bluuebunny/crossref_metadata_2025_split huggingface dataset:
The application of depletion curves for parameterization of subgrid variability of snow
Authors: Luce Charles H. , Tarboton David G. 
Published: May 2004

AbstractParameterization of subgrid‐scale variability in snow accumulation and melt is important for improvements in distributed snowmelt modelling. We have taken the approach of using depletion curves that relate fractional snow‐covered area to element‐average snow water equivalent to parameterize the effect of snowpack heterogeneity within a physically based mass and energy balance snowpack model. Comparisons of parameterization outputs with distributed model outputs and observations show performance comparable to the distributed model and reasonable performance relative to observations for time series modelling of snow water equivalent and snow‐covered area. Examination of the relationship between the shapes of the depletion curves and parametric distributions shows that the shapes of dimensionless depletion curves depend primarily on the coefficient of variation and to a lesser extent on the shape of the snow distribution function. The methods presented here are a generalization of several previously used methods to estimate depletion curve shapes. Comparison of several years of observed depletion curves from the study basin show that the shapes of the depletion curves change little from year to year. Copyright © 2004 John Wiley & Sons, Ltd.
Process parameterization and temporal scaling in surface runoff and erosion modelling
Authors: Kandel D. D. , Western A. W. , Grayson R. B. , Turral H. N. 
Published: May 2004

AbstractIt is common for runoff and erosion models to be run at coarse time steps (e.g. daily) owing to limited data availability. However, such models are unable to capture adequately the small‐scale surface runoff and erosion processes that are dominated by, for example, precipitation characteristics at time‐scales of minutes. This dilemma calls for the development of approaches that appropriately capture short time‐scale processes when running the models at daily scales. In this paper, we assess two scaling approaches that are simple and are intended to preserve prediction quality as time scales become coarser: (i) use of effective rates of precipitation and runoff, and (ii) use of a rainfall disaggregation scheme. Runoff and erosion are simulated using a six‐parameter surface runoff model and a one‐parameter erosion model. A downhill simplex optimization algorithm is applied for parameterization at 2 min and daily time steps, using measured 2 min and daily precipitation data respectively, against measured daily runoff and erosion. The 2 min simulation results are aggregated to daily values to make comparisons with the measured plot‐scale daily runoff and erosion data for 2 years (1997–98) from six sites in the Jhikhu Khola catchment in Nepal. The runoff and erosion simulation results calibrated from the 2 min precipitation data are good (E = 0·92 for runoff and 0·80 for erosion, all sites collectively), whereas other results, particularly the erosion simulation from the calibrated daily model, are very poor. These results are taken as the reference to compare with the two different scaling approaches. The effective rate approach is poor compared with the 2 min estimates but is a considerable improvement over daily erosion estimates. The rainfall disaggregation scheme is comparable to the 2 min estimates and produces better results than the effective rate approach. This study illustrates that rainfall scaling has significant scope for temporal scaling of hydrologic processes, particularly where continuous simulation is preferred. Copyright © 2004 John Wiley & Sons, Ltd.
Exploring streamflow response to effective rainfall across event magnitude scale
Authors: Kokkonen Teemu , Koivusalo Harri , Karvonen Tuomo , Croke Barry , Jakeman Anthony 
Published: May 2004

AbstractSets of flow events from four catchments were selected in order to study how dynamics in the conversion of effective rainfall into streamflow depends on the event size. The approach taken was to optimize parameters of a linear delay function and effective rainfall series concurrently from precipitation–streamflow data without imposing a functional form of the precipitation filter a priori. The delay function is an instantaneous unit hydrograph (IUH) having a mathematical form of the two‐parameter gamma distribution. Results from two small research catchments (0·18 and 0·63 km2) with sub‐daily data suggest a clear relationship between the event magnitude and response dynamics. The effect of the sampling frequency of data was addressed by gradually increasing aggregation interval of rainfall and flow data and repeating the optimization for each aggregated dataset. IUHs for different data aggregation intervals (for a single event) tended to be similar unless the aggregation changed the locations of data peaks. IUHs identified in larger catchments (58 and 1235 km2) also showed variability through events; however, no systematic event magnitude dependence, as was visible in the small research catchments, was detected. Finally, the dependency detected in the small catchments was exploited in a rainfall‐runoff model, where the scale parameter of the gamma distribution was linearly related to the effective rainfall intensity. Prediction of peak flows improved when the event dependency was taken into account. Copyright © 2004 John Wiley & Sons, Ltd.
Low‐dimensional modelling of numerical groundwater flow
Authors: Vermeulen P. T. M. , Heemink A. W. , te Stroet C. B. M. 
Published: May 2004

