A theoretical analysis of the free vibration of discretely stiffened cylindrical shells with arbitrary end conditions

Theoretical analysis of free vibration of discretely stiffened cylindrical shells with arbitrary end condition

Electrochemical Boron-Doped Diamond Film Microcells Micromachined with Femtosecond Laser: Application to the Determination of Water Framework Directive Metals

Planar electrochemical microcells were micromachined in a microcrystalline boron-doped diamond (BDD) thin layer using a femtosecond laser (Photo 1). The electrochemical performances of the new laser-machined BDD microcell were assessed by differential pulse anodic stripping voltammetry (DPASV) determinations, at nM level, of the four heavy metal ions of the European Water Framework Directive (WFD): Cd(II), Ni(II), Pb(II), Hg(II). The results are compared with those of previously published BDD electrodes [1]. The calculated detection limits are 0.4 nM, 6.8 nM and 5.5 nm 2.3 nM, and the linearities go up to 35nM, 97nM, 48nM and 5nM for respectively Cd(II), Ni(II) Pb(II) and Hg(II). The detection limits meet with the environmental quality standard of the WFD for three of the four metals. It was shown that the four heavy metals could be detected simultaneously, in the concentration ratio usually measured in sewage or runoff waters

Species Richness, Species Identity and Ecosystem Function in Managed Temperate Grasslands

Manipulation of plant species diversity may provide a way to improve the ecosystem functioning of managed systems by increasing productivity and suppressing weedy species. As yet, the functional role of species richness is not well-enough understood to enable practical application. We investigated the effects of differing species richness on community stability and invasion resistance in a grazed temperate grassland

Intake and Milk Production of Lactating Dairy Cows Grazing Diverse Forage Mixtures Over Two Grazing Seasons

Voluntary intake and stocking rate are key determinants of animal performance on pasture. Greater plant diversity in grassland plant communities has been linked to increased primary production, greater stability in response to disturbance, and reduced weed pressure. Thus, increasing plant diversity may be one approach to improving animal productivity. An experiment was conducted to determine the effects of forage diversity on intake and milk production of lactating dairy cows over two grazing seasons

Managing Interspecies Competition to Improve Spring Pasture

Orchardgrass (Dactylis glomerata L.) is one of the earliest maturing pasture grasses utilized in the northeastern United States. However, wet springs can delay forage harvesting resulting in advanced forage maturity and reduction in nutritive value. Chicory (Cichorium intybus L.) is a tall, upright-growing forb that shows promise as a high-energy companion crop to orchardgrass and may delay orchardgrass maturity through shading effects on plant morphology. The objective of this study was to evaluate monocultures and mixtures of orchardgrass, chicory, and white clover (Trifolium repens L.) over two consecutive springs to determine the effects of species diversity on plant maturity, nutritive characteristics, and botanical composition of forage mass. Forage monocultures and mixtures were planted in central Pennsylvania in August 2018 and were observed for two years with three harvests occurring each year (one each in spring, summer, and fall). In the first spring, orchardgrass demonstrated nine days delay in maturity when grown with chicory as compared to when grown in monocultures or in orchardgrass-white clover mixtures. Although orchardgrass was at an earlier developmental stage, fiber concentrations were similar when grown with or without chicory. Additionally, in the first spring, orchardgrass mixtures containing chicory had 1.5x greater forage mass than orchardgrass monocultures and orchardgrass-white clover mixtures. Chicory biomass was low in the second spring, likely due to winterkill following a late fall harvest the previous year, resulting in a negligible effect on orchardgrass. However, orchardgrass-chicory-white clover mixtures (even with low amounts of chicory in the second year) had the greatest forage mass and nutritive value yield over both years, indicating that these mixtures can provide greater agronomic benefits than orchardgrass monocultures

Diverse Forage Mixtures Effect on Herbage Yield, Sward Composition, and Dairy Cattle Performance

Managing complex mixtures of plants to take advantage of spatial and temporal variability in land and climate may be one ecological approach to increase productivity of pastures. We tested the hypothesis that complex mixtures of forage species would yield more herbage and reduce weed competition compared with a simple grass-legume mixture in grazed pastures

MecE, MecB, MecC proteins orchestrate methyl group transfer during dichloromethane fermentation

