bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of dimensions of ellipsoidal microparticles via electron microscopy
Authors: Keville K. M. , Caruthers J. M. , Franses E. I.
Published: August 2011

The analysis and the use of metallic shadow casting and specimen tilting for accurately determining the dimensions of microellipsoids by electron microscopy (EM) are presented. The procedure uses the direct image and two different shadows or two different specimen tilts to unambiguously determine the dimensions of an ellipsoid. A novel computer‐aided matching procedure is used to determine dimensions and orientations. The analysis was applied to a sample of polymer prolate microspheroids, which have recently been synthesized in our laboratory. The shape of the particles was confirmed and their dimensions and orientations were determined. The particles were shown to have a length (twice the principal axis) of 3.30±0.02 μm and a diameter (twice the minor axis) of 1.66±0.04 μm. Thus, both EM techniques were demonstrated to be practical and precise for determining dimensions of individual microellipsoids.
Reconstitution of molecule images analysed by correspondence analysis: A tool for structural interpretation
Authors: Bretaudiere Jean‐Pierre , Frank Joachim
Published: August 2011

Correspondence analysis is gaining increasing importance in the analysis of electron micrographs of macromolecules. Partial or complete reconstitution of images from their factorial representations is introduced as a useful tool in interpreting variational patterns and tracing their physical origin. The value of image reconstitution is demonstrated with two examples, one using a set of model images and the other a set of images of a haemocyanin molecule assembly product.
Imaging intracellular elemental distribution and ion fluxes in cultured cells using ion microscopy: a freeze‐fracture methodology
Authors: Chandra Subhash , Morrison George H. , Wolcott Christine C.
Published: August 2011

A freeze‐fracture methodology was standardized for tissue culture cells to study intracellular distribution of diffusible elements with ion microscopy. Chinese hamster ovary (CHO) and normal rat kidney (NRK) cells grown on a silicon substrate were sandwiched using another smooth surface (silicon, glass, mica) in the presence of spacers and fast frozen in liquid nitrogen slush. The sandwich was fractured by prying the two halves apart under liquid nitrogen. This procedure produced large areas on the silicon substrate containing hundreds of cells grouped together and fractured at the apical cell surface. After freeze‐drying, these cells revealed a subcellular distribution of Na, K, Ca, Mg, P, Cl and S with the ∼0·5 μm lateral resolution of the ion microscope. Between the nuclei and the cytoplasm of cells, no major differences were observed for Na, K, Mg, P, Cl and S intensities. Calcium alone, however, exhibited a remarkable distribution. Calcium accumulated more in the cytoplasm than in the nuclei of cells. Even within the cytoplasm its distribution was heterogeneous, suggesting Ca binding sites. The fractured cells consistently exhibited high K‐low Na intensities. The injured or dead cells were easily recognized among the healthy ones due to their abnormal ion composition. This simple freeze‐fracture methodology allowed fracturing of cells without removing the cells from the substrate. In addition, it eliminated the need for washing the nutrient media away and cryo‐sectioning before ion microanalysis. The methodology was successfully extended to 3T3 mouse fibroblast, PtK2 rat kangaroo and L5 rat myoblast cultures.
Astronomical hypersensitization techniques applied to photomicrography: Kodak Technical Pan Film 2415
Authors: Smith Alex G.
Published: August 2011

Kodak Technical Pan Film 2415 is a valuable recording medium because of its unusually fine grain and high resolution. Hypersensitization techniques developed by astronomers can increase its normally low speed several‐fold in the range of exposures commonly employed in microscopy. The speed gains are even larger for very long exposures such as those encountered in fluorescence work. Troublesome effects from reciprocity failure are virtually eliminated. When active development is added to hypersensitization, well‐exposed negatives can be obtained at ISO indexes as high as 1600. As in astronomy, the same general techniques can be applied to a wide variety of emulsions.
In situ oxidation and reduction of the oxides of cerium, praseodymium and terbium by high‐voltage electron microscopy
Authors: Schweda E. , Kang Z. C. , Eyring L.
Published: August 2011

In situ oxidation and reduction of the oxides of cerium, praseodymium and terbium in a controlled atmosphere and temperature have been studied utilizing a high‐voltage electron microscope. Experiments were carried out in the environmental cell of the Berkeley KRATOS EM 1500 HVEM at temperatures between 298 K and 1023 K in an atmosphere of oxygen, hydrogen or vacuum. Electron diffraction patterns revealed the course of small fragments of the crystalline oxides. In nearly all cases, the degree of reduction recorded was greater than expected from equilibrium tensimetric studies in the absence of an electron beam. Furthermore, reoxidation appeared to be more sluggish and to a lesser extent than is observed in specimens outside the microscope.
The relative efficiency of cryogens used for plunge‐cooling biological specimens
Authors: Ryan K. P. , Purse D. H. , Robinson S. G. , Wood J. W.
Published: August 2011

