Sediment-adsorbed total mercury flux through Yolo Bypass,the primary floodway and wetland in the Sacramento Valley,California

The fate and transport of mercury are of critical concern in lowland floodplains and wetlands worldwide, especially those with a history of upstream mining that increases the mobility of both dissolved and sediment-bound Hg in watersheds. A mass budget of total mercury (THg) quantifies sources and storage for particular areas — knowledge that is required for understanding of management options in lowland floodplains. In order to assess contaminant risk in the largest flood-control bypass, prime wetland, and restoration target in the Sacramento River basin, we estimated empirical relationships between THg, suspended sediment concentration (SSC), and streamflow (Q) for each of the major inputs and outputs using data from various publicly available sources. These relationships were improved by incorporating statistical representations of the dynamics of seasonal and intra-flood exhaustion (hysteresis) of sediment and mercury. Using continuous records of Q to estimate SSC suspended sediment flux and SSC to estimate THg flux, we computed the net transfer of sediment-adsorbed mercury through the Yolo Bypass over a decade, 1993–2003. Flood control weirs spilling Sacramento River floodwaters into the bypass deliver ~ 75% of the water and ~ 50% of the river's suspended sediment load, while one Coast Range tributary of the bypass, Cache Creek, contributes twice the THg load of the mainstem Sacramento. Although estimated sediment flux entering Yolo Bypass is balanced by efflux to the Sacramento/San Francisco Bay-Delta, there is much evidence of deposition and remobilization of sediment in Yolo Bypass during flooding. These factors point to the importance of the bypass as sedimentary reservoir and as an evolving substrate for biogeochemical processing of heavy metals. The estimates of mercury flux suggest net deposition of ~ 500 kg in the 24,000 ha floodway over a decade, dominated by two large floods, representing a storage reservoir for this important contaminant.     

The crystallography of ferrous martensites

The applicability of the phenomenological crystallographic theory to martensitic transformations in ferrous alloys is discussed, and it is concluded that only for the {3, 15, 10} _F and {252} _F transformations are experimental data sufficiently complete for detailed comparisons with predictions of the theory. Since crystallographic measurements have proved more difficult to obtain in the {252}F case a detailed assessment of electron microscopy observations and of reported measurements of the shape strain and orientation relationship is given for this transformation. The basic theory introduced, in the 1950's accounts satisfactorily for the {3, 15, 10} _F transformation but not for the {252} _F , case. Recent modifications of the theory based on multiple lattice invariant shears are also reviewed and are examined in the light of the crystallographic measurements. The use of experimental information to infer possible inhomogeneous deformation modes is emphasized.     

Impact of Multiresolution Active and Passive Microwave Measurements on Soil Moisture Estimation Using the Ensemble Kalman Smoother

An observing system simulation experiment is developed to test tradeoffs in resolution and accuracy for soil moisture estimation using active and passive L-band remote sensing. Concepts for combined radar and radiometer missions include designs that will provide multiresolution measurements. In this paper, the scientific impacts of instrument performance are analyzed to determine the measurement requirements for the mission concept. The ensemble Kalman smoother (EnKS) is used to merge these multiresolution observations with modeled soil moisture from a land surface model to estimate surface and subsurface soil moisture at 6-km resolution. The model used for assimilation is different from that used to generate "truth." Consequently, this experiment simulates how data assimilation performs in real applications when the model is not a perfect representation of reality. The EnKS is an extension of the ensemble Kalman filter (EnKF) in which observations are used to update states at previous times. Previous work demonstrated that it provides a computationally inexpensive means to improve the results from the EnKF, and that the limited memory in soil moisture can be exploited by employing it as a fixed lag smoother. Here, it is shown that the EnKS can be used in large problems with spatially distributed state vectors and spatially distributed multiresolution observations. The EnKS-based data assimilation framework is used to study the synergy between passive and active observations that have different resolutions and measurement error distributions. The extent to which the design parameters of the EnKS vary depending on the combination of observations assimilated is investigated     

Microstructural Development during the Microwave Sintering of Yttria—Zirconia Ceramics

The microstructural development of 3 and 8 mol% yttria—zirconia ceramics during microwave sintering was studied and compared to conventionally heated samples. Microwave heating enhanced the densification processes occurring during constant-rate heating for both materials. No change was found in the grain size—density relationship for the 8 mol% yttria—zirconia. However, a small, but statistically significant shift favoring densification was found for the 3 mol% yttriazirconia. Differences in the responses of the two materials are not completely understood but may be due to the differences in the activation energy for grain growth and grain-boundary mobility.     

Hydroxyapatite bone substitutes developed via replication of natural marine sponges

The application of synthetic cancellous bone has been shown to be highly successful when its architecture mimics that of the naturally interconnected trabeculae bone it aims to replace. The following investigation demonstrates the potential use of marine sponges as precursors in the production of ceramic based tissue engineered bone scaffolds. Three species of natural sponge, Dalmata Fina (Spongia officinalis Linnaeus, Adriatic Sea), Fina Silk (Spongia zimocca, Mediterranean) and Elephant Ear (Spongia agaricina, Caribbean) were selected for replication. A high solid content (80 %wt), low viscosity (126 mPas) hydroxyapatite slurry was developed, infiltrated into each sponge species and subsequently sintered, producing a scaffold structure that replicated pore architecture and interconnectivity of the precursor sponge. The most promising of the ceramic tissue engineered bone scaffolds developed, Spongia agaricina replicas, demonstrated an overall porosity of 56–61% with 83% of the pores ranging between 100 and 500 μm (average pore size 349 μm) and an interconnectivity of 99.92%.     

