Seasonal patterns of groundwater and sediment microbial communities were explored in a hydrologically dynamic alpine oligotrophic porous aquifer, characterized by pronounced groundwater table fluctuations. Rising of the groundwater level in consequence of snow melting water recharge was accompanied by a dramatic drop of bacterial Shannon diversity in groundwater from H ′ = 3.22 ± 0.28 in autumn and winter to H ′ = 1.31 ± 0.35 in spring and summer, evaluated based on T‐RFLP community fingerprinting. Elevated numbers of bacteria in groundwater in autumn followed nutrient inputs via recharge from summer rains and correlated well with highest concentrations of assimilable organic carbon. Sterile sediments incubated to groundwater in monitoring wells were readily colonized reaching maximum cell densities within 2 months, followed by a consecutive but delayed increase and leveling‐off of bacterial diversity. After 1 year of incubation, the initially sterile sediments exhibited a similar number of bacteria and Shannon diversity when compared to vital sediment from a nearby river incubated in parallel. The river bed sediment microbial communities hardly changed in composition, diversity, and cell numbers during 1 year of exposure to groundwater. Summing up, the seasonal hydrological dynamics were found to induce considerable dynamics of microbial communities suspended in groundwater, while sediment communities seem unaffected and stable in terms of biomass and diversity.

A method is introduced for predicting control voltages that will generate a prescribed surface shape on a MEMS deformable mirror. The algorithm is based upon an analytical elastic model of the mirror membrane and an empirical electromechanical model of its actuators. It is computationally simple and inherently fast. Shapes at the limit of achievable mirror spatial frequencies with up to 1.5 microm amplitudes have been achieved with less than 15 nm rms error.

The Second Songhua River was subjected to a large amount of raw or primary effluent from chemical industries in Jilin city in 1960s to 1970s, resulting in serious mercury pollution. However, an understanding of other trace metal pollution has remained unclear. The objective of this study was to investigate trace metal contamination in the sediment of the river. Bottom sediment samples were taken in the river between Jilin city and Haerbin city in 2005. An uncontaminated sediment profile was taken in the Nen River at the same time. Total concentrations of Al, Fe, Mg, Ca, K, Na, Ti, Mn, V, Sc, Co, Cu, Cr, Ni, Pb and Zn in the sediment samples were measured by ICP-MS or ICP-OES, following digestion with various acids. Concentrations of Co, Cu, Cr, Ni, Pb and Zn in the surface sediments were 5.1-14.7, 18.5-78.9, 2.4-75.4, 7.2-29.0, 13.5-124.4, and 21.8-403.1 mg/kg, respectively, generally decreasing along the course of the river from Jilin city to Haerbin city. Background concentrations of trace metals were reconstructed by geochemical normalization to a conservative element scandium. Results showed that concentrations of Co, Cr, and Ni in the sediment were generally only slightly higher than or equal to their background values, while concentrations of Cu, Pb, and Zn in the some sediment samples were significantly higher than their background values. In detail, the sediment at Jilin city was moderately contaminated by Cu, and the sediment of the Second Songhua River was moderately contaminated by Pb and Zn. The top layer (0-10 cm depth) and bottom layers (30-46 cm depth) of one sediment profile at Wukeshu town were generally moderately polluted by Pb and Zn. Synthetically, the surface sediment in the studied river section was classified as natural sediment without ecological risk by the sediment pollution index (SPI) of Cu, Cr, Ni, Pb and Zn. Only the 30-45 cm depth of the sediment profile at Wukeshu town was classified as low polluted sediment by the SPI of these metals, recording a historical contamination of the river in the 1960s to 1970s. This buried contamination of trace metals might pose a potential risk to water column under disturbance of sediment.

The frequency-dispersed birefringence and dichroism of an electronically nonresonant liquid excited and probed by ultrafast pulses in an optically heterodyned detected configuration is reported. The nominally putative dichroic response of a transparent sample is shown to result from π out-of-phase contributions of Stokes and anti-Stokes third-order polarization components on, respectively, the red and blue sides of the probe pulse spectrum and are derived from CSRS and CARS type resonances. The strong corresponding nondispersed birefringent response, in contrast, results from the in-phase combination of these Stokes and anti-Stokes polarization components. Thus, by observing the dispersed probe pulse to the red or blue of the central carrier frequency, the various density matrix components, or pathways in time evolution history, contributing to either a dichroic or birefringent measurement may be more selectively viewed. The contribution of a particular nuclear response is enhanced when the observed frequency within the probe pulse spectrum is tuned to be either one quantum to the red or blue of the carrier frequency. This frequency-filtering technique can be used to enhance weak features in the total response, allow the determination of isotropic and anisotropic contributions to a nuclear response, and help probe the homogeneous and inhomogeneous character of the low-frequency Raman active density of states commonly observed in these two-pulse responses of nonresonant liquids. These effects are illustrated by the OHD birefringence and dichroism of CHCl3.