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Magnetic Micromotors for Multiple Motile Sperm Cells Capture, Transport, and Enzymatic Release
Get PDFAn integrated system combining a magnetically-driven micromotor and a synthetized protein-based hyaluronic acid (HA) microflake is presented for the in situ selection and transport of multiple motile sperm cells (ca. 50). The system appeals for targeted sperm delivery in the reproductive system to assist fertilization or to deliver drugs. The binding mechanism between the HA microflake and sperm relies on the interactions between HA and the corresponding sperm HA receptors. Once sperm are captured within the HA microflake, the assembly is trapped and transported by a magnetically-driven helical microcarrier. The trapping of the sperm-microflake occurs by a local vortex induced by the microcarrier during rotation-translation under a rotating magnetic field. After transport, the microflake is enzymatically hydrolyzed by local proteases, allowing sperm to escape and finally reach the target location. This cargo-delivery system represents a new concept to transport not only multiple motile sperm but also other actively moving biological cargoes
Reliability Assessment and Modeling of High-k Dielectric Thin Films
No full textMethods for reliability assessment and a deep understanding of degradation mechanisms are important for product and process development. In this work, reliability under electrical stress of a state-of-the-art integrated low-temperature PVD PZT Film stack is discussed. DC and AC lifetime under electric stress are investigated experimentally over wide ranges of temperature and applied electric field. Empirical Weibull analysis and comparison of the obtained Weibull slope is used to evaluate suitable acceleration ranges for empirical testing. Changes of the Weibull slope above a temperature of 150 °C and gradual change over voltage acceleration in the range of 100 kV/cm to 200 kV/cm were found. This indicates
that accelerated lifetime testing in the temperature range below 150 °C is possible and caution is required for voltage acceleration. The results of this study are also published in Ref. (a).
Closing the literature gap, time to breakdown data under unipolar AC electric stress is presented. Comparison with results obtained under DC electric stress reveals that the DC degradation mechanism still dominates under unipolar AC load. This observation was found to hold over tested AC frequency, DC offset, and temperature ranges. As consequence, AC lifetime can be predicted based on DC time to breakdown experiments (b).
To enhance the physical understanding of degradation and breakdown, variation of the leakage current over time during electrical load is analyzed. An enhanced physical model for leakage current degradation is proposed and degradation kinetics are studied experimentally.
For the first time, more than one defect species being active and manifesting in
leakage current degradation of perovskite oxides are proposed and experimental evidence is presented to substantiate the hypotheses. Model predictions and experimental results are found to be in excellent agreement. The proposed characterization method allows for characterization of contributing defect types by associated charge and true activation energy (c).
Based on experimental observations, a direct connection between leakage current degradation mechanism and time dependent dielectric breakdown (TDDB) mechanism is proposed and formulated in a physical model. For the first time, kinetics of leakage current degradation and TDDB are successfully linked, using new evaluation methods for the experimental data obtained under DC and AC electrical stress. This pioneering connection between leakage current and breakdown ultimately leads to the fundament of a comprehensive HALT model. Fundamental implications of the new findings on reliability testing of high-k
dielectrics are discussed.Methoden zur Zuverlässigkeitsbewertung und ein tiefes Verständnis der Degradationsmechanismen sind wichtig für die Produkt- und Prozessentwicklung. In dieser Arbeit wird
die Zuverlässigkeit eines auf dem Stand der Technik befindlichen integrierten niedertemperatur PVD PZT Dünnschichtstapels unter elektrischer Last diskutiert. Lebenszeit unter
Gleichstrom- (DC) und Wechselstromlast (AC) werden experimentell über weite Bereiche der Temperatur und angelegter Feldstärke untersucht. Empirische Weibull Analyse und
Vergleich der erhaltenen Weibull-Module werden verwendet, um Beschleunigungsbereiche für empirische Testverfahren zu bewerten. Eine Veränderung der Weibull-Module
oberhalb von 150 °C und eine graduelle Veränderung für Spannungsbeschleunigung im Bereich von 100 kV/cm bis 200 kV/cm wurden festgestellt. Dies weist darauf hin, dass
beschleunigte Lebenszeittests im Temperaturbereich unterhalb von 150 °C möglich sind, Spannungsbeschleunigung jedoch mit hoher Vorsicht zu bewerten ist. Die Ergebnisse
dieser Untersuchung sind ebenfalls in Ref. (a) veröffentlicht.
