bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scanning thermal microscopy (SThM) of polymer blends: Phase separation, localised calorimetric analysis
Authors: Hammiche A. , Pollock H. M. , Leckenby J. N. , Song M. , Reading M. , Hourston D. J. 
Published: June 2020

We are combining thermal analysis with the ability of thermal waves to give sub-surface imageing at sub-micron resolution. Our aim is that the image contrast will be determined by the “modulated-temperature differential scanning calorimetry” peak (M-T DSC) or feature chosen according to the particular component of the specimen that is of interest. As described elsewhere, this will allow us to distinguish in the image between reversible processes such as amorphous-to-glass transitions, from recrystallisations, cure reactions and other irreversible processes within the polymer.The SThM probe gives micron-resolution images whose contrast is determined by spatial variations in thermal properties. Either the temperature at any point is held constant, or we generate and detect evanescent thermal waves whose penetration depth depends on the frequency chosen.The evidence is that a 1 μm-radius probe in air will give a lateral resolution of ca. 200 nm, with a depth detection of a few μm.
Microprobe study of diode corrosion
Authors: Hlava Paul , Braithwaite Jeff , Sorensen Rob 
Published: June 2020

A few diodes from a production lot were discovered to have unacceptable current leak rates after about 5 years of storage. Inspection revealed the presence of copper sulfide deposits that bridged the external body of the diode and presumably provided a leakage path. Figure 1 shows the physical configuration of a diode. The function of this device is performed by a silicon-based semiconductor that is bonded between two cylinders of tungsten with copper headpins (Cu wire with a flat “nail-head” formed on one end) brazed to the opposite ends of the cylinders. A toroidal ring of glass protects the Si chip. All exposed metal parts are covered by an immersion plating of Ag. Then the entire assembly is coated with black epoxy and a band of green ink is applied to the cathode end. During storage, each diode was placed in a cardboard holder and secured in stacks of about ten with rubber bands.Analytical and environmental exposure studies were performed at Allied Signal and Sandia to determine the cause and potential long-term significance of this corrosion-related degradation problem. The objective of the analytical work was to characterize the corrosion product and help identify the corrosion mechanism. Tools included optical microscopy, scanning electron microscopy, electron microprobe analysis, SIMS, and x-ray diffraction.
Mullite Phase Separation in Nanocomposite Powders
Authors: Yao Nan , Dabbs Daniel M. , Aksay Ilhan A. 
Published: June 2020

Mullite/alumina composite materials are of considerable interest in many applications because of their high-temperature properties, such as creep resistance, and thermal shock resistance. Although mullite has relatively low fracture toughness and strength at low temperature (2.2 MPa.m1/2 and 200-500 MPa, respectively), it retains the greater part of its physical strength up to 1500°C. We seek to improve the mechanical properties of mullite monoliths by using nanosized (<100nm diameter) inclusions in the matrix, where the nanosized inclusions would act to strengthen the matrix in a manner akin to precipitation hardening in metals. Our approach is to make nanocomposite powders and monoliths with controlled chemical composition and phase distribution on the nanometer length scale (1-10 nm).We have recently formed nanocomposite powder using spray pyrolyzed precursors. The precursor was formed from a solution of TEOS and aluminum nitrate nonahydrate in ethanol, mixed in proportions equivalent to the stoichiometry of a mullite/alumina composite composed of 20 wt% alumina in a mullite matrix.
Protein Crystallography Using Capillary-Focused X-Rays
Authors: Balaic D. X. , Barnea Z. , Nugent K. A. , Garrett R. F. , Varghese J. N. , Wilkins S. W. 
Published: June 2020

