bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined quick freezing, freeze‐drying, and embedding tissue at low temperature and in low viscosity resins
Authors: Chiovetti Robert , McGuffee Linda J. , Little Sally A. , Wheeler‐Clark Ellyn , Brass‐Dale Jutta
Published: February 2005

The techniques of quick freezing and freeze‐drying provide an alternative to the more classical methodologies of chemical fixation and dehydration with organic solvents. It is possible to embed freeze‐dried tissue in low viscosity resins, either at room temperature or at subzero temperatures in Spurr's resin or Lowicryl K4M, respectively. The choice of embedding medium affords additional flexibility in postdrying and embedding conditions, since Spurr's resin allows vapor fixation with osmium tetroxide and thermal polymerization. Osmium tetroxide is not recommended for Lowicryl resins, but these media permit polymerization at subzero temperatures with ultraviolet light. Both resins have unique advantages that may be utilized, depending upon the purpose of the embedding.

In this paper, we discuss the details of preparing smooth muscle, from rabbit renal artery, by quick freezing and freeze‐drying, as well as methods for the embedding of the freeze‐dried tissue in both Spurr's resin and Lowicryl K4M. Although we have previously reported the ultrastructure of smooth muscle embedded in Spurr's low viscosity resin, the combination of freeze‐drying and infiltration in Lowicryl K4M represents a new approach that allows the elimination of chemical fixation, dehydration with organic solvents, and heat polymerization of the embedding medium.
Imaging of thermal and elastic surface properties by scanning electron acoustic microscopy
Authors: Holstein W. L.
Published: February 2005

Scanning electron acoustic microscopy is a new technique for imaging the thermal and elastic properties of surfaces and detecting subsurface flaws. It can be carried out in a modified scanning electron microscope. The effects of electron beam energy and phase angle on scanning electron acoustic images of the thermal and elastic properties of surfaces were studied with an alumina fiber/aluminum matrix composite for fiber directions both transverse and coaxial to the surface. Images produced with 10‐ and 30‐keV electrons at beam modulation frequencies of 80–1200 kHz appeared to be identical, with the exception of a lower signal‐to‐noise ratio for the lower electron energy. This observation suggests that the energy input from the beam can be considered to occur at the surface for electron energies below 30 keV and frequencies below 1200 kHz. Images recorded at 0° phase angle mapped regions of different thermal and elastic properties. Images recorded at 90° phase angle highlighted the boundaries between such regions. Scanning electron acoustic microscopy can image features of different thermal and elastic properties at greater depth than traditional imaging with backscattered electrons. The practical application of the technique to the study of surfaces is illustrated by the imaging of grain structure and subsurface particles for an extruder barrel.
Sectionable microcarrier beads: An improved method for the preparation of cell monolayers for electron microscopy
Authors: Hogan M. E. , Hassouna H. I. , Klomparens K. L.
Published: February 2005

Cross‐linked dextran beads provide an excellent surface for tissue‐cultured cell monolayers, and can be processed for transmission (TEM) and scanning (SEM) electron microscopy, as well as light microscopy (LM). Cells are grown to confluency on the surface of the microcarriers, where at any point aliquots can be removed and experimentally treated as desired (e.g. immunocytochemistry) providing a representative sample. Sample preparation for TEM follows standard procedures for any cell monolayer, but infiltration times must be at least doubled to allow penetration of the beads. The polymerized blocks can then be sectioned for TEM or LM with no additional steps required. SEM sample preparation involves attaching the fixed bead/cell suspension to a glass coverslip with poly‐1‐lysine, dehydration, critical point drying, and coating for conductivity. The fixed and dried sample can also be attached directly to the SEM stub as free beads and subsequently gold coated. These beads provide (1) an increased surface area of cells visible per area of thin section, (2) eliminates the careful orientation required for flat substrate methods of embedding, (3) decreases the amount of sample manipulation in the forms of re‐embedding and gluing, and (4) decreases the amount of drying artifact seen as cracking in SEM monolayer preparations.
Size changes of polystyrene latex particles in the electron microscope under controlled physical conditions
Authors: Cermola Michele , Schreil Werner‐Hans
Published: February 2005

In the early days of electron microscopy polystyrene latex particles were used as magnification standards. But in contrast to optical diffraction grating replicas made with carbon or SiO with precise line spacings resistant to electron irradiation, the latex spheres undergo changes, and conflicting reports have created some confusion. We used a highly stabilized electron microscope with controlled unchanging objective current in contamination‐free conditions to expose standard Dow latex spheres of 0.399 μm (±0,0060 μm) under defined electron beam conditions. We measured the direct intensity of the electron current impinging on the screen. Removing the object from the beam, it is possible to measure the quantity of electrons absorbed by the latex spheres, expressed in nA/μ2. We used two standard intensities: a low intensity with widespread beam, equivalent to a 2‐sec exposure time on Kodak electron image plates, and a higher intensity, obtained by increasing Condenser II current (two coarse plots towards crossover) that gives rise to a brightly illuminated observation screen. This is equivalent to a 1‐sec exposure time on the same type of plates. It could be shown that all polystyrene particles uniformly decrease in size. This loss of material manifests itself immediately after the start of irradiation. The decrease follows a hyperbolic curve and reaches values of 14.35% size decrease for low radiation intensity after 15 min. An even greater decrease (namely 16.08% size decrease) was found for medium intensity electron bombardment. Sandwiching the particles with thin carbon film has no protective effect. Particle size has been determined on the photographic plates by measuring the shadow cast by 30° angle platinum shadowing and the shrinking particle itself. Particles “shadowed” with an angle 90° permit us to measure the annular concentric “shadow” once the spheres initiate shrinking.
Automated jet polishing of transmission electron microscope specimens for in situ straining
Authors: Hardiman B. , Clark W. A. T. , Wagoner R. H.
Published: February 2005

