bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental study of the response of a gravel streambed to increased sediment supply
Authors: Podolak Charles Joseph Pena , Wilcock Peter R. 
Published: July 2013

ABSTRACTIf increased sediment supply to a river channel exceeds its transport capacity, deposition necessarily occurs as the bed adjusts to accommodate the increased supply. Both the mean and spatial patterns in bed elevation and grain size may change and an ability to understand their relative importance is needed to predict bed response. We report on an experiment in a field‐scale flume in which sediment supply is increased to a gravel bed with alternate bars. Sediment was recirculated in the experiments, but augmented in two steps, after which the bed was allowed to reach a new steady state. The transport rate at the end of the experiment was three times larger than at the start. High‐resolution sediment flux and topographic measurements, grain size derived from photographs, and hydrodynamic modeling allow us to document the topographic and textural response of the bed to increased sediment supply. The spatial patterns of bed topography and texture were forced by the flume setup and the initial and final steady states included long stationary alternate bars with associated grain size sorting. The transient bed contained several scales of shorter wavelength migrating bedforms superimposed on, and temporarily replacing the stationary alternate bars. Bed topography and textural patterns adjusted to increased sediment supply over different timescales. Bed slope and mean stress increased directly with sediment supply rate to produce a new transport steady state in a time about 2.5 times the minimum needed to deposit the required sediment wedge, indicating a trap efficiency of about 40% for the aggrading wedge. Adjustments in local topography and sorting, primarily in the form of smaller, migrating bars, continued for a period approximately equal to that required to initially reach transport steady state. Copyright © 2013 John Wiley & Sons, Ltd.
Forecasting Simultaneously High‐Dimensional Time Series: A Robust Model‐Based Clustering Approach
Authors: Wang Yongning , Tsay Ruey S. , Ledolter Johannes , Shrestha Keshab M. 
Published: July 2013

ABSTRACTThis paper considers the problem of forecasting high‐dimensional time series. It employs a robust clustering approach to perform classification of the component series. Each series within a cluster is assumed to follow the same model and the data are then pooled for estimation. The classification is model‐based and robust to outlier contamination. The robustness is achieved by using the intrinsic mode functions of the Hilbert–Huang transform at lower frequencies. These functions are found to be robust to outlier contamination. The paper also compares out‐of‐sample forecast performance of the proposed method with several methods available in the literature. The other forecasting methods considered include vector autoregressive models with ∕ without LASSO, group LASSO, principal component regression, and partial least squares. The proposed method is found to perform well in out‐of‐sample forecasting of the monthly unemployment rates of 50 US states. Copyright © 2013 John Wiley & Sons, Ltd.
Forecasting Volatility with Many Predictors
Authors: Ke Tsung‐Han , Hu Yu‐Pin 
Published: July 2013

ABSTRACTThis study investigates the forecasting performance of the GARCH(1,1) model by adding an effective covariate. Based on the assumption that many volatility predictors are available to help forecast the volatility of a target variable, this study shows how to construct a covariate from these predictors and plug it into the GARCH(1,1) model. This study presents a method of building a covariate such that the covariate contains the maximum possible amount of predictor information of the predictors for forecasting volatility. The loading of the covariate constructed by the proposed method is simply the eigenvector of a matrix. The proposed method enjoys the advantages of easy implementation and interpretation. Simulations and empirical analysis verify that the proposed method performs better than other methods for forecasting the volatility, and the results are quite robust to model misspecification. Specifically, the proposed method reduces the mean square error of the GARCH(1,1) model by 30% for forecasting the volatility of S&P 500 Index. The proposed method is also useful in improving the volatility forecasting of several GARCH‐family models and for forecasting the value‐at‐risk. Copyright © 2013 John Wiley & Sons, Ltd.
Advances in Metal Supported Cells in the METSOFC EU Consortium
Authors: McKenna B. J. , Christiansen N. , Schauperl R. , Prenninger P. , Nielsen J. , Blennow P. , Klemensø T. , Ramousse S. , Kromp A. , Weber A. 
Published: July 2013

