Computation of optical properties of chromophores in different environments using QM/MM methods

Die theoretische Beschreibung der Wechselwirkung zwischen Molekülen und Licht kann herausfordernd sein, insbesondere dann, wenn es sich um flexible Farbstoffe in einer komplexen und dynamischen Umgebung handelt. Obgleich quantenmechanische (QM) Methoden den angeregten Zustand eines Moleküls beschreiben können, sind sie zu rechenaufwändig, um strukturelle Fluktuationen simulieren zu können. Darüber hinaus ist die mögliche Systemgröße, die beschrieben werden kann, durch die Rechenkosten begrenzt. Aus diesem Grund kommen für die Untersuchung von Farbstoffen in Proteinumgebung semiempirische und Multiskalenansätze ins Spiel. Die semiempirische Time-Dependent Long-range Corrected Density Functional Tight Binding (TD-LC-DFTB2) Methode wurde als effiziente Alternative zu ab initio Methoden oder der Dichtefunktionaltheorie in Bezug auf Geometrien im angeregten Zustand und Anregungsenergien getestet. Sie wurde in QM/MM Simulationen angewandt, in denen sie einen angeregten Fluorophor beschrieb, dessen Umgebung von einem klassischen Kraftfeld beschrieben wurde. Diese neue Strategie für die Untersuchung von Fluoreszenz wurde sorgfältig anhand von Literaturergebnissen bewertet, indem die Ergebnisse sowohl mit experimentellen als auch mit theoretischen Studien, die auf anderen Ansätzen basieren, verglichen wurden. Es wurde herausgefunden, dass TD-LC-DFTB2 im Allgemeinen Geometrien und Anregungsenergien von ausreichender Qualität liefert, aber es wurden auch einige Schwächen entdeckt. Außerdem wurde ein optischer Glukosesensor untersucht, der aus dem Glukosebindeprotein und einem angefügten Fluorophor besteht. Mit Hilfe von klassischen Molekulardynamiksimulationen (MD Simulationen) konnten Zusammenhänge zwischen der Anwesenheit von Glukose, den Proteinkonformationen und dem Aufenthaltsort des Farbstoffs gefunden werden. Daraus ergab sich ein starker Hinweis auf die Funktionsweise des Sensors. Schließlich wurde der Energietransfer in einem Pigment-Protein-Komplex untersucht. Der Fenna-Matthews-Olson-Komplex von Photosynthese betreibenden grünen Schwefelbakterien beinhaltet mehrere Bakteriochlorophyll a -- Pigmente in seinem Proteingerüst. Diese leiten die im Chlorosome gesammelte Anregungsenergie mit erstaunlicher Effizienz zum Reaktionszentrum weiter. Es wird Vorarbeit für eine Simulation der Exzitonenpropagation durch den Komplex gezeigt. Anregungsenergien und die Kopplungen zwischen den Pigmenten, das heißt die Elemente des exzitonischen Hamiltonoperators, wurden mit TD-LC-DFTB2 für Strukturen aus klassischen MD Simulationen berechnet. Dadurch wurde ein Eindruck zu deren Entwicklung über die Zeit und den Einfluss der Proteinumgebung gewonnen. Weiterhin wurden diese Daten genutzt, um neuronale Netze zu trainieren, die Anregungsenergien und Kopplungen noch schneller als TD-LC-DFTB2 vorhersagen können

India’s Strategies on its Periphery: A Case Study in the India–Bhutan Relationship

This paper explores India’s foreign policy strategies in its relationship with its neighbor Bhutan — probably one of the most asymmetric regional relationships in the world, and one that has come center stage in the context of the tensions between India and China over disputed territory in Doklam in 2017. Against this backdrop this paper takes a look back at the India–Bhutan relationship during the years 2007 to 2016, following Bhutan’s transition to democracy. It focuses on two specific policy fields: Bhutan’s diplomacy, and particularly its efforts to establish relations with China, India’s rival in the region; and Indo–Bhutanese development cooperation in the field of hydropower projects. The paper uses an analytical framework focused on three ideal-typical strategies that regional powers like India can pursue: empire, hegemony, and leadership. The findings show that while India tends to pursue a “leadership” strategy on hydropower projects, it has a contrasting approach when it comes to Bhutan’s diplomacy, indicating several incidences of “hard hegemony” These divergent strategies are related to the different interests connected to the two policy fields: while India is willing to establish an equal partnership in the economic-driven policy field of bilateral hydropower projects, it tends to pursue a very unequal and hard hegemonic strategy in the one of Bhutan's diplomacy because closer Bhutan–China ties are considered India’s own security interests

