bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of The Electronic and Structural Properties of
Semiconductors by Scanning Transmission Electronmicroscopy (Stem)
Authors: Petroff P. M.
Published: June 2020

The simultaneous probing of the structural and electronic properties of
a semiconductor on a very localized scale with the medium energy (50 ≤
Eo ≤ 200 KeV) (STEM) instruments offers new
possibilities for understanding the properties of defects and interfaces.
The advantages of working with thin films and high electron beam energies as
opposed to bulk samples and low energy electrons are sizable since they
bring: a) an improved spatial resolution and sensitivity in the analysis of
the electronic properties of the probed volume and b) a direct and
simultaneous observation of the structure and chemistry in the probed area
making simple the comparison between the two types of analysis. Selected
examples are given to illustrate the advantages and limitations of the STEM
techniques implemented for probing the recombination and radiative
properties of defects.
Characterization of Tempered 4340 Steel after 1200°C
Austenitization
Authors: Datta K. P. , Kannan V. C.
Published: June 2020

Considerable research is in progress to improve the fracture toughness
of low alloy ultra-high strength steels such as 4340 while maintaining the
same level of yield strength. One such methodis high temperature
austenitization (1200° C). Subsequent tempering, in general, renders still
higher toughness and hence this study is aimed at characterization of
tempered 4340 steel after 1200° C austenitization.
Microstructural Characterization of Rapidly Solidified Ti Modified 316
Stainless Steels for Irradiation Environments
Authors: Arnberg L. , Sande J. B. Vander
Published: June 2020

One of the prime candidates for a fusion reactor first wall material is
Ti modified 316 stainless steel (0.32% Ti). The interface between TiC and
the austenitic matrix has been shown to be a good nucleation site for helium
formed during neutron irradiation, thus reducing swelling and preventing
helium bubbles from forming elsewhere, e.g., at grain boundaries. This
material and another alloy, where the TiC content has been increased, have
been rapidly solidified (105K/sec) by means of a roller
quencher to give a very fine dispersion of TiC. The effects of subsequent
extrusion and thermomechanical treatment have been evaluated by TEM and STEM
to give materials with optimum irradiation performance.

The microstructures of alloys chosen for irradiation experiments have
been carefully characterized by electron microscopy. The morphology, size,
and distribution of different intermetallic phases have been studied by
conventional TEM techniques and their compositions have been determined by
energy dispersive X-ray- and electron energy loss spectroscopy. The size
distribution of TiC particles have been determined using a computerized
image analyzer.
In-Situ TEM Observations of Different Growth Modes of Small Iron
Particles on Sapphire
Authors: Anton R. , Heinemann K.
Published: June 2020

An in-situ study was performed of the growth kinetics of individual
crystallites during the deposition of iron onto electron-transparent
singlecrystalline α-Al2O3
(sapphire) substrates. Clean sapphire films were produced in-situ under UHV
conditions by electron-beam induced crystallization of amorphous
Al2O3 (1). Iron was
electron-beam vapor-deposited at constant rates (0.2-0.5 nm/min) and
elevated substrate temperatures (750 – 900°C) immediately following the
crystallization. The nucleation, growth, and eventual coalescence of the
metal particles were observed in-situ by transmission electron microscopy
and recorded on video tape at 30 frames per second. In fig. 1, a growth and
coalescence sequence of several Fe-particles on
[100]-α-Al2O3 is shown. The
images were selected and photographed from the TV monitor during video
playback. The particles marked with letters were analyzed in detail.
Noteworthy is that particle A (after about 30 min. of growth) started a
rapid increase of its length-to-width ratio. Particle H, formed in a
coalescence event, exhibited a preferred growth in a special direction,
presumably in order to develop a certain crystallographic habit. Particle K
developed a fast lateral growth ab-initio and remained a thin platelet until
it coalesced with a neighboring particle about 25 min. after the beginning
of the deposition.
STEM and ELS Observation of Early Oxide Formation on the Surface of Cr
Thin Films
Authors: Watari Fumio , Cowley J. M.
Published: June 2020

STEM coupled with the optical system was used for the investigation of
the early oxidation on the surface of Cr. Cr thin films (30 – 1000Å) were
prepared by evaporation onto the polished or air-cleaved NaCl substrates at
room temperature and 45°C in a vacuum of 10−6 Torr with
an evaporation speed 0.3Å/sec.

Rather thick specimens (200 – 1000Å) with various preferred orientations
were used for the investigation of the oxidation at moderately high
temperature (600 − 1100°C). Selected area diffraction patterns in these
specimens are usually very much complicated by the existence of the
different kinds of oxides and their multiple twinning. The determination of
the epitaxial orientation relationship of the oxides formed on the Cr
surface was made possible by intensive use of the optical system and
microdiffraction techniques. Prior to the formation of the known
rhombohedral Cr2O3, a thin spinel
oxide, probably analogous to γ
-Al203 or γ
-Fe203, was formed. Fig. 1a
shows the distinct epitaxial growth of the spinel (001) as well as the
rhombohedral (125) on the well-oriented Cr(001) surface. In the case of the
Cr specimen with the (001) preferred orientation (Fig. 1b), the rings
explainable by spinel structure appeared as well as the well defined
epitaxial spots of the spinel (001). The microdif fraction from 20A areas
(Fig. 2a) clearly shows the same pattern as Fig. Ia with the weaker oxide
spots among the more intense Cr spots, indicating that the thickness of the
oxide is much less than that of Cr. The rhombohedral
Cr2O3 was nucleated preferably
at the Cr(011) sites provided by the polycrystalline nature of the present
specimens with the relation Cr2O3
(001)//Cr(011), and by further oxidation it grew into full coverage of the
rest of the Cr surface with the orientation determined by the initial
nucleation.
A Microanalytic study of Foreign Body Vasculitis in Infantile Pulmonary
Hypertension
Authors: Bowen J. H.
Published: June 2020

