bluuebunny/crossref_metadata_2025 huggingface dataset:
STM imaging of noble metal electrodes in solution under potentiostatic control
Authors: Otsuka I. , Iwasaki T.
Published: August 2011

We have combined a three‐electrode cell arrangement with a scanning tunnelling microscope (STM) to image the surfaces of polycrystalline noble metal electrodes under potentiostatic conditions. STM imaging was made in the potential range where a tip and the electrodes are ideally polarized. We have observed on a submicron scale that the electrochemically roughened Ag electrode surface relaxed over times of 40 min at −0·16 V versus SCE in 0·1 m KCl. We have also imaged a dynamic process (formation and dissociation) of the submicron‐scale reconstruction of the Au electrode subjected to electrochemical oxidation‐reduction cycles. The results can be explained by the absorption of Cl− ions and the surface diffusion of adatoms or clusters. STM imaging under potentiostatic control leads to the discovery of phenomena occurring at solid metal/electrolyte interfaces.
Photon emission experiments with the scanning tunnelling microscope
Authors: Coombs J. H. , Gimzewski J. K. , Reihl B. , Sass J. K. , Schlittler R. R.
Published: August 2011

We have detected the light emitted from an STM at both ultraviolet (9·5 eV) and optical (1–4 eV) energies. We show that this light contains spectroscopic information on the sample surface comparable to conventional inverse photoelectric spectroscopy, but with nearly atomic spatial resolution. At optical energies we found sufficiently high intensities to allow spatial imaging of the emission probability. We propose that the high quantum efficiency is due to resonance phenomena, and present fluorescence spectra of the emitted light that support this view. We believe that atomic resolution inverse photoemission microscopy and spectroscopy will provide an important new dimension to surface studies.
STM study of the effects of pulsed laser irradiation on semiconductor surfaces
Authors: Tomitori Masahiko , Katsuki Futoshi , Nishikawa Osamu
Published: August 2011

A clean Si(111) flat surface was irradiated by pulsed Nd‐YAG laser beams. STM observation of the irradiated surfaces indicates that the laser irradiation generates two kinds of corrugations: rounded hills 100 Å high and 600 Å wide and small spikes 20 Å high and 35 Å wide. The corrugations grew and spread with repeated irradiation and increased laser power. The heating of the irradiated surface at 1200°C for 5 s smoothed the surface atomically, but no ordered structure was observed, possibly due to the covering contaminants released from the surfaces surrounding the specimen by laser irradiation and heating.
STM and AFM investigations of high‐Tc superconductors
Authors: Heinzelmann H. , Anselmetti D. , Wiesendanger R. , Hidber H.‐R. , Güntherodt H.‐J. , Düggelin M. , Guggenheim R. , Schmidt H. , Güntherodt G.
Published: August 2011

We have studied the (001) surface of single crystal YBa2Cu3O7‐x high‐Tc superconductors using scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) at room temperature at ambient pressure. Both methods show flat terraces with steps which are multiples of the c‐axis lattice constant (of 1·17 nm) high. Our results show that the bulk crystal structure extends to the surface and that the crystals were formed by island growth. Only occasionally tunnelling was possible with sample bias voltages below +1·0 V. We interpret the observed voltage dependence and the difficulty to get good STM images to be due to the presence of a less‐conducting surface layer. Auger spectroscopy indicates that carbon is present at the surface, which is probably related to a contamination layer.
Surface structures of YBa2Cu3O7‐x, BiCa1·7Sr0·7Cu2Ox and TlCaBaCuO4·5±x investigated by scanning tunnelling microscopy
Authors: Laiho R. , Aarnio M. , Heikkilä L. , Snellman H. , Kirschner I. , Halász I.
Published: August 2011

Surface structures of the high‐Tc superconductors YBa2Cu3O7‐x, BiCa1·7Sr0·7Cu2Ox and TlCaBaCuO4·5±x have been investigated with scanning tunnelling microscopy. The observed features include well‐organized stripe corrugations in Y‐Ba‐Cu‐O as well as orientated flake‐like structures and steps with various heights in the Bi‐ and Tl‐compounds. These observations suggest strong local variations of the elastic and electronic properties of the investigated materials.
Nucleation and growth of Cu and Ag on Si(111)7×7
Authors: Tosch St. , Neddermeyer H.
Published: August 2011

By using scanning tunnelling microscopy and spectroscopy we have studied condensation of Cu and Ag on Si(111)7×7 between room temperature and 130°C in the submonolayer and monolayer range. For submonolayer coverage, both metals develop regular clusters on top of the inner adatoms of 7×7 unit cell halves, which we assign to the initial nuclei of metal condensation. The metal film growth continues by adding further metal atoms to these clusters until one half of the 7×7 unit cell is covered completely with a triangular 2‐D metal island. For a coverage of three monolayers neither Cu nor Ag grows in a layer‐by‐layer mode. Characteristic differences observed for both metals may be explained by the more reactive nature of Cu.
Imaging of individual atoms on an Al(111) surface by scanning tunnelling microscopy
Authors: Wintterlin J. , Wiechers J. , Gritsch Th. , Höfer H. , Behm R. J.
Published: August 2011

