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The containment of radionuclides over very long periods of time is based on the interposition of a multi-barrier system between the waste and the biosphere. A performance allocation study is usually conducted for each barrier. Each barrier is then designed, in terms of geometry and composition, to cope with the performance it has been allocated. However geochemical interactions will occur between the different barriers. An alkaline plume will be generated by cement materials, a redox front will be generated by container corrosion and geochemical gradients will be generated by the dissolution of artificial barriers by natural groundwater. Radionuclide retention mechanisms are strongly pH and Eh dependent, therefore the impact of these geochemical transients on retention must be quantitatively evaluated to check the performance of each barrier for realistic in-situ situations. To assess this impact, two types of engineered barriers (clay and cement) for a spent fuel repository are simulated with a coupled hydrogeochemical model. Comparisons between hydraulic heterogeneous (fractured) and simple homogeneous systems are also carried out in terms of waste dissolution.
The is insufficient knowledge of arthropod communities occurring in specific microhabitats. In this study, we characterize the arthropod assemblages inhabiting burrows of the common hamster (Cricetus cricetus L.) and factors that determine their diversity and abundance. We tested the following hypotheses: (1) arthropod assemblages are associated with a particular dominant vegetation occurring in the vicinity of burrows; (2) a correlation exists between fine-scale geographic distances among burrows and assemblage dissimilarity; and (3) the type of trap influences the sampling success of captured arthropods. We found 73 morphospecies belonging to 16 families in 109 burrows, most of which were in the families Staphylinidae (Coleoptera) and Parasitidae (Arachnida: Acari: Mesostigmata). The most abundant families were Staphylinidae, Cryptophagidae (Coleoptera), Parasitidae, and Macrochelidae (Mesostigmata) (78.89%). Among the identified species, we found Aleochara irmgardis (Staphylinidae) and Poecilochirus sexclavatus (Parasitidae) which had not yet been reported in Poland, and several other rare species. Meat-baited traps captured 64.34% more individuals, which were more diverse and species-rich than the non-baited control traps, but the former was more selective for saprophages, necrophages, and coprophages. The burrows located in areas overgrown by triticale (a hybrid of wheat and rye) were inhabited by 69.86% of the identified arthropod species, and these also had the highest abundance (64.07%) in comparison with other habitats. However, differences in sample size biased our results toward and overestimate arthropods associated with this vegetation. This study underlines that the species composition detected in burrows was affected by the methods used and hamster preferences for a specific habitat rather than the geographic proximity of the burrows. More extensive sampling across multiple habitats will be necessary to confirm our findings.
Background: Cognitive behavioural treatments are recommended for people with psychosis. Core beliefs regarding the self and others are a key part of the models underpinning cognitive behavioural therapy but detailed understanding of these putative beliefs in people with psychosis are limited. A greater understanding of these mechanisms is necessary to improve and refine treatments.
Aims: This study utilized a qualitative approach to explore core schematic beliefs in psychosis (strongly held positive and negative beliefs about the self and others) and their relation to hallucinations and delusions.
Method: Twenty individuals with psychosis participated in individual semi-structured interviews. Inductive thematic analysis was used to analyse the interviews.
Results: Four emergent themes were identified: (i) the solidity and permanency of core beliefs, (ii) the causes and development of core beliefs, (iii) a synergistic relationship between core beliefs and symptoms, and (iv) core beliefs associated with images and their influence on psychotic symptoms.
Conclusions: This study provides new insights into the range and character of core beliefs in psychosis and provides important data to guide ongoing and future development of treatment approaches for psychosis.
Sophisticated matrix correction techniques have been successfully applied to analysis in an interactive laboratory environment (1-3). The present paper describes their application, to an on-line industrial environment, where reliable operation is to be maintained with a minimum of operator intervention. Out of bound situations must be detected and corrected automatically to the extent possible. Programming must be substituted for human judgement, within restricted circumstances.
Rapid changes in methods of energy production and utilization are occurring in California, as elsewhere. The affects of such changes upon atmospheric aerosols have been monitored since January, 1973, as part of the continuing study of California aerosols undertaken by U.C. Davis for the California Air Resources Board. A primary goal of the program is to identify aerosol sources in detail, thus allowing energy related components to be isolated and evaluated at many locations throughout the state.
Use of ion-excited x-ray emission as the major (although not exclusive) method of elemental analysis is well suited to this program for a number of reasons. Among them include; 1. The sensitivity allows particle-sized aerosol samples to be easily collected, 2. The low cost (under $6, per sample) allows many samples to be run within a fixed budget, 3, The large number of elements seen in the average sample allows source identification by element to element to weather correlations. In addition, the samples are suitable for light element analysis by alpha scattering, for elements H through Cl, thus allowing an inventory to be made of all the aerosol mass in the atmosphere within the size range of the sampler.
X-ray fluorescence analysis (XRF) is an analytical method which has been adapted with considerable success to on-line industrial process analysis with various degrees of sophistication. Process analysis XRF systems range from relatively simple units utilizing radioisotope sources with non-dispersive analyzers to complex wavelength dispersive systems in a central location receiving samples from a number of process streams. The advantages of on-line process analytical instrumentation for quality control, regulatory 2 compliance and safety considerations are well documented. ' Advances in the development of low maintenance thermoelectrically cooled Si(Li) detectors have made energy dispersive X-ray fluorescence analysis (EDXRF) even more amendable to on-line process analysis. EDXRF is an important method of on-line instrumentation because of its ability to simultaneously detect many elements.
