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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    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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  • 2
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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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  • 3
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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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  • 4
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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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  • 5
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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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  • 6
    ISSN: 1539-6924
    Keywords: risk perception ; CRESP ; trust ; DOE Savannah River site ; risk assessment ; stakeholder ; economic dependence
    Source: Springer Online Journal Archives 1860-2000
    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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  • 7
    ISSN: 1539-6924
    Keywords: risk assessment ; uncertainty ; formaldehyde ; decision analysis
    Source: Springer Online Journal Archives 1860-2000
    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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  • 8
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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
    Source: Springer Online Journal Archives 1860-2000
    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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  • 9
    ISSN: 1539-6924
    Keywords: municipal waste incineration ; risk assessment ; Monte-Carlo simulation ; time activity patterns
    Source: Springer Online Journal Archives 1860-2000
    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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  • 10
    ISSN: 1539-6924
    Keywords: MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.
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  • 11
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    Risk analysis 19 (1999), S. 577-584 
    ISSN: 1539-6924
    Keywords: risk assessment ; exposure point concentration ; bootstrapping ; gamma distribution ; lognormal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The U.S. Environmental Protection Agency (EPA) recommends the use of the one-sided 95% upper confidence limit of the arithmetic mean based on either a normal or lognormal distribution for the contaminant (or exposure point) concentration term in the Superfund risk assessment process. When the data are not normal or lognormal this recommended approach may overestimate the exposure point concentration (EPC) and may lead to unecessary cleanup at a hazardous waste site. The EPA concentration term only seems to perform like alternative EPC methods when the data are well fit by a lognormal distribution. Several alternative methods for calculating the EPC are investigated and compared using soil data collected from three hazardous waste sites in Montana, Utah, and Colorado. For data sets that are well fit by a lognormal distribution, values for the Chebychev inequality or the EPA concentration term may be appropriate EPCs. For data sets where the soil concentration data are well fit by gamma distributions, Wong's method may be used for calculating EPCs. The studentized bootstrap-t and Hall's bootstrap-t transformation are recommended for EPC calculation when all distribution fits are poor. If a data set is well fit by a distribution, parametric bootstrap may provide a suitable EPC.
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  • 12
    ISSN: 1539-6924
    Keywords: regulation ; radioactive waste ; performance assessment ; risk assessment ; regulatory assessment ; bias evaluation ; international collaboration ; underground disposal ; quantitative risk analysis ; public debate ; decision process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Much has been written about the development and application of quantitative methods for estimating under uncertainty the long-term radiological performance of underground disposal of radioactive wastes. Until recently, interest has been focused almost entirely on the technical challenges regardless of the role of the organization responsible for these analyses. Now the dialogue between regulators, the repository developer or operator, and other interested parties in the decision-making process receives increasing attention, especially in view of some current difficulties in obtaining approvals to construct or operate deep facilities for intermediate or high-level wastes. Consequently, it is timely to consider the options for regulators' review and evaluation of safety submissions, at the various stages in the site selection to repository closure process, and to consider, especially, the role for performance assessment (PA) within the programs of a regulator both before and after delivery of such a submission. The origins and broad character of present regulations in the European Union (EU) and in the OECD countries are outlined and some regulatory PA reviewed. The issues raised are discussed, especially in regard to the interpretation of regulations, the dangers from the desire for simplicity in argument, the use of regulatory PA to review and challenge the PA in the safety case, and the effects of the relationship between proponent and regulator. Finally, a very limited analysis of the role of PA in public hearings is outlined and recommendations are made, together with proposals for improving the mechanisms for international collaboration on technical issues of regulatory concern.
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  • 13
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    Risk analysis 18 (1998), S. 679-688 
    ISSN: 1539-6924
    Keywords: Air quality ; benchmarking ; best available control technology ; contaminant exposure ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Although occupational exposure limits are sought to establish health-based standards, they do not always give a sufficient basis for planning an indoor air climate that is good and comfortable for the occupants in industrial work rooms. This paper considers methodologies by which the desired level, i.e., target level, of air quality in industrial settings can be defined, taking into account feasibility issues. Risk assessment based on health criteria is compared with risk-assessment based on “Best Available Technology” (BAT). Because health-based risk estimates at low concentration regions are rather inaccurate, the technology-based approach is emphasized. The technological approach is based on information on the prevailing concentrations in industrial work environments and the benchmark air quality attained with the best achievable technology. The prevailing contaminant concentrations are obtained from a contaminant exposure databank, and the benchmark air quality by field measurements in industrial work rooms equipped with advanced ventilation and production technology. As an example, the target level assessment has been applied to formaldehyde, total inorganic dust and hexavalent chromium, which are common contaminants in work room air.
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  • 14
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    Risk analysis 19 (1999), S. 23-32 
    ISSN: 1539-6924
    Keywords: Software failures ; software hazard analysis ; safety-critical systems ; risk assessment ; context
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As the use of digital computers for instrumentation and control of safety-critical systems has increased, there has been a growing debate over the issue of whether probabilistic risk assessment techniques can be applied to these systems. This debate has centered on the issue of whether software failures can be modeled probabilistically. This paper describes a “context-based” approach to software risk assessment that explicitly recognizes the fact that the behavior of software is not probabilistic. The source of the perceived uncertainty in its behavior results from both the input to the software as well as the application and environment in which the software is operating. Failures occur as the result of encountering some context for which the software was not properly designed, as opposed to the software simply failing “randomly.” The paper elaborates on the concept of “error-forcing context” as it applies to software. It also illustrates a methodology which utilizes event trees, fault trees, and the Dynamic Flowgraph Methodology (DFM) to identify “error-forcing contexts” for software in the form of fault tree prime implicants.
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  • 15
    ISSN: 1539-6924
    Keywords: Benchmark ; mercury ; risk assessment ; epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7-year-old New Zealand children were correlated with the mercury concentration in their mothers' hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.
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  • 16
    ISSN: 1539-6924
    Keywords: Remediation ; stakeholders ; deliberation ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The National Research Council has recommended the use of an analytic/deliberative decision-making process in environmental restoration decisions that involve multiple stakeholders. This work investigates the use of the results of risk assessment and multiattribute utility analysis (the “analysis”) in guiding the deliberation. These results include the ranking of proposed remedial action alternatives according to each stakeholder's preferences, as well as the identification of the major reasons for these rankings. The stakeholder preferences are over a number of performance measures that include the traditional risk assessment metrics, e.g., individual worker risk, as well as programmatic, cultural, and cost-related impacts. Based on these results, a number of proposals are prepared for consideration by the stakeholders during the deliberation. These proposals are the starting point for the formulation of actual recommendations by the group. In our case study, these recommendations included new remedial action alternatives that were created by the stakeholders after an extensive discussion of the detailed analytical results.
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  • 17
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    Risk analysis 19 (1999), S. 327-334 
    ISSN: 1539-6924
    Keywords: Biological introductions ; binucleate Rhizoctonia ; biocontrol ; risk assessment ; seedlings ; susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article describes an application of a method for assessing risks associated with the introduction of an organism into a new environment. The test organism was a binucleate Rhizoctonia fungal isolate that has potential for commercial development as a biological control agent for damping-off diseases in bedding plants. A test sample of host plant species was selected using the centrifugal phylogenetic host range principles, but with an emphasis on economic species. The effect of the fungus on the plant was measured for each species and expressed on a logarithmic scale. The effects on weights of shoots and roots per container were not normally distributed, nor were the effects on the number of plants standing (those which survived). Statements about the effect on the number standing and the shoot weight per container involved using the observed (empirical) distribution. This is illustrated with an example. Problems were encountered in defining the population of species at risk, and in deciding how this population should be formally sampled. The limitations of the method are discussed.
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  • 18
    ISSN: 1539-6924
    Keywords: dose-response ; models ; food-borne ; pathogens ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Food-related illness in the United States is estimated to affect over six million people per year and cost the economy several billion dollars. These illnesses and costs could be reduced if minimum infectious doses were established and used as the basis of regulations and monitoring. However, standard methodologies for dose-response assessment are not yet formulated for microbial risk assessment. The objective of this study was to compare dose-response models for food-borne pathogens and determine which models were most appropriate for a range of pathogens. The statistical models proposed in the literature and chosen for comparison purposes were log-normal, log-logistic, exponential, β-Poisson and Weibull-Gamma. These were fit to four data sets also taken from published literature, Shigella flexneri, Shigella dysenteriae,Campylobacter jejuni, and Salmonella typhosa, using the method of maximum likelihood. The Weibull-gamma, the only model with three parameters, was also the only model capable of fitting all the data sets examined using the maximum likelihood estimation for comparisons. Infectious doses were also calculated using each model. Within any given data set, the infectious dose estimated to affect one percent of the population ranged from one order of magnitude to as much as nine orders of magnitude, illustrating the differences in extrapolation of the dose response models. More data are needed to compare models and examine extrapolation from high to low doses for food-borne pathogens.
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  • 19
    ISSN: 1539-6924
    Keywords: ethylene oxide ; risk assessment ; epidemiology ; cancer guidelines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Ethylene oxide (EO) research has significantly increased since the 1980s, when regulatory risk assessments were last completed on the basis of the animal cancer chronic bioassays. In tandem with the new scientific understanding, there have been evolutionary changes in regulatory risk assessment guidelines, that encourage flexibility and greater use of scientific information. The results of an updated meta-analysis of the findings from 10 unique EO study cohorts from five countries, including nearly 33,000 workers, and over 800 cancers are presented, indicating that EO does not cause increased risk of cancers overall or of brain, stomach or pancreatic cancers. The findings for leukemia and non-Hodgkin's lymphoma (NHL) are inconclusive. Two studies with the requisite attributes of size, individual exposure estimates and follow up are the basis for dose-response modeling and added lifetime risk predictions under environmental and occupational exposure scenarios and a variety of plausible alternative assumptions. A point of departure analysis, with various margins of exposure, is also illustrated using human data. The two datasets produce remarkably similar leukemia added risk predictions, orders of magnitude lower than prior animal-based predictions under conservative, default assumptions, with risks on the order of 1 × 10−6 or lower for exposures in the low ppb range. Inconsistent results for “lymphoid” tumors, a non-standard grouping using histologic information from death certificates, are discussed. This assessment demonstrates the applicability of the current risk assessment paradigm to epidemiological data.
