bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure Studies of Supported Metal Catalyst Particles by Microdiffraction Technique
Authors: Pan M. , Cowley J.M. , Chan I.Y. , Garcia R. 
Published: June 2020

Understanding the structures of the small metal particles (<5nm) in supported metal catalysts can provide some basis for understanding the properties and performance of these catalysts. High resolution transmission electron microscopy (HRTEM) has been extensively used to characterize the structures of small particles in the past few years. As a complement to HRTEM, microdiffraction technique has its unique advantage of being able to provide local structure information within regions of diameter 1-2nm.In our VG HB-5 STEM an electron beam with diameter of 1-1.5nm can be easily generated at the specimen level and microdiffraction patterns from such small regions are routinely observed with the help of the attached optical system. Two series of catalyst samples, Pt/γ-Al2 O3 and Rh/CeO2 with various metal loadings and reduction temperatures, have been studied. The series of Pt/γ-Al2 O3 catalyst included both calcined and reduced samples. Both series of catalysts contain high dispersions of metal particles (<5nm). In the case of Rh/CeO2 Rh particles usually have sizes of 2-3nm.
Electron optical studies of the formation of vanadium pentoxide catalyst
Authors: Legrouri A. 
Published: June 2020

The oxides of vanadium, especially vanadium pentoxide, have been extensively studied because of their interesting physical properties particularly in catalysis. Vanadium pentoxide is generally used in the oxidation and ammoxidation of hydrocarbons.This catalyst has been prepared via the thermal decomposition of ammonium metavanadate (AMV) in air. Thermogravimetric analysis (TGA), infrared spectroscopy (IRS) and x-ray diffraction (XRD) techniques together with high resolution electron microscopy (HREM) and scanning electron microscopy (SEM) have enabled us to elucidate the physicochemical changes occurring during the decomposition process.According to TGA results, the decomposition of AMV commences at 150°C and is complete by 320°C leading to vanadium pentoxide by loss of ammonia and water with the formation of two intermediate compounds, namely at 190°C, ammonium bivanadate: (NH4)2V4 O11, and at 230°C, ammonium hexavanadate AHV: (NH4)2V6O16 . Samples for structural correlation studies were prepared by heating AMV in a stream of air for 2 hours at selected temperatures of 140, 190, 230, 320 and 400°C.
Freezing Dynamical Sol-gel processes with the controlled environment vitrification system (CEVS)
Authors: Bellare J. R. , Bailey J. K. , Mecartney M. L. 
Published: June 2020

A sol is a stable suspension of submicron particles in a liquid while a gel is a three dimensional network of these particles which is bicontinuous with the liquid phase. Sol particles are stabilized by surface charges or by steric hindrance of molecules on the particle surface. Sols can be gelled by the agglomeration of the particles; for example, by reducing the inter-particle repulsion with the addition of a salt. The sol-gel transformation is an important industrial, biological and household process. Novel ceramic processing techniques, blood-clotting, and white-sauce manufacturing are some diverse examples. Therefore, there has been extensive interest in relating the gel structure to changes in the physical properties that occur during gelation.Direct observation of thin vitrified films is the preferred technique for microstructural determination of colloidal dispersions in the size range of 1-1000nm.
Transmission electron microscopy of alpha-decay damage and alteration of betafite
Authors: Lumpkin G. R. , Ewing R. C. 
Published: June 2020

The pyrochlore structure type occurs as a constituent of crystalline nuclear waste form assemblages proposed for the long term isolation of actinides. Betafite, the Ti-rich end-member of the pyrochlore group, is a natural analogue similar in composition to waste form pyrochlores. This study examines the effects of alpha-recoil damage and geochemical alteration on a specimen of betafite from Antanifotsy, Madagascar (Harvard no. 87876, UNM no. 205).Electron microprobe analyses were performed using a JEOL 733 Superprobe operated at 15 kV and 20 nA sample current crushed fragments of the sample were dispersed on holey-carbon grids and examined with a JEOL 2000 EX TEM operated at 200 kV. Phase compositions were checked using a Tracor TN5500 EDS.The 1.5 cm diameter betafite crystal displays an unusual zonal sequence of alteration. The core consists of relatively unaltered betafite containing ca. 27 wt.% U02 and 2.5 wt.% CaO (TABLE 1, analysis 1).
Topography of gallium arsenide substrates following various surface treatments
Authors: Mescher J. A. , Grant J. T. 
Published: June 2020

