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Can Photo- And Cathodoluminescence Be Regarded As Complementary Techniques?, S. Myhajlenko, R. A. Puechner, J. L. Edwards, D. B. Davito

Scanning Microscopy

Photoluminescence (PL) usually provides macroscopic, high quality spectroscopic data. Cathodoluminescence (CL), on the other hand, offers the same information with microscopic imaging. However, replicating PL signatures in a CL system is not straightforward since matching experimental conditions, such as temperature and excitation density, is difficult. The matter is further exacerbated by inherent differences in the nature of excitation: electrons versus photons. Our work with high purity semiconductors suggests that CL is generally more sensitive to excitation "circumstance" than PL. For example, electrons can cause sample charging and contamination-related phenomena that dramatically affect CL. Changes in surface attributes (e.g., by chemical …

A New Model Of Low Temperature Photoluminescence In Amorphous Semiconductors, Mathieu Kemp, Marvin Silver

Scanning Microscopy

Recent low temperature a-Si:H photoluminescence experiments show the presence of two peaks in the lifetime distribution, and a dependence of the efficiency on generation rate. These results contradict every existing model of amorphous semiconductor photoluminescence. The reason for the discrepancy is that every model predicts diffusive motion of the photo-generated pairs. We show how the inclusion of coulomb interaction between photocarriers, spin selection effects, and Auger recombination gives back agreement of theory with experiment. This new picture of the phenomenon also explains the transient behavior of the luminescence intensity.

Advances In Research Of Defects In Quartz Based On Luminescence, A. Halperin

Scanning Microscopy

The first part of this paper reviews the observation of the unconventional thermoluminescence {TL(M), where M = Li or Na} peaks observed in the glow curve of Li-and Na-containing quartz, and describes the full solution of the puzzling effect of the TL(M) peaks which needed a two irradiation procedure for their formation. Of interest is the intermediate warming (IW) method, which consisted of two irradiations and warming of the sample to 150-300 K between the two irradiations. This was explained as follows: the first low temperature irradiation produces {AlO₄/M/h}⁺ centers, when the now loosely bound M ions …

Thermoluminescence Of Zircon, Philibert Iacconi

Scanning Microscopy

The thermoluminescence (TL) of synthetic zircons into which some impurities have been individually insert-ed is investigated. The results obtained show that, after X-irradiation at 77K, the synthetic zircons present three kinds of thermoluminescent emissions. The first is related to the OH^- ions, the second is typical of the SiO₄^4-groups, and the third is characteristic of RE³⁺ ions with RE = Dy, Tb, Gd, Eu, or Sm (RE = rare earth).

The OH^- emission is a large band at 285 nm which appears at 115 and 160K.

The SiO₄^4- TL emission consists of …

Cathodoluminescence Of Carbonates: New Applications In Geology And Archaeology, V. Barbin

Scanning Microscopy

Several new applications of cathodoluminescence (CL) have been developed during the last few years, including: combined CL imaging and/or spectroscopy and CL observations of carbonates previously considered to be non-luminescent or of minor interest. Basically, two previously unstudied types of carbonates were investigated: marbles, and recent shells. From numerous classical white marble samples, cathodomicrofacies were defined and described. A single cathodomicrofacies is generally characteristic of a given area. This finding permits identification of the source of white marbles and has been successfully applied to ancient marbles from different collections. Despite the well established idea that CL in biogenic carbonates is …

Plagioclase Studies By Ionoluminescence (Il) And Particle-Induced X-Ray Emission (Pixe) Employing A Nuclear Microprobe, N. P. -O. Homman, C. Yang, K. G. Malmqvist, K. Hanghöj

Scanning Microscopy

When an ion beam in the energy range of a few MeV/amu impacts on a mineral, visible light can often be observed. This light, termed ionoluminescence (IL), has been shown to be a very useful tool for investigating geological specimens when it is combined in a nuclear microprobe with a well-established, quantitative, trace element method such as Particle Induced X-ray Emission (PIXE). When plagioclases from the Skaergaard intrusion, East Greenland, were irradiated with protons, bluish luminescence was observed. Spectroscopic IL studies were undertaken with 1.5 and 2.5 MeV protons with power densities ranging from about 6 to 160 W/cm^{2 …}

Cathodoluminescence Of Some Synthetic Calcite Crystals. Investigation On The Role Played By Cerium, Rémy Chapoulie, Françoise Bechtel, Daniel Borschneck, Max Schvoerer, Guy Rémond

