bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SUMMARYThe 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

SUMMARYThe 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

SUMMARYThe 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

SUMMARYA 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.
Microtomography
Authors: Sasov A. Yu. 
Published: August 2011

SUMMARYThe 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

SUMMARYThe 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

SUMMARYInflated 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.
An electron microscopy study of the phase Al3Fe
Authors: Skjerpe Per 
Published: August 2011

SUMMARYThe 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

SUMMARYA 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

SUMMARYBased 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

SUMMARYFractal 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

SUMMARYNeedle‐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

SUMMARYThe 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

SUMMARYSIMS 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

SUMMARYAutomatic 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

SUMMARYWe 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

SUMMARYWe 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

SUMMARYUnder 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

SUMMARYIn 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

SUMMARYA 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

SUMMARYDue 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

SUMMARYWe 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

SUMMARYThe 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

SUMMARYWe 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.