bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uncertainty in index flood modelling due to calibration data sizes
Authors: Wan Jaafar Wan Zurina , Han Dawei 
Published: April 2011

AbstractRegional frequency analysis is an important tool in estimating design flood for ungauged catchments. Index flood is an important component in regionalized flood formulas. In the past, many formulas have been developed based on various numbers of calibration catchments (e.g. from less than 20 to several hundred). However, there is a lack of systematic research on the model uncertainties caused by the number of calibration catchments (i.e. what is the minimum number of calibration catchment? and how should we choose the calibration catchments?). This study uses the statistical resampling technique to explore the impact of calibration catchment numbers on the index flood estimation. The study is based on 182 catchments in England and an index flood formula has been developed using the input variable selection technique in the data mining field. The formula has been used to explore the model uncertainty due to a range of calibration catchment numbers (from 15 to 130). It is found that (1) as expected, the more catchments are used in the calibration, the more reliable of the models developed are (i.e. with a narrower band of uncertainty); (2) however, poor models are still possible with a large number of calibration catchments (e.g. 130). In contrast, good models with a small number of calibration catchments are also achievable (with as low as 15 calibration catchments). This indicates that the number of calibration catchments is only one of the factors influencing the model performance. The hydrological community should explore why a smaller calibration data set could produce a better model than a large calibration data set. It is clear from this study that the information content in the calibration data set is equally if not more important than the number of calibration data. Copyright © 2011 John Wiley & Sons, Ltd.
Evapotranspiration and crop coefficient for a temperate desert steppe ecosystem using eddy covariance in Inner Mongolia, China
Authors: Zhang Feng , Zhou Guangsheng , Wang Yu , Yang Fulin , Nilsson Christer 
Published: April 2011

AbstractEvapotranspiration (ET), which links water, energy and the carbon cycle in terrestrial ecosystems, is an important eco‐hydrological process, especially in arid and semi‐arid regions. To determine the crop coefficient (Kc) over a 2‐year period for a temperate desert steppe in Inner Mongolia, China, ET was measured using the eddy covariance method and the reference evapotranspiration (ET0) was estimated from site meteorological data. The results showed that the seasonal variation of ET differed on an annual timescale between the 2 consecutive years, exhibiting a multi‐peak curve in 2008 and a single peak in 2009. The mean daily Kc values were 0·15 and 0·17 in 2 years, varying from 0·009 to 0·75 in 2008 and from 0·005 to 0·58 in 2009. The 5‐day moving average for Kc values was mainly affected by SWC10cm and Rn, and the regression coefficients (R2) were 58·9 and 69·5%, respectively. These results will aid in making accurate and quantitative assessments of the vulnerability of the sparse vegetation to climate change. Copyright © 2011 John Wiley & Sons, Ltd.
Linking metrics of hydrological function and transit times to landscape controls in a heterogeneous mesoscale catchment
Authors: Capell R. , Tetzlaff D. , Hartley A. J. , Soulsby C. 
Published: April 2011

AbstractLong‐term river flow data and one year of isotopic tracer data in a nested 749 km2 catchment were analysed conjunctively to evaluate the relationships between hydrometric statistics, transit times, and catchment characteristics. The catchment comprised two distinct geomorphic provinces; upland headwaters draining glaciated landscapes underlain by crystalline geology and lowland headwaters draining a major regional sandstone aquifer. In the uplands, flow regimes were ‘flashy’ with high runoff coefficients for storm hydrographs, steep recession curves and strong nonlinearity in event responses. In the lowlands, runoff coefficients were low, recessions less steep, and event responses more linear. Flow data from the catchment outfall showing damping of these extremes, but was most strongly influenced by the upland headwaters where precipitation was highest. The damping of variability in stable water isotopes between precipitation inputs and streamflow outputs reflected this; with upland tributaries least damped and lowland tributaries most damped. Attempts to quantify the mean transit times of the sampling points met with mixed success; partly reflecting the short run (1 year) of data, but mainly as a result of the marked damping in lowland sites. As a consequence, MTT estimates can only be said to be in the order of a few years in upland sites, but are probably decadal or greater in lowland tributaries. Again, the catchment outfall averages these extremes, but is more similar to the upland headwaters. Despite the difficulties in quantifying MTTs, it is clear that they, like the hydrological response, primarily reflect the dominant control of catchment soil cover, which in turn is determined by geology and glacial history. Copyright © 2011 John Wiley & Sons, Ltd.
Spatial distribution and temporal variation of reference evapotranspiration in arid and semi‐arid regions of Iran
Authors: Tabari Hossein , Aeini Ali , Talaee P. Hosseinzadeh , Some'e B. Shifteh 
Published: April 2011

