bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microscopic Characterization of a Sperm Mutant Line of the Fern Ceratopteris Richardii
Authors: Davidson Kelly A , Hickok Leslie G , Renzaglia Karen S 
Published: July 2020

Abstract
Mature sperm cells of Ceratopteris richardii are spiraled over three revolutions and contain a locomotory apparatus with approximately 70 flagella attached at the cell anterior (Fig. 1). Abundant organelles are dispersed along the inner surface of an elongated, coiled nucleus (Figs. 1, 3, 8). The cytoskeleton comprises a network of microfilaments that encases the nucleus (Fig. 6) and two distinct microtubule arrays: a microtubular ribbon (spline) and flagella with anchoring basal bodies (Fig. 3). This study uses light, fluorescence, transmission electron (TEM), and scanning electron microscopy (SEM) to characterize cell organization in a motility impaired sperm mutant line of Ceratopteris. Because motility mutations likely involve the cytoskeleton, emphasis was placed on observing microtubule and actin arrays in the mutant compared to wild-type sperm cells. Protocols follow Hoffman and Vaughn for TEM and Schmitt and Renzaglia for SEM. Microfilament arrays in relation to the nucleus were examined by rhodamine-phalloidin and DAPI fluorescence.
Characterization of Dislocation Reactivity and Dynamics in Thin Metal Films Using Scanning Tunneling Microscopy
Authors: Hwang RQ 
Published: July 2020

Abstract
The accommodation of strain in metal films can lead to complex phenomena, both structurally and chemically. It can generically lead to the formation of dislocations. These dislocations play an important role in defining the evolution and response of the film to further growth and external forces. The structures of the dislocations are directly analogous to bulk dislocations, but their properties are very different due to the presence of the surface. In addition, the strain can greatly affect the chemical properties of the film, leading to alternative strain relief mechanisms involving vacancy formation resulting from reaction with gases such as sulfur and oxygen. Using STM and LEEM, we have investigated these phenomena in the prototype systems of Cu and Ag on Ru(0001).
For example, figure la - d shows a sequence of STM images of a 2 layer Cu film on Ru(0001) during exposure to oxygen. Dislocations present in the film are altered by reaction with oxygen.
Evaporation Spirals on {111} and {001} Surfaces of MgAl2O4 Spinel
Authors: Bailey GW , McKernan S , Price RL , Walck SD , Charest P-M , Gauvin R , Yanina Svetlana V , Barry Carter C 
Published: July 2020

Abstract
Processes at dislocation sites are frequently predominant mechanisms of surface evaporation or growth and thus determine resulting surface morphologies. Dislocation-induced evaporation patterns are also a convenient object for observation of dynamics of step motion on crystal surfaces, as such patterns have “fixed” origins, being pinned at the point of dislocation emergence. In the present work, observations of evaporation spirals formed on ﹛111﹜ and ﹛001﹜ surfaces of MgAl2O4 spinel are reported.
2x2x1 mm samples of single-crystal MgAl2O4 spinel of ﹛111﹜ and ﹛001﹜ orientation were annealed in a spinel crucible in vacuum (10-4—10-5 Torr) in a Centorr™ furnace at 1800°C for 8 hours. SPM images were collected in air in contact mode on a Nanoscope III (Digital Instruments, Santa Barbara, CA), using Si3N4 cantilevers (Ultralevers, Park Inst., Sunnyvale, CA) with a nominal spring constant of 0.12 N/m. Selected sample surfaces were examined for impurities by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoemission spectroscopy (XPS).
Surfaces of Gadolinium Gallium Garnet
Authors: Gilliss S R , Yanina S V , Ravishankar N , Carter C B 
Published: July 2020

Abstract
Sintering and many problems in adsorption and catalysis require an understanding of the surface structures of crystals, which have been subjected to various types of heat treatment. For example, heat treatment of m-plane sapphire surfaces can cause a transformation from a flat vicinal surface into those of a faceted hill-and-valley structure. Many technologically interesting materials form with the garnet structure, including YIG, YAG, GGG and many silicates. However, there has been relatively little discussion of the structure and behavior of such surfaces. This paper illustrates the use of visible-light microscopy (VLM), atomic-force microscopy (AFM) and scanning electron microscopy (SEM) for studying the ﹛111﹜ surface of gadolinium gallium garnet (GGG or Gd3Ga5O12).
2x2x1 mm samples of monocrystalline GGG with ﹛111﹜ surface orientation were heat treated in air at 1575°C for 24 hours in order to study the processes a surface undertakes while reaching its equilibrium state.
Characterization of Large-Area Silicon Drift Detectors at High Count Rates
Authors: Patt BE , Iwanczyk JS , Tull CR 
Published: July 2020

