bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic focusing in the confocal scanning microscope
Authors: Wilson T. , Hamilton D. K. 
Published: August 2011

SUMMARYThe previously reported depth discrimination property of the confocal scanning microscope, whereby detail outside the focal plane is effectively suppressed from the image, is exploited to give a high resolution system with in principle an indefinitely large depth of focus. The object is scanned axially, and the image built up as each section of the object passes through the focal plane.
Reliable use of resistance evaporation of Pt and C for high resolution freeze‐fracturing and a crystal surface image complementary to the E‐face of yeast plasma membranes
Authors: Steere Russell L. 
Published: August 2011

SUMMARYFreeze‐fracture specimens of bakers yeast plasma membrane faces were prepared in both a modified Denton DFE‐2 freeze‐etch module and a modified Balzers BAF‐301 freeze‐etch unit. Each unit was equipped with a liquid nitrogen cooled shroud, resistance evaporators with PT‐C and C sources 7 cm from the specimens and with a resistance monitor to control PT‐C shadow film thickness. Optical diffraction patterns of specimens prepared in these units have fourth, fifth or sixth order spots. Therefore, on the basis of optical diffraction patterns, resolution of yeast plasma membrane specimens prepared in these units is equivalent to or better than that obtained by others with an ultrahigh vacuum system equipped with specially redesigned electron guns. A new image with tube‐like particles in hexagonal arrays, each surrounded by six substructure particles, nearly perfect high‐resolution complement to the hexagonal array of ring‐like depressions and the six surrounding subunit depressions of the E‐face, has been revealed on the surfaces of cubic crystals (presumably ice) which formed in the gap between the P‐ and E‐faces within fissures that occurred when the samples were frozen in liquid Freon 22. When the samples were subsequently freeze‐fractured at 77 K at a chamber vacuum of 13 μPa in which the specimens were protected from surface contamination by a liquid nitrogen cooled shroud, these crystals remained attached to the P‐face but pulled away from the E‐face against which they had apparently made molecular contact.
Ice formation in aqueous systems
Authors: Rasmussen Don H. 
Published: August 2011

SUMMARYA recent treatment of the energetics of homogeneous nucleation brings classical nucleation theory into conformity with classical thermodynamic limits for supersaturated phase stability called spinodals. This energetic treatment, when extended to crystal nucleation from the liquid state, predicts that nucleation of ice cannot be avoided simply by rapid quenching. Nucleation will occur on cooling an aqueous system to a temperature called the physical spinodal because at and below this temperature icelike clusters in the aqueous system can grow without any free energy barrier whatsoever. Interpretation of microscopic observations of rapidly quenched biological systems must account for the fact that ice nuclei are certain to have been present throughout.
The relative efficiency of various fluids in the rapid freezing of protozoa
Authors: Silvester N. R. , Marchese‐Ragona S. , Johnston D. N. 
Published: August 2011

SUMMARYThe cooling efficiencies of various fluids at low temperature were compared by measuring the temperature decay in 3 μl water samples plunged into them. A simple model of cooling was used in order to discuss the results. Liquid ethane was found to produce a cooling rate of 660 K s−1, about twice that of liquid propane, while ethanol was almost as effective as ethane between 273 to 223 K. The heat‐transfer coefficient of liquid ethane was estimated to be between 1500 and 5000 W m−2 K−1, depending on the physical state assumed for the water sample. Samples of flagellated organisms, after being frozen rapidly in the above way, were freeze‐substituted by the method of Barlow & Sleigh (1979). Although this fixation did not give good definition of the microtubules of the flagellar axoneme, it exhibited reasonable tissue preservation in thin sections of the cell body. The fixation method resulted in preserved flagellar wave shapes, which were observed under the light microscope and in critical‐point dried cells examined by scanning and conventional electron microscopy. It was concluded (a) that methods for preserving the wave shape of the flagellum and for preserving its internal structure may not be compatible, and (b) that although the present cooling method (with ethane) approaches the speed required to arrest a flagellar wave, further improvements in the speed of the method are desirable.
A procedure for selecting specific areas of sections for comparative light and electron microscopic studies
Authors: Nilsen Rune , Dalen Helge , Røli Jakob 
Published: August 2011

