Atmospheric corrosion of quaternary bronzes (Cu-Sn-Zn-Pb): laboratory tests (accelerated ageing in wet & dry conditions)and field studies (the Bottego monument in Parma, Italy).

The interactions between outdoor bronzes and the environment, which lead to bronze corrosion, require a better understanding in order to design effective conservation strategies in the Cultural Heritage field. In the present work, investigations on real patinas of the outdoor monument to Vittorio Bottego (Parma, Italy) and laboratory studies on accelerated corrosion testing of inhibited (by silane-based films, with and without ceria nanoparticles) and non-inhibited quaternary bronzes are reported and discussed. In particular, a wet&dry ageing method was used both for testing the efficiency of the inhibitor and for patinating bronze coupons before applying the inhibitor. A wide range of spectroscopic techniques has been used, for characterizing the core metal (SEM+EDS, XRF, AAS), the corroded surfaces (SEM+EDS, portable XRF, micro-Raman, ATR-IR, Py-GC-MS) and the ageing solutions (AAS). The main conclusions were: 1. The investigations on the Bottego monument confirmed the differentiation of the corrosion products as a function of the exposure geometry, already observed in previous works, further highlighting the need to take into account the different surface features when selecting conservation procedures such as the application of inhibitors (i.e. the relative Sn enrichment in unsheltered areas requires inhibitors which effectively interact not only with Cu but also with Sn). 2. The ageing (pre-patination) cycle on coupons was able to reproduce the relative Sn enrichment that actually happens in real patinated surfaces, making the bronze specimens representative of the real support for bronze inhibitors. 3. The non-toxic silane-based inhibitors display a good protective efficiency towards pre-patinated surfaces, differently from other widely used inhibitors such as benzotriazole (BTA) and its derivatives. 4. The 3-mercapto-propyl-trimethoxy-silane (PropS-SH) additivated with CeO2 nanoparticles generally offered a better corrosion protection than PropS-SH.

Design, implementation and evaluation of a virtual laboratory for Computer Engineering Education

Broad consensus has been reached within the Education and Cognitive Psychology research communities on the need to center the learning process on experimentation and concrete application of knowledge, rather than on a bare transfer of notions. Several advantages arise from this educational approach, ranging from the reinforce of students learning, to the increased opportunity for a student to gain greater insight into the studied topics, up to the possibility for learners to acquire practical skills and long-lasting proficiency. This is especially true in Engineering education, where integrating conceptual knowledge and practical skills assumes a strategic importance. In this scenario, learners are called to play a primary role. They are actively involved in the construction of their own knowledge, instead of passively receiving it. As a result, traditional, teacher-centered learning environments should be replaced by novel learner-centered solutions. Information and Communication Technologies enable the development of innovative solutions that provide suitable answers to the need for the availability of experimentation supports in educational context. Virtual Laboratories, Adaptive Web-Based Educational Systems and Computer-Supported Collaborative Learning environments can significantly foster different learner-centered instructional strategies, offering the opportunity to enhance personalization, individualization and cooperation. More specifically, they allow students to explore different kinds of materials, to access and compare several information sources, to face real or realistic problems and to work on authentic and multi-facet case studies. In addition, they encourage cooperation among peers and provide support through coached and scaffolded activities aimed at fostering reflection and meta-cognitive reasoning. This dissertation will guide readers within this research field, presenting both the theoretical and applicative results of a research aimed at designing an open, flexible, learner-centered virtual lab for supporting students in learning Information Security.

Phytoplankton Response to Environmental Variables and Organic Pollutants. Laboratory Cultures and Numerical Simulations Experiments

Herbicides are becoming emergent contaminants in Italian surface, coastal and ground waters, due to their intensive use in agriculture. In marine environments herbicides have adverse effects on non-target organisms, as primary producers, resulting in oxygen depletion and decreased primary productivity. Alterations of species composition in algal communities can also occur due to the different sensitivity among the species. In the present thesis the effects of herbicides, widely used in the Northern Adriatic Sea, on different algal species were studied. The main goal of this work was to study the influence of temperature on algal growth in the presence of the triazinic herbicide terbuthylazine (TBA), and the cellular responses adopted to counteract the toxic effects of the pollutant (Chapter 1 and 2). The development of simulation models to be applied in environmental management are needed to organize and track information in a way that would not be possible otherwise and simulate an ecological prospective. The data collected from laboratory experiments were used to simulate algal responses to the TBA exposure at increasing temperature conditions (Chapter 3). Part of the thesis was conducted in foreign countries. The work presented in Chapter 4 was focused on the effect of high light on growth, toxicity and mixotrophy of the ichtyotoxic species Prymnesium parvum. In addition, a mesocosm experiment was conducted in order to study the synergic effect of the pollutant emamectin benzoate with other anthropogenic stressors, such as oil pollution and induced phytoplankton blooms (Chapter 5).