Foreign body vasculitis has been seen in the pulmonary vessels of
infants requiring extensive intravenous therapy but their clinical
significance and origin has been unclear. Commercially prepared intravenous
solutions and medications can contain a variety of particulates. The chronic
injection of illicit solutions prepared from tablets designed for oral use
has caused foreigrubody vasculitis in pulmonary vessels with resulting
pulmonary hypertension and death. This study demonstrates the utility of
scanning electron microscopy (SEM) and energy dispersive x-ray analysis
(EDX) in the characterization of pulmonary vascular inclusions in an infant
who developed foreign body vasculitis and fatal pulmonary
hypertension.
Electron Microscopic Study of Histoplasmosis in Mouse Liver
Authors: Edwards Mercedes R.
Published: June 2020

Histoplasmosis, which has a worldwide distribution, is either a
generalized and fatal or a benign infection of man and some domestic or wild
animals.

The etiologic agent of this disease is a dimorphic fungus which shows
predilection for the reticuloendothelial system, but other tissues may also
be affected. The fungus can be found in soil samples from endemic areas
(e.g. central Mississippi valley, Ohio valley, Appalachian mountains) where
it disseminates by means of characteristic spores. The large tuberculate
spores of Histoplasma capsulatum have been studied in our laboratory
(1).
The Use of Urine Sediments in the Diagnosis of Fabry's Disease
Authors: McMahon J. T. , Tubbs R. R. , Gephardt G. N.
Published: June 2020

Fabry's disease is a hereditary, metabolic disorder leading to tissue
accumulation of ceramide trihexoside principally in the kidneys and
arteriole walls due to a deficiency in catabolic alpha galactosidase
activity. During the course of the disease, affected patients may present
with angiokeratotic skin lesions, corneal opacities, complaints of extremity
pain, and angina pectoris. Proteinuria usually appears between the second
and third decade of life and may be the factor leading to correct
diagnosis.
A Sensitive On-Grid Immunoelectron Microscopic Procedure for Diagnosis of
Rotavirus Infection
Authors: Miller M. F. , Rubenstein A. R.
Published: June 2020

Studies of rotavirus particles in humans, monkeys and various
non-primates with acute gastroenteritis have involved detection of virus in
fecal material by electron microscopy. The EM techniques most commonly
employed have been the conventional negative staining (Fig. 1) and immune
aggregation (Fig. 2) procedures. Both methods are somewhat insensitive and
can most reliably be applied to samples containing large quantities of virus
either naturaLly or as a result of concentration by ultracentrifugation. The
formation of immune complexes by specific antibody in the immune aggregation
procedures confirms the rotavirus diagnosis, but the number of particles per
given microscope field is effectively reduced by the aggregation process. In
the present communication, we describe use of an on-grid immunoelectron
microscopic technique in which rotavirus particles are mounted onto
microscope grids that were pre-coated with specific antibody. The technique
is a modification of a method originalLy introduced by Derrick (1) for
studies of plant viruses.
An Ultrastructural Study of Mouse Brain Following Rapid Fixation by
Microwave Irradiation
Authors: Berry V. K. , Modak A. T. , Stavinoha W. T.
Published: June 2020

The accurate analyses of many labile neurochemicals is depended on the
rapid inactivation of the synthetic and degradative enzymes. To achieve
rapid in-activation, recently, a 2450 MHz microwave instrument with a power
deposition of 7 kW has been designed and built in our laboratory. This
device has been utilized to preserve the short lived neurochemicals, such as
acetylcholine, choline, γ aminobutyric acid, dopamine and cyclic adenosin
monophosphate. This method has several advantages and is superior to
freezing technique. little is known about the effects of heating by
microwave on the cellular and subcellular structure of the brain. In the
present studies the effect of heating with 2450 MHz microwave radiation for
100 milliseconds (temp. 60°C)1 on the ultrastructure of different regions of
mice brain has been examined. The ultrastructural changes in the anterior
portion of the brain are described.
Ultrastructure of Schwann Cells in the Auerbach Plexus of the Small
Intestines of Shetland Ponies
Authors: Al-Bagdadi F. , Ochoa R.
Published: June 2020

A review of current literature reveals that Auerbach’s plexus is
involved in grass sickness in horses. Mortality of horses with this
condition is very high. Except in laboratory animals relatively little
electron microscope study on the Auerbach’s plexus has been done.
Morphological definition of this plexus in the intestine of the horse is
necessary to fill in the gap of the literature review and to describe the
normal picture of Auerbach’s plexus for a better reading and interpretation
of pathological slides. Samples of the small intestine were collected from
the duodenum, jejunum and ileum of six Shetland ponies. The samples were
fixed in 3% gluteraldehyde in a phosphate buffer (pH 7.4), postfixed in 1%
oso4 and embedded in epon. Ultra-thin sections were
examined by a Zeiss 10 electron microscope.
Studies of Vegetative Plant Tissue Compatibility/Incompatibility: The
Role of Acid Phosphatase in Lethal Cell Senescence in an Incompatible
Heterograft
Authors: Moore Randy
Published: June 2020

Previous work has indicated that the graft incompatihility between
Sedrmi telephoides and Solanum pennellil involves cell necrosis that results
In a thick layer of collapsed cells at the graft Interface. This necrotic
layer insulates the stock from the scion, which results in abscission of the
Sedum scion after 4-6 weeks due to desiccation and starvation. Thus, cell
autolysis (which is restricted to Sedum) characterizes the Incompatibility
response in this system (1).

