Life Sciences Commons^™

Stress Corrosion And Stress Induced Surface Morphology Of Epitaxial Films, Michael Grinfeld

Scanning Microscopy

In addition to several new predictions, the general theory of thermodynamic stability of heterogeneous systems with rearrangement has allowed us to understand the roots of several experimental and theoretical results of the past. One of them is an outstanding paper of Asaro and Tiller on stress corrosion cracking by surface diffusion published two decades ago. We compare results of Asaro and Tiller with conclusions of thermodynamic theory of solids with rearrangement and develop some Asaro-Tiller results in the directions dictated by the needs of thin films technology and experiment. A surface diffusion model in a prestressed elastic solid is studied …

Utilization Of An Electron-Beam Tester For Determining Internal Electric Field Profiles In Micro-Structured Thin-Film Semiconductor Devices, A. Jank, M. Jung, M. Lambert, G. Lichter, H. Schmoranzer

Scanning Microscopy

An electron-beam tester was used to determine the depth profile of the internal potential distribution in an a-Si:H solar cell and hence the internal electric field profile. The a-Si:H solar cells were prepared for the measurements with the electron-beam tester by low-energy chemical plasma beam etching through a plasma-resistant mask structured by electron-beam lithography. In contrast to an earlier work, the solar cells were in situ illuminated and the electric field profiles were determined for new, degraded and in situ annealed solar cells at various cell temperatures. The measuring results demonstrate that the electron-beam testing technique in combination with a …

Comparative Scanning, Transmission And Atomic Force Microscopy Of The Microtubular Cytoskeleton In Fenestrated Liver Endothelial Cells, Filip Braet, Ronald De Zanger, Wouter Kalle, Anton Raap, Hans Tanke, Eddie Wisse

Scanning Microscopy

Endothelial fenestrae control the exchange of fluids, solutes and particles between the sinusoidal lumen and the microvillous surface of the parenchymal cells. Fenestrae have a critical dimension in the order of 150-200 nm, making it necessary to use microscopes with a resolution better than the light microscope. Comparative whole-mount preparations of isolated, purified and cultured rat liver sinusoidal endothelial cells (LEC) were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Examination of detergent-extracted LEC by SEM and TEM shows an integral cytoskeleton: sieve plates are delineated by a sieve plate-associated cytoskeleton ring and …

Characterizing The Outlines Of Degraded Fine-Particles By Fractal Dimension, Andrew Hunt, David L. Johnson

Scanning Microscopy

Fractal dimension has been used extensively as a descriptor of the rugged outlines of fine-particles. Potentially, it may be a useful parameter for characterizing the outlines of fine-particles which have been subjected to some form of chemical degradation. Here, fractal dimension values have been computed for the outlines of microscopic lead fine-particles both before and after weak hydrochloric acid dissolution experiments. Values obtained for the post-dissolution rugged profiles were greater than those of the pristine fracture grains which had a Euclidean form. The profiles of the degraded fine-particles could be characterized by a single fractal dimension value, or they exhibited …

Recognition And Phagocytosis Of Apoptotic Cells, Luciana Dini, Maria Teresa Ruzittu, Laura Falasca

Scanning Microscopy

Physiological elimination of unwanted cells within the organism occurs via cell death by apoptosis and phagocytosis of these cells represents a key event in the apoptotic process. Macrophages, which are the dedicated phagocytes, and other occasionally phagocytic cells ingest the apoptotic cells while they are still intact, thus preventing the leakage of potentially harmful materials from the dying cells. Although evidence has been presented that the elimination of apoptotic bodies from the tissue operates by means of specific recognition systems, the molecular mechanisms by which an apoptotic cell is recognized are poorly understood. Recent data indicate that phagocyte recognition of …

Scanning Electron Microscopic Study Of The Postnatal Development Of The Rabbit Cochlea, With An Emphasis On Innervation, Hirofumi Morita, Tomoyuki Hoshino, Kunihiro Mizuta, Satoshi Iwasaki

