bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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

AbstractWe 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

AbstractTemporal 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

AbstractThe 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

AbstractMercury 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

AbstractFreshwater 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.
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

AbstractThe 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

AbstractWe 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.
Azimuthal Dependence of GNSS‐R Scattering Cross‐Section in Hurricanes
Authors: Balasubramaniam Rajeswari , Ruf Christopher 
Published: June 2020

AbstractGlobal Navigation Satellite System‐Reflectometry (GNSS‐R) measurements of the ocean surface are sensitive to roughness scales ranging from a few cms to several kms. Inside a hurricane the surface roughness changes drastically due to varying sea age and fetch length conditions and complex wave‐wave interactions caused by its cyclonic rotation and translational motion. As a result, the relationship between the surface roughness at different scale sizes becomes azimuthally dependent, as does the relationship between scattering cross‐section and wind speed as represented by a Geophysical Model Function (GMF). In this work, the impact of this azimuthal variation on the scattering cross‐section is assessed. An empirical GMF is constructed using measurements by the NASA CYclone GNSS (CYGNSS) matched to HWRF reanalysis surface winds for 19 hurricanes in 2017 and 2018. The analysis reveals a 2–8% variation in scattering cross‐section due to azimuthal location, and the magnitude of the azimuthal dependence is found to grow with wind speed.
Assessing Temporal Changes in Groundwater Recharge Using Spatial Variations in Groundwater Ages
Authors: McCallum James L. , Dogramaci Shawan , Bai Albert , Cook Peter G. , Engdahl Nicholas B. , Simmons Craig T. , Skrzypek Grzegorz , Grierson Pauline F. 
Published: June 2020

AbstractDetermining variations in groundwater replenishment over a variety of time scales remains a challenge in the management and protection of groundwater resources. Specifically, capacity to use hydraulic data collected in small windows of time to infer long‐term changes can be limited by system responses. Groundwater ages offer an alternative approach as they represent the time since recharge occurred. Here we use spatial variations in groundwater ages and environmental tracer concentrations to infer temporal variations in groundwater recharge and apply the method to a mine site in northwest Australia, where a stream has been modified from ephemeral to perennial, resulting in enhanced recharge to groundwater. Measurements of 14C and CFC‐12 at five transects along an ephemeral stream were interpreted with the new model to identify recharge rates and the proportion of recharge attributable to enhanced versus natural recharge from flood events. Enhanced recharge varied between 0.03 and 0.66 m/year compared to flood‐generated recharge values ranging between 0.07 and 1.3 m/year. Our results show that spatial variations of groundwater ages and environmental tracer concentrations preserve information about past flow regimes. While our study has demonstrated decadal variations in recharge, application of the method on larger scales could infer much greater extent of temporal variability in recharge, with the potential for significant insight into climate effects on groundwater.
Exosomes: roles and therapeutic potential in osteoarthritis
Authors: Ni Zhenhong , Zhou Siru , Li Song , Kuang Liang , Chen Hangang , Luo Xiaoqing , Ouyang Junjie , He Mei , Du Xiaolan , Chen Lin 
Published: June 2020

AbstractExosomes participate in many physiological and pathological processes by regulating cell–cell communication, which are involved in numerous diseases, including osteoarthritis (OA). Exosomes are detectable in the human articular cavity and were observed to change with OA progression. Several joint cells, including chondrocytes, synovial fibroblasts, osteoblasts, and tenocytes, can produce and secrete exosomes that influence the biological effects of targeted cells. In addition, exosomes from stem cells can protect the OA joint from damage by promoting cartilage repair, inhibiting synovitis, and mediating subchondral bone remodeling. This review summarizes the roles and therapeutic potential of exosomes in OA and discusses the perspectives and challenges related to exosome-based treatment for OA patients in the future.
Spin injection through energy-band symmetry matching with high spin polarization in atomically controlled ferromagnet/ferromagnet/semiconductor structures
Authors: Yamada Michihiro , Kuroda Fumiaki , Tsukahara Makoto , Yamada Shinya , Fukushima Tetsuya , Sawano Kentarou , Oguchi Tamio , Hamaya Kohei 
Published: June 2020

AbstractElectrical injection of spin-polarized electrons from ferromagnets into semiconductors has been generally demonstrated through a tunneling process with insulator barrier layers that can dominate the device performance, including the electric power at the electrodes. Here, we show an efficient spin injection technique for a semiconductor using an atomically controlled ferromagnet/ferromagnet/semiconductor heterostructure with low-resistive Schottky-tunnel barriers. On the basis of symmetry matching of the electronic bands between the top highly spin-polarized ferromagnet and the semiconductor, the magnitude of the spin signals in lateral spin-valve devices can be enhanced by up to one order of magnitude compared to those obtained with conventional ferromagnet/semiconductor structures. This approach provides a new solution for the simultaneous achievement of highly efficient spin injection and low electric power at the electrodes in semiconductor devices, leading to novel semiconductor spintronic architectures at room temperature.