bluuebunny/crossref_metadata_2025 huggingface dataset:
Topographic parameterization in continental hydrology: a study in scale
Authors: Armstrong Robert N. , Martz Lawrence W.
Published: December 2003

Digital elevation models (DEMs) are useful and popular tools from which topographic parameters can be quickly and efficiently extracted for various hydrologic applications. DEMs coupled with automated methods for extracting topographic information provide a powerful means of parameterizing hydrologic models over a wide range of scales. However, choosing appropriate DEM scales for particular hydrologic modelling applications is limited by a lack of understanding of the effects of scale and grid resolution on land‐surface representation. The scale effects of aggregation on square‐grid DEMs of two continental‐scale basins are examined. Base DEMs of the Mackenzie and Missouri River basins are extracted from the HYDRO1k DEM of North America. Successively coarser grids of 2, 4, 8, … 64 km were generated from the ‘base’ DEMs using simple linear averaging. TOPAZ (Topographic Parameterization) was applied to the base and aggregated DEMs using constant critical source area and minimum source channel length values to extract topographic variables at varying scales or resolutions. The effects of changing DEM resolution are examined by considering changes in the spatial distribution and statistical properties of selected topographic variables of hydrological importance. The effects of increasing grid size on basin and drainage network delineation, and derived topographic variables, tends to be non‐linear. In particular, changes in overall basin extent and drainage network configuration make it impractical to apply a simple scaling function to estimate variable values for fine‐resolution DEMs from those derived from coarse‐resolution DEMs. Results also suggest the resolution to which a DEM can be reduced by aggregation and still provide useful topographic information for continental‐scale hydrologic modelling is that at which the mean hydraulic slope falls to approximately 1%. In this study, that generally occurred at a resolution of about 10 km. Copyright © 2003 John Wiley & Sons, Ltd.
Detection of trends in annual extreme rainfall
Authors: Adamowski Kaz , Bougadis John
Published: December 2003

Information on intensity–duration–frequency of rainfall is commonly required for a variety of hydrologic applications. In this study, trends are estimated for different durations of annual extreme rainfall using the regional average Mann–Kendall S trend test. The method of L‐moments was employed to delineate homogeneous regions. The trend test was modified to account for observed autocorrelation, and a bootstrap methodology was used to account for the observed spatial correlation.

Numerical analysis was performed on 44 rainfall stations from the province of Ontario, Canada, for a 20 year time frame. This was done using data from homogeneous regions established using the L‐moments procedure for the annual maximum observations for the following durations: 5, 10, 15 and 30 min, and 1, 2, 6 and 12 h. Depending on different rainfall durations, four or five homogeneous regions were delineated.

Based on a 5% significance level, approximately 23% of the regions tested had a significant trend, predominantly for short‐duration storms. Serial dependency was observed in 2·3% of data sets and spatial correlation was found in 18% of the regions. The presence of serial and spatial correlation had a significant impact on trend determination. Copyright © 2003 John Wiley & Sons, Ltd.
Regional dimensionless hydrograph for Alberta foothills
Authors: Muzik Ivan , Chang Chiadih
Published: December 2003

The majority of hydrologic engineering applications deal with ungauged watersheds. Various empirical methods are available for synthesizing unit hydrographs for ungauged watersheds from information obtained from maps or field inspection of the watershed. An alternative to the employment of generalized synthetic unit hydrographs is to develop a regional dimensionless hydrograph to characterize the local rainfall‐runoff processes better. The derivation of such a dimensionless hydrograph is described for Alberta foothills, based on the analysis of 31 basins and 61 rainfall‐runoff events. The analysis shows that it is possible to derive a representative dimensionless hydrograph for the region with reasonable accuracy by averaging the observed direct runoff hydrographs converted into a dimensionless form. However, considerable uncertainty is associated with the estimation of the excess rainfall duration and the lag time of the events analysed. The lag time is the key parameter needed to convert the regional dimensionless hydrograph into an ungauged watershed unit hydrograph. Possible reasons for unexplained lag time variations are discussed. The regional dimensionless hydrograph developed and lag time curve were used to regenerate the original 61 hydrographs. Results were compared with the generalized Soil Conservation Service dimensionless unit hydrograph which tended to produce larger errors in predicted peak flows. Error analysis indicates the limits of accuracy that may be expected from the method. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical modelling of ice‐jam flooding on the Peace–Athabasca delta
Authors: Beltaos Spyros
Published: December 2003

