bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Water Interactions With Apollo Lunar Regolith Grains
Authors: Jones Brant M. , Aleksandrov Aleksandr , Dyar M. Darby , Hibbitts Charles A. , Orlando Thomas M.
Published: June 2020

Desorption activation energies of chemisorbed water on Apollo lunar Samples 14163 and 10084 were determined by temperature program desorption (TPD) experiments conducted under ultrahigh vacuum conditions. Desorption at the grain/vacuum interface and desorption/transport of water though the porous medium with readsorption were found to reproduce the experimental TPD signal. Signal from the grain/vacuum interface yielded desorption activation energies and site probability distributions. Highland sample 14163 exhibited a broad distribution of binding site energies peaking at 60 kJ mol−1, while mare sample 10084 exhibited a narrower distribution of binding site energies peaking at 65 kJ mol−1. The highland sample adsorbed approximately 30% more water than the more space weathered and mature mare sample, suggesting maturity may not be a good predictor of the degree of molecular water uptake on lunar regolith. Water desorption from the lunar surface over a typical lunar day was simulated with the measured coverage‐dependent activation energies of the mare and highland samples. The resulting desorption profile of water through a lunar temperature cycle is in general agreement with Lunar Reconnaissance Orbiter (LRO) Lyman‐α Mapping Project (LAMP) spacecraft‐based observations of trends for both highland and mare assuming ~1% submonolayer coverage and that photon stimulated desorption is neglected.
Fault Structure and Origin of Compressional Tectonic Features Within the Smooth Plains on Mercury
Authors: Peterson Georgia A. , Johnson Catherine L. , Byrne Paul K. , Phillips Roger J.
Published: June 2020

The major physiographic “smooth plains” units on Mercury are dominantly composed of volcanic deposits that have been deformed by horizontal compressive stresses. An open issue is whether these features formed by stresses induced by global contraction, bending stresses due to volcanic loading, or some combination of both. In this study, we model the surface expression of 12 shortening structures within several smooth plains units across Mercury to determine the geometries of the underlying faults. We implement an elastic dislocation model, using both listric and planar fault geometries, to place estimates on the depth of faulting for each feature. We show that a majority of smooth plains shortening structures penetrate the lithosphere to depths greater than 15 km. Thrust faults of this scale have not previously been recognized within the planet's smooth plains units and require a large horizontal stresses to form, which is best explained if this stress arises from global contraction. Further, our results suggest that the observed relief and length contrast between features in the smooth plains units and older intercrater plains units can be explained by interior layering of, and/or a shallower brittle‐ductile transition underlying, the smooth plains units.
Influence of Calcium Perchlorate on Organics Under SAM‐Like Pyrolysis Conditions: Constraints on the Nature of Martian Organics
Authors: Millan M. , Szopa C. , Buch A. , Summons R. E. , Navarro‐Gonzalez R. , Mahaffy P. R. , Johnson S. S.
Published: June 2020

Most of the organics detected on Mars so far are aliphatic and aromatic organo‐chlorine compounds. The smallest were first identified by the thermal treatment of the solid samples by Viking in 1976; although at the time, they were attributed to contamination. Since 2012, a larger variety of structures have been identified by the Sample Analysis at Mars experiment aboard the Curiosity rover. Evidence suggests that the chlorohydrocarbons formed during pyrolysis of sedimentary materials. Laboratory experiments show that heating of samples containing oxychlorines, such as chlorates (ClO3−) and perchlorates (ClO4−), along with organic matter present at Mars' surface is the logical source of these compounds. Nevertheless, this discovery of indigenous organic matter in the Mars regolith raises important questions: How do the oxychlorines influence the pyrolysis of organics? What are the organics precursors of the organo‐chlorinated molecules detected on Mars? Is there a way to identify the parent molecules in a sample after pyrolysis? This paper presents the results of systematic laboratory experiments of the products formed during the pyrolysis of organic compounds from three chemical families—polycyclic aromatic hydrocarbons, amino acids, and carboxylic acids—in presence of calcium perchlorates. Results show that the polycyclic aromatic hydrocarbon parent molecules and most of the carboxylic acids are still detectable after pyrolysis in presence of calcium perchlorate and that the degradation and/or evolution of all parent molecules mostly depends on their chemical nature. In addition, we demonstrate that the chlorohydrocarbons detected on Mars by the Sample Analysis at Mars instrument could come from the three chemical families studied.
Arctic Amplification of Global Warming Strengthened by Sunlight Oxidation of Permafrost Carbon to CO2
Authors: Bowen J. C. , Ward C. P. , Kling G. W. , Cory R. M.
Published: June 2020

Once thawed, up to 15% of the ∼1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO2) by 2,100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO2 in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000–6,300 a BP) derived from soil lignin and tannin. Rates of CO2 production from photomineralization of permafrost DOC are twofold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO2 to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2,299 may be too low by ~14%.
Dilatory and Downward Development of 3‐m Scale Irregularities in the Funnel‐Like Region of a Rapidly Rising Equatorial Plasma Bubble
Authors: Tulasi Ram S. , Ajith K. K. , Yokoyama T. , Yamamoto M. , Hozumi K. , Shiokawa K. , Otsuka Y. , Li G.
Published: June 2020