AbstractAnalysis of spatial and temporal variations of reference evapotranspiration (ETo) is important in arid and semi‐arid regions where water resources are limited. The main aim of this study was to analyse the spatial distribution and the annual, seasonal and monthly trends of the Penman–Monteith ETo for 21 stations in the arid and semi‐arid regions of Iran. Three statistical tests the Mann‐Kendall, Sen's slope estimator and linear regression were used for the analysis. The analysis revealed that ETo increased from January to July and deceased from July to December at almost all stations. Additionally, higher annual ETo values were found in the southeast of the study region and lower values in the northwest of the region. Although the results showed both positive and negative trends in annual ETo series, ETo generally increased, significantly so in six (∼30%) of the stations. Analysis of the impacts of meteorological variables on the temporal trends of ETo indicated that the increasing trend of ETo was most likely due to a significant increase in minimum air temperature, while decreasing trend of ETo was mainly caused by a significant decrease in wind speed. At the sites where increasing ETo trends were statistically significant, the rate of increase varied from (+)8·36 mm/year at Mashhad station to (+)31·68 mm/year at Iranshahr station. On average, an increasing trend of (+)4·42 mm/year was obtained for the whole study area during the last four decades. Seasonal and monthly ETo have also tended to increase at the majority of the stations. The greatest numbers of significant trends were observed in winter on the seasonal time‐scale and in September on the monthly time‐scale. Copyright © 2011 John Wiley & Sons, Ltd.
Variations in water and CO2 fluxes over a saline desert in western China
Authors: Liu Ran , Li Yan , Wang Qin‐Xue 
Published: April 2011

AbstractWe studied the variations in water and carbon dioxide fluxes of a saline desert in western China using the eddy covariance technique. In addition, bare‐soil evaporation was measured using the micro‐lysimeter method. The following three inquiries were made: (1) the magnitude of evapotranspiration (ET) and net ecosystem carbon exchange (NEE) and how these components vary seasonally; (2) how NEE and ET vary following rain pulses of different magnitudes; and (3) how ET divides into evaporation and transpiration and its relationship to carbon dioxide exchange. The saline desert acted as a net C sink of − 49 g C m−2 year−1, with a gross ecosystem productivity (GEP) of 345 g C m−2 year−1 and an ecosystem respiration (Reco) of 296 g C m−2 year−1. Rainfall pulses exerted strong control over ecosystem‐scale water and CO2 fluxes. There was a 1 to 2 days lag in maximal ET despite the magnitude of rainfall pulses, while NEE took 4–5 days to reach its peak if the rainfall was large enough to increase the photosynthetic activity of vascular plants. Overall, the ratio of total transpiration to ET was 38%, but it was about 92% during the months when the vascular plants were active. The NEE was increasingly more negative as the growing season progressed, indicating a greater net uptake of CO2 and a greater water use efficiency. Copyright © 2011 John Wiley & Sons, Ltd.
Characteristics of δ13CDIC in lakes on the Tibetan Plateau and its implications for the carbon cycle
Authors: Lei Yanbin , Yao Tandong , Sheng Yongwei , Zhang Enlou , Wang Weicai , Li Junli 
Published: April 2011