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  • 20
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    Risk analysis 19 (1999), S. 1223-1234 
    ISSN: 1539-6924
    Keywords: risk assessment ; standard-setting ; carcinogens ; OSHA ; ACGIH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract For carcinogens, this paper provides a quantitative examination of the roles of potency and weight-of-evidence (WOE) in setting permissible exposure limits (PELs) at the U.S. Occupational Safety and Health Administration (OSHA) and threshold limit values (TLVs) at the private American Conference of Governmental Industrial Hygienists (ACGIH). On normative grounds, both of these factors should influence choices about the acceptable level of exposures. Our major objective is to examine whether and in what ways these factors have been considered by these organizations. A lesser objective is to identify outliers, which might be candidates for further regulatory scrutiny. Our sample (N=48) includes chemicals for which EPA has estimated a unit risk as a measure of carcinogenic potency and for which OSHA or the ACGIH has a PEL or TLV. Different assessments of the strength of the evidence of carcinogenicity were obtained from EPA, ACGIH, and the International Agency for Research on Cancer. We found that potency alone explains 49% of the variation in PELs and 62% of the variation in TLVs. For the ACGIH, WOE plays a much smaller role than potency. TLVs set by the ACGIH since 1989 appear to be stricter than earlier TLVs. We suggest that this change represents evidence that the ACGIH had responded to criticisms leveled at it in the late 1980s for failing to adopt sufficiently protective standards. The models developed here identify 2-nitropropane, ethylene dibromide, and chromium as having OSHA PELs significantly higher than predicted on the basis of potency and WOE.
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  • 21
    ISSN: 1539-6924
    Keywords: Extreme events ; risk assessment ; risk management ; extreme value theory ; judgmental distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In this paper, we review methods for assessing and managing the risk of extreme events, where “extreme events” are defined to be rare, severe, and outside the normal range of experience of the system in question. First, we discuss several systematic approaches for identifying possible extreme events. We then discuss some issues related to risk assessment of extreme events, including what type of output is needed (e.g., a single probability vs. a probability distribution), and alternatives to the probabilistic approach. Next, we present a number of probabilistic methods. These include: guidelines for eliciting informative probability distributions from experts; maximum entropy distributions; extreme value theory; other approaches for constructing prior distributions (such as reference or noninformative priors); the use of modeling and decomposition to estimate the probability (or distribution) of interest; and bounding methods. Finally, we briefly discuss several approaches for managing the risk of extreme events, and conclude with recommendations and directions for future research.
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  • 22
    ISSN: 1539-6924
    Keywords: Market response ; risk assessment ; airplane accidents ; airline industry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The risk of catastrophic failures, for example in the aviation and aerospace industries, can be approached from different angles (e.g., statistics when they exist, or a detailed probabilistic analysis of the system). Each new accident carries information that has already been included in the experience base or constitutes new evidence that can be used to update a previous assessment of the risk. In this paper, we take a different approach and consider the risk and the updating from the investor's point of view. Based on the market response to past airplane accidents, we examine which ones have created a “surprise response” and which ones are considered part of the risk of the airline business as previously assessed. To do so, we quantify the magnitude and the timing of the observed market response to catastrophic accidents, and we compare it to an estimate of the response that would be expected based on the true actual cost of the accident including direct and indirect costs (“full-cost information” response). First, we develop a method based on stock market data to measure the actual market response to an accident and we construct an estimate of the “full-cost information” response to such an event. We then compare the two figures for the immediate and the long-term response of the market for the affected firm, as well as for the whole industry group to which the firm belongs. As an illustration, we analyze a sample of ten fatal accidents experienced by major US domestic airlines during the last seven years. In four cases, we observed an abnormal market response. In these instances, it seems that the shareholders may have updated their estimates of the probability of a future accident in the affected airlines or more generally of the firm's future business prospects. This market reaction is not always easy to explain much less to anticipate, a fact which management should bear in mind when planning a firm's response to such an event.
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  • 23
    ISSN: 1539-6924
    Keywords: Uncertainty ; variability ; risk assessment ; risk management ; ozone ; clean air act ; social policy ; analysis of benefits and costs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper is a challenge from a pair of lifelong technical specialists in risk assessment for the risk-management community to better define social decision criteria for risk acceptance vs. risk control in relation to the issues of variability and uncertainty. To stimulate discussion, we offer a variety of “straw man” proposals about where we think variability and uncertainty are likely to matter for different types of social policy considerations in the context of a few different kinds of decisions. In particular, we draw on recent presentations of uncertainty and variability data that have been offered by EPA in the context of the consideration of revised ambient air quality standards under the Clean Air Act.
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  • 24
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    Risk analysis 19 (1999), S. 135-152 
    ISSN: 1539-6924
    Keywords: Probability ; uncertainty ; data ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Risk assessors attempting to use probabilistic approaches to describe uncertainty often find themselves in a data-sparse situation: available data are only partially relevant to the parameter of interest, so one needs to adjust empirical distributions, use explicit judgmental distributions, or collect new data. In determining whether or not to collect additional data, whether by measurement or by elicitation of experts, it is useful to consider the expected value of the additional information. The expected value of information depends on the prior distribution used to represent current information; if the prior distribution is too narrow, in many risk-analytic cases the calculated expected value of information will be biased downward. The well-documented tendency toward overconfidence, including the neglect of potential surprise, suggests this bias may be substantial. We examine the expected value of information, including the role of surprise, test for bias in estimating the expected value of information, and suggest procedures to guard against overconfidence and underestimation of the expected value of information when developing prior distributions and when combining distributions obtained from multiple experts. The methods are illustrated with applications to potential carcinogens in food, commercial energy demand, and global climate change.
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  • 25
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    Stochastic environmental research and risk assessment 13 (1999), S. 85-99 
    ISSN: 1436-3259
    Keywords: Key words: Hydraulic diffusivity ; groundwater ; spectral analysis ; stochastic boundaries.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: This study uses the cyclical frequency to develop the mathematical relationship between hydraulic diffusivity and spectral density functions calculated from groundwater level variation. Such relationship can be applied to (1) unsteady state, one-dimensional confined aquifer with time-dependent water level on both end boundaries, and (2) linearized unconfined aquifer with or without vertical recharge. The spectral density functions of groundwater fluctuations are largely affected by the spectral density functions obtained from time-dependent end boundaries and their cross-spectral density functions. Hydraulic diffusivity of an aquifer can be solved by type-curve matching technique at a specified frequency band under the conditions of (1) confined aquifer having equal time-dependent boundaries on both ends, (2) unconfined aquifer having equal time-dependent boundaries on both ends with surface recharge, and (3) unconfined aquifer subjected to surface recharge but neglecting the water table fluctuations on both end boundaries.
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  • 26
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    Fire technology 32 (1996), S. 297-307 
    ISSN: 1572-8099
    Keywords: fire ; safety ; design ; regulations ; performance ; guidelines ; risk assessment ; evaluation ; criteria ; technology transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract Australia is quickly moving toward adopting performance-based regulations for building fire safety. This approach offers owners and designers more flexibility, greater opportunity for innovation, and more cost-effective construction. To help introduce a performance approach, the Fire Code Reform Centre has developedFire Engineering Guidelines, which document an agreed methodology for performance-based design and draws on earlier Australian research and similar developments in a number of countries. The guidelines are the first step in a broader research program to develop a full risk assessment methodology as the basis for fire safety design in Australia.
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  • 27
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    Journal of chemical crystallography 25 (1995), S. 841-844 
    ISSN: 1572-8854
    Keywords: Crystal structure ; bismuth chloride complexes ; diphenylammonium
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    Topics: Geosciences , Physics
    Notes: Abstract [(C6H5)2NH2]4 +[Bi4Cl16]4− crystallizes in the triclinic space group $$P\bar 1$$ witha=11.835(2),b=12.393(2),c=12.625(3)Å, α=108.37(3), β=108.69(3), γ=96.00(3)° andD c=2.135 g cm−3 forZ=1. The [Bi4Cl16]4− anion is a centrosymmetric cluster of four distorted edge-sharing BiCl6 octahedra. The ranges of the Bi−Cl bonds are 2.484(4)–2.606(3)Å for Bi−Cl(terminal), 2.691(3)–2.956(4)Å for Bi-Cl(µ2), and 2.960(3)–3.120(4)Å for Bi-Cl(µ3). The cations and anions are held in place by weak hydrogen bonds.
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  • 28
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    Journal of chemical crystallography 25 (1995), S. 215-218 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclic sulfite ; pentacycloundecane-8 ; 11-dione
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    Topics: Geosciences , Physics
    Notes: Abstract The structure of the cyclic sulfite derived from the reaction of thionyl chloride withendo-8-hydroxy-exo-8-(endo-8′-hydroxypentacyclo[5.4.0.0.2,6.03,10.05,9]undec-exo-8′-yl)pentacyclo-[5.4.0.0.2,6.03,10.05,9]undecane is reported. All bond lengths and angles are consistent with the strained cage geometry. A static disorder of the terminal oxygen was found to be present.
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  • 29
    ISSN: 1572-8854
    Keywords: Crystal structure ; pinacol ; reductive dimerization
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    Topics: Geosciences , Physics
    Notes: Abstract The pinacol resulting from sodium promoted reductive coupling of a methyleneheptacyclo-[6.6.02,6.03,13.04,11.05,9.010,14]tetradecanone possesses a conformation in which equivalent groups on the pinacol carbon are virtually perpendicular to each other. This rotation minimizes steric interactions, thus the geometries of all the fragments in the molecule are within expected values.
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  • 30
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    Journal of chemical crystallography 25 (1995), S. 601-603 
    ISSN: 1572-8854
    Keywords: Crystal structure ; imidazolium ; vinyl
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    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes with two independent molecules in the unit cell. The two molecules arecis-trans isomers. Crystal data: orthorhombic, P212121,a=7.0417(6),b=9.5341(9),c=25.411(2) Å,Z=8. The crystal structure has been solved by automated Patterson methods and refined toR=0.024 for 1843 observed reflections.
