bluuebunny/crossref_metadata_2025_split huggingface dataset:
Image contrast of dielectric specimens in transmission mode near‐field scanning optical microscopy: imaging properties and tip artefacts
Authors: VALASKOVIC G. A. , HOLTON M. , MORRISON G. H. 
Published: August 2011

SUMMARYNear‐field scanning optical microscopy (NSOM) is a scanned probe technique utilizing a subwavelength‐sized light source for high‐resolution imaging of surfaces. Although NSOM has the potential to exploit and extend the experimental utility of the modern light microscope, the interpretation of image contrast is not straightforward. In near‐field microscopy the illumination intensity of the source (probe) is not a constant value, rather it is a function of the probe–sample electronic environment. A number of dielectric specimens have been studied by NSOM to elucidate the contrast role of specimen type, topography and crystallinity; a summary of metallic specimen observations is presented for comparative purposes. Near‐field image contrast is found to be a result of lateral changes in optical density and edge scattering for specimens with little sample topography. For surfaces with considerable topography the contributions of topographic (Z) axis contrast to lateral (X,Y) changes in optical density have been characterized. Selected near‐field probes have also been shown to exhibit a variety of unusual contrast artefacts. Thorough study of polarization contrast, optical edge (scattering) contrast, as well as molecular orientation in crystalline specimens, can be used to distinguish lateral contrast from topographic components. In a few cases Fourier filtering can be successfully applied to separate the topographic and lateral contrast components.
Viability assessment of bacteria in mixed populations using flow cytometry*
Authors: CARON G. NEBE‐VON , BADLEY R. A. 
Published: August 2011

SUMMARYIn microbiology cells are called viable when they can be shown to proliferate. Due to long lag phases and the cells' sensitivity to the conditions around them, this definition presents problems when investigating stressed or injured cells. Colony counts only show reproduction, whilst direct single‐cell investigation can divide the status of cells into four stages: (i) reproductive viable cells, (ii) vital cells, (iii) intact cells and (iv) dead cells.Multicolour staining flow cytometry has been found to provide a powerful method for investigating these various states of viability. This is illustrated with examples with some emphasis on mixed bacterial populations.
Imaging small spinel particles in an NiO matrix
Authors: RASMUSSEN D. R. , SUMMERFELT S. R. , MCKERNAN S. , CARTER C. B. 
Published: August 2011

SUMMARYThe possibility of imaging NiFe2O4 spinel particles, with a dimension of only 1–3 nm, which are embedded in an NiO matrix has been examined. Computer image simulation studies based on the multislice method and complete, atomistic models of the particle–matrix structure have been performed. The effects of double diffraction in this geometry have been investigated, and the visibility of the particles determined for four different imaging modes: centred darkfield (CDF) imaging, high‐resolution structure imaging, ‘brightfield lattice (BFL) imaging’, and ‘darkfield lattice (DFL) imaging’. It is found that, if two complementary DFL images are obtained, the smallest particle will be detectable irrespective of its position within the foil. In the presence of an amorphous layer on the sample, however, the images at certain foil thicknesses may have insufficient contrast to be detectable above the background noise.
Past, present and future of electron holography
Authors: TONOMURA A. 
Published: August 2011

SUMMARYElectron holography, originally devised for improving the resolution of electron microscopes, progressed significantly with the advent of the ‘coherent’ field‐emission electron beam. This permitted high‐resolution microscopy (Lichte, 1986), and opened up such new fields as high‐precision electron interferomentry. This paper briefly describes the developments in electron holography.
High‐order and multipole aberrations by aberration integral and direct ray‐tracing methods
Authors: MUNRO E. , ZHU X. , ROUSE J. 
Published: August 2011

