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Results for “Microscopy, Scanning Probe”

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At least 487 records · Page 27Linked to original sources
PubMed2004

Observation of polarization property in near-field optical imaging by a polarization-maintaining fiber probe.

We fabricated an original near-field scanning optical microscopy (NSOM) fiber probe made of polarization-maintaining and attenuation-reducing (PANDA)-type polarization-maintaining optical fiber, and observed the polarization property of propagation light in a polymer optical waveguide. The distribution of the transmission coefficient in polarization angles through this NSOM probe showed that the linear polarization is maintained in the two crossing directions: the fast and slow axes. The polarization degree parallel to the slow axis decreases from 1000:1 to 2:1 by bending the fiber probe and the decrease is independent of the bending direction. Using this PANDA-type NSOM probe, we investigated the polarization property of periodic intensity modulation. It was found that the intensity modulation was observed clearly with the electric vector parallel to the radius direction of the waveguide, but was observed vaguely with the electric vector perpendicular to the radius direction.

Journal Article↗
PubMed1991

Cytoskeleton in microridges of the oral mucosal epithelium in the carp, Cyprinus carpio.

Microridges produce a characteristic fingerprint-like pattern on the surface of fish oral mucosa. The cytoskeleton in these microridges was examined by immunofluorescence microscopy and transmission electron microscopy after detergent extraction and decoration with myosin subfragment 1. The effect of cytochalasin B on microridges was probed with scanning electron microscopy. Immunofluorescence microscopy revealed that actin filaments were present throughout the periphery of the epithelial cells and were especially localized beneath the free surface of the epithelium. In thin sections treated with Triton X-100, the majority of filaments in the microridges and their bases were found to be actin filaments and a plexus of keratin filaments that underlay the network of actin filaments. A part of the plexus of keratin filaments entered the microridges. After extraction with Triton X-100 and decoration with myosin subfragment 1, decorated actin filaments were found in the microridge cores, connected to the keratin filaments. The keratin filaments aggregated in the pattern of microridges and a few of them protruded into the microridges. Treatment with cytochalasin B caused microridges to disappear or to become thinner and lower or to change short or microvillus-like microridges. When most microridges disappeared, the surface of the superficial cells was prominently swollen, but the cell boundaries were fastened, and the microridges in the periphery were preserved. On the basis of these observations, the possible roles of actin and keratin filaments in the maintenance and the formation of microridges are discussed.

Actins↗
PubMed2005

On the correlation between surface roughness and work function in copper.

Both surface roughness (SR) and work function (WF) are important characteristics of a solid surface. Understanding the relationship between SR and WF is necessary in order to apply the Kelvin probe technique to characterize surface behavior. In this study, SR and WF of copper surfaces were measured using atomic force microscopy and scanning Kelvin probe, respectively. Experimental results showed that WF decreased with increase of SR. Using sine functions, a capacitor model was proposed and a correlation between WF and SR was established. The theoretical predictions of WF were in good agreement with experimental results. The model is also useful for analyzing the effect of tip geometry on measurements of WF.

Journal Article↗
PubMed2003

Near-field imaging of surface plasmon on gold nano-dots fabricated by scanning probe lithography.

We obtained scanning near-field optical microscopy images to study the excitation of surface plasmons on metallic dots fabricated using scanning probe lithography. Gold nano-dots were fabricated by applying electric voltages to conducting probes installed in an atomic force microscope using the mechanism of field-induced diffusion and nano-oxidation plus Au-coating. High spatial resolution of scanning near-field optical microscopy revealed a 'bifold' pattern of surface plasmon mode on fabricated Au dots in the polarization direction of incident light. We found that scanning near-field optical microscopy imaging combined with scanning probe lithography is able to provide a systematic study of surface plasmon excitation on nano-metallic structures.

Aluminum↗
PubMed2004

Dentine structure and mineralization in hypocalcified amelogenesis imperfecta: a quantitative X-ray histochemical study.

