bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Gallium Sulfide in Srs:Ce Grain Growth
Authors: Evans N D , Naman A , Rice P M , Jones K S , Holloway P H
Published: July 2020

Whereas efficient red (ZnS:Mn) and green (ZnS:Tb) phosphors are available for full-color flat-panel display technology, efficient blue phosphors are still under development. SrS:Ce is being investigated as a suitable material. As part of a larger study, annealed SrS:Ce films produced from sputter targets incorporating Ga2S3 were found to be five times brighter than films produced from targets containing no Ga2S3. Consequently, the significance of added gallium sulfide to the morphology of SrS:Ce films during annealing is being investigated.

Following deposition, plan view specimens of films were prepared for transmission electron microscopy by mechanical grinding, dimpling, and Ar+ milling. Films were examined in a Philips CM 12, and a JEOL 200CX. Additionally, EDS line scans were obtained in the scanning-transmission mode of a Philips CM200FEG, integrated with an EMiSPEC Vision acquisition system. The EDS line scans were defined as a series of 40 points along a line, spaced approximately 3.6 nm apart.
Electron Energy-Loss and Energy Dispersive X-Ray Spectros-Copy Studies of Diffusion Bonded Cu-Al2O3 Interfaces
Authors: Hashimoto R , Menon E S K , Saunders M , Fox A G
Published: July 2020

The metal-ceramic interface between copper and alumina has been studied by TEM, Electron Energy-Loss Spectroscopy (EELS), and Energy Dispersive X-ray spectroscopy (EDX). of partic-ular interest is the potential role of silicon which is the major impurity in commercial alumina. This investigation focuses on the presence and distribution of silicon within the bulk alumina and at the diffusion bonded CU-AI2O3 interface using a Topcon 002B TEM equipped with an EDAX EDX detector and a Gatan Imaging Filter. The interface was created under vacuum by diffusion bonding of 100/xm copper foils (99.999% purity) pressed between polished alumina substrates (∼99.5% purity) for several hours at ∼90% of the melting temperature of the metal.

An initial investigation of the bulk AI2O3 indicated that the majority of the Si occurred at the triple points. A typical example is shown in Fig. la. EDX spectra acquired with a 6nm probe from the center of the junction (Fig. lbi) and at the grain boundary indicate that the Si wets the grain boundary to a limited extent.
The Study of Ti-Mcm-41 by Transmission Electron Microscopy
Authors: Blanford CF , Aronson BJ , McKernan S , Stein A , Carter CB
Published: July 2020

In 1992, researchers at Mobil Research and Development created a new class of porous silicates, most notably MCM-41. This material features a hexagonal arrangement of pores and surface areas in excess of 1000 m2 g-1. Typically, MCM-41 exhibits pore diameters around 2.5 nm and a d-spacing around 4.0 nm, but slight variations in the synthesis of MCM-41 can produce a range of pore sizes from 2 to 10 nm. Zeolites, in comparison, have pore openings smaller than 1.3 nm and surface areas of a few hundred square meters per gram.

Recently, Aronson et al. have been studying the grafting of TiO2 to MCM-41. TiO2 is a versatile photocatalyst in many selective organic oxidations and other reactions, including the degradation of environmental toxins. by dispersing TiO2 on the internal surface of a mesoporous support one can increase the active surface area significantly and introduce some size-selectivity.
Resolution Issues in Scanned Probe Microscopy
Authors: Russell P E
Published: July 2020

Scanned Probe Microscopy first received widespread recognition in the form of scanning tunneling microscopy (STM) images clearly showing atomic resolution of the Si 111 surface in the characteristic 7×7 surface reconstruction. For this sample, STM imaging under carefully controlled ultrahigh vacuum conditions reveals the clear image of each atom position within the surface unit cell with excellent contrast and clearly atomic resolution. Over the past few years, versions of scanning force microscopy (commonly referred to as atomic force microscopy or AFM) have become much more widespread than STM. A very common, and very difficult question, is: What is the resolution of AFM? The simple answer is that SPM in general, and STM and AFM in particular, routinely obtain sub-angstrom resolution—in the z axis, or the sample height direction. This high resolution capability is easily demonstrated by scanning a cleaved crystal of known lattice spacing and observing single and multiple atomic steps.
Studies of Supported Metal Catalysts Using Low Voltage Biased Secondary Electron Imaging in a JSM-6320f Fe-SEM
Authors: Liu J , Ornberg R L , Ebner J R
Published: July 2020

Many industrial catalysts have a complex geometric structure to enable reacting gases or fluids to reach as much of the active surface of the catalyst as possible. The catalyzing surface frequently consists of a complex chemical mixture of different phases produced by an evolved chemical process. The active components are often very small particles dispersed on high-surface-area supports. The catalytic properties of this type of catalyst depend on the structure, composition, and morphology of the active species as well as the supports. TEM/STEM and associated techniques have been used extensively to characterize the structure and composition of supported catalysts. Surface morphology of supported catalysts is generally examined by secondary electron imaging, especially at low incident beam energies. It is, however, frequently found that small metal particles are not usually seen in SE images because of the complication of support topography
Surface Morphology of Mechanically Strained Silicate Glass Films on Alumina Substrates
Authors: Zagrebelny AV , Carter CB
Published: July 2020

