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End date: 2019 × Start date: 2016 × Type: Text × Type: article × Version: publishedVersion × Publisher: Amsterdam : Elsevier ×

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Now showing 1 - 10 of 25
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    Cohesive detachment of an elastic pillar from a dissimilar substrate
    (Amsterdam : Elsevier, 2017) Fleck, Norman A.; Khaderi, Syed Nizamuddin; McMeeking, Robert M.; Arzt, Eduard
    The adhesion of micron-scale surfaces due to intermolecular interactions is a subject of in- tense interest spanning electronics, biomechanics and the application of soft materials to engineering devices. The degree of adhesion is sensitive to the diameter of micro-pillars in addition to the degree of elastic mismatch between pillar and substrate. Adhesion- strength-controlled detachment of an elastic circular cylinder from a dissimilar substrate is predicted using a Dugdale-type of analysis, with a cohesive zone of uniform tensile strength emanating from the interface corner. Detachment initiates when the opening of the cohesive zone attains a critical value, giving way to crack formation. When the cohe- sive zone size at crack initiation is small compared to the pillar diameter, the initiation of detachment can be expressed in terms of a critical value H c of the corner stress inten- sity. The estimated pull-offforce is somewhat sensitive to the choice of stick/slip boundary condition used on the cohesive zone, especially when the substrate material is much stiffer than the pillar material. The analysis can be used to predict the sensitivity of detachment force to the size of pillar and to the degree of elastic mismatch between pillar and sub- strate.
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    Recovery and techno-functionality of flours and proteins from two edible insect species: Meal worm (Tenebrio molitor) and black soldier fly (Hermetia illucens) larvae
    (Amsterdam : Elsevier, 2016) Bußler, Sara; Rumpold, Birgit A.; Jander, Elisabeth; Rawel, Harshadrai M.; Schlüter, Oliver K.
    Depending on the species, edible insects are highly nutritious and thus represent a noteworthy alternative food and feed source. The current work investigates the protein extractability and techno-functionality of insect flour fractions recovered from Tenebrio molitor and Hermetia illucens. T. molitor and H. illucens flours contained about 20% crude fat and 60% and 36 % crude protein, respectively. Defatting reduced the crude fat content to 2.8% (T. molitor) and 8.8% (H. illucens) and increased the crude protein content to 68% and 47%, respectively. To isolate proteins from the flours, protein solubility was optimized by varying the pH, the ionic strength, and the extraction temperature of the solvent. All products and by-products accumulated in the protein production process were characterized by composition, selected techno-functional properties, protein solubility, composition and structure as well as their microbial load.
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    Significant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area
    (Amsterdam : Elsevier, 2015) Kecorius, Simonas; Kivekäs, Niku; Kristensson, Adam; Tuch, Thomas; Covert, David S.; Birmili, Wolfram; Lihavainen, Heikki; Hyvärinen, Antti-Pekka; Martinsson, Johan; Sporre, Moa K.; Swietlicki, Erik; Wiedensohler, Alfred; Ulevicius, Vidmantas
    In this study, we evaluated 10 months data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden), Utö (upwind, Finland), and Preila (downwind, Lithuania). Differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, were used to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50–400 nm) in the Lithuanian background coastal environment. A clear increase in particle number concentration could be noticed, by a factor of 1.9 from Utö to Preila (the average total number concentration at Utö was 791 cm−3), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm−3). The simultaneous measurements of absorption Ångström exponents close to unity at Preila supported our conclusion that ship emissions in the Baltic Sea contributed to the increase in particle number concentration at Preila.
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    Awassi sheep keeping in the Arabic steppe in relation to nitrous oxide emission from soil
    (Amsterdam : Elsevier, 2013) Hijazi, Omar; Berg, Werner; Moussa, Samouil; Ammon, Christian; von Bobrutzki, Kristina; Brunsch, Reiner
    Sheep husbandry is the main source of income for farmers in arid zones. Increasing sheep production on steppes may increase the greenhouse gas production. The objective of this study was to investigate the nitrous oxide (N2O) emissions from the steppes for Awassi sheep keeping and feed cropping in arid zones such as Syria. The methodology developed by the Intergovernmental Panel on Climate Change (IPCC) was used to estimate N2O emissions. A survey was conducted on 64 farms in Syria to gather data for analysis. Precipitation and crop yield data from 2001 to 2009 were also used for calculation and modelling. Sheep-keeping systems, precipitation, year and the region have significant effects on N2O emissions (p<0.05). Emissions of N2O from lands with extensive, semi-intensive and intensive systems were 0.30 ± 0.093, 0.598± 0.113 and 2.243± 0.187 kg sheep1year1, respectively. Crop production was higher in regions with high precipitation levels, which helped to reduce N2O emissions. Using more residuals of wheat, cotton and soya as feed for sheep in the keeping systems evaluated may decrease the overuse of steppe regions and N2O emissions. Nitrous oxide emissions of N2O from sheep-keeping areas can be reduced by changing sheep-keeping systems and increasing the crop production in arid zones through artificial irrigation.
