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Irrigated water, polymer application in

In the past decade, water-soluble polyacrylamide (PAM) was identified as an environmentally safe and highly effective erosion preventing and infiltration enhancing polymer when applied in furrow irrigation water at 1 mg L-1 - 10 mg L-1 , i.e., 1 ppm- 10 ppm.[1-9] Various polymers and biopolymers have long been recognized as viable soil conditioners because they stabilize soil surface structure and pore continuity. The new strategy of adding the conditioner, high molecular weight anionic PAM, to irrigation water in the first several hours of irrigation implies a significant costs savings over traditional application methods, in which hundreds of kilograms per hectare of soil additives are tilled into the entire (15 cm deep) soil surface layer. By adding PAM to the irrigation water, soil structure is improved in the important 1-5 mm thick layer at the soil/water interface of the 25%-30% of field surface contacted by flowing water. In 1995, the U.S. Natural Resource Conservation Service (NRCS) published a PAM-use conservation practice standard for PAM-use in irrigation water." 01 A 3-year study[21 applying these standards showed that PAM at dosage rates of 1 kg ha-1 -2 kg ha-1 per irrigation eliminated 94% (80%-99% range) of sediment loss in furrow irrigation runoff, while increasing infiltration 15%-50%. Seasonal application rates using the NRCS standard typically total 3 kg ha -1 -5 kg ha-1 . As PAM-use is one of the most effective and economical technologies for reducing soil-runoff, it has branched into stabilization of construction sites and road cuts, with formal statewide application standards set in Wisconsin and several southern states. Recent studies with biopolymers such as charged polysaccharides,[11-143 whey," 51 and industrial cellulose derivatives[11.141 introduce potential biopolymer alternatives to PAM

Structural and Morphological Characterization of Micro and Nanofibers Produced by Electrospinning and Solution Blow Spinning: A Comparative Study

Nonwoven mats of poly(lactic acid) (PLA), poly(ethylene oxide) (PEO), and poly(ε-caprolactone) (PCL) were prepared at a nano- and submicron scale by solution blow spinning (SBS) and electrospinning in order to compare crystalline structure and morphology developed by both processes during fiber formation. Polymer solutions were characterized by rheometry and tensiometry. Spun fibers were characterized by several analytical steps. SEM analyses showed that both solution blow spun and electrospun fibers had similar morphology. Absence of residual solvents and characteristic infrared bands in the solution blow spun fibers for PLA, PCL, and PEO was confirmed by FTIR studies. XRD diffraction patterns for solution blow spun and electrospun mats revealed some differences related to distinct mechanisms of fiber formation developed by each process. Significant differences in thermal behavior by DSC were observed between cast films of PLA, PCL, and PEO and their corresponding spun nanofibers. Furthermore, the average contact angles for spun PLA and PCL were higher than for electrospun mats, whereas it was slightly lower for PEO. When comparing electrospun and solution blow spun fibers, it was possible to verify that fiber morphology and physical properties depended both on the spinning technique and type of polymer

Biopolymer additives to reduce erosion-induced soil losses during irrigation

A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more than 80%. None of these biopolymers, however, exhibited the > 90% runoff sediment reduction shown by the present industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow, with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to > 2.5mM. Calcium improved the sedimentation of the polyelectrolytic polymers in this study

Polymer additives in irrigation water to reduce erosion and better manage water infiltration

Water-soluble polyacrylamide (PAM) was identified as an environmentally safe and highly effective erosion preventing and infiltration-enhancing polymer when applied in furrow irrigation water at 1-10 g m-3, i.e. 1-10 ppm. The agricultural use of polyacrylamide, PAM, as an additive in irrigation water has grown rapidly since commercial introduction in 1995 because it improves water infiltration and reduces erosion-induced soil losses up to 97%, saving tons of topsoil per hectare per year. Various polymers and biopolymers have long been recognized as viable soil conditioners because they stabilize soil surface structure and pore continuity. The new strategy of adding the conditioner, high molecular weight anionic PAM, to the irrigation water in the first several hours of irrigation enables a significant costs savings over traditional application methods of tilling soil conditoner into the entire (15 cm deep) soil surface layer. By adding PAM to the irrigation water, soil structure is Unproved in the all-important 1-5 mm thick layer at the soil/water interface of the 25 to 30% of field surface contacted by flowing water. Recent studies with biopolymers such as chitosan, charged polysaccharides, whey, and industrial cellulose derivatives show potential as biopolymer alternatives to PAM. Their success will depend on production economics

