bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Study on the Photodegradation Mechanism of Nona‐BDEs in Methanol
Authors: Pan Lu , Bian Wensheng 
Published: February 2013

AbstractPolybrominated diphenyl ethers (PBDEs) have received special environmental concern due to their potential toxicity to humans and wildlife worldwide, however, it is difficult to reveal their dominant photochemical degradation pathways by experiment. We explored the reaction mechanisms of photochemical degradation–debromination of three nona‐BDEs in methanol using theoretical calculations, in which time‐dependent density functional theory (TDDFT) combined with the polarizable continuum (PCM) model is applied. The selectivity of debromination was studied, and the major octa‐BDE products photochemically debrominated from nona‐BDEs were identified. We find that the debromination reaction results from the electronic transitions from π to σ* orbitals when nona‐BDEs are exposed to UV‐light in the sunlight region, at which point the two low‐lying excited states for each nona‐BDE are πσ*(5Br) and πσ*(4Br), which correlate to the σ* orbitals located on the penta‐Br and tetra‐Br substituted phenyls, respectively. Our calculations indicate that each nona‐BDE may degrade to form three kinds of octa‐BDE products via the πσ*(5Br) state, whereas only one kind of octa‐BDEs can be formed via the πσ*(4Br) state. Our calculations can interpret the recent experiments successfully.
Accurate estimation of Doppler shift in mobile communications with high vehicle speed
Authors: Hua J.Y. , Yuan D.H. , Li G. , Meng L.M. 
Published: February 2013

SUMMARYRepresenting the channel varying rate and the mobile speed of a mobile terminal directly, Doppler shift is an important parameter in vehicular mobile communications and therefore is widely used in mobile target detection and adaptive applications. Hence, this paper puts forward an accurate Doppler shift estimator in mobile communications with high vehicle speeds, which can also be treated as a vehicular speed estimator due to the well‐known relation between the Doppler shift and the mobile speed. Specifically, the proposed estimator is based on the channel level crossing rate, and an iterative process is presented to achieve signal‐to‐noise ratio (SNR) insensitive estimates in accordance with the level crossing rate estimation error analysis. Moreover, we prove the convergency of the iterative Doppler shift estimator in theory. Computer simulations conducted under a wide range of noise corruption clearly show that the proposed estimator substantially outperforms several existing estimators in terms of accuracy and achieves a good SNR‐insensitive performance in a wide range of velocities and SNRs. Copyright © 2013 John Wiley & Sons, Ltd.
Cobalt(II)–Porphyrin‐Catalyzed Aerobic Oxidation: Oxidative Coupling of Phenols
Authors: Jiang Qing , Sheng Wenbing , Tian Mi , Tang Jie , Guo Cancheng 
Published: February 2013

AbstractThe first example of the cobalt–porphyrin‐catalyzed aerobic oxidative coupling of phenols through oxidative C–H functionalization has been developed. In the presence of T(p‐OMe)PPCo and Na2CO3, the oxidative coupling of phenols with different substituents proceeded smoothly with O2 as a terminal oxidant to give the corresponding biaryl compounds in satisfactory yields. The biaryl derivatives are important in the area of pharmaceuticals and as ligands in metal catalysis. Preliminary mechanistic studies of this oxidative coupling reaction are also reported.
Copper(II)‐Mediated Synthesis of Indolequinones from Bromoquinones and Enamines
Authors: Inman Martyn , Moody Christopher J. 
Published: February 2013

AbstractThe reaction of enamines and bromoquinones in the presence of copper(II) acetate and potassium carbonate results in a regiospecific synthesis of indolequinones. The reaction is broad in scope and scalable and provides a route to the core structure that is present in several biologically interesting natural and synthetic compounds.
Short migration of methane into a gas hydrate‐bearing sand layer at Walker Ridge, Gulf of Mexico
Authors: Cook Ann E. , Malinverno Alberto 
Published: February 2013

