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| 2. |
- Ichii, Kazuhito, et al.
(författare)
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New data-driven estimation of terrestrial CO2 fluxes in Asia using a standardized database of eddy covariance measurements, remote sensing data, and support vector regression
- 2017
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953. ; 122:4, s. 767-795
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Tidskriftsartikel (refereegranskat)abstract
- The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial CO2 fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated CO2 fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8days are reproduced (e.g., r2=0.73 and 0.42 for 8day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r2=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land CO2 fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land CO2 fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land CO2 fluxes. These data-driven estimates can provide a new opportunity to assess CO2 fluxes in Asia and evaluate and constrain terrestrial ecosystem models.
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| 3. |
- Ma, Wenzhong, et al.
(författare)
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Membrane formation by thermally induced phase separation : materials, involved parameters, modeling, current efforts and future directions
- 2023
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 669
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Tidskriftsartikel (refereegranskat)abstract
- Thermally-induced phase separation (TIPS) is one of the most popular methods considered for membrane preparation. Since its introduction by Castro in 1981, there has been significant progress in understanding, controlling, and implementing TIPS. This review provides a critical and integrative evaluation of the literature in this area that effectively defines the current state-of-the-art. It begins with an overview of the basic principles of TIPS and the used materials (polymers, diluents and additives) paying particular attention to the sustainability of the TIPS process. The subsequent sections examine the parameters affecting the outcome of TIPS technique, the role of mass transfer, and methods for modeling TIPS. This is followed by a discussion of current and potential applications of TIPS membranes. Finally, the review concludes with a discussion of likely future developments and prospects for the TIPS process.
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| 4. |
- Matsuura, Takeshi, et al.
(författare)
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Polymeric Membranes
- 2005
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Ingår i: Encyclopaedia of Chemical Processing. - New York : Marcel Dekker. ; , s. 2323-
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Bokkapitel (refereegranskat)abstract
- In this entry, properties of polymers, such as crystallinity, hydrophilicity/hydrophobicity, molecular weight, chemical property, thermal property, mechanical property, and electrochemical property are first discussed in relation to suitability of polymers for membrane materials. Various methods of membrane preparation from polymeric materials are described. These methods include the phase inversion technique, methods to coat a thin layer on a porous substrate, methods to modify membrane surfaces, and methods to prepare dry membranes. Examples of polymers used to prepare the membranes for different membrane processes such as reverse osmosis, nanofiltration, ultrafiltration, microfiltration, membrane gas and vapor separation, pervaporation, electrodialysis, and fuel cell are also given.
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| 5. |
- Rafat, Mehrdad, et al.
(författare)
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PEG-stabilized carbodiimide crosslinked collagen-chitosan hydrogels for corneal tissue engineering
- 2008
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 29:29, s. 3960-3972
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Tidskriftsartikel (refereegranskat)abstract
- Implantable biomaterials that mimic the extracellular matrix (ECM) in key physical and physiological functions require components and microarchitectures that are carefully designed to maintain the correct balance between biofunctional and physical properties. Our goal was to develop hybrid polymer networks (HPN) that combine the bioactive features of natural materials and physical characteristics of synthetic ones to achieve synergy between the desirable mechanical properties of some components with the biological compatibility and physiological relevance of others. In this study, we developed collagen-chitosan composite hydrogels as corneal implants stabilized by either a simple carbodiimide cross-linker or a hybrid cross-linking system comprised of a long-range bi-functional cross-linker (e.g. poly(ethylene glycol) dibutyraldehyde (PEG-DBA)), and short-range amide-type cross-linkers (e.g. 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and N-hydroxysuccinimide (NHS)). Optimum hybrid hydrogel demonstrated significantly enhanced mechanical strength and elasticity by 100 and 20%, respectively, compared to its non-hybrid counterpart. It demonstrated excellent optical properties, optimum mechanical properties and suturability, and good permeability to glucose and albumin. It had excellent biocompatibility and when implanted into pig corneas for 12 months, allowed seamless host-graft integration with successful regeneration of host corneal epithelium, stroma, and nerves. © 2008 Elsevier Ltd. All rights reserved.
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| 6. |
- Rafat, Mehrdad, et al.
