bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereological microstructure analysis as a tool for quantitative quality control and property determination
Authors: Ondracek Gerhard , Pejsa R. 
Published: August 2011

SUMMARYIn the present paper the use of stereological microstructure analysis is considered—to describe quantitatively the microstructure by stereological factors and to determine indirectly the properties of two‐phase matrix materials.Three stereological factors are determined from quantities measured in optical images (microscope/epidiascope‐electronic image analyser) concerning the shape, orientation and concentration of the particles of the dispersed phase. Using these the microstructure of a two‐phase matrix material can be described sufficiently quantitatively. These stereological factors take into account the effect of the microstructure on properties such as the electrical resistivity, Youngs modulus or thermal expansion coefficient, if used in microstructure‐property equations. Using equations of this type the calculation of such properties without measuring them directly becomes possible assuming that the stereological factors of the microstructure of a two‐phase material and its phase properties are known. The way to do this is demonstrated for WC‐Co hard metals. As a consequence it follows that the combined quantitative description of microstructures and property determination (stereological microstructure analysis) extends the application of microstructure analysis in quality control and opens the way to calculate optimum microstructures to obtain special property values (tailor‐made‐materials).
Electron irradiation of dilute aluminium alloys
Authors: Mayer R. M. 
Published: August 2011

SUMMARYZone‐refined aluminium and dilute alloys with silicon and indium have been irradiated inside a high voltage electron microscope. Interstitial dislocation loops nucleated and grew in all samples, but no voids could be observed. The precipitation of silicon was observed during irradiation. The effect of alloying on the loop growth rate is discussed.
Biological freezing and cryofixation
Authors: Franks F. 
Published: August 2011

SUMMARYFreezing and freeze fixation are commonly used to achieve ultrastructural and biological preservation. Freezing in biological materials is complex because of their heterogeneous nature—water is unevenly distributed and the various domains are separated by semi‐permeable membranes. Processes to be considered include: (1) osmotic gradients leading to redistribution of water, (2) nucleation and uncontrolled growth of ice crystals, (3) recrystallization of nucleated aqueous substrate.To avoid ultrastructural deformation in biological specimens cryofixatives are commonly employed. These are water soluble molecules, able to penetrate cell membranes (e.g. glycerol and dimethylsulphoxide). Interacting strongly with water, ions and bipolymers, they give rise to metabolic and physiological changes which render them useless for X‐ray microprobe analytical studies. However, they can enable tissues to survive low temperature storage. Some plants and animals develop in vivo mechanisms which enable them to avoid or tolerate freezing.Alternative means of cryofixation have recently been developed. They rely on non‐penetrating polymers of high and specific water binding capacity. These polymers enable the extracellular spaces to be vitrified rather than frozen. Such suppression of ice nuclei enables the cell contents to be maximally subcooled, resulting in the formation of nm dimension ice crystals. Since the polymers have a low osmotic activity and do not penetrate membranes, the interior of the cell is substantially undisturbed. Also hydrophilic polymers used as cryofixatives are physiologically less active than conventional cryoprotectants at equivalent weight concentrations, and their mechanical properties render them useful as matrices for cryosectioning.
Structural and functional aspects of biological freezing techniques
Authors: Farrant J. , Walter C. A. , Lee H. , Morris G. J. , Clarke K. J. 
Published: August 2011

SUMMARYThe cooling procedures used to prepare samples for ultrastructural examination at low temperatures often differ markedly from those used to recover optimal function of cells on thawing. The implications of these differences are reviewed. Damage and alteration to the structure and function of the cells may be caused by the high concentrations of cryoprotective agents such as glycerol or dimethyl sulphoxide (DMSO) often added to reduce ice crystal artefacts. Under the rapid cooling conditions commonly employed for structural studies, these additives are not cryoprotective; low rates of cooling are necessary for them to be effective. Rapidly cooled cells that contain intracellular ice are only injured during re warming so their structure may be as yet unaltered by any damaging effects at low temperatures. Most cells able to recover on thawing are grossly shrunken at low temperatures but since they are potentially functional they are of interest structurally. These cryobiological principles are illustrated with freeze‐fracture, freeze substitution and functional assays. The cell types chosen were Chlorella sp. and mammalian tissue culture cells.
Cold stage for electron probe microanalyser
Authors: Taylor Peter G. , Burgess Antony 
Published: August 2011

