bluuebunny/crossref_metadata_2025_split huggingface dataset:
WETTRANS: a flow‐path‐oriented decision‐support system for the assessment of water and nitrogen exchange in riparian peatlands
Authors: Trepel Michael , Kluge Winfrid 
Published: January 2004

AbstractEnvironmental authorities require quantitative predications of the nitrogen retention ability of riparian peatlands to aid in the selection of effective water management strategies for restoration. To support this decision‐making process, a matrix model connecting flow paths and nitrogen transformation was developed with a quasi‐stationary mass balance approach. The model concept is based on the assumptions that wetlands (1) receive water and nitrogen along several hydrological pathways, and (2) transformation of nitrogen occurs inside the wetland with different efficiencies, depending on the transition pattern between inflow and outflow pathways. These assumptions are formalized in a set of vectors describing the amount of water and the nitrogen concentration for each inflow pathway, a water distribution matrix between the inflowing water and several outflow pathways, a nitrogen transformation coefficient matrix of each inflow and outflow combination and, finally, two outflow vectors with the amount of water flowing out and the calculated nitrogen concentrations of each outflow pathway. The matrix model is applied to a drained valley peatland in order to quantify the effect of different water management options on an increase in nitrogen retention. Copyright © 2004 John Wiley & Sons, Ltd.
Extreme hydrochemical conditions in natural microcosms entombed within Antarctic ice
Authors: Tranter Martyn , Fountain Andrew G. , Fritsen Christian H. , Berry Lyons W. , Priscu John C. , Statham Peter J. , Welch Kathy A. 
Published: January 2004

AbstractCryoconite holes are near‐vertical tubes that form in the surface of glaciers when solar‐heated debris melts into the ice. Those that form in the McMurdo Dry Valleys of Antarctica are distinctive, in that they have ice lids and are closed to the atmosphere for periods of years to decades. Photoautotrophs and heterotrophs grow within this closed environment, perturbing the poorly buffered water chemistry, yet maintaining the potential for photosynthesis. Microbial excretion and decomposition of organic matter produces dissolved organic carbon (DOC): dissolved inorganic carbon ratios of ∼1:2. Much of the dissolved nitrogen pool (80–100%) exists as dissolved organic nitrogen (DON). The DON:DOC ratio is ∼1:11 (mol/mol), typical of organic particulate material at the Earth's surface. The combination of photoautotrophy, heterotrophy and weak chemical buffering within these microcosms promotes values of pH, pCO2, O2 saturation and percentage total dissolved nitrogen as DON that reach 10·99, 10−7·6 atm, 160% and 100% respectively, which are a unique combination among the surface waters on Earth. These ice‐sealed cryoconite holes could be important analogues of refugia on Snowball Earth and other icy planets. Copyright © 2004 John Wiley & Sons, Ltd.
Integrated strategies for maize irrigation and fertilization under water scarcity and environmental pressure in Bulgaria
Authors: Popova Zornitsa , Kercheva Milena 
Published: January 2004

AbstractIntegrated management of irrigation and fertilization could meet global increasing demand from maize production and environmental pressures under water scarcity. The objective of this paper was to evaluate the long‐term impact of irrigation scheduling and rates and timing of fertilization on water stress indicators, nitrogen uptake and leaching under maize on Chromic Luvisol (Sofia region). Modeling of the soil–plant system by the CERES‐maize model was used. Adjusted and modified CERES‐maize was run with different irrigation and fertilization scenarios and 30‐year weather data. Scenario analyses proved that grain yield and N‐uptake were severely affected on drylands under the conditions studied. Drought indicators showed that irrigation was required in 70% of the years. The sensitivity of maize drylands to precipitation in the critical (15 July–15 September) period caused great variability in maize yield (Cv=42%) and N‐uptake (Cv=25%) under nonlimited fertilization conditions. In addition, low vegetative precipitation proved to be a reason for fallow state leaching on drylands. All the irrigation scheduling tested improved N‐uptake efficiency, mitigated drought and significantly reduced yield and N‐uptake variability (Cv=5–6%). An integrated management strategy of N‐application timed to coincide with the period of maximum crop uptake and irrigation scheduled at 85% of field capacity reduced N available for leaching in the risky years. A drainage‐controlling scenario, developed for 75–80% of the required irrigation depth and satisfying predominantly the most sensitive phases of maize development, saved up to 95 mm yr−1 of water and reduced drainage in medium wet to wet fallow states by 30–40%. Significant early‐season N‐losses (25% of applied N) were associated with precipitation extremes and poor N‐dressing and could potentially happen in 3% of the years studied. Exceedance frequency of N‐uptake under nonlimited fertilization conditions and different irrigation strategies was used to adjust more accurately the fertilizer rates and timing for the soil and climate variability studied. Copyright © 2004 John Wiley & Sons, Ltd.
Advances in PLC‐based irrigation canal automation
Authors: Burt Charles M. , Piao Xianshu 
Published: January 2004