Abstract
Silicon Drift Detectors (SDD) are being developed for analytical x-ray spectrometry having large active area, high-energy resolution and capability of operating at high counting rates. The development derives from the charged coupled device (CCD) for light-signal imaging, utilizing the extremely low capacitance of the detector and readout electronics and subsequent developments of silicon drift detectors for high-energy physics applications and more recently, x-ray spectroscopy applications. The now well-known advantage of the drift detector design is that, unlike traditional planar detectors, it allows for relatively large active area while still maintaining a very low anode capacitance (60 fF). This low value of detector capacitance results in a lowering of the series-noise component and hence the overall inherent electronic noise. Additionally, the reduction of the series noise leads to faster optimal shaping time, and as a consequence this provides for extremely high count rates.
Distribution and Behaviour of Positive Ions in the Environmental Scanning Electron Microscope (ESEM)
Authors: Craven John P , Baker Frank S , Thiel Bradley L 
Published: July 2020

Abstract
Electron detection in the environmental scanning electron microscope relies upon the presence of a small pressure of a gaseous phase inside the microscope chamber. The presence of this gas controls two important mechanisms by which the microscope functions. The conventional gaseous secondary electron detector (GSED) applies a variable positive bias (0 to +600 V) directly above the specimen. Electrons ejected from the specimen surface due to the incident scanning probe are accelerated by this field towards the positively biased detector. Whilst traversing the gap between specimen and detector the electrons undergo ionizing collisions with gas molecules. These result in an amplification of the incident electron signal through the production of ejected ‘daughter’ electrons and leave behind positively charged ions. After production these ions are repelled by the detector bias and drift back towards the microscope stage where they aid charge neutralization on the surface of the specimen.
Applying Dynamic Experiments and Stereo Measurements to Evaluation of Dentin Specimen Preparation Techniques for Environmental and Conventional SEM
Authors: Dusevich VM , Eick JD 
Published: July 2020

Abstract
The acid etching process is the primary stage for preparation of dental composite restorations. Dentin specimens from extracted teeth are usually prepared by fracturing etched pieces of dentin. Etching creates a demineralized layer on the dentin surface with the thickness of a few microns. The layer consists of wet collagen and dissolved proteins; its drying process is of special interest in dentistry since it affects the bonding of the resin adhesives to dentin. Observations of fractured surfaces can be performed in either a conventional or an environmental SEM.
Three wet dentin samples were observed (XL30 FEG ESEM, FEI/Philips) in wet mode at 5°C Peltier cooling stage temperature and 5.8 MPa water vapor pressure. Samples with excess water on their top surface were put in an ESEM. Thickness measurements of the demineralized zone were begun immediately after the evaporation of this water layer with subsequent measurements taken after 5, 10, 20, 40, 60 and 100 minutes of drying.
Introducing a Method for In Situ Electro-Rheology & Electrophoresis of Complex Fluids by Electron Microscopy.
Authors: Stokes DJ , Baker FS 
Published: July 2020

Abstract
It has previously been shown that liquid microstructures can be observed, in their natural state, by use of Environmental SEM (ESEM). In order to take full advantage of the ability to observe the dynamics of complex fluids, efforts are now being directed at developing in situ experimental methodologies. For example, we have recently shown that the coalescence of oil droplets in emulsion systems can be observed in real time. The purpose of the present study is to tackle the challenge of making EM observations of complex fluids under electrical stress (and ultimately electrical & mechanical stress combined) by subjecting particle dispersions to an electric field.
The technique of attracting charged particles to one of two electrodes (electrophoresis) is commonly used as a means of determining the nature and density of charges on such particles. Another technique, using uncharged particle systems, involves applying an electric field across a sample as well as, for example, a shear strain (electro-rheology).
X-Ray Microanalysis of Insulators in the ESEM
Authors: Phillips MR , Toth M , Griffin BJ 
Published: July 2020

