Simulating the effect of aerobic biodegradation on soil vapor intrusion into buildings: influence of degradation rate, source concentration, and depth

Steady-state vapor intrusion scenarios involving aerobically biodegradable chemicals are studied using a three-dimensional multicomponent numerical model. In these scenarios, sources of aerobically biodegradable chemical vapors are placed at depths of 1-14 m beneath a 10 m x 10 m basement or slab-on-grade construction building, and the simultaneous transport and reaction of hydrocarbon and oxygen vapors are simulated. The results are presented as Johnson and Ettinger attenuation factors alpha (predicted indoor air hydrocarbon concentration/source vapor concentration), and normalized contour plots of hydrocarbon and oxygen concentrations. In addition to varying the vapor source depth, the effects of source concentration (2-200 mg chemical/L vapor) and oxygen-limited first-order reaction rates (0.018-1.8 h(-1)) are studied. Hydrocarbon inputs were specific to benzene, although the relevant properties are similar to those for a range of hydrocarbons of interest. Overall, the results suggest that aerobic biodegradation could play a significant role in reducing vapor intrusion into buildings (decreased alpha-values) relative to the no-biodegradation case, with the significance of aerobic biodegradation increasing with increasing vapor source depth, decreasing vapor source concentration, and increasing first-order biodegradation rate. In contrast to the no-biodegradation case, differences in foundation construction can be significant in some settings. The significance of aerobic biodegradation is directly related to the extent to which oxygen is capable of migrating beneath the foundation. For example, in the case of a basement scenario with a 200 mg/L vapor source located at 3 m bgs, oxygen is consumed before it can migrate beneath the foundation, so the attenuation factors for simulations with and without aerobic biodegradation are similar for all first-order rates studied. For the case of a 2 mg/L vapor source located at 8 m bgs, the oxygen is widely distributed beneath the foundation, and the attenuation factor for the biodegradation case ranges from about 3 to 18 orders-of-magnitude less than that for the no-biodegradation case.     

Enhanced performance of HFCVD nanocrystalline diamond self-mated tribosystems by plasma pretreatments on silicon nitride substrates

Nanocrystalline diamond (NCD) coatings were grown by the hot-filament chemical vapour deposition (HFCVD) method on hydrogen plasma pretreated silicon nitride (Si₃N₄) substrates. The friction and wear behaviour of self-mated NCD films, submitted to unlubricated sliding and high applied loads (up to 90 N), was assessed using an oscillating ball-on-flat configuration in ambient atmosphere. The reciprocating tests revealed an initially high friction coefficient peak, associated to the starting surface roughness of NCD coatings (R_q = 50 nm). Subsequently, a steady-state regime with low friction coefficient values (0.01–0.04) sets in, related to a smoother (R_q = 17 nm) tribologically modified surface. A polishing wear mechanism governing the material loss was responsible for mild wear coefficients (k  10^− 7 mm³ N^− 1 m^− 1). The hydrogen etching procedure notably increased the film adhesion with respect to untreated surfaces as demonstrated by the high threshold loads (60 N; 3.5 GPa) prior to film delamination.     

Myosin heavy chain fibre types and fibre sizes in nuliparous and primiparous ovariectomized Iberian sows: Interaction with two alternative rearing systems during the fattening period

To investigate the effects of the reproductive background (nuliparous/primiparous) on skeletal muscle phenotype and their interaction with two alternative finishing systems (indoors/outdoors) in Iberian sows, 32 contemporary piglets were assigned to four different groups: indoors-nuliparous, indoors-primiparous, outdoors-nuliparous and outdoors-primiparous. Nuliparous sows were ovariectomized at 4 months of age, whereas primiparous were castrated at 14 months of age, after their first lactation. Indoors sows were fattened (2 months prior to slaughter) intensively, whereas outdoors sows were finished in an extensive land with natural resources. Muscle samples (semimembranosus, gluteobiceps) were analyzed for myosin fibre types and fibre sizes. Sows finished out-of-doors had more type I and IIA fibres and smaller fibres than indoor-fattened pigs. Primiparous reared indoors had a significantly lower IIX:IIB fibre ratio and showed a clear tendency for having larger fibres than nuliparous reared indoors. Reproductive background effect interacted with rearing condition effect inducing relevant muscular adaptations. Thus, the influence of reproductive background on muscle characteristics was not significant in sows reared out-of-doors but highly significant in sows finished intensively. This interaction resulted in muscular traits less favourable for meat quality in primiparous vs. nuliparous reared indoors.     