A daily perspective on work interruptions

Diese Dissertation basiert auf einem theoretischen Artikel und zwei empirischen Studien.rnrnDer theoretische Artikel: Es wird ein theoretisches Rahmenmodell postuliert, welches die Kumulierung von Arbeitsunterbrechung und deren Effekte untersucht. Die meisten bisherigen Studien haben Unterbrechungen als isoliertes Phänomen betrachtet und dabei unberücksichtigt gelassen, dass während eines typischen Arbeitstages mehrere Unterbrechungen gleichzeitig (oder aufeinanderfolgend) auftreten. In der vorliegenden Dissertation wird diese Lücke gefüllt, indem der Prozess der kumulierenden Unterbrechungen untersucht wird. Es wird beschrieben,rninwieweit die Kumulation von Unterbrechungen zu einer neuen Qualität vonrn(negativen) Effekten führt. Das Zusammenspiel und die gegenseitige Verstärkung einzelner Effekte werden dargestellt und moderierende und mediierende Faktoren aufgezeigt. Auf diese Weise ist es möglich, eine Verbindung zwischen kurzfristigen Effekten einzelner Unterbrechungen und Gesundheitsbeeinträchtigungen durch die Arbeitsbedingung ‚Unterbrechungen‘rnherzustellen.rnrnStudie 1: In dieser Studie wurde untersucht, inwieweit Unterbrechungen Leistung und Wohlbefinden einer Person innerhalb eines Arbeitstages beeinflussen. Es wurde postuliert, dass das Auftreten von Unterbrechungen die Zufriedenheit mit der eigenen Leistung vermindert und das Vergessen von Intentionen und das Irritationserleben verstärkt. Geistige Anforderung und Zeitdruck galten hierbei als Mediatoren. Um dies zu testen, wurden 133 Pflegekräften über 5 Tage hinweg mittels Smartphones befragt. Mehrebenenanalysen konnten die Haupteffekte bestätigen. Die vermuteten Mediationseffekte wurden für Irritation und (teilweise) für Zufriedenheit mit der Leistung bestätigt, nicht jedoch für Vergessen von Intentionen. Unterbrechungen führen demzufolge (u.a.) zu negativen Effekten, da sie kognitiv anspruchsvoll sind und Zeit beanspruchen.rnrnStudie 2: In dieser Studie wurden Zusammenhänge zwischen kognitiven Stressorenrn(Arbeitsunterbrechungen und Multitasking) und Beanspruchungsfolgen (Stimmung und Irritation) innerhalb eines Arbeitstages gemessen. Es wurde angenommen, dass diese Zusammenhänge durch chronologisches Alter und Indikatoren funktionalen Alters (Arbeitsgedächtniskapazität und Aufmerksamkeit) moderiert wird. Ältere mit schlechteren Aufmerksamkeitsund Arbeitsgedächtnisleistungen sollten am stärksten durch die untersuchten Stressoren beeinträchtigt werden. Es wurde eine Tagebuchstudie (siehe Studie 1) und computergestützternkognitive Leistungstests durchgeführt. Mehrebenenanalysen konnten die Haupteffekte für die abhängigen Variablen Stimmung (Valenz und Wachheit) und Irritation bestätigen, nicht jedoch für Erregung (Stimmung). Dreifachinteraktionen wurden nicht in der postulierten Richtung gefunden. Jüngere, nicht Ältere profitierten von einem hohen basalen kognitivenrnLeistungsvermögen. Ältere scheinen Copingstrategien zu besitzen, die mögliche kognitive Verluste ausgleichen. rnrnIm Allgemeinen konnten die (getesteten) Annahmen des theoretischen Rahmenmodellsrnbestätigt werden. Prinzipiell scheint es möglich, Ergebnisse der Laborforschung auf die Feldforschung zu übertragen, jedoch ist es notwendig die Besonderheiten des Feldes zu berücksichtigen. Die postulieren Mediationseffekte (Studie 1) wurden (teilweise) bestätigt. Die Ergebnisse weisen jedoch darauf hin, dass der volle Arbeitstag untersucht werden muss und dass sehr spezifische abhängige Variablen auch spezifischere Mediatoren benötigen. Des Weiteren konnte in Studie 2 bestätigt werden, dass die kognitive Kapazität eine bedeutsamernRessource im Umgang mit Unterbrechungen ist, im Arbeitskontext jedoch auch andere Ressourcen wirken.

