bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinematical and Dynamical CBED Pattern Models: Increasing the Accuracy of the Unit-Cell Parameter Measurements Based on CBED Patterns
Authors: Yadhikov I.N. , Maksimov S.K.
Published: June 2020

Convergent beam electron diffraction (CBED) is widely used as a microanalysis tool. By the relative position of HOLZ-lines (Higher Order Laue Zone) in CBED-patterns one can determine the unit cell parameters with a high accuracy up to 0.1%. For this purpose, maps of HOLZ-lines are simulated with the help of a computer so that the best matching of maps with experimental CBED-pattern should be reached. In maps, HOLZ-lines are approximated, as a rule, by straight lines. The actual HOLZ-lines, however, are different from the straights. If we decrease accelerating voltage, the difference is increased and, thus, the accuracy of the unit cell parameters determination by the method becomes lower.

To improve the accuracy of measurements it is necessary to give up the HOLZ-lines substitution by the straights. According to the kinematical theory a HOLZ-line is merely a fragment of ellipse arc described by the parametric equation

with arc corresponding to change of β parameter from -90° to +90°, where

vector, h - the distance between Laue zones, g - the value of the reciprocal lattice vector, g‖ - the value of the reciprocal lattice vector projection on zero Laue zone.
Recent developments with blind deconvolution for 3-D light microscopy
Authors: Holmes T.J. , Bhattacharyya S. , O'Connor N. , Ancin H. , Gregorio J. , Roysam B. , Szarowski D. , Turner J.N.
Published: June 2020

A novel deblurring method is under development for 3D light microscopic image deblurring, including the widefield fluorescence, confocal fluorescence and transmitted light brightfield modalities.

The main practical advantage of the approach is that it does not require the point spread function (PSF) to be measured. It produces a reconstruction of the PSF along with the deblurred image, which is possible because we mathematically constrain the PSF to have physically justified and reasonable properties, such as bandlimitedness, a missing frequency cone (for widefield) and nonnegative values.

Recent developments have included robustizing the reconstruction for confocal data, so that it will repeatedly perform well under various adverse conditions and for a wide variety of sample types. Among other refinements, additional PSF mathematical constraints are being integrated.

Evaluation testing is underway with known fabricated test objects. An example is shown in Fig. 1. A specially drawn glass micropipette tip was filled with 0.2% eosin, mounted in Refractive Index Liquid (n= 1.460; Cargille Labs, NJ) and scanned with a BioRad MRC 600 confocal microscope having a 40X, 1.0 N.A. oil objective lens.
Molecular microscopy of DNA for genome analysis: optical mapping of restriction digests
Authors: Huff Edward J. , Cai Weiwen , Hu Xinghua , Huang John , Jing Junping , Meng Xun , Perlov Eugene , Reed Jason , Schwartz David C.
Published: June 2020

Optical microscopy of individual DNA molecules has been an interesting technique for the past 15 years, but until recently has not been useful for genome analysis. We have developed Optical Mapping an emerging single molecule approach for the rapid generation of ordered restriction maps. Many identical individual DNA molecules from a single clone are elongated and fixed onto derivatized glass surfaces, digested with a restriction enzyme which cuts the DNA wherever a specific sequence pattern is found, stained with YOYO, and imaged with a cooled CCD camera attached to an automated epi-fluorescence microscope. Images are automatically processed to correct for non-uniform illumination, remove background, locate the DNA fragments, reject objects which do not look like single DNA molecules, recognize which fragments originate from an original uncut molecule, and calculate the relative sizes of the fragments by apparent length and fluorescence intensity. Results from many molecules are combined by clustering to recognize a consistent cutting pattern. Molecules which match the pattern are averaged to improve the sizing accuracy.
Orientation of actin filaments during motion in motility assay
Authors: Borejdo J. , Burlacu S.
Published: June 2020

Polarization of fluorescence is a classical method to assess orientation or mobility of macromolecules. It has been a common practice to measure polarization of fluorescence through a microscope to characterize orientation or mobility of intracellular organelles, for example anisotropic bands in striated muscle. Recently, we have extended this technique to characterize single protein molecules. The scientific question concerned the current problem in muscle motility: whether myosin heads or actin filaments change orientation during contraction. The classical view is that the force-generating step in muscle is caused by change in orientation of myosin head (subfragment-1 or SI) relative to the axis of thin filament. The molecular impeller which causes this change resides at the interface between actin and SI, but it is not clear whether only the myosin head or both SI and actin change orientation during contraction. Most studies assume that observed orientational change in myosin head is a reflection of the fact that myosin is an active entity and actin serves merely as a passive "rail" on which myosin moves.
Correlation of micromagnetic structure and microstructure in thin film longitudinal magnetic recording media
Authors: Tang Kai
Published: June 2020

Lorentz transmission electron microscopy (LTEM) has long been used as a tool for imaging the magnetic domain structure in materials and has occasionally been applied to thin film longitudinal magnetic recording media. Conventional/high-resolution electron microscopy (TEM) has shown its power in revealing the detailed microstructure of these materials. The combination of these two techniques can result in a more complete understanding of the interdependence of micromagnetic structure and microstructure and provide insight into how to improve the magnetic performance.