It has been well established over recent years that synchrotron radiation possesses some unique features as a source of primary x-rays for x-ray fluorescence analysis. Advantage has been taken of the high intensity emanating from the bending magnets of storage rings to develop x-ray microprobes utilizing apertures or focussing optics, or both, to provide a beam spot at the specimen of the order of micrometers. The use of insertion devices wigglers and undulatora, can further increase the available intensity, especially for the high energy photons. Beam Line X-17C at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, accepts the unmodified continuum radiation from a superconducting wiggler in the storage ring. Some initial XRF measurements have been made on this beam line using apertures in the 10 to 100 micrometer range. The fluorescent radiation was measured by an intrinsic Ge detector having an energy resolution of 300 eV at 15 kev, and located at 90° to the incident beam in the plane of the electron orbit. In samples containing many elements, detection limits of a few ppm were achieved with 100 μm beams.
It is important to establish precision and accuracy of an X-ray diffraction (XRD) residual stress measurement procedure in order to compare capabilities of instrumentation and techniques, as well as to provide confidence limits for experimental data. There is no broadly acceptable method for establishment of precision and accuracy. This paper describes a proposed approach and one which is used at The Pennsylvania State University.
One impediment to the measurement of precision and accuracy is that no standard specimen with a known residual stress level is available. Proposed standard specimens have been abandoned for various reasons, including the concern for stability of the original stress condition and the existence of stress gradients, i.e., stress inhomogeneity, in the specimens. However, there is one type of specimen which has been accepted by ASTM as an alignment and zero residual stress confirmation standard. That type of specimen is a powdered sample of metal or ceramic which provides XRD peaks in the vicinity of the Bragg angle in which residual stress measurements are to be performed.
Some researchers tend to report detector counting statistics as the uncertainty of stress measurement but such statistical scatter accounts for only one part of uncertainty in precision and accuracy. The total uncertainty is best determined directly through repeated residual stress measurements performed by removal and readdressing the test specimen or through a repetition of measurements under predictably changing conditions.
This paper describes results from the use of powder specimens to establish the repeatability of measurements with a portable instrument after removal and readdressing of the specimens. Also, results showing the uncertainty of the measured stress change in specimens subjected to known loads are discussed.
Low-energy x-rays can undergo considerable absorption in the sample material when EDX spectrometry is used in multi-element analysis of aerosol-loaded filters. An expression which corrects for the effects of absorption, based on counting aerosol filters and standards on both sides, is derived. The method is experimental verified by using the absorption of the 60 keV gamraa-ray of 241Am in aluminium and also by comparison with PIXE results for environmental filters.
Synchrotron radiation (SR) has several unique properties which cause it to be used for many purposes in science and technology. It is continuous spectrally, collimated spatially, short-pulsed yet continuously-operating temporally, as well as polarized( 1). Many applications of SR have already been demonstrated. These range from production of fine scale structures by lithography to numerous studies of materials. Determination of atomic structure by diffraction and other scattering experiments and by absorption spectroscopy (EXAFS), and emission spectroscopic studies of electronic structure have been given most attention(2). Only limited attention has been paid to determination of materials composition by x-ray fluorescence analysis (XRF) employing synchrotron radiation. Sparks et al.(3-5) have performed the most notable experiments, examining mica inclusions for the presence of primordial super heavy elements and irradiating two National Bureau of Standards Standard Reference Materials (SRM 1571, Orchard Leaves and SRM 1632, Coal) to measure the fluorescent x—ray intensity from the trace elements.
Chronic opioid exposure is common world-wide, but behavioural performance remains under-investigated. This study aimed to investigate visuospatial memory performance in opioid-exposed and dependent clinical populations and its associations with measures of intelligence and cognitive impulsivity.
We recruited 109 participants: (i) patients with a history of opioid dependence due to chronic heroin use (n = 24), (ii) heroin users stabilised on methadone maintenance treatment (n = 29), (iii) participants with a history of chronic pain and prescribed tramadol and codeine (n = 28) and (iv) healthy controls (n = 28). The neuropsychological tasks from the Cambridge Neuropsychological Test Automated Battery included the Delayed Matching to Sample (DMS), Pattern Recognition Memory, Spatial Recognition Memory, Paired Associate Learning, Spatial Span Task, Spatial Working Memory and Cambridge Gambling Task. Pre-morbid general intelligence was assessed using the National Adult Reading Test.
As hypothesised, this study identified the differential effects of chronic heroin and methadone exposures on neuropsychological measures of visuospatial memory (p < 0.01) that were independent of injecting behaviour and dependence status. The study also identified an improvement in DMS performance (specifically at longer delays) when the methadone group was compared with the heroin group and also when the heroin group was stabilised onto methadone. Results identified differential effects of chronic heroin and methadone exposures on various neuropsychological measures of visuospatial memory independently from addiction severity measures, such as injecting behaviour and dependence status.