Scanning Microscopy

The development of nerve fiber arrangements of the organ of Corti was studied in rabbits 1, 3, 5, 7 and 12-days-old using thick sections from celloidin-embedded cochleas which were examined under a scanning electron microscope. The arrangements of nerve fibers varied with developmental age. The tunnel spiral bundle was thick and loosely collected in the immature cochlea. The outer spiral fibers were recognized even in the narrow space of Nuel in the one-day-old cochlea. As Nuel's space is extending, the fibers course along the medial side of Deiters' cells. The arrangement of the outer spiral fibers was irregular and sparse …

Volume Determination Of Human Metaphase Chromosomes By Scanning Force Microscopy, Wolfgang Fritzsche, Eric Henderson

Scanning Microscopy

The scanning force microscope (SFM) yields the topography of the investigated surface. A procedure was developed which starts from this three-dimensional information to estimate the volume of a biological specimen. The volume of spread human metaphase chromosomes was determined in air and rehydrated in aqueous buffer. A difference of the determined volume of a air-dried metaphase chromosome set was found compared to values from electron microscopic investigations, and could be correlated with differences in the hydration state of the chromosomes. SFM-based relative volumes of air-dried chromosomes resembles literature data regarding volume range and distribution. Possible application of SFM-based relative volume …

The Phase Effect In Electronic Stopping: A Survey Of The Contributing Physical Processes, P. Bauer, E. Steinbauer, F. Kastner

Scanning Microscopy

The phase effect in electronic stopping deals with the question whether the energy loss of an ion due to the interaction with electrons depends on the state of aggregation of the target. It is commonly accepted that charge changing collisions of the projectile and changes in the electronic states of the target contribute to the phase effect In addition, the energy loss measurements might possibly be influenced by different impact parameter selection in the two experiments (solid and gas phase). Quantitative results of our calculations show that generally the impact parameter selection inherently present in a transmission experiment is quenched …

Evaluation Of The Surface Changes In Enamel And Dentin Due To Possibility Of Thermal Overheating Induced By Erbium:Yag Laser Radiation, Tat̂Jana Dostálová, Helena Jelíková, Otakar Krejsa, Karel Hamal

Scanning Microscopy

This study investigates the thermal danger of Erbium (Er):YAG laser ablation. Classical preparation techniques have many disadvantages caused by unfavorable changes of temperature, pressure, and by mechanical vibrations. The effect of mechanical vibrations and pressure is eliminated by use of laser ablation technique. The purpose of this study was to analyze the side effects resulting from thermal changes of enamel and dentin in extracted human teeth subjected to pulsed Er:YAG laser radiation using both wet and dry ablation methods.

The micrographs of the sections were checked and measured afterwards. The effect of the investigated laser irradiation on the origin of …

Spatial Dependence Of Electron-Hole Pair Creation In Ion-Solid And Electron-Solid Interactions, F. J. García De Abajo

Scanning Microscopy

The problem of electron excitation induced by interaction of charged particles with solids is investigated on theoretical grounds. The excitation probability is calculated both in homogeneous media and at surfaces. The surface wake potential, needed in the latter, is reviewed. The cases of transmission and aloof geometries are considered separately. Surface plasmons are shown to play a crucial role in the latter. An application to coincidence scanning transmission electron microscopy (STEM) experiments is also discussed. Finally, a spatial representation of the excitation probability is presented.