LTEM requires specimens with large uniformly thin areas so that the deflection angle of the incident electron beam is proportional to the magnetic field within the specimen plane. Conventional specimen preparation methods, which normally generate a wedge, are therefore no longer suitable. Previous work has used specially designed substrates to facilitate preparation of LTEM specimens of Co alloy/Cr magnetic media. In the present study a chemical etching technique was introduced to successfully produce LTEM specimens directly from the C/Co alloy/Cr/NiP/Al(substrate) structures, typical of those currently used in the magnetic disk industry.
A new approach to alchemi: the ordering tie line method
Authors: Hou D.H. , Fraser H.L.
Published: June 2020

The ALCHEMI (Atom Location by CHanneling Enhanced Microanalysis) technique has been first developed by Spence and Taftø to determine site occupancies of alloying elements in ordered crystals. Based on their work, a number of formulations have been developed to improve'the accuracy by using multivariant analysis, to extend the analysis to a more general case, and to incorporated anti-site defects and derealization effect. However, all these formulations can be replaced by a new formulation based on the Ordering Tie Line (OTL) concept.

The OTL concept can be illustrated by using a ternary compound (C°=AxByCz), with a B2 crystal structure, as an example. In the B2 crystal structure (Fig.1), the sublattices of α and β can be treated as two ' phases" with compositions Cα and Cβ (for B2 ordering ⇔ Cα ≠ Cβ). The OTL is then defined as the tie-line connecting Cα and Cβ(Fig. 1). Similar to a regular tie-line, the OTL describes mass conservation in a B2 crystal and its mid point will locate at C°.
Direct observation of hymenes in diatoms by low-voltage SEM
Authors: Yao Nan , Aksay Ilhan A.
Published: June 2020

From the early days of Kolkwitz and Marsson (1908) diatoms have proved to be valuable in pollution studies, especially of river systems. Economic applications have developed because the remains of sedimentary diatoms were found to be useful for many industrial processes owing to the fine structure and inert nature of the siliceous materials. Their ecological significance arises from observing that diatoms that grew in oceanic and freshwater sediments contain indications of past environmental conditions; more recently, diatoms have been used to detect pH changes attributed to 'acid rain.' The first record of a diatom can be traced back to the early 1700s when an English gentleman looked at roots of the pond-weedLemnausing his simple microscope. Today, extensive studies using TEM and SEM techniques have provided much new information about the fixed and variable details of the diatom, yet research focusing on the morphology of the shell structure remains very active.
In situ observation of orientation changes on metallic surfaces
Authors: Weiland H. , Field D.P. , Adams B.L.
Published: June 2020

The characterization of crystalline aggregates by the crystallographic orientations of their grains and subgrains has become a subject of increasing interest. The information obtained is not only used for the characterization of materials, but also more importantly for the determination of properties. To mention only a few, applications have been found in the areas of fracture analysis, recrystallization, and plastic deformation.

Most commonly, crystallographic orientations are determined from Backscattered Kikuchi Diffraction (BKD) in the SEM and from Kikuchi patterns obtained by microdiffraction in the TEM. Since the development of fully automatic pattern analysis routines for the BKD, the SEM based techniques currently finds the most applications. In conjunction with computer controlled stage or beam displacements, the technique is known as Orientation Imaging Microscopy (OIM). In this manner, thousands of diffraction patterns are analyzed automatically within a short time. This leads to a statistical description of the distribution of crystallographic orientations, which sufficiently represent the bulk material.
Theoretical modelling of the size and shape of atomic images formed with inelastically scattered electrons
Authors: Holbrook O.F. , Bird D.M.
Published: June 2020

In electron diffraction the study of inelastic scattering processes has been revolutionised with the development of imaging PEELS. It is now relatively straightforward to produce images from fast electrons which have lost a specific amount of energy (to within about 5eV). Therefore electrons which have been inelastically scattered via an atomic transition, loosing a characteristic amount of energy, can in principle be used to form an equally characteristic image. It should be noted that such images will not be perfect since other single and multiple inelastic events may result in a similar energy loss which will tend to obscure the ideal picture. An important issue is the ultimate resolution limit of this type of atomic imaging. Although practical questions (such as signal-to-noise ratio) are important it is still interesting to ask what theoretical limit might be imposed by the underlying physics of the inelastic scattering and imaging processes. The work presented here is an initial investigation of the typical radial size and shape which can be expected when imaging a single atom and how these depend upon the transition and energy loss being considered.
Non-equilibrium silicate glass in contact with faceted {1010} α-Al2O3 surface: a SEM study
Authors: Ramamurthy Sundar , Hebert Brian C. , Barry Carter C.
Published: June 2020