Durch die Präsentation von Durchbruchzeiten unter unipolarer AC-Belastung wird eine Forschungslücke geschlossen. Ein Vergleich mit Ergebnissen, die unter Gleichstrombelastung erhoben wurden zeigt, dass Degradationsmechanismen, die unter DC aktiv sind unter unipolarer AC-Belastung das Durchbruchverhalten weiterhin dominieren. Diese
Beobachtung hat Bestand über die untersuchten Bereiche von AC-Frequenz, DC-Versatz und Temperatur. Daraus folgt, dass Lebenszeit unter AC-Belastung durch Experimente
unter DC vorhergesagt werden kann (b).
Um das physikalische Verständins von Degradation und Durchbruch zu erweitern, wird die Veränderung des Leckstroms über elektrischer Belastungszeit analysiert. Ein erweitertes
physikalisches Modell für die Leckstromdegradation wird vorgeschlagen und die Degradationskinetik wird experimentell untersucht. Zum ersten Mal, werden mehr als zwei aktive
Defektarten, die sich in der Leckstromdegradation von Perowskit Oxiden abzeichnen eingebracht und durch experimentelle Befunde untermauert. Modellvorhersagen und
experimentelle Ergebnisse zeigen eine exzellente Übereinstimmung. Die vorgeschlagene Charakterisierungsmethode erlaubt die Charakterisierung der beteiligten Defektarten über
zugeordneter Ladung und wahrer Aktivierungsenergie (c).
Basierend auf experimentellen Beobachtungen wird ein direkter Zusammenhang zwischen Leckstromdegradation und zeitabhängigem dielektrischen Durchbruchmechanismus
(TDDB) vorgeschlagen und in einem physikalischen Modell abgebildet. Zum ersten Mal werden die Kinetik hinter Leckstromdegradation und TDDB über neue Auswerteverfahren
der erhobenen experimentellen Daten unter DC- und AC-Belastung erfolgreich verknüpft. Dieser wegweisende Zusammenhang zwischen Leckstromdegradation und Durchbruch
legt das Fundament zu einer verständnisbasierten stark beschleunigten Grenzlastprüfung. Grundlegende Auswirkungen der neuen Ergebnisse auf Zuverlässigkeitstestmethoden von
high-k Dielektrika werden diskutiert
Prozessorientierter Gesamtaktenplan (GESA) für die Universität Hamburg
No full textDas Universitätsarchiv Hamburg entwarf aufgrund des Musteraktenplans für Hochschulen einen prozessorientierten Gesamtaktenplan, der die spätere Einführung eines Dokumentenmanagementsystems (DMS) an der gesamten Universität ermöglicht. Noch müssen die einzelnen Organisationseinheiten für die Identifikation der Geschäftsprozesse eingebunden und befragt werden, weil kein Geschäftsverteilungsplan und keine Prozesslandkarte existieren.On the basis of Germany’s sample filing plan for universities, the Hamburg University Archives designed a process-oriented filing plan which will later enable the introduction of a records management system throughout the whole university. Units and departments still have to be involved and surveyed in order to identify business processes because there is no previous business process map
Panel Regression Models for Causal Analysis in Structural Equation Modeling: Recent Developments and Applications
No full textEstablishing causal relationships is arguably the most important task of the social sciences. While the relationship between the social sciences and the concept of causality has been rocky, the randomized experiment gives us a concrete definition of a causal effect as the difference in outcomes due to the researcher's intervention. However, many interesting questions cannot be easily examined using experiments. Feasibility and ethics limit the use of randomized experiments in some situations and retrospective questions, i.e., working from the observed outcome to uncover the cause, require a different logic. Observational studies in which we observe pairs of variables without any intervention lend themselves to such situations but come with many difficulties. That is, it is not immediately clear whether an observed relationship between two variables is due to a true causal effect, or whether the relationship is due to other common causes.
Panel data describe repeated observations of the same units over time. They offer a powerful framework for approaching causal questions with observational data. Panel analysis allows us to essentially use each unit as their own control. In an experiment, random assignment to either treatment and control group makes both groups equal on all characteristics. Similarly, if we compare the same individual pre- and post-treatment, then the two are equal at least on the things that do not change over time, such as sex, date of birth, nationality, etc.
Structural equation modeling (SEM) is a group of statistical methods for assessing relationships between variables, often at the latent (unobserved) variable level. The use of SEM for panel analysis allows for a great deal of flexibility. Latent variables can be incorporated to account for measurement error and rule out alternative models.