Due to the delocalized character of metal valence electrons the atomic corrugation of metal surfaces observed in Scanning Tunnelling Microscopy (STM) is found to be much smaller than in the case of semiconductor surfaces. In fact, there is only a single study in the literature which reports the resolution of the individual atoms on a metal surface (Hallmark et al., 1987). The present paper demonstrates the resolution of individual atoms on a close packed surface of a nearly free electron metal, Al(111), and presents systematic experiments on the physical origin of this phenomenon. A more detailed discussion will be given elsewhere (Wintterlin et al., 1988).
STM study of the structure of the sulphur (1×2) overlayer on molybdenum (001) in air: ordered domains, phase boundaries and defects
Authors: Marchon B. , Ogletree D. F. , Bussell M. E. , Somorjai G. A. , Salmeron M. , Siekhaus W.
Published: August 2011

A (001) surface of molybdenum, covered by one monolayer of sulphur was prepared in UHV and characterized by LEED, Auger and XPS. This surface was found to be stable in air for periods of several days. STM images of the surface, obtained in air in the topographic and local barrier height modes, revealed the atomic arrangement of sulphur atoms in domains with 1×2 and 2×1 periodicities. Boundaries between domains, adsorbate and substrate defect structures and crystallites formed during the initial oxidation of the Mo substrate were observed.
Electric field‐induced changes of W(110) and W(111) tips
Authors: Neddermeyer H. , Drechsler M.
Published: August 2011

Using field emission and scanning electron microscopy we have studied the influence of strong electric fields on the thermally induced growth behaviour of field emission tips. For smaller fields (i.e. smaller than needed for a satisfactory field emission image) we observe an enlargement of low‐index faces, which for higher fields develops into a building‐up of micro‐structures and roughening on the initially spherical part of the tip surface. In an intermediate state only the region near the (111) directions contributes to the field emission pattern. For the highest fields employed the results indicate the growth of local protrusions preferentially near (100) faces. Our results show that in scanning tunnelling microscopy W(111) tips should be superior to the commonly used W(110) tips.
Comparison of LEED and STM measurements of vicinal Si(111)
Authors: Wang X.‐S. , Phaneuf R. J. , Williams E. D.
Published: August 2011

LEED beam‐profile and STM measurements have been used in combination to study the ordering of stepped Si(111) surfaces misoriented by 4° toward the [***211] direction. LEED measurements show that ordering of the surface steps is dependent on the thermal history of the sample, but give little clue about the reasons. An initial cleaning at 1250°C followed by slow cooling is required to obtain a well‐ordered step structure. STM measurements show that cleaning at a lower temperature (850°C) results in a surface containing highly disordered patches which are possibly correlated with residual carbon. These disordered regions evidently inhibit step order. STM images of rapidly quenched surfaces show a very different sort of disorder consisting of long wavelength (5–10 nm) corrugations of rms vertical amplitude 2 nm.
Scanning tunnelling microscopy of 1‐D and 2‐D charge‐density wave systems
Authors: Gammie G. , Skala S. , Hubacek J. S. , Brockenbrough R. , Lyons W. G. , Tucker J. R. , Lyding J. W.
Published: August 2011

We have used a new variable temperature scanning tunnelling microscope (STM) to study quasi‐1D and 2‐D charge‐density wave (CDW) systems. The 1‐D systems, typified by NbSe3 and TaS3, are of special interest since they exhibit unusual transport phenomena associated with moving CDW above a threshold electric field. In the case of NbSe3, room temperature STM images show both major and subtle details of the lattice structure. At present, however, images taken below the Peierls transition temperature of TP=144 K resolve major lattice details but are not sufficiently clear to resolve the CDW. On the other hand, for the fully gapped CDW system orthorhombic‐TaS3, the CDW modulation superimposed on the lattice structure and having the correct period of four times the S‐S spacing of 3·3 Å, is observed below TP=215 K. Above TP, the main observable feature is the S‐S spacing along the chains. STM measurements have also been performed on the 2‐D CDW system 1T‐TaS2 in its incommensurate, nearly commensurate, fully commensurate and trigonal phases. For the nearly commensurate phase, STM images show uniform commensurability with a relatively low concentration of small, time‐varying discommensurations in contrast to models pradicting a regular domain structure. In the trigonal phase, however, evidence is seen for the striped phase composed of long, nearly parallel discommensurations.
Donor graphite intercalation compounds studied with a high stability STM
Authors: Anselmetti D. , Wiesendanger R. , Geiser V. , Hidber H. R. , Güntherodt H.‐J.
Published: August 2011

We have designed a small, rigid and easy operable scanning tunnelling microscope (STM) which shows low thermal drift rates due to its compact construction and the chosen materials. Using this instrument we have studied stage 1 donor graphite intercalation compounds (C6Li and C8K) with atomic resolution either in the current imaging, constant current or local tunnelling barrier height mode of operation. Ordered superlattices commensurate as well as incommensurate with the graphite lattice have been observed on the C6Li surface. STM images on C8K revealed a graphitic surface structure.
Anomalous voltage dependence of tunnelling microscopy in WSe2
Authors: Akari S. , Stachel M. , Birk H. , Schreck E. , Lux M. , Dransfeld K.
Published: August 2011

