Digital Commons Network^™

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 …

Specimen Catalog & Field Notes, Angela L. Adams

Division of Mammals - Field Notes and Catalogs

No abstract provided.

Sex And Extinction, Jennifer M. Eckman

Honors Theses, 1963-2015

Sexual reproduction, the process of generating offspring through genetic recombination, is viewed as evolutionarily advantageous to a population by enabling it to respond more readily to environmental change. Support of this hypothesis comes from the observation that the majority of species employ some mode of sexual reproduction. Asexual reproduction is relatively rare, suggesting that these species reduce their chances of survival. This project examines some of the parameters that relate to a population's ability to respond to its environment. Using a program coded in FORTRAN, a Monte Carlo model has been developed to test the role of recombination on population …

Pre- And Post-Zygotic Isolation Between Sibling Species Of Drosophila, Heidi Skundberg

Honors Theses, 1963-2015

Speciation, the process by which new species arise, is not well understood. Even less is known about the underlying genetics of this process. This study examines the level of reproductive isolation between two closely related species, Drosophila melanogaster and D. simulans. All combinations of intra- and inter-specific single-pair matings were set up in a total of 288 crosses. In all cases, intra- specific crosses (controls) were more successful than inter-specific crosses (PD. melanogaster) is the most discriminating (PD. melanogaster, but not when it is D. simulans.

The Influence Of A Bamboo Diet On The Evolutionary Adaptations Of The Giant Panda, Beth A. Pettitt

Honors Theses, 1963-2015

The giant panda (Ailuropoda melanoleuca) of China is, anatomically, a carnivore trying to get by on an herbivorous diet (Dolnick, 1989). While it is a member of the order Carnivora, ninety-nine percent of the panda's feedstuff is bamboo. The giant panda has survived on a bamboo diet for millions of years and throughout its history has evolved numerous adaptations for obtaining and processing this plant efficiently. Various characteristics of bamboo are considered, including: anatomy, strength, cyanogenic capabilities, reproductive cycle, nutrition and abundance. Following these characteristics, specific adaptations that appear to correspond with these properties of bamboo are examined. …

Regulating Factors Of Ovarian Development In Paper Wasps Of The Genus Polistes, Jean Mengelkoch

Honors Theses, 1963-2015

Wasps of the genus Polistes were used to determine the effects of larval nutrition, position within the nest, and parasitism on ovarian development. Polistes nests were collected from Iowa, Minnesota, and Utah during the summer of 1994. The wasps were reared out, dissected, and their ovaries examined. The total number of oocytes and the size of the largest oocyte were used as measurements of ovarian development. Due to difficulties hand feeding the larvae, no data was obtained concerning the effect of larval nutrition on ovarian development. Data from first emergence nests of Minnesota were inconclusive. However, data from the second …

Transmittance Electron Microscopy: A Comparison Of The Rotifers Asplanchna Herricki And Asplanchna Brightwelli, Nichole M. Hecimovich

Honors Theses, 1963-2015

The rotifers, A. brightwelli and A. herricki were surveyed under SEM and TEM. The overall external features were compared under SEM to determine significant differences in morphology. The widths of the coronal surface and midsection were larger in A. herricki than that of A. brightwelli. A. herricki was prepared for view under E M , and integument was compared to A. brightwelli. The integument of A. brightwelli was substantially thicker than that of A. herricki, which disagreed with the hypothesis. Further studies must be conducted to determine the nature of this difference.

Characterization Of A Mutant Strain Of Saccharomyces Cerevisiae With A Deletion Of The Rad27 Gene, A Structural Homolog Of The Rad2 Nucleotide Excision Repair Gene, Michael S. Reagan, Christopher Pittenger, Wolfram Siede, Errol C. Friedberg

Biology Faculty Publications

We have constructed a strain of Saccharomyces cerevisiae with a deletion of the YKL510 open reading frame, which was initially identified in chromosome XI as a homolog of the RAD2 nucleotide excision repair gene (A. Jacquier, P. Legrain, and B. Dujon, Yeast 8:121–132, 1992). The mutant strain exhibits increased sensitivity to UV light and to the alkylating agent methylmethane sulfonate but not to ionizing radiation. We have renamed the YKL510 open reading frame the RAD27 gene, in keeping with the accepted nomenclature for radiationsensitive yeast mutants. Epistasis analysis indicates that the gene is in the RAD6 group of genes, which …

Reproductive Energetics Of Adult Male Yellow- Bellied Marmots (Marmota Flaviventris), Carmen M. Salsbury, K. B. Armitage

