bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implementation of a physiographic complexity‐based multiresolution snow modeling scheme
Authors: Baldo Elisabeth , Margulis Steven A. 
Published: April 2017

AbstractUsing a uniform model resolution over a domain is not necessarily the optimal approach for simulating hydrologic processes when considering both model error and computational cost. Fine‐resolution simulations at 100 m or less can provide fine‐scale process representation, but can be costly to apply over large domains. On the other hand, coarser spatial resolutions are more computationally inexpensive, but at the expense of fine‐scale model accuracy. Defining a multiresolution (MR) grid spanning from fine resolutions over complex mountainous areas to coarser resolutions over less complex regions can conceivably reduce computational costs, while preserving the accuracy of fine‐resolution simulations on a uniform grid. A MR scheme was developed using a physiographic complexity metric (CM) that combines surface heterogeneity in forested fraction, elevation, slope, and aspect. A data reduction term was defined as a metric (relative to a uniform fine‐resolution grid) related to the available computational resources for a simulation. The focus of the effort was on the snowmelt season where physiographic complexity is known to have a significant signature. MR simulations were run for different data reduction factors to generate melt rate estimates for three representative water years over a test headwater catchment in the Colorado River Basin. The MR approach with data reductions up to 47% led to negligible cumulative snowmelt differences compared to the fine‐resolution baseline case, while tests with data reductions up to 60% showed differences lower than 2%. Large snow‐dominated domains could therefore benefit from a MR approach to be more efficiently simulated while mitigating error.
Time‐dependent velocity‐field controls on anomalous chemical transport in porous media
Authors: Nissan Alon , Dror Ishai , Berkowitz Brian 
Published: April 2017

AbstractTemporal variations in the subsurface velocity field are often (if not always) present in the real world to at least some degree. However, an accounting of their effects on chemical transport has been largely neglected. Here we demonstrate experimentally the effects of a time‐varying velocity field on conservative chemical tracer transport in porous media, as compared to constant velocity conditions. We find that velocity‐field fluctuations increase chemical tracer spreading and residence time, which intensify the anomalous nature of the transport. This behavior is modeled by a continuous time random walk particle tracking method formulated to account for time‐dependent velocity fields. The model matches the experimental results with a parsimonious and consistent set of parameters. The model is then applied to study the effects of different magnitudes in velocity‐field fluctuations, as well as different degrees of porous media heterogeneity, on 1‐D and 2‐D spatiotemporal propagation of an injected, point‐source, chemical plume. Increased intensity of velocity‐field fluctuations, and increased porous medium heterogeneity, each serve to increase the extent of chemical spreading and anomalous behavior.
Picoplankton contribution to biogenic silica stocks and production rates in the Sargasso Sea
Authors: Krause Jeffrey W. , Brzezinski Mark A. , Baines Stephen B. , Collier Jackie L. , Twining Benjamin S. , Ohnemus Daniel C. 
Published: April 2017

AbstractPicocyanobacteria in the Sargasso Sea accumulate significant amounts of Si, a finding which questions how we interpret previous regional measurements of biogenic silica (bSi) production and the role of diatoms in the open ocean. The picoplankton (<3 μm cells) contributed a measurable, and at times significant, proportion of both the total bSi standing stock and its rate of production. The 100 m integrated bSi stock and bSi production rate in the <3 μm size fraction averaged 14% and 16%, respectively, of the total. At some stations, specific rates of bSi production in the <3 μm cells were up to threefold higher than for larger cells. But among all stations and depths, the two size fractions had statistically indistinguishable specific production rates (~0.35 day−1). The estimated contributions of Synechococcus alone to the 100 m integrated bSi stock and bSi production in cells <3 μm were 15% and 55%, respectively, suggesting that half of bSi production in this small size fraction could be sustained by Synechococcus, but a majority of the bSi was not associated with living Synechococcus. Our results suggest that picoplankton have a small but persistent regional contribution to bSi stocks, which is masked by a dynamic bSi pool driven by larger cells. While a significant fraction of bSi production is attributable to picoplankton, their contributions are likely to have been included in previous analyses, making prior regional budgets still relevant. However, our understanding of the factors controlling regional bSi production and our interpretations of particulate matter elemental ratios (e.g., Si:C) may require revision.
Climate impacts of the Atlantic Multidecadal Oscillation simulated in the CMIP5 models: A re‐evaluation based on a revised index
Authors: Lyu Kewei , Yu Jin‐Yi 
Published: April 2017