We present scanning tunnelling microscopy (STM) investigations of the layered semiconductor WSe2. The tunnelling experiments were performed in air and under silicone oil with markedly different results. In air, atomic resolution images of the hexagonally structured surface could be obtained for sample‐to‐tip voltages of both negative and positive polarities, from −1·5 to −0·3 V for negative sample and from +0·6 to +1·6 V for positive sample, respectively. Under silicone oil, however, good atomic images could be seen for negative sample biases down to at least −14 V, while for positive sample biases no difference with respect to the tunnelling in air was found.
STM imaging of molecular collagen and phospholipid membranes
Authors: Voelker Mark A. , Hameroff Stuart R. , He Jackson D. , Dereniak Eustace L. , McCuskey Robert S. , Schneiker Conrad W. , Chvapil Thomas A. , Bell L. Stephen , WEISS Lawrence B.
Published: August 2011

The application of STM to biological materiais has been limited by poor conductivity, sample geometry and stability of biological materials. In this paper we describe an STM study of the monomeric helical forms of collagen, a stable, conductive and widely prevalent structural protein. We have also used STM to image artificial Langmuir DPE (dipalmitoyl phosphatidyl ethanolamine) phospholipid membranes. Both molecular collagen and the phospholipid membranes were dried in air on highly oriented pyrolytic graphite (HOPG). Our STM images of collagen dried on HOPG reveal strands 15Å in diameter with a periodicity of about 30Å which correlates with that known to occur in collagen. Spikes which periodically protrude from strands in our STM images of collagen appear to represent pyrrolidine ring structures in the amino acids proline and hydroxyproline. Thus, we report the first STM imaging of native biomolecules revealing intramolecular details and what appear to be specific amino acids. STM imaging of phospholipid membranes show a lattice pattern with densities spaced ∼4–5Å apart. These are thought to represent individual phospholipid molecules in an artificial membrane formed on the HOPG. We believe STM and its related technologies will have great future utility in biomolecular studies.
Scanning tunnelling engineering
Authors: Schneiker Conrad , Hameroff Stuart , Voelker Mark , He Jackson , Dereniak Eustace , McCuskey Robert
Published: August 2011

The great potential for building molecular scale machines and other structures was first noted by Richard Feynman (1960). He also proposed the development of tools to construct nanoscale mechanisms and devices. The range of technology that he proposed is now called nanotechnology, a term coined by Taniguchi (1974). Emergence of STM and related technology should greatly facilitate the development of nanotechnology in the decades to come. Franks' (1987b) review of nanotechnology notes the tremendous potential of STM‐derived tools for what he terms ‘scanning tunneling engineering’. However, STM technology can also augment the ‘bottom up’ approaches to nanotechnology, exemplified for example by Forrest Carter's (1979, 1980, 1982, 1983) proposals for building molecular electronic devices (nanocomputers) using synthetic ‘modular chemistry’ and related techniques of supramolecular chemistry (Kuhn & Mobius, 1971; Kuhn, 1983; Lehn, 1980, 1988). A multi‐tip STM system integrated with an optical microscope was proposed in 1986 as a ‘nanotechnology workstation’ suitable for scanning tunnelling engineering (Schneiker & Hameroff, 1988). In this paper, we describe an overview of scanning tunnelling engineering, present concepts for nanosensors and nanoswitches, and discuss design considerations for dual tip STM. Finally, we repeat an announcement of a series of ‘Feynman’ prizes for miniature STM.
Limits of topographic measurement by the scanning tunnelling and atomic force microscopes
Authors: Stedman M.
Published: August 2011

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface‐measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude‐wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first‐order analysis the STM and AFM are considered as equivalent to contact‐stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.
Arrangement and stability of atoms at the apex of a scanning tip
Authors: Nishikawa Osamu , Tomitori Masahiko , Katsuki Futoshi
Published: August 2011

A field ion microscope was used to examine the stability of the atomic arrangement at tip apexes. Although a single W atom at the top layer of a [111]‐orientated tip apex protrudes from the underneath layer by only 0·91 Å, the present study suggests that the (111)‐orientated W tip is the most desirable tip for scanning tunnelling microscopes because a large activation energy for surface diffusion on the (111) plane immobilizes the apex atom while the tip scans over a specimen surface and the tip apex can be resharpened by simply heating the tip.
A fully automated, ‘thimble‐size’ scanning tunnelling microscope
Authors: Lægsgaard E. , Besenbacher F. , Mortensen K. , Stensgaard I.
Published: August 2011