Ice jamming during the spring breakup of the ice cover in the lower reaches of the Peace River has been identified as the main agent of flooding and replenishment of the Peace–Athabasca delta (PAD) ecosystems. The relative rarity of major ice jams in the lower Peace River following construction of the Bennett Dam has resulted in serious habitat degradation and risk to local ecology, and concern has been raised over potential climate change impacts. This issue is under active study that encompasses use of various types of model, field data collection, and analysis of archived records. An important component of the study aims at determination of threshold flows that can result in significant flooding when a jam is in place in the PAD reach of the Peace. This question is investigated by means of RIVJAM, a numerical model that computes the water surface and thickness profiles of a jam in a given river reach. First, the model is calibrated using field data obtained during the 1996 and 1997 ice‐jam floods. Calibration coefficients are shown to be the same for both events and consistent with default values determined from previous applications in other rivers. A by‐product of the calibration process is the quantification of the flow reversals occurring under high‐stage conditions in the three major tributaries of the lower Peace. Next, the model is applied with increasing flow values and the resulting water surface profiles are compared with bank elevations. These comparisons indicate that an incoming flow of at least 4000 m3 s−1 is required to produce significant flooding of the delta. The calibrated model can also be used to examine the efficacy of controlled water releases at the Bennett Dam as a means of enhancing flooding potential. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Phosphate retention in an agricultural stream using experimental additions of phosphate
Authors: Macrae M. L. , English M. C. , Schiff S. L. , Stone M. A.
Published: December 2003

In‐stream experiments involving additions of phosphate were conducted to determine the soluble reactive phosphorus (SRP) retention potential of a perennial first‐order stream that drains a 2·7 km2 agricultural catchment in southern Ontario. SRP retention was determined in relation to highly elevated SRP concentrations under low flow conditions. Point source treatments of phosphate were added to three reaches of this stream during two time periods when baseline SRP concentrations were notably different (early summer and early autumn). The reaches selected varied with respect to streambed shape and gradient, direction of groundwater flow, and channel vegetation type and density. One of the three experimental stream reaches was dredged between the two sampling periods, so that all vegetation and the top 25 cm of sediments were removed.

SRP retention in the stream ranged from 0·8 to 24·1 µg m−2 s−1. Dredging the stream sediments did not alter the ability of the stream to remove SRP from the water column. SRP retention over the experimental reaches was generally 5–10% of the elevated concentration (0·7–4·2 mg l−1, a factor of 8–53 above pre‐experiment conditions), although low‐flow conditions in the stream were conducive to retention by stream sediments. Copyright © 2003 John Wiley & Sons, Ltd.
Cryptic wetlands: integrating hidden wetlands in regression models of the export of dissolved organic carbon from forested landscapes
Authors: Creed I. F. , Sanford S. E. , Beall F. D. , Molot L. A. , Dillon P. J.
Published: December 2003

This study examines the relationship between wetlands hidden beneath the forest canopy (‘cryptic wetlands’) and dissolved organic carbon (DOC) export to streams and lakes in forested ecosystems. In the Turkey Lakes Watershed (TLW), located in the Algoma Highlands of central Ontario, Canada, there is substantial natural variation in average annual DOC export (kgC ha−1 year−1), ranging from 11·4 to 31·5 kgC ha−1 year−1 in catchments with no apparent wetlands. We hypothesized that the natural variation in DOC export was related to cryptic wetlands. Cryptic wetlands were derived manually from geographic coordinates that were surveyed with a differential global positioning system, and automatically from identification of topographic depressions and flat slopes (<1·5° ) within a digital elevation model (DEM) in a geographic information system. For the TLW catchments, which are characterized by shallow soils over bedrock, a significant correlation (r2 ≥ 0·9, p < 0·001) between manual and automated methods was observed for scales up to 50 m when a light detection and ranging DEM was used for the topographic analysis. Regression models indicated that cryptic wetlands (%) explained the majority of the natural variation in DOC export (kgC ha−1 year−1), with r2 = 0·88 (p < 0·001) for the model based on the manually derived wetlands and r2 = 0·85 (p < 0·001) for the model based on the automatically derived wetlands. The strength and significance of the automatically derived wetlands (%) versus DOC export (kgC ha−1 year−1) regression model diminished when other sources of DEMs were used. This study emphasizes the importance of including cryptic wetlands in predictive models of DOC export, particularly in catchments where the topography includes depressions and flat areas but no apparent wetlands. Copyright © 2003 John Wiley & Sons, Ltd.
The effects of soil bulk density, clay content and temperature on soil water content measurement using time‐domain reflectometry
Authors: Gong Yuanshi , Cao Qiaohong , Sun Zongjia
Published: December 2003

