bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of volcanic aerosols on stratospheric ozone recovery
Authors: Naik Vaishali , Horowitz Larry W. , Daniel Schwarzkopf M. , Lin Meiyun 
Published: August 2017

AbstractWe use transient GFDL‐CM3 chemistry‐climate model simulations over the 2006–2100 period to show how the influence of volcanic aerosols on the extent and timing of ozone recovery varies with (a) future greenhouse gas scenarios (Representative Concentration Pathway (RCP)4.5 and RCP8.5) and (b) halogen loading. Current understanding is that elevated volcanic aerosols reduce ozone under high halogen loading but increase ozone under low halogen loading when the chemistry is more NOx dominated. With extremely low aerosol loadings (designated here as “background”), global stratospheric ozone burden is simulated to return to 1980 levels around 2050 in the RCP8.5 scenario but remains below 1980 levels throughout the 21st century in the RCP4.5 scenario. In contrast, with elevated volcanic aerosols, ozone column recovers more quickly to 1980 levels, with recovery dates ranging from the mid‐2040s in RCP8.5 to the mid‐2050s to early 2070s in RCP4.5. The ozone response in both future emission scenarios increases with enhanced volcanic aerosols. By 2100, the 1980 baseline‐adjusted global stratospheric ozone column is projected to be 20–40% greater in RCP8.5 and 110–200% greater in RCP4.5 with elevated volcanic aerosols compared to simulations with the extremely low background aerosols. The weaker ozone enhancement at 2100 in RCP8.5 than in RCP4.5 in response to elevated volcanic aerosols is due to a factor of 2.5 greater methane in RCP8.5 compared with RCP4.5. Our results demonstrate the substantial uncertainties in stratospheric ozone projections and expected recovery dates induced by volcanic aerosol perturbations that need to be considered in future model ozone projections.
Analyses of electron runaway in front of the negative streamer channel
Authors: Babich L. P. , Bochkov E. I. , Kutsyk I. M. , Neubert T. , Chanrion O. 
Published: August 2017

AbstractX‐ray and γ‐ray emissions, observed in correlation with negative leaders of lightning and long sparks of high‐voltage laboratory experiments, are conventionally connected with the bremsstrahlung of high‐energy runaway electrons (REs). Here we extend a focusing mechanism, analyzed in our previous paper, which allows the electric field to reach magnitudes, required for a generation of significant RE fluxes and associated bremsstrahlung, when the ionization wave propagates in a narrow, ionized channel created by a previous streamer. Under such conditions we compute the production rate of REs per unit streamer length as a function of the streamer velocity and predict that, once a streamer is formed with the electric field capable of producing REs ahead of the streamer front, the ionization induced by the REs is capable of creating an ionized channel that allows for self‐sustained propagation of the RE‐emitting ionization wave independent of the initial electron concentration. Thus, the streamer coronas of the leaders are probable sources of REs producing the observed high‐energy radiation. To prove these predictions, new simulations are planned, which would show explicitly that the preionization in front of the channel via REs will lead to the ionization wave propagation self‐consistent with RE generation.
Observing System Simulation Experiments for an array of autonomous biogeochemical profiling floats in the Southern Ocean
Authors: Kamenkovich Igor , Haza Angelique , Gray Alison R. , Dufour Carolina O. , Garraffo Zulema 
Published: August 2017

AbstractThis study uses Observing System Simulation Experiments (OSSEs) to examine the reconstruction of biogeochemical variables in the Southern Ocean from an array of autonomous profiling floats. In these OSSEs, designed to be relevant to the Southern Ocean Carbon and Climate Observation and Modeling (SOCCOM) project, the simulated floats move with oceanic currents and sample dissolved oxygen and inorganic carbon. The annual mean and seasonal cycle of these fields are then reconstructed and compared to the original model fields. The reconstruction skill is quantified with the reconstruction error (RErr), defined as the difference between the reconstructed and actual model fields, weighted by a local measure of the spatiotemporal variability. The square of the RErr is small (<0.5) for 150 floats in most of the domain, which is interpreted to mean that the reconstruction skill is high. An idealized analytical study demonstrates that the RErr depends on the magnitude of the seasonal cycle, spatial gradients, speed of float movement, amplitude of mesoscale variability, and number of floats. These factors explain a large part of the spatial variability in the RErr and can be used to predict the reconstruction skill of the SOCCOM array. Furthermore, our results demonstrate that an array size of 150 floats is a reasonable choice for reconstruction of surface properties and annual‐mean 2000 m inventories, with the exception of the seasonal cycle in parts of the Indo‐Atlantic, and that doubling this number to 300 results in a very modest increase in the reconstruction skill for dissolved oxygen.
Characterizing the chaotic nature of ocean ventilation
Authors: MacGilchrist Graeme A. , Marshall David P. , Johnson Helen L. , Lique Camille , Thomas Matthew 
Published: August 2017