Perhaps the most striking feature about α-A12O3 lies in the anisotropy of its crystal structure. Surface energies, γ, (relaxed and unrelaxed) have been theoretically calculated for different low-index planes in alumina. As an example to illustrate the anisotropy, the reported values of γ for two unrelaxed planes ( {100} and {102} ) vary by a factor of about 2 while the factor is only about 15% between {110} and {111} planes in a fcc metal. Among the low-index planes in α-Al2O3, the {100} plane has been reported to have the largest value of γ. Experimental observations of heat-treated {100} surfaces indicate a breakdown of the surface into an array of facets containing inclined steps. This faceting behavior has also been observed when the surface is in contact with calcium aluminosilicate glass at 1600°C. The {100} surface was found to be replaced by two sets of facets parallel to the {101} and {102} planes respectively. In that study the glass was a near-anorthite (CaAl2Si2O8) composition which is in equilibrium with A12O3 at 1600°C in air.
The role of epitaxial strain in the properties of high Tc thin films
Authors: Williams E.J. , Cretton A. , Jaccard Y. , Locquet J.-P. , Mächler E. , Martinoli P. , Fischer Ø.
Published: June 2020

The difference observed between the critical temperatures measured for bulk material or very thick films (> 500 nm for the ‘214’ system) and those measured for thin films (< 65 nm) has long been of curiosity. Thin films never attain the high values of Tc achieved in bulk or thick film material. Various mechanisms have been proposed to explain this phenomenon, for example Kosterlitz-Thouless effects, inadequate or unstable oxygenation, and strain itself. Formally the role of strain has remained insubstantiated.

The system on which we have concentrated our efforts is that of La2-xSrxCuO4 (LSCO) deposited using MBE, mainly onto (001) SrTiO3 (STO) substrates. These films have been grown at about 700°C at ~3 × 10-6 torr oxygen pressure and cooled after growth at -10° min-1. The films have subsequently been examined using several microstructural and electronic probes, including x-ray diffraction, AFM, resistivity, Hall effect and kinetic inductance.
Z-contrast imaging of catalysts in the 300 kV STEM
Authors: Pennycook S. J. , Jesson D. E. , Liu D. R.
Published: June 2020

Z-contrast imaging in the scanning transmission electron microscope has become the accepted technique for imaging sub-nanometer catalyst clusters, utilizing the high angle annular detector introduced by Howie. The lack of coherent phase contrast effects greatly assists the identification of small clusters, especially near the resolution limit of the microscope. The choice of inner detector angle depends on the system being studied. The highest signal to noise ratio is obtained with the smallest inner detector angle, but increasing this angle significantly reduces the contribution of coherently scattered electrons, which is advantageous for crystalline support materials. In this case, small metal clusters may be unambiguosly distinguished from diffracting regions of the support, and their size distributions determined. Fig 1 compares two preparations of 1 wt% Pd on γ-Al2O3, prepared from palladium nitrate solution, and aged at 600°C for (a) 6 hours, and (b) 24 hours. Images were taken with a VG Microscopes HB501UX 100 kV STEM, using a probe size of ∼3Å The narrower size distribution resulting from the longer aging time is clearly observed.
Scanning tunneling microscopy studies of reactions at surfaces
Authors: Leibsle F.M.
Published: June 2020

Scanning tunneling microscopy (STM) can image clean and adsorbate-covered surfaces with atomic/molecular resolution. This enables us to obtain detailed information on how catalytic reactions proceed on surfaces. Information on such topics as initiation sites for chemical reactions, reaction trends, the development of molecular order, and mesoscopic surface restructuring can be obtained. In addition, variable temperature STM experiments can yield insight into the decomposition of molecules at surfaces.

Studies using STM under ultra-high vaccuum conditions have shown how the oxidation of CO occurs on oxygen-precovered Rh(110) surfaces. Figure 1 shows an STM image of an oxygen-precovered Rh(110) surface displaying areas of oxygen-induced c(2×6) and c(2×8) reconstructions following exposure to 5 Langmuirs of CO. Images like this show that the reaction between the CO and adsorbed oxygen initiates at step edges and defects sites. The CO reaction fronts then proceed in a onedimensional manner stripping away the oxgyen from two and three atom wide islands.
Iodopropionic acid staining of waterborne epoxy films
Authors: Shaffer O. L. , Walker F.H. , El-Aasser M. S.
Published: June 2020

The examination of polymer material by transmission electron microscopy (TEM) often relies on staining in order to improve contrast or preferentially stain a polymer phase. Stains such as osmium tetroxide for unsaturated polymers and ruthenium tetroxide for unsaturated as well as certain saturated polymers have been used quite extensively. A new stain, 3-iodopropionic acid, has been found to be very useful to stain preferentially the amine rich domains in waterborne epoxy films.

An epoxy dispersion (epoxy equivalent weight, EEW=625) and a polyamine adduct curing agent (AHEW=163) at a 1.5:1 stoichiometry was prepared. The volatile organic content (VOC) was 2.6 lb./gal., and the solvent blend was 90.6% propoxy ethanol and 9.4% Aromatic 150. The particles size of the starting dispersion was obtained by TEM and disk centrifuge and found to be approximately 500 nm. Films (approximately 1.2 mil dry film thickness[DFT]) were cast on a partially fluorinated polyethylene film, 0.5, 2, 4, and 8 hours after hand mixing and cured for two or more weeks at 25° C and 50% relative humidity.
The nucleation of recrystallization at second phase particles in 7000 series deformed aluminum alloy
Authors: Hidalgo-Prada B. , Guilarte J.J. , Paredes S.Y.
Published: June 2020

An investigation was carried out to determine the effect of a thermomechanical process (TMP) in the precipitation of dispersed second phase particles, and to assess the recrystallization behavior of a deformed ALCANVEN-7475 commercial aluminum alloy. The TMP included solution anneal treatment at Ts = 482°C for 3 hours, overaging at temperatures (To) in the range from 160 - 400°c for 1 to 30 hours, cold and warm deformation up to 90% reduction of thickness (RA) and recrystallization at Tr = 482 °C for 15 to 60 minutes.