AbstractThe mechanisms governing distribution of natural gas hydrates in marine sediment systems are not well understood. We focus on a hole in the Gulf of Mexico, Walker Ridge Block 313 Hole H, where a 2.5‐m‐thick gas hydrate‐bearing sand occurs within a 152‐m‐thick fine‐grained mud interval containing gas hydrate in fractures. The gas hydrate‐bearing sand is surrounded by two distinct hydrate‐free zones (10‐m‐thick above and 3‐m‐thick below). We hypothesize that microbial methane generated within the hydrate‐free zones diffused into the sand and formed gas hydrate. We show that the amount of methane produced in the hydrate‐free zones is likely enough to explain the gas hydrate content of the sand layer. Additionally, we show that there is enough time for dissolved methane to diffuse from the hydrate‐free zones into the sand. We conclude that methane transport over significant distances via fluid flow is not required but that microbial methane could migrate short distances to form gas hydrate in the sand layer.
Seasonal moisture sources and the isotopic composition of precipitation, rivers, and carbonates across the Andes at 32.5–35.5°S
Authors: Hoke Gregory D. , Aranibar Julieta N. , Viale Maximiliano , Araneo Diego C. , Llano Carina 
Published: February 2013

AbstractConstraining the influence of different moisture sources across the flanks of mountain ranges is important for understanding tectonic, geomorphic, and paleoclimate problems at geologic timescales, as well as evaluating climate change and water resources on human time scales. The stable isotope compositions of stream waters and precipitation are an ideal tool for this task. This study reports the results of a 2 year monthly precipitation sampling campaign on the eastern flank of the Andes in the Mendoza Province of Argentina, which began in September 2008. A total of 104 precipitation samples spanning some 2500 m of relief from nine sites were analyzed for δD and δ18O. In addition, 81 samples from Andean rivers collected on both sides of the range in 2002 and 2007 were analyzed. We employ a Rayleigh isotope fractionation modeling approach to explore spatial and temporal variations in precipitation and river water compositions. The results indicate that precipitation on the eastern slopes of the Andes at ~33°S, at elevations above 2 km, is largely derived from a westerly, Pacific‐source component and a mixture of easterly and westerly sources below 2 km. Further south at ~35°S, river water compositions exhibit a strong winter influence. At 33°S, rivers have an isotopic minimum of ~ −18‰ across the core of the range, which has an average elevation of 4000 m, and are topographically offset from similar isotopic values of precipitation by +1000 m. Comparison of precipitation and river water data with temperature‐corrected δ18O estimates from pedogenic carbonates illustrates that carbonates capture the range of variability observed in modern precipitation and Rayleigh fractionation models.
Trophic regions of a hydrothermal plume dispersing away from an ultramafic‐hosted vent‐system: Von Damm vent‐site, Mid‐Cayman Rise
Authors: Bennett Sarah A. , Coleman Max , Huber Julie A. , Reddington Emily , Kinsey James C. , McIntyre Cameron , Seewald Jeffrey S. , German Christopher R. 
Published: February 2013

AbstractDeep‐sea ultramafic‐hosted vent systems have the potential to provide large amounts of metabolic energy to both autotrophic and heterotrophic microorganisms in their dispersing hydrothermal plumes. Such vent‐systems release large quantities of hydrogen and methane to the water column, both of which can be exploited by autotrophic microorganisms. Carbon cycling in these hydrothermal plumes may, therefore, have an important influence on open‐ocean biogeochemistry. In this study, we investigated an ultramafic‐hosted system on the Mid‐Cayman Rise, emitting metal‐poor and hydrogen sulfide‐, methane‐, and hydrogen‐rich hydrothermal fluids. Total organic carbon concentrations in the plume ranged between 42.1 and 51.1 μM (background = 43.2 ± 0.7 μM (n = 5)) and near‐field plume samples with elevated methane concentrations imply the presence of chemoautotrophic primary production and in particular methanotrophy. In parts of the plume characterized by persistent potential temperature anomalies but lacking elevated methane concentrations, we found elevated organic carbon concentrations of up to 51.1 μM, most likely resulting from the presence of heterotrophic communities, their extracellular products and vent larvae. Elevated carbon concentrations up to 47.4 μM were detected even in far‐field plume samples. Within the Von Damm hydrothermal plume, we have used our data to hypothesize a microbial food web in which chemoautotrophy supports a heterotrophic community of microorganisms. Such an active microbial food web would provide a source of labile organic carbon to the deep ocean that should be considered in any future studies evaluating sources and sinks of carbon from hydrothermal venting to the deep ocean.
Depths and temperatures of <10.5 Ma mantle melting and the lithosphere‐asthenosphere boundary below southern Oregon and northern California
Authors: Till Christy B. , Grove Timothy L. , Carlson Richard W. , Donnelly‐Nolan Julie M. , Fouch Matthew J. , Wagner Lara S. , Hart William K. 
Published: February 2013