OBJECTIVE: This study was undertaken in order to establish the structural and mineralization pattern of the response of dentine to alterations in enamel in hypocalcified amelogenesis imperfecta (AI). DESIGN: The images and data obtained with scanning electron microscopy and electron probe X-ray microanalysis in enamel and dentine specimens from control and affected teeth were compared in this study. PATIENTS AND METHODS: We compared 46 fragments of permanent teeth from patients with clinically diagnosed hypocalcified AI and 20 normal permanent teeth. All specimens were prepared for electron probe X-ray microanalysis. RESULTS: Dentine is characterized by thickening of the peritubular dentine and partial obliteration of the dentinal tubules that does not give rise to a compact sclerotic cast. In dentine, calcium levels were significantly higher in teeth with clinically hypocalcified AI in relation with control teeth (P < 0.001). CONCLUSIONS: Dentine is affected in hypocalcified AI increasing mineralization (narrower tubules and higher content of calcium) in response to enamel disorder.

Adolescent↗
PubMed2005

Noble metal nanoparticles deposited on self-assembled monolayers by pulsed laser deposition show coulomb blockade at room temperature.

Nanometer-sized noble-metal clusters are fabricated on top of alkylthiolate self-assembled monolayers (SAMs) on annealed gold by pulsed laser deposition at elevated pressures. The size distribution of the clusters depends on the metal and on the pressure during the deposition. Scanning tunneling microscopy (STM) and conductive probe atomic force microscopy (CP-AFM) showed that the metal clusters are insulated from the substrate on top of the SAM. Coulomb blockades could be measured at room temperature by STM for palladium clusters on decanethiol SAMs.

Electric Conductivity↗
PubMed2000

DNA probes on chip surfaces studied by scanning force microscopy using specific binding of colloidal gold.

Single-stranded DNA was covalently bound on chip surfaces using two different silanization procedures. The resulting surfaces were characterized by fluorescence and scanning force microscopy using sequence-complementary DNA molecules with labels. Colloidal gold (30 nm) was used as the topographic label. Scanning force microscopy revealed the individual labels on the surface and their distribution. Steps of silane layers or DNA-modified surfaces prepared using an elastomeric mask provided internal controls for comparison of modified with unmodified surfaces.

Base Sequence↗
PubMedDate not supplied

Research on double-probe, double- and triple-tip effects during atomic force microscopy scanning.

Information obtained by atomic force microscopy (AFM) depends strongly on the kind of probe or tip used; therefore, probe and tip effects have to be taken into account when verifying or interpreting the data acquired. In many papers, double-tip effects have been mentioned while other research was done; however, there are only a few special reports on double- or triple-tip effects, especially double-probe effects. In our paper, metaphase chromosomes of Chinese hamster ovary (CHO) cells, aggregates of pectin molecules, membrane surface of mouse embryonic stem cells, and R-phycoerythrin-conjugated immunoglobulin G complexes were imaged by AFM with high-quality probes, double-probe cantilever, and double-tip and triple-tip probes, respectively, in order to determine double-probe, double-tip, and triple-tip effects during AFM scanning. We found that the double-probe, double-tip, and triple-tip effects share the same principle, and that these effects correlate with distance and height differences between probes of double-probe cantilever or tips of double-tip or multiple-tip probes. Since many other factors influence double-probe or double-tip effects, more in-depth studies must be undertaken. However, this initial research will make all users of AFM techniques aware of double-probe and double-tip or triple-tip effects during AFM scanning and aid in verifying or interpreting the data acquired.

Animals↗
PubMed2000

Mucous granule exocytosis and CFTR expression in gallbladder epithelium.

