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Single-Molecule Spectroscopy And Imaging Studies Of Protein Folding-Unfolding Conformational Dynamics: The Multiple-State And Multiple-Channel Energy LandscapeWang, Zijian 20 April 2016 (has links)
No description available.
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Phase dynamics of irregular oscillationsSchwabedal, Justus Tilmann Caspar January 2010 (has links)
In der vorliegenden Dissertation wird eine Beschreibung der Phasendynamik
irregulärer Oszillationen und deren Wechselwirkungen vorgestellt. Hierbei
werden chaotische und stochastische Oszillationen autonomer dissipativer Systeme
betrachtet. Für eine Phasenbeschreibung stochastischer Oszillationen müssen zum
einen unterschiedliche Werte der Phase zueinander in Beziehung gesetzt werden,
um ihre Dynamik unabhängig von der gewählten Parametrisierung der Oszillation
beschreiben zu können. Zum anderen müssen für stochastische und chaotische
Oszillationen diejenigen Systemzustände identifiziert werden, die sich in der
gleichen Phase befinden.
Im Rahmen dieser Dissertation werden die Werte der Phase über eine gemittelte
Phasengeschwindigkeitsfunktion miteinander in Beziehung gesetzt. Für
stochastische Oszillationen sind jedoch verschiedene Definitionen der mittleren
Geschwindigkeit möglich. Um die Unterschiede der Geschwindigkeitsdefinitionen
besser zu verstehen, werden auf ihrer Basis effektive deterministische Modelle
der Oszillationen konstruiert. Hierbei zeigt sich, dass die Modelle
unterschiedliche Oszillationseigenschaften, wie z. B. die mittlere Frequenz
oder die invariante Wahrscheinlichkeitsverteilung, nachahmen. Je nach Anwendung
stellt die effektive Phasengeschwindigkeitsfunktion eines speziellen Modells
eine zweckmäßige Phasenbeziehung her. Wie anhand einfacher Beispiele erklärt
wird, kann so die Theorie der effektiven Phasendynamik auch kontinuierlich und
pulsartig wechselwirkende stochastische Oszillationen beschreiben.
Weiterhin wird ein Kriterium für die invariante Identifikation von Zuständen
gleicher Phase irregulärer Oszillationen zu sogenannten generalisierten
Isophasen beschrieben: Die Zustände einer solchen Isophase sollen in ihrer
dynamischen Entwicklung ununterscheidbar werden. Für stochastische
Oszillationen wird dieses Kriterium in einem mittleren Sinne interpretiert. Wie
anhand von Beispielen demonstriert wird, lassen sich so verschiedene Typen
stochastischer Oszillationen in einheitlicher Weise auf eine stochastische
Phasendynamik reduzieren. Mit Hilfe eines numerischen Algorithmus zur Schätzung
der Isophasen aus Daten wird die Anwendbarkeit der Theorie anhand eines Signals
regelmäßiger Atmung gezeigt. Weiterhin zeigt sich, dass das Kriterium der
Phasenidentifikation für chaotische Oszillationen nur approximativ erfüllt
werden kann. Anhand des Rössleroszillators wird der tiefgreifende Zusammenhang
zwischen approximativen Isophasen, chaotischer Phasendiffusion und instabilen
periodischen Orbits dargelegt.
Gemeinsam ermöglichen die Theorien der effektiven Phasendynamik und der
generalisierten Isophasen eine umfassende und einheitliche Phasenbeschreibung
irregulärer Oszillationen. / Many natural systems embedded in a complex surrounding show irregular
oscillatory dynamics. The oscillations can be parameterized by a phase variable
in order to obtain a simplified theoretical description of the dynamics.
Importantly, a phase description can be easily extended to describe the
interactions of the system with its surrounding. It is desirable to define an
invariant phase that is independent of the observable or the arbitrary
parameterization, in order to make, for example, the phase characteristics
obtained from different experiments comparable.