AbstractA short history of canal automation is given. PLC‐based canal automation is relatively new. Advances in PLC‐based canal automation are listed. Also listed are some of the remaining challenges. Recent advances have been made in understanding unsteady flow simulation procedures, the form of the control algorithms used, the tuning procedures for these control algorithms, and the field programming of the algorithms into PLCs. The experiences of the Cal Poly Irrigation Training and Research Center (ITRC) in automating a variety of canals with upstream and downstream control are given. Copyright © 2004 John Wiley & Sons, Ltd.
Optimization of water management in the RUT Irrigation District, Colombia
Authors: Depeweg Herman , Fabiola Otero Martha 
Published: January 2004

AbstractThe RUT Irrigation District is a flat polder area with an infrastructure for irrigation, drainage and flood protection. Water is pumped out for drainage, mainly during the wet season and is pumped in for irrigation during the two growing seasons. The RUT Irrigation District is one of the 16 districts that were transferred by the Colombian government to a water users' association. During this process the farmers agreed to take over the management and to give up governmental subsidies. It appeared that the farmers grossly underestimated the future energy costs and nowadays they complain about high costs for operation and maintenance of the pumping stations. In addition, the service provided is not adequate and the condition of the pumps is declining.The supplementary irrigation is based on the rainfall deficit, but a distinct criterion to supply water according to daily rainfall and cropping calendar does not exist. Hence, it is possible that more water than required is supplied to the area, affecting not only the pumping costs for irrigation but also for drainage. The present situation has been evaluated with a water balance at scheme level and an analysis of the measured groundwater fluctuations. Consecutively, a water balance at field level with an unsaturated groundwater flow model has been simulated to determine the irrigation requirements, yield reduction and drain flow based on a 20‐year analysis. The water balance at field level and the one‐, two‐ and three‐day rainfall with a return period of 5 years resulted in design drain flows. Finally, these flows were used in hydrodynamic simulations to analyse the pumping requirements for optimal drainage. The simulations also indicated the inundated areas to be expected for different rainfall intensities and frequencies. Copyright © 2004 John Wiley & Sons, Ltd.
On‐farm management of saline drainage water in arid and semi‐arid regions
Authors: Sharma D. P. , Tyagi N. K. 
Published: January 2004

AbstractThe irrigated arid and semi‐arid zones in India face twin problems of overall water scarcity and waterlogging accompanied by salinity. Subsurface drainage has proved successful in the rehabilitation and conservation of waterlogged saline soils. Drainage water from subsurface drainage systems seems to be an important source of water in the next millennium to tide us over the anticipated water scarcity problem in agriculture. However, the drainage waters from subsurface drainage systems are often saline and in the absence of a natural outlet, their disposal creates a problem. Various possible options have been discussed to mitigate the environmental threat posed by low quality drainage waters. Issues relating to potential reuse of low quality drainage waters along with management practices are addressed. Effects of factors influencing the long‐term sustainable use of saline drainage waters are presented and it is emphasized that special management practices have to be followed/evolved for site‐specific water quality, soil, crop and climatic conditions. However, the extent of salt leaching and crop establishment will depend on the total amount of monsoon rains and adequate subsurface drainage. It has been concluded that the use of a part of the saline drainage water in the post‐reclamation phase will not only augment the water supply but also minimize effluent disposal requirements. Copyright © 2004 John Wiley & Sons, Ltd.
Land preparation methods efficiency on the highland Vertisols of Ethiopia
Authors: Erkossa Teklu , Gizaw Assefa , Stahr Karl 
Published: January 2004