In order to elucidate the events that lead to cell autolysis, and thus
better understand the cellular site and mode of action of cellular
incompatibility, the appearance and fate of the hydrolytlc enzyme acid
phosphatase (AP) was followed in both the compatible Sedum autograft and the
incompatible Sedum/Solanum heterograft. Acid phosphatase was localized by a
modified Gomori-type reaction; positive (i.e., including NaF inhibitor) and
negative (lacking substrate) controls showed no enzymatic precipitate.
Following an initial association with the endoplasmic reticulum (ER) and
dictyosomes at 6-10 hours after grafting, AP activity in the compatible
Sedum autograft is associated primarily with the plasmalemma (Fig. 1). By
18-24 hours after grafting, the AP activity is restricted to the tono-plast
and vacuole (Fig. 2). This strict compartmentation and absence of enzyme
from the cytosol is maintained throughout the development of the compatible
graft. While AP activity in the incompatible Sedum/Solanum heterograft is
Initially similar to the compatible Sedum autograft (i.e., initially found
on the ER and dictyosomes), there is a marked difference in enzyme
localization in the two graft partners as the incompatibility response
develops. As in the compatible autograft, Solanum cells at the graft
interface show an Increase in AP activity that Is restricted to the vacuole
and tonoplast, with little or no enzyme activity in the cytosol (Fig. 3). In
comparable Sedum cells, however, there is a dramatic Increase In AP activity
in the cytosol (Fig. h); this cytosollc AP activity is associated with thin
fibril-like structures (Fig. 5) measuring approximately 60 A in diameter.
This high cytoplasmic AP activity In Sedum cells results in cell autolysis,
death, and eventual cell collapse to form the characteristic necrotic layer
separating the two graft partners.
Studies on The Mechanism of Nuclear Expulsion in Mammalian Erythroid
Cells
Authors: Repasky E. A.
Published: June 2020

As mammalian erythroid cells mature, the nucleus is ejected from the
cell by a mechanism not yet known. Other vertebrates have nucleated
circulating red cells and recent literature suggests that cytoplasmic
cytoskeletal elements may anchor the nucleus within the cell. In the
anucleate mammalian red cell, cytoskeletal elements are not seen. It has,
however, been suggested that the process of nuclear expulsion resembles a
form of unipolar cytokinesis. This implies that there may be a contractile
ring present or other cytoskeletal ele ments, such as microtubules, which
are usually found in association with divid ing cells. The purpose of this
study is to examine enucleating erythroid cells in the mouse for these
elements and evaluate their possible functions.
Studies on Calcium in the Eye of the Snail Helix Asiersa
Authors: Eakin Richard M. , Brandenburger Jean L.
Published: June 2020

We have given much attention to unique microvesicles (uniform spherical
shape and uniform 800 A diameter) that occur in remarkable aggregations in
the photosensory cells of gastropod mollusk eyes (Fig. 1). We obtained
evidence that these vesicles may carry the photopigment or its precursors.
We have termed them photic vesicles. But they may serve another function
important in vision:transport of calcium. This hypothesis was suggested by
electron probe evidence of calcium in the retina of the snail Helix aspersa.
The resolution, however, was not sufficient to conclude that the calcium was
in the microvesicles. The present study supports that conclusion.
Histochemical and Ultrastructural Studies of the Digestive Epithelium in
a Gastropod Gametolytic Organ
Authors: Reeder R. L. , Rogers S. H. , Shannon W. A.
Published: June 2020

Numerous morphological studies have dealt with the spermatheca of
pulmonate gastropods. This globular organ, which is attached to the female
portion of the reproductive tract by a long duct in these monoecious
animals, has had various functions ascribed to it. Recent histochemical
demonstrations of deoxyribonuclease, ribonuclease, protease, and acid
phosphatase have provided, however, conclusive evidence that it is a
digestive organ for the degradation of superfluous sperm and genital tract
secretions. Only limited information concerning the spermatheca is available
at the ultrastructural level, a fact providing the stimulus for the present
study of this organ in Sonorella santaritana, a desert mountain snail from
Arizona.
Heart Muscle Cells Enzymatically Isolated from Ventricular Wall: Case
Studies of Myofilament Overlap Configurations
Authors: Robinson T.F. , Aronson R.S. , Cohen-Gould L. , Sorenson A.L. , Wittenberg B.A. , Sonnenblick E.H.
Published: June 2020

