Large scale Micro-Photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

Micro-fluidic pumps as well as artificial micro-swimmers are conveniently realized exploiting phoretic solvent flows based on local gradients of temperature, electrolyte concentration or pH. We here present a facile micro-photometric method for monitoring pH gradients and demonstrate its performance and scope on different experimental situations including an electro-osmotic pump and modular micro-swimmers assembled from ion exchange resin beads and polystyrene colloids. In combination with the present microscope and DSLR camera our method offers a 2 \mu m spatial resolution at video frame rate over a field of view of 3920x2602 \mu m^2. Under optimal conditions we achieve a pH-resolution of 0.05 with about equal contributions from statistical and systematical uncertainties. Our quantitative micro-photometric characterization of pH gradients which develop in time and reach out several mm is anticipated to provide valuable input for reliable modeling and simulations of a large variety of complex flow situations involving pH-gradients including artificial micro-swimmers, microfluidic pumping or even electro-convection.Comment: 5 figures, 15 page

Confined colloidal crystals in and out of equilibrium

Recent studies on confined crystals of charged colloidal particles are reviewed, both in equilibrium and out of equilibrium. We focus in particular on direct comparisons of experiments (light scattering and microscopy) with lattice sum calculations and computer simulations. In equilibrium we address buckling and crystalline multilayering of charged systems in hard and soft slit confinement. We discuss also recent crystalline structures obtained for charged mixtures. Moreover, we put forward possibilities to apply external perturbations, in order to drive the system out of equilibrium. These include electrolyte gradients as well as the application of shear and electric fields.Comment: Review article, 18 pages, 5 figure

Optische Mikroskopie an elektrostatisch stabilisierten kolloidalen Suspensionen unter dem Einfluss geladener Wände - ausgewählte Gleichgewichts- und Nichtgleichgewichtsphänomene

Das Verhalten kolloidaler Suspensionen unter räumlich beschränkter Geometrie ist von großer Bedeutung für die statistische Physik wie auch für die Technologie. Von speziellem Interesse sind Modellsysteme geladener kolloidaler Sphären aufgrund ihrer langreichweitigen und veränderbaren Wechselwirkungen. In dieser Arbeit wurde ein experimenteller Aufbau für die optische mikroskopische Untersuchung solcher, zwischen ebenen Wänden beschränkter Systeme realisiert. Anhand von Piezo-Aktuatoren kann die Zellgeometrie flexibel und präzise eingestellt werden. Unter Verwendung eines Pumpkreislaufs mit einer Ionentauschersäule können kolloidale Suspensionen unter stark entsalzten Bedingungen effizient präpariert werden. Anhand dieses Aufbaus wurde zunächst das Gleichgewichtsphasendiagramm monodisperser geladener kolloidaler Sphären zwischen parallelen Wänden untersucht. Es wurden quantitative Resultate für den Grenzfall starker Entsalzung erzielt, welche mit theoretischen Grundzustandsvorhersagen übereinstimmen. In Doppellagensystemen konnte die Existenz transienter kolloidaler Moiré-Rotationsmuster demonstriert werden, welche besondere zweidimensionale Kristallstrukturen mit komplexer Basis darstellen. Es wurden ferner Nichtgleichgewichtsphänomene untersucht, welche durch Gradienten von lokal freigesetzten Elektrolyten verursacht werden. Durch hauptsächlich diffusioosmotischen Partikeltransport entlang einer einzelnen geladenen Substratoberfläche konnten die Bildung kristalliner Ordnung sowie komplexe, selbstorganisierte Bewegungszustände in einem verdünnten kolloidalen Monolagenfluid bei kleinen Reynolds-Zahlen induziert werden. Interessante Perspektiven für die zukünftige Verwendung des experimentellen Aufbaus ergeben sich aus Beobachtungen verschiedener weiterer Phänomene.The behavior of colloidal suspensions under confinement is of great importance for statistical mechanics and application. Of particular interest are model systems of charged colloidal spheres for their long-ranged and tunable particle interactions. In this work, a new experimental setup for optical microscopic studies of colloids confined between two planar substrates is presented. Comprising piezo actuators, cell geometry can fast, flexibly and precisely be adjusted. Employing a pump circuit including an ion exchanger column, colloidal suspensions can efficiently be prepared under strongly deionized conditions. Using this setup, the equilibrium phase behavior of charged monodisperse colloidal spheres in a narrow parallel slit was addressed. Quantitative results for low background salt concentrations could be obtained in agreement with theoretical ground state predictions. For double layer systems, existence of transient colloidal Moiré rotation patterns representing two-dimensional crystal structures with complex bases could be demonstrated. Further, non-equilibrium phenomena involving gradients of locally released electrolyte were investigated. Mainly based on diffusioosmotic particle transport along a single charged substrate, novel crystalline order formation and self-organized complex propulsion could be induced within a thermodynamically stable colloidal fluid at low Reynolds numbers. Interesting perspectives for future investigations employing the new experimental setup arise from further different observed phenomena.200 S

"Die anderen aber glaubten nicht"

