bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress Models of the Annual Hydrospheric, Atmospheric, Thermal, and Tidal Loading Cycles on California Faults: Perturbation of Background Stress and Changes in Seismicity
Authors: Johnson Christopher W. , Fu Yuning , Bürgmann Roland 
Published: December 2017

AbstractStresses in the lithosphere arise from multiple natural loading sources that include both surface and body forces. The largest surface loads include near‐surface water storage, snow and ice, atmosphere pressure, ocean loading, and temperature changes. The solid Earth also deforms from celestial body interactions and variations in Earth's rotation. We model the seasonal stress changes in California from 2006 through 2014 for seven different loading sources with annual periods to produce an aggregate stressing history for faults in the study area. Our modeling shows that the annual water loading, atmosphere, temperature, and Earth pole tides are the largest loading sources and should each be evaluated to fully describe seasonal stress changes. In California we find that the hydrological loads are the largest source of seasonal stresses. We explore the seasonal stresses with respect to the background principal stress orientation constrained with regional focal mechanisms and analyze the modulation of seismicity. Our results do not suggest a resolvable seasonal variation for the ambient stress orientation in the shallow crust. When projecting the seasonal stresses into the background stress orientation we find that the timing of microseismicity modestly increases from an ~8 kPa seasonal mean‐normal‐stress perturbation. The results suggest that faults in California are optimally oriented with the background stress field and respond to subsurface pressure changes, possibly due to processes we have not considered in this study. At any time a population of faults are near failure as evident from earthquakes triggered by these slight seasonal stress perturbations.
The Small Effect of Poroelastic Pressure Transients on Triggering of Production‐Induced Earthquakes in the Groningen Natural Gas Field
Authors: Postma Tom , Jansen Jan‐Dirk 
Published: December 2017

AbstractOver the past decade, a steep increase in the number of seismic events has been observed in the Groningen gas field, the Netherlands. It is generally accepted that these are induced by compaction of the reservoir rock due to extensive depletion, causing a buildup of strain energy in faults that may be released seismically. We address the possible triggering of fault slip by the transient pressure field surrounding a well that has undergone a sudden rate change. Assuming a unilateral decoupling between displacement and pressure, numerical experiments are conducted using a sequential finite volume‐finite element solution strategy that fully incorporates second‐order terms in the radial flow equation. We investigate an idealized Groningen‐like geometry to discover whether the hypothesized possibility of triggering‐induced seismicity exists, explore how some controllable and uncontrollable variables influence its severity, and possibly provide clues on how production strategy might be able to avoid its occurrence. The results demonstrate that sudden production changes can indeed trigger near‐well seismic events, but that the effect is very small compared to other potential causes. Changing from sudden to gradual changes in well rates is therefore not expected to lead to a significant reduction in the number or magnitude of production‐induced earthquakes in the Groningen field.
Hydrothermal Alteration Promotes Humic Acid Formation in Sediments: A Case Study of the Central Indian Ocean Basin
Authors: Sarma Nittala S. , Kiran Rayaprolu , Rama Reddy M. , Iyer Sridhar D. , Peketi A. , Borole D. V. , Krishna M. S. 
Published: December 2017

AbstractAnomalously high concentrations of humic‐rich dissolved organic matter (DOM) in extant submarine hydrothermal vent plumes traveled far from source are increasingly being reported. This DOM, able to mobilize trace metals (e.g., Fe2+) has been hypothesized as originating from organic matter produced by thermogenic bacteria. To eliminate a possible abiogenic origin of this DOM, study is required of well‐preserved organic compounds that can be attributed to thermogenic bacteria. The Central Indian Ocean Basin (CIOB) is part of a diffuse plate boundary and an intraplate deformation zone. Coarse fraction (>63 µ) characteristics, mineralogy, magnetic susceptibility, and geochemistry were examined in sediments of a core raised close to a north‐south fracture zone near the Equator. Two horizons of distinctly brown‐colored sediments were shown as hydrothermally altered from their charred fragments and geochemistry (CaCO3, Corg, Ti/Al, Al/(Al + Fe + Mn), Sr/Ba, Mg/Li, Mn micronodules, Fe/Mn). We examined whether humic substances were preserved in these sediments, and if so whether their carbon isotope distribution would support their hydrothermal origin. Alkali extraction of sediments afforded humic acids (HA) in yields up to 1.2% in the brown sediments. The remaining portions of the core had nil or low concentrations of HA. The carbon of hydrothermal HA is isotopically heavier (average δ13C, ∼ −16.3‰) compared to nonhydrothermal HA (–18.1‰), suggesting that they were probably formed from organic matter that remained after elimination of lighter carbon enriched functional groups during diagenesis. The results provide compelling evidence of HA formation from lipids originating from thermogenic bacteria.
Changes in Bottom Water Physical Properties Above the Mid‐Atlantic Ridge Flank in the Brazil Basin
Authors: Zhao Jian , Thurnherr Andreas M. 
Published: December 2017