Scholarship and Professional Work - LAS

We examined the energy expenditure of adult male yellow-bellied marmots and its relationship to various female-defense characteristics critical to male reproductive success. Resting metabolic rates of males were estimated in the laboratory via oxygen-consumption analysis, and field metabolic rates were estimated using a doubly Labeled water technique. Male home-range size, number of females defended by males, dispersion of females in the habitat, and date into the active season were considered to be predictors of male energy expenditure in excess of maintenance costs (field metabolic rate minus resting metabolic rate). Energy expenditure was best explained by a defensibility index based on …

The Rare, Serpentine Endemic Streptanthus Morrisonii (Brassicaceae) Species Complex, Revisited Using Isozyme Analysis, Rebecca W. Dolan

Scholarship and Professional Work - LAS

The Streptanthus morrisonii (Brassicaceae) complex is a group of six narrowly-distributed obligate serpentine endemic taxa whose habitat is threatened by geothermal development. Isozyme analysis of this little-studied complex supports the delineation of two species, S. morrisonii and S. brachiatus, but is at odds with the treatment of two subspecies based on morphology. These results may be influenced by small sample sizes but genetic studies of other Streptanthus taxa have shown patterns of relatedness that often transgress subspecies boundaries based on morphology. The present study further shows that members of the S. morrisonii complex share high genetic identity values (mean …

Ca2+ And Zn2+ Are Transported By The Electrogenic 2na+/1h+ Antiporter In Echinoderm Gastrointestinal Epithelium, Zhenpeng Zhuang, Jeff Duerr, Gregory A. Ahearn

Faculty Publications - Department of Biological & Molecular Science

45Ca2+ uptake by purified brush-border membrane vesicles of starfish (Pycnopodia helianthoides) pyloric ceca was stimulated by an outwardly directed H+ gradient and this stimulation was enhanced by the simultaneous presence of an induced membrane potential (inside negative; K+/valinomycin). External amiloride (competitive inhibitor; Ki=660mmol l21) and a monoclonal antibody raised against proteins associated with the lobster (Homarus americanus) electrogenic 2Na+/1H+ antiporter both inhibited approximately half of the proton-gradient stimulated 45Ca2+ uptake. These results suggested that Ca2+ might be transported by the electrogenic antiporter and that the crustacean antibody was inhibitory to the exchange function in echinoderms, as was recently shown in …

The Vascular Flora, Rare Species And Plant Migrations Of New River Gorge National River, West Virginia, Dale William Suiter

Theses, Dissertations and Capstones

In 1978, the United States Congress designated 83.5 km/53 mi. of the New River in southern West Virginia as New River Gorge National River. The vascular flora of selected sites in NRGNR was surveyed from September 1992 through October 1994. A total of 904 taxa of vascular plants was recorded, 79.2% of which are native to West Virginia. Currently, 1337 vascular plant taxa have been documented from the New River Gorge as a result of this work as well as the work of Grafton and McGraw and Phillips. A comparison of species with the West Virginia Natural Heritage Program's rare …

Germination Ecophysiology Of Leymus Cinerus (Poaceae), S. E. Meyer, Julie Beckstead, P. S. Allen, H. Pullman

Biology Faculty Scholarship

We studied seed germination responses of 41 collections of Leymus cinereus (basin wildrye), a native perennial bunchgrass widely distributed in western North America. Collections made in 1987 and 1988 were largely nondormant in midautumn but relatively slow to germinate at optimal temperatures (mean germination time 6-16 d). Seeds germinated more quickly after a 2-wk chilling pretreatment (mean germination time 2-11 d). Mean germination time under conditions simulating prolonged snowpack (1⚬C) varied among collections from 6 to 12 wk and was negatively correlated with mean January temperature at the collection site. In dry-afterripening experiments with four 1992 collections, seeds showed only …

Effects Of Afterripening On Cheatgrass (Bromus Tectorum) And Squirreltail (Elymus Elymoides) Germination, Julie Beckstead, Susan E. Meyer, Phil Stewart Allen

Biology Faculty Scholarship

No abstract provided.

Defining The Recognition Of K^(Bm3) And L^D By The Alloreactive 2c T Cell, Kevin Ratliff '95

Honors Projects

The immune system consists (in part) of cells and their products that protect the body from attack by infectious agents. Without this vital system, the body would soon succumb to one or more of these death-causing agents. Fortunately, the immune system eliminates many of these infectious agents before there is any sign of infection. One of the most important groups of cells in this system are the T lymphocytes, or T cells. A specific subset of T cells called cytotoxic T lymphocytes, or CTLs, are responsible for surveying the cell surfaces for foreign substances. Upon recognition of one of these …

Comparison Of The Effects Of Saporin-Igg Injections Into The Nucleus Basalis Magnocellularis And Medial Septal Area Of Male Rat As Assessed By The Morris Water Maze Task, Alexander R. V. Mccampbell '95