SUMMARYThis paper describes methods for computing high‐order aberrations and multipole aberrations in electron optical systems. Two approaches are discussed – the first involves obtaining aberration integrals for the high‐order aberration coefficients, in terms of paraxial rays and axial field functions, while the second method uses direct ray‐tracing through fields computed accurately by finite element or finite difference methods. The methods are illustrated by several examples, including a wide‐angle focusing and deflection system with fifth‐order aberrations, a combined magnetic and electrostatic lens, a ‘supertip’ ion source, an electron mirror with negative spherical and chromatic aberration, and a chromatically corrected quadrupole lens.
Observation of lens aberrations for very high‐resolution electron microscopy. I. Theory
Authors: SAXTON W. O. 
Published: August 2011

SUMMARYLeast‐squares fitting methods are described, currently the most accurate known, for determining the imaging aberrations and other important parameters. The data required are either the image displacement or the image diffractogram shape (or both), as a function of injected beam tilt; the analysis is largely common to the two cases. Explicit solutions are given for some simple cases (e.g. coma‐free alignment on the basis of three images only) and some promising developments are considered; the relevant aberration theory is set out in detail. Experimental work reported in a companion paper has confirmed the presence of threefold astigmatism at significant levels, but has not shown any evidence of other higher order aberrations.
HREM structure characterization of interfaces in semiconducting multi‐layers using molecular‐dynamics‐supported image interpretation
Authors: SCHEERSCHMIDT K. , RUVIMOV S. , WERNER P. , HÖPNER A. , HEYDENREICH J. 
Published: August 2011

SUMMARYMulti‐layer structures in binary systems, for example InAs/AlSb and AlSb/GaSb, as well as ternary InGaAs/AlGaAs quantum wells grown by molecular beam epitaxy (MBE) are investigated by high‐resolution electron miscroscopy (HREM). Interpretation of the micrographs requires methods of image analysis and the computer simulation of the HREM contrast. The relaxed atomic structure of the interfaces is modelled by molecular dynamics (MD) and energy minimization. The importance of strain relaxations to the image interpretation will be demonstrated and compared with the image spread and shift caused by the microscope aberrations. The possibility of revealing the compositional variations and the elastic deformations at the interfaces by HREM imaging under special defocus and sample thickness conditions will be discussed.
On the extinction coefficient in confocal polarization microscopy
Authors: WILSON T. , JUŠKAITIS R. 
Published: August 2011

SummaryThe extinction coefficient in conventional polarized light microscopes is non‐zero, even with perfect polars, solely because of the image formation process in these instruments. The imaging in confocal microscopes is different from conventional instruments and it is shown that in this case an infinite extinction coefficient results in the ideal case whereas a finite value is always to be expected with conventional instruments. Images of the same microelectronic specimen taken in both conventional and confocal polarized light microscopes are compared.
A simple and effective method for reducing wool for electron microscopy
Authors: GARLICK R. A. , ALLEN D. E. 
Published: August 2011

SummaryA simple, yet effective, method for preparing wool for ultrastructural studies is described. Usually such procedures incorporate a reduction step to convert the disulphide bonds of keratin to thiol groups, which enhances subsequent staining. This reduction process generally involves exposing the wool fibres to severe chemical treatments, which may modify their ultrastructure. Additionally, many of the reagents employed are highly toxic and unpleasant to use. A method of reduction is reported that provides images of ultrastructure at least comparable to previous methods whilst exposing the wool fibres to much milder conditions. Tris(2‐carboxyethyl)phosphine has been used to reduce both bulk samples and ultrathin sections of wool, prior to staining with silver methenamine.
Improved staining procedures for photographic documentation of phenolic deposits in semithin sections of plant tissue
Authors: GUTMANN M. 
Published: August 2011

SummarySeveral modifications of the toluidine blue O and safranin O staining procedures and a differential staining method with safranin O/azure II are described. These modifications include prestaining oxidation with sodium hypochlorite and/or poststaining treatment with iodine/potassium iodide. Greatly enhanced contrast of phenolic vacuolar inclusions is achieved by prestaining oxidation. Additionally, poststaining treatment with iodine results in a characteristic colour change of all stained tissue constituents except phenolic vacuolar inclusions. In particular, cellulose walls and cytoplasm exhibit a marked shift in colour from violet to brown (toluidine blue O) or from red to orange (safranin O). It is concluded that the methods presented can be recommended for superior photographic documentation of vacuolar polyphenol deposition in semithin sections of glycol‐methacrylate‐embedded plant tissue.
A non‐invasive photographic modification for recording early vascular development in the chick
Authors: GILES J. J. , KAVANAGH H. J. , BANNIGAN J. G. 
Published: August 2011

