Analysis of UK river restoration using broad‐scale data sets

This paper uses data from the UK River Restoration Centre's National River Restoration Inventory (NRRI) and the UK Environment Agency's River Habitat Survey (RHS) to analyse the relationship between restoration technique and the physical catchment context in which they have been implemented. Specifically we tested the relationship between categories of restoration technique and energy conditions, the relationship between restoration project and degree of channel modification, and whether the associations between restoration and physical catchment attributes have changed over time. Significant associations between categories of restoration technique and catchment variables were found, with direct morphological interventions needed in lower energy conditions; however, the analysis shows no change over time. This work shows that analysis of existing data sets can provide useful information to support the science and practice of river restoration and suggests that further analysis of existing ecological and geomorphological data sets provides an important learning opportunity to strengthen river restoration.     

Audience-induced inhibition of overt practice during learning.

Three experiments with 204 undergraduates examined the hypothesis that an audience can inhibit overt practice and thereby impair learning of unfamiliar words and enhance learning of familiar words. This hypothesis was derived from an analysis of motoric and symbolic mediation during learning. In comparison with learning while alone, the results show that the audience inhibited overt practice of unfamiliar and familiar words and that reduced practice was detrimental to learning unfamiliar words. Inhibition of overt practice with an audience enhanced learning of familiar words in only 1 of the experiments. Instructions to practice overtly reduced the audience-inhibition effect in learning unfamiliar words. The studies are discussed in the context of drive-theory explanations for social facilitation effects in learning. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biological/biomedical accelerator mass spectrometry targets. 2. Physical, morphological, and structural characteristics

The number of biological/biomedical applications that require AMS to achieve their goals is increasing, and so is the need for a better understanding of the physical, morphological, and structural traits of high quality of AMS targets. The metrics of quality included color, hardness/texture, and appearance (photo and SEM), along with FT-IR, Raman, and powder X-ray diffraction spectra that correlate positively with reliable and intense ion currents and accuracy, precision, and sensitivity of fraction modern ( F m). Our previous method produced AMS targets of gray-colored iron-carbon materials (ICM) 20% of the time and of graphite-coated iron (GCI) 80% of the time. The ICM was hard, its FT-IR spectra lacked the sp (2) bond, its Raman spectra had no detectable G' band at 2700 cm (-1), and it had more iron carbide (Fe 3C) crystal than nanocrystalline graphite or graphitizable carbon (g-C). ICM produced low and variable ion current whereas the opposite was true for the graphitic GCI. Our optimized method produced AMS targets of graphite-coated iron powder (GCIP) 100% of the time. The GCIP shared some of the same properties as GCI in that both were black in color, both produced robust ion current consistently, their FT-IR spectra had the sp (2) bond, their Raman spectra had matching D, G, G', D +G, and D ' bands, and their XRD spectra showed matching crystal size. GCIP was a powder that was easy to tamp into AMS target holders that also facilitated high throughput. We concluded that AMS targets of GCIP were a mix of graphitizable carbon and Fe 3C crystal, because none of their spectra, FT-IR, Raman, or XRD, matched exactly those of the graphite standard. Nevertheless, AMS targets of GCIP consistently produced the strong, reliable, and reproducible ion currents for high-throughput AMS analysis (270 targets per skilled analyst/day) along with accurate and precise F m values.     

Comparative study of arsenic removal by iron using electrocoagulation and chemical coagulation