Time‐domain reflectometry (TDR) is increasingly used for field soil water estimation because the measurement is non‐destructive and less affected by soil texture, bulk density and temperature. However, with the increase in instrument resolution, the influences of soil bulk density and temperature on TDR soil moisture measurements have been reported. The influence is primarily caused by changes in soil and water dielectric permittivity when soil compaction and temperature varies. The objective of this study is to quantify the influence of soil bulk density and temperature, and to provide the corresponding correction methods. Data collected from sand, sandy loam, loam and clay loam show a linear relationship between the square root of dielectric constant of dry soil and bulk density, and a bulk density correction formula has been developed. The dielectric permittivity of soil solids estimated using this formula is close to that of oxides of aluminium, silicon, magnesium and calcium. Data collection from sandy loam show a noticeable decrease in measured soil moisture with increase in temperature when the volumetric soil water content is above 0·30 m3 m−3. A temperature‐correction equation has been developed, which could provide the corrected soil moisture based on soil temperature and TDR‐measured moisture. The effect of clay content has been detected, but it is not statistically significant. High clay contents cause the underestimation of soil water content in the low moisture range and overestimation of soil water content in the high moisture range. Copyright © 2003 John Wiley & Sons, Ltd.
Application of fuzzy logic to forecast seasonal runoff
Authors: Mahabir C. , Hicks F. E. , Fayek A. Robinson
Published: December 2003

Each spring in Alberta, Canada, the potential snowmelt runoff is forecast for several basins to assess the water supply situation. Water managers need this forecast to plan water allocations for the following summer season. The Lodge Creek and Middle Creek basins, located in southeastern Alberta, are two basins that require this type of late winter forecast of potential spring runoff. Historically, the forecast has been based upon a combination of regression equations. These results are then interpreted by a forecaster and are modified based on the forecaster's heuristic knowledge of the basin. Unfortunately, this approach has had limited success in the past, in terms of the accuracy of these forecasts, and consequently an alternative methodology is needed.

In this study, the applicability of fuzzy logic modelling techniques for forecasting water supply was investigated. Fuzzy logic has been applied successfully in several fields where the relationship between cause and effect (variable and results) are vague. Fuzzy variables were used to organize knowledge that is expressed ‘linguistically’ into a formal analysis. For example, ‘high snowpack’, ‘average snowpack’ and ‘low snowpack’ became variables. By applying fuzzy logic, a water supply forecast was created that classified potential runoff into three forecast zones: ‘low’, ‘average’ and ‘high’. Spring runoff forecasts from the fuzzy expert systems were found to be considerably more reliable than the regression models in forecasting the appropriate runoff zone, especially in terms of identifying low or average runoff years. Based on the modelling results in these two basins, it is concluded that fuzzy logic has a promising potential for providing reliable water supply forecasts. Copyright © 2003 John Wiley & Sons, Ltd.
Connectivity and storage functions of channel fens and flat bogs in northern basins
Authors: Quinton W. L. , Hayashi M. , Pietroniro A.
Published: December 2003

The hydrological response of low relief, wetland‐dominated zones of discontinuous permafrost is poorly understood. This poses a major obstacle to the development of a physically meaningful meso‐scale hydrological model for the Mackenzie basin, one of the world's largest northern basins. The present study examines the runoff response of five representative study basins (Scotty Creek, and the Jean‐Marie, Birch, Blackstone and Martin Rivers) in the lower Liard River valley as a function of their major biophysical characteristics. High‐resolution (4 m × 4 m) IKONOS satellite imagery was used in combination with aerial and ground verification surveys to classify the land cover, and to delineate the wetland area connected to the drainage system. Analysis of the annual hydrographs of each basin for the 4 year period 1997 to 2000, demonstrated that runoff was positively correlated with the drainage density, basin slope, and the percentage of the basin covered by channel fens, and was negatively correlated with the percentage of the basin covered by flat bogs. The detailed analysis of the water‐level response to summer rainstorms at several nodes along the main drainage network in the Scotty Creek basin showed that the storm water was slowly routed through channel fens with an average flood‐wave velocity of 0·23 km h−1. The flood‐wave velocity appears to be controlled by channel slope and hydraulic roughness in a manner consistent with the Manning formula, suggesting that a roughness‐based routing algorithm might be useful in large‐scale hydrological models. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
An assessment of global climate model‐simulated climate for the western cordillera of Canada (1961–90)
Authors: Bonsal Barrie R. , Prowse Terry D. , Pietroniro Alain
Published: December 2003

Climate change is projected to significantly affect future hydrologic processes over many regions of the world. This is of particular importance for alpine systems that provide critical water supplies to lower‐elevation regions. The western cordillera of Canada is a prime example where changes to temperature and precipitation could have profound hydro‐climatic impacts not only for the cordillera itself, but also for downstream river systems and the drought‐prone Canadian Prairies. At present, impact researchers primarily rely on global climate models (GCMs) for future climate projections. The main objective of this study is to assess several GCMs in their ability to simulate the magnitude and spatial variability of current (1961–90) temperature and precipitation over the western cordillera of Canada. In addition, several gridded data sets of observed climate for the study region are evaluated.

