Digital Commons Network^™

High Precision, High Spatial Resolution Analysis Of Sulfur Isotopes By Laser Combustion Of Natural Sulfide Minerals, S. P. Kelley, A. E. Fallick, P. Mcconville, A. J. Boyce

Scanning Microscopy

Laser induced combustion provides a powerful new technique for sulfur isotope measurements in natural sulfides. A high power continuous laser, focused through a modified microscope system onto a sulfide mineral target, produces highly localized heating. The laser beam is focused to a spot 25 μm in diameter at the sample surface. In the presence of low pressure oxygen, temperatures at the centre of the spot are sufficiently high to produce localized oxidation. Resultant SO₂ is transferred to a gas source isotope ratio mass spectrometer, where the 𝛿³⁴S can be measured to a precision better than 0.25‰. Sulfur …

Comparative Stress Dynamics Of Brood Stock Striped Bass Morone Saxatilis Associated With Two Capture Techniques, Reginal M. Harrell, Mark A. Moline

Biological Sciences

Mature striped bass (Morone saxatilis) were collected from the spawning reaches of the Choptank River, Maryland for the purpose of evaluating stress effects associated with capture. Two commonly used capture devices were evaluated—gillnetting and electrofishing. Results indicated that stress, as measured by changes in plasma corticosteroid and chloride concentrations, was significantly lower and recovery time quicker in those fish captured by electrofishing compared to gillnetting. By the end of the study period (48 h), those fish captured by electrofishing had recovered from the initial capture shock as evidenced by corticosteroid levels returning to near baseline levels. Conversely, at …

Cathodoluminescence Spectroscopy: An Accurate Technique For The Characterization Of The Fabrication Technology Of Gaalas/Gaas Heterojunction Bipolar Transistors, A. C. Papadopoulo, C. Dubon-Chevallier, J. F. Bresse

Scanning Microscopy

Cathodoluminescence (CL) spectroscopy and imaging performed at low temperature have been used to qualify the heterojunction bipolar transistor fabrication technology, particularly the etching and ion implantation steps. CL has been used to optimize low defect technological processes. The protection of the active region during the insulation process has been optimized. The best result is obtained when using a bilayer of silicon nitride and photoresist. In order to minimize it, the damage induced by the etching process has also been studied. The best result is obtained when combining Ar ion beam etching and chemical etching. The possibilities to perform localized spectroscopy, …

The Mayfly Newsletter, Peter M. Grant

The Mayfly Newsletter

The Mayfly Newsletter is the official newsletter of the Permanent Committee of the International Conferences on Ephemeroptera.

Essential Cysteines In 3-Deoxy-D-Arabino-Heptulosonate-7-Phosphate Synthase From Escherichia Coli., Craig Stephens, Ronald Bauerle

Biology

The phenylalanine-sensitive isozyme of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli was inactivated by the sulfhydryl modifying reagents 5,5-dithiobis-(2-nitrobenzoate), bromopyruvate, and N-ethylmaleimide and protected from inactivation by the presence of its metal activator, Mn2+, and substrate, phosphoenolpyruvate. Inactivation by 5,5-dithiobis-(2-nitrobenzoate) was correlated with modification of two of the seven cysteine sulfhydryls of the enzyme monomer. The kinetics of 5,5-dithiobis-(2-nitrobenzoate) modification were altered significantly and distinctively by both substrates (phosphoenolpyruvate and erythrose 4-phosphate), by Mn2+, and by L-phenylalanine, suggesting that ligand binding has significant effects on the conformation of the enzyme. Site-directed mutagenesis was used to create multiple substitutions at the two invariant …

Development Of Mass-Rearing Techniques For Aphelinus Asychis Walker For Use In A Biological Control Program Against Russian Wheat Aphid, Robin Lynn Whitaker-Deerberg

Theses and Dissertations - UTB/UTPA

Mass-rearing techniques were developed for the parasitoid Aphelinus asychis Walker (Hymenoptera:Aphelinidae) for use in a biological control program against the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera:Aphididae). Daily ovipositional activity, host-feeding behavior, effects of population density in the rearing cages and effects of cold storage on mummies were determined.