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  • 31
    ISSN: 1572-8854
    Keywords: Crystal structure ; epoxy ester
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    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of an epoxy ester is described. The structure has been solved by vector search methods and refined by least squares methods toR 1=0.0372 [I〉2σ(I)]. The structure consists of two independent molecules in the asymmetric unit. These molecules are chemically the same. Crystal data: C11H12O4, triclinic, space group $$P\bar 1$$ ,a=10.324(3),b=10.553(7),c=10.869(5)Å, α=61.77(4), β=88.64(4), γ=88.16(6)°,V=1042.7(9)Å3,Z=4.
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  • 32
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    Journal of chemical crystallography 26 (1996), S. 341-346 
    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrated phosphate ; layer-type structure ; strontium phosphate ; strontium phosphate hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of a highly hydrated tristrontium phosphate, nonastrontium hexakis(phosphate) hexadecahydrate, Sr9(PO4)6·16H2O, has been determined by single crystal X-ray diffraction. The crystals are monoclinic,a=15.203(2),b=6.488(1),c=18.984(7) Å, β=98.42(2)o, space groupP2/c (No. 13),Z=2,V=1852.3 Å3,d c =2.951 Mg·m−3. The structure was refined by full-matrix least-squares techniques toR=0.038,R w =0.051, for 2329 reflections with I≥3σ(I). The structure can be described in terms of a layer-type arrangement parallel to (100). One layer consists of a compact assembly of columns of Sr and PO4 ions in a pseudohexagonal arrangement resembling an apatitic structure. A second layer containing all the water molecules and one PO4 ion that occupies the interstitial space may be referred to as the hydrated layer. The structure has an overall similarity to that of octacalcium phosphate and can be considered as a model for amorphous calcium phosphate.
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  • 33
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    Journal of chemical crystallography 26 (1996), S. 563-567 
    ISSN: 1572-8854
    Keywords: Crystal structure ; aluminum ; amide
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    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of [(tBu)2Al(μ-NHtBu)]2 has been determined. The unit cell contains two independent molecules with only slight variation in the orientation of thetert-butyl ligands. Crystal data: Triclinic, $$P\bar 1$$ ,a=9.0138(6),b=10.2944(8),c=15.791(1) Å, α=91.262(6), β=89.822(6), γ=106.141(6)°,V=1407.2(2) Å3,Z=2,R=0.039,R w=0.041.
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  • 34
    ISSN: 1572-8854
    Keywords: Crystal structure ; diphenyl amines ; AM1 calculations ; phenothiazines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structural determination by X-ray crystallography of the titled N-arylamine 4a, as well as AM1 calculations on a series of derivatives (4b–c, 5a–c), are reported. The compound 4a is monoclinic P21/c with a = 7.656(3), b = 23.655(5), c = 7.686(9) Å, β = 112.59(6)°, V = 1285.2(2) Å3 and Z = 4. This structure has been used as a template for the building of some others derivatives used for AM1 calculations. The results show that the cyclization position on the aromatic rings, which can lead to two regioisomers, depends on the nature of the benzylic substituants.
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  • 35
    ISSN: 1572-8854
    Keywords: Crystal structure ; noncentrosymmetric ; disulfide ; imidazolidinedione ; homocystine hydantoin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Di-(2,4-imidazolidinedione-5-ethyl)disulfide or homocystine hydantoin, C10H14N4O4S2 (I), crystallizes in the non-centrosymmetric space group P21 (No. 4) with two molecules in the unit cell with a = 7.132(1), b = 9.282(2), c = 10.770(2) Å and β = 105.68(1)°. The two imidazolidinedione rings are planar with a dihedral angle of 46.9°. The rings are joined by a diethyl disulfide bridge at chiral centers on the rings. The C-S-S-C torsion angle is −80°(−sc). The absolute stereochemistry of the chiral centers was determined to be (5S, 5′S), η = + 0.92 (11). Important bond distances include: S-S = 2.022(4); S-C (mean) = 1.809(8); and C=O (mean) = 1.224(7) Å. The compound is stabilized by a network of intermolecular carbonyl-to-amine hydrogen bonding and van der Waals cohesive forces.
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  • 36
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    Journal of chemical crystallography 28 (1998), S. 831-834 
    ISSN: 1572-8854
    Keywords: Crystal structure ; macrocyclic tetraamine ; isocyanato zinc(II) complex
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    Topics: Geosciences , Physics
    Notes: Abstract The complex, [Zn(L)(NCO)]Cl · 3H2O (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane), has been synthesized and structurally characterized. 1 crystallizes in the monoclinic system, space group P21/n with a = 10.530(3), b = 9.315(2), c = 27.188(3) Å, β = 92.58(1)°, V = 2664.1(9)Å3, and Z = 4. The zinc atom is in a distorted squarepyramidal environment with the four nitrogen atoms of the macrocycle and one nitrogen atom of the isocyanate ligand.
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  • 37
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    Journal of chemical crystallography 28 (1998), S. 867-870 
    ISSN: 1572-8854
    Keywords: Crystal structure ; macrocyclic nickel(II) complex ; chromate
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    Topics: Geosciences , Physics
    Notes: Abstract A novel compound catena-(μ-CrO4-O,O′)[Ni(L1)Ni(L2)] 3H2O (1) (L1 = 3,5,10,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane and L2 = 2,5,9,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized for the first time and structurally characterized. 1 crystallizes in the triclinic space group Pī with a = 9.623(1), b = 10.084(1), c = 12.723 (3) Å, α = 66.74(2), β = 75.20(1), γ = 72.02(1)°, V = 1066.2(3) Å3, and Z = 2. The coordination environment around the Ni(II) ions is an axially elongated octahedron with the secondary amines of the isomeric ligands and two oxygen atoms of [CrO4]2−.
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  • 38
    ISSN: 1572-8854
    Keywords: Crystal structure ; ir/nmr ; β-amino-α ; β-unsaturaled ketone ; noncentrosemmtric ; enamino ketones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystallographic structural refinement of E-4-(N-methylanilino)-3-pentene-2-one (I) has been carried out by means of three-dimensional single-crystal X-ray diffractometry. The title compound crystallizes in space group C2 (No. 5,Z = 4). The lattice constants are a = 21.543(4), b = 6.433(1), c = 8.019(2) Å, and β = 97.82(3)°. Characterizations include physical property determinations and spectrometric identifications employing IR, 1H and 13C NMR, and X-ray powder analyses. The molecules in the crystal lattice are held together by van der Waals forces. Selected bond distances and angles are presented and discussed as well as synthesis and peripheral studies.
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  • 39
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    Journal of chemical crystallography 28 (1998), S. 145-147 
    ISSN: 1572-8854
    Keywords: Crystal structure ; benzimidazole ; antimicrobial activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine, C14H11N3Cl2, M r = 292.17, crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 10.707(2), b = 9.615(2), c = 25.944(6) Å. The benzimidazole ring system is planar and makes a dihedral angle of 77.8(1)° with the phenyl ring. The structure is stabilized by an N–H···N hydrogen bond.
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  • 40
    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; praseodymium(III) carboxylate complex ; double betaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel polymeric Pr(III) complex with a new double betaine, namely [{Pr(L1)1.5(H2O)2} n ][ClOli4]3 n ·nH2O (1) (L1 = 1,4-diazoniobicyclo[2,2,2]octane-1,4-dipropionate), has been synthesized and characterized by X-ray analysis. In the title complex, the Pr(III) atom is nine-coordinated by seven oxygen atoms from five L1 ligands and two aqua ligands. Each pair of adjacent praseodymium(III) atoms is linked by a pair of μ3 chelating and bridging carboxylate groups, thus forming an infinite metal···metal chain running parallel to the a direction, and such chains are cross-linked by flexible backbones of L1 ligands into a three-dimensional network with the perchlorate anions and lattice water molecules accommodated in the interstitial space. The title complex crystallizes in the monoclinic space group P21/n with a = 8.085(2), b = 14.316(3), c = 29.775(6) Å, β = 103.04(3)° and Z = 4.
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  • 41
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    Journal of chemical crystallography 28 (1998), S. 251-258 
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecane
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    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of three compounds formed via ultimate nucleophilic attack of unsaturated hydrocarbon fragments are reported. Geometries of the bis(vinyl)-, mono(vinyl), and bis(ethynyl)-substituted PCU species are unexceptional. The crystal structures are dictated by the availability of intermolecular hydrogen bonding.
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  • 42
    ISSN: 1572-8854
    Keywords: Crystal structure ; tricyclodecadienone ; enaminone ; resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of (+)-(1R, 2S, 6R, 7S, 1′R)-5-(1′-phenylethylamino)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one is described. Based on the known absolute configuration (R) of the α-phenylethylamine moiety the X-ray analysis revealed the absolute configuration of the title compound. The structure was refined to R 1 = 0.0298 for 1950 reflections (with I 〉 2σ(I)). Crystal data: C18H19NO, monoclinic, space group P21, a = 6.7406(4), b = 9.959(2), c = 11.3123(8)Å, β = 102.969(5), V = 740.0(2)Å3, and Z = 2.
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  • 43
    ISSN: 1572-8854
    Keywords: Crystal structure ; tricyclodecadienone ; enaminone ; dynamic kinetic resolution
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    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of (−)-(1R, 2S, 6R, 7S, 2′S)-5-(2′-hydroxymethyl-pyrrolidin-1′-yl)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one is described. Knowing the absolute configuration of the prolinol moiety (S) the X-ray diffraction study established the absolute configuration of the title compound. The structure was refined to R 1 = 0.0322 for 1237 reflections (with I 〉 2σ(I)). Crystal data: C15H19NO2, monoclinic, space group P21, a = 6.0757(4), b = 11.3473(5), c = 9.5114(7)Å, β = 104.686(6)°, V = 634.32(7)Å3, and Z = 2.
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    Journal of chemical crystallography 28 (1998), S. 239-241 
    ISSN: 1572-8854
    Keywords: Crystal structure ; ergosterol peroxide
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    Topics: Geosciences , Physics
    Notes: Abstract Ergosterol acetate, in pyridine, reacts with hydrogen peroxide and catalytic amounts of FeCl3 to afford the unusual product 5α,9α-peroxyergosta-7,22-dien-6-one-3β-ol acetate. The peroxide, in the title structure, is seen to bridge the C5 and C9 positions of the sterol backbone. Crystal data: C30H44O5, orthorhombic, P212121, a = 6.552(2), b = 11.048(8), c = 37.60(2), V = 2772(3)Å3, Z = 4.