It has been long recognized that the understanding of mechanical properties of thin films on substrates requires an understanding of the stresses in the film structures as well as a knowledge of mechanisms by which thin films deform. It has also been shown that these stresses may compromise the performance of integrated circuits, magnetic media, etc. The presence of residual and thermal stresses between the matrix and intergranular films in structural multiphase ceramics is the most common mechanism of failure that often causes deformation and fracture

In this paper, the effect of residual stress on mechanical properties of silicate-glass films on single-crystal α-Al2O3 substrates has been studied with AFM with the emphasis on the changes in surface morphology associated with the film strain and relaxation. The deformation of thin layers of glass on crystalline materials has also been examined using newly developed experimental methods for nanomechanical testing.
Monte Carlo Simulation Of X-Ray Spectra In Absolute Units In The Energy Regime Between 1 And 50 Kev
Authors: Schiebl C O , Ambrose V , Wernisch J
Published: July 2020

SeSAME, a Monte Carlo simulation program which can handle totally arbitrarily shaped twodimensional geometries, has been extended for the modeling of whole x-ray spectra in absolute units. The so called single scattering model has been used for the simulations presented here. Elastic scattering processes are modeled using a partial wave approach according to a relativistic expression derived by Mott. For the calculation of the electron energy loss the stopping power formula from Joy and Luo has been applied.

Two different double differential cross sections for continuous x-ray production have been implemented into SeSAME. The first one is an analytical model derived by Kirkpatrick and Wiedmann and is based on a non-relativistic theory developed by Sommerfield and Elwert. The second one uses tabulated values for the shape function for atomic-field Bremsstrahlung and scaled Bremsstrahlung cross sections differential only in photon energy according to Kissel at al.
Atom Probe Tomography Of Interfaces
Authors: Miller M K
Published: July 2020

The technique of atom probe tomography (APT) enables the x, y, and z coordinates and the elemental identities of the atoms in a small volume to be determined at the atomic level. Therefore, the APT technique may be used to characterize solute segregation to interfaces and precipitation in terms of concentration gradients and precipitate morphology. This type of information may be used to optimize the design of alloys.

The material that was used to illustrate the capabilities of atom probe tomography is a complex polycrystalline nickel-based superalloy, Alloy 718. The composition of this commercial superalloy is Ni- 3.2 at. % Nb, 0.96% Al, 1.15% Ti, 20.3% Fe, 21.8% Cr, 0.26% Co, 1.8% Mo, 0.16% Mn, 0.21% Si and 0.26% C. The material was characterized after a heat treatment oM h at 1038°C + 8 h at 870°C + 500 h at 600°C. Previous atom probe field ion microscopy characterizations of this material has demonstrated that there is no intragranular precipitation after the anneal at 1038°C.
Direct Observation Of Iodine Atomic Chains In I-Doped Carbon Nanotubes
Authors: Fan X , Dickey EC , Pennycook SJ , Grigorian L , Eklund PC , R. BuczkoM  , Pantelides S T
Published: July 2020

Single wall carbon nanotubes (SWNT) were doped with iodine, resulting in charge transfer between the iodine and carbon [1]. It was found that the iodine intercalation is air stable and also reversible by simple heat treatment. This behavior is in contrast to graphite and fullerenes which do not form charge transfer compounds with iodine. Although the iodine-induced charge transfer was not found in any other carbon polymorph solid, it has been found in some low dimensional organic polymers such as polyaniline,[2] forming charged linear-chain polyiodides (I3)- and (I5)-. This suggests that the geometric configuration of the carbon may play a very important role in iodine intercalation. In this study, we use Z-contrast imaging[3] in a VG Microscopes HB603U STEM to directly observe the configuration of iodine within the nanotube bundles. First-principles density-functional calculations are then used to explain the preference for the observed iodine configuration within the nanotubes.
Creep Deformation Microstructures in DS Nb-Hf-Ti-Si In-Situ Composites
Authors: Sitzman SD , Bewlay BP
Published: July 2020

Directionally solidified (DS) in-situ composites based on (Nb) and (Nb) silicides, such as Nb5Si3 and Nb3Si, are presently under investigation as high-temperature structural materials [1, 2]. Alloying additions of elements such as Hf, Ti and Mo to these silicides are also being explored. The present paper describes the microstructure of a DS Nb-silicide based composite before and after creep deformation.

Alloys were prepared from high purity elements (>99.9%) using induction levitation melting in a segmented water-cooled copper crucible. The alloys were directionally solidified using the Czochralski method [2]. Creep tests were conducted at 1200°C to 50% deformation. Characterization was performed using scanning electron microscopy, electron microprobe analysis (EMPA), and electron backscatter diffraction pattern analysis (EBSP).
Orientation Relationships and Constituent Phases
Authors: GUI Jianian , CHEN Xiaomei , LIU Jing , WANG Jianbo , WANG Renhui
Published: July 2020