Dichloromethane (DCM), a common hazardous industrial chemical, is anaerobically metabolized by four bacterial genera: Dehalobacter, Dehalobacterium, Ca. Dichloromethanomonas, Ca. Formimonas. However, the pivotal methyltransferases responsible for DCM transformation have remained elusive. In this study, we investigated the DCM catabolism of Dehalobacterium formicoaceticum strain EZ94, contained in an enriched culture, using a combination of biochemical approaches. Initially, enzymatic assays were conducted with cell-free protein extracts, after protein separation by blue native polyacrylamide gel electrophoresis. In the slices with the highest DCM transformation activity a high absolute abundance of the methyltransferase MecC was revealed by mass spectrometry. Enzymatic activity assays with heterologously expressed MecB, MecC, and MecE from strain EZ94 showed complete DCM transformation only when all three enzymes were present. Our experimental results, coupled with the computational analysis of MecB, MecC, and MecE sequences enabled us to assign specific roles in DCM transformation to each of the proteins. Our findings reveal that both MecE and MecC are zinc-dependent methyltransferases responsible for DCM demethylation and re-methylation of a product, respectively. MecB functions as a cobalamin-dependent shuttle protein transferring the methyl group between MecE and MecC. This study provides the first biochemical evidence of the enzymes involved in the anaerobic metabolism of DCM

Respiratory protein interactions in Dehalobacter sp. strain 8M revealed through genomic and native proteomic analyses

Dehalobacter (Firmicutes) encompass obligate organohalide-respiring bacteria used for bioremediation of groundwater contaminated with halogenated organics. Various aspects of their biochemistry remain unknown, including the identities and interactions of respiratory proteins. Here, we sequenced the genome of Dehalobacter sp. strain 8M and analysed its protein expression. Strain 8M encodes 22 reductive dehalogenase homologous (RdhA) proteins. RdhA D8M_v2_40029 (TmrA) was among the two most abundant proteins during growth with trichloromethane and 1,1,2-trichloroethane. To examine interactions of respiratory proteins, we used blue native gel electrophoresis together with dehalogenation activity tests and mass spectrometry. The highest activities were found in gel slices with the highest abundance of TmrA. Protein distributions across gel lanes provided biochemical evidence that the large and small subunits of the membrane-bound [NiFe] uptake hydrogenase (HupL and HupS) interacted strongly and that HupL/S interacted weakly with RdhA. Moreover, the interaction of RdhB and membrane-bound b-type cytochrome HupC was detected. RdhC proteins, often encoded in rdh operons but without described function, migrated in a protein complex not associated with HupL/S or RdhA. This study provides the first biochemical evidence of respiratory protein interactions in Dehalobacter, discusses implications for the respiratory architecture and advances the molecular comprehension of this unique respiratory chain

Divergent dual C-H isotopic fractionation pattern during anaerobic biodegradation of toluene within Aromatoleum species under nitrate-reducing conditions

Toluene is a pollutant frequently detected in contaminated groundwater, mostly due to leakage from underground gasoline storage tanks and pipeline ruptures. Multi-element compound-specific isotope analysis provides a framework to understand transformation processes and design efficient remediation strategies. In this study, we enriched an anaerobic bacterial culture derived from a BTEX-contaminated aquifer that couples toluene and phenol oxidation with nitrate reduction and the concomitant production of carbon dioxide and biomass. The 16S rRNA gene amplicon data indicated that the toluene-degrading consortium was dominated by an Aromatoleum population (87 ± 2 % relative abundance), and metagenome sequencing confirmed that the genome of this Aromatoleum sp. encoded glycyl-radical enzyme benzylsuccinate synthase (BssABC) and phenylphospate synthase (PpsA1BC) homologous genes involved in the first step of toluene and phenol transformation, respectively. Carbon and hydrogen isotopic fractionation were εbulk, C = - 3.5 ± 0.6 ‰ and εrp, H = - 85 ± 11 ‰, respectively, leading to a dual C-H isotope slope of ΛH/C = 26 ± 2. This value fits with a previously reported value for a consortium dominated by an Azoarcus species (ΛH/C = 19 ± 5) but differs from that reported for Aromatoleum aromaticum (ΛH/C = 14 ± 1), both of which grow with toluene under nitrate-reducing conditions. Overall, this suggests the existence of different BssABC enzymes with different mechanistic motifs even within the same Aromatoleum genus