Results reveal a close correspondence among the four gridded data sets of observed climate, particularly for temperature. There is, however, considerable variability regarding the various GCM simulations of this observed climate. The British, Canadian, German, Australian, and US GFDL models are superior at simulating the magnitude and spatial variability of mean temperature. The Japanese GCM is of intermediate ability, and the US NCAR model is least representative of temperature in this region. Nearly all the models substantially overestimate the magnitude of total precipitation, both annually and on a seasonal basis. An exception involves the British (Hadley) model, which best represents the observed magnitude and spatial variability of precipitation. This study improves our understanding regarding the accuracy of GCM climate simulations over the western cordillera of Canada. The findings may assist in producing more reliable future scenarios of hydro‐climatic conditions over various regions of the country. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Impact of meteorological predictions on real‐time spring flow forecasting
Authors: Coulibaly Paulin
Published: December 2003

Meteorological predictions, such as precipitation and temperature, are commonly used to improve real‐time hydrologic forecasting, despite their inherent uncertainty and their absence in the model calibration stage. In this study, we quantify the effect of meteorological prediction errors on the accuracy of daily spring reservoir inflow forecasts using weather predictions in both the model calibration and testing phases. Different modelling experiments are compared using an operational conceptual model and nonlinear empirical models to assess the effects of using daily numerical weather predictions as opposed to the use of historical observations. It is found that, even with large prediction errors, meteorological forecasts can provide significant improvement of spring flow forecast for up to 7 days lead time, particularly for low flows. Spring flow prediction errors associated with the type of hydrological model used are significantly larger than those related to the meteorological predictions, particularly for 1 to 4 days ahead forecasts. The experimental results also indicate that multiple model‐based forecasting using an iterative prediction approach appears to be the most effective method for an adequate use of weather predictions. Copyright © 2003 John Wiley & Sons, Ltd.
A pose‐invariant approach for hypothesis support
Authors: Amador José J.
Published: December 2003

This article presents a tractable and empirically accurate algorithm realizing a midlevel visual process for pattern recognition. The algorithm takes advantage of hypotheses provided by a high‐level visual process, thereby, attempting to extract a region in an image based on these hypotheses. The main focus is to recognize quadrilateral as well as arbitrarily shaped objects from synthetic and real‐world images. The novel approach is based on a study of the Hough Transform and its generalized version. To show overall usefulness of the algorithm, an extensive series of experiments was performed. In particular, occlusion and multiple object‐instances were tested, indicating the effectiveness of this work's approach.© 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 13, 201–207;2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10056
A fast BNM (Best Neighborhood Matching): Algorithm and parallel processing for image restoration
Authors: Li Wen , Zhang David , Liu Zhiyong , Qiao Xiangzhen
Published: December 2003

Best Neighborhood Matching (BNM) algorithm is a good approach of error concealment in terms of restored image quality. However, this kind of error concealment algorithm is commonly computation‐intensive, which restricts their real applications on large‐scale image or video sequence restoration. In this article, we propose a fast method, named Jump and look around Best Neighborhood Matching (JBNM), which reduces computing time to one sixth of that by BNM, while the quality of the restored images remains almost the same. To further reduce processing time and meet large‐scale image restorations, a parallel JBNM working on a cluster of workstations is proposed. Several critical techniques, including reading policy, overlap stripe data distribution, and communication strategies, have been developed to obtain high performance. Both theoretical analysis and experiment results indicate that our parallel JBNM provides an efficient technique for image restoration applications. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 13, 189–200, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10057
Automatic vergence control based on hierarchical segmentation of stereo pairs
Authors: Marfil R. , Urdiales C. , Rodríguez J. A. , Sandoval F.
Published: December 2003

This article presents a video system to focus an object of interest in the field of view by means of a stereo robotic head. The system relies on a new hierarchical segmentation technique that split the stereo pair into regions in a combined way. After segmentation is achieved, resulting regions in both images are implicitly related by a set of links and, consequently, their disparity can be estimated. Then, the cameras vergence is changed according to the estimated disparity until the object of interest is focused. The system has proven to be robust against mild noise and illumination changes. Its main advantage is that calibration is not a critical issue for the system to work. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 224–233, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10058
A locally adaptive region growing algorithm for vascular segmentation
Authors: Yi Jaeyoun , Ra Jong Beom
Published: December 2003

To segment vascular structures in 3‐D CTA/MRA images, this article presents a new region growing algorithm based on local cube tracking. In the proposed algorithm, a small local cube is segmented to detect a vessel segment, and the following local cube(s) is determined based on the segmentation result. This procedure is repeated until the segmentation is completed. By confining the segmentation inside each local cube, a robust result can be obtained even in a tubular structure of steadily changing intensity. For segmentation, a locally adaptive and competitive region growing scheme is adopted to obtain well‐defined vessel boundaries. It should be emphasized that the proposed algorithm can detect all branches with practically acceptable computational complexity. In addition, its segmentation result is represented as a tree structure having many branches so that a user may easily correct the result branch‐by‐branch, if necessary. Experimental results from real images prove that the proposed algorithm produces prospective vessel segmentation results for 3‐D CTA/MRA images and segments vessels of various sizes well, including stenoses and aneurysms. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 208–214, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10059
Image segmentation via local higher order statistics
Authors: Farhadi Ali , Shahshahani Mehrdad
Published: December 2003