Abstract
We have investigated the affect of accelerating voltage (E0), pressure (P), GSED bias (VGSED), field line geometry and specimen conductivity on the landing energy of the primary beam in an XL30 ESEM. The landing energy of the primary beam can be measured by using the Duane-Hunt cut-off energy, EDH, in EDS X-ray spectra. We present experimental evidence that the landing energy of the primary beam can be significantly altered when analyzing insulators in an ESEM. Shifts in EDH result from electric fields produced by the presence of positive ions in the ESEM chamber and electrons trapped in the bulk. No shift in EDH was observed with conductive specimens at all E0 and P. Changes in the landing energy of the primary beam can significantly effect the relative intensity of characteristic peaks in EDS spectra measured in the ESEM (Figure 1).
The magnitude and sign of the shift in EDH is determined by E0 and P for a specific insulator specimen and stage geometry.
Factors Affecting Quantitative Analysis Error in ESEM-EDS
Authors: Carlton R A , Lyman C E , Roberts J E 
Published: July 2020

Abstract
Standard Reference Material (SRM) 482 of the National Institute of Standards and Technology is a set of 6 gold/copper wires, ranging in concentration from 0 to 100% Cu in 20% steps, intended for calibration studies of electron beam microanalyzers. This is an appropriate standard to test the accuracy of energy dispersive x-ray spectrometry (EDS) in the Environmental Scanning Electron Microscope (ESEM). While the presence of the gas in the sample chamber gives the ESEM its unique capabilities, it also is the source of complications to x-ray spectrometry. The gas can spread the primary electron beam into a wide skirt of electrons with the consequent production of x-rays many micrometers from the target location of the beam.
The six wires (∼ 500 jam in diameter) were embedded and polished in one epoxy mount. The mount was carbon coated in one set of experiments. The coating was removed and the sample retested.
Phosphor Imaging Plate Measurement of Electron Scattering in the Environmental Scanning Electron Micrsoscope
Authors: Wight SA , Zeissler CJ 
Published: July 2020

Abstract
In this work, phosphor imaging plate technology is applied to measure electron scattering directly in the environmental scanning electron microscope (ESEM) specimen chamber. The scattering of electrons from the primary electron beam, under relatively high-pressure conditions (266 Pa) in the ESEM sample chamber, degrades the analytical accuracy of elemental analysis. The degree of this degradation is poorly known. To date, attempts to measure experimentally the spatial distribution of the scattered electrons have been limited to observing secondary effects such as the intensity of x-rays produced from copper targets positioned at various distances from the primary electron beam interaction point. A more accurate distribution of the scattered electron intensity can be obtained from a direct measurement of both the scattered and unscattered electrons over a large area with single electron sensitivity. Improvements to the accuracy of Monte Carlo models of the scattering process will be made possible by the direct measurement data.
Cell Boundary Detection and Volume Approximation of Confocal Microscope Images for Bioinformatics
Authors: Fernandez Cybelle , Habets Damiaan , Kremer Stefan C , Maguer Marc Le 
Published: July 2020

Abstract
Bioinformatics is the science of developing computer databases and algorithms for the purpose of speeding up and enhancing biological research. This paper will detail the application of a three-dimensional cell boundary detection algorithm to compute the volumes of osmotically dehydrated apple cells in an effort to better understand the effects of this treatment.
Osmotic dehydration is an efficient pre-treatment technique in food processing. However, the changes that occur in the food material at the cellular level have not been thoroughly understood and this has limited the full industrial application of the process. During osmotic dehydration, plant tissues when placed in hypertonic solutions undergo plasmolysis that can be directly observed under light microscopy. The usual phenomenon observed during plasmolysis is the separation of the cytoplasm from the cell wall, due to the removal of water from the protoplast (Frey-Wyssling and Muhlethaler, 1965). Although readily observed under the microscope, however, the quantitative changes that occur during the process are not easily measurable.
Analisis of A-Kinase Anchoring Protein Interactions With PKA Using Fluorescence Resonance Energy Transfer
Authors: Ruehr M L , Damron D S , Bond M 
Published: July 2020