AbstractVertisols are among the major high potential soils in the central highlands of Ethiopia. Their productivity is constrained by severe waterlogging. Under traditional management systems, yield from these soils is far below the potential. To bridge the gap, several surface drainage methods were introduced and have shown a yield advantage over some of the traditional methods. However, alternative technologies for better crop yield and improved land resources management are still needed for sustainable use of the soils and water resources. As part of a concerted effort to improve productivity, field experiments were conducted during the 1996 and 1997 at Gincii, and 1998–2000 growing seasons at Caffee Doonsaa. Three land preparation methods, broad bed and furrows (BBF), ridge and furrows (RF) and flat seedbeds (FL) for the former, and four alternatives, BBF, RF, reduced tillage (RT) and green manuring (GM) for the latter, were evaluated. A randomized complete block design (RCBD) was used with three replications on permanent plots. Surface runoff and crops yields were considered as indicators of the efficiency of the land preparation methods. BBF gave the highest runoff at both locations over the years, but the effects on crop yields were inconsistent at both locations. BBF gave the lowest and the highest grain and straw yields in the first and the second years, respectively, at Gincii. GM and RT for cereals and BBF for a legume have shown better yield advantage at Caffee Doonsaa. To arrive at reliable conclusions, it is recommended that the experiment be continued under the prevailing cropping systems, taking soil quality and other sustainability indicators into account. Copyright © 2004 John Wiley & Sons, Ltd.
Responsive and recognitive hydrogels using star polymers
Authors: Oral Ebru , Peppas Nicholas A. 
Published: January 2004

AbstractPolymeric networks that have inherent capabilities to recognize different molecules and chemical changes in their environment are the next generation of materials that will aid in the diagnosis and treatment of diseases. We have prepared new networks based on star polymers that were designed to be responsive and recognitive. Using molecular imprinting with D‐glucose and crosslinking with poly(ethylene glycol) dimethacrylate with an ethylene glycol chain of nominal molecular weight 600, we prepared star polymer networks, which exhibited over 300% more uptake for D‐glucose compared to D‐fructose. Using copolymerization with methacrylic acid, we prepared star polymer networks with pH‐sensitivity, which showed a sharp transition in swelling around a pH of 4.5. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 439–447, 2004
Anti‐inflammatory effects of a titanium‐peroxy gel: Role of oxygen metabolites and apoptosis
Authors: Larsson Jenny , Persson Carina , Tengvall Pentti , Lundqvist‐Gustafsson Helen 
Published: January 2004

AbstractPolymorphonuclear neutrophils (PMN) are among the first inflammatory cells to arrive at an implant interface, where they encounter with the foreign material and may produce reactive oxygen species (ROS). During the interaction between titanium and ROS, titanium‐peroxy (Ti‐peroxy) compounds may be formed. We used a Ti‐peroxy gel, made from titanium and hydrogen peroxide, to study the effects of Ti‐peroxy compounds on PMN. In the absence of serum, the Ti‐peroxy gel decreased the oxidative response of PMN to yeast and PMA and reduced PMN apoptosis without inducing necrosis. These effects could not be ascribed to the release of hydrogen peroxide from the Ti‐peroxy gel, because a steady‐state hydrogen peroxide producing system failed to mimic the effects of the gel. The effects were similarly unaffected when PMN were preincubated with β2‐integrin antibodies, questioning the involvement of adhesion molecules. Nevertheless, when a filter was used to separate the Ti‐peroxy gel from the cells, the gel effect on PMN life span was abolished, pointing to a contact‐dependent mechanism. In the presence of serum, the Ti‐peroxy gel had no effect on the PMN oxidative response and life span, but appeared rather inert. In summary, this study demonstrates that the Ti‐peroxy gel has potentially anti‐inflammatory properties through a combined peroxide and physical contact effect, supporting the notion that interactions between titanium and inflammatory cells are responsible for the good performance of titanium in vivo. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 448–457, 2004
Polymeric sustained local drug delivery system for the prevention of vascular intimal hyperplasia
Authors: Kanjickal Deenu , Lopina Stephanie , Evancho‐Chapman M. Michelle , Schmidt Steven , Donovan Duane , Springhetti Sara 
Published: January 2004