This dissertation focuses on the use of panel data in SEM for causal analysis. It comprises an introduction, four main chapters and a conclusion.
After a short introduction (Chapter 1) outlining the goals and scope of the dissertation, Chapter 2 provides an overview of the topic of causality in the social sciences. Since the randomized experiment is often not feasible in social research, special emphasis has been placed on non-experimental, i.e., observational data. The chapter outlines some competing views on causality with non-experimental data, then discusses the two currently dominant frameworks for causal analysis, potential outcomes and directed graphs. It goes on to outline empirical methods and notes their compatibility with SEM.
Chapter 3 discusses how panel data can be used to deal with unobserved time-invariant heterogeneity, i.e., stable characteristics that might normally confound analyses. It attempts to show in detail how basic panel regression in SEM works. It also discusses some issues that are not normally addressed outside of SEM, e.g., measurement error in observed variables, effects that change over time, model comparisons, etc. This discussion of the more basic panel regression setup provides a sort of basis for the more complex discussion in the following chapters.
Chapter 4 compares and contrasts several ways to model dynamic processes, where the outcome at a particular point in time may affect future outcomes or even the presumed cause later on. It shows that popular recently proposed modeling techniques have much do to with their older counterparts. In fact, the newer modeling techniques do not seem to offer benefit with regards to estimating the causal effects of interest. The chapter focuses on arguably common situations in which the newer techniques may have serious drawbacks.
Chapter 5 provides an applied example. It looks to better assess the causal effect of environmental attitudes on environmental behaviour (mobility, consumption, willingness to sacrifice). It touches on many of the aspects from the previous chapters, including the use of latent variables for constructs that are not directly observable, unobserved time-invariant confounders, state dependence (feedback from outcome to outcome), and reverse causality (feedback from outcome to cause). It shows that failure to account for time-invariant confounders leads to biased estimates of the effect of attitudes on behaviour. After controlling for these factors, the effects disappear in terms of mobility and consumption behaviour: when a person's attitudes become more positive, their behaviour does not become more environmentally-friendly. There is, however, a fairly robust effect of attitudes on willingness to sacrifice, even after controlling for unobserved time-invariant confounders, state dependence and reverse causality. This suggests changing attitudes do affect willingness to make sacrifices, holding potential time-invariant confounders, outcome to outcome feedback (essentially habits), as well as some time-varying confounders constant.
Finally, Chapter 6 summarizes the previous chapters and provides an outlook for future work.:1. Introduction
2. Causal Inference in the Social Sciences
3. A Closer Look at Random and Fixed Effects Panel Regression in Structural Equation Modeling Using lavaan
4. Equivalent Approaches to Dealing with Unobserved Heterogeneity in Cross-Lagged Panel Models?
5. Re-Examining the Effect of Environmental Attitudes on Behaviour in a Panel Setting
6. Conclusio
Analyse von Einflussfaktoren auf die Gurtkräfte am Rucksack
Get PDFZur Evaluierung des mechanischen Tragekomforts von Rucksäcken wurden die Einflussfaktoren Geschlecht, Last und Bewegung auf die Gurtkräfte am Rucksack untersucht. Dazu wurde ein individuelles Messsystem entwickelt. Aus der Datenanalyse lässt sich folgern, dass die Gurtkraft nicht vom Geschlecht des Rucksackträgers abhängt. Die Rucksacklast und die Form der Aktivität hingegen sind relevante Indikatoren.To evaluate the mechanical wearing comfort of backpacks, the factors influencing the strap forces on the backpack were investigated, namely gender, load and movement. An individual measurement system was developed for this purpose. From the data analysis, it can be concluded that the strap force does not depend on the gender of the backpack wearer. The backpack load and the form of the activity, on the other hand, are relevant indicators
Synthese von Indacenodithiophen-basierten Copolymeren mittels direkter C-H-Arylierungspolykondensation
Get PDFOrganic semiconducting polymers are widely employed in organic electronics such as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs). Their remarkable mechanical and charge transport properties as well as solution processability allow low-cost fabrication of light-weight and flexible devices. Among them indacenodithiophene (IDT)-based materials are promising candidates for application in organic electronics. Due to their low energetic disorder, extended conjugation and high electron density the IDT-based polymers show high field-effect mobilities and high absorption coefficients. However, their synthesis suffers from long reaction sequences and is often accomplished using toxic materials. Commercialization requires development of more efficient and sustainable reaction pathways to ease tailoring of structures and to limit molecular defects.