During the cardiac cycle more than 70% of the end-diastolic ventricular
volume of blood can be ejected with each stroke as the heart contracts. As
the contraction and subsequent recoil occurs, the muscular walls undergo a
distinct change in shape characterized by changes in wall thickness and
volume-filling by shortened, thickened papillary muscles and infoldings of
the walls. These striking three-dimensional phenomena are produced by the
geometrical interplay of a large population of variously oriented muscle
cells and ultimately by the myofilament lattices that produce the forces and
change their lengths 10-15%. In order to determine the central role of the
myofilaments in the contractile process of the heart it is important to
ascertain the ratios and relative dispositions of thin filaments to thick
filaments and to contralateral thin filaments at known sarcomere lengths of
cells from the ventricle itself rather than from linear model systems such
as papillary muscles and trabeculae. We have made case studies of
enzymaticalIy isolated ventricular myocytes fixed at rest or in
mid-contraction. Although these cells are small, approximately 20 x 100 μm,
and require exacting techniques for manipulation, after their isolation
sarcomere lengths can be carefully measured, both in the living state and in
subsequent stages of preparation (Fig. 1).
Calcium Enriched Plasma Membrane-Associated Amorphous Deposits in
Chondrocytes of Calcifying Cartilage
Authors: Dougherty W.J.
Published: June 2020

In previous studies on rat and mouse alveolar bone and rat incisor
mantle predentin, amorphous-appearing deposits approximately 5 to 35 nm in
diameter were seen to be associated with matrix vesicles in each of these
mineralized tissues and with the plasma membranes of osteoblasts and young
odontoblasts. It was concluded that these membrane-associated amorphous
appearing deposits (MAADs) were mineral because of (1) their inherent
electron density in gl utaraldehyde-only fixed tissue and (2) their
extract-ability from ultrathin sections by neutral solutions of EDTA
(ethylene diamine tetraccetic acid) and EGTA (ethylene glycol
bis-(β-aminoethyl ether) N,N1-tetracetic acid).
Distilled water and 50% ethanol failed to extract the MAADs from ultrathin
sections. While these observations are indicative, they do not offer
conclusive evidence for the mineral nature the MAADs. It was considered
important to demonstrate the presence of Ca in the deposits by
non-destructive analytical methods and to show that these deposits occurred
in other calcifying tissues. For these purposes, tibial epiphyses of young
growing rats were prepared for routine electron microscopy and
energy-dispersive x-ray analysis in the STEM mode of a JE0L-100-CX using
previously published procedures (Dougherty, 1978). Ultrathin sections of gl
utaral dehyde/osmi urn tetroxide fixed tissue samples were viewed unstained.
Figure 1 shows a low magnification TEM image of two chondrocytes in the
proliferative zone of the tibial epiphyseal plate. MAADs are present. Figure
2 illustrates in a STEM image at higher magnification two MAADs on another
chondrocyte in the proliferative zone. The energy dispersive spectra of
point C (an MAAD) and point E (plasma membrane lacking an MAAD) are
illustrated in figures 3 and 4. It can be seen that the MAAD at point C is
enriched in Ca, while point E is lacking in Ca. Other MAADs on other
chondrocytes were enriched in Ca also. Thus, it can be concluded that the
MAADs are mineral in nature and that they occur in another major calcifying
tissue. It is possible that the MAADs represent the initial nucleation
centers in calcifying tissues.
Sliding Velocity Between Outer Doublet Microtubules of Sea-Urchin Sperm Axonemes
Authors: Yano Y. , Miki-Noumura T.
Published: June 2020

The flagellar axonemes have a cylindrical form, which consists of nine doublet microtubules surrounding a central pair of single microtubules. Each doublet tubule has two parallel rows of projections, called outer and inner arms. Sliding movement between doublet microtubules was first reported by Summers and Gibbons, who observed that doublet tubules were extruded from trypsin-treated axonemes of sea-urchin sperm flagella on addition of ATP. Their observation indicated that the bending movement of flagella results basically from these active sliding movements between the adjacent doublet tubules in the axonemes. Experimental evidence suggests that the dynein arms projecting from the doublet tubules interact with the adjacent tubules and by hydrolysing ATP, produce the mechanical force to slide. According to Gibbons and Gibbons the outer arms were removed from the doublet tubules by extracting the demembranated sea-urchin sperm with 0.5 M KCl or NaCl, while the inner arms and other axonemal structures remained apparently intact. Although the form of their bending waves was not significantly altered, the KCl-extracted sperm had only about half the flagellar beat frequency of the demembranated sperm. The 21S latent ATPase activity form of dynein 1 restored up to 90% of the outer arms on the doublet tubules and increased the beat frequency of KCl-extracted sperm from 14 Hz to 25 Hz. We found that the NaCl-extracted axonemes of sea-urchin sperm had the ability to extrude outer doublet tubules on addition of ATP and trypsin, in a similar manner to that of the intact axonemes. We attempted to compare the sliding velocity of the outer doublet tubules in the arm-depleted axonemes and in the arm-recombined axonemes, with that in the intact axonemes, in order to find the relationship between the sliding velocity and the number of arms in these axonemes.
Role of Spectrin in Human Erythrocyte IMP Aggregation
Authors: Doerschuk CM. , Weinstein R.S. , Steck T.L.
Published: June 2020

A wide variety of perturbations result in aggregation of intramembrane
particles (IMP) in human erythrocytes1–3.
Experimentally induced aggregation may involve partial removal of the
spectrin-actin reticulum from the inner surface of the membrane followed by
incubations under conditions which decrease the solubility of spectrin and
promote rebinding of spectrin to the cytoplasmic
surface2. In this study, we have re-evaluated the
role of spectrin in IMP aggregation induced by low pH and by
proteolysis1, 3.
Membrane Specializations in Developing Nodes of Ranvier
Authors: Tao-Cheng J.H. , Rosenbluth J.
Published: June 2020

Mature myelinated nerve fibers exhibit distinctive structural features
at nodes of Ranvier and the adjacent paranodal regions. In order to obtain
information about the interrelationships between these specializations
during development, thin sections and freeze-fracture replicas of immature
peripheral nerve fibers from grass frog tadpole hind legs were examined
during the period of myelinogenesis.