The equatorial plasma bubbles, once developed, grow nonlinearly into topside ionosphere, and simultaneous secondary instabilities lead to the development of shorter scale irregularities. The altitudinal growth and generation of smaller scale irregularities determine the spatio‐temporal occurrence and the intensity of ionospheric scintillations at wide spectrum of radio waves and have significant implications on the GNSS/Satellite Based Augmentation Systems. In this letter, we present a unique equatorial plasma bubble observation from equatorial atmosphere radar that provides hitherto undisclosed evidence for the smaller (3‐m) scale irregularities initially developing at higher altitudes and subsequently developing to lower altitudes in a narrow funnel‐like structure. The responsible mechanisms for early development of shorter scale irregularities in the topside and their subsequent development at lower altitudes are discussed in light of difference between the time scales of altitudinal growth and cascading rate of secondary instabilities through high‐resolution bubble model simulations.
Stress‐Dependent b Value Variations in a Heterogeneous Rate‐and‐State Fault Model
Authors: Dublanchet P.
Published: June 2020

The magnitudes of earthquakes are known to follow a power law distribution referred to as the Gutenberg‐Richter empirical law. Seismological observations and laboratory experiments suggest a decrease of the decay exponent (b value) with differential stress. The physical mechanism controlling this decrease, however, remains unclear. The present study is dedicated to the origin of relative b value variations with stress obtained in a 2‐D rate‐and‐state planar fault model considering a population of asperities with size‐dependent fracture energy. The simulations show that both b value in the intermediate magnitude range and mainshock magnitude increase with normal stress. Analytical relationships are derived, showing that the increase of b value is related to the decrease of critical nucleation length with normal stress, enhancing the productivity of small‐magnitude events and partial ruptures. The theoretical formulas also show how the increase of mainshock magnitude is a consequence of normal stress dependence of stress drop.
The Insulating Effect of Methane Clathrate Crust on Titan's Thermal Evolution
Authors: Kalousová Klára , Sotin Christophe
Published: June 2020

Saturn's largest moon Titan is unique for its dense, methane‐rich atmosphere, with ongoing complex organics chemistry, and the hydrocarbon lakes and seas on its frigid surface. Titan also harbors a subsurface water ocean, and its ice shell is likely capped by a thick crust of low‐conductivity methane clathrates that are very stable under Titan's surface conditions. Here, we investigate the effect of this insulating clathrate crust on convection in the ice shell. Without the clathrate crust, convection occurs below a stagnant lid that is a few tens of kilometers thick and limits the exchange between the surface and the deep ocean. We show that a 5–10 km thick clathrate crust reduces the stagnant lid thickness about threefold thus increasing the potential for the ocean‐surface exchange. Moreover, the insulating effect of clathrates dramatically decreases the amount of extracted heat thus limiting the freezing rate of Titan's ocean.
Antarctic Surface Mass Balance: Natural Variability, Noise, and Detecting New Trends
Authors: King Matt A. , Watson Christopher S.
Published: June 2020

The emergence of new, statistically robust trends in Antarctic surface mass balance (SMB) requires an understanding of the underlying SMB variability (noise). We show that simple white or AR[1] noise models do not adequately represent the variability of SMB in both the RACMO2.3p2 SMB model output (1979–2017) and composite ice core records (1800–2010), underestimating low‐frequency variability. By testing a range of noise models, we find that a Generalized Gauss Markov (GGM) model better approximates the noise around a linear trend. The general preference for GGM noise applies over spatial scales from the total ice sheet down to individual drainage basins. Over the longest timescales considered, trend uncertainties are 1.3–2.3 times larger using a GGM model compared to using an AR1 model at the ice sheet scale. Overall, our results suggest that larger trends or longer periods are required before new SMB trends can be robustly separated from background noise.
Factors Affecting the 2019 Atlantic Hurricane Season and the Role of the Indian Ocean Dipole
Authors: Wood Kimberly M. , Klotzbach Philip J. , Collins Jennifer M. , Caron Louis‐Philippe , Truchelut Ryan E. , Schreck Carl J.
Published: June 2020

The 2019 Atlantic hurricane season exhibited above‐average Accumulated Cyclone Energy—60% of which was produced by Hurricanes Dorian and Lorenzo. Most tropical cyclone (TC) activity was concentrated in a ~6‐week period from late August to early October. During the early part of the season, relatively TC‐unfavorable conditions persisted in the main development region (MDR). The MDR environment became largely favorable in September, followed by an abrupt shift back to less conducive conditions in October coincident with a strongly positive Indian Ocean Dipole (IOD). The IOD produced an El Niño‐like teleconnection pattern observed through 200‐hPa velocity potential anomalies. In the subtropical Atlantic, above‐average sea surface temperatures persisted for much of the season, which may have contributed to increased activity at higher latitudes. Given the neutral El Niño‐Southern Oscillation conditions during the 2019 hurricane season, our study highlights the need for further analysis of IOD impacts on Atlantic TC activity.
Spring Barrier to the MJO Eastward Propagation
Authors: Li Kuiping , Yu Weidong , Yang Yang , Feng Lin , Liu Shouhua , Li Lili
Published: June 2020