SUMMARYInvestigators wishing to examine and analyse biological specimens in the electron probe microanalyser (EPMA) in as near the original physiological and morphological state as possible have found that a cold environment is necessary to reduce the rate of sublimation and radiation damage to a low level.A low temperature cold stage has been designed and constructed for this purpose, to be used with a J.E.O.L. JXA 50A microanalyser. The cold stage will maintain the specimen holder at a temperature of 108 K for a period of 2 h before refilling of the liquid nitrogen Dewar flask becomes necessary. The fitting of a cold stage in place of the regular room temperature standard stage greatly increases the risk of contamination from the condensation of residual gases present in the specimen chamber. We have constructed an ami‐contamination plate (cold plate) that prevents this.
Freeze‐fracture for scanning electron microscopy
Authors: Haggis G. H. , Phipps‐Todd Beverly 
Published: August 2011

SUMMARYTwo different freeze‐fracture methods are explored for preparation of biological material for scanning electron microscopy. In the simpler method the tissues are first fixed and dehydrated. They are then frozen and fractured, and after thawing, critical‐point dried. This method has already been used in a number of studies of animal tissues (heart, liver, kidney). It is applied here to the examination of plant material (leaf mesophyll cells). In the second method tissues, or cells, are first infiltrated with cryoprotectant (dimethylsulphoxide) then frozen and fractured, and not fixed until after thawing. The fixed tissues are finally dehydrated and critical‐point dried. This method also has previously been used in the study of animal tissues, and is applied here to carrot protoplasts, chicken erythrocytes, and leaf mesophyll cells.
Cryo‐ultramicrotomy and myofibrillar fine structure: a review
Authors: Sjöström Michael , Squire John M. 
Published: August 2011

SUMMARYIn the past, the techniques of electron microscopy and X‐ray diffraction have both been very informative about the ultrastructure of the muscle myofibril. But X‐ray diffraction patterns are difficult to interpret unambiguously and until now specimen preservation in plastic embedded muscle has been sufficiently poor to make it difficult to use electron micrographs of muscle as a means of interpreting the available X‐ray diffraction evidence.The possibility of using ultrathin sections of frozen muscle, in which the disruptive steps of chemical dehydration and plastic embedding can be avoided, promises to help to bridge the information gap between present X‐ray and electron microscope results. For this reason we here review the application of the cryosectioning technique to muscle, we assess the technique in terms of the improvements in preservation which have so far been obtained and which might be expected and we discuss some of the many potential advantages and uses of this technique for studies of muscle ultrastructure and function.It is concluded that this technique should be developed vigorously since it promises to play a very important role in muscle research in the future.
A light microscope attachment for isolating small specific areas from slide embedded monolayers: an aid in electron microscopy
Authors: Bird R. G. , Chapman P. 
Published: August 2011

SUMMARYBased on the idea of a spring‐loaded microscope objective, a boring attachment has been designed and constructed to fit a standard revolving multi‐objective holder. It enables many small specific areas of a slide embedded specimen to be selected, ringed and bored out without removing the slide from the microscope stage.
Principles of sampling, preparation and constituent selection for microphotometry in measurement of maturation of sedimentary organic matter
Authors: Bostick N. H. , Alpern B. 
Published: August 2011

SUMMARYSamples may be obtained from outcrops, cuttings, cores, modern sediments and old collections. Coals, brown or grey siltstones and fine‐grained sandstones generally yield the most satisfactory organic matter for maturation analysis, while red beds and evaporites are often barren. Shales with a high organic content are not especially desirable for optical studies of maturation because the organic matter is likely to be very fine‐grained and high in pyrite. The whole rock or a concentrate of organic particles may be prepared for microscopical study, the former being preferred for analysis of solid bitumens and fluorescence study, the latter for measurement of vitrinite reflectance, microspore translucency and refractive index. Crushing, ultrasonic disintegration, handpicking, heavy liquid separation, flotation, settling, sieving and demineralization with HC1 and HF are used to concentrate organic particles. Preparations include polished rock slabs, concentrate briquettes and strew mounts.The constituents with the lowest maturation in a rock must be selected if maturation indigenous to the rock is to be measured. Organic matter that has been previously altered at its site of origin, reworked and altered during diagenesis, or redeposited from older rocks, must be excluded from consideration. The organic constituents are recognized most easily by reflected light microscopy. A combination of fluorescence and reflectance techniques is useful for low rank samples.
Optical properties of oxidized vitrinite and exinite
Authors: Prado J. G. 
Published: August 2011