Tapered glass capillaries for X-ray beam concentration have been a topic of much interest for the synchrotron X-ray community in recent years. These optics have long held the promise of high-intensity microbeam generation for the “hard” X-ray energies used in crystallography and fluorescence analysis.X-ray concentration is achieved by exploiting the total external reflection property of glass surfaces for glancing angles of incidence. X-rays directed into the entrance aperture of the capillary are reflected toward an exit aperture of smaller dimensions, resulting in an increased X-ray flux per unit area at the exit aperture. Capillary designs with a true geometrical focus beyond the capillary exit are also possible.Our group has recently demonstrated a paraboloidally-tapered glass capillary optic which produced a focused X-ray beam using a monochromatised synchrotron source. The optic was designed to produce a focal region for singly-reflected X-rays at a point 40 mm from the end of the capillary. Such a focal region was observed, with a FWHM intensity gain of two orders of magnitude over the incident X-ray intensity from the channel-cut monochromator. Moreover, this gain was achieved for X-ray energies from 5 to 20 keV. We subsequently used a similar optic to obtain X-ray diffraction patterns from a crystal of hen egg-white lysozyme on image plates. The use of the capillary-focused beam yielded diffraction patterns 70 to 100 times faster than using an unfocused beam from the channel-cut monochromator alone. Placement of the crystal at different positions in the capillary-focused beam demonstrated the focusing of Bragg reflections and diffraction from a small volume of crystal.
Spectral Imaging through the light microscope: Application to the image analysis of colored structures in histology
Authors: Omberg R. L. 
Published: June 2020

Color is an important factor in defining structures in both biological and materials microscopy. Indeed, the field of histology/pathology is founded on the use of special dyes and staining procedures which label features of interest with a defining color. Of particular interest is the use of colorigenic substrates in enzyme linked – immunochemistry on tissue sections and the subsequent measurement of the amount of labeling in a given tissue. Typically, colored image objects such as the red deposit produced by the reaction of AEC (aminoethylcarbazole) substrate with peroxidase enzyme can be detected in RGB (red, green, blue) images by a combination of RGB pixel intensities or by HSI (hue, saturation, intensity) pixel intensities. Using a new color imaging system with spectral image acquisition capabilities, we have develop an imaging algorithm based on the absorption spectra of the colored object and the counter stained surrounding space that provides optimal images of segmentation and morphological measurement.The basic system consists of a low light level CCD coupled to a liquid crystal tunable filter (Cambridge Research Instruments). The filter is based on the Lyot-type birefringent filter and provides continuous wavelength selection from 400 - 720 nm with wavelength dependent resolution of about 10 nm at 500 nm. The system is controlled by a Silicon Graphic workstation and Isee software written by Inovision Corp. Spectral images, i.e., images at a given wavelength, can be obtained and the intensity of objects with in a given image can be sampled as a function of wavelength for microspectro -photometric or -fluorometric analysis.
Crack analysis of unfilled natural rubber using infrared microspectroscopy
Authors: Neumeister L. A. , Koenig J. L. 
Published: June 2020

Several spectroscopic methods are available for characterizing the crack tip region of natural rubber on the molecular scale to develop a material with fatigue resistant properties. Attenuated total reflectance or ATR-IR has been used to characterize the structure of many different polymers, including rubbers. Transmission has also been well established as a viable technique for the molecular characterization of transparent materials including thin films of unfilled natural rubber.Unfilled natural rubber was stretched to 629% elongation until cracks appeared in the surface. A cross section of the sample containing a crack was then microtomed at -85°C into slices approximately 0.5 µm thick. Similarly, samples were cut with a razor and microtomed under the same conditions. The crack tip region was mapped using the IRμs™/SIRM Molecular Microanalysis System. The map consisted often spectra taken in the x and y directions as shown in Figure 1. The same region was analyzed for orientation of molecular structures. Points were selected along the crack tip, crack edges, and the bulk. Dichroic ratios of all prominent peaks were calculated. ATR was used to verify the results of the mapping experiments for both stressed and unstressed material.
Ion-Beam Milling Materials with Applications to TEM Specimen Preparation
Authors: Anderson Ron 
Published: June 2020