AbstractNumerical models are often used for simulating groundwater flow. Written in state‐space form, the dimension of these models is of the order of the number of grid cells used and can be very high (more than a million). As a result, these models are computationally very demanding, especially if many different scenarios have to be simulated. In this paper we introduce a model reduction approach to develop an approximate model with a significantly reduced dimension. The reduction method is based upon several simulations of the large‐scale numerical model. By computing the covariance matrix of the model results, we obtain insight into the variability of the model behaviour. Moreover, by selecting the leading eigenvectors of this covariance matrix, we obtain the spatial patterns that represent the directions in state space where the model variability is dominant. These patterns are also called empirical orthogonal functions. We can project the original numerical model onto those dominant spatial patterns. The result is a low‐dimensional model that is still able to reproduce the dominant model behaviour. Copyright © 2004 John Wiley & Sons, Ltd.
Body size and breast cancer risk: Findings from the European prospective investigation into cancer and nutrition (EPIC)
Authors: Lahmann Petra H. , Hoffmann Kurt , Allen Naomi , van Gils Carla H. , Khaw Kay‐Tee , Tehard Bertrand , Berrino Franco , Tjønneland Anne , Bigaard Janne , Olsen Anja , Overvad Kim , Clavel‐Chapelon Françoise , Nagel Gabriele , Boeing Heiner , Trichopoulos Dimitrios , Economou George , Bellos George , Palli Domenico , Tumino Rosario , Panico Salvatore , Sacerdote Carlotta , Krogh Vittorio , Peeters Petra H.M. , Bueno‐de‐Mesquita H. Bas , Lund Eiliv , Ardanaz Eva , Amiano Pilar , Pera Guillem , Quirós José R. , Martínez Carmen , Tormo María J. , Wirfält Elisabet , Berglund Göran , Hallmans Göran , Key Timothy J. , Reeves Gillian , Bingham Sheila , Norat Teresa , Biessy Carine , Kaaks Rudolf , Riboli Elio 
Published: May 2004

AbstractThe evidence for anthropometric factors influencing breast cancer risk is accumulating, but uncertainties remain concerning the role of fat distribution and potential effect modifiers. We used data from 73,542 premenopausal and 103,344 postmenopausal women from 9 European countries, taking part in the EPIC study. RRs from Cox regression models were calculated, using measured height, weight, BMI and waist and hip circumferences; categorized by cohort‐wide quintiles; and expressed as continuous variables, adjusted for study center, age and other risk factors. During 4.7 years of follow‐up, 1,879 incident invasive breast cancers were identified. In postmenopausal women, current HRT modified the body size–breast cancer association. Among nonusers, weight, BMI and hip circumference were positively associated with breast cancer risk (all ptrend ≤ 0.002); obese women (BMI > 30) had a 31% excess risk compared to women with BMI < 25. Among HRT users, body measures were inversely but nonsignificantly associated with breast cancer. Excess breast cancer risk with HRT was particularly evident among lean women. Pooled RRs per height increment of 5 cm were 1.05 (95% CI 1.00–1.16) in premenopausal and 1.10 (95% CI 1.05–1.16) in postmenopausal women. Among premenopausal women, hip circumference was the only other measure significantly related to breast cancer (ptrend = 0.03), after accounting for BMI. In postmenopausal women not taking exogenous hormones, general obesity is a significant predictor of breast cancer, while abdominal fat assessed as waist–hip ratio or waist circumference was not related to excess risk when adjusted for BMI. Among premenopausal women, weight and BMI showed nonsignificant inverse associations with breast cancer. © 2004 Wiley‐Liss, Inc.
Keeping off the grass? An econometric model of cannabis consumption in Britain
Authors: Pudney Stephen 
Published: May 2004

AbstractThis paper presents estimates of a dynamic individual‐level model of cannabis consumption, using data from a 1998 survey of young people in Britain. The econometric model is a split‐population generalization of the non‐stationary Poisson process, allowing for separate dynamic process for initiation into cannabis use and subsequent consumption. The model allows for heterogeneity in consumption levels and behavioural shifts induced by leaving education and the parental home. Copyright © 2004 John Wiley & Sons, Ltd.
Dynamics of the federal funds target rate: a nonstationary discrete choice approach
Authors: Hu Ling , Phillips Peter C. B. 
Published: May 2004

