Transport of ferrihydrite nanoparticles in saturated porous media: role of ionic strength and flow rate

The use of nanoscale ferrihydrite particles, which are known to effectively enhance microbial degradation of a wide range of contaminants, represents a promising technology for in situ remediation of contaminated aquifers. Thanks to their small size, ferrihydrite nanoparticles can be dispersed in water and directly injected into the subsurface to create reactive zones where contaminant biodegradation is promoted. Field applications would require a detailed knowledge of ferrihydrite transport mechanisms in the subsurface, but such studies are lacking in the literature. The present study is intended to fill this gap, focusing in particular on the influence of flow rate and ionic strength on particle mobility. Column tests were performed under constant or transient ionic strength, including injection of ferrihydrite colloidal dispersions, followed by flushing with particle-free electrolyte solutions. Particle mobility was greatly affected by the salt concentration, and particle retention was almost irreversible under typical salt content in groundwater. Experimental results indicate that, for usual ionic strength in European aquifers (2 to 5 mM), under natural flow condition ferrihydrite nanoparticles are likely to be transported for 5 to 30 m. For higher ionic strength, corresponding to contaminated aquifers, (e.g., 10 mM) the travel distance decreases to few meters. A simple relationship is proposed for the estimation of travel distance with changing flow rate and ionic strength. For future applications to aquifer remediation, ionic strength and injection rate can be used as tuning parameters to control ferrihydrite mobility in the subsurface and therefore the radius of influence during field injection

Controlling cooperation and recovery in nested transactions

Recovery is a hard problem in environments where transactions perform work in a cooperative style (e.g., design environments). We propose concepts to control cooperation and recovery within nested transaction hierarchies. By allowing different nodes to run different protocols, we can build so-called recovery spheres with well-defined properties. We characterize those properties and illustrate them by examples from design environments.<br/

Spin pumping at interfaces with ferro- and paramagnetic Fe60Al40films acting as spin source and spin sink

We present a study of spin pumping efficiency and determine the spin mixing conductance and spin diffusion length in thin bilayer films based on 3d transition metal alloy Fe60Al40. Due to its magnetostructural phase transition, Fe60Al40 can be utilized as a ferromagnetic (FM) or paramagnetic (PM) material at the same temperature depending on its structural order; thus a thin Fe60Al40 film can act as a spin source or a spin sink when interfaced with a paramagnet or a ferromagnet, respectively. Ferromagnetic resonance measurements were performed in a frequency range of 5-35 GHz on bilayer films composed of FM-Fe60Al40/Pd and PM-Fe60Al40/Ni80Fe20 (permalloy). The increase in damping with the thickness of the paramagnetic layer was interpreted as a result of spin pumping into the paramagnet. We determine the spin mixing conductance g P d ↑↓ = (3.8 ± 0.5) × 10 18 m - 2 at the FM-Fe60Al40/Pd interface and the spin diffusion length λ P d = 9.1 ± 2.0 nm in Pd. For the PM-Fe60Al40/permalloy interface, we find a spin mixing conductance g F e A l ↑↓ = (2.1 ± 0.2) × 10 18 m - 2 and a spin diffusion length λ F e A l = 11.9 ± 0.2 nm for PM-Fe60Al40. The demonstrated bi-functionality of the Fe60Al40 alloy in spin pumping structures may be promising for spintronic applications

Double-resonant x-ray and microwave absorption: Atomic spectroscopy of precessional orbital and spin dynamics

We show that double-resonance spectra recorded during the simultaneous absorption of x-ray and microwave (MW) photons are a fingerprint of the perturbed electronic configuration of atomic species driven to ferromagnetic resonance. X-ray absorption measurements performed as a function of x-ray energy and polarization over the Fe L2,3 edges of single-crystal yttrium-iron garnet reveal MW-induced multiplet features related to angular momentum transfer from the MW field to localized Fe 3d magnetic sublevels. O K-edge absorption spectra demonstrate the formation of dynamic 2p-orbital magnetization components at O sites coupled to the Fe magnetic moments at tetrahedral and octahedral sites. These results are compared with double-resonance x-ray absorption spectra of Permalloy, showing that the MW transition probability is distributed according to the hybridization character of the 3d states and proportional to the unperturbed unoccupied magnetic density of states of metals and insulators

Purification, characterization, and cloning of a bifunctional molybdoenzyme with hydratase and alcohol dehydrogenase activity

A bifunctional hydratase/alcohol dehydrogenase was isolated from the cyclohexanol degrading bacterium Alicycliphilus denitrificans DSMZ 14773. The enzyme catalyzes the addition of water to α,β-unsaturated carbonyl compounds and the subsequent alcohol oxidation. The purified enzyme showed three subunits in SDS gel, and the gene sequence revealed that this enzyme belongs to the molybdopterin binding oxidoreductase family containing molybdopterins, FAD, and iron-sulfur clusters