AbstractPlagioclase and spinel lherzolite thermometry and barometry are applied to an extensive geochemical dataset of young (<10.5 Ma) primitive basaltic lavas from across Oregon's High Lava Plains, California's Modoc Plateau, and the central‐southern Cascades volcanic arc to calculate the depths and temperatures of mantle melting. This study focuses on basalts with low pre‐eruptive H2O contents that are little fractionated near‐primary melts of mantle peridotite (i.e., basalts thought to be products of anhydrous decompression mantle melting). Calculated minimum depths of nominally anhydrous melt extraction are 40–58 km below Oregon's High Lava Plains, 41–51 km below the Modoc Plateau, and 37–60 km below the central and southern Cascades arc. The calculated depths are very close to Moho depths as determined from a number of regional geophysical studies and suggest that the geophysical Moho and lithosphere‐asthenosphere boundary in this region are located in very close proximity to one another (within 5–10 km). The basalts originated at 1185–1383°C and point to a generally warm mantle beneath this area but not one hot enough to obviously require a plume contribution. Our results, combined with a range of other geologic, geophysical, and geochemical constraints, are consistent with a regional model whereby anhydrous mantle melting over the last 10.5 Ma in a modern convergent margin and back arc was driven by subduction‐induced corner flow in the mantle wedge, and to a lesser extent, toroidal flow around the southern edge of the subducting Juan de Fuca and Gorda plates, and crustal extension‐related upwelling of the shallow mantle.
Delamination vs. break‐off: the fate of continental collision
Authors: Magni Valentina , Faccenna Claudio , van Hunen Jeroen , Funiciello Francesca 
Published: February 2013

AbstractThe fate of a convergent continental margin is investigated. We perform a set of 2D numerical models to study how and why continental collision can evolve in different scenarios. Since the rheology of continental lithosphere has a major control on the dynamics of subduction, we explore a range of different lithosphere and lower crust viscosity values to understand their sensitivity on the possible scenarios. We find that with a rheologically layered crust both delamination and break‐off are feasible. We identify three modes: (1) slab detachment, in which the lithospheric mantle and the crust are strongly coupled, subduction slows down and the slab eventually breaks; (2) delamination of the lithospheric mantle that separates from the crust and continue to subduct and (3) an intermediate mode where the lithospheric mantle and the crust remain partially coupled, resulting in an initial stage of delamination followed by the slow down and cessation of subduction.
Thermal elasticity of (Fex,Mg1−x)2SiO4 olivine and wadsleyite
Authors: Núñez‐Valdez M. , Wu Z. , Yu Y. G. , Wentzcovitch R. M. 
Published: February 2013

AbstractWe present first‐principles results for elastic moduli (bulk, K, and shear, G) and acoustic velocities (compressional, VP, shear, VS, and bulk VΦ) of olivine (α) and wadsleyite (β) (Fex,Mg1 − x)2SiO4, at high pressure (P) and temperature (T) with varying iron content (0 ≤ x ≤ 0.125). Pressure and temperature derivatives of these properties are analyzed. We show that adding 12.5% of Fe in forsterite softens VP and VS by ∼3–6%, the same effect as raising temperature by ∼1000 K in dry olivine at 13.5 GPa—the same is true in wadsleyite. This study suggests that Fe is effective in producing seismic velocity heterogeneity at upper mantle and transition zone conditions and should be another key ingredient, in addition to temperature and water content variations, in interpreting seismic heterogeneities in the transition zone. The effect of Fe on density, elastic, and velocity contrasts across the α → β transition is also addressed at relevant conditions. We show that simultaneous changes of composition, temperature, and pressure do not affect significantly the relative density contrasts. We also find that compressional and shear impedance contrasts result primarily from velocity discontinuities rather than density discontinuity.
Real‐time high‐rate co‐seismic displacement from ambiguity‐fixed precise point positioning: Application to earthquake early warning
Authors: Li Xingxing , Ge Maorong , Zhang Xiaohong , Zhang Yong , Guo Bofeng , Wang Rongjiang , Klotz Jürgen , Wickert Jens 
Published: February 2013