The aim of this work is to present a method for the segmentation of images based on local higher order statistics. The algorithm can be applied for the separation of objects from a texture background and the segmentation of textures. The proposed technique makes no use of a data bank and its complexity is O(𝒩) where 𝒩 is the number of pixels. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 215–223, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10069
Wear evaluation of cobalt–chromium alloy for use in a metal‐on‐metal hip prosthesis
Authors: St. John Kenneth R. , Zardiackas Lyle D. , Poggie Robert A.
Published: December 2003

Wear of the polyethylene in total joint prostheses has been a source of morbidity and early device failure, which has been extensively reported in the last 20 years. Although research continues to attempt to reduce the wear of polyethylene joint‐bearing surfaces by modifications in polymer processing, there is a renewed interest in the use of metal‐on‐metal bearing couples for hip prostheses. Wear testing of total hip replacement systems involving the couple of metal or ceramic heads on polymeric acetabular components has been performed and reported, but, until recently, there has been little data published for pin‐on‐disk or hip‐simulator wear studies involving the combination of a metallic femoral head component with an acetabular cup composed of the same or a dissimilar metal. This study investigated the in vitro wear resistance of two cobalt/chromium/molybdenum alloys, which differed primarily in the carbon content, as potential alloys for use in a metal‐on‐metal hip‐bearing couple. The results of pin‐on‐disk testing showed that the alloy with the higher (0.25%) carbon content was more wear resistant, and this alloy was therefore chosen for testing in a hip‐simulator system, which modeled the loads and motions that might be exerted clinically. Comparison of the results of metal‐on‐polyethylene samples to metal‐on‐metal samples showed that the volumetric wear of the metal‐on‐polyethylene bearing couple after 5,000,000 cycles was 110–180 times that for the metal‐bearing couple. Polyethylene and metal particles retrieved from either the lubricant for pin‐on‐disk testing or hip simulator testing were characterized and compared with particles retrieved from periprosthetic tissues by other researchers, and found to be similar. Based upon the results of this study, metal‐on‐metal hip prostheses manufactured from the high carbon cobalt/chromium alloy that was investigated hold sufficient promise to justify human clinical trials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 1–14, 2004
Abrasion resistance of medical glove materials
Authors: Walsh Donna L. , Schwerin Matthew R. , Kisielewski Richard W. , Kotz Richard M. , Chaput Maria P. , Varney George W. , To Theresa M.
Published: December 2003

Due to the increasing demand for nonlatex medical gloves in the health‐care community, there is a need to assess the durability of alternative glove materials. This study examines durability characteristics of various glove materials by abrasion resistance testing. Natural rubber latex (latex), polyvinyl chloride (vinyl), acrylonitrile butadiene (nitrile), polychloroprene (neoprene), and a styrene‐ethylene/butylene‐styrene block copolymer (SEBS) were tested. All test specimens, with the exception of the vinyl, were obtained from surgical gloves. Unaged out‐of‐the‐box specimens as well as those subjected to various degrees of artificial aging were included in the study. After the abrasion sequence, the barrier integrity of the material was assessed through the use of a static leak test. Other traditional tests performed on these materials were viral penetration to validate the abrasion data and tear testing for comparative purposes. The results indicate that specific glove‐material performance is dependent upon the particular test under consideration. Most notably, abrasion, even in controlled nonsevere conditions, may compromise to varying degrees the barrier integrity of latex, vinyl, SEBS, nitrile, and neoprene glove materials. However, as evidenced by the results of testing three brands of neoprene gloves, the abrasion resistance of any one glove material may be significantly affected by variations in production processes. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 81–87, 2004
Factors affecting the structure and properties of bioactive foam scaffolds for tissue engineering
Authors: Jones Julian R. , Hench Larry L.
Published: December 2003

Resorbable 3D macroporous bioactive scaffolds have been produced for tissue‐engineering applications by foaming sol‐gel–derived bioactive glasses of the 58S (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) composition with the aid of a surfactant. Bioactive glasses are known to have the ability to regenerate bone, and to release ionic biological stimuli that promote bone‐cell proliferation by gene activation. The foams exhibit a hierarchical structure, with interconnected macropores (10–500 μm), which provide the potential for tissue ingrowth and mesopores (2–50 nm), which enhance bioactivity and release of ionic products. Many factors in the sol‐gel and foaming processes can be used to control these pore sizes and distributions. This work concentrates on the effect of the processing temperature, gelling agent concentration, and the amount of water used for the foam generation on the structure, pore morphology, and the properties of the foam scaffold. The simplest and most reproducible method for controlling the modal pore diameter was by the amount of water added during the foaming process. The in vitro dissolution and bioactivity of the bioactive foams were compared to that of unfoamed monoliths and powders (< 20 μm in diameter) of the same composition. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 36–44, 2004
Tendon surface modification by chemically modified HA coating after flexor digitorum profundus tendon repair
Authors: Yang Chao , Amadio Peter C. , Sun Yu‐long , Zhao Chunfeng , Zobitz Mark E. , An Kai‐Nan
Published: December 2003

