Optical assessment of gel-like mechanical and structural properties of surface layers: single particle tracking and molecular rotors

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Thin gel-like layers form at many surfaces of natural or artificial origin. Important properties of such layers include thickness, viscosity and density. Here we discuss two optical approaches which allow assessment of these properties with high resolution. The first approach relies on centroid calculation and defocus imaging based 3D tracking of fluorescent tracer particles, which is based on standard fluorescent microscopy and allows a precision of particle detection in the range of 10nm. The size of the particle and its surface charge and polarity will determine the particle invasion into the layer. Thus simultaneous application of different colored beads with different size and properties can reveal the thickness and nature of the layer. Via tracking the thermal vibration of particles invading the layer the bulk viscosity of the layer can be calculated. The second approach uses “molecular rotor” fluorophores (MR). Due to their molecular structure, the MR’s fluorescence quantum yield increases as their internal rotation is hampered by e.g. high viscosity of the embedding medium. The MRs are several orders of magnitude smaller than the structural (macro) molecules of a gel-like layer and therefore the MRs are not necessarily directly sensitive toward the bulk viscosity of the layer. In contrast, the MRs internal rotation will be attenuated by the MRs interaction with the structural elements of the layer or the solvent included in it. Depending on their molecular structure MRs exhibit different sensitivity to the mechanical properties of the large macromolecules or the solvent in a layer. Thus, they may be used to assess the microdomain’s viscosity or density in a surface layer. Using a ratiometric imaging approach, they can be used for continuous measurements in very different experimental settings

Dugoperiodički modovi u tropskoj atmosferi Drugi dio: Analitičko modeliranje Kelvinovih valova povezanih s konvekcijom uz konvekcijsku raspoloživu potencijalnu energiju

The thermal assumption of the model is based on the convective available potential energy (CAPE) closure, i.e. increased CAPE, represented by decreased midlevel potential temperature, results in increased precipitation. The dynamic assumption of the model is that the vertical heating profile has the shape of the first baroclinic mode, while the vertical dependence of modeled fields is calculated, i.e. the model is vertically resolved. The modeled modes are free Kelvin waves and convectively coupled Kelvin waves. It is shown that the CAPE closure is not sufficient to produce the observed destabilization of the Kelvin mode, but that the dynamical properties of the model give the observed phase speeds.Termalna pretpostavka modela je da konvekcijski raspoloživa potencijalna energija utječe na količinu oborine. Konvekcijski raspoloživa potencijalna energija ovisi o potencijalnoj temperaturi u srednjoj troposferi. Uzrok povećane količine oborine je smanjena potencijalna temperatura u srednjoj troposferi. Dinamika modela je razvijena uz pretpostavku da vertikalni profil grijanja ima oblik prvog baroklinog moda dok se u modelu računa ovisnost termodinamičkih polja po vertikali. Modelirani valovi su slobodni Kelvinovi valovi i Kelvinovi valovi povezani s konvekcijom. Iz modela se vidi da konvekcijski raspoloživa potencijalna energija nije dovoljna za opaženu nestabilnost Kelvinovih valova povezanih s konvekcijom, ali dinamika modela daje opaženu faznu brzinu

CUSLI Experts\u27 Roundtable Report on Canada-United States Relations -- Looking Forward

On Nov. 14, 2018, the Canada-United States Law Institute hosted an expert panel discussion on the subject of Canada-United States Relations -- Looking Forward in order to discuss the United States-Mexico-Canada Agreement (USMCA) that is projected to replace the North American Free Trade Agreement (NAFTA). The panelists examined USMCA negotiation and compared the USMCA to the NAFTA