For the last thirty years, ion milling has been an indispensable part of preparing TEM specimens in the physical sciences. While great improvements have been made in our ability to thin most materials to the point where ion milling may not be a requirement, there will still be a need to utilize ion milling to clean and polish specimens and to provide small amounts of incremental thinning as needed. Thanks mainly to the work of Bama we now understand a great deal about the physics of ion milling. We also benefit from the works of a number of investigators who have studied the artifacts produced by ion milling (see Barber for a review).Ion milling is a subset of the topic “dry etching,” which consists of two major categories: glow discharge methods and ion beam methods. Glow discharge methods include plasma etching, reactive ion etching, and glow discharge sputter etching. These techniques have little application in TEM specimen preparation aside from surface cleaning. The reactive ion etching literature is a source for suggesting gas/specimen combinations to perform chemically-assisted ion beam etching (CAIBE), to be discussed below. The other major dry etching category, ion beam methods, includes ion milling, reactive ion beam etching, and CAIBE.
Five-Dimensional Microscopy using Widefield-Deconvolution: Practical Considerations and Biological Applications
Authors: Marshall W.F. , Oegema K. , Nunnari J. , Straight A.F. , Agard D.A. , Sedat J.W. 
Published: June 2020

The ability to image cells in three dimensions has brought about a revolution in biological microscopy, enabling many questions to be asked which would be inaccessible without this capability. There are currently two major methods of three dimensional microscopy: laser-scanning confocal microscopy and widefield-deconvolution microscopy. The method of widefield-deconvolution uses a cooled CCD to acquire images from a standard widefield microscope, and then computationally removes out of focus blur. Using such a scheme, it is easy to acquire time-lapse 3D images of living cells without killing them, and to do so for multiple wavelengths (using computer-controlled filter wheels). Thus, it is now not only feasible, but routine, to perform five dimensional microscopy (three spatial dimensions, plus time, plus wavelength).Widefield-deconvolution has several advantages over confocal microscopy. The two main advantages are high speed of acquisition (because there is no scanning, a single optical section is acquired at a time by using a cooled CCD camera) and the use of low excitation light levels Excitation intensity can be much lower than in a confocal microscope for three reasons: 1) longer exposures can be taken since the entire 512x512 image plane is acquired in parallel, so that dwell time is not an issue, 2) the higher quantum efficiently of a CCD detect over those typically used in confocal microscopy (although this is expected to change due to advances in confocal detector technology), and 3) because no pinhole is used to reject light, a much larger fraction of the emitted light is collected. Thus we can typically acquire images with thousands of photons per pixel using a mercury lamp, instead of a laser, for illumination. The use of low excitation light is critical for living samples, and also reduces bleaching. The high speed of widefield microscopy is also essential for time-lapse 3D microscopy, since one must acquire images quickly enough to resolve interesting events.
3D Microscopy using Confocal Microscopy
Authors: Stelzer Ernst H. K. , Lindek Steffen 
Published: June 2020

The importance of confocal fluorescence microscopy in modem biological research results from its optical sectioning capability, which allows the three-dimensional analysis of thick specimens. This property is due to the combination of a point-like light source and a point-like detector, which restrict the illumination and detection volumes, respectively. Only the volume that is illuminated and detected is relevant to the confocal observation volume. The smaller it is, the better is the resolution. The performance of a confocal microscope is thus primarily specified by the spatial extent of the confocal point spread function (PSF). The extent can be estimated, e.g., by the volume enclosed by the isosurface at half maximum of the PSF (VHM – volume at half maximum).The relationship of the parameters that determine the lateral resolution of a microscope has been described by Ernst Abbé. The diameter of a light spot in the focal plane Δx is proportional to the wavelength λ of the incident light and inversely proportional to the numerical aperture of the optical
system (N.A. = n, ∙ sin α).
Time-Resolved Stimulated-Emission Fluorescence Microscope
Authors: So P. T. C. , Dong C. Y. , Buhler C. , Gratton E. 
Published: June 2020