AbstractThe Atlantic Multidecadal Oscillation (AMO) has pronounced influences on weather and climate across the globe. This study provides a direct comparison of the observed AMO‐related surface temperature and precipitation anomalies to those simulated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. It is found that the model‐simulated AMO‐related features are obscured by the global signal in some key regions if the North Atlantic sea surface temperature (SST) itself is used to represent the AMO as in previous studies. After the global mean SST is removed from the North Atlantic SST, the CMIP5 models show substantially better agreement with the observations in terms of the AMO‐related worldwide impacts, such as the Pacific SST and the rainfall over the United States and India. These results suggest the removal of the global signal or signals originating in other ocean basins is a necessary procedure to uncover the AMO features in climate model simulations.
Close packing effects on clean and dirty snow albedo and associated climatic implications
Authors: He Cenlin , Takano Yoshi , Liou Kuo‐Nan 
Published: April 2017

AbstractPrevious modeling of snow albedo, a key climate feedback parameter, follows the independent scattering approximation (ISA) such that snow grains are considered as a number of separate units with distances longer than wavelengths. Here we develop a new snow albedo model for widely observed close‐packed snow grains internally mixed with black carbon (BC) and demonstrate that albedo simulations match closer to observations. Close packing results in a stronger light absorption for clean and BC‐contaminated snow. Compared with ISA, close packing reduces pure snow albedos by up to ~0.05, whereas it enhances BC‐induced snow albedo reduction and associated surface radiative forcing by up to 15% (20%) for fresh (old) snow, with larger enhancements for stronger structure packing. Finally, our results suggest that BC‐snow albedo forcing and snow albedo feedback (climate sensitivity) are underestimated in previous modeling studies, making snow close packing consideration a necessity in climate modeling and analysis.
Decadal dynamics and predictability of oxygen and subsurface tracers in the California Current System
Authors: Pozo Buil Mercedes , Di Lorenzo Emanuele 
Published: April 2017

AbstractThe oxygen of the source waters that feed the upwelling in the California Current System shows prominent multidecadal fluctuations that are not significantly correlated with the dominant modes of Pacific climate variability. By combining observations and ocean reanalysis products between 1950 and 2010, we show that decadal changes in oxygen are linked to subsurface salinity variability and primarily controlled by ocean circulation dynamics. We find that subsurface anomalies in the core of the North Pacific Current propagate the oxygen signal downstream into the coastal upwelling system following the path of the mean gyre circulation with a time scale of 10 years. These results suggest that decadal variability in the ocean subsurface is a key process for understanding, and potentially predicting, hypoxia and other biogeochemical tracers in upwelling systems. According to the current sign of the subsurface tracer anomalies in the gyre, California may experience a new period of strong decline in oxygen by 2020.
Air‐Sea exchange of biogenic volatile organic compounds and the impact on aerosol particle size distributions
Authors: Kim Michelle J. , Novak Gordon A. , Zoerb Matthew C. , Yang Mingxi , Blomquist Byron W. , Huebert Barry J. , Cappa Christopher D. , Bertram Timothy H. 
Published: April 2017

