IA Scholar Query: Fast and stable evaluation of the exact absorbing boundary condition for the semi-discrete linear Schrödinger equation in unbounded domains.
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgThu, 21 Jul 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440Nonlinear optical functionalities of VO2- and GaN-based nanocomposites
https://scholar.archive.org/work/5glwc2pvurcnvi72v4ncrdjhuu
This thesis presents fundamental research and concepts for active photonic elements operating in the telecom wavelength regime. The aim of the study is to determine the characteristics of the investigated nanostructures and to evaluate the implementation of the proposed materials in potential optical devices. In the first part of this thesis the optical properties as well as the photonic application of vanadium dioxide (VO2) nanocrystals (NCs) are studied. VO2 exhibits an easily accessible insulator-to-metal phase transition (IMT) near ambient temperatures. Upon excitation it undergoes an atomic rearrangement that is accompanied by a substantial modification of the complex dielectric function. When VO2 undergoes the IMT, the near-infrared transmission peaks of a moderate-finesse etalon containing a sub-wavelength layer of VO2 NCs are found to markedly shift in their spectral position and peak transmissivity. Both heat deposition and optical excitation permit to actively control the etalon's functionality. Much less is known about the nonlinear optical properties of VO2 beyond the established IMT. To this end the nonlinear optical response of a thin film of VO2 NCs is investigated with open aperture z-scans involving femtosecond near-infrared pulses. A pronounced saturable absorption on the short-wave side of the resonance as well as a marked reverse saturable absorption in the telecom window are observed. The results hold promise for the use of VO2 nanocrystals as a saturable absorber, e.g., to mode-locked near-infrared lasers. In the second part a semiconductor heterostructure based on hexagonal ultranarrow GaN/AlN multi-quantum wells (MQWs) is investigated. The tailored inter-miniband (IMB) transition is characterized in terms of its linear as well as ultrafast nonlinear optical properties using the established pump-probe scheme. In line with theoretical predictions for LO-phonon scattering, a fast relaxation is found for resonant IMB excitation. In stark contrast, significantly larger relaxation times are obse [...]Jan Mundry, Technische Universität Dortmundwork_5glwc2pvurcnvi72v4ncrdjhuuThu, 21 Jul 2022 00:00:00 GMTQuantum machine learning for chemistry and physics
https://scholar.archive.org/work/ts35ancqmvay5fhyqya6degva4
Machine learning (ML) has emerged as a formidable force for identifying hidden but pertinent patterns within a given data set with the objective of subsequent generation of automated predictive behavior. In recent years, it is safe to conclude that ML and its close cousin, deep learning (DL), have ushered in unprecedented developments in all areas of physical sciences, especially chemistry. Not only classical variants of ML, even those trainable on near-term quantum hardwares have been developed with promising outcomes. Such algorithms have revolutionized materials design and performance of photovoltaics, electronic structure calculations of ground and excited states of correlated matter, computation of force-fields and potential energy surfaces informing chemical reaction dynamics, reactivity inspired rational strategies of drug designing and even classification of phases of matter with accurate identification of emergent criticality. In this review we shall explicate a subset of such topics and delineate the contributions made by both classical and quantum computing enhanced machine learning algorithms over the past few years. We shall not only present a brief overview of the well-known techniques but also highlight their learning strategies using statistical physical insight. The objective of the review is not only to foster exposition of the aforesaid techniques but also to empower and promote cross-pollination among future research in all areas of chemistry which can benefit from ML and in turn can potentially accelerate the growth of such algorithms.Manas Sajjan, Junxu Li, Raja Selvarajan, Shree Hari Sureshbabu, Sumit Suresh Kale, Rishabh Gupta, Vinit Singh, Sabre Kaiswork_ts35ancqmvay5fhyqya6degva4Mon, 18 Jul 2022 00:00:00 GMTQuantum simulation with an optical kagome lattice