A jet‐polishing technique has been developed for use in the preparation of microtensile specimens for HVEM examination. The technique requires the use of a pair of Teflon sheet inserts with rectangular openings in a conventional specimen holder. When inserts with optimum opening dimensions are used, specimens having elliptical holes close to the center of the gauge section are produced with large electron‐transparent areas at both ends of the long axis. Annealed metal specimens, such as brass or aluminum, prepared by this method are stronger, and can be handled more easily, than those prepared by conventional methods. An advantage of the technique is that reproducible electropolishing conditions and the automatic detection of perforation by a photocell can be used in the normal way.
X‐ray microanalysis of plants containing the platinum group metals
Authors: Parsons Patrick J. , Farago Margaret E.
Published: February 2005

It has been demonstrated that Water hyacinths, grown hydroponically in a solution containing the platinum group metals, accumulate and concentrate some of these metals in their roots. Root samples were examined in a scanning electron microscope, equipped with an energy dispersive spectrometer (SEM‐EDS), and platinum was detected on the surface. Further examination in an electron microprobe analyser (EMPA), using both wavelength dispersive spectrometry (WDS) and EDS, show platinum localized in the epidermal region of the root. Ruthenium was detected in root material taken from plants that had accumulated the complexed metal ion from solution.
Use of uranyl acetate en bloc to improve tissue preservation and labeling for post‐embedding immunoelectron microscopy
Authors: Erickson Page A. , Anderson Don H. , Fisher Steven K.
Published: February 2005

We have developed a protocol for post‐embedding immunoelectron microscopy that utilizes uranyl acetate, en bloc, as a secondary tissue fixative. Squirrel and cat retinas were fixed in 1% paraformaldehyde‐1% glutaraldehyde for one hour. Secondary fixation was by 2% uranyl acetate, en bloc, (1 hour) during tissue dehydration. The tissue was embedded in LR White or Lowicryl K4M resin. Post‐embedding immunoelectron microscopy (indirect immunogold) was performed on thin sections with antibodies to four different classes of proteins (filamentous, cytoplasmic, membrane, and extracellular matrix). The sections were then stained sequentially on drops of uranyl acetate and lead citrate, and by vapors of osmium tetroxide. Uranyl acetate fixation and/or staining of the sections by osmium tetroxide was omitted from the control experiments. Differences after secondary fixation with uranyl acetate and staining of the thin sections with osmium tetroxide were better overall preservation and enhanced contrast of the extracellular matrix, membranes, cytoplasm, and DNA. Antigenicity, as evidenced by the immunolabeling of the four proteins, was retained. Quantitation of the immunolabeling for the cytoplasmic and membrane proteins revealed significantly increased labeling densities in tissue postfixed with uranyl acetate. The improved tissue preservation and immunolabeling of proteins indicate that secondary fixation with uranyl acetate can be a valuable addition to post‐embedding immunocytochemistry.
High resolution analysis of paired helical filaments in Alzheimer's disease
Authors: Wen G. Y. , Wisniewski H. M.
Published: February 2005

Results of this comparative study indicated that electron microscopy of supra‐ultrathin sections provided the best resolution, revealing the subunit structures, globules (32 Å ± 4), and longitudinal bars (47 Å ± 6) of paired helical filaments (PHF). A three‐dimensional model of PHF substructure is therefore presented. The image of brightfield electron micrographs of isolated PHF positively stained with 2% phosphotungstic acid (PTA) also provided high resolution and revealed the presence of the beaded structures of these heavily stained filaments in the crossing‐over region of PHF. Noisy background of the negatively stained preparation of isolated PHF substantially reduced the resolution. Severe flattened morphology of this preparation further complicated the interpretation of image analysis. Darkfield electron micrographs offered high‐image contrast with low noise in the background clearly demonstrating the ropelike twisting configuration of PHF, but did not reveal the substructures of PHF. The tilting (±45°) analysis of these PHF prepared by uranyl acetate staining and rotary‐shadowing and unidirectional shadowing methods with platinum showed that these heavy metals were deposited on the top filaments (away from the carbon film on the grid) in the crossing‐over region of PHF.
Growing and embedding monolayer cells in situ in beem capsule caps for light and electron microscopy
Authors: Asafo‐Adjei Edward , Bernard Eugene F. , Hase Tatsuo
Published: February 2005