SUMMARYThe optical properties of vitrinite and exinite from a low‐rank coal (volatile matter = 37.3% dry ash free) oxidized with air on a fluidized bed at 300°C over periods up to 24 h have been studied. Reflectivities in air and oil of the unoxidized maceral areas within the particles and of the oxidized rims were measured at five wavelengths between 436 and 644 nm and the absorptive and refractive indices calculated using Beer's equation. The reflectivity spectra and the variation of the optical properties of the oxidized macerals with time of oxidation are discussed. It is concluded that the spectrum of oxidized exinite is a good parameter to indicate oxidation and that in low‐temperature oxidation experiments, when no oxidation rims appear, the inner part of the particles may not be oxidized.
Quantitative characterization of the texture of coke
Authors: Patrick J. W. , Sims M. J. , Stacey A. E. 
Published: August 2011

SUMMARYCoke texture can be shown to be a factor of prime importance in considerations of coke strength and a method has been developed whereby relevant details of the coke texture can be obtained from the microscopic examination of polished coke sections using a Quantimet 720 image analyser. The specimens examined consisted of 10 mm cylindrical cores of the same type as those used for the diametral‐compression test of tensile strength, the cores being mounted in resin and prepared as polished blocks. For a variety of cokes produced on the laboratory scale, and covering a range of porosity from 40 to 60%, the median sizes of pores and pore walls, as determined under the experimental conditions used, varied from about 50–80 μm and 60–120 μm respectively. The number of pores per field of view examined, varied widely from 20 to 220 and the average pore perimeter per field analysed, varied from 70 to 140 mm. The results indicated correlations between the median tensile strength and several of the textural parameters, such as the volume porosity and the average pore‐wall thickness.
The use of light and electron microscopy in the study of experimentally altered spores and pollen grains
Authors: Sengupta S. , Muir M. D. 
Published: August 2011

SUMMARYPlant spores and pollen grains were heated to different temperatures, from room temperature to 350°C at atmospheric pressure, in a nichrome‐wire resistance furnace, and to different temperatures from 100 to 500°C at 1 kb pressure in a modified apparatus normally used for triaxial rock‐deformation studies. In the temperature and pressure experiments, the grains were mixed with silica sand and sea water in the proportions of 1:4:5. For optical microscopy, the pollen grains were mounted in glycerine jelly: for SEM, they were mounted on aluminium stubs rinsed with water and sputter‐coated with gold. STEM and HVEM were used on thick sections of spores of Lycopodium clavatum embedded in Epon‐Araldite.The different layers of the spore or pollen‐grain (i.e. exine+intine) degrade differently. The ornamented part of the exine (the sexine−mainly composed of sporopollenin, lipids and polysaccharides) begins to degrade at approximately 300–350°C and 1 kb pressure, exposing the non‐ornamented nexine layer. The nexine seems able to withstand high temperatures and pressures. Between 300 and 500°C with 1 kb pressure, the grains begin to form an amorphous mass. Compared with other work in which the outer exine layer of L. clavatum was removed by oxidation with ozone, here the same layer was gradually removed by pressure and temperature effects. The smell of phenolic compounds is very prominent at higher temperatures (400°C with 1 kb pressure and upwards) and production of other gas, unidentified so far, is evident from about 300°C and 1 kb pressure.The degraded exposed nexine layer at 500°C resembles thin plates in the SEM. A similar structure was also found in L. clavatum heated at 300°C and 1 kb pressure. The exposed nexine of L. clavatum was sectioned and examined in the TEM, which showed the trilamellar units, of which the main bulk of the nexine is composed, to be very resistant to high temperatures and pressures. STEM and HVEM have been used to study globular structures observed in the L. clavatum spore cavity.
A note on spherical structures in chars from vitrinites of coking rank
Authors: Goodarzi F. , Murchison D. G. 
Published: August 2011