https://scholar.archive.org/work/hxflqab5tvbtlm5qe6tezhxzxm
This thesis reports on the construction and operation of an ultracold atom- based quantum simulator for studying the kagome lattice and the associated flat band. Despite a copious amount of theoretical effort to elucidate the physics of the kagome lattice, experimental kagome physics is still in its infancy. In the case of ultracold atoms, this is mainly due to considerable technical challenges involved in creating an optical kagome lattice, such as the need for active phase stabilization for bichromatic superlattices. We show that we have overcome these challenges and give a thorough account of our machine's technical details. Furthermore, we present calculations and measurements that fully characterise the kagome quantum simulator. Much of the theoretical work on the kagome lattice has focussed on its flat band. Populating flat bands with ultracold atoms has proven to be difficult and it has so far not been possible to prepare flat bands in thermodynamic equilibrium. We show a route towards studying quantum manybody physics in the flat band of the kagome lattice using negative temperatures. In addition we report, for the first time, on the creation of a negative temperature state in a triangular lattice. This thesis additionally serves to collect and consolidate theoretical research that we can directly study with our machine. In particular, we will discuss the properties of bosons in flat bands and their experimental signatures, with the aim of guiding and accelerating the near-term developments and experiments. Finally, we detail our progress towards realizing a quantum gas microscope for the kagome lattice. In this context, we present a new method for super-resolution microscopy of ultracold atoms in optical lattices.Max Melchner Von Dydiowa, Apollo-University Of Cambridge Repository, Ulrich Schneiderwork_hxflqab5tvbtlm5qe6tezhxzxmWed, 13 Jul 2022 00:00:00 GMTHigh-Resolution CMB Bispectrum Estimator
https://scholar.archive.org/work/3aoxzfjta5es7nrwhavsuuhzzq
The Cosmic Microwave Background (CMB) is one of the most valuable probes of the universe we have today. Anisotropies present in the ancient light contain rich statistical information about the perturbations in the early universe and their subsequent evolution until now. The CMB bispectrum, the Fourier equivalent of the three-point correlation function, allows us to study weak non-Gaussian signatures of the primordial fluctuations. Primordial non-Gaussianity is a key prediction of many physically well-motivated inflation models, and measuring its shape and amplitude allows us to constrain various models of the early universe. This thesis comprises two sections. In the first section, we present forecasts on primordial non-Gaussianity constraints from upcoming CMB surveys. We focus our attention on models favoured by the Planck analysis, where a sharp feature in either the inflationary potential or sound speed causes oscillations in the bispectrum. Using preliminary specifications, we find that the Simons Observatory will have up to a factor of 1.6 improvements over Planck, increased to 1.7-2.2 for the CMB Stage-4 experiment. Motivated by bright prospects, we developed a novel CMB bispectrum estimator suited for the resolution and sensitivity of future surveys. We discuss our high-resolution bispectrum estimator in the second section. Our code, named CMB-BEst, utilises a set of general basis functions to accurately constrain a wide variety of models. Implementing such a flexible and precise estimator was a computationally challenging task. We detail our algorithm design, code optimisation and parallelisation for high-performance computing clusters, which made this challenging computation tractable. Validation tests, both for internal consistency and comparisons against conventional estimators, are provided together with a proof-of-concept application. We highlight how CMB-BEst can be used for both general and targeted analyses of previously unconstrained models.Wu Hyun Sohn, Apollo-University Of Cambridge Repository, James Fergusson, Edward Shellardwork_3aoxzfjta5es7nrwhavsuuhzzqFri, 08 Jul 2022 00:00:00 GMTLectures on Introduction to Quantum Field Theory
https://scholar.archive.org/work/avutkhkzhfevloqcx63rbzei2y