A Hitachi H-600 TEM operated at 100 KV was utilized to examine the microstructural evolution of the alloy leading to the nucleation of recrystallization as a consecuence of the previously described four steps TMP.

It was determined that the nucleation of recrystallized grains is promoted by the presence of second phase particles with critical sizes between 0.5 and 1.0 μm.
Differential phase contrast in TEM for magnetic micro structure observation
Authors: Kruit P. , Buist A.H. , McCartney M.R. , Scheinfein M.R.
Published: June 2020

Phase contrast in TEM can only give information in a limited band of spatial frequencies. The differential phase contrast mode in STEM does not have this limitation, since one simply measures the angle over which the electron beam is deflected by the specimen. This is useful, for example, for determining the magnetic field distribution in magnetic thin films. Recently, a form of electron holography was developed, also in STEM, to obtain differential phase contrast images. In this method, the illuminating beam is split by a biprism in such a way that there are two mutually coherent electron source images close to the specimen. On a far away CCD detector, two shadow images are formed which interfere to give a fringe pattern. It is this fringe pattern that contains the differential phase information. Here, we show that differential phase contrast can also be obtained in a TEM.

In the TEM, two coherent illuminating beams are created by a beam splitter in the condenser system. These beams can be treated as two plane waves, creating a fringe pattern in the plane of observation,as shown in figure 1.
The NCEM public domain software library of extensions to digital micrograph
Authors: Kilaas Roar , Paciornik Sidnei
Published: June 2020

The National Center for Electron Microscopy (NCEM) develops software for use in image processing and image interpretation as they are needed in ongoing research at the center. Some routines are esoteric and of little use to others, while some are more general and could be considered to be of interest to a large number of scientists. This represents the first announcement of the NCEM's dedication to making software developed at the center available to the general microscopy community.

An unfortunate by-product of software development is the often necessary connection of the software to a hardware platform and/or another software platform. Most of the image processing carried out at the NCEM is done under Digital Micrograph running on the Macintosh, either through the built in functionality of the program or through extensions that are written at the center. Some of the functionality that we added were routines that were available under the SEMPER image processing software which was retired not because of limitations of the program, but because of the death of the hardware on which it was running.
Using correlative microscopy (LM, EM, and SFM) in biological problem solving
Authors: Albrecht R.M. , Wetzel B.
Published: June 2020

Conventional morphologic approaches generally place a heavy reliance on standardized preparative methodology and often are narrowly designed to provide supporting documentation for preexisting lines of evidence or for a particular interpretation thereof. Visual images constitute a particularly convincing form of data and several well chosen micrographs can be the difference between studies which are deemed publishable and those that are not.

The potential, however, for imaging methodology to go beyond a “supporting” role and allow investigators to ask and answer questions not approachable by other methodologies is considerable. This has always been the case but relatively recent developments have strongly reinforced this potential. The application of several imaging based technologies to parallel specimens or, preferably, to the exact same specimen in series is the basis for correlative microscopy. Appropriate tracking and imaging of living cells and the subsequent correlative observation of the same cells following immobilization by various physical or chemical based preparative procedures can provide a wealth of information, which bears not only on the biological question at hand but on the likelihood and/or extent of preparative “artifact” as well.
The multianalytic approach; or yes, you can get there from here! Problem solving in semiconductor manufacturing
Authors: Ecker M. M.
Published: June 2020

Manufacturing, development and failure mode analysis problems, in the semiconductor industry, present unique challenges and opportunities, not only to utilize several analytical techniques, but to process and deprocess samples into an appropriate format for analysis. In today' s' cleanrooms a great deal of development is integrated into the manufacturing line. This, combined with the ever decreasing size and increasing density of components on a single integrated circuit, creates the need for accurate as well as precise measurements. The method of measure must be appropriate to the task, compatible with the manufacturing environment, and useful in a process control system.