AbstractWarming of abyssal waters in recent decades has been widely documented around the global ocean. Here repeat hydrographic data collected in 1997 and 2014 near a deep fracture zone canyon in the eastern Brazil Basin are used to quantify the long‐term change. Significant changes are found in the Antarctic Bottom Water (AABW) within the canyon. The AABW in 2014 was warmer (0.08 ± 0.06
), saltier (0.01 ± 0.005), and less dense (0.005 ± 0.004
) than in 1997. In contrast, the change in the North Atlantic Deep Water has complicated spatial structure and is almost indistinguishable from zero at 95% confidence. The resulting divergence in vertical displacement of the isopycnals modifies the local density stratification. At its peak, the local squared buoyancy frequency (
) near the canyon is reduced by about 20% from 1997 to 2014. Similar reduction is found in the basinwide averaged profiles over the Mid‐Atlantic Ridge flank along 25
W in years 1989, 2005, and 2014. The observed changes in density stratification have important implications for internal tide generation and dissipation.
SAR Observation and Numerical Simulation of Internal Solitary Wave Refraction and Reconnection Behind the Dongsha Atoll
Authors: Jia T. , Liang J. J. , Li X.‐M. , Sha J. 
Published: December 2017

AbstractThe refraction and reconnection of internal solitary waves (ISWs) around the Dongsha Atoll (DSA) in the northern South China Sea (SCS) are investigated based on spaceborne synthetic aperture radar (SAR) observations and numerical simulations. In general, a long ISW front propagating from the deep basin of the northern SCS splits into northern and southern branches when it passes the DSA. In this study, the statistics of Envisat Advanced SAR (ASAR) images show that the northern and southern wave branches can reconnect behind the DSA, but the reconnection location varies. A previously developed nonlinear refraction model is set up to simulate the refraction and reconnection of the ISWs behind the DSA, and the model is used to evaluate the effects of ocean stratification, background currents, and incoming ISW characteristics at the DSA on the variation in reconnection locations. The results of the first realistic simulation agree with consecutive TerraSAR‐X (TSX) images captured within 12 h of each other. Further sensitivity simulations show that ocean stratification, background currents, and initial wave amplitudes all affect the phase speeds of wave branches and therefore shift their reconnection locations while shapes and locations of incoming wave branches upstream of the DSA profoundly influence the subsequent propagation paths. This study clarifies the variation in reconnection locations of ISWs downstream of the DSA and reveals the important mechanisms governing the reconnection process, which can improve our understanding of the propagation of ISWs near the DSA.
A Hybrid Multiscale Model of Miscible Reactive Fronts
Authors: Siuliukina Natalia , Tartakovsky Daniel M. 
Published: December 2017

AbstractSubsurface processes can be simulated at multiple scales with variable degrees of fidelity. Some microscopic (pore‐scale) features of reactive transport cannot be properly resolved in macroscopic (Darcy‐scale) models. While microscopic descriptors might be closer to reality, they are computationally unfeasible when deployed on a macroscale. Hybrid algorithms combine the physical fidelity of a microscopic model with the computational efficiency of its macroscopic counterpart. We develop a hybrid model of dynamic reactive fronts in an open fracture, with a chemical reaction occurring in the zone of contact between two dissolved species. Away from the front, both fluid flow and solute transport are described by one‐dimensional models. In the front's proximity, two‐dimensional Stokes equations are used to model fluid flow, and solute transport is described with advection‐diffusion‐reaction equations. These two descriptors are coupled via an iterative procedure, which enforces the continuity of concentrations and mass fluxes across the interface between the two models. Our numerical experiments demonstrate that the hybrid model outperforms its microscopic and macroscopic counterparts in terms of computational time and representational accuracy, respectively.
Unifying adaptive control with the nonlinear PI methodology: Designs for unknown strict‐feedback nonlinear systems with nonsmooth actuator nonlinearities
Authors: Psillakis H.E. , Lagos A.‐R. 
Published: December 2017