Scanning Microscopy

Cathodoluminescence (CL) from undoped and cerium-doped synthetic calcite is examined at room temperature and at liquid nitrogen temperature, using a scanning electron microscope. At room temperature, all of the samples exhibit a CL emission in the near ultra-violet (UV), centered at approximately 370 nm with some possible shoulders at 345 nm. At low temperature, the samples show an emission of CL in the near UV but with two well defined maxima for the Ce-doped crystals (460 ppm and 4600 ppm) peaking at 345 and around 380 nm. The third Ce-doped crystal (1.74%) presents a maximum at 375 nm and a …

Multi-Laboratory Results For The Cathodoluminescence Emission Spectrum From A Synthetic Zircon Standard, John M. Hanchar, Donald J. Marshall

Scanning Microscopy

The Standards Committee of the Society for Luminescence Microscopy and Spectroscopy (SLMS) circulated doped zircon crystals as a standard for comparison of cathodoluminescence (CL) emission spectra obtained at different laboratories. Eleven laboratories have submitted spectra acquired from this standard. The crystals are synthetic zircons doped with 1.4 wt.% of Dy₂O₃

The participating laboratories used a variety of CL instrumentation including cold cathode optical micro-scope attachments, hot cathode optical microscope attachments, and EMPA/SEM-based systems. Two laboratories provided both uncorrected and corrected spectra. All other spectra are uncorrected. A variety of different spectrometers/spectrographs and detector systems were used. Photomultiplier …

Can Cathodoluminescence And Scanning Electron Acoustic Microscopy Be Considered Complementary Techniques?, J. F. Bresse

Scanning Microscopy

Cathodoluminescence (CL) and Scanning Electron Acoustic Microscopy (SEAM) give complementary information on direct bandgap semiconductors when dopant impurities are introduced. CL deals with the electrical properties of the semiconductor and SEAM deals with the thermal and elastic properties and eventually with the piezoelectric properties in low doped III-V compounds. As function of the introduction of impurities for the doping of the semiconductor, the Near-Band-Edge (NBE) CL emission increases up to a maximum. and decreases when the impurities are no longer introduced in electrically active sites, but create complexes giving rise to the appearance of a Deep Level (DL) emission. The …

Luminescence Spectroscopy Of Semiconductor Surfaces And Interfaces, L. J. Brillson, S. Chang, A. D. Raisanen, I. M. Vitomirov

Scanning Microscopy

Low energy cathodoluminescence spectroscopy (CLS) employing incident electron energies in the range of a few kV or less enable measurement of electronic structure near semiconductor surfaces and interfaces. Coupled with photoluminescence spectroscopy (PL), the CLS technique has been extended to characterize electronic structure tens of nanometers below the free surface at metal-semiconductor and semiconductor-semiconductor junctions. CLS has revealed discrete, deep electronic states for clean and metallized semiconductor surfaces as a function of atomic ordering as well as vicinal surfaces as a function of misorientation. A combination of CLS and PL reveals deep level features associated with strain relaxation and dislocations …

Final Environmental Impact Statement Union Pacific Resources Company Greater Wamsutter Area Ii Natural Gas Development Project, United States Department Of The Interior Bureau Of Land Management

Final Environmental Impact Statements (WY)

This final Environmental Impact Statement assesses the environmental consequences of a proposed natural gas development project in southwestern Carbon and eastern Sweetwater Counties, approximately 45 miles southwest of Rawlins, Wyoming. Public scoping commenced on December 13, 1993. All issues raised during scoping and interdisciplinary team preparation of the analysis were addressed in the Draft Environmental Impact Statement (DEIS). This document should be used in conjunction with the DEIS. Copies of the DEIS are available from the Great Divide Resource Area at the address given on the bottom of this page. The DEIS was made available to the EPA and the …

Hs Resources, Inc., Natural Gas Exploration Project, Finding Of No Significant Impact Decision Record, United States Department Of The Interior Bureau Of Land Management

Record of Decisions (WY)

HS Resources Incorporated and Lario Oil and Gas Company (HS Resources) propose to drill three natural gas exploration wells (one discovery, one confirmation, and one delineation well) on public lands in the Essex Mountain area located east of the Sand Dunes Wilderness Study Area (WSA) in Sweetwater County, Wyoming (see Maps 1-1 and 1-2). These public lands are administered by the Green River Resource Area (GRRA), Rock Springs District of the Bureau of Land Management.