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    The quest for research information
    (Amsterdam : Elsevier, 2014) Blümel, Ina; Dietze, Stefan; Heller, Lambert; Jäschke, Robert; Mehlberg, Martin
    Research information, i.e., data about research projects, organisations, researchers or research outputs such as publications or patents, is spread across the web, usually residing in institutional and personal web pages or in semi-open databases and information systems. While there exists a wealth of unstructured information, structured data is limited and often exposed following proprietary or less-established schemas and interfaces. Therefore, a holistic and consistent view on research information across organisational and national boundaries is not feasible. On the other hand, web crawling and information extraction techniques have matured throughout the last decade, allowing for automated approaches of harvesting, extracting and consolidating research information into a more coherent knowledge graph. In this work, we give an overview of the current state of the art in research information sharing on the web and present initial ideas towards a more holistic approach for boot-strapping research information from available web sources.
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    Development, design, and realization of a proficiency test for the forensic determination of shooting distances - FDSD 2015
    (Amsterdam : Elsevier, 2016) Niewöhner, Ludwig; Barth, Martin; Neimke, Dieter; Latzel, Silke; Stamouli, Amalia; Nys, Bart; Gunaratnam, Lawrence; Fries, Kira; Uhlig, Steffen; Baldauf, Henning
    Within the framework of the ENFSI Expert Working Group Firearms/GSR a novel proficiency test on the Forensic Determination of Shooting Distances – FDSD 2015 – was implemented. This proficiency test was developed out of collaborative studies which were previously carried out by a number of pre-selected ENFSI laboratories. The aim of this test was to assess the laboratories’ performance in visualizing the lead patterns on a shot object, and compare the questioned patterns with provided test shot patterns. The participating laboratories were requested to estimate the presumed shooting distance following their individual laboratory specific methods (SOPs) for shooting distance/muzzle-to-target determination. The submitted results were compiled by means of z scores according to the IUPAC and EURACHEM guidelines, and an extended statistical evaluation was performed. This is one of the first proficiency tests in the field of qualitative forensic methods where z scores were successfully utilized. This paper summarizes the results of the study and presents the overall performance of the participating laboratories.
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    Adhesion and relaxation of a soft elastomer on surfaces with skin like roughness
    (Amsterdam : Elsevier, 2018) Fischer, Sarah; Boyadzhieva, Silviya; Hensel, René; Kruttwig, Klaus; Arzt, Eduard
    For designing new skin adhesives, the complex mechanical interaction of soft elastomers with surfaces of various roughnesses needs to be better understood. We systematically studied the effects of a wide set of roughnesscharacteristics, film thickness, hold time and material relaxation on the adhesive behaviour of the silicone elastomer SSA 7–9800 (Dow Corning). As model surfaces, we used epoxy replicas obtained from substrates with roughness ranging from very smooth to skin-like. Our results demonstrate that films of thin and intermediate thickness (60 and 160 μm) adhered best to a sub-micron rough surface, with a pull-off stress of about 50 kPa. Significant variations in pull-off stress and detachment mechanism with roughness and hold time were found. In contrast, 320 μm thick films adhered with lower pull-off stress of about 17 kPa, but were less sensitive to roughness and hold time. It is demonstrated that the adhesion performance of the siliconefilms to rough surfaces can be tuned by tailoring the film thickness and contact time.
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    Numerical simulation of the edge stress singularity and the adhesion strength for compliant mushroom fibrils adhered to rigid substrates
    (Amsterdam : Elsevier, 2016) Balijepalli, R.G.; Begley, M.R.; Fleck, N.A.; McMeeking, R.M.; Arzt, E.