AbstractWe report simultaneous, underway eddy covariance measurements of the vertical flux of isoprene, total monoterpenes, and dimethyl sulfide (DMS) over the Northern Atlantic Ocean during fall. Mean isoprene and monoterpene sea‐to‐air vertical fluxes were significantly lower than mean DMS fluxes. While rare, intense monoterpene sea‐to‐air fluxes were observed, coincident with elevated monoterpene mixing ratios. A statistically significant correlation between isoprene vertical flux and short wave radiation was not observed, suggesting that photochemical processes in the surface microlayer did not enhance isoprene emissions in this study region. Calculations of secondary organic aerosol production rates (PSOA) for mean isoprene and monoterpene emission rates sampled here indicate that PSOA is on average <0.1 μg m−3 d−1. Despite modest PSOA, low particle number concentrations permit a sizable role for condensational growth of monoterpene oxidation products in altering particle size distributions and the concentration of cloud condensation nuclei during episodic monoterpene emission events from the ocean.
The role of uplift and erosion in the persistence of saline groundwater in the shallow subsurface
Authors: Yager R. M. , McCoy K. J. , Voss C. I. , Sanford W. E. , Winston R. B. 
Published: April 2017

AbstractIn many regions of the world, the shallow (<300 m) subsurface is replenished with meteoric recharge within a few centuries or millennia, but in some regions saline groundwater persists despite abundant rainfall. Analyses of the flushing rate of shallow groundwater usually consider the permeability and recharge rate and a static landscape. The influence of landscape evolution can become important over millions of years, however. Here we present numerical simulations of fluid flow and transport in the top 1 km of a sedimentary foreland basin dominated by aquitards, where the rate of uplift and erosion (20 m Ma−1) balances that of meteoric flushing. Paleozoic age saline groundwater and brine persist at shallow depths that might otherwise have contained potable water. Similar hydrogeologic conditions, and uplift and erosion rates, likely exist in many other regions of the world, where a moving landscape has probably never been considered as an important contributor to groundwater quality.
Slow and fast responses of mean and extreme precipitation to different forcing in CMIP5 simulations
Authors: Sillmann Jana , Stjern Camilla Weum , Myhre Gunnar , Forster Piers M. 
Published: April 2017

AbstractWe are investigating the fast and slow responses of changes in mean and extreme precipitation to different climate forcing mechanisms, such as greenhouse gas and solar forcing, to understand whether rapid adjustments are important for extreme precipitation. To disentangle the effect of rapid adjustment to a given forcing on the overall change in extreme precipitation, we use a linear regression method that has been previously applied to mean precipitation. Equilibrium experiments with preindustrial CO2 concentrations and reduced solar constant were compared with a four times CO2 concentration experiment for 10 state‐of‐the‐art climate models. We find that the two forcing mechanisms, greenhouse gases and solar, impose clearly different rapid adjustment signals in the mean precipitation, while such difference is difficult to discern for extreme precipitation due to large internal variability. In contrast to mean precipitation, changes in extreme precipitation scale with surface temperature trends and do not seem to depend on the forcing mechanism.
On the relationship between the meridional overturning circulation, alongshore wind stress, and United States East Coast sea level in the Community Earth System Model Large Ensemble
Authors: Little Christopher M. , Piecuch Christopher G. , Ponte Rui M. 
Published: April 2017

AbstractBy the late twenty‐first century, climate models project enhanced dynamic sea level (DSL) rise along the western boundary of the North Atlantic associated with a decline in the Atlantic meridional overturning circulation (AMOC). In contrast, coastal DSL variability over the last few decades has been driven largely by local winds, with limited evidence for coupling to AMOC strength. The unclear forcing‐dependence and timescale‐dependence of relationships between local winds, AMOC strength, and DSL obscures: (1) the validity of tide gauge‐derived DSL gradients as a proxy of AMOC strength and (2) the assessment of climate model reliability. Here we analyze these relationships in the Community Earth System Model Large Ensemble (CESM‐LE) over the 1920–2100 period. In CESM‐LE, the amplitude of interannual to multidecadal DSL variability and its along‐coast correlation are comparable to detrended annual mean tide gauge records. A “crossover timescale” of approximately 5–15 years partitions a local wind‐driven coastal DSL regime from an overturning‐related regime. Processes unrelated to either AMOC strength or local winds are important at interannual to decadal timescales. As external forcing increases in strength over the twenty‐first century, DSL variability associated with the overturning circulation becomes dominant. While the largely externally forced, AMOC‐associated, component explains only 29 ± 12% of DSL variance over the 1920–2010 period, it explains 89 ± 3% of the variance in the 2011–2100 period. We discuss the implications of these results on the reliability of climate model projections of regional DSL, the use of coastal DSL as a proxy for AMOC, and the origins of multidecadal DSL variability.
Strongly nonlinear internal solitons: Models and applications
Authors: Ostrovsky L. A. , Irisov V. G. 
Published: April 2017