AbstractVentilation of the upper ocean plays an important role in climate variability on interannual to decadal timescales by influencing the exchange of heat and carbon dioxide between the atmosphere and ocean. The turbulent nature of ocean circulation, manifest in a vigorous mesoscale eddy field, means that pathways of ventilation, once thought to be quasi‐laminar, are in fact highly chaotic. We characterize the chaotic nature of ventilation pathways according to a nondimensional “filamentation number,” which estimates the reduction in filament width of a ventilated fluid parcel due to mesoscale strain. In the subtropical North Atlantic of an eddy‐permitting ocean model, the filamentation number is large everywhere across three upper ocean density surfaces—implying highly chaotic ventilation pathways—and increases with depth. By mapping surface ocean properties onto these density surfaces, we directly resolve the highly filamented structure and confirm that the filamentation number captures its spatial variability. These results have implications for the spreading of atmospherically‐derived tracers into the ocean interior.
Spatiotemporal changes in extreme sea levels along the coasts of the North Atlantic and the Gulf of Mexico
Authors: Marcos Marta , Woodworth Philip L. 
Published: August 2017

AbstractExtreme sea levels along the densely monitored coasts of the North Atlantic Ocean and the Gulf of Mexico have been investigated using high‐frequency tide gauge measurements in the GESLA‐2 data set (www.gesla.org). Our results, based on nontidal residuals and skew surges in records since 1960, confirm that mean sea level (MSL) is a major, but not a unique, driver of extremes. Regionally coherent linear trends and correlations with large‐scale climate patterns are found in extreme events, even after the removal of MSL. A similar conclusion, that MSL is a major but not the only driver of extremes, comes from a small number of long records starting in the mid‐19th century. The records show slight increases in the intensity of extreme episodes at centennial time scales, together with multidecadal variability unrelated to MSL. Objective statistical criteria have been used to investigate whether extreme sea level distributions are stationary or not, resulting in nonstationarity being favored in many records, with or without accounting for changes in MSL. Extremes have been found to favor a non‐Gumbel behavior at many locations, with implications for the accuracy of return levels for coastal engineering.
Evaluation and analysis of AMSR‐2, SMOS, and SMAP soil moisture products in the Genhe area of China
Authors: Cui Huizhen , Jiang Lingmei , Du Jinyang , Zhao Shaojie , Wang Gongxue , Lu Zheng , Wang Jian 
Published: August 2017

AbstractHigh‐precision soil moisture products play an important role in estimating forest carbon storage and carbon emissions in Genhe, China. In this paper, we evaluated the Soil Moisture and Ocean Salinity (SMOS) L3 product, the Soil Moisture Active Passive (SMAP) L3 product, and four soil moisture products derived from the Advanced Microwave Scanning Radiometer 2 (AMSR‐2), i.e., the Dual Channel Algorithm based on the Qp model (QDCA) product, the Japan Aerospace Exploration Agency (JAXA) L3 product, and the Land Parameter Retrieval Model (LPRM) C band and X band products in the Genhe area of China. The results indicated that the root‐mean‐square error (RMSE) and bias of the QDCA product were lower than those of the other AMSR‐2 products, although the QDCA still fell outside of the acceptable range with a volumetric error of no greater than 6%. The JAXA product underestimated the soil moisture and had a constant bias of 0.089–0.099 m3 m−3. The LPRM C‐band and X‐band products had a constant variable season bias of 0.261–0.576 m3 m−3. The quality of the SMOS was better than that of the AMSR‐2 products; however, the results were noisy and unstable. The SMAP was closest to the ground measurements and presented a low RMSE (0.039–0.063 m3 m−3) and bias (0.022–0.050 m3 m−3). Finally, an assessment was performed on the parameters in these soil moisture algorithms.
The characteristics of the lower stratospheric gravity wavefield above Halley (75°S, 26°W), Antarctica, from radiosonde observations
Authors: Moffat‐Griffin T. , Colwell S. R. 
Published: August 2017