    Bio-inspired adhesion of micropatterned surfaces due to intermolecular interactions has attracted much research interest over the last decade. Experiments show that the best adhesion is achieved with compliant “mushroom”-shaped fibrils. This paper analyses numerically the effects of different mushroom shapes on adhesion to a rigid substrate. When a remote stress is applied on the free end of a fibril perfectly bonded to a rigid substrate, the resultant stress distribution along the fibril is found to change dramatically between the straight punch and mushroom fibrils. A singular stress field is present at the edge of the fibril where it contacts the substrate and, in this work, the amplitude of the singularity is evaluated for fibrils perfectly bonded to a flat substrate so that sliding cannot occur there. This exercise is carried out for fibril geometries involving combinations of different diameters and thicknesses of the mushroom cap. By assuming a pre-existing detachment length at the corner where the stress singularity lies, we predict the adhesive strength for various mushroom cap shapes. Our study shows that a smaller stalk diameter and a thinner mushroom cap lead to higher adhesive strengths. A limited number of results are also given for other shapes, including those having a fillet radius connecting the stalk to the cap. The results support the rational optimization of synthetic micropatterned adhesives.
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    Thermal conductivity and temperature profiles in carbon electrodes for supercapacitors
    (Amsterdam : Elsevier, 2014) Burheim, Odne S.; Aslan, Mesut; Atchison, Jennifer S.; Presser, Volker
    The thermal conductivity of supercapacitor film electrodes composed of activated carbon (AC), AC with 15 mass% multi-walled carbon nanotubes (MWCNTs), AC with 15 mass% onion-like carbon (OLC), and only OLC, all mixed with polymer binder (polytetrafluoroethylene), has been measured. This was done for dry electrodes and after the electrodes have been saturated with an organic electrolyte (1 M tetraethylammonium-tetrafluoroborate in acetonitrile, TEA-BF4). The thermal conductivity data was implemented in a simple model of generation and transport of heat in a cylindrical cell supercapacitor systems. Dry electrodes showed a thermal conductivity in the range of 0.09-0.19 W K-1 m-1 and the electrodes soaked with an organic electrolyte yielded values for the thermal conductivity between 0.42 and 0.47 W K-1 m-1. It was seen that the values related strongly to the porosity of the carbon electrode materials. Modeling of the internal temperature profiles of a supercapacitor under conditions corresponding to extreme cycling demonstrated that only a moderate temperature gradient of several degrees Celsius can be expected and which depends on the ohmic resistance of the cell as well as the wetting of the electrode materials.
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    Direct production of lactic acid based on simultaneous saccharification and fermentation of mixed restaurant food waste
    (Amsterdam : Elsevier, 2016) Pleissner, Daniel; Demichelis, Francesca; Mariano, Silvia; Fiore, Silvia; Gutiérrez, Ivette Michelle Navarro; Schneider, Roland; Venus, Joachim
    This study introduces to a one-step process for the fermentative production of L(+)-lactic acid from mixed restaurant food waste. Food waste was used as carbon and nitrogen source in simultaneous saccharification and fermentation (SSF) using Lactobacillus sp. or Streptococcus sp. strains for L(+)-lactic acid production. Waste consisted of (w/w) 33.5% starch, 14.8% proteins, 12.9% fat and 8.5% free sugars. Lactobacillus sp. strains showed a productivity of 0.27–0.53 g L−1 h−1 and a yield of 0.07–0.14 g g−1 of theoretically available sugars, while Streptococcus sp. more efficiently degraded the food waste material and produced lactic acid at a maximum rate of 2.16 g L−1 h−1 and a yield of 0.81 g g−1. For SSF, no enzymes were added or other hydrolytic treatments were carried out. Outcomes revealed a linear relationship between lactic acid concentration and solid-to-liquid ratio when Streptococcus sp. was applied. Statistically, from a 20% (w/w) dry food waste blend 52.4 g L−1 lactic acid can be produced. Experimentally, 58 g L−1 was achieved in presence of 20% (w/w), which was the highest solid-to-liquid ratio that could be treated using the equipment applied. Irrespective if SSF was performed at laboratory or technical scale, or under non-sterile conditions, Streptococcus sp. efficiently liquefied food waste and converted the released nutrients directly into lactic acid without considerable production of other organic acids, such as acetic acid. Downstream processing including micro- and nanofiltration, electrodialysis, chromatography and distillation gave a pure 702 g L−1 L(+)-lactic acid formulation.