Inter-Alpha-Inhibitor: A Protein Family Involved In The Inhibition Of Calcium Oxalate Crystallization, Fouad Atmani, Jacques Mizon, Saeed R. Khan

Scanning Microscopy

Inter-α-inhibitor (IαI) is a serine protease inhibitor present in human plasma. It has a molecular weight of about 220 kDa which encompasses 3 chains including two heavy chains and one light chain. The light chain, known as bikunin, is responsible for the antitryptic activity of IαI in the inhibition of various enzymes, such as trypsin and chymotrypsin. Under physiologic or certain pathologic circumstances, several macromolecules related to IαI appear in plasma and urine. However, the physiologic role of IαI remains unclear. As far as urolithiasis is concerned, two urinary macromolecules related to IαI have been isolated and shown to be …

In Vivo Metal Substitutions In Metal Sequestering Subcellular Compartments: X-Ray Mapping In Cryosections, A. J. Morgan, C. Winters, A. Yarwood, N. Wilkinson

Scanning Microscopy

Qualitative digital X-ray mapping techniques were employed to determine the distributions of essential and non-essential elements in three invertebrate "models": (1) Pb, Zn, Cd, Cu, Fe in thin cryosections of the hepatopancreas of the terrestrial isopod, Oniscus asellus; (2) Pb, Zn, Cd, Ca in thin cryosections of the chloragogenous tissue of the earthworm, Lumbricus rubellus; and (3) As in air-dried smears and thin cryosections of chloragogen in L. rubellus. Four general conclusions were drawn from the results of these studies: (a) non-essential elements can accumulate, distribute and be compartmentalized because they, or the organo-complexes that they form, …

Mgo·1.5al2o3 Spinel Grain Growth And Microstructure Characterization By Scanning Electron Microscopy And Digital Image Analysis, G. Bonifazi, E. Proverbio

Scanning Microscopy

The microstructure of sintered polycrystalline MgO·1.5Al₂O₃ ceramic is strongly affected by the sintering conditions due to the precipitation of α-alumina at a temperature lower than about 1400°C. Consequently, the mechanical properties, depending on grain size distribution, are greatly influenced. Three different microstructures were obtained by a two step sintering process adopting an intermediate sintering temperature of 1050°C, 1100°C and 1300°C respectively, and a final sintering temperature of 1500°C. Comparable samples obtained directly by firing at 1500°C were used. Digital image analysis (DIA) carried out on scanning electron microscope (SEM) images was performed in order to better describe …

Quantitative Imaging In Electron And Confocal Microscopies For Applications In Biology, N. Bonnet, L. Lucas, D. Ploton

Scanning Microscopy

Among the large number of topics related to the quantification of images in electron and confocal microscopies for applications in biology, we selected four subjects that we consider to be representative of some recent tendencies. The first is the quantification of three-dimensional data sets recorded routinely in scanning confocal microscopy. The second is the quantification of the textural and fractal appearance of images. The two other topics are related to image series, which are more and more often provided by imaging instruments. The first kind of series concerns electron energy-filtered images. We show that the parametric (modelling) approach can be …

Target Geometry Dependence Of Electron Energy Loss Spectra In Scanning Transmission Electron Microscopy (Stem), A. Rivacoba, J. Aizpurura, N. Zabala

Scanning Microscopy

In the frame of the Self-Energy formalism, we study the interaction between STEM electrons and small particles in the range of the valence electron excitations. We first calculate the energy loss probability for an isolated sphere and study the loss spectrum dependence on the size of the particle and on the relative impact parameter. Then we analyze the loss spectra in more realistic situations: (a) the effect of the coupling between the particle and supporting surface is studied in a simple geometrical model; and (b) we analyze the dependence of the losses on the geometrical shape of the target by …

X-Ray Standing Wave Studies Of Ad-Dimers On Si(001), Y. Qian, P. F. Lyman, M. J. Bedzyk

Scanning Microscopy

X-ray standing waves generated by dynamical Bragg diffraction were used as an element-specific structural probe for investigating Ga and Sb adsorption on Si(001). Using the (004) and (022) reflections, we precisely measured Ga and Sb ad-dimer bond lengths and ad-dimer heights above the bulk-extrapolated Si(001) surface. The room temperature [001] thermal vibration amplitudes of Ga and Sb adatoms on Si(00l) were also directly determined by combining the fundamental (004) and high-order harmonic (008) X-ray standing wave measurements. These high-resolution measurements reveal important quantitative structural information regarding the dimerized surface structures, and provide a stringent test for structural models proposed by …