SummaryIn this paper, we extend the nonlinear PI control methodology within an adaptive control framework. An adaptive nonlinear PI controller is proposed for output tracking of strict‐feedback nonlinear systems with nonsmooth actuator nonlinearities and unknown control directions. The current approach relaxes the standard assumption of known bounds for the associated system nonlinearities made in earlier nonlinear PI schemes. New theoretical boundedness results have been proved that enable the successful combination of backstepping and linear parametric approximators with the nonlinear PI approach and ensure semiglobal approximate tracking of the output to some reference trajectory. Following recent extensions of the nonlinear PI method to strict‐feedback systems, the intermediate virtual control laws are derived through suitable integral equations. Simulation results are also presented in this paper that verify our theoretical analysis.
Part II: Diastereoselective Reactions Involving β‐Mono‐ and β,β′‐Disubstituted Alkylidene Oxindoles: Pondering Alkene Geometry
Authors: Ganesh Madhu , Rao Madhuri P. 
Published: December 2017

AbstractPart II encompasses synthetic efforts towards the construction of acyclic and cyclic structures that contain carbon and heteroatoms by employing diastereoselective reactions of β,β′‐disubstituted alkylidene oxindole as the primary substrate. In addition to the construction of acyclic structures, carbocyclic and heterocyclic rings that contain three‐, five‐, six‐, and seven‐membered spirocycles or fused‐rings are also described. A few examples of the arylative cyclization of dienes have also been presented.
Rhodium(III)‐Catalyzed Thiolation of Azobenzenes
Authors: Yang Jun , Deng Bowen , Guo Xiaofei , Li Zhengkai , Xiang Haifeng , Zhou Xiangge 
Published: December 2017

AbstractA rhodium(III)‐catalyzed C−H activation and thiolation of azobenzene with disulfide was developed. A broad range of azobenzenes were thiolated with high regioselectivity to form mono‐ortho‐substituted products in moderate to excellent yields of up to 99 %. The catalytic system could also be applied for the synthesis of a selenylated product and a benzothiophene.
Age estimation in older adults: Use of pulp/tooth ratios calculated from tooth sections
Authors: D'Ortenzio Lori , Prowse Tracy , Inskip Michael , Kahlon Bonnie , Brickley Megan 
Published: December 2017

AbstractObjectivesAccurate age estimates are foundational for bioarchaeological research, yet the ability to accurately age older adult skeletons remains elusive. This study uses a new version of pulp/tooth area calculations to investigate chronological age of older archaeological individuals.Materials and MethodsPulp/tooth area ratios were calculated on modern control teeth (n = 10) that were first radiographed and then sectioned for comparative analysis. Pulp/tooth area ratios were determined on sectioned teeth using ImageJ software for: (a) modern individuals of known age (n = 26); (b) individuals from Belleville, Ontario, Canada (1821–1874) with documented age (n = 50); and (c) Belleville individuals with skeletally estimated age (n = 122).ResultsCalculations from tooth sections on modern teeth (n = 10) resulted in a mean absolute error (MAE) of ±3.9 years, whereas the radiographic method for the same teeth had an MAE of ±14.45 years. Results indicate that sectioned pulp/tooth area ratios are a significant predictor of chronological age (p < .005), with MAEs of ±4.53 years for Belleville and ±3.77 years for modern individuals. There were no statistically significant differences in age estimations between modern and archaeological individuals, or with respect to tooth type, sex, or intra/inter‐observer estimations.DiscussionThis study provides a new more accurate method for estimating age‐at‐death, particularly for individuals in the 50+ age category. Sectioning the teeth and directly measuring exposed pulp chambers results in age estimations that were within ±4.15 years for both modern and archaeological individuals, thus presenting a method that will enhance the ability to age older individuals.
Kontrollierte Polymermikrostruktur in anionischer Polymerisation durch Kompartimentierung
Authors: Rieger Elisabeth , Blankenburg Jan , Grune Eduard , Wagner Manfred , Landfester Katharina , Wurm Frederik R. 
Published: December 2017