A method of growing and embedding monolayer cells in situ on the inner surface of the Beem capsule for light and electron microscopy is described. The results demonstrate that wandering cells in tissue and collected cells in suspension are readily grown on the Beem capsule and embedded in situ by a slight modification of the routine embedding procedure. The method seems to be particularly suited for studies of interactions between growing monolayer cells and various substances, infectious agents, or other types of cells added during the incubation period, where disruption by scraping and pelleting, or enzymatic reaction to remove the cells, would prevent such data from being gathered. The method is also suited for light and electron microscopic studies of minute tissue or organs, such as dissected mosquito salivary glands, whose embedding by the routine procedure is difficult.
Prediction of holz pattern shifts in convergent beam diffraction
Authors: Jackson A. G.
Published: February 2005

In general, diffraction patterns from the higher‐order Laue zones are shifted with respect to the zero‐order pattern. Expressions for the shift (t) have been derived in terms of the indices [u, v, w] of a zone, the interplanar spacing (H), and a reciprocal lattice vector [gL (hkl)] in a holz. The resulting vector possesses the direction of t in terms of a zolz reciprocal lattice vector and has a magnitude which is a fraction of that of the zolz vector. Hence, the calculation of t allows quantitative determination of the location of specific planes in a holz with respect to the zolz, thus simplifying the determination of plane indices consistent with those used in the zolz. The expressions for determining t for cubic, hexagonal close‐packed (hep), tetragonal, orthorhombic, and monoclinic crystal types are presented in a table and, when applied, allow calculation of t expressed as a fraction of a zolz vector. An example for graphite is presented to illustrate the use of the equation, and t vectors for several zones for the simple cubic system are tabulated.
Electron microscopic analysis of residual asbestos remaining in preparative vials following bleach digestion
Authors: Corn Carolyn J. , Williams Marion G. , Dobson Ronald F.
Published: February 2005

A recurring question that concerns researchers who use digestion techniques for the electron microscopic study of asbestos and ferruginous body (FB) load in tissue is: “Do appreciable numbers of the total fibers or FBs remain adhered to the walls of preparative vials after digestion?”

A test series was devised to evaluate the fiber and FB content remaining in digestion vials (glass or plastic) as well as the effectiveness of removing these particulates through variations in the rinsing procedure. The material used for all studies was digested lung tissue from a former amosite asbestos worker. The digestion procedure was based on the bleach technique of Smith and Naylor (Am. J. Clin. Pathol.: 58:250–54, 1972), as modified by Williams et al. (J. Toxicol. Environ. Health:10:627–628, 1982). Aliquots (1.5 ml) of the digests were used to create reproducible standards. These were placed in either the clean glass or polystyrene vials that had been cut to fit in an AMRAY 1000A scanning microscope interfaced with an X‐ray energy dispersive analysis system. The aliquots were allowed to remain in the vials for 10 min or 24 h before rinsing was initiated. Aliquots used for the glass vials contained 5.1 × 106 fibers and 20 × 103 FBs, while aliquots for the polystyrene vials contained 6.9 × 106 fibers and 64 × 103 FBs.

The maximum errors encountered for the glass and polystyrene vials were, respectively, 0.094% and 0.12% for fibers and 0.0098% and 0.0084% for FBs and are considered small when compared with potential sources for errors in the other stages of the preparative techniques. Also, it was concluded that if at least three thorough rinses are applied, the loss was minimal in either the glass or polystyrene vials.
Steedman's polyester wax embedment and de‐embedment for combined light and scanning electron microscopy
Authors: Norenburg Jon L. , Barrett J. Michael
Published: February 2005

Steedman's polyester wax mixture is a good, general‐purpose histological embedding medium that is suitable and convenient to use when it is desirable to combine light microscopy with scanning electron microscopy (SEM). A range of properties recommend this wax: it has a low melting temperature (37°C), is readily soluble in most dehydrating agents, results in negligible tissue shrinkage, preserves tissue antigenicity, and may even be used as a solvent for fixative agents. We prepare and embed tissues in polyester for light microscopy much as they would be for paraffin wax. For SEM, the block surface is micro‐ or ultraplaned, utilizing, respectively, a standard rotary microtome with razor blade knives or an ultramicrotome with glass knives. The block is de‐waxed in absolute alcohol and then taken to critical point drying. Similarly, sections mounted on coverslips or glass slides may be brought to the SEM after removing the wax. This enables one to bring to the SEM relatively large block faces or sections with good control over orientation. We find the results to be superior to similar procedures employing paraffin. We believe it to be more versatile and equivalent or superior to a variety of other techniques designed to gain access to the interior of tissues with SEM.
Geometric analysis of surface resonance conditions in reflection high energy electron diffraction
Authors: Peng L. M. , Cowley J. M.
Published: February 2005

