter and daily variations in nonaccidental mortality have been extensively investigated. Although it is now widely recognized that such an association exists, the form of the concentration–response model is still in question. Linear, no threshold and linear threshold models have been most commonly examined. In this paper we considered methods to detect and estimate threshold concentrations using time series data of daily mortality rates and air pollution concentrations. Because exposure is measured with error, we also considered the influence of measurement error in distinguishing between these two completing model specifications. The methods were illustrated on a 15-year daily time series of nonaccidental mortality and particulate air pollution data in Toronto, Canada. Nonparametric smoothed representations of the association between mortality and air pollution were adequate to graphically distinguish between these two forms. Weighted nonlinear regression methods for relative risk models were adequate to give nearly unbiased estimates of threshold concentrations even under conditions of extreme exposure measurement error. The uncertainty in the threshold estimates increased with the degree of exposure error. Regression models incorporating threshold concentrations could be clearly distinguished from linear relative risk models in the presence of exposure measurement error. The assumption of a linear model given that a threshold model was the correct form usually resulted in overestimates in the number of averted premature deaths, except for low threshold concentrations and large measurement error.
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  • 9
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    Risk analysis 19 (1999), S. 527-545 
    ISSN: 1539-6924
    Keywords: breast-feeding ; chlorinated compounds ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Exposure to persistent organochlorines in breast milk was estimated probabilistically for Canadian infants. Noncancer health effects were evaluated by comparing the predicted exposure distributions to published guidance values. For chemicals identified as potential human carcinogens, cancer risks were evaluated using standard methodology typically applied in Canada, as well as an alternative method developed under the Canadian Environmental Protection Act. Potential health risks associated with exposure to persistent organochlorines were quantitatively and qualitatively weighed against the benefits of breast-feeding. Current levels of the majority of contaminants identified in Canadian breast milk do not pose unacceptable risks to infants. Benefits of breast-feeding are well documented and qualitatively appear to outweigh potential health concerns associated with organochlorine exposure. Furthermore, the risks of mortality from not breast-feeding estimated by Rogan and colleagues exceed the theoretical cancer risks estimated for infant exposure to potential carcinogens in Canadian breast milk. Although levels of persistent compounds have been declining in Canadian breast milk, potentially significant risks were estimated for exposure to polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans. Follow-up work is suggested that would involve the use of a physiologically based toxicokinetic model with probabilistic inputs to predict dioxin exposure to the infant. A more detailed risk analysis could be carried out by coupling the exposure estimates with a dose–response analysis that accounts for uncertainty.
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  • 10
    ISSN: 1539-6924
    Keywords: air dispersion ; models ; validation ; Rocky Flats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Five atmospheric transport models were evaluated for use in Phase II of the Historical Public Exposures Studies at the Rocky Flats Plant. Models included a simple straight-line Gaussian plume model (ISCST2), several integrated puff models (RATCHET, TRIAD, and INPUFF2), and a complex terrain model (TRAC). Evaluations were based on how well model predictions compared with sulfur hexafluoride tracer measurements taken in the vicinity of Rocky Flats in February 1991. Twelve separate tracer experiments were conducted, each lasting 9 hr and measured at 140 samplers in arcs 8 and 16 km from the release point at Rocky Flats. Four modeling objectives were defined based on the endpoints of the overall study: (1) the unpaired maximum hourly average concentration, (2) paired time-averaged concentration, (3) unpaired time-averaged concentration, and (4) arc-integrated concentration. Performance measures were used to evaluate models and focused on the geometric mean and standard deviation of the predicted-to-observed ratio and the correlation coefficient between predicted and observed concentrations. No one model consistently outperformed the others in all modeling objectives and performance measures. About 75% of the maximum hourly concentration predictions were within a factor of 5 of the observations. About 64% of the paired and 80% of the unpaired time-averaged model predictions were within a factor of 5 of the observations. The overall performance of the RATCHET model was somewhat better than the other models. All models appeared to experience difficulty defining plume trajectories, which was attributed to the influence of multilayered flow initiated by terrain complexities and the diurnal flow patterns characteristic of the Colorado Front Range.
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  • 11
    ISSN: 1539-6924
    Keywords: initiation ; Monte Carlo methods ; promotion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We present the results of a quantitative assessment of the lung cancer risk associated with occupational exposure to refractory ceramic fibers (RCF). The primary sources of data for our risk assessment were two long-term oncogenicity studies in male Fischer rats conducted to assess the potential pathogenic effects associated with prolonged inhalation of RCF. An interesting feature of the data was the availability of the temporal profile of fiber burden in the lungs of experimental animals. Because of this information, we were able to conduct both exposure–response and dose–response analyses. Our risk assessment was conducted within the framework of a biologically based model for carcinogenesis, the two-stage clonal expansion model, which allows for the explicit incorporation of the concepts of initiation and promotion in the analyses. We found that a model positing that RCF was an initiator had the highest likelihood. We proposed an approach based on biological considerations for the extrapolation of risk to humans. This approach requires estimation of human lung burdens for specific exposure scenarios, which we did by using an extension of a model due to Yu. Our approach acknowledges that the risk associated with exposure to RCF depends on exposure to other lung carcinogens. We present estimates of risk in two populations: (1) a population of nonsmokers and (2) an occupational cohort of steelworkers not exposed to coke oven emissions, a mixed population that includes both smokers and nonsmokers.
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  • 12
    ISSN: 1539-6924
    Keywords: accident risk ; population distribution ; RADTRAN ; transportation ; radioactive materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Calculation of accident dose-risk estimates with the RADTRAN code requires input data describing the population likely to be affected by the plume of radioactive material (RAM) released in a hypothetical transportation accident. In the existing model, population densities within 1/2 mile (0.8 km) of the route centerline are tabulated in three ranges (Rural, Suburban, and Urban). These population densities may be of questionable validity since the plume in the RADTRAN analysis is assumed to extend out to 120 km from the hypothetical accident site. We present a GIS-based population model which accounts for the actual distribution of population under a potential plume, and compare accident-risk estimates based on the resulting population densities with those based on the existing model. Results for individual points along a route differ greatly, but the cumulative accident risks for a sample route of a few hundred kilometers are found to be comparable, if not identical. We conclude, therefore, that for estimation of aggregate accident risks over typical routes of several hundred kilometers, the existing, simpler RADTRAN model is sufficiently detailed and accurate.
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  • 13
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    Risk analysis 19 (1999), S. 685-687 
    ISSN: 1539-6924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 14
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    Risk analysis 19 (1999), S. 703-710 
    ISSN: 1539-6924
    Keywords: probabilistic risk analysis ; subjective judgment ; risk-informed regulation ; robust Bayesian analysis ; human performance ; human error ; management and organizational factors ; corporate culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper discusses a number of the key challenges to the acceptance and application of probabilistic risk analysis (PRA). Those challenges include: (a) the extensive reliance on subjective judgment in PRA, requiring the development of guidance for the use of PRA in risk-informed regulation, and possibly the development of “robust” or “reference” prior distributions to minimize the reliance on judgment; and (b) the treatment of human performance in PRA, including not only human error per se but also management and organizational factors more broadly. All of these areas are seen as presenting interesting research challenges at the interface between engineering and other disciplines.
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  • 15
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    Risk analysis 19 (1999), S. 689-701 
    ISSN: 1539-6924
    Keywords: risk ; risk perception ; risk assessment ; risk communication ; risk management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Risk management has become increasingly politicized and contentious. Polarized views, controversy, and conflict have become pervasive. Research has begun to provide a new perspective on this problem by demonstrating the complexity of the concept “risk” and the inadequacies of the traditional view of risk assessment as a purely scientific enterprise. This paper argues that danger is real, but risk is socially constructed. Risk assessment is inherently subjective and represents a blending of science and judgment with important psychological, social, cultural, and political factors. In addition, our social and democratic institutions, remarkable as they are in many respects, breed distrust in the risk arena. Whoever controls the definition of risk controls the rational solution to the problem at hand. If risk is defined one way, then one option will rise to the top as the most cost-effective or the safest or the best. If it is defined another way, perhaps incorporating qualitative characteristics and other contextual factors, one will likely get a different ordering of action solutions. Defining risk is thus an exercise in power. Scientific literacy and public education are important, but they are not central to risk controversies. The public is not irrational. Their judgments about risk are influenced by emotion and affect in a way that is both simple and sophisticated. The same holds true for scientists. Public views are also influenced by worldviews, ideologies, and values; so are scientists' views, particularly when they are working at the limits of their expertise. The limitations of risk science, the importance and difficulty of maintaining trust, and the complex, sociopolitical nature of risk point to the need for a new approach—one that focuses upon introducing more public participation into both risk assessment and risk decision making in order to make the decision process more democratic, improve the relevance and quality of technical analysis, and increase the legitimacy and public acceptance of the resulting decisions.
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  • 16
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    Risk analysis 19 (1999), S. 727-738 
    ISSN: 1539-6924
    Keywords: mitigation ; insurance ; catastrophic risk ; building codes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper examines the impact that insurance coupled with specific risk mitigation measures (RMMs) could have on reducing losses from hurricanes and earthquakes as well as improving the solvency position of insurers who provide coverage against these hazards. We first explore why relatively few individuals adopt cost-effective RMMs by reporting on the results of empirical studies and controlled laboratory studies. We then investigate the impact that an RMM has on both the expected losses and those from a worst case scenario in two model cities—Oakland (an earthquake-prone area) and Miami/Dade County (a hurricane-prone area) which were constructed respectively with the assistance of two modeling firms. The paper then explores three programs for forging a meaningful public-private sector partnership: well-enforced building codes, insurance premium reductions linked with long-term loans, and lower deductibles on insurance policies tied to mitigation. We conclude by briefly examining four issues for future research on linking mitigation with insurance.