Early in myelination axons are enwrapped individually by a few loose
Schwann cell layers whose edges overhang each other forming "terminal loops"
against the axolemma. Unlike those of the mature node, these loops are
widely sepa-rated and irregularly spaced (Fig.l), and similarly the
presumptive nodal region between successive developing myelin segments is
usually much longer than adult nodes of Ranvier. The presumptive nodal
axolemma may exhibit a cytoplasmic "undercoating." However, the density of
this coating is highly variable. Usually it is much lower than at adult
nodes, and in some cases the undercoating is not distinguishable. The
outermost layers of the Schwann cell are usually the first to form axoglial
junctional specializations character¬ized by the presence of "transverse
bands" and ER cisternae applied to the junctional Schwann cell membrane. In
some instances the outermost layer con¬tacts the axon over an extensive area
and forms multiple small junctional specializations at widely separated
intervals along the length of the axolemma.
Problem of Subsurfae Observation in Backscattered Electron Mode
Authors: Ogura K. , Laudate A.
Published: June 2020

Recently, the study of biological tissues by means of the SEM has not
been limited to the observation of specimens' surface structures, but
extended to the observation of their inner structures using various
techniques. The most widely used methods of observing inner structures by
secondary electron (SE) image include the frozen solvent fracturing method
and the frozen resin fracturing method using epoxy resin and
others.1)

The information obtained from a specimen when irradiated with an
electron beam includes SEs and backscattered electrons (BEs) . It is well
known that the yield of BEs is mainly dependent on the meen atomic numbers
of the constituent elements of the specimen, and the mean energy of BEs is
almost the same as that of incident electrons.2)
Accordingly, the BEs which are scattered back from the inside of the
specimen can be easily released from the specimen surface, so that BEs are
useful signals for obtaining the inner information on the
specimen.3)
Chromium Tagged Norepinephrine Content Shown by X-Ray Analysis
Authors: Munkres M. , Waymire J. , Wood J.
Published: June 2020

Specific tags for endogenous biological compounds are reaching new
importance with the advent of x-ray analysis, especially when an element,
chromium (Cr), is attached to a neurotransmitter, norepinephrine (NE), and
the amounts of NE studied experimentally. With the specific biochemically
confirmed technique to identify NE plus high instrument sensitivity, it is
possible to detect minute and varying amounts of Cr within tissue and thus
bring together the fields of histochemistry and neurobiology via the
electron optics.

NE-containing granules were from intact rat adrenal medullary tissue and
bovine medullary tissue which was present in the form of intact glands,
per¬fused glands, or cultured cells. The NE histochemical technique was that
of Wood, 1975, and the culture techniques were those of Waymire et al. (in
press). Tissues were fixed, incubated, and prepared according to TABLE
I.
The Response of Testis Cells to High Energy Particle Irradiation
Authors: Philpott D. E. , Sapp R. , Corbett S. , Black F. , D'Amelioh F. , Miquel I.
Published: June 2020

Seventy-seven years ago AIbers-Schonberg (1) described the
radio-sensitivity of germ cells, and three years later, Regand and Blanc (2)
reported sperma-tagonia to be the most radio sensitive structural part of
the testis. Forty-seven years later, NebeI (3) described the ultrastructural
appearance of dead and damaged spermatogonia after 1000 rads of X-rays.
Hugon and Borgers (4) reported radiation induced weight loss of the testis
and Krebs (5) computed the dose required to kill 37% of the radio-sensitive
spermatogonia after irradiation. Dose dependant testis weight loss has been
reported by Risius and Alpen (6) after high energy particle (HZE)
irradiation. They found a significant weight loss in doses as low as 5
rads.
Microinjection of Fluorescently Labeled 130K Protein into Living Fibroblasts: Localization at the Ends of Actin Microfilament Bundles and in Close Relation to Fibronectin
Authors: Feramisco J. R. , Burridge K.
Published: June 2020

Understanding the interactions between cell surface components and the underlying cytoskeleton continues to be a major goal in cell biology. In particular, little is known about the molecules involved in linking actin filaments to the plasma membrane in cells such as fibroblasts. A protein with a molecular weight of 130,000 (the 130K protein) was recently purified from smooth muscle by Geiger and localized to the ends of microfilament bundles in a variety of cell types. Independently we had purified this protein and were studying its possible interactions with other structural proteins when we learned of its interesting location, one that would be consistent with some role in the attachment of actin filaments to the plasma membrane. We were prompted to investigate this interesting protein further by microinjection of the f1uorescent1y labeled protein into living cells, a technique which had recently been successfully applied to the study of α-actinin.
Lanthanum Penetration into Cancerous Colonic Cells, A Microanalytical
Study
Authors: Humbert W. , Arnaud J. P. , Eloy R. , Adloff M.
Published: June 2020

