bluuebunny/crossref_metadata_2025 huggingface dataset:
The Organization of Actin Filaments in the Stereocilia of the Bird
Cochlea
Authors: Battles E.J. , DeRosier D. , Saunders J.C. , Tilney L.G.
Published: June 2020

Extending from the apical surface of each hair cell of the chick cochlea
are from 75 to 200 microvilli or stereocllia and one true cllium, the
kinocilium. The stereocllia are arranged in rows of progressively increasing
length (Fig. 1). Within each tapering sterocilium is a bundle of actin
filaments with over 900 filaments near the tip yet only approximately 25 at
the base where filaments are enmeshed in a dense material (Fig. 1); from
here some of the filaments enter the apical surface of the cell (cuticular
plate) as a rootlet. Examination of longitudinal sections of the stereocilia
(Fig. 2) show that the filaments are aligned parallel to each other and show
considerable order. Examination of an optical diffraction pattern of this
bundle (Fig. 4) reveal that the actin filaments are packed such that the
crossover points of adjacent actin filaments are inregister. A prominent
reflection at 125Å−1 demonstrates that the filaments
are cjossbridged by a macromolecular bridge situated at an average of
125Å−1 intervals (Fig. 4) in transverse sections
the filaments appear hexagonally packed although there are regions where the
filaments are less ordered (Fig. 3). In images processed in the computer to
remove, noise and enhance detail periodic nature of the bridge can be
clearly seen (see arrows Fig. 5). This image resembles that of an actin
paracrystal formed from sea urchin extract composed of bundles of actin
filaments crossbridged by a second protein. Thus the actin filaments in the
bird stereocilia by being cross-bridged and packed with a high degree of
order and produces a structure with considerable structural rigidity.
Embryos were studied at various stages in development in an attempt to
determine how the stereocilia form and how does the actin packing develops.
These stages will be discussed.
Intracellular Accumulation of Uranium and Lead in Collembolan
(Insect)
Authors: Humbert W.
Published: June 2020

The midgut epithelium of Collembola contains cytoplasmic inclusions
known to be important intracellular sites of mineral sequestration (1). The
present study is focused on the role played by these inclusions in cases of
heavy metal poisoning. Ultrastructural and X-ray microanalytical studies
allowed us to find out different possible mechanisms involved in storage and
excretion of these metals.

Experiments have been made by rearing the Insects on diet impregnated
with the heavy metal (1 % aqueous solutions of uranyl acetate and lead
citrate). For each series 100 animals were tested. Animals alive after 2
months were fixed for electron microscopy with glutaraldehyde and osmium
tetroxyde. Semi-thin sections were analysed with an electron microprobe
analyser CAMECA MS 46 equipped with wavelength dispersive spectrometers
(W.D.S.) at 15 KV ; beam current was 40 nA. X-ray microanalysis of thin
unstained sections was performed on a “CAMEBAX” microanalyser equipped for
transmission with W.D.S. at 50 KV and with a beam current of 100 nA. The use
of R.E.T. crystal to detect uranium and lead avoids any misinterpretation
(2).
Morphogenesis Of Rabbit Corneal Stroma
Authors: Cintron Charles , Covington Henry
Published: June 2020

A morphological description of the developing rabbit cornea was deemed
necessary for future biochemical analyses and comparisons with healing adult
corneas to understand why normal fetal corneas go on to produce a normal
adult tissue, while healing corneas remain in the “fetal” condition. Corneas
from fetal and young albino rabbits of various ages were examined by light
and transmission electron microscopy.
Effects of Hypophysectomy on the Occurrence and Calcifiability of Matrix
Vesicles in the Epiphyseal Growth Plate of Immature Rats
Authors: Coleman S. I. , Dougherty W. J.
Published: June 2020

In the cellular secretion theory of mineral deposition, extracellular
matrix vesicles are believed to play an integral role in hard tissue
mineralization (1). Membrane limited matrix vesicles arise from the plasma
membrane of epiphyseal chondrocytes and tooth odontoblasts by a budding
process (2, 3). Nutritional and hormonal factors have been postulated to
play essential roles in mineral deposition and apparently have a direct
effect on matrix vesicles of calcifying cartilage as concluded by Anderson
and Sajdera (4).

Immature (75-85 gm) Long-Evans hooded rats were hypophysectomized by the
parapharyngeal approach and maintained fourteen (14) days post-surgery. At
this time, the animals were anesthetized and perfusion fixed in cacodylate
buffered 2.5% glutaraldehyde. The proximal tibias were quickly dissected out
and split sagittally. One half was used for light microscopy (LM) and the
other for electron microscopy (EM). The halves used for EM were cut into
blocks approximately 1×3 mm. The tissue blocks were prepared for ultra-thin
sectioning and transmission EM. The tissue was oriented so as to section
through the epiphyseal growth plate from the zone of proliferating cartilage
on down through the hypertrophic zone and into the initial trabecular bone.
Sections were studied stained (double heavy metal) and unstained.
Collagen-Producing, Vitamin A-Storing Lipocytes of the Liver
Authors: Inouye T. , Minick O.T. , Nayyar R.P. , Volini F. , Kent G.
Published: June 2020