AbstractAnastomotic intimal hyperplasia (IH) is a major cause of both autologous vein and synthetic vascular graft failure. We have previously published data suggesting that cyclosporin may reduce the development of IH in a canine model. However, systemic administration of cyclosporin could create serious adverse effects. Therefore, it is our long‐term goal to test the hypothesis that the controlled local release of cyclosporin from a polymeric vascular wrap will prevent the development of IH. To test this hypothesis, we developed a controlled release vascular wrap (sheet/ring) using a poly(ethylene glycol) (PEG) hydrogel. Sterilization of the polymers was performed using the ethylene oxide and hydrogen peroxide sterilization methods. It was found that except for one combination (8000 molecular weight and 1:1 crosslinking ratio), the differences in the swelling ratios for the sterilized and unsterilized hydrogels were not statistically significant. Release studies from unsterilized and ethylene oxide‐sterilized PEG hydrogels were conducted. It was found that release lasted for approximately 50 h for sterilized as well as unsterilized PEG hydrogels. Acute animal studies, to test the deployment of both the polymeric sheets and rings to the adventitial surface of native arteries and veins, were completed successfully. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 489–495, 2004
Macroporous poly(ϵ‐caprolactone) with antimicrobial activity obtained by iodine polymerization
Authors: de Arruda Almeida Kleber , de Queiroz Alvaro Antonio Alencar , Higa Olga Zazuco , Abraham Gustavo Abel , San Román Julio 
Published: January 2004

AbstractThe most serious problem usually encountered in the field of implanted biomedical devices is infectious morbidity as a primary source of mortality. In this work, the synthesis and characterization of a macroporous iodine‐based sanitizer (iodophor), poly(caprolactone)‐iodine (PCL‐I2), are presented. Characterization methods include nuclear magnetic resonance spectroscopy, gel permeation chromatography, nitrogen adsorption‐desorption, and scanning electron microscopy. The in vitro cytotoxicity to CHO cells based on cell viability with Chinese hamster ovary cells (CHO) and antimicrobial activities against Escherichia coli and Staphylococcus aureus were examined. The obtained macropore PCL‐I2 structures had a rather narrow size distribution. The PCL‐I2 iodophor was noncytotoxic to Chinese hamster ovary cells. The antimicrobial activities of the PCL‐I2 were assessed against E. coli and S. aureus. The tested PCL‐I2 showed better antimicrobial activity against E. coli than against S. aureus. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 473–478, 2004
Small changes in the polymer structure influence the adsorption behavior of fibrinogen on polymer surfaces: Validation of a new rapid screening technique
Authors: Weber Norbert , Bolikal Durgadas , Bourke Sharon L. , Kohn Joachim 
Published: January 2004