AbstractWe apply a discrete choice approach to model the empirical behaviour of the Federal Reserve in changing the federal funds target rate, the benchmark of short‐term market interest rates in the US. Our methods allow the explanatory variables to be nonstationary as well as stationary. This feature is particularly useful in the present application as many economic fundamentals that are monitored by the Fed and are believed to affect decisions to adjust interest rate targets display some nonstationarity over time. The chosen model successfully predicts the majority of the target rate changes during the time period considered (1994–2001) and helps to explain strings of similar intervention decisions by the Fed. Based on the model‐implied optimal interest rate, our findings suggest that there is a lag in the Fed's reaction to economic shocks during this period. Copyright © 2004 John Wiley & Sons, Ltd.
Making inferences about the polarization, welfare and poverty of nations: a study of 101 countries 1970–1995
Authors: Anderson Gordon 
Published: May 2004

AbstractStochastic Dominance techniques are adapted and employed to study the extent and progress of Polarization, Welfare and Poverty of 101 nations over the period 1970–1995. The adaptations provide methods of comparing mass relocation by evaluating various degrees of right and left separation between distributions. The results reveal that, whilst welfare increased and then diminished and poverty diminished and then increased, polarization between rich and poor countries continued unabated throughout the period emphasizing the distinction between polarization and inequality. Copyright © 2004 John Wiley & Sons, Ltd.
Social security, pensions and retirement behaviour within the family
Authors: Gustman Alan L. , Steinmeier Thomas L. 
Published: May 2004

AbstractThis paper estimates a structural model of family retirement using US data from the Health and Retirement Study (HRS). It provides further insight into household retirement decision making and the reasons for interdependence in the retirement decisions of each spouse. Improvements in HRS data and matched employer provided pension histories allow more precise identification of key parameters governing interdependent behaviour within the household.In an earlier study we found that interdependence was due to preferences rather than coordination of retirement incentives in the budget, and in particular that it is not a correlation in preferences, but the appearance of the spouse's retirement status in the husband's and wife's utility function that is largely responsible for coordination of retirement between spouses. We now find that a measure of how much each spouse values being able to spend time in retirement with the other accounts for a good portion of that apparent interdependence. For the wife, the husband's retirement status influences her retirement decision only if she values spending time in retirement with her husband. For husbands, the effect of having the wife already retired on his retirement decision is roughly doubled if he enjoys spending time in retirement with his wife, but there is some effect even if he does not. This is consistent with our earlier findings that the husband is more influenced by having a retired spouse than the wife is. The increase in the extent of the dependence of the wife's labour supply on the husband's retirement from our past work probably is traceable to better measurement of the opportunity set facing the husband in HRS data.Once estimated, we use the model to investigate the labour supply effects of alternative social security policies, examining the effect of dividing credit for earnings evenly between spouses, or of basing social security benefits on the amounts accumulated in private accounts. Both policies change the relative importance of spouse and survivor social security benefits within the household and both raise the relative reward to work later in the life cycle. The incentives created are modest, and retirement responds accordingly. Nevertheless, at some ages, such as 65, there may be as much as a 6% increase in the old age work force under privatized accounts. Copyright © 2004 John Wiley & Sons, Ltd.
In vivo evaluation of a novel electrically conductive polypyrrole/poly(D,L‐lactide) composite and polypyrrole‐coated poly(D,L‐lactide‐co‐glycolide) membranes
Authors: Wang Zhaoxu , Roberge Christophe , Dao Lê H. , Wan Ying , Shi Guixin , Rouabhia Mahmoud , Guidoin Robert , Zhang Ze 
Published: May 2004

AbstractThis study evaluated the in vivo biocompatibility and biodegradation behavior of a novel polypyrrole (PPy)/poly(D,L‐lactide) (PDLLA) composite and PPy‐coated poly(D,L‐lactide‐co‐glycolide) membranes. Test membranes were implanted subcutaneously in rats for 3–120 days. The biocompatibility was assessed by quantifying the alkaline and acid phosphatase secretion, the immunohistochemical staining of the ED‐2‐positive macrophages, and the histology at the tissue/material interface. The degradation was investigated using scanning electron microscopy. Pure PDLLA and poly(D,L‐lactide‐co‐glycolide) membranes were used as references, whereas expanded polytetrafluoroethylene and a commercial styrene‐butadiene rubber were used as controls. The enzyme activity of the PPy‐containing specimens was shown to be similar to that of the references. The histological findings were consistent with the enzymatic results, showing a mild‐to‐moderate acute inflammation followed by a resolution of the inflammatory response with a decrease in inflammatory cells for each biodegradable membrane. The tissue reactions to the PPy, which was either in the form of nanoparticles or surface coating, were comparable to the response to the neighboring biodegradable materials. Elevated ED‐2‐positive macrophage populations appeared as early as day 3 in the loose connective tissue surrounding the implants. The density of these populations was related to the degree of inflammation. Scanning electron microscopy showed that the degradation of the PPy/PDLLA composite was not affected by the presence of PPy. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 28–38, 2004
Electrochemical behavior of different preparations of plasma‐sprayed hydroxyapatite coatings on Ti6Al4V substrate
Authors: Souto Ricardo M. , Lemus M. Mercedes , Reis Rui L. 
Published: May 2004