The lipocytes (Ito cells) of the liver are located in the perisinusoidal
space of Disse and are surrounded by a scaffold of type III collagen. They
are known to store vitamin A and may be identified by (a) their
characteristic location, (b) an abundance of lipid droplets and (c) a
rapidly fading, greenish autofluorescence. We have previously reported that,
following certain experimental hepatic injuries, lipocytes undergo
morphologic transformation to active fibroblasts and are then found in close
association with newly-formed collagen. The findings suggested that
lipocytes, under these conditions, synthesize collagen.
Possible Involvement of Calcium, Calmodulin and Intramembrane Particle
Arrays in Regulation of Secretion
Authors: Satir Birgit H.
Published: June 2020

Ca2+ is found to be a common denominator involved
in the control of membrane fusion and release in many biological secretory
systems ranging from the classical mammalian secretory systems such as the
pancreas, salivary gland, neurosecretion, single cell “glands” such as mast
cells, to protozoa such as Tetrahymena and Paramecium with their release of
mucocysts and trichocysts, respectively. In all of these systems,
Ca2+ has been shown to be an important ion in the
process of stimulus-secretion-coupling, a term coined by Douglas (1968), in
analogy to excitation-contraction coupling in muscle. Individual degrees of
specificity are shown by each of these systems as to exactly which membrane
the secretory vesicles migrate to and dock prior to release.
Fusion and Fission Processes in Exocytosis: Possible Roles for Synexin and Osmotic Lysis in the Two Events
Authors: Pollard H.B. , Creutz C.E. , Pazoles C.J. , Scott J.H.
Published: June 2020

Exocytosis is a general concept describing secretion of enzymes, hormones and transmitters that are otherwise sequestered in intracellular granules. Chemical evidence for this concept was first gathered from studies on chromaffin cells in perfused adrenal glands, in which it was found that granule contents, including both large protein and small molecules such as adrenaline and ATP, were released together while the granule membrane was retained in the cell. A number of exhaustive reviews of this early work have been published and are summarized in Reference 1. The critical experiments demonstrating the importance of extracellular calcium for exocytosis per se were also first performed in this system (2,3), further indicating the substantial service given by chromaffin cells to those interested in secretory phenomena over the years.
Rates of Lateral Diffusion of Intramembrane Particles in a
Biomembrane
Authors: Sowers Arthur E. , Hackenbrock Charles R.
Published: June 2020

Introduction: A number of studies from this laboratory have shown that
intra-membrane particles (integral proteins) in the inner mitochondrial
membrane are free to difuse laterally and independently of one another in
the plane of the membrane (1). Such lateral diffusion of catalytically
interacting integral proteins has been shown to be rate limiting in
collision-required catalytic events (2). The purpose of the present study
was to develop a new method which would permit the measurement of the rate
of lateral diffusion of inte¬gral proteins in the mitochondrial inner
membrane which appear as intramem-brane particles in freeze-fracture
electron micrographs. In this method (see Fig. 1), integral proteins are
displaced from their normal random distribution in the membrane plane by a
pulse of electric current. After the pulse the integral proteins diffuse
back to a random distribution. The degree of intra-membrane particle
displacement (reflecting integral protein displacement) in samples quick
frozen at various known times during the electric current pulse permits the
electrophoretic mobility of the intramembrane particles to be de¬termined.
The degree of rerandomization of intramembrane particles in samples frozen
at known times after the termination of the electric current pulse permits
the lateral diffusion coefficient to be determined.
New Evidence for Membrane Specialization in the Diatom Thalassiosira
Antarctica Comber
Authors: Doucette Gregory J.
Published: June 2020

The present investigation was undertaken to examine the nonsiliceous
ultra-structure of diatoms (BacilIariophyta) by means of freeze fracture
electron microscopy. Freeze fracture procedures are complicated by the
difficulties encountered in fracturing silica-based components and the
removal of these materials subsequent to replica casting. Supplementary data
was obtained through conventional thin section methodologies. This report is
a prelim¬inary account of observations made on selected nonsiliceous,
cellular con¬stituents of Thalassiosira antarctica Comber, a planktonic,
marine diatom.
Freeze-Fractured Studies on the Myocardial Cell Membrane Under Varying
Degrees of Temperature During Calcium Paradox
Authors: Ashraf M. , Lepera Ross , Onda M. , Hirohata Y. , Benedict J.
Published: June 2020

Reperfusion of hearts that are initially perfused with Ca-H-free medium,
with normal Ca++-containing medium (called calcium paradox), is known to
cause an irreversible injury to the cells. However, if the temperature of
Ca-H-free medium is kept below normal temperature, the re introduction of
Ca++ induces release of less intracellular enzymes and reduced amount of
injury (1-2). This leads to a suggestion that hypothermia may minimize the
structural alterations in the cell membrane (CM) to avoid cellular damage
during calcium paradox. This study is aimed to elucidate the morphological
changes in the cell manbrane lipid bilayer during Ca++ paradox.
Freeze-Fracture Studies of Membranes in Developing Sieve Elements in a
Plant Tissue Culture
Authors: Sjolund R. D. , Shih C. Y.
Published: June 2020

The differentiation of phloem in plant tissue cultures offers a unique
opportunity to study the development and structure of sieve elements in a
manner that avoids the injury responses associated with the processing of
similar elements in intact plants. Short segments of sieve elements formed
in tissue cultures can be fixed intact while the longer strands occuring in
whole plants must be cut into shorter lengths before processing. While iyuch
controversy surrounds the question of phloem function in tissue cultures ,
sieve elements formed in these cultured cells are structurally similar to
those of Intact plants. We are particullarly Interested In the structure of
the plasma membrane and the peripheral ER in these cells because of their
possible role in the energy-dependent active transport of sucrose into the
sieve elements.
A Rapid Diamond Knife Alignment Procedure
Authors: Heusser Robert C.
Published: June 2020

The purpose of this paper is to present a rapid and accurate means of
accomplishing two of the more difficult manipulations in diamond knife thin
sectioning, namely precise block align¬ment and advancement of the knife to
a point of contact.