A three‐dimensional analysis in reciprocal space is used to analyse reflection high energy electron diffraction (RHEED) patterns. Particular emphasis is placed on investigating the surface resonance phenomenon, the resonance conditions, and the diffraction mechanisms. The surface resonance regions defined by the resonance beam threshold conditions are related to the limits for the specular reflection spot in the diffraction pattern. The introduction of an Ewald sphere of varying radius is shown to be useful in understanding the surface phenomenon. Simulations based on the geometric theory, taking account of the surface refraction effect, describe very well the RHEED pattern geometry from the (111) surface of a platinum single crystal.
Comparison of Two Digestive Techniques for Preparation of Vascular Elastic Networks for SEM Observation
Authors: Crissman Robert S.
Published: February 2005

Two digestion procedures are now available to expose and isolate networks of vascular elastic fibers for three‐dimensional SEM observation. This study was designed to observe and elucidate the differences between the two types of digestion (sodium hydroxide vs. formic acid) and the differences between the two types of dehydration (ethanol‐critical‐point drying vs. freeze drying) used in each procedure. Canine venous valve segments, containing delicate networks of elastic fibers, and femoral arteries, containing large elastic lamellae, were used to compare the effects of the digestion and dehydration procedures on two types of vessels with different content and organization of elastic tissue. Results indicated there was no significant difference in the architecture of the elastic networks of either vessel based on the method of digestion. The major architectural changes in the elastic networks occurred as a result of the dehydration procedure used following digestion. Freeze drying is probably the best for arterial specimens due to their prominent lamellae, which give added support to maintain their normal architecture. It is suggested that both methods of dehydration be used on corresponding venous specimens containing delicate elastic networks. In this way, the investigator can benefit from the advantages of each method and overcome their respective disadvantages to get a more accurate picture of the three‐dimensional architecture of these delicate networks.
Practical Aspects of Lattice Imaging of Cellulose
Authors: Kuga Shigenori , Brown R. Malcolm
Published: February 2005

The lattice imaging technique for cellulose, a typical electronbeam‐sensitive material, was developed by using a conventional 120 kV electron microscope. Routine procedures for specimen preparation and high resolution, low dose electron microscopy are described in detail. A new, simple method was introduced for the preparation of a Formvar micronet to support the thin carbon film. The lattice imaging technique was successfully applied to algal celluloses as well as bacterial cellulose, which is composed of much smaller crystallites than the former. Digital image processing was found to be effective in enhancing the lattice images. The bacterial cellulose ribbon contained crystallites 10–25‐nm wide, which is much greater than the basic unit of cellulose fibril extruded from the cell surface. This shows that unit fibrils can fasciate with each other, merging into a single crystallite.
Postreplication labeling of E‐leaflet molecules: Membrane immunoglobulins localized in sectioned, labeled replicas examined by TEM and HVEM
Authors: Dinchuk Joseph E. , Johnson Timothy J. A. , Rash John E.
Published: February 2005

Conventional freeze‐fracture techniques were combined with immunogold labeling and with plastic embedding and sectioning to analyze the distribution of membrane immunoglobulins (mIgs) and their associated intramembrane particles (IMPs) in E‐face replicas of murine B‐lymphocyte plasma membranes. Immunogold labels were applied to cells after the process of freeze‐fracture and replication. Conventional stereoscopic transmission electron microscopic examination of sectioned, labeled replicas (SLRs) revealed that the gold‐labeled mIgs were bound to and localized on the outer leaflets of split and replicated membranes. The gold labels were attached to the external determinants of the mIg molecules, which were retained beneath and contiguous with the replicated E‐faces. The mIgs were also localized on the external surface of unreplicated microvilli. In addition, thick sections examined by high‐voltage transmission electron microscopy (HVEM) revealed large expanses of replica with well‐resolved IMPs. mIgs colocalized with small‐diameter (<60 Å) IMPs in E‐face replicas of B‐lymphocytes whose mIgs were patched by anti‐immunoglobulin. Thus, postreplication E‐surface labeling of split and replicated membranes is a high‐resolution technique that is suitable for the study of membrane protein distribution in E‐face replicas and contiguous nonreplicated tissue.
Quantitative electron microscopy applied to traditional Chinese medicine
Authors: Liu Hepei , Tang Dangsheng , Hou Yanming , Yang Yun , Wang Shulan
Published: February 2005

In the present report, quantitative electron microscopy is applied to the basic theory of traditional Chinese medicine (TCM). The theory of TCM indicates that pi (spleen in TCM) has important roles in human health. One such function of the pi is nourishing the muscles, and our work examines the ultrastructural basis of the pi actins in this role. The number of mitochondria of skeletal muscle per area was measured and analyzed. The results indicate a significant decrease in the number of mitochondria with normal structure and a significant increase in the number of mitochondria with abnormal structure in piqixuzheng (spleen energy deficiency in TCM) rats. Such changes are thought to reduce the energy supply of the muscles. After treatment with sijunzitang (herbs which invigorate functioning of the pi), the data do not show a significant difference when compared with normal rats. It is considered that the energy metabolism of the cells is one of the functions of pi.
Effects of the coherence of illumination on electron microdiffraction pattern intensities
Authors: Zhu Jing , Peng L.‐M. , Cowley J. M.
Published: February 2005

