@article{sun_noormets_chen_mcnulty_2008, title={Evapotranspiration estimates from eddy covariance towers and hydrologic modeling in managed forests in Northern Wisconsin, USA}, volume={148}, ISSN={["0168-1923"]}, DOI={10.1016/j.agrformet.2007.08.010}, abstractNote={Direct measurement of ecosystem evapotranspiration by the eddy covariance method and simulation modeling were employed to quantify the growing season (May–October) evapotranspiration (ET) of eight forest ecosystems representing a management gradient in dominant forest types and age classes in the Upper Great Lakes Region from 2002 to 2003. We measured net exchange of water vapor fluxes in a 63-year-old mature hardwood (MHW) stand, a 60-year-old mature red pine (MRP) stand, a 3-year-old young hardwood (YHW) stand, a 17-year-old intermediate hardwood (IHW) stand, a young red pine (YRP age 8) stand, an intermediate red pine (IRP age 21) stand, and two pine barren ecosystems burned 12 years (PB1) and 2 years (PB2) ago. Field data suggested that there were no significant differences in growing season (June–September) ET/precipitation ratio among all ecosystems in 2002. However, PB2 had significantly lower ET/precipitation than those of other ecosystems in 2003. The ratios were much higher for all ecosystems, up to 0.90 for IHW, during the peak summer months (June–July). PB2 was the lowest (0.64) during that period. Stand leaf area index alone did not explain ecosystem ET at the landscape scale. Seasonal ET values measured by the eddy covariance method were significantly lower than those simulated with a process-based hydrologic model, MIKE SHE. Our integration approach combined with field measurements and simulation modeling proved to be useful in providing a full picture of the effects of forest cover type change on landscape scale water balance at multiple temporal scales. The ET procedure used in the MIKE SHE model needs improvement to fully account for the effects of vapor pressure deficit on tree transpiration. Seasonal distributions of ET coincided with precipitation in the growing season, when fluxes estimated by both field and models were the highest. The simulation model suggests that removal of conifer forests in the study region may reduce ET immediately by 113–30 mm/year or about 20%, but our field data suggests that ET can recover within 8–25 years from re-growth of hardwood forests.}, number={2}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Sun, G. and Noormets, A. and Chen, J. and McNulty, S. G.}, year={2008}, month={Feb}, pages={257–267} }
 @article{chen_hubbe_heitmann_argyropoulos_rojas_2004, title={Dependency of polyelectrolyte complex stoichiometry on the order of addition - 2. Aluminum chloride and poly-vinylsulfate}, volume={246}, ISSN={["1873-4359"]}, DOI={10.1016/j.colsurfa.2004.07.021}, abstractNote={In the first part of this series it was shown that the stoichiometry of complexation between oppositely charged polyelectrolytes became increasingly dependent on the order of addition as the concentrations of monovalent and divalent ions were increased. This study considers the effect of aluminum ions on titrations between solutions of a strong poly-acid and a strong poly-base. In addition, the titratable charge of aluminum ion itself was also investigated. It was found that aluminum ions can interfere with the results of charge titrations, in the sense that the titration results became unpredictable. Stoichiometric relationships between the amount of aluminum present and the amount of titrant required to achieve streaming current values of zero were obtained only at pH values associated with a maximum in the amount of titrant needed to neutralize a given concentration of dissolved aluminum. The results are consistent with complexation between the anionic titrant and polynuclear species of aluminum, where the relative proportion of such species depends strongly on the molar ratio of OH to Al.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Chen, JH and Hubbe, MA and Heitmann, JA and Argyropoulos, DS and Rojas, OJ}, year={2004}, month={Oct}, pages={71–79} }
 @article{chen_heitmann_chang_hubbe_venditti_2004, title={The effect of paper additives on toner agglomeration during the recycling process}, volume={13}, number={14}, journal={Progress in Paper Recycling}, author={Chen, J. and Heitmann, J. A. and Chang, H.-M. and Hubbe, M. A. and Venditti, R. A.}, year={2004}, pages={16–23} }
 @article{chen_heitmann_hubbe_2003, title={Dependency of polyelectrolyte complex stoichiometry on the order of addition. 1. Effect of salt concentration during streaming current titrations with strong poly-acid and polybase}, volume={223}, ISSN={["0927-7757"]}, DOI={10.1016/S0927-7757(03)00222-X}, abstractNote={Titrations were carried out between solutions of a strong poly-acid (polyvinylsulfate, potassium salt) and a strong poly-base (poly-diallyldimethylammonium chloride (poly-DADMAC)) over a range of salt concentrations. Streaming current (SC) analysis of the titration endpoints appeared to show increasing deviations from 1:1 stoichiometry of complexation with increased salt. The results depended on the direction of the titration, such that a stoichiometric excess of the titrant (second additive) was required to achieve a SC reading of zero. These symmetrical results, depending on the order of addition, were obtained despite the fact that the plastic surfaces of the SC device had a slight negative charge and differing adsorption tendencies for the two kinds of polymer. A qualitative model of molecular events, based on non-equilibrium entrapment of non-complexed polymer segments was found to be inconsistent with results of tests carried out over a range of initial polymer concentration. Results were better described by a qualitative model involving formation of polyelectrolyte complexes (PECs) in solution, in which near-stoichiometric core complexes are stabilized by an excess of the second additive on their surface. Implications of the latter model were compared with the results of turbidimetric tests, aqueous contact angles on polymer-treated plastic surfaces, and microelectrophoresis of PECs. Results of this study have consequences for interpretation of polyelectrolyte titrations, as well as for industrial operations that involve the mixing of oppositely charged polyelectrolytes.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Chen, JH and Heitmann, JA and Hubbe, MA}, year={2003}, month={Aug}, pages={215–230} }
 @article{hubbe_chen, title={Charge-related measurements: A reappraisal. Part 1: Streaming current}, volume={45}, number={8}, journal={Paper Technology (Leatherhead, England)}, author={Hubbe, M. A. and Chen, J.}, pages={17–23} }
 @article{hubbe_chen_heitmann, title={Measurement and impact of charge: A practical guide}, volume={87}, number={11}, journal={Solutions! (Norcross, Ga.)}, author={Hubbe, M. A. and Chen, J. and Heitmann, J. A.}, pages={47–49} }
 @inproceedings{chen_hubbe_heitmann, title={Measurement of colloidal charge in the paper mill by streaming current}, booktitle={Proceedings, TAPPI Papermakers Conference, 2001}, publisher={Atlanta, GA: TAPPI Press}, author={Chen, J. and Hubbe, M. A. and Heitmann, J. A.} }