SUMMARYThe paper describes a method which enables correlative light and electron microscopical studies to be made of specific tissue structures or of individual cells. For this purpose a new specimen marker has been constructed. The device, which is attached to the objective of a light microscope, permits the operator to examine and exactly encircle the selected area without changing the objective. The technique is illustrated by two examples using immunoelectronmicroscopy.
Preparing the liverwort Ricciocarpus natans for scanning electron microscopy
Authors: Kronestedt Eva , Echlin Patrick 
Published: August 2011

SUMMARYFreeze‐drying, and chemical preparations followed by critical point drying, were tried on the aerenchymatous plant Ricciocarpus natans, which was to be studied by scanning electron microscopy. Promising results were obtained by the freeze‐drying technique.
Correlated optical and electron microscopy of Leeuwenhoek's elder‐pith sections
Authors: Ford Brian J. 
Published: August 2011

SUMMARYA section of elder‐pith cut from Sambucus nigra in May 1674 by the pioneer Dutch microscopist, Antony van Leeuwenhoek, has been imaged under SEM, a modern Leitz photomicroscope, and the original Leeuwenhoek microscope at the University of Utrecht. The coordinated findings are examined.
Sampling of particulate suspensions for morphological evaluation: a simple method for routine and quantitative use
Authors: Aaronson Robert Peter 
Published: August 2011

SUMMARYA general method for obtaining representative samples of particulate suspensions for morphologic evaluation is presented. The key to the method is the orientation of a suitable substrate for sample collection normal to an applied centrifugal field. Precise orientation is achieved by floating the substrate on a dense water‐immiscible fluid of low viscosity. Centrifugation may be performed in common angle‐head centrifuge rotors.Two variations of the method are described which permit direct visualization or embedding of the particulate sample. Both variations are simple, can be performed routinely, and require only small amounts of material. They can also be performed simultaneously with centrifugation of the bulk samples.
Video‐enhanced microscopy with a computer frame memory
Authors: Allen Robert Day , Allen Nina Stromgren 
Published: August 2011

SUMMARYVideo‐enhanced microscopy combined with the use of a computer frame memory extends considerably the useful range of our video enhanced contrast (AVEC) methods for polarizing, double‐beam interference and differential interference contrast microscopy. Increased visual contrast is achieved by two stages of amplifications: the first optical, by using high bias retardation settings, and the second electronic. These steps are followed by a reduction of background brightness by means of a clamp voltage applied to a DC restoration circuit of the video camera. One of the limitations of the AVEC method alone is the inevitable appearance under high gain conditions of a pattern of mottle due to inaccessible dirt and defects in the lenses even of high quality. This limitation has been circumvented by storing the mottle pattern in the frame memory (frame store) and continuously subtracting it from each succeeding frame to clear the image. A major gain in image quality has resulted. In polarizing microscopy, the frame memory can be used also to subtract the image at one compensator setting from that at the equivalent setting of opposite sign, thus removing from the final image not only most of the mottle pattern but also the contrast due to the bright‐field contrast. In the polarizing microscope, these manipulations of the raw video image make it possible to observe and measure the birefringence of various organelles and elements such as microtubules, intermediate filaments and bundles of as few as a half dozen actin filaments. Since scattered light is also removed from the image, features hidden from view in the unprocessed image become visible. In differential interference microscopy, the AVEC method makes visible (i.e. detectable) many linear elements and particles that are an order of magnitude smaller than the resolution limit and not visible in the optical image. Such features are inflated by diffraction, however, to Airy disk size.
Total internal reflection fluorescent microscopy
Authors: Axelrod Daniel , Thompson Nancy L. , Burghardt Thomas P. 
Published: August 2011