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  • 17
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    Risk analysis 19 (1999), S. 711-726 
    ISSN: 1539-6924
    Keywords: variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.
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  • 18
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    Risk analysis 19 (1999), S. 751-758 
    ISSN: 1539-6924
    Keywords: nuclear waste ; high-level waste ; performance assessment ; Yucca Mountain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The management of spent nuclear fuel and high-level nuclear waste has the deserved reputation as one of the most intractable policy issues facing the United States and other nations using nuclear reactors for electric power generation. This paper presents the author's perspective on this complex issue, based on a decade of service with the Nuclear Waste Technical Review Board and Board on Radioactive Waste Management of the National Research Council.
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  • 19
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    Risk analysis 19 (1999), S. 763-807 
    ISSN: 1539-6924
    Keywords: risk assessment ; probabilistic risk assessment ; performance assessment ; policy analysis ; history of technology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article describes the evolution of the process for assessing the hazards of a geologic disposal system for radioactive waste and, similarly, nuclear power reactors, and the relationship of this process with other assessments of risk, particularly assessments of hazards from manufactured carcinogenic chemicals during use and disposal. This perspective reviews the common history of scientific concepts for risk assessment developed until the 1950s. Computational tools and techniques developed in the late 1950s and early 1960s to analyze the reliability of nuclear weapon delivery systems were adopted in the early 1970s for probabilistic risk assessment of nuclear power reactors, a technology for which behavior was unknown. In turn, these analyses became an important foundation for performance assessment of nuclear waste disposal in the late 1970s. The evaluation of risk to human health and the environment from chemical hazards is built on methods for assessing the dose response of radionuclides in the 1950s. Despite a shared background, however, societal events, often in the form of legislation, have affected the development path for risk assessment for human health, producing dissimilarities between these risk assessments and those for nuclear facilities. An important difference is the regulator's interest in accounting for uncertainty.
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  • 20
    ISSN: 1539-6924
    Keywords: performance assessment ; nuclear waste ; risk-informed regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The U.S. Nuclear Regulatory Commission (NRC) staff has developed a performance assessment capability to address three programmatic areas in nuclear waste management: high-level waste, low-level waste, and decommissioning of licensed facilities (license termination). The NRC capability consists of: (1) methodologies for performance assessment; (2) models and computer codes for estimating system performance; (3) regulatory guidance in various forms, such as regulations, Branch Technical Positions, and Standard Review Plans; and (4) a technical staff experienced in executing and evaluating performance assessments for a variety of waste systems. Although the tools and techniques are refined for each programmatic area, general approaches and similar issues are encountered in all areas.
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  • 21
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    Risk analysis 19 (1999), S. 903-913 
    ISSN: 1539-6924
    Keywords: nuclear waste ; performance assessment ; Yucca Mountain ; probability ; repository ; high-level waste ; risk ; engineered barriers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In this paper the problem of high-level nuclear waste disposal is viewed as a five-stage, cascaded decision problem. The first four of these decisions having essentially been made, the work of recent years has been focused on the fifth stage, which concerns specifics of the repository design. The probabilistic performance assessment (PPA) work is viewed as the outcome prediction for this stage, and the site characterization work as the information gathering option. This brief examination of the proposed Yucca Mountain repository through a decision analysis framework resulted in three conclusions: (1) A decision theory approach to the process of selecting and characterizing Yucca Mountain would enhance public understanding of the issues and solutions to high-level waste management; (2) engineered systems are an attractive alternative to offset uncertainties in the containment capability of the natural setting and should receive greater emphasis in the design of the repository; and (3) a strategy of “waste management” should be adopted, as opposed to “waste disposal,” as it allows for incremental confirmation and confidence building of a permanent solution to the high-level waste problem.
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  • 22
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    Risk analysis 19 (1999), S. 915-931 
    ISSN: 1539-6924
    Keywords: Yucca Mountain ; performance assessment ; logic tree ; high-level radioactive waste ; Monte Carlo ; expert judgment ; repository ; groundwater ; climate ; infiltration ; percolation ; hydrothermal ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Electric Power Research Institute (EPRI) has sponsored the development of a model to assess the long-term, overall “performance” of the candidate spent fuel and high-level radioactive waste (HLW) disposal facility at Yucca Mountain, Nevada. The model simulates the processes that lead to HLW container corrosion, HLW mobilization from the spent fuel, and transport by groundwater, and contaminated groundwater usage by future hypothetical individuals leading to radiation doses to those individuals. The model must incorporate a multitude of complex, coupled processes across a variety of technical disciplines. Furthermore, because of the very long time frames involved in the modeling effort (≫104 years), the relative lack of directly applicable data, and many uncertainties and variabilities in those data, a probabilistic approach to model development was necessary. The developers of the model chose a logic tree approach to represent uncertainties in both conceptual models and model parameter values. The developers felt the logic tree approach was the most appropriate. This paper discusses the value and use of logic trees applied to assessing the uncertainties in HLW disposal, the components of the model, and a few of the results of that model. The paper concludes with a comparison of logic trees and Monte Carlo approaches.
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  • 23
    ISSN: 1539-6924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 24
    ISSN: 1539-6924
    Keywords: compliance certification application ; engineering analysis ; geochemistry ; geohydrology ; performance assessment ; probabilistic systems analysis ; radioactive waste ; scientific validity ; uncertainty ; 40 CFR 191
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Performance Assessment (PA) is the use of mathematical models to simulate the long-term behavior of engineered and geologic barriers in a nuclear waste repository; methods of uncertainty analysis are used to assess effects of parametric and conceptual uncertainties associated with the model system upon the uncertainty in outcomes of the simulation. PA is required by the U.S. Environmental Protection Agency as part of its certification process for geologic repositories for nuclear waste. This paper is a dialogue to explore the value and limitations of PA. Two “skeptics” acknowledge the utility of PA in organizing the scientific investigations that are necessary for confident siting and licensing of a repository; however, they maintain that the PA process, at least as it is currently implemented, is an essentially unscientific process with shortcomings that may provide results of limited use in evaluating actual effects on public health and safety. Conceptual uncertainties in a PA analysis can be so great that results can be confidently applied only over short time ranges, the antithesis of the purpose behind long-term, geologic disposal. Two “proponents” of PA agree that performance assessment is unscientific, but only in the sense that PA is an engineering analysis that uses existing scientific knowledge to support public policy decisions, rather than an investigation intended to increase fundamental knowledge of nature; PA has different goals and constraints than a typical scientific study. The “proponents” describe an ideal, six-step process for conducting generalized PA, here called probabilistic systems analysis (PSA); they note that virtually all scientific content of a PA is introduced during the model-building steps of a PSA; they contend that a PA based on simple but scientifically acceptable mathematical models can provide useful and objective input to regulatory decision makers. The value of the results of any PA must lie between these two views and will depend on the level of knowledge of the site, the degree to which models capture actual physical and chemical processes, the time over which extrapolations are made, and the proper evaluation of health risks attending implementation of the repository. The challenge is in evaluating whether the quality of the PA matches the needs of decision makers charged with protecting the health and safety of the public.
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    Risk analysis 19 (1999), S. 1003-1016 
    ISSN: 1539-6924
    Keywords: WIPP ; radioactive waste ; repository ; performance assessment ; transuranic waste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Waste Isolation Pilot Plant (WIPP) is a geological repository for disposal of U.S. defense transuranic radioactive waste. Built and operated by the U.S. Department of Energy (DOE), it is located in the Permian age salt beds in southeastern New Mexico at a depth of 655 m. Performance assessment for the repository's compliance with the 10,000-year containment standards was completed in 1996 and the U.S. Environmental Protection Agency (EPA) certified in 1998 that the repository meets compliance with the EPA standards 40 CFR 191 and 40 CFR 194. The Environmental Evaluation Group (EEG) review of the DOE's application for certification identified a number of issues. These related to the scenarios, conceptual models, and values of the input parameters used in the calculations. It is expected that these issues will be addressed and resolved during the first 5-year recertification process that began with the first receipt of waste at WIPP on March 26, 1999, and scheduled to be completed in March 2004.
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  • 26
    ISSN: 1539-6924
    Keywords: risk perception ; CRESP ; trust ; DOE Savannah River site ; risk assessment ; stakeholder ; economic dependence
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Environmental managers are increasingly charged with involving the public in the development and modification of policies regarding risks to human health and the environment. Involving the public in environmental decision making first requires a broad understanding of how and why the public perceives various risks. The Savannah River Stakeholder Study was conducted with the purpose of investigating individual, economic, and social characteristics of risk perceptions among those living near the Savannah River Nuclear Weapons Site. A number of factors were found to impact risk perceptions among those living near the site. One's estimated proximity to the site and relative river location surfaced as strong determinants of risk perceptions among SRS residents. Additionally, living in a quality neighborhood and demonstrating a willingness to accept health risks for economic gain strongly abated heightened risk perceptions.
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  • 27
    ISSN: 1539-6924
    Keywords: risk assessment ; uncertainty ; formaldehyde ; decision analysis
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A call for risk assessment approaches that better characterize and quantify uncertainty has been made by the scientific and regulatory community. This paper responds to that call by demonstrating a distributional approach that draws upon human data to derive potency estimates and to identify and quantify important sources of uncertainty. The approach is rooted in the science of decision analysis and employs an influence diagram, a decision tree, probabilistic weights, and a distribution of point estimates of carcinogenic potency. Its results estimate the likelihood of different carcinogenic risks (potencies) for a chemical under a specific scenario. For this exercise, human data on formaldehyde were employed to demonstrate the approach. Sensitivity analyses were performed to determine the relative impact of specific levels and alternatives on the potency distribution. The resulting potency estimates are compared with the results of an exercise using animal data on formaldehyde. The paper demonstrates that distributional risk assessment is readily adapted to situations in which epidemiologic data serve as the basis for potency estimates. Strengths and weaknesses of the distributional approach are discussed. Areas for further application and research are recommended.
