Konzeption, Durchführung und Analyse eines Probandenexperiments zur Wirksamkeit der qualitativen Modellbildung mit dem Contact & Channel Ansatz = Design, Implementation and Analysis of a Human Subjects Experiment on the Efficacy of Qualitative Modelling with the Contact & Channel Approach

Diese Arbeit untersuchte die Wirksamkeit der qualitativen Modellbildung mit dem Contact & Channel Ansatz bezüglich der Verbesserung des Systemverständnisses von Probanden mit geringem Vorwissen. Zu diesem Zweck wurde ein Detailprozess zur Entwicklung von quantitativen Studien mit dem Fokus Wirksamkeit angewendet. Die daraus resultierende Forschungsmethode untersuchte die Wirkung qualitativer Modellbildung auf das Systemverständnis von Probanden in einer kontrollierten Testumgebung auf zwei Verständnisebenen: der System- und Detailebene. Die Messung auf der Systemebene erfolgte durch sechs Aufgaben, in denen jeweils das Verhalten von technischen Systemvarianten bestimmt werden musste. Das Verständnis auf der Detailebene wurde durch eine webbasierte Konstruktionsaufgabe abgefragt, in der eine bestimmte Funktionsbeschreibung erfüllt werden musste. Die Forschungsmethode wurde zur Untersuchung der qualitativen Modellbildung mit dem Contact & Channel Ansatz in die ILIAS-Plattform des Karlsruher Instituts für Technologie implementiert. Die Lehre der Modellbildungsmethode erfolgte dabei durch ein Trainingsvideo und eine geführte Modellbildung mit Rückmeldung. Die Studie wurde in Lehrveranstaltungen mit Studierenden im ersten und dritten Bachelorsemester durchgeführt. Dabei wurde auf keiner der Verständnisebenen eine signifikante Verbesserung des Systemverständnisses identifiziert. Auf der Detailebene wurde in dem Durchlauf mit den Drittsemestern eine signifikante Verschlechterung des Systemverständnisses identifiziert. Die Untersuchung der Eignung der Forschungsmethode sprach für die Plausibilität der Messungen, auch wenn weitere Forschung zu den Einflüssen innerhalb der Forschungsmethode und Operationalisierung von Systemverständnis notwendig ist. Die plausiblen Ergebnisse deuteten demnach darauf hin, dass die Verschlechterung auf die Modellbildung zurückzuführen war. Demzufolge muss der Grund für die Verschlechterung untersucht werden, wobei das individuelle Verhalten der Probanden bei der Anwendung und deren Umgang mit der Modellbildung betrachtet werden sollte

Lateral Organization and Thermodynamics of Coiled-coil Lipopeptides - Implications for Docking and Fusion Efficiency

Specific cellular membrane interaction is a crucial point in nature as it facilitates key processes like cell-cell communication or membrane fusion. The latter one is highly controlled frequently mediated by the superfamily of SNARE proteins (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) in eukaryotic cells. The definite mechanism behind this process is still poorly understood, but the coiled-coil formation of the SNARE core complex consisting of four α-helices seems to generate the fusogenic driving force. This offers the possibility to design a straightforward experimental setup to mimic the complex protein-mediated membrane-membrane interaction by using mere protein fragments or peptides attached to artificial lipid bilayers, which self-assemble into a coiled-coil structure. In this work, three different sets of artificial coiled-coil forming peptides were synthesized and subsequently attached to maleimide containing phospholipids in membranes via an in situ coupling reaction generating a highly controllable functionalization protocol. Thus, secondary structure changes, kinetics as well as thermodynamic characteristics were monitored during coiled-coil formation in solution and on solid supported membranes with e.g. time-resolved ellipsometry, IR and CD spectroscopy. A distinct loss of entropy upon heterodimerization of peptides on surfaces was found. This could be correlated with a self-assembled lateral clustering of lipopeptides in membranes leading to translational immobilization of hybrid structures. Strikingly, these dense and highly ordered clusters, which act as obstacles for surrounding matrix lipids, undergo a slow but detectable reorganization process causing a partial dissolution of the found clusters upon coiled-coil formation. Furthermore, an increasing fusogenicity was shown, which was correlated to the degree of cluster formation. Upon focusing on energetic and as well structural characteristics, the established model system gives the possibility to screen the docking and fusion ability of different coiled-coil forming peptides leading to an ideal mimic for SNARE mediated membrane fusion

