733 research outputs found
Chemical characterization methods for the analysis of structural extracellular polymeric substances (EPS)
No full textBiofilm structure and functionality depend on extracellular polymeric substances (EPS), but analytical methods for EPS often lack specificity which limits progress of biofilm research. EPS were extracted from aerobic granular sludge and analyzed with frequently applied colorimetric methods. The colorimetric methods were evaluated based on their applicability for EPS analysis. EPS fractions of interest were proteins, sugars, uronic acids and phenolic compounds. The applied methods (Lowry method, bicinchoninic acid assay, phenol sulfuric acid method, carbazole sulfuric acid method) were investigated in terms of their sensitivity towards the selected standard compound. Interference of compounds present in EPS with the colorimetric methods was further evaluated. All methods showed to be highly depending on the choice of standard compound and susceptible towards interference by compounds present in EPS. This study shows that currently used colorimetric methods are not capable of accurately characterizing EPS. More advanced methods are needed to be able to draw conclusions about biofilm composition, structure and functionality.BT/Environmental BiotechnologyOLD BT/Cell Systems Engineerin
Impact of metal ions on structural EPS hydrogels from aerobic granular sludge
No full textStructural extracellular polymeric substances (structural EPS) can form stable hydrogels and are considered to be responsible for the stability of biofilms and aerobic granular sludge. Structural EPS were extracted from aerobic granular sludge and characterized for their gel-forming capacity with different alkaline earth and transition metal ions. The structural EPS hydrogels were compared to alginate hydrogels. Alginate is a well characterized polymer which is able to form stiff hydrogels with multivalent ions. The stiffness of the obtained hydrogels was measured with dynamic mechanical analysis and quantified by the Young's modulus. Furthermore the stability of structural EPS hydrogels towards disintegration in the presence of ethylenediaminetetraacetic acid (EDTA) was evaluated at pH 4.5–10.5 and compared to that of alginate, polygalacturonic acid and κ-carrageenan. The stiffness of alginate hydrogels was multiple times higher than that of structural EPS. Alkaline earth metals resulted in stiffer alginate hydrogels than transition metals. For structural EPS this trend was opposite to alginate. Independent of the pH, polysaccharide hydrogels were quickly disintegrated when being exposed to EDTA. Structural EPS hydrogels demonstrated greater stability towards EDTA and were still intact after one month at pH 4.5–8.5. It is suggested that the gelling mechanism of structural EPS is not only related to metal ion complexation of the polymers, but to a combination of interactions of multiple functional groups present in structural EPS. This study helps to further understand and characterize structural EPS from aerobic granular sludge, and therewith understand its stability and that of biofilms in general.</p
Cloud Arch: Application of an EPS composite to create an ultra-lightweight long-span sustainable structure
No full textExpanded Polystyrene foam (EPS) is a chemically inert and 100% recyclable material that is lightweight and has a good compression strength per weight ratio; however, its current construction use is mostly limited to insulation or landfill. The key concept of this paper is to develop an EPS composite to create an ultra-lightweight long-span sustainable roofing structure by integrating the minimum necessary structural tension layer with a certified fire protection system. The authors present this concept in the following four steps, 1) EPS composite structural specimen test, 2) structural optimisation of the reversed displacement model, 3) discretisation with developable surfaces and 4) CNC hotwire rapid prototyping and assembly in scaled prototypes. The Cloud Arch is an economical, material-efficient, thermally insulated, quickly assembled ultra-lightweight construction that eliminates the need for formworks for long-span structures. It can be applied to many types of column-free spaces, such as in factories, gymnasiums, markets and cafeterias
Project work on wellbeing in multidisciplinary student teams: A triple testimonial on eps at artesis
No full textThe European Project Semester (EPS) programme offers an educational framework to support students to practice problem-and project-based cross-disciplinary product innovation and research, in small multidisciplinary and international teams. To explore the potential and the restrictions of this international educational concept, in 2012 the Artesis University College became the first Belgian EPS provider to offer a multidisciplinary EPS programme in close collaboration with the following study programs: product development, engineering, business studies, social work and teacher training. This paper reflects on the learning process for the teaching staff and the 16 students who have participated to the first edition. First, insights related to the preparation, initiation and overall implementation of this new multidisciplinary teaching approach and interdepartmental semester program are discussed. Second, we focus especially on one specific EPS project which addressed the development of smart textile applications in health care. Reflections and lessons learned are shared from the complementary perspective of the EPS study programme coordinator, the ’smart textile applications’ team supervisor and an engineering student who participated in this project.Design EngineeringIndustrial Design Engineerin