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    Risk analysis 19 (1999), S. 1059-1069 
    ISSN: 1539-6924
    Keywords: spatial statistics ; optimal sequential search ; adaptive sampling ; simulation-optimization ; multiple imputation
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Suppose that a residential neighborhood may have been contaminated by a nearby abandoned hazardous waste site. The suspected contamination consists of elevated soil concentrations of chemicals that are also found in the absence of site-related contamination. How should a risk manager decide which residential properties to sample and which ones to clean? This paper introduces an adaptive spatial sampling approach which uses initial observations to guide subsequent search. Unlike some recent model-based spatial data analysis methods, it does not require any specific statistical model for the spatial distribution of hazards, but instead constructs an increasingly accurate nonparametric approximation to it as sampling proceeds. Possible cost-effective sampling and cleanup decision rules are described by decision parameters such as the number of randomly selected locations used to initialize the process, the number of highest-concentration locations searched around, the number of samples taken at each location, a stopping rule, and a remediation action threshold. These decision parameters are optimized by simulating the performance of each decision rule. The simulation is performed using the data collected so far to impute multiple probable values of unknown soil concentration distributions during each simulation run. This optimized adaptive spatial sampling technique has been applied to real data using error probabilities for wrongly cleaning or wrongly failing to clean each location (compared to the action that would be taken if perfect information were available) as evaluation criteria. It provides a practical approach for quantifying trade-offs between these different types of errors and expected cost. It also identifies strategies that are undominated with respect to all of these criteria.
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    Risk analysis 19 (1999), S. 1113-1125 
    ISSN: 1539-6924
    Keywords: OSHA ; environmental health regulation ; risk ambiguity ; indoor/workplace air quality
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Political context may play a large role in influencing the efficiency of environmental and health regulations. This case study uses data from a 1989 update of the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs) program to determine the relative effects of legislative mandates, costly acquisition of information by the agency, and pressure applied by special interest groups upon exposure standards. The empirical analysis suggests that federal agencies successfully thwart legislative attempts to limit agency discretion, and that agencies exercise bounded rationality by placing greater emphasis on more easily obtained information. The 1989 PELs were less significantly related to more costly information, contained “safety factors” for chemicals presenting relatively more ambiguous risks, and the proposed standard stringencies showed evidence of being influenced by vying industry and labor interests.
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  • 30
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    Keywords: aldrin ; dieldrin ; epidemiology ; occupational exposure ; cancer dose-response modeling ; proportional hazards ; hormesis ; distributional characterizations of added cancer risk
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The paper applies classical statistical principles to yield new tools for risk assessment and makes new use of epidemiological data for human risk assessment. An extensive clinical and epidemiological study of workers engaged in the manufacturing and formulation of aldrin and dieldrin provides occupational hygiene and biological monitoring data on individual exposures over the years of employment and provides unusually accurate measures of individual lifetime average daily doses. In the cancer dose-response modeling, each worker is treated as a separate experimental unit with his own unique dose. Maximum likelihood estimates of added cancer risk are calculated for multistage, multistage-Weibull, and proportional hazards models. Distributional characterizations of added cancer risk are based on bootstrap and relative likelihood techniques. The cancer mortality data on these male workers suggest that low-dose exposures to aldrin and dieldrin do not significantly increase human cancer risk and may even decrease the human hazard rate for all types of cancer combined at low doses (e.g., 1 μg/kg/day). The apparent hormetic effect in the best fitting dose-response models for this data set is statistically significant. The decrease in cancer risk at low doses of aldrin and dieldrin is in sharp contrast to the U.S. Environmental Protection Agency's upper bound on cancer potency based on mouse liver tumors. The EPA's upper bound implies that lifetime average daily doses of 0.0000625 and 0.00625 μg/kg body weight/day would correspond to increased cancer risks of 0.000001 and 0.0001, respectively. However, the best estimate from the Pernis epidemiological data is that there is no increase in cancer risk in these workers at these doses or even at doses as large as 2 μg/kg/day.
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    Risk analysis 19 (1999), S. 1157-1171 
    ISSN: 1539-6924
    Keywords: risk assessment ; transportation risk ; diesel exhaust ; fugitive dust ; vehicle emissions
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract When the transportation risk posed by shipments of hazardous chemical and radioactive materials is being assessed, it is necessary to evaluate the risks associated with both vehicle emissions and cargo-related risks. Diesel exhaust and fugitive dust emissions from vehicles transporting hazardous shipments lead to increased air pollution, which increases the risk of latent fatalities in the affected population along the transport route. The estimated risk from these vehicle-related sources can often be as large or larger than the estimated risk associated with the material being transported. In this paper, data from the U.S. Environmental Protection Agency's Motor Vehicle-Related Air Toxics Study are first used to develop latent cancer fatality estimates per kilometer of travel in rural and urban areas for all diesel truck classes. These unit risk factors are based on studies investigating the carcinogenic nature of diesel exhaust. With the same methodology, the current per-kilometer latent fatality risk factor used in transportation risk assessments for heavy diesel trucks in urban areas is revised and the analysis expanded to provide risk factors for rural areas and all diesel truck classes. These latter fatality estimates may include, but are not limited to, cancer fatalities and are based primarily on the most recent epidemiological data available on mortality rates associated with ambient air PM-10 concentrations.
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    Keywords: transportation risk ; Hydraxine ; sensitivity analysis ; simulation
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The US Department of Transportation was interested in the risks associated with transporting Hydrazine in tanks with and without relief devices. Hydrazine is both highly toxic and flammable, as well as corrosive. Consequently, there was a conflict as to whether a relief device should be used or not. Data were not available on the impact of relief devices on release probabilities or the impact of Hydrazine on the likelihood of fires and explosions. In this paper, a Monte Carlo sensitivity analysis of the unknown parameters was used to assess the risks associated with highway transport of Hydrazine. To help determine whether or not relief devices should be used, fault trees and event trees were used to model the sequences of events that could lead to adverse consequences during transport of Hydrazine. The event probabilities in the event trees were derived as functions of the parameters whose effects were not known. The impacts of these parameters on the risk of toxic exposures, fires, and explosions were analyzed through a Monte Carlo sensitivity analysis and analyzed statistically through an analysis of variance. The analysis allowed the determination of which of the unknown parameters had a significant impact on the risks. It also provided the necessary support to a critical transportation decision even though the values of several key parameters were not known.
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    Risk analysis 19 (1999), S. 1205-1214 
    ISSN: 1539-6924
    Keywords: Monte Carlo ; correlation ; copulas ; bivariate distributions ; dioxins
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Monte Carlo methods in risk assessment are finding increasingly widespread application. With the recognition that inputs may be correlated, the incorporation of such correlations into the simulation has become important. Most implementations rely upon the method of Iman and Conover for generating correlated random variables. In this work, alternative methods using copulas are presented for deriving correlated random variables. It is further shown that the particular algorithm or assumption used may have a substantial effect on the output results, due to differences in higher order bivariate moments.
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    Keywords: municipal waste incineration ; risk assessment ; Monte-Carlo simulation ; time activity patterns
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract During the modernization of the municipal waste incinerator (MWI, maximum capacity of 180,000 tons per year) of Metropolitan Grenoble (405,000 inhabitants), in France, a risk assessment was conducted, based on four tracer pollutants: two volatile organic compounds (benzene and 1, 1, 1 trichloroethane) and two heavy metals (nickel and cadmium, measured in particles). A Gaussian plume dispersion model, applied to maximum emissions measured at the MWI stacks, was used to estimate the distribution of these pollutants in the atmosphere throughout the metropolitan area. A random sample telephone survey (570 subjects) gathered data on time-activity patterns, according to demographic characteristics of the population. Life-long exposure was assessed as a time-weighted average of ambient air concentrations. Inhalation alone was considered because, in the Grenoble urban setting, other routes of exposure are not likely. A Monte Carlo simulation was used to describe probability distributions of exposures and risks. The median of the life-long personal exposures distribution to MWI benzene was 3.2·10−5 μg/m3 (20th and 80th percentiles = 1.5·10−5 and 6.5·10−5 μg/m3), yielding a 2.6·10−10 carcinogenic risk (1.2·10−10–5.4·10−10). For nickel, the corresponding life-time exposure and cancer risk were 1.8·10−4 μg/m3 (0.9.10−4 – 3.6·10−4 μg/m3) and 8.6·10−8 (4.3·10−8–17.3·10−8); for cadmium they were respectively 8.3·10−6 μg/m3 (4.0·10−6–17.6·10−6) and 1.5·10−8 (7.2·10−9–3.1·10−8). Inhalation exposure to cadmium emitted by the MWI represented less than 1% of the WHO Air Quality Guideline (5 ng/m3), while there was a margin of exposure of more than 109 between the NOAEL (150 ppm) and exposure estimates to trichloroethane. Neither dioxins nor mercury, a volatile metal, were measured. This could lessen the attributable life-long risks estimated. The minute (VOCs and cadmium) to moderate (nickel) exposure and risk estimates are in accord with other studies on modern MWIs meeting recent emission regulations, however.