Der Gegenstand dieser Arbeit ist Verstockung im Neuen Testament – ein Motiv, das die deutsche Sprache einerseits mittels eines Terminus (z.B. „Verstockung“, „verstocken“, „verstockt“) ausdrückt, andererseits als Phänomen (z.B.: „sehen – aber nicht erkennen; hören – aber nicht verstehen“) beschreibt. Der Terminus „Verstockung“ ist allerdings ein erst seit dem Mittelhochdeutschen existierender Kunstbegriff, den die Koine, die Sprache des Neuen Testaments, nicht kennt. Sie gebraucht hierfür Begriffe wie „sklerünein - härten“ oder „pachünein (pass.) – fett/stumpf werden“, die erst im biblischen Kontext ihre theologische Bedeutung erhalten und damit zum Terminus Technicus „verstocken“ werden. Bei Verstockung geht es, unabhängig davon, ob das Motiv terminologisch oder phänomenologisch gebraucht wird, um die Ablehnung des Evangeliums, also um Unglauben. Im Neuen Testament ist eine Affinität von Unglauben und Verstockung in acht Perikopen auszumachen. Die Dissertation untersucht, erklärt und definiert das Motiv der Verstockung, indem sie in einer historisch-kritischen Exegese diesen Konnex herausarbeitet und die Bedeutung von Verstockung ausgehend von dem fest umrissenen Begriff des Unglaubens relational ergründet. Da es sich, wie die Einzeluntersuchungen zeigen, bei Verstockung um ein Verschließungsgeschehen handelt, lässt sich dieses Geschehen in die folgenden fünf Strukturelemente rekonstruieren: (1.) Urheber der Verstockung, (2.) Anlass der Verstockung, (3.) Inhalt der Verstockung, (4.) Empfänger der Verstockung, (5.) Wirkung der Verstockung. Anhand dieser Strukturelemente bildet sich die Verstockungsdefinition, mittels der das Verstockungsmotiv im gesamten Neuen Testament ausfindig gemacht und kurz untersucht wird. Diese Zusammenstellung aller neutestamentlichen Verstockungsbelege zeigt zudem die Entwicklung des Verstockungsmotivs auf und macht deutlich, dass Verstockung für die junge Kirche ein adaptionsfähiges und bekanntes Motiv war, um auf die Herausforderungen, mit denen sie sich konfrontiert sah, reagieren zu können. Die Dissertation schließt nach dieser soziologischen Einordnung und dem entwicklungsgeschichtlichen Überblick über dieses Motiv mit dem Hinweis auf dessen mögliche theologische Wirkungsfelder in der Gegenwart.The concept of impenitence, impiety or the “hardening of hearts” as used in the New Testament, is the subject of this dissertation. In the German language, the concept of impiety is expressed through the use of both terminology (hard, dull, impious) and phenomenology (seeing but not perceiving; hearing but not understanding). The German term “Verstockung“ or “impenitence, impiety” first appeared in the German language during the middle ages, around the 10th to the 11th centuries and is, as well, an unknown term in the original language of the New Testament. There, use was made of the common words “fattening, dulling or hardening” to explain the idea of impenitence or impiety; simple words which first gain theological significance and then become in and of themselves theological terms (the hardening of hearts) through their use in biblical imagery. Whether the term “Verstockung” – impiety – is used as a term or as a phenomenon, it is used in reference to the rejection of the gospel and, with that, a lack of faith in God. Eight pericopes within the New Testament bring the idea of a lack of faith together with the concept “Verstockung” – a hardening of heart or soul. Using the historical / critical method, this dissertation will examine, explain and define the concept of “Verstockung” – a hardening – and its relationship to the lack of faith. As each of the eight examples will show, impiety is the process of closing down or sealing off. This occurrence can be broken down into five structural elements: 1.) the originator or cause of the hardening, 2.) the occasion for the hardening, 3.) the context of the hardening, 4.) the recipient of the hardening, 5.) the effect of the hardening. By locating and defining the concept of impiety throughout the New Testament and by applying the five structural elements to these cases, a definition of impiety will take shape. The compiling of these New Testament examples will show the development of impiety und will make it clear that impiety, or a hardening, was a usable and known concept in the early church; a concept useful in response to the challenges with which emerging Christendom was confronted. After examining the developmental and sociological history of this concept, the dissertation will conclude with the suggestion of possible theological consequences for our contemporary context

Variability of aerosol, gaseous pollutants and meteorological characteristics associated with changes in air mass origin at the SW Atlantic coast of Iberia