SummaryThe chick embryo shell‐less culture technique allows continuous observation and access to the developing vessels of the area vasculosa (AV): hence, its value as an angiogenesis assay system. The main drawback of the method is that adequately contrasted photographs cannot be achieved without injection of a contrast medium which kills the embryo making further observation of the same specimen impossible. Furthermore, injection prior to 72 h incubation has a high failure rate. In an attempt to overcome these problems, we explored the possibility of using a high‐contrast photographic process. Embryos were explanted into shell‐less culture after 48 h incubation and photographed through a stereo microscope. After trials with different films we found that Kodalith ortho Type 3 (Kodak) and Technical Pan film (Kodak) produced images of the vasculature which were identical in contrast and detail to India‐ink‐injected specimens photographed with conventional film. In addition, excellent images could be recorded as early as 48 h of incubation.
In situ formation of composite microstructures
Authors: HANDWERKER C. A. , WALLACE J. S. , FOECKE T. J. , KATTNER U. R. , BLENDELL J. E. 
Published: August 2011

SummaryMicrostructural evolution in two in situ reinforced composite systems, one produced by partial reduction and the other by grain growth, has been examined over a range of size scales using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Metal‐ceramic matrix composites were formed by the partial reduction of Al2O3–Cr2O3 solid solutions to form Cr metal particles in an Al2O3–Cr2O3 matrix which had a lower Cr2O3 concentration. In a second system, grain growth of Si3N4 during liquid phase sintering produced large, whisker‐like grains in a fine‐grained Si3N4 matrix, bonded by an oxynitride phase. The mechanisms controlling microstructural evolution in these two systems were examined.
Surface rendering in electron tomography: A heuristic approach
Authors: TOSONI L. , LANZAVECCHIA S. , BELLON P. L. 
Published: August 2011

SummaryThe final result of an electron tomographic reconstruction, computed from several projections, is a 3‐D array of data which resides in the computer memory as a long string (from 323 to 2563) of numbers. It is vital to retrieve information relevant to biology from this vast amount of numbers, and to share it with the scientific community. This is done with the use of visualization processes that may represent the most time consuming task in a reconstruction. The present article describes a technique of surface rendering designed by the authors to represent structures characterized by the presence of a number of subunits and of features such as branching, holes and cavities. The software used produces a ‘structure’ (an array containing different types of variables, peculiar to the C programming language) that is able to exploit the resources of the graphic engines embedded in modern workstations and of graphic libraries. This structure can be used to produce visual presentations in the form of wireframe‐ and surface‐rendered models with shading determined by the Gouraud algorithm.
Atomic contrast transfer in annular darkfield images
Authors: TREACY M. M. J. , GIBSON J. M. 
Published: August 2011

SUMMARYWe examine some of the assumptions underlying the standard optical equation as used for modelling high‐resolution annular darkfield (Z‐contrast) images of thin specimens. The validity of the approximations (i) that scattering occurs as spherical waves (atoms are point potentials) and (ii) that the depth of focus is infinite is found to be resolution‐dependent.The correction to the optical equation for non‐spherical wave scattering is found to be important when the probe size is of the order of 0·1 nm or smaller, and does not vanish in the ideal case of a large annular detector with no hole. Depth of focus becomes an important consideration at 100 kV for probes smaller than about 0·2 nm when the specimen thickness exceeds 10 nm. Both corrections can significantly degrade the effective point‐to‐point resolution of high‐resolution Z‐contrast images relative to that predicted by the standard optical equation.
Quantitative imaging of green fluorescent protein in cultured cells: Comparison of microscopic techniques, use in fusion proteins and detection limits
Authors: NISWENDER K. D. , BLACKMAN S. M. , ROHDE L. , MAGNUSON M. A. , PISTON D. W. 
Published: August 2011