AbstractDissolved inorganic carbon isotope (δ13CDIC) is an important tool to reveal the carbon cycle in lake systems. However, there are only few studies focusing on the spatial variation of δ13CDIC of closed lakes. Here we analyze the characteristics of δ13CDIC of 24 sampled lakes (mainly closed lakes) across the Qiangtang Plateau (QTP) and identify the driving factors for its spatial variation. The δ13CDIC value of these observed lakes varies in the range of − 15·0 to 3·2‰, with an average value of − 1·2‰. The δ13CDIC value of closed lakes is close to the atmospheric isotopic equilibrium value, much higher than that in rivers and freshwater lakes reported before. The high δ13CDIC value of closed lakes is mainly attributed to the significant contribution of carbonate weathering in the catchment and the evasion of dissolved CO2 induced by the strong evaporation of lake water. The δ13CDIC value of closed lakes has a logarithmic correlation with water chemistry (TDS, DIC and pCO2), also suggesting that the evapo‐concentration of lake water can influence the δ13CDIC value. The δ13CDIC value shows two opposite logarithmic correlations with lake size depending on the δ13CDIC range. This study suggests that the δ13C in carbonates in lacustrine sediments can be taken as an indicator of lake volume variation in closed lakes on QTP. Copyright © 2011 John Wiley & Sons, Ltd.
In situ quantification of spatial and temporal variability of hyporheic exchange in static and mobile gravel‐bed rivers
Authors: Rosenberry Donald O. , Klos P. Zion , Neal Andrew 
Published: April 2011

AbstractSeepage meters modified for use in flowing water were used to directly measure rates of exchange between surface and subsurface water in a gravel‐ and cobble bed river in western Pennsylvania, USA (Allegheny River, Qmean = 190 m3/s) and a sand‐ and gravel‐bed river in Colorado, USA (South Platte River, Qmean = 9·7 m3/s). Study reaches at the Allegheny River were located downstream from a dam. The bed was stable with moss, algae, and river grass present in many locations. Median seepage was + 0·28 m/d and seepage was highly variable among measurement locations. Upward and downward seepage greatly exceeded the median seepage rate, ranging from + 2·26 (upward) to − 3·76 (downward) m/d. At the South Platte River site, substantial local‐scale bed topography as well as mobile bedforms resulted in spatial and temporal variability in seepage greatly in exceedence of the median groundwater discharge rate of 0·24 m/d. Both upward and downward seepage were recorded along every transect across the river with rates ranging from + 2·37 to − 3·40 m/d. Despite a stable bed, which commonly facilitates clogging by fine‐grained or organic sediments, seepage rates at the Allegheny River were not reduced relative to those at the South Platte River. Seepage rate and direction depended primarily on measurement position relative to local‐ and meso‐scale bed topography at both rivers. Hydraulic gradients were small at nearly all seepage‐measurement locations and commonly were not a good indicator of seepage rate or direction. Therefore, measuring hydraulic gradient and hydraulic conductivity at in‐stream piezometers may be misleading if used to determine seepage flux across the sediment‐water interface. Such a method assumes that flow between the well screen and sediment‐water interface is vertical, which appears to be a poor assumption in coarse‐grained hyporheic settings. Copyright © 2011 John Wiley & Sons, Ltd.
Modelling of groundwater flow in heterogeneous porous media by finite element method
Authors: Smaoui Hassan , Zouhri Lahcen , Ouahsine Abdellatif , Carlier Erick 
Published: April 2011

AbstractThe HySuf‐FEM code (Hydrodynamic of Subsurface Flow by Finite Element Method) is proposed in this article in order to estimate the spatial variability of the transmissivity values of the Berrechid aquifer (Morocco).The calibration of the model is based on the hydraulic head, hydraulic conductivity and recharge. Three numerical tests are used to validate the model and verify its convergence. The first test case consists in using the steady analytical solution of the Poisson equation. In the second, the model has been compared with the hydrogeological system which is characterized by an unconfined monolayer (isotropic layer) and computed by using PMWIN‐MODFLOW software. The third test case is based on the comparison between the results of HySuf‐FEM and the multiple cell balance method in the aquifer system with natural boundaries case.Good agreement between the Hydrodynamic of Subsurface Flow, the numerical tests and the spatial distribution of the thickening of the hydrogeological system is deduced from the analysis and the interpretations of hydrogeological wells. Copyright © 2011 John Wiley & Sons, Ltd.
Influences of watershed landscape composition and configuration on lake‐water quality in the Yangtze River basin of China
Authors: Liu Wenzhi , Zhang Quanfa , Liu Guihua 
Published: April 2011