Measurements of the ambient aerosol were performed at the Southern coast of Spain, within the framework of the DOMINO (<b>D</b>iel <b>O</b>xidant <b>M</b>echanisms <b>I</b>n relation to <b>N</b>itrogen <b>O</b>xides) project. The field campaign took place from 20 November until 9 December 2008 at the atmospheric research station "El Arenosillo" (37°5'47.76" N, 6°44'6.94" W). As the monitoring station is located at the interface between a natural park, industrial cities (Huelva, Seville) and the Atlantic Ocean, a variety of physical and chemical parameters of aerosols and gas phase could be characterized in dependency on the origin of air masses. Backwards trajectories were examined and compared with local meteorology to classify characteristic air mass types for several source regions. Aerosol number and mass as well as polycyclic aromatic hydrocarbons and black carbon concentrations were measured in PM<sub>1</sub> and size distributions were registered covering a size range from 7 nm up to 32 μm. The chemical composition of the non-refractory submicron aerosol (NR-PM<sub>1</sub>) was measured by means of an Aerosol Mass Spectrometer (Aerodyne HR-ToF-AMS). Gas phase analyzers monitored various trace gases (O<sub>3</sub>, SO<sub>2</sub>, NO, NO<sub>2</sub>, CO<sub>2</sub>) and a weather station provided meteorological parameters. <br><br> Lowest average submicron particle mass and number concentrations were found in air masses arriving from the Atlantic Ocean with values around 2 μg m<sup>−3</sup> and 1000 cm<sup>−3</sup>. These mass concentrations were about two to four times lower than the values recorded in air masses of continental and urban origins. For some species PM<sub>1</sub>-fractions in marine air were significantly larger than in air masses originating from Huelva, a closely located city with extensive industrial activities. The largest fraction of sulfate (54%) was detected in marine air masses and was to a high degree not neutralized. In addition, small concentrations of methanesulfonic acid (MSA), a product of biogenic dimethyl sulfate (DMS) emissions, could be identified in the particle phase. <br><br> In all air masses passing the continent the organic aerosol fraction dominated the total NR-PM<sub>1</sub>. For this reason, using Positive Matrix Factorization (PMF) four organic aerosol (OA) classes that can be associated with various aerosol sources and components were identified: a highly-oxygenated OA is the major component (43% OA) while semi-volatile OA accounts for 23%. A hydrocarbon-like OA mainly resulting from industries, traffic and shipping emissions as well as particles from wood burning emissions also contribute to total OA and depend on the air mass origin. <br><br> A significant variability of ozone was observed that depends on the impact of different air mass types and solar radiation

Bacterial foodborne pathogens of concern

Microbial Contaminants and Contamination Routes in Food Industry - 1st Open Seminar arranged by SAFOODNET; Espoo; Finland; 22 January 2007 through 23 January 2007A high level of protection of public health is one of the fundamental objectives of food law as laid down in regulations (EC) No 178/2002 and 852/2004. Throughout the European Union (EU) consumers are requiring the food industry to provide them with an increasing range of safe, nutritious and healthy foods of high sensory quality and increased shelf life. To meet the demand for healthier food of high sensory quality, the use of additives and preservatives is being reduced or eliminated and minimal processing techniques introduced. To increase food safety and quality considerable amount of time, effort and money has been spent to food safety control and management (ISO 22000:2005) systems including better packaging methods and improved new pathogen detection methods

Application of mobile aerosol and trace gas measurements for the investigation of megacity air pollution emissions: the Paris metropolitan area

For the investigation of megacity emission development and the impact outside the source region, mobile aerosol and trace gas measurements were carried out in the Paris metropolitan area between 1 July and 31 July 2009 (summer conditions) and 15 January and 15 February 2010 (winter conditions) in the framework of the European Union FP7 MEGAPOLI project. Two mobile laboratories, MoLa and MOSQUITA, were deployed, and here an overview of these measurements and an investigation of the applicability of such measurements for the analysis of megacity emissions are presented. Both laboratories measured physical and chemical properties of fine and ultrafine aerosol particles as well as gas phase constituents of relevance for urban pollution scenarios. The applied measurement strategies include cross-section measurements for the investigation of plume structure and quasi-Lagrangian measurements axially along the flow of the city's pollution plume to study plume aging processes. Results of intercomparison measurements between the two mobile laboratories represent the adopted data quality assurance procedures. Most of the compared measurement devices show sufficient agreement for combined data analysis. For the removal of data contaminated by local pollution emissions a video tape analysis method was applied. Analysis tools like positive matrix factorization and peak integration by key analysis applied to high-resolution time-of-flight aerosol mass spectrometer data are used for in-depth data analysis of the organic particulate matter. Several examples, including a combination of MoLa and MOSQUITA measurements on a cross section through the Paris emission plume, are provided to demonstrate how such mobile measurements can be used to investigate the emissions of a megacity. A critical discussion of advantages and limitations of mobile measurements for the investigation of megacity emissions completes this work

Ion size effects on the electrokinetics of salt-free concentrated suspensions in ac fields

We analyze the influence of finite ion size effects in the response of a salt-free concentrated suspension of spherical particles to an oscillating electric field. Salt-free suspensions are just composed of charged colloidal particles and the added counterions released by the particles to the solution, that counterbalance their surface charge. In the frequency domain, we study the dynamic electrophoretic mobility of the particles and the dielectric response of the suspension. We find that the Maxwell-Wagner-O'Konski process associated with the counterions condensation layer, is enhanced for moderate to high particle charges, yielding an increment of the mobility for such frequencies. We also find that the increment of the mobility grows with ion size and particle charge. All these facts show the importance of including ion size effects in any extension attempting to improve standard electrokinetic models.Comment: J. Colloid Interface Sci., in press, 13 pages, 9 figure