Coolants used for freezing biological specimens were tested for cooling performance in the continuous plunge mode. Results from bare thermocouples showed that ethane cooled faster than propane or a propane: pentane mixture, even when warmed to 25 K above its freezing point. Propane coolants were more efficient than Freon 22 and the slowest cooling occurred in boiling liquid nitrogen. Hydrated gelatin specimens showed similar results with ethane cooling about 33% faster than propane. Epoxy resin specimens cooled faster than hydrated gelatin specimens of similar size. Hydrated and resin specimens cooled over increasing distances as plunge velocity increased. A bare thermocouple, however, cooled over a constant distance when plunged above a critical velocity. This phenomenon may reflect vapour formation and its suppression at high plunge velocities. The rate of cooling in hydrated specimens is shown to have an absolute limit and cannot be modelled by bare thermocouples or resin specimens.
A simple, practical ‘swiss roll’ method of preparing tissues for paraffin or methacrylate embedding
Authors: Park Carol M. , Reid Philip E. , Walker David C. , MacPherson Brian R.
Published: August 2011

A simple method of preparing ‘swiss rolls' from strips of tissue up to 500 mm in length is described. This procedure has been applied to a variety of tissues and is suitable for the preparation of both paraffin‐ and methacrylate‐embedded specimens.
The comparison of transition metal concentration ratios determined by EELS and EDX
Authors: Crozier P. A. , Chapman J. N. , Craven A. J. , Titchmarsh J. M.
Published: August 2011

The correlation that exists between elemental concentration ratios determined using EDX and EELS is examined. EELS and EDX were recorded simultaneously from the second phase carbides of a ferritic steel and the Cr/Fe and Mn/Fe concentration ratios were determined from each spectrum. For this system, it was found that the Cr/Fe ratios could be determined by EDX to within an accuracy of 4% and these were then used to provide a check on the EELS analysis procedures. The effects of using different partial ionization cross‐section models and methods of applying these models were examined. It was found that an overall agreement of 3% between EDX and EELS was obtained in this particular experiment. Much poorer agreement was found to exist between the two techniques for the Mn/Fe ratios. The discrepancy is attributed mainly to the inadequacies of the procedure used for extracting the Mn characteristic signal in the EELS spectra.
Histochemical implications of the chemical and biological properties of SITS and some related compounds
Authors: Horobin Richard W. , Payne J. Nicholas , Jakobsen Palle
Published: August 2011

Since commercial samples of the fluorochrome SITS (sodium 4‐acetamido‐4′‐isothiocyanatostilbene‐2,2′disulphonate) are of varied, and often of uncertain, composition, the synthesis of SITS has been repeated. The identities of SITS and certain of its precursors and derivatives have been established using modern spectroscopic methods (IR, 1H and 13C NMR), as well as microanalysis. When pure SITS underwent hydrolysis at room temperature the products were amines, not the expected thioureas. This suggests that SITS, contrary to previous expectations, will not bind covalently to proteins, whether immunoglobulins or membrane constituents. Again contrary to earlier statements, pure SITS is not retrogradely transported in neuronal axons. The transported material is a red‐orange impurity which arises very occasionally during the preparation of SITS. A possible structure for this red‐orange compound is proposed: namely a dimeric azo or azoxy condensation product. Comparison of pure SITS with commercial samples indicated that the latter were extremely varied in composition, with SITS contents varying from high to trivial.
A simple method for quantitative SEM at low magnifications
Authors: Waitz W. , Ennemoser O.
Published: August 2011

A method for quantitative scanning electron microscopy (SEM) at low magnifications has been developed. Quantitative measurements in SEM are rare and often not accurate, because of a systematical error, i.e. a nominal magnification exists only in one direction of the photograph. Our method is suitable for smooth surfaces as it proves the changes of magnification within the two‐dimensional range. In a first step EM‐grids are used as samples. In a second step it is shown how the method can be applied to biological specimens. We took the microstructure of Helix pomatia shells as example.
A synthetic corundum knife for ultrathin sectioning*
Authors: Hodgson Clague P. , Cunningham William P.
Published: August 2011

A synthetic corundum (Al2O3, synthetic ruby, synthetic sapphire) knife has been constructed which is suitable for the preparation of thin sections (less than 90 nm) of biological specimens for electron microscopy. The method involved cleavage or fracture of the flame‐fusion crystalline product, followed by mounting in a standard knife holder for ultramicrotomy. The cutting edge appeared flawless under 400 × and produced sections in which subcellular organelles were clearly resolved. Scanning electron microscopy of the knife revealed conchoidal fractures typical for corundum, terminating in apparent cleavage of the crystal along the knife edge. X‐ray microanalysis of the knife edge revealed essentially 100% aluminium, indicating that the aluminium oxide crystal was of a high purity. The superior toughness and low cost of synthetic corundum suggest that it may be a useful alternative to diamond or glass knives.
Three‐dimensional reconstruction from a single‐exposure, random conical tilt series applied to the 50S ribosomal subunit of Escherichia coli
Authors: Radermacher M. , Wagenknecht T. , Verschoor A. , Frank J.
Published: August 2011

We present a new reconstruction method that takes advantage of the fact that many biological macromolecular assemblies show a preferred orientation with respect to the plane of the specimen grid in the electron microscopic preparation. From one micrograph taken of such a specimen tilted by a large angle, a conical tilt series with random azimuthal angles can be extracted and used for a three‐dimensional reconstruction. Our technique allows the determination of the molecular structure under low‐dose conditions, which are not achievable with reconstruction methods that use conventional tilt series. The reconstruction method combines a number of existing image processing techniques with a newly developed weighted back‐projection algorithm designed for three‐dimensional reconstruction from projections taken with arbitrary projecting directions. The method is described as it was applied to the three‐dimensional reconstruction of the structure of the 50S ribosomal subunit ofEscherichia coli (E. coli).
Colour‐coded stereo images from the tandem scanning reflected light microscope (TSRLM)
Authors: Boyde A.
Published: August 2011