The Maritime Continent (MC) often exerts barrier effect on the eastward propagation of the Madden‐Julian Oscillation (MJO), and the strongest (weakest) effect occurs in spring (winter). After passing over the MC, the MJO slightly weakens by approximately 10% in winter and it sharply decays by more than 50% in spring. The physics for this spring barrier are understood from the perspective of the frictionally coupled Kelvin‐Rossby wave theory. In spring, the abrupt reduction in the boundary layer moisture convergence that occurs at the MC causes the decoupling of the Kelvin‐Rossby wave packet associated with the MJO: Kelvin waves emit from the major convection, while Rossby wave component rapidly decays in the Indian Ocean. An intermediate atmospheric model involving both the fundamental dynamics of the frictionally coupled Kelvin‐Rossby wave theory and the mean states confirms that the spring barrier is determined primarily by the mean surface moisture, particularly by its zonal distribution.
Krill Hotspot Formation and Phenology in the California Current Ecosystem
Authors: Fiechter Jerome , Santora Jarrod A. , Chavez Francisco , Northcott Devon , Messié Monique
Published: June 2020

In the California Current Ecosystem, krill represent a key link between primary production and higher trophic level species owing to their central position in the food web and tendency to form dense aggregations. However, the strongly advective circulation associated with coastal upwelling may decouple the timing, occurrence, and persistence of krill hotspots from phytoplankton biomass and nutrient sources. Results from a coupled physical‐biological model provide insights into fundamental mechanisms controlling the phenology of krill hotspots in the California Current Ecosystem, and their sensitivity to alongshore changes in coastal upwelling intensity. The simulation indicates that dynamics controlling krill hotspot formation, intensity, and persistence on seasonal and interannual timescales are strongly heterogeneous and related to alongshore variations in upwelling‐favorable winds, primary production, and ocean currents. Furthermore, regions promoting persistent krill hotspot formation coincide with increased observed abundance of top predators, indicating that the model resolves important ecosystem complexity and function.
Assessing Global and Local Radiative Feedbacks Based on AGCM Simulations for 1980–2014/2017
Authors: Zhang Rudong , Wang Hailong , Fu Qiang , Rasch Philip J.
Published: June 2020

We examine radiative feedbacks based on short‐term climate variability by analyzing atmospheric general circulation model (AGCM) simulations, including Atmospheric Model Intercomparison Project within CMIP phase 6 (AMIP6) with known effective radiative forcing (ERF) for 1980–2014 and one with zero ERF for 1980–2017. We first verify the Kernel‐Gregory feedback calculation by showing that both clear‐sky radiative fluxes and all‐sky radiative feedbacks from the kernel method agree with model simulations. We find that global‐mean net feedback for 1980–2017/2014 is −2 W m−2 K−1, about twice the feedback estimated for long‐term warming (4 × CO2) experiments. This difference is mainly caused by a near‐zero global‐mean net cloud feedback for 1980–2017/2014. We show that the lapse rate feedback for 1980–2017/2014 is the largest contributor to the amplified temperature change over the three poles (Arctic, Antarctic, and Tibetan Plateau), followed by surface albedo feedback and Planck feedback deviation from its global mean. Except for a higher surface albedo feedback in Antarctic, other feedbacks are similar between Arctic and Antarctic.
Improving AI System Awareness of Geoscience Knowledge: Symbiotic Integration of Physical Approaches and Deep Learning
Authors: Jiang Shijie , Zheng Yi , Solomatine Dimitri
Published: June 2020

Modeling dynamic geophysical phenomena is at the core of Earth and environmental studies. The geoscientific community relying mainly on physical representations may want to consider much deeper adoption of artificial intelligence (AI) instruments in the context of AI's global success and emergence of big Earth data. A new perspective of using hybrid physics‐AI approaches is a grand vision, but actualizing such approaches remains an open question in geoscience. This study develops a general approach to improving AI geoscientific awareness, wherein physical approaches such as temporal dynamic geoscientific models are included as special recurrent neural layers in a deep learning architecture. The illustrative case of runoff modeling across the conterminous United States demonstrates that the physics‐aware DL model has enhanced prediction accuracy, robust transferability, and good intelligence for inferring unobserved processes. This study represents a firm step toward realizing the vision of tackling Earth system challenges by physics‐AI integration.
Seasonally Modulated Stratospheric Aerosol Geoengineering Alters the Climate Outcomes
Authors: Visioni Daniele , MacMartin Douglas G. , Kravitz Ben , Richter Jadwiga H. , Tilmes Simone , Mills Michael J.
Published: June 2020

By reflecting some incoming solar radiation, stratospheric aerosol intervention using SO2 would reduce global mean temperature. Previous research has shown that multiple injection latitudes can be used to maintain not only global mean temperature, but also interhemispheric and equator‐to‐pole temperature gradients. However, the regional climate response depends not only on where the SO2 is injected, but also on when. We show here that even with these same objectives and same choices of latitudes, injecting in only one season instead of continuously throughout the year results in significant differences in regional climate, for instance in the magnitude of precipitation changes over India. The differential outcomes highlight the potential for underlying trade‐offs, with different choices regarding deployment leading to a different distribution of benefits or harms. This aspect of climate engineering should be considered in developing governance and emphasizes the need for a deeper understanding of the mechanisms underlying the regional responses.
Puzzling Haze Events in China During the Coronavirus (COVID‐19) Shutdown
Authors: Chang Yunhua , Huang Ru‐Jin , Ge Xinlei , Huang Xiangpeng , Hu Jianlin , Duan Yusen , Zou Zhong , Liu Xuejun , Lehmann Moritz F.
Published: June 2020