A novel, fully automated high‐stability, high‐eigenfrequency scanning tunnelling microscope (STM) has been developed. Its key design feature is the application of two piezoelectric ceramic tubes, one for the x‐y‐z motion of the tip and one for a linear motor (‘nano‐worm’) used for the coarse positioning of the tip relative to the specimen. By means of the nano‐worm, the tip can be advanced in steps between 16 and 0·2 nm. The walking distance is >2 mm, with a maximum speed of 2000 steps/s. The nano‐worm positioning implies that this STM is fully controlled by electronic means, and that no mechanical coupling is needed, which makes operation of the STM extremely convenient. The axial‐symmetry construction is rigid, small and temperature‐compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. The sample is simply placed on a piece of invar which surrounds the scanner tube and the nano‐worm and is held by gravity alone. This allows for easy sample mounting. The performance of the microscope has been tested in air by imaging a variety of surfaces, including graphite and biological samples.
A scanning tunnelling microscope for operation in air
Authors: Yao I. E. , Shang G. Y. , Jiao Y. K. , Yi Y. , Bai C. L. , He J. , Zhong J. C. , Rong D. N.
Published: August 2011

In this paper a scanning tunnelling microscope for operation in air is described with emphasis on the coarse and fine sample positioning mechanism, piezoelectric scanner and vibration isolation. Line scan (amplitude modulation), top view (brightness modulation) and combined shaded topographical images of the surface of highly orientated pyrolitic graphite are shown.
Influence of adsorbed oxygen on the tunnel current from an Al(111) surface
Authors: Kopatzki E. , Doyen G. , Drakova D. , Behm R. J.
Published: August 2011

The tunnel current from an Al(111) surface with an adsorbed oxygen atom into a tungsten tip has been calculated. The tip is represented by a single tungsten atom adsorbed on a flat W(110) surface. The evaluation of the tunnel current is based on the generalized Ehrenfest theorem. The wave functions are obtained as self‐consistent solutions of a model Hamiltonian. The lines of constant tunnel current are similar to those of constant charge density at the Fermi level, but the latter shows fine details which are not discernible in the tunnel current. The main feature is an oxygen induced protrusion of about 0·3 Å height and 5 Å width. The height of the protrusion is nearly unchanged over the investigated range of tip‐sample separations. This contrasts the behaviour of the tunnel current found in a former investigation of the system O/Ni(100), where the oxygen‐induced feature in the contours of constant tunnel current revealed a strong distance dependence. This difference is discussed in terms of the closer equilibrium distance and different screening behaviour for oxygen on Al(111).
Investigation of mercury adsorption on gold films by STM
Authors: George M. A. , Glaunsinger W. S. , Thundat T. , Lindsay S. M.
Published: August 2011

Scanning tunnelling microscopy, combined with complementary electrical and analytical measurements, provides a powerful method for examining the behaviour of mercury on gold‐film sensors under actual sensor operating conditions. The films exhibit a linear increase in resistance upon adsorption of mercury, and this resistive change is accompanied by a decrease in measured barrier height at submonolayer coverages of mercury. STM studies of changes in the effective barrier height upon mercury adsorption provide evidence that mercury migrates to grain boundaries for films exposed at submonolayer coverages. Coverages in excess of a monolayer result in a nearly constant, reduced effective barrier height across the entire surface, which is indicative of a more uniform distribution of mercury over the surface. This behaviour is interpreted in terms of the adsorption of mercury onto defective, contaminated gold surfaces.
Voltage‐dependent imaging of antimony on the GaAs(110) surface
Authors: Mårtensson P. , Feenstra R. M.
Published: August 2011

Using a scanning tunnelling microscope, voltage‐dependent imaging of antimony on the GaAs(110) surface has been performed. For negative sample voltages, the images reflect surface dangling bonds. Depending on the magnitude of the voltage, either one or both of the Sb atoms in the surface unit cell are seen. At positive voltage the density of surface‐states is observed to be greatly reduced compared to negative voltages. The results are analysed within the context of a simple tight‐binding model for a one‐dimensional biatomic chain.
A graphite study with a new air operating scanning tunnelling microscope
Authors: Cricenti A. , Selci S. , Generosi R. , Gori E. , Chiarotti G.
Published: August 2011

A scanning tunnelling microscope working in air with good atomic resolution is described. Atomic corrugation of graphite samples cleaved in air has been observed with a lateral resolution considerably less than 1 Å. The height of the potential barrier is measured as a function of the time the system tip‐sample is exposed to air. An explanation for the observed giant corrugation is given.
Scanning tunnelling microscopic images of amino acids
Authors: Feng L. , Hu C. Z. , Andrade J. D.
Published: August 2011

We present images of amino acids adsorbed on highly orientated pyrolytic graphite (HOPG) obtained with the scanning tunnelling microscope (STM) in air. Individual molecules can be observed although the majority of adsorbates appear to form clusters. In the case of leucine, methionine, and tryptophan, two molecules often associate together to form a dimer. Single or dimer glycine molecules were not seen, but a cluster of a number of them was observed. The various adsorbed states may be related to the different interactions between the amino acids and the graphite surface. The mechanism of image formation of the amino acids is probably related to charge transfer mechanisms.
Atomic force microscopy of purple membranes
Authors: Worcester D. L. , Miller R.G. , Bryant P. J.
Published: August 2011

