bluuebunny/crossref_metadata_2025_split huggingface dataset:
River‐aquifer interactions in a semiarid environment investigated using point and reach measurements
Authors: McCallum Andrew M. , Andersen Martin S. , Rau Gabriel C. , Larsen Joshua R. , Acworth R. Ian 
Published: March 2014

AbstractA critical hydrological process is the interaction between rivers and aquifers. However, accurately determining this interaction from one method alone is difficult. At a point, the water exchange in the riverbed can be determined using temperature variations over depth. Over the river reach, differential gauging can be used to determine averaged losses or gains. This study combines these two methods and applies them to a 34 km reach of a semiarid river in eastern Australia under highly transient conditions. It is found that high and low river flows translate into high and low riverbed Darcy fluxes, and that these are strongly losing during high flows, and only slightly losing or gaining for low flows. The spatial variability in riverbed Darcy fluxes may be explained by riverbed heterogeneity, with higher variability at greater spatial scales. Although the river‐aquifer gradient is the main driver of riverbed Darcy flux at high flows, considerable uncertainty in both the flux magnitude and direction estimates were found during low flows. The reach‐scale results demonstrate that high‐flow events account for 64% of the reach loss (or 43% if overbank events are excluded) despite occurring only 11% of the time. By examining the relationship between total flow volume, river stage and duration for in‐channel flows, we find the loss ratio (flow loss/total flow) can be greater for smaller flows than larger flows with similar duration. Implications of the study for the modeling and management of connected water resources are also discussed.
Soil organic carbon sequestration in upland soils of northern China under variable fertilizer management and climate change scenarios
Authors: Jiang Guiying , Xu Minggang , He Xinhua , Zhang Wenju , Huang Shaomin , Yang Xueyun , Liu Hua , Peng Chang , Shirato Yasuhito , Iizumi Toshichika , Wang Jinzhou , Murphy Daniel V. 
Published: March 2014

AbstractWe determined the historical change in soil organic carbon (SOC) stocks from long‐term field trials that represent major soil types and climatic conditions of northern China. Soil carbon and general circulation models were validated using these field trial data sets. We then applied these models to predict future change in SOC stocks to 2100 using two net primary production (NPP) scenarios (i.e., current NPP or 1% year−1NPP increase). The conversion rate of plant residues to SOC was higher in single‐cropping sites than in double‐cropping sites. The prediction of future SOC sequestration potential indicated that these soils will be a net source of carbon dioxide (CO2) under no fertilizer inputs. Even when inorganic nutrients were applied, the additional carbon input from increased plant residues could not meet the depletion of SOC in parts of northern China. Manure or straw application could however improve the SOC sequestration potential at all sites. The SOC sequestration potential in northern China was estimated to be −4.3 to 18.2 t C ha−1by 2100. The effect of projected climate change on the annual rate of SOC change did not differ significantly between climate scenarios. The average annual rate of SOC change under current and increased NPP scenarios (at 850 ppm CO2) was approximately 0.136 t C ha−1yr−1in northern China. These findings highlight the need to maintain, and where possible increase, organic carbon inputs into these farming systems which are rapidly becoming inorganic fertilizer intensive.
Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data
Authors: Nam Christine C. W. , Quaas Johannes , Neggers Roel , Siegenthaler‐Le Drian Colombe , Isotta Francesco 
Published: March 2014

AbstractThree different boundary layer cloud models are incorporated into the ECHAM5 general circulation model (GCM) and compared to CloudSat and CALIPSO satellite observations. The first boundary layer model builds upon the standard Tiedtke (1989) parameterization for shallow convection with an adapted convective trigger; the second is a bulk parameterization of the effects of transient shallow cumulus clouds; and lastly the Dual Mass Flux (DMF) scheme adjusted to better represent shallow convection. The three schemes improved (Sub)Tropical oceanic low‐level cloud cover, however, the fraction of low‐level cloud cover remains underestimated compared to CALIPSO observations. The representation of precipitation was improved by all schemes as they reduced the frequency of light intensity events <0.01 mm d−1, which were found to dominate the radar reflectivity histograms as well as be the greatest source of differences between ECHAM5 and CloudSat radar reflectivity histograms. For both lidar and radar diagnostics, the differences amongst the schemes are smaller than the differences compared to observations. While the DMF approach remains experimental, as its top‐of‐atmosphere radiative balance has not been retuned, it shows the most promise in producing nonprecipitating boundary layer clouds. With its internally consistent boundary layer scheme that uses the same bimodal joint distribution with a diffusive and an updraft component for clouds and turbulent transport, the ECHAM5_DMF produces the most realistic boundary layer depth as indicated by the cloud field. In addition, it reduced the frequency of large‐scale precipitation intensities of <0.01 mm d−1 the greatest.
Angular and RMS delay spread modeling in view of THz indoor communication systems
Authors: Priebe Sebastian , Jacob Martin , Kürner Thomas 
Published: March 2014