AbstractNowadays more and more high‐rate real‐time GPS data become available that provide a great opportunity to contribute to earthquake early warning (EEW) system in terms of capturing regional surface displacements, as an independent information source, useful for promptly estimating the magnitude of large destructive earthquake. In our study, we demonstrate the performance of the real‐time ambiguity‐fixed precise point positioning (PPP) approach using 5 Hz GPS data collected during El Mayor‐Cucapah earthquake (Mw 7.2, 4 April 2010). The PPP‐based displacements show to agree with accelerometer‐based displacement at centimeter level. The key for successfully obtaining high precision displacements is the efficient ambiguity resolution. PPP with ambiguity fixing can result in correct permanent co‐seismic offsets and correct recovery of moment magnitude and fault slip inversion at levels comparable to post‐processing.
Relative sea level variations in the Chukchi region ‐ Arctic Ocean ‐ since the late Eocene
Authors: Hegewald Anne , Jokat Wilfried 
Published: February 2013

AbstractRelative sea level (RSL) variations are a result of tectonic activity, changing of the water volume in ocean basins (e.g. due to increasing/decreasing of ice volume, evaporation) and variations in regional to global climate, which influence erosional processes and material transport. We present multi‐channel seismic data combined with dated sediment horizons from the Chukchi Shelf, Arctic Ocean. Based on a series of prograding sequences in the upper 4 km of sediments and the method of seismic sequence stratigraphy, we introduce the first RSL curve for the Chukchi region, beginning in the late Eocene (40 Ma). The comparison of the Chukchi RSL curve with the global RSL curve shows that RSL lowering events in the Chukchi region do not correlate with global events for the Eocene/Oligocene ‐ early Miocene. Between the Eocene/Oligocene and the late Oligocene, the Chukchi RSL variations were small (< 100 m). Since the late Oligocene the Chukchi RSL increased until the opening of the Fram Strait in the early Miocene. We show that the Chukchi RSL variations are representative for the Arctic Ocean, and conclude that the Arctic Ocean was an isolated basin for the Eocene/Oligocene ‐ early Miocene.
Decadal prediction of observed and simulated sea surface temperatures
Authors: DelSole Timothy , Jia Liwei , Tippett Michael K. 
Published: February 2013

AbstractA multivariate regression model derived from climate model simulations is shown to produce skillful predictions of unforced, annual mean sea surface temperature variations on multiyear time scales in observations and climate model simulations. Patterns that can be predicted with skill are identified explicitly and shown to arise from a combination of persistence and coupled interactions in the Pacific Ocean. Adding the regression model predictions to an estimate of the response to anthropogenic and natural forcing yields a prediction with higher skill than either alone, demonstrating the contribution of initial condition information to skill on multiyear time scales.
The impact of an intense summer cyclone on 2012 Arctic sea ice retreat
Authors: Zhang Jinlun , Lindsay Ron , Schweiger Axel , Steele Michael 
Published: February 2013

AbstractThis model study examines the impact of an intense early August cyclone on the 2012 record low Arctic sea ice extent. The cyclone passed when Arctic sea ice was thin and the simulated Arctic ice volume had already declined ~40% from the 2007–2011 mean. The thin sea ice pack and the presence of ocean heat in the near surface temperature maximum layer created conditions that made the ice particularly vulnerable to storms. During the storm, ice volume decreased about twice as fast as usual, owing largely to a quadrupling in bottom melt caused by increased upward ocean heat transport. This increased ocean heat flux was due to enhanced mixing in the oceanic boundary layer, driven by strong winds and rapid ice movement. A comparison with a sensitivity simulation driven by reduced wind speeds during the cyclone indicates that cyclone‐enhanced bottom melt strongly reduces ice extent for about 2 weeks, with a declining effect afterward. The simulated Arctic sea ice extent minimum in 2012 is reduced by the cyclone but only by 0.15 × 106 km2 (4.4%). Thus, without the storm, 2012 would still have produced a record minimum.
Analytical solution for slip flow and heat transfer due to a stretching sheet
Authors: Nandeppanavar Mahantesh M. , Siddalingappa M.N. , Satyanarayana A.V.V. , Kemparaju M.C. 
Published: February 2013