These are lecture notes of the QFT-I course I gave in an online mode at Chennai Mathematical Institute. The course focussed on the free relativistic quantum fields, their interactions in the perturbative scattering framework, standard computations of QED processes, radiative corrections at 1-loop with renormalization and an introduction to the toolbox of path integrals.Ghanashyam Datework_avutkhkzhfevloqcx63rbzei2yTue, 05 Jul 2022 00:00:00 GMTMajorana nanowires for topological quantum computation: A tutorial
https://scholar.archive.org/work/rsn6pak6ibag5gn2ulpkducu7i
Majorana bound states are quasiparticle excitations localized at the boundaries of a topologically nontrivial superconductor. They are zero-energy, charge-neutral, particle-hole symmetric, and spatially-separated end modes which are topologically protected by the particle-hole symmetry of the superconducting state. Due to their topological nature, they are robust against local perturbations and, in an ideal environment, free from decoherence. Furthermore, unlike ordinary fermions and bosons, the adiabatic exchange of Majorana modes is noncommutative, i.e., the outcome of exchanging two or more Majorana modes depends on the order in which exchanges are performed. These properties make them ideal candidates for the realization of topological quantum computers. In this tutorial, I will present a pedagogical review of 1D topological superconductors and Majorana modes in quantum nanowires. I will give an overview of the Kitaev model and the more realistic Oreg-Lutchyn model, discuss the experimental signatures of Majorana modes, and highlight their relevance in the field of topological quantum computation. This tutorial may serve as a pedagogical introduction for graduate and undergraduate students and researchers new to the field.Pasquale Marrawork_rsn6pak6ibag5gn2ulpkducu7iWed, 29 Jun 2022 00:00:00 GMTMolecular Dynamics for Synthetic Biology
https://scholar.archive.org/work/tjd3uiulavgb5bvr5cf6af2ify
Synthetic biology is the field concerned with the design, engineering, and construction of organisms and biomolecules. Biomolecules such as proteins are nature's nano-bots, and provide both a shortcut to the construction of nano-scale tools and insight into the design of abiotic nanotechnology. A fundamental technique in protein engineering is protein fusion, the concatenation of two proteins so that they form domains of a new protein. The resulting fusion protein generally retains both functions, especially when a linker sequence is introduced between the two domains to allow them to fold independently. Fusion proteins can have features absent from all of their components; for example, FRET biosensors are fusion proteins of two fluorescent proteins with a binding domain. When the binding domain forms a complex with a ligand, its dynamics translate the concentration of the ligand to the ratio of fluorescence intensities via FRET. Despite these successes, protein engineering remains laborious and expensive. Computer modelling has the potential to improve the situation by enabling some design work to occur virtually. Synthetic biologists commonly use fast, heuristic structure prediction tools like ROSETTA, I-TASSER and FoldX, despite their inaccuracy. By contrast, molecular dynamics with modern force fields has proven itself accurate, but sampling sufficiently to solve problems accurately and quickly enough to be relevant to experimenters remains challenging. In this thesis, I introduce molecular dynamics to a structural biology audience, and discuss the challenges and theory behind the technique. With this knowledge, I introduce synthetic biology through a review of fluorescent sensors. I then develop a simple computational tool, Rangefinder, for the design of one variety of these sensors, and demonstrate its ability to predict sensor performance experimentally. I demonstrate the importance of the choice of linker with yet another sensor whose performance depends critically thereon. In chapter 6, I investigate the [...]Josh Mitchell, University, The Australian Nationalwork_tjd3uiulavgb5bvr5cf6af2ifyWed, 15 Jun 2022 00:00:00 GMTStructural and functional analysis of non-canonical tandem-thioesterases
https://scholar.archive.org/work/o4lbceb2cffbnesyhgqibsephu