AbstractLake‐water quality is highly dependent on the landscape characteristics in its respective watershed. In this study, we investigated the relationships between lake‐water quality and landscape composition and configuration within the watershed in the Yangtze River basin of China. Water quality variables, including pH, electrical conductivity (EC), dissolved oxygen (DO), Secchi depth (SD), NO2−, NO3−, NH4+, TN, TP, chemical oxygen demand (CODMn), chlorophyll‐a (Chl‐a), and trophic state index (TSI), were collected from 16 lakes during the period of 2001–2003. Landscape composition (i.e. the percentage of vegetation, agriculture, water, urban, and bare land) and landscape configuration metrics, including number of patches (NP), patch density (PD), largest patch index (LPI), edge density (ED), mean patch area (MPA), mean shape index (MSI), contagion (CONTAG), patch cohesion index (COHESION), Shannon's diversity index (SHDI), and aggregation index (AI), were calculated for each lake's watershed. Results revealed that the percentage of agriculture was negatively related to NO2−, TN, TP, Chl‐a concentrations, and TSI, while the percentage of urban was significantly correlated with EC, NH4+, and CODMn concentrations. Among landscape‐level configuration metrics, only ED showed significant relationships with TN, TP concentrations, and TSI. However, at the class level, the PD, LPI, ED, and AI of agriculture and urban land uses were significantly correlated with two or more water quality variables. This study suggests that, for a given total area, large and clustered agricultural or urban patches in the watershed may have a greater impact on lake‐water quality than small and scattered ones. Copyright © 2011 John Wiley & Sons, Ltd.
Influence of drought and total phosphorus on diel pH in wadeable streams: Implications for ecological risk assessment of ionizable contaminants
Authors: Valenti Theodore W , Taylor Jason M , Back Jeffrey A , King Ryan S , Brooks Bryan W 
Published: April 2011

Abstract
Climatological influences on site-specific ecohydrology are particularly germane in semiarid regions where instream flows are strongly influenced by effluent discharges. Because many traditional and emerging aquatic contaminants, such as pharmaceuticals, are ionizable, we examined diel surface water pH patterns (i.e., change in pH over a 24-h period) at 23 wadeable streams in central Texas, USA, representing a gradient of nutrient enrichment during consecutive summers of 2006 and 2007. The years of our study were characterized by decidedly different instream flows, which likely affected production:respiration dynamics and led to distinctions in diel pH patterns between 2006 and 2007. Site-specific ambient water quality criteria for NH3 and the aquatic toxicity of the model weak base pharmaceutical sertraline were predicted using continuous water quality monitoring data from the sites. Drought conditions of 2006 significantly increased (p &lt; 0.05) diel pH changes compared to high instream flows of 2007,and the magnitude of diel pH variability was most pronounced at nutrient-enriched sites in 2006. Differences in diel pH change patterns between 2006 and 2007 affected predictions of the environmental fate and effects for model weak base pharmaceuticals and NH3. Overall, site-specific diel pH was more variable at some sites than the difference in mean surface water pH between the 2 summers. Diel pH variability affected regulatory criteria, because 20% of the study sites in 2006 experienced greater than 5-fold differences in National Ambient Water Quality Criteria for NH3 over 24-h periods. Our study emphasizes the potential uncertainty that diel pH variability may introduce in site-specific assessments and provides recommendations for environmental assessment of ionizable contaminants. Integr Environ Assess Manag 2011;7:636–647. © 2011 SETAC
Risk aversion, intertemporal substitution, and the term structure of interest rates
Authors: Garcia René , Luger Richard 
Published: April 2011

SUMMARYWe build and estimate an equilibrium model of the term structure of interest rates based on a recursive utility specification. We contrast it with an arbitrage‐free model, where prices of risk are estimated freely without preference constraints. In both models, nominal bond yields are affine functions of macroeconomic state variables. The equilibrium model accounts for the tent‐shaped pattern and magnitude of coefficients from predictive regressions of excess bond returns on forward rates and the hump‐shaped pattern in the term structure of volatilities, while the reduced‐form no‐arbitrage model does not account for these important features of the yield curve. Copyright © 2011 John Wiley & Sons, Ltd.
Prophylactic role of D‐saccharic acid‐1,4‐lactone in tertiary butyl hydroperoxide induced cytotoxicity and cell death of murine hepatocytes via mitochondria‐dependent pathways
Authors: Bhattacharya Semantee , Chatterjee Srabasti , Manna Prasenjit , Das Joydeep , Ghosh Jyotirmoy , Gachhui Ratan , Sil Parames C. 
Published: April 2011