It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH‐20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID‐19) outbreak, than in 2019 (NYH‐19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH‐19 and NYH‐20. Much higher secondary aerosol fraction in PM2.5 were observed during NYH‐20 (73%) than during NYH‐19 (59%). During NYH‐20, PM2.5 levels correlated significantly with the oxidation ratio of nitrogen (r2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH‐20, despite the overall low atmospheric NO2 levels.
Asymmetric Development of Auroral Surges in the Northern and Southern Hemispheres
Authors: Uchida H. A. , Kataoka R. , Kadokura A. , Murase K. , Yukimatu A. S. , Miyoshi Y. , Shiokawa K. , Ebihara Y. , Hosokawa K. , Matsuoka A. , Kurita S. , Fujita S. , Shinohara I.
Published: June 2020

Simultaneous eastward and westward traveling surges were observed at Tjörnes, Iceland, and Syowa station, Antarctica, respectively. Several remarkable differences were identified. (1) The position of the initial bright spot was shifted by 1.7 to 2.3 MLT between both hemispheres. (2) The surges differ in traveling speed between the eastward traveling surge (6.5 km s−1) and the westward traveling surge (1.3 km s−1). (3) The Arase satellite was located on a geomagnetic field line connecting both ground stations and observed a significant excess in westward component of the magnetic field, which is consistent with the large shifts of the initial bright spots in both hemispheres. (4) The background Hall current flows eastward (Northern Hemisphere) and westward (Southern Hemisphere). The observed north‐south asymmetry of the traveling surges suggests that the ionosphere can play an essential role in controlling the fundamental spatiotemporal development of auroras in both hemispheres.
Statistical Relations Between Auroral Electrical Conductances and Field‐Aligned Currents at High Latitudes
Authors: Robinson R. M. , Kaeppler Stephen R. , Zanetti Larry , Anderson Brian , Vines Sarah K. , Korth Haje , Fitzmaurice Anna
Published: June 2020

Field‐aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) were combined with simultaneous and coincident observations of ionospheric conductivities made by the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska for 20 geomagnetically active days. The height‐integrated conductivities (conductances) were determined from the electron densities measured by the radar between 80 and 200 km altitude. Binning and averaging the data by field‐aligned current density and magnetic local time, we find that the currents correlate with conductances in both upward and downward current regions over some magnetic local times. The strongest correlation is seen in the late evening and morning sectors, with the Hall conductances two to three times larger than the Pedersen conductances for the same values of the field‐aligned current. The observed correlations reflect the mean energy of auroral precipitation, the contributions from electrons and protons to producing enhanced conductances, and the availability of charge carriers on auroral field lines. We apply linear fitting and smoothing to the correlations to construct an empirical model for specifying auroral conductances globally from AMPERE field‐aligned current maps. The energy fluxes from precipitating particles derived from the model conductances compare well with those derived using AMPERE data combined with satellite‐based measurements of far ultraviolet emissions, suggesting the results obtained at Poker Flat may be applicable to all high latitude locations. The ability to estimate conductances from AMPERE field‐aligned current maps provides the means to develop a global conductance model for the auroral ionosphere.
Magmatic Intrusions Control Io's Crustal Thickness
Authors: Spencer Dan C. , Katz Richard F. , Hewitt I. J.
Published: June 2020

Io, the most volcanically active body in the solar system, loses heat through eruptions of hot lava. Heat is supplied by tidal dissipation and is thought to be transferred through the mantle by magmatic segregation, a mode of transport that sets it apart from convecting terrestrial planets. We present a model that couples magmatic transport of tidal heat to the volcanic system in the crust, in order to determine the controls on crustal thickness, magmatic intrusions, and eruption rates. We demonstrate that magmatic intrusions are a key component of Io's crustal heat balance; around 80% of the magma delivered to the base of the crust must be emplaced and frozen as plutons to match rough estimates of crustal thickness. As magma ascends from a partially molten mantle into the crust, a decompacting boundary layer forms, which can explain possible observations of a high‐melt‐fraction region.
Pulmonary hypertension in bronchopulmonary dysplasia
Authors: Hansmann Georg , Sallmon Hannes , Roehr Charles C. , Kourembanas Stella , Austin Eric D. , Koestenberger Martin ,   for the European Pediatric Pulmonary Vascular Disease Network (EPPVDN)
Published: June 2020

Bronchopulmonary dysplasia (BPD) is a major complication in prematurely born infants. Pulmonary hypertension (PH) associated with BPD (BPD-PH) is characterized by alveolar diffusion impairment, abnormal vascular remodeling, and rarefication of pulmonary vessels (vascular growth arrest), which lead to increased pulmonary vascular resistance and right heart failure. About 25% of infants with moderate to severe BPD develop BPD-PH that is associated with high morbidity and mortality. The recent evolution of broader PH-targeted pharmacotherapy in adults has opened up new treatment options for infants with BPD-PH. Sildenafil became the mainstay of contemporary BPD-PH therapy. Additional medications, such as endothelin receptor antagonists and prostacyclin analogs/mimetics, are increasingly being investigated in infants with PH. However, pediatric data from prospective or randomized controlled trials are still sparse. We discuss comprehensive diagnostic and therapeutic strategies for BPD-PH and briefly review the relevant differential diagnoses of parenchymal and interstitial developmental lung diseases. In addition, we provide a practical framework for the management of children with BPD-PH, incorporating the modified definition and classification of pediatric PH from the 2018 World Symposium on Pulmonary Hypertension, and the 2019 EPPVDN consensus recommendations on established and newly developed therapeutic strategies. Finally, current gaps of knowledge and future research directions are discussed.