A method is described for the production of stereo‐pair images in the tandem scanning reflected light microscope in which depths within the field imaged are coded in colour. The two images are recorded photographically whilst focusing vertically through the layer which is to be imaged. A horizontal component of motion is applied at the same time, but in opposing senses for the two images. Colour coding for depth is obtained by changing colour filters so that reflective features lying within different depth bands are imaged in corresponding colours.
Some characteristics of the buffer vehicle in glutaraldehyde‐based fixatives
Authors: Coetzee J. , van der Merwe C. F.
Published: August 2011

The pH of sixteen different buffer vehicles is lowered by the addition of glutaraldehyde. This is the case even if the concentration of the buffer is as high as 0.2 m and that of the glutaraldehyde as low as 2%. Graphs are given which make it possible to determine which buffer has the highest buffering capacity at pH‐values between 6.5 and 8. Graphs illustrating the influence of concentrations of glutaraldehyde between 1% and 5% on the dissociation constant of these buffers make it possible to formulate a glutaraldehyde‐based fixative in which an optimally‐buffered vehicle can contribute to the attainment of an osmotically‐balanced fixative.
Should we be counting immunogold marker particles on cell surfaces with the SEM?
Authors: de Harven E. , Soligo D. , Christensen H.
Published: August 2011

The lymphocyte in Fig. 1 was incubated with a 1/10 dilution of a murine monoclonal antibody (Leu‐1) directed against a surface antigen expressed on circulating human T‐cells. It was labelled with a colloidal gold/immunoglobulin conjugate and examined with the scanning electron microscope (SEM) in the backscattered electron imaging (BEI) mode. It was easy to count the number of gold particles seen on this cell; actually, we counted 471 of them. For biologists, is this number relevant? We will discuss the principal factors involved in answering this question.
Determination of areal densities of blood vessel wall components in histological sections by means of image analysis
Authors: Verheyen A. , Minten J. , Cornelissen F. , Rombauts W. , Geest H. De
Published: August 2011

A technique is described which allows quantification of specifically stained, intermingled vessel wall components in paraffin‐embedded tissue. The dissociation of elastic, muscular and connective tissue and the determination of their areal densities in the superior vena cava and in the ascending aorta of the dog, was performed by automated image analysis. The percentages of elastic+connective tissue, determined by this technique, correlated significantly with the data derived from biochemical measurements. It was further found that the structure of the vena cava wall was a function of the distance from the right atrium.
The projection method: Fourier transforms and projected patterns
Authors: Duneau Michel , Katz André
Published: August 2011

The projection method is the current basis of numerous research for structural models of quasicrystals. The method provides structures which are quasiperiodic and present an icosahedral symmetry, and allows a simple computation of their Fourier transforms. The two‐dimensional projections of the structures can also be obtained by the same method and are quasiperiodic and discrete.
The substructure of quasicrystalline Al‐Mn alloy observed by TEM
Authors: Cheng‐gao Fan , Zi‐qin Wu , Yuan‐sheng Wang , Ling‐chao Tsien
Published: August 2011

The morphology of the icosahedral phase in Al86Mn14 alloy has been observed as flower‐like and of granular shape by TEM. These two kinds of morphologies may be regarded as the different sections of a three‐dimensional flower‐like grain. Inside these grains, a fine substructure of a few nm in size has been found. A dendritic morphology with a diffraction pattern showing five‐fold symmetry have also been observed in the Al86Mn14 alloy. On the basis of these observations, a model based on nucleation, growth and aggregation has been proposed to explain the formation process of the quasicrystalline state.
Al‐Mn μ phase and its relation to quasicrystals
Authors: Bendersky Leonid
Published: August 2011

The potential interrelationship between the Al‐Mn μ phase and icosahedral structures is investigated by a systematic study of the electron diffraction behaviour of the crystalline phase. The presence of systematic absences in selected area diffraction patterns is used to propose a space group for the μ phase and similarities with the icosahedral and decagonal diffraction patterns are argued to imply the presence in both the crystalline and quasicrystalline phases of icosahedral units with different stacking arrangements.
Measurement of increased uptake of osmium in skin and in a gelatin model ‘tissue’ treated with tannic acid
Authors: Caceci Thomas , Frankum Kelly E.
Published: August 2011

The effect of tannic acid (TA) on the deposition of osmium was studied in discs of hamster skin and in fixed gelatin. Pieces of skin treated with 1·0% TA before OsO4 fixation absorbed almost twice as much as untreated pieces. Gelatin, used here as a model ‘tissue’ showed an even greater degree of enhancement. Treated gelatin capsule halves and strips took up 4–6 times as much osmium as untreated ones. The deposition of osmium was verified by neutron activation analysis.
Development and analysis of an automated dimension measuring microscope
Authors: Kirk C. P.
Published: August 2011

A theoretical model is developed to describe the operation of a bright field, optical microscope intended to be used for making automated measurements of features as small as 0·3 μm. The measurement of gap lengths in magnetic recording heads and linewidths on integrated circuit photomasks is discussed in detail. Different measurement techniques are investigated theoretically and their perfomances in the presence of aberrations, focus errors and non‐ideal transducer responses are assessed.