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    Risk analysis 19 (1999), S. 1235-1249 
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    Keywords: soil contamination ; remediation urgency ; standards ; human exposure ; ecotoxicological risks ; risk due to contaminant migration
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract To assess soil and groundwater quality two generic (i.e. multifunctional) risk-based standards, Target and Intervention Value, have been developed, in the framework of the Dutch Soil Protection Act. These standards allow soil and groundwater to be classified as clean, slightly contaminated or seriously contaminated. The Target Value is based on potential risks to ecosystems, while the Intervention Value is based on potential risks to humans and ecosystems. In the case of serious soil contamination the site has, in principle, to be remediated, making it necessary to determine the remediation urgency on the basis of actual (i.e. site-specific) risks to humans and ecosystems and, besides, actual risks due to contaminant migration.
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    Notes: Abstract The spectrum of platinum is studied in the region from 250 to 1250 Å. The twenty-two 5d6s-5d6p spectral lines of the PtIX are assigned. All levels of the 5d6s configuration are found. The assignment of the previously known 5d6p levels is confirmed and their positions are refined. The 5d 2, 5d6s, and 5d6p configurations are theoretically described by the method of orthogonal operators. These calculations are compared with the data obtained by a conventional method using the Cowan program.
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    Optics and spectroscopy 88 (2000), S. 1-6 
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    Notes: Abstract The process of resonant multiphoton ionization of a hydrogen atom in the ground 1s state is studied by direct numerical integration of the nonstationary Schrödinger equation for a quantum system in an electromagnetic field. The dependence of photoionization probability on the radiation intensity is found to be nonmonotonic. It is established that the minima of ionization correspond to multiphoton resonances between the ground state and one of the excited (Rydberg) atomic states perturbed by the laser field. It is shown that ionization is suppressed due to rearrangement of Rydberg states in a strong electromagnetic field and is accompanied by efficient Raman Λ transitions, which connect a set of closely lying Rydberg states via the continuum.
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    Optics and spectroscopy 88 (2000), S. 96-101 
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    Topics: Physics
    Notes: Abstract An analysis of a specific feature of the interaction of an ultrashort pulse with a slit is made. Analytical expressions for a monochromatic wave in the form of an ultrashort pulse diffracted by an infinite slit are obtained.
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    Notes: Abstract The observation of “spatial-modulation” resonances of saturated absorption in the interaction of iodine-127 vapors with a superposition of frequency-nondegenerate TEM01 and TEM10 transverse modes of a linear laser is reported. The modulation of the total radiation power of the probing wave, recorded at twice the beating frequency of transverse modes of the laser, is interpreted to be the result of the transformation of modulation of the spatial distribution of the field into its amplitude modulation under the action of nonlinearly absorbing iodine vapors. Resonances of saturated absorption of the weak line R(127)11-5 of iodine-127 (633 nm) in an extracavity cell are observed by the method proposed.
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    Optics and spectroscopy 88 (2000), S. 127-131 
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    Notes: Abstract The shape of the transmission band of an active interferometer, a resonator with amplification and absorption cells excited by an external signal, is studied. Upon tuning the external signal frequency, the narrow saturated absorption resonances can be observed in the transmission band of the interferometer. It is shown that, by varying the gain, the resonance absorption amplitude can be compensated for one order of smallness in pressure. The effect of amplitude and frequency noises of the external signal on the results obtained is studied.
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    Optics and spectroscopy 88 (2000), S. 38-41 
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    Notes: Abstract The electronic and spatial structures of the impurity hydroxyl ion in LiF, NaF, and KF crystals are studied using a molecular cluster model by the Hartree-Fock-Roothaan method in the semiempirical INDO (intermediate neglect of differential overlap) approximation. The equilibrium geometry of the impurity ion is determined. The hydroxyl ion is oriented in all the three matrices along the 〈110〉-axis, which is caused by the formation of the selected chemical bond between the hydrogen ion and the nearest lattice fluorine ion located on the same axis. The optical absorption energies are calculated.
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    Optics and spectroscopy 88 (2000), S. 50-54 
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    Notes: Abstract Processes of the electron-hole pair generation and excited-state relaxation at earlier stages of the latent image formation in the AgBr nanocrystals are studied theoretically. The experimental dependence of the photographic blackening D in the field of the intense laser light on the light pulse energy I is analyzed in the range of pulse durations τi from 10−13 to 10−8 s. The values of I needed to obtain a fixed blackening D at τi∼10−10 s exceeded those at τi∼10−8 s by three orders of magnitude. However, as τi further decreased to hundreds of fs, these values decreased by two orders of magnitude. It is shown that experimental nonmonotonic dependences can be explained by saturation of the one-photon interband generation of electron-hole pairs accompanied by the development of the two-photon generation. For shortest pulses and, correspondingly, greatest light intensities, the pair generation rate varies more strongly than upon usual two-photon absorption, which is caused by the resonance optical Stark effect.
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    Notes: Abstract A study is reported of the scattering of surface magnetic polaritons in the vicinity of second-order spin-reorientational phase transitions, which is caused by spatial fluctuations of the order parameter. A four-sublattice antiferromagnet α-Fe2O3 is used as an example to derive expressions for the vacuum-scattered radiation near exchange magnetic-vibration frequencies. The scattering of surface magnetic polaritons is shown to be resonantly enhanced in characteristic regions of their spectrum. Estimates made for α-Fe2O3 indicate a possibility of experimental observation of surface magnetic-polariton scattering from fluctuations of the refractive index near second-order spin-reorientational phase transitions.
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    Astronomy letters 26 (2000), S. 49-60 
    ISSN: 1562-6873
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    Topics: Physics
    Notes: Abstract Phase retrieval of a signal given its intensity is considered as a problem of statistically estimating a set of unknown parameters, the Zernike coefficients. Specifically, the phase problem is presented in the context of classical wave optics in the Fresnel approximation. Investigating the stability in this case suggests first learning if the Zernike coefficients can be restored in principle. If this is indeed the case, it then suggests determining the accuracy of their estimation. The stability of a solution to the phase problem depends, as it does for the other inverse problems, on the spectrum of the Fisher information matrix. An explicit representation of the Fisher matrix is given, and its spectrum is calculated for in-focus and out-of-focus images of a pointlike source. Simulations show that the solutions in the latter case are generally stable, so the coefficients of the Zernike series can be determined with an acceptable accuracy. The principal components, the mutually independent combinations of aberrations that are a generalization of the coefficients of the well-known Karhunen-Loeve decomposition, are calculated. As an example of this approach, the maximum-likelihood method is used to determine the aberrations of the optical system.
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    Optics and spectroscopy 88 (2000), S. 151-157 
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    Notes: Abstract The afterglow of a discharge in helium with a small admixture of hydrogen is studied spectroscopically (p=40 Torr, [e]≤1011 cm−3). The time-resolved measurements of intensities of the first four lines of the Balmer series are performed. The concentrations of metastable helium atoms and molecules are evaluated from the relative intensity of the absorption lines. The ratios of excitation transfer rates from atoms He(2 3 S 1) k 1(n) and molecules of helium He2(a 2sσ 3Σ u + ) k 2(n) to atomic hydrogen H*(n) are measured to be k 1(n=3)/k 2(n=3)=0.04±0.02 and k 1(n=4)/k 2(n=4)=0.01±0.02. The ratios of excitation rate constants k 2(n) corresponding to different states H(n) are measured to be k 1(n=4)/k 2(n=3)=0.023±0.01; k 1(n=5)/k 2(n=3)≤0.013; and k 1(n=6)/k 2(n=3)≤0.007.
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    Optics and spectroscopy 88 (2000), S. 238-241 
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    Notes: Abstract An analysis is made of the dynamics of the transverse structure of the field in the scheme of a layer of a medium with nonlinear amplitude-phase transmittance and a feedback mirror separated from it by a linear spacing. For the case of small field changes in a single passage, an approximate equation is derived, which is close in form to the equation used in the average-field approximation for nonlinear interferometers excited with external emission. For the nonlinearity of threshold type, an analytical form is presented for the field distribution corresponding to localized dissipative structures (dissitons).
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    Notes: Abstract The question of applicability of the approximation of an elastic isotropic medium to the description of elastooptic distortions in the second-harmonic generation in nonlinear crystals is analyzed. A method for a change to this approximation is proposed and the numerical calculation of elastooptic distortions in the secondharmonic generation is made for some crystals.
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    Optics and spectroscopy 88 (2000), S. 253-259 
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    Notes: Abstract Results of laboratory measurements of the weak-localization effect for light scattered by surfaces with different characteristics are presented. The measurements were made in a range of phase angles of 0.2°–3.5°. The aim of the measurements was to study the influence of the choice of surface material (metal, dielectric), the size of particles of the scattering surface, their packing density, the reflectivity of a sample, and the wavelength of incident radiation on the effect. For the measurements, both nonpolarized and linearly polarized light was used. Powders of dielectric materials were found to enhance the weak-localization effect with increasing particle size, but the effect weakened starting with a certain size of the order of wavelength. The pressing of powders of dielectric transparent materials enhanced the opposition effect. This was most pronounced for samples with small-sized particles. The phase dependence of brightness became wider and more linear with decreasing reflectivity of the surface. A qualitative difference in the behavior of the phase dependence for the ratio of cross-and copolarized components was observed. For metals and metal-like materials, the ratio increased with decreasing phase angle. Dielectrics were found to have an opposite dependence.
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    Optics and spectroscopy 88 (2000), S. 297-301 
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    Topics: Physics
    Notes: Abstract Spectral and temporal characteristics of xenon flashlamps are studied theoretically for the case of high-power nonstationary discharges of microsecond lengths. It is shown that several factors affect them simultaneously under these conditions: parameters of electric discharge pulse, thermal inertia of a heated gas, and the region of transparency of a lamp envelope.