The formation of OH radicals from Criegee intermediates: a LIF-FAGE study from laboratory to ambient

Das Hydroxyl Radikal ist, auf globalem Maßstab, das bedeutendste Oxidant in der Atmosphäre. Es initiiert den Abbauprozess vieler, teilweise schädlicher, Spurengase und insbesondere den von flüchtigen Kohlenwasserstoffen (VOC). Die OH Konzentration ist somit ein gutes Maß für die augenblickliche Selbstreinigungskapazität der Atmosphäre. Messungen zu nächtlicher Zeit mit LIF-FAGE-Instrumenten (engl.: laser-induced fluorescence - fluorescence assay by gas expansion) haben Konzentrationen des Hydroxylradikals (OH) ergeben, die signifikant höher waren, als sich mit der bekannten Chemie erklären ließ. Um herauszufinden, ob ein solches Signal wirklich atmosphärisches OH ist oder von einer störenden Spezies stammt, die im Messinstrument OH produziert, wurde das LIF-FAGE-Instrument des Max-Planck-Instituts für Chemie (MPIC) im Rahmen dieser Doktorarbeit modifiziert und getestet. Dazu wurde ein so genannter Inlet Pre-Injector (IPI) entwickelt, mit dem in regelmäßigen Abständen ein OH-Fänger in die Umgebungsluft abgegeben werden kann, bevor das OH vom Instrument erfasst wird. Mit dieser Technik ist es möglich, ein Hintergrund-OH (OHbg), d. h. ein im Instrument erzeugtes OH-Signal, vom gemessenen OH-Gesamtsignal (OHtot) zu trennen. Die Differenz zwischen OHtot und OHbg ist die atmosphärische OH-Konzentration (OHatm). Vergleichsmessungen mit der hier entwickelten Technik, dem IPI, in zwei verschiedenen Umgebungen mit Instrumenten basierend auf Massenspektrometrie mit chemischer Ionisation (CIMS, engl.: chemical ionization mass spectrometry) als alternativer Methode des OH-Nachweises, zeigten eine weitgehende Übereinstimmung. Eine umfassende Beschreibung des Systems zur Ermittlung der Ursache des OHbg hat ergeben, dass es weder von einem Artefakt des Instruments noch von hinlänglich bekannten und beschriebenen LIF-FAGE-Interferenzen stammt. Zur Bestimmung der Spezies, die das OHbg-Signal verursacht, wurden verschiedene Laborstudien durchgeführt. Die Arbeit im Rahmen dieser Doktorarbeit hat ergeben, dass das LIF-FAGE-Instrument leicht auf OH reagiert, das beim monomolekularen Zerfall stabilisierter Criegee-Intermediate (SCI) im Niederdruckbereich des Instruments gebildet wird. Criegee-Intermediate oder Carbonyloxide entstehen bei der Ozonolyse ungesättigter flüchtiger Kohlenwasserstoffverbindungen (VOC, engl.: volatile organic compounds) und können daher in der Umgebungsluft vorkommen. Anhand von Tests mit verschiedenen Verweilzeiten der SCI im Niederdruckbereich des Instruments in Verbindung mit einem detaillierten Modell mit der neuesten SCI-Chemie wurde die monomolekulare Zerfallsgeschwindigkeit von 20  10 s-1 für den syn-Acetaldehyd-Oxykonformer bestimmt. Der in Feldkampagnen gemessene OHbg-Wert wurde dahingehend untersucht, ob SCI die Quelle des beobachteten Hintergrund-OH im Feld sein könnten. Das Budget für die SCI-Konzentration, das für die Kampagnen HUMPPA-COPEC 2010 und HOPE 2012 berechnet wurde, ergab eine SCI-Konzentration zwischen ca. 103 und 106 Molekülen pro cm3. In der Kampagne HUMPPA-COPEC 2010 ergab die Schwefelsäurekonzentration, dass die OH-Oxidation von SO2 allein die gemessene H2SO4-Konzentration nicht erklären konnte. In dieser Arbeit konnte gezeigt werden, dass das Hintergrund-OH mit dieser ungeklärten Produktionsrate von H2SO4 korreliert und somit die Oxidation von SO2 durch SCI als mögliche Erklärung in Frage kommt. Ferner korreliert das Hintergrund-OH in der Kampagne HOPE 2012 mit dem Produkt aus Ozon und VOC und konnte mit SO2 als SCI Fänger entfernt werden. Qualitativ zeigen wir somit, dass das in der Umgebungsluft gemessene Hintergrund-OH wahrscheinlich durch den monomolekularen Zerfall von SCI verursacht wird, doch sind weitere Studien notwendig, um die quantitativen Beziehung für diese Spezies und dem Hintergrund-OH in unserem Instrument zu bestimmen.