Nichtribosomale Peptidsynthetasen (NRPS) sind dafür bekannt eine vielfältige Palette an bioaktiven Naturstoffen zu produzieren, deren Wirkungsbereiche häufig im Einsatz als Antibiotikum, Immunsuppressivum oder Zytostatika sind. Diese pharmakologisch bedeutsamen Eigenschaften haben verstärkt wissenschaftliches Interesse auf sich gezogen, um zum einen die Entdeckung neuer Naturstoffe voran zu treiben. Zum anderen erhofft man sich, über die mechanistische Aufklärung dieser komplexen Synthesestraßen, die katalytischen Eigenschaften für zielgerichtetes Medikamentendesign nutzen zu können. Im Hinblick auf die mechanistische Aufklärung ist die Forschung besonders auf die strukturelle Aufklärung einzelner Domänen und Module angewiesen um für die Funktion essentielle Interaktionen aufzuzeigen, Substratspezifitäten zu erklären und die gezielte Modifikation bestimmter Funktionseinheiten zu erleichtern. Ein besonderes Interesse gilt hier der Funktionsanalyse von Terminationseinheiten, wie der Thioesterase (Te), die für die Produktfreisetzung aus dem NRPS erforderlich ist. Innerhalb der letzten Jahre wuchs das Interesse insbesondere für die Erforschung der ungewöhnlichen Tandem-Te, die bislang überwiegend in NRPS Systemen beschrieben wurde, deren Biosynthese überwiegend makrozyklische Naturprodukte zu vertreten scheint. In dieser Arbeit ist die strukturelle und funktionelle Analyse von ungewöhnlichen Tandem-Te auf Basis des Modellorganismus Xenorhabdus nematophila ATCC 19061 beschrieben. In voran gehenden Arbeiten von BODE et al. konnte bereits gezeigt werden, dass das biosynthetische Gencluster von Xenoamicin, einem Naturstoff aus der Gruppe der zyklischen Depsipeptide, diese Didomäne beherbergt. Eine im Fokus stehende Fragestellung dieser Arbeit befasst sich mit der kristallographischen Strukturaufklärung dieser Tandem-XncTe, die bei einer Auflösung von 3.4 Å hier genauer beschrieben wird. Zudem zeigt eine C-terminale Teilstruktur, bei einer Auflösung von 1.9 Å, Eigenschaften der isolierten Subdomänen auf. Die strukturellen [...]Maximilian Biermeier, Essen, Lars-Oliver (Prof. Dr.), Chemiework_o4lbceb2cffbnesyhgqibsephuMon, 30 May 2022 00:00:00 GMTA Review of Transparent and Artificial Boundary Conditions Techniques for Linear and Nonlinear Schrödinger Equations
https://scholar.archive.org/work/bw4fspg32zh5rkcu5jk47osvcy
In this review article we discuss different techniques to solve numerically the time-dependent Schrödinger equation on unbounded domains. We present and compare several approaches to implement the classical transparent boundary condition into finite difference and finite element discretizations. We present in detail the approaches of the authors and describe briefly alternative ideas pointing out the relations between these works. We conclude with several numerical examples from different application areas to compare the presented techniques. We mainly focus on the one-dimensional problem but also touch upon the situation in two space dimensions and the cubic nonlinear case.Xavier Antoine, Anton Arnold, Christophe Besse, Matthias Ehrhardt, Achim Schädle, Technische Universität Berlinwork_bw4fspg32zh5rkcu5jk47osvcyWed, 11 May 2022 00:00:00 GMTTransport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions
https://scholar.archive.org/work/qkcrsyuoyfcebbwp4m32mfxjye
Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.Hermann Wolterwork_qkcrsyuoyfcebbwp4m32mfxjyeWed, 04 May 2022 00:00:00 GMTCapillary gravity water waves linearized at monotone shear flows: eigenvalues and inviscid damping
https://scholar.archive.org/work/hb5ej3fkxnd6xe3acyibprrbpa
This paper is concerned with the eigenvalues and linear inviscid damping of the 2D capillary gravity water waves of finite depth x_2∈(-h,0) linearized at a monotone shear flow U(x_2). Unlike the linearized Euler equation in a fixed channel where eigenvalues exist only in low horizontal wave number k, we first prove the linearized capillary gravity wave has two branches of eigenvalues -ikc^±(k), where the wave speeds c^±(k)=O(√(|k|)) for |k|≫1 have the same asymptotics as the those of the linear irrotational capillary gravity waves. Under the additional assumption of U"0, we obtain the complete continuation of these two branches, which are all the eigenvalues in this (and some other) case(s). Particularly -ikc^-(k) could bifurcate into unstable eigenvalues at c^-(k)=U(-h). The bifurcation of unstable eigenvalues from inflection values of U is also proved. Assuming no singular modes, i.e. no embedded eigenvalues for any wave number k, linear solutions (v(t,x),η(t,x_1)) are studieded in both periodic-in-x_1 and x_1∈ R cases, where v is the velocity and η the surface profile. Solutions can be split into (v^p,η^p) and (v^c,η^c) whose k-th Fourier mode in x_1 correspond to the eigenvalues and the continuous spectra of wave number k, respectively. The component (v^p,η^p) is governed by a (possibly unstable) dispersion relation given by the eigenvalues, which are simply k→-ikc^±(k) in the case of x_1∈ R. The other component (v^c,η^c) satisfies the inviscid damping as fast as |v_1^c|_L_x^2,|η^c|_L_x^2=O(|t|^-1) and |v_2^c|_L_x^2=O(t^-2) as |t|≫1. Additional decay of tv_1^c,t^2v_2^c in L_x^2L_t^q, q∈(2,∞], is obtained after leading asymptotic terms are removed, which are in the forms of t-dependent translations in x_1 of certain functions of x.Xiao Liu, Chongchun Zengwork_hb5ej3fkxnd6xe3acyibprrbpaSun, 27 Mar 2022 00:00:00 GMTThis Week's Finds in Mathematical Physics (1-50)
