bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new method for the preparation of ‘double‐fixed’, quick‐frozen, freeze‐substituted cells for whole‐cell transmission electron microscopy
Authors: Nagele R. G. , Lee H. 
Published: August 2011

SUMMARYA method is described in which quick‐frozen, freeze‐substituted, cultured cells can be prepared for whole‐cell transmission electron microscopy (WCTEM). This method is simple and reliable and can be carried out in most laboratories without special equipment. Cells grown on Formvar‐carbon‐coated nickel grids are quick‐frozen in Freon 22, freeze‐substituted in an ethanolic solution of glutaraldehyde, post‐fixed in osmium tetroxide and critical‐point‐dried. The quality of ultrastructural preservation using this ‘double fixation’ protocol is comparable to that of conventional WCTEM. However, the combination of quick‐freezing and WCTEM has the decided advantage over conventional WCTEM in that cellular activities are arrested almost instantaneously. Thus, this new method could potentially yield a more faithful representation of cytoarchitecture and is especially useful for studies on the structural basis of rapid cytoplasmic events which may remain undetected when using conventional fixation methods.
Fasga: A new polychromatic method for simultaneous and differential staining of plant tissues
Authors: Tolivia D. , Tolivia J. 
Published: August 2011

SUMMARYA new method based on the simultaneous action of Safranin and Alcian Blue (or green) is reported. The main advantages of this method are its simplicity and the absence of differentiation processes. Free‐hand, frozen and paraffin sections can be stained with this technique. Sections are placed in 10% sodium hypochlorite for 1–5 min, rinsed in 5% acetic acid and stained for 10 min. Sections are then washed in distilled water for 1 min, rinsed in distilled water for 5 min and mounted.
A compact parallel‐recording detector for EELS
Authors: Egerton R. F. , Crozier P. A. 
Published: August 2011

SUMMARYWe designed and constructed the prototype of a parallel‐recording system for a Gatan 607 electron energy‐loss spectrometer attached to a conventional transmission electron microscope. Quadrupole lenses were used to project a magnified energy‐loss spectrum onto a 65 μm thick screen of single‐crystal yttrium aluminium garnet (YAG), where the electrons are converted to photons which are transferred by coherent fibre optics to a 1024‐channel photodiode array. When used in conjunction with a tungsten‐filament electron source, the system achieves an energy resolution close to 2eV and can record inner‐shell ionization edges with good signal/noise ratio in exposure times not exceeding 5 s.
Minima equalization: A useful strategy in automatic processing of microscopic images
Authors: McMillan Paul J. , Yakush Andrew , Frykman Gary , Nava P. Ben , Ras Vicky R. 
Published: August 2011

SUMMARYSpecifically stained features in microscopic images rarely have a unique range of grey levels which would permit selection of the features by simple thresholding. The spaces between features and immediately surrounding them are often as dark or darker than the more lightly stained features. An algorithm for minima equalization which facilitates the extraction and segmentation of such features was designed and is explained in intuitive terms. It is applied to the analysis of cross‐sections of peripheral myelinated nerve fibres. It is shown that the binary image obtained can be combined with a gradient image to give a binary image which accurately reflects the thickness of the myelin in the original image. Using silver‐impregnated nerve endings and bile canaliculi stained for thiamine pyrophosphatase, binary images like those prepared manually from thick specimens using a camera lucida can be obtained using the minima equalization procedure. The image processor is used to develop a composite image by combining images at various focal planes through the thick specimen. This image is then processed to obtain the binary image.
Improvements in the fabrication of thin foil apertures for electron microscopy
Authors: Fabergé A. C. 
Published: August 2011

SUMMARYSchabtach (1974) developed a process for making ‘thin’ (i.e. self‐cleaning) apertures for electron microscopes. Several improvements in this process are described, the most important of which is the deposition of a heavy metal by DC sputtering rather than by evaporation, making the process much easier.
Voltage dependence of the tunnelling current: an exact expression
Authors: Noguera Claudine 
Published: August 2011