Abstract
The clustering of components of a signaling pathway at a specific subcellular location raises the local concentration of the appropriate messengers and serves to amplify the signal. The cAMP dependent-protein kinase (PKA) pathway is regulated by compartmentalization of its components. A-kinase anchoring proteins (AKAPs) tether PKA to specific subcellular sites, thus presumably increasing substrate specificity. Phosphorylation of the type II regulatory subunit of PKA (RII) increases its affinity for AKAPs in vitro (1). The purpose of this study was to investigate whether altering the phosphorylation state of RII in live cells changes its affinity for an AKAP. Specifically, we investigated the binding kinetics between Ht31, a peptide containing the PKA binding portion of an AKAP from human thyroid (2), and RII, in response to PKA activators or inhibitors.
Fluorescence resonance energy transfer (FRET) was used to monitor binding events between RII and the catalytic subunit (C) of PKA, Ht31, or Ht31P, a mutated form of Ht31 which does not bind RII.
Oxidant Stress-Induced Alterations in Mitochondrial Physiology in the Presence and Absence of BCL-2
Authors: Takahashi Akiyuki , Herman Brian 
Published: July 2020

Abstract
Apoptosis is an actively regulated process of cell death necessary for proper control of tissue growth. In humans, ∼100,000 cells die every second by apoptosis and are replaced by new cells of the same number. Apoptosis was originally described by Kerr, Wyllie, and Currie in 1972 as an event characterized by plasma membrane blebbing, cell shrinkage, chromatin condensation, and degradation of DNA (1). Apoptotic death is a tightly controlled process, and the cellular pathways that regulate apoptosis have been well conserved in multicellular organisms from simple to complex animals.
One of the most reproducible inducers of apoptosis is mild oxidative stress. Oxidative modification of proteins and lipids has also been observed in cells undergoing apoptosis in response to nonoxidative stimuli, suggesting that intracellular oxidation may be a general feature of the effector phase of apoptosis. Several incompletely reduced forms of oxygen are highly reactive and quite cytotoxic.
Spectral Imaging for Separation of Fluorescent Signals from Autofluorescence
Authors: Levenson Richard M 
Published: July 2020

Abstract
Autofluorescence, also known as adventitious fluorescence or background fluorescence, ofter poses a significant problem in many applications of fluorescence microscopy. It contributes to unwanted noise and can swamp the desired signal. Particularly difficult samples to image include many pathology specimen that have been processed using crosslinking fixatives (typically formaldehyde). This procedure dramatically increase the autofluorescence level, leading to bright, broad spectrum emissions, particularly from connective tissue components. Unprocessed plant tissue and neuronal tissue also have extremely high levels of endogenous autofluorescence that can make many convenient labeling strategies, including most (green fluorescent protein (GFP) labels, extremely problematic. Various solutions have been proposed for the reduction or elimination of autofluorescence. These include using narrow bandpass emission filters to try to isolate the desired fluorescence signal, the use of labels which can be excited at wavelengths that are much less likely to induce autofluorescence (moving the excitation towards the NIR is effective), and post-processing aldehyde-fixed samples with such reagents as sodium borohydride or toluidine blue to chemically suppress the autofluorescence signal.However, in many cases, these approaches are either infeasible or ineffective.
Cationic Liposome-DNA Complexes: Polymorphism versus Transfection Activity
Authors: Sternberg-Papahadjopoulos B , Hong K , Zheng W , Papahadjopoulos D 
Published: July 2020

Abstract
Complexes formed during interaction of cationic liposomes with polynucleotides such as DNA (CLDC) self-assemble into a variety of polymorphic structures. They display bilayer (FIG. 1-5) and non-bilayer structures (FIG. 6). We have recorded bilayer structures such as spaghetti/meatball-type structures (FIG. I), map-pins (FIG. 2) spherical particles and invaginated liposomes (FIG. 3, 4) and oligolamellar structures (FIG. 5). The non-bilayer lipid arrangements include honeycombtype structure (Hn, FIG. 6) and cubic phase lipids.
We have chosen mainly freeze-fracture electron microscopy (FIG. 1-3, 5,6) but also cryo-electron microscopy (FIG.4) for recording polymorphic structures, and for studying factors and conditions triggering the formation and stabilization of specific structure types. Furthermore, we took microscopically snapshots of the interaction of specific structure types with cultured cells. In order to find out the “active” structure in terms of transfection, we investigated the transfection activity both in vivo and in vitro of CLDC, and studied in parallel their morphology in serum as well as in cell medium.
Ultrastructure of the Tertiary Envelope of the Cyst of the Tadpole Shrimp Triops longicaudatus (Branchiopoda; Notostraca)
Authors: Rosowski James R , Bartels Terry L , Colburn James F , Colton Jannell L , Belk Denton , Lee Kit W 
Published: July 2020