Microdiffraction is capable of revealing the local structure within an area of the specimen consisting of only a few, or a few tens of, unit cells. However, the extent to which the diffraction pattern intensities can show the local structure depends strongly on the coherence of the illumination. If the coherence width of the illumination is smaller than the diameter of the electron probe at the specimen level, the details within the diffraction spots, which indicate deviations of the local structure from the periodicity of the crystal, will be lost. The differences in the amount of spot splitting observed in microdiffraction patterns from out‐of‐phase domain boundaries, observed with two instruments, are attributed to differences in the effective source sizes.
New cryoultramicrotome with a feedback‐advance system
Authors: Wolf Bernhard
Published: February 2005

Cryoultramicrotomy is gaining in significance and use as technical improvements are made. In comparison with epoxy resin procedures, cryopreparations are more rapid; there is only a negligible loss of material and thus antigenicity is well preserved.

The present work contains some newly developed details for the exact determination of the advancement of the sample in the direction of the knife in a microtome. It is a software‐controlled ultramicrotome advance drive system with feedback regulation as well as repeatedly patented devices for advancement sensors.
Electron microscopic visualization of fatty acids in tissues
Authors: Blanchette‐Mackie E. Joan , Amende Lynn M.
Published: February 2005

Long‐chain fatty acids are important structural and metabolic functions in tissues. Fatty acids are derived from triacylglycerol‐rich particles in capillaries (chylomicrons and very‐low‐density lipoproteins) and from triacylglycerol stored in cells (lipid droplets) by the hydrolytic activity of tissue lipases.

The identification and localization of fatty acids in tissues has been considered difficult to obtain by using conventional ultrastructural techniques. However, structural findings from our studies on fatty acid transport in tissue became interpretable due to the use of many overlapping techniques. We present here these ultrastructural techniques developed to study fatty acids in tissues and review data which demonstrate lipase activity and fatty acid production from triacylglycerol in aldehyde‐fixed tissue. Accumulations of fatty acid in tissue are present as lamellar structures with periodicity of 40–50 Å in sections of resin‐embedded tissue and as hydrated myelin figures in freeze fracture replicas of unfixed and fixed tissue. Finally, a new method, using the ionization properties of fatty acids combined with freeze fracture, locates these amphipathic molecules to leaflets of membrane bilayers.
Chromatin organization in detergent‐lysed chicken erythrocyte nuclei
Authors: Seki Shuji , Nakamura Takashi , Suma Fumihiko , Murakami Masao , Mori Shigeru , Oda Takuzo
Published: February 2005

A method for electron microscopic demonstration of supranucleosomal (20–30 nm chromatin) fiber loops was developed. Chicken erythrocytes were treated with varying concentrations of detergents, such as Joy®, sodium N‐lauroyl sarcosinate, and sodium laurylsulfate, and then fixed with a formalin solution. The fixed cells were centrifuged onto an electron microscope grid, followed by staining and metal shadowing. Thin‐sectioned specimens of the fixed cells were prepared routinely. Although supranucleosomal fiber loops could be observed when any one of these detergents was used, Joy gave the best result. Electron micrographs of rotary‐shadowed specimens of erythrocyte ghosts formed by treatment with a low concentration (0.07–0.11 w/w%) of Joy showed a halolike, radial arrangement of supranucleosomal fiber loops around the ghost cells. The width of the halo was about 3μm. By increasing the detergent concentration (∼0.18% Joy), nucleosome fibers and naked DNA appeared and increased in number, indicating that the supranucleosomal fibers were disassembled by the action of the detergent. Thin‐sectioned specimens of cells treated with 0.09% Joy showed granulofibrillar chromatin radially dispersed from the nuclear cage. The fibers were thought to be identical with the supranucleosomal fibers observed in the rotary‐shadowed specimens.
High‐resolution electron microscopy and its applications
Authors: Li F. H.
Published: February 2005

A review of research on high‐resolution electron microscopy (HREM) carried out at the Institute of Physics, the Chinese Academy of Sciences, is presented. Apart from the direct observation of crystal and quasicrystal defects for some alloys, oxides, minerals, etc., and the structure determination for some minute crystals, an approximate image‐contrast theory named pseudo‐weak‐phase object approximation (PWPOA), which shows the image contrast change with crystal thickness, is described. Within the framework of PWPOA, the image contrast of lithium ions in the crystal of R‐Li2Ti3O7 has been observed. The usefulness of diffraction analysis techniques such as the direct method and Patterson method in HREM is discussed. Image deconvolution and resolution enhancement for weak‐phase objects by use of the direct method are illustrated. In addition, preliminary results of image restoration for thick crystals are given.
Application of convergent beam electron diffraction in the structural study of high‐temperature superconducting oxides
Authors: Zou X. D. , Yang C. Y. , Zhou Y. Q.
Published: February 2005