AbstractNumerous studies conclude that the selective adsorption of plasma proteins on materials contacting blood or tissue affects all subsequent interactions related to the biocompatibility of artificial surfaces. However, there are only a few studies available, which clearly demonstrate that there is a correlation between surface chemistry and selective protein adsorption. Detailed knowledge of such correlations would facilitate the design of biocompatible materials. In this study, a rapid, fluorescence‐based, screening technique using a 384‐well format for polymer–protein interactions was developed. The screening assay was used to measure the adsorption of human fibrinogen on 46 test polymers (44 polyarylates selected from a combinatorial library of tyrosine‐derived polyarylates, and two lactide‐based polymers). In this library of polyarylates, structural changes are generated by variations in either the polymer backbone or the polymer pendent chain. Although no overall trend between polymer hydrophobicity and fibrinogen adsorption could be identified using the entire set of test polymers (R2 = 0.43), fibrinogen adsorption was clearly correlated with variations in the pendent chain structure. Thus, when the test polymers were grouped by backbone composition, increased hydrophobicity of the pendent chain was significantly correlated with reduced fibrinogen adsorption. The following R2 coefficients within the polymer backbone groups were determined: 0.87 (diglycolates); 0.98 (glutarates); 0.73 (adipates); 0.87 (suberates); 0.67 (3‐methyl‐adipates). Our results demonstrate that it is possible to screen for protein–material interactions in a cost‐effective fashion using a miniaturized immunofluorescence technique. Further, we demonstrate that small changes in chemical composition can significantly influence the adsorption of human fibrinogen on polymer surfaces. The lactide‐based polymers were among those polymers exhibiting the highest tendency to adsorb fibrinogen. This information may be useful when polymers have to be selected for specific biomaterial applications. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 496–503, 2004
In vivo cancellous bone remodeling on a strontium‐containing hydroxyapatite (sr‐HA) bioactive cement
Authors: Wong C. T. , Lu W. W. , Chan W. K. , Cheung K. M. C. , Luk K. D. K. , Lu D. S. , Rabie A. B. M. , Deng L. F. , Leong J. C. Y. 
Published: January 2004

AbstractThe purpose of this study was to investigate the in vivo bone response to the strontium‐containing hydroxyapatite (Sr‐HA) bioactive bone cement injected into the cancellous bone. Sr‐HA cement was injected into the iliac crest of rabbits for 1, 3, and 6 months. Active bone formation and remodeling were observed after 1 month. Newly formed bone was observed to grow onto the bone cement after 3 months. Thick osteoid layer with osteoblasts formed along the bone and guided over the bone cement surface reflected the stimulating effect of Sr‐HA. From scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) analysis, high calcium and phosphorus levels were detected at the interface with a thick layer of 70 μm in width, and fusion of Sr‐HA with the bone was observed. Blood vessels were found developing in remodeling sites. The affinity of bone on Sr‐HA cement was increased from 73.55 ± 3.50% after 3 months up to 85.15 ± 2.74% after 6 months (p < 0.01). In contrast to Sr‐HA cement, poly(methyl methacrylate) (PMMA) bone cement was neither osteoconductive nor bioresorbable. Results show that the Sr‐HA cement is biocompatible and osteoconductive, which is suitable for use in treating osteoporotic vertebral fractures. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 513–521, 2004
Dissolution control and cellular responses of calcium phosphate coatings on zirconia porous scaffold
Authors: Kim Hae‐Won , Kim Hyoun‐Ee , Salih Vehid , Knowles Jonathan C. 
Published: January 2004

AbstractDifferent types of calcium phosphates [hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), and their composites (HA + FA, HA + TCP)] were coated on a zirconia (ZrO2) porous scaffold using a powder slurry method. The ZrO2 porous scaffold was intended for a load‐bearing implant, and the apatite layers were coated to improve osteoconductivity. The insertion of an FA intermediate layer between the coating layer and ZrO2 scaffold effectively suppressed the reaction between the calcium phosphate and ZrO2 and maintained the coating layer at the initial powder composition. The obtained coating layer, of a thickness of ∼30 μm, was relatively microporous and firmly adherent to the ZrO2 scaffold. Dissolution tests in physiological solution showed typical differences depending on the coating layers, with the dissolution rate increasing in the order TCP > HA + TCP > HA > HA + FA > FA. This result suggests the functional coating of the calcium phosphates in view of tailoring the solubility. Osteoblast‐like cells, MG63 and HOS, responded similarly in terms of cell growth, morphology, and proliferation rate regardless of the coating types, indicating favorable and comparable cell viability. However, the alkaline phosphatase (ALP) activity of the cells on the pure HA and HA composite coatings (HA + FA and HA + TCP) expressed at higher levels compared to those on pure FA and pure TCP coatings for both MG63 and HOS cells, suggesting a selective cell activity depending on the coating types. All the calcium phosphate‐coated‐ZrO2 scaffolds showed higher ALP levels compared to pure ZrO2 scaffold. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 522–530, 2004