Current complimentary bipolar technologies, utilizing shallow junction implants, require additional as well as less robust processing in order to maintain the depth and latitude of the junction. Additional processing includes the formation of a contact window spacer. The spacer is formed, following implant and thermal anneal, by growing and subsequently removing a thermal oxide layer. In the manufacturing process, oxide removal is verified by optical measure using visible light.
Structure of ATP synthase by SFM and single-particle image analysis
Authors: Keller David , Singh Seema , Turina Paola , Capaldi Roderick , Bustamante Carlos
Published: June 2020

F1FoATP synthases are the proteins responsible for the synthesis of ATP in oxidative phosphorylation, and are present in some form in all aerobic organisms, both prokaryotic and eukaryotic. They use the energy stored in a transmembrane proton gradient (which is generated by other members of the oxidative phosphorylation pathway) to synthesize ATP from ADP and Pior, working in reverse, to pump protons across the membrane using the energy of ATP hydrolysis. The full protein has two sectors, F1and Fo. F1is normally bound to Fo(which is membrane integrated), but is water soluble when dissociated. The F1sector contains the sites which bind ADP and catalyze its conversion to ATP. The Fo sector contains a channel which allows protons to to cross the membrane, dissipating the transmembrane chemical potential. By an unknown mechanism this translocation of protons through Fo is coupled to the hydrolysis or synthesis of ATP in F1, so that the energy released in hydrolysis of ATP can drive the motion of protons against an electrochemical potential, or the energy of translocating protons can be used to form high energy ADP-Pibonds.
Microscopic detection of Giardia trophozoites in archival pathology specimens of human small intestine: light microscopy, low voltge SEM, and confocal scanning laser microscopy using fluorescent in situ hybridization
Authors: Macechko P.T. , Mulgrew T. , van Keulen H. , Jarroll E.L. , Snover D.C. , Erlandsen S.L.
Published: June 2020

In situ hybridization methods have been widely used for the analysis of chromosomal markers, and for the detection and identification of various species of bacteria in environmental samples. In situ hybridization probes to ribosomal RNA have been used as a diagnostic tool for the study of various parasitic protozoa, and fluorescent in situ hybridization (FISH) probes have been used to study the intracellular distribution of mRNA.

The intestinal protozoan, Giardia, colonizes the small intestine of a variety of different animals, including humans, and forms an infective cyst stage which is responsible for host-to-host transmission. Light microscopic detection in environmental or fecal samples has relied on the detection of cysts whose presence may be infrequent. In human giardiasis, confirmation of diagnosis has often required microscopic analysis of intestinal biopsies for detection of trophozoites. Analysis of the molecular sequence of 16s rDNA (small subunit) in Giardia isolates has permitted the development of species specific probes for Giardia.
Structural analysis of endothelial cell mediated prolongation of t-PA driven lysis of an “aged clot”
Authors: Jerome W.G. , Handt S. , Hantgan R.R.
Published: June 2020

In an effort to reestablish blood flow in blocked coronary arteries, heart attack victims are now routinely treated with thrombolytic (clot busting) drugs. However, thrombolytic therapy fails to restore sufficient flow in approximately 20% of cases. The reasons for these failures are undoubtedly multifactorial and difficult to study in vivo. We have developed an “in vitro” model blood vessel which allows controlled study of factors influencing thrombolysis. In the studies reported here, we investigated the 3-D distribution of HUVEC secreted PAI-1 within the clot using immuno-gold cytochemistry and intermediate voltage electron microscopy (IVEM).

Human umbilical vein endothelial cells (HUVEC) were grown on the inside surface of fibronectin-coated glass tubes. The cells are stimulated for 4 hours with 1000 U/ml of TNF-α. Clot formation was initiated by addition of 2.3 μM fibrinogen, 100 nM plasminogen, and then 2 nM thrombin in HEPES buffered Gey's salts + 0.5% human serum albumin. After aging the clot for up to 4 hours (to mimic the time delay between heart attack and treatment), 0.5 nM rt-PA (thrombolytic agent) was perfused through the clot for 10 min. at 5 ml/hr. Formation and dissolution of the clot were monitored by laser light scattering.
Exhaustive photon reassignment™: a method for performing high-resolution, quantitative 3-D fluorescence microscopy
Authors: Moorthy Ramkumar K. , Hitrys David C.
Published: June 2020

Fluorescence microscopy is an increasingly popular technique in the field of light microscopy. However, when one uses an objective lens of high magnification and numerical aperture, only a very shallow plane within the specimen is in optimal focus. Out-of-focus fluorescent objects in planes above and below this plane of focus contribute light haze to this plane, compromising the visual quality of the specimen image. This haze also renders it impossible to accurately quantify light intensities of fluorescent objects present in this plane.

Confocal microscopy is one technique that allows researchers to obtain a highly resolved, high-contrast image of a specimen plane by excluding or rejecting light emanating from out-of-focus planes. Most biologists, however, can illafford to discard valuable fluorescence energy, because its efficient use would allow for optimal imaging conditions, and because it does contain useful information even if emanating from out-of-focus structures. There are also other drawbacks associated with confocal technology. The laser used as the excitation source in a confocal microscope is not really suitable for live cell studies, and also limits the range of fluorochrome labels that may be used.
3-D structure of single macromolecules at 15Å resolution by cryo-microscopy and angular reconstitution
Authors: Dube Prakash , Stark Holger , Orlova Elena V. , Schatz Michael , Beckmann Erich , Zemlin Friedrich , van Heel Marin
Published: June 2020

Electron cryo-microscopy of individual non-crystallized macromolecules (“single particles”) is a very rapid technique for probing the three-dimensional (“3D”) structure of biological macromolecules. By exploiting the different orientations of the macromolecules in the embedding medium, one may extract 3D information from the data without ever collecting tilt series in the microscope. The angular reconstitution approach, designed for this purpose, was recently extended with a number of refinements which allow its use as a routine technique for finding 3D structures of macromolecules with arbitrary pointgroup symmetry, from entirely asymmetric ribosomes to viruses with icosahedral symmetry.