AbstractDaily radiosonde observations between 2003 and 2013 from Halley research station, Antarctica (75°S, 26°W), are used to determine climatologies of gravity wave properties in the lower stratosphere (between 15 km and 22 km altitude). Individual waves are extracted from the radiosonde profile using wavelet analysis and separated into upward and downward propagating waves. An increase in the percentage of downward propagating waves (~30% of the waves) is seen during the winter months. For the upward and downward propagating waves, their horizontal and vertical wavelength, intrinsic frequency, energy density, pseudomomentum flux, and direction of propagation are determined. The upward propagating wavefield is found to be dominated by waves with short vertical wavelength (~1 km) and low intrinsic frequency (ω ~ f). The downward propagating wavefield is composed of a wider distribution of vertical wavelength waves and has a larger proportion of higher‐frequency waves present. The upward propagating waves show an increase in total energy density in autumn and spring; the larger increase occurs during spring (up to 1.7 J kg−1 in September). The downward propagating waves increase in total energy density occurs during wintertime (up to 0.7 J kg−1 in June). During winter the contributions of the upward and downward propagating waves to the total energy density and pseudomomentum flux are almost equal. This paper details the first study of individual gravity wave properties combined into upward and downward propagating wave climatologies in the lower stratosphere above Halley.
Metal‐Loaded Dielectric Resonator Metasurfaces for Radiative Cooling
Authors: Zou Chengjun , Ren Guanghui , Hossain Md Muntasir , Nirantar Shruti , Withayachumnankul Withawat , Ahmed Taimur , Bhaskaran Madhu , Sriram Sharath , Gu Min , Fumeaux Christophe 
Published: August 2017

AbstractTailoring emissivity and absorptivity of structured material surfaces to match atmospheric transmission spectral windows can lead to radiative cooling that consumes no external energy. Recent advances in nanofabrication technology have facilitated progress in the realization of structured metasurfaces. In particular, subwavelength dielectric resonator metasurface supporting various resonance modes can be efficient absorbers. Here, such metasurfaces are proposed and experimentally demonstrated enhanced by metal loading to obtain strong broadband thermal emission over a wide angle at mid‐infrared frequencies. This concept results in passive cooling devices that can lower temperature by 10 °C below ambient temperature. Importantly, the utilization of standard constituent materials and processes lead to scalable fabrication compatible with silicon photonics integration, which will enable effective and energy‐efficient applications in passive cooling and thermodynamic control.
Interfaces in Perovskite Solar Cells
Authors: Fakharuddin Azhar , Schmidt‐Mende Lukas , Garcia‐Belmonte Germà , Jose Rajan , Mora‐Sero Ivan 
Published: August 2017

AbstractRapid improvement in photoconversion efficiency (PCE) of solution processable organometallic hybrid halide based perovskite solar cells (PSCs) have taken the photovoltaic (PV) community with a surprise and has extended their application in other electronic devices such as light emitting diodes, photo detectors and batteries. Together with efforts to push the PCE of PSCs to record values >22% – now at par with that of crystalline silicon solar cells – origin of their PV action and underlying physical processes are also deeply investigated worldwide in diverse device configurations. A typical PSC consists of a perovskite film sandwiched between an electron and a hole selective contact thereby creating ESC/perovskite and perovskite/HSC interfaces, respectively. The selective contacts and their interfaces determine properties of perovskite layer and also control the performance, origin of PV action, open circuit voltage, device stability, and hysteresis in PSCs. Herein, we define ideal charge selective contacts, and provide an overview on how the choice of interfacing materials impacts charge accumulation, transport, transfer/recombination, band‐alignment, and electrical stability in PSCs. We then discuss device related considerations such as morphology of the selective contacts (planar or mesoporous), energetics and electrical properties (insulating and conducting), and its chemical properties (organic vs inorganic). Finally, the outlook highlights key challenges and future directions for a commercially viable perovskite based PV technology.
Selective α‐Oxyamination and Hydroxylation of Aliphatic Amides
Authors: Li Xinwei , Lin Fengguirong , Huang Kaimeng , Wei Jialiang , Li Xinyao , Wang Xiaoyang , Geng Xiaoyu , Jiao Ning 
Published: August 2017