Impact

PH in BPD substantially increases mortality. Treatment of BPD-PH should be conducted by an interdisciplinary team and follow our new treatment algorithm while still kept tailored to the individual patient.

We discuss recent developments in BPD-PH, make recommendations on diagnosis, monitoring and treatment of PH in BPD, and address current gaps of knowledge and potential research directions.

We provide a practical framework, including a new treatment algorithm, for the management of children with BPD-PH, incorporating the modified definition and classification of pediatric PH (2018 WSPH) and the 2019 EPPVDN consensus recommendations on established and newly developed therapeutic strategies for BPD-PH.
Unusual marine cyanobacteria/haptophyte symbiosis relies on N2 fixation even in N-rich environments
Authors: Mills Matthew M , Turk-Kubo Kendra A , van Dijken Gert L , Henke Britt A , Harding Katie , Wilson Samuel T , Arrigo Kevin R , Zehr Jonathan P
Published: June 2020

The microbial fixation of N2 is the largest source of biologically available nitrogen (N) to the oceans. However, it is the most energetically expensive N-acquisition process and is believed inhibited when less energetically expensive forms, like dissolved inorganic N (DIN), are available. Curiously, the cosmopolitan N2-fixing UCYN-A/haptophyte symbiosis grows in DIN-replete waters, but the sensitivity of their N2 fixation to DIN is unknown. We used stable isotope incubations, catalyzed reporter deposition fluorescence in-situ hybridization (CARD-FISH), and nanoscale secondary ion mass spectrometry (nanoSIMS), to investigate the N source used by the haptophyte host and sensitivity of UCYN-A N2 fixation in DIN-replete waters. We demonstrate that under our experimental conditions, the haptophyte hosts of two UCYN-A sublineages do not assimilate nitrate (NO3−) and meet little of their N demands via ammonium (NH4+) uptake. Instead the UCYN-A/haptophyte symbiosis relies on UCYN-A N2 fixation to supply large portions of the haptophyte’s N requirements, even under DIN-replete conditions. Furthermore, UCYN-A N2 fixation rates, and haptophyte host carbon fixation rates, were at times stimulated by NO3− additions in N-limited waters suggesting a link between the activities of the bulk phytoplankton assemblage and the UCYN-A/haptophyte symbiosis. The results suggest N2 fixation may be an evolutionarily viable strategy for diazotroph–eukaryote symbioses, even in N-rich coastal or high latitude waters.
Atypical processing of tones and phonemes in Rett Syndrome as biomarkers of disease progression
Authors: Sysoeva Olga V. , Molholm Sophie , Djukic Aleksandra , Frey Hans-Peter , Foxe John J.
Published: June 2020

Due to severe motor impairments and the lack of expressive language abilities seen in most patients with Rett Syndrome (RTT), it has proven extremely difficult to obtain accurate measures of auditory processing capabilities in this population. Here, we examined early auditory cortical processing of pure tones and more complex phonemes in females with Rett Syndrome (RTT), by recording high-density auditory evoked potentials (AEP), which allow for objective evaluation of the timing and severity of processing deficits along the auditory processing hierarchy. We compared AEPs of 12 females with RTT to those of 21 typically developing (TD) peers aged 4–21 years, interrogating the first four major components of the AEP (P1: 60–90 ms; N1: 100–130 ms; P2: 135–165 ms; and N2: 245–275 ms). Atypicalities were evident in RTT at the initial stage of processing. Whereas the P1 showed increased amplitude to phonemic inputs relative to tones in TD participants, this modulation by stimulus complexity was absent in RTT. Interestingly, the subsequent N1 did not differ between groups, whereas the following P2 was hugely diminished in RTT, regardless of stimulus complexity. The N2 was similarly smaller in RTT and did not differ as a function of stimulus type. The P2 effect was remarkably robust in differentiating between groups with near perfect separation between the two groups despite the wide age range of our samples. Given this robustness, along with the observation that P2 amplitude was significantly associated with RTT symptom severity, the P2 has the potential to serve as a monitoring, treatment response, or even surrogate endpoint biomarker. Compellingly, the reduction of P2 in patients with RTT mimics findings in animal models of RTT, providing a translational bridge between pre-clinical and human research.
SHQ1 is an ER stress response gene that facilitates chemotherapeutics-induced apoptosis via sensitizing ER-stress response
Authors: Liu Huimin , Xie Siqi , Fang Fang , Kalvakolanu Dhananjaya V. , Xiao Weihua
Published: June 2020