Abstract
Tadpole shrimp inhabit temporary freshwater pools and ponds where their occurrence is largely regulated by rainfall events and water temperature. When dry basins are flooded, cysts of Triops imbibe water and hatch to produce rapidly growing, carapaced larvae. While previous studies show anostracan (fairy shrimp) cyst-surface morphology often species specific, few studies illustrate shell ultrastructure of Triops and none has considered T. longicaudatus. Here we examine the shell of T. longicaudatus (Notostraca) and compare its fine structure to other species of Triops and to that of Artemiafranciscana(Anostraca), which we previously studied.
Cysts, produced in culture from Utah broodstock, were purchased from Triops, Inc., 1924 Creighton Rd., Pensacola, FL 32504. Thin sections of cysts were prepared for transmission electron microscopy (TEM) as previously described (Fig. 1). Cysts were also examined with scanning electron microscopy (SEM), dry, whole or fractured (Figs. 2,3), or after imbibition and/or hatching in oxygen saturated, double-distilled water, at 25 ° C.
A Freeze-Fracture Study of Nuclear Pore Complex Structure in Intact Dunaliella Cells
Authors: Parthasarathy MV , Daugherty CS 
Published: July 2020

Abstract
The nuclear envelope in all eukaryotic cells is perforated by nuclear pores, that consist of the nuclear pore complex (NPC). The NPC is a highly complex supramolecular structure that plays a pivotal role in the trafficking of macromolecules and particles between the nucleus and the cytoplasm. During the past two decades a large body of information has accumulated on both the structure and role of the NPC. The diameter of NPC is about 120 nm and is composed of approximately 100 proteins.
The NPC structure has been elucidated using various electron microscopy techniques. The basic structure of the NPC is comprised of three concentric rings, each displaying an 8-fold symmetry. The cytoplasmic and nuclear rings are vertically integrated by eight spokes that approximately span the width of the nuclear envelope. A set of eight fibers extends from the nucleoplasmic ring into the nucleus, and are joined at the distal ends by a ring to form the so called basket.
Induction of Apoptic Features in Human Colon Cancer Cells After Exposure to Specific Vitamin Combinations
Authors: Brown B , Garvin K R , Hughes B G , Standing M D , O'Neill K L , Murray B K 
Published: July 2020

Abstract
Proper nutrition and vitamin consumption have long been associated with lower risks for many human cancers. Data from recent studies have suggested that exposure to antioxidant vitamins and vitamin combinations can induce genetic programed cell death, apoptosis, in human cancer cells. ‘“3 In this study, we report on the induction of apoptosis in HT-29 human colon adenocarcinoma cells after exposure to low doses of 13- c/s-retinoic acid (RA) and vitamin E succinate (VES). Induction of apoptosis was seen only in cancerous colon cells and not in normal human colon cells when exposed to RA and VES in combination, but not when exposed to either vitamin alone.
Cultures of HT-29 cells were seeded in 6 well plates at 10,000 cells/well and grown at 37°C, 5% C02 in RPMI 1640 medium supplemented with 10% fetal bovine serum.
Nanomechanical Properties of a Biocomposite, Mollusk Shell Nacre
Authors: William N. Mercer  , Sopp J M , Fong H , Katti K S , Katti D R , Sarikaya M 
Published: July 2020

Abstract
Mechanical properties of the structural elements of mollusk hard tissues were determined using nanoindentation techniques. Red abalone (Haliotis refuscens) has a dual laminate ceramic/polymer biocomposite, evolved for protection against impact. The nacre (mother-of-pearl) section of the shell has excellent bending strength (180 MPa) and fracture toughness (12 MPa m1/2), orders of magnitude stronger and tougher than monolithic CaCO3, it's primary component. The outer prismatic structure is comprised of columnar calcite (rhombohedral CaCO3) crystallites oriented normal to the shell surface and the inner nacreous structure consists of layers of pseudo-hexagonal shaped aragonite (orthorhombic CaCO3) platelets arranged in a brick and mortar microarchitecture (Fig. 1). The platelets (0.25 μm thick and 5 μm edge length) are surrounded by a thin layer (10-25 nm) of organic phase within and between the individual layers. This sub-um layered structure results in excellent bulk properties, not present in man-made composites of similar phase composition.