bluuebunny/crossref_metadata_2025_split huggingface dataset:
CBED and HREM study of decagonal quasicrystals
Authors: Tanaka M. , Tsuda K. , Saitoh K. 
Published: June 2020

Decagonal quasicrystals have been investigated by convergent-beam electron diffraction (CBED) and transmission electron microscopy. Figure 1 shows possible pentagonal and decagonal point groups. The CBED method has revealed that the decagonal quasicrystals found so far belong to the space groups of noncentrosymmetric P10m2 and centrosymmetric P1O5mmc.Dark-field microscopy has revealed the existence of inversion domains with an antiphase shift of c/2 at the domain boundaries in the alloys with space group m2.2 High-resolution electron microscopy (HREM) has revealed the existence of specific pentagonal atom clusters in the Al-Ni-Fe, Al-Cu-Co and Al-Ni-Co alloys. Figure 2 shows a HREM image of Al70Ni15Fe15 belonging to space group m2. The atom clusters of an about 2nm diameter are clearly seen as indicated by a black circle. The clusters are polar or noncentrosymmetric due to the dark pentagon at their centers. All the clusters in domain A have one sense of polarity and those in domain B the other sense. It should be noted that the HREM image of the cluster columns was found to be pentagonal at an accelerating voltage of 200kV but nearly decagonal at higher than 300kV.
Ultrastructural morphology of the dorsal lobe of the prostate gland in cadmium and zinc-treated rats
Authors: Bataineh Z.M. , Hailat N. , Lafi S. , Hani I. Bani 
Published: June 2020

We have demonstrated in previous study that the nucli of the cells of the posterior lobe of the prostate gland sequesters less zinc in cadmium and zinc treated rats compared to the normal ones. In this study we will evaluate if the variation in the nuclear zinc concentration is associated with a concomitant variation in ultrastructural morphology. Two groups of animals were injected with 2mg/kg and 10 mg/kg cadmium chloride and zinc sulfate, respectively. Another group served as control. Dorsal lobe of the prostate gland from the three groups were prepared for conventional E.M study. Grids were examined and photographed by Hitachi-700 electron microscope.Figure (1) shows prostatic cells from the posterior lobe of the prostate gland of a normal rat. The rough endoplasmic reticulum form a narrow continuous cisternae, most abundant at the lateral portion of the cell and sometimes acquired whorl-shaped appearance. Well-developed Golgi apparatus with abundant secretory vesicles are shown.
Seminal cytology in infertile men with chlamydia trachomatis and ureaplasma urealyticum infections. observations through electron microscopy
Authors: Gallegos A. M. G. , Díaz G. O. G. , Vazquez H. M. J. , Rositas M. R. , Ramirez B. E. 
Published: June 2020

Among non gonococcic uretritis 60 % of them are caused by C. trachomatis and U. urealyticum, organisms transmited by sexual contact. These are frecuently presented like asymptomatic infections and involved a diminish sperm quality. The defects in motility and morphology of spermatozoa associated with these infections have not to date been explained clearly, although, in the case of U. urealyticum it has been shown that sperm motility is decreased by the physical adherence of the organism to the tail of the spermatozoon.Although, some descriptions of the ultraestructure of semen in pacients with U. urealyticum and C trachomatis infections exist, there has not been a detailed description of alterations of the fine structure of the spermatozoa that can or can't be related to astenozoospermia.
Cytoplasmic dynamics of the tubulin and actin cytoskeletons during teliospore germination and basidiospore formation in a rust fungus
Authors: Roberson Robert W. , Sharp William P. , Shields John P. , Sayegh Steve , Al-Anzi Bader F. 
Published: June 2020