Convergent beam electron diffraction (CBED) is a powerful technique for symmetry study of crystal. It has widespread application in physics and material sciences, as demonstrated in a recent superconducting oxide study. Using this technique, we have studied Ba‐La‐Cu‐O superconductors with a transition temperature of about 40°K and Ba‐Y‐Cu‐O superconductors with a critical temperature (Tc) of about 90°K. We have found that in Ba‐La‐Cu‐O superconductors the superconducting phase La2−xBaxCuO4−y has a distorted K2NiF4‐type structure and the space group Fmmm. The two other phases in Ba‐La‐Cu‐O superconductors have also been studied. In our Ba‐Y‐Cu‐O superconductors, the Ba2YCu3O7−x compound, which is responsible for 90°K superconductivity, has two different space groups: An orthorhombic space group Pmmm and a tetragonal space group P4mm or P4/mmm.
High‐resolution electron microscopy and domain structures of pentagonal frank‐kasper phases
Authors: Ye H. Q.
Published: February 2005

The Laboratory of Atomic Imaging of Solids is dedicated to the direct imaging of materials in various fields of solid‐state sciences at the atomic or molecular level. The main programs of this laboratory are briefly described, including quasicrystals, new phases and microdomains in Frank‐Kasper phases, suboxides of metals, catalysts, minerals found in China, and molecular structure of organic substances. A recent systematic investigation of domain structures consisting of juxtaposed icosahedral columns is also presented.
Some nanostructural features in ceramics
Authors: Wen Shulin
Published: February 2005

Nanostructural features in some ceramics have been discussed and reviewed. Based on our research results and recent published investigations, many topics, such as grain, grain boundary, interface film, grain boundary engineering, microcrack, microdomain, nanodomain, domain boundary, and phase transformation, etc., have been dealt with; and many materials, such as Si3N4, β″‐Al2O3, MgO, SiC, (Hg, Cd) Te, BNN, ZrO2, PLZT, CdSe, Ca10(PO4)6, (OH)2, etc., have been involved. The results are important to understand the relation between the structure and property of materials and to improve the materials' technology.
Standardless EDS analysis of bulk and thin specimens
Authors: Wu Ziqin
Published: February 2005

A direct relationship between the x‐ray intensity ratio and the concentration ratio for bulk and thin specimens has been established by use of a revised full‐diffusion model of electron scattering. The suitable ionization cross section, the most important parameter influencing the accuracy of the calculated Cliff‐Lorimer factors, has been found after comparing the experimental intensity ratio I(L)/I(K) of eight elements (from Ge to Sn) and I(M)/I(L) of six elements (from Sm to Bi) with the calculated values. The quantitative standardless EDS analysis of bulk samples obtained by this direct method is more satisfactory than the commercial indirect method which gives the composition through ZAF correction after calculating the intensity factors of pure elements. The quantitative standardless analysis of thin samples has been improved by the suitable cross section significantly. This method has been applied to the analysis of film on substrate either without any common element or with one common element (P‐Si glass film on Si). It has also been used to calculate the intensity factors of pure bulk samples and the backscattering correction factor in Auger electron spectroscopy.
Utilization of digital image processing to study dynein arms (ATPase) in normal and immotile cilia
Authors: Kennedy John R. , Dunlap John R. , Bunn Rod D. , Edwards David F.
Published: February 2005

Tracheal ciliary cross sections were examined with scanning transmission electron microscopy and the resultant images were digitized for image enhancement. A gray‐scale histogram of each ciliary image was produced and manipulated to enhance the image for dynein arms. Tracheal epithelial tissue from the pig, rabbit, and dog, including dogs with immotile cilia syndrome, was examined by using this technique. Tissue from each animal was fixed with each of three different fixatives and sections were evaluated for preservation of dynein arms. The same fixative did not consistently provide optimal fixation for ciliary dynein arms in all three species examined. Each species, therefore, must be evaluated to determine the optimal fixative for preservation of normal ciliary ultrastructure. Digital image processing provides a mechanism for enhancing dynein arms in situ without the need for addition of special stains or the use of techniques such as image summation. With this technique it has been shown that about two‐thirds of outer dynein arms are partially or completely missing on cilia from dogs with immotile cilia syndrome.
Object‐marking, a bridge between light and analytical electron microscopy for particles characterization
Authors: Dumortier P. , De Vuyst P.
Published: February 2005

In problems of air or water pollution, or in evaluation of exposure to pathogenic dusts from biological specimens ( e.g., asbestos fibers) some typical particles can be used as tracers. As far as they have sufficiently typical properties (shape, color, anisotropy,…) particles are rapidly recognized and quantified by light microscopy (LM), even if they are very scarce or dispersed among large amounts of unsignificant ones. For accurate characterization, analytical electron microscopy (scanning or transmission) is required, but cannot be efficiently applied for low concentrations of particles. A technique using a high precision object‐marker under LM has been developed in the past by Jedwab (1975) to be used with SEM, but there is actually no equivalent for TEM. Such a technique is proposed in this paper. Its major interest resides in the greater amount of analytical data available for one single particle (high magnification morphology, crystallographic structure, chemistry). Practical results were obtained with asbestos fibers and bodies recovered from biological specimens, but the technique can be extended to many other problems concerning micron‐sized particles.
Evaluation of high‐resolution electron microscopy as a method for studying Y‐Ba‐Cu‐O superconductors
Authors: Krakow William , Shaw Thomas M.
Published: February 2005