A benzene-degrading nitrate-reducing microbial consortium displays aerobic and anaerobic benzene degradation pathways

All sequence data from this study were deposited at the European Bioinformatics Institute under the accession numbers ERS1670018 to ERS1670023. Further, all assigned genes, taxonomy, function, sequences of contigs, genes and proteins can be found in Table S3.In this study, we report transcription of genes involved in aerobic and anaerobic benzene degradation pathways in a benzene-degrading denitrifying continuous culture. Transcripts associated with the family Peptococcaceae dominated all samples (2136% relative abundance) indicating their key role in the community. We found a highly transcribed gene cluster encoding a presumed anaerobic benzene carboxylase (AbcA and AbcD) and a benzoate-coenzyme A ligase (BzlA). Predicted gene products showed >96% amino acid identity and similar gene order to the corresponding benzene degradation gene cluster described previously, providing further evidence for anaerobic benzene activation via carboxylation. For subsequent benzoyl-CoA dearomatization, bam-like genes analogous to the ones found in other strict anaerobes were transcribed, whereas gene transcripts involved in downstream benzoyl-CoA degradation were mostly analogous to the ones described in facultative anaerobes. The concurrent transcription of genes encoding enzymes involved in oxygenase-mediated aerobic benzene degradation suggested oxygen presence in the culture, possibly formed via a recently identified nitric oxide dismutase (Nod). Although we were unable to detect transcription of Nod-encoding genes, addition of nitrite and formate to the continuous culture showed indication for oxygen production. Such an oxygen production would enable aerobic microbes to thrive in oxygen-depleted and nitrate-containing subsurface environments contaminated with hydrocarbons.This study was supported by a grant of BE-Basic-FES funds from the Dutch Ministry of Economic Affairs. The research of A.J.M. Stams is supported by an ERC grant (project 323009) and the gravitation grant “Microbes for Health and Environment” (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science. F. Hugenholtz was supported by the same gravitation grant (project 024.002.002). B. Hornung is supported by Wageningen University and the Wageningen Institute for Environment and Climate Research (WIMEK) through the IP/OP program Systems Biology (project KB-17-003.02-023).info:eu-repo/semantics/publishedVersio

Emergence of anisotropic Gilbert damping in ultrathin Fe layers on GaAs (001)

As a fundamental parameter in magnetism, the phenomenological Gilbert damping constant a determines the performance of many spintronic devices. For most magnetic materials, a is treated as an isotropic parameter entering the Landau-Lifshitz-Gilbert equation. However, could the Gilbert damping be anisotropic? Although several theoretical approaches have suggested that anisotropic a could appear in single-crystalline bulk systems, experimental evidence of its existence is scarce. Here, we report the emergence of anisotropic magnetic damping by exploring a quasi-two-dimensional single-crystalline ferromagnetic metal/semiconductor interface-that is, a Fe/GaAs(001) heterojunction. The observed anisotropic damping shows twofold C-2v symmetry, which is expected from the interplay of interfacial Rashba and Dresselhaus spin-orbit interaction, and is manifested by the anisotropic density of states at the Fe/GaAs (001) interface. This discovery of anisotropic damping will enrich the understanding of magnetization relaxation mechanisms and can provide a route towards the search for anisotropic damping at other ferromagnetic metal/semiconductor interfaces

Genetic Basis of Myocarditis: Myth or Reality?

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Anaerobic naphthalene degradation by Gram-positive, iron-reducing bacteria.

An anaerobic naphthalene-degrading culture (N49) was enriched with ferric iron as electron acceptor. A closed electron balance indicated the total oxidation of naphthalene to CO(2) . In all growing cultures, the concentration of the presumed central metabolite of naphthalene degradation, 2-naphthoic acid, increased concomitantly with growth. The first metabolite of anaerobic methylnaphthalene degradation, naphthyl-2-methyl-succinic acid, was not identified in culture supernatants, which does not support a methylation to methylnaphthalene as the initial activation reaction of naphthalene, but rather a carboxylation, as proposed for other naphthalene-degrading cultures. Substrate utilization tests revealed that the culture was able to grow on 1-methyl-naphthalene, 2-methyl-naphthalene, 1-naphthoic acid or 2-naphthoic acid, whereas it did not grow on 1-naphthol, 2-naphthol, anthracene, phenanthrene, indane and indene. Terminal restriction fragment length polymorphism and 16S rRNA gene sequence analyses revealed that the microbial community of the culture was dominated by one bacterial microorganism, which was closely related (99% 16S sequence similarity) to the major organism in the iron-reducing, benzene-degrading enrichment culture BF [ISME J (2007) 1: 643; Int J Syst Evol Microbiol (2010) 60: 686]. The phylogenetic classification supports a new candidate species and genus of Gram-positive spore-forming iron-reducers that can degrade non-substituted aromatic hydrocarbons. It furthermore indicates that Gram-positive microorganisms might also play an important role in anaerobic polycyclic aromatic hydrocarbon-degradation