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The traditional medium for collecting two-dimensional x-ray scattering patterns is photographic film. While x-ray film has excellent resolution, several factors make it a poor choice as a detection device: slow speed, limited dynamic range, the “human factor” (developing, fixing, film handling), and the lack of a commercial scanning system designed for reading two-dimensional x-ray films. Until recently, there were no practical alternatives to the use of photographic film for obtaining two-dimensional x-ray scattering data using a conventional x-ray source. In the past few years, two different detection systems have become available for collecting high quality two-dimensional x-ray scattering data: (1) the Siemens (Xentronics) area detector system, which is a gas filled, wire grid detector, and (2) the Fuji imaging-plate system, which utilizes a phosphor storage plate for imaging the x-ray scattering and a laser scanner to process the image.
Due to the difficulty of analyzing materials at high temperatures and in reactive atmospheres, solid-state catalysts have often been developed with little knowledge of the true chemical behavior of the catalyst, except on a bulk scale. In the field of solid-state catalysis research, a great deal of time and effort is presently being spent to better characterize the chemical and physical properties which determine a particular catalyst‘s efficiency, lifetime, and selectivity. Recently, we have undertaken a study of model copper catalysts at The Dow Chemical Company in an effort to better understand the chemical and physical properties which determine the efficiency, regenerability, and lifetime of this type of solid state catalyst.
The analysis of multi-phase pharmaceuticals, particularly when similar structures are involved (i.e. polymorphs, salts or hydrates), can often be a difficult task. Historically, x-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) have been utilized to study pharmaceutical samples. Relative to other materials, diffraction data for pharmaceuticals are often complex due to the large number of diffraction maxima caused by the size of the molecule and/or the molecular symmetry. Multi-phase mixtures tend to have a large number of overlapping peaks which can hinder the difftactionist's ability to identify phases and interpret the data. When similar structures are analyzed calorimetrically, their thermal events may severely overlap (as will be shown), preventing accurate interpretation of the data. In addition there are several types of thermal events which may not be related to structural transitions. A common one in pharmaceuticals is the loss of solvent or absorbed (versus molecular) water.
Capillary collimators have found a number of uses in fluorescence, diffraction and other x-ray fields. Most of these applications are realized with single, straight glass capillaries. Focussing of synchrotron x-radiation beams has been shown with tapered capillaries. In addition, numerous straight and bent capillaries, bundled into lens-like optics, offer experimenters many other possibilities for better use of the x-radiation from tubes, synchrotron radiation, and plasma sources or the x-ray intensity collected from samples.
Over the past 25 years, numerous studies utilizing both X-ray diffraction (XRE) and differential scanning calorimetry (DSC) have been reported In the literature. Generally, conventional high-temperature X-ray data identifies solid-state transitions, then attempts to correlate them with thermal events observed by the calorimeter. Since changes occur in the sample during studies such as these, separate portions of the sample must be used for XRD and DSC experiments. When comparing results of the two experiments, questions arise concerning sample homogeniety as well as temperature and environmental differences. In fact, no conventional high-temperature X-ray diffraction instrument can give the precise control over temperature and heating rate available with a DSC, The problems of sample inhomogeneltles and Instrumental differences could be avoided if X-ray diffraction and DSC could be performed simultaneously on one sample.
The following study is an evaluation of several different types of instrumentation available for use in powder x-ray diffraction work. The particular units used are those at the Dow Chemical Company x-ray diffraction lab. The variety of instrumentation allows analyses from routine phase identification to more specialized work such as low-angle x-ray diffraction of polymers and high-resolution analysis for cell parameter refinements.
The purpose of this work is to compare the relative capabilities of these different instruments under typical day-to-day operating conditions. While not a comprehensive study, the conclusions drawn should be applicable to powder x-ray diffraction in general.