Gymnosporangium clavipes C. & P. is a basidiomycetous fungus belonging to a common and destructive group of plant pathogens known to as the rusts. The rusts are best known for their damage to economically important crops including corn, wheat, oats, and barley and have become important model organisms in cell biology studies. Of all the stages in their complex life cycle, perhaps the most interesting are those involved in teliospore germination and basidiospore formation.As illustrated with scanning electron microscopy teliospores of G. clavipes are ellipsoidal spores consisting of an apical and basal cell (Fig. 1). Upon germination of the teliospore, four discrete morphological events occur that give rise to mature basidiospores. These events include: i) emergence of germ tubes (Fig. 2), ii) formation of three septal cross walls segmenting the germ tube into four compartments (Fig. 3), iii) growth of a single sterigma from each compartment, (Fig. 4) and iv) enlargement of sterigmal tips to form individual basidiospores (Fig. 5). The objective of this research was to determine whether these developmental stages were temporally correlated with changes in the organization of the tubulin and actin cytoskeletons.
Application of high-pressure scanning electron microscopy (ECO-SEM) in forensic sample analysis
Authors: Kubic Thomas A. , Buscaglia JoAnn 
Published: June 2020

Traditionally to obtain satisfactory images and reasonable resolution with a Scanning Electron Microscope (SEM), it has been necessary to employ a high vacuum within the sample chamber.High vacuum can result in the dehydration of materials with an alteration of sample morphology and in some cases the introduction of artifacts. In such an environment, samples that are nonconductive experience extensive charging with image degradation. Samples of forensic concern, such as textile bundles or swatches, exhibit this problem even after the application of metal coating. The problem is even more pronounced when carbon coating is used, as is often the preference of forensic microscopists in order to simplify interpretation of the EDX spectra.The commercial availability of "high pressure" or controlled environment SEMs that operate with sample chamber pressures from 50 to 4000 millitorr, while the electron guns and columns are kept at high vacuum conditions have solved these problems. The presence of this "higher" pressure retards dehydration while charging effects are nearly eliminated.
Near-field scanning optical microscopy imaging of luminescent polymers
Authors: Kerimo J. , Vanden Bout D. A. , Higgins D. A. , Barbara P.F. 
Published: June 2020

Conjugated polymers such as poly(p-pyridyl vinylene)(PPyV) have interesting photoluminescence and electroluminescence properties. These polymers have a high quantum yield of luminescence and are of great practical importance as light-emitting diodes or organic semiconductors. We have performed studies on thin films(about 50nm) of these polymers using the high spatial optical resolution of NSOM.The luminescent polymer film was excited with 488nm light and the fluorescence was collected with a high numerical aperture microscope objective. Topography and NSOM fluorescence images were collected simultaneously and used for studying the morphology and optical properties of the film. An example of topography and fluorescence NSOM images of the film is shown in Fig. 1a. The films are very flat (2nm rms variations in topography) and have very few features. The NSOM fluorescence image shows great film inhomogeneity with bright features varying in size from 80-250nm observed throughout (Fig. 1b). These features do not correlate with the topography, indicating they may be located in the bulk of the polymer or are simply not resolvable in the topography image.
High-precision calibration of a scanning-probe microscope (SPM) for manufacturing applications
Authors: Chernoff Donald A. , Lohr Jason D. , Hansen Douglas , Lines Michael 
Published: June 2020

Introduction. For ordinary SPM (Scanning Probe Microscope) work, accuracy of XYZ length measurements of about 5% is acceptable. This is accomplished by periodic calibration checks (and adjustments, if required). Measurement of critical dimensions such as feature width and spacing on integrated circuits or compact discs requires much higher accuracy. For example, the new DVD (digital video disc) standard calls for a mean track pitch of 740 nm with a maximum allowable jitter (range) of 30 nm. To achieve a range of 30 nm, the standard deviation should be 10 nm or less. According to the gage-maker's rule, the measurement tool should be 4x more precise than the object being measured, so we need a standard deviation of 2.5 nm. This report describes the combined use of a new type of calibration standard and new software to meet these requirements.Materials. Recently, MOXTEK has produced 1- and 2-dimensional holographic gratings as calibration standards for use with SEMs (Scanning Electron Microscopes).
Imaging free Carriers in Electronic Material using a Scanning Probe Microscope: Scanning Capacitance Microscopy
Authors: Erickson A , Adderton D , Day T , Alvis R 
Published: June 2020