SHQ1 was reported to control the biogenesis and assembly of H/ACA ribonucleoprotein particles (RNPs). It was independently isolated as a growth suppressor, GRIM1, in a genetic screen. Recent studies have indicated that SHQ1 inhibits prostate cancer growth and metastasis. SHQ1 facilitates MYC RNA splicing to promote T-acute lymphoblastic leukemia (T-ALL) development. Thus, the mechanisms of SHQ1 in cancers remain largely unknown. We report here that SHQ1 promotes tumor apoptosis and chemo-sensitivity in hepatocellular carcinoma (HCC) cells. In HCC tissues from patients, expression of SHQ1 was significantly decreased in the tumor compared to adjacent tissues. Experiments with HCC xenograft models revealed that restoring SHQ1 levels enhanced the anti-tumor activity of the endoplasmic reticulum (ER) stress inducer tunicamycin (TM) and common chemotherapy drug paclitaxel (PTX). Mechanistically, SHQ1 is an ER-stress response gene which is regulated by p50ATF6 and XBP1s through an ER stress response like element located on the SHQ1 promoter. SHQ1 interacts with the ER chaperone GRP78 to release ER sensors PERK/IRE1α/ATF6 from GRP78/ER-sensor complexes, leading to hyper-activation of unfolded protein response (UPR). In the persistent ER stress conditions of a HepG2 xenograft tumor model, SHQ1-mediated hyper-activation of ER-sensor signaling induces apoptosis. Our study thus demonstrates a SHQ1-mediated ER-stress response feedback loop that promotes tumor sensitivity to chemotherapeutics.
Expression profiling of microRNAs and isomiRs in conventional central chondrosarcoma
Authors: Parafioriti Antonina , Cifola Ingrid , Gissi Clarissa , Pinatel Eva , Vilardo Laura , Armiraglio Elisabetta , Di Bernardo Andrea , Daolio Primo Andrea , Felsani Armando , D’Agnano Igea , Berardi Anna Concetta
Published: June 2020

Conventional central chondrosarcoma (CCC) is a malignant bone tumor that is characterized by the production of chondroid tissue. Since radiation therapy and chemotherapy have limited effects on CCC, treatment of most patients depends on surgical resection. This study aimed to identify the expression profiles of microRNAs (miRNAs) and isomiRs in CCC tissues to highlight their possible participation to the regulation of pathways critical for the formation and growth of this type of tumor. Our study analyzed miRNAs and isomiRs from Grade I (GI), Grade II (GII), and Grade III (GIII) histologically validated CCC tissue samples. While the different histological grades shared a similar expression profile for the top abundant miRNAs, we found several microRNAs and isomiRs showing a strong different modulation in GII + GIII vs GI grade samples and their involvement in tumor biology could be consistently hypothesized. We then in silico validated these differently expressed miRNAs in a larger chondrosarcoma public dataset and confirmed the expression trend for 17 out of 34 miRNAs. Our results clearly suggests that the contribution of miRNA deregulation, and their targeted pathways, to the progression of CCC could be relevant and strongly indicates that when studying miRNA deregulation in tumors, not only the canonical miRNAs, but the whole set of corresponding isomiRs should be taken in account. Improving understanding of the precise roles of miRNAs and isomiRs over the course of central chondrosarcoma progression could help identifying possible targets for precision medicine therapeutic intervention.
Varietal variation and chromosome behaviour during meiosis in Solanum tuberosum
Authors: Choudhary Anushree , Wright Liam , Ponce Olga , Chen Jing , Prashar Ankush , Sanchez-Moran Eugenio , Luo Zewei , Compton Lindsey
Published: June 2020

Naturally occurring autopolyploid species, such as the autotetraploid potato Solanum tuberosum, face a variety of challenges during meiosis. These include proper pairing, recombination and correct segregation of multiple homologous chromosomes, which can form complex multivalent configurations at metaphase I, and in turn alter allelic segregation ratios through double reduction. Here, we present a reference map of meiotic stages in diploid and tetraploid S. tuberosum using fluorescence in situ hybridisation (FISH) to differentiate individual meiotic chromosomes 1 and 2. A diploid-like behaviour at metaphase I involving bivalent configurations was predominant in all three tetraploid varieties. The crossover frequency per bivalent was significantly reduced in the tetraploids compared with a diploid variety, which likely indicates meiotic adaptation to the autotetraploid state. Nevertheless, bivalents were accompanied by a substantial frequency of multivalents, which varied by variety and by chromosome (7–48%). We identified possible sites of synaptic partner switching, leading to multivalent formation, and found potential defects in the polymerisation and/or maintenance of the synaptonemal complex in tetraploids. These findings demonstrate the rise of S. tuberosum as a model for autotetraploid meiotic recombination research and highlight constraints on meiotic chromosome configurations and chiasma frequencies as an important feature of an evolved autotetraploid meiosis.
Ultrafast photochemistry produces superbright short-wave infrared dots for low-dose in vivo imaging
Authors: Santos Harrisson D. A. , Zabala Gutiérrez Irene , Shen Yingli , Lifante José , Ximendes Erving , Laurenti Marco , Méndez-González Diego , Melle Sonia , Calderón Oscar G. , López Cabarcos Enrique , Fernández Nuria , Chaves-Coira Irene , Lucena-Agell Daniel , Monge Luis , Mackenzie Mark D. , Marqués-Hueso José , Jones Callum M. S. , Jacinto Carlos , del Rosal Blanca , Kar Ajoy K. , Rubio-Retama Jorge , Jaque Daniel
Published: June 2020

Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag2S superdots) derived from chemically synthesized Ag2S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag2S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm−2) and doses (<0.5 mg kg−1), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.
mTADA is a framework for identifying risk genes from de novo mutations in multiple traits
Authors: Nguyen Tan-Hoang , Dobbyn Amanda , Brown Ruth C. , Riley Brien P. , Buxbaum Joseph D. , Pinto Dalila , Purcell Shaun M. , Sullivan Patrick F. , He Xin , Stahl Eli A.
Published: June 2020

Joint analysis of multiple traits can result in the identification of associations not found through the analysis of each trait in isolation. Studies of neuropsychiatric disorders and congenital heart disease (CHD) which use de novo mutations (DNMs) from parent-offspring trios have reported multiple putatively causal genes. However, a joint analysis method designed to integrate DNMs from multiple studies has yet to be implemented. We here introduce multiple-trait TADA (mTADA) which jointly analyzes two traits using DNMs from non-overlapping family samples. We first demonstrate that mTADA is able to leverage genetic overlaps to increase the statistical power of risk-gene identification. We then apply mTADA to large datasets of >13,000 trios for five neuropsychiatric disorders and CHD. We report additional risk genes for schizophrenia, epileptic encephalopathies and CHD. We outline some shared and specific biological information of intellectual disability and CHD by conducting systems biology analyses of genes prioritized by mTADA.
Development of CRISPR-Cas13a-based antimicrobials capable of sequence-specific killing of target bacteria
Authors: Kiga Kotaro , Tan Xin-Ee , Ibarra-Chávez Rodrigo , Watanabe Shinya , Aiba Yoshifumi , Sato’o Yusuke , Li Feng-Yu , Sasahara Teppei , Cui Bintao , Kawauchi Moriyuki , Boonsiri Tanit , Thitiananpakorn Kanate , Taki Yusuke , Azam Aa Haeruman , Suzuki Masato , Penadés José R. , Cui Longzhu
Published: June 2020

The emergence of antimicrobial-resistant bacteria is an increasingly serious threat to global health, necessitating the development of innovative antimicrobials. Here we report the development of a series of CRISPR-Cas13a-based antibacterial nucleocapsids, termed CapsidCas13a(s), capable of sequence-specific killing of carbapenem-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus by recognizing corresponding antimicrobial resistance genes. CapsidCas13a constructs are generated by packaging programmed CRISPR-Cas13a into a bacteriophage capsid to target antimicrobial resistance genes. Contrary to Cas9-based antimicrobials that lack bacterial killing capacity when the target genes are located on a plasmid, the CapsidCas13a(s) exhibit strong bacterial killing activities upon recognizing target genes regardless of their location. Moreover, we also demonstrate that the CapsidCas13a(s) can be applied to detect bacterial genes through gene-specific depletion of bacteria without employing nucleic acid manipulation and optical visualization devices. Our data underscore the potential of CapsidCas13a(s) as both therapeutic agents against antimicrobial-resistant bacteria and nonchemical agents for detection of bacterial genes.
The halogen bond with isocyano carbon reduces isocyanide odor
Authors: Mikherdov Alexander S. , Novikov Alexander S. , Boyarskiy Vadim P. , Kukushkin Vadim Yu.
Published: June 2020

Predominantly, carbon atoms of various species function as acceptors of noncovalent interactions when they are part of a π-system. Here, we report on the discovery of a halogen bond involving the isocyano carbon lone pair. The co-crystallization or mechanochemical liquid-assisted grinding of model mesityl isocyanide with four iodoperfluorobenezenes leads to a series of halogen-bonded adducts with isocyanides. The obtained adducts were characterized by single-crystal and powder X-ray diffraction, solid-state IR and 13C NMR spectroscopies, and also by thermogravimetric analysis. The formation of the halogen bond with the isocyano group leads to a strong reduction of the isocyanide odor (3- to 46-fold gas phase concentration decrease). This manipulation makes isocyanides more suitable for laboratory storage and usage while preserving their reactivity, which is found to be similar between the adducts and the parent isocyanide in some common transformations, such as ligation to metal centers and the multi-component Ugi reaction.
Eosinophil function in adipose tissue is regulated by Krüppel-like factor 3 (KLF3)
Authors: Knights Alexander J. , Vohralik Emily J. , Houweling Peter J. , Stout Elizabeth S. , Norton Laura J. , Alexopoulos Stephanie J. , Yik Jinfen. J. , Mat Jusoh Hanapi , Olzomer Ellen M. , Bell-Anderson Kim S. , North Kathryn N. , Hoehn Kyle L. , Crossley Merlin , Quinlan Kate G. R.
Published: June 2020

The conversion of white adipocytes to thermogenic beige adipocytes represents a potential mechanism to treat obesity and related metabolic disorders. However, the mechanisms involved in converting white to beige adipose tissue remain incompletely understood. Here we show profound beiging in a genetic mouse model lacking the transcriptional repressor Krüppel-like factor 3 (KLF3). Bone marrow transplants from these animals confer the beige phenotype on wild type recipients. Analysis of the cellular and molecular changes reveal an accumulation of eosinophils in adipose tissue. We examine the transcriptomic profile of adipose-resident eosinophils and posit that KLF3 regulates adipose tissue function via transcriptional control of secreted molecules linked to beiging. Furthermore, we provide evidence that eosinophils may directly act on adipocytes to drive beiging and highlight the critical role of these little-understood immune cells in thermogenesis.
Overcoming evanescent field decay using 3D-tapered nanocavities for on-chip targeted molecular analysis
Authors: Kumar Shailabh , Park Haeri , Cho Hyunjun , Siddique Radwanul H. , Narasimhan Vinayak , Yang Daejong , Choo Hyuck
Published: June 2020