Over the past 25 years, numerous studies of polymers utilizing both X-ray diffraction (XRD) and differential scanning calorimetry (DSC) have been reported in the literature. These studies have suffered because the two techniques must be performed on separate samples and under conditions that are often dissimilar. By combining the two techniques into one instrument, typical problems encountered with variations in sample preparation and thermal and atmospheric environment are eliminated. This is quite important in the study of polymers since one must match not only temperatures between the two techniques, but also heating rates as well. Matched thermal conditions are necessary because polymer properties such as crystallinity and crystallite size depend on both the temperature and thermal history of the sample under study.
A new method for the collection and analysis of high temperature Guinier x-ray data has been devised at The Dow Chemical Co. This technique can be used to monitor various types of structural transformation and thermal expansions up to 900°C. The thermal expansions of α-Al2O3 and two TiO2 structures, anatase and rutile, have been characterized for their use as high temperature internal standards.
Let A be an n X n non-negative matrix, that is, a matrix whose entries are non-negative numbers. The permanent of A is the scalarvalued function of A defined by
where the summation extends over all permutations i1 … , in of the integers 1, … , n. The purpose of this paper is to prove several inequalities involving the permanent of A and the permanent of submatrices of A when suitable restrictions are placed on the row sums.
From a physiological-behavioral perspective, it has been shown that fish with a higher density of black eumelanin spots are more dominant, less sensitive to stress, have higher feed intake, better feed efficiency and therefore are larger in size. Thus, we hypothesized that genetic (co)variation between skin pigmentation patterns and growth exists and it is advantageous in rainbow trout. The objective of this study was to determine the genetic relationships between skin pigmentation patterns and BW in a breeding population of rainbow trout. We performed a genetic analysis of pigmentation traits including dorsal color (DC), lateral band (LB) intensity, amount of spotting above (SA) and below (SB) the lateral line, and BW at harvest (HW). Variance components were estimated using a multi-trait linear animal model fitted by restricted maximum likelihood. Estimated heritabilities were 0.08±0.02, 0.17±0.03, 0.44±0.04, 0.17±0.04 and 0.23±0.04 for DC, LB, SA, SB and HW, respectively. Genetic correlations between HW and skin color traits were 0.42±0.13, 0.32±0.14 and 0.25±0.11 for LB, SA and SB, respectively. These results indicate positive, but low to moderate genetic relationships between the amount of spotting and BW in rainbow trout. Thus, higher levels of spotting are genetically associated with better growth performance in this population.
Plant species or vegetation characteristics (e.g. sward height) are often distributed in patches within a background of continuous vegetation. Grazing animals exploit this spatial heterogeneity by concentrating their foraging in patches that are of preferred species or in patches that offer high rates of intake (Bazely, 1988). However, little is known of the mechanisms or individual behaviours that animals use to accomplish this preferential patch use. One hypothesis proposed to account for the preferential patch use is that animals remember information about the spatial distribution of the patches they encounter and use this information on subsequent foraging bouts to increase the rate at which they encounter preferred food patches (Bell, 1991). In this study, we tested whether sheep could remember the spatial location of patches in simple and complex environments or whether they needed continually to sample to know what was located in each area.
Recent grazing preference studies show that sheep offered a choice between large adjacent monocultures of perennial ryegrass and white clover choose a diet that is a mixture of the two species (ca. 0·7 white clover) (Parsons et al., 1994). One possible hypothesis to explain this is that animals need to sample different areas to know what is located there or the different plant species to know what eating each species represents and because of this include apparently less desirable foods (here ryegrass) in the diet (see Parsons et al., 1994). Edwards et al., (1996) showed that sheep can use spatial memory and so may not need to sample on an area basis. In this study, we tested directly whether sheep could distinguish between ryegrass and white clover without grazing them and whether they can form associations between the appearance of the vegetation and the food reward it represents.