Rethinking how we describe product models in engineering design research

Product models are an important part of a designer’s daily practice, and as such, they require the continuous attention of design researchers for further progress. However, there is no common vocabulary or structure to describe product models in engineering design. This weakens the discourse by preventing a common understanding and fostering ambiguity. To address this problem, this research note formulates three stances on product models that incorporate a vocabulary within a contextual structure as a contribution towards a shared understanding when describing product models and their underlying concepts. These stances are classification-oriented, functionality-oriented, and message-oriented. By discussing the implications of using these stances, it is illustrated how they facilitate comparability, avoid misunderstandings, and reveal links to the state of research

Investigation of copper corrosion inhibition with frequency-dependent alternating-current scanning electrochemical microscopy

Alternating current scanning electrochemical microscopy (AC-SECM) is used to investigate the inhibition of copper corrosion by four model organic molecules, namely benzotriazole (BTAH), 5-methyl-benzotriazole (MBTAH), 2-mercaptobenzimidazole (MBI), and ethyl xanthate (EX). It is shown that the formation of inhibitor films on the metal can be followed from the decrease of the substrate’s conductivity associated with the formation of inhibitor-containing surface layers. Very sensitive 3D imaging can also be performed that accounts for changes in chemical reactivity of the modified surfaces, as well as for their corrosive attack from the environment. AC-SECM is considered a powerful technique for the investigation of corrosion processe

Direct evidence of early blister formation in polymer-coated metals from exposure to chloride-containing electrolytes by alternating-current scanning electrochemical microscopy

This work contributes to establish the development of an early specific effect of chloride ions in defect-free coated metals leading to the heterogeneous swelling at the metal-polymer interface. Frequency-dependent alternating-current scanning electrochemical microscopy (AC-SECM) was successfully applied to visualize spatially-resolved differences in the topography of the coated sample, thus allowing direct evidence of chloride ion permeation through the polymer matrix simultaneous to water uptake to be obtained. The implications of this finding are particularly relevant towards the development of a new mechanistic model for blister initiation in coated metals

Investigation of early degradation processes at coated metals by AC-scanning electrochemical microscopy

Alternating-current scanning electrochemical microscopy (AC-SECM) is employed to characterize the early stages of the degradation reactions occurring in metal-coating systems upon exposure to an aqueous environment. The spatial resolution of the technique results from the measurement of changes in the resistance of the thin electrolyte layer comprised between the tip and the surface of the coating due to variations in the tip-substrate distance. Resistance measurements are conducted at various frequencies of the AC perturbation signal effectively allowing topographic changes to be monitored as a function of time. Furthermore, AC-SECM can be used to determine the tip-substrate distance without the addition of redox mediators to the electrolyte, which might affect the chemical properties of the system. In this way, the effect of chloride ions from the aqueous phase to induce either the heterogeneous absorption of water by the coating, or its accumulation at the metal-substrate interface, has been image

Риски в сфере оказания логистических услуг при транснациональных транспортировках

Риски в сфере оказания логистических услуг при транснациональных транспортировках необходимо идентифицировать и минимизировать на стадии подготовки товарной партии к транспортировке; освещены этапы организации транснациональных транспортировок и возникающие на каждом этапе риски, а также способы их минимизации; проанализирована судебная практика для определения наиболее распространённых видов риска при оказании логистических услуг.Risks in the field of providing logistic services for transnational transportation should be identified and minimized at the stage of preparation of the goods lot for transportation; the stages of organization of transnational transportation and the risks arising at each stage, as well as ways to minimize them, are covered; the court practice is analyzed to determine the most common types of risk in the provision of logistics services

Hydrophobic mismatch sorts SNARE proteins into distinct membrane domains

The clustering of proteins and lipids in distinct microdomains is emerging as an important principle for the spatial patterning of biological membranes. Such domain formation can be the result of hydrophobic and ionic interactions with membrane lipids as well as of specific protein–protein interactions. Here using plasma membrane-resident SNARE proteins as model, we show that hydrophobic mismatch between the length of transmembrane domains (TMDs) and the thickness of the lipid membrane suffices to induce clustering of proteins. Even when the TMDs differ in length by only a single residue, hydrophobic mismatch can segregate structurally closely homologous membrane proteins in distinct membrane domains. Domain formation is further fine-tuned by interactions with polyanionic phosphoinositides and homo and heterotypic protein interactions. Our findings demonstrate that hydrophobic mismatch contributes to the structural organization of membranes