https://scholar.archive.org/work/7dqichdfjraltdavtghiqngis4
These are the first 50 issues of This Week's Finds of Mathematical Physics, from January 19, 1993 to March 12, 1995. These issues focus on quantum gravity, topological quantum field theory, knot theory, and applications of n-categories to these subjects. However, there are also digressions into Lie algebras, elliptic curves, linear logic and other subjects. They were typeset in 2020 by Tim Hosgood. If you see typos or other problems please report them. (I already know the cover page looks weird).John C. Baezwork_7dqichdfjraltdavtghiqngis4Mon, 28 Feb 2022 00:00:00 GMTAdvances in QED with intense background fields
https://scholar.archive.org/work/5jea64cypnbyzfxc2izxycbwre
Upcoming and planned experiments combining increasingly intense lasers and energetic particle beams will access new regimes of nonlinear, relativistic, quantum effects. This improved experimental capability has driven substantial progress in QED in intense background fields. We review here the advances made during the last decade, with a focus on theory and phenomenology. As ever higher intensities are reached, it becomes necessary to consider processes at higher orders in both the number of scattered particles and the number of loops, and to account for non-perturbative physics (e.g. the Schwinger effect), with extreme intensities requiring resummation of the loop expansion. In addition to increased intensity, experiments will reach higher accuracy, and these improvements are being matched by developments in theory such as in approximation frameworks, the description of finite-size effects, and the range of physical phenomena analysed. Topics on which there has been substantial progress include: radiation reaction, spin and polarisation, nonlinear quantum vacuum effects and connections to other fields including physics beyond the Standard Model.A. Fedotov, A. Ilderton, F. Karbstein, B. King, D. Seipt, H. Taya, G. Torgrimssonwork_5jea64cypnbyzfxc2izxycbwreMon, 28 Feb 2022 00:00:00 GMTAperiodic Order and Singular Spectra
https://scholar.archive.org/work/fsgzlfugyrcurk36o36prhw5kq
This work focuses on several models of aperiodic order and their applications in different areas of mathematics and mathematical physics. After a short introduction to the theory of dynamicals systems, we present random substitutions as a stochastic variant of substitutions which create symbolic dynamical systems that combine long-range order with a positive entropy. Using renormalization techniques, we obtain expressions for the entropy, diffraction, and ergodic measures of such systems. In the second part, we investigate spectral properties of Schrödinger operators that are associated with non-primitive substitution systems and dynamically defined product systems. Finally we perform a multifractal analysis of a particular spectral measure that has become known as the Thue--Morse measure.Philipp Gohlkework_fsgzlfugyrcurk36o36prhw5kqThu, 10 Feb 2022 00:00:00 GMTControl of topologically non-trivial spin excitations [Kumulative Dissertation]
https://scholar.archive.org/work/yqhsoc3ujnbonoutxeh3matvny
In dieser Dissertation wird die Manipulation von Spinanregungen mit einer nicht-trivialen Realraumtopologie in magnetischen Festkörpern untersucht. Magnetische Skyrmionen sind wirbelartige Quasiteilchen, die eine hohe Mobilität und Stabilität aufweisen und daher vielversprechende Kandidaten zur Anwendung in Speichermedien sind. Theoretische Konzepte und numerische Simulationen zur Kontrolle von magnetischen Quasiteilchen werden präsentiert. Anschließend wird die Existenz von twisted magnons (gewundene Magnonen) demonstriert. Twisted magnons sind Spinwellenmoden in magnetischen Materialien, die einen Bahndrehimpuls tragen. Kontrollmechanismen, Transporteffekte und die Robustheit ihrer topologischen Ladung gegenüber Störungen werden untersucht. Aufgrund der möglichen Verbesserungen hinsichtlich Geschwindigkeit und Energieeffizienz, sind die präsentierten Konzepte von direkter Relevanz für Anwendungen in der Datenspeicherung und Informationsübertragung.Alexander Frederic Schäffer, Universitäts- Und Landesbibliothek Sachsen-Anhalt, Martin-Luther Universität, Jamal Berakdar, Steffen Trimper, Karin Everschor-Sittework_yqhsoc3ujnbonoutxeh3matvnyThu, 03 Feb 2022 00:00:00 GMTStochastic modelling of bacterial dynamics : adhesion & range expansion