AbstractEine ideale, statistische anionische Copolymerisation wird durch physikalische Trennung der beiden Monomere in Kompartimente einer Emulsion gezwungen, um so Gradientencopolymere zu bilden. Das eine Monomer (M) ist vorzugsweise in den Tröpfchen löslich, während das andere (D) die kontinuierliche Phase einer DMSO‐in‐Cyclohexan‐Emulsion bevorzugt. Die lebende anionische Copolymerisation von zwei aktivierten Aziridinen ist auf die DMSO‐Kompartimente beschränkt, da die Polymerisation selektiv in diesen Tröpfchen stattfindet. Über die Verdünnung der kontinuierlichen Phase wird die lokale Konzentration von Monomer D in den Tröpfchen bestimmt und folglich der Gradient des resultierenden Copolymers. Die Copolymerisationen in der Emulsion werden durch Echtzeit‐1H‐NMR‐Kinetiken überwacht, was die Änderung der Copolymerisationsparameter beider Monomere bei Verdünnung der kontinuierlichen Phase von ideal statistischen Copolymeren zu Gradientencopolymeren zeigt.
A Flexible Solid Electrolyte Interphase Layer for Long‐Life Lithium Metal Anodes
Authors: Li Nian‐Wu , Shi Yang , Yin Ya‐Xia , Zeng Xian‐Xiang , Li Jin‐Yi , Li Cong‐Ju , Wan Li‐Jun , Wen Rui , Guo Yu‐Guo 
Published: December 2017

AbstractLithium (Li) metal is a promising anode material for high‐energy density batteries. However, the unstable and static solid electrolyte interphase (SEI) can be destroyed by the dynamic Li plating/stripping behavior on the Li anode surface, leading to side reactions and Li dendrites growth. Herein, we design a smart Li polyacrylic acid (LiPAA) SEI layer high elasticity to address the dynamic Li plating/stripping processes by self‐adapting interface regulation, which is demonstrated by in situ AFM. With the high binding ability and excellent stability of the LiPAA polymer, the smart SEI can significantly reduce the side reactions and improve battery safety markedly. Stable cycling of 700 h is achieved in the LiPAA‐Li/LiPAA‐Li symmetrical cell. The innovative strategy of self‐adapting SEI design is broadly applicable, providing opportunities for use in Li metal anodes
Evidence for Dynamic Chemical Kinetics at Individual Molecular Ruthenium Catalysts
Authors: Easter Quinn T. , Blum Suzanne A. 
Published: December 2017

AbstractCatalytic cycles are typically depicted as possessing time‐invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Evidence is presented for variable chemical kinetics at individual catalysts, with a focus on ring‐opening metathesis polymerization catalyzed by the second‐generation Grubbs’ ruthenium catalyst. Fluorescence microscopy is used to probe the chemical kinetics of the reaction because the technique possesses sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged.
Synthese α‐chiraler Ketone und chiraler Alkane durch eine radikalisch/ionische Kreuzungsreaktion von Vinyl‐Bor‐At‐Komplexen
Authors: Gerleve Carolin , Kischkewitz Marvin , Studer Armido 
Published: December 2017

AbstractVinyl‐Bor‐At‐Komplexe, hergestellt aus Enantiomeren‐angereicherten Alkylpinakolboronsäureestern, durchlaufen stereospezifische, radikalisch induzierte 1,2‐Wanderungen in radikalisch/ionischen Kreuzungsreaktionen. In dieser Dreikomponentenreaktion können verschiedene kommerziell erhältliche Alkyliodide als Radikalvorstufen verwendet werden, und Licht fungiert als Ketteninitiator. Eine nachfolgende Oxidation oder Protodeborylierung führt zu wertvollen α‐chiralen Ketonen und chiralen Alkanen mit exzellenten Enantiomerenreinheiten.
Reduktive Aminierung durch Photoredoxkatalyse über polaritätsangepassten Wasserstoffatomtransfer
Authors: Guo Xingwei , Wenger Oliver S. 
Published: December 2017

