bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of the transport properties of polymer composites by geodesic propagation
Authors: BRÉMOND R. , JEULIN D. , GATEAU P. , JARRIN J. , SERPE G. 
Published: August 2011

SummaryThe purpose of this study is to estimate the transport coefficients (diffusion, permeability) of polymer composites from two‐dimensional images of these media (polyethylene/polyamide alloys) obtained by the scanning electron microscope. The main characteristics of the media investigated are a wide morphological variability (nodular and lamellar media) and transport properties that are very different according to the phase. The computation tools used must accordingly have a wide range of validity. The idea of the proposed algorithm is to calculate the distance from an edge of the image, with a modified distance according to the phase crossed. The results obtained are compared with those obtained by finite difference integration of Fick's laws, and with permeability measurements of hydrocarbons in the materials.
Intracellular localization of the antitumour drug adriamycin in living cultured cells: A confocal microscopy study
Authors: MESCHINI S. , MOLINARI A. , CALCABRINI A. , CITRO G. , ARANCIA G. 
Published: August 2011

The intracellular distribution of the anthracyclinic antibiotic adriamycin in living cultured cells has been investigated by confocal microscopy.In human melanoma cells (M14), adriamycin was localized inside the nuclei. When adriamycin‐treated M14 cells were allowed to recover in drug‐free medium, a complete efflux of the drug from the nucleus was revealed. In recovered cells, a weakly fluorescent signal was observed in the perinuclear region. When M14 cells were recovered in a medium containing colcemid, a microtubule depolymerizing agent, the drug transport from the nucleus to the cell periphery appeared to be inhibited, suggesting that the microtubule network is strongly involved in drug transport mechanisms. In multidrug‐resistant (MDR) cells the intracellular location of adriamycin was shown to be noticeably different from that of the parental wild‐type cells. In particular, in resistant human breast carcinoma cells (MCF‐7), adriamycin appeared to be exclusively located within the cytoplasm whereas the nuclei were shown to be completely negative. When adriamycin treatment was performed in association with MDR revertants, such as Lonidamine (inhibitor of the energy metabolism) or verapamil (inhibitor of the P‐glycoprotein efflux pump), a marked enhancement of the cytoplasmic signal was observed in resistant cells. Under these conditions, adriamycin appeared concentrated in the perinuclear region, but the nuclei were still negative. Confocal microscopy proved to be a very useful method for the study of the intracellular transport of fluorescent substances, such as anthracyclinic antibiotics, and for the investigation of the multidrug resistance phenomenon in tumour cells.
LIP‐model‐based three‐dimensional reconstruction and visualization of HIV‐infected entire cells
Authors: GREMILLET P. , JOURLIN M. , PINOLI J.‐C. 
Published: August 2011

SummaryThis paper presents a global solution from acquisition to visualization for the three‐dimensional reconstruction of cell sections. Original techniques are proposed for the correct handling of the geometrical section distortions, and a new interpretation based on the logarithmic image processing (LIP) model is applied in order to create normalized grey‐level sections where these are missing. Finally, a new method for generating a mesh of triangles to describe the envelope of the reconstructed cell is proposed, as well as a visualization mixing image synthesis and grey‐level information. The product allows the user to explore the reconstructed cellular block in any desired direction, by showing user‐defined grey‐level sections inside the block mixed to a synthetic view of the cell envelope.
A simple method for processing individual oocytes and embryos for electron microscopy
Authors: NOGUÉS C. , MARTÍ M. , BOADA M. , PONSÁ M. 
Published: August 2011

SummaryA simple method for handling individual specimens that must be processed either for scanning or transmission electron microscopy studies is described. For scanning microscope processing, dehydration is carried out with samples enclosed in small cages made from TAAB capsules in which top and bottom are substituted by plankton nets, and for transmission electron microscopy, samples are pre‐embedded in agarose. This procedure significantly reduces mouth pipetting, dissecting microscope observations, is less labour intensive and, most importantly, reduces sample loss.
A novel method of Z‐contrast imaging in STEM applied to double‐labelling
Authors: TICHELAAR W. , FERGUSON C. , OLIVO J.‐C. , LEONARD K. R. , HAIDER M. 
Published: August 2011