An automated measurement technique based on image shearing is presented and compared with other measurement techniques based on bright field image scanning. It is demonstrated that the automated image shearing method is much less prone to measurement errors due to system parameters.

The model was used to develop an optimized design for the measurement system and a complete instrument was built. The performance of the practical measurement system agreed well with theoretical predictions. A calibration standard and a simple but accurate calibration algorithm were also developed.
Determination of the site occupation probability and the degree of order by APFIM
Authors: Miller M. K.
Published: August 2011

Experimental procedures to determine the local degree of order and the site occupation of a substitutional element in an ordered alloy by atom probe field‐ion microscopy is described. The procedures are demonstrated with a series of examples of the Ll2‐ordered nickel aluminides.
Microtomography
Authors: Sasov A. Yu.
Published: August 2011

The study of the internal structure of objects is the main purpose of practically all microstructural investigations. At present there are several direct and indirect methods for the analysis of the internal microstructure of specimens. The most popular of them is scanning electron microscopy in which inferences on microstructure are made from the images of cleavage or microsection surfaces. The only non‐destructive possibility for obtaining information on the internal microstructure of a specimen is by eliminating the need to break it. Information on the internal structure of an object can in this case be obtained in the form of shadow images in transmission, for instance, by means of X‐radiation (X‐ray microscopy). Unfortunately the images obtained are two‐dimensional projections and fail to give an adequate idea of the spatial microstructure.

A three‐dimensional reconstruction from two‐dimensional projections constitutes the subject of computerized tomography (Herman, 1980). At present the main works in tomography are oriented for medical applications (New et al., 1974; Hounsfield, 1973; Wood et al., 1979). An elaborate mathematical apparatus for reproducing a three‐dimensional structure from projections enables similar methods to be used also in other fields, from the astronomy (Bracewell, 1979) to the transmission electron microscopy (Negeri, 1982). Most commercial X‐ray tomography systems permit of reconstructing objects more than 0·1 m in size with a spatial resolution to within fractions of a centimetre. In transmission electron microscopy the size of reconstructed objects is of an order of 1 μm with the spatial resolution of reconstruction to some units of nanometres. The reconstruction of the internal structure of the millimetre and micron size range specimens is the subject of the present work. Three‐dimensional reconstruction of specimens in the millimetre size range with a spatial resolution to within some micrometres proves necessary in the numerous fields of science and technology, such as materials science, defect studies (particularly for semiconductor devices and integrated circuits), biology, geology, physics, etc.
Microtomography
Authors: Sasov A. Yu.
Published: August 2011

The possibility of reconstructing the interior arrangement of a specimen non‐destructively is determined by the degree of absorption of X‐ray radiation in the object. Microtomography systems based on X‐ray TV microscopes enable objects with a high absorption (including metals), and up to several millimetres in size, to be investigated with a spatial resolution of tens of microns. SEM‐based microtomography systems permit specimens up to 1–2 mm in size to be studied with a resolution up to several microns. Furthermore, the SEM gives the unique possibility of reconstructing objects from other characteristic properties affecting the electron beam, such as magnetic fields.
Low‐temperature scanning electron microscopy of particle‐exposed mouse lung
Authors: Finch Gregory L. , Bastacky S. Jacob , Hayes Thomas L. , Fisher Gerald L.
Published: August 2011

Inflated frozen mouse lungs were examined using low‐temperature scanning electron microscopy (LTSEM) following bulk fracture under vacuum. Various aspects of pulmonary architecture were identified and correlated with structures revealed by SEM following conventional fixation and preparation techniques. Surface etching of selected samples was performed by radiant heating, revealing characteristic cytoplasmic, nuclear and extracellular lattice patterns resulting from ice crystal formation during freezing. These patterns aided in distinguishing between intra‐ and extracellular spaces. Pulmonary fluids such as mucus and surfactant were identified. Iron oxide particles were introduced into the lungs of some animals by intratracheal instillation and were subsequently identified in frozen‐hydrated lung tissue using characteristic X‐ray identification and mapping techniques. Particles were observed both intra‐and extracellularly and were commonly found in large deposits. These observations confirm the utility of LTSEM techniques for examination of particles within pulmonary tissue. Particle exposure by intratracheal instillation was found to result in a non‐uniform distributional pattern.
The efficiency of systematic sampling in stereology and its prediction*
Authors: Gundersen H. J. G. , Jensen E. B.
Published: August 2011

The superior efficiency of systematic sampling at all levels in stereological studies is emphasized and various commonly used ways of implementing it are briefly described. Summarizing recent theoretical and experimental studies a set of very simple estimators of efficiency are presented and illustrated with a variety of biological examples. In particular, a nomogram for predicting the necessary number of points when performing point counting is provided. The very efficient and simple unbiased estimator of the volume of an arbitrary object based on Cavalieri's principle is dealt with in some detail. The efficiency of the systematic fractionating of an object is also illustrated.
The assessment of compositional changes in Nimonic PE16 by convergent beam electron diffraction
Authors: Randle Valerie , Ralph Brian
Published: August 2011

