Life Sciences Commons^™

A Simulation Model For Electron Irradiation Induced Specimen Charging In A Scanning Electron Microscope, D. S. H. Chan, K. S. Sim, J. C. H. Phang

Scanning Microscopy

A numerical model has been formulated to simulate the dynamics of specimen charging in a scanning electron microscope. In this model, the electric field due to imposed boundary conditions and fixed charges is solved by the finite element method. The empirical electron yield data are stored in "Universal Yield Curves (UYC)". These UYCs control the generation of secondary and backscattered electrons from various materials. The electrons emitted from electron-solid interactions are tracked using a leapfrog integration scheme. Excess charges generated on the surface of electrically floating solids are assigned to numerical grids using a linear charge redistribution scheme. The validity …

Scanning Electron Microscopy Of Human Esophageal Mucosa In Patients With Carcinoma Of The Esophagus, M. Cwikiel, M. Q. Yang, M. Albertsson, C. -H. Håkansson, M. Palmegren

Scanning Microscopy

Specimens taken at surgery from 15 patients with carcinoma of the esophagus were examined with scanning electron microscopy. Nine patients were treated with chemotherapy (cisplatin + 5-fluorouracil), surgery and radiotherapy; one received preoperative radiotherapy only; and the remaining five primary surgery only. Scanning electron microscopy was performed on specimens of both tumor tissue and the mucosa at least 5 cm from the tumor. In adjacent non-tumor tissue, damage due to treatment was observed in the form of changes in microridges and increased cell loss. In tumor tissue, the degree of damage was correlated to tumor response to treatment. For patients …

A Combined Near Field Optical And Force Microscope, M. H. P. Moers, R. G. Tack, N. F. Van Hulst, B. Bölger

Scanning Microscopy

Scanning near field optical microscopy (SNOM) is the optical alternative of the scanning probe microscopical techniques which enables a lateral resolution down to about 10 nm, unlimited by diffraction. Moreover, the potential of non-destructive imaging of chemical and biological samples with nanometer resolution in ambient conditions is a crucial advantage over electron microscopy.

An integrated microscope has been constructed which allows simultaneous detection of optical and force interaction between a microfabricated SiN probe and a sample surface. Images are obtained in a transmission mode by detection of the light emanating from a "supertip" in contact with the sample surface and …

Nuclear Microprobe For Integrated Circuit Process Inspection, Mikio Takai, Ryoh Mimura, Hiroshi Sawaragi, Ryuso Aihara

Scanning Microscopy

A nuclear microprobe with a minimum beam-spot diameter of less than 100 nm, intended for application to IC (integrated circuit) process inspection, has been designed and installed at Osaka University. An ultra high-vacuum sample-chamber with a three-axis goniometer stage and a toroidal electrostatic analyzer for medium energy ion scattering (MEIS) was combined with a short acceleration column for a focused ion beam. A liquid metal ion source (LMIS) for light metal ions such as Li⁺ or Be⁺ was mounted on the short column. A minimum beam spot-size of about 80 nm with a current of 30 pA was …

Characterization Of The Complex Sulfide Ore Of Sotiel (Spain) By Scanning Electron Microscopy And Electron Microprobe Analysis, Giuseppe Bonifazi, Roberto Gorga

Scanning Microscopy

This study complements a more exhaustive examination on the complex sulfide mineralization of Sotiel, (Spain), by optical microscopy and multispectral digital analysis of images. Electron microscopy analyses were carried out to document specific associations which are difficult to detect with conventional optical microscopy. This study utilizes the application of digital techniques to image processing, in an attempt to define microstructural and microtextural characteristics of the ore, since they play an important role in the subsequent beneficiation operations (i.e., flotation).

Scientific and economic information bound to complex metallogenic phenomenology and referred to particular paragenetic scenes was acquired by the study in …

Nanometer-Scale Synthesis And Atomic-Scale Modification With The Scanning Tunneling Microscope, Reginald M. Penner

Scanning Microscopy

The structure or composition of a surface may be locally altered in either of two fundamental ways using the scanning tunneling microscope (STM). A modification of the surface may be induced resulting in the rearrangement and/or removal of surface atoms, or in the transfer of atoms from the tip to the sample surface. In many recent experiments, the modification of surfaces has involved a single atom or an ensemble of a few atoms. Alternatively, the localized synthesis of a new material from reactants external to the STM tip and sample can be induced using at least three experimental strategies. A …

Scanning Electron Microscopic Examination Of Intracanal Wall Dentin: Hand Versus Laser Treatment, H. E. Goodis, J. M. White, S. J. Marshall, G. W. Marshall Jr.