An empirical investigation into the sources of supply chain disruptions

Master's thesis Industrial Economics and Technology Management IND590 - University of Agder 2019Firms are facing a vast array of risks which can cause disruptions to the normal operation of their supply chains. Managers striving to prepare for and overcome these disruptions have a broad selection of literature and risk reports at their disposal when assessing risks to their supply chain. These risk reports and academic works provide differentiated and compelling answers to what are the most pressing risks to supply chains, but are they accurate? This study aims at providing managers with an empiricalfoundation on what the main sources of supply chain disruptions have been the last decade by addressing the following research question:What have been the main sources of supply chain disruptions over the last decade, and do observed patterns correspond with expectations put forward in the scholarly literature and the risk management communities?Based on a content analysis of 11 504 articles from the Financial Times archive from 2009-2018, 445 articles describing sources of supply chain disruptions were retrieved. The samples were later analysed using statistical methods. The results of this investigation revealed that disruptions originating from within the supply chain were in sum the most prevalent. The majority of these disruptions were associated with risks that have traditionally been the concerns of supply chain managers. These risks include operational struggles at suppliers that are unable to deliver the desired quantity and quality, as well as challenges with forecasting demand and navigating the legal and bureaucratic process that emerge from operating a complex global supply chain across multiple regions. The study also revealed that supply chain disruptions stemming from risk sources external to the supply chain such as asset price collapse, natural hazards, terrorism and political turmoil have accounted for a relatively constant number of supply chain disruptions over the last decade. This observation is contrary to the seemingly increasing focus on these risks by the global community. However, even though there has not been an increase in disruptions caused by external events, catastrophic events still stood out as one of the biggest threats facing supply chains. Catastrophic incidents encompass high impact-low probability events including natural hazards such as earthquakes and hurricanes together with man-made acts both deliberate e.g. war and terrorism, and unintentional such as fires. Somewhat contrary to the attention given o acts of terrorism in the wake of the 9/11 attacks, disruptions associated with acts of terrorism constituted a surprisingly small number of the supply chain disruptions, with the vast majority of disruptions related to catastrophic events attributed to natural hazards. Lastly, the findings showed that disruptions originating from risks associated with information and communication technology, in particular, cyber-crime and unplanned IT outage, have been an increasingly common source of supply chain disruptions during the decade in conjunction with the advancing digitalisation of supply chains.Comparing the findings against the focus of academia and the risk management communities it is apparent that the strong focus on risks external to the supply chain is somewhat warranted given the frequent occurrences of catastrophic events that disrupt supply chains. However, the study revealed that too much attention has been given to these high-profile events, and in the process the more mundane risks facing supply chains have received less attention. As a consequence,these risks continue to pose a significant threat to the performance of supply chains. The findings highlight the importance of using several sources of information when assessing risks to supply chains. No single source of information, may it be scholarly literature, risk reports or internal reporting are able to grasp all the current, and future, patterns of supply chain disruptions by themselves. Managers should keep this in mind when identifying and assessing the risks to their supply chain. Diligence in seeking out alternative sources of information on supply chain risks can aid in creating a more advantageous supply chain risk management process and foster greater resilience in supply chains

Konvektivno udruženi Kelvinovi valovi i konvektivna inhibicija

We use a thermodynamic assumption that the vertical heating profile has the shape of the first baroclinic mode, and that the analytical expression for vertical velocity has two modes, representing shallow and deep convection. The thermal assumption of the model is given through the convective inhibition closure, i.e. negative convective inhibition results in increased precipitation. These modeled modes are the free Kelvin waves and the convectively coupled Kelvin waves. We find the latter mode to be unstable, with maximum growth rate at wavelengths of 6 000 kilometers. The model successfully captures the observed nature of the Kelvin waves and shows that convective inhibition closure is sufficient to trigger the observed destabilization of the convectively coupled Kelvin mode.Termodinamičke pretpostavke modela uključuju vertikalni profil grijanja koji ima oblik prvog baroklinog moda. Pretpostavljeni oblik vertikalne brzine sastoji se od dva dijela koji odgovaraju plitkoj i dubokoj konvekciji. Za parametrizaciju oborine uzeta je negativna konvektivna inhibicija (CIN). Dobiveni modovi su slobodni Kelvinovi valovi i Kelvinov val povezan s konvekcijom. Kelvinov val povezan s konvekcijom je nestabilan, a najveću nestabilnost pokazuje pri valnoj duljini od 6 000 km. Ovim modelom uspješno je reproducirana opažena priroda Kelvinovih valova, a iz modela se vidi da je konvektivna inhibicija dovoljna za modeliranje opažene nestabilnosti Kelvinovih valova povezanih s konvekcijom