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    Optics and spectroscopy 88 (2000), S. 310-311 
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    Notes: Abstract The spectral and luminescent properties of the Cu+ ion in an NaCl crystal are studied and the amplification is obtained at the 3d 10→3d 94P transition, which is under excitation by the fourth harmonic of an Nd:YAG laser (λ=266 nm). It is found that the short-lived absorption is related to an uncontrollable nickel impurity in the crystal.
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    Notes: Abstract The fine-structure parameters are calculated semiempirically in the intermediate coupling scheme for the np 5 n′p configurations of rare gas atoms and a number of ions. The calculation is based on the two-electron matrix of the energy operator, which takes into account, along with the electrostatic interaction, all magnetic interactions. Diagonalizing the energy matrix with the calculated values of the fine-structure parameters yields energy values exactly coinciding with the experimental data, as well as the coupling coefficients and the gyromagnetic ratios. The results obtained are compared with the available literature data.
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    Notes: Abstract The infrared and Raman spectra of the octachlorodibenzo-p-dioxine molecule are measured and all normal vibrational modes of the molecule are calculated. Each vibrational mode was assigned to the vibrations of certain functional groups of atoms in the molecule, taking into account the local symmetry characteristics of the vibration mode. A correlation of vibrational modes by their shape was established in a series of molecules: dibenzo-p-dioxine, 2,3,7,8-tetrachlorodibenzo-p-dioxine, and OCDX. The influence of substituents on vibrational frequencies was also examined.
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    Optics and spectroscopy 88 (2000), S. 380-386 
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    Notes: Abstract A theory of quasi-resonance for the model of atoms with an arbitrary number of levels is developed by the method of unitary transformation without recourse to Bloch’s equations. Corrections to the results known from the theory of adiabatic following, which refine these results and take into account dispersion of the nonlinear response of the resonant system, are obtained. The condition for quasi-resonance with a single atomic transition is shown to impose stringent limitations on the form of the nonlinear evolution equation for the electric field envelope of the pulse with dispersion of the nonlinear response taken into account, which prohibit the reduction of the equation indicated to familiar, fully integrable systems.
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    Optics and spectroscopy 88 (2000), S. 334-338 
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    Notes: Abstract The line phosphorescence spectrum of octachlorodibenzo-p-dioxine (OCDX) is obtained and interpreted. The symmetry of the lowest triplet state of this molecule is established. The vibrational frequencies found from the vibronic phosphorescence spectrum at 4.2 k are assigned to the vibrational modes of certain symmetry related to individual functional atomic groups of the molecule. The relation between contributions from the spin-orbit (SO) and vibronic-spin-orbit (VSO) interactions to the phosphorescence rate constant k ph of the OCDX molecule is found from the vibronic line intensities. It is found that the increase in the number of Cl atoms in OCDX compared to that in tetrachlorobenzo-p-dioxine results in the increase in the relative contribution of the VSO interaction to k ph.
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    Optics and spectroscopy 88 (2000), S. 327-333 
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    Notes: Abstract Using the decay of a single exponential function to a nonzero level as an example, the following numerical methods for determining lifetimes are considered: the least-squares method, the differentiation method, and two modifications of the method of moments. Domains of efficient application of one method or the other, depending on the form of the noise distribution, are determined on the basis of computer simulation in parameter space of the problem. For the Poisson noise distribution, a domain of parameters is found, where the error of determining the decay rate in the method of moments is smaller than in the least-squares method.
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    Astronomy letters 26 (2000), S. 691-698 
    ISSN: 1562-6873
    Keywords: pulsars ; neutron stars ; X-ray sources ; scattering
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    Topics: Physics
    Notes: Abstract We present the results of our comparative timing and spectral analysis of the high and low (off) states in the X-ray pulsar Her X-1 based on data from the ART-P telescope onboard the Granat observatory. A statistically significant (several mCrab) persistent flux with a simple power-law spectrum was detected during the low state. The spectral slope changed from observation to observation by almost a factor of 2. Pulsations were detected only during the high state of the source, when its flux was a factor of ∼25 larger than the low-state flux. The spectral shape of Her X-1 in its high state was complex, with the parameters depending on pulse phase.
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    Astronomy letters 26 (2000), S. 679-690 
    ISSN: 1562-6873
    Keywords: interstellar medium ; circumstellar shells
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    Notes: Abstract The temperatures of prolate and oblate spheroidal dust grains in the envelopes of stars of various spectral types are calculated. Homogeneous particles with aspect ratios a/b≤10 composed of amorphous carbon, iron, dirty ice, various silicates, and other materials are considered. The temperatures of spherical and spheroidal particles were found to vary similarly with particle size, distance to the star, and stellar temperature. The temperature ratio T d(spheroid)/T d(sphere) depends most strongly on the grain chemical composition and shape. Spheroidal grains are generally colder than spherical particles of the same volume; only iron spheroids can be slightly hotter than iron spheres. At a/b≈2, the temperature differences do not exceed 10%. If a/b≥4, the temperatures can differ by 30–40%. For a fixed dust mass in the medium, the fluxes at wavelengths λ≥100 are higher if the grains are nonspherical, which gives overestimated dust masses from millimeter observations. The effect of grain shape should also be taken into account when modeling Galactic-dust emission properties, which are calculated when searching for fluctuations of the cosmic microwave background radiation in its Wien wing.
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    Astronomy letters 26 (2000), S. 699-724 
    ISSN: 1562-6873
    Keywords: neutron stars ; luminosity ; disk accretion ; X-ray bursters
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    Notes: Abstract The energy release L s on the surface of a neutron star (NS) with a weak magnetic field and the energy release L d in the surrounding accretion disk depend on two independent parameters that determine its state (for example, mass M and cyclic rotation frequency f) and is proportional to the accretion rate. We derive simple approximation formulas illustrating the dependence of the efficiency of energy release in an extended disk and in a boundary layer near the NS surface on the frequency and sense of rotation for various NS equations of state. Such formulas are obtained for the quadrupole moment of a NS, for a gap between its surface and a marginally stable orbit, for the rotation frequency in an equatorial Keplerian orbit and in the marginally stable circular orbit, and for the rate of NS spinup via disk accretion. In the case of NS and disk counterrotation, the energy release during accretion can reach $$0.67\dot Mc^2 $$ . The sense of NS rotation is a factor that strongly affects the observed ratio of nuclear energy release during bursts to gravitational energy release between bursts in X-ray bursters. The possible existence of binary systems with NS and disk counterrotation in the Galaxy is discussed. Based on the static criterion for stability, we present a method of constructing the dependence of gravitational mass M on Kerr rotation parameter j and on total baryon mass (rest mass) m for a rigidly rotating neutron star. We show that all global NS characteristics can be expressed in terms of the function M(j, m) and its derivatives. We determine parameters of the equatorial circular orbit and the marginally stable orbit by using M(j, m) and an exact solution of the Einstein equations in a vacuum, which includes the following three parameters: gravitational mass M, angular momentum J, and quadrupole moment Ф2. Depending on Ф2, this solution can also be interpreted as a solution that describes the field of either two Kerr black holes or two Kerr disks.
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    Optics and spectroscopy 88 (2000), S. 619-622 
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    Notes: Abstract Results of computer simulation of the shading effect in systems of opaque spherical particles scattering light in accordance with the Lambert law are presented. Two types of systems are studied: a semi-infinite medium and statistically uniform clusters of a finite number of particles. The simulation makes it possible to obtain photometric characteristics of systems with an accuracy better than 1%. The phase dependence of the shading effect is shown to become steeper as the packing density of particles in clusters decreases and their number increases. For statistically uniform media, the following relation takes place: The lower the packing density, the more pronounced the shadow decrease in brightness with an increasing phase angle.
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    Notes: Abstract The generalizations of the original Fresnel theory and original theory of natural gyrotropy as manifestations of the first-order natural dispersion in uniaxial crystals are considered. The generalizations are made for magnetic crystals, taking into account the magnetic gyrotropy. The region of application of the corresponding generalized theories is found to be restricted by a particular case of the wave normal s directed parallel to the optic axis C of a uniaxial crystal.
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    Notes: Abstract Granular gallium films deposited in high vacuum on the rough surfaces of NaCl and KCl single crystals maintained at 400°C consist of two layers, in which two resonance bands are excited simultaneously. In isolated grains of the upper layer, a band at the normal electron oscillation frequency ω0 is excited. As a result of supercooling, the grains are in the liquid state. The gallium plasma frequency calculated from the measured ω0 and dielectric constants of NaCl and KCl coincides with that obtained by other authors by metallooptic methods. In gallium deposited on room-temperature substrates, only one resonance band is excited, with the interband absorption band superposed on its low-frequency edge.
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    Notes: Abstract The absolute values of probabilities of the I 1Π g − , v′, J′; J 1 Δ g − , v′, J′→C 1Π u ± , v″, J″ spontaneous transitions in the H2 molecule (for the vibrational and rotational quantum numbers v′=v″=0–3, J′=1–6, and J″=J′, J′ ±1) are calculated by using ab initio and semiempirical data on the dipole moments of the 3dπ 1Πg, 3dδ1Δg→2pπ1Πu electronic transitions. In both cases, the calculations are performed both in the adiabatic approximation and with an allowance for the nonadiabatic effect of electronic-rotational interaction. The coefficients of expansion of the wave functions of perturbed rovibronic states in the Born-Oppenheimer basis functions used in the calculations were obtained in the approximation of pure precession from experimental values of the terms. It was found that the values of transition probabilities based on the ab initio calculations systematically exceed the corresponding semiempirical data by a factor of 1.2–1.9 for the I 1Πg→C 1Π u ± transition and by a factor of 1.4–1.6 for the J 1Δ g − →C 1Π u ± transition. It was established that the difference between the ab initio and semiempirical values of electronic transition moments virtually has no effect on the dependence of the transition probabilities on the vibrational quantum numbers. The discrepancies between the results of adiabatic and nonadiabatic calculations are significant and reach two orders of magnitude, which is indicative of the important role of perturbations in the probabilities of the transitions considered.