Scanning Microscopy

Conventional cleaning and shaping of root canal spaces involves the use of hand and rotary instruments with irrigation. The procedure results in the formation of a smear layer consisting of dentin shavings, organic tissue remnants and microorganisms. The laser has been suggested as an aid in root canal preparation. In this study, pulsed and continuous wave 1.06 μm wavelength Nd:YAG lasers were used to compare their abilities to clean and shape root canal spaces to conventional methods. After preparation, the test teeth were sectioned longitudinally and examined by scanning electron microscopy. The results demonstrated that the laser was capable of …

The Present Status Of Cathodoluminescence Attachments For Optical Microscopes, Donald J. Marshall

Scanning Microscopy

The serious use of cathodoluminescence (CL) in petrography began about 30 years ago with the electron microprobe analyzer. Investigators soon began to use simpler instruments mounted directly on optical microscopes - cathodoluminescence microscope attachments (CMAs).

A major advantage of the CMA, compared to a scanning electron microscope (SEM) or electron microprobe analyzer (EMPA), is the capability to switch quickly between CL observations and high quality conventional optical microscope observations. Beam currents available in the CMA are higher than in the SEM or EMPA and one sees an instantaneous real time true color display of the CL pattern.

CMAs are based …

Morphological Characterization Of The Radiation Sensitive Cell Line, Xrs-5, Carol C. Korte, Linda S. Yasui

Scanning Microscopy

Morphometric analysis was performed on the radiation sensitive Chinese hamster ovary (CHO) xrs-5 cell line, reverting xrs-5 cells and parental K1 cells. Several ultrastructural parameters (increased nuclear envelope membrane separation, cell and nuclear volume, nuclear to cytoplasmic ratio, and the nuclear surface area per unit volume of the cell) were measured and correlated with radiation sensitivity. A trend in increased cell size and radiosensitivity was observed. However, only the substantially increased nuclear envelope membrane separation in sensitive xrs-5 cells significantly correlated with radiation sensitivity. The maximal nuclear envelope membrane separation in sensitive xrs-5 cells was 270.8 nm. The maximal K1 …

New Methods For Depositing And Imaging Molecules In Scanning Tunneling Microscopy, Victor N. Morozov, Nadrian C. Seeman, Neville R. Kallenbach

Scanning Microscopy

Methods and apparatus are described to deposit and image molecules by scanning tunneling microscopy (STM) under an inert atmosphere. Three methods of applying molecules have been evaluated: equilibrium adsorption from the vapor phase, sublimation, and electrospraying. Using these methods, a variety of organic and biopolymer molecules have been deposited and imaged on graphite and on gold (111), grown epitaxially on mica. Compared with alternatives, such as the use of high vacuum apparatus or glove boxes, these procedures offer some important advantages: they are inexpensive, convenient, and more rapid. Mercaptoethanol, ethanolamine, ethanol, acetic acid, and water produce two-dimensional crystalline adlayers on …

The Interaction Between Nephrocalcin And Tamm-Horsfall Proteins With Calcium Oxalate Dihydrate, Sergio Deganello

Scanning Microscopy

Studies of crystals of calcium oxalate dihydrate (COD) grown by vapor diffusion from solutions contain-ing 5.1 x 10^-7, 1.5 x 10^-6, and 1.0 x 10^-5 M nephrocalcin (NC), indicate that NC profoundly affects COD's habit, size and structure. The decrease in COD size is such that at 1.0 x 10^-5 M NC, the dimensions of the crystals are reduced about five-fold with respect to those of a NC-free control. In addition, the planes of the {101} form disappear, the original habit is lost, and the diffraction pattern deteriorates to such an extent that only …

Three-Dimensional Cytoskeletal Structures Of The Chinchilla Organ Of Corti: Scanning Electron Microscopy Application Of The Polyethylene Glycol Method, A. Nagasawa, R. V. Harrison, R. J. Mount, Y. Harada

Scanning Microscopy

We describe the application of a polyethylene glycol (PEG) embedding technique to examine the sensory and supporting structures of the inner ear. The chinchilla organ of Corti was exposed by cracking PEG embedded cochleas. A range of PEG molecular weights (2000-8000) were utilized; PEG 2000, with a melting point of 57°C was preferred. After removal of the PEG, the three-dimensional aspects of intracellular structures were observed using scanning electron microscopy. Filamentous elements in the hair cell cuticular plate and in the supporting cells were clearly observed, as was the mesh work of cross-linked actin filaments in the cuticular portion of …

High Resolution Electron Microscopy Of The Junction Between Enamel And Dental Calculus, Yoshihiko Hayashi

Scanning Microscopy

Newly formed dental calculus grows on the enamel surface after the tooth crown is exposed to the oral environment. In order to demonstrate the crystal coherence, the junction between enamel and dental calculus was examined in the high resolution electron microscope. Ultrathin sections were also used for selected area electron diffraction to reveal any newly formed mineral phase.