We report here our preliminary results on orientation determination and phase identification using the electron backscatter diffraction (EBSD) technique. Using a scanning electron microscope (SEM) equipped with the EBSD attachment. it is now possible to study the correspondence and orientation relationships of parent-phase and martensite variants in shape memory alloys (SMAs). Previously, such an information was obtained from large single crystals studied by micro-beam X-ray Laue diffraction and supplemented by transmission electron microscopy study of thin foils. Figs. 1(a), (b) and (c) are three EBSD patterns taken from neighboring areas in a Cu-12.55Al-4.86Ni (wt%) SMA. Computer simulation reveals that Fig. 1(a) belongs to the parent-phase of D03-structure type, and Figs. 1(b) and (c) belong to variants A and D of 2H martensite, respectively. Corresponding simulated EBSD patterns are shown in Figs. 1(d), (e) and (f). Fig. 1 indicates that the (0 0 2)A basal plane of the martensite variant A is transformed from the (-2-2 0)p plane of the parent-phase and its [0-1 0]A direction from the [0 0 1]P direction. The (0 0 2)D basal plane of the martensite variant D is transformed from the (2-2 0)P plane of the parent-phase and its [0 1 0 ]D direction from the [0 0 1]P direction.
3D Reconstructions Using Charge Contrast Imaging
Authors: Baroni Travis C , Griffin Brendan J , Lincoln Frank J
Published: July 2020

Three-dimensional reconstructions are a useful visualisation aid for understanding the volumetric relationships between features in an object. Typically, three dimensional reconstructions have evolved with regards to biological applications, where the collection and manipulation of the data has matured to a point where volumetric rendering has become almost routine. Two common data collection procedures involve either virtual sectioning using CLSM, where layers within the object are imaged successively without mechanical sectioning, or alternatively the projection of the object is imaged, via TEM while being rotated through a range of angles. This paper describes a novel application of three dimensional imaging by collecting 2 dimensional serial section images using a recently described technique for imaging materials using a VPSEM, known as Charge Contrast Imaging.

Figure 1 shows a typical image of a polished grain of gibbsite. Previous work has correlated the appearance of the concentric rings to laboratory controlled precipitation events, thus showing the technique provides information on the precipitation history
What Do We Need to Look Out for When Doing Energy Dispersive Xray Analysis in the Environmental Scanning Electron Microscope?
Authors: Wight Scott
Published: July 2020

The environmental scanning electron microscope (ESEM) is not typically used for quantitative analysis by energy dispersive x-ray spectrometry (EDS) because the electron beam is scattered by the chamber gas forming a broad tail or skirt rather than a focused spot. Scattered electrons can contribute x-rays from areas not directly under the beam, which compromises the spectrum for quantitative analysis. For specimens compatible with high vacuum, quantitative EDS analysis in a conventional electron microscope is preferred. However, the ESEM has found its niche in providing a vehicle for investigating those specimens that for any of a variety of reasons are not suitable for high vacuum electron microscopy and microanalysis. For these specimens, it is important that we find the most accurate way to perform EDS analysis in the low vacuum environment.

Research has focused on reducing, accounting for, predicting, or measuring the electron scattering on a simplified system. Instrumental tricks to reduce the scattering of the primary electron beam have been reported in the past.
Nondestructive Imaging of Pin-Mounted Museum Insect Specimens Using the Field-Emission Environmental Scanning Electron Microscope (ESEM-FEG)
Authors: Robinson Scott , McNeill Billy , Irwin Michael
Published: July 2020

The abilities of researchers to obtain high-quality images and other data from pin-mounted museum insect specimens using conventional scanning electron microscopy (SEM) are hindered by several necessary constraints. The specimens may represent unique exemplars (e.g., holotypes) upon which the taxon name rests. In some cases the specimen may no longer be extant in any environment outside the museum. Thus these insects must always be handled with extreme care,Tegardless of how they are to be observed.

Normal preparation of an insect for SEM involves sputter coating it with a conductive metal to minimize the effects of charging, and conductive paint must be applied to an obscure or uninteresting area to complete the connection to the specimen mount and thus to ground. Generally, unless such specimens have been newly collected, they will have already been killed and allowed to air dry, with a mounting pin inserted through the thorax. The body of the insect shrinks against the pin, which cannot then be removed for observation and later reinserted without damage.
Cationic Peptide Mediated Oligonucleotide Delivery to DU145 Prostate Cancer Cells - Cell Surface Binding Detected by High Resolution SEM
Authors: Karr Joan F , Apkarian Robert P , Petros John A
Published: July 2020

Transfection of mammalian cells can be enhanced by forming complexes between exogenous DNA and cationic peptides which facilitate DNA transport through cell membranes. Although complexes of plasmid DNA and cationic peptides have been characterized by microscopy, little is known about the complexes formed between oligonucleotides (ODN) and cationic peptides or how the ultrastructure of these complexes affects the intracellular delivery via the cell membrane. Because ODN have potential as therapeutic reagents in the treatment of many diseases, there is a need to develop improved methods for effective delivery of these molecules. By analyzing molecular interactions between cationic peptides and ODN and their effects on cell membranes, cell viability, and DNA delivery, improved delivery compounds can be designed. In this paper, we compare the interactions of a 28 base ODN with three cationic peptides: a novel compound, MNLEK (H-Met-(Nle-Lys4)7-Nle-NH2), an established transfection reagent, poly(L-lysine) (∼ 54 kDa), and a recently described cationic peptide which delivers both plasmid DNA and antisense ODN to cells, KALA (WEAKLAKALAKALAKHLAKALAKALKACEA).

