bluuebunny/crossref_metadata_2025_split huggingface dataset:
On O+ Ion Heating by BBELF Waves at Low Altitude: Test Particle Simulations
Authors: Shen Yangyang , Knudsen David J. 
Published: July 2020

AbstractWe investigate mechanisms of wave particle heating of ionospheric O+ ions resulting from broadband extremely low frequency (BBELF) waves using numerical test particle simulations that take into account ion‐neutral collisions, in order to explain observations from the Enhanced Polar Outflow Probe (e‐POP) satellite at low altitudes (∼400 km) (Shen et al., 2018, https://doi.org/10.1002/2017JA024955). We argue that in order to reproduce ion temperatures observed at e‐POP altitudes, the most effective ion heating mechanism is through cyclotron acceleration by short‐scale electrostatic ion cyclotron (EIC) waves with perpendicular wavelengths λ⊥ ≤ 200 m. The interplay between finite perpendicular wavelengths, wave amplitudes, and ion‐neutral collision frequencies collectively determine the ionospheric ion heating limit, which begins to decrease sharply with decreasing altitude below approximately 500 km, where the ratio
becomes larger than 10−3, νc and fci denoting the O+‐O collision frequency and ion cyclotron frequency. We derive, both numerically and analytically, the ion gyroradius limit from heating by an EIC wave at half the cyclotron frequency. The limit is 0.28λ⊥. The ion gyroradius limit from an EIC wave can be surpassed either through adding waves with different λ⊥ or through stochastic “breakout,” meaning ions diffuse in energy beyond the gyroradius limit due to stochastic heating from large‐amplitude waves. Our two‐dimensional simulations indicate that small‐scale (<1 km) Alfvén waves cannot account for the observed ion heating through trapping or stochastic heating.
Multiscale Observation of Two Polar Cap Arcs Occurring on Different Magnetic Field Topologies
Authors: Reidy J. A. , Fear R. C. , Whiter D. K. , Lanchester B. S. , Kavanagh A. J. , Price D. J. , Chadney J. M. , Zhang Y. , Paxton L. J. 
Published: July 2020

AbstractThis paper presents observations of polar cap arc substructure down to scale sizes of meters and temporal resolution of milliseconds. Two case studies containing polar cap arcs occurring over Svalbard are investigated. The first occurred on 4 February 2016 and is consistent with formation on closed field lines; the second occurred on 15 December 2015 and is consistent with formation on open field lines. These events were identified using global‐scale images from the Special Sensor Ultra‐violet Spectrographic Imager (SSUSI) instruments on board Defense Meteorological Satellite Program (DMSP) spacecraft. Intervals when the arcs passed through the small‐scale field of view of the Auroral Structure and Kinetics (ASK) instrument, located on Svalbard, were then found using all sky images from a camera also located on Svalbard. These observations give unprecedented insight into small‐scale polar cap arc structure. The energy and flux of the precipitating particles above these arcs are estimated using the ASK observations in conjunction with the Southampton Ionospheric model. These estimates are then compared to in situ DMSP particle measurements, as well as data from ground‐based instrumentation, to infer further information about their formation mechanisms. This paper finds that polar cap arcs formed on different magnetic field topologies exhibit different behavior at small‐scale sizes, consistent with their respective formation mechanisms.
Quantitatively Tracking the Elevation of the Tibetan Plateau Since the Cretaceous: Insights From Whole‐Rock Sr/Y and La/Yb Ratios
Authors: Hu Fangyang , Wu Fuyuan , Chapman James B. , Ducea Mihai N. , Ji Weiqiang , Liu Shuwen 
Published: July 2020

AbstractCrustal thickness, elevation, and Sr/Y and (La/Yb)N of magmatic rocks are strongly correlated for subduction‐related and collision‐related mountain belts. We quantitatively constrain the paleo‐elevation of the Tibetan Plateau since the Cretaceous using empirically derived equations. The results are broadly consistent with previous estimates based on stable isotope and structural analyses, supporting a complex uplift history. Our data suggest that a protoplateau formed in central Tibet during the Late Cretaceous and was higher than the contemporaneous Gangdese arc. This protoplateau collapsed before the India‐Asia collision, during the same time period that elevation in southern Tibet was increasing. During the India‐Asia collision, northern and southern Tibet were uplifted first followed by renewed uplift in central Tibet, which suggests a more complicated uplift history than commonly believed. We contend that a broad paleovalley formed during the Paleogene in central Tibet and that the whole Tibetan Plateau reached present‐day elevations during the Miocene.
Lunar Titanium and Frequency‐Dependent Microwave Loss Tangent as Constrained by the Chang'E‐2 MRM and LRO Diviner Lunar Radiometers
Authors: Siegler Matthew A. , Feng Jianqing , Lucey Paul G. , Ghent Rebecca R. , Hayne Paul O. , White Mackenzie N. 
Published: July 2020