AbstractA strongly nonlinear evolution equation based on an approximate Hamiltonian is suggested and applied to the description of nonstationary processes of formation and evolution of strong internal solitons and their groups (solibores). Comparison with experimental data shows that such a simplified approach can be effectively applied to the description and prediction of strong internal waves’ evolution in the upper ocean.
Revised transport estimates of the Denmark Strait overflow
Authors: Jochumsen Kerstin , Moritz Martin , Nunes Nuno , Quadfasel Detlef , Larsen Karin M. H. , Hansen Bogi , Valdimarsson Hedinn , Jonsson Steingrimur 
Published: April 2017

AbstractThe major export route of dense water from the Nordic Seas into the North Atlantic is in the deep channel in Denmark Strait. Here currents have been monitored with one or two moored Acoustic Doppler Current Profilers (ADCPs) since 1996. Volume transport estimates of the Denmark Strait Overflow Water (DSOW) so far were based on these data, which were regressed to the total transport of dense water in a numerical model. The resulting transport has been used in many publications. Here we present results from an extended five‐mooring array deployed in 2014/2015, which included measurements outside the swift overflow core. This array provided the basis for new calculations to estimate the DSOW transports. Furthermore, a correction is proposed for biases detected on some ADCPs, which led to earlier underestimation of the flow in the lower part of the plume. Using the new method, the mean DSOW transport is estimated to be 3.2 Sv in the period 1996–2016, without a significant trend. Uncertainties are typically ±0.5 Sv. Beyond variations on the eddy scale, an empirical orthogonal functions (EOF) analysis of the velocity field reveals three dominant modes of variability: the first mode is roughly barotropic and corresponds to pulsations of the plume, the second mode represents the laterally shifting component of the plume's core position, and the third mode indicates the impact of the varying overflow thickness. Finally, DSOW transports are compared to the Faroe Bank Channel overflow transports, but no clear relationship is found.
Dosimetric impacts of endorectal balloon in CyberKnife stereotactic body radiation therapy (SBRT) for early‐stage prostate cancer
Authors: Xiang Hong F. , Lu Hsiao‐Ming , Efstathiou Jason A. , Zietman Anthony L. , De Armas Ricardo , Harris Kathryn , Bloch B. Nicolas , Qureshi Muhammad Mustafa , Keohan Sean , Hirsch Ariel E. 
Published: April 2017

AbstractPurposeIn SBRT for prostate cancer, higher fractional dose to the rectum is a major toxicity concern due to using smaller PTV margin and hypofractionation. We investigate the dosimetric impact on rectum using endorectal balloon (ERB) in prostate SBRT.Materials and MethodsTwenty prostate cancer patients were included in a retrospective study, ten with ERB and 10 without ERB. Optimized SBRT plans were generated on CyberKnife MultiPlan for 5 × 7.25 Gy to PTV under RTOG‐0938 protocol for early‐stage prostate cancer. For the rectum and the anterior half rectum, mean dose and percentage of volumes receiving 50%, 80%, 90%, and 100% prescription dose were compared.ResultsUsing ERB, mean dose to the rectum was 62 cGy (P = 0.001) lower per fraction, and 50 cGy (P = 0.024) lower per fraction for the anterior half rectum. The average V50%, V80%, V90%, and V100% were lower by 9.9% (P = 0.001), 5.3% (P = 0.0002), 3.4% (P = 0.0002), and 1.2% (P = 0.005) for the rectum, and lower by 10.4% (P = 0.009), 8.3% (P = 0.0004), 5.4% (P = 0.0003), and 2.1% (P = 0.003) for the anterior half rectum.ConclusionsSignificant reductions of dose to the rectum using ERB were observed. This may lead to improvement of the rectal toxicity profiles in prostate SBRT.
Gezielte Spaltung von durch direktes Laserschreiben hergestellten Mikrostrukturen
Authors: Zieger Markus M. , Mueller Patrick , Quick Alexander S. , Wegener Martin , Barner‐Kowollik Christopher 
Published: April 2017