SUMMARYAn exact expression for the tunnelling current measured with a scanning tunnelling microscope (STM) is obtained. It clarifies the information deducible from the ‘spectroscopic mode’ of the STM and raises the question of the observability of surface states. The connection with the Transfer Hamiltonian approach is made, and the conditions of validity of the latter are analysed.
The heat transfer between a heated tip and a substrate: fast thermal microscopy
Authors: Dransfeld K. , Xu J. 
Published: August 2011

SUMMARYHere we describe a new mechanism of heat transfer between two solids separated by a distance. This mechanism does not involve the ambient air or adsorbed vapour films, and is therefore expected to remain active under perfect vacuum conditions. As will be described in detail, thermal charge fluctuations of one solid substrate kept at finite temperatures create an electromagnetic field—at infrared frequencies and of a short coherence length—which extends across the gap and effectively transports heat to the other solid. In our view this mechanism is responsible for the effective heat transfer observed recently by C. C. Williams and H. K. Wickramasinghe between a heated tip and a substrate.
Imaging of granular high‐Tc thin films using a scanning tunnelling microscope with large scan range
Authors: Niedermann Ph. , Fischer Ø. 
Published: August 2011

SUMMARYSTM images are presented in the micron scale, taken in UHV with a single‐tube scanner STM with SEM control of the tip position. For calibration, a carbon grid was used from which the coupling of x and y scan axes has been determined as well as the piezo‐sensitivity factors. Images taken of a YBa2Cu3O7‐δ, film display the granular structure of the crystallites formed during the post‐evaporation annealing. A direct comparison of STM scans with SEM micrographs was made which demonstrates the complementary information obtained by the two methods. The obtained resolution is compared to the tip shape which becomes crucial for the imaging of corrugated surfaces on the micron scale. With a simple geometric model, an attempt has been made to reconstruct the surface topography from STM scans based on the knowledge of the tip shape.
Tip‐bias induced surface modification on gold surfaces
Authors: Nagahara L. , Lindsay S. M. , Thundat T. , Knipping U. 
Published: August 2011

SUMMARYWe have observed drastic modification of gold surfaces at tip biases above a threshold value. These modifications were observed only on surfaces which are not atomically flat and only with negative tip bias. We tentatively attribute these surface modifications to formation of Taylor cones.
Scanning tunnelling microscopy studies of heteroepitaxy: CaF2 on Si(111)
Authors: Wolkow R. , Avouris Ph. 
Published: August 2011

SUMMARYWe apply scanning tunnelling microscopy and tunnelling spectroscopy to study the initial stages of CaF2 epitaxy on Si(111)‐(7×7) for a range of deposition temperatures. We find that deposition at surface temperatures <700°C leads to CaF2 clustering. At temperatures between 750 and 800°C two new structures, a 2×3 and a (√3 X √3***)R30°, are observed. Tunnelling spectra and topographs obtained at different energies allow us to measure interface band gaps, and determine the valence state of Ca bonded directly to silicon and the valence state of Ca in the second layer. More importantly, we demonstrate that STM can be used to image thick insulating layers of CaF2 by tunnelling into the conduction band of the films.One of our goals in this study has been to test the ability of STM to image insulating multilayers. It is generally believed that STM cannot be applied to insulators. We find, however, that despite the large band gap of ∼12 eV, the CaF2 conduction band is accessible, and that insulating films can be imaged by STM.
Imaging an optical disc by the combined use of scanning tunnelling microscopy and scanning electron microscopy
Authors: Bartolomé A. , García R. , Vázquez L. , Baró A. M. 
Published: August 2011

SUMMARYWe present the data obtained by scanning tunnelling microscopy combined with scanning electron microscopy of the digitally encoded structure on a stamper used to fabricate optical discs. The combination allows us to focus the STM tip on a preselected spot with a precision of ≅0·3 μm. The data show the superiority of STM for a more detailed characterization of shape, width, length, height and fine structure appearing on the sample. We also show the influence of tip shape on STM resolution. Simultaneous use of both microscopes is possible but high electron doses produce an insulating layer of contaminants thick enough to make STM operation impossible.
Force sensing in scanning tunnelling microscopy: observation of adhesion forces on clean metal surfaces
Authors: Dürig U. , Züger O. , Pohl D. W. 
Published: August 2011