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    Optics and spectroscopy 88 (2000), S. 705-712 
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    Notes: Abstract Properties of collision transfer of vibrational energy in the vibrational quasi-continuum of mixed singlet-triplet levels of anthraquinone are studied by the method of time-resolved delayed fluorescence. The two-exponential fluorescence decay is analyzed in the kinetic approximation. It is shown that dependences of the intensities and decay rates of the fast and slow components on pressure can be used for estimating the rates of the establishment of the vibrational (V-V) and thermal (V-T) equilibrium. The efficiency β and the average energy 〈ΔE〉 transferred in collisions are estimated for these processes. It is found that the V-V process is characterized by high values of β, which, however, are lower in the quasi-continuum of mixed singlet-triplet states than the gas-kinetic values (β 〈 0.2). The transformation of the vibrational energy to the translational energy occurs with the low efficiency (10−2 〉 β 〉 10−5). The average energy 〈ΔE〉 transferred during a collision in the V-V process is comparable with the energy predicted by the statistical theory of ergodic transfer. The correlation between experimental and theoretical values improves when the time resolution of the experiment is sufficient for the separation of the V-V and V-T processes.
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    Optics and spectroscopy 88 (2000), S. 725-728 
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    Notes: Abstract The dynamics of switching waves in optically bistable systems on the basis of growing absorption is analyzed by quasi-optical description. A new scenario of kinks moving towards the optical beam under the action of a tubular optical beam is described. As opposed to an originally Gaussian beam focused on to the entrance face, a high intensity at the exit from the medium under the action of a collimated tubular beam is achieved due to the transformation of its profile. The structures formed are shown to be identical for both cases of action. The scenario of the development of moving switching waves found in this work is an alternative to that known in the literature earlier, which developed under the action of focused Gaussian beams and was analyzed with no regard for the variations of the phase of the optical beam.
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    Optics and spectroscopy 88 (2000), S. 852-856 
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    Notes: Abstract A new method for determining a fragment of the potential function of a bound state of a piatomic molecule from the phase of the matrix element of an electronic transition is proposed. As opposed to the method of WKB nodes [Opt. Spektrosk. 83, 906 (1997)], the new method (we call it the Franck-Condon factor phase method) is suitable for analyzing only those spectral regions free from interference structures. However, it is less demanding to the quality of experimental data and makes it possible to study situations where only a portion of the electronic band profile is accessible for analysis. Accuracy characteristics of the method are demonstrated using the analysis of the spectra of the transitions in Na2(23Σ g + (v=15, N=27; v=5, N=39)→3Σ u + ) as an example.
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    Optics and spectroscopy 88 (2000), S. 883-887 
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    Notes: Abstract The spectrum of the dielectric constant of three different samples of diamond in the 5–30-eV region is decomposed in thirteen elementary components. The main parameters of components are determined, and their nature is found on the basis of the band model.
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    Notes: Abstract The observation of the effect of mutual orientation of spin angular momenta of sodium atoms in the 32 S 1/2 state and helium atoms in the 23 S 1 state on the electrical conduction of a Na-He gas-discharge plasma is reported. In the experiments, a simultaneous optical orientation of atoms by the optical emission of sodium and helium lamps was carried out. The influence of the mutual orientation on the conduction was observed as a change in the high-frequency voltage across electrodes of a gas-discharge camera caused by the destruction of orientation of sodium atoms. The effect is explained by the dependence of Penning ionization in the interaction of sodium and helium atoms on the mutual orientation of spin angular momenta of partners.
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    Optics and spectroscopy 88 (2000), S. 696-704 
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    Notes: Abstract The formation of vibrational-rotational absorption spectra of small molecules in vibrationally non-equilibrium conditions, with the possibility of manifestation of partial population inversion of levels and negative absorption, is studied. Specific features of the partial inversion in linear and top molecules are analyzed. It is shown that water vapor is the best object among atmospheric gases for the realization of this effect. Formulas for the integrated line intensities and the absorption coefficient of two-and three-level nonequilibrium vibrational systems with a rotational structure are obtained. It is shown that the partial-inversion effect can be used to study weak vibrational-rotational transitions. Concrete calculations for the (000)-(010)-(020) bands of water molecules at different temperatures are made. The frequencies are determined for which negative absorption is the strongest.
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    Optics and spectroscopy 88 (2000), S. 921-925 
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    Notes: Abstract The diffraction of light by a corrugated surface of a layered structure is studied. It is shown that the excitation of waveguide modes in a layered structure substantially changes the diffraction efficiency of a corrugated structure. In the autocollimation regime, the diffraction efficiency of a grating with a moderate depth may reach 100%. An increased Q factor of leaky modes was found to be the condition of efficient interaction of light with a grating.
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    Optics and spectroscopy 88 (2000), S. 944-947 
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    Notes: Abstract The effect of reverse absorption saturation is studied in aromatic polyimides sensitized with fullerenes and a dye. The power density is estimated at which these systems can be most efficiently used to limit the laser radiation power. The data obtained are explained within the framework of the Förster model.
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    Optics and spectroscopy 89 (2000), S. 169-174 
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    Notes: Abstract Results of the experimental study of excitation of transitions of singly charged barium atoms in collisions of low-energy monokinetic electrons with barium atoms are presented. Regularities of the behavior of cross sections for excitation in spectral series of BaII are found. The results are compared with other authors’ results.
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    Optics and spectroscopy 89 (2000), S. 205-210 
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    Notes: Abstract A direct quantum-mechanical calculation of the relative intensities of lines in the resonance Raman scattering (RRS) spectra of uracil is performed by a method developed earlier by the authors on the basis of the adiabatic model in the Herzberg-Teller approximation [1]. It is shown that the main regularities in the intensity distribution of spectra can be explained only by taking into account the vibronic mixing of electronic states and the contribution to the scattering tensor components from the excited electronic states adjacent to the resonance state. The calculated results are in satisfactory agreement with the results of experimental studies of the RRS spectra of uracil excited by laser radiation at 266, 240, 218, and 200 nm.
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    Optics and spectroscopy 89 (2000), S. 211-215 
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    Notes: Abstract The burning kinetics of closely spaced equidistant holes in impurity absorption spectra of glasses and polymers is theoretically studied in an alternating electric field (alternating in the magnitude, sign, and direction). The height of barriers between wells of the burnt multiwell spectral hole depends on the shape of the distribution of impurity molecules over the Stark dipole moments. Centrally symmetric impurity molecules are considered whose Stark moment is determined exclusively by the interaction with matrix molecules. Model calculations performed for different hypothetical distribution functions of Stark moments yield substantially different kinetics. Therefore, the method described allows one to verify experimentally various hypotheses about the nature of matrix-induced Stark moments.
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    Notes: Abstract The intensities of vibronic lines are experimentally measured in fluorescence and fluorescence excitation spectra of jet-cooled anthracene. An original method is developed for calculating geometrical parameters of benzene hydrocarbons in the ground and excited electronic states. Using these parameters, the intensities of vibronic lines in fluorescence and absorption spectra of anthracene are calculated in the Franck-Condon approximation taking into account the mixing of all the twelve normal coordinates of totally symmetric vibrational modes. After correction for the quantum yield of fluorescence, good agreement is obtained between the calculated line intensities in the absorption spectrum and the measured line intensities in the fluorescence excitation spectrum. Based on these data, a new assignment of the lines in the fluorescence excitation spectrum corresponding to totally symmetric modes 7 and 8 is suggested.
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    Notes: Abstract The localization of molecular orbitals in 2,4,6-substituted derivatives of pyrylium is studied. The conformation of three asymmetrical molecules with oxyethyl substituents in positions 2 and 4 and different substituents in position 6 of the pyrylium ring is calculated by the AM1 method. The localization of the four upper occupied and two lower unoccupied MOs is determined, the fragment localization numbers are found, and the energies of five optical transitions, localization numbers, and the numbers of charge transfer between fragments are calculated. The conformation analysis of molecules in the S 0 and S 1 states is performed. Solid and liquid pyrylium solutions of different viscosity and polarity are experimentally investigated. The absorption spectra are recorded and absorption cross sections are measured, as well as fluorescence spectra and fluorescence anisotropy spectra. The following conclusions are made. In nonplanar molecules of pyrylium salts, four absorption transitions are localized at different parts of the molecule containing the pyrylium ring and one of the substituents. Upon excitation of molecules with complex substituents in position 6, the molecular fragment in position 2 turns around. This results in a flattening of the molecular fragment containing the pyrylium ring and substituents 2 and 6 on which the fluorescence transition is localized. The rearrangement involves the lowamplitude motion; it occurs almost without a loss of the excitation energy and only slightly affects the localization of molecular orbitals. As a result, two excited conformers are formed that possess close absorption and fluorescence properties. The radiative transitions in these conformers completely determine fluorescence of liquid solutions of any viscosity, including glycerol solutions. Strong solvatochromism is related to the nonplanar structure of stable pyrylium molecules, whereas the weak solvatochromism of liquid solutions is caused by localization of radiative transitions on a planar fragment of unstable fluorescing conformers.