In routine thin sectioning, the desire for serial continuity from a
previously sectioned block is universal. Specialized embedding procedures
such as: tissue culture monolayers, re-sectioning of large plastic sections
and flat embedding molds for specially oriented tissue require extremely
accurate block ori¬entation due to an unusually restricted range of tissue
thick¬ness and critical orientation.
Variations in Sample Preparation that Affect Contrast Enhancement by Lead
Aspartate
Authors: Yoshiyama J.M. , Goff D. , Walton J.
Published: June 2020

We recently described a new en bloc lead contrast stain for transmission
electron microscopy (Walton, 1979). Several laboratories report great
success with lead aspartate staining but some others have found that its
contrast enhancement is insufficient. We undertook the present study to
determine how differences in sample protocol affect lead aspartate contrast
enhancement, making a strict effort to obtain comparable samples.

Gastrointestinal duodenum provided a tissue of uniform diameter. A 1"
length of duodenum was flushed with warm saline and fixed in 4%
paraformaldehyde-1% glutaraldehyde solution buffered at pH 7.3 with 0.1 M
cacodylate. After a 2 hr fixation period, the sample was cross-sectioned
into blocks 1.0 mm thick. Samples were then post-fixed with 1% osmium
tetroxide buffered with veronal acetate at pH 7.3, washed, stained with lead
aspartate, rinsed, dehydrated, and embedded. Standard staining conditions
were pH 5.5 lead aspartate heated to 60°C for 1 hr. This procedure was
varied by adjusting either the pH of lead aspartate, the staining time, or
the temperature. Additional variations were made in the dehydration times,
osmium fixation times, and choice of wash buffer. Silver sections were cut
from all samples. Micrographs were taken using uniform settings at either
high or low magnifications. All negatives were developed and printed under
the same conditions.
A Simplified Procedure for Critical Point Drying of Dilute Biologic
Suspensions
Authors: Smucker R.A. , Hanson J.M. , Pfister R.M.
Published: June 2020

Preparations of low concentrations of particulates such as living cells
or inert materials subject to surface alterations due to forces occurring
during dessication may be made with relative ease using the following
techniques.

Working with small quantities of samples which may be essentially a
powder when dry is very difficult. This work describes a technique which
permits processing very small amounts of cells with minimal handling and
loss of starting material. Dialysis tubing preparation was as follows:
Dialysis tubing (9 mm or 10 mm) was soaked in warm double distilled water
for several hours. The softened dialysis tubing was connected to latex
tubing. Ninetyfive percent ETOH was recirculated for two hours through
vertically oriented tubing (0.5 m long) positioned over a beaker so that
ethanol ascended through interior walls of the tubing and overflowed down
the outside walls into the beaker. The ETOH washing was essential to remove
any material absorbed to interior walls of the tubing. After the alcohol
washing, the tubing was rinsed in Millipore filtered double distilled water
several times.
Technique for Obtaining One-Piece Grid-Size Replicas
Authors: Thomas Virginia L.
Published: June 2020

Obtaining intact replicas from the surface of a desired sample is
frequently difficult. This technique gives a nearly complete replica over
the whole electron microscope grid and can be applied to a wide variety of
samples. Application to tissue culture cells is demonstrated.

Cells were grown to the desired concentration on Thermanox plastic
coverslips (Microbiological Associates, Bethesda, Maryland), fixed,
dehydrated and critical point dried in the Sorval critical point drier. Pt-C
shadow casting and replication were carried out on a Denton DV502 vacuum
evaporator. Replicating was with carbon from two sources and two angles
(∽1:4 and ∽6:1) with sample rotating on a plain rotary stage. Carbon was
evaporated slowly with the pressure maintained at roughly 10∽ by opening and
closing the main valve of the evaporator to cut in the diffusion pump when
the pressure approached 15∽. The lower pressure gives a more uniform
coating.
Structural Investigation of Invertebrate Hemoglobins Using the Stem
Authors: Kapp O.H. , Ohtsuki M. , Vinogradov S.N.
Published: June 2020

Scanning transmission electron microscopy (STEM) was used to study the structure of the extracellular hemoglobins of the annelids Lumbricus, Arenicola, and Nephtys. These are giant molecules, possessing a molecular weight of 3-4 x IO6,a sedimentation constant of about 60s and consisting of about five to seven different polypeptide chains (1,2,3). The samples were diluted to 100-200μg/ml with distilled water just before application to a very thin(∽15Å) carbon substrate supported on a microgrid. One percent (w/v) uranyl acetate solution was used for negative staining for 2 min. and dried in air. The specimens were examined with an electron energy of 22-35keV.
Atom Motion Observed at Various Temperatures with a Fast Scan
Authors: Hainfeld J. F. , Wall J.
Published: June 2020

High atomic number atoms can be clearly visualized with a high
resolution STEM (see Fig. 1). Crewe, Isaacson and co-workers first
documented that some atoms moved from one exposure to the next. Previous
results have been extended with the Brookhaven STEM by use of 1) a fast scan
that produces atom images at TV rates, and 2) a temperature controlled stage
that permits observation over a wide range (+30°C to -120°C used in this
report).