Honors Projects

Alzheimer's disease currently afflicts approximately 4 million people in the United States, with 100,000 new cases being reported each year. As post mortem examination of AD patientsI brains has revealed a significant decrease in the number of cholinergic neurons, one approach we have taken is to look at the correlation between the depletion of certain cholinergic markers in animals and the resulting behavioral deficits. Two regions of specific interest are the medial septal area (MSA) and the nucleus basalis magnocellularis (NBM). These regions are important because they are the major source of cholinergic neurons in the brain, they are selectively …

Measurement Of Fungal Biomass In Wooden Art Objects Using Atp Photometry And Energy Charge, Fernando Nieto

Dissertations, Theses, and Capstone Projects

In this study ATP photometry and energy charge (EC) measurements were used to detect and quantify fungal biomass in wood. Three species of wood decaying fungi were used: Phanerochaete chrysosporium (white rot), Poria placenta (brown rot), and Chaetomnium globosum (soft rot). The fungi were grown in malt extract broth (MEB) for one month at 25 °C, and sampled at selected intervals to measure the ATP content and the EC of the mycelium. The mycelia were ground and extracted with cold 5% trichloroacetic acid (TCA) for 20 hours. The conversion factors calculated were based upon the EC of the mycelium. When …

Effect Of Feathers As Nest Insulation On Incubation Behavior And Reproductive Performance Of Tree Swallows (Tachycineta Bicolor), Michael P. Lombardo, Ruth M. Bosman, Christine A. Faro, Stephen G. Houtteman, Timothy S. Kluisza

Peer Reviewed Publications

Many species of birds line their nests with feathers, presumably because of the insulative qualities of feathers and because feathers may act as a barrier between nest parasites and nestlings. In 1993, we experimentally examined the role of feathers as nest insulation on the incubation behavior, nestling growth, and reproductive performance of Tree Swallows (Tachycineta bicolor) nesting in boxes in western Michigan. There were no significant differences between the incubation rhythms of females with experimental nests (i.e. no feathers) and females with control nests (i.e. with feathers). Nestlings that were reared in control nests had significantly longer right …

Within-Pair Copulations: Are Female Tree Swallows Feathering Their Own Nests?, Michael P. Lombardo

Peer Reviewed Publications

A variety of hypotheses has been proposed to explain why socially monogamous birds copulate repeatedly with their mates when only a single copulation is necessary to fertilize an entire clutch (Birkhead and Møller 1992, Petrie 1992, Hunter et al. 1993). Petrie (1992) hypothesized that a female should copulate frequently with her mate so as to reduce her mate’s involvement in extrapair copulations. By reducing her mate’s involvement in extrapair copulations, a female may: (1) avoid the transmission of parasites and sexually transmitted diseases (Hamilton 1990); (2) may avoid sperm depletion by her mate; and (3) may monopolize her mate’s paternal …

Translational Coupling Of Pseudomonas Aeruginosa Phna And Phnb Genes In Escherichia Coli, Patrick L. Splinter, David W. Essar

Journal of the Minnesota Academy of Science

Pseudomonas aeruginosa has two anthranilate synthase (AS) gene pairs. One AS enzyme participates in tryptophan synthesis; its genes are designated trpE and trpG The other AS enzyme, encoded by phnA and phnB, participates in the synthesis of pyocyanin, the characteristic phenazine pigment of the organism. The phenazine pathway genes phnA and phnB overlap by 23 base pairs, excluding the phnB Shine-Dalgarno region, with pbnA upstream from phnB. Our objective was to examine the cloned P. aeruginosa phnA and pbnB gene pair for translational coupling in Escherichia coli. The first 113 base pairs of phnB were fused with either LacZ or …

Unstable And Stable Classifications Of Scombroid Fishes, Kent E. Carpenter, Bruce B. Collette, Joseph L. Russo

Biological Sciences Faculty Publications

Many cladists believe that a classification should strictly reflect a cladistic hypothesis. Consequently, they propose classifications that often differ markedly from existing ones and are potentially unstable due to phylogenetic uncertainty. This is problematic for economically or ecologically important organisms since changing classifications can cause confusion in their management as resources. The classification of the 44 genera of scombroid fishes (the mackerels, tunas, billfishes, and their relatives) illustrates this problem of instability. Previous cladistic analyses and analyses presented in this paper, using different data sets, result in many different cladistic hypotheses. In addition, the inferred cladograms are unstable because of …

A New Approch To Low Drift Ta₂O₅ By Ph Reactive Sputtering And Sol-Gel Method, Chang-Soo Kim, Dae-Hyuk Kwon, Byung-Woog Cho, Byung-Ki Sohn

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.