bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of two subsampling methods for electron microscopic morphometry*
Authors: Müller A. E. , Cruz‐Orive L. M. , Gehr P. , Weibel E. R. 
Published: August 2011

SUMMARYThe purpose of the present paper is twofold. Firstly, to compare the accuracy per unit cost achieved by two different methods of subsampling micrographs from sections of a material for stereology when the sections cannot be analysed as a whole at the required magnification. Secondly, to illustrate, by means of real data, the application of some of the methods and formulae proposed in the companion paper (Cruz‐Orive & Weibel, 1981) for estimating ratios at the electron microscopic level.The final estimates of a same ratio obtained by either subsampling method (namely systematic (SQ) and systematic area‐weighted quadrats (SAWQ)) agreed in the mean and they were about equally precise. The former fact indicates that the new SAWQ method is at least as reliable as the SQ method as far as bias is concerned. The latter result is a consequence of the well‐known fact that subsampling is relatively unimportant in two‐stage sampling. Yet, SAWQ subsampling enjoys definite practical advantages over other subsampling methods in certain situations.
A modification of the oil emulsion freezing technique for freeze‐etching studies of hydrogels
Authors: Buchheim Wolfgang , Hermansson Anne‐Marie 
Published: August 2011

SUMMARYA preparation technique is described which is especially applicable to hydrous gels and allows an improved cryofixation of such systems for freeze‐etching. The method is a modification of the oil emulsion freezing technique where the gelling system is dispersed in liquid paraffin before sol‐gel transformation. Gel formation within the microscopically small sol droplets is then induced, e.g. by suitable thermal treatment. The effectiveness of this technique has been demonstrated with heat‐induced soy protein gels.
The fixation, dehydration, drying and coating of cultured cells for SEM
Authors: Brunk Ulf , Collins V. Peter , Arro Erik 
Published: August 2011

SUMMARYCultivated cells form a valuable model system for studies on the effects of various preparative protocols for scanning electron microscopy (SEM). The various effects of each preparative step can be followed in detail in the light microscope and no diffusion gradients complicate the fixation and other procedures as in the case of solid tissues.Studies on cultivated cells indicate that the glutaraldehyde component of a glutaraldehyde‐based fixative does not contribute to the effective osmotic pressure of the fixative and thus the osmolarity of the buffer, and other components, must be equalized to that of the medium in which the cells grow. Even small deviations from this ideal effective osmotic pressure will result in osmotically induced artefacts.Disturbances of pH and temperature of the cultures prior to and during fixation will result in changes in the appearance of many cellular structures such as microspikes and ruffles.We find that osmium fixation is advisable in most instances for best possible membrane preservation and that even long periods of glutaraldehyde fixation do not compensate for osmium fixation.Dehydration always results in shrinkage. Freeze drying (FD) and critical point drying (CPD) also give rise to shrinkage, the former to a lesser degree than the latter.A gold‐palladium alloy gives a less granular coating that does gold alone. When cultured cells are studied, a metal thickness of between 5 and 15 nm is usually sufficient to give rise to an adequate secondary electron production and to avoid charging even at accelerating voltages of 30–40 kV. Without treatment with OsO4 a thicker metal coating is required.
Applications of the SEM to the analysis of morphogenetic events
Authors: England Marjorie A. 
Published: August 2011

SUMMARYScanning electron microscopy (SEM) is a valuable tool for the analysis of morphogenetic events. The role of extracellular materials in primary neural induction in the early stage 5 chick embryo may be analysed by SEM as well as by histochemical techniques.During primary neural induction, extracellular materials in the early stage 5 chick embryo form a fan‐shaped region on the ectoderm anterior to Hensen's node. Fibronectin and sulphated glycosaminoglycans are present anterior to Hensen's node on the ventral ectoderm layer. It is proposed that the fanshape of extracellular materials has a dual function; as a chemical substrate to form close contacts between the inducing cells and the target ectoderm cells, and to serve as a contact guidance system for the pre‐notochordal cells.
Cell surface labelling with gold colloid particulates: the use of avidin and staphylococcal protein A‐coated gold in conjunction with biotin and fc‐bearing ligands
Authors: Tolson N. D. , Boothroyd B. , Hopkins C. R. 
Published: August 2011