AbstractD‐Saccharic acid 1,4‐lactone (DSL) is a derivative of D‐glucaric acid. It is a beta‐glucuronidase inhibitor and possesses anticarcinogenic, detoxifying, and antioxidant properties. In the present study, the protective effects of DSL were investigated against tertiary butyl hydroperoxide (TBHP) induced cytotoxicity and cell death in vitro using murine hepatocytes. Exposure of TBHP caused a reduction in cell viability, enhanced the membrane leakage, and disturbed the intracellular antioxidant machineries in murine hepatocytes. Investigating the signaling mechanism of TBHP‐induced cellular pathophysiology and protective action of DSL, we found that TBHP exposure disrupted mitochondrial membrane potential, facilitated cytochrome c release in the cytosol, and led to apoptotic cell death via mitochondria‐dependent pathways. DSL counteracted these changes and maintained normalcy in hepatocytes. Combining, results suggest that DSL possesses the ability to ameliorate TBHP‐induced oxidative insult, cytotoxicity, and apoptotic cell death probably due to its antioxidant activity and functioning via mitochondria‐dependent pathways. © 2011 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:341–354 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20393
Parameterization of Org27569: An allosteric modulator of the cannabinoid CB1G protein‐coupled receptor
Authors: Iliff Hadley A. , Lynch Diane L. , Kotsikorou Evangelia , Reggio Patricia H. 
Published: April 2011

AbstractThe cannabinoid CB1receptor is a class A G protein‐coupled receptor (GPCR) that is the most widely expressed GPCR in the brain. Many GPCRs contain allosteric binding sites for endogenous and/or synthetic ligands, which are topographically distinct from the agonist‐binding site that is known as the orthosteric site. While both endogenous and synthetic ligands that act at the CB1orthosteric site have been known for some time, compounds that act at a CB1allosteric site have only recently been discovered. The most studied of these is 5‐chloro‐3‐ethyl‐1H‐indole‐2‐carboxylic acid [2‐(4‐piperidin‐1‐ylphenyl)ethyl]amide (Org27569). Because allosteric ligands are thought to act through conformational changes in the receptor that are transmitted from the allosteric to the orthosteric site, computational studies of the structural and dynamic interactions of Org27569 with the CB1receptor are crucial to achieve a molecular level understanding of the basis of action of this important new class of compounds. To date, such computational studies have not been possible due to the lack of a complete set of molecular mechanics force field parameters for Org27569. Here, we present the development of missing CHARMM force field parameters for Org27569 using previously published methods and the validation and application of these new parameters using normal mode analysis and molecular dynamics simulations combined with experimental infrared measurements. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
Empirical prediction of protein pKavalues with residue mutation
Authors: Burger Steven K. , Ayers Paul W. 
Published: April 2011

AbstractA fast, empirical method, Mut‐pKa, is presented for predicting the pKa values of ionizable residues in proteins based on mutation. The method compares the effect of mutating each residue that may act as a hydrogen bond donor or acceptor for the ionizable residue. The energetic effect of each type of mutation, along with a desolvation measure and the overall background charge, is fit against pKa data for histidine and carboxyl residues. A total of 214 residues from 35 different proteins were used in the dataset. Using 11 parameters for each type of ionizable residue, a root mean squared error (RMSE) of 0.78 and 1.12 pH units were obtained for carboxyl and histidines residues, respectively, using leave one out cross validation (LOOCV). The results were particularly promising for buried residues, which had RMSE values of 0.99 and 1.13 for carboxyl and histidine residues, respectively. A number of desolvation measures were tested. The simplest measure, the number of atoms surrounding the residue, was found to work best. The effect of using dynamics was also studied using short molecular dynamics runs, followed by minimization of the structures. Mut‐pKa has significantly fewer parameters than, but similar performance to, other empirical methods. Because of this and the LOOCV results, we believe the model is robust and that overfitting is not a problem. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011