1,721,111 research outputs found
SUNDS probabilistic human health risk assessment methodology and its application to organic pigment used in the automotive industry
No full textThe increasing use of engineered nanomaterials (ENMs) in nano-enabled products (NEPs) has raised societal concerns about their possible health and ecological implications. To ensure a high level of human and environmental protection it is essential to properly estimate the risks of these new materials and to develop adequate risk management strategies. To this end, we propose a quantitative Human Health Risk Assessment (HHRA) methodology, which was developed in the European Seventh Framework research project SUN (Sustainable Nanotechnologies) and implemented in the web-based SUN Decision Support System (SUNDS). One of the major strengths of this probabilistic approach as compared to its deterministic alternatives is its ability to clearly communicate the uncertainties in the estimated risks in order to support better risk communication for more objective decision making by industries and regulators. To demonstrate this methodology, we applied it in a real case study involving a nanoscale organic red pigment used in the automotive industry. Our analysis clearly showed that the main source of uncertainty was the extrapolation from (sub)acute in vivo toxicity data to long-term risk. This extrapolation was necessary due to a lack of (sub)chronic in vivo studies for the investigated nanomaterial. Despite the high uncertainty in the final results due to the conservative assumptions made in the risks assessment, the estimated risks are acceptable for all investigated exposure scenarios along the product lifecycle
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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Thermal Decomposition of Nano-Enabled Products: Potential Environmental Health and Safety Implications
No full textThe widespread use of engineered nanomaterials (ENMs) in consumer products inevitably raises concern for potential exposure to ENMs released from such nano-enabled products (NEPs). It is therefore important to understand the scenarios and mechanisms by which ENMs are released over the NEP lifecycle causing exposure and potential environmental health implications.
In this dissertation, I focus on understanding the fundamentals related to the incineration/thermal decomposition of industrially relevant NEPs, such as thermoplastics and coatings, widely used in many applications. The potential release of ENMs (used as nanofillers in NEPs) into the environment and the physicochemical, morphological (PCM) and toxicological properties of the released byproducts (released aerosol, residual ash and off-gases) are assessed. The role of NEP matrix composition, nanofiller type/size/mass-loading and thermal process conditions on the thermal decomposition behavior, release dynamics and byproduct PCM properties is investigated in detail. The potential cellular toxicological implications of the released aerosol are assessed and linked to PCM properties of the NEPs.
Key findings suggest that inorganic (and catalytic) metal oxide nanofillers such as TiO2, Fe2O3 and CuO are more likely to be released into the aerosol compared to carbonaceous nanofillers (e.g., CNTs (carbon nanotubes)) and inert metalloid oxide nanofillers (e.g., SiO2). Moreover, majority of inorganic nanofillers are retained loosely in the residual ash as flaky clusters, prompting the concern for their subsequent release into the environment (due to weathering, leaching, etc.), whereas CNTs are completely combusted at the high temperatures (>800 °C). More importantly, in the case of released catalytic metal oxide nanofillers, due to their synergistic interactions with gaseous semi-volatile organic byproducts, carcinogenic polycyclic aromatic hydrocarbons (PAHs) could be formed and thus present a significant inhalation exposure hazard for incineration facility operators, firefighters and surrounding community. Furthermore, increased bioactivity and toxicity of the released aerosol compared to the control (no nanofiller) are also confirmed in cellular studies. Future studies should investigate effects of sequential lifecycle stresses such as weathering on thermal decomposition of NEPs. Additionally, environmental fate and transport of ENMs from residual ash should be performed to assess potential environmental health risks and develop mitigation strategies associated with incineration/thermal decomposition of NEPs.engineered nanomaterials; nanofiller; host matrix; nano-enabled product; nano-enabled thermoplastic; nano-enabled coating; lifecycle; end-of-life; incineration; thermal decomposition; release; aerosol; inhalation exposure; residual ash; fate and transport; environmental health and safety implication
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Femtosekunden-Spektroskopie biologischer Systeme mittels kohärenter Kontrolle
Full text linkThis doctoral thesis presents new approaches for the characterisation of ultrafast energy flow in complex systems, based on concepts of coherent control. By initiating a photoreaction with femtosecond pulses whose temporal phase and amplitude are shaped in such a manner that specific molecular vibrations and states are addressed, the energy flow can be steered at will. The comparison between the ensuing energy flow patterns following shaped and unshaped excitation pulses constitutes a differential measurement of the function of the controlled vibrations and states within the photoreaction.