SUMMARYProcedures for preparing gold colloid particles stabilized with either avidin or protein A are described. Methods of using these general utility tracers for localizing biotinylated and fc bearing immunoglobulins are outlined and, as examples of the way in which these methods can be applied, procedures for identifying epidermal growth factor receptors and surface fibronectin on ovarian granulosa cells are described.
The quantitation of electron energy loss spectra
Authors: Joy David C. , Maher Dennis M. 
Published: August 2011

SUMMARYAn interactive computer program which allows the quantitation of electron energy loss spectra is described. The program performs a standardless analysis using hydrogenic cross‐section models. The accuracy of the results obtained for a wide range of experimental conditions is typically within 20% of expected values for well characterized samples. The lack of agreed thin film standards is a limit to the improvement of the cross‐section models, but under most practical operating conditions the largest errors arise from instrumental factors such as the effect of finite beam convergence and chromatic errors in the coupling optics.
An application of EELS in the examination of inclusions and grain boundaries of a SiC ceramic
Authors: Bourdillon A. J. , Jepps N. W. , Stobbs W. M. , Krivanek O. L. 
Published: August 2011

SUMMARYElectron energy loss spectroscopy (EELS) has been used in conjunction with high resolution microscopy (HREM) to identify second phase regions in polycrystalline SiC ceramic compacts. Most inclusions were graphitic and contained no boron, though some borides were also identified. Boron could not be detected at grain boundaries, so its role in sintering remains unclear.
A microcomputer‐based system for stereogrammetric analysis
Authors: Roberts S. G. , Page T. F. 
Published: August 2011

SUMMARYA system for the quantitative analysis of stereo‐pairs of photomicrographs has been devised using a Commodore ‘PET’ microcomputer coupled to a digitizing pad, plotter and printer. The system need not use any form of stereo‐viewer and does not require any particular alignment of the photographs. Height differences, derived from parallax measurements, can be obtained quickly even by operators who might normally experience difficulties with stereoscope‐based systems due to either poor stereo vision or inexperience. Three‐dimensional coordinates, input from point‐pairs, are stored inside the computer and may be sorted to draw line profiles along any operator‐selected line. Such profiles may be referred to either the projection of the median plane of the two images or rotated (‘levelled’) to the 0° tilt plane.The operation of the system is described and illustrated using both specially‐constructed left‐ and right‐hand ‘images’ from test contours and also real SEM stereo pairs. Finally, both the potential and limitations of such a system for development and application are discussed.
Evaporation behaviour of metallic aerosol condensates
Authors: Buckle E. R. , Tsakiropoulos P. 
Published: August 2011

SUMMARYThe particles in sediment from condensation aerosols of zinc and cadmium were exposed to hot, inert gas or radiant heat to investigate the structure revealed by evaporation. The smallest prisms retained their shape but the larger ones evaporated back to the dendritic form characteristic of an earlier stage in their development. It is concluded that large prisms grow with a flawed structure because of strain present in the dendritic skeleton.On spheres, the curved surface surrounding the basal flat tends to become smoother on evaporation of the vapour‐grown layer texture although deep pits develop eventually. The texture opposite the flat, where the growth helix emerges from the solidifying melt, is more persistent. The basal flat remains flat, indicating that the high degree of crystalline perfection achieved in the slowly‐growing basal raft is retained after solidification.
Lichen weathering of rock‐forming minerals: application of scanning electron microscopy and microprobe analysis
Authors: Jones D. , Wilson M. J. , McHardy W. J. 
Published: August 2011