Investigating the V(II)/V(III) electrode reaction in a vanadium redox flow battery – A distribution of relaxation times analysis

Vanadium Redox Flow Batteries (VRFBs) are already commercially available and promise to provide excellent prerequisites to face the challenge of large-scale energy storage. Nevertheless, the VRFB itself has to overcome challenges regarding lifetime and efficiency. Polarization and pumping losses due to a high electrolyte flow-through resistance in the electrode contribute to much of the efficiency losses. We investigated the reaction and processes in the negative VRFB half-cell using electrochemical impedance spectroscopy combined with the distribution of relaxation times analysis. We identify the individual processes in the negative half-cell by varying several parameters. One peak is observed in the low-frequency range below 2 mHz, attributed to the ion transport. In the range from 2 mHz to 1 Hz, several peaks are identified and assigned to the redox-active species\u27 transport processes through the electrode\u27s porous structure. In the high-frequency range above 1 Hz, the single peak was assigned to the electrochemical reaction in the negative half-cell. The processes in this half-cell are slower than in the positive half-cell. The technique is beneficial to gain a fundamental understanding of the catalytic process of the V(II)/V(III) reaction to optimize novel electrode materials or monitor electrode degradation processes

Ultrastable long-distance frequency dissemination through optical fibres

Nowadays, a large number of applications require highly stable frequency dissemination, such as deep space networks for interferometric imaging with arrays formed by antennas located very far apart. To accomplish this demand for stability, optical fibre links are used due to the advantages of low cost, low attenuation, and immunity to electromagnetic interference. The system studied in this thesis guarantees a high precision among the signals of all the antennas in an array by connecting them coherently in a fibre ring architecture. Through recirculation of a phase conjugated signal, the compensation of the phase instability generated in long distance fibre links by temperature changes and vibrations of the environment is achieved. Nevertheless, the non-idealities of the system?s components may add a random effect in this phase compensation that is analysed using the Allan deviation as a metric factor, with the aim to establish the loss in stability of the frequency dissemination system.Actualmente, un gran número de aplicaciones requieren de una alta estabilidad en la propagación de frecuencia, como las redes del espacio profundo para la interferometría de imagen del cielo con agrupaciones de antenas muy separadas geográficamente. Para satisfacer esta demanda de estabilidad, se usan enlaces de fibra óptica debido a sus ventajas como el bajo precio, baja atenuación e inmunidad a la interferencia electromagnética. El sistema que se estudia en esta tesis garantiza una alta precisión entre las señales de todas las antenas de una agrupación, conectándolas de manera coherente en una arquitectura de anillo de fibra. Por medio de la recirculación de una señal conjugada en fase, se consigue la compensación de la inestabilidad de fase que se genera en los enlaces de fibra largos por los cambios de temperatura y las vibraciones del medio. Sin embargo, las no idealidades de los componentes del sistema pueden añadir un efecto aleatorio a esta compensación de fase, que se analiza usando la desviación de Allan como parámetro de medida con el objetivo de determinar las pérdidas en la estabilidad del sistema de propagación de frecuencia.Actualment, un gran nombre d?aplicacions requereixen d?una alta estabilitat en la propagació de freqüència, com les xarxes de l?espai profund per la interferometria d?imatge del cel amb agrupacions d?antenes molt allunyades geogràficament. Per satisfer aquesta demanda d?estabilitat, s?utilitzen enllaços de fibra òptica degut a avantatges com el seu baix preu, baixa atenuació i immunitat a la interferència electromagnètica. El sistema que s?estudia en aquesta tesi garanteix una alta precisió entre les senyals de totes les antenes d?una agrupació, connectant-les coherentment en una arquitectura d?anell de fibra. Per mitjà de la recirculació d?una senyal conjugada en fase, s?aconsegueix la compensació de la inestabilitat de fase que es genera als enllaços de fibra llargs pels canvis de temperatura i les vibracions del medi. Tanmateix, les no idealitats dels components del sistema poden afegir un efecte aleatori a aquesta compensació de fase, que és analitzat utilitzant la desviació d?Allan com a paràmetre de mesura amb l?objectiu de determinar les pèrdues en l?estabilitat del sistema de propagació de freqüència

How can the Norwegian Maritime Industry Successfully Work Toward Net Zero-Emission Supply Chain Operations by 2050?