AbstractFuture wireless communication systems will most likely be operated at carrier frequencies above 300 GHz, where the indoor radio channel behaves entirely differently compared to legacy radio communication frequencies. Being highly relevant for system performance evaluations and channel modeling, the spatial as well as the temporal dispersions are studied for a representative office wireless LAN scenario in this paper. Ray tracing serves as the means for the accurate simulation of the THz radio wave propagation. Simple stochastic models are derived to approximate and reproduce the distance‐dependent behavior of the angular spread as well as of the RMS delay spread. Based on the results, the maximum symbol rates achievable without any intersymbol interference are quantified and can be shown to reach up to several 100 GSymbols/s provided that highly directive antennas are used.
Assessing groundwater policy with coupled economic‐groundwater hydrologic modeling
Authors: Mulligan Kevin B. , Brown Casey , Yang Yi‐Chen E. , Ahlfeld David P. 
Published: March 2014

AbstractThis study explores groundwater management policies and the effect of modeling assumptions on the projected performance of those policies. The study compares an optimal economic allocation for groundwater use subject to streamflow constraints, achieved by a central planner with perfect foresight, with a uniform tax on groundwater use and a uniform quota on groundwater use. The policies are compared with two modeling approaches, the Optimal Control Model (OCM) and the Multi‐Agent System Simulation (MASS). The economic decision models are coupled with a physically based representation of the aquifer using a calibrated MODFLOW groundwater model. The results indicate that uniformly applied policies perform poorly when simulated with more realistic, heterogeneous, myopic, and self‐interested agents. In particular, the effects of the physical heterogeneity of the basin and the agents undercut the perceived benefits of policy instruments assessed with simple, single‐cell groundwater modeling. This study demonstrates the results of coupling realistic hydrogeology and human behavior models to assess groundwater management policies. The Republican River Basin, which overlies a portion of the Ogallala aquifer in the High Plains of the United States, is used as a case study for this analysis.
LiDAR‐derived snowpack data sets from mixed conifer forests across the Western United States
Authors: Harpold A. A. , Guo Q. , Molotch N. , Brooks P. D. , Bales R. , Fernandez‐Diaz J. C. , Musselman K. N. , Swetnam T. L. , Kirchner P. , Meadows M. W. , Flanagan J. , Lucas R. 
Published: March 2014

AbstractAirborne‐based Light Detection and Ranging (LiDAR) offers the potential to measure snow depth and vegetation structure at high spatial resolution over large extents and thereby increase our ability to quantify snow water resources. Here we present airborne LiDAR data products at four Critical Zone Observatories (CZO) in the Western United States: Jemez River Basin, NM, Boulder Creek Watershed, CO, Kings River Experimental Watershed, CA, and Wolverton Basin, CA. We make publicly available snow depth data products (1 m2 resolution) derived from LiDAR with an estimated accuracy of <30 cm compared to limited in situ snow depth observations.
Characterization of groundwater and surface water mixing in a semiconfined karst aquifer using time‐lapse electrical resistivity tomography
Authors: Meyerhoff Steven B. , Maxwell Reed M. , Revil André , Martin Jonathan B. , Karaoulis Marios , Graham Wendy D. 
Published: March 2014