High‐resolution transmission electron microscopes operating at 300 and 400 kV were used to investigate the crystallography and microstructure of the perovskitelike YBa2Cu3O7−x. In this paper, we evaluate the performance attainable with these microscopes both empirically and by computer modelling. Based upon the assumption that oxygen may be a key to superconductivity properties, we have also investigated the visibility of the oxygen sites as well as the heavier yttrium and barium ion positions and the lighter Cu atom positions. We propose a scheme for observing different twin orientations in these structures and hence the oxygen atom positions seen in projection for the [100] and [010].

Our observations of both thick and thin regions of Y‐Ba‐Cu‐O materials are reported as well as the problems of adjusting microscope parameters and specimen alignment to obtain interpretable images. We also give a preliminary report on the effects of heat treatment as seen in high‐resolution micrographs to assess disorder of the heavy atoms and oxygen vacancies.
Oxygen ordering and twinning in YBa2Cu3O7−x
Authors: Barry J. C.
Published: February 2005

Direct structure images of the YBa2Cu3O7−x high Tc superconducting ceramic (also called the 1–2–3 compound) at 1.7 Å resolution have been obtained for the [100] and [001] orientations. It was found that for the purposes of studying oxygen ordering in this compound it is better to use lattice images of lower resolution. The oxygen ordering was studied via the measurement of the bending of (100) and (110) lattice planes on crossing the (110) twin boundaries in crystals oriented in the [001] zone. Significant variations were found in the b/a ratios, owning to a variation in oxygen ordering, between different crystal grains, and between different regions in the same grain. For the three different 1–2–2 samples studied, the average b/a ration was 1.016, the same value as was found in neutron diffraction studies. The twin boundaries in the orthorhombic 1–2–3 phase are sharp and planar. It seems likely that the transformation from the high‐temperature tetragonal phase to the lower‐temperature orthorhombic phase is martensitic in nature. A new phase has been discovered on some of the twin boundaries. The new phase can be indexed as tetragonal with a = 7.5 ± 0.2 Å, and c = 6.8 ± 0.2 Å. It is possible that the new phase is stabilized by the stress which occurs at the twin boundaries.
Backscattered electron imaging of lectin binding sites in tissues following freeze‐fracture cytochemistry
Authors: Kan Frederick W. K. , Nanci Antonio
Published: February 2005

Recently, cytochemical techniques have been applied for localizing membrane components; however, transmission electron microscopy only provides two‐dimensional information about their distribution. Scanning electron microscopy, on the other hand, offers the possibility of examining the three‐dimensional architecture of biological samples. The fracture‐label cytochemical technique was combined with the backscattered electron imaging (BEI) mode of the scanning electron microscope to visualize the in vivo distribution of lectin binding sites on freeze‐fractured biological membranes in tissues and cells. Pancreatic and testicular tissues, fixed with glutaraldehyde, were freeze‐fractured and labeled with Helix pomatialectin‐gold or Ricinus communis I‐gold complexes. The labeled specimens were then critical‐point dried and replicated with platinum‐carbon for routine transmission electron microscopy or with carbon alone for BEL. Lectin‐gold labeling of fractured plasma and intracellular membranes observed with BEI showed a labeling pattern similar to that seen by the replica method. However, BEI‐fracturelabel provided additional information about the distribution of the labeling with respect to three‐dimensional organization of tissues and cells. Large sample areas could be examined, making this technique particularly useful as a survey method for specimens that are either differentially labeled or composed of heterogenous cell populations.
Introduction to X‐ray microanalysis in biology
Authors: Roomans Godfried M.
Published: February 2005

This paper gives an introduction to X‐ray microanalysis for biologists. The physical principles of X‐ray microanalysis and the instrumentation used in wavelength‐dispersive and energy‐dispersive analysis are reviewed. A special problem in biological microanalysis is the adequate preparation of the specimen: The preparative method must retain the localization of the element(s) of interest and allow identification of morphological features at the level of analytical resolution. Conventional preparation methods for electron microscopy have only a limited applicability in biological X‐ray microanalysis, and often cryomethods have to be used. Methods for qualitative analysis and some common pitfalls and artefacts are discussed. The possibilities and limitations of electron‐probe X‐ray microanalysis with regard to biological specimens are compared to those of other microanalytical techniques.
Low temperature techniques for X‐ray microanalysis in pathology: Alternatives to cryoultramicrotomy
Authors: Wroblewski Joanna , Wróblewski Romuald , Roomans Godfried M.
Published: February 2005