A thin carbon substrate (15Å thick) was treated with 0.1% uranyl acetate
for 15 sec. and rinsed 2 times with water. A 32 x 32 scan raster over a 38Å
x 38Å area produced images that were recorded from an oscilloscope display
with a video camera and video tape recorder. The scan rate was 30
frames/sec. A typical dose per frame was 45,000
electrons/A2 at 40 kV.
Radiation Damage in Organic Molecules
Authors: Misra Manoj , Egerton R.F.
Published: June 2020

Radiation damage is the main limiting factor in attempting high
resolution electron microscopy of biological
macromolecules1,2. To better understand the process
of radiation damage, a systematic study of various amino acids, peptides and
nucleic acid bases has been undertaken.

We report here some preliminary results obtained with glycine,
glycyl-glycine, cystine, cysteine and uracil at room temperature. Specimens
of these compounds were prepared by slow evaporation of their aqueous
solutions (except of glycylglycine which gave better crystals when the
solvent used was N-propanol) on carbon coated grids.
Image Distortion in the Reconstruction of Periodic Images: Effect and
Correction
Authors: Rigden Jon , Wiggins J.W.
Published: June 2020

There are two electron optical aberrations which are commonly ignored
because they are unimportant, even ignored, in most electron micrographs.
These aberrations are radial distortion - also known as pincushion or barrel
distortion, depending on the sign - and spiral distortion, an effect which
never occurs in light optics. They are both illustrated in Figure 1. Since
these distortions are generally uninteresting, microscope manufacturers do
not provide substantial information about their instruments. Typically,
either there is no information at all, or a single number related to the
distortion constant is provided with no indication as to where in the field
of view it was measured or at what magnification, although both items are
needed to actually assess the distortion constant. Taking the most
optimistic view of the missing information, one can still determine that
radial distortion is a major factor in limiting the resolution attained by
Unwin and Henderson in their reconstruction of the two-dimensional structure
of bacteriorhodopsin.
Evidence for Major Cation Deposits at the Exterior Surface of the
Echinoderm EGG
Authors: Decker Glenn L. , Schön Elizabeth A.
Published: June 2020

As recently reviewed by Scheul and Epel, several studies have documented
the directional flow of different metal ions during echinoderm
fertilization. Little, however, is known about the precise cellular pathways
of calcium or other ions during gamete interaction and
embryogenesis.

In the current study we examine several new fixation approaches which we
hope will lead to localization of the major cations involved in egg
activation and development.
High Resolution Immunoelectron Microscopy of Cellular
Ultrastucture
Authors: Singer S. J. , Tokuyasu K. T. , Dutton Anne H. , Geiger Benjamin
Published: June 2020

This presentation addresses specifically the application of high
resolution immunoelectron microscopy to problems of cellular ultrastrucutre,
and is focused largely on studies from our laboratory utilizing procedures
that we have developed over a period of years. Our experimental objectives
have been to provide a general method whereby any given antigen in cells or
tissues, whatever its location, could be immunolabeled at high resolution.
Procedures involving the immunolabeling of fixed and permeabilized cells,
followed by conventional embedding and sectioning techniques, have been
adequate to certain immuno-labeling purposes, but in the general case, and
particularly with tissues, procedures involving the immunolabeling of
ultrathin-sectioned specimens avoid ambiguities regarding antigen
accessibility to the antibody reagents.
Structure Determination by Stem Studies of Labeled Systems
Authors: Beer Michael
Published: June 2020

The organization of macromolecules or macromolecular complexes can be
elucidated using heavy atom labels attached to particular constituents. The
selective binding can be brought about either through the appropriate
specificity of the labeling reaction or the assembly of the complex from
components, some of which carry labels. The instruments with the
capabilities of modern STEM'S are particularly suitable for such work in
view of their ability to detect even single heavy atoms, their high spatial
resolution and the ready quantitiation of scattering data. We shall describe
three projects now under investigation in which these approaches are
used.
Correlative Electron Microscopic and Cytofluorometric Study of Chromatin
Conformation in Human Leukemia Cells
Authors: Ahearn M. J. , Trujillo J. M.
Published: June 2020

In order to establish a sensitive probe to analyze and interpret the
changes in chromatin conformation expressed in individual leukemic cell
nuclei we have correlated data from a concomitant ultrastructural and
cytofluorometric study on high blast count leukemic bone marrows utilizing
the nuclear probe and metachromatic fluorochrome, acridine orange. At the
electron microscopic level, the incorporation of this dye into “active
euchro- matin” of morphologically identifiable leukemic blasts is visualized
as Frenster’s1 electron dense reaction product (Fig 1).
Cytofluorometrically, in the absence of RNA, acridine orange differentially
stains double stranded DNA green (F530) and single stranded DNA red
(F>600). Darzynkiewicz2 has demonstrated that the
sensitivity of DNA in situ to denaturation is higher in quiescent cells than
in actively cycling ones.
Ultrastructure of Mouse Basal Cell Carcinoma Exhibiting Sebaceous
Differentiation
Authors: Wade Victoria L. , Sheldon Winslow G. , Townsend James W. , Allaben William
Published: June 2020