Daily ovipositional activity peaked at day 5 after emergence of the parasitoid. Ninety-two percent of mummies resulting from ovipositional activity were oviposited the first 13 days of the parasitoid’s life. Since mummification occurred 11 days after oviposition and emergence occurred 11 days after mummification, day 24 was determined to be the …

Lek Formation In Sage Grouse: The Effect Of Female Choice On Male Territory Settlement, Robert M. Gibson

School of Biological Sciences: Faculty Publications

Previous studies of female choice in sage grouse, Centrocercus urophasianus, have identified two processes that could drive the local clustering of male territories at leks: (1) fidelity of females to previous mating sites (“temporal spillover” hypothesis), and (2) “spatial spillover” of matings from an attractive male to his immediate neighbors (“hotshot” hypothesis). The effects of each process on male territory settlement were investigated using observations of the resettlement of vacant territories and of individual site fidelity during a 7-year field study. The frequency with which vacant territories were resettled both within and between seasons increased with mating success of …

Influence Of Bragg Scattering On Plasmon Spectra Of Aluminum, P. Schattschneider, D. -S. Su, P. Pongratz

Scanning Microscopy

Plasmon spectrometry is an important method to obtain information on many-body effects in the solid state. The plasmon halfwidth and the dispersion coefficient are well investigated for a number of materials, and compare well with quantum mechanical predictions. The excitation strength of the coherent double plasmon has been investigated to a lesser extent. Experimental results are at variance with one another and with theory. This is partly due to the plural scattering which masks the coherent double plasmon.

Accurate analysis of plasmon spectra requires not only to remove the inelastic plural processes but also to take into account the coupling …

The Distribution Of Impurities In Antarctic Ice, W. T. W. Potts, K. Oates, E. W. Wolff, R. Mulvaney

Scanning Microscopy

Antarctic snow and ice contain very low concentrations of ions, < 10 μmole/l Na, Cl and SO₄ but these ions may play a significant part in determining the physical properties of the ice and atmospheric chemistry. At the temperatures pertaining in the Antarctic sulphuric acid would still be liquid and information on the distribution of these ions, whether they are disseminated through the crystals or concentrated in a liquid phase at the triple junctions between the crystals, is essential in order to model some of the physical properties of the ice, including electrical conductivity, rigidity and transparency to radar.

Samples of 125 year old ice from …

Levels Of Complexity In The Microstructure Of Mammalian Enamel And Their Application In Studies Of Systematics, W. V. Koenigswald, W. A. Clemens

Scanning Microscopy

Description and analysis of the complex structure of enamel can be facilitated through the application of a system of hierarchical levels of structural complexity. Five interdependent levels are distinguished. These are the levels of:

1) crystallites,

2) prisms,

3) enamel types,

4) schmelzmuster, and

5) dentition.

This system provides a basis for analysis of both variation of particular structures and variation of structural types throughout a mammal's dentition. Optimally, in wide ranging systematic and biomechanical studies, all levels of structural complexity should be considered, but lack of information about one level does not prevent significant analyses at other levels.

Correlative Transmission Electron Microscopy And High Resolution Scanning Electron Microscopy Studies On The Fine Structural Organization Of The Chicken Pituitary Gland, Susan Tai

Scanning Microscopy

The present study employs transmission (TEM) and high-resolution scanning electron microscopy (HR-SEM) to examine the inter- and intra-cellular organization of the pars distalis of the chicken anterior pituitary gland. The overall view of the cryofractured surface of the par distalis illustrates the arrangement of different pituitary cells and tissues in the follicles. Fine structural examination by HR-SEM shows that the membrane of the mitochondria has a similar configuration to that of the rough endoplasmic reticulum. Granule-like structures, on the surface of the mitochondrial membrane, are similar in size to ribosomes. Standard imaging and three-dimensional imaging demonstrated the formation of developing …

The Ionic Composition Of Ion Transporting Cells In Stonefly Nymphs, W. T. W. Potts, I. Bricknell

Scanning Microscopy

Freshwater stonefly larvae take up sodium and chloride ions from low concentrations in water and concentrate them into haemolymph. The ions are transported by mitochondria rich cells (MRITCs) which are easily identified by their windows in the cuticle. Sodium uptake is generally inhibited at low pH but a few species of stoneflies live in acid waters. Acid tolerance is associated with presence of caviform or bulbiform MRITCs while nymphs possessing only the more common coniform cells are sensitive to acid conditions.

