1,834 research outputs found
Changes in soil bacterial communities and diversity in response to long-term silver exposure
No full textData source: Supplementary data, http://femsec.oxfordjournals.org/content/suppl/2015/09/20/fiv114.DC10Silver-induced selective pressure is becoming increasingly important due to the growing use of silver (Ag) as an antimicrobial agent in biomedical and commercial products. With demonstrated links between environmental resistomes and clinical pathogens, it is important to identify microbial profiles related to silver tolerance/resistance. We investigated the effects of ionic Ag stress on soil bacterial communities and identified resistant/persistent bacterial populations. Silver treatments of 50–400 mg Ag kg−1 soil were established in five soils. Chemical lability measurements using diffusive gradients in thin-film devices confirmed that significant (albeit decreasing) labile Ag concentrations were present throughout the 9-month incubation period. Synchrotron X-ray absorption near edge structure spectroscopy demonstrated that this decreasing lability was due to changes in the Ag speciation to less soluble forms such as Ag0 and Ag2S. Real-time PCR and Illumina MiSeq screening of 16S rRNA bacterial genes showed β-diversity changes, increasing α-diversity in response to Ag pressure, and immediate and significant reductions in 16S rRNA gene counts with varying degrees of recovery. These effects were more strongly influenced by exposure time than by Ag dose at these rates. Ag-selected dominant OTUs principally resided in known persister taxa (mainly Gram positive), including metal-tolerant bacteria and slow-growing Mycobacteria.Sotirios Vasileiadis, Edoardo Puglisi, Marco Trevisan, Kirk G. Scheckel, Kate A. Langdon, Mike J. McLaughlin, Enzo Lombi, Erica Donne
N,N'-dimethyl-1,4,5,8-naphthalene-carboxylicdimide as electrode material for cheap & large scale sodium ion batteries
No full textEnergy storage plays a key role in the transit from fossil fuels, as main energy source, to sustainable ones. In this work, it is tried to find an electrode material which can eventually be used in potentially cheap, large scale rechargeable sodium-ion batteries. This application would ideally be made of abundant, safe and environmental friendly materials. The organic material N,N’-dimethyl-1,4,5,8-naphthalene-carboxylicdimide (NDMe) as electrode material potentially meets those demands and has here been electrochemically tested versus sodium in a half-cell. NDMe appeared to have good cycling properties delivering an initial charge capacity of 87.3 mAh g-1 and going to 60.0 mAh g-1 in 75 cycles. By making use of the colour change NDMe undergoes (pink to black upon sodiation), it is determined that dissolution of NDMe in the organic electrolyte was the main reason for the slow capacity decay upon cycling.Applied SciencesRST/Radiation, Science and TechnologyRST/Fundamental Aspects of Materials and Energ
Silver Toxicity Thresholds for Multiple Soil Microbial Biomarkers
No full textMaterial flow analysis shows that soil is a key repository for silver (Ag) from (nano)silver-functionalized consumer products, but the potential effects of Ag toxicity, via Ag+ release, on soil microbial communities and their ecosystem services remains largely unknown. We examined the responses of multiple microbial biomarkers to increasing Ag+ doses (nine concentrations, 0-2000 mg kg-1) in nine different soils representing a wide range of soil properties. Analyses included substrate-induced microbial respiration, nine different soil enzyme activities, and quantification of bacterial 16S-rRNA (SSU) and fungal intergenic spacer (ITS) copies. The resulting half-maximal effective concentrations (EC50) for Ag ranged from ∼1 to >500 mg kg -1 and showed soil-specific responses, including some hormesis-type responses. Carbon cycle-associated enzyme activities (e.g., cellobiohydrolase, xylosidase, and α/β-glucosidase) responded similarly to Ag. Sulfatase and leucine-aminopeptidase activities (linked to the sulfur and nitrogen cycles) were the most sensitive to Ag. Total organic carbon, and to a lesser extent pH, were identified as potentially useful response predictors, but only for some biomarkers; this reflects the complexity of soil Ag chemistry. Our results show Ag toxicity is highly dependent on soil characteristics and the specific microbial parameter under investigation, but end point redundancies also indicated that representative parameters for key microbial functions can be identified for risk assessment purposes. Sulfatase activity may be an important Ag toxicity biomarker; its response was highly sensitive and not correlated with that of other biomarkers
Mobility and potential bioavailability of antimony in contaminated soils: Short-term impact on microbial community and soil biochemical functioning