AbstractBasierend auf einem neuartigen Photolack wurden 3D‐Mikrostrukturen durch direktes Laserschreiben (DLW) hergestellt, die gezielt und vollständig spaltbar sind. Die Netzwerke bestehen ausschließlich aus reversiblen Bindungen, die unter Bestrahlung eines Phenacylsulfid‐Vernetzers entstehen. In einer radikalfreien Stufenwachstumsreaktion zwischen den sich bildenden reaktiven Thioaldehyden und einer Thiol‐Komponente bilden sich Disulfidbrücken. Die Reaktion wurde in Lösung durch ESI‐MS nachgewiesen. Induziert wird die Spaltung durch einen Thiol‐Disulfidbrücken‐Austausch mit Dithiothreitol, der die geschriebenen Strukturen “löscht”. Die milde Spaltung des Disulfidbrücken‐Netzwerkes ist z. B. orthogonal zu Acrylat‐basierten DLW‐Strukturen. Um diesen Aspekt hervorzuheben, wurden DLW‐Strukturen hergestellt, die reversible Strukturelemente in nicht‐reversible Acrylat‐basierte Standardgerüste integrieren. Im Anschluss wurde die selektive Spaltung gezeigt. Die Erreichbarkeit hoher lateraler Auflösung wurde durch Anfertigen definierter Liniengitter mit Linienabständen bis 300 nm nachgewiesen.
Oxidation‐Initiated Cyclizations of Pentadienyl Ethers: An Alternative Entry to the Nazarov Reaction
Authors: Fradette Ryan J. , Kang Minkyu , West F. G. 
Published: April 2017

AbstractOxidation‐initiated Nazarov reactions of 1,4‐pentadien‐3‐yl ethers take place in the presence of DDQ. Termination by regioselective elimination preserves both stereocenters created during electrocyclization, providing cyclopentanone products bearing an exocyclic methylene unit. Use of catalytic DDQ with MnO2 as terminal oxidant is also described.
Enantioselective Chemo‐ and Biocatalysis: Partners in Retrosynthesis
Authors: Hönig Moritz , Sondermann Philipp , Turner Nicholas J. , Carreira Erick M. 
Published: April 2017

AbstractRecent developments of stereoselective biocatalytic and chemocatalytic methods are discussed. The review provides a guide to the use of biocatalytic methods in the area of chemical synthesis with focused attention on retrosynthetic considerations and analysis. The transformations presented are organized according to bond disconnections and attendant synthetic methods. The review is expected to lead to better understanding of the characteristics and distinctions of the two complementary approaches. It depicts for researchers in bio‐ and chemocatalysis a road map of challenges and opportunities for the evolution (and at times revolution) in chemical synthesis.
An Oxygen‐Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum‐Based Layer for Overall Water Splitting
Authors: Garcia‐Esparza Angel T. , Shinagawa Tatsuya , Ould‐Chikh Samy , Qureshi Muhammad , Peng Xuyuan , Wei Nini , Anjum Dalaver H. , Clo Alain , Weng Tsu‐Chien , Nordlund Dennis , Sokaras Dimosthenis , Kubota Jun , Domen Kazunari , Takanabe Kazuhiro 
Published: April 2017

AbstractFor overall water‐splitting systems, it is essential to establish O2‐insensitive cathodes that allow cogeneration of H2 and O2. An acid‐tolerant electrocatalyst is described, which employs a Mo‐coating on a metal surface to achieve selective H2 evolution in the presence of O2. In operando X‐ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx/Pt/SrTiO3 with inhibited water formation from H2 and O2, which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.