SUMMARYUsing the scanning electron microscope with microprobe analysis, observations have been made on the weathering of rock‐forming minerals—feldspars, ferromagnesian minerals, quartz and serpentine—principally by crustose lichens. A variety of phenomena can be recognized, namely, etching patterns, decomposition features and secondary products which can be related to differences in mineral structure and composition. Such weathering has been proved to involve the chelating effects of oxalic acid in certain lichens, although lichen acids could also be implicated.
A STEM/X‐ray microanalytical study of the equilibrium segregation of bismuth in copper
Authors: Baumann S. F. , Williams D. B. 
Published: August 2011

SUMMARYCombined scanning transmission electron microscopy (STEM) and X‐ray microanalysis have been used to detect the equilibrium segregation of bismuth to grain boundaries in copper. Quantification of the X‐ray data gives grain boundary bismuth concentrations close to those reported previously by Auger electron spectroscopy (AES). Samples tempered at low temperatures (773,873 K) had detectable bismuth concentrations at more boundaries than those samples tempered at high temperature (1073 K). There is evidence that the degree of segregation varies strongly from boundary to boundary.
Electron probe analysis of microdroplets: Factors affecting the proportionality between measured X‐ray intensity and concentration
Authors: Roinel Nicole 
Published: August 2011

SUMMARYFactors liable to limit the validity of liquid sample analysis by electron microprobe are investigated. For lyophilized samples composed of large 2–6 μm crystals, linear calibration curves may still be obtained for Na, Mg, P, Cl, K and Ca by raising the accelerating voltage to 18 kV, provided the X‐ray take‐off angle of the electron microprobe is 40°. Routinely prepared lyophilized samples are composed of discrete crystals. Their size is reproducible, depending on the composition of the dried deposit, and ranges from 0.1 to 0.5 μm for deposits mainly composed of NaCl. Within this range, the proportionality of X‐ray intensity to concentration is not affected by particle size. The concentration range for which X‐ray intensities remain proportional to concentrations is experimentally determined for the six elements above as a function of sample mass thickness and accelerating voltage. For certain elements, the proportionality constant is shown to vary with the composition of the solution. As regards chlorine concentration determinations, analysis of plasma ultrafiltrate and recovery experiments suggest that the proportionality constant is definitely 10% higher for this ultrafiltrate than for standard solutions.
A pipetting device for staining electron microscopic grids
Authors: Goodman Steven L. 
Published: August 2011

SUMMARYA simple device for staining EM grids in small batches is described. The device easily produces high quality well‐stained grids and is adaptable to most stain techniques.The most common method for staining EM grids is certainly the droplet technique (Kay, 1965) in which grids are individually floated, section‐side down, on droplets of stain. Since this requires repeated handling, electron microscopists have devised various methods for batch staining. These generally fall into two categories: partitioned grid boxes which are either immersed in, or filled with stain (Sjostrom et al., 1973; Polysciences Inc., EM Multiple Grid Staining Unit*), and clamp arrangements which grip a number of grids while they are placed in various baths (Baratz, 1976; Fisher, 1972; Gorycki, 1966; Hiraoka, 1972; Robertson & Roberts, 1972; Springer, 1974). These types of devices increase contrast and detail, over the droplet technique, by staining both section surfaces (Shalla et al., 1964). However, these require large and/or open baths of stain which are wasteful and prone to contamination. Contamination is especially critical with lead stains which precipitate lead carbonate on exposure to air (Peachy, 1959).Recently, Forsdyke (1979) described a flow‐through tube for staining. The device consists of an S‐tube with an internal grid holder. Stains are introduced into the tube by siphon. This arrangement greatly reduces the amount of stain required as well as the air‐stain interface. This paper details an adaptation of Forsdyke's device designed for easier handling, flexibility in use, and further improved staining quality.The device described herein is used to draw a few millilitres of stain directly from their containers, thus reducing contamination, air exposure, and waste. The device is used as the first receptacle for freshly cut sections on grids. The grids remain in the closed device until all sectioning and staining is completed. Since the device is closed all the sections remain damp, including those first prepared, until stained. In our laboratory we have observed that epoxy embedded tissue sections stain more evenly and intensely with uranyl acetate and lead citrate when kept moist prior to staining. Shalla et al. (1964) also reported improved staining of moist sections for another stain and different embedding plastics.
Values of K‐shell partial cross‐section for electron energy‐loss spectrometry
Authors: Egerton R. F. 
Published: August 2011