AbstractPassive microwave frequency (~300 MHz to 300 GHz) observations of the Moon have a long history and have been suggested as a plausible orbital instrument for the Moon and other bodies. However, global, orbital multifrequency measurements of lunar passive microwave emission have only recently been made by the Chinese Chang'E‐1 and ‐2 microwave radiometer (MRM) instruments. These missions carried nearly identical 4‐channel (3.0, 7.8, 19.35, and 37 GHz) instruments into lunar orbit in 2007–2009 and 2010–2011, respectively. Over the same time period, the ongoing Lunar Reconnaissance Orbiter (LRO) mission carried the Diviner Lunar Radiometer, which collected surface temperature measurements in the far infrared (~7.8–400 μm) from 2009 to present. By combining these data and associated thermal models, we provide new constraints on the relationship between physical temperature and microwave brightness temperature to reveal novel information about regolith thermal and dielectric properties which can reveal unique geologic information about the Moon. Here, we describe several first‐order global results to come from this combined data set, focusing primarily on the ability to detect, map, and quantify dielectric loss tangent variations of the Moon, including those from the presence of titanium‐bearing ilmenite. We update the loss tangent models for both highlands and mare and identify a clear frequency dependence that differs in sign between the two. We use the correlation with visible wavelength TiO2 mapping to provide a means to separate out the loss from rocks and from that of composition.
Clouds and Convective Self‐Aggregation in a Multimodel Ensemble of Radiative‐Convective Equilibrium Simulations
Authors: Wing Allison A. , Stauffer Catherine L. , Becker Tobias , Reed Kevin A. , Ahn Min‐Seop , Arnold Nathan P. , Bony Sandrine , Branson Mark , Bryan George H. , Chaboureau Jean‐Pierre , De Roode Stephan R. , Gayatri Kulkarni , Hohenegger Cathy , Hu I‐Kuan , Jansson Fredrik , Jones Todd R. , Khairoutdinov Marat , Kim Daehyun , Martin Zane K. , Matsugishi Shuhei , Medeiros Brian , Miura Hiroaki , Moon Yumin , Müller Sebastian K. , Ohno Tomoki , Popp Max , Prabhakaran Thara , Randall David , Rios‐Berrios Rosimar , Rochetin Nicolas , Roehrig Romain , Romps David M. , Ruppert James H. , Satoh Masaki , Silvers Levi G. , Singh Martin S. , Stevens Bjorn , Tomassini Lorenzo , van Heerwaarden Chiel C. , Wang Shuguang , Zhao Ming 
Published: July 2020

AbstractThe Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) is an intercomparison of multiple types of numerical models configured in radiative‐convective equilibrium (RCE). RCE is an idealization of the tropical atmosphere that has long been used to study basic questions in climate science. Here, we employ RCE to investigate the role that clouds and convective activity play in determining cloud feedbacks, climate sensitivity, the state of convective aggregation, and the equilibrium climate. RCEMIP is unique among intercomparisons in its inclusion of a wide range of model types, including atmospheric general circulation models (GCMs), single column models (SCMs), cloud‐resolving models (CRMs), large eddy simulations (LES), and global cloud‐resolving models (GCRMs). The first results are presented from the RCEMIP ensemble of more than 30 models. While there are large differences across the RCEMIP ensemble in the representation of mean profiles of temperature, humidity, and cloudiness, in a majority of models anvil clouds rise, warm, and decrease in area coverage in response to an increase in sea surface temperature (SST). Nearly all models exhibit self‐aggregation in large domains and agree that self‐aggregation acts to dry and warm the troposphere, reduce high cloudiness, and increase cooling to space. The degree of self‐aggregation exhibits no clear tendency with warming. There is a wide range of climate sensitivities, but models with parameterized convection tend to have lower climate sensitivities than models with explicit convection. In models with parameterized convection, aggregated simulations have lower climate sensitivities than unaggregated simulations.
Recent Trends in Individual and Multivariate Compound Flood Drivers in Canada's Coasts
Authors: Jalili Pirani F. , Najafi M. R. 
Published: July 2020