Bone Absorptiometry In Metabolic Bone Disease: Baseline Values And Long-Term Treatment With Calcitriol (Post-Menopausal Osteoporosis Versus Osteomalacia), A. Caniggia, B. Frediani

Cells and Materials

Total body bone absorptiometry reveals low mineral density in both postmenopausal osteoporosis and osteomalacia patients. The method was used to investigate the effect of calcitriol administration on patients suffering from one of these conditions. In osteomalacia, the administration of calcitriol resulted in a dramatic improvement in bone mineral density (sometimes up to 50% in 12 months), indicating the rapid mineralization of previously uncalcified bone tissue as a result of the normalization of the Ca x P product. In osteoporosis a similar treatment was seen to halt the progressive decrease in bone mineral levels and sometimes resulted in minor increases in …

Urban Bias In Price Risk: The Geography Of Food Price Distributions In Low-Income Economies, Christopher B. Barrett

Economic Research Institute Study Papers

The geography of agricultural marketing has important implications for the stochastic distribution of agricultural commodity prices. This paper proposes that objective food price risk differs between rural and urban areas of infrastructure-poor economies characterized by spatially concentrated patterns of foodgrains storage. This difference implies an urban bias having adverse welfare effects for peasants who seasonally switch between net food seller and net food buyer positions. Empirical analysis of rice price data from Madagascar suggests that price variability and skewness indeed differ between rural and urban areas in ways that adversely influence the relative welfare of rural peasants.

Department Of Energy Programmatic Spent Nuclear Fuel Management And Idaho National Engineering Laboratory Environmental Restoration And Waste Management Programs Final Environmental Impact Statement, Volume 1, Appendix F, United States Department Of Energy

All U.S. Government Documents (Utah Regional Depository)

This appendix addresses the interim storage of spent nuclear fuel (SNF) at two U.S. Department of Energy sites, the Nevada Test Site (NTS) and the Oak Ridge Reservation (ORR). These sites are being considered to provide a reasonable range of alternative settings at which future SNF management activities could be conducted. These locations are not currently involved in management of large quantities of SNF; NTS has none, and ORR has only small quantities. But NTS and ORR do offer experience and infrastructure for the handling, processing and storage of radioactive materials, and they do exemplify a broad spectrum of environmental …

Department Of Energy Programmatic Spent Nuclear Fuel Management And Idaho National Engineering Laboratory Environmental Restoration And Waste Management Programs Final Environmental Impact Statement, Volume 3, Part A, United States Department Of Energy

All U.S. Government Documents (Utah Regional Depository)

This document analyzes at a programmatic level the potential environmental consequences over the next 40 years of alternatives related to the transportation, receipt, processing, and storage of spent nuclear fuel under the responsibility of the U.S. Department of Energy. It also analyzes the site-specific consequences of the Idaho National Engineering Laboratory sitewide actions anticipated over the next 10 years for waste and spent nuclear fuel management and environmental restoration. For programmatic spent nuclear fuel management, this document analyzes alternatives of no action, decentralization, regionalization, centralization and the use of the plans that existed in 1992/1993 for the management of these …

Tailholt Administrative Research Study Final Environmental Impact Statement, United States Forest Service

Final Environmental Impact Statements (ID)

This Final Environmental Impact Statement documents the analysis of three alternatives, including the "No Action" alternative, that were developed for the proposed Tailholt Administrative Research Study. The alternatives respond to the major issues and resources that were identified for this project. The action alternatives would allow timber harvest, using helicopter yarding and no road construction, to be conducted as part of an ongoing study designed to provide forest managers with information on minimizing resource damage when conducting forest management activities.