For high resolution scanning electron microscopy (HRSEM), DU145 human prostate cancer cells were grown overnight on poly-(D-lysine) coated, UV irradiated silicon chips.
Freeze Substitution of Porcine Heart Valves
Authors: Lightfoot F , Song Y , Taylor M , Brockbank K
Published: July 2020

Freeze Substitution has historically been used for processing small pieces of tissue for microscopic examination. These small pieces of tissue have usually been ultra-rapidly frozen by either metal mirror, high pressure or immersion fixation. In today's expanding field of cryobiology, freeze substitution is being employed to better understand the effects of ice formation and possible deformation of cell structure in tissues that have been processed by controlled-rate freezing. This technique is of extreme importance in laboratories focused on developing methods of preservation by freezing tissues, such as heart valves or veins, which are intended, for clinical applications.

Overview: Many laboratories use methods of substitution, which incorporate acetone as the ice dissolution solvent. We have done comparative studies using both acetone and methanol as a substitution media at -80° C and -90° C. Theoretically, either of the two methods should give satisfactory results provided one uses extremely small tissue samples and follows the accepted guidelines for substitution. Since our protocol requires the use of relatively large samples, which are encased in a voluminous amount of media it is obligatory to adhere strictly to a methanol (-90° C) substitution regimen to be assured complete substitution has taken place (Table 1). Porcine heart valves were dissected into segments consisting of the aortic wall and leaflet. Segments were exposed to a variety of new cryoprotective agents (CPAs) and placed in the center of a parafilm sleeve with 1.5ml of CPA and cooled at 1° C/min to −80°and stored in the vapor phase of liquid nitrogen. Samples were processed for either routine histological studies or freeze-substituted to obtain profiles of ice formation.
Biological Labeling and Correlative Microscopy
Authors: Robinson JM , Takizawa T
Published: July 2020

A variety of biological labeling techniques has been developed in order to obtain specific chemical and spatial information from cells and tissues. Traditionally theses labeling techniques have been categorized as cytochemistry, immunocytochemistry, and in situ hybridization. Another special category relates to fluorescence analog cytochemistry in which specific fluorescently-labeled molecules become incorporated into the pool of endogenous molecules of the cell. They can thus serve as reporters for analysis of the dynamic properties of the population of molecules of interest. Such molecules are usually introduced into cells by microinjection or expressed within the cell (e.g., green fluorescent protein derivatives).

The past few years have witnessed a renaissance in biological optical microscopy. Many of the advances in the elucidation of cell structure-function relationships made through the use of optical microscopy have relied upon fluorescence labeling technology. These advances notwithstanding there remain experimental situations in cell biology that require the higher spatial resolution afforded by electron microscopy. Combining fluorescence and electron microscopy to study the same structures would be very useful in many experimental situations in cell biology. Such an examination of the same structures with more than one imaging modality can be referred to as correlative or integrated microscopy. The number of such studies is relatively small; this is probably due to technical difficulties encountered by various investigators.
Two-Photon Excitation Imaging of Biofilm
Authors: Gerritsen HC , de Grauw CJ
Published: July 2020

Dental plaque is the biofilm which forms on the surface of teeth, comprising a multitude of bacterial species embedded in microbe- and host-derived polymers. Confocal microscopy (CLSM) studies revealed an open architecture in which palisades of biofilm biomass were shown to be interspersed with water channels of lower density. However, the penetration depth of CLSM in these samples is limited to around 20-40 μm, depending on the density of the samples. Therefore, thick biofilms associated with, for example, fissures in the tooth surface, can not be investigated using this technique. The limited depth penetration of CLSM can be overcome by employing two-photon excitation microscopy (TPEM). Due to the use of the longer wavelength excitation light in TPEM, a two to four fold higher penetration into the sample is obtained than in CLSM, see fig. 1. This, together with the reduced photobleaching of the fluorescent probes, makes TPEM well suited for in-depth imaging studies of strongly scattering samples such as biofilm.

The biofilm nature of plaque allows the development of gradients of key biochemical parameters such as ion concentrations. These gradients may result in extreme conditions at certain sites within the plaque that are often associated with the development of the diseased state. Conditions in the oral cavity are overtly aerobic, and the pH of saliva is near neutral.
Breaking the Resolution Limit of Far Field Optical Microscopy: Imaging Molecular and Cellular Interatction on the Nanometer Scale
Authors: Cragg G , Kwon H S , Dong C Y , So P T C
Published: July 2020

Historically, high-resolution optical microscopy has played a vital role in biomedical research. The resolution of conventional optical microscopy is limited by the diffraction effect to about 200 nm and 500-900 nm in the radial and axial directions, respectively. This modest resolution is a major limitation in using optical microscopy for demanding applications. New techniques such as near field optical microscopy, scanning tunneling microscopy, and atomic force microscopy have been developed to circumvent this problem and have achieved atomic resolution in solid state specimens. Unfortunately, the applications of these new techniques have been difficult in biological systems. First, scanning probe techniques require mechanical interaction with the specimens. The mechanical forces exerted by the probe tip may cause sample deformation. This interaction further degrades the achievable image resolution. Resolutions in the range of 50 to 100 nm are often reported for near field optical systems. Second, scanning probe technique has a relatively low frame rate since the required high precision position control imposes severe bandwidth limitations. Scanning probe techniques are more suitable for studying static sample but often have difficulties in addressing many inherently dynamical phenomena in biology. Third, these are surface imaging techniques and are inherently limited in their ability to investigate the 3-D structures of biological specimens.
X-Ray Mapping with Energy-Dispersive and Wavelength-Dispersive X-Ray Spectrometry in the Scanning Electron Microscope: a Tutorial
Authors: Newbury Dale E , Bright David S
Published: July 2020