Carbodiimide derivatized HA (cd‐HA) is less soluble in water than normal HA, and therefore has an increased tissue residence time. The purpose of this study was to study the effect of cd‐HA gel on gliding and repair integrity during simulated repetitive motion of a repaired tendon in vitro. A total of 36 flexor digitorum profundus (FDP) tendons from six adult mongrel dogs were used and divided into three groups of control, simple HA, and cd‐HA. The gliding resistance between the FDP and the proximal pulley, FDS, and bone was measured before laceration and after modified Kessler technique repair at 1, 5, 10, 50, 100, 200, 300, 400, and 500 cycles. After gliding testing, failure load, tendon stiffness, and resistance to gap formation were measured. The results showed from the first cycle to the 10th cycle, there were no significant differences in gliding resistance between the three testing groups (p > 0.05). From the 50th cycle onwards, the friction was significantly lower in the cd‐HA gel group than in the control group (p < 0.05). Neither breaking strength, nor tendon stiffness, nor resistance to gap formation of the repairs were significantly different between the three groups (p > 0.05). © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 15–20, 2004
Does low‐intensity pulsed ultrasound stimulate maturation of tissue‐engineered cartilage?
Authors: Duda Georg N. , Kliche Alexander , Kleemann Ralf , Hoffmann Jan E. , Sittinger Michael , Haisch Andreas
Published: December 2003

Traumatic events are a primary cause of local lesions of articular cartilage. Tissue engineered, cartilage‐like structures represent an alternative to current treatment methods. The time necessary for tissue maturation and the mechanical quality of the regenerate at implantation are both critical factors for clinical success. Low‐intensity pulsed ultrasound has proven to accelerate chondrogenesis in vitro. The goal of this study was to evaluate whether low‐intensity pulsed ultrasound is capable of accelerating the process of cartilage maturation and increasing regenerate stability. Hyaline‐like cartilage specimens were generated in vitro and subcutaneously implanted in the backs of nude mice. Twenty‐eight animals received 20 min of low‐intensity pulsed ultrasound treatment daily, and 28 animals received a sham treatment. Specimens were explanted after 1, 3, 6, and 12 weeks, mechanically tested with the use of an indentation test, histologically examined, and processed for RT‐PCR. The Young's moduli significantly increased from 3 to 12 weeks, and at 6 weeks were comparable to those of native articular cartilage. In histological examination, specimens showed neocartilage formation. There was no significant difference between ultrasound‐treated and sham‐treated groups. The mechanical stability of the neocartilage specimens increased with treatment time and reached values of native cartilage after 6 weeks in vivo. Low‐intensity pulsed‐ultrasound stimulation showed no stimulatory effect on tissue maturation. In contrast, ultrasound‐treated specimens showed a reduced Col 2 expression at 1 week and were significantly less stiff compared to native cartilage at 6 and 12 weeks. An acceleration of the maturation of tissue‐engineered neocartilage in a clinical setting by means of low‐intensity pulsed ultrasound therefore appears rather unrealistic. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 21–28, 2004
Attachment of artificial cartilage to underlying bone
Authors: Ushio Kazuyasu , Oka Masanori , Hyon Suong‐Hyu , Hayami Takashi , Yura Shigeto , Matsumura Kazuaki , Toguchida Junya , Nakamura Takashi
Published: December 2003

The key problem with artificial joint materials is obtaining quick and firm attachment onto the underlying bone. In developing artificial articular cartilage, composed of polyvinyl alcohol hydrogel (PVA‐H), this problem was solved by using a composite osteo‐chondral device (COD). This enables attachment within four weeks post‐operation by massive bone ingrowth into the pores. The COD consists of PVA‐H as an artificial cartilage and titanium fiber mesh (TFM) as porous artificial bone. In this study, the strength of the shear resistance force at the interface of the PVA‐H and the TFM fabricated by injection molding and the changes in the mechanical properties of the PVA‐H fabricated by high temperature during the injection‐molding process were examined. The shear resistance force was strengthened markedly by using injection molding and no important deterioration of the PVA‐H was found. Morphological examination of canine spines, to which artificial intervertebral discs made of the COD were implanted, showed good bonding of the COD with the vertebral bodies for an extended period of 30 months, and encouraged us to use the COD clinically. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 59–68, 2004
The effects of lubricant composition on in vitro wear testing of polymeric acetabular components
Authors: Wang A. , Essner A. , Schmidig G.
Published: December 2003