The surface structure of purple membranes was imaged using an atomic force probe mounted in a scanning tunnelling microscope. One of the two different membrane surfaces showed protruding, disc‐shaped features forming an hexagonal lattice with about 6 nm centre to centre spacing. These are identified as the cytoplasmic surfaces of trimers of bacteriorhodopsin molecules and are correlated with the structural information on bacteriorhodopsin obtained from numerous earlier electron microscope and diffraction studies.
Scanning near‐field optical microscopy (SNOM)
Authors: Pohl D. W. , Fischer U. Ch. , Dürig U. T.
Published: August 2011

SNOM is a non‐contact stylus microscopy analogous to STM. Optical near‐field interaction is used to sense approach and optical properties on the nanometre scale (≅1 nm normal, 20–50 nm lateral). SNOM was demonstrated in transmission and reflection, in a topographic mode, and with amplitude as well as phase objects. The excitation of plasmons in the SNOM ‘tip’, a very recent development, greatly enhances sensitivity and permits intriguing new optical experiments. Overcoming the limit of diffraction, SNOM turns a long‐held dream of optical microscopists into reality.
Quantitative analysis of intramembranous particles in rapidly frozen 10T1/2 cell monolayers
Authors: Fassel Theresa A. , Hui Sek‐Wen
Published: August 2011

A simple method for ultrarapid freezing of cell cultures in monolayers was developed. Unfixed and unglycerinated cells were grown on glass substrates. No special treatments of the glass or cells were necessary to facilitate freeze‐fracture along the upper plasma membranes.

A reliable nonbiased method was developed to detect intramembranous particles (IMP) from the background by totally automatic means using the Cambridge Instruments Quantimet 920 Image Analysis system. Size and density data of IMP from a large number of electron micrographs can be rapidly and objectively quantitated. The automatic determination of locational coordinates for each IMP enables subtle determination of spatial distributional differences by the nearest neighbour function and the differential density distribution function, which are measurements of randomness. Quantitative analysis of the IMP distribution on the fracture face of C3H/10T1/2 mouse embryo fibroblasts upon various drug treatments was demonstrated.
Depth of field in optical microscopy
Authors: Sheppard C. J. R.
Published: August 2011

Various expressions for the depth of field of a microscope are compared, with particular regard to their behaviour at high apertures.
Modification of the LKB 7800 series KnifeMaker for symmetrical breaking of ‘cryo’ knives
Authors: Stang Espen
Published: August 2011

This note describes how to modify the LKB 7800 series KnifeMaker in such a way that one can make good ‘cryo’ knives reproducibly by symmetrical (balanced) breaking.
Distortion of orientation data introduced by digitizing procedures
Authors: Heilbronner Renée Panozzo
Published: August 2011

For a given set of lines or outlines, the orientation distribution function, h(α), i.e. the line length per angle of orientation, is a useful measure of anisotropy. In order to obtain this function, it is most convenient to digitize the original, continuously curved lines, that is to replace them by an approximate set of straight line segments. h(α) is then given by the total length of line segment per angular interval. It is generally assumed that the orientation distribution function of the digitized lines approaches that of the original lines if the line segments are sufficiently small. However, in as much as the point density of a square lattice is not constant for all directions, the digitized lines, whose end points are lattice points of the digitizing grid, cannot represent all directions equally well. In this paper, the nature of the distortions introduced by the digitizing procedure and their dependence on sampling length and angular sampling interval are explored, and conditions for minimal distortions are discussed. For computer applications, it is recommended to perform a two‐dimensional smoothing spline operation on the digitized input. In doing so the distortion problem is altogether avoided.
Variable wavelength microinterferometry of textile fibres
Authors: Pluta M.
Published: August 2011

A specific microinterferometric method, referred to as variable wavelength interferometry (VAWI), and its object‐adapted version (AVAWI) are proposed for measuring the spectral dispersion of birefringence and/or spectral dispersion of the refractive indices n and n⊥ of textile fibres. The method uses monochromatic light with variable wavelength (Λ). The only parameters that are directly measured are the inter‐fringe spacings (b) and the fibre thickness (or diameter), while other quantities are observed, read from the calibration graph b(Λ), and derived from quite simple formulae. A double‐refracting interference microscope fitted with a tungsten‐halogen lamp (12 V/100 W) and a wedge interference filter are used. No liquid immersion is required, and the fibre under study can simply be surrounded by an air medium. Results of measurements made on PPT and PA‐6 fibres are given as an example.
The influence of the aperture of illumination on the accuracy of microscope‐photometric measurements of internal transmittance
Authors: Boguth W. , Piller H.
Published: August 2011

The conical shape of the bundle of illuminating rays in the microscope causes a systematic error of transmittance measured with a microscope photometer in comparison with the (true) transmittance measured with a macrophotometer in which the ray bundle is cylindrical. The error is evaluated by the ratio of transmittance measured with the microscope photometer to the true transmittance. It is calculated for the following model objects: parallel‐sided plates, wedges, spheres and circular cylinders. The results of calculations show that the error increases with decreasing transmittance, increasing angle of the cone of rays (evaluated by the effective numerical aperture of illumination), and increasing relative size of photometric field. On the whole, the error can be neglected if the true internal transmittance is greater than 0.1 (10%), the numerical aperture is less than 0.45 and the radius of the photometric field (in the object plane) is less than one‐fifth of the thickness of the object.
Real‐time graphics display of mass variation or elemental concentration during electron beam microanalysis using a general purpose computer
Authors: Davilla S. D. , Ingram P. , LeFurgey A. , Lamvik M. K.
Published: August 2011