Utilization of EPS Geofoam for Bridge Approach Structure on Soft Bangkok Clay
No full textDifferential settlement along bridge approach structure is one of the continuing problems for highway construction in Bangkok and its vicinities due to soft ground foundation. To minimize the differential settlement and serviceability failure, an approach slap on piles with varies pile length is a current geotechnical engineering practice for the bridge approach structure construction. Instead of ground reinforcement by piles as a bearing unit, EPS Geofoam could be utilized as a lightweight embankment along the bridge approach, and could be an alternative solution to reduce differential settlement problem and repair works in the city area in which fast construction time is the main requirement. Two case studies of bridge approach structure were investigated, and different types of bridge approach structure, including approach slap on pile with different pile length distributions, and application of EPS, were evaluated in terms of engineering performance and construction and maintenance cost, and time. The results show that utilizing domestic EPS Geofoam for bridge approach structure could increase the construction cost by 20 to 30%, however, it could save construction period and could reduce the long-term maintenance cost
Stochastic inflation in general relativity
No full text\ua9 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article\u27s title, journal citation, and DOI. We provide a formulation of stochastic inflation in full general relativity that goes beyond the slow-roll and separate universe approximations. We show how gauge-invariant Langevin source terms can be obtained for the complete set of Einstein equations in their Arnowitt-Deser-Misner formulation by providing a recipe for coarse-graining the spacetime in any small gauge. These stochastic source terms are defined in terms of the only dynamical scalar degree of freedom in single-field inflation and all depend simply on the first two time derivatives of the coarse-graining window function, on the gauge-invariant mode functions that satisfy the Mukhanov-Sasaki evolution equation, and on the slow-roll parameters. It is shown that this reasoning can also be applied to include gravitons as stochastic sources, thus enabling the study of all relevant degrees of freedom of general relativity for inflation. We validate the efficacy of these Langevin dynamics directly using an example in uniform field gauge, obtaining the stochastic e-fold number in the long wavelength limit without the need for a first-passage-time analysis. As well as investigating the most commonly used gauges in cosmological perturbation theory, we also derive stochastic source terms for the coarse-grained Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein\u27s equations, which enables a well-posed implementation for 3+1 numerical relativity simulations
Effect of Using Recycled Instead of Virgin EPS in Lightweight Mortars
No full textAbstractPerformances of structural, moderate and heat insulating lightweight mortars manufactured by replacing sand volume with virgin or recycled expanded polystyrene (EPS) are compared. At the same dosage, replacing virgin EPS with recycled one improves the mechanical performance of mortars without a significant variation in capillary water absorption and water vapour permeability. Recycled EPS mortars have lower thermal insulation properties than those manufactured with a virgin one, but this can be counteracted by increasing the percentage of EPS. To obtain mortars with a certain thermal insulating capacity, an economical saving over than 25% can be reached by using recycled EPS
Contribution of extracellular polymeric substances fractions to the adsorption of silver nanoparticles by activated sludge
No full textThe extracellular polymeric substances (EPS) from activated sludge played significant roles in the removal of nanoparticles from wastewater. A series of batch experiments were carried out to determine the adsorption mechanism of three nano-Ag by activated sludge, as well as the contributions of EPS fractions including dissolved EPS (DEPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). The results demonstrated that the adsorption of nano-Ag by sludge biomass agreed with pseudo-second-order kinetic reaction model and Freundlich isotherm model. About 26.0-41.2% of nano-Ag was trapped by the bound EPS (BEPS) matrix of activated sludge (especially LB-EPS) and 42.5-52.6% of them was adsorbed onto the inner cells after the adsorption. Moreover, the interaction energy contributions of EPS fractions followed the order of EDE > 0 > ETB > ELB, suggesting DEPS in wastewater went against the removal of nano-Ag due to steric repulsion while LB-EPS and TB-EPS were positive to nano-Ag adsorption by modifying biomass surface and providing extensive binding sites. Besides, EPS fractions played significant roles in the adsorption of nano-Ag with low initial concentrations but had limited effect at high concentrations. Overall, this study investigated the effect of EPS fractions on the adsorption behaviors of nano-Ag by activated sludge biomass, which is meaningful to understand the removal mechanism of nanoparticles in sewage and the potential role of EPS fractions.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Sanitary Engineerin
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