SUMMARYThis review discusses applications of fluorescence microscopy using totally internally reflected excitation light. When totally internally reflected in a transparent solid at its interface with liquid, the excitation light beam penetrates only a short distance into the liquid. This surface electromagnetic field, called the ‘evanescent wave’, can selectively excite fluorescent molecules in the liquid near the interface. Total internal reflection fluorescence (TIRF) has been used to examine the cell/substrate contact regions of primary cultured rat myotubes with acetylcholine receptors labelled by fluorescent α‐bungarotoxin and human skin fibroblasts labelled with a membrane‐incorporated fluorescent lipid. TIRF examination of cell/substrate contacts dramatically reduces background from cell autofluorescence and debris. TIRF has also been combined with fluorescence photobleaching recovery and correlation spectroscopy to measure the chemical kinetic binding rates and surface diffusion constant of fluorescent labelled serum protein binding (at equilibrium) to a surface.
Scanning acoustic microscopy: a review
Authors: Wickramasinghe H. K. 
Published: August 2011

SUMMARYThe main features of the scanning acoustic microscope are reviewed with particular reference to applications in biology and non‐destructive evaluation. Recent developments on imaging the interior of solids are discussed. Proper interpretation of recorded images can lead to maps of velocity and density via the V(z) response. Further improvements in resolving power (using cryogenic liquids or high pressure gases) should make the acoustic microscope a powerful tool in many areas of science and technology.
Semi‐automatic analysis of microscopic images of the human cerebral cortex using the grey level index
Authors: Sauer Bernward 
Published: August 2011

SUMMARYA new semi‐automatic method is introduced which makes possible the quantitative examination of cresyl‐fast‐violet stained sections of the cerebral cortex. These sections are divided into measuring fields of 20 × 20 μm in a well‐defined area. A scanning procedure then automatically determines the grey level index of every single field. The image of the histological section can be compared with the grey level index data matrix by means of a plotted image, the density of the plotted points of which is proportional to the measured grey level index. By overlaying this plotted image with the original section, the boundaries of the laminae can be fixed in the data matrix. The grey level index profiles—the grey level data plot as a function of the cortical depth—after smoothing and standardization are typical of special cortical areas. The mean thickness and the mean portion of the grey level index profile of the different laminae of the striate area are compared with data from other publications.
Electron microscopy of frozen biological suspensions
Authors: Lepault J. , Booy F. P. , Dubochet J. 
Published: August 2011

SUMMARYThe methodology for preparing specimens in the frozen, hydrated state has been assessed using crystals and T4 bacteriophages. The methods have also been demonstrated with lambda bacteriophages, purple membrane of Halobacterium halobium and fibres of DNA. For particles dispersed in an aqueous environment, it is shown that optimum structural preservation is obtained from a thin, quench‐frozen film with the bulk aqueous medium in the vitreous state. Crystallization of the bulk water may result in solute segregation and expulsion of the specimen from the film. Contrast measurements can be used to follow directly the state of hydration of a specimen during transition from the fully hydrated to the freeze‐dried state and permit direct measurement of the water content of the specimen. By changing the concentration and composition of the aqueous medium the contrast of particles in a vitreous film can be controlled and any state of negative, positive or zero contrast may be obtained. At 100 K, frozen‐hydrated, freeze‐dried or sugar embedded crystals can withstand a three‐ to four‐fold increase in electron exposure for the same damage when compared with similar sugar‐embedded or freeze‐dried samples at room temperature.
The preparation of leaf surfaces for scanning electron microscopy: a comparative study
Authors: Sargent J. A. 
Published: August 2011