Enhancement of optical emission on plasmonic nanostructures is intrinsically limited by the distance between the emitter and nanostructure surface, owing to a tightly-confined and exponentially-decaying electromagnetic field. This fundamental limitation prevents efficient application of plasmonic fluorescence enhancement for diversely-sized molecular assemblies. We demonstrate a three-dimensionally-tapered gap plasmon nanocavity that overcomes this fundamental limitation through near-homogeneous yet powerful volumetric confinement of electromagnetic field inside an open-access nanotip. The 3D-tapered device provides fluorescence enhancement factors close to 2200 uniformly for various molecular assemblies ranging from few angstroms to 20 nanometers in size. Furthermore, our nanostructure allows detection of low concentration (10 pM) biomarkers as well as specific capture of single antibody molecules at the nanocavity tip for high resolution molecular binding analysis. Overcoming molecule position-derived large variations in plasmonic enhancement can propel widespread application of this technique for sensitive detection and analysis of complex molecular assemblies at or near single molecule resolution.
An iron (II) dependent oxygenase performs the last missing step of plant lysine catabolism
Authors: Thompson Mitchell G. , Blake-Hedges Jacquelyn M. , Pereira Jose Henrique , Hangasky John A. , Belcher Michael S. , Moore William M. , Barajas Jesus F. , Cruz-Morales Pablo , Washington Lorenzo J. , Haushalter Robert W. , Eiben Christopher B. , Liu Yuzhong , Skyrud Will , Benites Veronica T. , Barnum Tyler P. , Baidoo Edward E. K. , Scheller Henrik V. , Marletta Michael A. , Shih Patrick M. , Adams Paul D. , Keasling Jay D.
Published: June 2020

Despite intensive study, plant lysine catabolism beyond the 2-oxoadipate (2OA) intermediate remains unvalidated. Recently we described a missing step in the D-lysine catabolism of Pseudomonas putida in which 2OA is converted to D-2-hydroxyglutarate (2HG) via hydroxyglutarate synthase (HglS), a DUF1338 family protein. Here we solve the structure of HglS to 1.1 Å resolution in substrate-free form and in complex with 2OA. We propose a successive decarboxylation and intramolecular hydroxylation mechanism forming 2HG in a Fe(II)- and O2-dependent manner. Specificity is mediated by a single arginine, highly conserved across most DUF1338 proteins. An Arabidopsis thaliana HglS homolog coexpresses with known lysine catabolism enzymes, and mutants show phenotypes consistent with disrupted lysine catabolism. Structural and biochemical analysis of Oryza sativa homolog FLO7 reveals identical activity to HglS despite low sequence identity. Our results suggest DUF1338-containing enzymes catalyze the same biochemical reaction, exerting the same physiological function across bacteria and eukaryotes.
Infrared driven hot electron generation and transfer from non-noble metal plasmonic nanocrystals
Authors: Zhou Dongming , Li Xufeng , Zhou Qiaohui , Zhu Haiming
Published: June 2020

Non-noble metal plasmonic materials, e.g. doped semiconductor nanocrystals, compared to their noble metal counterparts, have shown unique advantages, including broadly tunable plasmon frequency (from visible to infrared) and rich surface chemistry. However, the fate and harvesting of hot electrons from these non-noble metal plasmons have been much less explored. Here we report plasmon driven hot electron generation and transfer from plasmonic metal oxide nanocrystals to surface adsorbed molecules by ultrafast transient absorption spectroscopy. We show unambiguously that under infrared light excitation, hot electron transfers in ultrafast timescale (<50 fs) with an efficiency of 1.4%. The excitation wavelength and fluence dependent study indicates that hot electron transfers right after Landau damping before electron thermalization. We revealed the efficiency-limiting factors and provided improvement strategies. This study paves the way for designing efficient infrared light absorption and photochemical conversion applications based on non-noble metal plasmonic materials.
Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
Authors: Ju Long , Wang Lei , Li Xiao , Moon Seongphill , Ozerov Mike , Lu Zhengguang , Taniguchi Takashi , Watanabe Kenji , Mueller Erich , Zhang Fan , Smirnov Dmitry , Rana Farhan , McEuen Paul L.
Published: June 2020

Selection rules are of vital importance in determining the basic optical properties of atoms, molecules and semiconductors. They provide general insights into the symmetry of the system and the nature of relevant electronic states. A two-dimensional electron gas in a magnetic field is a model system where optical transitions between Landau levels (LLs) are described by simple selection rules associated with the LL index N. Here we examine the inter-LL optical transitions of high-quality bilayer graphene by photocurrent spectroscopy measurement. We observed valley-dependent optical transitions that violate the conventional selection rules Δ|N| = ± 1. Moreover, we can tune the relative oscillator strength by tuning the bilayer graphene bandgap. Our findings provide insights into the interplay between magnetic field, band structure and many-body interactions in tunable semiconductor systems, and the experimental technique can be generalized to study symmetry-broken states and low energy magneto-optical properties of other nano and quantum materials.