No full textAntimony (Sb) and its compounds are emerging priority pollutants which pose a serious threat to the environment. The aim of this study was to evaluate the short-term fate of antimonate added to different soils (S1 and S2) with respect to its mobility and impact on soil microbial communities and soil biochemical functioning. To this end, S1 (sandy clay loam, pH 8.2) and S2 (loamy coarse sand, pH 4.9) soils were spiked with 100 and 1000 mg Sb(V) kg−1 soil and left in contact for three months. Sequential extractions carried out after this contact time indicated a higher percentage of labile antimony in the Sb-spiked S1 soils than S2 (e.g. ~13 and 4% in S1 and S2 treated with 1000 mg Sb(V) kg−1 respectively), while the opposite was found for residual (hardly bioavailable) Sb. Also, a reduced number of culturable heterotrophic bacteria was recorded in Sb-spiked S1 soil (compared to the unpolluted S1), while an increased one was found in S2. Heterotrophic fungi followed the opposite trend. Actinomycetes and heat-resistant aerobic bacterial spores showed a variable trend depending on the soil type and Sb(V) treatment. The Biolog community level physiological profile indicated a reduced metabolic activity potential of microbial communities from the Sb-spiked S1 soils (e.g. <50% for Sb-1000 compared to the unpolluted S1), while an increase was recorded for those extracted from the Sb-spiked S2 soils (e.g. >2-fold for Sb-1000). The soil dehydrogenase activity followed the same trend. High-throughput 16S rRNA amplicon sequencing analysis revealed that Sb did not influence the bacterial α-diversity in both soils, while significantly affected the composition of the respective soil bacterial communities. Several phyla (e.g. Nitrosospira Nitrososphaeraceae, Adheribacter) were found positively correlated with the concentration of water-soluble Sb in soil. Overall, the results obtained suggest that the risk assessment in soils polluted with antimony should be a priority especially for alkaline soils where the high mobility of the anionic Sb(OH)6ˉ species can pose, at least in the short-term, a serious threat for soil microbial abundance, diversity and functionality, soil fertility and eventually human health
Chemical characterisation, antibacterial activity, and (nano)silver transformation of commercial personal care products exposed to household greywater
No full textThe objective of this study was to test the original speciation of silver (Ag) in eight different commercially available personal care products and investigate the chemical transformation of Ag during exposure to two types of synthetic greywater. The antimicrobial activity of the products was examined to determine the relationship between Ag content and speciation with the antibacterial functionality of the products. The Ag content of each product was quantified and X-ray absorption near-edge structure (XANES) analysis was used to investigate the initial speciation in the products and the changes occurring upon mixture with greywater. The results showed that the total Ag concentration in the products ranged from 17 to 30 mg kg-1, and was usually below the value reported on the label. Analyses revealed the complexity of Ag speciation in these products and highlighted the importance of characterisation studies to help elucidate the potential risks of nano-Ag in the environment. The antibacterial results confirmed that the antibacterial efficacy of the products depends on the concentration, form and speciation of Ag in the products, but is also significantly affected by product formulation. For instance, many of the products contained additional bactericidal ingredients, making it difficult to determine how much of the bactericidal effect was due directly to the Ag content/species. This paper offers some suggestions for standard methodologies to facilitate cross-comparison of potential risks across different studies and nano-enabled products
Modeling Electrode Materials: Bridging Nanoscale to Mesoscale
No full textComputational modeling is shaping the fundamental understanding of key thermodynamic and kinetic properties in batteries, the importance of which is undeniable for the implementation of next-generation batteries, mobile and large-scale applications (chapter 1). In the present thesis, we employ density functional theory (DFT) at the nanoscale and phase field modeling at the mesoscale (chapter 2) to study both state-of-the-art and novel battery chemistries...RST/Storage of Electrochemical Energ
Azadirachtin and trifloxystrobin had no inhibitory effects on key soil microbial functions even at high dose rates
