Generalized Cross-Validation as a Method of Hyperparameter Search for MTGV Regularization

The concept of generalized cross-validation (GCV) is applied to modified total generalized variation (MTGV) regularization. Current implementations of the MTGV regularization rely on manual (or semi-manual) hyperparameter optimization, which is both time-consuming and subject to bias. The combination of MTGV-regularization and GCV allows for a straightforward hyperparameter search during regularization. This significantly increases the efficiency of the MTGV-method, because it limits the number of hyperparameters, which have to be tested and, improves the practicality of MTGV regularization as a standard technique for inversion of NMR signals. The combined method is applied to simulated and experimental NMR data and the resulting reconstructed distributions are presented. It is shown that for all data sets studied the proposed combination of MTGV and GCV minimizes the GCV score allowing an optimal hyperparameter choice

Full-Scale Treatment Wetlands for Metal Removal from Industrial Wastewater

Acknowledgements This research was conducted and the document was prepared in connection with work under U.S. Department of Energy contract DE-AC09-96SR18500. Extensive collaboration with Clemson University and Weston Engineering were essential during the design and construction phases of the wetland facility. Abstract The A-01 NPDES outfall at the Savannah River Site receives process wastewater discharges and stormwater runoff from the Savannah River National Laboratory. Routine monitoring indicated that copper concentrations were regularly higher than discharge permit limit, and water routinely failed toxicity tests. These conditions necessitated treatment of nearly one million gallons of water per day plus storm runoff. Washington Savannah River Company personnel explored options to bring process and runoff waters into compliance with the permit conditions, including source reduction, engineering solutions, and biological solutions. A conceptual design for a constructed wetland treatment system (WTS) was developed and the full-scale system was constructed and began operation in 2000. The overall objective of our research is to better understand the mechanisms of operation of the A-01 WTS in order to provide better input to design of future systems. The system is a vegetated surface flow wetland with a hydraulic retention time of approximately 48 hours. Copper, mercury, and lead removal efficiencies are very high, all in excess of 80% removal from water passing through the wetland system. Zinc removal is 60%, and nickel is generally unaffected. Dissolved organic carbon in the water column is increased by the system and reduces toxicity of the effluent. Concentrations of metals in the A-01 WTS sediments generally decrease with depth and along the flow path through the wetland. Sequential extraction results indicate that most metals are tightly bound to wetland sediments. Introduction The ability of natural wetlands to improve many aspects of water quality has been recognized for many years. This natural process has been utilized in many different forms and applications to use constructed treatment wetlands for the purpose of water quality improvement Removal of metals from the water occurs by two primary mechanisms: sorption and precipitation. Sorption of metal ions to organic matter and/or clay particles begins immediately

Dynamic buckling and fragmentation in brittle rods

We present experiments on the dynamic buckling and fragmentation of slender rods axially impacted by a projectile. By combining the results of Saint-Venant and elastic beam theory, we derive a preferred wavelength lambda for the buckling instability, and experimentally verify the resulting scaling law for a range of materials including teflon, dry pasta, glass, and steel. For brittle materials, buckling leads to the fragmentation of the rod. Measured fragment length distributions show two clear peaks near lambda/2 and lambda/4. The non-monotonic nature of the distributions reflect the influence of the deterministic buckling process on the more random fragmentation processes.Comment: 4 pages, 5 figures, submitted to Physical Review Letter

Spin-orbit coupling in interacting quasi-one-dimensional electron systems

We present a new model for the study of spin-orbit coupling in interacting quasi-one-dimensional systems and solve it exactly to find the spectral properties of such systems. We show that the combination of spin-orbit coupling and electron-electron interactions results in: the replacement of separate spin and charge excitations with two new kinds of bosonic mixed-spin-charge excitation, and a characteristic modification of the spectral function and single-particle density of states. Our results show how manipulation of the spin-orbit coupling, with external electric fields, can be used for the experimental determination of microscopic interaction parameters in quantum wires.Comment: 5 pages including 4 figures; RevTeX; to appear in Phys.Rev.Let

Geochemical and physical properties of wetland soils at the Savannah River site

The Savannah River Site (SRS), located in Aiken, Allendale, and Barnwell Counties, South Carolina, is a nuclear production facility operated for the U.S. Department of Energy (DOE) by Westinghouse Savannah River Company (WSRC). To facilitate future human health and ecological risk assessments, treatability studies, remedial investigations, and feasibility studies for its wetland areas, SRS needs a database of background geochemical and physical properties of wetland soils. These data are needed for comparison to data collected from wetland soils that may have been affected by SRS operations. SRS contains 36,000 acres of wetlands and an additional 5,000 acres of bottom land soils subject to flooding. Recent studies of wetland soils near various waste units at SRS show that some wetlands have been impacted by releases of contaminants resulting from SRS operations (WSRC, 1992). Waste waters originating from the operations facilities typically have been discharged into seepage basins located in upland soils, direct discharge of waste water to wetland areas has been minimal. This suggests that impacted wetland areas have been affected indirectly as a result of transport mechanisms such as surface runoff, groundwater seeps, fluvial or sediment transport, and leaching. Looney et al. (1990) conducted a study to characterize the geochemical and physical properties of upland soils and shallow sediments on the SRS. A primary objective of the upland study was to collect the data needed to assess the qualitative and quantitative impacts of SRS operations on the environment. By comparing the upland soils data to data collected from waste units located in similar soils, SRS impacts could be assessed. The data were also intended to aid in selection of remediation alternatives. Because waste units at SRS have historically been located in upland areas, wetland soils were not sampled. (Abstract Truncated

Bacterial diversity dynamics in microbial consortia selected for lignin utilization.