The preparation of a clean and defect-free GaAs surface is an ideal starting point for making GaAs based devices. Contaminants can also dramatically affect the adhesion of metals on GaAs. The effect of particulates or pits is more obvious. The purpose of this study was to evaluate differences in morphology and elemental composition of GaAs substrates subjected to commonly used wet etching techniques.The samples used in this study were cut from a polished LEC Zn-doped (100) GaAs wafer and were approximately 5x5 mm in size. Samples were treated by various means including organic solvents, freon vapor, acid etchants, alkaline etchants as well as no treatment. The solvents appeared to clean the wafer of particulates and polishing residues. The most extensive etching was observed on three samples now to be described.
EELS characterization of bulk crystal surfaces in Rem: Surface micro analysis and surface channelling effect
Authors: Wang Z.L. , Cowley J.M. 
Published: June 2020

Electron energy-loss spectroscopy (EELS) is used in parallel with reflection electron microscopy (REM) for studying surface chemical characterization. The successful observation of Pt and Au M4,5 edge modifications in the REM case has shown that it is possible to do surface chemical analysis for those heavy elements [1]. The reflection of electrons from the surface is critically affected by the surface resonance condition; it has been shown that the electrons will propagate parallel to the surface for some distance if the incident angle satisfies the surface resonance (SR) condition[2-3], then surface channeling is likely to be observed in this SR case. There is less propagation along the surface under the surface non-resonance (SNR) condition.The GaAs bulk crystal (011) surface was chosen for observing the surface channeling effect in REM case, using a Philips 400T TEM. The surface absorbed oxygen is identified with the O-K edge (fig.l(A)).
Generation of surface plasmons in a supported metal particles with an external electron beam:II Classical energy loss theory
Authors: Wang Z.L. , Cowley J.M. 
Published: June 2020

The theoretical predictions of the relative excitation probabilities of surface plasmons, using the coherent-state theory, are in good agreement with the experimentally observed relative heights of the surface plasmon peaks, This is partially because the field created by the induced charges on the support surface is not properly taken into account in the quantum theory.The Classical energy loss theory is based on Ritchie's work. Consider the total potential distribution in the space created by an incident electron under the non-retardation approximation (as shown in fig. 1),
is the field created by the induced charges. Matching the solution of ψ on the boundaries, as a function of the incident electron position rt, the excitation probability of the surface plasmon as a function of ω is:
The role of silicon in forages: A quantitative X-Ray study
Authors: Woodward Janet H. , Akin D. E. 
Published: June 2020

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.
Some biological materials observed by a new high-resolution SEM
Authors: Tanaka K. , Mitsushima A. , Takayama H. 
Published: June 2020

Recently we made a high resolution SEM (UHS-T1) with a aid of Hitachi Co. Ltd. It was equipped with a field emission source and the objective lens with short focal length (3.6 mm). The electron probe is estimated to 0.4 nm on calculation, and the probe diameter of 0.5 nm is confirmed by observation in STEM mode. On observation of a biological material (a rat motor nerve cell) which was coated with platinum by an ion sputter coater, the SEM shows 0.5 nm resolution when the width of the dark space criterion was used. In the present study some biological materials are observed with this new SEM. The results are as follows.Specimens were prepared by the aldehyde prefix osmium-DMSO-osmium method. In the specimens, mitochondria, Golgi complex, endoplasmic reticulum and so on, were very clearly observed (Fig.1) in comparison with those observed by ordinary SEM.
Electron microscopic pathology of urinary stones
Authors: Kim K. M. 
Published: June 2020

