1,720,990 research outputs found
Suspension Feeders as Biological Models to Develop Biomimetic Filter Modules and Reduce Microplastic Emissions
Get PDFWith every wash cycle, microplastic fibres are released from textiles and enter the environment via the wastewater system. In order to develop an innovative washing machine filter, a biomimetic approach was employed. In biomimetics, biological working principles are analysed, abstracted models are created, and products and processes are developed that solve technical problems. The problem of microplastic release was studied for kitchen sponges by conducting a citizen science experiment. The results indicate that 58 - 355 t of microplastic particles are released annually from kitchen sponges into wastewater in Germany. The separation of microplastics from wastewater is a liquid-solid separation and the biological analogue to this was identified in suspension feeders. Suspension feeders are aquatic organisms that separate particles from the surrounding water for feeding. Within the framework of a literature study, 35 separation mechanisms were described on the basis of 18 biological and technical parameters and evaluated with regard to their biomimetic potential. Two filtration mechanisms were selected for more in-depth analysis: Mucus filtration and cross-flow filtration.
Mucus surfaces are formed by biofilms. Field and laboratory experiments showed that surfaces with biofilms absorb up to 12 times more microplastic particles than surfaces without biofilms. A biomimetic abstraction was not pursued due to the lack of technical materials that have the same particle-separating properties.
In cross-flow filtration, parallel flow is applied to the filter medium, preventing particle deposition and sebsequent clogging. In order to study this filtration mechanism, five ram-feeding fish species were selected. As ram-feeders swim forward, water flows into their mouths and food particles are retained by the gill arch system. Based on morphometric data, micro-CT scans, and behavioural experiments, three morphotypes were described that differ in terms of geometry, surface structuring, and materials. A modification of cross-flow filtration was identified as the underlying filtration mechanism, which is described for the first time as semi-cross-flow filtration. In further experiments, it was confirmed that the angle of attack of the filter medium to the fluid is decisive in semi cross-flow filtration in order to avoid the accumulation of particles. Subsequently, filter elements were created based on the conical geometry, the arrangement of the gill arches and the mesh size of the gill arch system. A filter housing generates a turbulent inflow and discharges the clean permeate and the particle-containing concentrate. Initial laboratory tests demonstrated a proof-of-concept of the biomimetic filter module that has an average filter efficiency of 97.3%.Mit jedem Waschgang werden Mikroplastikfasern aus Textilien freigesetzt, die über das Abwassersystem in die Umwelt gelangen. Um einen innovativen Waschmaschinenfilter zu entwickeln, wurde ein bionisches Vorgehen gewählt. In der Bionik werden biologische Funktionsprinzipien analysiert, abstrahierte Modelle erstellt und Produkte und Prozesse entwickelt, die technische Probleme lösen sollen. Zuerst wurde das Problem der Mikroplastikfreisetzung am Bespiel von Spülschwämmen im Rahmen eines Citizen-Science-Experiments untersucht. Die Ergebnisse zeigen, dass pro Jahr in Deutschland etwa 58 – 355 t an Mikroplastikpartikeln aus Spülschwämmen ins Abwasser freigesetzt werden. Die Abscheidung von Mikroplastik aus Abwasser ist eine flüssig-fest Trennung. Die biologische Analogie dazu wurde in Suspensionsfressern identifiziert. Suspensionsfresser sind aquatische Organismen, die Partikel zur Nahrungsaufnahme aus dem umgebenden Wasser trennen. Im Rahmen einer Literaturstudie wurden 35 Separationsmechanismen anhand von 18 biologischen und technischen Parametern beschrieben und hinsichtlich ihres bionischen Potentials bewertet. Zwei Filtrationsmechanismen wurden für eine tiefergehende Analyse ausgewählt: Schleimfiltration und Querstromfiltration.
Schleimige Oberflächen werden durch Biofilm gebildet. In Feld- und Laborversuchen konnte gezeigt werden, dass Oberflächen mit Biofilm bis zu 12-mal mehr Mikroplastikpartikel aufnehmen als Oberflächen ohne Biofilm. Eine bionische Abstraktion wurde aufgrund von fehlender technischer Materialien, die über die gleichen partikelbindenden Eigenschaften verfügen, nicht weiterverfolgt.
In der Querstromfiltration wird das Filtermedium parallel angeströmt, sodass Partikel nicht anlagern und zu Verstopfung führen können. Um diesen Filtrationsmechanismus zu untersuchen wurden fünf Fischarten ausgewählt, die als ‚ram-feeders‘ bezeichnet werden. Durch ihr Vorwärtsschwimmen wird Wasser ins Maul geströmt und Nahrungspartikel werden mit dem Kiemenreusensystem herausgefiltert. Basierend auf morphometrischen Daten, micro-CT Scans und Verhaltensversuchen wurden drei Morphotypen beschrieben, die sich hinsichtlich Geometrie, Oberflächenstrukturierung und Materialien unterscheiden. Als zugrunde liegender Filtrationsmechanism wurde eine Abwandlung der Querstromfiltration identifiert, die erstmals als Semi-Querstromfiltration beschrieben wird. In weiterführenden Versuchen bestätigte sich, dass der Ausrichtungswinkel des Filtermediums zum Fluid in der Semi-Querstromfiltration ausschlaggebend ist, um eine Anlagerung von Partikeln zu vermeiden. Anschließend wurden basierend auf der konischen Geometrie, der Anordnung der Kiemenbögen und der Maschenweite des Kiemenreusensystems Filterelemente erstellt. Ein Filtergehäuse erzeugt einen turbulenter Anstrom und leitet das saubere Permeat und das partikelenthaltende Konzentrat ab. In ersten Laborversuchen konnte ein Proof-of-Concept des bionischen Filters mit einer durchschnittlichen Filtereffizient von 97.3% gezeigt werden
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Brittleness of twig bases in the genus Salix: fracture mechanics and ecological relevance
No full textUntersuchungen zur Ökologie und Biomechanik der Uferweiden Salix alba, Salix fragilis und des Hybridschwarms Salix x rubens
No full textVariations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