SummaryA novel method of Z‐contrast imaging in the scanning transmission electron microscope (STEM) is presented. The technique relies on the element dependence of the angular distribution of the scattered electrons, and is realized with a detector consisting of a set of concentric rings. It is possible to discriminate 9‐nm colloidal gold and silver specifically distributed on thin sections. In addition to this practical work, numerical evaluations are used to assess the method. With two smaller markers, this approach will be useful in discriminating closely spaced antigenic sites when steric hindrance occurs with double‐labelling using probes of different sizes.
High‐pressure freezing of cell suspensions in cellulose capillary tubes
Authors: HOHENBERG H. , MANNWEILER K. , MÜLLER M. 
Published: August 2011

SummaryA procedure for efficient cryoimmobilization of large volumes of cell suspensions or micro‐organisms by high‐pressure freezing is described. This procedure uses transparent, porous cellulose capillary tubes with an inner diameter of 200 μm, into which the suspensions are drawn by capillary action. The tubes are processed by high‐pressure freezing and freeze‐substitution as if they were tissue samples. Centrifugation of suspensions at low temperatures is no longer necessary and cryopreparation is greatly facilitated.A very high yield of adequately frozen specimens is obtained due to the constant, defined sample geometry. This approach can also be used to process suspensions by conventional chemical fixation, eliminating the need to embed pellets in low‐melting‐point agarose, for example, prior to chemical fixation.The preparation procedure is demonstrated with suspensions of nematodes, paramecia and bacteria.
Nucleotide and protein distribution in BrdU‐labelled polytene chromosomes revealed by ion probe mass spectrometry
Authors: LEVI‐SETTI R. , CHABALA J. M. , SMOLIK S. 
Published: August 2011

SummaryDetailed chemical maps of BrdU‐labelled polytene chromosomes of Drosophila melanogaster, obtained by imaging secondary ion mass spectrometry, reveal separately the distribution of DNA and proteins in the chromosomes. The thymidine‐analogue BrdU within the chromosomal DNA is localized by detecting the Br− secondary ion signal, while both nucleic acid and protein content are mapped through the abundantly emitted CN− signal. This novel approach supercedes, and helps explain the origin of, the banding patterns that are observed by conventional staining techniques. The high spatial resolution and chemical and isotopic sensitivity of this technique should enhance the localization of specific genes by in situ hybridization in mitotic chromosomes.
Application of back‐scattered electron imaging to the study of the lichen‐rock interface
Authors: WIERZCHOS J. , ASCASO C. 
Published: August 2011

SummaryIn the study of the lichen‐rock interface, light microscopy, scanning electron microscopy (SEM) in secondary emission mode and transmission electron microscopy are the most commonly used techniques. As these methods have some limitations, there is a need to explore other techniques for observation of the lichen‐substrate interface. One of the most promising methods is the application of SEM in the back‐scattered electron (BSE) emission mode.The thallus ofAspicilia intermutans(Nyl.) Arn. growing on granitic rock was examined by SEM in BSE mode. The detailed preparation of transverse sections of the lichen‐rock contact zone is presented. The BSE scanning images of the lichen‐rock interface obtained present new insights into the ultrastructural features of the biological components, providing more information about the biogeophysical and biogeochemical weathering of rock.
Semi‐automated measurement of true chord length distributions and moments by video microscopy and image analysis
Authors: OLDMIXON E. H. , BUTLER J. P. , HOPPIN F. G. 
Published: August 2011