The intracellular concentrations of Na, K, Cl and P in coniform cells of Perla bipunctata and bulbiform cells of …

Simulating Ion Microtomography Data For Improving Reconstruction Quality, A. J. Antolak, A. E. Pontau

Scanning Microscopy

Ion Microtomography (IMT) provides quantitative, fine resolution density imaging of samples for materials characterization. Reconstructed tomographic images are obtained by application of a filtered backprojection algorithm to the collected data. The attainable resolution and data acquisition rate are affected by several parameters. These include the number of ions measured per spot, using either the mean or median residual energy, utilizing Bragg additivity, changing the number of rays or the number of projections and oversampling the data. A tomography simulation computer program is described and used to study the contributions from these effects on the numerical reconstruction of an array of …

The Structure Of Human Lymphotoxin (Tumor Necrosis Factor-Β) At 1.9-Å Resolution, Michael J. Eckt, Mark Ultsch, Ernst Rinderknecht, Abraham M. De Vos, Stephen R. Sprang

Biological Sciences Faculty Publications

The three-dimensional structure of recombinant human lymphotoxin (residues 24-171 of the mature protein) has been determined by x-ray crystallography at 1.9-Å resolution (R_cryst = 0.215 for I > 3_σ(I)). Phases were derived by molecular replacement using tumor necrosis factor (TNF-α) as a search model. Like TNF-α, lymphotoxin (LT) folds to form a "jellyroll" β-sheet sandwich. Three-fold related LT subunits form a trimer stabilized primarily by hydrophobic interactions. A cluster of 6 basic residues around the 3-fold axis may account for the acid lability of the trimer. Although the structural cores of TNF-α and LT are similar, insertions and …

A Light, Transmission And Scanning Electron Microscope Study Of Snuff-Treated Hamster Cheek Pouch Epithelium, S. H. Ashrafi, A. Das, R. Worowongvasu, B. Mehdinejad, J. P. Waterhouse

Scanning Microscopy

The effects of smokeless tobacco (snuff) on hamster cheek mucosa were studied by light microscopy, transmission (TEM) and scanning electron microscopy (SEM). Two grams of commercially available smokeless tobacco were placed into the blind end of the right cheek pouch of each experimental animal, once a day and five days a week for 24 months. The control animals did not receive smokeless tobacco. After 24 months treatment with smokeless tobacco, hamster cheek mucosal epithelium lost its translucency and had become whitish in color. By light microscopy hyperorthokeratosis, prominent granular cell layers with increased keratohyalin granules and hyperplasia were seen. At …

Nitrogen And Carbon Isotope Studies Of A Bat Guano Core From Eagle Creek Cave, Arizona, Usa, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya

WM Keck Science Faculty Papers

Nitrogen and carbon isotope ratios were studied in a stratified deposit of guano of Mexican Free-tailed bats in Eagle Creek Cave, Arizona, U.S.A. Little diagenetic change was observed over the 25-year time span of the guano deposit. High aridity and reduced circulation of air in the cave are hypothesized to have slowed the normally rapid decomposition of the excreta and the subsequent escape of resultant ammonia. The results suggest the high dependency of the speed of diagenetic change on specific physical and other conditions of the caves and indicate that great care need be exercised in the interpretation of the …

Carbon And Nitrogen Isotopic Signatures Of Bat Guanos As A Record Of Past Environments, Hiroshi Mizutani, Donald A. Mcfarlane, Yuko Kabaya

WM Keck Science Faculty Papers

Carbon and nitrogen isotope ratios were measured for various ecogeochemical samples relevant to bat guano ecosystems. In particular, ca. 800-year-old subfossil guano from Jackson's Bay Cave Compex, Jamaica, yielded ratios similar to the modern guano from other Jamaican bat caves but quite different from modern guano of the same area. Diagenetic change and differences in bat food habits were unlikely explanations for the observation. Instead, insects that feed on C4 and CAM plants were the main prey for the bats in present Jackson's Bay area, while the ultimate source of organic matter for bats in other Jamaican caves and for …

The Latent Tendencies Of Pai-1, Stephen R. Sprang

Biological Sciences Faculty Publications

No abstract provided.