Lanthanum nitrate is used as a selective stain of cell surface and
extracellular structures. It has been used detect permeability defects after
thermal injuries (1) and this marker is able to penetrate dark cells of the
Collem- bolan midgut (2), cells which are on the way to degenerate. Similar
results have been obtained with midgut cells infected with Rickettsia-like
organisms and which are predying cells. The aim of the present study was to
analyse the permeability of human colonic cancerous epithelial cells to
lanthanum.
Evaluation of Surface Markers on Lymphocytes Containing Parallel Tubular
Arrays:- A Quantitative Ultrastructural Study
Authors: Payne C.M. , Glasser L.
Published: June 2020

It has been well documented that normal lymphocytes from the peripheral
circulation represent a heterogeneous population of cells with different
surface markers and different functions. Some of these lymphocytes contain
cytoplasmic inclusions called parallel tubular
arrays1-3 (Figure) which are only identifiable
under the electron microscope. There is considerable controversy as to
whether this ultrastructurally-defined lymphocyte constitutes the major cell
type of the T-lymphocyte population, B-lymphocyte population or third
population of lymphocytes (i.e. K-cells, L-cells, null cells). In this
study, we performed a quantitative ultrastructural analysis of these cells
using three surface marker assays commonly used to identify the three major
populations. These surface marker assays were specifically chosen because of
the ease with which the test cell could be identified under the electron
microscope.4
Comparative Ultrastructure of Synapses in Normal and Weaver-Syndrome
Bovine Brains
Authors: Sue Aitchison C. , Westfall Jane A. , Leipold Horst W.
Published: June 2020

The Weaver syndrome is a familial disease affecting Brown Swiss cattle
of both sexes at an average age of 9-10 months. The onset of the syndrome is
characterized by an abnormal gait. The motor dysfunction progresses to an
imbalanced, swinging gait and recumbency by 2-3 years of age. Previous light
microscopy studies have shown pathological changes in the muscular system of
the hind legs and loin muscles. However, the central nervous system (CNS)
and sciatic and femoral nerves appeared normal.1 To
investigate the ultra- structural involvement of the CNS in this muscular
disease we conducted a preliminary comparison of the synaptic complexes in
the cerebral cortex from Weaver-syndrome and normal bovine brains.
Halos on Membrane-Associated Particles: A Freeze-Fracture Artifact
Associated With Extremely Thin Carbon Films
Authors: Steere Russell L. , Erbe Eric F.
Published: June 2020

In order to increase the resolution of specimens prepared by the freeze-
fracture and similar procedures, one would like to decrease the shadow film
thickness to the absolute minimum which will provide a reliable, nongranular
image of the replicated object. The contrast of such thin shadow films is
low compared to the heavy shadow films customarily used but can be enhanced
by reducing the thickness of the replica film and by mounting the replicas
on uncoated grids.
Bringing the Real World Inside the High Voltage Microscope
Authors: Butler E. Paul
Published: June 2020

Although much useful information can come from the microstructural
characterisation at room temperature of a single specimen in a modern
conventional TEM, it is a knowledge of the structural evolution of a
material under changing conditions of temperature, stress, irradiation,
environment, etc., which is frequently of most interest. The normal indirect
way of providing this information suffers from the disadvantage that the
external forces responsible for the changes must be relaxed, and a number of
separate specimens need to be examined. The postulation of the course of a
reaction on the basis of such evidence can be further complicated by
microstructural ambiguities of sectioning. The in situ technique avoids
these difficulties and allows changes to be followed continuously in a
single specimen via the use of special stages which alter the state of the
specimen in a controlled and measurable way during observation. The response
of a material to any change in state or environment imposed upon it in the
real world can therefore be directly investigated.
Radiation Damage as the High-Resolution Limit in HVEM
Authors: Hobbs L. W.
Published: June 2020

Electron microscopy (EM) is concerned fundamentally with the elucidation
of the structure of solids, ultimately at the level of atomic resolution.
Recent advances [1-3] in the design and construction of magnetic lenses and
associated supplies for focusing electrons with energies U substantially
greater than 100 keV have enabled utilization of the smaller wavelength of
these electrons to lower the resolution limit to 0.2 nm. At this level of
structural information, it is necessary to be aware that the same electron/
atom Coulomb interactions which are the origin of ‘elastic’ electron
scattering and diffract ion phenomena can be responsible for a substantial
perturbation on the positional stability of an atom through the ‘inelastic’
transfer of momentum, directly or indirectly, to the atom nucleus. This is
what is meant by radiation damage.
How to Produce and Utilize Super-High-Resolution Structure Images in a
High Voltage Electron Microscope
Authors: Horiuchi Shigeo
Published: June 2020

