Density functional and electron correlated study offive linear birefringences --- Kerr, Cotton---Mouton, Buckingham,Jones and magnetoelectric ---in gaseous benzene

We present the results of an extended study of five birefringences—Kerr, Cotton–Mouton, Buckingham, Jones, and Magnetoelectric—on benzene in the gas phase. The relevant molecular quantities—first-order properties, linear, quadratic, and cubic response functions—are computed employing the density-functional theory ~DFT! response theory, with a choice of functionals. In some cases, different functionals are employed for the wave-function computational step and for the subsequent analytical response calculation to determine the combination yielding at the same time the optimal energy and energy derivative results. Augmented correlation consistent basis sets of double and triple zeta quality are used. The DFT results are compared to those obtained at the Hartree–Fock level and in some cases within a coupled cluster singles and doubles electronic structure model. The study tries to assess the ability of the DFT response theory to describe a wide range of properties in a system of rather large size and high complexity. The relative strength of the five birefringences for plausible experimental conditions is determined and, when possible, comparison is made with the results of the measurements

Multiple techniques for lake restoration

Lake Finjasjön is a shallow, eutrophic lake (area 1100 ha, mean depth 3 m, maximum depth 13 m) in southern Sweden. In the 1920s, the lake was clear, with a summer Secci depth of about 2 m. During the first half of the 20th century, untreated sewage from the town polluted the lake. In the 1930s, the lake began to show eutrophic characteristics, and in the 1940s, the cyanobacterium Gloetrichia echinulata dominated in summer. In 1949, the first municipal sewage treatment plant was built. The treatment was, however, insufficient, since the lake continued to be the recipient of the effluent with the result that the occurrence of cyanobacteria became more frequent. Species such as Microcystis and Anabaena caused skin rash and allergic symptoms among swimmers. The phosphorus load on Lake Finjasjön increased as the population of Hässleholm grew and reached a peak value of 65 tons annum1 in 1965. In 1977, the sewage plant was rebuilt to include chemical flocculation, reducing the total external phosphorus load to about 5 tons annum1. Despite this improvement the lake did not recover from its chronic and toxic cyanobacterial blooms. Phosphorus-leaking black sediments were identified as the cause of the lake’s failure to recover. Some 60 % of lakebed area is covered with sediments on average 3 m thick. Dredging the sediments was started on a large scale in 1987. Five years later, 25 % of the sediment area had been removed but the dredging was stopped since phosphorus continued to be released into the water from these areas. In 1992