AbstractThe EU‐sponsored project “METSOFC”, completed at the end of 2011, resulted in a number of advancements toward implementing a mechanically robust metal support as the structural element in SOFC. Technical University of Denmark (DTU) Energy Conversion's research into planar metal supported cells (MSCs) has produced an advanced cell design with high performance and mechanical robustness. At low operation temperatures (650 °C), these cells have shown low Area‐specific resistances (ASRs): 0.35 Ω cm2 in cell tests (16 cm2 active area) and under 0.3 Ω cm2 in button cells (0.5 cm2 active area). Further success was attained with even larger cell areas of 12 × 12 cm2 squares, which facilitated integration into small stacks at Topsoe Fuel Cell having powers approaching 1/2 kW. Development of MSC stacks showed that the MSCs could achieve similar or better performance, compared to most standard industrial anode supported ceramic cells. The best stacked MSCs had power densities approaching 275 mW cm–2 (at 680 °C and 0.8 V). Furthermore, extended testing at AVL determined extra stack performance and reliability characteristics, including behavior toward sulfur and simulated diesel reformate, and tolerance to thermal cycles and load cycles. These and other key outcomes of the METSOFC consortium are covered, along with associated work supported by the Danish National Advanced Technology Foundation.
SOFC System Design Using Ideal Efficiency Modeling – Model and Experimental Implementation
Authors: Heddrich M. P. , Jahn M. , Michaelis A. , Näke R. , Weder A. 
Published: July 2013

AbstractA simple thermodynamic system model for the analysis and evaluation of possible SOFC system concepts with regard to reachable electric efficiency is presented. All reforming concepts, various available fuels and anode off‐gas recirculation are included in the model. Furthermore, the model allows the characterization of the reforming conditions necessary to reach the calculated and desired electric efficiencies by the use of two dimensionless energy flow ratios, which are introduced. It is presented how to quickly assess system concepts and identify system concepts that are particularly interesting due to a simple process, high electric efficiency, or preferably a combination of those. Within the experimental section, the model is used to support the system design process of a biogas‐driven SOFC system with partial oxidation as reforming concept, without anode off‐gas recirculation. Since adjustable operating parameters are input into the model, the parameters' influence on efficiency and reforming conditions can be analyzed. With the model real system effects are investigated making it possible to reach a maximum gross electric efficiency of 0.55 with the real designed system.
Degradation Mechanism of Anode‐Supported Solid Oxide Fuel Cell In Planar‐Cell Channel‐Type Setup
Authors: Lim H.‐T. , Hwang S. C. , Jung M. G. , Park H. W. , Park M. Y. , Lee S.‐S. , Jung Y.‐G. 
Published: July 2013

AbstractThe degradation mechanism of anode‐supported planar solid oxide fuel cells is investigated in the present work. We fabricate a large‐area (10 cm × 10 cm) cell and carry out a long‐term test with the assembly components. A constant current of ∼0.4 A cm–2 is applied to the cell for ∼3,100 h, and the furnace temperature is controlled in the sequence 750–800–750 °C to investigate the effect of operating temperature and thermal cycling on the degradation rate. Impedance spectra and current–voltage characteristics are measured during the operation in order to trace any increase in Ohmic and non‐Ohmic resistance as a function of time. The degradation rate is rapid during the operation at the higher temperature of ∼800 °C compared to that during the operation at ∼750 °C. Even after cooling down to ∼750 °C, that rate is still accelerated. The main contribution to the cell degradation is from an increase in the Ohmic resistance. Postmaterial analyses indicate that the cathode is delaminated at the electrolyte/cathode interface, which is attributed to the difference in thermal expansion coefficient (TEC). Thus, the present results emphasize the importance of matching the TEC between cell layers, especially under severe operating conditions such as long duration and complex thermal cycling.
Soil organic carbon sequestration potential of cropland in China
Authors: Qin Zhangcai , Huang Yao , Zhuang Qianlai 
Published: July 2013