High resolution electron microscopy (HREM) revealed that lattice fringes of dental calculus crystals directly coincided with those of enamel crystals. Two types of coherence were identified at the junction: in one type, a dental calculus crystal contacted the side of an enamel …

Scanning Tunneling Microscopy: A Chemical Perspective, C. Julian Chen

Scanning Microscopy

In this review article, scanning tunneling microscopy (STM) is presented in a chemical perspective. The typical distance from the nucleus of the apex atom of the tip to the top-layer nuclei of the sample is 4-6 Å, where a strong attractive atomic force, i.e., a partial covalent bond, arises between the tip and the sample. The origin of the covalent bond is the back-and-forth transfer of electrons between two atoms, which Pauling has called resonance. While a bias voltage is applied between them, a net electron current in a specific direction arises. This tunneling current is a result of …

Immunological Pathogenesis Of Endolymphatic Hydrops And Its Relation To Meniere's Disease, S. Tomiyama, T. Yagi, M. Sakagami, K. Fukazawa

Scanning Microscopy

This study was designed to investigate an immunologically induced endolymphatic hydrops (ELH) and to focus on the issue of its pathogenesis in relation to Meniere's disease. The time course of ELH was evaluated by light microscopy in a 2-hour to 7-month period following direct antigen challenge to the endolymphatic sac (ELS) in systemically pre-sensitized guinea pigs. ELH began to appear in the vestibule and the basal turn 5-7 hours after inner ear challenge and developed gradually. During the interval from the second day to the first week, ELH rapidly developed in all the cochlear turns and reached a maximum size. …

An Energy Dependent Model For Type I Magnetic Contrast In The Scanning Electron Microscope, W. K. Chim, D. S. H. Chan, J. C. H. Phang, T. S. Low, S. Thirumalai

Scanning Microscopy

The modelling of the magnetic contrast phenomenon in the scanning electron microscope (SEM) is important in understanding the physics of the contrast mechanism and the associated signal detection. In this paper, we report an improved analytical model for Type I magnetic contrast calculations using an approximate form of the Chung and Everhart secondary electron (SE) energy distribution. Previous studies have neglected this factor by assuming a mono-energetic model in order to simplify the calculations. This new model can be used to study different material specimens by appropriate choice of the work function and field-distance integral. The effect of energy filtering …

Scanning Electron Microscopy Of Age-Related Changes In The C57bl/6j Mouse Cochlea, Kunihiro Mizuta, Osamu Nozawa, Hirofumi Morita, Tomoyuki Hoshino

Scanning Microscopy

Hair cells and nerve fibers inside the organ of Corti of the C57BL/6J mouse, which is known as the precocious presbycusis model, were studied using the scanning electron microscope. For this study, we used thick serial sections cut from celloidin blocks.

In the 5-week-old mice, hair cell loss was not seen. The upper tunnel radial fibers crossed the upper part of the tunnel of Corti and entered the Nuel's space between the outer pillar cells. The fibers varied in diameter and showed many varicosities. The basilar fibers emerged into the tunnel of Corti beneath the upper tunnel radial fibers …

Evaluation Of Erbium:Yag Laser Radiation Of Hard Dental Tissues: Analysis Of Temperature Changes, Depth Of Cuts And Structural Effects, A. F. Paghdiwala, T. K. Vaidyanathan, M. F. Paghdiwala

Scanning Microscopy

Temperature elevations, depths of cuts and structural changes produced by 2.94 micron pulsed Erbium:YAG laser radiation of hard dental tissues, at different power levels and exposure times of the laser, were studied. The depth of cut produced was found to vary significantly as a function of power level and exposure time on dry teeth. The mean temperature rise with laser radiation was also influenced both by power level and time of exposure. The effect of water flow on the teeth during laser exposure was evaluated; the results indicate that the ablation efficiency was better, temperature elevations lower and structural changes …

Sample Preparation Techniques For Conventional And High Resolution Scanning Electron Microscopy Of The Central Nervous System. The Cerebellum As A Model, Orlando J. Castejon