Enamel Prism Morphology In Molar Teeth Of Small Eutherian Mammals, Elizabeth R. Dumont

Scanning Microscopy

Data summarizing enamel prism shape, sire and spacing are reported for the molar enamel of 55 species of small eutherian mammals including primates, bats, tree shrews, flying lemurs, insectivorans and representatives of a variety of fossil families. Confocal photomicrographs reveal that the subsurface enamel of most species is characterized by arc-shaped prisms. The lack of a clear distinction between pattern 2 and pattern 3 prism configurations within single specimens suggests that the broad category "arc-shaped prisms" is the most appropriate descriptive grouping for these species. Of the total sample, three species exhibit only circular prisms while no evidence of prismatic …

Immunogold Labeling For The Diagnosis Of Leukemia By Transmission And Scanning Electron Microscopy, Etienne De Harven, Davide Soligo, Hilary Christensen

Scanning Microscopy

For the cell type diagnosis of leukemia in adult patients, particularly when the sampling of bone marrow is difficult, the study of peripheral blood leukocytes (PBLs) by immuno-electron microscopy provides significant information, as illustrated here in two cases of hairy cell leukemia and seven cases tentatively identified as megakaryoblastic leukemia (M7). Indirect immunogold labeling with the B-ly7 monoclonal antibody (CD103) proved valuable in confirming the diagnosis of hairy cell leukemia. Immunogold labeling for the GplIIa platelet glycoprotein (CD61) was used in cases where the light microscopy of blood films revealed possible megakaryoblastic leukemia. Under the electron microscope, however, the CD61 …

Zinc Deficiency Produces Time-Related Ultrastructural Changes In Rat Cheek Epithelium, Shahid H. Ashrafi, Nasser A. H. Said-Al-Naief

Scanning Microscopy

The subject of this study was whether the ultrastructural changes in cheek epithelium of zinc-deficient rats are time related. Weanling male Sprague Dawley rats were fed a zinc-deficient diet containing 0.4 ppm zinc (ZD) ad libitum and controls were pair-fed zinc adequate diet containing 40 ppm zinc. After 9, 18, and 27 days of zinc deficiency, specimens from cheek epithelium of both groups were processed for transmission electron microscopy. Partial conversion of the orthokeratinized cheek epithelium to parakeratinized was seen as early 9 days. An electron-lucent band surrounding the nucleus was observed in ZD cells. Mitochondria, tonofilaments, keratohyalin granules and …

Alterations In Intestinal Transport Of Oxalate In Disease States, Marguerite Hatch, Robert W. Freel

Scanning Microscopy

Normally, absorption of oxalate from dietary sources can occur in all segments of the intestinal tract. However, alterations in both the magnitude and direction of oxalate fluxes across the intestine can occur in disease states. In enteric hyperoxaluria, enhanced absorption of oxalate by the large intestine is caused by increased permeability of a shunt conductance induced by malabsorbed bile salts and fatty acids. In this condition, the contribution of a paracellular passive flux of oxalate moving along its electrochemical gradient will predominate when intraluminal concentrations of free oxalate are high. In contrast, in chronic renal failure, secretion of oxalate can …

Zeta Potential Measurement And Particle Size Analysis For A Better Understanding Of Urinary Inhibitors Of Calcium Oxalate Crystallization, L. C. Cao, G. Deng, E. R. Boeve, W. C. De Bruijn, R. De Water, C. F. Verkoelen, J. C. Romijn, F. H. Schroder

Scanning Microscopy

To better understand urinary inhibitors of calcium oxalate crystallization, both zeta potential measurement and particle size analysis were chosen to illustrate: (1) the potential therapeutic efficacy of G872, a semi-synthetic sulfated polysaccharide, in stone prevention; and (2) the relative contribution of various urinary fractions {e.g., ultrafiltered urine (UFU), Tamm-Horsfall protein (THP), urinary polyanionsprecipitated with cetylpyridinium chloride (CPC), urinary macromolecular substances with different concentration ratios (UMSl0,50,90 and UMS'l0,50,90) and THP-free urine (THPFU)} to total urinary inhibitory activity. The results showed: (1) addition of G872 significantly enhances urinary inhibitory activity and negative zeta potential values; (2) re-addition of the CPC to UFU …