Weighted argument systems: Basic definitions, algorithms, and complexity results

We introduce and investigate a natural extension of Dung's well-known model of argument systems in which attacks are associated with a weight, indicating the relative strength of the attack. A key concept in our framework is the notion of an inconsistency budget, which characterises how much inconsistency we are prepared to tolerate: given an inconsistency budget β, we would be prepared to disregard attacks up to a total weight of β. The key advantage of this approach is that it permits a much finer grained level of analysis of argument systems than unweighted systems, and gives useful solutions when conventional (unweighted) argument systems have none. We begin by reviewing Dung's abstract argument systems, and motivating weights on attacks (as opposed to the alternative possibility, which is to attach weights to arguments). We then present the framework of weighted argument systems. We investigate solutions for weighted argument systems and the complexity of computing such solutions, focussing in particular on weighted variations of grounded extensions. Finally, we relate our work to the most relevant examples of argumentation frameworks that incorporate strengths.     

Choice of similarity measure,likelihood function and parameters for histogram based particle filter tracking in CCTV grey scale video

The choice of particle filter dissimilarity distance measures and likelihood functions is considered in the context of object tracking in grey scale CCTV video. The geometrical interpretation of the Bhattacharyya coefficient and distance is reviewed and the relationships between the Bhattacharyya, Matusita, histogram intersection and χ² distances are examined. It is argued that as long as the likelihood function satisfies certain criteria its analytical form is not critical in the stated tracking context. This is demonstrated through an experimental comparison between the use of the standard Bhattacharyya distance/Gaussian likelihood combination and the potentially computationally simpler histogram intersection distance/triangular likelihood combination in particle filter tracking sequences. It is shown that the differences between the approaches are marginal when the likelihood criteria are applied. Whilst the analysis was focused on a specific application and context, we suggest that the findings will be of value to particle filter tracking in general.     

Physical health problems, depressive mood, and cortisol secretion in old age: Buffer effects of health engagement control strategies.

Objective: This study examined the protective role played by control behaviors aimed at overcoming physical health problems (health engagement control strategies; HECS) in the associations between older adults' physical health problems, depressive mood, and diurnal cortisol secretion. It was expected that adaptive levels of HECS would buffer the adverse effects of physical health problems on depressive mood and diurnal cortisol secretion. Design and Measures: Physical health problems and HECS were measured in a cross-sectional sample of 215 community-dwelling older adults. In addition, participants' depressive mood and patterns of diurnal cortisol secretion were assessed across 3 days. Results: The findings demonstrate that physical health problems predicted high levels of depressive mood and diurnal cortisol secretion, but only among older adults who reported low levels of HECS (and not among older adults who reported high levels of HECS). Moreover, depressive mood completely mediated the buffering effect of HECS on the association between physical health problems and cortisol secretion. Conclusion: The results suggest that adaptive levels of HECS represent a psychological mechanism that can protect older adults from experiencing the adverse emotional and biological consequences of physical health problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of Leakage Resistance in Pb(Zr,Ti)O3 Thin Films by Donor Doping

Donor doping, with La and Nb, has been used successfully to improve the leakage resistance of Pb(Zr,Ti)O₃ (PZT) films. Donor doping of Pb(Zr_0.5Ti_0.5)O₃ films has led to an improvement in the leakage resistance of over 2 1/2 orders of magnitude at elevated temperatures (T 100°C). The effect on leakage resistance is the same for the A-site (La) and B-site (Nb) dopants. However, the improvement is only about 1 order of magnitude near room temperature. This temperature effect is due to an increase in the transition temperature from a low activation energy mechanism to a higher activation energy mechanism. Similar improvements in leakage resistance have also been obtained by increasing the Pb concentration in the starting solution, which implies that Pb vacancies are the dominant acceptor species in the undoped films. In addition, donor doping has been effective in improving the electrical breakdown strength at elevated temperatures. Consequently, donor-doped PZT films have been shown to be superior to undoped films for applications requiring high leakage resistance, such as decoupling capacitors.     

Effect of NbC and TiC precipitation on shape memory in an iron-based alloy

This paper examines the effects of TiC and NbC precipitation and prior cold rolling on the shape memory behaviour of an iron-based alloy. A precipitate-free alloy was used as a reference to investigate the relative contributions of prior-deformation and precipitation on shape memory. Heat treatment of the Nb- and Ti-containing alloys at 700 °C and 800 °C resulted in carbide precipitates between 120 nm and 220 nm in diameter. Bend testing of these samples showed a marginal increase in shape memory compared to the precipitate-free alloy. Under these conditions TiC precipitation exhibited slightly better shape memory than for NbC. However, this small increase was over-shadowed by the marked increase in shape memory that can be produced by subjecting the alloys to cold rolling followed by recovery annealing. When processed in this way, fine carbides are formed in the Ti- and Nb-containing alloys during the heat treatment. For particles >25 nm in diameter the shape memory is unaffected, but, it was found that small <5 nm particles have a detrimental effect on shape memory due to pinning of the martensite plates, thereby inhibiting their reversion to austenite. The optimum shape memory was observed in the precipitate-free alloy after cold rolling and recovery annealing.