(författare)
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Plasma surface modification and characterization of collagen-based artificial cornea for enhanced epithelialization
- 2007
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Ingår i: Journal of Applied Polymer Science. - : Wiley-Blackwell. - 0021-8995 .- 1097-4628. ; 106:3, s. 2056-2064
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Tidskriftsartikel (refereegranskat)abstract
- Argon plasma treatment enhanced the attachment of epithelial cells to a collagen-based artificial cornea crosslinked using glutaraldehyde (GA) and glutaraldehyde-polyethylene oxide dialdehyde (GA-PEODA) systems. The epithelialization of untreated and treated surfaces was evaluated by the seeding and growth of human corneal epithelial cells. Characterization of polymer surface properties such as surface hydrophilicity and roughness was also made by contact angle measurement and atomic force microscopy, respectively. Contact angle analysis revealed that the surface hydrophilicity significantly increased after the treatment. In addition, AFM characterization showed an increase in surface roughness through argon plasma treatment. Based on the biological and surface analysis, argon plasma treatment displays promising potential for biocompatibility enhancement of collagen-based artificial corneas. It was also found that the cell attachment to artificial cornea surfaces was influenced by the combined effects of surface chemistry (i.e., surface energy), polymer surface morphology (i.e., surface roughness), and polar interactions between functional groups at the polymer surface and cell membrane proteins.
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| 7. |
- Rafat, Mehrdad, et al.
(författare)
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Surface Characterization of Hollow Fibre Membranes Used in Artificial Kidney
- 2006
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Ingår i: Journal of Applied Polymer Science. - : John Wiley & Sons. - 0021-8995 .- 1097-4628. ; 101:6, s. 4386-4400
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Tidskriftsartikel (refereegranskat)abstract
- The internal and external curved surfaces of polysulfone hollow fiber membranes were characterized by atomic force microscopy (AFM), contact angle measurement (CAM), and scanning electron microscopy (SEM) with the aim of improving the membrane surface properties for blood compatibility. Novel approaches were applied to evaluate a number of properties, including the roughness, pore size, nodule size, and wettability of the surfaces of the hollow fibers. CAM studies were carried out by directly observing the liquid meniscus at the surfaces of hollow fibers. Observation of the meniscus and measurement of the contact angle became possible by using an imaging system developed in our laboratory. AFM and SEM studies were also conducted on the surfaces of the hollow fiber membranes by cutting them at an inclined angle. The effect of the molecular weight of poly(ethylene glycol) (PEG) in the polymer blend on the surface properties of the hollow fibers was studied. Increasing the PEG molecular weight increased the average pore size whereas it decreased the contact angle. The contact angle depended on the microscopic surface morphology, including nodule size and roughness parameters. The theoretical prediction along with the experimental data showed that the measured contact angle would be greater than the value intrinsic to the membrane material because of the formation of composite surface structures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4386–4400, 2006
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| 8. |
- Rafat, Mehrdad, et al.
(författare)
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Surface modification of collagen-based artificial cornea for reduced endothelialization
- 2009
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley-Blackwell. - 1549-3296 .- 1552-4965. ; 88A:3, s. 755-768
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to develop collagen-based hydrogels as tissue substitutes for corneal transplantation The design of the full-thickness corneal grafts includes prevention of cell migration onto the posterior surface of the implants, using a plasma-assisted surface modification technique. Briefly, the hydrogel materials were Subjected to ammonia plasma functionalization followed by grafting of alginate macromolecules to the target surface. The treated materials Surfaces showed observable decreases in endothelial cell attachment. The decrease in cell attachment and adhesion was dependant upon the concentration of alginate and plasma radio frequency (RF) power. High concentrations of alginate 5%, (w/v) and high I F power of 100 W produced surfaces with minimal cell attachment. The plasma-alginate treatment did not adversely affect the optical or swelling properties of the constructs. Contact angle measurement analysis revealed that the posterior surface hydrophilicity significantly increased after the treatment. The grafting of alginate to the implants surfaces was confirmed by fourier transform infrared spectroscopy. Both of the untreated and alginate grafted corneal materials were found to be superior to human cornea in optical and swelling properties.
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| 9. |
- Yuan, Wenping, et al.
(författare)
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Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome.
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The satellite-derived normalized difference vegetation index (NDVI), which is used for estimating gross primary production (GPP), often includes contributions from both mosses and vascular plants in boreal ecosystems. For the same NDVI, moss can generate only about one-third of the GPP that vascular plants can because of its much lower photosynthetic capacity. Here, based on eddy covariance measurements, we show that the difference in photosynthetic capacity between these two plant functional types has never been explicitly included when estimating regional GPP in the boreal region, resulting in a substantial overestimation. The magnitude of this overestimation could have important implications regarding a change from a current carbon sink to a carbon source in the boreal region. Moss abundance, associated with ecosystem disturbances, needs to be mapped and incorporated into GPP estimates in order to adequately assess the role of the boreal region in the global carbon cycle.
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