AbstractSoil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance and to agricultural productivity, but it is highly sensitive to human activities such as irrigation and crop rotation. It has been observed that under certain improved management practices, cropland soils can sequestrate additional C beyond their existing SOC level before reaching the C saturation state. Here we use data from worldwide, long‐term agricultural experiments to develop two statistical models to determine the saturated SOC level (SOCS) in upland and paddy agroecosystems, respectively. We then use the models to estimate SOC sequestration potential (SOCP) in Chinese croplands. SOCP is the difference between SOCS and existing SOC level (SOCE). We find that the models for both the upland and paddy agroecosystems can reproduce the observed SOCS data from long‐term experiments. The SOCE and SOCS stock in Chinese upland and paddy croplands (0–30 cm soil) are estimated to be 5.2 and 7.9 Pg C with national average densities of 37.4 and 56.8 Mg C ha−1, respectively. As a result, the total SOC sequestration potential is estimated to be 2.7 Pg C or 19.4 Mg C ha−1 in Chinese cropland. Paddy has a relatively higher SOCE (45.4 Mg C ha−1) than upland (34.7 Mg C ha−1) and also a greater SOCP at 26.1 Mg C ha−1 compared with 17.2 Mg C ha−1 in the upland. The SOC varies dramatically among different regions. Northeast China has the highest SOCE and SOCS density, while the Loess Plateau has the greatest SOCP density. The time required to reach SOC saturation in Chinese cropland is highly dependent on management practices applied. Chinese cropland has relatively low SOC density in comparison to the global average but could have great potentials for C sequestration under improved agricultural management strategies.
A Kernel Regression Approach to Gene‐Gene Interaction Detection for Case‐Control Studies
Authors: Larson Nicholas B. , Schaid Daniel J. 
Published: July 2013

ABSTRACTGene‐gene interactions are increasingly being addressed as a potentially important contributor to the variability of complex traits. Consequently, attentions have moved beyond single locus analysis of association to more complex genetic models. Although several single‐marker approaches toward interaction analysis have been developed, such methods suffer from very high testing dimensionality and do not take advantage of existing information, notably the definition of genes as functional units. Here, we propose a comprehensive family of gene‐level score tests for identifying genetic elements of disease risk, in particular pairwise gene‐gene interactions. Using kernel machine methods, we devise score‐based variance component tests under a generalized linear mixed model framework. We conducted simulations based upon coalescent genetic models to evaluate the performance of our approach under a variety of disease models. These simulations indicate that our methods are generally higher powered than alternative gene‐level approaches and at worst competitive with exhaustive SNP‐level (where SNP is single‐nucleotide polymorphism) analyses. Furthermore, we observe that simulated epistatic effects resulted in significant marginal testing results for the involved genes regardless of whether or not true main effects were present. We detail the benefits of our methods and discuss potential genome‐wide analysis strategies for gene‐gene interaction analysis in a case‐control study design.
Crustal evolution across the southern Appalachians: Initial results from the SESAME broadband array
Authors: Parker E. Horry , Hawman Robert B. , Fischer Karen M. , Wagner Lara S. 
Published: July 2013

AbstractReceiver functions from the EarthScope Southeastern Suture of the Appalachian Margin Experiment broadband deployment and U.S. Transportable Array were analyzed to constrain average crustal thickness and composition across the southern Appalachians. Low Vp/Vs ratios (1.69–1.72) across the Carolina terrane and parts of the Inner Piedmont indicate that the crust has a felsic average composition. The results are consistent with models of thin‐skinned thrusting of Carolina arc fragments over Laurentian basement, whereas arc collision models require significant crustal modification to explain the low Vp/Vs. New crustal thickness estimates provide constraints on the extent of the Blue Ridge crustal root. The present root may be a remnant of a broader structure formed by Alleghanian thrust loading. Root preservation is attributed to Mesozoic heating and thinning of the lower crust beneath outboard terranes, leaving colder Blue Ridge crust largely intact. However, thickened crust (50–55 km) across the region may also be inherited from continental collision during the Proterozoic Grenville orogeny.
The cooling‐rate effect on microwave archeointensity estimates
Authors: Poletti Wilbor , Hartmann Gelvam A. , Hill Mimi J. , Biggin Andrew J. , Trindade Ricardo I. F. 
Published: July 2013