Lattice parameter changes can be detected by the use of a previously established technique which is based upon computer simulation of HOLZ patterns. This simulation technique is then applied to two precipitation phenomena in Nimonic PE16. Firstly, the growth of gamma prime, γ, precipitates from a solid solution is monitored via the decrease in lattice parameter of the parent phase, and secondly the lattice parameter of coarsened, overaged γ is measured for precipitates sited both at grain boundaries and within grains. The variations thus detected between intergranular and intragranular precipitates are attributed to changes in the Ti/Al ratio due to preferential γ coarsening at the grain boundary. The very subtle compositional changes inferred (∼1 at. % Ti) would have been very difficult to establish by chemical analysis, but can be easily measured by convergent beam electron diffraction.
Safety considerations regarding the use of propane and other liquefied gases as coolants for rapid freezing purposes
Authors: Ryan Keith P. , Liddicoat Malcolm I.
Published: August 2011

Liquid propane and similar coolants are used in the rapid freezing of biological specimens. These coolants form explosive gas mixtures with air, with a 14,000−fold increase in volume over that of the liquid. The liquefied gases have high vapour pressures and, unless they are maintained below their flashpoint, the vapour above them will reach ignitable concentrations. The flashpoint of liquid propane is −104°C. Ethane has a higher vapour pressure, and vapour mixed with air above liquid ethane can be ignited at a coolant temperature of −130°C. The danger is minimized if the coolant is maintained near its freezing point and under a nitrogen atmosphere, in a fume cupboard. Liquid nitrogen evaporates to a 690‐fold increase in volume at room temperature. It is important to ventilate the working area, especially when cryo‐sectioning in a small room, otherwise there is a possibility of asphyxiation.
Platinum‐shadowed, whole‐mounts for transmission electron microscopy of cells cultured on plastic
Authors: Sanan David A.
Published: August 2011

A simple and convenient method is described whereby cells cultured on polystyrene plastic substrata may be critical point‐dried, rotary‐shadowed with platinum/carbon and finally released by means of propylene oxide for examination whole in the transmission electron microscope. The technique is particularly useful for the localization of colloidal gold probes, both intra‐ and extra‐cellularly. The problem of premature melting of polystyrene at about 307 K after prolonged exposure to carbon dioxide is solved by limiting the residence time in the critical point‐drier to 1 h. Details for cleaning and mounting the released films of cells on specimen grids are given. The technique expands the application of the ‘whole‐mount’ approach of Hopkins and co‐workers (Hopkins et al., 1981; Hopkins, 1985) to cells cultured directly on polystyrene substrata, that is, in conventional plastic culture vessels.
An electron microscopy study of the phase Al3Fe
Authors: Skjerpe Per
Published: August 2011

The phase Al3Fe (monoclinic C2/m, a = 1·549 nm, b = 0·808 nm, c = 1·248 nm, β = 107·8°) has been studied by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Crystals were obtained from a direct chill‐cast ingot of an Al‐0·25 wt% Fe‐0·13 wt% Si alloy. Extracted crystals were prepared by dissolving the aluminium phase in butanol and filtering off the particles. The extracted Al3Fe crystals were mainly (100) platelets. The monclinic lattice was confirmed by tilt experiments and the mirror plane was confirmed by convergent beam electron diffraction. Experimental HREM images from the [100] and [110] projection agreed with images calculated by the multislice method. The interpretation of images in terms of a projected crystal structure is discussed. Common defects in Al3Fe crystals were: twins on (100) and faults on (001). The (001) faults could be described by a displacement 1/2·[100] on a fault plane at z = 0·5 in the unit cell. A model for (001) faults, based on multiple twinning, is proposed.
Improved specimen support cups and auxiliary devices for the Balzers high pressure freezing apparatus
Authors: Craig Stuart , Gilkey John C. , Staehelin L. Andrew
Published: August 2011

A new design for interlocking specimen support cups that permits reliable and reproducible freezing under high pressures of a range of different biological specimens is described. A stronger holder in which the support cups are tightly held during pressurization and freezing, and a sliding wedge for separating the cups after freezing are also described. Used in conjunction with the Balzers HPM 010 high pressure freezing apparatus, these modifications permit routine freezing of tissue for freeze‐fracture and freeze‐substitution for electron microscopy.
Theory of self‐similar network structures in sedimentary and igneous rocks and their investigation with microscopical and physical methods
Authors: Pape Hansgeorg , Riepe Lutz , Schopper Jürgen R.
Published: August 2011

Based on self organized growth, a self‐similar geometrical model of rock materials is established. The structural mode of the internal surface is carried over to the three‐dimensional structure of the pore space and solid phase, which can be described as a fractal network. It is characterized by the fractal dimension of surface, which can be measured by physical and stereological methods. From this, the fractal behaviour of other geometrical properties, relevant for physical processes, such as porosity, number of solid connections, tortuosity and constrictivity of the capillary system and of the solid phase can be derived.
Fractal agglomeration during crystallization of Pd‐Si alloy films
Authors: Jian‐Zhong Duan , Zi‐Qin Wu
Published: August 2011