Sebaceous gland tumors and other tumors exhibiting sebaceous
differentiation have been described in humans (1,2,3). Tumors of the
sebaceous gland can be induced in rats and mice following topical
application of carcinogens (4), but spontaneous mixed tumors of basal cell
origin rarely occur in mice.
Preparation of Cell Monolayers for Correlative Thin Section and High-
Resolution Surface Analysis
Authors: Ulrich R. G. , Quinlan D. C.
Published: June 2020

It is suspected that modulation of cell surfaces through the action of
cytoskeletal elements plays a role in the regulation of cellular activities
(1). Furthermore, changes in the organization and/or distribution of
microfilaments and microtubules during cell transformation may result in an
altered surface morphology. When working with thin sections alone, it is
difficult to reconstruct the three-dimensional aspects of cell surface
topography. Additionally, many structures of interest are not within the
resolving capabilities of the scanning electron microscope. To alleviate
these problems, we employ methods which allow for thin section and
high-resolution surface analysis of cells from within the same monolayer
utilizing thin-film embedding and carbon surface replicas. When used in
conjunction with fixation procedures that maximize the preservation and
visualization of cytoskeletal components (eg., 2) these methods provide for
a detailed examination of microfilaments and microtubules within cells and
subtle differences in surfact topography.
Cryofixation of Plant Material for Ultrastructura1 and Analytical
Studies
Authors: Echlin Patrick , Lai Clifford , Saubermann Albert , Hayes Thomas , Skaer Helen , Franks Felix
Published: June 2020

Studies (1—4) have shown that high-molecular weight, water soluble
polymers such as polyvinylpyrrolidone (PVP) and hydroxyethyl starch (HES)
are useful in reducing ice-crystal damage in rapidly frozen samples of plant
and animal tissues as judged by their appearance in freeze-etch replicas,
frozen sections, and frozen fracture faces of bulk material. We have
extended these studies to the preparation of material for correlative
ultrastructural and analytical studies where it is important both to retain
diffusible elements in their natural position in cell as well as preserving
adequate cell morphology.
Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips
Authors: Echlin Patrick , Hayes Thomas , Lai Clifford , Hook Greg
Published: June 2020

Studies (1—4) have shown that it is possible to distinguish different
stages of phloem tissue differentiation in the developing roots of Lemna
minor by examination in the transmission, scanning, and optical microscopes.
A disorganized meristem, immediately behind the root-cap, gives rise to the
vascular tissue, which consists of single central xylem element surrounded
by a ring of phloem parenchyma cells. This ring of cells is first seen at
the 4-5 cell stage, but increases to as many as 11 cells by repeated radial
anticlinal divisions. At some point, usually at or shortly after the 8 cell
stage, two phloem parenchyma cells located opposite each other on the ring
of cells, undergo an unsynchronized, periclinal division to give rise to the
sieve element and companion cell. Because of the limited number of cells
involved, this developmental sequence offers a relatively simple system in
which some of the factors underlying cell division and differentiation may
be investigated, including the distribution of diffusible low atomic weight
elements within individual cells of the phloem tissue.
“Getting High Resolution Out of A High Voltage Microscope”
Authors: Smith David J.
Published: June 2020

The initial attractions of the high voltage electron microscope (HVEM)
stemmed mainly from the possibility of considerable increases in electron
penetration through thick specimens compared with conventional 100KV
microscopes, although the potential improvement in resolution associated
with the decrease in election wavelength had been fully appreciated for many
years (eg. Cosslett, 1946)1, even if not realizable in
practice. Subsequent technological advances enabled the performance of lower
voltage machines to be brought closer to the theoretical limit, to be
followed in turn by more recent projects which have been successful,
eventually, in achieving even higher resolution with dedicated higher
voltage instruments such as those at Kyoto (500KV)2,
Munich (400KV)3, Ibaraki (1250KV)4
and Cambridge (600KV)5. It does not necessarily follow
however that the performance of journal high voltage microscopes can be
easily upgraded, retrospectively, to the same level, as will be discussed in
detail below.
A TEM/STEM Hybrid Scanning Module
Authors: Thompson M.N.
Published: June 2020

INTRODUCTION

Hybrid scanning modes can be generated by applying the output of the
scan generator of the STEM unit to T.E.M. deflection coils located above or
below the specimen plane. For operator convenience five hybrid modes have
been incorporated in a single module designed for operation with an
EM400T-STEM system.

The modes are subdivided into those based upon the beam scanning
(pivoting) of the illumination and those based upon the beam scanning of the
imaging system. The modes, their associated optics, the location of the scan
pivot point and basic applications are collated in Table 1.
Materials Science Applications of Analytical Electron Microscopy
Authors: Zaluzec Nestor J.
Published: June 2020

Analytical electron microscopy (AEM) has during the last several years
attained great popularity in materials science circles. As the potentials of
this field are beginning to become appreciated by those not directly
associated with the development of AEM, it is appropriate at this time to
illustrate several applications to investigations in metallurgical and
ceramic studies. Those readers interested in specific information concerning
the various techniques used here are referred to the series of tutorial
lectures presented at the 1979 EMSA meeting for detailed
discussions.
CRITICAL LENGTH FOR THE SPREADING–VANISHING DICHOTOMY IN HIGHER DIMENSIONS
Authors: SIMPSON MATTHEW J.
Published: June 2020