SUMMARYCryopreservation is the superior technique for viewing leaf surfaces in the SEM. Epidermal cells become distorted when freeze dried and disrupt the orientation of epicuticular wax structures. The latter are largely lost during critical point drying. Nevertheless, the appearance of surface structures after subjecting them to each drying method is valuable in interpreting the features observed by cryopreservation.
A double lead stain method for enhancing contrast of ultrathin sections in electron microscopy: a modified multiple staining technique
Authors: Daddow L. Y. M. 
Published: August 2011

SUMMARYA modification of the conventional method for the staining of ultrathin sections resulted in an increase in contrast of ultrastructural detail in tissues. Tissues embedded in Spurr's low viscosity embedding medium were stained with freshly centrifuged Reynolds' lead citrate for 1–5 min, rinsed in double distilled water and dried prior to staining with a saturated solution of uranyl acetate for 40 min, and freshly centrifuged Reynolds' lead citrate for 20 min.Sections treated by this procedure showed enhanced staining of cellular organelles and cytoplasmic matrix. This procedure is recommended for tissues with poor staining qualities resulting from either prolonged fixation or from inadequacies in the buffer or embedding medium used.
The characterization of the arrangement of feature centroids in planes and volumes
Authors: Schwarz Helmut , Exner Hans Eckart 
Published: August 2011

SUMMARYThe quantitative characterization of the arrangement of microstructural features is important for understanding the properties or function of materials or tissues. In this paper, the well‐known analysis of nearest neighbour distances is modified in order to separate clusters from a background of randomly disposed features and to characterize significant parameters of such sets. In addition, simple procedures are indicated to detect and to characterize regular arrangements, and computer simulated examples are used to demonstrate the efficiency of the suggested algorithms. Each step of the procedures can be used for three‐dimensional arrangements as well.
Freeze substitution sample preparation for ion microscopy of plant tissue
Authors: Ross Gary D. , Morrison George H. , Sacher Robert F. , Staples Richard C. 
Published: August 2011

SUMMARYTomato leaf sections were freeze substituted with either ethanol, n‐propanol, 20·0% acrolein: diethyl ether or acetone and then examined with an ion microscope to determine Na, K and Ca distributions. Thin sections were also examined for ultrastructural preservation using a transmission electron microscope. Generally, the 20·0% acrolein: diethyl ether and to a lesser degree the n‐propanol substituted materials demonstrated better ultrastructural preservation than the ethanol or acetone substitued materials. Ion micrographs for Na, K and Ca2+ of the 20·0% acrolein:diethyl ether and n‐propanol substituted leaves revealed a low contrast, well‐graded response with more informational content while tissue substitued with ethanol gave a high contrast response with little or no gradation. Ion losses from the leaf sections after substitution were monitored with neutron activation analysis (NAA) and initial experiments revealed significant contamination by molecular sieve desiccants. Empirically derived correction factors compensated for these contaminants; however, further experimentation utilizing silica gel as a solvent desiccant demonstrated ion retention values in excess of 80%.
Vertical sections of cultivated anchorage‐dependent cells for electron microscopy
Authors: Pentz S. , Amthor S. , Vergani G. 
Published: August 2011

SUMMARYA method is described for electron microscopic preparation of cultivated cells for vertical sections using the test chamber system TCSC‐1. The cells are cultivated on a special foil. They can be fixed and embedded directly in the chamber. After polymerization of the resin, the foil can be easily taken off and a second resin layer is poured upon the embedded cells. Then distinct cells can be marked under an inverted light microscope. The bilayer of the resin allows optimal conditions for vertical sections of anchorage‐dependent cells.
An investigation of order/disorder in a chromia‐doped rutile by high‐resolution electron microscopy
Authors: Wood G. J. , Bursill L. A. , Smith David J. 
Published: August 2011

SummaryComputer image simulations predict that the detailed atomic arrangements along extended CS defects in slightly‐reduced rutile may be identified in 500 kV high‐resolution electron micrographs. Experimental images from a chromia‐doped rutile have generally confirmed these predictions although also indicating that considerable disorder remains. The need for very careful control of sample preparation, including heat treatments, is emphasized.
The use of moiré techniques to measure rigid body displacements
Authors: Ecob R. C. , Stobbs W. M. 
Published: August 2011