AbstractOver half of the global population and the majority of the cities in coastal zones are at risk of coastal flooding. Changes in the occurrence of individual extremes and the interactions between hydrological and coastal variables can exacerbate flood risks. While extensive research has been conducted to understand and predict different types of flood hazards in isolation, spatial and temporal trends and variability of compound flooding, that is, flooding caused by multiple drivers, remain an open question. This study investigates the individual and joint temporal variations of multiple drivers that can cause compound flooding in Canada's coasts including total water level, storm surge, precipitation, and streamflow. Long‐term changes in the frequency and intensity of extremes are analyzed over the Atlantic, Pacific, and the Great Lakes regions. Univariate and multivariate trend tests including Mann Kendall, Covariance Inversion Test, Covariance Sum Test, and Covariance Eigenvalue Test are applied. In addition, a new multivariate index based on the contributing flood drivers transformed into a probability space is proposed, and its application to study compound flooding is investigated. Overall, results show increased risks of individual and compound flooding over the Atlantic coast and varying trends in the Pacific and Great Lakes regions. The multivariate trend indices show consistent results in most scenarios. The proposed index provides a simple and flexible measure to analyze the spatial and temporal variation of compound flooding risks at different thresholds. The results highlight the importance of considering nonstationary compound flood events to develop resilience strategies in coastal environments.
Room-temperature lasing from nanophotonic topological cavities
Authors: Smirnova Daria , Tripathi Aditya , Kruk Sergey , Hwang Min-Soo , Kim Ha-Reem , Park Hong-Gyu , Kivshar Yuri 
Published: July 2020

AbstractThe study of topological phases of light underpins a promising paradigm for engineering disorder-immune compact photonic devices with unusual properties. Combined with an optical gain, topological photonic structures provide a novel platform for micro- and nanoscale lasers, which could benefit from nontrivial band topology and spatially localized gap states. Here, we propose and demonstrate experimentally active nanophotonic topological cavities incorporating III–V semiconductor quantum wells as a gain medium in the structure. We observe room-temperature lasing with a narrow spectrum, high coherence, and threshold behaviour. The emitted beam hosts a singularity encoded by a triade cavity mode that resides in the bandgap of two interfaced valley-Hall periodic photonic lattices with opposite parity breaking. Our findings make a step towards topologically controlled ultrasmall light sources with nontrivial radiation characteristics.
Higher-order topological insulators in synthetic dimensions
Authors: Dutt Avik , Minkov Momchil , Williamson Ian A. D. , Fan Shanhui 
Published: July 2020

AbstractConventional topological insulators support boundary states with dimension one lower than that of the bulk system that hosts them, and these states are topologically protected due to quantized bulk dipole moments. Recently, higher-order topological insulators have been proposed as a way of realizing topological states with dimensions two or more lower than that of the bulk due to the quantization of bulk quadrupole or octupole moments. However, all these proposals as well as experimental realizations have been restricted to real-space dimensions. Here, we construct photonic higher-order topological insulators (PHOTIs) in synthetic dimensions. We show the emergence of a quadrupole PHOTI supporting topologically protected corner modes in an array of modulated photonic molecules with a synthetic frequency dimension, where each photonic molecule comprises two coupled rings. By changing the phase difference of the modulation between adjacent coupled photonic molecules, we predict a dynamical topological phase transition in the PHOTI. Furthermore, we show that the concept of synthetic dimensions can be exploited to realize even higher-order multipole moments such as a fourth-order hexadecapole (16-pole) insulator supporting 0D corner modes in a 4D hypercubic synthetic lattice that cannot be realized in real-space lattices.
A long-term dataset on wild bee abundance in Mid-Atlantic United States
Authors: Kammerer Melanie , Tooker John F. , Grozinger Christina M. 
Published: July 2020