Time-resolved stimulated-emission fluorescence microscopy is a novel technique for obtaining super-diffraction limited spatial resolution and sub-nanosecond time resolution using a multi-photon process. This technique is inspired by traditional asynchronous stimulated-emission pump-probe spectroscopy. Fluorescence sample is first excited by a pump laser pulse, tuned to the molecular absorption band of the molecule. Within the chromophore lifetime, a second probe pulse, tuned to the emission band, stimulates fluorescence emission.The spatial resolution enhancement originates from the bilinear dependence of the stimulated emission efficiency on both the pump and probe beam intensities. At the objective focal point, the stimulated emission point spread function is the product of the point spread functions of the pump and probe beams. This situation is mathematically equivalent to both the confocal and the two-photon methods. 3-D depth discrimination and superior spatial resolution is expected.
Going Beyond 3-D Imaging: Automated 3-D Montaged image Analysis of Cytological Specimens
Authors: Roysam Badrinath , Ancin Hakan , Becker Douglas E. , Mackin Robert W. , Chestnut Matthew M. , Ridder Gregg M. , Dufresne Thomas E. , Szarowski Donald H. , Turner James N. 
Published: June 2020

This paper summarizes recent advances made by this group in the automated three-dimensional (3-D) image analysis of cytological specimens that are much thicker than the depth of field, and much wider than the field of view of the microscope. The imaging of thick samples is motivated by the need to sample large volumes of tissue rapidly, make more accurate measurements than possible with 2-D sampling, and also to perform analysis in a manner that preserves the relative locations and 3-D structures of the cells. The motivation to study specimens much wider than the field of view arises when measurements and insights at the tissue, rather than the cell level are needed.The term “analysis” indicates a activities ranging from cell counting, neuron tracing, cell morphometry, measurement of tracers, through characterization of large populations of cells with regard to higher-level tissue organization by detecting patterns such as 3-D spatial clustering, the presence of subpopulations, and their relationships to each other. Of even more interest are changes in these parameters as a function of development, and as a reaction to external stimuli. There is a widespread need to measure structural changes in tissue caused by toxins, physiologic states, biochemicals, aging, development, and electrochemical or physical stimuli. These agents could affect the number of cells per unit volume of tissue, cell volume and shape, and cause structural changes in individual cells, inter-connections, or subtle changes in higher-level tissue architecture. It is important to process large intact volumes of tissue to achieve adequate sampling and sensitivity to subtle changes. It is desirable to perform such studies rapidly, with utmost automation, and at minimal cost. Automated 3-D image analysis methods offer unique advantages and opportunities, without making simplifying assumptions of tissue uniformity, unlike random sampling methods such as stereology.12 Although stereological methods are known to be statistically unbiased, they may not be statistically efficient. Another disadvantage of sampling methods is the lack of full visual confirmation - an attractive feature of image analysis based methods.
Ion Gradients Across Contractile Vacuole Membranes of Amoebae Grown Under Different Osmotic Conditions
Authors: Shi S.-L. , Bowers B. , Leapman R.D. 
Published: June 2020

The contractile vacuole (CV) regulates internal osmolality of free-living protozoa such as amoebae. The CV membrane is known to contain a V-H+ ATPase but the other ion transporters involved in the water pumping mechanism are not yet established. Here we continue our earlier investigation by analytical electron microscopy to measure vacuolar and cytoplasmic ion concentrations inAcanthamoeba castellanii. The present aim is to determine concentrations of ions transported across the CV membrane of amoebae grown under different osmotic conditions.Subcellular ion concentrations in freeze-dried cryosections can generally be determined from x-ray microanalysis using the Hall method.4However, this approach is not suitable for measuring ion concentrations in the CV, which contains mainly inorganic salts and little, if any, organic compounds. A new method based on electron scattering measurements was therefore devised to deal with this highly aqueous compartment. This method involves: (i) measuring the volume of water in the hydrated cryosectioned vacuole with parallel electron energy loss spectroscopy (PEELS); (ii) measuring the mass of vacuolar salt in the freeze-dried cryosection by dark-field scanning transmission electron microscopy (STEM); and (iii) measuring the ratios of ions by energy-dispersive x-ray spectroscopy (EDXS).
Secretory PITS in Backswimmers (Heteroptera: Notonectidae).
Authors: Williams R. J. , Dollahon N. R. , Larsen E. , O’Neill S. , Chapman R. 
Published: June 2020