We consider an extension of the classical Fisher–Kolmogorov equation, called the “Fisher–Stefan” model, which is a moving boundary problem on $0<xL_{\text{c}}$ will eventually spread as $t\rightarrow \infty$, whereas solutions where $L(t)\ngtr L_{\text{c}}$ will vanish as $t\rightarrow \infty$. In one dimension it is well known that the critical length is $L_{\text{c}}=\unicode[STIX]{x1D70B}/2$. In this work, we re-formulate the Fisher–Stefan model in higher dimensions and calculate $L_{\text{c}}$ as a function of spatial dimensions in a radially symmetric coordinate system. Our results show how $L_{\text{c}}$ depends upon the dimension of the problem, and numerical solutions of the governing partial differential equation are consistent with our calculations.
Perinatal maternal undernutrition does not result in offspring capillary rarefaction in the middle-aged male baboon at rest
Authors: Kuo Anderson H. , Li Cun , Huber Hillary F. , Nathanielsz Peter W. , Clarke Geoffrey D.
Published: June 2020

Microvascular health is a main determinant of coronary blood flow reserve and myocardial vascular resistance. Extracardiac capillary abnormality has been reported in subjects at increased coronary heart disease risk, such as prehypertension, hypertension, diabetes, hyperlipidemia, and atherosclerosis. We have reported cardiovascular dysfunction in a cohort of maternal nutrient reduction (MNR)-induced intrauterine growth restriction (IUGR) baboon offspring. Here we test the hypothesis that there is oral capillary rarefaction associated with MNR-induced IUGR. Capillary density was quantified using in vivo high-power capillaroscopy on seven middle-aged (~10.7 yr; human equivalent ~40 yr) male IUGR baboons and seven male age-matched controls in the lateral buccal and inferior labial mucosa. While no difference was found between groups in either area by fraction area or optical density for these vascular beds derived from fetal preductal vessels, further studies are needed on post-ductal vascular beds, retina, and function.
Enhancing Engagement through Job Resources: The Moderating Role of Affective Commitment
Authors: Dominguez Daniel , Chambel María José , Carvalho Vânia Sofia
Published: June 2020

Research has shown that affective commitment, one of three components of organizational commitment defined by Meyer and Allen (1991), can act as a moderator in relationships between job stressors and worker´s psychological tension. However, due to the scarcity of studies that investigate the moderating effect of this commitment component on relationships between positive variables, the purpose of this study is to examine the moderating role of affective commitment in the relationship between autonomy, peer support, supervisory support and perceived organizational support (POS), as job resources, on engagement. In this sense, we analyzed the data provided by a sample of Portuguese employees (N= 554), from an organization belonging to the consultancy sector. Firstly, we aimed to examine the direct effects of those job resources on engagement, and, then, examine the impact of affective commitment as a moderator on these relationships. The results partially support the hypotheses formulated. Indeed, there was a positive relationship between the job resources studied - work autonomy, peer support, supervisory support and POS - and engagement. Furthermore, according to our hypothesis, the interaction established between affective commitment and autonomy, significantly exacerbates the positive effect of this job resource on workers well-being, that is, on their engagement (b= .08,p< .05). However, contrary to our hypothesis, the affective commitment does not moderate the relationship between the other job resources and engagement. This study contributes to a deepest knowledge about the potentialities of affective commitment, reinforcing the importance of consider it as a contextual resource.
Sexual Transgressions in Couples: The Influence of Dependence and Commitment on their Perception and Handling
Authors: Garrido-Macías Marta , Valor-Segura Inmaculada , Expósito Francisca
Published: June 2020

Transgressions occur frequently in romantic relationships, and how they are perceived is influenced by the type of transgression that occurred. By means of an experimental study of 399 participants (75.9% women and 24.1% men) aged 18 to 64 years old (Mage = 31.20, SD = 10.48), we examined the relationship between the type of sexual transgression (infidelity versus coercion), and perceived severity, strategies individuals would use in response to the transgression, and the probability they would leave the relationship, as well as levels of dependence and commitment. Results revealed higher perceived severity (p < .001, η2p = .24) and probability of leaving the relationship (p < .001, η2p = .39) in the infidelity scenario (versus coercion). Meanwhile, women (compared to men) rated sexual transgressions as more severe (p < .001, η2p = .04) and reported a higher probability of leaving the relationship (p < .001, η2p = .03), as well as a higher use of active conflict resolution strategies (exit, p = .048, η2p = .01, and voice, p < .001, η2p = .06) and lower use of passive strategies (loyalty, p < .001, η2p = .08). Finally, high levels of commitment and dependence predicted lower perceived severity (commitment, p < .001, 95% CI [–.72, –.20]; dependence, p < .001, 95% CI [–1.73, –.85]) and lower probability of leaving the relationship (commitment, p = .048, 95% CI [–.55, –.01]; dependence, p < .001, 95% CI [–1.66, –.73]) in coercion (versus infidelity) transgressions. These results highlight the normalization of sexual coercion in romantic relationships, which is not viewed as negatively as infidelity, and that commitment and dependence contribute to minimizing the negative impressions of it.
“It's a Jihad”: Justifying Violence towards the Ahmadiyya in Indonesia
Authors: Burhani Ahmad Najib
Published: June 2020