X-ray mapping is one of the most popular modes for displaying information obtained with x-ray spectrometry performed in the scanning electron microscope. This popularity arises from the ready accessibility and apparent simplicity of information presented in a pictorial fashion, especially when used in conjunction with other SEM imaging modes, such as backscattered, secondary, and specimen current electron images. Further, the rise of powerful, inexpensive computer systems capable of image processing and display has given the analyst a dedicated, on-line tool with the capacity and flexibility needed for problem solving. Figure 1 shows a typical example of mapping. Although the interpretation of x-ray images obtained with a modern digital control and recording system would seem to be straightforward and relatively trivial, there are significant pitfalls and limitations that can easily fool the unwary. In Figure 1, within an individual x-ray map, the observer can reasonably judge where the concentration is lower or higher, at least for a group of contiguous pixels. Can such judgments be made among a set of maps of the same region for different elements, or even for the same element from different regions of the same specimen? With current x-ray processing and display systems, the answers are generally no. In fact, problems that can influence interpretation can arise at each stage of x-ray generation/emission, x-ray spectral collection, processing, and display.
EDS and WDS Automation: Past Development and Future Technology
Authors: McCarthy J J , Frief J J
Published: July 2020

Early Development Automation of electron probe analysis began to flourish in the early 1970s spurred on by advances in computer technology and the availability of operating systems and programming languages that the individual researcher could afford to dedicate to a single instrument. By the end of the decade, most researchers and vendors in the microanalysis field had adopted the PDP-11 minicomputer, and languages such as FOCAL, FORTRAN and BASIC that ran on these computers. A good summary of these early efforts was given by Hatfield. The first use of the energy dispersive detector on the electron probe in 1968 added the need to control the acquisition, display and processing of EDS spectra. As a result, the 70’s were also a time when much attention was focussed on development of software for on-line data reduction and analysis. These efforts produced a suite of programs to provide matrix corrections and spectral processing, and automation of WDS data collection. The culmination of these development efforts was first reported in 1977 with the analysis of a lunar whitlockite mineral by simultaneous EDS/WDS measurement. This analysis determined the concentration of 23 elements, 8 by EDS and took a total of 37 minutes for data collection and analysis. In this paper, the authors noted the complementary use of the EDS and WDS (WDS for trace elements and severe peak overlaps, EDS for other elements and rapid qualitative analysis) in their automated instrument, a convention that remains common on the electron probe even today. Toward the end of the decade the analytical accuracy and precision achieved by automated analysis of bulk samples approached the limits of the instrumentation, with the exception of analysis of light element concentrations.

Two Decades of Improvements The explosive growth in digital electronics and microprocessors for data processing and control functions during the 80’s was rapidly applied to electron probe automation. Second and third generation automation systems included direct control of many microscope functions, beam position and imaging conditions. Motor positioning was more precise and far faster. As a result, the data collection and analysis of 23 elements reported in 1977 could be accomplished at least three times faster on a modern instrument.
SEM and EDS Characterization of Titanium Cathodes Before and After Electrolysis in Heavy Water
Authors: Warner J , Dash J
Published: July 2020

A series of experiments were conducted with titanium cathodes and platinum anodes electrolyzed in heavy water-sulfuric acid electrolyte in closed cells. Each of the cathodes in these experiments was cut from the same titanium foil (99.99% Ti). Each cathode underwent a pre-experiment and a post-experiment SEM (ISI-SS40) and EDS (LINK AN10000) analysis. Of the eight experimental cathodes, three showed post-experimental evidence of localized chemical changes. This is consistent with other findings from this lab. Results obtained on one of these cathodes are presented here.

This cathode was electrolyzed for 115 hours at 0.40A (current density about 2A/cm2). The cathode was ultrasonically cleaned in deionized water for five minutes prior to the pre experiment analysis. Fig. 1 shows the smooth surface of the cathode before electrolysis. No other elements besides titanium were found. After electrolysis in 19.4g D2O +l.0g H2SO4 the cathode was removed from the cell and rinsed by gentle agitation in deionized water for several minutes.
Cryogenic Microcalorimeters for High Resolution Energy Dispersive X-Ray Spectrometry
Authors: J.Höhne  , Altmann M , Angloher G , Bühler M , Feilitzsch Fv , Frank T , Hettl P , Hertrich T , Jochum J , Nüßle T , Pfnür S , Schnagl J , Wänninger S
Published: July 2020

Abstract

Cryogenic detectors with excellent energy resolution and low energy threshold far beyond the level of semiconducting detectors open a variety of new. applications in physics including search for Dark Matter in the universe [2], neutrino physics [3], and IR-, UV- and X-ray astrophysics [4, 9]. Interdisciplinary fields where cryogenic detectors have already shown promising results are the detection of biomolecules [5] and X-ray spectroscopy at synchrotron beam lines [6] and in scanning electron microscopes (SEMs) [7]. For both, astrophysical and analytical use, the development of high resolution microcalorimeters based on iridium/gold phase transition thermometers and aluminum tunnel junctions for use in a compact and universal detector system was initiated.

