A guided wave inspection technique for nuclear steam generator tubing

The utility of guided ultrasonic waves for increasing the efficiency and sensitivity of nuclear steam generator tubing evaluation by nondestructive means is explored. The basic theoretical background of guided waves in tubes is presented, with major emphasis placed on those results with direct relevance to NDE applications. The possibility of increasing the inspection range of the guided wave modes as well as their sensitivity to defects by proper choice of mode and frequency is also discussed.     

The Transmogrifier-2: a 1 million gate rapid-prototyping system

This paper describes the Transmogrifier-2 (TM-2), a second-generation multifield programmable gate array (FPGA) rapid-prototyping system. The largest version of the system will comprise 16 boards that each contain two Altera 10K50 FPGA's, four I-Cube interconnect chips, and up to 8 Mbytes of memory. The inter-FPGA routing architecture of the TM-2 uses a novel interconnect structure, a nonuniform partial crossbar, that provides a constant delay between any two FPGA's in the system. The TM-2 architecture is modular and scalable, meaning that systems of various sizes can be constructed from copies of the same board, while maintaining routability and the constant delay feature. Other features include a system-level programmable clock that allows single-cycle access to off-chip memory, and programmable clock waveforms with edge resolution of 10 ns. The first Transmogrifier-2 boards have been manufactured and are functional. They have recently been used successfully in some simple graphics acceleration applications     

X-ray microtomography shows pore structure and tortuosity in alkali-activated binders

Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography (μCT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, μCT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with ≥ 50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate (‘geopolymer’) gels which do not chemically bind water of hydration.     

The effects of run‐of‐river dam spill on Columbia River microplankton

Dams, increasingly common in riverine systems worldwide, are particularly prevalent on the Columbia River (CR) in the United States. Hydroelectric projects, including both storage and run‐of‐river (i.e., minimal storage) structures, on the mainstem CR highly manage water flow, often by releasing water over (rather than through) dams as “spill.” To test the effects of run‐of‐river dam spill on microplankton abundance and composition, we sampled above and below two dams in the lower CR before and during spill conditions in spring 2016 and during and after spill conditions in late summer 2007. We tested the effects of location (i.e., above vs. below dams), spill condition (i.e., before, during, and after spill), and their interaction on microplankton abundance. Generally, diatoms were most abundant during springtime, whereas cyanobacteria were most abundant in late summer. Most taxa were not significantly different in abundance above and below dams, regardless of spill status; although cyanobacteria abundance was marginally higher below dams in summer 2007 (p = .04). Abundances of all taxa were significantly different between pre‐spill and spill periods in spring 2016, whereas only diatom and flagellate abundances were significantly different between spill and post‐spill periods in summer 2007. We conclude that spill conditions may influence microplankton abundance, but are not likely to affect microplankton communities on either side of run‐of‐river dams on the CR. This is important information for dam managers concerned about ecosystem impacts of spill.     

Ontogenetic changes in pharyngeal morphology correlate with a diet shift from arthropods to dreissenid mussels in round gobies (Neogobius melanostomus)

The potential of predators to regulate populations of dreissenid mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) has been addressed since early in the dreissenid invasion of North America. Round gobies (Neogobius melanostomus) larger than approximately 60 mm have been shown to prey extensively on dreissenids, whereas smaller round gobies feed mainly on aquatic insects and crustaceans. We propose that ontogenetic changes in pharyngeal morphology may contribute to this diet shift in round gobies. Pharyngeals of 69 round gobies ranging from 31 to 164 mm total length were investigated using light microscopy and scanning electron microscopy. Areas of lower pharyngeals and pharyngobranchial 2 increased allometrically with fish length. Pharyngeals of round gobies smaller than 50 mm contained narrow (< 0.1 mm diameter) papilliform teeth that are consistent with eating soft-bodied prey. By the time round gobies reached approximately 80 mm in length, pharyngeals contained larger diameter (0.3-0.5 mm) molariform teeth typical of those found in molluscivorous fish. Pharyngeal teeth of the largest round gobies also showed considerable wear. Although changes in pharyngeal morphology may contribute to the previously described diet shift in round gobies as they age, genetic and environmental factors both likely influence pharyngeal remodeling and therefore merit further investigation.     

A customised approach to determining the geomorphic effectiveness of small flood events in a regulated river

The construction of dams significantly alters flow and sediment regimes with subsequent deleterious effects on the morphological and ecological character of rivers. Effective experimental floods can ameliorate the downstream geomorphic impacts of dams. The traditional view is that large floods are required to perform effective geomorphic work, and the geomorphic outcomes of small floods are often overlooked. Many river restoration frameworks do not consider small floods. Yet, there is evidence that the hydrological characteristics that ameliorate specific geomorphic impacts in a river are unique to each river, and a customised approach to setting the right mix of floods (including small experimental floods) is needed. In this study, we modify an existing flood effectiveness model developed for large floods, for determining the geomorphic effectiveness of small floods in a highly regulated Australian river. Two flood classes were added to the model (medium peak stream power and moderate total energy expenditure), and the flood power characteristics were rescaled to reflect the relative difference in the magnitude of the small floods and the magnitude of the geomorphic work performed. Using a step‐wise approach, this customised model determined the geomorphic effectiveness of small floods. The best flood for ameliorating the geomorphic impacts of flow regulation had medium to long duration (10 to 51 days), high peak unit stream power (77 to 123 Wm^?2) and moderate to large total energy expenditure (78,600 to 342,320 × 10³ J). This approach to determining flood effectiveness for small floods is applicable to other geomorphically impacted river channels downstream of dams and can be used to inform experimental flood releases for geomorphic outcomes.     