A mechanistic model of mucous granule exocytosis by columnar epithelial cells must take into account the unique physical-chemical properties of mucin glycoproteins and the resultant mucus gel. In particular, any model must explain the intracellular packaging and the kinetics of release of these large, heavily charged species. We studied mucous granule exocytosis in gallbladder epithelium, a model system for mucus secretion by columnar epithelial cells. Mucous granules released mucus by merocrine exocytosis in mouse gallbladder epithelium when examined by transmission electron microscopy. Spherules of secreted mucus larger than intracellular granules were noted on scanning electron microscopy. Electron probe microanalysis demonstrated increased calcium concentrations within mucous granules. Immunofluorescence microscopic studies revealed intracellular colocalization of mucins and the cystic fibrosis transmembrane conductance regulator (CFTR). Confocal laser immunofluorescence microscopy confirmed colocalization. These observations suggest that calcium in mucous secretory granules provides cationic shielding to keep mucus tightly packed. The data also suggests CFTR chloride channels are present in granule membranes. These observations support a model in which influx of chloride ions into the granule disrupts cationic shielding, leading to rapid swelling, exocytosis and hydration of mucus. Such a model explains the physical-chemical mechanisms involved in mucous granule exocytosis.

Animals↗
PubMed1997

The fine structure of fenestrated adrenocortical capillaries revealed by in-lens field-emission scanning electron microscopy and scanning transmission electron microscopy.

Cell biologists probing the physiologic movement of macromolecules and solutes across the fenestrated microvascular endothelial cell have used electron microscopy to locate the postulated pore within the fenestrae. Prior to the advent of in-lens field-emission high-resolution scanning electron microscopy (HRSEM) and ultrathin metal coating technology, quick-freeze, platinum-carbon replica and grazing thin-section transmission electron microscopy (TEM) methods provided two-dimensional or indirect imaging methods. Wedge-shaped octagonal channels composed of fibrils interwoven in a central mesh were depicted as the filtering structures of fenestral diaphragms in images of platinum replicas enhanced by photographic augmentation. However, image accuracy was limited to replication of the cell surface. Subsequent to this, HRSEM technology was developed and provided a high-fidelity, three-dimensional topographic image of the fenestral surface directly from a fixed and dried bulk adrenal specimen coated with a 1 nm chromium film. First described from TEM replicas, the "flower-like" structure comprising the fenestral pores was readily visualized by HRSEM. High-resolution images contained particulate ectodomains on the lumenal surface of the endothelial cell membrane. Particles arranged in a rough octagonal shape formed the fenestral rim. Digital acquisition of analog photographic recordings revealed a filamentous meshwork in the diaphragm, thus confirming and extending observations from replica and grazing section TEM preparations. Endothelial cell pockets, first described in murine renal peritubular capillaries, were observed in rhesus and rabbit adrenocortical capillaries. This report features recent observations of fenestral diaphragms and endothelial pockets fitted with multiple diaphragms utilizing a Schottky field-emission electron microscope. In-lens staging of bulk and thin section specimens allowed tandem imaging in HRSEM and scanning TEM modes at 25 kV.

Adrenal Cortex↗
PubMed2005

Interrelations between the parasitophorous vacuole of Toxoplasma gondii and host cell organelles.

Toxoplasma gondii, the causative agent of toxoplasmosis, is capable of actively penetrating and multiplying in any nucleated cell of warm-blooded animals. Its survival strategies include escape from fusion of the parasitophorous vacuole with host cell lysosomes and rearrangement of host cell organelles in relation to the parasitophorous vacuole. In this article we report the rearrangement of host cell organelles and elements of the cytoskeleton of LLCMK2 cells, a lineage derived from green monkey kidney epithelial cells, in response to infection by T. gondii tachyzoites. Transmission electron microscopy made on flat embedded monolayers cut horizontally to the apical side of the cells or field emission scanning electron microscopy of monolayers scraped with scotch tape before sputtering showed that association of mitochondria to the vacuole is much less frequent than previously described. On the other hand, all parasitophorous vacuoles were surrounded by elements of the endoplasmic reticulum. These data were complemented by observations by laser scanning microscopy using fluorescent probes from mitochondria and endoplasmic reticulum and reinforced by three-dimensional reconstruction from serial sections observed by transmission electron microscopy and labeling of mitochondria and endoplasmic reticulum by fluorescent probes.

Animals↗
PubMed2005

Role of the anion in the underpotential deposition of cadmium on a Rh(111) electrode: probed by voltammetry and in situ scanning tunneling microscopy.

In situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) were employed to examine the underpotential deposition (UPD) of cadmium on a rhodium(111) electrode in sulfuric and hydrochloric acids. The (bi)sulfate and chloride anions in the electrolytes played a main role in controlling the number and arrangement of Cd adatoms. Deposition of Cd along with hydrogen adsorption occurred near 0.1 V (vs reversible hydrogen electrode) in either 0.05 M H2SO4 or 0.1 M HCl containing 1 mM Cd(ClO4)2. These coupled processes resulted in an erroneous coverage of Cd adatoms. The process of Cd deposition shifted positively to 0.3 V and thus separated from that of hydrogen in 0.05 M H2SO4 containing 0.5 M Cd2+. The amount of charge (80 microC/cm2) for Cd deposition in 0.5 M Cd2+ implied a coverage of 0.17 for the Cd adatoms, which agreed with in situ STM results. Regardless of [Cd2+], in situ STM imaging revealed a highly ordered Rh(111)-(6 x 6)-6Cd + HSO4- or SO42- structure in sulfuric acid,. In hydrochloric acid, in situ STM discerned a (2 x 2)-Cd + Cl structure at potentials where Cd deposition commenced. STM atomic resolution showed roughly one-quarter of a monolayer of Cd adatoms were deposited, ca. 50% more than in sulfuric acid. Dynamic in situ STM imaging showed potential dependent, reversible transformations between the (6 x 6) Cd adlattices and (square root 3 x square root 7)-(bi)sulfate structure, and between (2 x 2) and (square root 7 x square root 7)R19.1 degrees -Cl structures. The fact that different Cd structures observed in H2SO4 and HCl entailed the involvement of anions in Cd deposition, i.e. (bi)sulfate and chloride anions were codeposited with Cd adatoms on Rh(111).

Journal Article↗
PubMed2006

Microstructures of beta-titanium orthodontic wires joined by infrared brazing.

The microstructures and interdiffusion in brazed beta-titanium orthodontic wires were investigated by scanning electron microscopy and electron probe microanalysis, respectively. Beta-titanium wire (Ti-11Mo-6Zr-4Sn) with cross-section dimensions of 0.032 in. x 0.032 in., titanium-based braze alloy (Ti-30Ni-20Cu), and silver-based braze alloy (Ag-22Cu-17Zn-5Sn) were selected for the study. Brazing was performed using infrared radiation (RS-1) under an argon atmosphere. Specimens were etched with two solutions (2.5% HF + 2.5% HNO(3) + 95% H(2)O; 25% HN(4)OH + 30% H(2)O(2) + 45%H(2)O). It was found that the silver-based braze alloy has a eutectic structure. In the diffusion layer between the beta-titanium wire and this silver-based braze alloy, Cu and Ti were enriched on the wire side, and Sn and Ti were enriched on the braze alloy side. The titanium-based braze alloy has a dendritic structure. Beta-titanium wire specimens brazed with the titanium-based braze alloy had a thicker intermediate area compared to the silver alloy; Ti in the diffusion layer had an irregular concentration gradient, and the braze alloy side had higher Ti concentration. The original microstructure of the beta-titanium wire was not altered with the use of either braze alloy. Infrared brazing of beta-titanium orthodontic wire is acceptable for clinical use, since the wire microstructure did not deteriorate with either the titanium-based or silver-based braze alloy. The differing microstructures of the joint regions for the two braze alloys suggest that the joint strengths may also differ.

Dental Soldering↗
PubMed1985

Cross-linked polypentapeptide of elastin as a calcifiable matrix: molecular weight dependence.

The polypentapeptide, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, when cross-linked by gamma-irradiation was shown to calcify when exposed to dialysates of calcium and phosphate augmented fetal bovine sera and the molecular weight dependence of this calcification is investigated. Five molecular weight fractions, labeled I to V in order of increasing polymer size from under 12,000 dalton (I), that is, n less than 30, to over 100,000 daltons (V), that is, n greater than 240, were gamma-irradiation cross-linked at 10-12 MRAD to form matrices I-V. Calcium-45 was used to follow the time course and relative amount of calcium uptake from the sera. Scanning electron microscopy and electron probe microanalysis were used to characterize the extent of matrix calcification. All matrices took up calcium-45 from the sera; however, only matrices formed from polypentapeptide with n greater than 100 calcified, that is, matrices III, IV, and V. Matrix V with n greater than 240 calcified massively and in a manner comparable to chemically cross-linked polypentapeptide with n approximately 40 using nonaugmented sera. Presumably, gamma-irradiation results in chain breakage. The gamma-irradiation cross-linked matrices with values of n ranging from under 30 to greater than 240 establish the molecular weight dependence of matrix calcification.