Urolithiasis occurs commonly. With modern technology, stones can be easily removed. However, the major threat of urolithiasis is in its high recurrence rate. Many recurrences can be medically prevented. For medical prevention, proper knowledge of stone components is essential.Urinary stones have been analyzed mainly by x-ray diffraction, infrared spectroscopy and chemical analysis. Each method suffers from limitations in sensitivity and reliability. Primarily because of their inability to detect minor components of the stones, two or more methods are frequently combined. Recently it has become apparent that scanning electron microscopy (SEM), especially when combined with x-ray analysis (XA), has a sensivity in stone analysis exceeding other conventional methods.SEM of urinary stones did not gain popularity mainly due to the perceived high cost, the difficulty of sectioning stones, and the variability of crystal morphology.
High-resolution, low-dose electron cryomicroscopy of negatively stained matrix porin, a transmembrane protein from Escherichia coli outer membranes
Authors: Massalski A. , Sass H. J. , Zemlin F. , Beckmann E. , van Heel M. , Buldt G. , Dorset D.L. , Zeitler E. , Rosenbusch J. P. 
Published: June 2020

Porin (ompF gene product), an integral channel-forming protein in the outer membrane of Escherichia coli, is regarded as a molecular sieve allowing non-specific passive diffusion for low-molecular-weight (Mr < 700d) hydrophilic solutes.Electron microscopic studies of the negatively stained membrane vesicles reconstituted with porin and phospholipids have shown the presence of the stain-filled triplet indentation. Subsequent 3D image reconstruction demonstrated that three channels on the outer surface of the cell merge into a single channel at the periplasmatic face. Both 2D and 3D image reconstructions, based on electron micrographs from negatively stained preparations, are very informative about the size and distribution of the transmembrane channels but they contain very little or no information on the protein trimers which form the channels. This lack of information about the trimer structure and location is not surprising since the diffraction resolution limit, in our previous studies, is around 22Å.
Morphologic differences between abdominal and inguinal testes in stallions
Authors: Al-Bagdadi F. , Hoyt D. , Karns P. , Martin G. , Memon M. , McClure J. , McCoy D. 
Published: June 2020

The most frequently occuring abnormality of the male genital system in mammals is the failure of one or both testes to descend into the scrotum. The reasons for abdominal or inguinal retention of testes could be anatomic malformation, faulty development or hormone imbalance.Cryptorchidism has been associated with either greatly reduced or absent spermatogenesis (Kaueakami et al, 1984), and being a source of neoplasia. According to Stick (1980), germinal carcinoma cells have been believed to be the cause of teratomas in equine cryptorchid testicles. Neoplasia has been reported in descended testes of unilateral cryptorchid patients (Martin et al, 1981).No distinction has been made in relating the problem of cryptorchid testes to inguinal or abdominal retention. The purpose of this study is to record the morphological differences between inguinal and abdominal cryptorchid testes as an aid in diagnosis and prognosis.
Electron microscopic localization of sulfated glycosaminoglycansans and proteoglycans in chordoma
Authors: Lam Ronald , McGowan Mary Ellen 
Published: June 2020

Although several electron microscopic studies of chordoma have been published, the origin of the chondroitin sulfate rich extracellular matrix is still not clear. Based on the ultrastructural similarities between the extracellular matrix, contents of the rough endoplasmic reticulum and cytoplasmic vacuoles, some authors assume that the two latter structures of chordoma cells contain mucosubstance. The intent of this study is to localize the sulfated glycosaminoglycans intracellularly in a chordoma, which provides cytochemical evidence of the origin of extracellular matrix.A sacrococcygeal chordoma from a 65 year old man was examined by electron microscopy after fixation in 2.5% gluta-raldehyde, 0.2% ruthenium red-glutaraldehyde, and pre-embedment staining with high iron diamine (HID), a method specific for sulfated glycoconjugates. Routine electron microscopic examination revealed stellate nonvacuolated and vacuolated “physaliferous” cells embedded in an abundant extracellular matrix. In general the chordoma cells possessed prominent Golgi complex, rough endoplasmic reticulum, mitochondria, glycogen and intermediate filaments.
Ultrastructural changes in isolated rat liver perfused with cyclic heptapeptide toxins from norwegian freshwater cyanobacteria (blue-green algae)
Authors: Dabholkar A.S. , Carmichael W.W. , Berg K. , Wyman J. 
Published: June 2020