The development of methods to measure electrical properties, which are suitable to directly yield the desired carrier distributions on a nanometer scale has greatly benefited from the development of scanning probe technology over the last decade. Scanning Probe Microscopes (SPMs) offer inherent two-dimensionality and have been shown to have applications ranging from Magnet force to electro-chemistry. We have used an SPM in contact mode to simultaneously measure topography (and therefore physical structure) and capacitance variations (due to an applied bias) of various electronic materials such asdoped silicon, poly silicon, SiC, and III-V materials.The technique aptly named Scanning Capacitance Microscopy (SCM) takes advantage of the fact that electrical carrier response to an applied electric field is largely dependent upon the local carrier concentration. Using a high 'Q' GHz resonant circuit, SCM measures capacitance variations due to an applied bias between the metalized nano-probe tip and semiconductor sample during scanning. Since thesevariations are directly related to dopant (carrier) concentration, the SCM generates a two-dimensional image with contrast corresponding to near-surface variations in carrier density. Because the measurement is done with an extremely sharp probe, we have been able to resolve features as small as lOnm, corresponding to attofarad (le-18 farad) capacitance changes.
TEM characterization of LPCVD Ta2O5 films fabricated by pre-deposition rapid thermal nitrtdation
Authors: Park J.C , Choi J.M. , Oh J.W. , Choi J.T. , Kim S.S. , Choi H.M. , Hahn S.B. 
Published: June 2020

Chemical vapor deposited tantalum pentoxide (Ta2O5) films have been a promising dielectric material for a storage capacitor in high-density DRAM with three-dimensional cell architecture, due to its higher dielectric constant than that of conventional SiO2 or Si3N4/SiO2 films. The effective dielectric constant of Ta2O5 films is influenced by the thickness of interfacial lower-dielectric Si02 layer which could be a native oxide or a thermally grown oxide during deposition and annealing. In general, the capacitor with the thinner SiO2 layer has the larger effective dielectric constant. In this work, the capacitor structure films prepared with or without RTN treatment, which was performed to inhibit the growth of SiO2, were studied by various TEM techniques.Two samples were prepared to compare the characteristics of the Ta2O5 films fabricated with or without RTN treatment Ta2O5 films were deposited on a phosphorus-doped polysilicon on a p-type silicon substrate by low pressure chemical vapor deposition (LPCVD).
Structure of contact sites between the outer and inner mitochondrial membranes investigated by HVEM tomography
Authors: Mannella C.A. , Buttle K.F. , O‘Farrell K.A. , Leith A. , Marko M. 
Published: June 2020

Early transmission electron microscopy of plastic-embedded, thin-sectioned mitochondria indicated that there are numerous junctions between the outer and inner membranes of this organelle. More recent studies have suggested that the mitochondrial membrane contacts may be the site of protein complexes engaged in specialized functions, e.g., import of mitochondrial precursor proteins, adenine nucleotide channeling, and even intermembrane signalling. It has been suggested that the intermembrane contacts may be sites of membrane fusion involving non-bilayer lipid domains in the two membranes. However, despite growing interest in the nature and function of intramitochondrial contact sites, little is known about their structure.We are using electron microscopic tomography with the Albany HVEM to determine the internal organization of mitochondria. We have reconstructed a 0.6-μm section through an isolated, plasticembedded rat-liver mitochondrion by combining 123 projections collected by tilting (+/- 70°) around two perpendicular tilt axes. The resulting 3-D image has confirmed the basic inner-membrane organization inferred from lower-resolution reconstructions obtained from single-axis tomography.
Microstructure of GaAs nanocrystals formed inside single crystalline silicon
Authors: Zhu Jane G. , White C. W. , Budai J. D. , Yacaman M. J. , Mondragon G. 
Published: June 2020

Semiconductor nanocrystals exhibit novel properties that are important for electronic and opto-electronic device applications. Many methods have been developed to synthesize semiconductor nanocrystals. Among them is the ion implantation technique, which is compatible with the semiconductor technology. It has been recently reported that the compound semiconductor GaAs can be formed inside Si by sequential implantation of Ga and As and thermal annealing.In this study, GaAs nanocrystals were formed by sequential implantation of As and Ga, with the same dose of 1 x 1017 cm-2, into (100) Si substrates at 550°C. The implantation energies were chosen so that the Ga and As ions are overlapped over a few hundred nanometers in depth. The samples were then annealed at 1000°C for 1 h in flowing Ar + 4%H2 atmosphere to form GaAs precipitates. Transmission electron microscopy (TEM) has been used to study the microstructures of these samples.The cross-sectional TEM image in Fig. 1 shows the GaAs precipitates formed inside the Si substrateimplanted with As and then Ga.
TEM observations of hydrogen nanobubbles in implanted amorphous silicon
Authors: Jones K.M. , Williamson D.L. , Acco S. , Al-Jassim M.M. 
Published: June 2020