The specimen preparation technique associated with the angular reconstitution approach is simple and fast since crystallization experiments are avoided altogether. The vitreous-ice embedding specimen preparation technique remains one of our favorite specimen preparation techniques. We are, however, currently experimenting with specimens embedded in glucose and ammonium molybdate or other heavy-metal salts. Collecting good micrographs can also be quite straightforward since the images are taken from untilted specimens, while exposing each image area only once.
En face dual fluorescence staining of fatty streaks allows observation of initiation and progression of atherosclerotic lesions
Authors: Klinkner Anne M. , Waites Crystal R. , Bugelski Peter J. , Kerns William D.
Published: June 2020

A primary effort in the understanding of the progression of atherosclerotic disease has been methods development for visualization of the atherosclerotic plaque. We introduce a new method for the qualitative analysis of lipids in atherosclerotic fatty streaks which also retains those lipids for biochemical evaluation. An original aspect of the process is the ability to view an entire fatty streak en face, selectively stained for specific lipid classes within the lesion.

New Zealand white rabbits were fed a high cholesterol diet(0.15%-0.3% for 14 wks). The aorta was removed and fixed in Carson's phosphate buffered formaldehyde followed by dual staining in the fluorescent dyes Nile red and filipin. Stock solutions of nile red(0.5mg/ml acetone) and filipin(2.5mg/ml dimethyl formamide) were prepared and kept at -20°C; all subsequent steps were at RT. 0.5cm × 1.0cm pieces of aorta were trimmed and adventitia removed. The pieces were then washed 3×15 min in PBS w/o CaMg, soaked in Nile red(NR)/filipin(Fl) stain(100(il NR stock + 200μl Fl stock in 10 ml PBS for 30 min, washed in PBS 3×30 min, rinsed with distilled water, mounted(Crystal Mount, Biomedia) and coverslipped and viewed by fluorescence microscopy.
Accumulation of smooth tubular membrane aggregates in the vitellogenic oocytes of an insect, Dysdercus cingulatus
Authors: Kömüvest László G. , Sasst Miklós
Published: June 2020

The accumulation of vitellogenins in the oocytes of insects is a receptor-mediated endocytic process, which leads to the formation of yolk granules. We have been studying the hormonal regulation of vitellogenin accumulation and yolk granule formation in the red cotton stainer, Dysdercus cingulatus (Insecta, Hemiptera). During our investigation we observed the appearance of extensive aggregates of smooth tubular membranes in the vitellogenic oocytes. In this report we describe the ultrastructural features of these new cellular organelles.

In D. cingulatus (as in other insects) the onset of vitellogenesis (i.e. yolk accumulation) is marked by the appearance of coated pits between the microvilli (Fig. 1). The coated pits transform into electron dense coated vesicles upon invagination into the cortical ooplasm and their subsequent fusion leads to the formation of yolk granules. At a later stage the fusion and continuous growth of yolk granules gives rise to large yolk platelets. During the early phase of yolk accumulation the cortical ooplasm also contains non-coated vesicles of different size in a large number (Fig. 1).
Nuclear pores in apoptosis and necrosis induced by cisplatin intoxication
Authors: Montpetit V.J.A. , Mikhael N. , Goel R. , Stewart D.J. , Molepo J. M. , Luck B. T.
Published: June 2020

Nuclear pore complexes (NPC) are an extensively studied cell component involved in the trafficking of macromolecules between the nucleus and cytoplasm. The distribution of NPC is reported to be altered during apoptosis in five different apoptotic models. Cisplatin (DDP) is an important anticancer drug that induces apoptosis in renal epithelial cells. Falcieri's findings prompted us to study the distribution and structural alterations of NPC during DDP intoxication in both necrotic and apoptotic cells. Six BDF1 mice were injected intraperitoneally at a dose of 10 or 20 mg/Kg and were sacrificed after 2 or 4 days. The kidneys were removed and processed for conventional electron microscopy. An examination of random sections of the renal cortex from different mice showed that there was significant apoptosis although the predominant process of cell death was necrosis. The characteristics of apoptosis were readily identified by the chromatin margination adjacent to the inner nuclear membrane, clearing of the granules in the nucleoplasm as well as the relatively intact cytoplasm. Earlier changes appeared to be preceeded by nucleolar segregation.
Insulin-like growth factor i and demyelination: cytochemical evidence for free radical derived oxidant mediation
Authors: Ann Ellis E. , Grant Maria B. , Mames Robert N.
Published: June 2020

The peptide hormone, insulin-like growth factor I (IGF-I) is a growth factor which has been shown in elevated concentrations in the serum and vitreous of diabetic patients with proliferative diabetic retinopathy. Studies with an animal model of IGF-I induced proliferative retinopathy2 showed demyelination in the optic nerves and along the medullary rays of rabbit eyes which received intravitreal injections of IGF-I, basic fibroblast growth factor (bFGF), or a combination of the two growth factors. Biochemical studies have demonstrated a role for oxidative injury in complications of diabetes including lipid peroxidation and demyelination in peripheral neuropathy. The cerium NADH-oxidase technique has been used to demonstrate free radical derived oxidant production in several pathological conditions including demyelination in experimental allergic encephalomyelitis (EAE). We investigated the role of free radical derived oxidants in growth factor-induced demyelination.