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  • 45
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    Journal of chemical crystallography 28 (1998), S. 593-596 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cage compound ; hexabenzoylhexaazaisowurtzitane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of an interesting cage compound is described. Crystal data: C48H36N6O6·(CH3)2CO; monoclinic; space group: P2 1 /n; a = 14.948(3) Å, b = 15.079(3) Å, c = 19.539(4)Å, β = 93.93(3)°, V = 4394(2)Å3; and Z = 4.
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  • 46
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    Journal of chemical crystallography 29 (1999), S. 121-125 
    ISSN: 1572-8854
    Keywords: Crystal structure ; brucine ; pantolactone ; molecular complex ; chiral resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have determined an X-ray crystal structure, a = 12.482(1), b = 14.349(1), c = 14.342(1) Å, orthorhombic, P212121 for a molecular complex of brucine with pantolactone. The crystal structure is composed of corrugated sheets of brucine molecules containing the guest pantolactone molecules. The conformational twist of the pyrrolidine ring in brucine may probably be important in projecting the amine N2 to provide a strong and specific binding site for a chiral complexation. The pseudo-equatorial orientation of the hydroxyl group of the pantolactone anchors itself for binding via hydrogen bonding. In the crystal packing, the pantolactone molecules form helices and the brucine molecules are attached to these helices by O=H···N hydrogen bonds.
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  • 47
    ISSN: 1572-8854
    Keywords: Crystal structure ; norbornene ; stereoselective reduction
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    Notes: Abstract Racemicendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene was stereoselectively reduced by sodium borohydride to give only theS,S orR,R diastereomers. The crystal structure of the product displays no unusual features.
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  • 48
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    Journal of chemical crystallography 25 (1995), S. 291-294 
    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,2-di(1-adamantyl)ethene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone is reported. The steric requirements of the two adamantyl groups affect the structure in three ways—a slight elongation of the central bond, a small expansion of the angles about the central bond, and a conformation in which the C(sp2)-connected adamantyl group virtually bisects the large substituents attached to the sp3 carbon.
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  • 49
    ISSN: 1572-8854
    Keywords: Crystal structure ; pinacol ; reductive dimerization
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    Topics: Geosciences , Physics
    Notes: Abstract The pinacol resulting from sodium promoted reductive coupling of pentacyclo[5.4.0.02,6.-03,10.05,9]undecane-8,11-dione monoethylene ketal possesses a conformation, dictated by intramolecular hydrogen bonding, that lies midway between eclipsed and staggered. The C−C and C−O distances in the pinacol unit are, respectively, longer and shorter than usual, and all parameters are as expected.
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  • 50
    ISSN: 1572-8854
    Keywords: Crystal structure ; rubidium nitroprusside ; IR ; Raman ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, Rb2[Fe(CN)5NO], crystallizes in the space group P212121, witha=5.687(1),b=15.956(2),c=12.645(3) Å, andZ=4. Anions are in equivalent C1 sites (one per asymmetric unit) and are slightly distorted octahedra (C4v ideal symmetry). TGA and DTA curves and vibrational (infrared and Raman) spectra of Rb2[Fe(CN)5NO] were obtained. Results are interpreted in view of the crystal structure of the compound and the behavior of related substances.
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  • 51
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    Journal of chemical crystallography 26 (1996), S. 281-286 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclopentadiene ; 2,3-dicyano-p-benzoquinone ; Diels-Alder reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Diels-Alder cycloaddition of cyclopentadiene (1a) to 2,3-dicyano-p-benzoquinone (2a), when performed in methanol solvent at ambient temperature, proceeds with kinetic control to afford 1α,4α,4aβ,8aβ-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-4a,8a-dicarbonitrile (7, 77% yield). However, when this cycloaddition is performed by refluxing an equimolar solution of1a and2a in benzene for 3 h, the product of thermodynamic control, i.e., 1α,4α,4aα,8aα-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-6,7-dicarbonitrile (3a) is obtained in 64% yield. The structure of3a was confirmed by an analysis of the reduced intramolecular photocyclization product,9.
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  • 52
    ISSN: 1572-8854
    Keywords: Crystal structure ; undecen-olid ; nor-patulolide
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    Topics: Geosciences , Physics
    Notes: Abstract The stereogeometry and absolute configuration of the title compound has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, P21,a=7.7976(2),b=7.8288(2),c=8.9791(4) Å, β=90.331(4)o, Z=2. The crystal structure has been solved by vector search methods and refined toR=0.042 for 1798 observed reflections.
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  • 53
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    Journal of chemical crystallography 26 (1996), S. 361-364 
    ISSN: 1572-8854
    Keywords: Crystal structure ; carboxylic acid ; phosphine oxide ; hydrogen bonding
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    Topics: Geosciences , Physics
    Notes: Abstract Diphenylphosphinylacetic acid crystallizes in the monoclinic space groupP2l/n with unit cell dimensionsa=5.6875(7),b=17.049(4),c=13.471(2) Å, β=93.36(1)° and Z=4. The molecular packing consists of hydrogen bonded chains arising from intermolecular interactions between a carboxylic acid hydroxyl group and an oxygen of an adjacent phosphine oxide moiety.
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  • 54
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    Journal of chemical crystallography 26 (1996), S. 425-428 
    ISSN: 1572-8854
    Keywords: Crystal structure ; tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione
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    Topics: Geosciences , Physics
    Notes: Abstract The compound crystallizes in the triclinic space group, $$P\bar 1$$ , witha=6.7702(4),b=7.0180(4),c=9.1960(7) Å, α=92.457(6), β=96.150(6), γ=93.444(5)°, andZ=2. The structure contains a rather short intramolecular H...H contact of 2.26(4) Å.
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  • 55
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    Journal of chemical crystallography 28 (1998), S. 741-746 
    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrated ions ; ionic hydration ; strontium arsenate ; struvites ; struvite-type structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of strontium potassium arsenate octahydrate, SrKAsO4·8H2O, has been determined by single crystal X-ray diffraction. The crystals are tetragonal, a = 7.144(1), c = 23.613(2) Å, space group I41md (No. 109), Z = 4, V = 1205.1(1) Å3, and d c = 2.258 g cm−3. All cations and anions in this compound are completely surrounded by water molecules. Sr2+ and K+ ions are each coordinated to eight water molecules arranged in an approximately square antiprism. The [Sr(H2O)8]2+ polyhedron shares one face of four water molecules with a [K(H2O)8]+ polyhedron forming O4-Sr-O4-K-O4 polyhedra. The O4-Sr-O4-K-O4 units are linked together through a pair of edge-sharing linkages of the outer water molecules, alternating along the a-axis and b-axis. The hydrated cation polyhedra appear to define the host lattice, which accommodates the AsO 4 3- ion in the interstitial space. The environment of the AsO 4 3- ion consists of 16 water molecules; each oxygen atom is the acceptor in hydrogen bonds from four water molecules. The pair distances associated with this environment may be used in investigations of the structure of hydrated 4 n- ions in solutions. Each water molecule is coordinated to one Sr and one K, and hydrogen bonded to two O atoms of two different AsO 4 3- ions. There is no hydrogen bonding between water molecules.
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  • 56
    ISSN: 1572-8854
    Keywords: Crystal structure ; bicyclononane ; triazene ; bis-triazene ; nitrile substituent ; nitro substituent ; trifluoromethyl substituent ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a series of 3,7-bis(arylazo)-1,3,5,7-tetraazabicyclo[3.3.1] nonanes (1a–d) have been determined by single crystal X-ray diffraction analysis. All four compounds have the same feature, that the tetraazabicyclononane unit assumes a cage-like structure with the aryltriazene moieties lying parallel to one another so that the aryl rings are held together by π – π stacking. Crystal data: 1a C17H18N10O4, triclinic, space group P − 1, a = 9.8899(10), b = 13.0845(13), c = 16.458(2) Å, α = 94.095(2)°, β = 107.004(2)°, γ = 111.027(2)°, V = 1863.5(3) Å3 and Z = 4; 1b, C19H18F6N8, orthorhombic, space group Pbca, a = 15.3210(8), b = 10.9512(6), c = 24.5698(13) Å, V = 4122.4(4) Å3 and Z = 8; 1c C19H18N10, monoclinic, space group P21/n a = 6.3742(6), b = 13.7343(13), c = 21.542(2)Å, β = 97.738(2)°, V = 1868.8(3) Å3, and Z = 4; 1d, C19H18N10, monoclinic, space group P21/c, a = 18.205(2), b = 17.398(2), c = 12.784(12) Å, β = 109.480(2)°, V = 3818.0(6) Å3, and Z = 8.
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  • 57
    ISSN: 1572-8854
    Keywords: Crystal structure ; centrosymmetric ; methoxybenzo [b] thiophene ; estrogen receptor ; tubulin
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    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of two methoxybenzo [b] thiophenes have been determined by three-dimensional, single-crystal X-ray diffractometry. Both 3-(3′,4′,5′-trimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene and 3-(3′,4′,5′-triethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene (hereafter referred to as I and II, respectively) crystallize in the triclinic centrosymmetric space group $$P \bar 1$$ (No. 2, C1) with two formula units per cell with a = 6.842(1) Å, b = 12.602(2) Å, c = 13.815(2) Å, α = 94.80(1)°, β = 98.27(2)°, and γ = 100.59(2)° and a = 10.600(1), b = 11.415(2), c = 12.137(2) Å, α = 94.57(1)°, β = 101.18(1)°, and γ = 110.45(1)°, respectively. The phase problems were solved by direct methods and the respective final full-matrix least-squares refinements converged to R = 0.039 and 0.068. The structures differ in the orientation of the trimethoxy and triethoxy groups of the benzoyl ligands. The molecules in the crystal lattice are held together by van der Waals forces. Selected bond distances, angles, and torsion angles are tabularized as well as reference to the synthesis of the title compounds and peripheral studies.