AbstractWith documented global declines in insects, including wild bees, there has been increasing interest in developing and expanding insect monitoring programs. Our objective here was to organize, validate, and share an analysis-ready version of one of the few existing long-term monitoring datasets for wild bees in the United States. Since 1999, the Native Bee Inventory and Monitoring Lab (BIML) of the United States Geological Survey has sampled wild-bee communities in the Mid-Atlantic U.S., but samples were collected in multiple studies and the datasets are not fully integrated. Furthermore, critical information about sampling methodology was often lacking, though these factors can significantly influence collection outcomes and must be considered in analyses. We cleaned and verified BIML data from Maryland, Delaware, and Washington DC, USA, and generated sampling methodology for over 84% of the 99,053 pan-trapped occurrences in this region. We enthusiastically invite creative analyses of this rich dataset to advance understanding of the biology and ecology of wild bees, inform conservation efforts, and perhaps help design a nationwide bee monitoring program.
Targeting ESKAPE pathogens with anti-infective medicinal plants from the Greater Mpigi region in Uganda
Authors: Schultz Fabien , Anywar Godwin , Tang Huaqiao , Chassagne François , Lyles James T. , Garbe Leif-Alexander , Quave Cassandra L. 
Published: July 2020

AbstractAntibiotic resistance poses one of the greatest threats to global health today; conventional drug therapies are becoming increasingly inefficacious and limited. We identified 16 medicinal plant species used by traditional healers for the treatment of infectious and inflammatory diseases in the Greater Mpigi region of Uganda. Extracts were evaluated for their ability to inhibit growth of clinical isolates of multidrug-resistant ESKAPE pathogens. Extracts were also screened for quorum quenching activity against S. aureus, including direct protein output assessment (δ-toxin), and cytotoxicity against human keratinocytes (HaCaT). Putative matches of compounds were elucidated via LC–FTMS for the best-performing extracts. These were extracts of Zanthoxylum chalybeum (Staphylococcus aureus: MIC: 16 μg/mL; Enterococcus faecium: MIC: 32 μg/mL) and Harungana madagascariensis (S. aureus: MIC: 32 μg/mL; E. faecium: MIC: 32 μg/mL) stem bark. Extracts of Solanum aculeastrum root bark and Sesamum calycinum subsp. angustifolium leaves exhibited strong quorum sensing inhibition activity against all S. aureus accessory gene regulator (agr) alleles in absence of growth inhibition (IC50 values: 1–64 μg/mL). The study provided scientific evidence for the potential therapeutic efficacy of these medicinal plants in the Greater Mpigi region used for infections and wounds, with 13 out of 16 species tested being validated with in vitro studies.
Preference and familiarity mediate spatial responses of a large herbivore to experimental manipulation of resource availability
Authors: Ranc Nathan , Moorcroft Paul R. , Hansen K. Whitney , Ossi Federico , Sforna Tobia , Ferraro Enrico , Brugnoli Alessandro , Cagnacci Francesca 
Published: July 2020

AbstractThe link between spatio-temporal resource patterns and animal movement behaviour is a key ecological process, however, limited experimental support for this connection has been produced at the home range scale. In this study, we analysed the spatial responses of a resident large herbivore (roe deer Capreolus capreolus) using an in situ manipulation of a concentrated food resource. Specifically, we experimentally altered feeding site accessibility to roe deer and recorded (for 25 animal-years) individual responses by GPS tracking. We found that, following the loss of their preferred resource, roe deer actively tracked resource dynamics leading to more exploratory movements, and larger, spatially-shifted home ranges. Then, we showed, for the first time experimentally, the importance of site fidelity in the maintenance of large mammal home ranges by demonstrating the return of individuals to their familiar, preferred resource despite the presence of alternate, equally-valuable food resources. This behaviour was modulated at the individual level, where roe deer characterised by a high preference for feeding sites exhibited more pronounced behavioural adjustments during the manipulation. Together, our results establish the connections between herbivore movements, space-use, individual preference, and the spatio-temporal pattern of resources in home ranging behaviour.
Computational cognitive modeling and validation of Dp140 induced alteration of working memory in Duchenne Muscular Dystrophy
Authors: Tyagi Rahul , Aggarwal Palvi , Mohanty Manju , Dutt Varun , Anand Akshay 
Published: July 2020