AbstractThe corrosion behavior of four different preparations of plasma‐sprayed hydroxyapatite (HA) coatings on Ti6Al4V substrates in static Hank's balanced salt solution was investigated using dc potentiodynamic and ac impedance techniques. Two different nominal thicknesses, 50 μm and 200 μm, and two different spraying conditions, were considered. The electrochemical impedance experiments proved this technique to be very suitable for the investigation of the electrochemical behavior of surgical implant alloys when they are coated with HA, which is characterized by the dissolution and passivation characteristics of the underlying metal substrate. Because the coatings are porous, ionic paths between the electrolytic medium and the base material can eventually be produced, resulting in the corrosion of the coated metal. Differences in the corrosion resistance of the coated materials were detected, and a relevant model for the description of the coating degradation in the biosimulating solution was proposed. The model consisted of the description of the coated system in terms of a two‐layer model of the surface film. Significant differences in electrochemical behavior for similar nominal thicknesses of HA coatings obtained under different spraying conditions were found. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 59–65, 2004
Differential expression of osteogenic factors associated with osteoinductivity of human osteosarcoma cell lines
Authors: Yu Yan , Harris Richard I. , Yang Jia‐Lin , Anderson H. Clarke , Walsh William R. 
Published: May 2004

AbstractDifferential expression of multiple osteogenic factors may be responsible for the different osteoinductivity of osteosarcoma cell lines. We compared in vivo osteoinductivity of human osteosarcoma cell lines (Saos‐2 vs. U‐2 OS) in nude mice, and their in vitro expression of various osteogenic factors of protein level by quantitative immunocytochemistry and mRNA level by RT‐PCR and/or in situ hybridization. Saos‐2 cells, but not U‐2 OS, were osteoinductive in vivo. Significantly higher expression (independent t‐test, all p < 0.005) of osteogenic factors were observed in Saos‐2 cells compared with U‐2 OS, which included bone morphogenetic proteins (particularly BMPs‐2, 3, 4, and 7), transforming growth factor‐beta (TGF‐β), BMP receptor (BMPR)‐1A, receptor‐regulated Smads (R‐Smads), Smads 1, 2, and 5, and common‐mediator Smad (Co‐Smad), Smad 4. In contrast, U‐2 OS cells expressed higher levels of inhibitory Smad 6 (I‐Smad) protein than Saos‐2 cells (p < 0.001). These results suggest that a combination of osteogenic factors (BMPs, TGF‐β, BMPRs, and R/Co‐Smads) against I‐Smad may play important roles in the Saos‐2 cell osteoinductivity. This may have a clinical implication in selecting key osteogenic factors for combined therapy for bone defect diseases. The characterized cell lines can be used as positive and negative controls for the assessments of both in vitro and in vivo bone formation capabilities of designed tissues or biomaterials. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 122–128, 2004
Ultramorphological analysis of resin–dentin interfaces produced with water‐based single‐step and two‐step adhesives: Nanoleakage expression
Authors: Reis André F. , Arrais Cesar A.G. , Novaes Pedro D. , Carvalho Ricardo M. , De Goes Mário F. , Giannini Marcelo 
Published: May 2004

AbstractThis study evaluated the nanoleakage patterns in bonded interfaces using two single‐step, self‐etching adhesives (Adper Prompt—AD, and One‐up Bond F—OB), two two‐step, self‐etching primers (Clearfil SE Bond—CF, and Unifil Bond—UB), and one two‐step, total‐etch adhesive (Single Bond—SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37°C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm‐thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO3 for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin‐embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 μm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 90–98, 2004
Bond strength of a silicone lining material to alumina‐abraded and lased denture resin
Authors: Usumez Aslihan , Inan Ozgur , Aykent Filiz 
Published: May 2004

AbstractThe aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast‐B) to alumina‐abraded or lased heat‐cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning‐electron microscopy (SEM) was also determined. Laser‐treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina‐abraded and untreated (control‐group) specimens (p < .05). There were no statistically significant differences in surface roughness between alumina‐abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > .05). Molloplast‐B applied to alumina‐abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser‐treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 196–200, 2004