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  • 58
    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; erbium(III)–sodium(I) carboxylate complex ; picolinic acid N-oxide
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    Topics: Geosciences , Physics
    Notes: Abstract A new Er(III)–Na(I) coordination polymer of stoichiometry [NaEr2L5(H2O)6(NO3)](NO3)·3.5H2O (HL = picolinic acid N-oxide) has been synthesized and characterized by single-crystal X-ray analysis. Crystals are triclinic, PĪ with a = 9.823(2), b = 12.453(2), c = 20.643(4) Å; α = 98.49(3), (β = 101.40(3), γ = 108.69(3)°; V = 2284(1) Å3; Z = 2. Of the two independent eight-coordinate erbium(III) ions in this complex, one is surrounded by four bidentate chelating L ligands, and the other by one bidentate chelating L ligand, four aqua ligands and two anti-carboxylate oxygen atoms from two neighboring [ErL4] units. The sodium(I) ion is in a distorted octahedral environment, being coordinated by a unidentate nitrate anion, three aqua ligands and two anti-carboxylate oxygen atoms from two adjacent [ErL4] units. The complex is built from zigzag chains of syn-anti carboxylate-bridged erbium(III) moieties directed in the a direction, which are cross-linked pairwise by aqua-bridgeddimericsodium(I) units. The resulting composite polymeric chains are further connected by hydrogen bonds to form a three-dimensional network.
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  • 59
    ISSN: 1572-8854
    Keywords: Crystal structure ; tin porphyrin ; two-stage hydrolysis ; methanolate ; trans equivalent axial ligand
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    Topics: Geosciences , Physics
    Notes: Abstract In this work, we determine the crystal structure of dimethoxo(meso-tetra(4-methoxyphenylporphyrinato))tin(IV), Sn(tmpp)(OMe)2 (1). Experimental results indicate that the tin atom has an octahedral geometry. The geometry around the tin center has Sn(1)–O(5) = 2.020(6), Sn(1)–O(6) = 2.003(7) Å and an average Sn(1)–N = 2.10(1) Å. The two methoxo groups are unidentately coordinated to the tin(IV) atom. Two-stage hydrolysis of Sn(tmpp)(OMe)2 in CDCl3 was observed by 1H and 13C NMR spectroscopy. Compound (1) crystallizes in the space group P21/n with a = 14.7492(1), b = 19.2022(3), c = 16.0806(2) Å, β = 94.104(1)°, and Z = 4.
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  • 60
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    Journal of chemical crystallography 28 (1998), S. 475-479 
    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; gadolinium(III)-copper(II) complex ; iminodiacetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel polymeric Gd2Cu3 complex of iminodiacetic acid (H2L1=NH{CH2COOH}2), namely, Gd2Cu3(L1)6, 1, has been synthesized and structurally characterized. In the title complex, the Gd3+ ion is nine-coordinated by six O atoms from three bidentate chelating carboxylate groups and three O atoms from three anti-anti bridging carboxylic groups of six L1 ligands; the Cu2+ ion is six-coordinated by four O and two N atoms from two chelating L1 ligands. Each pair of Gd(III) atoms is bridged by three L1 ligands, each of which also chelates with one copper(II) ion, thus forming a Gd2Cu3 cluster unit. Such cluster units are cross-linked by flexible L1 ligands into a three-dimensional coordination framework. The title complex crystallizes in the trigonal space group P-3c1 (No. 165) with a = b = 13.433(4), c = 14.770(6) Å; V = 2308(1) Å3; Dcalca = 1.859 g cm−3; Z = 2.
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  • 61
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    Journal of chemical crystallography 29 (1999), S. 15-18 
    ISSN: 1572-8854
    Keywords: Crystal structure ; dimer ; triazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the monoclinic space group, P21/n; a = 9.0024(5), b = 5.8135(3), c = 15.2232(8) Å, β = 91.153(4)° Z = 4; and R = 0.050 based on 853 observed, unique reflections. The structure consists of two fused five-membered triazole rings, oriented relative to each other at 152°.
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  • 62
    ISSN: 1572-8854
    Keywords: Crystal structure ; biphenyl ; mutual orientation ; strong H-bonds
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    Notes: Abstract 5,5′-Di t-butyl-2,2′-biphenyldiol (I), C20H26O2, crystallizes in the orthorhombic space group P212121 with a = 18.243(2), b = 9.947(2), c = 9.685(3) Å, and Z = 4; 5,5′-dimethyl-2,2′-biphenyldiol (II), C14H14O2, crystallizes in the monoclinic space group P21/c with a = 9.959(2), b = 7.932(3), c = 15.392(2) Å, β = 105.43(2)°, and Z = 4. The aromatic rings are tilted by 52.7(1) and 43.8(1)° to each other in compounds (I) and (II), respectively. Strong intra- and inter-molecular H-bonds connect the molecules in the crystals.
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  • 63
    ISSN: 1572-8854
    Keywords: Crystal structure ; indium complexes ; isothiocyanate complexes ; octahedral coordination
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The reaction of a 1:10 molar ratio between indium chloride and tetra-n-butylammonium thiocyanate in ethanol affords the complex [(n-C4H9)4N]3[In(NCS)6] (1), the structure of which has been established by X-ray diffraction. This compound crystallizes in the cubic space group Pa3¯ with eight formula units in the unit cell. The formula unit consists of three separate cationic tetra-n-butylammonium groups and an independent hexakisisothiocyanatoindium anionic group. The six near linear thiocyanate ligands coordinate octahedrally through the nitrogen atom to the indium metal center. The coordination of the n-butyl groups to the ammonium-nitrogen atom is tetrahedral. The complex has also been characterized by IR, 1H and 13C NMR, physical properties, and X-ray powder analysis.
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  • 64
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    Journal of chemical crystallography 29 (1999), S. 145-156 
    ISSN: 1572-8854
    Keywords: Crystal structure ; bicycloundecane ; triazene ; bis-triazene ; nitro substituent ; carboalkoxy substituent ; π–π stacking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a series of 3,8-di[-2-aryl-1-azenyl]-1,3,6,8-tetraazabicyclo[4.4.1]undecanes (1–5) have been determined by single crystal X-ray diffraction analysis. In all five compounds, the tetraazabicycloundecane portion of the molecule assumes a cage-like, folded structure with the aryltriazene moieties aligned approximately parallel; the structure is held in the folded configuration by either intramolecular or intermolecular π–π stacking forces. Crystal data: 1 C19H22N10O4, monoclinic space group P21/c, a = 10.1846(7), b = 9.9556(7), c = 20.819(2) Å, β = 98.725(1)°, V = 2086.5 (3) Å3, Z = 4; 2 C23H28N8O4, triclinic, space group Pī, a = 6.7064(7), b = 12.9662(14), c = 14.054(2) Å, α = 94.796(2), β = 91.621(2), γ = 104.836(2)°, V = 1175.7(2) Å3, Z = 2; 3 C19H22N10O4, monoclinic, space group P21/c, a = 14.237(2), b = 13.520(2), c = 11.5805(12) Å, β = 113.514(2)°, V = 2044.0(4) Å3, Z = 4; 4 C21H22N10, monoclinic, space group C2/c, a = 54.247(3), b = 11.5531(7), c = 12.9670(7) Å, β = 95.710(1)°, V = 8086.4(8) Å3, Z = 16; 5 C25H32N8 04, monoclinic, space group P21/c, a = 10.2908(7), b = 16.5687(12), c = 15.1662(10) Å, β = 94,188(1)°, V = 2579.0(3) Å3, Z = 4.
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  • 65
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    Journal of chemical crystallography 29 (1999), S. 351-354 
    ISSN: 1572-8854
    Keywords: Crystal structure ; dibromotriblattene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction of 4-bromopentacyclo[7.3.0.02,7.03,11.06,10]dodec-11-ene (1) with Br2—CCl4 afforded 4,4,5-tribromopentacyclo[7.3.0.02,7.03,11.06,10]dodecane (2) in 89–94% yield. Subsequent treatment of 2 with KOt-Bu-t-BuOH resulted in competitive elimination of the elements of HBr and of Br2 with concomitant formation of 4,5-dibromopentacyclo[7.3.0.02,7.03,11.06,10]dodec-11-ene (3, 76%) and 1 (17%), respectively. The structure of 3 was established unequivocally via application of X-ray crystallographic methods. Crystal data for 3: monoclinic, C2/c, a = 9.895(1), b = 9.0963(7), c = 12.471(1) Å, β = 106.875(8)°, z = 4.
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  • 66
    ISSN: 1572-8854
    Keywords: Crystal structure ; AM1 ; x-ray diffraction ; dihydropiridines
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    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and structural characterization of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1,4-dihydropyridine-3-carboxylate is described. The structure was refined to R1 = 0.0470 for 2665 reflections (with I 〉 2σ(I)). Crystal data: C15H13C12NO3, monoclinic,space group P21/c, a = 11.163(9), b = 14.484(8), c = 9.422(7) Å, V = 1512.9(19) Å3, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The Cl atom attached to the phenyl group has two possible orientations, having 75% (sp) and 25% (ap) occupancy, respectively. The molecules in the crystal are held together by means of intermolecular hydrogen bonds of the type N=H...O and by C=H...O interactions.
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  • 67
    ISSN: 1572-8854
    Keywords: Crystal structure ; manganese(IV) cluster ; adamantane-shaped complex ; tetranuclear complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A tetranuclear manganese (IV) complex, [L4Mn4O6](ClO4)4·2H2O (1), with 1,4,7-triazacyclononane (L) as the capping ligands, has been synthesized and characterized by X-ray diffraction; monoclinic, space group P21/n with a = 21.335(6) Å, b = 11.387(3) Å, c = 21.788 (6) Å, β = 111.410 (6)°, V = 4928 (2) Å, Z = 4. Each manganese atom has a distorted octahedral environment comprised of three facially coordinated amine nitrogen atoms and three oxygen atoms, and the cation is an idealized tetrahedron. The Mn4O6 4+ cation corresponds to an adamantane skeleton.
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  • 68
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    Journal of chemical crystallography 25 (1995), S. 747-750 
    ISSN: 1572-8854
    Keywords: Crystal structure ; trishomocubanone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of a bis(benzyloxy)trishomocubanone with molecular C2 symmetry reveals that substitution of benzyloxy groups has little effect on the trishomocubane cage.
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  • 69
    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,3-oxazoline-2-thione ; resonance structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound C13H13NO3S2 crystallizes in the triclinic space group $$P\bar 1$$ (Z=2) with lattice constantsa=8.382(2),b=10.042(2),c=10.134(2) Å, α=119.35(1)°, β=101.40(1)° and γ=90.54(1)°. The interplanar angle between the least squares planes of the 1,3-oxazoline ring and the phenyl ring amounts to 90.2°, thus hindering conjugation between the benzene and heterocyclic system. The observed bond parameters of the five-membered heterocycle suggest a significant contribution from a zwitterionic dipolar limiting structure [38.7(5)%] to the description of this ring system. The particular contributions of the resonance structures were estimated by calculations using the HOSE model on the base of the observed bond lengths.