SUMMARYSpherulitic aromatic structures with relatively simple optical characters that form as a transitional phase in the development of mosaic textures are well known in pitch fractions and certain polymers when carbonized. Their occurrence in coal macerals that soften prior to the formation of a mosaic is less certain. Other spherulitic structures, much larger in size than mesophase spherules, can, however, develop from vitrinites with a high potential fluidity under certain carbonization conditions, when fast heating rates are employed. These bodies, besides displaying optical characters that indicate structural symmetry, also show mosaic textures.
Organometallic and organometalloid compounds as standards for microprobe analysis of epoxy resin embedded tissue
Authors: Roomans Godfried M. , Gaal Henk L. M. van 
Published: August 2011

SUMMARYX‐ray microanalysis of phosphorus, transition elements and heavy metals in biological tissue is frequently carried out on thin sections of specimens embedded in epoxy resin. A logical choice for the quantitive microprobe analysis of these specimens is a standard, consisting of a homogeneous solution of the elements of interest in the epoxy resin. Four kinds of compounds were found suitable for this purpose: (1) phenyl compounds containing group Vb elements, (2) cyclopentadienyl‐derivatives, (3) a pentanedione derivative (acetylacetonate) and (4) complexes of metals with dialkyldithiocarbamates. In the latter case, the standard also contains sulphur. Standards for P, Sb (1) Mn, Fe (2) Ni (3) Cu, Zn, Cd, Hg, Pb, Bi (4) were prepared in Epon 812 or Spurr epoxy resin. The compounds were mixed with the resin (without accelerator) to which some propylene oxide may be added, and dissolved immediately or after short heating. The maximal concentration of metal was in the order of magnitude of several promilles to 1%. Solubility in the Spurr resin was better than in Epon 812. After addition of the accelerator, polymerization was carried out as usual. The compounds used are commercially available at low cost or can be easily prepared.
X‐ray, light and scanning electron microscopy of manganese sulphide and lead inclusions in free‐cutting steel
Authors: Dench W. A. , Pugh D. J. , Stoddart C. T. H. 
Published: August 2011

SUMMARYMnS and Pb inclusions in some commercial free‐cutting steel bars are of high length‐to‐thickness ratio and are also sinuous in form. Individual inclusions are then not seen in their entirety in metallographically polished longitudinal sections examined in the light or scanning electron microscope. X‐ray microradiography of thinned specimens forms images of inclusions that lie completely within the thickness of the specimen. By using both Co and Fe radiation, MnS, Pb and the steel matrix may all be clearly distinguished.
On The Feasibility of Imaging, By High Resolution Electron Microscopy, Isolated Individual Sheets of Graphitic Carbon
Authors: Millward G. Robert , Jefferson David A. , Thomas John M. 
Published: August 2011

SUMMARYA comparative survey of computer simulated and experimentally obtained images shows that it is feasible to observe, end‐on, isolated single sheets of trigonally bonded carbon atoms in graphitic substances directly by electron microscopy, provided that certain imaging conditions are employed. For a typical commercial instrument (Philips EM300 with a spherical aberration coefficient of 1.6 mm) authentic images are found whenever the objective lens is set at underfocus positions between 65 and 110 nm, with optimum contrast occurring near the ‘Scherzer’ imaging condition of 95 nm underfocus.At this latter focus position the fringe contrast is maximal when the sheet extends in the direction of the electron beam for a distance of about 5.5 nm; but sheets as narrow as 1.0 nm (i.e. containing some four widths of benzene rings in the direction of the electron beam) should be detectable.
Particle Number or Density Can Be Stereologically Estimated By Wedge Sections
Authors: Miles R. E. , Davy Pamela 
Published: August 2011