AbstractNew microwave (MW) paleointensity data on historical bricks from Northeast Brazil presented a bias toward higher fields when compared to previous cooling‐rate corrected double‐heating paleointensity estimates; the same relates to the previously reported values for pottery from Southwestern Pacific islands. A simple theoretical approach suggests that the MW bias in both collections is due to a cooling‐rate effect on MW estimates. We then experimentally corrected the MW cooling‐rate effect on Brazilian fragments, increasing the degree of consistency between the previous and new results (reducing discrepancies from 25% to 8%). Results indicate similar experimental behavior between microwave and thermal procedures despite the different ways in which the energy is transferred into the spin system. Finally, they allow cooling times of less than 90 s to be empirically estimated in most of these MW experiments highlighting the need for systematic cooling‐rate corrections to be applied in similar MW paleointensity studies in the future.
PATIENT SAFETY IN HOSPITALS – A BAYESIAN ANALYSIS OF UNOBSERVABLE HOSPITAL AND SPECIALTY LEVEL RISK FACTORS
Authors: Zhang Xiaohui , Hauck Katharina , Zhao Xueyan 
Published: July 2013

ABSTRACTThis paper demonstrates how Bayesian hierarchical modelling can be used to evaluate the performance of hospitals. We estimate a three‐level random intercept probit model to attribute unexplained variation in hospital‐acquired complications to hospital effects, hospital‐specialty effects and remaining random variations, controlling for observable patient complexities. The combined information provided by the posterior means and densities for latent hospital and specialty effects can be used to assess the need and scope for improvements in patient safety at different organizational levels. Posterior densities are not conventionally presented in performance assessment but provides valuable additional information to policy makers on what poorly performing hospitals and specialties may be prioritized for policy action. We use surgical patient administrative data for 2005/2006 for 16 specialties in 35 public hospitals in Victoria, Australia. We use posterior means for latent hospital and specialty effects to compare hospital performance in patient safety. Posterior densities and variances are also compared for different specialties to identify clinical areas with greatest scope for improvement. We also show that the same hospital may rank markedly differently for different specialties. Copyright © 2013 John Wiley & Sons, Ltd.
GENDER DIFFERENCES IN ALCOHOL DEMAND: A SYSTEMATIC REVIEW OF THE ROLE OF PRICES AND TAXES
Authors: Nelson Jon P. 
Published: July 2013

ABSTRACTGender differences in drinking patterns are potentially important for public policies, especially policies that rely extensively on higher alcohol taxes and prices. This paper presents a systematic review of alcohol prices and gender differences in drinking and heavy drinking by adults and young adults. Starting with a database of 578 studies of alcohol demand and other outcomes, 15 studies are reviewed of adult drinking including discussion of samples, measurement issues, econometric models, special variables, and key empirical results. A similar discussion is presented for eight studies of drinking by young adults, ages 18–26 years. Four conclusions are obtained from the review. First, adult men have less elastic demands compared with women. Second, there is little or no price response by heavy‐drinking adults, regardless of gender. Third, although the sample is small, price might be important for drinking participation by young adults. Fourth, the results strongly suggest that heavy drinking by young adults, regardless of gender, is not easily dissuaded by higher prices. Policy implications, primary study limitations, and suggestions for future research are discussed. Copyright © 2013 John Wiley & Sons, Ltd.
Control of river stage on the reactive chemistry of the hyporheic zone
Authors: Byrne P. , Binley A. , Heathwaite A. L. , Ullah S. , Heppell C. M. , Lansdown K. , Zhang H. , Trimmer M. , Keenan P. 
Published: July 2013

AbstractWe examined the influence of river stage on subsurface hydrology and pore water chemistry within the hyporheic zone of a groundwater‐fed river during the summer baseflow period of 2011. We found river stage and geomorphologic environment to control chemical patterns in the hyporheic zone. At a high river stage, the flux of upwelling water in the shallow sediments (>20 cm) decreased at sample sites in the upper section of our study reach and increased substantially at sites in the lower section. This differential response is attributed to the contrasting geomorphology of these subreaches that affects the rate of the rise and fall of a river stage relative to the subsurface head. At sites where streamward vertical flux decreased, concentration profiles of a conservative environmental tracer suggest surface water infiltration into the riverbed below depths recorded at a low river stage. An increase in vertical flux at sites in the lower subreach is attributed to the movement of lateral subsurface waters originating from the adjacent floodplain. This lateral‐moving water preserved or decreased the vertical extent of the hyporheic mixing zone observed at a low river stage. Downwelling surface water appeared to be responsible for elevated dissolved organic carbon (DOC) and manganese (Mn) concentrations in shallow sediments (0–20 cm); however, lateral subsurface flows were probably important for elevated concentrations of these solutes at deeper levels. Results suggest that DOC delivered to hyporheic sediments during a high river stage from surface water and lateral subsurface sources could enhance heterotrophic microbial activities. Copyright © 2013 John Wiley & Sons, Ltd.
Persistent mechanical allodynia positively correlates with an increase in activated microglia and increased P‐p38 mitogen‐activated protein kinase activation in streptozotocin‐induced diabetic rats
Authors: Cheng K.‐I. , Wang H.‐C. , Chuang Y.‐T. , Chou C.‐W. , Tu H.‐P. , Yu Y.‐C. , Chang L.‐L. , Lai C.‐S. 
Published: July 2013