Fractal agglomeration or irregular hole formation has been obtained during the crystallization of evaporated Pd‐Si alloy films. The morphologies of the fractal‐like structures observed by TEM are similar to patterns simulated by computer according to the Witten‐Sander diffusion‐limited aggregation (DLA) model. The scale‐invariance was tested by the density‐density correlation method and the size‐radius of gyration method. The results from these two methods show that fractal‐like structures in the specimens with different compositions have different fractal dimensions; 1·58·0·04 and 1·78·0·04 for Pd‐Si 62 at.% and Pd‐Si 44 at.% alloy films, respectively. A model is proposed for describing the formation process.
A study of factors influencing the accuracy of quantitative X‐ray analysis of thin foil specimens
Authors: Wirmark G. , Nordén H.
Published: August 2011

Needle‐shaped specimens were used to determine experimental values of X‐ray intensity ratios for L/K and M/L lines. These ratios can be used to determine kAB factors for L and M lines. They also provide necessary data for absorption correction with the X‐ray intensity ratio method. Recent theoretical calculations of kAB factors are evaluated and new constants in the parametrization of ionization cross‐sections for L and M lines are presented.

The average X‐ray production per unit thickness has been measured as a function of mass thickness for a stainless steel specimen using acceleration voltages of 100 and 200 kV. An increase in X‐ray production by more than 20% was found at 100 kV for mass thicknesses up to 1 mg/cm2 while at 200 kV the increase was about 5%.

The contamination spot method for thickness measurements has also been investigated using needle‐shaped specimens. The reported overestimate of thickness using this method can be explained by the formation of broad contamination layers around the deposited spots.
Application of the GTGO‐AD procedure in the scanning electron microscopy of streptococci adhered to pellicle‐coated dental enamel
Authors: Edwards P. J. , Jeffryes C. A.
Published: August 2011

The scanning electron microscope (SEM) offers a direct and visually effective means of examining streptococci adhering to pellicle‐coated dental enamel. The GTGO‐AD (Glu‐taraldehyde‐Tannic acid‐Guanidine hydrochloride‐Osmium tetroxide‐Air‐Drying procedure) has the advantage that critical point‐drying or freeze‐drying need not be employed. It was found that both the structural and spatial integrity of the adherent streptococci and the pellicle were maintained with the GTGO‐AD procedure.
Evaluation of matrix effects in ion microscopic analysis of freeze‐fractured, freeze‐dried cultured cells
Authors: Chandra Subhash , Ausserer Walter A. , Morrison George H.
Published: August 2011

SIMS matrix effects (mass interferences, sputter yield variations and practical ion yield variations) were evaluated in freeze‐fractured, freeze‐dried cultured cells at the ∼0.5 μm spatial resolution of the Cameca IMS‐3f ion microscope. Cell lines studied include normal rat kidney (NRK), 3T3 mouse fibroblast, L6 rat myoblast, chinese hamster ovary (CHO) and rat kangaroo kidney (PtK2) cells. High mass resolution studies indicated that the secondary ion signals of H—, C—, O—, Na+, Mg+, CN—, P—, S—, Cl—, K+ and Ca+ were free from major mass interferences. However, a large mass interference was observed for nitrogen at mass 14. No significant sputtering yield difference between the nuclear and cytoplasmic compartments of the cells studied was observed. The subcellular distributions of the major (H, C, N and O) and minor (P, S, K, Cl, Na, Mg and Ca) matrix elements were found to be largely homogeneous with the exception of Ca, which was observed mainly in the cell cytoplasm. Practical ion yield variations were compared by three different approaches: (i) by the use of cells doped with known electrolyte concentrations, (ii) by quantitative ion implantation, and (iii) by analysis of the same cell with both electron probe and ion microscope. Each approach indicated an absence of significant practical ion yield differences between the nuclear and cytoplasmic regions of these specimens. These observations indicate that secondary ion signals in this type of sample are not significantly affected by local matrix effect variations. Hence, qualitative imaging of such specimens provides a true representation of subcellular elemental distribtions. These observations should allow the development of quantitative ion imaging methodologies and enhance the applicability of ion microscopy to biomedical problems.
Automatic discrimination of features in grey‐scale images
Authors: Russ John C. , Russ J. Christian
Published: August 2011

Automatic setting of discriminator thresholds to select features from grey‐scale images is desirable to reduce variations due to operator variability, and to adapt to changing illumination or sample characteristics. This can be carried out in several ways. One locates minima in the original brightness histogram. For images in which minima are absent or poorly defined other techniques are preferred. Settings that minimize the change in total feature area or perimeter with changes in the threshold setting are suitable for a wide variety of images. After processing to extract edges a fixed percentage of the number of pixels in the image may be useful.
On the determination of inner‐shell cross‐section ratios from NiO using EELS
Authors: Crozier P. A. , Chapman J. N. , Craven A. J. , Titchmarsh J. M.
Published: August 2011

We have attempted to measure the O/Ni inner‐shell cross‐section ratios from a sample of NiO using EELS in an electron microscope. The results lay within roughly 10% of the predictions of both the hydrogenic and Hartree‐Slater theories. However, the data showed a spread of around 20% which may have been caused by artefacts introduced during the specimen preparation.
Deadtime corrections for a pulse counting system in electron energy loss spectroscopy
Authors: Cheng S. C. , Crozier P. A. , Egerton R. F.
Published: August 2011

We have measured the relationship between the input and output pulse rates for an EELS pulse counting system. Two simple formulae for predicting the behaviour of such a system are compared with the data. One is for a system which has extendible deadtime. The other is for the counting system which has non‐extendible deadtime. The latter provides agreement with our experimental results over the range 0–20 MHz.
Stereological determination of curvature distributions of spatial fibre systems
Authors: Stoyan Dietrich , Gerlach Wolfgang
Published: August 2011