In order to visualize the crystal structure in an atomic scale by
high-resolution transmission electron microscopy (HRTEM), as many of the
scattered waves as possible must be used for imaging. The optimum size of
the objective aperture is however limited by both the spherical and
chromatic aberrations. The analysis of our 1 MV EM structure images using a
computer simulation has shown that the resolution limit of the EM is nearly
2 Å. The aperture size is outlined by a large circle in the diffraction
pattern of Fig.1(a), which was taken from a
Nb22o54 crystal. The radius is
about two times larger than that for recent 100 KV EM equipped with a
goniometer stage, which corresponds to the small circle in Fig.1(a), and the
number of scattered waves used is then about four times more. (Fig.1) is the
corresponding image taken at 1 MV. Comparing to the structure model
inserted, it is clear that each cation is resolved as a dark spot. The
super-high-resolution of the present EM may be attributable principally to
the short wave length of electrons (0.0087 Å at 1 MV) and technically to the
high stability of the accelerating voltage.
Exploring the Drivers of Global and Local Sea‐Level Change Over the 21st Century and Beyond
Authors: Palmer M. D. , Gregory J. M. , Bagge M. , Calvert D. , Hagedoorn J. M. , Howard T. , Klemann V. , Lowe J. A. , Roberts C. D. , Slangen A. B. A. , Spada G.
Published: June 2020

We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5, and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including (i) more comprehensive treatment of uncertainties, (ii) direct traceability between global and local projections, and (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios, and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon, and emissions scenario. Our analysis highlights the importance of local variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlight the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large ( > 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see substantial differences in the breakdown of model variance as a function of location, time scale, and emissions scenario.
Temporal and Spatial Variations of Total Electron Content Enhancements During a Geomagnetic Storm on 27 and 28 September 2017
Authors: Shinbori Atsuki , Otsuka Yuichi , Sori Takuya , Tsugawa Takuya , Nishioka Michi
Published: June 2020

Temporal and spatial evolutions of total electron content (TEC) and electron density in the ionosphere during a geomagnetic storm that occurred on 27 and 28 September 2017 have been investigated using global TEC data obtained from many Global Navigation Satellite System stations together with the ionosonde, geomagnetic field, Jicamarca incoherent scatter and Super Dual Auroral Radar Network (SuperDARN) radar data. Our analysis results show that a clear enhancement of the ratio of the TEC difference (rTEC) first occurs from noon to afternoon at high latitudes within 1 hr after a sudden increase and expansion of the high‐latitude convection and prompt penetration of the electric field to the equator associated with the southward excursion of the interplanetary magnetic field. Approximately 1–2 hr after the onset of the hmF2 increase in the midlatitude and low‐latitude regions associated with the high‐latitude convection enhancement, the rTEC and foF2 values begin to increase and the enhanced rTEC region expands to low latitudes within 1–2 hr. This signature suggests that the ionospheric plasmas in the F2 region move at a higher altitude due to local electric field drift, where the recombination rate is smaller, and that the electron density increases due to additional production at the lower altitude in the sunlit region. Later, another rTEC enhancement related to the equatorial ionization anomaly appears in the equatorial region approximately 1 hr after the prompt penetration of the electric field to the equator and expands to higher latitudes within 3–4 hr.
Dipole Tilt Effect on Magnetopause Reconnection and the Steady‐State Magnetosphere‐Ionosphere System: Global MHD Simulations
Authors: Eggington J. W. B. , Eastwood J. P. , Mejnertsen L. , Desai R. T. , Chittenden J. P.
Published: June 2020

The Earth's dipole tilt angle changes both diurnally and seasonally and introduces numerous variabilities in the coupled magnetosphere‐ionosphere system. By altering the location and intensity of magnetic reconnection, the dipole tilt influences convection on a global scale. However, due to the nonlinear nature of the system, various other effects like dipole rotation, varying interplanetary magnetic field (IMF) orientation, and nonuniform ionospheric conductance can smear tilt effects arising purely from changes in coupling with the solar wind. To elucidate the underlying tilt angle dependence, we perform magnetohydrodynamic (MHD) simulations of the steady‐state magnetosphere‐ionosphere system under purely southward IMF conditions for tilt angles from 0–90°. We identify the location of the magnetic separator in each case and find that an increasing tilt angle shifts the 3‐D X line southward on the magnetopause due to changes in magnetic shear angle. The separator is highly unsteady above 50° tilt angle, characteristic of regular flux transfer event (FTE) generation on the magnetopause. The reconnection rate drops as the tilt angle becomes large, but remains continuous across the dayside such that the magnetosphere is open even for 90°. These trends map down to the ionosphere, with the polar cap contracting as the tilt angle increases, and region I field‐aligned current (FAC) migrating to higher latitudes with changing morphology. The tilt introduces a north‐south asymmetry in magnetospheric convection, thus driving more FAC in the Northern (sunward facing) hemisphere for large tilt angles than in the Southern independent of conductance. These results highlight the strong sensitivity to onset time in the potential impact of a severe space weather event.
Influence of Mercury's Exosphere on the Structure of the Magnetosphere
Authors: Exner Willi , Simon Sven , Heyner Daniel , Motschmann Uwe
Published: June 2020

