The Impact of Extreme Low Flows on the Water Quality of the Lower Murray River and Lakes (South Australia)

The impact of extreme low flows on the water quality of the Lower Murray River and Lower Lakes (Alexandrina and Albert) in South Australia was assessed by comparing water quality from five sites during an extreme low flow period (March 2007?CNovember 2009) and a preceding reference period (March 2003?CNovember 2005). Significant increases in salinity, total nitrogen, total phosphorus, chlorophyll a and turbidity were observed in the Lower Lakes during the low flow period. Consequently, water quality guidelines for the protection of aquatic ecosystems were greatly exceeded. Principal Component Analysis, empirical and mass balance model calculations suggested these changes could be attributed primarily to the lack of flushing resulting in concentration of dissolved and suspended material in the lakes, and increased sediment resuspension as the lakes became shallower. The river sites also showed significant but more minor salinity increases during the extreme low flow period, but nutrient and turbidity concentrations decreased. The most plausible reasons for these changes were decreased catchment inputs and increased influence of saline groundwater inputs. The results highlight the vulnerability of arid and semi-arid lake systems to reduced flow conditions as a result of climatic changes and/or water management decisions.     

Wickability behaviour of single-knit structures

Wicking is the spontaneous flow of a liquid in a porous substrate, driven by capillary force. This flow in aporous medium, caused by capillary action, is governed by the properties of the liquid such as surface tension, viscosity and density as well as the surface-wetting forces and geometric configuration of the pore structure such as yarn construction, number of fibres in the cross section, the randomness of the internal structure, twist and the fabric structure. In this study of wickability, the most widely used structures such as single jersey, single pique, double pique and honeycomb with two structural-cell stitch lengths have been considered. Wickability increases with structural-cell stitch length. Among the different structures of fabrics, single jersey with higher structural-cell stitch length shows better performance of wickability and absorption of water when drop is placed on the fabric. The wickability of knitted fabrics was also evaluated in different directions such as wale, course, and bias direction. Among these, wale-wise specimen shows better wicking behaviour. The effect of different liquids like distilled water, artificial sweat solution, tap water, hot water and so on was also tested. The distilled water shows good wicking behaviour as compared with other liquids.     

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Electrochemical study in both classical cell and microreactors of flavin adenine dinucleotide as a redox mediator for NADH regeneration

The electrochemical reduction of flavin adenine dinucleotide (FAD) is studied in a classical electrochemical cell as well as in two types of microreactors: the first one is a one-channel reactor and the other one, a multichannel filter-press reactor. The ultimate goal is to use the reduced form of flavin (FADH₂), in the presence of formate dehydrogenase (FDH), in order to continuously regenerate the reduced form of nicotinamide adenine dinucleotide (NADH) for chiral syntheses. Various voltammetric and adsorption measurements were carried out for a better understanding of the redox behavior of the FAD as well as its adsorption on gold. Diffusivity and kinetic electrochemical parameters of FAD were determined.     

Achieving Optimum Performance in a High Pressure Sodium Lighting System

In spite of the many advantages of a high pressure sodium (HPS) lighting system, some problems do exist and compromises must be made. The lighting designer should be thoroughly familiar with the characteristics of all the integral components which make it up, such as lamps, ballasts, starters, luminaires, and poles. The most pertinent characteristics of these components are discussed. By proper selection of various components, they can function well together to achieve an optimum system performance.     

Chemical and Colloidal Dynamics of MnO2 Nanosheets in Biological Media Relevant for Nanosafety Assessment

Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are manganese dioxide (MnO₂) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO₂ is its sensitivity to chemical reduction leading to dissolution and Mn²⁺ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO₂ biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO₂ nanosheets in biological media for environmental and human health risk assessment. MnO₂ nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO₂ internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn²⁺ release. The results are used to classify MnO₂ nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO₂ transformations for nanotoxicity testing and nanosafety assessment are discussed.     

A real-time polymerase chain reaction method for monitoring anaerobic,hydrocarbon-degrading bacteria based on a catabolic gene

We have developed a real-time polymerase chain reaction (PCR) method that can quantify hydrocarbon-degrading bacteria in sediment samples based on a catabolic gene associated with the first step of anaerobic toluene and xylene degradation. The target gene, bssA, codes for the alpha-subunit of benzylsuccinate synthase. The primer-probe set for real-time PCR was based on consensus regions of bssA from four denitrifying bacterial strains; bssA sequences for two of these strains were determined during this study. The method proved to be sensitive (detection limit ca. 5 gene copies) and had a linear range of >7 orders of magnitude. We used the method to investigate how gasohol releases from leaking underground storage tanks could affect indigenous toluene-degrading bacteria. Microcosms inoculated with aquifer sediments from four different sites were incubated anaerobically with BTEX (benzene, toluene, ethylbenzene, and xylenes) and nitrate in the presence and absence of ethanol. Overall, population trends were consistent with observed toluene degradation activity: the microcosms with the most rapid toluene degradation also had the largest numbers of bssA copies. In the microcosms with the most rapid toluene degradation, numbers of bssA copies increased 100-to 1000-fold over the first 4 days of incubation, during which time most of the toluene had been consumed. These results were supported by slot blot analyses with unamplified DNA and by cloning and sequencing of putative bssA amplicons, which confirmed the real-time PCR method's specificity for bssA. Use of a companion real-time PCR method for estimating total eubacterial populations (based on 16S rDNA) indicated that, in some cases, ethanol disproportionately supported the growth of bacteria that did not contain bssA. The real-time PCR method for bssA could be a powerful tool for monitored natural attenuation of BTEX in fuel-contaminated groundwater. To our knowledge, this is the first reported molecular method that targets anaerobic, hydrocarbon-degrading bacteria based on a catabolic gene.     

Real-time measurement of ultrashort laser pulses using principalcomponent generalized projections

Frequency-resolved optical gating (FROG) is a technique to measure ultrashort laser pulses that optically constructs a spectrogram of a laser pulse. A two-dimensional (2-D) phase retrieval algorithm is used to extract the intensity and phase of a pulse from its spectrogram. We have improved a recently presented principal component generalized projections algorithm (PCGPA) making it easier to implement and fast enough to allow real-time inversion of FROG spectrograms. A femtosecond oscilloscope, based on second-harmonic generation (SHG) FROG, that displays the intensity and phase of ultrashort laser pulses in real time utilizing the improved PCGP phase retrieval algorithm is presented     

Use of mismatched grating pairs in chirped-pulse amplification systems

We demonstrate for the first time to our knowledge the use of mismatched grating pairs between the stretching and compression systems in a chirped-pulse amplification laser. Pulses as short as 57 fs are generated with 2000-lines/mm gratings in the compressor and 1200-lines/mm gratings in the stretcher.