Intracellular changes in the hepatocytes of isolated rat livers perfused with cyclic heptapeptide toxins are described. The toxins used are 1) -Ala-Leu- β-methyl isoAsp-Arg-ADDA-isoGlu-mdha (M.W. 944) from Microcystis aeruginosa- Lake Akersvatn, Norway; 2) -Ala-Arg-isoAsp-Arg-ADDA-isoGlu-mdha (M.W. 1023) from Oscillatoria agardhii var. - Lake Kolbatnvatn, Norway; 3) -Ala-Arg-isoAsp-Arg-ADDA-isoGlu-dha (M.W. 1009) from Oscillatoria agardhii var. isothrix - Lake Froylandsvatn, Norway. Approximate LD intraperitoneal mouse for the toxins is 50, 500 and 1000 μg/kg respectively.Livers were removed from male Sprague Dawley rats and perfused for 15 min with a blood-free perfusate (50 ml) followed by 60 min with perfusate containing i) 25, 50, or 200 μg of M. aeruginosa toxin ii) 50, 250, 500 or 1000 μg of O. agardhii var. toxin and iii) 1000, 2000, 2500 or 5000 μg of O. agardhii var. isothrix toxin. Control livers were perfused for 75 min with the blood-free perfusate.
Use of lanthanum to detect changes in the permeability barrier of rat skin after dermal exposure to organic chemicals
Authors: Mattie D. R. , McDougal J. N. , Chase M. R. , Hixson C. J. 
Published: June 2020

Occupational dermal exposures to organic solvents are of importance due to local effects in the skin and systemic toxicity if penetration occurs through the skin. Repeated or prolonged contact with organic solvents may cause dry skin and cutaneous irritation. Although organic solvents have been shown to penetrate the skin, little information is available concerning the effects on the barrier properties of skin after dermal exposure to solvents. The purpose of this investigation was to examine the ultra- structural changes in rat skin after exposure to 3 organic chemicals and to correlate changes with the location of an electron dense tracer, lanthanum, which is normally excluded by the permeability barrier in the stratum corneum.Male rats, 6 for saline and 6 for each chemical, were exposed for 24 h to sterile saline, trichloroethylene (TCE), perchloroethylene (PERC), or toluene using dermal exposure cells developed in this laboratory. The cells were filled with 2 mL of saline or the neat chemical.
Electron microscopic study of rat myocardial infarcts induced by a free radical generator system
Authors: Feldman Dorothy , Cavallo Gary , Rosenberger Lois 
Published: June 2020

The role of oxygen free radicals in the development of tissue injury and necrosis, including myocardial ischemic damage, is well documented. In this investigation, application of a free radical generator system (FRG) to rat myocardium resulted in ECG alterations typical of myocardial infarction; 24 hours after treatment, plasma lactate dehydrogenase (LDH) levels were elevated and 20% of the left ventricle was infarcted. In order to characterize the type of cellular damage and the ultrastructural changes in the affected cells, myocardial infarcts and myocardium from control rats were examined in the electron microscope.Six spontaneously hypertensive rats were lightly anesthetized with sodium pentobarbital and infused for 10 minutes through a carotid cannula near the ostium of the coronary artery. Three rats were infused with a FRG consisting of purine (2.3 mM), xanthine oxidase (0.02 μ/ml), and Fe -loaded transferrin (0.06 μM), and 3 sham-operated rats served as controls.
Comparative SEM analyses of primary palate fusion in mouse and ferret embryos
Authors: Steffek A.J. , Lenke J.W. 
Published: June 2020

Formation of the medial nasal, lateral nasal and maxillary midfacial processes is accomplished by extensive migrations of cranial neural crest cells followed by cellular and tissue interactions that lead to the fusion of these processes at the region of the isthmus. Fusion of the midfacial processes is an important developmental event since any genetic and/or environmental factors that prevent it produce cleft lip. SEM analyses were undertaken during midfacial fusion in mouse and ferret embryos to determine the surface similarities or differences that occur during this critical time of primary palate development.Mice of the A/J strain and ferret embryos were obtained by laparotomy at the appropriate stage of midfacial fusion and washed with cold physiological saline (0.85%). They were then fixed in cold phosphate buffered (pH 7.3) glutaraldehyde for at least 48 hours, after which they were subsequently washed in cold, phosphate buffer and then placed in 70% ethyl alchohol.
Ultrastructural morphology of nontumorous lactotrophs in human pituitaries exposed to high prolactin levels
Authors: Jalalah S. , Kovacs K. , Horvath E. 
Published: June 2020