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    Optics and spectroscopy 89 (2000), S. 232-235 
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    Notes: Abstract The formation of complexes in the fullerene C70-toluene-liquid crystal system is investigated. The precision study of spectral manifestations of the intermolecular interaction in this system is performed for two low-frequency absorption bands of C70. These manifestations are found to be specific for each of the bands analyzed.
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    Optics and spectroscopy 88 (2000), S. 911-915 
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    Notes: Abstract An analysis is made of acoustooptic Bragg diffraction in a paratellurite crystal in the case of a slow shear acoustic wave. It is shown that the isotropic acoustooptic interaction in crystals has characteristic physical features, which distinguish it from the well-known anisotropic interaction. The isotropic interaction under study is shown to be a more complicated process than diffraction in optically isotropic media. A theoretical and experimental study of the dependences of Bragg angle of incidence on the ultrasound frequency was made. Expressions for the calculation of this dependence are presented, which give results that agree well with the experimental data. The dependences of the isotropic-diffraction efficiency on the acoustic power were studied. For the first time, it was found that the corresponding dependences for anisotropic and isotropic interactions are substantially different. It is shown that the isotropic interaction under study is weaker than the anisotropic interaction. However, the isotropic-diffraction efficiency has a noticeable value and can reach tens of a percent.
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    Optics and spectroscopy 89 (2000), S. 185-191 
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    Notes: Abstract Using extended crossing beams and optical spectroscopy, the excitation of transitions in the quintet system of MnII terms from the ground state of the manganese atom were studied. The results are compared with other authors’ data. For the levels z 5 P 1,2,3 0 , the branching ratios, the contribution of cascade transitions, and the cross sections for level excitation were determined.
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    Optics and spectroscopy 89 (2000), S. 179-184 
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    Notes: Abstract Excitation of individual components of the resonance 4p 2 P 1 2,3/2/0 doublet of a Zn+ ion by electron impact is studied for the first time by the spectroscopic method in crossed beams. A distinct structure (above the ionization potential of an ion as well) found in the energy dependences of the effective excitation cross section is associated mainly with the decay to the resonance levels (direct or cascade) of autoionization states of zinc atoms and ions formed through the excitation of electrons from the subvalence 3d 10 shell. The results obtained are compared with data of other experiments and theoretical calculations by the method of strong coupling of five and fifteen states, as well as with the semiempirical calculation using the Van Regemorter formula.
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    Optics and spectroscopy 89 (2000), S. 287-289 
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    Notes: Abstract Optical self-induced transparency for extraordinary waves in anisotropic crystals is theoretically studied. Crystals in which dipole moments of impurity optically active atoms are arbitrarily oriented relative to the optic axis are analyzed in detail. Explicit analytic expressions for the parameters of nonlinear extraordinary wave are presented, which yield known results in limiting cases.
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    Notes: Abstract An analysis is made of the evolution of polarization of nonmonochromatic radiation travelling through single-mode optical fibers in the presence of random coupling between orthogonally polarized modes, which is caused by the random twist of axes of natural linear birefringence of an SMF, and in the presence of a regular axis twist. It is shown that the depolarization length of nonmonochromatic radiation in an SMF increases with increasing regular SMF twist, regardless of the presence of a random axis twist. Using the Monte Carlo method, the dependences of the mathematical expectation and the mean-square deviation of the degree of polarization of nonmonochromatic radiation on the fiber length for SMFs with different linear birefringences and regular axis twists are calculated. It is shown that the fiber length on which the degree of polarization of nonmonochromatic radiation reaches its limiting value increases and the limiting value itself decreases with an increasing regular twist. It is also shown that an induced SMF twist is able to improve parameters of a fiber interferometer, in particular, to decrease random phase changes and intensity fadings of the interference signal, which are caused by random coupling between polarization modes.
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    Optics and spectroscopy 89 (2000), S. 397-401 
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    Notes: Abstract The estimate of the root-mean-square roughness of a rough surface σ1 is studied experimentally as a function of the angle of incidence. A surface with σ=1.3 μm is illuminated by laser radiation with a wavelength of 0.633 μm. The angle of incidence of radiation on the surface under study is varied from 85° to 87.5°. σ1 is estimated under the assumption that the regime of a slightly rough surface is fulfilled for the surface studied. Theoretical estimates of σ1 are calculated in the Kirchhoff approximation with rough surface shadowing taken into account. The greatest relative difference between experimental and theoretical estimates of σ 1 does not exceed 0.07. The effect of rough surface shadowing on the estimate of σ is analyzed, and the possibility for exact measurement of σ1 of a shaded rough surface is demonstrated in the case of a priori knowledge of the angle of incidence, for which this measurement is possible. A method that makes it possible to determine the angle of incidence, for which a good agreement between the measured value and the true value of σ of a shaded rough surface is possible, is proposed.
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    Optics and spectroscopy 89 (2000), S. 348-351 
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    Notes: Abstract A method for diagnostics of a magnetic field is suggested. The method is based on spectropolarimetry of the decaying emission of an ensemble of particles whose angular momenta were ordered by pulsed axially symmetric perturbation.
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    Optics and spectroscopy 89 (2000), S. 356-359 
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    Notes: Abstract The spectrum of absorption of light by a molecule colliding with a fast proton is considered. It is shown that the envelope of spectrum is an oscillating function with two maxima shifted toward lower and higher frequencies compared to the frequency of a Franck-Condon transition.
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  • 85
    ISSN: 1562-6911
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    Topics: Physics
    Notes: Abstract We studied sensitization of Eu(III) and Tb(III) ions by molecules of 1,10-phenanthroline and 2,2-bipyridil in D2O and d 6-ethanol and the influence of Nd(III), Pr(III), Sm(III), Gd(III), and Ho(III) ions on the luminescence intensity I lum and lifetime τlum of Eu(III) and Tb(III) in solutions. The stability constants of complexes of Eu(III) and Gd(III) with 2,2′-bipyridil are measured by spectrophotometric and luminescence methods. It is shown that luminescence of Eu(III) is quenched by Gd(III) ions at the ion concentration equal to 10−2–10−1 M, which is caused by competing between these ions for a sensitizer. At the concentration of Ln(III) ions equal to 10−6−10−3 M, the sensitized luminescence of Eu(III) and Tb(III) was quenched and τlum decreased in the presence of Nd(III) ions, whereas in the presence of Gd(III) the luminescence intensity increased. It is proved that a bridge that connects the two ions upon energy transfer is formed by hydroxyl groups. The intensity of luminescence of Eu(III) and Tb(III) in aqueous solutions and its lifetime decreased in the presence of hydroxyl groups, while upon addition of Gd(III) to these solutions these quantities were restored. We also found that the addition of Gd(III) to deoxygenated ethanol solutions of 2,2′-bipyridil and Eu(III) slows down photochemical and thermal reactions between bipyridil and Eu(III), resulting in the increase in the luminescence intensity of Eu(III).
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  • 86
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectroscopic studies of sorbing devices on the basis of silica capillaries coated by sorbing polymer films are carried out by methods of spectroscopy of multiple attenuated total internal reflection with the use of combined elements of internal reflection. A technique for inspecting and improving the technological process of manufacture of sorbing devices for solid-phase microextraction and subsequent chromatographic analysis of organic compounds is developed.
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  • 87
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    Optics and spectroscopy 89 (2000), S. 422-428 
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A version of perturbation theory is developed that intends to determine the field distribution of spatial solitons with a 2D transverse profile in a Kerr medium in the case of small deviations from paraxial conditions. An approximate master equation for transverse components of the electric field in the case of wide solitons is derived. By solving this equation starting from the unperturbed soliton, i.e., Townes mode with linear polarization of radiation, a solution with an axially symmetric field distribution is found. Dependences of the main soliton characteristics on the degree of paraxiality are determined.
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  • 88
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    Optics and spectroscopy 89 (2000), S. 408-412 
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dielectric layers with silver nanoparticles, which are synthesized in a soda-silicate glass by implantation of 60-keV ions with a dose of 7.0×1016 Ag+/cm2 at an ion current density of 10 μmA/cm2, are analyzed. The depth of silver distribution was measured by Rutherford backscattering. Data on optical characteristics of composite layers were obtained from the transmission spectra and from the reflection, which were measured both from the side of an implanted glass surface and from the unimplanted side. To calculate reflection spectra, a multilayer plane-parallel film structure was considered, which was modeled on the basis of the matrix method using complex Fresnel coefficients. Dielectric functions of separate layers were determined using the Maxwell-Garnet theory of an effective medium. A qualitative agreement between the experimental and the model optical spectra was obtained taking into account a nonuniform depth distribution of metal nanoparticles in a composite material.
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  • 89
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of experiments on recording three-dimensional holographic images of extended diffuse objects using an SHG hologram generating the second harmonic are presented. In this case, the object image is formed by the second-harmonic radiation whose wavelength is smaller than the wavelength of object and reference waves recorded on a hologram by a factor of two. Elements of the theory of an SHG hologram are considered. A holographic image of a transparency object illuminated with diffuse light is obtained. It is shown that the resolving power of this image is close to the limit determined by diffraction effects. An experiment on defocusing the reconstructed image showed that it was localized in one spatial plane and, therefore, was three-dimensional.
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  • 90
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    Optics and spectroscopy 89 (2000), S. 756-760 
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The possibility of taking into account concentration effects in the determination of optical constants of latex in the visible and near IR regions of the spectrum is demonstrated, and the limits of applicability of the methods proposed for this purpose are determined. The limiting concentration of particles in suspensions for which these effects should be taken into account depend on the particle size. Using latex as an example, ways of increasing the accuracy of reconstruction of optical constants of weakly absorbing particles of micron and submicron size are shown. Similar concentration effects can take place in the study of blood substituents, proteins, and other weakly absorbing particles in weakly absorbing media.