Scanning Microscopy

In the present paper some basic sample preparation techniques for scanning electron microscopy of nervous tissue are described. These basic preparative methods include conventional scanning electron microscopy or slicing technique, ethanol-cryofracturing technique, freeze-fracture method using either liquid nitrogen (slow freezing) or Freon 22 cooled by liquid nitrogen (fast freezing), improved freeze-fracture method with delicate specimen preparation and chromium coating, ultrasonic microdissection, and "creative tearing" technique. Some basic principles, advantages and limitations are critically considered. In addition, some specific applications in neurobiological research are reported. Emphasis is placed upon understanding the sources and nature of artifacts that are likely to be …

A Review Of New Concepts In Renal Stone Research, L. C. Cao, E. R. Boevé, W. C. De Bruijn, W. G. Robertson, F. H. Schröder

Scanning Microscopy

Clinical and basic research in the field of urolithiasis has developed rapidly in recent years. Progress in extracorporeal shock wave lithotripsy (ESWL) and percutaneous nephrolithotomy (PNL) has brought about a revolution in the surgical treatment of urolithiasis and research at the cellular and molecular level is now expanding. In spite of these advances, however, clinical treatment of urolithiasis remains far from satisfactory. Stone recurrence in many patients cannot be predicted and is beyond control of urologists mainly because the mechanisms of stone formation are still not fully understood. It is necessary to study the process of stone formation more intensely …

Analysis Of Synthetic Dnas And Dna-Protamine Complexes With The Scanning Tunneling Microscope, Michael J. Allen, Robert J. Tench, Joe A. Mazrimas, Mehdi Balooch, Wigbert J. Siekhaus, Rod Balhorn

Scanning Microscopy

Three duplex DNAs 22, 47, and 100 base-pairs in length have been imaged with the scanning tunneling microscope (STM) after deposition on highly oriented pyrolytic graphite (HOPG). Images of the 47 base-pair (bp) molecules are resolved sufficiently to identify the two phosphodiester strands, the direction of helical coiling (this molecule contains three turns of left-handed helix), and single-stranded ends. Length measurements indicate that all three DNA sequences have adopted an "A-like" conformation. DNA-protamine complexes were also prepared and imaged under similar conditions. Length measurements of the complexes demonstrate that the binding of bull protamine 1 to the 47-mer stabilizes the …

Specimen Preparation And Chamber For Confocal Microscopy Of The Ex Vivo Eye, Barry R. Masters

Scanning Microscopy

A chamber is described for maintaining the mechanical and physiological stability of the ex vivo eye during observation with confocal microscopy. The mechanical stability is provided by a plastic ring situated on the limbal region of the eye. The ring and supporting chamber are designed to reduce mechanical motion of the specimen. The ring and chamber size vary with the species and size of the eye under examination. The physiological stability over a period of approximately one hour is provided by immersing the eye in a bicarbonate Ringer's solution that is exchanged every five minutes. This fluid exchange is made …

Scanning Electron Microscopy Of 2,8-Dihydroxyadenine Crystals And Stones, P. Winter, A. Hesse, K. Klocke, R. M. Schaefer

Scanning Microscopy

The lack of purine salvage enzyme, adenine phosphoribosyltransferase (APRT), leads to 2,8-dihydroxyadenine stone formation and/or crystalluria because it is insoluble in urine. Urolithiasis composed of 2,8-dihydroxyadenine is not only formed in a complete defect of APRT, but also in a partial deficiency of this enzyme. The defect is inherited as an autosomal recessive trait, the homozygous state is associated with high urinary levels of 2,8-dihydroxyadenine and with crystalluria, calculus formation, and potential nephrotoxicity. Determination of the APRT activity will facilitate quantification of the enzyme deficiency and elucidation of the hereditary history. 2,8-dihydroxyadenine excretion in the 24-hour urine and its circadian …

Protein Inhibitors Of Calcium Salt Crystal Growth In Saliva, Bile And Pancreatic Juice, J. M. Verdier, B. Dussol, Y. Berland, J. C. Dagorn

Scanning Microscopy

The control of the formation of crystals in biological fluids is one of the most exciting field of research involving both organic and biochemical areas. Many organisms have evolved mechanisms which minimize or avoid the effects of nucleation and crystal growth formation. One of the most important mechanism is the interaction of specific proteins, called inhibitors, with crystals which alters their habits and leads to their elimination. This article, focused on saliva, pancreatic juice and bile, reviews our present knowledge on the structure-function relationships existing between these proteins and their ability to inhibit the growth of different calcium salt crystals.