SUMMARYTip sample interaction forces were investigated during normal tunnelling operation of the STM using an Ir tip and a polycrystalline Ir sample. Metallic adhesion interaction was observed for tunnel conductivity ranging from 10−6 to 19−9 Ω‐1 implying that the actual gap width was of the order of 1–4 Å. Similar experiments performed on a polycrystalline Al sample exposed to 1 Langmuir O2 showed that tip sample interaction changed from attractive to repulsive on well‐defined areas extending over ∼100 Å2 which we identified with the oxidized Al surface.
The STM learning curve and where it may take us*
Authors: Demuth J. E. , Koehler U. , Hamers R. J. 
Published: August 2011

SUMMARYThe scanning tunnelling microscope (STM) has proved to be an extraordinary method to investigate surfaces in vacuum, air and liquid environments. Several issues regarding the use of the STM for atomic resolution studies are discussed. These include electronic contributions to STM images, the role of the tip in resolution and spectroscopy, as well as the need for complementary information about chemical composition or sub‐surface structure.
A frictional force microscope controlled with an electromagnet
Authors: Kaneko R. 
Published: August 2011

SUMMARYFrictional forces are usually measured by detecting spring displacement. To obtain high‐resolution measurements of frictional force distributions, a sharp tip and a light load are required. In measuring frictional force on relatively rough surfaces, using very sharp tips (submicron radii), significant stick‐slip motions are observed, and continuously varying dynamic frictional forces can not be measured.To measure continuous friction distributions between sharp tips and surfaces with light loads, a new frictional force microscope (FFM) is developed. This FFM has an electromagnet to maintain the tip suspension spring in a non‐deflected position. The frictional force is then measured from the magnet current. Using this FFM, continuous friction distributions between 0·1 μm radius diamond tips and magnetic disk surfaces with light loads (less than 10 μN) are obtained.
Study of Au surfaces by scanning tunnelling microscopy
Authors: Kuk Y. , Silverman P. J. , Chua F. M. 
Published: August 2011

SUMMARYThe reconstructions of Au surfaces have been studied by scanning tunnelling microscopy. Topographs of Au(110)‐(1×2) as a function of annealing temperature show changes in the long range order, in good agreement with diffraction measurements and theoretical studies. Some insight into the nucleation and growth of the (1×2) reconstruction was obtained by imaging the surface after deposition of Cs or O. A new structural model for Au(100)‐(5×20) is proposed with a high resolution topograph. Adsorption of Si clusters on Au(100) will be described.
In situ, atomic scale observation of electrode topography and reactions
Authors: Twomey T. , Wiechers J. , Kolb D.M. , Behm R. J. 
Published: August 2011

SUMMARYThe topographical changes occurring on a Au(111) electrode during simple electrochemical reactions have been followed with an STM capable of operating in situ, i.e. in the electrochemical environment, and of yielding atomic scale resolution. Changes in the surface structure induced by adsorption and desorption of Cl− ions could be observed and the effects of subjecting the sample to an oxidation‐reduction cycle could be monitored.
Measurements of polyphosphoric acid on HOPG
Authors: Mizutani Wataru , Shigeno Masatsugu , Saito Kazuhiro , Morita Naotake , Yoshioka Toru , Ono Masatoshi , Kajimura Koji 
Published: August 2011

SUMMARYAs a sample for initial study on biological materials by using scanning tunnelling microscope (STM), we selected phosphoric acid consisting of phosphorous atoms which play biologically an important role. We measured polyphosphoric acid coated on HOPG by STM and scanning tunnelling spectroscopy (STS) in air. In order to identify molecules on STM images, local I‐V curves were taken simultaneously. The averaged I‐V curves and the normalized conductance spectra of graphite coated with the acid show characteristics different from those of clean graphite surface. Around a step of the substrate, we found domains where normalized conductance spectra were different from those of clean graphite surface and ascribable to that of the adsorbed molecules.
Differential scanning tunnelling microscopy
Authors: Abraham David W. , Williams C. C. , Wickramasinghe H. K. 
Published: August 2011