Model basierte Analyse von planktischen Reaktionen auf Variationen der Nährstoffstöchiometrie in Sauerstoffminimumzonen

The present study aims to investigate the effect of nitrogen (N) and phosphorus (P) cycling on elemental stoichiometry of marine plankton across different trophic ecosystem levels in the Eastern Tropical South Pacific boundary system of Peru. The Peruvian upwelling region is one of the most productive upwelling systems of the world. However, the upwelling area is accompanied by oxygen deficient water masses, known as the Peruvian oxygen minimum zone (OMZs). Oxygen deficient water masses influence marine N and P inventories, may lead to shifts in the community composition (e.g., fish) and affect marine environments and humans. The present study suggests that microbial processes can contribute significantly to the food web dynamics and the N and P cycles in the Peruvian Upwelling region. Furthermore, this modeling study will permit to investigate the intimate interplay of marine biogeochemical cycles by observing changes of the N and P stoichiometry, at the organisms’ level throughout the planktonic food web. Moreover, the sixth chapter suggests the implementation of the planktonic lipid metabolism in physiological process models as a next step, in order to investigate more closely the effects of environmental changes on food quality for consumers of the planktonic food web.Die hier vorgelegte Studie untersucht Auswirkungen von Stickstoff (N) und Phosphor (P) auf die Nährstoffstöchiometrie von marinem Plankton über mehrere trophische Ökosystemebenen in den Küstenauftriebsgebieten des östlichen tropischen Südpazifiks vor Peru. Das Auftriebsgebiet vor Peru ist eine der produktivsten Auftriebzonen der Erde. Jedoch ist diese Auftriebszone von sauerstoffarmen Wassermassen begleitet, welche auch als Sauerstoff-Minimum-Zone bezeichnet werden (SMZ). Wassermassen mit geringer Sauerstoffsättigung beeinflussen Nährstoffspeicher und können möglicherweise zu Verschiebungen der Gemeinschaftsstruktur (z. Bsp., von Fischen) führen und somit die marinen Lebensräume und den Menschen beeinflussen. Die vorgelegte Studie besagt, dass mikrobiologische Prozesse ausschlaggebend an der Nahrungsnetzdynamik und dem Stickstoff- und Phosphatkreislauf des Peruvianischen Auftriebssystems beteiligt sind. Die Modellierung ermöglicht die sukzessive Beobachtung von Wechselwirkungen zwischen den marinbiogeochemischen Kreisläufen und den Veränderungen der N- und P-Stöchiometrie auf Organismusebene über das planktische Nahrungsnetz. Des Weiteren weist diese Studie als nächsten Schritt im sechsten Kapitel auf die Einführung des planktischen Fettstoffwechsels in physiologischen Prozessmodellen hin, um die Auswirkungen von Umweltveränderungen auf Nahrungsqualität der Konsumenten im planktischen Nahrungsnetz näher zu untersuchen

‘Antiflammins’: Two nonapeptide fragments of uteroglobin and lipocortin I have no phospholipase A2 -inhibitory and anti-inflammatory activity

AbstractThe ‘antiflammin’ nonapeptides P1 and P2 [(1988) Nature 335, 726-730] were synthesized and tested for inhibition of phospholipase A2 and release of prostaglandin E2, and leukotriene C4 in stimulated cells in vitro, and in vivo for anti-inflammatory activity in rats with carrageenan-induced paw oedema. Porcine pancreatic phospholipase A2, was not inhibited at concentrations of 0.5–50 μM. Prostaglandin E2, and leukotriene C4 release by mouse macrophages stimulated with zymosan or ATP was not affected up to a concentration of 10 μm, nor was prostaglandin release by interleukin 1β-stimulated mesangial cells and angiotensin II-stimulated smooth muscle cells. Both peptides exhibited no anti-inflammatory activity in carrageenan-induced rat paw oedema after topical (250 μg/paw) or systemic administration (1 or 4 mgkg s.c.). These results do not support the claim of potent phospholipase A2-inhibitory and anti-imflammatory activity of the ‘antiflammins’ P1 and P2 [1]