Lubricant composition is known to affect in vitro (simulator) wear of polymeric acetabular components. Clinical acetabular components, fabricated from both ultrahigh molecular weight polyethylene (UHMWPE) and polytetrafluoroethylene (PTFE), were tested against cobalt–chromium 32‐mm ball heads, with the use of various lubricants, with different compositions and concentrations of bovine and calf serum as well as hyaluronic acid, in tests which lasted one million cycles. The type of proteins and their relative concentration in the lubricant affected the wear rate of both UHMWPE and PTFE. Increasing protein concentration reduced the UHMWPE wear rate but increased the PTFE wear rate. For a given total protein concentration, increasing the albumin/globulin (A/G) ratio led to a significant reduction in the wear rate for PTFE. A similar but smaller effect was found for UHMWPE. The relative wear‐rate ratio between PTFE and UHMWPE depends on both the total protein concentration and the specific protein concentration (albumin/globulin ratio). The average clinical wear rates for both PTFE and UHMWPE and the average wear‐rate ratios between them were reproduced when the serum lubricant contained total protein concentration and A/G ratio within normally observed physiological ranges. It is recommended that lubricants for simulator testing be standardized to control total protein content as well as albumin/globulin ratio. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 45–52, 2004
Deproteinizing effects on resin–tooth bond structures
Authors: Yoshida Eiji , Hashimoto Masanori , Hori Minoru , Kaga Masayuki , Sano Hidehiko , Oguchi Haruhisa
Published: December 2003

This study investigated the effects of NaOCl on resin–tooth bonds to simulate the situations of long‐term durability and caries invasion. Resin–tooth bonded specimens were produced with the use of two resin adhesives (Excite and One‐Bond). Resin–tooth bonded beams (adhesive area; 0.9 mm2) were serially sectioned and the specimens were immersed in 10% NaOCl medium for 0 (control), 2, 4, and 6 h after being stored in water for 24 h. After immersion, microtensile bond tests were performed. SEM fractography was conducted to calculate each failure mode by image analysis. In addition, the adhesive interface was examined with the use of TEM. In the control specimens, enamel bond strengths had no difference between Excite (45.6 ± 15.0) and One‐Bond (56.9 ± 12.9). On the other hand, dentin bond strengths had significant difference between Excite (80.6 ± 21.2) and One‐Bond (50.7 ± 11.2). The bond strengths decreased with increased storage time for both systems with enamel and dentin bonds. The deteriorated mineralized dentin of beams resulted in bond‐strength reduction for resin–enamel bonds. For dentin bonding, the adhesive interface was gradually dissolved from the outer to the center portion of the beam. The depletion of collagen fibrils within the demineralized dentin or hybrid layer deformation was found under SEM and TEM examinations. These morphological changes are responsible for bond strength reduction of resin‐dentin bonds. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 29–35, 2004
Comparison of Th1/Th2 cytokine profiles of initial wound healing of rats induced by PDCM and e‐PTFE
Authors: Lu Hsein‐Kun , Ko Meng‐Tsung , Wu Ming‐Fang
Published: December 2003

Because periodontal regeneration is vital in the modern treatment of periodontal defects, artificial membranes have become a key component for predictable outcomes. Herein a new ranking system to analyze the expression of different cytokines around regenerative membranes is introduced. Porcine dermal collagen membranes (PDCMs) and GORE‐TEX® (e‐PTFE) membranes were used for implantation in a Sprague Dawley rat model. Tissue samples were harvested at three time intervals (7, 10, and 14 days); then an immunohistochemical ranking process was conducted to determine the intensity of the selected Th1/Th2 cytokines [Th1: interleukin‐2 (IL‐2) and interferone‐γ (IFN‐γ); Th2: IL‐4, IL‐10, and IL‐13]. The results show that the intensities of IL‐2 cytokine in PDCM groups were slightly higher than those of e‐PTFE groups but without statistical significance. The level of interferon‐γ in PDCM groups was lower than that of e‐PTFE groups, but also without significant differences. However, expressions of Th2 cytokines (IL‐4, IL‐10, and IL‐13) induced by e‐PTFE were generally higher than those of PDCM and control groups at all times (Mann‐Whitney U test, p < 0.05). In a comparison of the mean ratio of IL‐2/IL‐4 with the use of the Mann‐Whitney U test, data for the PDCM group were generally higher than those of the e‐PTFE group, with statistical significance at all time intervals (p < 0.05). A descending order of the intensity ratio of IL‐2/IL‐4 was PDCM groups > control groups > e‐PTFE groups. These findings indicate that the cytokine profiles of PDCM, in connection with the GTR technique, demonstrate a higher trend toward Th1‐dominated responses and may protect against periodontal tissue destruction, as compared to the Th2‐dominated responses of e‐PTFE. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 75–80, 2004
Platelet adhesion and aggregation on polyethylene: Effect of exhaustive exercise
Authors: Bonifazi Marco , Aloisi Anna Maria , Ceccarelli Ilaria , Lamponi Stefania , Lodi Leda , Scaramuzzino Andrea , Stabile Elena , Lupo Concetta
Published: December 2003