With the aim of creating novel ceramics for applications in nuclear materials with high radiation tolerance, multiple samples with A-B-O stoichiometries ranging from 215 to 227 were synthesized and characterized by a combination of SEM, XRD, and TEM methods. Single-phase defect-fluorite-type compounds with A = Sm or Yb and B = Ti, Zr, and/or Sn are reported; whereas, pyrochlore structured compounds and lanthanide sesquioxide phases were found as major phases in numerous samples. A series of Y-b-Sn-O samples was successfully prepared as nearly single phase or single phase materials. These are essentially defect fluorites with extra weak peaks, most likely due to X-ray scattering from oxygen or oxygen and metal cations. We describe some interesting TEM data and describe selected area diffraction patterns with complex modulations.
A new species of Roscoea is described and illustrated. Roscoea megalantha Tosh.Yoshida & R.Yangzom occurs in the Eastern Zone of Bhutan and neighbouring Arunachal Pradesh in India. A distribution map and an IUCN conservation assessment are given. A key to the three species of Roscoea found in Bhutan is provided.
This review represents the Southern Ocean community’s satellite data needs for the coming decade. Developed through widespread engagement and incorporating perspectives from a range of stakeholders (both research and operational), it is designed as an important community-driven strategy paper that provides the rationale and information required for future planning and investment. The Southern Ocean is vast but globally connected, and the communities that require satellite-derived data in the region are diverse. This review includes many observable variables, including sea ice properties, sea surface temperature, sea surface height, atmospheric parameters, marine biology (both micro and macro) and related activities, terrestrial cryospheric connections, sea surface salinity, and a discussion of coincident and in situ data collection. Recommendations include commitment to data continuity, increases in particular capabilities (sensor types, spatial, temporal), improvements in dissemination of data/products/uncertainties, and innovation in calibration/validation capabilities. Full recommendations are detailed by variable as well as summarized. This review provides a starting point for scientists to understand more about Southern Ocean processes and their global roles, for funders to understand the desires of the community, for commercial operators to safely conduct their activities in the Southern Ocean, and for space agencies to gain greater impact from Southern Ocean-related acquisitions and missions.
There is increasing interest among developmental psychopathologists in broad transdiagnostic factors that give rise to a wide array of clinical presentations (multifinality), but little is known about how these processes lead to particular psychopathological manifestations over the course of development. We examined whether individual differences in the error-related negativity (ΔERN), a neural indicator of error monitoring, predicts whether early persistent irritability, a prototypical transdiagnostic construct, is associated with later internalizing versus externalizing outcomes. When children were 3 years old, mothers were interviewed about children's persistent irritability and completed questionnaires about their children's psychopathology. Three years later, EEG was recorded while children performed a go/no-go task to measure the ΔERN. When children were approximately 9 years old, mothers again completed questionnaires about their children's psychopathology. The results indicated that among children who were persistently irritable at age 3, an enhanced or more negative ΔERN at age 6 predicted the development of internalizing symptoms at age 9, whereas a blunted or smaller ΔERN at age 6 predicted the development of externalizing symptoms. Our results suggest that variation in error monitoring predicts, and may even shape, the expression of persistent irritability and differentiates developmental trajectories from preschool persistent irritability to internalizing versus externalizing outcomes in middle to late childhood.
This list contains analyses completed between January, 1976 and April, 1977. Details of laboratory operation are contained in our first list (R, 1975, v 18, p 205). Samples submitted for analysis are reviewed by a committee consisting of W DeBoer, E Hansen, Anthropology; L Marcus, Biology; W S Newman, D L Thurber, Earth and Environmental Sciences; and Richard Pardi, Radiocarbon Laboratory.
The following list includes radiocarbon analyses of samples related to studies of Holocene sea levels completed since the publication of the last list (R, 1980, v 22, p 1073–1083). Sample preparation and counting for liquid scintillation samples remain the same. However, an additional gas-proportional facility was added in 1981 to handle the analyses of small samples, some of which are included in this list. The new system consists of two 660cc OFHC copper counters built at Queens College. Samples are counted over at least two 2800 minute intervals alternating with backgrounds and standards counted over 1400 minute intervals. Ages are based on the Libby half-life of 5568 years and include 1σ standard deviations of sample, standard, and background activities.