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  • 70
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecan-8-one ; pentacycloundecane-8,11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of an asymmetric pentacyclo[5.4.0.02,6.03,10.05,9]undecan-8,11-dione derivative is reported, in which Me3SiCN has been added across one of the keto groups. The cage structure demonstrates the expected effects of this addition.
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  • 71
    ISSN: 1572-8854
    Keywords: Crystal structure ; diyne ; oxidative dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units.
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  • 72
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    Journal of chemical crystallography 26 (1996), S. 695-699 
    ISSN: 1572-8854
    Keywords: Crystal structure ; 2,2'-bi-1H-imidazole ; cadmium chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction between cadmium(II) chloride and 2,2'-bi-1H-imidazole (H2biim) in an acidic solution affords [Cd(H3biim)2Cl4] (H3biim=2-(2-1H-imidazolyl)-1H-imidazolium) in 63% yield. The compound crystallizes in the triclinic space groupP1, wherea=8.072(2),b=8.100(2),c=8.593(2) Å, α=75.89(2), β=62.94(2), γ=63.29(1)°,V=446.4(2) Å3, andZ=1. The central Cd atom exhibits an octahedral geometry composed of a Cl4N2 core. The Cd-N bond distance is 2.392(2) Å. Cd−Cl distances are 2.5919(9) and 2.671(1) Å.
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  • 73
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    Journal of chemical crystallography 26 (1996), S. 801-806 
    ISSN: 1572-8854
    Keywords: Crystal structure ; centrosymmetric ; methoxybenzo[b]thiophene ; estrogen receptor ; tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of two methoxybenzo[b]thiophenes have been determined by three-dimensional, single-crystal X-ray diffractometry. Both 3-(4′-hydroxy-3′, 5′-dimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene and 3-(2′,6′-dimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene (hereafter referred to asI andII, respectively) crystallize in the monoclinic centrosymmetric space groupP21/n (No. 14, C 2h 5 ) with four formula units-per cell witha=6.866(1),b=28.638(2),c=11.830(2) Å, and β=105.52(1)° anda=9.328(1),b=7.977(1),c=29.650(4) Å, and β=97.87(1)°, respectively. The phase problems were solved by direct methods and the respective final full-matrix least-squares refinements converged toR=0.046 and 0.031. The structures differ in the positioning of the dimethoxy groups of the benzoyl ligands and the addition of a hydroxyl group inI. The molecules in the crystal lattice are held together by van der Waals forces plus the addition of hydrogen bonding in compoundI. Selected bond distances and angles and torsion angles are tabularized.
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  • 74
    ISSN: 1572-8854
    Keywords: Crystal structure ; hexacyclopentadeca-5,7-diene-3,10-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction between vinylmagnesium bromide and the cage dione leads to attack of only one equivalent of Grignard and intramolecular nucleophilic attack on the second ketone. The product compound crystallizes in the monoclinic space group, P21/a, witha=9.509(1),b=11.071(2),c=12.492(4) Å, β=104.32(2)°, andZ=4.
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  • 75
    ISSN: 1572-8854
    Keywords: Crystal structure ; receptor ; clip shaped molecule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a clip containing molecule is described. The structure was solved by vector search methods and refined by least squares methods toR l=0.0768 [I〉2σ(I)]. Crystal data: C40H30N4O2·HCCl3, triclinic, space group $$P\bar 1$$ ,a=9.302(2),b=12.981(2),c=15.765(2)Å, α=65.91(2)°, β=76.40(2)°, γ=80.15(1)°,V=1682.9(4)Å3, Z=2.
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  • 76
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    Journal of chemical crystallography 26 (1996), S. 639-642 
    ISSN: 1572-8854
    Keywords: Crystal structure ; chiral auxiliaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a new azetidine-2-carboxylic amide derivative is described. The structure was solved by direct methods and refined by least squares methods toR1=0.0393 for 4264 reflections (withI〉2σ(I)) The structure consists of two independent molecules which are chemically the same with slight differences in geometry. Crystal data: C17H24N2O, monoclinic, space groupP21,a=8.3782(4),b=20.0342(13),c=9.7769(8) Å, β=109.687(6)°,V=1545.1(2)Å3,Z=4.
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  • 77
    ISSN: 1572-8854
    Keywords: Crystal structure ; triazene ; bis-triazene ; nitrile substituent ; methoxy substituent ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 1,2-bis-{1-(2-cyanophenyl)-3-methyltriazen-3-yl-}ethane (1) and 1,2-bis-{1-(2-methoxyphenyl)-3-methyltriazen-3-yl-}ethane (2) have been determined by single crystal X-ray diffraction analysis. Bis-triazene (1) exists as the “staggered” conformation in the solid state, with an anti-anti configuration around the N2–N3 bond of the triazene units, whereas 2 assumes a “gauche” conformation with the syn-syn configuration in the triazene units. Crystal data: 1 C18H18N8, triclinic, space group P −1, a = 6.108(2), b = 8.118(3), c = 9.600(4)Å, α = 101.37(7)°, β = 96.47(7)°, γ = 102.71(5)°, V = 449.1(3)Å3, Z = 2; 2 C18H24N6O2, monoclinic, space group P 21/n, a = 13.119(5), b = 7.745(2), c = 19.201(2)Å, β = 96.47(7)°, V = 1910.3(9)Å3, Z = 4.
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  • 78
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    Journal of chemical crystallography 28 (1998), S. 39-46 
    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid ; 3,4,5,6-tetracarboxyacridine-1,8-disulfonate ; paraquat ; hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two hydrated salts of 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid, H2L, have been characterized by single-crystal X-ray analysis. Compound 1, Na2L·9 $$ - \frac{1}{2}$$ H2O, crystallizes in the monoclinic space group C2/c with a = 42.005(1), b = 6.838(1), c = 23.807 (1) Å, β = 122.71 (1)°, and Z = 8. Compound 2, (paraquat)L·2H2O, belongs to the triclinic space group $${P\bar 1}$$ with a = 9.940(1), b = 11.543(1), c = 14.033(1) Å, α = 105.45(1), β = 95.82(1), γ = 100.14(1)° and and Z = 2. All four carboxyl groups in the 3,4,5,6-tetracarboxyacridine-1,8-disulfonate dianion L2− are un-ionized. In 1 the distorted octahedrally coordinated sodium cations, the anions, and the lattice water molecules are joined together by hydrogen bonds to generate a three-dimensional network. In the crystal structure of 2, a host framework composed of L2− ions and water molecules accommodate the paraquat dications within two channel systems running parallel to the a and b axes.
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  • 79
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    Journal of chemical crystallography 28 (1998), S. 259-266 
    ISSN: 1572-8854
    Keywords: Crystal structure ; heptacyclotetradecane ; hexacyclotetradecane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structures of four dibromomethylene-functionalized hexa- and heptacyclotetradecane cages are reported. 7-(Dibromomethylene)heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14]tetradecane (3): orthorhombic, Pnma, a = 14.744(1), b = 11.237(1), c = 7.4625(7) Å Z = 4; R = 0.0531 for 504 observed reflections. 7,12-Bis(dibromomethylene)heptacyclo[6.6.0.02,6.03,13-04,11 .05,9.010,14]tetradecane (4): monoclinic, I2/a, a = 11.257(1), b = 9.5844(8), c = 13.884(2) Å, β = 92.254(8)° Z = 4; R = 0.0413 for 663 observed reflections. 10,14-bis(dibromomethylene)hexacyclo[6.6.0.02,6.03,13.04,11.05,9]tetradecane (6): monoclinic, P21/n, a = 8.118(1), b = 15.273(4), c = 12.826(3) Å, β = 104.20(1)° Z = 4; R = 0.0384 for 1392 observed reflections. 14-(dibromomethylene)hexacyclo[6.6.0.02,6.03,13.04,11.05,9]tetradecan-10-one (7): monoclinic, P21/n, a = 8.2879(7), b = 15.273(1), c = 10.0565(9) Å, β = 92.271(8)° Z = 4; R = 0.0320 for 1402 observed reflections. The functional groups lead to slight shortening of bond lengths.
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  • 80
    ISSN: 1572-8854
    Keywords: Crystal structure ; samarium(III) complexes ; iron(III) complexes ; cyanide-bridges ; dinuclear complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new complex, [Sm(DMF)4(H2O)4Fe(CN)6]·H2O (DMF = N, N-dimethylformamide), has been synthesized and characterized by X-ray single crystal structure and thermogravimetric analyses. The complex crystallizes in the P21/n space group, with lattice parameters a = 17.583(4) Å, b = 8.870(2) Å, c = 19.845(6) Å, β = 95.98(3)°, V = 3078(1) Å3, D x = 1.679 Mg m−3, D m = 1.65(1) Mg m−3, Z = 4. The molecular structure shows that a cyano-bridged bimetallic structure is obtained. The Sm atom is coordinated by eight oxygen atoms of four water molecules and four DMF molecules and one nitrogen atom of the bridging cyanide ligand. The iron atom assumes approximately an octahedral environment surrounded by six CN ligands. The hydrate water molecule is hydrogen-bonded to one of the O atoms bound to Sm. Each terminal CN ligand of the Fe(CN) 6 3− entity is hydrogen-bonded to some O atoms of water molecules. An infrared spectrum is also reported.
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  • 81
    ISSN: 1572-8854
    Keywords: Crystal structure ; complexes ; pteridine ; lumazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In aqueous hydrobromic medium, Na[AuCl4] reacts with 1,3-dimethyllumazine (1,3-dimethyl-pteridine-2,4(1H,3H)-dione, DLM) or 1,3,6,7-tetramethyllumazine (DLMD) to give three adducts with simplified formulas Na[AuBr4](DLMD), Na[AuBr4](DLM), and Na[AuBr4](DLM)2. These compounds have been characterized by means of analytical techniques, and IR and NMR spectroscopies. Single-crystal x-ray diffraction studies have been made on the Na[AuBr4](DLM)2 compound. The crystals belong to the orthorhombic Pbca space group, with a = 15.249(1), b = 15.238(2), c = 21.563(2) Å, Z = 8, and R = 0.053. The structure consists of planar [AuBr4]− anions and Na+ cations weakly linked to two crystallographically independent DLM molecules. The Na+ cation interacts weakly with four oxygen and one nitrogen atoms from four different pteridine molecules, its environment may be described as a very distorted square pyramid.