Over the last two decades extensive studies on the optical and electrical properties of hydrogenated amorphous Si (a-Si:H) have been reported. However, less attention was given to the structural characterization of this material partly due to the insensitivity to hydrogen of structural probes such as x-rays and electron diffraction. From a recent set of experiments, results on the solubility limit of hydrogen in a special type of a-Si:H and the characterization of hydrogen induced complexes or nanobubbles has been reported. In this study, we report TEM observations of the structural morphology ofhydrogen related defects that support these recent measurements obtained by secondary ion mass spectrometry (SIMS) and small-angle x-ray scattering (SAXS).a-Si:H thin films for solar cells and other applications are produced by a variety of methods. In each case, the deposited films are usually not homogeneous as they have been found to contain low density inhomogenities in the size range of 1-10 nm. These defects are commonly referred to as microvoids or hydrogen-rich clusters.
Electron holography of p-n junctions
Authors: Frost B.G. , Joy D.C. , Allard L.F. , Voelkl E. 
Published: June 2020

A wide holographic field of view (up to 15 μm in the Hitachi-HF2000) is achieved in a TEM by switching off the objective lens and imaging the sample by the first intermediate lens. Fig.1 shows the corresponding ray diagram for low magnification image plane off-axis holography. A coherent electron beam modulated by the sample in its amplitude and its phase is superimposed on a plane reference wave by a negatively biased Möllenstedt-type biprism.Our holograms are acquired utilizing a Hitachi HF-2000 field emission electron microscope at 200 kV. Essential for holography are a field emission gun and an electron biprism. At low magnification, the excitation of each lens must be appropriately adjusted by the free lens control mode of the microscope. The holograms are acquired by a 1024 by 1024 slow-scan CCD-camera and processed by the “Holoworks” software. The hologram fringes indicate positively and negatively charged areas in a sample by the direction of the fringe bending (Fig.2).
In-situ investigation of ion-implantation effects on radiation-induced segregation in Ni-Al alloys
Authors: Giacobbe M.J. , Lam N.Q. , Okamoto P.R. , Zaluzec N.J. , Stubbins J.F. 
Published: June 2020

In-situ experiments using the HVEM (high voltage electron microscope)/Tandem accelerator facility at Argonne National Laboratory were performed to determine the effects of 400-keV Zr+ and 75-keV Ne+ implantation on electron radiation-induced segregation (RIS) in Ni-9at.%Al at 550°C and 450°C, respectively. The alteration of RIS kinetics by Ne implantation was studied at two different doses. A highly-focused 900-keV electron beam, which produces a radial defect flux away from the beam center, was used to induce segregation of Al atoms in the opposite direction via the inverse-Kirkendall effect. Within the irradiated zone, Al enrichment drives the formation of γ′-Ni3Al precipitates, and the radial segregation rate of Al was monitored by measuring the growth of the precipitate zone.When a thin film is subject to a focused, electron beam, a non uniform defect distribution is produced. The effective beam diameter, D∘, is defined by IT= I∘ (πD∘/2)2 where IT is the total electron current and I∘ is the peak electron flux.
High-resolution EM investigation about effect of stress on formation of ω-phase crystals in β-tttanium alloys
Authors: Sukedai E. , Shimoda M. , Fujita A. , Nishizawa H. , Hashimoto H. 
Published: June 2020