Under the assumption of homogeneity and isotropy, this paper solves the problem of determining spatial curvature distributions of fibre processes from curvatures of projection curves from thin sections. As an example, a sample of dislocation lines in a hot‐rolled Fe‐Ni alloy is discussed.
An exact calculation of the voltage‐dependent tunnelling current in simple one‐dimensional models: comparison with the Bardeen perturbation approach
Authors: Sacks W. S. , Noguera C.
Published: August 2011

In this paper we present an exact calculation of the tunnelling current for two different one‐dimensional barrier potentials. The purpose is twofold: First, we demonstrate the feasibility of applying the new method of C. Noguera as a direct analytical tool for solving tunnelling problems in the case of independent electrons. In this approach, the tunnelling current is expressed in terms of the logarithmic derivative of the Green's function which must be evaluated at the cutting surface. This can be done analytically in the one‐dimensional case. Secondly, we compare these results with the corresponding tunnelling current obtained using the Bardeen perturbation method, valid only in the large barrier limit. In particular, we investigate the use of the Bardeen approach in describing tunnelling spectroscopy. The dynamic conductance dI/dV, as a function of bias and barrier width, is compared in both cases.
Lateral resolution of the scanning tunnelling microscope
Authors: Laloyaux Th. , Lucas A. A. , Vigneron J.‐P. , Lambin Ph. , Morawitz H.
Published: August 2011

A theoretical study of the current distribution in a model which extracts the prominent characteristics of a tip‐surface geometry in a scanning tunnelling microscope is presented. The sample is a Sommerfeld metal with a planar surface while the tip, also made of a Sommerfeld metal with a planar surface, presents a hemispherical protrusion. Schrödinger's equation is solved by using a form of the finite element method suitable to treat the three‐dimensional tunnelling problem.

We have derived the current distribution for several values of the protrusion radius and for various gaps between the electrodes. From these results, we investigate the ideal resolution of the scanning tunnelling microscope for realistic values of these geometrical parameters.

Though applied to a rather simple model, at this stage, our method appears to be a suitable scheme for further, more refined computations, accounting for the detailed atomic structure of the electrodes.
Tunnelling accelerometer
Authors: Baski A. A. , Albrecht T. R. , Quate C. F.
Published: August 2011

Due to the strong distance dependence of tunnelling current on electrode spacing, tunnelling can be used to measure sub‐ångström‐scale displacements. The sensitivity and relative simplicity of this technique make it well suited for applications in highly sensitive accelerometers. We have constructed a cantilever‐type accelerometer in which a mass‐loaded lever deflects freely in response to accelerations. Deflection is measured by tunnelling in the constant current mode between an electrode on the lever and a tunnelling tip positioned by a piezoelectric transducer. Using a lever/mass system with a force constant of 2·3 × 104N/m and an effective mass of 2·4g, we obtained a sensitivity of 79***V/g with a bandwidth greater than 200Hz. Accelerations smaller than 10−4g could be detected using this device.
Tunnelling spectroscopy of high‐temperature superconductors
Authors: de Lozanne A. L. , Ng K. W. , Pan S. , Silver R. M. , Berezin A.
Published: August 2011

We measured samples of La1·85Sr0·15CuO4‐y and YBa2Cu3O7‐y with a UHV low‐temperature scanning tunnelling microscope using tips made out of tungsten, aluminium and indium. The samples are either sintered pellets, single crystals, or thin films.

A wide variety of I‐V curves were obtained ranging from nearly ideal S‐I‐N and S‐I‐S characteristics, to strongly asymmetric and multiple‐peaked characteristics. The best data are obtained with thin film samples and indium tips. Large values of 2δ/kTc (∼ 11) are observed in most cases. We discuss possible explanations for these large values. New data are presented obtained with thin films of Y‐Ba‐Cu‐O made by e‐beam evaporation in our laboratory. A system of loadlocks is used to ensure that these films are never exposed to the atmosphere.
Arsenic‐terminated silicon and germanium surfaces studied by scanning tunnelling microscopy
Authors: Becker R. S. , Klitsner T. , Vickers J. S.
Published: August 2011

The epitaxial growth of As on the (111) and (100) faces of Si and the (111) face of Ge has been studied with vacuum tunnelling microscopy. The (111) faces of both semiconductors display a principally 1×1 termination, but differ with the presence of point defects on the Si(111): As‐1×1 surface and trenches separating large (∼ 100 Å) domains on the Ge(111): As‐1×1 surface. I‐V characteristics of the tunnel junction show a surface energy gap of approximately 1·9 eV for the Si(111): As‐1×1 surface and 0·9 eV for the Ge(111): As‐1×1 surface, in good agreement with recent theoretical calculations for these systems. As deposition on Si(001) results in a nominal 2×1 reconstruction of symmetric As dimers and elimination of missing dimer defects characteristic of the native Si(001) 2×1 surface. Further studies on vicinal, double‐stepped substrates shows the orientation of the dimers with respect to the substrate depends critically on the substrate temperature during the growth phase, with destruction of the single principle domain surface order occurring at temperatures in excess of 700°C.
STM study of silver intercalation into 2H‐NbSe2 crystals
Authors: Watanabe M. , Dahn D. C. , Blackford B. , Jericho M. H.
Published: August 2011