A method is described for using a general purpose multi‐process minicomputer for the real‐time display of graphic summaries of a variety of spectroscopic results while the spectrum acquisition is simultaneously underway.
Three‐dimensional reconstruction of semi‐gross biostructures using ‘macroserials’—1‐mm‐thick serial organ slices
Authors: Suzuki Masanori , Takahashi Tohru , Ohuchi Kiyoaki
Published: August 2011

A method for reconstructing a gross or semi‐gross organ structure was developed in a pathological analysis of liver lobes surgically excised from patients with bile duct carcinoma, where the extent of the tumour was to be demonstrated three‐dimensionally. Fixed material was serially sliced with a ham‐slicer, producing flawless slices as thin as 1 mm. Prior to slicing, the material was temporarily ‘embedded’ in gelatine to hold it in shape throughout slicing. These slices (‘macroserials’) could be directly brought into macroscopic 3‐D reconstruction, but in the case of bile duct carcinoma, microscopic examination of the slices was indispensable in determining the extent of carcinoma and precarcinomatous (dysplastic) changes. Slices 1 mm thick were embedded in paraffin using a special holder made of plywood plates which kept a slice in a flat, extended state through the dehydration process. This method of preparing thin slices not only allows the reconstruction of a gross organ structure with less effort than before, but also ensures a certain amount of accuracy in the reproduction of submacroscopic structures.
The relative sensitivities of autoradiographic emulsions to negative chemography
Authors: Rogers Andrew W. , Watanabe Masahito
Published: August 2011

Nuclear emulsions from Ilford, Kodak (U.K.), Eastman Kodak and Sakura have been exposed under comparable conditions to sections known to cause negative chemography. Kodak AR‐10 and Eastman Kodak NTB‐2 and NTB‐3 emulsions did not show negative chemography. Ilford K5, K2 and L4 and Sakura NR‐M2 showed varying degrees of chemography. The results suggest a correlation between mean crystal diameter and susceptibility to this artefact.
Total number of neurons and glial cells in human brain nuclei estimated by the disector and the fractionator
Authors: Pakkenberg B. , Gundersen H. J. G.
Published: August 2011

Unbiased estimates of the total number of neurons and glial cells from central regions of grey matter in human brains are obtained using the disector principle in modifications which are unaffected by the histological processing of paraffin‐embedded tissue. Section thickness does not enter into the estimator and need not be known. An analysis of the contributions from all sampling levels to the variance of the estimator of total cell number has been used to design an optimimal sampling scheme. Using this method, a precise and unbiased estimate of the total number of neurons in a defined brain region can be obtained in less than 1 h.
The preparation of plan‐view TEM samples of ZnSe epilayers on GaAs (100) substrates by selective photoelectrochemical etching
Authors: Ng T. L. , Pemble M. F. , Williams J. O. , Wright A. C. , Zainal Z.
Published: August 2011

Selective photoelectrochemical etching has been employed in order to thin samples of ZnSe epilayers grown on GaAs (100) substrates by metal organic vapour phase epitaxy (MOVPE). The difference in band‐gap between the epilayer and substrate was exploited such that only the substrate material was subject to the etching procedure. Samples prepared in this way have been studied by transmission electron microscopy (TEM) and the results of these studies are compared to results obtained by alternative cross‐sectional analysis.
Microcomputer video image analysis
Authors: Jarvis L. R.
Published: August 2011

A review of aspects relating to microcomputer video image analysis is presented. The technical limitations of early systems have been surpassed by high performance video digitizers and microcomputers which are now widely marketed. Commercial systems based on these devices are increasingly available. Also, with the programming skills in most laboratories today, software development for specific applications is a practical proposition provided that sufficient expertise in video and computer technology is available. Considerations necessary for effective hardware selection and software design are discussed by example of the application to light microscope densitometry. Attention is drawn to errors which can arise when employing conventional video systems for analytical purposes.
A new heat transfer model to predict cooling rates for rapid freezing fixation
Authors: Zasadzinski Joseph A. N.
Published: August 2011

A simple heat transfer model is presented to show that convection from the cryogen to the specimen is the limiting step in rapid freezing of small samples for electron microscopy when the Biot modulus, which measures the ratio of convective to conductive heat transfer, (hd/k) < 1. In comparison to the commonly accepted conduction‐limited model, the convection‐limited model predicts that cooling rates are proportional to the surface area/volume ratio, independent of the sample thermal conductivity, and inversely proportional to the product of sample density and heat capacity. Literature values of experimentally measured cooling rates fit the convection limited model. Simple analogies to predict the heat transfer coefficient as a function of cryogen properties, specimen geometry and cryogen velocity are presented.
Comparison of methods for the estimation of the thickness of ultrathin tissue sections
Authors: Groot Didima M.D. De
Published: August 2011

