Effects of fluctuating river flow on groundwater/surface water mixing in the hyporheic zone of a regulated,large cobble bed river

Physicochemical relationships in the boundary zone between groundwater and surface water (i.e. the hyporheic zone) are controlled by surface water hydrology and the hydrogeologic properties of the riverbed. We studied how sediment permeability and river discharge altered the vertical hydraulic gradient (VHG) and water quality of the hyporheic zone within the Hanford Reach of the Columbia River. The Columbia River at Hanford is a large, cobble‐bed river where water level fluctuates up to 2 m daily because of hydropower generation. Concomitant with river stage recordings, continuous readings were made of water temperature, specific conductance, dissolved oxygen and water level of the hyporheic zone. The water level data were used to calculate VHG between the river and hyporheic zone. Sediment permeability was estimated using slug tests conducted in piezometers installed into the river bed. The response of water quality measurements and VHG to surface water fluctuations varied widely among study sites, ranging from no apparent response to covariance with river discharge. At some sites, a hysteretic relationship between river discharge and VHG was indicated by a time lag in the response of VHG to changes in river stage. The magnitude, rate of change and hysteresis of the VHG response varied the most at the least permeable location (hydraulic conductivity (K) = 2.9 × 10^?4 cms^?1) and the least at the most permeable location (K = 8.0 × 10^?3 cms^?1). Our study provides empirical evidence that sediment properties and river discharge both control the water quality of the hyporheic zone. Regulated rivers, like the Columbia River at Hanford, that undergo large, frequent discharge fluctuations represent an ideal environment in which to study hydrogeologic processes over relatively short time periods (i.e. days to weeks) that would require much longer periods (i.e. months to years) to evaluate in unregulated systems. Copyright © 2006 John Wiley & Sons Ltd.     

Biogeochemical processes and microbial characteristics across groundwater-surface water boundaries of the Hanford Reach of the Columbia River

Biogeochemical processes within riverbed hyporheic zones (HZ) can potentially impact the fate and transport of contaminants. We evaluated a modified freeze core technique for the collection of intact cobble-bed samples from the Columbia River HZ along a stretch of the Hanford Reach in Washington State and investigated microbiological and geochemical parameters of corresponding frozen and unfrozen samples. During three sampling periods (March, May, and November 2000), relatively high numbers of viable aerobic heterotrophic bacteria were recovered from both unfrozen (10(6)-10(7) cfu/g) and frozen samples (10(5)-10(6) cfu/g). Relatively large populations of sulfate-, nitrate-, and iron-reducing bacteria were present, and significant concentrations of acid-volatile sulfide were measured in some samples, indicating that anoxic regions exist within this zone. Cr(VI), a priority groundwater pollutant on adjacent U.S. Department of Energy lands, was probably removed from solution in HZ samples by a combination of microbial activity and chemical reduction, presumably via products of anaerobic microbial metabolism. These results suggest that biogeochemical processes in the Columbia River HZ may contribute to the natural attenuation of Cr(VI). Although freezing modestly diminished recovery of viable bacteria, freeze core techniques proved reliable for the collection of intact hyporheic sediments.     

Influence of molecular tilt angle on the SHG response of pyroelectric liquid crystal polymers

Second harmonic generation in novel pyroelectric liquid crystal polymers (PLCP) made from a series binary mixtures, was studied using 1100 nm as the fundamental wavelength. The PLCPs were prepared by photo-polymerization of binary mixtures of two monomers which exhibit a smectic C^* phase, A2c (4″-(R)-(−)-2-[(10-acrylo-yloxy)decyl]oxy-3-nitrophenyl 4-{4′-[(11-acryloyloxy)-undecyloxy]phenyl}benzoate) and Alb (4″-((R)-(+)-2-octyloxy)-3″-nitrophenyl 4-(4′-(11-acryloyloxy)undecyloxy)-phenyl)-benzoate). The highest d₁₆ and d₂₃ coefficients were found to be in the range 0.65–0.8 pm/V, and differed depending on the detailed preparation of the sample. All cases of polymers formed from the chiral smectic C* phase showed an SHG-signal with no external field present, indicating that polar order became fixed. The SHG-signal was found to increase with the tilt angle of the FLC molecules.     

Edible vaccine protects mice against Escherichia coli heat-labile enterotoxin (LT): potatoes expressing a synthetic LT-B gene

The authors have designed and constructed a plant-optimize synthetic gene encoding the Escherichia coli heat-labile enterotoxin B subunit (LT-B), for use in transgenic plants as an edible vaccine against enterotoxigenic E. coli. Expression of the synthetic LT-B gene in potato plants under the control of a constitutive promoter yielded increased accumulation of LT-B in leaves and tubers, as compared to the bacterial LT-B gene. The plant-derived LT-B assembled into native pentameric structures as evidenced by its ability to bind ganglioside. The authors demonstrated immunogenicity by feeding mice the raw tubers and comparing the anti-LT-B serum IgG and faecal IgA to that produced in mice gavaged with bacterial LT-B. Mice were fed three weekly doses of 5 g tuber tissue containing either 20 or 50 micrograms LT-B, or gavaged weekly with 5 micrograms of LT-B from recombinant E. coli. One week after the third dose, mice immunized with potato LT-B had higher levels of serum and mucosal anti-LT-B than those gavaged with bacterial LT-B. Mice were challenged by oral administration of 25 micrograms LT, and protection assessed by comparing the gut/carcass mass ratios. Although none of the mice were completely protected, the higher dose potato vaccine compared favourably with the bacterial vaccine. These findings show that an edible vaccine against E. coli LT-B is feasible.     