Mercury is embedded in a tenuous and highly anisotropic sodium exosphere, generated mainly by plasma‐surface interactions. The absolute values of the sodium ion density are still under debate. Observations by MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) instrument suggest the density of exospheric ions to be several orders of magnitude lower than the upstream solar wind density, indicating that the sodium exosphere has no substantial influence on the magnetospheric current systems. However, MESSENGER magnetic field observations of field line resonances revealed sodium ion densities comparable to the upstream solar wind density. To investigate how a dense exosphere would affect the current systems within Mercury's magnetosphere, we apply an established hybrid (kinetic ions, fluid electrons) model and conduct multiple model runs with gradually increasing exospheric density, ranging from no sodium ions at all to comet‐like configurations. We demonstrate how a sufficiently dense exosphere leads to self‐shielding of the sodium ion population from the ambient electric field and a significant inflation and symmetrization of Mercury's magnetosphere, which is decreasingly affected by the dipole offset. Once the sodium ion density is sufficiently high, Region 2 field‐aligned currents emerge close to the planet. The modeled Region 2 currents are located below the orbit of MESSENGER, thereby providing a possible explanation for the absence of these currents in observations. The sodium exosphere also closes a significant fraction of the Region 1 currents through Pedersen and Hall currents before the “guiding” magnetic field lines even reach the planetary surface. The modeled sodium ion and solar wind densities agree well with observations.
Emergent Hydrodynamics and Skimming Flow Over Mussel Covered Beds in Rivers
Authors: Sansom B. J. , Bennett S. J. , Atkinson J. F. , Vaughn C. C.
Published: June 2020

Freshwater mussels are dominant ecosystem engineers in many streams throughout North America, yet they remain among the world's most imperiled fauna. Extensive research has quantified the ecological role of mussels in aquatic habitats, but little is known about the interaction between mussels and their surrounding physical and hydrodynamic habitat. Here the physical interactions of mussels with near‐bed flow are investigated in an experimental channel using model mussels. The results show that (1) mussels disrupt the distributions and magnitudes of time‐averaged values of longitudinal flow velocity and Reynolds shear stress depending on mussel density, and (2) at densities of approximately 25 mussels m−2and greater, a hydrodynamic transition occurs where the maximum Reynolds shear stress is displaced from the bed to the height of the mussel canopy, near‐bed longitudinal flow velocity is reduced, and average turbulent shear stresses acting on the mussels are reduced by as much as 64%, thus markedly decreasing the dislodgement potential of the mussels by these stresses. These results provide strong empirical evidence for a positive density‐dependent effect related to flow‐organism interactions and their ecological success, such as enhancing river bed hydrodynamic habitat complexity or decreasing the turbulent shear stresses acting to dislodge mussels from the river bed. This information will improve the understanding of the long‐term persistence of mussel beds and help focus future conservation strategies.
In Appreciation of AGU’s Outstanding Reviewers of 2019
Authors: Giampoala Matt
Published: June 2020

AGU editors recognize the contributions of reviewers, whose valuable expertise continues to raise our journals’ high standards.
Understanding Mass Resolution of Foil‐Based Time‐of‐Flight Mass Spectrometry
Authors: Vira A. D. , Fernandes P. A. , Skoug R. M. , Funsten H. O. , Reisenfeld D. B.
Published: June 2020

The fractional mass uncertainty of linear, foil‐based time‐of‐flight space instruments is affected by the energy, path length, and timing uncertainties. Carbon foils are typically used in time‐of‐flight instruments to generate secondary electrons, but carbon foils also add unwanted effects to the instrument response. We present a complete characterization that studies the extent to which carbon foils degrade the mass resolution by parameterizing each component of the fractional mass uncertainty. Using the parametrization, the limiting factors of the fractional mass resolution are determined for a range of incident ion energies. The parametrization can be used as a tool for instrument developers to quickly assess the mass resolution and possibly mitigate the limiting factors of the mass resolution.
Distinctive Features of Langmuir and Ion‐Acoustic Turbulences Induced by O‐ and X‐Mode HF Pumping at EISCAT
Authors: Blagoveshchenskaya N. F. , Borisova T. D. , Kalishin A. S. , Yeoman T. K. , Häggström I.
Published: June 2020

We report experimental results regarding the distinctive features and behaviors of high‐frequency (HF)‐induced Langmuir and ion‐acoustic turbulences induced by ordinary (O‐mode) and extraordinary (X‐mode) polarized powerful HF radio waves injected into the high‐latitude ionosphere F region toward the magnetic zenith at EISCAT (European Incoherent SCATter). Alternating O‐/X‐mode pumping was produced at high heater frequencies in the range fH = 6–8 MHz during magnetically quiet background geophysical conditions. An effective radiated power of 450–600 MW was utilized. The radical distinction between the temporal evolution of the O‐ and X‐mode Langmuir and ion‐acoustic plasma waves after the HF heater is switched on in conjunction with the development of artificial field‐aligned irregularities (FAIs) was analyzed. It was found that the excitation thresholds of the Langmuir and ion‐acoustic turbulences significantly differed for the O‐ and X‐mode HF pumping. We have revealed that the X‐mode excitation thresholds for HF‐induced plasma and ion line backscatter are 0.47 and 0.61 V/m, respectively. The persistent O‐mode plasma and ion line backscatters that coexisted with FAIs showed excitation thresholds of 0.62 and 0.73 V/m, respectively, which exceeded the thresholds for the X‐mode plasma and ion lines, while their intensity was 2 orders of magnitude less. For the same background conditions, the “classic” resonance parametric decay instability and modulation instability, excited as the momentary response to the O‐mode HF pump wave switching on (the so‐called overshoot), have thresholds of 0.17 and 0.25 V/m, respectively, which are much below the excitation thresholds of persistent O‐mode plasma and ion lines.