Dredged sediment for agriculture: Lake Paradise

Lake Paradise, a water supply lake for Mattoon, Illinois, has lost much of its capacity due to sediment. This was a study to determine the agricultural benefit of Lake Paradise sediment when applied to farmland on the lake watershed. About 170 cubic yards of sediment were hauled to a demonstration site. While this method is probably not practical economically on an agricultural scale, it did provide a way to evaluate the sediment productivity during the short (one year) term of this project. About 2100 yards of sediment were also pumped to the demonstration site using a hydraulic dredge. This was stored behind agricultural terraces and is being dewatered using three subsurface drainage methods. A study was also conducted of the water chemistry of Lake Paradise during the dredging operation. Results showed a significant yield increase of corn yields on the hauled sediment plots compared to the original farmland. About $100 per acre increased net returns resulted which would help defray some costs of lake reclamation. It was found that the costs of lake reclamation by applying dredged sediment to farmland using terraces is directly related to the steepness of the land slope. Spray irrigating sediment was found to be comparable in cost to storing behind terraces with the disadvantage that spray irrigation is limited to soils or special soil management practices where erosion can be controlled. A study was conducted of the water chemistry of Lake Paradise during the dredging operation. Results showed that the project had a minimal effect on lake water quality.U.S. Geological SurveyU.S. Department of the InteriorOpe

Stripes, Pseudogaps, and Van Hove Nesting in the Three-band tJ Model

Slave boson calculations have been carried out in the three-band tJ model for the high-T_c cuprates, with the inclusion of coupling to oxygen breathing mode phonons. Phonon-induced Van Hove nesting leads to a phase separation between a hole-doped domain and a (magnetic) domain near half filling, with long-range Coulomb forces limiting the separation to a nanoscopic scale. Strong correlation effects pin the Fermi level close to, but not precisely at the Van Hove singularity (VHS), which can enhance the tendency to phase separation. The resulting dispersions have been calculated, both in the uniform phases and in the phase separated regime. In the latter case, distinctly different dispersions are found for large, random domains and for regular (static) striped arrays, and a hypothetical form is presented for dynamic striped arrays. The doping dependence of the latter is found to provide an excellent description of photoemission and thermodynamic experiments on pseudogap formation in underdoped cuprates. In particular, the multiplicity of observed gaps is explained as a combination of flux phase plus charge density wave (CDW) gaps along with a superconducting gap. The largest gap is associated with VHS nesting. The apparent smooth evolution of this gap with doping masks a crossover from CDW-like effects near optimal doping to magnetic effects (flux phase) near half filling. A crossover from large Fermi surface to hole pockets with increased underdoping is found. In the weakly overdoped regime, the CDW undergoes a quantum phase transition ($T_{CDW}\to 0$), which could be obscured by phase separation.Comment: 15 pages, Latex, 18 PS figures Corrects a sign error: major changes, esp. in Sect. 3, Figs 1-4,6 replace

Novel Electrospun Scaffolds for the Molecular Analysis of Chondrocytes Under Dynamic Compression

Mechanical training of engineered tissue constructs is believed necessary to improve regeneration of cartilaginous grafts. Nevertheless, molecular mechanisms underlying mechanical activation are not clear. This is partly due to unavailability of appropriate scaffolds allowing exposure of cells to dynamic compressive strains (DCS) in vitro while permitting subsequent molecular analyses. We demonstrate that three-dimensional macroporous electrospun poly(ɛ-caprolactone) scaffolds can be fabricated that are suitable for the functional and molecular analysis of dynamically loaded chondrocytes. These scaffolds encourage chondrocytic proliferation promoting expression of collagen type II, aggrecan, and Sox9 while retaining mechanical strength after prolonged dynamic compression. Further, they exhibit superior infiltration of exogenous agents into the cells and permit easy retrieval of cellular components postcompression to allow exploration of molecular mechanisms of DCS. Using these scaffolds, we observed that chondrocytes responded to DCS in a magnitude-dependent manner exhibiting antiinflammatory and proanabolic responses at low physiological magnitudes. Proinflammatory responses and decreased cellular viability were observed at hyperphysiological magnitudes. These scaffolds provide a means of unraveling the mechanotransduction-induced transcriptional and posttranslational activities involved in cartilage regeneration and repair