AbstractDie Anregung eines RuII‐Photosensibilisators in Gegenwart von Ascorbinsäure führt zur Reduktion von Iminium‐Ionen zu elektronenreichen α‐Aminoalkylradikalen, die durch einen thiolvermittelten Wasserstoffatomtransfer (HAT) in Produkte der reduktiven Aminierung umgewandelt werden. Mit diesem Konzept erfolgt die photoredoxkatalytische reduktive Aminierung von Carbonylverbindungen mit Aminen in guten bis hervorragenden Ausbeuten, wobei viele funktionelle Gruppen toleriert werden. Die drei entscheidenden Besonderheiten dieser Arbeit sind: (i) Das schnelle Abfangen elektronenreicher α‐Aminoalkylradikale durch polaritätsangepassten HAT, (ii) die eigentliche Methode der reduktiven Aminierung durch Photoredoxkatalyse und (iii) die Anwendung dieser neuen Methode für zeitlich und räumlich kontrollierte Reaktionen auf festen Trägermaterialen, wie durch das Anbringen eines Fluoreszenzfarbstoffs auf einem aktivierten Celluloseträger durch photoredoxkatalytische reduktive Aminierung veranschaulicht wird.
Photoinduced Cobalt(III)−Trifluoromethyl Bond Activation Enables Arene C−H Trifluoromethylation
Authors: Harris Caleb F. , Kuehner Christopher S. , Bacsa John , Soper Jake D. 
Published: December 2017

AbstractVisible‐light capture activates a thermodynamically inert CoIII−CF3 bond for direct C−H trifluoromethylation of arenes and heteroarenes. New trifluoromethylcobalt(III) complexes supported by a redox‐active [OCO] pincer ligand were prepared. Coordinating solvents, such as MeCN, afford green, quasi‐octahedral [(SOCO)CoIII(CF3)(MeCN)2] (2), but in non‐coordinating solvents the complex is red, square pyramidal [(SOCO)CoIII(CF3)(MeCN)] (3). Both are thermally stable, and 2 is stable in light. But exposure of 3 to low‐energy light results in facile homolysis of the CoIII−CF3 bond, releasing .CF3 radical, which is efficiently trapped by TEMPO. or (hetero)arenes. The homolytic aromatic substitution reactions do not require a sacrificial or substrate‐derived oxidant because the CoII by‐product of CoIII−CF3 homolysis produces H2. The photophysical properties of 2 and 3 provide a rationale for the disparate light stability.
Bis(perchlorocatecholato)silane—A Neutral Silicon Lewis Super Acid
Authors: Maskey Rezisha , Schädler Marcel , Legler Claudia , Greb Lutz 
Published: December 2017

AbstractNo neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO‐CCSD(T)) and experiment (fluoride abstraction from SbF6−). The exceptional affinity towards donors is further demonstrated by, for example, the characterization of an unprecedented SiO4F2 dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.
Assessment of degradation of plasticized poly(vinyl chloride) films through polyene formation under isothermal conditions
Authors: Tüzüm Demir A. P. , Ulutan S. 
Published: December 2017

ABSTRACTThe aim of this work is to assess the degradation of flexible poly(vinyl chloride) (PVC) films produced using orthophthalate based and recently introduced nonorthophthlate plasticizers which have compliance with recent environmental regulations. The plasticized PVC films were subjected to several heat treatments at 85–160 °C up to 420 min. Ultraviolet–visible spectroscopy was utilized to follow polyene formation upon dehydrochlorination of PVC. The amount of polyenes formed exhibited difference amongst the films those plasticized with diethyl hexylphthalate, diisodecyl phthalate, dioctyl terephthalate (DOTP), and diisononyl 1,2‐cyclohexanedicarboxylic acid (DINCH). The order of polyene concentration formed at the utmost level severe heat treatment is in line with the molecular weight ranking from highest to lowest, as the films with diisodecyl phthalate > DINCH > DOTP > diethyl hexylphthalate. Discoloration assessed in terms of yellowness index revealed that the films having recently introduced plasticizers as DOTP and DINCH were competing well with the films having orthophthalate based plasticizers. Scanning electron microscopy images revealed that the longer times for gelation during their production would improve the maturation of the films although they are already coherent and strong. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2018,135, 46092.