AbstractGroundwater flow in karst includes exchange of water between large fractures, conduits, and the surrounding porous matrix, which impacts both water quality and quantity. Electrical resistivity tomography combined with end‐member mixing analysis (EMMA) and numerical flow and transport modeling was used to study mixing of karst conduit and matrix waters to understand spatial and temporal patterns of mixing during high flow and base flow conditions. To our knowledge, this is the first time EMMA and synthetic geophysical simulations have been combined. Here we interpret an 8 week time‐lapse electrical resistivity data set to assess groundwater‐surface mixing. We simulate flow between the karst conduits and the porous matrix to determine fractions of water recharged to conduits that has mixed with groundwater stored in the pore space of the matrix using a flow and transport model in a synthetic time‐lapse resistivity inversion. Comparing the field and synthetic inversions, our results enable us to estimate exchange dynamics, spatial mixing, and flow conditions. Results showed that mixing occurred at a volumetric flux of 56 m3/d with a dispersivity around 1.69 m during the geophysical experiment. For these conditions, it was determined that conduit water composition ranged from 75% groundwater during base flow conditions to less than 50% groundwater in high flow conditions. Though subject to some uncertainties, the time‐lapse inversion process provides a means to predict changing hydrologic conditions, leading to mixing of surface water and ground water and thus changes to water quantity and quality, as well as potential for water‐rock reactions, in a semiconfined, sink‐rise system.
Carbon storage in mountainous headwater streams: The role of old‐growth forest and logjams
Authors: Beckman Natalie D. , Wohl Ellen 
Published: March 2014

AbstractWe measured wood piece characteristics and particulate organic matter (POM) in stored sediments in 30 channel‐spanning logjams along headwater streams in the Colorado Front Range, USA. Logjams are on streams flowing through old‐growth (>200 years), disturbed (<200 years, natural disturbance), or altered (<200 years, logged) subalpine conifer forest. We examined how channel‐spanning logjams influence riverine carbon storage (measured as the total volatile carbon fraction of stored sediment and instream wood). Details of carbon storage associated with logjams reflect age and disturbance history of the adjacent riparian forest. A majority of the carbon within jams is stored as wood. Wood volume is significantly larger in old‐growth and disturbed reaches than in altered reaches. Carbon storage also differs in relation to forest characteristics. Sediment from old‐growth streams has significantly higher carbon content than altered streams. Volume of carbon stored in jam sediment correlates with jam wood volume in old‐growth and disturbed forests, but not in altered forests. Forest stand age and wood volume within a jam explain 43% of the variation of carbon stored in jam sediment. First‐order estimates of the amount of carbon stored within a stream reach show an order of magnitude difference between disturbed and altered reaches. Our first‐order estimates of reach‐scale riverine carbon storage suggest that the carbon per hectare stored in streams is on the same order of magnitude as the carbon stored as dead biomass in terrestrial subalpine forests of the region. Of particular importance, old‐growth forest correlates with more carbon storage in rivers.
A statistical approach to estimating evapotranspiration from diurnal groundwater level fluctuations
Authors: Wang Ping , Pozdniakov Sergey P. 
Published: March 2014

AbstractOver the last few decades, automatic sensors that record groundwater levels at high‐frequency intervals have become widely used in groundwater monitoring practice. These sensors provide large amounts of data regarding diurnal groundwater fluctuations, which can be treated as stochastic periodic time series. In this study, a simple relationship between the average standard deviation of diurnal groundwater level fluctuations and the daily evapotranspiration over relatively short periods (days or weeks) was developed for estimating groundwater consumption by phreatophytes in arid/semiarid areas. Our approach allows estimating groundwater evapotranspiration (
) using stable statistical characteristics of diurnal groundwater fluctuations, and it is useful for analyzing large amounts of data obtained from digital groundwater level monitoring sensors. A comparison of the
results from a synthetic set of groundwater level fluctuations with predefined values shows that this technique behaves consistently and is robust. A numerical analysis of one‐dimensional saturated‐unsaturated water flow to a root system using Richards' equation indicates that this method provides a reliable estimate of
when the basic assumptions of the White method are met. The method was also applied to two phreatophyte‐dominated riparian sites in New Mexico to demonstrate its usefulness, which provides better results than the commonly used White method.
MaxPHOS Ligand: PH/NH Tautomerism and Rhodium‐ Catalyzed Asymmetric Hydrogenations
Authors: Cristóbal‐Lecina Edgar , Etayo Pablo , Doran Séan , Revés Marc , Martín‐Gago Pablo , Grabulosa Arnald , Costantino Andrea R. , Vidal‐Ferran Anton , Riera Antoni , Verdaguer Xavier 
Published: March 2014