The aim of the present study was to evaluate the effect of an exhaustive exercise on platelet adhesion and aggregation on polyethylene (PE) in relation to changes in plasma cortisol concentration in order to ascertain the effect of physical stress response in the blood‐contacting properties of polymeric materials. Twelve healthy sedentary subjects, six males and six females, were studied. Each subject performed an exercise test on a bicycle ergometer at intensity corresponding to 70% VO2 max until exhaustion. One month after the exercise session, each subject participated in a control rest session. In both sessions, blood samples were drawn every 5 min for cortisol, lactate, hemoglobin, and hematocrit determinations and every 15 min for evaluation of platelet adhesion and aggregation. Individual comparisons between the rest and exercise cortisol patterns identified three categories of cortisol responders to exercise: positive responders (C +, showing higher concentrations during exercise than during rest), negative responders (C −, showing lower concentrations during exercise than during rest), and nonresponders (NR, showing similar concentrations during exercise and rest). The results revealed that C + had lower platelet adhesion and aggregation scores during exercise than during rest; moreover C − had higher scores than C + and NR during exercise. The results obtained demonstrated no effects of sex or exercise on either cortisol plasma levels or platelet adhesion and aggregation on PE surface. With regard to cardiovascular risk, the results suggest that exercise favorably affects platelet functions when mechanisms of metabolic adaptation to prolonged muscular work, expressed by a cortisol increase, are activated during exercise. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 53–58, 2004
Chemical, structural properties, and osteoconductive effectiveness of bone block derived from porcine cancellous bone
Authors: Kim Su‐Hyang , Shin Jung‐Wook , Park Su‐A , Kim Young Kon , Park Mun Soo , Mok James M. , Yang Woo Ick , Lee Jin Woo
Published: December 2003

The purpose of this study is to determine the efficacy of bioactive calcium phosphate obtained from porcine cancellous bone for the treatment of bone defects and nonunion. Porcine cancellous bone blocks were heat treated at 1300 °C for 2 h. The chemical composition, calcium‐to‐phosphate ratio, and microstructure of the porcine bone blocks were examined. For in vivo implantation, bone defects were created on the anteromedial aspect of the proximal tibia in seven beagle dogs and the xenograft bone blocks were placed into these defects. Plain radiographs were taken at 2‐week intervals for roentgenographic evaluation. At 12 weeks, the specimens were stained with hematoxylin and eosin (H&E). The composition and morphology of heat‐treated porcine cancellous bone were found to be similar to heat‐treated human cancellous bone. Radiographs showed union between the host bone/bone‐block interfaces. At 12 weeks, uniform and substantial new bone formation was observed. It is concluded that heat‐treated porcine cancellous bone demonstrated effective osteoconductivity. This high‐temperature heat‐treatment technique has several advantages, including decreased risk of disease transmission and immunoreactivity, while also offering excellent biocompatibility. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 69–74, 2004
Porous Ti‐6Al‐4V alloy fabricated by spark plasma sintering for biomimetic surface modification
Authors: Kon Masayuki , Hirakata Luciana M. , Asaoka Kenzo
Published: December 2003

Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti‐6Al‐4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as‐received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as‐received Ti alloy powders were 128–178 MPa and 16–18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 88–93, 2004
Injectable acrylic bone cements for vertebroplasty with improved properties
Authors: Carrodeguas Raúl García , Lasa Blanca Vázquez , del Barrio Julio San Román
Published: December 2003

Currently commercially available acrylic bone cements lack adequate radiopacity and viscosity when they are used in percutaneous vertebroplasty (PVP). In this work improved formulations of radiopaque and injectable poly(methyl methacrylate) bone cements were prepared with different amounts (10–50 wt.%) of BaTiO3 or SrTiO3 particles as the radiopaque agent. Two sets of cements were prepared by using untreated or silanated radiopaque particles, respectively. The influence of the content and nature of the radiopaque agent as well as its silanation with 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), on the curing parameters, residual monomer content, radiopacity, mechanical properties, and injectability of the resulting materials, was examined. Doughing and setting times, maximum temperature, and compressive strength of all formulations fulfilled the requirements of standard specifications, with values of peak temperature in the range 57–72 °C and those of compressive strength between 114 and 135 MPa. Formulations containing at least 20 wt.% BaTiO3 or SrTiO3 had radiopacities equal to or greater than that corresponding to 2 mm of Al as required for surgical plastics. Injectability of any of the formulations provided 75–80 wt.% of the total mass manually injected through a conventional biopsy needle 4 min after mixing. Silanation of the BaTiO3 or SrTiO3 particles led to formulations with improved mechanical properties and injectability compared to those obtained with the untreated fillers. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 94–104, 2004