SummaryTo determine the application limits of green fluorescent protein (GFP) as a reporter gene or protein tag, we expressed GFP by itself and with fusion protein partners, and used three different imaging methods to identify GFP fluorescence. In conventional epifluorescence photomicroscopy, GFP expressed in cells could be distinguished as a bright green signal over a yellow‐green autofluorescence background. In quantitative fluorescence microscopy, however, the GFP signal is contaminated by cellular autofluorescence. Improved separation of GFP signal from HeLa cell autofluorescence was achieved by the combination of confocal scanning laser microscopy using 488‐nm excitation, a rapid cut‐on dichroic mirror and a narrow‐bandpass emission filter. Two‐photon excitation of GFP fluorescence at the equivalent of ≅ 390 nm provided better absorption than did 488‐nm excitation. This resulted in increased signal/background but also generated a different autofluorescence pattern and appeared to increase GFP photobleaching. Fluorescence spectra similar to those of GFP alone were observed when GFP was expressed as a fusion protein either with glutathione‐S‐transferase (GST) or with glucokinase. Furthermore, purified GST•GFP fusion protein displayed an extinction coefficient and quantum yield consistent with values previously reported for GFP alone. In HeLa cells, the cytoplasmic GFP concentration must be greater than ≅ 1 μM to allow quantifiable discrimination over autofluorescence. However, lower expression levels may be detectable if GFP is targeted to discrete subcellular compartments, such as the plasma membrane, organelles or nucleus.
New polarized light microscope with precision universal compensator
Authors: OLDENBOURG R. , MEI G. 
Published: August 2011

SummaryA new type of polarized light microscope (‘new pol‐scope’) for fast and orientation‐independent measurement of birefringent fine structure has been developed. The design of the new pol‐scope incorporates a precision universal compensator made from two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at all points of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen. The sensitivity of the current instrument is 0·1 nm of specimen retardance, measured with data gathered in 0·43 s at all 640 × 480 image points. Examples of birefringence measurements in biological (microtubule arrays) and industrial (magneto‐optical disc substrate) specimens are presented.
Polarization contrast in photon scanning tunnelling microscopy combined with atomic force microscopy
Authors: PROPSTRA K. , VAN HULST N. F. 
Published: August 2011

SummaryPhoton scanning tunnelling microscopy combined with atomic force microscopy allows simultaneous acquisition and direct comparison of optical and topographical images, both with a lateral resolution of about 30 nm, far beyond the optical diffraction limit. The probe consists of a modified microfabricated silicon nitride tip mounted on a cantilever, commercially available for atomic force microscopy. The lateral resolution is further improved using ‘supertips’, by depositing a small needle on the silicon nitride tip. The combined microscopic technique is applied to thin films of indium tin oxide because of the small grain size and high surface flatness, providing high‐resolution optical contrast and limited far‐field scattering contribution. Polarization contrast is shown in experiments both changing the polarization of the incident and detected light. Approach curves, both measuring the optical signal and force interaction, show a difference in the optical coupling between p‐ and s‐polarized incident light. p‐Polarized light always provides optical contrast more correlated to topography than s‐polarized light, both for incident and detected light, in agreement with theoretical models.
Volume fraction measurement of dispersoids in a thin foil by parallel energy‐loss spectroscopy: development and assessment of the technique
Authors: BOTTON G. A. , L'ESPÉRANCE G. , GALLERNEAULT C. E. , BALL M. D. 
Published: August 2011