AbstractMaxPHOS is an active and robust P‐stereogenic ligand for asymmetric catalysis. The presence of an NH bridge between the two phosphine moieties allows the NH/PH tautomerism to take place. The neutral ligand, in which the NH form predominates, is an air‐sensitive compound. However, protonation of MaxPHOS leads to the stable PH form of the ligand, in which the overall positive charge is distributed on both P centers. This protonation turns the MaxPHOS⋅HBF4 salt 3 into an air‐stable compound both in the solid state and in solution.	The salt 3 is also a convenient precursor for the preparation of rhodium(I) complexes by direct ligand exchange with the complex [Rh(acac)(cod)]. Finally, the corresponding rhodium(I)‐MaxPHOS complex was tested in the asymmetric hydrogenation of a wide range of substrates. The complex proved to be a highly selective and robust system in these reactions.magnified image
Fine‐Tunable Tris(triazolyl)methane Ligands for Copper(I)‐ Catalyzed Azide–Alkyne Cycloaddition Reactions
Authors: Ozkal Erhan , Llanes Patricia , Bravo Fernando , Ferrali Alessandro , Pericàs Miquel A. 
Published: March 2014

AbstractThe preparation of a small library of modular tris(triazolyl)methane ligands for copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reactions is reported. The synthesis of the first generation ligand, tris(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methanol (1a), suitable for work in aqueous systems, is reported at the 50–100 mmol scale through a one‐stage, environmentally benign procedure. One‐stage procedures for the synthesis of tris(aryltriazolyl)methanol structures (1b, phenyl; 1c, para‐trifluoromethylphenyl; 1d, para‐methoxyphenyl) designed for electronic fine‐tuning of catalytic properties, and of 1a‐derived ethers 2c (OBn) and 2d (OMe), designed for CuAAC reactions in organic solvents, are also reported. The complete set of ligands (1a–d, 2c–d) has been tested in the reaction of phenylacetylene with benzyl azide in six different solvents (water, hexane, toluene, dichloromethane, tetrahydrofuran, and acetonitrile), and this has allowed the identification of 1b, 1c and 2c as the ligands depicting the highest tolerance to changes in solvent polarity within the considered family. The comparative performance of ligands 1b–d and 2c in the cycloaddition of a small family of alkynes with benzyl azide in two very different reaction media (1:1 t‐BuOH/H2O and toluene) has been studied as a guide for catalyst selection in specific applications. The applicability of 1c in CuAAC reactions involving functional substrates in toluene has been explored under thermal and microwave‐accelerated (tandem azide formation plus CuAAC reaction) reaction conditions.magnified image
Asymmetric Synthesis of Substituted Thiolanes through Domino Thia‐Michael–Henry Dynamic Covalent Systemic Resolution using Lipase Catalysis
Authors: Zhang Yan , Vongvilai Pornrapee , Sakulsombat Morakot , Fischer Andreas , Ramström Olof 
Published: March 2014

AbstractDynamic systems based on consecutive thia‐Michael and Henry reactions were generated and transformed using lipase‐catalyzed asymmetric transformation. Substituted thiolane structures with three contiguous stereocenters were resolved in the process in high yields and high enantiomeric excesses.magnified image
Generation of Arylated Quinones by Iron‐Catalyzed Oxidative Arylation of Phenols: Formal Synthesis of Phellodonin, Sarcodonin ε, Leucomelone and Betulinan A
Authors: Deb Arghya , Agasti Soumitra , Saboo Tapish , Maiti Debabrata 
Published: March 2014

AbstractBiologically and pharmaceutically relevant arylated quinones (Quin‐Ar) have been synthesized via direct CH arylation of a variety of phenols using arylboronic acids. An inexpensive, environmentally friendly iron catalyst, ferric sulphate, Fe2(SO4)3, was employed in this operationally simple and efficient method.magnified image
Unprecedented Control of Selectivity in Nickel‐Catalyzed Hydrophosphorylation of Alkynes: Efficient Route to Mono‐ and Bisphosphonates
Authors: Khemchyan Levon L. , Ivanova Julia V. , Zalesskiy Sergey S. , Ananikov Valentine P. , Beletskaya Irina P. , Starikova Zoya A. 
Published: March 2014