Herein, the development of new synthetic pathways towards IDT-based polymers is presented in which all C-C coupling steps are achieved by C-H activation – an atom-economic alternative to conventional transition-metal catalyzed cross couplings. Two different strategies were established to synthesize a series of well-defined IDT-based homo- and copolymers with different side chain patterns and varied molecular weights. The first way starts by synthesis of a precursor polymer and subsequent cyclization affording IDT homopolymers. In the second approach, cyclized IDT monomers were prepared first and then polymerized using direct arylation polycondensation (DAP) yielding IDT homo- and copolymers. The synthetic pathways were optimized in terms of maximizing molecular weights and limiting defect structures. While the first pathway enables synthesis of well-defined homopolymers, the latter is the method of choice for preparation of IDT-based copolymers in high yields and adjustable molecular weights. The polymers were further characterized in detail by optical, thermal, electrical and morphological analyses. OFETs as well as all-polymer solar cells (all-PSCs) were fabricated to investigate the influence of structural modifications and molecular weight on their optoelectronic performance. Thus, this thesis provides a comprehensive study of the structure-property correlations of IDT-based polymers and simplified synthetic protocols for the design and preparation of donor-acceptor copolymers in the future
Streamlining-Berechnung des erweiterten Zeitkonstantendichtespektrums aus Zeitdaten für die Diagnose von Lithium-Ionen-Batterien
Get PDFDie stark zunehmende Verbreitung leistungsfähiger Akkumulatoren im Rahmen der Energiewende erfordert elektrische Diagnoseverfahren für Batterien wie die Impedanzspektroskopie. Sie ermöglicht durch die Messung des elektrischen Verhaltens einen Einblick ins Innere einer Batterie. Die Auswertung der gemessenen Impedanzspektren mit Modellen stellt aufgrund der Komplexität der ablaufenden elektrochemischen Vorgänge, einer damit verbundenen hohen Modellkomplexität und dem resultierenden Regressionsaufwand eine große Hürde dar. Einen Ausweg bieten Zeitkonstantendichtespektren (DRT), die sich aus Impedanzdaten berechnen lassen. Sie ermöglichen eine schnelle Identifikation der Anzahl der wirkenden Mechanismen zusammen mit deren Stärken und Zeitkonstanten und vereinfachen durch die erleichterte Trennbarkeit der Mechanismen die weitere Auswertung. Bei der Berechnung aus Impedanzdaten ist die Lösung eines unterbestimmten Gleichungssystems unter Nebenbedingungen notwendig. Insbesondere die Zahl der für die Berechnung zur Verfügung stehenden Impedanzmesspunkte schränken die Lösungsqualität stark ein und machen stabilisierende Regularisierungsverfahren erforderlich. Ein weiteres Problem stellen induktive Effekte dar, die mit der klassischen DRT nicht analysiert werden können.
Um eine einfache Berechnung zu ermöglichen wurde im Rahmen der Arbeit ein Berechnungsverfahren entwickelt, dass digitale Filter mit einem iterativen Lösungsupdate kombiniert, um die DRT direkt aus Zeitdaten zu berechnen. Das Verfahren zeichnet sich durch seine numerische Einfachheit bei gleichzeitig stabiler Berechnung der DRT aus. Durch die große Datenbasis wird keine aufwendige Regularisierung bei der DRT Berechnung benötigt, die Auflösung verbessert sich und das Verfahren ist durch seine minimalen Anforderung für die Implementierung in Embedded Systemen geeignet. Um auch Spektren mit induktiven Anteilen auswerten zu können, wurde die DRT und die zugehörige Berechnung erweitert. Im Ergebnis erhält man zusätzlich zum bekannten kapazitiven ein induktives Zeitkonstantendichtespektrum, mit dem sich induktives Verhalten analog der klassischen DRT beschreiben lässt.The rapidly increasing spread of powerful accumulators requires electrical diagnostic methods for batteries such as impedance spectroscopy. By measuring the electrical behavior, it provides an insight into the interior of a battery. The evaluation of the measured impedance spectra with models is a complicated task, due to the complexity of the electrochemical processes taking place, an associated high model complexity and the resulting regression effort. Distribution of Relaxation Times spectra (DRT), which can be calculated from impedance data, offer a way out. They allow a quick identification of the number of acting mechanisms together with their strengths and time constants and simplify further analysis by facilitating the separability of the mechanisms. The calculation from impedance data requires the solution of an underdetermined system of equations under constraints. In particular, the number of impedance measurement points available for the calculation severely limits the solution quality and necessitates regularization procedures during calculation. Another problem is posed by inductive effects, which cannot be analyzed with classical DRT.