Boise River Wildfire Recovery Project Final Environmental Impact Statement, United States Forest Service

Final Environmental Impact Statements (ID)

The Final Environmental Impact Statement (FEIS) describes three alternative approaches for salvage harvest and reforestation across 102,000 acres of National Forest System land that burned in 1994. The project area is northeast of the city of Boise and is located on the Idaho City and Mountain Home Ranger Districts. The proposed action (Alternative 2) would harvest fire-killed timber on approximately 81,000 acres, including Inventoried Roadless Areas (IRAs), and maintain trees for site protection, regeneration, and wildlife. Alternative 3 would implement the same management prescriptions, but harvesting activities would take place over 64,400 acres outside IRAs. Alternative 1 is the no …

A Morphological Assessment Of Bovine Chondrocytes Cultured On Poly(Ethyl Methacrylate)/Tetrahydrofurfuryl Methacrylate, R. M. Sawtell, M. V. Kayser, S. Downes

Cells and Materials

A heterocyclic methacrylate polymer system, PEMA/THFMA, has shown potential as a biomaterial for cartilage repair in a rabbit model and has properties making it suitable for use clinically. The ability of the polymer system, PEMA/THFMA, and a related system, PEMA/HEMA, to support chondrocytes in vitro was assessed by scanning electron microscopy. Chondrocytes adhered to the surface of the PEMA/THFMA by day one, having a rounded morphology and clustered appearance opposed to the Thermanox® control, where the cells had spread out and become fibroblastic in appearance. The chondrocytes divided rapidly on the PEMA/ THFMA system by day three and had completely …

Adsorption Of Bovine Serum Albumin Onto Octacalcium Phosphate And Its Hydrolyzates, O. Suzuki, H. Yagishita, M. Yamazaki, T. Aoba

Cells and Materials

Octacalcium phosphate (OCP) has been advocated to be a precursor of biomineral s. Tn this report , we aimed at investigating OCP hydrolysis and the interaction of OCP and its hydrolyzates (apatitic products) with bovine serum albumin (BSA). A batch of synthetic OCP was allowed to hydrolyze either (a) in deionized water at 70°C or (b) in Tris buffer (pH 7.4) containing 2 ppm fluoride at 37°C. OCP hydrolysis was completed within reasonable experimental periods: after 48 hours at 70°C and after 10 days at 37°C in the presence of fluoride. The adsorption isotherms of BSA onto the original OCP …

Some Biological And Physical Properties Of Laser Deposited Hydroxyapatite Based Films, Tatjana Dostalova, Lucie Himmlova, Miroslav Jelinek, Jirina Bartova

Cells and Materials

The preliminary results of biological and physical tests of hydroxyapatite thin films deposited on dental implants by a new technology with the KrF excimer laser ablation method were evaluated. Biological and physical properties were studied and analyzed by the lymphocyte proliferation test and scanning electron microscopy (SEM), X-ray analysis, Rutherford backscattering analysis (RBS) and particle induced X-ray emission (PIXE) methods. Ten bioceramic films from 45 samples had very good physical and biological properties. Creation of hydroxyapatite thin films with laser ablation can have a positive effect on adhesion of the film and protection for corrosion.

Adsorption Of Proteins At Solid-Liquid Interfaces, Willem Norde

Cells and Materials

This paper concisely reviews the general principles underlying protein adsorption from aqueous solution onto a solid surface. The discussion includes the various stages of the adsorption process, i. e., transport of the protein molecules towards the surface, the absorbed amount under equilibrium conditions, desorption and re-adsorption. Among the interactions that determine the overall protein adsorption process (1 ) redistribution of charged groups in the interfacial layer, (2) changes in the hydration of the sorbent and the protein surface, and (3) structural rearrangements in the protein molecule play major roles. Special attention is given to the relation between the structural stability …

Some Observations On The Structure Of Encrusting Biofilms Of Proteus Mirabilis On Urethral Catheters, C. Winters, D. J. Stickler, N. S. Howe, T. J. Williams, N. Wilkinson, C. J. Buckley

Cells and Materials

A physical model of the bladder has been used to study the process of urinary catheter encrustation. Techniques have been devised for the preparation of sections through these encrustations in situ on the luminal surfaces of catheters and for mapping the distribution of calcium and magnesium in the biofilms. Transmission electron microscopy on these sections showed struvite-like crystals lying in the matrix and in direct contact with the catheter surface. Calcium phosphate ("bioapatite") was distributed throughout the film and many of these amorphous particles appear to have cells at their cores. Freeze-substituted sections of biofilms also showed electron dense materials …

Inorganic Nitrogen Determined By Laboratory And Field Extractions Of Two Forest Soils, H. Van Miegroet