SummaryThe distribution of the lengths of airspace chords in pulmonary parenchyma characterizes many architectural features of the alveoli and alveolar ducts. Laborious to obtain manually, the distributions and density functions may be acquired semi‐automatically by video microscopy, digitization and image processing. The accuracy of the estimation is influenced by the microscopical methods and also by the techniques used (i) to convert the digitized grey‐scale picture to a two‐valued image, (ii) to collect the chord lengths and (iii) to compensate for finite field widths. The last problem arises because some chords are completely visible within a field while others are only partially seen, since one of the two air‐tissue boundaries lies outside the field of view. This error systematically biases the observed distribution. This paper contains solutions to hardware, software and analytic problems encountered while developing the capability to measure airspace chord length density functions semi‐automatically. Formulas for estimating the true chord length density function from samples of observed chord lengths are presented. Also given are formulas for the estimation of the first and second moments of the true chord length distribution from the means of observed chord lengths. These techniques of image preparation and analysis should be suitable for characterizing particle, grain or cell size distributions, especially where many profiles fall partially outside the field of view.
A simple algorithm to measure the volume‐weighted and number‐weighted mean volume of particles
Authors: LAROYE G. J. , GRANT K. 
Published: August 2011

SummaryAn algorithm is presented which offers an alternative approach for measuring volume‐ and number‐weighted mean volume and standard deviation of particles. Using a computer‐assisted manual method the following intermediate steps are performed automatically: generation of linear probes emanating from the sampling point of the object and intersecting the profile periphery, measurement of their lengths, and measurement of the area of the transect required for estimating the standard deviation of the volume‐weighted mean volume. By first tracing manually the outline of the periphery of the object with a cursor, on a magnetic tablet or on an image acquired into the computer with a video camera, the location of all pixels of the periphery is registered and the area of the transect is measured concurrently. The computer is informed of the coordinates of the selection point in the uniform random (UR) sampling grid by clicking the cursor. All ensuing operations are automatic. In the case of isotropic UR (IUR) sections the algorithm traces a series of uniform systematic random linear probes between the sampling point and the object profile periphery emanating from this selection point, radiating at angular intervals of 29–30° to the periphery. In the case of vertical sections, similar lines are generated at intervals where the sine of the angle changes by a value of 0·33. The volume‐weighted mean volume of the object is estimated from the average of all the products , where l represents the length of each individual random linear probe. As the periphery is traced, the algorithm can automatically determine the area of the cross‐section of the object, from which the standard deviation of the volume‐weighted mean volume can be calculated. Some elements of the above algorithm are also used for the measurement of the number‐weighted mean volume. The latter procedure is facilitated using an acoustic vertical depth monitor attached to the microscope. The impact of truncation (‘lost caps’) on the precision of the measurements is discussed. The algorithm is of particular use in light microscopy for measuring cell nuclei by direct visual inspection of the microscopic field using a side‐arm mirror assembly interfaced with a magnetic tablet.
Microspectroscopic measurement of the optical properties of rat liver in the visible region
Authors: SEIYAMA A. , CHEN S.‐S. , KOSAKA H. , SHIGA T. 
Published: August 2011

SummaryMicrospectroscopy is used to investigate optical properties of haemoglobin‐free perfused rat liver. Visible spectra of 20 μm diameter spot size were measured in transmission and/or reflection modes as a function of the thickness (< 1200 μm) of the liver‐edge. Optical density (OD) in transmission mode increased with the increasing liver thickness, whereas in reflection mode OD decreased but became almost constant above a certain thickness (c. 600 μm) of the liver. The Kubelka‐Munk (KM) two‐flux model, with a minor modification, was applied successfully to the analysis of the changes in OD as a function of the thickness. This approach estimates the KM absorption coefficient (EKM), KM scattering coefficient (SKM) and effective penetration depth (δeff) of the liver. The optical properties were similar to reported values, obtained with different methods.
Quantitative water mapping of cryosectioned cells by electron energy‐loss spectroscopy
Authors: SUN S. Q. , SHI S‐L. , HUNT J. A. , LEAPMAN R. D. 
Published: August 2011