Pigmented rabbits were injected intravitreally with 500μg of IGF-I or bFGF and sacrificed at 4, 8,12 and 18 days.
Endophytic relationship between an entomopathogenic fungus Beauveria bassiana and corn (zea mays)
Authors: Wagner Bruce L. , Lewis Leslie C.
Published: June 2020

Fungi are known to colonize plants, usually as phytopathogens or symbionts. This is the first report of the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) penetrating and colonizing a plant in a manner similar to when it invades a typical insect host Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae). Electron microscopy was used to document this fungus penetrating the leaves of corn (Zea mays) and establishing an endophytic relationship within the plant.

Several studies have shown B. bassiana to adhere to insect cuticle and penetrate with or without forming appressorial penetration structures. Investigations have concluded that the young, germinating hyphae may produce sequentially a proteinase followed by chitinase to dissolve the cuticular envelope of target insects. Within three days after inoculation, viable B. bassiana conidia germinated and formed vegetative mycelia which grew randomly over the corn leaf surface (Fig. 1). Often a germ tube is formed from a conidium and elongates only a short distance before terminating its growth and penetrating the leaf surface (Figs. 2 and 3).
Sequential detection of mRNA for the chemokine IL-8 and macrophages (F4/80) in human melanoma
Authors: Bucana C.D. , Sanchez R. , Singh R. , Fidler I.J.
Published: June 2020

The purpose of this study was to demonstrate by ISH the presence of IL-8 mRNA, and by immunohistochemistry (IHC) the presence of the chemokine IL-8 and the distribution of infiltrating macrophages in subcutaneous melanomas in the same tumor. IL-8 is a multifunctional cytokine produced by melanoma cells, activated macrophages and monocytes and it has been shown to be a growth and angiogenic factor for tumor cells. More recently it was shown that constitutive expression of IL-8 correlated directly with metastatic potential of human melanoma cells in nude mice. IL-8 content of a solid tumor as determined by Western blot analysis does not take into account the contribution of macrophages. Previous studies showed that murine tumors contain many infiltrating cells interspersed among tumor cells whereas human tumors growing in nude mice exhibit macrophages at the periphery or between tumor islands. In this study we demonstrate the expression of IL-8 and the distribution of macrophages by immunoperoxidase assay and IL-8 mRNA by ISH.
Thin sectioning for cryo transmission electron microscopy (cryo TEM)
Authors: McDowall A.W. , Smith J.M. , Dubochet J.
Published: June 2020

Processing whole cells and tissues for conventional TEM is known to cause structural alterations. Much effort has been devoted, therefore, to developing techniques which avoid specimen preparation artefacts. Recently, research using a cryo-electron microscope has shown that biological suspensions embedded in vitreous ice retain their structural integrity, and when compared with conventionally prepared TEM specimens, are free from many of the classical artefacts. In order to extend the advantage of cryo TEM to whole cells and tissues, we have developed a method of thin sectioning vitrified material.
The organic matrix of the sea urchin embryo spicule visualized by electron microscopic immunocytochemistry
Authors: Benson N.C. , Benson S.C. , Wilt F.
Published: June 2020

The embryonic spicule of the sea urchin, Strongylocentrotus purpuratus is first detected at the late gastrula stage of development. The calcite spicule elongates within an intracellular vacuole of a syncytium of primary mesenchyme cells (PMC) originating at the ventral end of the blastocoel cavity and continues to form upward within a cytoplasmic cable until fully formed at the prism larval stage. The calcite is laid down as concentric lamallae on an organic matrix that extends within and through the spicule. The matrix has been characterized as a glycoprotein with major bands of molecular weights of about 47, 50, 57 and 64 kd. The PMCs surrounding the spicule are presumably the sites of synthesis and glycosylation of the organic matrix.
Structural studies of Na,K-ATpase
Authors: Mohraz M. , Yee M. , Smith P.R.
Published: June 2020

Na,K-ATPase, an integral protein of the plasma membrane of eukaryotic cells, derives energy from ATP hydrolysis for the active, coupled transport of Na+ out of the cell and K+ into the cell. The enzyme can be purified in membrane-associated form (1). It consists of two polypeptide chains: α(Mr=100,000) and β(Mr=50-60,000).