Adaptive memory search for multidemand multidimensional knapsack problems

We describe a simple adaptive memory search method for the 0/1 Multidemand Multidimensional Knapsack Problem (0/1 MDMKP). The search balances the level of infeasibility against the quality of the solution, and uses a simple dynamic tabu search mechanism. A weighting scheme to balance out the differences in the tightness of the constraints is also implemented. Computational results on a portfolio of test problems taken from the literature are reported, showing very favorable results, both in terms of solution quality and the ability of the search to find feasible solutions.     

Optical investigation of the hydrogenation and dehydrogenation mechanisms of evaporated MgNi films

We prepared thin films of magnesium nickel with a wide compositional range from pure magnesium to the intermetallic compound Mg₂Ni by e-beam evaporation. Capped with a thin Pd film such layers act as switchable mirrors upon exposure to gases containing hydrogen and oxygen. We investigated the reaction kinetics by measurement of the transmittance, and the reflectances both from the film side and the substrate side. We found that the hydrogenation kinetics and the optical performance are strongly dependent on the layer composition. The best results were obtained for Mg₄Ni to Mg₈Ni. It is shown that this is due to the different nucleation and growth behavior of the layers.     

Habitat quality of historic Snake River fall Chinook salmon spawning locations and implications for incubation survival. Part 1: substrate quality

We evaluated substrate quality at two historic fall Chinook salmon (Oncorhynchus tshawytscha) spawning sites in the Snake River, Idaho, USA. The primary objective of this evaluation was to measure sediment permeability within these areas to determine the potential quality of the habitat in the event that anadromous salmonids are reintroduced to the upper Snake River. Riverbed sediments within the two sites in the upper Snake River were sampled using freeze cores and hydraulic slug tests. Sediment grain size distributions at both sites were typical of gravel‐bed rivers with the surface layer coarser than the underlying substrate, suggesting the riverbed surface was armoured. Despite the armoured nature of the bed, the size of the largest material present on the riverbed surface was well within the size limit of material capable of being excavated by spawning fall Chinook salmon. The percentage of fines was low, suggesting good quality substrate for incubating salmon embryos. Geometric mean particle sizes found in this study compared to a 55% to 80% survival to emergence based on literature values. Hydraulic slug tests showed moderate to high hydraulic conductivity and were comparable to values from current fall Chinook salmon spawning areas in the Hells Canyon Reach of the Snake River and the Hanford Reach of the Columbia River. Predicted estimates of mean egg survival at both sites (48% and 74%) equalled or exceeded estimates from fall Chinook salmon spawning areas in the Hells Canyon Reach and the Hanford Reach. Copyright © 2005 John Wiley & Sons, Ltd.     

Mixed oxide coatings for optics

Material mixtures offer new possibilities for synthesizing coating materials with tailored optical and mechanical properties. We present experimental results on mixtures of HfO2, ZrO2, and Al2O3, pursuing applications in UV coating technology, while the mixtures are prepared by magnetron sputtering, ion beam sputtering, plasma ion-assisted deposition (PIAD), and electron beam evaporation without assistance. The properties investigated include the refractive index, optical gap, thermal shift, and mechanical stress. The first high reflectors for UV applications have been deposited by PIAD.     

Switched-capacitor DC/DC converters with resonant gate drive

In this paper, we examine how switched-capacitor (SC) converters can be used in low-voltage low-power DC/DC applications with power management. Analysis of losses is presented to facilitate SC converter design and optimization. A resonant gate drive is proposed to reduce switching losses and simplify control of switches in SC converters. A closed-loop controller is designed to enable and disable oscillations of the resonant gate drive so that the output DC voltage is well regulated down to zero load and so that high efficiency is maintained for a very wide range of loads. Results are experimentally verified on two low-power (0.2 and 5 W) five-one step-down converters with regulated 3 Vdc output and efficiency greater than 80% in a 100-1 load range     

Reduced production of PGE2 and PGF2 alpha from decidual cell cultures supplemented with N-3 polyunsaturated fatty acids

A diet rich in n-3 polyunsaturated fatty acid (PUFA) may reduce the intrauterine production of prostaglandins and prolong pregnancy. We tested this hypothesis by assessing the influence of various PUFAs on the spontaneous production of PGE2 and PGF2 alpha from decidual cell cultures. In addition, we assessed prostaglandin and cytokine production stimulated by lipopolysaccharides (LPS) in order to mimic parturition where infection is involved. In both settings, we found that after supplementing with n-3 PUFA, PGE2 and PGF2 alpha were significantly reduced. After supplementing with n-6 PUFA, there was a significant increase in both prostaglandins. Both n-3 and n-6 PUFAs reduced the production of interleukin 1 (IL-1), while n-6 PUFAs reduced TNF production. PUFAs did not influence IL-6 production. Our findings support the hypothesis that dietary n-3 PUFA may prolong pregnancy by reducing intrauterine production of prostaglandins.