SummaryA direct technique based on electron energy‐loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) has been developed to map subcellular distributions of water in frozen‐hydrated biological cryosections. Previously, methods for water determination have been indirect in that they have required the cryosections to be dehydrated first. The new approach makes use of spectrum‐imaging, where EELS data are collected in parallel at each pixel. Several operations are required to process the spectra including: subtraction of the detector dark current, deconvolution by the detector point‐spread function, removal of plural inelastic scattering and correction for the support film. The resulting single scattering distributions are fitted to standard reference spectra at each pixel, and water content can be determined from the fitting coefficients. Although the darkfield or brightfield image from a hydrated cryosection shows minimal structure, the processed EELS image reveals strong contrast due to variations in water content. Reference spectra have been recorded from the major biomolecules (protein, lipid, carbohydrate, nucleic acid) as well as from vitrified water and crystalline ice. It has been found that quantitative results can be obtained for the majority of subcellular compartments by fitting only water and protein reference spectra, and the accuracy of the method for these compartments has been estimated as ± 3·5%. With the present instrumentation the maximum allowed dose of 2 × 103 e/nm2 limits the useful spatial resolution to around 80 nm for ± 5% precision at a single pixel. By averaging pixel intensities a value of 56·8% with a precision of ± 2·0% has been determined for the water content of liver mitochondria. The water mapping technique may prove useful for applications to cell physiology and pathophysiology.
Hybrid scanning transmission electron/scanning tunnelling microscope system for the preparation and investigation of biomolecules
Authors: KNAPP H. F. , WYSS R. , HÄRING R. , HENN C. , GUCKENBERGER R. , ENGEL A. 
Published: August 2011

SummaryA hybrid scanning transmission electron/scanning tunnelling microscope vacuum system is introduced, which allows freeze drying and metal coating of biological samples and their simultaneous observation by scanning transmission electron microscopy and scanning tunnelling microscopy (STM). Different metal coatings and STM tips were analysed to obtain the highest possible resolution for such a system. Bovine liver catalase was used as a test sample and the STM results are compared to a molecular scale model.
Backscattered electron imaging of the undersurface of resin‐embedded cells by field‐emission scanning electron microscopy
Authors: RICHARDS R. G. , GWYNN I. AP 
Published: August 2011

SummaryIn this study backscattered electron (BSE) imaging was used to display cellular structures stained with heavy metals within an unstained resin by atomic number contrast in successively deeper layers. Balb/c 3T3 fibroblasts were cultured on either 13‐mm discs of plastic Thermanox, commercially pure titanium or steel. The cells were fixed, stained and embedded in resin and the disc removed. The resin block containing the cells was sputter coated and examined in a field‐emission scanning electron microscope. The technique allowed for the direct visualization of the cell undersurface and immediately overlying areas of cytoplasm through the surrounding embedding resin, with good resolution and contrast to a significant depth of about 2 μm, without the requirement for cutting sections. The fixation protocol was optimized in order to increase heavy metal staining for maximal backscattered electron production. The operation of the microscope was optimized to maximize the number of backscattered electrons produced and to minimize the spot size. BSE images were collected over a wide range of accelerating voltages (keV), from low values to high values to give ‘sections' of information from increasing depths within the sample. At 3–4 keV only structures a very short distance into the material were observed, essentially the areas of cell attachment to the removed substrate. At higher accelerating voltages information on cell morphology, including in particular stress fibres and cell nuclei, where heavy metals were intensely bound became more evident. The technique allowed stepwise ‘sectional’ information to be acquired. The technique should be useful for studies on cell morphology, cycle and adhesion with greater resolution than can be obtained with any light‐microscope‐based system.
Tomographic reconstruction of the cross‐sectional refractive index distribution in semi‐transparent, birefringent fibres
Authors: WEDBERG T. C. , WEDBERG W. C. 
Published: August 2011

SummaryOptical diffraction tomography (ODT) is used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres. The selected fibres were polymer and animal fibres of either circular or non‐circular cross‐section with average thicknesses in the range 8–110 μm. This choice of samples was made to illustrate the imaging capabilities of ODT, and also to demonstrate some potential applications of the technique. The images representing the reconstructed refractive index distributions have a spatial resolution of about 2 μm, and show noticeable image contrast for refractive index variations of about 0·001. The ODT reconstructions compare well with refractive index information provided with the samples, and with scanning electron micrographs of cross‐sections of the same fibre samples. From these results it appears that ODT can be used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres.
Imaging periodic surface relief structures
Authors: SHERIDAN J. T. , KÖURNER T. O. 
Published: August 2011

