1,721,011 research outputs found
A recipe for plastic: Expert insights on plastic additives in the marine environment
Full text linkThe production and consumption of plastic products had been steadily increasing over the years, leading to more plastic waste entering the environment. Plastic pollution is ubiquitous and comes in many types and forms. To enhance or modify their properties, chemical additives are added to plastic items during manufacturing. The presence and leakage of these additives, from managed and mismanaged plastic waste, into the environment are of growing concern. In this study, we gauged, via an online questionnaire, expert knowledge on the use, characteristics, monitoring and risks of plastic additives to the marine environment. We analysed the survey results against actual data to identify and prioritise risks and gaps. Participants also highlighted key factors for future consideration, including gaining a deeper understanding of the use and types of plastic additives, how they leach throughout the entire lifecycle, their toxicity, and the safety of alternative options. More extensive chemical regulation and an evaluation of the essentiality of their use should also be considered.publishedVersio
Developing and optimising a cost- and time-effective method for the detection and identification of microplastics in the marine environment
No full textMicroplastics (MPs) zijn wijdverspreid en persistent in het mariene milieu. Het monitoren van MP-concentraties is hierdoor cruciaal voor het kunnen beoordelen van mogelijke risico's. Er bestaan reeds talloze analysetechnieken, maar veel hiervan zijn duur, tijdrovend en foutgevoelig, met name voor verweerde MPs. Daarenboven heeft de snelle diversificatie van analysemethoden voor MPs geleid tot een gebrek aan vergelijkbaarheid tussen studies vanwege verschillen in resolutie, focus en kwaliteit. Om deze problemen aan te pakken werd binnen dit doctorataatsonderzoek een innovatieve, betrouwbare methode ontwikkeld voor de kosten- en tijdseffectieve analyse van MPs in het mariene milieu. Verder werden ook protocollen voor de extractie van MPs uit zeewater, sediment en biota geoptimaliseerd. De ontwikkelde, semiautomatische analysemethode combineert de fluorescerende kleuring van deeltjes gekleurd met de kleurstof Nile red met machine learning algoritmes voor de detectie en identificatie van frequent voorkomende MPs. Twee modellen werden gecreëerd, gebaseerd op random forest (RF) algoritmes, waarvan één model deeltjes kan classificeren als plastic/niet-plastic (Plastic Detection Model - PDM), terwijl het andere model de plastic deeltjes verder classificeert op basis van hun polymeertype (Polymer Identification Model - PIM). De prestaties van de modellen werden getest en gevalideerd in vier stappen. Eerst werd hun prestatie getest voor pristine MPs (1), gevolgd door MPs die verweerd werden onder semi-gecontroleerde omstandigheden in oppervlaktewater en diepzeewater (2). Daarnaast werd ook de ondergrens van hun detectiegrootte bepaald. Als derde stap werd een validatie van de ontwikkelde methode uitgevoerd door het spiken van milieurelevante MPs in mariene biota, deze opnieuw te extraheren en te analyseren, gevolgd door de bepaling van belangrijke validatieparameters (3). Tot slot werden de prestaties van beide modellen getest voor echte zeewater- en sedimentstalen uit het Belgische deel van de Noordzee (BDNZ) d.m.v. FTIR-validatie (4). De RF modellen bleek betrouwbaar voor de detectie en identificatie van pristine plastics (nauwkeurigheid > 88%) en de meeste verweerde plastics (> 70%). Nauwkeurigheden > 90% werden verkregen voor deeltjes van 2 - 10 µm. Tijdens de laatste testfase bleken de geoptimaliseerde extractieprotocollen in combinatie met de modellen ook betrouwbaar voor het analyseren van niet-vezelige MPs in echte mariene stalen. Bovendien werd binnen deze case study baggerstortplaats Loswal Zeebrugge Oost geïdentificeerd als een MP-hotspot. Tot slot werd een kosteneffectiviteitsanalyse uitgevoerd van veelgebruikte MP-analysemethoden in zeewater, waarbij predictive tools ontwikkeld werden ter ondersteuning van o.a. onderzoekers en beleidsmakers bij het kiezen tussen verschillende MP-analysemethoden. Voor het uitvoeren van de analyse werd gebruik gemaakt van gegevens van MP-experten verzameld tijdens een online enquête. Drie verschillende simulaties werden uitgevoerd op basis van het bruto nationaal inkomen per capita van de tewerkstellingslanden van de respondenten, waarbij rekening werd gehouden met de arbeidskosten, apparatuurskosten en de intensiteit van het apparatuurgebruik. De ontwikkelde tools bieden objectieve informatie om financiële middelen efficiënt toe te wijzen en weloverwogen beslissingen te nemen
Advanced oxidation of quinolone antibiotics in water by ozone and the peroxone process
No full textQuinolone antibiotics can be found in WWTP effluent and surface waters at ng.l-1 - µg.l-1 concentration range. Induction of bacterial resistance against these antibiotics and toxicity to aquatic organisms are possible adverse effects. Since quinolones are not readily biodegradable, physical chemical removal technologies are indispensable for their removal. In this work, ozonation and the peroxone process were selected as removal technologies.
A first experimental part focuses on quinolone analysis. Chromatographic separation of ciprofloxacin stock solutions resulted in 2 chromatographic peaks with pH dependent peak area ratio. Next, an analytical procedure, based on SPE-LC-UV, was developed for separation of the quinolones ciprofloxacin, levofloxacin and flumequine at a concentration range of 0.03 – 45.3 µM.
Ozonation of ciprofloxacin and levofloxacin is discussed in the second part of this thesis. Degradation occurred at the piperazinyl substituent and the quinolone moiety. This is mainly influenced by the parameter pH while H2O2 addition had only limited effect. For levofloxacin, approximately two times faster ozonation was observed at pH 10 compared to pH 3 and 7 while for ciprofloxacin, degradation was 25 and 10% faster at pH 3 compared to pH 7 and 10, respectively. Degradation at the piperazinyl substituent is favoured at pH 10 due to fast ozonation at the unprotonated amine of the piperazinyl substituent.
At pH 7, degradation at the quinolone moiety is enhanced which results in the formation of isatin and anthranilic acid analogues. Addition of an excess t-butanol to the ozonation experiments excluded formation of these compounds, suggesting the necessity of radicals for formation of isatin and anthranalic acid analogues. This was confirmed by calculating the Fukui function for radical attack, which predicted the C2-atom of the quinolone moiety as one of the main sites for radical attack.
Agar diffusion tests with P. fluorescens, E. coli and B. coagulans for ozonated quinolone samples in deionized water revealed that ozonation efficiently reduces antibacterial activity, related to the parent compound degradation rate. In hospital WWTP effluent, however, degradation products affect the residual antibacterial activity against B. coagulans. The ciprofloxacin degradation rate in hospital WWTP effluent was influenced by sorption
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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