SUMMARYMaking use of a hydrogenic approximation, partial cross‐sections for K‐shell ionization are calculated for the elements beryllium to fluorine. The cross‐sections are presented graphically as a function of collection angle, for 60, 80 and 100 keV incident electrons and for energy windows of 50, 70 and 100 eV.
Electron microscopy of PbO2 deposited on a titanium substrate
Authors: Stevens R. , Gilroy D. 
Published: August 2011

SUMMARYThe nucleation and growth of lead dioxide on titanium substrate has been observed using scanning electron microscopy. The size and morphology of the PbO2 nodules have been measured in an attempt to elucidate the nucleation and growth mechanism. The effects of temperature, current density and fluorine ion addition have been qualitatively determined.The structure of a film of PbO2 formed on the titanium has been examined using TEM and found to be heavily strained and to contain lattice defects such as dislocations and stacking faults.
The microstructure of non‐ohmic zinc oxide ceramics
Authors: Trontelj Marija , Kolar D. , Kraŝevec V. 
Published: August 2011

SUMMARYThe microstructure and the nature of some crystal phases in non‐ohmic ZnO ceramics containing 0·5 Bi2O3, 0·5 CoO, 0·5 MnO and 0·5 TiO2 mol% were investigated by using various analytical techniques. The ceramics consist primarily of ZnO grains, and in addition, two titanium containing phases were found, a needle‐like Zn2TiO4 spinel phase doped with bismuth and cobalt, and a cubic‐Zn2Ti3O8 phase with some cobalt and manganese. The Bi2O3 phase among the grains was found to be TiO2 stabilized γ* Bi2O3.
Polarizing light microscopy of intestine and its relationship to mechanical behaviour
Authors: Fackler K. , Klein L. , Hiltner A. 
Published: August 2011

SUMMARYThe polarizing optical microscope has been used to observe morphologically the effect of stress on rat and bovine intestine. Collagen fibres about 6 μm in diameter were found to be biaxially oriented at approximately +30° and −30° to the longitudinal direction. The fibres are arranged in layers with the fibres in each layer densely packed in parallel undulating arrays. The undulations give rise to the extinction pattern observed in the polarizing optical microscope. The initial response to stress is straightening of the fibres. Gradual straightening of the fibres is related to the increasing stiffness of the tissue observed in the stress‐strain relationship. Once the fibres are straightened, the biaxial orientation of the fibres produces higher strength in the longitudinal direction than in the transverse direction. This organization of intestinal collagen fibres has not been reported previously and is not observed in other biaxial tissues such as skin and aorta. Thus, intestine is a unique tissue for studying the relationships of mechanical behaviour to structure and organization of collagen.
Shadow photography: An aid to microscopy
Authors: Edgerton Harold E. 
Published: August 2011

SUMMARYThe use of a small‐size electronic flash lamp, as a point source, makes possible a useful system for recording silhouette photographs of many subjects, such as plankton. Limitations of conventional microscopy methods, such as (1) small areas covered, (2) depth of field, and (3) subject motion, are partly overcome for some examples.
Optimizing thin film X‐ray spectra for quantitative analysis
Authors: Nicholson W. A. P. , Gray C. C. , Chapman J. N. , Robertson B. W. 
Published: August 2011