Scanning Electron Microscopy Of Cyclosporine-Induced Gingival Overgrowth, Shahid H. Ashrafi, Krzysztof Slaski, Kyaw Thu, Eli S. Neiman, Michael P. Cunningham

Scanning Microscopy

Overgrown human gingival specimens were examined histologically and by scanning electron microscopy (SEM) to study structural changes caused by cyclosporine. The biopsy specimens were from organ transplant recipients receiving cyclosporine to suppress the rejection of the transplanted organ. The epithelium of the overgrown gingiva was thickened, acanthotic and parakeratotic. Retepegs were anastomosing and extending into connective tissue. The SEM examination of the outer surface of the attached gingival showed loss of cellular attachments and cells were exfoliating. The normal honeycomb structure formed by interconnecting microvilli surrounding the pits was distorted. Outer gingival cell surface showed numerous round, ovoid and dome-like …

Examination Of Injected Specimens By Confocal Laser Scanning Microscopy And Scanning Electron Microscopy, A. Castenholz

Scanning Microscopy

Although corrosion casts commonly examined by scanning electron microscopy (SEM) offer good insights into the general arrangement of the microvasculature of certain organs, no information can be obtained from such specimens on special morphological data or dynamic events. Thus, most investigators are obliged to make their interpretations of cast structures only on the basis of indirect criteria. A synopsis, which considers the most important data in that respect, is given for the blood and lymphatic microvessels. Moreover, a methodological approach is introduced, based on the application of fluorescent resin, which allows the examination of cast structures in uncorroded specimens together …

Dietary Oxalate And Its Intestinal Absorption, Ross P. Holmes, Harold O. Goodman, Dean G. Assimos

Scanning Microscopy

Dietary oxalate is currently believed to make only a minor contribution (< 20%) to urinary oxalate excretion. A recent prospective study of stone disease suggested that dietary oxalate may be a significant risk factor. This observation led us to re-evaluate the contribution of dietary oxalate to urinary oxalate excretion. Previous studies have been hampered by inaccurate food composition tables for oxalate and inadequate methods for studying intestinal oxalate absorption. This evidence as well as factors that modify oxalate absorption are reviewed. New approaches to measure food oxalate and intestinal oxalate absorption have been examined. Capillary electrophoresis appears to be well suited for the analysis of the oxalate content of food. Two individuals consumed an oxalate-free formula diet for 7 days. This diet decreased urinary oxalate excretion by an average of 67% (18.6 mg per 24 hours) compared to oxalate excretion on self-selected diets. The absence of detectable oxalate in feces by day 6 of the diet suggested that the intestinal absorption was minimal. However, an effect of the formula diet on endogenous oxalate synthesis cannot be excluded. Restoring oxalate to the formula diet increased urinary oxalate excretion and illustrates that this experimental protocol may be well-suited for studying oxalate absorption and factors that modify it. Our results suggest that the intestinal absorption of dietary oxalate makes a substantial contribution to urinary oxalate excretion and that this absorption can be modified by decreasing oxalate intake or increasing the intakes of calcium, magnesium, and fiber.