No full textSynthetic pesticides may have non-target effects on soil microorganisms which have been identified as a specific protection goal in pesticide environmental risk assessment. Most studies to date have focused on the effects of synthetic pesticides on soil microorganisms, whereas little is known about the response of the soil microbial community to the so-called low-risk pesticide classes. The main objective of this study was to assess the impact of a botanical (azadirachtin) and a low-dose pesticide (trifloxystrobin), applied as commercial formulations, on soil microbial functions. In a microcosm study, pesticides were applied in soil at increasing dose rates (up to ×100 the recommended dose rate). Their dissipation and the formation of the major transformation product (TP) of trifloxystrobin were determined. Enzymatic activities and the abundance of key functional microbial groups were measured via fluorometric assays, potential nitrification (PNT) and q-PCR. Trifloxystrobin and azadirachtin did not persist in soil at all dose rates with DT 50s of 1.1–1.4 and 1.3 days respectively. No pesticide dose-dependent inhibitory effects on the activity of soil enzymes, the abundance of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), sulfur-oxidizing bacteria (SOB) and on PNT were seen. Instead the application of both pesticides at all dose rates stimulated PNT. Trifloxystrobin was transformed to trifloxystrobin acid (TFSA), which persisted in soil. However its formation did not correlate with adverse effects on soil microbial functions. We provide first evidence that trifloxystrobin and azadirachtin do not impose unacceptable effects on soil microbial functions even at high dose rates
Feasibility Study for PV Park in TU Delft Campus Zuid
No full textTU Delft, being in the frontier of research and progress in Europe and worldwide, is always interestedin exploring the possibilities of renewable energy production. In that respect, the Facility ManagementDepartment (FMD) of the university approached the Photovoltaic Materials and Devices (PVMD) group,whose research covers a wide area in the renewable energy sector, in order for the solar potential of anextensive available area in the South of the TU Delft Campus to be investigated. This thesis project aimsat shining a light on the latter, while also proposing a best business case scenario for realization.In order to deal with the issue at hand, a complete MATLAB-based modelling tool has been developedfor the simulation and evaluation of PV module and PV system performance. Additionally, a locationsurvey was conducted, which resulted in the recreation of the skyline profile and the study of the reflectivityof the ground. In case of using a bifacial PV module, the PVMD Toolbox can be integrated in theapproach.Using the developed modelling approach, different PV technologies were investigated. The bifacialmono-Si PV modules by LG were found to outperform the competition on yield and cost criteria. Theresults indicated that the best performance is achieved for a tilt of 40o and an azimuth of 165o. A sensitivityanalysis was also carried out, based on which a ground clearance height of 1.5 [m] was selected.Furthermore, the results extracted using the modelling tool were cross-validated using the PVMD Toolboxand the System Advisor Model (SAM), showing a satisfactory performance with the maximum deviationsbeing 1.5% and 3%, respectively.Moreover, two different potential loads were studied in conjunction with the solar modules. The firstwas the 1.25 [GWh] annual demand of the EXACT building, closely located to the investigated area. Inthis case a grid-connected PV system was designed with the total amount of modules being calculatedas 2,520. The second was an electrolyzer of a nominal capacity of 1.25 [MW], scheduled to be installedat the Process and Energy (P&E) Department of the university. The electrolyzer was assumed to supplyhydrogen to two fuel cell buses, and its respective PV system was designed both as grid-independent aswell as grid-connected. In the independent approach the total number of required PV modules was foundto be 4,000, while in the grid-connected approach the size of the PV system was chosen similar to theone designed for the EXACT building. Moreover, two hydrogen production strategies, a minimum anda maximum, were investigated. The respective produced hydrogen was found to be 9,100 and 20,619[kg].The choice of the best business case was based on a performance and cost analysis that was conducted.The conclusion drawn from this analysis was that decentralized PV systems have a better performance dueto higher inverter efficiency and lower cable losses, while the centralized approach has a better behaviourcost-wise due to the initial investment being smaller by 2%. Additionally, systems with a higher lifetimeyield better results. All in all, the grid-connected, decentralized, electrolyzer-coupled PV system with themaximum hydrogen production strategy was deemed as the best business case. The initial investment of1.28 [M €] is won back over a period of 5.1 [yr], having an LCoE of 8.2 [cts €/kWh]. The area requiredto fit the PV system is comprised of Zones B1, B2 and B3, which show the greatest potential.Electrical Engineering | Sustainable Energy Technolog
The H.E.S.S experimental project
No full textThe H.E.S.S experiment (for High Energy Stereoscopic System) consists of four imaging Cherenkov telescopes situated in the Namibia Khomas Highland desert (1800 m asl). Its main characteristics are the low energy threshold (100 GeV) and substantial flux sensitivity (1% Crab units). The combination of the four telescope data analysis provide good background rejection and angular resolution. Recent results on the performance and operation are reported here
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