SUMMARYWe review the principle of differential imaging and its application to scanning tunnelling microscopy (STM). It is shown that placing a lateral dither on an STM tip at high frequency provides the means for transfering topographic information to a frequency range where noise is small. Differential STM imaging on graphite and gold is demonstrated. A simple relation between the differential image and the conventional topographic image is described.
Spatially resolved ballistic electron spectroscopy of subsurface interfaces
Authors: Bell L. D. , Kaiser W. J. 
Published: August 2011

SUMMARYBuried interfaces have traditionally been inaccessible to direct investigation by surface‐sensitive techniques. A unique and novel electronic probe, which is sensitive to subsurface electronic structure, has been utilized to probe Schottky barrier interfaces. The method, ballistic electron emission microscopy (BEEM), is based on scanning tunnelling microscopy (STM) techniques. A theoretical treatment has been developed to describe the ballistic electron spectra obtained by BEEM and this treatment is applied to data obtained on the Au‐Si Schottky barrier interface system. Excellent agreement between experiment and theory is obtained. In addition, the treatment pradicts nanometre spatial resolution for interface imaging by BEEM.
The STM as an information storage device
Authors: Thomson D. J. 
Published: August 2011

SUMMARYThe high spatial resolution of the scanning tunnelling microscope (STM) makes its use as an information storage device very attractive. However, even without specifying the means of information storage, several limits can be placed on the characteristics of these devices. One would expect that a bit of information could not be stored in a dimension smaller than an atom. This limits the storage density to 1015 bits/cm2. Present‐day STM have fields of view that range up to 2times10−6cm2 yielding a total potential capacity of 2times109 bits. This capacity would be expected to grow as STM design becomes more refined. At 1 nA, shot noise will limit the read rate to 20 Mbits/s. This limit can only be overcome by using larger currents. The write rate may also be limited by this phenomenon if the writing mechanism demands that a certain charge threshold be reached to write a bit. For a particular device structure, operating conditions will be identified where the above limitations will become important. The above analysis leads to the conclusion that an STM storage device with reasonable read/write rates and a large storage capacity should be possible.
The STM system constructed for analytical application
Authors: Okumura Akihiko , Miyamura Kazuo , Gohshi Yohichi 
Published: August 2011

SUMMARYAn STM equipment capable of measuring I‐V characteristics of a sample surface has been constructed, and some preliminary measurements have been made. Carbon atoms in graphite were resolved. Reproducible and low noise I‐V characteristics were obtained, which allowed to observe dI/dV and d2I/dV2.
Imaging of tip‐sample compliance in STM
Authors: Anders M. , Heiden C. 
Published: August 2011

SUMMARYAn STM was built, in which the substrate is mounted on a piezoelectric bimorph. The compliance of the tip‐surface contact region is measured by modulating the vertical position of the tip and detecting the induced deflection of the bimorph. Tip‐surface compliances between 5 and 200 N/m were measured during STM operation. It is possible to use the compliance signal for operating the microscope's feedback loop. Stable feedback loop operation can be achieved for tip‐surface distances up to about 200 nm. By operating the microscope in this constant compliance mode, surfaces of arbitrary conductance can be imaged. For conductive surfaces the tunnelling current can be recorded simultaneously. On a Nb3Sn film conducting and isolating patches were detected using this method.
The effect of a vacancy on the STM image of graphite
Authors: Soto M. R. 
Published: August 2011

SUMMARYTheoretical studies have been done on graphite with a vacancy using the extended Huckel tight‐binding (EHTB) method. The results of the singly‐ and doubly‐layered samples show that there is an unexpected distance dependence of the charge density directly over the vacancy. Furthermore, the vacancy acts as a perturbation to distinguish two sublattices which exist in pristine graphite and it creates a charge enhancement in the atoms directly surrounding it.
Scanning tunnelling and atomic force microscopy performed with the same probe in one unit
Authors: Bryant P. J. , Miller R. G. , Deeken R. , Yang R. , Zheng Y. C. 
Published: August 2011

