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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.
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.
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.
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.
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.
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.
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.
Results of protein residue and lithic microwear analyses are reported for Paleoindian and Early Archaic stone tools from a Carolina bay sand rim on the Aiken Plateau of South Carolina, USA. Protein residue analysis is performed using crossover Immunoelectrophoresis (CIEP), and indicates positive results for Bovidae, Cervidae, Galliformes, and Meleagris gallopavo. These results are complemented by a larger immunological study of 135 diagnostic hafted bifaces from South Carolina and Georgia. Among other species identified, bovid residue was found on multiple Paleoindian hafted bifaces, an Early Archaic hafted biface, and a Middle Archaic hafted biface. Results suggest continuity of species selection and availability across the Pleistocene/Holocene boundary and provide no support for the exploitation of extinct fauna. The data do provide compelling evidence for a demographic shift and/or regional extirpation of Bovidae possibly as late as the early mid-Holocene in the Southeast. In addition, microwear analysis of artifacts from Flamingo Bay indicate intensive hide scraping, antler boring, bone graving/planing/pointing, wood whittling, and hafting traces. Microwear data suggest intentional snap-fracture or bipolarization of exhausted or broken Clovis points for reuse as hide scrapers, and use of large bifacial knives and unifacial scrapers in intensive defleshing activities consistent with large animal butchery.
High quality and lattice matched buffer layers are needed for the growth of device quality GaN thin films on sapphire for optoelectronic applications. In this context, we report the fabrication of AlN thin films having low defect densities through a novel process called solid phase epitaxial recrystallization (SPER). In this process, as-grown crystalline AlN thin films, having a large defect concentration (such as threading dislocations due to a large lattice mismatch between AlN and sapphire and low angle grain boundaries), were thermally annealed in an inert atmosphere at various temperatures ranging from 1200-1600° for 30 min. The as-grown and annealed samples were characterized using x-ray diffraction, transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and UV-visible spectroscopy. The ion channeling/RBS and TEM results clearly indicate a substantial reduction in the defect density for the recrystallized AlN films. The surface morphology of the SPER AlN films was smooth with a surface roughness close to the unit cell height. The optical bandgap was sharp as compared to as-grown films, with a bandgap of 6.2 eV. The recrystallized films having smooth surface morphology and low defect densities may be useful for the growth of device quality GaN films on sapphire.
Contemporary hand-made Iznik-style ceramics continue to be popular in Turkey. Made in some 50 workshops in Kiitahya and one workshop in Iznik, these wares generally show the same stratigraphy as the traditional Iznik wares produced during the Ottomon Empire from the 15th-17th centuries. While the materials utilized in the modern wares show some similarities to the traditional wares, the modern ceramicists have adopted many modern materials. For this paper, crossections of ceramics from four modern workshops were analyzed in an electron beam microprobe and the results compared with published information on traditional Iznik ceramics.
Epitaxial layers of GaAs grown by MBE or MOCVD and doped with silicon impurities have been studied using FTIR spectroscopy. Vibrational modes are observed for Si(Ga), Si(As), Si(Ga)-Si(As) and a defect labelled SI-X. This latter defect appears to be responsible for the compensation effects found in some highly doped material. The Si(Ga) mode is modified in AlGaAs but understood in terms of a simple statistical model. Epitaxial GaAs layers doped with silicon or beryllium are passivated by exposing the samples to an RF hydrogen plasma which leads to the formation of Si-H and Be-H close pairs.
Recent results indicate that certain organic molecules whose electronic structures are characterized by extended pi-molecular orbitals can exhibit significant second and third order nonlinear optical (NLO) effects . Unfortunately, this same arrangement which leads to the NLO effects, can also result in essentially one-dimensional bonding coordination. This in turn means that crystals grown from these materials do not readily form good three-dimensional optical-quality crystals, but rather tend to form needles. In addition, pure organic crystals are usually bonded by weak van der Waals forces, often resulting in poor mechanical properties. Indeed, organic impurities are frequently incorporated into these systems during crystallization resulting in poor crystallinity, spurious absorptions, and low damage thresholds. This is particularly true in the case of polymeric NLO materials, where impurities result from the polymerization steps and/or starting materials.
Epitaxial regrowth of deposited amorphous silicon has been previously described utilizing ion implantation amorphization, ion mixing and thermal anneal. This paper evaluates the effects of these process steps on crystalline quality utilizing Rutherford Backscattering (RBS), x-ray diffraction rocking curves and Raman scattering.
In situ (during implantation) regrowth results in defective crystallinity. In contrast, when there is no in situ regrowth, the post anneal crystallinity is equivalent by RBS and x-ray evaluation to virgin single crystal wafers. In situ regrowth is most pronounced during the high beam current ion mixing type implants which produce wafer temperatures of about 250°C. The final crystalline quality which results from different sequences of amorphization and ion mixing implants, is strongly dependent upon the amount of in situ regrowth which has occurred. The greater the in situ regrowth the poorer the final crystalline quality.
Bulk single crystals of GaN were used for epitaxial growth of GaN films by molecular beam epitaxy. Low temperature photoluminescence yields much higher intensity emission in the near bandedge region for epitaxial films with respect to the situation in bulk crystals. Character of this luminescence changes also. Dominant band-to-band transitions in the bulk crystals are exchanged by bound exciton and/or donor-acceptor pair transitions observed in the epitaxial layers. We will compare the obtained results with the available data on the homoepitaxial samples grown by metalorganic chemical vapor deposition method and discuss the importance of establishing the basic information on energetic positions of excitonic transitions in stress free samples.
An environmental friendly, aqueous based, thin film technology is investigated that is quite versatile in forming a variety of polymer substrates. The polymer substrates are potentially capable of being utilized as high resolution resists for semiconductor chip production. This process is based on polymerization of monomers partitioned within a two dimensional surfactant template adsorbed on the surface of a silicon wafer. The surfactant template (bilayer) serves to localize the polymerization reaction at the liquid‐solid interface and thereby resulting in the coverage of the silicon wafer with a nano‐thin polymer film. On a polished silicon wafer with a 4 nm silicon oxide layer, film thickness up to 130 nm have been obtained for polystyrene and for poly(methyl methacrylate) (PMMA) which is also used as a standard photoresist mask in electron beam lithography.