We have made scanning tunnelling microscope (STM) studies of the lattice expansion and topography of cleaved crystals of 2H‐NbSe2 which were intercalated in situ with silver ions entering along one edge of the samples. The measurements confirm the high surface mobility of silver seen in earlier electrochemical studies. The expansion measurements made with optimum 2 Å resolution showed no convincing evidence of silver staging domains. Topographic images revealed noisy patches and shallow depressions on cleaved surfaces of intercalated samples. It is suggested that these depressions might represent silver‐poor regions in the first intercalation layer.
Study of 4Hb‐TaS2 and graphite intercalation compound by STM/STS
Authors: Tanaka M. , Mizutani W. , Nakashizu T. , Morita N. , Yamazaki S. , Bando H. , Ono M. , Kajimura K.
Published: August 2011

Investigations of charge‐density waves (CDW) in 4Hb‐TaS2 and the shifted Fermi level in a CoCl2 graphite intercalation compound (GIC) were performed by scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS) A discrimination of the surface electronic structure of the octahedral structure and of the trigonal‐prismatic structure in 4Hb‐TaS2 was made successfully in terms of the electronic properties. The measured value of the charge‐density‐wave gap in 4Hb‐TaS2 at room temperature was about 85 meV. The shifted Fermi level in CoCl2‐GIC was measured to be about 400 meV.
Observation of very thin gold island films vacuum‐deposited onto MoS2 surface by STM
Authors: Uozumi Kiyohiko
Published: August 2011

A gold film of about half a monolayer in thickness was vacuum‐deposited onto air‐cleaved MoS2 surface at room temperature at a pressure of 10−5 Pa. Quasi‐two‐dimensionally grown gold islands made of several atomic layers were observed by scanning an area of 40×30 nm2. The shape of them was oblate and about 20 nm in diameter. Atomic corrugations which reflect the Au(111) surface were observed. The islands were found to move and changed their shape during the microscopy.
Observation and manipulation of polymers by scanning tunnelling and atomic force microscopy
Authors: Dovek M. M. , Albrecht T. R. , Kuan S. W. J. , Lang C. A. , Emch R. , Grütter P. , Frank C. W. , Pease R. F. W. , Quate C. F.
Published: August 2011

The properties of monolayer films of organic materials are important for a variety of technologies. We have employed STM and AFM to study Langmuir‐Blodgett films of a variety of polymers on substrates of graphite, MoS2, and Au(111) on mica. The polymers were poly(octadecyl acrylate) (PODA), atactic and syndiotactic poly(methyl methacrylate) (PMMA) and poly(2‐methyl‐1‐pentene sulphone) (PMPS). One striking feature was the degree of order observed; a second was the morphological difference between films of submonolayer thickness (long, thin fibrils) and those of at least monolayer thickness (lumpy structures arranged in domains). By pulsing the STM bias voltage to values in excess of 4V, we were able to bring about local modification of the polymer morphology.
STM imaging of the complete bacterial cell sheath of Methanospirillum hungatei
Authors: Blackford B. L. , Watanabe M. O. , Jericho M. H. , Dahn D. C.
Published: August 2011

Using a large range scanning tunnelling microscope (STM) we have obtained images of the complete outer cell wall of the archaebacterium Methanospirillum hungatei, deposited on a graphite substrate and over‐coated with an Au or Pt evaporated film. The width of the collapsed cylindrical sheath structure was found to be 5000 Å ± ***10%, which agrees closely with the value from previously published electron microscope (EM) studies. The double thickness of the collapsed sheath was found to be 160 Å ± 10%, which is about 20% smaller than that from the EM results. Higher resolution STM images taken on top of the collapsed sheaths show corrugations running perpendicular to the cylinder axis and having widths which are multiples of ∼ 30 Å, the minimum period expected from EM studies. The height of the corrugations have a minimum value of about 4 Å. The expected 2‐D crystalline structure was not seen in the STM images.
Effects of sputtering on the surface of graphite
Authors: Nakagiri Nobuyuki , Koga Yasunori , Miyazaki Yasumichi
Published: August 2011

We present STM images of the sputtered surfaces of graphite after different sputtering times. The roughness (r.m.s.) and the peak‐to‐valley distance were calculated from the digitized STM signals. The roughness versus etching time graph shows that the roughness increases with etching time initially, but does not change with increased sputtering later. The peak‐to‐valley distance is proportional to the roughness with a coefficient of 8·7. The Fourier transform shows peaks corresponding to the size of mountains created on the sputtered surfaces.
Calculation of the Bloch wall contrast in magnetic force microscopy
Authors: Hartmann U. , Heiden C.
Published: August 2011

The magnetic force microscope (MFM) is a promising analytical tool for the mapping of magnetic microfield distributions on a nanometre scale. The detailed interpretation of experimentally obtained data requires a rigorous micromagnetic analysis of the underlying magnetostatic tip‐sample interactions. We have performed model calculations yielding the MFM image contrast obtained for 180° Bloch walls using ferromagnetic microscope tips. The actually observed wall image is shown to depend critically upon the mesoscopic tip design. The spatial resolution and also values for the resulting interaction forces and tip‐sample compliances are derived.