SUMMARYThe technique demonstrated here provides features of both scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). The metallic probe acts to record current variations and sense forces from the same sample area simultaneously. Thus, separate images may be recorded, in registry. The collected data allows real space correlations between some electrical properties and the geometric structure of a sample surface. The same tip is used since the geometry and condition of the tip can effect the data recordings. Platinum alloys, tungsten and graphite tips have been employed successfully. An AFM lever can respond to surface contact forces, within the elastic limits of the sample, while electric current is sensed by the tip of the lever. The usefulness of this experimental procedure is tested here by an application to semiconducting samples of Ag‐doped CdTe in air and in paraffin oil media.
Contrast in confocal scanning microscopy with a finite detector
Authors: Shuman H. 
Published: August 2011

SUMMARYThe optical properties of a general scanning microscope are determined within the framework of Fourier imaging theory. For a simple model optical system, with Gaussian lens and detector apertures, the contrast transfer function can be expressed in terms of elementary functions. The theory predicts that spatial resolution and depth discrimination vary continuously with detector aperture and that defocus phase contrast is present in transmission images obtained with a symmetric objective, collector lens confocal microscope.
A simple, direct method for the collection of particles from air samples for transmission electron microscopy and digital image analysis
Authors: Farrants George , Reith Albrecht , Schüler Barbara , Feren Kari 
Published: August 2011

SUMMARYA method is presented for the collection of small (< 1 μm) particles from air samples. Examples of its application are the monitoring of environmental pollutants in the working environment, personal monitoring of exposure to such pollutants and the characterization of particular environments such as clean rooms in the semiconductor industry. Electron microscope grids are attached to Nuclepore filters with carbon cement, the filter mounted in a standard disposable holder and air drawn through the filter with a pump. The method is simple, reproducible, allows a wide range of experimenter control, and provides specimens suitable for electron microscopy, followed by automatic image analysis.
Microscopic tomography by laser scanning microscopy and its three‐dimensional reconstruction
Authors: Takamatsu Tetsurou , Fujita Setsuya 
Published: August 2011

SUMMARYWe have developed a new confocal laser scanning microscope equipped with two galvanometer mirrors which swing the laser beam. With this set up we can observe large and fragile specimens. Using a focused laser beam as light source to minimize ‘flare’ and a pinhole in front of a photodetector to eliminate out‐of‐focus data, we could obtain a depth‐discriminated fluorescence image. The scanning apparatus of our system can eliminate mechanical vibration and sweep widely, to obtain images at a low magnification. A thinly sectioned image with high resolution and high contrast could be obtained optically from an in situ thick specimen. We have called this technique ‘microscopic tomography’. Combining the laser scanning microscope with the colour image analyser generated semi‐automatically a three‐dimensional picture of the biological material with information on its interior.
Automated image segmentation by mathematical morphology and fractal geometry
Authors: Rigaut Jean Paul 
Published: August 2011

SUMMARYA new method for automated image segmentation is presented. It makes use of a combination of principles derived from mathematical morphology and fractal geometry.The method consists of searching for regions in which the grey‐tone function defining the black‐and‐white image can be represented, inside a certain range of resolutions, by a fractal surface with a given fractal dimension.The probability for a planar, circular structuring element, randomly positioned on a grey‐level plane inside a region of the digitized image, to intersect the surface which represents the grey‐tone function, is derived by two methods, fractal geometry and mathematical morphology.A fundamental equation is finally derived, relating, in a fractal region of the grey‐tone surface, the sum of discrete (pixel) grey‐level differences between the images obtained by ***multi‐grey‐level dilation and erosion of the original image, respectively, to the size of the structuring element and the fractal dimension.This equation represents the basis of the method. The automated image analysis program, written for the IBAS (Kontron), works on several memorized images, each produced by a subtraction between the images obtained by dilation and erosion of the original image, using several sizes for the structuring element.Although minimal computations are made, the algorithms are too slow for practical applications and will require massive parallel processing for future use.The method relies on the assumption that regions of an image having a particular structure will usually produce a fractal grey‐tone surface, with a particular value of the fractal dimension. The feasibility of such an approach is demonstrated with segmentations obtaining the isolation of various objects on different biological images. The natural structures we have studied indeed show a fractal grey‐tone surface, at least within a certain range of (low) resolutions.Our studies also allow us to consider whether human vision uses a combination of image transformations and principles of self‐similarity to segment images.