SUMMARYBecause of shadowing, multiple scatter and polarization effects, the interpretation of images of gratings with fine periods, isolated deep structures, and multiple scattering volume objects is seriously complicated. In this paper a review of the methods used to model such effects is presented. Periodic surface relief gratings are of particular current importance because of the possibility of producing calibration samples using them. Several examples which illustrate electromagnetic volume effects are examined. General trends which help in validating the use of Fourier‐transform‐based scalar transmittance theory are then indicated. The angular spectrum approach, which can be used, together with a scatter function generated using the rigorous electromagnetic theory, to calculate coherent, partially coherent and confocal images of volume objects, is also discussed.
Forbidden light scanning near‐field optical microscopy
Authors: HEINZELMANN H. , HECHT B. , NOVOTNY L. , POHL D. W. 
Published: August 2011

SUMMARYNear‐field optics (NFO) opens the door to light microscopy techniques with resolutions well beyond the diffraction limit. The richness of optical investigations is now applicable on a near‐molecular level. Among the novel scanning near‐field optical microscopy (SNOM) schemes, the most prominent representatives are aperture SNOM and scanning tunnelling optical microscopy (STOM or PSTM).New experimental and theoretical work has to be performed to study the phenomena specific to NFO. One such example is the angular dependence of light emission in aperture SNOM. The detection of radiation at angles greater than the critical angle of total internal reflection αc = arcsin(n−1), where n is the sample refractive index, can represent a microscopy scheme that combines the respective advantages of both aperture SNOM and STOM. Recent experiments have demonstrated the expected exponential dependence of light intensity on gap width (for fixed emission angle α > αc). The decay length as a function of α is in agreement with the Fresnel description of the evanescent field when total reflection occurs at an interface. These investigations were additionally motivated by calculations based on the multiple multipole method.
Automated correction of linear deformation due to sectioning in serial micrographs
Authors: JANSSON T. , GUSTAVSSON T. , RYDMARK M. , BERTHOLD C. H. , PASCHER R. , SKOGLUND T. 
Published: August 2011

SUMMARYThis paper describes an objective and automatic method for detection and correction of sectioning deformations in digitized micrographs, as well as an evaluation of the method applied to light and electron microscopic images of semi‐thin and ultra‐thin serial sections from brain cortex. The detection is based on matching of image subregions and the deformation model is bi‐linear, i.e. two first‐order polynomials are used for modelling compression/expansion in perpendicular directions. The procedure is applicable to prealigned serial two‐dimensional sections and is primarily aimed at three‐dimensional reconstruction of tissue samples consisting of a large number of cells with random distribution and morphology.
Microfractography of granitic rocks under confocal scanning laser microscopy
Authors: MONTOTO M. , MARTÍNEZ‐NISTAL A. , RODRÍGUEZ‐REY A. , FERNÁNDEZ‐MERAYO N. , SORIANO P. 
Published: August 2011

SUMMARYScanning laser microscopy, in the confocal mode (CSLM) has been applied to a granitic rock to characterize its fissure space. The technique provides a unique three‐dimensional picture of the rock microfractography. CSLM is unique in observing fine details of the fractographic network (connectivity, tortuosity, etc.), its geometry and its relation to other rock‐forming components.The fractographic images with standard fluorescence microscopy are compared with those obtained with CSLM. The examples presented emphasize the advantages of CSLM: three‐dimensional visualization of the microfractographic network, crack connectivity, automatic evaluation of direction and slope of fissures.These studies are related to the migration of radionuclides in the geosphere. The relations between potentially water‐conducting open fissures, and the rock‐forming minerals provide a means of modelling the ‘radionuclide retardation mechanism’, a security factor in their definitive storage in rock masses.