For a number of quantitative electron microscopical techniques it is relevant to obtain an estimate of the thickness t‘ of the section which, in general, will differ from the actual distance t between the two cuts that generate the section. To estimate t’ of ultrathin sections, several techniques have been adopted in the past, both with and without the aid of the electron microscope and additional equipment, which are summarized in an appendix. In the present study five methods have been evaluated experimentally using sections of ten different interference colours: (a) the ‘small‐fold’ technique, (b) the ‘electron scattering’ method, (c) interference microscopy with (A) the Vicker's M86® scanning microinterferometer and (B) the Jenoptik Amplival Interphako® interference microscope and (d) the ‘re‐embedding’ method. Reliable, reproducible and comparable results were obtained with the small‐fold technique, with the Vickers M86® scanning microinterferometer and with the electron scattering method. For the last method, standard test lines for the different settings of the electron microscope were developed. The results obtained with the Jenoptik Amplival Interphako® interference microscope are reproducible, but show a constant difference, i.e. a factor of 1 “36, in thickness compared with the other three techniques. The possible cause of this ‘systematic error’ is discussed. The re‐embedding method proved to be more laborious and slightly less reliable than the other techniques.

The variation in t' between sections of a particular interference colour (inter‐section variation) was found to be larger than the variation in t' within a section (intra‐section variation).
A videomicrographic low‐frequency movement analyser (VLMA) and perifusion chamber for recording and analysis of the physical behaviour of seminiferous tubules and other contractile tissues in vitro
Authors: Worley R. T. S. , Leendertz J. A.
Published: August 2011

A method has been developed for the recording and analysis of low frequency movements such as those of the surfaces of live seminiferous tubules. The method involves time‐lapse videomicrographic recording of the tubules followed by frame‐by‐frame measurement of the position of the edge of the tubule image in the video field. These measurements, which describe the movement of the tubule, may be analysed into a series of power spectra relating to sequential time periods through the recording. The group of spectrum plots for each tubule preparation can be plotted as isometric, pseudo three‐dimensional figures, with time represented on the s‐axis. The shapes of the spectra represent the contractile activity of the seminiferous tubules. Alterations in the level of activity and/or in the position of the frequency peaks, between control and experimentally treated preparations, are readily apparent. We also describe the construction and features of the perifusion chamber used with the VLMA.
A method for quick‐freezing live muscles at known instants during contraction with simultaneous recording of mechanical tension
Authors: Padrón Raúl , Alamo Lorenzo , Craig Roger , Caputo Carlo
Published: August 2011

We have developed a quick‐freezing method, using a copper block cooled with liquid helium or nitrogen, which permits us to freeze muscles without any cryoprotectant at predetermined, precisely measured points in the recorded tension time‐course of a single twitch or tetanus. Our aim is to arrest structural intermediates of the cross‐bridge cycle for observation in the electron microscope. Chemically stimulated, demembranated muscles as well as electrically stimulated, live muscles can be frozen on the same apparatus. Good freezing of relaxed and contracting muscles has been obtained to a depth of 10–20 μm, with excellent structural preservation after freeze‐substitution.
Infinite thickness in autoradiographs of iodine‐125
Authors: Williams M.A.
Published: August 2011

Infinite thickness for iodine‐125 in autoradiographs was measured by autoradiography using four types of nuclear emulsion. Using Ilford K5, Kodak AR 10 and Hyperfilm‐3H, a value of 20 μm was obtained. Using Hyperfilm Betamax, infinite thickness was greater than 60 μm. The results are discussed in relation to the types of radiation emitted as a result of iodine‐125 decay and in relation to published image spread data for this radioisotope.
The influence of the scene parameters and of noise on the behaviour of automatic focusing algorithms
Authors: Vollath D.
Published: August 2011

A systematic study is presented of the properties of autofocus criteria. Special importance is attributed to their behaviour with respect to noise, working range and image sharpness, whose reproducibility has been investigated. It can be demonstrated that autofocus algorithms have either a large working range and do not focus in an unambiguous way or vice versa. From considerations of the properties of autofocus algorithms two novel algorithms have been developed which are insensitive to noise. One of these algorithms is characterized by a particularly large working range, whereas the other is capable of achieving maximum sharpness in a reproducible manner.
High resolution electron microscope observations of microstructures in A15 type Nb3X superconductors
Authors: Takeda M. , Yoshida H. , Endoh H. , Hashimoto H.
Published: August 2011

Microstructures of superconducting Nb3X(A15) compounds are studied by means of high resolution electron microscopy. Structure images are obtained with the 400kV high resolution electron microscope for both the annealed and ion‐irradiated crystals. The images obtained from the annealed crystals show bright contrast patterns similar to the projections of Nb and X atoms comprising the A15 structure. Defects observed in the annealed crystal irradiated with 40 kV Nb+ ions show characteristic features in contrast. The dependence of image contrast on the element X and the atomic structures of the defects are discussed by comparison with the calculated images.
Various TEM methods for the study of metal matrix composites
Authors: Withers P. J. , Stobbs W.M , Bourdillon A. J.
Published: August 2011