AbstractCompared to the α‐functionalization of aldehydes, ketones, even esters, the direct α‐modification of amides is still a challenge because of the low acidity of α‐CH groups. The α‐functionalization of N−H (primary and secondary) amides, containing both an unactived α‐C−H bond and a competitively active N−H bond, remains elusive. Shown herein is the general and efficient oxidative α‐oxyamination and hydroxylation of aliphatic amides including secondary N−H amides. This transition‐metal‐free chemistry with high chemoselectivity provides an efficient approach to α‐hydroxy amides. This oxidative protocol significantly enables the selective functionalization of inert α‐C−H bonds with the complete preservation of active N−H bond.
The Helix to Super‐Helix Transition in the Self‐Assembly of π‐Systems: Superseding of Molecular Chirality at Hierarchical Level
Authors: Hifsudheen Mohamed , Mishra Rakesh K. , Vedhanarayanan Balaraman , Praveen Vakayil K. , Ajayaghosh Ayyapanpillai 
Published: August 2017

AbstractHigher‐order super‐helical structures derived from biological molecules are known to evolve through opposite coiling of the initial helical fibers, as seen in collagen protein. A similar phenomenon is observed in a π‐system self‐assembly of chiral oligo(phenyleneethylene) derivatives (S)‐1 and (R)‐1 that explains the unequal formation of both left‐ and right‐handed helices from molecule having a specific chiral center. Concentration‐ and temperature‐dependent circular dichroism (CD) and UV/Vis spectroscopic studies revealed that the initial formation of helical aggregates is in accordance with the molecular chirality. At the next level of hierarchical self‐assembly, coiling of the fibers occurs with opposite handedness, thereby superseding the command of the molecular chirality. This was confirmed by solvent‐dependent decoiling of super‐helical structures and concentration‐dependent morphological analysis.
β‐Functionalized Push–Pull opp‐Dibenzoporphyrins as Sensitizers for Dye‐Sensitized Solar Cells
Authors: Hu Yi , Yellappa Shivaraj , Thomas Michael B. , Jinadasa R. G. Waruna , Matus Alex , Shulman Max , D'Souza Francis , Wang Hong 
Published: August 2017

AbstractA novel class of β‐functionalized push–pull zinc opp‐dibenzoporphyrins were designed, synthesized, and utilized as sensitizers for dye‐sensitized solar cells. Spectral, electrochemical, and computational studies were systematically performed to evaluate their spectral coverage, redox behavior, and electronic structures. These porphyrins displayed much broader spectral coverage and more facile oxidation upon extension of the π conjugation. Free‐energy calculations and femtosecond transient absorption studies (charge injection rate in the range of 1011 s−1) suggested efficient charge injection from the excited singlet state of the porphyrin to the conduction band of TiO2. The power conversion efficiency (η) of YH3 bearing acrylic acid linkers (η=5.9 %) was close to that of the best ruthenium dye N719 (η=7.4 %) under similar conditions. The superior photovoltaic performance of YH3 was attributed to its higher light‐harvesting ability and more favorable electron injection and collection, as supported by electrochemical impedance spectral studies. This work demonstrates the exceptional potential of benzoporphyrins as sensitizers for dye‐sensitized solar cells.
Atrial fibrillation variability on long‐term monitoring of implantable cardiac rhythm management devices
Authors: Kaplan Rachel M. , Ziegler Paul D. , Koehler Jodi , Glotzer Taya V. , Passman Rod S. 
Published: August 2017