The concept ofal-wala’ wa-l-bara’(loyalty and disavowal) has become the ideology of modern Salafism; it is used to justify unfriendly relationships with non-Muslims. This concept is usually implemented by reserving love only for fellow Muslims and showing insularity towards non-Muslims. What is the ideological concept that guides some Muslims in their relationship with groups that are considered heretics? This article intends to scrutinize the theological matrix used by vigilante groups in their anti-heresy campaign or attacks on the Ahmadiyya. It also aims to determine why some people believe that persecuting the Ahmadiyya is a theologically justifiable idea. What theological and ideological reasons can be used to justify attacks against the Ahmadiyya community? How do they cope with the conflict between divine law and human/state law? This article argues that instead of feeling guilty, the perpetrators of faith-based violence often feel they have just fulfilled a good religious duty. Committing violence against religious groups deemed heretics is believed to be more thanal-amr bi al-màrūf wa al-nahy `an al-munkar(“commanding right and forbidding wrong”)—it is a jihad. Violence is seen not as an illegal act, but as a “virtue” or an effort to save them from the punishment of God in Hell. In justifying the breaching of state law, the idea of a hierarchy in the law is constructed, i.e. state/human law is hierarchically lower than divine law, so attacking the Ahmadiyya is seen as a transgression of human law for the sake of upholding the divine view.
Dawnside Auroral Polarization Streams
Authors: Liu Jiang , Lyons L. R. , Wang Chih‐Ping , Hairston M. R. , Zhang Yongliang , Zou Ying
Published: June 2020

Although the postmidnight‐to‐dawn sector of the auroral ionosphere contains interesting dynamic phenomena that may significantly impact the magnetosphere‐ionosphere‐thermosphere system, it has been much less studied than the dusk‐to‐premidnight sector. We discuss a dynamic phenomenon in the postmidnight‐to‐dawn sector of the auroral oval, eastward fast flows mainly within the expanse of the Region 1 current (its part equatorward of the polar cap). These flows peak and have a steep speed gradient (increase from low to high latitude) near the interface between the Region 1 and Region 2 currents. Because such flows correspond to an electric field that most likely comes from enhanced Region 2 currents and an associated spatial conductivity gradient, their generation mechanism is analogous to that of a subauroral polarization stream. Therefore, we refer to such an eastward flow as a dawnside auroral polarization stream (DAPS). We show several examples of the presence and absence of DAPS under different geomagnetic activity levels. A DAPS' electric field can heat the ionosphere (and thus the thermosphere), change the convection pattern of the magnetosphere‐ionosphere system, and modify the drift path of magnetospheric particles. Because a DAPS' flow peak maps to a major site of magnetic‐kinetic energy conversion in the magnetosphere (the transition region between dipole and stretched field), it may be important for the conversion. A DAPS' steep flow gradient is also potentially important; it may lead to instabilities, such as that responsible for auroral Omega bands. Given its potential importance, knowledge of DAPS is fundamental for understanding the magnetosphere‐ionosphere‐thermosphere system.
Realistic Simulation of Tropical Atmospheric Gravity Waves Using Radar‐Observed Precipitation Rate and Echo Top Height
Authors: Bramberger Martina , Alexander M. Joan , Grimsdell Alison W.
Published: June 2020

Gravity waves (GWs) generated by tropical convection are important for the simulation of large‐scale atmospheric circulations, for example, the quasi‐biennial oscillation (QBO), and small‐scale phenomena like clear‐air turbulence. However, the simulation of these waves still poses a challenge due to the inaccurate representation of convection, and the high computational costs of global, cloud‐resolving models. Methods combining models with observations are needed to gain the necessary knowledge on GW generation, propagation, and dissipation so that we may encode this knowledge into fast parameterized physics for global weather and climate simulation or turbulence forecasting. We present a new method suitable for rapid simulation of realistic convective GWs. Here, we associate the profile of latent heating with two parameters: precipitation rate and cloud top height. Full‐physics cloud‐resolving WRF simulations are used to develop a lookup table for converting instantaneous radar precipitation rates and echo top measurements into a high‐resolution, time‐dependent latent heating field. The heating field from these simulations is then used to force an idealized dry version of the WRF model. We validate the method by comparing simulated precipitation rates and cloud tops with scanning radar observations and by comparing the GW field in the idealized simulations to satellite measurements. Our results suggest that including variable cloud top height in the derivation of the latent heating profiles leads to better representation of the GWs compared to using only the precipitation rate. The improvement is especially noticeable with respect to wave amplitudes. This improved representation also affects the forcing of GWs on large‐scale circulation.
A Semikinetic Model of Plasmasphere Refilling Following Geomagnetic Storms and Comparison With Hydrodynamic Results
Authors: Chatterjee K. , Schunk R. W.
Published: June 2020

The objective of this paper is the development of a kinetic model for plasmasphere refilling following geomagnetic storms. The kinetic model is based on the “particle‐in‐cell” method, a method based on the simulation of particle motion and thus well suited to high altitude, low‐density regimes, where the plasma transport equations are not valid. The model was validated with exact, analytical benchmarks, which are provided in this paper. The refilling results obtained from the kinetic model were then compared with results from a recently developed hydrodynamic solution methodology based on the “flux‐corrected transport” method, and the limitations of hydrodynamic modeling for low‐density flow at high altitudes were explored.
S100A6 is a critical regulator of hematopoietic stem cells
Authors: Grahn Tan Hooi Min , Niroula Abhishek , Végvári Ákos , Oburoglu Leal , Pertesi Maroulio , Warsi Sarah , Safi Fatemeh , Miharada Natsumi , Garcia Sandra C. , Siva Kavitha , Liu Yang , Rörby Emma , Nilsson Björn , Zubarev Roman A. , Karlsson Stefan
Published: June 2020