In this thesis, we present an invariant phase description of irregular
oscillations and their interactions with the surrounding. The description is
applicable to stochastic and chaotic irregular oscillations of autonomous
dissipative systems. For this it is necessary to interrelate different phase
values in order to allow for a parameterization-independent phase definition.
On the other hand, a criterion is needed, that invariantly identifies the
system states that are in the same phase.
To allow for a parameterization-independent definition of phase, we interrelate
different phase values by the phase velocity. However, the treatment of
stochastic oscillations is complicated by the fact that different definitions
of average velocity are possible. For a better understanding of their
differences, we analyse effective deterministic phase models of the
oscillations based upon the different velocity definitions. Dependent on the
application, a certain effective velocity is suitable for a
parameterization-independent phase description. In this way, continuous as well
pulse-like interactions of stochastic oscillations can be described, as it is
demonstrated with simple examples.
On the other hand, an invariant criterion of identification is proposed that
generalizes the concept of standard (Winfree) isophases. System states of the
same phase are identified to belong to the same generalized isophase using the
following invariant criterion: All states of an isophase shall become
indistinguishable in the course of time. The criterion is interpreted in an
average sense for stochastic oscillations. It allows for a unified treatment of
different types of stochastic oscillations. Using a numerical estimation
algorithm of isophases, the applicability of the theory is demonstrated by a
signal of regular human respiration. For chaotic oscillations, generalized
isophases can only be obtained up to a certain approximation. The intimate
relationship between these approximate isophase, chaotic phase diffusion, and
unstable periodic orbits is explained with the example of the chaotic roes oscillator.
Together, the concept of generalized isophases and the effective phase theory
allow for a unified, and invariant phase description of stochastic and chaotic
irregular oscillations.
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Physiological effects of conditioned medium and passage number on Spodoptera frugiperda Sf9 serum free culturesSvensson, Ingrid January 2005 (has links)
<p>The aim of this study was to better understand the role of conditioned medium (CM) in Spodoptera frugiperda Sf9 insect cell proliferation and recombinant protein production using the baculovirus expression system.</p><p>CM was found to stimulate cell proliferation. Addition of CM and 10 kDa CM filtrate to an Sf9 culture decreased the lagphase and the maximum cell density was reached earlier than for cultures in fresh medium. The positive effect of 10 kDa CM filtrate showed that CM contains at least one small growth promoting factor. The effect was not eliminated by trypsin treatment. Addition of CM or 10 kDa CM filtrate to Sf9 cultures was found to have a negative effect on the recombinant protein production. The effect was thought to be indirect and most probably via the impact of CM on cell physiology. CM was also found to contain proteinase activity. The proteinase was identified as Sf9 cathepsin L. A proform with a molecular mass about 49 kDa and two active forms at about 39 and 22 kDa were found. The role of cathepsin L in Sf9 cultures is not yet clear. However, the knowledge of the presence of this proteinase in CM can be of great value for improving product quality and yield. Further, CM was found to have other properties as well: a concentrated fraction of CM exhibited strong antibacterial activity towards Bacillus megaterium and a weaker activity towards Escherichia coli. B. megaterium lysed rapidly after incubation in the CM fraction.</p><p>Repeated subculturing of Sf9 cells provoked a switch in growth kinetics. After 30-45 passages the cells started to proliferate earlier after inoculation and addition of CM had no longer a growth stimulating effect. However, CM still stimulated growth of a culture with low passage (LP) number (up to 45 passages). High passage cells (HP cells, over 100 passages) displayed a shorter lagphase than LP cells and the culture reached the maximum cell density 24-48 h earlier. Cell cycle analysis showed that the Sf9 cells were transiently synchronised in the G2/M phase 10 h after inoculation, before proliferation was initiated. This synchronisation was more pronounced for HP cells than for LP cells, which correlated to a higher recombinant protein production in baculovirus infected HP cells than in LP cells. Synchronisation of cells in G2/M by yeastolate-limitation before infection with baculoviruses suggested that the degree of synchronisation is connected to the cell density dependent decrease in recombinant protein production of Sf9 cultures.</p>