SUMMARYThe information derivable from the traces of a two‐phase medium on the faces of a wedge probe close to its edge is systematically investigated. It is shown that in principle the integral of gaussian curvature over a smooth phase‐phase interface can be estimated from this information. In simple terms, the method allows one to estimate the number of cherries in a cherry‐cake (or more generally the Euler topological characteristic of the cavities in an Emmental cheese) on the basis of observations on and near the edge of a wedge‐shaped slice of the cake (or cheese).
Recovery of Osmium Tetroxide From Used Fixative Solutions
Authors: Kiernan J. A. 
Published: August 2011

SUMMARYA technique has been developed whereby osmium tetroxide (OSO4) is reclaimed from solutions used as fixatives in electron microscopy. The osmium compounds in the collected residues are oxidized to OSO4, which is then extracted into carbon tetrachloride. Osmium dioxide is precipitated with alcohol, recovered by filtration and dried. This is a safe and convenient form in which to store the reclaimed material. An aqueous solution of OSO4 is prepared by oxidizing an aqueous suspension of osmium dioxide with hydrogen peroxide.The reclaimed product has been used for post‐fixation of aldehyde‐fixed specimens for transmission and scanning electron microscopy and for histochemical procedures in light microscopy. It is evidently just as satisfactory for these purposes as the newly bought substance. The equipment and reagents required for the reclamation procedure are readily available and inexpensive. 5 g can be recovered for the cost of less than 150 mg of new osmium tetroxide.
An inexpensive controlled temperature stage which allows high resolution optical microscopy
Authors: Mersey Brent , McCully M. E. , Fatica Enzo 
Published: August 2011

SUMMARYSpecifications are given for an inexpensive controlled temperature microscope stage which facilitates observation of living cells at temperatures down to 268 K. The design makes it possible to use an oiled 1.4 N.A. condenser thus allowing observation at high resolution and giving phase contrast and Nomarski interference contrast images of high quality.
Charging effect in electron‐irradiated ice
Authors: Fuchs Wolfgang , Brombach Jobst D. , Trösch Walter 
Published: August 2011

SUMMARYTo maintain the original distribution pattern of diffusible elements in biological samples, electron probe microanalysis is carried out with frozen hydrated bulk specimens and cryosections, analysed at temperatures below 130 K. Ice has a very low intrinsic conductivity at this working temperature and surface‐ and space‐charging appears, when uncoated specimens are irradiated with non‐penetrating electrons. Although coating with a grounded conductor abolishes the surface potential, the build‐up of an internal space‐charge field is possible, depending on the sample thickness and beam voltage used. Consequently, the geometry of the X‐ray source volume and the spectral distribution of the emitted continuous and characteristic X‐rays are affected. To simulate the situation for microanalysis of frozen hydrated specimens the charging process in electron irradiated ice is studied by recording simultaneous specimen currents from the top and bottom of ice layer preparations. The external currents yield information on the build‐up of internal space‐charge fields which result from the balance of charge injection, storage, and transport.Irradiation of uncoated bulk specimens with a finely focused beam results in the build‐up of a space‐charge field close to the surface, which causes a reduction of the depth of microprobe analysis. In coated bulk specimens the induced conductivity renders possible a current flow to the front electrode, thereby limiting the space‐charge field. Sections with an effective rear electrode will not charge appreciably if the electron range is larger than about half the section thickness.
Interference reflection microscopy of adhesion of Amoeba proteus
Authors: Opas Michal 
Published: August 2011

SUMMARYA simple method of observing the adhesive behaviour of large cells by means of interference reflection microscope is described, and some observations of mono‐podial Amoeba proteus are presented. Amoebae may contact with the substratum at any point along the long axis of the cells. Points of contact are usually few, small and temporary. Frequently the cell surface within the contact points oscillates, changing the separation distance from the substratum.
Nascent cellulose fibrils in green plants
Authors: Leppard Gary G. , Colvin J. Ross 
Published: August 2011

SUMMARYThe notion of a hydrated, swollen, linear aggregation of extended β1 → 4 polyglucosans as a transient nascent phase in the biosynthesis of a bacterial cellulose microfibril from Acetobacter xylinum may be broadened to include cellulose biosynthesis by green plants, on the basis of present experimental evidence.