We have investigated the applicability of a number of TEM techniques for the study of the metal/ceramic interface in a short fibre metal matrix composite (SFMMC). In particular, we found that dark field techniques were best suited to the study of any possible (0.4‐2 nm) amorphous layer. High resolution imaging was found to be difficult to use because of the absence of well defined ‘edge‐on’ interfaces, but EELS with parallel recording was found to be very useful for finding and identifying segregated particles at the fibre/matrix interface. It was also shown that micro‐mechanisms of fracture such as voiding and fibre breakage could be readily examined by TEM using a foil preparation method which resulted in an ‘edge‐on’ fracture surface and an observation region extending about 0.8 mm below it.
Granular porometry and fibrous structures
Authors: Calonnier M. , Laget B.
Published: August 2011

The purpose of this paper is to set up a new theoretical model of a fibrous structure in its filtering function. After the segmentation, using morphological transforms, of an image of a longitudinal cross‐section two models of penetration in the structure are proposed. They are developed from results of integral geometry like the Blaschke formula. These two approaches use different propagation laws: (1) gravitational transition; (2) turbulent flow transition. Finally, two sequences of coefficients are obtained characterizing a new vertical tortuosity law.
Two‐phase flow in porous media: obtaining sharp digitized images of serial sections for subsequent quantitative analysis
Authors: Macdonald I. F. , Yadav G. D. , Chatzis I. , Dullien F. A. L.
Published: August 2011

Microscopic studies of the distributions of oil and aqueous phases within the pore space of reservoir rocks, at various relative saturations, are of fundamental importance in understanding migration, distribution, mobilization and recovery of oil in the context of a particular (enhanced) oil recovery method. The most effective approach to use for these studies is three‐dimensional computer reconstruction with the data for the three‐phase system (rock, oil, aqueous phase) entered by video digitization of a set of serial sections.

A novel technique for creating accurate three‐phase digitized images from the serial section data is described. By use of appropriate pore cast materials and lighting conditions, three different two‐phase video images are created and digitized. In each image, a different one of the three phases in the pore cast is one of the two distinguishable phases. The two best two‐phase digitized images are combined to give the three‐phase digitized image.
A new method for cell culture on an electron‐transparent melamine foil suitable for successive LM, TEM and SEM studies of whole cells
Authors: Westphal Christel , Hörler Heide , Pentz Siegwald , Frösch Dieter
Published: August 2011

A new cell culture technique is described which is based on the observation that foils cast from the melamine resin hexamethylol‐melamine‐ether are suitable for the cultivation of beating heart muscle cells and fibroblasts of the rat. This foil can be flamed for sterilization, is about 80 nm in thickness, homogeneous and smooth, withstands dehydration and critical point‐drying, can be removed from glass and permits the imaging of whole cells successively by light microscopy, transmission and scanning electron microscopy.

The method is capable of narrowing the gap between light and electron microscopy, yielding excellent whole cell preparations in various kinds of microscopic studies to be performed on one and the same cell.
Anterograde tracing in the brain using autoradiography and HRP‐histochemistry. A comparison at the ultrastructural level
Authors: Holstege J. C. , Vrensen G. F. J. M.
Published: August 2011

The present paper decribes the use of 3H‐leucine and WGA‐HRP as anterograde tracers in the brain at the ultrastructural level. In addition the different aspects of the two tracing techniques are compared, including the analysis of the results, the reliability and relative efficiency.
Video microscopic image processing facilitates the evaluation of light microscopic autoradiography at high magnification
Authors: Montag M. , Trendelenburg M. F. , Spring H.
Published: August 2011

Light microscopic autoradiographs of H‐thymidine labelled unstained semithin sections of Xenopus laevis embryonic nuclei were examined with conventional Nomarski differential interference contrast, phase‐contrast and video microscopy.

Whereas at low magnification it was possible to obtain a photograph of the nuclear structure and the silver grains in one focal plain, at high magnification, with small depths of focus, a satisfactory image was not attainable. Therefore, we stored the images of the two different focus levels with a digital image processing system and combined both images by an arithmetic operation.

This video microscopic technique allows the use of high magnification light microscopy with oil immersion objectives and the application of additional electronic contrast enhancing methods for an adequate and rapid analysis of light microscopic autoradiographs.
Stereological estimation of mean nuclear volume in prostatic cancer, the reproducibility and the possible value of estimations on repeated biopsies in the course of disease
Authors: Nielsen K. , Berild G. H. , Bruun E. , Jorgensen P. E. , Weis N.
Published: August 2011

The reproducibility of stereological estimates of mean nuclear volume by using the principle of volume estimation of particles of arbitrary shape is investigated together with the possible prognostic value of the estimates in the course of advanced prostatic cancer.

Repeated transurethral resection of the prostate was performed 14–93 months after the first resection in 14 of 85 consecutive patients in whom prostatic cancer was newly diagnosed in the period 1979–1983. Twelve of these fourteen patients needed endocrine treatment because of progression of the metastatic disease.

The reproducibility of the estimations was excellent as the variation of the method was less than 1 % when the estimation of the mean nuclear volume was repeated at random on the same specimens after a time‐interval of 2 months.

The progression of the disease was evidenced by a significant histological upgrading and by a highly significant increase of the mean nuclear volume from the first to the second transurethral resection of the prostate.