Many diseases are associated with a change in the distribution of diffusible ions at the cell or tissue level. These diseases can profitably be studied by X‐ray microanalysis. This technique for the study of ion distribution requires the use of cryoprepared specimens. Analysis at low or medium resolution can be carried out on thick or semi‐thick cryosections, or on frozenhydrated or freeze‐dried embedded bulk samples. Such analyses are particularly useful in the initial stages of an investigation or when data from a large number of samples have to be acquired. Also X‐ray microanalysis of cultured or single cells prepared by freeze‐drying can be used to rapidly collect information on a large number of cells. Analysis at high resolution has to be carried out on thin sections: Cryosections or sections of freeze‐substituted or freeze‐dried embedded tissue. For the latter type of specimens, the use of low‐temperature embedding methods may have important advantages.
Reflection high resolution analytical electron microscopy: A technique for studying crystal surfaces
Authors: Wang Z. L.
Published: February 2005

Reflection electron microscopy (REM), reflection high energy electron diffraction (RHEED), reflection electron energy‐loss spectroscopy (REELS), and energy dispersion x‐ray spectroscopy (EDX) have been comprehensively used as a technique, termed reflection high resolution analytical electron microscopy (RHRAEM), for studying the structures of the bulk crystal GaAs (110) surfaces by transmission electron microscopy (TEM). The simultaneous observations of surface topography imaging, the surface diffraction mechanism with RHEED, surface atomic inner‐shell excitations with REELS, and surface chemical compositions with EDX provide a systematic description of the atomic structure and chemical structure of the surface. The surface channelling effect has been observed in GaAs (110) with REELS, which may provide a basis for localizing surface foreign atoms with ALCHEMI. The theoretically predicted surface‐resonance wave has been observed directly in the RHEED pattern; the surface‐captured Bragg reflection wave have been identified. It is shown that surface chemical compositions can be determined by analyzing the EDX spectra obtained in the REM case. Finally, the surface monolayer resonance characteristic of the RHRAEM has been confirmed by calculations with dynamical RHEED theory.
Controlled environment vitrification system: An improved sample preparation technique
Authors: Bellare J. R. , Davis H. T. , Scriven L. E. , Talmon Y.
Published: February 2005

The controlled environment vitrification system (CEVS) permits cryofixation of hydrated biological and colloidal dispersions and aggregates from a temperature‐ and saturation‐controlled environment. Otherwise, specimens prepared in an uncontrolled laboratory atmosphere are subject to evaporation and heat transfer, which may introduce artifacts caused by concentration, pH, ionic strength, and temperature changes. Moreover, it is difficult to fix and examine the microstructure of systems at temperatures other than ambient (e.g., biological systems at in vivo conditions and colloidal systems above room temperature). A system has been developed that ensures that a liquid or partially liquid specimen is maintained in its original state while it is being prepared before vitrification and, once prepared, is vitrified with little alteration of its microstructure. A controlled environment is provided within a chamber where temperature and chemical activity of volatile components can be controlled while the specimen is being prepared. The specimen grid is mounted on a plunger, and a synchronous shutter is opened almost simultaneously with the release of the plunger, so that the specimen is propelled abruptly through the shutter opening into a cryogenic bath. We describe the system and its use and illustrate the value of the technique with TEM micrographs of surfactant microstructures in which specimen preparation artifacts were avoided. We also discuss applications to other instruments like SEM, to other techniques like freeze‐fracture, and to novel “on the grid” experiments that make it possible to freeze successive instants of dynamic processes such as membrane fusion, chemical reactions, and phase transitions.
Membrane and cytoplasmic structure at synaptic junctions in the mammalian central nervous system
Authors: Landis Dennis M. D.
Published: February 2005

Application of rapid freezing, freeze substitution fixation, and freeze fracture techniques to the study of synaptic junctions in the mammalian central nervous system has revealed new aspects of synaptic structure that are consistent with and partially explicate advances in synaptic biochemistry and physiology. In the axoplasm adjacent to the presynaptic active zone, synaptic vesicles are linked to large spectrin‐like filamentous proteins by shorter proteins that resemble synapsin I in morphology. This mesh of presynaptic filamentous proteins serves to concentrate synaptic vesicles in the vicinity of the active zone. The affinity with which the vesicles are bound by the mesh is probably modulated by the extent of phosphorylation at specific sites on the constituent filamentous proteins, and changes in the binding affinity result in changes in transmitter release.

The structural organization of the postsynaptic density in Purkinje cell dendritic spines consists of very fine strands with adherent, heterogeneous globular proteins. Some of these globular proteins probably correspond to protein kinases and their substrates. The postsynaptic density, positioned at the site of the maximal depolarization caused by synaptic currents, apparently serves as a supporting framework for a variety of proteins, which respond to and transduce postsynaptic depolarization.

At least two classes of filamentous protein fill the cytoplasm of spines with a complex mesh, which presumably contributes to maintenance of the spine shape. Membrane bound cisterns are a ubiquitous feature of Purkinje cell dendritic spines. Studies of rapidly frozen tissue with electron probe microanalysis and elemental imaging reveal that these cisterns take up and sequester calcium, which is derived from the extracellular space, and which probably enters the spine as part of the synaptic current.