Our cryogenic microcalorimeters consist of an absorber, a temperature sensor and a weak coupling to a heat sink. An X-ray photon interacts with the absorber and raises its temperature. The sensor measures the temperature increase and the system then, mediated by the coupling, relaxes back to its operating temperature.
Characterization of FIB Damage in Silicon
Authors: Urbanik CA , Prenitzer BI , Gianhuzzi LA , Brown SR , Shofner TL , Rossie B , Irwin RB , Stevie FA
Published: July 2020

Focused ion beam (FIB) instruments are useful for high spatial resolution milling, deposition, and imaging capabilities. As a result, FIB specimen preparation techniques have been widely accepted within the semiconductor community as a means to rapidly prepare high quality, site-specific specimens for transmission electron microscopy (TEM) [1]. In spite of the excellent results that have been observed for both high resolution (HREM) and standard TEM specimen preparation applications, a degree of structural modification is inherent to FIB milled surfaces [2,3]. The magnitude of the damage region that results from Ga+ ion bombardment is dependent on the operating parameters of the FIB (e.g., beam current, beam voltage, milling time, and the use of reactive gas assisted etching).

Lattice defects occur as a consequence of FIB milling because the incident ions transfer energy to the atoms of the target material. Momentum transferred from the incident ions to the target atoms can result in the creation of point defects (e.g., vacancies, self interstitials, and interstitial and substitutional ion implantation), the generation of phonons, and plasmon excitation in the case of metal targets.
Effects of Protective Capping on Ultra-Thin SIMOX Structures
Authors: Wilson T , Jiao J , Seraphin S , Johnson B , Anc M , Cordts B
Published: July 2020

Devices for character recognition as well as cellular phones require computational elements that work at higher speeds with lower current requirements. Separation by IMplanted Oxygen (SIMOX) is one type of Silicon On Insulator (SOI) technology that shows great promise in meeting the future demands for faster and more efficient applications. The ultra-thin SIMOX substrates produced by low energy/low dose implant methods make possible the construction of large scale integrated circuits with fully depleted CMOS devices. One of the great challenges in the production of SIMOX technology is achieving high quality Si and Si02 layers. High energy implantation of 0+ ions causes damage to the Si crystal and therefore requires a high temperature annealing step to repair it. Annealing of SIMOX takes place in a mixed atmosphere of argon and oxygen. Having oxygen in the ambient creates a superficial Si02 layer. This reduces the thickness of the SOI layer but also protects the surface from pitting.
The Apex Structure of Co-Produced Helical Boron Nitride and Carbon Cones
Authors: Bourgeois L , Bando Y , Kurashima K , Sato T
Published: July 2020

Conical whiskers of layered compounds such as graphite and hexagonal boron nitride (h-BN)2 are interesting materials because their conical morphology results from the introduction of a local topological defect at the cone apex. In the honeycomb array characteristic of graphite and h-BN basal planes, this topological defect is thought to be a non-hexagonal ring (e.g. a pentagon or a square). These defects are known to form the basis of curved nanostructures like fullerenes and buckytubes. Therefore a comparison of their occurrence in two systems known to harbour nanostructures is worthy of study.

The defect structure at the apex of co-produced carbon and boron nitride whiskers was investigated by analytical transmission electron microscopy (TEM). The instrument used was a field-emission JEM3000F high-resolution electron microscope, equipped with a parallel electron energy loss spectrometer (EELS).
Electron Probe Microanalysis (EPMA) Characterization of Scales Formed on Laves Phase Reinforced Cr Alloys at 1100°C in Air
Authors: Walker LR , Brady MP
Published: July 2020

Laves phase (Cr2X) strengthened Cr solid solution [Cr(X)]-based alloys are under development for a variety of high-temperature structural applications. Among the most promising alloys are castings based on the Cr(Ta)-Cr2Ta eutectic, which exhibit room-temperature fracture toughness in the 10-12 MPa√m range and creep rupture lives in excess of 1000 h at 1000° (138 MPa) in air. These alloys exhibit superior high-temperature oxidation resistance to previously developed Cr(Nb)-Cr2 Nb based alloys despite the general similarities of Ta and Nb. In order to optimize high-temperature oxidation resistance an understanding of why the Cr(Ta)-Cr2Ta alloys are more oxidation resistant is needed. Detailed EPMA characterization of the oxidized scaleswas initiated as a first steptowards gaining this understanding.

