1,358 research outputs found
The structural and mechanical characterization of biological systems and interfaces for the study of protein misfolding diseases
My PhD project involved the use of high-resolution microscopy techniques to study the mechanisms driving neurodegeneration in protein aggregation diseases, and to investigate the effects of anti-aggregation drugs. Several pieces of evidence indicate that in neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, toxic behaviour could result from the action of amyloid aggregates. The latter are highly organized and insoluble aggregates that are formed upon misfolding and aggregation of soluble proteins which undergo destabilization of their native structure. These proteins share the common characteristic of aggregating into fibrillar structures, referred to as "amyloid fibrils" with a high content of β-sheets and specific cross-beta arrangement. The study was conducted using advanced atomic force microscopy (AFM) both as a single technique to mechanistically and structurally characterize biological systems and interfaces involved in the interaction with toxic protein aggregates (through imaging and analysis of force/distance curves), and as a combined technique, together with optical microscopy, to understand the molecular mechanisms of protein aggregation, which represents a crucial problem to counteract misfolded protein diseases
Various Applications of Methods and Elements of Adaptive Optics
This volume is focused on a wide range of topics, including adaptive optic components and tools, wavefront sensing, different control algorithms, astronomy, and propagation through turbulent and turbid media
LIPIcs, Volume 261, ICALP 2023, Complete Volume
LIPIcs, Volume 261, ICALP 2023, Complete Volum
2023-2024 Undergraduate Catalog
2023-2024 undergraduate catalog for Morehead State University
OPTICAL COHERENCE TOMOGRAPHY OPHTHALMIC SURGICAL GUIDANCE
Optical coherence tomography (OCT) performs high-resolution cross-sectional and volumetric tissue imaging in situ through the combination of confocal gating, coherence gating, and polarization gating. Because it is noninvasive, OCT has been used in multiple clinical applications such as tissue pathology assessment and interventional procedure guidance. Moreover, OCT can perform functional measurements such as phase-sensitive measurement of blood flow and polarization-sensitive measurement of tissue birefringence. These features made OCT one of the most widely used imaging systems in ophthalmology. In this thesis, we present several novel OCT methods developed for microsurgery guidance and OCT image analysis. The thesis mainly consists of five parts, which are shown as follows.
First, we present a BC-mode OCT image visualization method for microsurgery guidance, where multiple sparsely sampled B-scans are combined to generate a single cross-sectional image with an enhanced instrument and tissue layer visibility and reduced shadowing artifacts. The performance of the proposed method is demonstrated by guiding a 30-gauge needle into an ex-vivo human cornea.
Second, we present a microscope-integrated OCT guided robotic subretinal injection method. A workflow is designed for accurate and stable robotic needle navigation. The performance of the proposed method is demonstrated on ex-vivo porcine eye subretinal injection.
Third, we present optical flow OCT technique that quantifies accurate velocity fields. The accuracy of the proposed method is verified through phantom flow experiments by using a diluted milk powder solution as the scattering medium, in both cases of advective flow and turbulent flow.
Fourth, we present a wrapped Gaussian mixture model to stabilize the phase of swept source OCT systems. A closed-form iteration solution is derived using the expectation-maximization algorithm. The performance of the proposed method is demonstrated through ex-vivo, in-vivo, and flow phantom experiments. The results show its robustness in different application scenarios.
Fifth, we present a numerical landmark localization algorithm based on a convolutional neural network and a conditional random field. The robustness of the proposed method is demonstrated through ex-vivo porcine intestine landmark localization experiments
Critical transition and spatial organization in climate and engineering systems
Diese Arbeit zielt darauf ab, die raumzeitlichen Regelmäßigkeiten an Übergängen
aufzudecken, die in saisonalen Klima- und Ingenieursystemen beobachtet
werden, indem moderne Methoden der komplexen Systemwissenschaft verwendet
werden. Das erste System ist der indische Sommermonsun - eine Regenzeit,
deren jährliche Schwankungen das Leben und den Wohlstand von mehr als
einer Milliarde Menschen auf dem indischen Subkontinent beeinflussen und die
Wirtschaft des von der Landwirtschaft abhängigen Landes stark beeinträchtigen.
Insbesondere die Kenntnis des zeitlichen Ablaufs des Ăśbergangs vom Vormonsun
zum Monsun ist für die Planung landwirtschaftlicher Aktivitäten dringend erforderlich.