Coherent control as a spectroscopic tool is first applied to biological systems, specifically the light harvesting complex LH2 from the photosynthetic purple bacterium Rhodopseudomonas acidophila, and the isolated carotenoid donor of the same complex. The pump-probe method using shaped excitation pulses is shown to be successful for the first time in controlling the natural function of a biological system, namely the flow of excitation energy in the complex network of states in LH2. By means of a closed-loop optimisation of parametrised excitations, a bending mode in the carotenoid donor can be identified as being responsible for steering the energy flow. This bu vibrational mode couples the carotenoid S2-S1 states; its frequency is determined to be 160±25cm-1. Furthermore the deactivation of the carotenoid S2 state in LH2 and in solution is studied with pump-probe and pump-deplete-probe spectroscopy. Here it is shown that there exists an alternative singlet state S*T (1Bu-) involved in the deactivation process, though only in LH2. Its function as a precursor of ultrafast triplet population and as a donor for photosynthetic energy transfer is characterised with a novel evolutionary target analysis of conventional pump-probe spectra.
Secondly, coherent control as a measurement technique is applied to another extremely complex system, in this case a material dominated by non-linear interactions with instantaneous dynamics: Propagation of femtosecond pulses in optical fibres that are only a few micrometers in diameter to generate a supercontinuum of optical frequencies. Here shaped pump pulses succeed in resolving for the first time the sequential steps leading to the enormous spectral broadening. Open-loop variations of precompression allows the evolution and fission of optical solitons to be followed, while closed-loop optimisations render observable the coupling of solitons with phase-matched visible frequencies.
On atoms, finally, open-loop control of interfering pathways from the ground to the excited state by application of strongly modulated spectra seeks to establish a direct link between coherent control experiments and theory. The novel phenomenon of a Fresnel zone plate in the time domain is first developed in theory and then successfully realised in experiment.Die vorliegende Dissertation beschreitet neue Wege zur Charakterisierung des ultraschnellen Energieflusses in komplexen Systemen, indem Konzepte der kohärenten Kontrolle als neuartige Untersuchungsmethode in die Femtosekunden-Spektroskopie eingeführt werden. Die Anregung einer Photoreaktion mit Femtosekunden-Impulsen, deren zeitliche Phase und Amplitude derart geformt ist, daß spezifische Schwingungen und Zustände angesprochen werden, bewirkt die gezielte Steuerung des Energieflusses. Die Unterschiede des Energieflusses nach geformter oder ungeformter Anregung erlauben eine differentielle Messung der Funktion der kontrollierten Schwingungen und Zustände innerhalb der Photoreaktion.
Die kohärente Kontrolle als Werkzeug der Spektroskopie wird einerseits an biologischen Systemen angewandt, dem Lichtsammelkomplex LH2 aus Rhodopseudomonas acidophila, einem photosynthetischen Purpurbakterium, und am Carotinoid als isolierten Donor des Komplexes. Es gelingt mit der spektroskopischen Methode geformter-Pump-Probe erstmals, die natürliche Funktion eines biologischen Systems, den Fluß der Anregungsenergie im komplexen Netzwerk von Zuständen in LH2, zu kontrollieren. Mit Hilfe der closed-loop Optimierung parametrisierter Anregungen kann eine Biegeschwingung im Carotinoid als verantwortlich für die Steuerung des Energieflusses identifiziert werden. Diese Schwingung koppelt durch ihre bu Symmetrie die Carotinoid S2-S1 Zustände und konnte zu 160±25cm-1 bestimmt werden. Mit Pump-Probe und Pump-deplete-probe Spektroskopie an der Desaktivierung von Carotinoid S2 in LH2 und in Lösung wird die Existenz eines alternativen Singulettzustands S*T (1Bu-) bewiesen, der nur in LH2 aktiv an der Desaktivierung beteiligt ist. Seine Funktion als Zwischenzustand ultraschneller Besetzung von Tripletts und als Donor des photosynthetischen Energietransfers kann mit einer neuartigen evolutionären Target-Analyse von konventionellen Pump-Probe Spektren charakterisiert werden.
Die kohärente Steuerung als Meßmethode wird andererseits am gegensätzlichen Extrem eines komplexen Systems angewandt, das durch eine nichtlineare statt linearer Wechselwirkung beherrscht wird, aber dafür eine instantane und nicht molekulare Dynamik zeigt: Die Erzeugung eines Superkontinuums aus Femtosekunden-Impulsen in optischen Fasern mit wenigen Mikrometern Durchmesser. Hier können mittels geformter Pump-Impulse erstmals die einzelnen Schritte der extremen spektralen Verbreiterung aufgelöst werden: Mit der open-loop Variation der Vorkompression läßt sich die Bildung und Spaltung optischer Solitonen verfolgen, und mit closed-loop Optimierungen wird deren Kopplung mit phasenangepaßten sichtbaren Frequenzen direkt beobachtbar.
An Atomen wird schließlich eine mögliche direkte Verbindung der kohärenten Kontrolle zu theoretischen Rechnungen gesucht, indem die open-loop Kontrolle des Weges vom Grund- zum angeregten Zustand durch Anwendung komplex modulierter Spektren demonstriert wird. Es wird das neuartige Phänomen einer Fresnel-Zonenplatte in der Zeit zunächst theoretisch abgeleitet und darauf experimentell erfolgreich realisiert
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