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  • 91
    ISSN: 1562-6873
    Keywords: active galactic nuclei ; gamma-ray observations ; quasars and radio galaxies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present two-year-long observations of the flux of very-high-energy (∼1012 eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies 〉1012 eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10−11 and (3.7±0.6)×10−11 cm−2 s−1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ∼2×1043 erg s−1 sr−1.
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  • 92
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    Astronomy letters 26 (2000), S. 192-197 
    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Quasi-periodic variations in the thermodynamic and hydrodynamic fine-structure properties of the granulation field along the photospheric surface are estimated quantitatively. The darkest vast intergranular lanes, called the intergranular knots, are the most important indicator of their physical properties. The formulated new definitions of “granule” and “intergranular lane” require a revision of the previous results. The definition of mesogranulation is given, and the method of its detection in the granulation field is described. The following important quantitative results, which established the extent and nature of the physical relationship between the granulation and mesogranulation fields, have been obtained for the first time: (1) the intensity amplitude of granules in mesogranules (ΔI(gr)/I 0)msgr = +10.3% is a factor of 1.4 larger than that of granules in intermesogranular regions [(ΔI(gr)/I 0)imsgr = +7.3%], whereas the intensity amplitude of intergranular lanes in mesogranules [(ΔI(igr)/I 0)msgr = −6.0%] is a factor of 1.4 smaller than that of intergranular lanes in intermesogranular regions [(ΔI(igr)/I 0)imsgr = −8.4%]; (2) the mean intensities of photospheric granules and intergranular lanes are (ΔI(gr)/I 0)phot = +9.2% and (ΔI(igr)/I 0)phot = −7.5%, respectively; (3) granules cover 59% of the area of mesogranules, 45% of the area of the photosphere, and 31 % of the area of intermesogranular regions, while intergranular lanes cover 41, 55, and 69% of these areas, respectively; (4) intergranular knots and bright granules virtually never formed and do not exist in mesogranules and intermesogranular regions, respectively; (5) the amplitudes of intensity fluctuations in mesogranules and intermesogranular regions, as well as the areas occupied by them (49.4 and 50.6%, respectively), essentially level off, ΔI(msgr)/I 0 = +3.6% and ΔI(imsgr)/I 0 = −3.5%, respectively.
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  • 93
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    Astronomy letters 26 (2000), S. 204-207 
    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The observations of 34 extragalactic radio sources with the 22-m Crimean Astrophysical Observatory radio telescope at 36 GHz in 1985–1994 are presented. Intensity variations were detected in 27 objects, which may result from the appearance of new components in their cores.
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  • 94
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    Astronomy letters 26 (2000), S. 219-224 
    ISSN: 1562-6873
    Keywords: galaxies ; structure and photometry of galaxies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Photometric deprojection is used to determine the stellar-disk and bulge parameters for several edge-on galaxies from the FGC catalog. The assumption that the galaxies of our sample belonging to the fourth (i.e., lowest) surface-brightness class in the FGC are edge-on, low-surface-brightness (LSB) galaxies is considered.
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  • 95
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    Astronomy letters 26 (2000), S. 208-218 
    ISSN: 1562-6873
    Keywords: accretion ; jet theory and stellar wind
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A magnetohydrodynamic model is constructed for a cylindrical jet embedded in an external uniform magnetic field. It is shown that, as in the force-free case, the total electric current within the jet can be zero. The particle energetics and the magnetic-field structure are determined in a self-consistent way; all jet parameters depend markedly on the physical conditions in the external medium. In particular, we show that a region with subsonic flow can exist in the central jet regions. In real relativistic jets, most of the energy is transferred by the electromagnetic field only at a sufficiently large magnetization parameter σ〉106. We also show that, in general, the well-known solution with a central core B Z =B 0/(1+ϖ2/ϖ c 2 ) cannot be realized in the presence of an external medium.
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  • 96
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    Astronomy letters 26 (2000), S. 250-260 
    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamical stability of 38 observed hierarchical triple stars with known orbital elements of the internal and external binary subsystems and component masses is considered. Four different criteria of dynamical stability are used. The observed stability parameters and their critical values are calculated by taking into account errors in the orbital elements and component masses. Most triple systems are stable. According to some criteria, several triple stars (ADS 440, ξ Tau, λ Tau, ADS 3358, VV Ori, ADS 10157, HZ Her, Gliese 795, ADS 15971, and ADS 16138) may be dynamically unstable. This result is probably associated with unreliability of the empirical stability criteria and/or with errors in the observed quantities.
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  • 97
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    Astronomy letters 26 (2000), S. 233-243 
    ISSN: 1562-6873
    Keywords: stars—variable and peculiar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The UBVR photometry of XY Per in 1985–1998 is presented. At this epoch, XY Per exhibited variability with an amplitude of ≈1m in V. The photometric variability of XY Per can be divided into three components: (1) smooth year-to-year variations in mean brightness; (2) quasi-periodic variations with a characteristic time scale of 20–40 days and an amplitude of $$0\mathop .\limits^m 3$$ ; and (3) Algol-like minima with a duration of 15–20 days and an amplitude of $$0\mathop .\limits^m $$ . The CLEAN algorithm is used to refine the quasi-period of light variations in the interval 1988–1995, $$P = 22\mathop .\limits^d 7252$$ . The observed variability is assumed to be produced by two mechanisms: circumstellar absorption and nonstationary accretion. An ultraviolet excess was observed in the stellar radiation during the local minimum of 1991, which was associated with an eclipse of the star by a circumstellar formation. The probable reason why it emerged is that part of the eclipsing circumstellar formation fell into the accretion zone. A high-esolution spectrum in the wavelength range 3600–6700 Å contains both photospheric lines and circumstellar shell lines. The shell line profiles suggest mass accretion onto the star at a velocity of 90–140 km s−1. Of the Balmer lines, only Hα is in emission. Its equivalent width is E(E λ). The strongest Fe II lines, as well as Mg II 4481.33 Å and He I 5875.65 Å, have an emission component at the line center. The presence of emission components in lines with different excitation potentials suggests the presence of a hot gas shell around the star, which is heated very nonuniformly.
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  • 98
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    Astronomy letters 26 (2000), S. 225-232 
    ISSN: 1562-6873
    Keywords: stars—variable and peculiar ; T Tau stars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ultraviolet spectra of the star RU Lup obtained with the Hubble Space Telescope are analyzed. Emission lines are identified. The presence of absorption components with a nearly zero residual intensity in the Mg II resonance doublet lines is indicative of mass outflow with a velocity V ∞≃300 km s−1. These lines also exhibit a broad (≃1400 km s−1 at the base) component originating in the star itself. The profiles of the (optically thin) Si II] and Si III]1892 Å lines for the first time unequivocally prove that these lines originate in an accretion shock wave rather than in the chromosphere, with the gas infall velocity being V 0≃400 km s−1. The intensity ratio of the C IV 1550 Å and Si IV 1400 Å resonance doublet components was found to be close to unity, suggesting a high accreted-gas density, logN 0〉12.5. Molecular H2 Lyman lines formed in the stellar wind were detected. The H I Lα luminosity of RU Lup was found from their intensities to exceed 10% of L bol. Radiation pressure in the Lα line on atomic hydrogen may play a significant role in the initial acceleration of stellar-wind matter, but the effect of Lα emission on the dynamics of molecular gas is negligible.
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  • 99
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    Astronomy letters 26 (2000), S. 244-249 
    ISSN: 1562-6873
    Keywords: stars—structure and evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Published photoelectric measurements over a wide wavelength range (0.36–18 µm) are used to study the continuum spectrum of the star Θ1 Ori C. The model that assumes the following three radiation sources is consistent with observations: (1) a zero-age main-sequence O7 star (object 1) of mass M 1=20M ⊙, radius R 1=7.4R ⊙, effective temperature T 2=37 000 K, and absolute bolometric magnitude $$M\mathop {bol}\limits^1 = - 7\mathop .\limits^m 7$$ ; (2) object 2 with M 2=15M ⊙, R 2=16.2R ⊙, T 2=4000 K, and $$M\mathop {bol}\limits^2 = - 5\mathop .\limits^m 1$$ ; and (3) object 3 with R 310 700 R ⊙, T 3=190 K, and $$M\mathop {bol}\limits^3 = - 0\mathop .\limits^m 6$$ . The visual absorption toward the system is $$A_V = 0\mathop .\limits^m 95$$ and obeys a normal law. The nature of objects 2 and 3 has not been elucidated. It can only be assumed that object 2 is a companion of the primary star, its spectral type is K7, and it is in the stage of gravitational contraction. Object 3 can be a cocoon star and a member of the system, but can also be a dust envelope surrounding the system as a whole.
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  • 100
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    Astronomy letters 26 (2000), S. 269-276 
    ISSN: 1562-6873
    Keywords: gamma-ray bursts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the relativistic fireball model, the afterglow of a gamma-ray burst (GRB) is produced by synchrotron radiation of the electrons accelerated in the external shock that emerges as the relativistic flow moves. According to this model, the afterglow peaks on a time scale of ∼10 s when observed in the soft gamma-ray band. The peak flux can be high enough to be detected by modern all-sky monitors. We investigate the emission from short (ΔT〈1 s) GRBs on a time scale t≈10 s using BATSE/CGRO data. A significant flux is recorded for ∼20% of the events. In most cases, the observed persistent emission can be explained in terms of the model as an early burst afterglow. No early afterglows of most short GRBs are observed. The model parameters for these bursts are constrained.
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