Die Vorhersage des Monsunzeitpunkts ĂĽber dem indischen Kontinent
bleibt jedoch eine groĂźe wissenschaftliche Herausforderung. Das zweite ist ein
Verbrennungssystem, das anfällig für ein katastrophales Phänomen namens thermoakustische
Instabilität ist, das verhindert, dass das Verbrennungssystem unter
klimafreundlichen Bedingungen betrieben wird. Eine solche Brennkammer ist
typisch fĂĽr Energie- und Antriebssysteme wie Gasturbinentriebwerke, Boiler und
Raketen. Zu verstehen, wann der Übergang zur thermoakustischen Instabilität
auftritt und wie dieser Ăśbergang unterdrĂĽckt werden kann, sind SchlĂĽsselfragen
fĂĽr die Entwicklung klimafreundlicher Motoren. Diese Dissertation liefert ein
neues Verständnis des indischen Sommermonsuns und der thermoakustischen
Instabilität durch auf statistischer Physik basierende Ansätze, die verborgene
Merkmale in diesen Systemen nahe ihren jeweiligen Übergängen aufdecken.This thesis aims to reveal the spatiotemporal regularities at transitions observed
in seasonal climate and engineering systems by utilizing modern methods
of complex systems science. The first system is the Indian Summer Monsoon - a
rainy season whose yearly variability affects the life and prosperity of more than
a billion people in the Indian subcontinent and strongly impacts the economy of
the agriculture-dependent country. In particular, knowledge of the timing of the
transition from pre-monsoon to monsoon is greatly needed for the planning of
agriculture activities. However, the prediction of monsoon timing over the Indian
continent remains a significant scientific challenge. The second is a combustion
system prone to a catastrophic phenomenon called thermoacoustic instability,
which prevents the combustion system from being operated in climate-friendly
conditions. Such a combustor is typical in power and propulsion systems such
as gas turbine engines, boilers, and rockets. Understanding when the transition
to thermoacoustic instability occurs and how to suppress this transition are key
questions for developing climate-friendly engines. This thesis provides a new
understanding of the Indian Summer Monsoon and thermoacoustic instability
through statistical physics-based approaches that reveal hidden features in these
systems near their respective transitions
General Course Catalog [2022/23 academic year]
General Course Catalog, 2022/23 academic yearhttps://repository.stcloudstate.edu/undergencat/1134/thumbnail.jp
Dynamic life of a microtubule: From birth, growth and stabilization to damage and destruction
Microtubules are one of the major types of cytoskeletal filaments in cells. They are very dynamic polymers composed of αβ-tubulin dimers arranged longitudinally in head-to-tail fashion as well as laterally to assemble 13-protofilament hollow cylindrical tubes. The incorporation of GTP-bound αβ-tubulin dimers generates a fast growing plus end exposing β-tubulin and a slow growing minus end exposing α-tubulin. In cells, microtubules are assembled de novo from a template, called γ-TuRC, which interacts with α-tubulin. Microtubules can either remain capped by γ-TuRC and anchored to the microtubule-organizing centers (MTOCs) or be released if they are cut by microtubule severing enzymes like katanin. The release of microtubules from MTOC generates free minus ends, which are then stabilized by minus-end binding proteins called CAMSAPs. However, the plus ends remain very dynamic and undergo transitions from growth to shrinkage, termed “catastrophes”, and the opposite transitions termed “rescues”. Numerous microtubule regulatory proteins act at the plus ends, minus ends and the microtubule shafts connecting the two ends to control the organization and density of cellular microtubule networks. In this thesis, we focused on each of these aspects and explored the dynamic life of microtubules by reconstituting these processes in vitro using purified proteins. We first focused on the birth and growth of microtubules. We reconstituted microtubule nucleation using purified γ-TuRC and microtubule regulatory proteins and showed that CDK5RAP2, CLASP2 and chTOG promoted microtubule nucleation from γ-TuRC. We discovered that CAMSAPs can bind to γ-TuRC-capped microtubule minus ends and displace γ-TuRC from these ends, generating free and stable microtubule minus ends. Furthermore, we found out that CDK5RAP2, but not CLASP2 or chTOG, can inhibit CAMSAP binding and microtubule release. We propose that the destiny of a microtubule depends on the type of protein complex that activates its nucleation. We then described a mechanism for stabilization of microtubule lattice by TRIM46, a neuronal protein, which can bundle parallel microtubules and promote microtubule rescues within these bundles. We also revealed that Ankyrin-G, a scaffold protein, can recruit TRIM46-stabilized microtubule bundles to the axonal membrane to drive the assembly of the axon initial segment in neurons. We also uncovered a new role of CLASP2 as a microtubule repair factor participating in microtubule maintenance. We demonstrated that CLASP2, an anti-catastrophe factor, can promote complete repair of damaged microtubule lattices by inhibiting microtubule depolymerization and promoting tube closure at the damage sites, causing lattice renewal. Finally, we described a three-protein module involving katanin, CAMSAPs, and WDR47 that can regulate microtubule polymer mass and minus-end stability. We showed that katanin can cut and amplify CAMSAP2/3-stabilized microtubule minus ends. WDR47 can inhibit the binding of katanin to CAMSAP2/3-stabilized minus ends and protect them from severing. The presence of WDR47 shifts the balance from microtubule amplification to minus-end growth regulation. To conclude, we obtained mechanistic insights into the regulation of microtubule nucleation, minus-end dynamics, lattice stabilization and maintenance, microtubule number and the interplay between microtubule regulatory proteins. These insights will help to understand how microtubule arrays are organized in cells
Colloquium: Quantum Batteries
Recent years have witnessed an explosion of interest in quantum devices for
the production, storage, and transfer of energy. In this Colloquium, we
concentrate on the field of quantum energy storage by reviewing recent
theoretical and experimental progress in quantum batteries. We first provide a
theoretical background discussing the advantages that quantum batteries offer
with respect to their classical analogues. We then review the existing quantum
many-body battery models and present a thorough discussion of important issues
related to their open nature. We finally conclude by discussing promising
experimental implementations, preliminary results available in the literature,
and perspectives.Comment: 36 pages, 12 figures, 311 references. Review and perspective article
on quantum batteries. Commissioned for Reviews of Modern Physics. Comments
and feedback are welcom
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