Abstract:Lignin is nature?s largest source of phenolic compounds. Its recalcitrance to enzymatic conversion is still a limiting step to increase the value of lignin. Although bacteria are able to degrade lignin in nature, most studies have focused on lignin degradation by fungi. To understand which bacteria are able to use lignin as the sole carbon source, natural selection over time was used to obtain enriched microbial consortia over a 12-week period. The source of microorganisms to establish these microbial consortia were commercial and backyard compost soils. Cultivation occurred at two different temperatures, 30°C and 37°C, in defined culture media containing either Kraft lignin or alkaline-extracted lignin as carbon source. iTag DNA sequencing of bacterial 16S rDNA gene was performed for each of the consortia at six timepoints (passages). The initial bacterial richness and diversity of backyard compost soil consortia was greater than that of commercial soil consortia, and both parameters decreased after the enrichment protocol, corroborating that selection was occurring. Bacterial consortia composition tended to stabilize from the fourth passage on. After the enrichment protocol, Firmicutes phylum bacteria were predominant when lignin extracted by alkaline method was used as a carbon source, whereas Proteobacteria were predominant when Kraft lignin was used. Bray-Curtis dissimilarity calculations at genus level, visualized using NMDS plots, showed that the type of lignin used as a carbon source contributed more to differentiate the bacterial consortia than the variable temperature. The main known bacterial genera selected to use lignin as a carbon source were Altererythrobacter, Aminobacter, Bacillus, Burkholderia, Lysinibacillus, Microvirga, Mycobacterium, Ochrobactrum, Paenibacillus, Pseudomonas, Pseudoxanthomonas, Rhizobiales and Sphingobium. These selected bacterial genera can be of particular interest for studying lignin degradation and utilization, as well as for lignin-related biotechnology applications

A Carpet Cloak Device for Visible Light

We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nano-porous silicon oxide substrate with a very low refractive index. The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequency

Quantitative imaging of concentrated suspensions under flow

We review recent advances in imaging the flow of concentrated suspensions, focussing on the use of confocal microscopy to obtain time-resolved information on the single-particle level in these systems. After motivating the need for quantitative (confocal) imaging in suspension rheology, we briefly describe the particles, sample environments, microscopy tools and analysis algorithms needed to perform this kind of experiments. The second part of the review focusses on microscopic aspects of the flow of concentrated model hard-sphere-like suspensions, and the relation to non-linear rheological phenomena such as yielding, shear localization, wall slip and shear-induced ordering. Both Brownian and non-Brownian systems will be described. We show how quantitative imaging can improve our understanding of the connection between microscopic dynamics and bulk flow.Comment: Review on imaging hard-sphere suspensions, incl summary of methodology. Submitted for special volume 'High Solid Dispersions' ed. M. Cloitre, Vol. xx of 'Advances and Polymer Science' (Springer, Berlin, 2009); 22 pages, 16 fig

Metabolism during anaesthesia and recovery in colic and healthy horses: a microdialysis study

<p>Abstract</p> <p>Background</p> <p>Muscle metabolism in horses has been studied mainly by analysis of substances in blood or plasma and muscle biopsy specimens. By using microdialysis, real-time monitoring of the metabolic events in local tissue with a minimum of trauma is possible. There is limited information about muscle metabolism in the early recovery period after anaesthesia in horses and especially in the colic horse. The aims were to evaluate the microdialysis technique as a complement to plasma analysis and to study the concentration changes in lactate, pyruvate, glucose, glycerol, and urea during anaesthesia and in the recovery period in colic horses undergoing abdominal surgery and in healthy horses not subjected to surgery.</p> <p>Methods</p> <p>Ten healthy university-owned horses given anaesthesia alone and ten client-owned colic horses subjected to emergency abdominal surgery were anaesthetised for a mean (range) of 230 min (193–273) and 208 min (145–300) respectively. Venous blood samples were taken before anaesthesia. Venous blood sampling and microdialysis in the gluteal muscle were performed during anaesthesia and until 24 h after anaesthesia. Temporal changes and differences between groups were analysed with an ANOVA for repeated measures followed by Tukey Post Hoc test or Planned Comparisons.</p> <p>Results</p> <p>Lactate, glucose and urea, in both dialysate and plasma, were higher in the colic horses than in the healthy horses for several hours after recovery to standing. In the colic horses, lactate, glucose, and urea in dialysate, and lactate in plasma increased during the attempts to stand. The lactate-to-pyruvate ratio was initially high in sampled colic horses but decreased over time. In the colic horses, dialysate glycerol concentrations varied considerably whereas in the healthy horses, dialysate glycerol was elevated during anaesthesia but decreased after standing. In both groups, lactate concentration was higher in dialysate than in plasma. The correspondence between dialysate and plasma concentrations of glucose, urea and glycerol varied.</p> <p>Conclusion</p> <p>Microdialysis proved to be suitable in the clinical setting for monitoring of the metabolic events during anaesthesia and recovery. It was possible with this technique to show greater muscle metabolic alterations in the colic horses compared to the healthy horses in response to regaining the standing position.</p