In order to enable a simple computation, a computational method was developed in this thesis that combines digital filters with an iterative solution update to compute the DRT directly from time domain measurement data. The method is characterized by its numerical simplicity while providing a stable computation of the DRT. Due to the large number of measurement points, no regularization is needed in the DRT calculation, the resolution improves and the method is suitable for implementation in embedded systems due to its minimal requirement. In order to be able to evaluate spectra with inductive components, the DRT and the associated calculation were extended. As a result, an inductive DRT spectrum is obtained in addition to the known capacitive one, with which inductive behavior can be described analogously to the classical DRT
Records Management im Universitätsarchiv Hamburg
Get PDFDie Schriftgutverwaltung ist an der Universität Hamburg dem Universitätsarchiv angegliedert, das auch für die elektronische Aktenführung in der Präsidialverwaltung zuständig ist. Die Erstellung eines prozessorientierten Aktenplans und die Einführung eines Dokumentenmanagementsystems (DMS) in die gesamte Universität wären vorteilhaft in Sachen Zusammenarbeit, Nachvollziehbarkeit, Transparenz und Langzeitarchivierung, und würden ein ganz- und einheitliches Records Management ermöglichen.At the University of Hamburg, records management is attached to the University Archives, which is also responsible for the electronic record management in the presidential administration. The creation of a process-oriented filing plan and the introduction of a document management system (DMS) in the entire university would be advantageous in terms of teamwork, traceability, transparency and digital preservation. Also, it would enable a new, more comprehensive and uniform records management
Das elektronische Kommunalarchiv Sachsen (elKA)
Get PDFDie Kommunalarchive Sachsens verwalten nach dem Sächsischem Archivgesetz ihre Archive in eigener Zuständigkeit. Seit 2010 diskutieren sie auch über die elektronische Archivierung. Es wurde im Rahmen dieser Diskussion beschlossen, ein gemeinsames elektronisches Archiv
einzurichten. Nach einer umfassenden Marktanalyse wurde als Grundlage DIMAG ausgewählt. Die Daten werden in einem zentralen Rechenzentrum gespeichert und von den Archiven selbst verwaltet. Ab 01. Januar 2022 soll das elKA in den Wirkbetrieb gehen.The municipal archives in Saxony manage their archives under their own responsibility in accordance with the Saxon Archives Act. Since 2010, they have also been discussing electronic archiving. It was decided as part of this discussion to set up a joint electronic archive.
After a comprehensive market analysis, DIMAG was selected as the basis. The data will be stored in a central computer centre and managed by the archives themselves. The elKA is scheduled to go into operation on 1 January 2022
The 1st Advanced Manufacturing Student Conference (AMSC21) Chemnitz, Germany 15–16 July 2021
Get PDFThe Advanced Manufacturing Student Conference (AMSC) represents an educational format designed to foster the acquisition and application of skills related to Research Methods in Engineering Sciences. Participating students are required to write and submit a conference paper and are given the opportunity to present their findings at the conference. The AMSC provides a tremendous opportunity for participants to practice critical skills associated with scientific publication. Conference Proceedings of the conference will benefit readers by providing updates on critical topics and recent progress in the advanced manufacturing engineering and technologies and, at the same time, will aid the transfer of valuable knowledge to the next generation of academics and practitioners.
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The first AMSC Conference Proceeding (AMSC21) addressed the following topics: Advances in “classical” Manufacturing Technologies, Technology and Application of Additive Manufacturing, Digitalization of Industrial Production (Industry 4.0), Advances in the field of Cyber-Physical Systems, Virtual and Augmented Reality Technologies throughout the entire product Life Cycle, Human-machine-environment interaction and Management and life cycle assessment.:- Advances in “classical” Manufacturing Technologies
- Technology and Application of Additive Manufacturing
- Digitalization of Industrial Production (Industry 4.0)
- Advances in the field of Cyber-Physical Systems
- Virtual and Augmented Reality Technologies throughout the entire product Life Cycle
- Human-machine-environment interaction
- Management and life cycle assessmen