Masteroppgave(MSc) in Master of Science in Supply Chain and Operations Management - Handelshøyskolen BI, 2023The shipping sector plays a vital role in the Norwegian economy and significantly contributes to international shipping. Norway's rich maritime heritage has positioned the country favorably within the shipping industry. With the growing emphasis on climate action and industries striving to reduce emissions and mitigate greenhouse gases, the shipping sector shares a collective objective of achieving as close to zero-emission as possible by 2050. The purpose of this study is to explore strategies, opportunities and factors that can facilitate the industry’s transition toward sustainability, considering the unique strengths and resources of the Norwegian maritime sector. Therefore, the research question is: How can the Norwegian maritime industry successfully work toward zero-emission supply chain operations by 2050? To answer the research question this master thesis used a qualitative research method with semi-structured interviews. Following a review on relevant literature, empirical data was collected by interviews with experts in the industry, which provided valuable insights into the industry's perspectives, experiences, and challenges related to the emerging market of zero-emission shipping. Additional information from climate and sustainability reports was gathered to examine the current situation and evaluate drivers, conditions and barriers in the market of zero-emission. Our analysis of theoretical and empirical findings shows that collaboration between stakeholders is crucial in developing a robust market and for the industry to reach their goals by 2050. The market of zero-emission shipping needs supply and demand equilibrium, leading to an increased pressure on the authorities to engage and commit in the transition with leading players to ensure products and services are effectively managed in the end. The lack of certainty and development in the zero-emission market presents challenges for companies operating in the maritime industry. However, the findings highlight the Norwegian cluster's position as a frontrunner in innovation and the Norwegian cluster showcases its commitment to achieving sustainability objectives while concurrently driving economic growth. The Norwegian maritime sector has the potential, by working closely with stakeholders in the market and leveraging the driving forces, to overcome the barriers presented, to reach their goals by 2050

Circles, columns and screenings: mapping the institutional, discursive, physical and gendered spaces of film criticism in 1940s London

This article revisits the period considered within ‘The Quality Film Adventure: British Critics and the Cinema 1942-1948’, mapping the professional cultures, working contexts and industry relationships that underpinned the aesthetic judgements and collective directions which John Ellis has observed within the critics published writings. Drawing on the records of the Critics’ Circle, Dilys Powell’s papers and Kinematograph Weekly, it explores the evolution of increasingly organised professional cultures of film criticism and film publicity, arguing that the material conditions imposed by war caused tensions between them to escalate. In the context of two major challenges to critical integrity and practice – the evidence given by British producer R.J. Minney in front of the 1948 Royal Commission on the Press and an ongoing libel case between a BBC critic and MGM – the different spaces of hospitality and film promotion became highly contested sites. This article focuses on the ways in which these spaces were characterised, used, and policed. It finds that the value and purpose of press screenings were hotly disputed and observes the way the advancement of women within one sector (film criticism) but not the other (film publicity) created particular difficulties, as key female critics avoided the more compromised masculine spaces of publicity, making them harder for publicists to reach and fuelling trade resentment. More broadly, the article asserts the need to consider film critics as geographically and culturally located audiences, who experience films as ‘professional’ viewers within extended and embodied cultures of habitual professional practice and physical space

The untapped potential of plant thin cell layers

Thin cell layers (TCLs), which contain a small number of cells or tissues, are explants excised from different organs (stems, leaves, roots, inflorescences, flowers, cotyledons, hypocotyls/epicotyls, and embryos). After almost 45 years of research, this culture system has been used for several monocotyledonous and dicotyledonous plants of commercial importance, and for model plants. The limited amount of cells in a TCL is of paramount importance because marker molecules/genes of differentiation can be easily localized in situ in the target/responsive cells. Thus, the use of TCLs has allowed, and continues to allow, for the expansion of knowledge in plant research in a practical and applied manner into the fields of tissue culture and micropropagation, cell and organ genetics, molecular biology, biochemistry, and development. Starting from a brief historical background, the actual and potential uses of the TCL system are briefly reviewed