AbstractDuchenne Muscular Dystrophy has emerged as a model to assess cognitive domains. The DMD gene variant location and its association with variable degrees of cognitive impairment necessitate identification of a common denominator. Computer architectures provide a framework to delineate the mechanisms involved in the cognitive functioning of the human brain. Copy number variations in the 79 exons of DMD gene were screened in 84 DMD subjects by Multiplex Ligation-dependent Probe Amplification (MLPA). DMD subjects were categorized based on the presence or absence of DP140 isoform. The cognitive and neuropsychological assessments were carried out as per inclusion criteria using standard scales. Instance-based learning theory (IBLT) based on the partial matching process was developed to mimic Stroop Color and Word Task (SCWT) performance on Adaptive Control of Thought-Rational (ACT-R) cognitive architecture based on IBLT. Genotype–phenotype correlation was conducted based on the mutation location in DMD gene. Assessment of specific cognitive domains in DP140 − ve group corresponded to the involvement of multiple brain lobes including temporal (verbal and visual learning and memory), parietal (visuo-conceptual and visuo-constructive abilities) and frontal (sustained and focused attention, verbal fluency, cognitive control). Working memory axis was found to be the central domain through tasks including RAVLT trial 1, recency effect, digit span backward, working memory index, arithmetic subtests in the Dp140 − ve group. IBLT validated the non-reliance of DMD subjects on recency indicating affected working memory domain. Modeling strategy revealed altered working memory processes in DMD cases with affected Dp140 isoform. DMD brain was observed to rely on primacy than the recency suggesting alterations in working memory capacity. Modeling revealed lowered activation of DMD brain with Dp140 − ve in order to retrieve the instances.
Relationship between the actual fine dust concentration and media exposure that influenced the changes in outdoor activity behavior in South Korea
Authors: Kim Myung-Gwan , Lee Su-Jin , Park Donghwi , Kim Chul-hyun , Lee Ki- hoon , Hwang Jong-moon 
Published: July 2020

AbstractThe one reason of the decrease of walking time for adults in South Korea among various factors is the sense of fear about fine dust sparked by media reports, which has created a negative perception of fine dust. This study aimed to assess the change in concentration of fine dust, as well as individuals' walking time and health status, in South Korea, and to investigate the relationship between the media reports on fine dust. Using the national government statistics data, we analyzed the relationship between walking time, concentration of fine dust, and amount of media reports on fine dust. From 2008 to 2017, the average walking time and PM10 levels decreased from 76.17 to 49.47 min and 52 to 45 μg/m3; whereas PM10 media frequency increased from 349 to 9,234. No positive correlation existed between walking time in South Korea and exposure to fine dust. However, media reports on fine dust increased steadily from 2012 and peaked in 2015. The decrease in average walking time in South Korea was due to the negative perception created by the increase in media reports on fine dust, rather than the increase in the actual concentration of fine dust.
N-myristoyltransferase-1 is necessary for lysosomal degradation and mTORC1 activation in cancer cells
Authors: Chen Yu-Chuan , Navarrete Marian S. , Wang Ying , McClintock Natalie C. , Sakurai Reiko , Wang Feng , Chen Kathryn T. , Chou Tsui-Fen , Rehan Virender K. , Lee Delphine J. , Diaz Begoña 
Published: July 2020

AbstractN-myristoyltransferase-1 (NMT1) catalyzes protein myristoylation, a lipid modification that is elevated in cancer cells. NMT1 sustains proliferation and/or survival of cancer cells through mechanisms that are not completely understood. We used genetic and pharmacological inhibition of NMT1 to further dissect the role of this enzyme in cancer, and found an unexpected essential role for NMT1 at promoting lysosomal metabolic functions. Lysosomes mediate enzymatic degradation of vesicle cargo, and also serve as functional platforms for mTORC1 activation. We show that NMT1 is required for both lysosomal functions in cancer cells. Inhibition of NMT1 impaired lysosomal degradation leading to autophagy flux blockade, and simultaneously caused the dissociation of mTOR from the surface of lysosomes leading to decreased mTORC1 activation. The regulation of lysosomal metabolic functions by NMT1 was largely mediated through the lysosomal adaptor LAMTOR1. Accordingly, genetic targeting of LAMTOR1 recapitulated most of the lysosomal defects of targeting NMT1, including defective lysosomal degradation. Pharmacological inhibition of NMT1 reduced tumor growth, and tumors from treated animals had increased apoptosis and displayed markers of lysosomal dysfunction. Our findings suggest that compounds targeting NMT1 may have therapeutic benefit in cancer by preventing mTORC1 activation and simultaneously blocking lysosomal degradation, leading to cancer cell death.