ω-phase particles formed in β-titanium alloys (bcc structure) act important roles to their mechanical properties such as ductility and hardness. About the ductility, fine ω-phase particles in β–titanium alloys improve the ductility, because ω-phase crystals becomes nucleation sites of α-phase and it is well known that (β+α) duplex alloys have higher ductility. In the present study, the formation sites and the formation mechanism of ω-phase crystals due to external stress and aging are investigated using the conventional and high resolution electron microscopy.A β-titanium alloy (Til5Mo5Zr) was supplied by Kobe Steel Co., and a single crystal was prepared by a zone refining method. Plates with {110} surface were cut from the crystal and were pressured hydrostatically, and stressed by rolling and tensile testing. Specimens for aging with tensile stress were also prepared from Ti20Mo polycrystals. TEM specimens from these specimens were prepared by a twin-jet electron-polishing machine. A JEM 4000EX electron microscope operated at 400k V was used for taking dark field and HREM images.
Volumetric rendering of 3D SIMS depth profiles
Authors: McIntyre N.S. , Kingston D.M. , van der Heide P.A.W. , Wagter M.L. , Stanley M.B. , Clarke A.H. 
Published: June 2020

Dynamic secondary ion mass spectrometry (SIMS) can be used to uncover unique information about interfaces and whole structures which are “buried” within a solid. During a depth profile of a solid, a sequence of SIMS images is acquired for each element under study The sequence is correlated into a vertical “stack” which contains digitised three dimensional (3D) elemental distributions. Although such distributions are distorted by surface roughness, preferential sputtering and SIMS matrix effects, there is still considerable structural information contained in the volume and much potential for further information retrieval as the above-mentioned distorting effects are addressedOne of the major tools used to assess distributional information within the 3D volume has been visual rendering software. Using Sunvision software (Sun Microsystems Inc.) and a small workstation, images of the volume can be constructed which display pixels either in a “maximum value” perspective or in perspectives where the density of each phase can be adjusted to maximise structural detail.Several examples of the technique will be shown.
Molecular motors and fast axonal transport
Authors: Brady S. T. 
Published: June 2020

When video microscopy was first used to study fast axonal transport in isolated axoplasm from squid giant axons, a torrent of membrane traffic was seen to move in both directions. Images of membrane bounded organelles (MBOs) moving along individual microtubules (MTs) in axoplasm opened the way for characterization of the microscopic properties of fast axonal transport and led to the characterization of two molecular motors involved in fast axonal transport. The pharmacology of MBO movement ruled out previously identified molecular motors and a biochemical dissection of fast axonal transport in axoplasm demonstrated the existence of a new class of molecular motors. Subsequently, the polypeptides comprising a new class of molecular motor, kinesin, were discovered initiating a new era in the study of molecular motors and intracellular motility.The effects of ATP analogues on fast axonal transport led to dicovery of kinesin. When the nonhydrolyzable ATP analogue, adenylyl 5′-imidodiphosphate (AMP-PNP), was perfused into isolated axoplasm, all MBOs moving in both anterograde and retrograde directions stopped moving and remained attached to MTs. Unlike the effects of AMP-PNP on myosin and dynein, inhibition by AMP-PNP was rapid even in the presence of equimolar ATP, but was reversed by excess ATP.
Metaphase chromosome DNA mass fraction is independent of species
Authors: Williams S. , Jacobsen C. , Kirz J. , Lamm S. S. , Van’t Hof J. , Zhang X. 
Published: June 2020

Previous measurements of the composition of metaphase chromosomes yield values for the DNA mass fraction ranging from 15 - 32% (eg. 1), with a factor of two variation seen for chromosomes of a single species. The factors responsible for this variation are not known, but understanding them is of fundamental importance for constructing a realistic model of metaphase chromosome structure. The Scanning Transmission X-ray Microscope (STXM) provides the ability to make quantitative measurements of unstained, unfixed, thick wet specimens with a resolution of 55 nm. We have used the STXM to measure the total mass, density, size and shape of fixed wet chromosomes from three plant species and one marsupial species with differing amounts of DNA per chromosome. These measurements allow us to determine the dependence of chromosome composition on the amount of DNA per chromosome, and to determine whether chromosome composition differs between the plant and animal kingdoms.Metaphase chromosomes from the broad bean Vicia faba had a measured DNA mass fraction of 0.38. This value was obtained from both wet and freezedried specimens although the size and shape of the chromosomes resulting from these different treatments varied considerably (Fig. 1). This result indicates that the DNA mass fraction value obtained is not a property of the preparation procedure. Because dry specimens are not subject to mass loss at these exposure levels, the mass results for both the wet and dry specimens is not an artifact caused by radiation damage.