On the utility of SeaWinds/QuikSCAT data for the estimation of the thermodynamic state of first-year sea ice

The thermodynamic state of sea ice is important to accurately and remotely monitor in order to provide improved geophysical variable parameterizations in sea ice thermodynamic models. Operationally, monitoring the thermodynamic state of sea ice can facilitate eased ship navigation routing. SeaWinds/QuikSCAT (QuikSCAT) dual-polarization [i.e., horizontal (HH) and vertical (VV)] active microwave data are available at a sufficiently large spatial scale and high temporal resolution to provide estimates of sea ice thermodynamics. This analysis evaluated the temporal evolution of the backscatter coefficient (/spl sigma//spl deg/) and VV/HH copolarization ratio from QuikSCAT for estimating sea ice thermodynamics. QuikSCAT estimates were compared against RADARSAT-1 synthetic aperture radar (SAR) imagery and the Canadian Ice Service (CIS) prototype operational ice strength algorithm. In situ data from the Collaborative Interdisciplinary Cryospheric Experiment (C-ICE) for 2000, 2001, and 2002 were used as validation. Results indicate that the temporal evolution of /spl sigma//spl deg/ from QuikSCAT is analogous to RADARSAT-1. The QuikSCAT /spl sigma//spl deg/ temporal evolution has the ability to identify winter, snow melt, and ponding thermodynamic states. Moreover, the copolarization VV/HH ratio of QuikSCAT could provide a second estimate of the ponding state in addition to identifying the drainage state that is difficult to detect by single-polarization SAR. QuikSCAT detected thermodynamic states that were found to be in reasonable agreement to that of in situ observations at the C-ICE camp for all years. Operational implications of this analysis suggest QuikSCAT is a more effective and efficient medium for monitoring ice decay compared to RADARSAT-1 and can be utilized to provide more robust modeled ice strength thresholds.     

Ageing effects on α′ precipitation and resistance to corrosion of a novel Cr–Mo stainless steel with high Mo content

The consequences of ageing at 400 and 475 °C on α′ precipitation and corrosion resistance of a novel Cr–Mo ferritic SS with high Mo content were investigated. Combination of X-ray diffraction and Mössbauer spectroscopy results indicates the appearance of a small amount of a paramagnetic phase as a result of the ageing. This phase is iso-structural with the α phase and is thus associated with a Cr-rich α′ phase. The appearance of this phase is related to a decrease of the resistance to corrosion as studied by DL-EPR because the presence of this paramagnetic phase leads to discontinuities in the oxide layer thus reducing corrosion protection and exposing the steel to the action of the corrosive solution.     

A new IEEE Std 1459-2000—Compatible time-domain formulation for apparent power

This paper presents the development of new time-domain equations related to the definition of apparent power. These equations are compatible with the IEEE Std 1459-2000 Standard. When the application of these formulations involves an adequate quantity of samples, thus obeying the Nyquist Criterion, they can be utilized without restrictions regarding distortion, imbalance and asymmetry. Thus, they may be used in numeric meters for power measurements. In addition, unlike the above-mentioned standard, they do not oversimplify with respect to the phase and neutral resistance ratio or the percentage of delta-connected and wye-connected loads.     

Thermal conductivity as influenced by the temperature and apparent viscosity of dairy products

This study aimed to evaluate the rheological behavior and thermal conductivity of dairy products, composed of the same chemical components but with different formulations, as a function of temperature. Subsequently, thermal conductivity was related to the apparent viscosity of yogurt, fermented dairy beverage, and fermented milk. Thermal conductivity measures and rheological tests were performed at 5, 10, 15, 20, and 25°C using linear probe heating and an oscillatory rheometer with concentric cylinder geometry, respectively. The results were compared with those calculated using the parallel, series, and Maxwell-Eucken models as a function of temperature, and the discrepancies in the results are discussed. Linear equations were fitted to evaluate the influence of temperature on the thermal conductivity of the dairy products. The rheological behavior, specifically apparent viscosity versus shear rate, was influenced by temperature. Herschel-Bulkley, power law, and Newton's law models were used to fit the experimental data. The Herschel-Bulkley model best described the adjustments for yogurt, the power law model did so for fermented dairy beverages, and Newton's law model did so for fermented milk and was then used to determine the rheological parameters. Fermented milk showed a Newtonian trend, whereas yogurt and fermented dairy beverage were shear thinning. Apparent viscosity was correlated with temperature by the Arrhenius equation. The formulation influenced the effective thermal conductivity. The relationship between the 2 properties was established by fixing the temperature and expressing conductivity as a function of apparent viscosity. Thermal conductivity increased with viscosity and decreased with increasing temperature.     

Influence of molybdenum ion implantation on the localized corrosion resistance of a high strength aluminium alloy

The effect of Mo⁺ implantation on corrosion properties of AA 7075 (T6 and T73) has been studied. The induced modifications in the surfaces have been analysed by XPS and GAXRD. EXCO tests and electrochemical DC and AC techniques have been used to characterize the localized corrosion resistance. The effect of implantation is highly dependent on the ageing conditions. A marked increasing of the impedance of T6 samples after implantation has been measured, while the effect of Mo on T73 samples is less clear. Impedance spectra allow analysing the differences in the evolution of localized corrosion between both tempers.