Energy-Filtering Transmission Electron Microscopy Of Biological Specimens, W. C. De Bruijn, C. W. J. Sorber, E. S. Gelsema, A. L. D. Beckers, J. F. Jongkind

Scanning Microscopy

By energy-filtering transmission electron microscopy (EFTEM) electrons can be separated by their energy losses. An electron-energy filter, added to the microscope column allows the measurement of the energy distribution of transmitted electrons that have lost energy (< 2,000 eV, with an energy resolution of ~ 1 eV). These filtered electrons, recorded either as a spectrum or as an image, are composed of two parts superimposed on top of each other: (a) the unspecific energy-loss population (= the continuum) and (b) the specific element-related energy-loss population (= the edges). At the edges, electron data in spectra and images are mathematically processed, to obtain the desired element-related net-intensity values or images. These data are related to the total transmitted electron intensity, from the zero-and low-loss spectral region giving the relative spectral-or image intensity ratios (^SR*_x, ^IR*_x), which can be related to the element concentration. The acquisition of the zero-loss and low-loss data is hampered by the restricted dynamic range of the TV camera. By improvements through the introduction of calibrated attenuation filters in the optical path to the TV-camera, more reliable values for ^SR*_x and ^IR*_x can …

A Cationic Protein From A Urate-Calcium Oxalate Stone: Isolation And Purification Of A Shared Protein, J. P. Binette, M. B. Binette

Scanning Microscopy

A protein extracted from a urate - calcium oxalate stone by electrodialysis is also excreted in the urine which served as the source material for its purification by FPLC after separation on an ACA44 column. It has an amino acid composition appropriate for a cationic protein. One peptide obtained by cyanogen bromide cleavage has significant (approximately 60%) homology with CD59 protein (protectin). Both proteins have wide distribution, the unknown having been found in bile, cholesterol gallstones, and the wall of the aorta. However, the two proteins appear to be immunologically different.

Bcg Cell Imaging Using Scanning Probe Microscopy, Antonio A. Garcia, William C. Pettigrew, John Graham

Scanning Microscopy

Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) were used to obtain images of the surface of whole, intact BCG (bacille Calmette Guerin, a mycobacterium) cells in air and under solution by immobilizing the cells onto glass slides (AFM only) or highly oriented pyrolytic graphite. The technique used for AFM imaging involved depositing a submonolayer of cells under a centrifugal force followed by fixation/dehydration using polar organic solvents. AFM images agree well with images from light and electron microscopy and showed large numbers of BCG cells in their distinctive cord arrangement. The AFM also proved useful for identifying extracellular …

Absence Of A Transcellular Oxalate Transport Mechanism In Llc-Pk1 And Mdck Cells Cultured On Porous Supports, C. F. Verkoelen, J. C. Romijn, W. C. De Bruijn, E. R. Boevé, L. C. Cao, F. H. Schröder

Scanning Microscopy

Transepithelial oxalate transport across polarized monolayers of LLC-PK₁ cells, grown on collagen-coated microporous membranes in Transwell culture chambers, was studied in double-label experiments using [¹⁴C]-oxalate together with [³H]-D-mannitol as an extracellular marker. The [¹⁴C]-labeled glucose analog α-methyl-glucoside (α-MG) was used as functional marker for active proximal tubular sugar transport. Cellular uptake of oxalate and α-MG at both the apical and basolateral plasma membrane was determined. When added to the upper compartment, α-MG was actively taken up at the apical membrane, directed through the cells to the basolateral membrane and transported to the lower …

Comparative Aspects Of Splenic Microcirculatory Pathways In Mammals: The Region Bordering The White Pulp, E. E. Schmidt, I. C. Macdonald, A. C. Groom

Scanning Microscopy

Splenic microcorrosion casts prepared using minimal volumes of material show that most of the flow passes through the region bordering the white pulp. However, the nature of these microcirculatory pathways has received little attention. We have studied these in dog, cat, rat, mouse, and normal versus diseased human spleens. In all 5 species, a marginal sinus (MS) of anastomosing vascular spaces 5-10 μm thick lies between the white pulp and marginal zone (MZ). The morphology differs between species and the MS is absent in immune thrombocytopenia. The MS fills by circumferential flow before blood passes outward to the MZ. Many …

Studies On Structure Of Calcium Oxalate Monohydrate Renal Papillary Calculi. Mechanism Of Formation, F. Grases, A. Costa-Bauzá, A. Conte

Scanning Microscopy

A scanning electron microscopy study of the ultrastructure of 18 calcium oxalate monohydrate papillary calculi was performed with the purpose of establishing the main steps in calculus formation. It is concluded that these calculi originate in a "core" located near the central part of the calculus. Significant quantities of organic matter as well as calcium phosphates can be found in the "core" and at the surface of adhesion to the papilla and, in some cases, fibers and calcified tubules can also be found in the contact zone. In no case did this material affect the crystalline structure of the calculi, …