Elliptical-P Cells In The Avian Perilymphatic Interface Of The Tegmentum Vasculosum, C. D. Fermin, D. H. Lee, D. S. Martin

Scanning Microscopy

Elliptical cells (E-P) are present at the perilymphatic interface lumen (PIL) of the lagena. The E-P cells often separate from the tegmentum vasculosum (TV) and have touching processes that form a monolayer between the K⁺ rich perilymph and the Na⁺ rich endolymph, similar to the mammalian Reissner's membrane. We examined the TV of chicks (Gallus domesticus) and quantitated the expression of anti-S100ααββ and S100β. There was a 30% increase of S100β saturation in the light cells facing the PIL when compared to other TV light cells. We show that: (1) the dimer anti-S100ααββ and …

Penetration Of Positrons In Solid Targets, Maurizio Dapor

Scanning Microscopy

The study of the interaction of positron beams with solid targets has been approached by several investigators, also due to its importance for positron annihilation spectroscopy. This technique allows non-destructive investigations of the structural defects of surfaces and interfaces: in particular information is provided about the nature and distribution of point defects in solid materials. The solution of the diffusion equation, necessary to obtain the fractions of incident positrons annihilated at different depths inside the target, requires the knowledge of the positron stopping profile, i.e., the initial depth distribution of the thermalized positrons. Also transmission of positrons is of great …

Scanning Probe Microscope Gigahertz Measurements On 200 Nanometer Wave Guides, C. Böhm, J. Sprengepiel, E. Kubalek

Scanning Microscopy

Scanning probe microscopy is opening new applications in microelectronic engineering due to easy and reliable instrumentation in combination with superior resolution limits without any sample preparation under ambient conditions. Beside the standard topography imaging possible application are static and dynamic surface potential measurements, doping profiling, and scanning thermal applications. In this paper, we report dynamic voltage contrast measurements of analog and digital gigahertz signals on 200 nm wave guides within integrated microelectronic devices and components. The results are obtained by using a time resolved device internal test technique based on a scanning force microscope using the electrostatic force interaction. This …

Atomic Force Microscopy Study Of Fine Structures Of The Entire Surface Of Red Blood Cells, P. -C. Zhang, C. Bai, Y. -M. Huang, H. Zhao, Y. Fang, N. -X. Wang, Q. Li

Scanning Microscopy

Glutaraldehyde-fixed red blood cells were imaged by tapping mode atomic force microscopy (TMAFM) in air at room temperature. The results show that TMAFM can visualize the morphology of the red blood cell at both cellular and nanometer scales. The scan size covers the range from several hundred nanometers to more than one hundred micrometers. TMAFM not only has a higher resolution than the optical microscope, but also can observe biological samples without precoating as required for scanning electron microscopy (SEM). The AFM images of the entire surface of an uncoated red blood cell with nanometer resolution are successfully reconstructed by …

Vascular Architecture Of The Lactating And Non-Lactating Teat Of The Bitch: A Scanning Electron- And Light Microscope Study, F. J. Pérez-Aparicio, V. Dantzer, M. Navarro, A. Carretero, J. Ruberte

Scanning Microscopy

Tissues from fourteen mammary glands of eight bitches were prepared for scanning electron microscopy of vascular corrosion casts and for histology to study the vasculature of the lactating and non-lactating teats. The densely-meshed mammary dermal capillary network formed ridges and troughs. The teat ducts were vascularized by a relatively densely-meshed capillary network which drained into veins longitudinally oriented to the ducts. Between eight and fifteen teat duct openings were seen on the tip of the teat, that were sometimes divided by a septum. The inner vascularization of the teat showed that the main papillary arteries divided into undulating secondary papillary …

Photoemission And Free Electron Laser Spectromicroscopy: Photoemission At High Lateral Resolution, G. Margaritondo

Scanning Microscopy

The move of photoemission analysis from the macroscopic to the microscopic domain has been accelerated by the advent of new ultrabright synchrotron sources of soft-X-rays. This makes an overview of photoemission spectromicroscopy, photoemission at high lateral resolution, quite timely. The overview begins with the basic concepts and problems, both technical and of data-taking strategy. Then, it presents a small number of examples of results in physics and biology, such as local chemical fluctuations in superconductors, semiconductor interfaces and the microchemistry of biological systems. The presentation includes the first experimental results from two new ultrabright synchrotron facilities: ELETTRA (in Italy) and …