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  • 82
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    Journal of chemical crystallography 28 (1998), S. 649-651 
    ISSN: 1572-8854
    Keywords: Crystal structure ; aluminum ; hydride ; complex ; quinuclidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction of AlH3[N(CH2CH2)3CH] with hexamethyltrisiloxane, (OSiMe2)3, gives rise to the bis-quinuclidine complex AlH3[N(CH2CH2)3CH]2, which has been characterized by 1H and 13C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH3[N(CH2CH2)3CH]2 consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) Å3, and Z = 4.
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  • 83
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    Journal of chemical crystallography 29 (1999), S. 323-327 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclohexaphosphate ; hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and crystal structure of a novel hydrate of lithium cyclohexaphosphate are reported. Li6P6O18·10H2O crystallizes in the space group C2/c with a = 15.113(5), b = 12.006(2), c = 15.892(2) Å, β = 122.85(2)°, and Z = 4. The structure consists of P6O18 ring layers stacked along the c direction in between which are located the lithiumions and water molecules. Two LiO4 tetrahedra share common edges with LiO5 pseudosquare pyramids to form two independant Li3O9 units. About 50% of the water molecules have fractional occupancy rates and form fragments of molecules. A linear relationship is established between the relative cell volume V/Z and the hydration degree, n, for all the known hydrates: Li6P6O18·nH2O.
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  • 84
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    Journal of chemical crystallography 29 (1999), S. 347-349 
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecane ; triple bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Intramolecular dehydration of a cage-diol results in the title compound. This crystallizes in the monoclinic space group P21/c; a = 8.6403(8), b = 9.5698(7), c = 14.062(1) Å β = 107.47(7)° and Z = 4.
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  • 85
    ISSN: 1572-8854
    Keywords: Crystal structure ; complexes ; cobalt ; benzoylhydrazone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of bis-(6-amino-5-formyl-1,3-dimethyluracilato benzoylhydrazone)cobalt(II) dimethylformamide solvate is described. This compound crystallizes in the triclinic system, space group P1¯, Z = 2 with a = 9.7368(8), b = 12.346(1), c = 17.184(1) Å, α = 78.372(6), β = 74.585(6), γ = 71.113(5)°, and V = 1869.0(3) Å3. The coordination polyhedron around the metal ion displays a slightly flattened M(NNO)2 octahedral shape. Both ligands bind in a trident fashion through the benzoylic oxygen atom, the hydrazone nitrogen atom closer to the uracil ring, and the deprotonated nitrogen atom of the amino group. The two ligands exhibit quite different conformations: one of them is almost planar, whereas the other is severely twisted.
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  • 86
    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrogen bonds ; 1H and 13C NMR ; FTIR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new pyridine containing compound, 4,4′-bis(4-pyridylethyl)biphenyl 1, was synthesized and its structure was determined by X-ray crystallography. Two kinds of two-dimensional networks linked by hydrogen bonds were obtained with different crystal solvents: 1·2H2O, monoclinic, space group P21/n with a = 8.3280(10), b = 5.5990(10), c = 24.054(4) Å, β = 98.79(2)°, V = 1108.4(3) Å3, Z = 2, Dc = 1.200 g cm−3, R1 = 0.0558; 1·CH3OH·2H2O, triclinic, space group P-1 with a = 8.3310(10), b = 12.861(2), c = 13.111(2) Å, α = 64.110(10), β = 75.000(10), γ = 83.750(10)°, V = 1220.7(3) Å3, Z = 2, Dc = 1.177 g cm−3, R1 = 0.0529. It is interesting that in the hydrate the host molecule of 1 contains an essentially flat biphenyl section, while in the methanol complex the host molecule of 1 contains a substantial twist in the center of the biphenyl section. The compounds were also characterized by NMR and FTIR spectroscopies. The 1H and 13C NMR assignments for 1 were carried out by 2D NMR spectral measurements in acetonitrile-d 3.
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  • 87
    ISSN: 1572-9435
    Keywords: grade crossings ; level crossings ; railway safety ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This paper describes the application of probabilistic risk assessment techniques to level crossing safety on JR East, the largest of the six private railroads in Japan. The risk of a level crossing accident was defined as the product of the accident rate and the expected consequences per accident. Rail traffic volume, road traffic volume, visibility of the crossing from the road, road gradient, width of the crossing and the type of safety devices at the crossing were shown to influence the accident rate and the collective risk. The mean accident rate at all crossings was 0.74 per million trains. The accident rate was 0.59 per million trains at crossings equipped with barriers, 1.25 at crossings equipped with warning bells and 0.76 at pedestrian crossings. Crossings equipped with obstacle detectors had a lower accident rate (0.12 per million trains) than crossings without detectors (0.43 per million trains). Crossings with visibility less than 20 m had a 50% higher mean accident rate than crossings with visibility greater than 20 m. As the number of tracks increased, the accident rate monotonically increased due to the increased accident exposure. Risk assessment techniques were applied to determine the efficacy of the various level crossing safety devices. In addition to upgrading the safety of crossings, the management techniques stressed the importance of education campaigns in warning the public about the dangers of illegal crossings.
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  • 88
    ISSN: 1572-8854
    Keywords: Crystal structure ; poly(pyrazolyl)borate ligands ; zinc(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [HB(3,4,5-Me3pz)3]2Zn (1) and [H2B(3,4,5-Me3pz)2]Zn(μ-3,4,5-Me3pz)2Zn[H2B(3,4,5-Me3pz)2] (2) are present in equal amounts in a crystal in the triclinic space group, P-1 with a = 11.5924(11) Å, b = 12.7799(12) Å, c = 15.7317(14) Å α = 107.905(2)° β = 96.796(2)°, γ = 105.786(2)°, and Z = 1. The structure of 1 is a trigonally distorted octahedron and is very similar to the structure of [HB(3,5-Me2pz)3]2Zn showing that the introduction of the third methyl group on the pyrazolyl ring does not impact on structure. [H2B(pz)2]2Zn (3) is orthorhombic, Pca2(1) with a = 10.1473(3) Å, b = 11.1117(2) Å, c = 14.1831(5) Å, α = β = γ = 90° and Z = 4. The zinc(II) centers in both 2 and 3 are similar and have pseudotetrahedral structures.
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  • 89
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    Journal of chemical crystallography 30 (2000), S. 335-338 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cobalt(II) complex ; tetraaza macrocycle ; 2-pyridylmethyl pendant arms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex [Co(L)]Cl2·10H2O (1) (L = 2,13,-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane) has been synthesized and structurally characterized. Compound 1 crystallizes in the triclinic system, space group P-1 with a = 9.731(2) Å, b = 9.789(2) Å, c = 11.998(1) Å, α = 66.66(1)°, β = 76.95(1)°, γ = 87.99(2)°, V = 1020.4(3) Å3, and Z = 1. The crystal structure of 1 shows that the complex is centrosymmetric and the cobalt(II) ion has a slightly distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendent arms at the axial positions. Cyclic voltammetry for 1 undergoes reversible one-electron oxidation to the Co(III) and irreversible one-electron reduction to the Co(I).
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  • 90
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    Journal of chemical crystallography 30 (2000), S. 459-462 
    ISSN: 1572-8854
    Keywords: Crystal structure ; chemical synthesis ; 2,3-dihydronaphto[2,3-b] [1,5) dioxepin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray single crystal structure of C13H12O2 compound was determined. It crystallizes in the orthorombic space group P212121 with a = 7.8847(7), b = 9.639(1), c = 13.432(2) Å, Z = 4 and V = 1020.8(3) Å3. The final R converged to 0.037 for 1763 independent reflexions. The title compound forms layers parallel to (1 0 0) planes and the three dimensional cohesion of the crystal is assumed by Van der Waals interactions. The molecule consists of two six-membered rings (A and B) and a seven-membered ring (C). A and B rings are planar, whereas the C ring has a chair conformation
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  • 91
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    Natural hazards 22 (2000), S. 117-138 
    ISSN: 1573-0840
    Keywords: fatalities ; flood ; bushfire ; heatwave ; eastern Australia ; ENSO ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The interannual variability of flood, bushfire andheatwave fatality data for eastern Australia duringthe period 1876–1991 was analysed with respect to thephase of the El Niño-Southern Oscillation (ENSO)and the associated values of the Southern OscillationIndex (SOI). Heatwaves were found to be the mostserious peril in terms of the total number offatalities, while floods ranked first in the fatalityevent day statistics. None of the three monthly(absolute value) fatality data sets showed significantcorrelations with the corresponding values of the SOI,while the correlation analysis of annual (July toJune) data led to significant correlation coefficientsof 0.5 for floods and -0.3 for bushfires. AdditionalSOI value-related classification of the standardisedfatality event days into several ENSO categoriesconfirmed the correlation trends by showing anincrease (decrease) in the standardised bushfire(flood) fatality event day frequencies with increasingvalues of the SOI. In contrast to that, thestandardised heatwave fatality data showed aninconclusive distribution pattern, which hints at theinfluence of other possible factors (such as airpollution) on heatwave-related fatality numbers. The results of a risk assessment analysis have shownthat the probability of reaching the mean annualnumber of flood-fatality event days is roughly fourtimes higher during La Niña seasons (80%) thanthe corresponding probability associated with ElNiño periods (18%). The correspondingprobabilities associated with the mean bushfire andheatwave fatality event days displayed a reversedpattern, with the probabilities of El Niño-relatedyears being roughly twice as high as those associatedwith La Niña seasons (70% and 30% for bushfires,and 60% and 25% for heatwaves, respectively).Further probability calculations performed on thetotals of fatalities from all three perils identifiedthe La Niña years as potentially the mostdangerous in terms of suffering fatalities from theseperils. Furthermore, they highlighted the significantdifferences between the means of fatality event daynumbers recorded during years of extreme SOI values(9.8 for La Niña, and 9.1 for El Niño seasons)and those marked by near-zero SOI values (6.6). Themajor reason for the increase in risk associated withextreme ENSO phases was the higher variability ofthese perils during the respective seasons.