SUMMARYA method to determine the volume fraction of a dispersoid phase based on measurements carried out on thin foils is presented. The method involves the reconstruction of the shape and volume, by electron energy‐loss spectroscopy thickness measurements, of the analysed foil and the determination of the volume of the dispersoids using more conventional electron microscopy imaging techniques. Hence the technique does not require the use of stereology theorems. The procedure to measure the total inelastic mean free path and the linearity of its measurement for thicknesses (t) relative to the mean free path (t/λ) up to t/λ ∼ 4 is described. A method allowing the conversion of one single experimental λ‐value to various collection conditions either graphically or by parameterization is also outlined.Various imaging methods (CTEM, STEM and chemical mapping) were evaluated for their ability to retrieve the distribution of dispersoids and thus their volume. Artefacts of the technique and of the sample preparation method are also discussed. The possibility of applying such techniques using in‐column and post‐column imaging filters and the limitations of such methods are presented. Although the system has been applied to a relevant metallurgical system in the aluminium industry, it can be used for any other material provided that the values of the mean free path can be obtained.
Observations of changing fine structure in nanoscale EELS analysis of grain boundaries in stainless steels
Authors: YUAN J. , BROWN L. M. , WALMSLEY J. , FISHER S. B. 
Published: August 2011

SUMMARYIncreasingly sophisticated demands placed on metals in the modern world have stimulated the use of tailor‐designed multi‐component alloys in many applications. Solute segregation, whether due to thermodynamic or non‐equilibrium processes, can dramatically alter the alloy composition near the grain boundary leading to drastic (and often detrimental) change in the properties of the alloy. The solute segregation profile is often a nearly singular function centred at the boundary, leading to great difficulty in analysis. The traditional method of depth profiling using Auger electron spectroscopy can only examine fractured surfaces and, because of limited spatial resolution, yields laterally averaged information. Recent improvement in the efficiency of electron‐microscope‐based electron energy‐loss spectroscopy has allowed a new high‐resolution approach in analysing the chemical and electronic properties of buried interfaces on a nanometer scale, i.e. we can study the complicated details of the alloy boundary itself. As an example, we will present the result of a study on stainless‐steel alloys used in the U.K. nuclear industry. The effect of irradiation on the structure of the alloy boundary is investigated. The nanoscale change in the chemical state of the alloying element at the grain boundary is observed for the first time in situ. The result can be potentially utilized to predict the corrosion‐resistance of the stainless steels.
Two‐channel gastric pacing in patients with diabetic gastroparesis
Authors: Lin Zhiyue , Sarosiek Irene , Forster Jameson , Ross Robert A. , Chen Jiande D. Z. , McCallum Richard W. 
Published: August 2011

AbstractBackground  Our primary goals were to investigate the effects of two‐channel gastric pacing on gastric myoelectrical activity, and energy consumption with the secondary intent to monitor gastric emptying and symptoms in patients with severe diabetic gastroparesis.Methods  Four pairs of temporary pacing wires were inserted on the serosa of the stomach at the time of laparotomy to place the Enterra™ System in 19 patients with severe gastroparesis not responding to standard medical therapies. Two of the pairs were for electrical stimulation and the other two for recording. Five days after surgery the optimal pacing parameters for the entrainment of gastric slow waves in each patient were identified by serosal recordings. Two‐channel gastric pacing was then initiated for 6 weeks using a newly developed external multi‐channel pulse generator. Electrogastrogram (EGG), Total Symptom Score (TSS), and a 4‐h gastric emptying test were assessed at baseline and after 6 weeks of active gastric pacing. Enterra™ device was turned OFF during the duration of this study.Key Results  Two‐channel gastric pacing at 1.1 times the intrinsic frequency entrained gastric slow waves and normalized gastric dysrhythmia. After 6 weeks of gastric pacing, tachygastria was decreased from 15 ± 3 to 5 ± 1% in the fasting state and from 10 ± 2 to 5 ± 1% postprandially (P < 0.05), mean TSS was reduced from 21.3 ± 1.1 to 7.0 ± 1.5 (P < 0.05) and mean 4‐h gastric retention improved from 42 to 28% (P = 0.05).Conclusions & Inferences  Two‐channel gastric pacing is a novel treatment approach which is able to normalize and enhance gastric slow wave activity as well as accelerate gastric emptying in patients with diabetic gastroparesis with a goal safety profile.