AbstractA unique nickel‐based catalytic system was developed where the direction of the hydrophosphorylation reaction can be controlled by varying the catalyst loading. A flexible one‐pot access to vinylmonophosphonates and alkylbisphosphonates was demonstrated using simple starting materials in an atom‐economic reaction without any specific solvents or ligands. Monitoring of the reaction mechanism with joint NMR and MS studies revealed key information about the reaction intermediates. The synthetic scope of the developed catalytic system was explored and the utility of the synthesized products for the fire protection of cotton materials was demonstrated.magnified image
Symptom perception in healthy menopausal women: Can we predict concordance between subjective and physiological measures of vasomotor symptoms?
Authors: Stefanopoulou Evgenia , Hunter Myra S. 
Published: March 2014

ObjectivesPerception of physical symptoms is an important factor in medical help‐seeking. We aimed to examine both physiological and subjective measures of a commonly reported physical symptom—vasomotor symptoms (hot flushes and night sweats; HF/NS), and to investigate factors that might influence symptom perception, that is, concordance, over‐reporting, and under‐reporting of symptoms in healthy menopausal women.MethodsOne hundred and forty women completed questionnaires assessing depressed mood, anxiety, stress, somatic symptoms, beliefs about HF/NS, and somatic amplification. Subjective and objective (24‐h sternal skin conductance) measurements of HF/NS were obtained to assess concordance.ResultsThirty‐seven percent of HF/NS were concordant while 47 and 16 % were under‐reported and over‐reported, respectively. Depressed mood, anxiety, somatic symptoms, and negative beliefs about HF/NS were associated with (higher) concordance, (less) under‐, or (more) over‐reporting. Negative beliefs about night sweats and sleep were the strongest predictors of concordance, whereas additional somatic symptoms and smoking predicted over‐reporting.ConclusionsJust over one third of physiologically recorded HF/NS were perceived as hot flushes; under‐reporting of symptoms was more common than over‐reporting. Interestingly, women who were more accurate in detecting physiological HF/NS tended to report more psychological and somatic symptoms and negative beliefs about HF/NS. Both measures should be included as outcomes of clinical trials. Am. J. Hum. Biol. 26:389–394, 2014. © 2014 Wiley Periodicals, Inc.
Analyse von Protease‐Inhibitor‐Interaktionen unter Nutzung evolvierbarer tricyclischer Microviridine
Authors: Weiz Annika R. , Ishida Keishi , Quitterer Felix , Meyer Sabine , Kehr Jan‐Christoph , Müller Kristian M. , Groll Michael , Hertweck Christian , Dittmann Elke 
Published: March 2014

AbstractEin wichtiges Ziel in der therapeutischen Chemie ist das Verständnis und die Kontrolle von proteolytischen Prozessen. Unter den proteaseinhibierenden Naturstoffen nehmen Microviridine eine Sonderstellung ein. Microviridine sind ribosomal erzeugte und posttranslational modifizierte Peptide, die zu einer einzigartigen Struktur mit käfigartiger Gestalt prozessiert werden. Hier beschreiben wir einen kombinierten Ansatz aus rationaler und randomisierter Mutagenese, der grundlegende Erkenntnisse über die Bestandteile der Microviridinstruktur liefert, die zur Selektivität beitragen. Die aktive Variante Microviridin J wurde mit Trypsin kokristallisiert. Dabei wird erstmals die dreidimensionale Struktur von Microviridinen demonstriert und die Art der Inhibierung dargestellt.
Construction of Mesoporous Frameworks with Vanadoborate Clusters
Authors: Chen Hong , Yu Zheng‐Bao , Bacsik Zoltán , Zhao Huishuang , Yao Qingxia , Sun Junliang 
Published: March 2014

AbstractA new porous vanadoborate was synthesized by employing the scale chemistry theory with the vanadoborate cluster V10B28. The twofold interpenetrated lvt network was assembled with zinc‐containing elliptical vanadoborate clusters and Zn polyhedra. The single lvt framework contains a three‐dimensional 38×38×20 ring channel system with the pore size (24.7×12.7 Å) reaching the mesoscale, thus indicating the possibility of constructing 3D ordered mesopores with vanadoborate clusters. The porosity of the SUT‐7 structure was confirmed by CO2 adsorption of the as‐synthesized materials.