In studies of several families of aquatic heteropterans we have found exoskeletal pits not described in the literature. These structures are associated with the lateral margins of the pronotum and/or the dorsal surface, posterior to the scutellum in notonectids, nepids, and corixids. The function of these pits is unknown, but we presumed that they might be either sensory or secretory in nature. We undertook this study of the microscopy of pits in the notonectid, Buenoa margaritacea to learn if either of these functions is consistent with the fine structure.For TEM, adult insects were submerged in 1.0% paraformaldeyde and 2.0% glutaraldehyde in 0.02M sodium cacodylate buffer with 0.01% calcium chloride at a pH of 7.2, then dissected with a razor blade cleaned with acetone. Tissues were fixed overnight at 4°C in paraformaldehyde and glutaraldehyde, then fixed in 1% osmium tetroxide in cacodylate buffer, dehydrated in a graded series of acetone, embedded in Spurr resin and polymerized at 70°C for 21 hours. Blocks were thin sectioned with a diamond knife, and sections were stained with uranyl acetate and lead citrate. Whole specimens for SEM were similarly fixed, dehydrated in an ethanol series and critical point dried. SEM micrographs of internal pit anatomy were produced by adhering 500nm sections to a glass coverslip, then removing the embedding resin by incubation for 5 minutes in a saturated solution of potassium hydroxide in absolute ethanol, followed by three 20 minute rinses in absolute ethanol and air drying. Cover slips were attached to an aluminum specimen stub and sputter coated for 60 seconds with gold/palladium as were whole insects .
In Situ Electrical and Microstructural Characterization of Individual Boundaries
Authors: Laval J.Y. , Berger M.H. , Cabanel C. 
Published: June 2020

In order to get direct information on the relationships between the structural and electrical properties of interfaces, we developed in situ experiments in TEM-STEM and SEM for the characterization of the local behaviour of majority and minority carriers. In particular, we described here our new technique for local determination of interfacial potential barriers in electronic ceramics. This information is completed by voltage contrast imaging in SEM at 1 kV which enables a full map of the distribution of these interfacial barriers to be obtained.The TEM experiment is schematized in fig. 1. A tungsten microelectrode (100 nm diameter) can be micromanipulated in situ and gently set down on the TEM sample. The contact between the microelectrode and the sample is shown sharply by the modification of extinction contours in each adjacent grain (Fig. 2ab).
Resolution and Sensitivity of Electron Backscattered Diffraction in a Cold-Field Emission SEM
Authors: Isabell T.C. , Dravid V.P. 
Published: June 2020

With the advent and development of automated beam control and pattern identification software, the use of electron backscattered diffraction (EBSD) as an analytical tool has increased in recent years. EBSD has been used to determine local crystallography and identification of phases, texturing of polyscrytalline materials, ion implantation damage and the extent of crystal deformation. X-ray diffraction yields crystallographic information, but with lateral resolution on the order of a millimeter. TEM provides local information with resolution of a few angstroms, but this is only over a small lateral region of electron transparency and with poor statistics. EBSD provides a true link between the local crystallographic data and real space information.The tradeoff between sensitivity and spatial resolution is inherent in all analytical techniques. EBSD is no exception, and determining this tradeoff for this technique is the focus of our work. In a specimen with minimal interfacial strains, as the electron beam is brought near a crystal boundary, the interaction volume of scattered electrons will straddle both crystals, resulting in an overlapped Kikuchi pattern on the imaging phosphor. By aligning such a boundary parallel to the incident electron beam, the “best case” lateral resolution of EBSD can be determined by taking patterns as the probe is stepped in known increments across the boundary. Likewise, the “worst case” resolution can be determined by orienting the boundary perpendicular to the electron beam and stepping the probe. These two cases are shown schematically in Figure 1.