SummaryThe relative advantages and disadvantages of a variety of experimental electron microscopical techniques for the measurement of rigid body displacements are considered. The principles of the application of a moiré method of great simplicity and high potential accuracy are then further discussed as are the experimental difficulties associated with the superposition of suitable reference latices on a substrate. The method is then applied to obtain an upper limit for the rigid body displacement at {111} Σ3 twin boundaries in stainless steel.
Intergrowths and defect structures in Bi9Ti3Fe5O27 revealed by high‐resolution electron microscopy
Authors: Smith David J. , Hutchison John L. 
Published: August 2011

SummaryA high‐resolution 500 kV study of the long‐period (n = 8) perovskite Bi9Ti3Fe5O27 has revealed a variety of order/disorder effects, in marked contrast to low‐n materials, as well as the occurrence of a new two‐dimensional superlattice structure corresponding to a 3 × d110 ordering along the bismuthate layers. Intergrowths of the 2‐D SL phase with the ‘usual’ perovskite/bismuthate phase, as well as sharp interfaces between these two phases, were observed and the common occurrence of steps along these interfaces suggested ledge migration as one possible transformation mechanism. Coherent intergrowths of structural elements rather similar to tetragonal‐tungsten‐bronze (TTB)‐type were also found and these sometimes appeared to be relics of the super‐lattice phase. The chemical implications of the sevarious observations are briefly discussed.
Are the core structures of dislocations and grain boundaries resolvable by HREM?
Authors: Bourret A. , Thibault‐Desseaux J. , D'Anterroches C. , Penisson J. M. , De Crecy A. 
Published: August 2011

SummaryLinear or planar defect structures have been recently studied by high resolution electron microscopy (HREM). Defects are generally difficult to solve for several reasons: they are non‐periodic and their images are limited to a very few projections along low index axes. For edge dislocations in materials having a high lattice friction, image analysis is possible and relatively fine details are now available about core radii and location of the atom pairs. The accuracy, however, of the proposed structures is within ± 0·025 nm if a priori information is known. This is not always sufficient to distinguish between several models. For a high angle tilt grain boundary the situation is comparable. A discussion of the errors introduced by several factors (object orientation, optical axis alignment) and measurement of experimental parameters is presented. At present all the information content of an image is not used: intensity profiles and quantitative comparison of simulated and experimental images should provide better ways for solving an unknown structure. However, the improvement of the point resolution is the key factor for further progress in defect analysis.
Microstructure of Sm5Ni19 intermetallic compound observed by high‐resolution electron microscope
Authors: Takeda S. , Horikoshi H. , Komura Y. 
Published: August 2011

SummaryThe method of high‐resolution electron microscopy is applied to study the microstructure of the Sm–Ni intermetallic compound whose composition is near the Sm5Ni19. Several new polytypic structures (5T, 7T, 15R and 18R) are found and their crystal structures are analysed by high‐resolution imaging method combined with electron diffraction method. Various kinds of defects are observed and the atomic arrangements near the defects are deduced; the defects include stacking faults in Sm5Ni19, intergrowth of the Sm2Ni7 or other complex structures in between the matrix of Sm5Ni19, complicated defect structure which changes the stacking sequence of Sm5Ni19, and lattice defects in the region of terminating the intergrowth.
Melamine resins, a new class of water‐soluble embedding media for electron microscopy
Authors: Bachhuber Karlheinz , Frösch Dieter 
Published: August 2011

SUMMARYMelamine‐formaldehyde, a universally used technical aminoplast, can be modified into a water‐compatible electron microscopic embedding medium. The complete processing of tissues—from fixation to sectioning—is described in this paper. It produces stable sections showing remarkable ultrastructural detail.