SUMMARYEnergy dispersive X‐ray detectors are frequently attached to electron microscopes to enable microanalysis to be performed, but because such detectors accept X‐rays generated within an appreciable solid angle, the recorded spectra usually include some spurious contributions from the instrument. This paper describes instrumental modifications firstly to reduce and secondly to permit the subtraction of the residual extraneous contributions. The probable accuracy of this subtraction procedure is examined.Results are presented showing the effects of various instrumental modifications on spectra from thin specimens and demonstrate that by careful attention to experimental details it is possible to separate the spectrum due to the thin specimen alone from all other extraneous signals.Two test specimens and a number of test procedures for investigating the analytical performance of (scanning) transmission electron microscopes are presented.Sources of error and the method of their correction when the thin specimen Bremsstrahlung is used for quantitative analysis are discussed.
Multiplexed time‐lapse photomicrography of cultured cells
Authors: Heye R. R. , Kiebler E. W. , Arnzen R. J. , Tolmach L. J. 
Published: August 2011

SUMMARYA system of cinemicrography has been developed in which a single microscope and 16 mm camera are multiplexed to produce a time‐lapse photographic record of many fields simultaneously. The field coordinates and focus are selected via a control console and entered into the memory of a dedicated microcomputer; they are then automatically recalled in sequence, thus permitting the photographing of additional fields in the interval between exposures of any given field. Sequential exposures of each field are isolated in separate sections of the film by means of a specially designed random‐access camera that is also controlled by the microcomputer. The need to unscramble frames is thereby avoided, and the developed film can be directly analysed.
Effects of glutaraldehyde fixative osmolarities on smooth muscle cell volume, and osmotic reactivity of the cells after fixation
Authors: Lee R. M. K. W. , McKenzie R. , Kobayashi K. , Garfield R. E. , Forrest J. B. , Daniel E. E. 
Published: August 2011

SUMMARYThe contribution of glutaraldehyde (GA) to the effective osmolarity of GA fixatives, the osmotic reactivity of the cells after fixation in GA, and also the duration of fixation in GA on cell volume, were investigated using cultured smooth muscle cells (SMC) and spiral aortic strips. Four fixation procedures were studied. We found that GA contributes to the total effective osmolarity of the fixatives, and that the type of buffers used for the fixatives can also affect the cell volume differently during GA fixation. After GA fixation, the cells were still osmotically reactive, regardless of the buffer types for making up the GA fixatives, so that the osmolarity of the wash buffer after GA fixation is important. However, OsO4 eliminates osmotic responses, thus the osmolarity of OsO4 fixative and wash buffer have negligible influence on the cell volume. Longer fixation time up to 4 h had no effect on the cell volume.
Simple procedures for evaluating the cryofixation of biological samples
Authors: Costello M. J. , Fetter R. , Höchli M. 
Published: August 2011

SUMMARYUltra‐rapid cooling of biological material can be achieved in the absence of cryoprotectants by using thin samples. Three methods now employed to prepare thin samples for freeze‐fracture electron microscopy are compared: contacting the sample against a liquid helium‐cooled copper surface (Heuser et al., 1979), spraying the sample with a jet of propane (Mueller et al., 1980), and plunging a streamlined copper ‘sandwich’ into liquid propane (Costello, 1980). In the first method a thin surface layer of the sample is ultra‐rapidly cooled while in the other methods the entire sample sandwiched between sheets of conducting metals is cooled. The morphology of fracture‐faces of dilauryllecithin‐water systems is used to evaluate the effectiveness of cooling methods. At optimum cooling rates the initial disordered arrangement of lipid in the lamellar (Lα) phase is preserved, giving smooth fracture faces. At slower cooling rates a worm‐like texture appears which signals the formation of molecular ordering characteristic of the Pβ, phase. All three methods are capable of cooling these lipid‐water phases as well as other more dilute aqueous suspensions without evidence of ice crystal growth or damage. Measurement of cooling rates employing miniature thermocouples embedded in samples indicates that rates for all three methods are in excess of 10,000 K/s. The propane jet (32 times 103 K/s, slope at 273 K) exposes the sample to coolant more rapidly than the sandwich plunging method (10 times 103 K/s, slope at 273 K) and therefore produces slightly higher cooling rates for samples of equivalent mass and thickness. Each method has its advantages. The contact method is well suited for tissues; the sandwich method is simple and inexpensive; the jet method can potentially produce the highest cooling rates. The last two methods yield complementary replicas.