Laboratory-based ROTEM(®) analysis: implementing pneumatic tube transport and real-time graphic transmission

ROTEM(®) is considered a helpful point-of-care device to monitor blood coagulation. Centrally performed analysis is desirable but rapid transport of blood samples and real-time transmission of graphic results are an important prerequisite. The effect of sample transport through a pneumatic tube system on ROTEM(®) results is unknown. The aims of the present work were (i) to determine the influence of blood sample transport through a pneumatic tube system on ROTEM(®) parameters compared to manual transportation, and (ii) to verify whether graphic results can be transmitted on line via virtual network computing using local area network to the physician in charge of the patient.

Micro combined heat and power laboratory development

Micro Combined Heat and Power (Micro-CHP) system produces both electricity and heat required for residential or small business applications. Use of Micro-CHP in a residential application not only creates energy and economic savings but also reduces the carbon foot print of the house or small business. Additionally, micro-CHP can subsidize its cost of operation by selling excess electricity produced back to the grid. Even though Micro-CHP remains attractive on paper, high initial cost and optimization issues in residential scale heat and electrical requirement has kept this technology from becoming a success. To understand and overcome all disadvantages posed my Micro-CHP system, a laboratory is developed to test different scenarios of Micro-CHP applications so that we can learn and improve the current technology. This report focuses on the development of this Micro-CHP laboratory including installation of Ecopower micro-CHP unit, developing fuel line and exhaust line for Ecopower unit, design of electrical and thermal loop, installing all the instrumentation required for data collection on the Ecopower unit and developing controls for heat load simulation using thermal loop. Also a simulation of Micro-CHP running on Syngas is done in Matlab. This work was supported through the donation of ‘Ecopower’ a Micro-CHP unit by Marathon Engine and through the support of Michigan Tech REF-IF grand.

The Application of a Laboratory Induction Furnace to the Selective Smelting of a Montana Chromite Concentrate

The purpose of this experimental work was to determine with the utilization of a laboratory sized induction furnace a method whereby a high-iron Montana chromite concentrate could be successfully smelted to yield a product suitable for the subsequent production of standard ferrochrome.

Characterization of granite matrix porosity and pore-space geometry by in situ and laboratory methods

Most available studies of interconnected matrix porosity of crystalline rocks are based on laboratory investigations; that is, work on samples that have undergone stress relaxation and were affected by drilling and sample preparation. The extrapolation of the results to in situ conditions is therefore associated with considerable uncertainty, and this was the motivation to conduct the ‘in situ Connected Porosity’ experiment at the Grimsel Test Site (Central Swiss Alps). An acrylic resin doped with fluorescent agents was used to impregnate the microporous granitic matrix in situ around an injection borehole, and samples were obtained by overcoring. The 3-D structure of the porespace, represented by microcracks, was studied by U-stage fluorescence microscopy. Petrophysical methods, including the determination of porosity, permeability and P -wave velocity, were also applied. Investigations were conducted both on samples that were impregnated in situ and on non-impregnated samples, so that natural features could be distinguished from artefacts. The investigated deformed granites display complex microcrack populations representing a polyphase deformation at varying conditions. The crack population is dominated by open cleavage cracks in mica and grain boundary cracks. The porosity of non-impregnated samples lies slightly above 1 per cent, which is 2–2.5 times higher than the in situ porosity obtained for impregnated samples. Measurements of seismic velocities (Vp ) on spherical rock samples as a function of confining pressure, spatial direction and water saturation for both non-impregnated and impregnated samples provide further constraints on the distinction between natural and induced crack types. The main conclusions are that (1) an interconnected network of microcracks exists in the whole granitic matrix, irrespective of the distance to ductile and brittle shear zones, and (2) conventional laboratory methods overestimate the matrix porosity. Calculations of contaminant transport through fractured media often rely on matrix diffusion as a retardation mechanism.