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Physiological effects of conditioned medium and passage number on Spodoptera frugiperda Sf9 serum free culturesSvensson, Ingrid January 2005 (has links)
The aim of this study was to better understand the role of conditioned medium (CM) in Spodoptera frugiperda Sf9 insect cell proliferation and recombinant protein production using the baculovirus expression system. CM was found to stimulate cell proliferation. Addition of CM and 10 kDa CM filtrate to an Sf9 culture decreased the lagphase and the maximum cell density was reached earlier than for cultures in fresh medium. The positive effect of 10 kDa CM filtrate showed that CM contains at least one small growth promoting factor. The effect was not eliminated by trypsin treatment. Addition of CM or 10 kDa CM filtrate to Sf9 cultures was found to have a negative effect on the recombinant protein production. The effect was thought to be indirect and most probably via the impact of CM on cell physiology. CM was also found to contain proteinase activity. The proteinase was identified as Sf9 cathepsin L. A proform with a molecular mass about 49 kDa and two active forms at about 39 and 22 kDa were found. The role of cathepsin L in Sf9 cultures is not yet clear. However, the knowledge of the presence of this proteinase in CM can be of great value for improving product quality and yield. Further, CM was found to have other properties as well: a concentrated fraction of CM exhibited strong antibacterial activity towards Bacillus megaterium and a weaker activity towards Escherichia coli. B. megaterium lysed rapidly after incubation in the CM fraction. Repeated subculturing of Sf9 cells provoked a switch in growth kinetics. After 30-45 passages the cells started to proliferate earlier after inoculation and addition of CM had no longer a growth stimulating effect. However, CM still stimulated growth of a culture with low passage (LP) number (up to 45 passages). High passage cells (HP cells, over 100 passages) displayed a shorter lagphase than LP cells and the culture reached the maximum cell density 24-48 h earlier. Cell cycle analysis showed that the Sf9 cells were transiently synchronised in the G2/M phase 10 h after inoculation, before proliferation was initiated. This synchronisation was more pronounced for HP cells than for LP cells, which correlated to a higher recombinant protein production in baculovirus infected HP cells than in LP cells. Synchronisation of cells in G2/M by yeastolate-limitation before infection with baculoviruses suggested that the degree of synchronisation is connected to the cell density dependent decrease in recombinant protein production of Sf9 cultures. / QC 20101222
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Phase Dynamics and Physico-Mechanical Behaviors of Electronic Materials: Atomistic Modeling and Theoretical StudiesHong Sun (9500594) 16 December 2020 (has links)
<p></p><p>Global demand for high performance, low cost, and eco-friendly
electronics is ever increasing. Ion/charge transport ability and mechanical
adaptability constitute two critical performance metrics of battery and
semiconductor materials, which are fundamentally correlated with their
structural dynamics under various operating conditions. It is imperative to
reach the mechanistic understanding of the structure-property relationships of
electronic materials to develop principles of materials design. Nevertheless,
the intricate atomic structure and elusive phase behaviors in the operation of
devices challenge direct experimental observations. Herein, we employ a
spectrum of modeling methods, including quantum chemistry, ab-initio modeling,
and molecular dynamics simulation, to systematically study the phase dynamics
and physico-mechanical behaviors of multiple electronic materials, ranging from
transition-metal cathodes, polymer derived ceramics anodes, to organic
semiconductor crystals. The multiscale atomistic modeling enriches the
fundamental understanding of the electro-chemo-mechanical behaviors of battery
materials, which provides insight on designing state-of-the-art energy
materials with high capacity and high structural stability. By leveraging the
genetic-algorithm refined molecular modeling and phase transformation theory,
we unveil the molecular mechanisms of thermo-, super- and ferroelastic
transition in organic semiconductor crystals, thus promoting new avenues of
adaptive organic electronics by molecular design. Furthermore, the proposed
computational methodologies and theoretical frameworks throughout the thesis
can find use in exploring the phase dynamics in a variety of environmentally
responsive electronics.</p><p></p>
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