Fig. 1 shows a backscattered electron image of cast and heat treated and heat treated Cr-10Nb at.% after a 6 cycle, 120 h exposure at 1100°C in humid air. Most of the coupon was converted to a complex mixture of Cr-, Nb-, and Cr+ Nb- oxides.
Identification of Alpha Prime in an Aged Fe-12cr Steel Using Extraction Replicas and Energy Filtered TEM.
Authors: Larsen M , Angeliu T , Mukira C
Published: July 2020

Long term aging of martensitic Fe-12Cr steels at elevated temperatures can result in a significant decrease in toughness. The mechanism responsible for this has been generally attributed to either impurity segregation and/or precipitation of second phases. The aging embrittlement of higher Cr-containing ferritic steels has long been attributed to the precipitation of bcc Cr-rich alpha prime phase[l]. Alpha prime has also been shown to embrittle certain Ni base alloys [2]. The current work has shown that alpha prime forms in Fe-12Cr steels which have been aged at 450°C for up to 32khrs. Coincident with the precipitation of alpha prime is a marked decrease in toughness.

Historically, extraction replicas and to a limited extent thin-foil TEM microscopy have been used to identify alpha prime. However, both are not without problems in these magnetic, corrosion-resistant steels, due to the fact that the alpha prime is small (<20nm) and coherent with the matrix. Volume fraction studies have been essentially impossible.
Near Real-Time X-Ray Cone-Beam Microtomography
Authors: Ang Shih , Ge Wang , Ping-Chin Cheng
Published: July 2020

Due to the penetration ability and absorption contrast mechanism, cone-beam X-ray microtomography is a powerful tool in studying 3D microstructures in opaque specimens. In contrast to the conventional parallel and fan-beam geometry, the cone-beam tomography set up is highly desirable for faster data acquisition, build-in magnification, better radiation utilization and easier hardware implementation. However, the major draw back of the cone-beam reconstruction is its computational complexity. In an effort to maximize the reconstruction speed, we have developed a generalized Feldkamp cone-beam reconstruction algorithm to optimize the reconstruction process. We report here the use of curved voxels in a cylindrical coordinate system and mapping tables to further improve the reconstruction efficiency.

The generalized Feldkamp cone-beam image reconstruction algorithm is reformulated utilizing mapping table in the discrete domain as: , where .
Pc-Based Imaging System for Color Cell Identification and Scoring
Authors: Suri Jasjit S , Satyender Kumar
Published: July 2020

Pathologists, microbiologists and cytologists are very interested to automatically identify and quantify the sperms, cells or nucleus in the cellular level images. Complexities like voluminous data sets, variability in data sets, millions of colors, and different kinds of artifacts make the detection and quantification process very difficult. This paper is an attempt to design a sophisticated cellular diagnostic system based on color image processing, mathematical morphology and connected components based on run length encoding. This system runs on Windows ‘98/NT PC platform, in Visual C++, 6.0 environment using three different architectures: Single document interface, multiple document interface and dialog based applications. The system takes around 1.5 seconds per image of 512 x 484 square pixels using high speed threading architecture written on the on 400 MHz Pentiumll processor. The system has an accuracy of 95%. The software has been validated tested on NASA and machine vision real world images.
Tapping Mode Near-Field Scanning Optical Microscopy of Molecular Crystals and Thin Films
Authors: Daniel Frisbie C , Kosterin Andrey , Stadniychuk Helena
Published: July 2020

The diffraction of visible light limits the spatial resolution in conventional optical microscopy to about 200-300 nm. In near-field scanning optical microscopy (NSOM), resolution is improved by bringing the light source, such as the end of an optical fiber, very close to the sample surface. Laser light coupled into the opposite end of the fiber propagates down the fiber core and is emitted from the aperture of the tip. When the sample is in the near-field(roughly within one tip diameter of the end of the tip), the spatial resolution is essentially equal to the diameter of the aperture at the end of the tip and is not determined by diffraction effects. Two-dimensional imaging is accomplished by raster-scanning the sample underneath the fiber tip and collecting transmitted or reflected light at a photodetector.
Structural Studies of Dynamin Tubular Crystals by Cryo-Electron Microscopy
Authors: Zhang Peijun , Hinshaw Jenny E
Published: July 2020

Dynamin is a 100 kD GTPase that plays an essential role in clathrin-coated vesicle formation during receptor mediated endocytosis, and in caveolae internalization and may play a role in intracellular membrane trafficking (1). It shares an extensive sequence homology (70% identity) to shibiregene product in Drosophila(2,3). The shibiretsmutants exhibit a rapid and reversible paralysis at non-permissive temperature due to a depletion of synaptic vesicles in their nerve termini which is believed to be caused by a block in endocytosis since there is an accumulation of “collared” clathrin-coated pits at the plasma membrane (4). Synaptosomes treated with GTPγs produces elongated necks surrounded by dynamin (6). Purified recombinant dynamin itself can assemble to form spirals and bind to lipid vesicles to form tubes, which resemble the “collar” at the necks of coated pits (5). These dynamin tubes vesiculate upon GTP treatment (7), suggesting a unique role of dynamin acting as a mechanoenzyme which causes clathrin-coated vesicles to be pinched off plasma membrane.
Ultrastructural Morphology of Cationic Liposome/Dna Complexes for Gene Therapy: Correlation to Transfection Activity
Authors: Sternberg Brigitte , Hong Keelung , Zheng Weiwen , Papahadjopoulos Demetrios
Published: July 2020

Complexes formed during interaction of cationic liposomes with poly-nucleotides such as DNA (CLDC) display a variety of polymorphic and metastable structures. These include multilamellar structures of alternating lipid bilayers and DNA monolayers; fibrillar structures, among them spaghetti-liketubules (Figure 1), and map-pin-structures(Figure 2), and, finally, non-bilayer lipid arrangements, such as hexagonal (HII) (Figure 3) and cubic phases.