Antioxidant activity of pomegranate rind powder extract in cooked chicken patties

The radical scavenging activity, reducing power and phenolic composition of pomegranate rind powder extract (RP) were determined and antioxidant properties of RP was evaluated in cooked chicken patties compared with vitamin C (VC) during refrigerated storage. Freshly minced chicken meat were assigned to one of the following six treatments: control (meat without any antioxidant); RP 5, RP 10, RP 15 and RP 20 (5, 10, 15 and 20 mg equivalent RP phenolics 100 g^?1 meat, respectively) and VC 50 (50 mg VC 100 g^?1 meat). The RP exhibited significantly (P < 0.05) higher reducing power and 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity. Incorporation of RP into chicken patties significantly (P < 0.05) reduced the HunterLab L* values compared with control and VC patties. Total phenolic content (as tannic acid equivalent) significantly (P < 0.05) increased from 308 in control to 441 μg g^?1 in RP 20 patties. Addition of RP to chicken patties did not affect any of the sensory attributes. The values of thiobarbituric acid reactive substances were significantly (P < 0.05) reduced from 1.530 in control patties to 0.135 mg malonaldehyde kg^?1 samples in RP patties. Pomegranate rind powder extract treatment (RP 10, RP 15 and RP 20) substantially inhibited (P < 0.05) lipid oxidation in cooked chicken patties to a much greater extent than VC treatment. Therefore, pomegranate rind powder can be utilized as an excellent natural antioxidant source.     

A randomized trial of nicotine replacement therapy in combination with reduced-nicotine cigarettes for smoking cessation

A randomized double-blind, active controlled, parallel group, multi-center phase II clinical trial was conducted to evaluate the efficacy of reduced-nicotine cigarettes as a novel smoking cessation treatment (under Investigational Device Exemption 69,185). The concept for a reduced-nicotine cigarette designed to progressively wean smokers from the smoking habit is based on research demonstrating that successful smoking cessation is not only dependent on withdrawal of nicotine, but also on weaning from the habitual sensory and behavioral reinforcement of smoking. Treatment consisted of Quest brand of cigarettes (Quest 1, 2, and 3), which respectively deliver 0.59+/-0.06, 0.3+/-0.05, and less than 0.05 mg nicotine, either alone or in combination with nicotine replacement therapy (NRT). The primary endpoint was 4 weeks of continuous abstinence (Weeks 7-10), with additional follow-up at 3 and 6 months. Adult men and women smokers (N = 346), motivated to quit, were randomized to one of three treatment groups: Quest plus NRT (NRT pretreatment 2 weeks before, and NRT after the quit date), Quest plus placebo patch, or active control plus NRT (conventional cigarette, followed by NRT after quit date). Results showed that Quest plus NRT was more effective than active control plus NRT in achieving 4 weeks of continuous abstinence (32.8% vs. 21.9%). Quest plus placebo patch yielded an abstinence rate similar to that of the active control plus NRT (16.4% vs. 21.9%). No serious adverse events were attributable to the investigational product. Quest plus NRT offers promise as a new smoking cessation treatment.     

Air plasma spray processing and electrochemical characterization of SOFC composite cathodes

Air plasma spraying has been used to produce porous composite cathodes containing (La_0.8Sr_0.2)_0.98MnO_3−y (LSM) and yttria-stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs). Preliminary investigations focused on determining the range of plasma conditions under which each of the individual materials could be successfully deposited. A range of conditions was thereby determined that was suitable for the deposition of a composite cathode from pre-mixed LSM and YSZ powders. A number of composite cathodes were produced using different combinations of parameter values within the identified range according to a Uniform Design experimental grid. Coatings were then characterized for composition and microstructure using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes. A selection of coatings representative of the types of observed microstructures were then subjected to electrochemical testing to evaluate the performance of these cathodes. From these tests, it was found that, in general, the coatings that appeared to have the most suitable microstructures also had the highest electrochemical performances, provided that the deposition efficiency of both phases was sufficiently high.     

Temporal shifts in the biodiversity of nearshore small fishes in Lake Simcoe

Nearshore small fish species represent a large proportion of fish biodiversity in Lake Simcoe, a large inland lake in southern Ontario, Canada. Over the past 30 years, Lake Simcoe has experienced several changes to its aquatic habitat, benthic invertebrate communities and predatory fish populations. This study compared samples of the nearshore small fish community in three geographic areas of Lake Simcoe. Fish community data were grouped into two time periods: a contemporary period (2007–2009) and a historical period (1982–1995). The fish community was compared across time periods for each area to assess if observed ecological changes had an impact on the small fish community. Species richness significantly declined between time periods in two areas (Cook's Bay and the southeast shoreline), the number of individuals captured declined between time periods in one area of the lake (Kempenfelt Bay) and Simpson's diversity index declined between time periods in one area of the lake (southeast shoreline). There were no significant differences in the Shannon–Weiner evenness index between time periods in any of the study areas. Additional analyses of intra- and inter-annual variation in fish sampling results generally supported the findings that shifts in the fish community occurred between time periods. Overall, this study suggests that the nearshore small fish biodiversity of Lake Simcoe has shifted over time but these shifts are not clearly related to recent increases in water clarity, macrophyte growth and nearshore benthic invertebrate densities.