Animals↗
PubMed2006

Chemically imaging living cells by scanning electrochemical microscopy.

Scanning electrochemical microscopy (SECM) is useful in probing and characterizing interfaces at high resolution. In this paper, the general principles of this technique are described and several applications of SECM to biological systems, particularly to living cells, is discussed, along with several example systems. Thiodione was detected and monitored electrochemically during the treatment of hepatocytes with cytotoxic menadione. The antimicrobial effects of silver(I) was followed by SECM through bacterial respiration. Living HeLa cells were shown to accumulate ferrocencemethanol (FcMeOH) and generated positive feedback for FcMeOH oxidation that can be further used to monitor the cell viability. Finally, individual giant liposomes, as cell models, with encapsulated redox compounds were successfully probed by SECM. In general SECM has the advantage of very high spatial resolution and versatility, especially for the detection of electroactive substances.

Biosensing Techniques↗
PubMed2004

Multiple imaging techniques demonstrate the manipulation of surfaces to reduce bacterial contamination and corrosion.

Surface imaging techniques were combined to determine appropriate manipulation of technologically important surfaces for commercial applications. The complementarity of the microscopy methods, scanning electron microscopy, electron probe microanalysis and atomic force microscopy assessed and correlated form and function of the surface modifications. Stainless steel disks (1 cm in diameter) were laser-cut from the same sheets of stainless steel and treated by electropolishing or left untreated for controls. Each treatment was analysed separately using each technique. First, the disks were examined by visual inspection and electron probe microanalysis for surface characteristics and elemental composition, respectively. Aliquots of bacterial suspensions (saline rinses of poultry carcasses from a commercial broiler processing plant) were then diluted in broth and monitored for growth by spectrophotometry. Stainless steel disks (1 cm in diameter) were added and the cultures were grown to sufficient density to allow attachment of bacterial cells to test surfaces. Relative differences in the surface morphology shown by atomic force microscopy, including Z ranges, roughness and other measurements, corresponded by treatment with the differences in reduction of bacterial counts shown by scanning electron microscopy. A model of wet-processing conditions tested the effects of corrosive treatment of surfaces. Less bacterial attachment occurred after corrosive treatment on controls and electropolished samples. Electropolishing significantly reduced bacterial numbers and the effects of corrosive action compared to the controls. Thus, the multiple imaging techniques showed that engineered changes on stainless steel surfaces improved the resistance of the surface finish to bacterial attachment, biofilm formation, and corrosive action.

Bacteria↗
PubMed1995

Fluorescence lifetime imaging by asynchronous pump-probe microscopy.

We report the development of a scanning lifetime fluorescence microscope using the asynchronous, pump-probe (stimulated emission) approach. There are two significant advantages of this technique. First, the cross-correlation signal produced by overlapping the pump and probe lasers results in i) an axial sectioning effect similar to that in confocal and two-photon excitation microscopy, and ii) improved spatial resolution compared to conventional one-photon fluorescence microscopy. Second, the low-frequency, cross-correlation signal generated allows lifetime-resolved imaging without using fast photodetectors. The data presented here include 1) determination of laser sources' threshold powers for linearity in the pump-probe signal; 2) characterization of the pump-probe intensity profile using 0.28 microns fluorescent latex spheres; 3) high frequency (up to 6.7 GHz) lifetime measurement of rhodamine B in water; and 4) lifetime-resolved images of fluorescent latex spheres, human erythrocytes and a mouse fibroblast cell stained by rhodamine DHPE, and a mouse fibroblast labeled with ethidium bromide and rhodamine DHPE.

Animals↗