Shaping the PSF to nearly top-hat profile: CHEOPS laboratory results

Spreading the PSF over a quite large amount of pixels is an increasingly used observing technique in order to reach extremely precise photometry, such as in the case of exoplanets searching and characterization via transits observations. A PSF top-hat profile helps to minimize the errors contribution due to the uncertainty on the knowledge of the detector flat field. This work has been carried out during the recent design study in the framework of the ESA small mission CHEOPS. Because of lack of perfect flat-fielding information, in the CHEOPS optics it is required to spread the light of a source into a well defined angular area, in a manner as uniform as possible. Furthermore this should be accomplished still retaining the features of a true focal plane onto the detector. In this way, for instance, the angular displacement on the focal plane is fully retained and in case of several stars in a field these look as separated as their distance is larger than the spreading size. An obvious way is to apply a defocus, while the presence of an intermediate pupil plane in the Back End Optics makes attractive to introduce here an optical device that is able to spread the light in a well defined manner, still retaining the direction of the chief ray hitting it. This can be accomplished through an holographic diffuser or through a lenslet array. Both techniques implement the concept of segmenting the pupil into several sub-zones where light is spread to a well defined angle. We present experimental results on how to deliver such PSF profile by mean of holographic diffuser and lenslet array. Both the devices are located in an intermediate pupil plane of a properly scaled laboratory setup mimicking the CHEOPS optical design configuration. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Laboratory investigation of flow structure and resistance of high- and low-angle dunes

A prominent control on the flow over subaqueous dunes is the slope of the downstream leeside. While previous work has focused on steep (~30°), asymmetric dunes with permanent flow separation, little is known about dunes with lower lee-slope angles for which flow separation is absent or intermittent. Here, we present a laboratory investigation where we systematically varied the dune lee-slope, holding other geometric parameters and flow hydraulics constant, to explore effects on the turbulent flow field and flow resistance. Three sets of fixed dunes (lee-slopes of 10°, 20° and 30°) were separately installed in a 15 m long and 1 m wide flume and subjected to 0.20 m deep flow. Measurements consisted of high-frequency, vertical profiles collected with a Laser Doppler Velocimeter (LDV). We show that the temporal and spatial occurrence of flow separation decreases with dune lee-slope. Velocity gradients in the dune leeside depict a free shear layer downstream of the 30° dunes and a weaker shear layer closer to the bed for the 20° and 10° dunes. The decrease in velocity gradients leads to lower magnitude of turbulence production for gentle lee-slopes. Aperiodic, strong ejection events dominate the shear layer, but decrease in strength and frequency for low-angle dunes. Flow resistance of dunes decreases with lee-slope; the transition being non-linear. Over the 10°, 20° and 30° dunes, shear stress is 8%, 33% and 90 % greater than a flat bed, respectively. Our results demonstrate that dune lee-slope plays an important, but often ignored role in flow resistance.