Preventing soil erosion with polymer additives

The agricultural use of polyacrylamide, PAM, as an additive in irrigation water has grown rapidly since commercial introduction in 1995, with over l million acres treated in 1998. PAM provides both economic and environmental benefits by improving water infiltration and reducing up to 98% of erosion-induced soil losses — a yearly saving of tons of topsoil per acre. With as little as 5 ppm of PAM in the first irrigation water to run across the field, soil cohesion increases enough to prevent particle detachment and erosion. Stable soil/polymer flocs result from PAM's high molecular weight (typically > 12 million) and its affinity to soil via coulombic and Van der Waals attraction. Although water soluble linear PAM is the only class of commercial polymer presently used to reduce erosion during irrigation, other polymer additives have shown some potential. Biopolymers such as chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils reduce shear-induced erosion; however concentrations at least 6-10 times higher than PAM are required to obtain the > 90% runoff sediment reduction shown by commercial PAM. The application of PAM in agricultural irrigation water and potential biopolymer alternatives to PAM are discusse

Ernst Freund as Precursor of the Rational Study of Corporate Law

Gindis, David, Ernst Freund as Precursor of the Rational Study of Corporate Law (October 27, 2017). Journal of Institutional Economics, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2905547, doi: https://dx.doi.org/10.2139/ssrn.2905547The rise of large business corporations in the late 19th century compelled many American observers to admit that the nature of the corporation had yet to be understood. Published in this context, Ernst Freund's little-known The Legal Nature of Corporations (1897) was an original attempt to come to terms with a new legal and economic reality. But it can also be described, to paraphrase Oliver Wendell Holmes, as the earliest example of the rational study of corporate law. The paper shows that Freund had the intuitions of an institutional economist, and engaged in what today would be called comparative institutional analysis. Remarkably, his argument that the corporate form secures property against insider defection and against outsiders anticipated recent work on entity shielding and capital lock-in, and can be read as an early contribution to what today would be called the theory of the firm.Peer reviewe

Irrigated water, polymer application in

In the past decade, water-soluble polyacrylamide (PAM) was identified as an environmentally safe and highly effective erosion preventing and infiltration enhancing polymer when applied in furrow irrigation water at 1 mg L-1 - 10 mg L-1 , i.e., 1 ppm- 10 ppm.[1-9] Various polymers and biopolymers have long been recognized as viable soil conditioners because they stabilize soil surface structure and pore continuity. The new strategy of adding the conditioner, high molecular weight anionic PAM, to irrigation water in the first several hours of irrigation implies a significant costs savings over traditional application methods, in which hundreds of kilograms per hectare of soil additives are tilled into the entire (15 cm deep) soil surface layer. By adding PAM to the irrigation water, soil structure is improved in the important 1-5 mm thick layer at the soil/water interface of the 25%-30% of field surface contacted by flowing water. In 1995, the U.S. Natural Resource Conservation Service (NRCS) published a PAM-use conservation practice standard for PAM-use in irrigation water." 01 A 3-year study[21 applying these standards showed that PAM at dosage rates of 1 kg ha-1 -2 kg ha-1 per irrigation eliminated 94% (80%-99% range) of sediment loss in furrow irrigation runoff, while increasing infiltration 15%-50%. Seasonal application rates using the NRCS standard typically total 3 kg ha -1 -5 kg ha-1 . As PAM-use is one of the most effective and economical technologies for reducing soil-runoff, it has branched into stabilization of construction sites and road cuts, with formal statewide application standards set in Wisconsin and several southern states. Recent studies with biopolymers such as charged polysaccharides,[11-143 whey," 51 and industrial cellulose derivatives[11.141 introduce potential biopolymer alternatives to PAM

Biopolymer additives to reduce erosion-induced soil losses during irrigation

A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more than 80%. None of these biopolymers, however, exhibited the > 90% runoff sediment reduction shown by the present industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow, with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to > 2.5mM. Calcium improved the sedimentation of the polyelectrolytic polymers in this study