This research studied As(III) and As(V) removal during electrocoagulation (EC) in comparison with FeCl₃ chemical coagulation (CC). The study also attempted to verify chlorine production and the reported oxidation of As(III) during EC. Results showed that As(V) removal during batch EC was erratic at pH 6.5 and the removal was higher-than-expected based on the generation of ferrous iron (Fe²⁺) during EC. As(V) removal by batch EC was equal to or better than CC at pH 7.5 and 8.5, however soluble Fe²⁺ was observed in the 0.2-μm membrane filtrate at pH 7.5 (10-45%), and is a cause for concern. Continuous steady-state operation of the EC unit confirmed the deleterious presence of soluble Fe²⁺ in the treated water. The higher-than-expected As(V) removals during batch mode were presumed due to As(V) adsorption onto the iron rod oxyhydroxides surfaces prior to the attainment of steady-state operation. As(V) removal increased with decreasing pH during both CC and EC, however EC at pH 6.5 was anomalous because of erratic Fe²⁺ oxidation. The best adsorption capacity was observed with CC at pH 6.5, while lower but similar adsorption capacities were observed at pH 7.5 and 8.5 with CC and EC. A comparison of As(III) adsorption showed better removals during EC compared with CC possibly due to a temporary pH increase during EC. In contrast to literature reports, As(III) oxidation was not observed during EC, and As(III) adsorption onto iron hydroxides during EC was only 5-30% that of As(V) adsorption. Also in contrast to literature, significant Cl₂ was not generated during EC, in fact, the rods actually produced a significant chlorine demand due to reduced iron oxides on the rod. Although Cl₂ generation and As(III) oxidation are possible using a graphite anode, a combination of graphite and iron rods in the same EC unit did not produce As(III) oxidation. However, a two-stage process (graphite anode followed by iron anode in separate chambers) was effective in As(III) oxidation and removal. The competing ions, silica and phosphate interfered with As(V) adsorption during both CC and EC. However, the degree of interference depends on the concentration and presence of other competing ions. In particular, the presence of silica lowered the effect of phosphate with increasing pH due to silica’s own significant effect at high pHs.     

Virus removal by iron coagulation-microfiltration

This study was undertaken to determine virus removal efficiency by iron coagulation followed by microfiltration (MF) in water treatment using the MS2 bacteriophage (25 nm diameter) as a tracer virus. Results from these bench-scale studies were used to propose a mechanism for virus removal by iron coagulation–MF. Ferric chloride was used as coagulant, and the dosages were 0, 2, 5, and 10 mg/L as Fe(III) with pH adjusted during mixing to 6.3, 7.3 and 8.3. In the absence of iron-coagulation and with less than 2 mg/L Fe, MF alone achieved less than a 0.5 log removal of MS2 virus. However, iron-coagulation pretreatment dramatically improved virus removal, especially in the 5–10 mg/L Fe dose range, ultimately achieving more than 4-log removal at pH 6.3 with 10-mg/L Fe dose. For the 5 and 10 mg/L Fe dosages, decreasing pH in the 8.3–6.3 range resulted in significantly greater virus removal. For 0 and 2 mg/L iron dosages, decreasing pH in the 8.3–6.3 range also improved virus removal, but to a lesser extent. The experimental data indicates negatively charged MS2 viruses first adsorbed onto the positively charged iron oxyhydroxide floc particles before being removed by MF. MS2 viruses were not inactivated in iron or aluminum coagulation as evidenced by the fact that their concentrations before and after coagulation, settling, and re-suspension of the coagulated sludge were not statistically different.     

Synthesis of submicron barium carbonate using a high-gravity technique

The purpose of this study was to build a platform for producing fine particles by applying a high-gravity (higee) technique to achieve reactive precipitation. Barium carbonate was chosen as a model compound and was produced in a spinning disk reactor (SDR), which is one type of higee equipment, via a carbonation route and a once-through mode. For size measurement, a suitable dispersion method was developed to obtain reproducible particle size data, using a laser-light analyzer. Several factors that affected the particle size of barium carbonate, including the CO₂ flow rate, the feed rate of Ba(OH)₂ slurry, the rotation speed, and the solid-content of feed slurry, were investigated. A high rotating speed and low feeding rate of slurry yielded small particles. The optimum solid-content of feeding slurry for obtaining small particles was also determined. However, the effect of the CO₂ flow rate on the particle size of the product was not significant.     

Measuring solid-state quantum yields: The conversion of a frequency-doubled Nd:YAG diode laser pointer module into a viable light source

This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy.     

Instrumented impact properties of some advanced nuclear reactor pressure vessel steels

Steels used to construct nuclear reactor pressure vessels are low-alloy ferritic steels. These steels should have good impact properties, i.e., low transition temperature and high upper shelf energy, both before and during service conditions. The most important service condition is the neutron irradiation. Extensive research and development was conducted to develop such steels. Instrumented impact testing was conducted on three advanced pressure vessel steels and, for comparison, a conventional pressure vessel steel. Both microstructures and fracture surfaces were examined using optical and scanning electron microscopic (SEM) techniques. In general, the advanced steels showed much better impact properties (lower ductile-brittle transition temperature and higher upper shelf energy) than the conventional steel. Loadtime traces showed that increase in the fracture energy was mainly due to increase in the fracture propagation energy rather than the initiation energy. Improvement in the toughness level of the advanced steels compared to that of the HSST steel was related to the difference in chemical composition, microstructure, and fracture surface morphology.