https://scholar.archive.org/work/4d67shjbznfxzph5et3kvgqody
Bacteria, as one of the three domains in the tree of life, play an important role in many phenomena such as biocorrosion, pipe clogging and infections. Since treatment with antibiotics or mechanical removal can be difficult, it is paramount to understand the initial attachment to a substrate and the subsequent colony growth. To this end, this thesis investigates first the adhesion process of Staphylococcus aureus by Monte Carlo simulations and helps to reveal that the bacterium uses different binding mechanisms on hydrophobic and hydrophilic substrates. On hydrophobic substrates, the bacterium's macromolecules bind freely. Subsequently, the bacteria show large cell-to-cell variation in adhesion forces but only small variations by repetitions with the same cell. On hydrophilic substrates, the macromolecules need to overcome a potential barrier. This leads to a comparable variability between repetitions with the same cell and the cell-to-cell variance. As a second model system, I investigated the competitive range expansion of microbial colonies with heterogeneous mechanical interactions by stochastic simulations. This is, for instance, realised by a network of piliated bacteria such as Neisseria gonorrhoeae. The simulations reveal that a heterogeneous susceptibility to division generated pushing significantly affects the competition dynamics of growing bacteria. Furthermore, homogeneous pushing leads to a small but standing variation of a disadvantaged subpopulation inside the expanding colony. Publications Many results of this thesis are published in the following articles of peer-reviewed journals. Authors marked by † contributed equally.Erik Maikranz, Universität Des Saarlandeswork_4d67shjbznfxzph5et3kvgqodyThu, 03 Feb 2022 00:00:00 GMTNuclear Forces for Precision Nuclear Physics – a collection of perspectives
https://scholar.archive.org/work/4toszkczovcu7e2xbodshkagti
This is a collection of perspective pieces contributed by the participants of the Institute of Nuclear Theory's Program on Nuclear Physics for Precision Nuclear Physics which was held virtually from April 19 to May 7, 2021. The collection represents the reflections of a vibrant and engaged community of researchers on the status of theoretical research in low-energy nuclear physics, the challenges ahead, and new ideas and strategies to make progress in nuclear structure and reaction physics, effective field theory, lattice QCD, quantum information, and quantum computing. The contributed pieces solely reflect the perspectives of the respective authors and do not represent the viewpoints of the Institute for Nuclear theory or the organizers of the program.Ingo Tews, Zohreh Davoudi, Andreas Ekström, Jason D. Holt, Kevin Becker, Raúl Briceño, David J. Dean, William Detmold, Christian Drischler, Thomas Duguet, Evgeny Epelbaum, Ashot Gasparyan, Jambul Gegelia, Jeremy R. Green, Harald W. Grießhammer, Andrew D. Hanlon, Matthias Heinz, Heiko Hergert, Martin Hoferichter, Marc Illa, David Kekejian, Alejandro Kievsky, Sebastian König, Hermann Krebs, Kristina D. Launey, Dean Lee, Petr Navrátil, Amy Nicholson, Assumpta Parreño, Daniel R. Phillips, Marek Płoszajczak, Xiu-Lei Ren, Thomas R. Richardson, Caroline Robin, Grigor H. Sargsyan, Martin Savage, Matthias R. Schindler, Phiala E. Shanahan, Roxanne P. Springer, Alexander Tichai, Ubirajara van Kolck, Michael L. Wagman, André Walker-Loud, Chieh-Jen Yang, Xilin Zhangwork_4toszkczovcu7e2xbodshkagtiWed, 02 Feb 2022 00:00:00 GMTUnderstanding the Photogeneration Process in Organic Photovoltaics: From the Bulk to the Edges
https://scholar.archive.org/work/3rwnofzzn5gqzinb6h6kthffsi