In order to find out the “active” structure(s) in terms of transfection, we investigated the transfection activity both in vivoand in vitroof CLDC composed of the lipid DDAB (dimethyl-dioctadecylammonium bromide) and Choi (cholesterol) or DOPE (l,2-dioleoyl-sn-glycerol-3- phosphoethanolamine) as helper lipids. In parallel we studied their morphology by freeze-fracture electron microscopy.The in vivostudies were carried out in mice following i.v. injection and therefore the morphology of the CLDC was investigated in mouse serum.
Androgen-Responsive Lncap and Androgen-Independent Du145 Prostate Cancer Cells Display Different Taxol Sensitivities
Authors: Ripple Maureen , Taylo Meghan , Huese Chris , Schatte Heide
Published: July 2020

Taxol has been used as anti-cancer compound against prostate, ovarian, and metastatic breast cancer. While the most obvious effect of taxol is bundeling of microtubules and mitotic arrest, recent studies have demonstrated that taxol is able to induce intranucleosomal DNA fragmentation and typical morphological features of apoptosis in a number of solid tumor cells. These results indicate that taxol may exert its anti-tumor effects via secondary mechanisms which may or may not be related to its primary effects on microtubules. It has been shown that taxol-induced microtubular changes and G2/M arrest are associated with the release of the electron transfer protein cytochrome C from mitochondria into the cytosol. Cytochrome C then binds to APAF-1 (a human homolog of the ced-4 gene of C. elegans), which binds, cleaves, and activates caspase- 9, ultimately resulting in the cleavage and activity of caspase-3. We investigated the effects of taxol (100nM) on microtubules, on DNA, and on the pre-apoptotic mitochondrial events using LNCaP and DU145 prostate cancer cells.
Enhancement of Differential Interference Contrast Images of Live Cells Obtained With Digital Cameras
Authors: Parthasarathy MV
Published: July 2020

The usefulness of Differential Contrast Interference (DIC) light microscopy for observing fine details within transparent specimens is well known. However, when viewed by the eye or by recording with photographic emulsion, fine structural detail at the limit of resolution is often not visible because of lack of contrast. To overcome this problem, electronic contrast enhancement capabilities of video cameras have been used to enhance structural details that would otherwise be invisible. The technique, commonly referred to as VE-DIC (Video Enhanced DIC), uses first analog contrast enhancement of the image with a video camera followed by a real-time digital image processor to further enhance the image with. We are exploring the feasibility of achieving fine structural detail of live cells by directly acquiring digital images of them with a high resolution CCD camera.

High resolution cooled slow-scan 12-bit CCD cameras are well suited for DIC microscopy because of their greater dynamic range than video CCD cameras that are normally 8-bits or lower.
Application of Cryo-High Resolution (Hr) Sem Technique for Imaging Platelet Morphology
Authors: Wendt MC , Robinson KA , Chronos NAF , Caran KL , Apkarian RP
Published: July 2020

Platelets play a major role in hemostasis due to their ability to adhere and aggregate at sites of vessel wall injury. Damage to the inner surface of arteries includes ruptures or tears at the site of atherosclerotic plaques or injury resulting from interventional procedures. Uncontrolled platelet recruitment and aggregation at these sites can lead to complete occlusion of the vessel. Thus the understanding of platelet function and structure has become an important goal in preventing vascular disease. We employed cryo-HRSEM techniques to gain more insight into the surface morphology of both quiescent and thrombin stimulated platelets.

Platelet rich plasma (PRP) was obtained by mixing whole blood (21 ml) drawn from juvenile pigs with 3 ml of acid citrate dextrose and centrifugation at 300g for 10 min. To obtain washed platelets the PRP was washed three times with a citrate wash buffer consisting of 36mM citric acid, 5mM glucose, 5mM KCl, 2 mM CaCl2, 1 mM MgCl2, 90 mM NaCl, pH 6.5.
Laboratory Safety For the Electron and Correlative Microscopist
Authors: Miller S E , Howel D N
Published: July 2020

Laboratory safety in a diagnostic electron microscopy (EM) laboratory that deals with potentially infectious specimens is a complex issue. The risk of infection of laboratory personnel is an obvious concern, particularly in laboratories, such as diagnostic virology laboratories, which handle infected tissues and body fluids on a routine basis. A second hazard is introduced by the multitude of toxic, corrosive, and irritating chemical reagents required for the preparation of samples for EM. Physical hazards inherent in the complex machinery necessary for EM and other forms of microscopy must also not be overlooked. Attention to each of these concerns must be orchestrated over the course of a multistep process that often lasts several days. Success in this endeavor is facilitated by a comprehensive quality control program encompassing personnel, specimens, chemicals, and equipment.

The foundation for safe handling of samples in the clinical laboratory is the principle of universal precautions, under which all blood, other body fluids, and tissues are considered potentially infectious and handled using appropriate protective measures.