Model Of Dietary Fiber Utilization By Small Mammalian Herbivores, With Empirical Results For Neotoma, Felisa A. Smith, Keith E. Justice

Biology Faculty & Staff Publications

Allometric considerations have suggested that small herbivores are inefficient at or incapable of extracting energy from the microbial fermentation of structural carbohydrates. This notion is at odds with accumulating empirical evidence that demonstrates well-developed fiber digestion abilities for a number of small rodent genera. To examine the apparent inconsistency, we have constructed a model of plant fiber utilization tailored specifically for hindgut fermenters. Computer simulations provide estimates of fiber and overall dry-matter digestibilities as a function of body size, energy demand, and diet. Our calculations indicate that small mammals can obtain significant benefit from fiber fermentation, especially at moderate fiber …

Heterogeneous Nuclear Ribonucleoprotein A1 Catalyzes Rna.Rna Annealing, Stephen Munroe, Xiaofan Dong

Biological Sciences Faculty Research and Publications

Within the nucleus, pre-mRNA molecules are complexed with a set of proteins to form heterogeneous nuclear ribonucleoprotein complexes. A1, an abundant RNA binding protein present in these complexes, has been shown to bind selectively to single-stranded RNAs and destabilize base-pairing interactions. In this study.A1 is shown to promote the rate of annealing of complementary RNA strands greater than 300-fold under a wide range of salt concentration and temperature. Maximal annealing is observed under saturating or near saturating concentrations of protein, but annealing decreases sharply at both higher and lower concentrations of A1. Kinetic analysis shows that the rate of annealing …

Integrated Single Crystal Detector For Simultaneous Detection Of Cathodoluminescence And Backscattered Electrons In Scanning Electron Microscopy, Rudolf Autrata, Josef Jirák, Jiří Špinka, Otakar Hutař

Scanning Microscopy

The design of the majority of the available high efficiency cathodoluminescence (CL) detection systems allows the secondary electron (SE) and backscattered electron (BSE) image modes to be detected simultaneously to a limited degree only. The described CL-BSE detector is based on the single crystal YAG scintillator shaped as a spherical mirror which reflects photons emitted from the CL specimen and focuses them on to the entrance surface of a fibre optic light guide connected to the photomultiplier tube (PMT I). The backscattered electrons emitted from the CL specimen move through the reflecting layer of the mirror into the YAG scintillator …

Cathodoluminescence Applied To The Microcharacterization Of Mineral Materials: A Present Status In Experimentation And Interpretation, G. Remond, F. Cesbron, R. Chapoulie, D. Ohnenstetter, C. Roques-Carmes, M. Schvoerer

Scanning Microscopy

Experimentation and interpretation of cathodoluminescence (CL) microscopy and spectroscopy applied to the microcharacterization of material minerals are reviewed. The origins of the intrinsic (host lattice) and extrinsic (impurities) luminescence emissions in crystals are briefly discussed. Merits and limitations of the available techniques are illustrated. CL emission changes as a function of the incident electron dose are illustrated for the case of natural quartz and sphalerite (ZnS) crystals. These effects are discussed in terms of the development of bulk charging, production of heat, diffusion of impurities, and creation of lattice defects induced by the incident ionizing particles. Although CL emission is …

Nuclear Microprobe Application In Semiconductor Process Developments, Mikio Takai

Scanning Microscopy

Scanning nuclear microprobes using Rutherford backscattering (RBS) with light ions have been applied to semiconductor process steps, in which minimum feature sizes of several microns down to submicron and multi-layered structures were used. Two or three dimensional RBS mapping of processed semiconductor layers such as multi-layered wiring, semiconductor-on-insulator (SOI), focused ion implanted layers, and laser processed layers, has clearly revealed process failures and inhomogeneity in buried layers without layer removal processes. Radiation damage due to the probe beams was found to be induced by high probe doses at and above 10¹⁷/cm², in which the degradation of …

Structural Artifacts And Advantages Of Cytocentrifugation Of Cells As Viewed By Scanning Electron Microscopy, Mário N. D. Peão, Artur P. Águas, Carlos Moreira De Sá, Nuno R. Grande

Scanning Microscopy

Cytocentrifugation of cell suspensions onto glass slides is a widely used procedure in contemporary cytology. We employed here scanning electron microscopy (SEM) to investigate putative morphological changes induced in cells submitted to cytocentrifugation. The fine structure of murine pleural exudate cells (macrophages mainly) processed by spinning was compared with that of similar cells treated without centrifugation (poly-L-lysine attachment of the cells to glass slides at 1 g). Cells of cytocentrifuged preparations showed a significant increase in diameter and smoothening of the cell surface as compared with the morphology of non-centrifuged cells. Cytocentrifugation also induced the formation of thin elongations coming …

Architecture Of Mixed Calcium Oxalate Dihydrate And Monohydrate Stones, Hidenobu Iwata, Shouzo Iio, Shunji Nishio, Masafumi Takeuchi

Scanning Microscopy

Calcium oxalate dihydrate (COD) and monohydrate (COM) are the most frequent constituents of urinary stones, and there still exist some questions about the interrelation between the two hydrates. Architecture of mixed COD and COM stones was observed by electron microscopy to solve the questions.