The field of organic semiconductors have been brought under great attention from both the academia and the public when high efficiency organic light emitting diodes (OLEDs) quickly grew in to a huge market with a $40 billion annual revenue. However, the performance of the organic photovoltaics (OPVs) has yet to meet the criteria as a player in the solar industry, popping a big question: what is missing for OPVs? In this thesis, the whole photogeneration process of OPVs is reviewed from nanoscopic mechanisms to macroscopic device performance, in a hope to provide guidelines towards high performance OPVs that can be commercially adopted. The first part of this thesis is focused on the charge transfer (CT) states in organic bulk heterojunctions (BHJs). We use a combination of experimental, theoretical and computational methods to explore the optical and electrical properties of CT states and their relationship to molecular and morphological structures. In the second part, we move from the BHJ to the edges of the OPV device and study the interfacial energy loss between the BHJ and peripheral layers. By studying the energy landscape near the interface, the interfacial energy losses are quantitatively characterized. A counterintuitive way to reduce the interfacial energy loss by up to 30% and improve the device open-circuit voltage is provided by growing a thin layer of acceptors on the anode side of the BHJ. With the understanding of the interfacial voltage losses, we proceed to study the internal distribution of voltages on various layers of the OPV, which leads to the development of an analysis method that can separate the properties of the BHJ of and OPV from the peripheral structures by calculating its "bulk quantum efficiency" (BQE). The third part of this thesis presents studies of the photo- and thermal stability of OPVs. A major part of the effort is focused on non-fullerene acceptor (NFA) based OPVs which currently provide the highest efficiencies. With the help of various experimental tools and the BQE analy [...]Kan Ding, University, Mywork_3rwnofzzn5gqzinb6h6kthffsiWed, 19 Jan 2022 00:00:00 GMTKerr-Nonlinear Microresonators and Frequency Combs: Modelling, Design, and Applications
https://scholar.archive.org/work/q44to7peefby5mss7dsyl2j4wy
Zur Erlangung des akademischen Grades eines DOKTORS DER INGENIEURWISSENSCHAFTEN (Dr.-Ing.) von der KIT-Fakultät für Elektrotechnik und Informationstechnik des Karlsruher Instituts für Technologie (KIT) angenommene DISSERTATION vonPhilipp Trochawork_q44to7peefby5mss7dsyl2j4wyTheoretical Investigation on the Biomolecular Systems using Multiscale Modelling
https://scholar.archive.org/work/et66l6ezkrgo5gfhpbuq22i7qi
Die Untersuchung von Protein-Ligand-Wechselwirkungen ist für biomolekulare Systeme von entscheidender Bedeutung und eine Herausforderung. Insbesondere haben traditionelle Laborexperimente oft Schwierigkeiten, die Mechanismen der Reaktionen zu erklären, während klassische theoretische Berechnungsmethoden Defizite im Umgang mit der System- und Zeitskala biomolekularer Systeme aufweisen. In dieser Arbeit werden sogenannte enhanced Sampling-Methoden auf der Grundlage von Molekulardynamiksimulationen (MD) und Algorithmen für künstliche neuronale Netze (ANN), die auf semi-empirischen quantenmechanischen (QM) Ansätzen beruhen, zur Untersuchung verschiedener biomolekularer Systeme eingesetzt. Im ersten Teil wurde die Wirt-Gast-Chemie von [4+4]- und [2+3]-Iminkäfigen untersucht. Bei der Untersuchung von [4+4]-Käfigen wurde der Aufnahmeprozess von unterschiedlich großen Ammoniumionen in Käfigen mit alternativen Volumina durch wohltemperierte Metadynamik (MetaD) simuliert. Es wurden drei mögliche Mechanismen vorgeschlagen, um die Gastaufnahmeprozesse zu erklären. Bei der Untersuchung von [2+3]-Käfigen wurde der Stickstoffmolekültransfer in drei verschiedenen Käfigkristallen mit Funnel-Metadynamik (FM) berechnet. Die erhaltenen freien Energieflächen deuten auf die Existenz von zwei möglichen Wegen hin, auf denen der Stickstofftransfer erfolgen kann. Im zweiten Teil wurde eine neuartige Fluoreszenzsonde auf der Basis eines Glukose bindenden Proteins untersucht. Ein detailliertes molekulares Verständnis der Veränderungen an der Glukosebindestelle aufgrund von Mutationen und deren Auswirkungen auf die Glukosebindung wurde durch MD-Simulationen erreicht. Die Energetik der Dissoziation von Protein und Glukose wurde aufgedeckt und stimmte mit den experimentellen Ergebnissen überein. Schließlich wurde eine Reihe von künstlichen neuronalen Netzen (ANNs) trainiert, um die falsche Darstellung von angeregten Zuständen durch LC-DFTB zu korrigieren, wenn Energieniveaus kreuzen. Die meisten der trainierten Maschinen sind in der Lage, die [...]Ziwei Pang, Marcus Elstnerwork_et66l6ezkrgo5gfhpbuq22i7qi