Watershed Sciences Faculty Publications

To assess the effect of a delay in soil processing on inorganic N levels in N-rich soils, field and laboratory extractions were compared at two forested sites with high N mineralization and nitrification potential. At eight sampling dates in 1989 and 1990, five mineral soil cores per site were taken between 0- and 10-cm depth and transported on ice to the laboratory for KCl extraction and NH4-N and NO3-N analysis. At three sampling dates in 1990, soil extractions were performed in the field immediately following sampling, and inorganic N concentrations were compared between extractions. Nitrate-N increased four- to sevenfold (net …

Biodiversity On Rangelands: Definitions And Values, Neil E. West

Natural Resources and Environmental Issues

Biodiversity is not just one phenomenon but is a concept cluster that involves many facets of biological variety. These facets include taxonomic richness; genetic differences within each taxon; the communities, ecosystems, and landscapes organisms occupy; and the knowledge of nature local people living on the land possess. Biodiversity is prized for a variety of intertwined moral, aesthetic, and practical reasons. The role of biodiversity in the globe's life-support systems is poorly understood but probably pivotal. The world's rangelands possess biodiversity out of proportion to their area or productivity. Livestock grazing may influence biodiversity either positively or negatively depending on what …

Diversity Of Animal Communities On Southwestern Rangelands: Species Patterns, Habitat Relationships, And Land Management, Robert R. Parmenter, Sandra L. Brantley, James H. Brown, Clifford S. Crawford, David C. Lightfoot, Terry L. Yates

Natural Resources and Environmental Issues

The rangelands of the southwestern United States comprise a mosaic of biome types, including deserts, grasslands, chaparral, woodlands, forests, subalpine meadows, and alpine tundra. Taken together, these ecosystems support exceptionally high numbers of vertebrate and invertebrate animal species. Biogeographic patterns of mammal, bird, and reptile species across North America show trends of increasing species numbers for these vertebrate groups, and some invertebrate groups, occur in Texas, New Mexico, Arizona, and California, especially in the border region with Mexico. Underlying causes of the region's high biodiversity are related to (1) the elevational variability inherent in the basin-and-range topography, with its concomitant …

Diversity Of Rangeland Bird Populations, Peter B. Stacey

Natural Resources and Environmental Issues

Most discussion and management of biological diversity occurs at the local population level, which can be defined as that group of organisms of one species that live in a specific area and that tend to interact more frequently with each other than with individuals from other populations. Loss of diversity always occurs first with the extinction of local populations, and, if the process continues long enough, will ultimately lead to extinction at the regional and global scales. Among animals, most changes in the biological diversity of western rangelands have involved local extinctions, and I summarize the general factors that determine …

Landscape Diversity In The Western Great Basin, William S. Longland, James A. Young

Natural Resources and Environmental Issues

The biological diversity that is supported by a particular area is generally a positive function of the degree of environmental heterogeneity occurring over space and time within that area. Because heterogeneity or patchiness can occur from very small to very large spatial scales, biodiversity, at the extensive scales covered by landscapes can be affected by heterogeneity occurring in a nested series of smaller-scale patches. We discuss this relationship between patchiness and biodiversity in the context of nonequilibrium models of community organization, such as source/sink and metapopulation models, and contrast this with the traditional equilibrium view of ecological communities. We provide …

Factors Influencing The Context And Principles Of Ecosystem Management, Hal Salwasser

Natural Resources and Environmental Issues

The earth's population has grown eleven-fold in the last 300 years, therefore there are fewer resources and less space available for each individual, living thing: hence the biodiversity crisis. Human use of resources has increased at a greater rate than population growth. Agricultural and natural resources use and efficiency gains will be required to stop ecosystem degradation. All ecosystems have biological and physical limits, are complex and interconnected in space and time, are constantly changing in only partially predictable ways, and are renewable. Sustainable development, though a nebulous statement of intent, affirms maintaining healthy, productive land and natural resources. Ecosystem …

Flathead Basin, Montana, Ecosystem Case Study, Jack A. Stanford

Natural Resources and Environmental Issues

The Flathead Basin project began as a river-basin EIS, guided by a citizen-based steering committee which eventually evolved into the Flathead Basin Commission, a State-legislated body. Water quality has dominated the Commission's agenda, and has been the basis for assessing ecosystem change. Science has played a central role in providing information, driving adaptive management, developing an understanding of ecosystem structure and function, and informing the public. The ecosystem approach involved defining the system as the Flathead Lake catchment basin, synthesizing available information on the system with models, considering alternative management strategies, and making initial management decisions.