Lactotrophs, as many other endocrine cells, change their morphology in response to factors influencing their secretory activity. Secretion of prolactin (PRL) from lactotrophs, like that of other anterior pituitary hormones, is under the control of the hypothalamus. Unlike most anterior pituitary hormones, PRL has no apparent target gland which could modulate the endocrine activity of lactotrophs. It is generally agreed that PRL regulates its own release from lactotrophs via the short loop negative feedback mechanism exerted at the level of the hypothalamus or the pituitary. Accordingly, ultrastructural morphology of lactotrophs is not constant; it is changing in response to high PRL levels showing signs of suppressed hormone synthesis and secretion.By transmission electron microscopy and morphometry, we have studied the morphology of lactotrophs in nontumorous (NT) portions of 7 human pituitaries containing PRL-secreting adenoma; these lactotrophs were exposed to abnormally high PRL levels.
MacMeasure: A low cost, easy-to-operate quantitative morphometrics system for the Macintosh computer
Authors: Hook G.R. , Rasband W. 
Published: June 2020

We have developed a new software package called MacMeasure for counting and measuring structures in photographs by use of a Macintosh computer and a Micro Digi-Pad digitizing tablet. The length, perimeter and area of structures can be easily measured, sequentially numbered, scaled, mapped and stored on floppy disk. The hardware for the system (Fig. 1) costs under $2000 and MacMeasure is available at no cost from the authors.The intuitive Macintosh point and click paradigm for command selection is used to operate the software. The commands available include Point, Line, Area, Scale, Map and Help (Fig. 2). Point is used to count the number and location of items in the photograph. Line is used to measure the length of lines and Area measures the perimeter and area from which the shape factor F is calculated. The measured line or area is displayed on the Macintosh screen at high magnification after each measurement is made.
Immunoelectron microscopy of retinoblastoma
Authors: Rodrigues M.M. , Hackett J. , Wiggert B. , Chader G. 
Published: June 2020

The histogenesis of retinoblastoma is uncertain. The derivation of this tumor has been attributed to neuronal and/or glial cells, by routine transmission electron microscopy and light microscopic immunocytochemical staining. Immunoelectron microscopy can provide more precise localization of retinal proteins. We investigated the immunoelectron microscopic localization of photoreceptor cell specific proteins to determine their distribution in eyes enucleated for retinoblastoma.Surgically excised tissues were fixed in 1% glutaraldehyde 2%- paraformaldehyde in 0.1M phosphate buffer for 2 h at 4°C, dehydrated in 50%, 75% and 90% dimethyl-formamide and embedded in Lowicryl. Polymerization of Lowicryl was performed by exposure to UV light for 24 h at 4°, followed by polymerization at room temperature for 48-72 hr. Thin sections were incubated for 1 h at room temperature with primary antibodies against interphotoreceptor retinoid-binding protein (IRBP) (1:200 dilution), S-antigen (1:500 dilution) and opsin (1:500 dilution). Appropriate secondary antibodies either to mouse or rabbit IgG (1:20 dilution) were linked to colloidal gold (10-20 nm) and incubated for 30 min.
Three-dimensional reconstruction of the 40S ribosomal subunit from rabbit reticulocytes
Authors: Zhang Neng-Yu , Wagenknecht Terence , Radermacher Michael , Obrig Tom , Frank Joachim 
Published: June 2020

We have reconstructed the 40S ribosomal subunit at a resolution of 4 nm using the single-exposure pseudo-conical reconstruction method of Radermacher et al.Small (40S) ribosomal subunits were Isolated from rabbit reticulocytes, applied to grids and negatively stained (0.5% uranyl acetate) in a manner that “sandwiches” the specimen between two layers of carbon. Regions of the grid exhibiting uniform and thick staining were identified and photographed twice (magnification 49,000X). The first micrograph was always taken with the specimen tilted by 50° and the second was of the Identical area untilted (Fig. 1). For each of the micrographs the specimen was subjected to an electron dose of 2000-3000 el/nm2.Three hundred thirty particles appearing in the L view (defined in [4]) were selected from both tilted- and untilted-specimen micrographs. The untilted particles were aligned and their rotational alignment produced the azimuthal angles of the tilted particles in the conical tilt series.