Two dimensional arrays of the enzyme were induced by partial removal of its phospholipids by phospholipase A2, and in the presence of variousions. The arrays were exclusively dimeric with an (αβ)2 structure in the unit cell (Fig. 1). SDS polyacrylamide gel of the crystalline sheets is presented in Fig. 2. It shows an identical pattern with the same relative ratio of α:β subunits, to that of the pure enzyme.
Bacterial conjugation: Scanning Electron Microscopy confirms the lightoptical impressions and the TEM observations in Escherichia Coli K 12
Authors: Schreil W.H. , Ingoliç Elisabeth
Published: June 2020

Although 40 years have passed since the discovery of bacterial conjugation and earliest electron microscopic observation, the nature of the cellular interaction that occurs during DNA transfer from donor to recipient is still obscure. In particular, the question of whether this transfer requires close cell contact or whether some form of conjugation tube is involved, remained controversial. We had in the past identified some events in conjugation by thin sectioning and more recent by freeze etching techniques and did postulate a temporary fusion, but observations of the entire unsectioned and unfractured cells in their behaviour did present a missing link.
Cervical and vaginal surface epithelial changes in persistent estrous, chemically diabetic BB wistar rats observed by scanning electron microscope
Authors: Khosho F. K. , Kaufmann R. C. , Amankwah K. S.
Published: June 2020

Studies of the effects of diabetes on reproduction in the female BB Wistar rat are not available in the literature. Male reproduction has been studied in these spontaneously-diabetic BB Wistar rats, and abnormalities of the reproductive tract have been found. This investigation, therefore, compared the ultrastructure of the lower reproductive tract of the chemically-diabetic female BB Wistar rat which has developed persistent estrous(PE) to normalcycling controls.
Cardiac myocytes cultured on a basement membrane extract of the ehs tumor
Authors: Terracio L. , Dewey A. , Rubin K. , Borg T.K.
Published: June 2020

The recognition and interaction of cells with the extracellular matrix (ECM) effects the normal physiology as well as the pathology of all multicellular organisms. These interactions have been shown to influence the growth, development, and maintenance of normal tissue function. In previous studies, we have shown that neonatal cardiac myocytes specifically interacts with a variety of ECM components including fibronectin, laminin, and collagens I, III and IV. Culturing neonatal myocytes on laminin and collagen IV induces an increased rate of both cell spreading and sarcomerogenesis.
The three-dimensional structure of frozen-hydrated left- and right-handed forms of bacterial flagellar filaments from an identical serotype
Authors: Trachtenberg S. , DeRosier D. J.
Published: June 2020

The bacterial cell is propelled through the liquid environment by means of one or more rotating flagella. The bacterial flagellum is composed of a basal body (rotary motor), hook (universal coupler), and filament (propellor). The filament is a rigid helical assembly of only one protein species — flagellin. The filament can adopt different morphologies and change, reversibly, its helical parameters (pitch and hand) as a function of mechanical stress and chemical changes (pH, ionic strength) in the environment.
Liver alterations as a result of the 90-day continuous feeding of 2,3,7,8-tetrachlorodibenzo-p-dioxin
Authors: Turner J.N. , Collins D.N.
Published: June 2020

Chlorinated hydrocarbons are a highly toxic, ubiquitous class of environmental toxins of which 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic. PCB pyrolysates contain a complex mixture of these chemicals and have been shown to produce extensive alterations in the liver of guinea pig hepatocytes, including proliferated smooth endoplasmic reticulum (SER), concentric membrane arrays (CMA) which are a condensation of proliferated SER, and cytoplasmic vacuoles. A mechanism of membrane excretion into the bile canaliculi and sinusoids has been proposed to account for these alterations and their relationship to each other. This report demonstrates the proposed mechanism for a purified compound (TCDD) fed continuously for 90 days and further elucidates the role of the cytoplasmic vacuoles which are observed for dose levels at which no other alteration is present.
Lattice imaging of precipitates in Al-Zn-Mg alloy
Authors: Wu C. K.
Published: June 2020

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:

(i) heterogeneous nucleation at grain boundaries;

(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;

(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.
Microstructure-property hypermaps for shock-loaded materials
Authors: Murr L. E.
Published: June 2020

Residual deformation-induced metallurgical effects or structure (microstructure)-property relationships are now generally well documented to be the result of stress or strain-induced microstructures, or microstructural changes in polycrystalline metals and alloys. In many cases, strain hardening, work hardening, or other controlling deformation mechanisms can be described by the generation, movement, and interactions of dislocations and other crystal defects which produce drag, or a range of impedances, including obstacles to dislocation motion.
Determination of creep mechanisms in various silicon carbides via TEM
Authors: Carter C. H. , Lane J. E. , Bentley J. , Davis R. F.
Published: June 2020

Silicon carbide (SiC) is the generic name for a material which is produced and fabricated by a number of processing routes. One of the three SiC materials investigated at NCSU is Norton Company's NC-430, which is produced by reaction-bonding of Si vapor with a porous SiC host which also contains free C. The Si combines with the free C to form additional SiC and a second phase of free Si. Chemical vapor deposition (CVD) of CH3SiCI3 onto a graphite substrate was employed to produce the second SiC investigated. This process yielded a theoretically dense polycrystalline material with highly oriented grains. The third SiC was a pressureless sintered material (SOHIO Hexoloy) which contains B and excess C as sintering additives. These materials are candidates for applications such as components for gas turbine, adiabatic diesel and sterling engines, recouperators and heat exchangers.