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    Natural hazards 21 (2000), S. 347-360 
    ISSN: 1573-0840
    Keywords: volcanic hazard ; risk assessment ; GIS ; physical simulation models ; information systems ; emergency planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The incorporation of a set ofcomputer-based tools, such as Geographical InformationSystems and physical models, to the field of riskassessment, introduces a new perspective in thevolcanic risk maps production, increasing the analysisand modelling capabilities available through theapplication of conventional methodologies. Amethodology adapted to the requirements andcharacteristics of the new operating environment hasbeen applied at Tenerife island (Canary Islands,Spain) to carry out a study devoted to analyse thesuitability of these tools for near real-timemanagement of volcanic crises. With this in mind, aseries of potential eruption scenarios have beenselected to identify and characterise which elementsat risk would prove most vulnerable against a specificvolcanic phenomenon, depending on the socio-economiccharacteristics of the area affected and the resultingdistribution of the volcanic products. This kind ofinformation is fundamental to update, adapt or produceeffective risk management and emergency plans orprotocols, where the measures to mitigate or fightagainst a specific volcanic disaster have to be taken,incorporating the existing knowledge of the phenomenonbehaviour and taking into account their potentialeffects on the area of interest.
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  • 93
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    Natural hazards 20 (1999), S. 279-294 
    ISSN: 1573-0840
    Keywords: risk assessment ; groundwater contamination ; vulnerability ; GIS ; hazard ; economic ; value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The groundwater contamination risk map of a samplealluvial area was produced by using the IlwisGeographical Information System (GIS) to construct andto overlay thematic maps. The risk map has beenderived from the vulnerability map, the hazard map,where the potential contaminating sources wereidentified, and the socio-economic value of thegroundwater resource, represented by the wells. Thegroundwater quality map allowed thereliability of hazard and risk maps to be tested. The final map shows interesting results and stressesthe need for the GIS to test and improve on thegroundwater contamination risk assessment methods.
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    Natural hazards 21 (2000), S. 225-245 
    ISSN: 1573-0840
    Keywords: risk assessment ; emergency preparedness ; legislative measures ; flood prevention and mitigation ; forecasting and warning ; control structure ; public participation ; Canada ; Red River Valley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The prevention and/or mitigation offlood disasters requires continual research, numerouscapital investment decisions, and high-qualitymaintenance and modifications of flood-controlstructures. In addition, institutional and privatepreparedness is needed. The experience offlood-control in North America has shown mixedoutcomes: while flood frequency has declined duringthe last few decades, the economic losses havecontinued to rise. Recent catastrophic floods havealso been linked to major structural interventions inthe region. The flood diversions may cause harmfuleffects upon the floodplain inhabitants by influencingflood levels in areas which are not normallyflood-prone. The increasing vulnerability of thefloodplain inhabitants poses new challenges and raisesquestions concerning the existing risk assessmentmethods, institutional preparedness and responses todisaster-related public emergencies, and local-levelpublic involvement in flood mitigation efforts. In the context of the catastrophic 1997 floods of theRed River Valley, Manitoba, Canada, this researchfocuses on two aspects of flood-related emergencygovernance and management: (i) the functions andeffectiveness of control structures, and (ii) theroles, responsibilities and effectiveness oflegislative and other operational measures. The studyconcludes that the flood-loss mitigation measures,both in terms of effects of control structures andinstitutional interventions for emergency evacuation,were not fully effective for ensuring the well-beingand satisfaction of floodplain inhabitants. Althoughorganizational preparedness and mobilization to copewith the 1997 flood emergency was considerable, theirsuccess during the onset of the flood event waslimited. Lack of communication and understandingbetween institutions, a reluctance to implementup-to-date regulations, and minimal publicparticipation in the emergency decision-making processall contributed to the difficulties experienced byfloodplain inhabitants.
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  • 95
    ISSN: 1572-9729
    Keywords: natural attenuation ; biodegradation ; hydrocarbon ; groundwater ; BTEX ; MTBE ; site characterization ; fate and transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract After eighteen months of active remediation at a JP-4 jet-fuel spill, aresidual of unremediated hydrocarbon remained. Further site characterizationwas conducted to evaluate the contribution of natural attenuation to controlexposure to hazards associated with the residual contamination in thesubsurface. Activities included the detailed characterization ofground-water flow through the spill; the distribution of fuel contaminantsin groundwater; and the analysis of soluble electron acceptors moving intothe spill from upgradient. These activities allowed a rigorous evaluation ofthe transport of contaminants from the spill to the receptor of groundwater,the Pasquotank River. The transport of dissolved contaminants of concern,that is benzene, toluene, ethyl benzene, xylene isomers (BTEX) andmethyl-tertiary-butyl ether (MTBE), into the river from the source area wascontrolled by equilibrium dissolution from the fuel spill to the adjacentgroundwater, diffusion in groundwater from the spill to permeable layers inthe aquifer, and advective transport in the permeable layers. The estimatedyearly loading of BTEX compounds and MTBE into the receptor was trivial evenwithout considering biological degradation. The biodegradation ofhydrocarbon dissolved in groundwater through aerobic respiration,denitrification, sulfate reduction, and iron reduction was estimated fromchanges in ground-water chemistry along the flow path. The concentrations oftarget components in permanent monitoring wells continue to decline overtime. Long term monitoring will ensure that the plume is under control, andno further active remediation is required.
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  • 96
    ISSN: 1432-0495
    Keywords: Keywords contamination ; groundwater ; lindane ; waste disposal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A serious problem in Spain is presented, where the water and soil were contaminated by lindane produced by the chemical industry, at a time when environmental legislation was limited, and the hydrogeological characterization of the low permeability materials was insufficient. The waste-disposal sites where the lindane accumulated lacked suitable sealing and also had notable filtration. The non-existence of a safe waste-disposal site, and the economic and social problems of transporting lindane residues forced the alternative proposal of confining these residues in situ (Government of Aragón, 1995, 1996). Once the surface sealing was carried out, the problem centred on the site's underground confinement. The purpose of this publication is to present the particular hydrogeological behaviour of materials, which were initially considered impermeable because of the presence of very consolidated sandstone beddings and the vertical disposition of the strata, and so allowed the lindane to escape through the groundwater. In addition, this publication describes the procedures carried out in order to achieve effective underground confinement at the waste-disposal site.
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  • 97
    Electronic Resource
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    Physics and chemistry of minerals 26 (1999), S. 546-553 
    ISSN: 1432-2021
    Keywords: Key words Malayaite ; Infrared spectroscopy ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO5. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO6 octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite.
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  • 98
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    Physics and chemistry of minerals 27 (2000), S. 467-473 
    ISSN: 1432-2021
    Keywords: Key words Witherite ; High pressure ; Aragonite ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Natural witherite (Ba0.99Sr0.01CO3) has been studied by single-crystal X-ray diffraction in the diamond anvil cell at eight pressures up to 8 GPa. At ambient pressure, cell dimensions are a = 5.3164(12) Å, b = 8.8921(19) Å, c = 6.4279(16) Å, and the structure was refined in space group Pmcn to R(F) = 0.020 from 2972 intensity data. The unit cell and atom position parameters for the orthorhombic cell were refined at pressures of 1.2, 2.0, 2.9, 3.9, 4.6, 5.5, 6.2, and 7.0 GPa. The volume-pressure data are used to calculate equation of state parameters K T0 = 50.4(12) GPa and K′ = 1.9(4). At approximately 7.2 GPa, a first-order transformation to space group P3¯1c was observed. Cell dimensions of the high-pressure phase at 7.2 GPa are a = 5.258(6) Å, c = 5.64(1) Å. The high pressure structure was determined and refined to R(F) = 0.06 using 83 intensity data, of which 15 were unique. This high-pressure phase appears to be more compressible than the orthorhombic phase with an estimated initial bulk modulus (K 7.2GPa) of 10 GPa.
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  • 99
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    Physics and chemistry of minerals 24 (1997), S. 463-476 
    ISSN: 1432-2021
    Keywords: Key words Cu2+-beearing orthopyroxene ; Orthopyroxene ; Crystal structure ; Jahn-Teller effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Cu-bearing pyroxene, Mg(Cu.56,Mg.44)Si2O6, has been synthesized by a flux method and crystal structure refinement has been performed by single crystal X-ray diffraction. It is found that the crystal structure is orthorhombic (space group Pbca) with unit cell dimensions of a=18.221(4), b=8.890(1), c=5.2260(7)Å and the cell volume of 846.5( )3Å3. In the M2-site one of the M-O bonds(M-O3B) is extremely expanded from 2.444(2) in enstatite to 2.732(2), thus the coordination polyhedron around M2-site is regarded as square pyramidal rather than square planar or octahedral. It is also found that the M1-site in the pyroxene structure is occupied almost exclusively by Mg, while the M2-site is almost evenly occupied by Mg and Cu. The observed extreme site preference shown by Cu2+ is unusual among the divalent cations with similar ionic sizes.
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  • 100
    Electronic Resource
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    Aquatic geochemistry 4 (1998), S. 253-272 
    ISSN: 1573-1421
    Keywords: Inorganic tracers ; dilution factor ; leachate attenuation ; redox zones ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Groundwater downgradient from Trandum municipallandfill was investigated in summer 1996, with a viewto assessing the distribution of redox-sensitivespecies. The water table at Trandum is 10–26 metersbelow the surface. Monitoring well filters have beeninstalled at depths of up to 15 m below water table,covering an area of 400 m by 200 m. Groundwaterinfluenced by the landfill seems to be confined tothis area. Pristine groundwater has a chemicalsignature indicative of calcite and pyrite weathering.Groundwater influenced by leachate from the landfillexhibits an excess of alkalinity relative to calcium,which is likely to be derived from degradation oforganic matter in the landfill. Groundwaterimmediately below and downstream of the landfillcontains elevated concentrations of Fe and Mn, largelymobilized under reducing conditions from the aquifermatrix and reflected in depleted HNO3-extractable Feand Mn in sediment samples from the same area.Groundwater samples allow the tentative identificationof redox zones based on oxidized and reduced forms ofFe, Mn, N and S. A methanogenic zone is notobserved.
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