Direct visualization of solute locations in laboratory ice samples, links to videos

Many important chemical reactions occur in polar snow, where solutes may be present in several reservoirs, including at the air-ice interface and in liquid-like regions within the ice matrix. Some recent laboratory studies suggest chemical reaction rates may differ in these two reservoirs. While investigations have examined where solutes are found in natural snow and ice, similar research has not identified solute locations in laboratory samples, nor the possible factors controlling solute segregation. To address this, we examined solute locations in ice samples prepared from either aqueous cesium chloride (CsCl) or Rose Bengal solutions that were frozen using several different methods. Samples frozen in a laboratory freezer had the largest liquid-like inclusions and air bubbles, while samples frozen in a custom freeze chamber had somewhat smaller air bubbles and inclusions; in contrast, samples frozen in liquid nitrogen showed much smaller concentrated inclusions and air bubbles, only slightly larger than the resolution limit of our images (~2 µm). Freezing solutions in plastic versus glass vials had significant impacts on the sample structure, perhaps because the poor heat conductivity of plastic vials changes how heat is removed from the sample as it cools. Similarly, the choice of solute had a significant impact on sample structure, with Rose Bengal solutions yielding smaller inclusions and air bubbles compared to CsCl solutions frozen using the same method. Additional experiments using higher-resolution imaging of an ice sample show that CsCl moves in a thermal gradient, supporting the idea that the solutes in ice are present in liquid-like regions. Our work shows that the structure of laboratory ice samples, including the location of solutes, is sensitive to freezing method, sample container, and solute characteristics, requiring careful experimental design and interpretation of results.

Seawater carbonate chemistry and calcification of two mediterranean cold-water coral species in a laboratory experiment

Deep-water ecosystems are characterized by relatively low carbonate concentration values and, due to ocean acidification (OA), these habitats might be among the first to be exposed to undersaturated conditions in the forthcoming years. However, until now, very few studies have been conducted to test how cold-water coral (CWC) species react to such changes in the seawater chemistry. The present work aims to investigate the mid-term effect of decreased pH on calcification of the two branching CWC species most widely distributed in the Mediterranean, Lophelia pertusa and Madrepora oculata. No significant effects were observed in the skeletal growth rate, microdensity and porosity of both species after 6 months of exposure. However, while the calcification rate of M. oculata was similar for all colony fragments, a heterogeneous skeletal growth pattern was observed in L. pertusa, the younger nubbins showing higher growth rates than the older ones. A higher energy demand is expected in these young, fast-growing fragments and, therefore, a reduction in calcification might be noticed earlier during long-term exposure to acidified conditions.

Migration to an a on.line laboratory in mechanical engineering. The case of a cam follower design practice.

The European Higher Education Area (EHEA) has leaded to a change in the way the subjects are taught. One of the more important aspects of the EHEA is to support the autonomous study of the students. Taking into account this new approach, the virtual laboratory of the subject Mechanisms of the Aeronautical studies at the Technical University of Madrid is being migrated to an on-line scheme. This virtual laboratory consist on two practices: the design of cam-follower mechanisms and the design of trains of gears. Both practices are software applications that, in the current situation, need to be installed on each computer and the students carry out the practice at the computer classroom of the school under the supervision of a teacher. During this year the design of cam-follower mechanisms practice has been moved to a web application using Java and the Google Development Toolkit. In this practice the students has to design and study the running of a cam to perform a specific displacement diagram with a selected follower taking into account that the mechanism must be able to work properly at high speed regime. The practice has maintained its objectives in the new platform but to take advantage of the new methodology and try to avoid the inconveniences that the previous version had shown. Once the new practice has been ready, a pilot study has been carried out to compare both approaches: on-line and in-lab. This paper shows the adaptation of the cam and follower practice to an on-line methodology. Both practices are described and the changes that has been done to the initial one are shown. They are compared and the weak and strong points of each one are analyzed. Finally we explain the pilot study carried out, the students impression and the results obtained.

Student Reciprocal Peer Teaching as a Method for Active Learning: An Experience in an Electrotechnical Laboratory

Active learning is one of the most efficient mechanisms for learning, according to the psychology of learning. When students act as teachers for other students, the communication is more fluent and knowledge is transferred easier than in a traditional classroom. This teaching method is referred to in the literature as reciprocal peer teaching. In this study, the method is applied to laboratory sessions of a higher education institution course, and the students who act as teachers are referred to as ‘‘laboratory monitors.’’ A particular way to select the monitors and its impact in the final marks is proposed. A total of 181 students participated in the experiment, experiences with laboratory monitors are discussed, and methods for motivating and training laboratory monitors and regular students are proposed. The types of laboratory sessions that can be led by classmates are discussed. This work is related to the changes in teaching methods in the Spanish higher education system, prompted by the Bologna Process for the construction of the European Higher Education Area