AbstractAn analysis has been carried out to investigate the analytical solution to the flow and heat transfer characteristics of a viscous flow over a stretching sheet in the presence of second‐order slip in flow. The governing partial differential equations of flow and heat transfer are converted into non‐linear ordinary differential equations by using suitable similarity transformations. The exact solution of momentum equation is assumed in exponential form and analytical solutions of heat transfer for both PST and PHF cases are obtained by the power series method in terms of Kummer's hypergeometric function. The temperature profiles are drawn for different governing parameters. The numerical values of wall temperature gradient and wall temperature are compared with earlier numerical results which have a good agreement. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21044
A SIMPLIFIED METHODOLOGY FOR IDENTIFYING THE FUNCTION OF ELOPEMENT
Authors: Lehardy Robert K. , Lerman Dorothea C. , Evans Lindsay M. , O'Connor Alyson , LeSage Daniel L. 
Published: February 2013

AbstractFunctional analyses of elopement (i.e., leaving a specific area without permission) are challenging to conduct because clients must have repeated opportunities to elope from one room (or area) to another safely. These analyses often require two or more adjoining rooms and retrieval of the client following each instance of elopement (e.g., Piazza et al., 1997). These room arrangements may be impractical in some settings, and therapist delivery of attention or demands during retrieval may confound the results. To address these issues, we evaluated the viability of conducting a functional analysis (FA) of elopement within a single room. Participants were 2 children and 2 adults with developmental disabilities who eloped from rooms at their day programs. Results of the single‐room assessments were compared to those of a second FA that was conducted using methods similar to those described in previous studies. Function‐based treatments were implemented for each participant. Results suggest that the single‐room assessment may be a viable alternative for identifying the function of elopement.
The Intramembrane Protease SPPL2A Is Critical for Tooth Enamel Formation
Authors: Bronckers Antonius LJJ , Gueneli Nur , Lüllmann-Rauch Renate , Schneppenheim Janna , Moraru Andreea P , Himmerkus Nina , Bervoets Theodore J , Fluhrer Regina , Everts Vincent , Saftig Paul , Schröder Bernd 
Published: February 2013

ABSTRACT

Intramembrane proteases are critically involved in signal transduction and membrane protein turnover. Signal-peptide-peptidase-like 2a (SPPL2A), a presenilin-homologue residing in lysosomes/late endosomes, cleaves type II-oriented transmembrane proteins. We recently identified SPPL2A as the enzyme controlling turnover and functions of the invariant chain (CD74) of the major histocompatibility complex II (MHCII) and demonstrated critical importance of this process for B cell development. Surprisingly, we found that SPPL2A is critical for formation of dental enamel. In Sppl2a knockout mice, enamel of the erupted incisors was chalky white and rapidly eroded after eruption. SPPL2A was found to be expressed in enamel epithelium during secretory and maturation stage amelogenesis. Mineral content of enamel in Sppl2a−/− incisors was inhomogeneous and reduced by ∼20% compared to wild-type mice with the most pronounced reduction at the mesial side. Frequently, disruption of the enamel layer and localized detachment of the most superficial enamel layer was observed in the knockout incisors leading to an uneven enamel surface. In Sppl2a null mice, morphology and function of secretory stage ameloblasts were not noticeably different from that of wild-type mice. However, maturation stage ameloblasts showed reduced height and a characteristic undulation of the ameloblast layer with localized adherence of the cells to the outer enamel. This was reflected in a delayed and incomplete resorption of the proteinaceous enamel matrix. Thus, we conclude that intramembrane proteolysis by SPPL2A is essential for maintaining cellular homeostasis of ameloblasts. Because modulation of SPPL2A activity appears to be an attractive therapeutic target to deplete B cells and treat autoimmunity, interference with tooth enamel formation should be investigated as a possible adverse effect of pharmacological SPPL2A inhibitors in humans.