BackgroundAtrial fibrillation (AF) burden and duration are predictors of thromboembolic events. The random nature of these measures may affect clinical decision making. The objective of this study was to determine temporal changes in AF burden as detected by continuous monitoring.HypothesisAF burden changes over time when detected by continuous monitoring.MethodsA post hoc analysis of patients enrolled in the TRENDS (A Prospective Study of the Clinical Significance of Atrial Arrhythmias Detected by Implanted Device Diagnostics) study with ≥1 stroke risk factor(s) who were implanted with a dual‐chamber cardiac rhythm management device (CRMD) and had AF burden data available for ≥2 years was performed. AF burden was defined as no AF, low AF (<5.5 hours on any given day), or high AF burden (≥5.5 hours in a day), and was first assessed over the initial 30 days following enrollment and then reassessed at 6‐month intervals for 2 years.ResultsAmong 394 patients included, the average age was 70.2 ± 10.9 years, 71% were male, and mean CHA2DS2‐VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke or TIA, vascular disease, age 65–74 years, sex category) score was 3.7 ± 1.6. In the 30‐day baseline period, 75.1% of patients had no AF, 11.2% had low AF, and 13.7% had high AF. Over the subsequent 2 years, 40.0% of patients initially classified as no AF or low AF experienced periods with high AF, whereas 59.3% of patients initially classified as high AF experienced ≥6 consecutive months with no AF or low AF. Advanced age was the sole predictor of AF progression.ConclusionsSignificant temporal variability in AF burden exists when measured continuously with an implantable CRMD.
Generating and Maintaining Transgenic Cryptosporidium parvum Parasites
Authors: Pawlowic Mattie C. , Vinayak Sumiti , Sateriale Adam , Brooks Carrie F. , Striepen Boris 
Published: August 2017

AbstractThe apicomplexan parasite Cryptosporidium is a leading cause of diarrheal disease and an important contributor to overall global child mortality. We currently lack effective treatment and immune prophylaxis. Recent advances now permit genetic modification of this important pathogen. We expect this to produce rapid advances in fundamental as well as translational research on cryptosporidiosis. Here we outline genetic engineering for Cryptosporidium in sufficient detail to establish transfection in any laboratory that requires access to this key technology. This chapter details the conceptual design consideration, as well as the experimental steps required to transfect, select, and isolate transgenic parasites. We also provide detail on key in vitro and in vivo assays to detect, validate, and quantify genetically modified Cryptosporidium parasites. © 2017 by John Wiley & Sons, Inc.
Tree seed traits’ response to monsoon climate and altitude in Indian subcontinent with particular reference to the Himalayas
Authors: Singh Surendra P. , Phartyal Shyam S. , Rosbakh Sergey 
Published: August 2017

AbstractSeed traits are related to several ecological attributes of a plant species, including its distribution. While the storage physiology of desiccation‐sensitive seeds has drawn considerable attention, their ecology has remained sidelined, particularly how the strong seasonality of precipitation in monsoonal climate affects their temporal and spatial distribution. We compiled data on seed mass, seed desiccation behavior, seed shedding, and germination periodicity in relation to monsoon and altitude for 198 native tree species of Indian Himalayas and adjoining plains to find out (1) the adaptive significance of seed mass and seed desiccation behavior in relation to monsoon and (2) the pattern of change in seed mass in relation to altitude, habitat moisture, and succession. The tree species fall into three categories with respect to seed shedding and germination periodicities: (1) species in which both seed shedding and germination are synchronized with monsoon, referred to as monsoon‐synchronized (MS, 46 species); (2) species in which seed germination is synchronized with monsoon, but seeds are shed several months before monsoon, referred to as partially monsoon‐synchronized (PMS, 112 species); and (3) species in which both shedding and germination occur outside of monsoon months, referred to as monsoon‐desynchronized (MD, 39 species). The seed mass ofMSspecies (1,718 mg/seed) was greater than that ofPMS(627 mg/seed) andMD(1,144 mg/seed). Of the 40 species with desiccation‐sensitive seeds, 45% belong to theMScategory, almost similar (approx. 47%) to woody plants with desiccation‐sensitive seeds in evergreen rain forests. Seed mass differed significantly as per seed desiccation behavior and successional stage. No relationship of seed mass was found with altitude alone and on the basis of seed desiccation behavior. However, seed mass trend along the altitude differed among monsoon synchronization strategies. Based on our findings, we conclude that in the predicted climate change (warming and uncertain precipitation pattern) scenario, a delay or prolonged break‐spell of monsoon may adversely affect the regeneration ecology of desiccation‐sensitive seed‐bearing species dominant over large forest areas of monsoonal climate.