The fractured surface of a stone is composed of the fractured face of the crystals. In this situation a morphological criterion of typical dipyramid shape is useless to identify COD. But we could identify COD using the partial dissolution method, which etched square pits on COD crystals.

COD and COM formed distinctly separate layers. COD was …

Idiopathic Calcium Oxalate Nephrolithiasis: A Cellular Disease, Giovanni Gambaro, Bruno Baggio

Scanning Microscopy

Physico-chemical, metabolic and hormonal theories regarding the pathogenesis of calcium oxalate nephrolithiasis do not sufficiently explain many features of this disease. The recent findings of an abnormally faster oxalate self-exchange and higher phosphorylation of band 3 in erythrocytes of idiopathic calcium oxalate stone formers suggest the hypothesis that nephrolithiasis may be a cellular disease, characterized by a defect in the function of the anion-exchange. The cellular anomaly seems genetically controlled. Band 3 anion exchanger function seems to be biochemically regulated through modulation of band 3 phosphorylation, which depends on cyclic AMP- and phospholipid-sensitive Ca²⁺ independent protein kinases. In this …

Factors Affecting Fasting Urinary Calcium Excretion In Stone Former Patients On Different Dietary Calcium Intake, Piergiorgio Messa, Giuseppe Mioni, Rossana Franzon, Michele Messa, Aldo Cruciatti, Sandro Giannini, Angela D'Angelo

Scanning Microscopy

The effects of variable calcium content on daily and fasting urinary calcium and other lithogenic solutes excretion, on the bone turnover index (fasting hydroxyproline urinary excretion) and on the calciotropic hormones were studied in 312 stone former patients with an outpatient protocol and 15 stone former patients in an inpatient study. Furthermore in 60 of these patients, 30 while on a low calcium diet (LCD) and 30 on a free calcium home diet (FCD), the effects of an oral calcium load (OCL) on bone turnover index, calciotropic hormones and calcium excretion were evaluated. The results demonstrate that an LCD is …

Acquisition Hardware For Imaging, Peter Rez, J. K. Weiss, W. J. De Ruijter

Scanning Microscopy

In electron microscopy images can either be recorded in parallel (Transmission Electron Microscopy) or acquired as the variation in a signal as a probe is scanned over the specimen (Scanning Electron Microscopy). To extract the most information from an image requires that the best possible systems are used for acquiring image data. Ultimately, the limit to information capture is achieved when every electron from the scattering event of interest is recorded. The ideal system can be realised both for parallel recording with scientific grade CCD cameras, and for scanning microscopy with single electron counting electronics. The data rates from these …

Nonlinear Statistical Filtering And Applications To Segregation In Steels From Microprobe Images, C. Daly, D. Jeulin, D. Benoît

Scanning Microscopy

Microprobe images of solidification studies are well known to be subject to a Poisson noise. That is, the radiation count at a pixel x for a certain element may be considered to be an observation of a Poisson random variable whose parameter is equal to the true chemical concentration of the element at x. By modeling the image as a random function, we are able to use geostatistical techniques to perform various filtering operations. This filtering of the image itself may be done using linear kriging. For explicitely nonlinear problems such as the estimation of the underlying histogram of the …

Simulation For Scanning Electron Microscopy, G. R. Anstis, X. S. Gan

Scanning Microscopy

Simulations of images of surface steps obtained by high energy reflection electron microscopy are presented. It is shown that double images of simple steps, with no associated strain field, may occur when surface resonance conditions are established. Accurate calculation of image intensity requires large calculations and care is needed in relating the computed wave functions to those occurring for a semi-infinite incident wave. Estimates of the time to compute accurate wavefunctions are given and it is shown that they are reasonable for modem fast computers.