AbstractBackgroundIn experimental early painful diabetic neuropathy, persistent hyperglycaemia induces dys‐regulated sodium channel (Navs) expression in the dorsal root ganglion (DRG) and activates microglia in the spinal dorsal horn (SDH). However, information on diabetes‐induced chronic neuropathic pain is limited. Therefore, we investigated abnormal Navs in the DRG and activated glial cells in the SDH of diabetic rats with chronic neuropathic pain.MethodsSixty‐six rats were divided into diabetic and control groups: control rats (n = 18; 1 mL of normal saline via the right femoral vein) and diabetic rats [n = 48; 60 mg/kg streptozotocin (STZ) via the right femoral vein]. Hindpaw behavioural tests, Navs expression in the DRG, activation of glial cells in the SDH and the number of neurons in the SDH were measured at 1 and 2 weeks, and 1, 2, 3 and 6 months following saline and STZ administration.ResultsAll diabetic rats exhibited hyperglycaemia from day 7 to 6 months. The diabetic rats decreased withdrawal threshold to mechanical stimuli but had blunted responses to thermal stimuli. Consistent up‐regulation of Nav1.3 and down‐regulation of Nav1.8 was observed. Microglial cells were activated early in the SDH and lasted for 6 months. A positive correlation between mechanical allodynia, Nav1.3 and microglial activation was observed. In addition, microglia activation in the SDH of STZ‐induced diabetes was mediated, in part, by phosphorylation of p‐38 mitogen‐activated protein kinase.ConclusionsDiabetic rats showed hindpaw mechanical allodynia for 6 months. Persistent mechanical allodynia was positively associated with sustained increased activation of Nav1.3 and increased p38 phosphorylation in activated microglia.
Characteristics of older patients with back pain in general practice: BACE cohort study
Authors: Scheele J. , Enthoven W.T.M. , Bierma‐Zeinstra S.M.A. , Peul W.C. , van Tulder M.W. , Bohnen A.M. , Berger M.Y. , Koes B.W. , Luijsterburg P.A.J. 
Published: July 2013

AbstractBackgroundAlthough back pain is common among older people, limited information is available about the characteristics of these patients in primary care. Earlier research suggests that the severity of back symptoms increases with older age.MethodsPatients aged >55 years visiting a general practitioner with a new episode of back pain were included in the BACE study. Information on patients' characteristics, characteristics of the complaint and physical examination were derived from the baseline measurement. Cross‐sectional differences between patients aged >55–74 and ≥75 years were analysed using an unpaired t‐test, Mann–Whitney U‐test or a chi‐square test.ResultsA total of 675 back pain patients were included in the BACE study, with a median age of 65 (interquartile range 60–71) years. Patients aged >55–74 years had a mean disability score (measured with the Roland Disability Questionnaire) of 9.4 [standard deviation (SD) 5.8] compared with 12.1 (SD 5.5) in patients aged ≥75 years (p ≤ 0.01). The older group reported more additional musculoskeletal disorders and more often had low bone quality (based on ultrasound measurement of the heel) than patients aged >55–74 years. Average back pain severity over the previous week showed no difference (p = 0.11) between the age groups, but severity of back pain at the moment of filling in the questionnaire was higher (p = 0.03) in the older age group.ConclusionsIn this study, older back pain patients reported more disabilities and co‐morbidity. However, the clinical relevance of these differences for the course of the back pain episode in older patients remains a subject for further research.