The fate options of hematopoietic stem cells (HSCs) include self-renewal, differentiation, migration, and apoptosis. HSCs self-renewal divisions in stem cells are required for rapid regeneration during tissue damage and stress, but how precisely intracellular calcium signals are regulated to maintain fate options in normal hematopoiesis is unclear. S100A6 knockout (KO) HSCs have reduced total cell numbers in the HSC compartment, decreased myeloid output, and increased apoptotic HSC numbers in steady state. S100A6KO HSCs had impaired self-renewal and regenerative capacity, not responding to 5-Fluorouracil. Our transcriptomic and proteomic profiling suggested that S100A6 is a critical HSC regulator. Intriguingly, S100A6KO HSCs showed decreased levels of phosphorylated Akt (p-Akt) and Hsp90, with an impairment of mitochondrial respiratory capacity and a reduction of mitochondrial calcium levels. We showed that S100A6 regulates intracellular and mitochondria calcium buffering of HSC upon cytokine stimulation and have demonstrated that Akt activator SC79 reverts the levels of intracellular and mitochondrial calcium in HSC. Hematopoietic colony-forming activity and the Hsp90 activity of S100A6KO are restored through activation of the Akt pathway. We show that p-Akt is the prime downstream mechanism of S100A6 in the regulation of HSC self-renewal by specifically governing mitochondrial metabolic function and Hsp90 protein quality.
Understanding and tuning blue-to-near-infrared photon cutting by the Tm3+/Yb3+ couple
Authors: Yu Dechao , Yu Ting , van Bunningen Arnoldus J. , Zhang Qinyuan , Meijerink Andries , Rabouw Freddy T.
Published: June 2020

Lanthanide-based photon-cutting phosphors absorb high-energy photons and ‘cut’ them into multiple smaller excitation quanta. These quanta are subsequently emitted, resulting in photon-conversion efficiencies exceeding unity. The photon-cutting process relies on energy transfer between optically active lanthanide ions doped in the phosphor. However, it is not always easy to determine, let alone predict, which energy-transfer mechanisms are operative in a particular phosphor. This makes the identification and design of new promising photon-cutting phosphors difficult. Here we unravel the possibility of using the Tm3+/Yb3+lanthanide couple for photon cutting. We compare the performance of this couple in four different host materials. Cooperative energy transfer from Tm3+to Yb3+would enable blue-to-near-infrared conversion with 200% efficiency. However, we identify phonon-assisted cross-relaxation as the dominant Tm3+-to-Yb3+energy-transfer mechanism in YBO3, YAG, and Y2O3. In NaYF4, in contrast, the low maximum phonon energy renders phonon-assisted cross-relaxation impossible, making the desired cooperative mechanism the dominant energy-transfer pathway. Our work demonstrates that previous claims of high photon-cutting efficiencies obtained with the Tm3+/Yb3+couple must be interpreted with care. Nevertheless, the Tm3+/Yb3+couple is potentially promising, but the host material—more specifically, its maximum phonon energy—has a critical effect on the energy-transfer mechanisms and thereby on the photon-cutting performance.
Stable and luminescent halide perovskite fabricated in water
Authors: Na Guangren , Zhang Lijun
Published: June 2020

Lead bromide perovskite nanoparticles are fabricated in the water, which has been recognized previously as a severe source of damage to halide perovskite materials and devices. The perovskite nanoparticles exhibit a high photoluminescence quantum yield and excellent material stability.
Jellyfish genomes reveal distinct homeobox gene clusters and conservation of small RNA processing
Authors: Nong Wenyan , Cao Jianquan , Li Yiqian , Qu Zhe , Sun Jin , Swale Thomas , Yip Ho Yin , Qian Pei Yuan , Qiu Jian-Wen , Kwan Hoi Shan , Bendena William , Tobe Stephen , Chan Ting Fung , Yip Kevin Y. , Chu Ka Hou , Ngai Sai Ming , Tsim Karl Yk , Holland Peter W. H. , Hui Jerome H. L.
Published: June 2020

The phylum Cnidaria represents a close outgroup to Bilateria and includes familiar animals including sea anemones, corals, hydroids, and jellyfish. Here we report genome sequencing and assembly for true jellyfishSanderia malayensisandRhopilema esculentum. The homeobox gene clusters are characterised by interdigitation of Hox, NK, and Hox-like genes revealing an alternate pathway of ANTP class gene dispersal and an intact three gene ParaHox cluster. The mitochondrial genomes are linear but, unlike inHydra, we do not detect nuclear copies, suggesting that linear plastid genomes are not necessarily prone to integration. Genes for sesquiterpenoid hormone production, typical for arthropods, are also now found in cnidarians. Somatic and germline cells both express piwi-interacting RNAs in jellyfish revealing a conserved cnidarian feature, and evidence for tissue-specific microRNA arm switching as found in Bilateria is detected. Jellyfish genomes reveal a mosaic of conserved and divergent genomic characters evolved from a shared ancestral genetic architecture.