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A numerical investigation of optimal balance for rotating shallow water flow
No full textOptimal balance is a numerical decomposition method of geophysical flows into a balanced and unbalanced components without any asymptotic analysis. It was introduced under optimal potential vorticity (PV) balance by Viúdez and Dritschel (2004) in a special semi-Lagrangian PV-based scheme. The method adiabatically deforms the nonlinear model into its linear form where mode decomposition is exact. It leads to a boundary value problem in time where gravity waves are removed at the linear end and a base-point coordinate is restored at the nonlinear end. This problem is solved by an iterative backward-forward nudging scheme. As global geophysical ocean models use primitive variables, we study optimal balance on an existing f-plane shallow water model in the primitive velocity-height variables. Our model, nevertheless, includes kinematic PV-inversion formulas if the PV is base point.
We, here, systematically investigate our numerical model for several design parameters. We found that optimal balance works with PV-based projectors which are the most robust choice with primitive variable-based projectors which are useful for general domains and global models. The PV-based projectors are the linear oblique projector and the base point PV. The linear oblique projector can be reformulated as a PDE-based projector preserving linear PV. Besides, the height field as a prominent candidate of base point and a linear PDE-based projector support more general cases.
The method returns high-quality balance with rapid convergence of the nudging scheme, but its convergence is, still, an open question. We proved the ''quasi-converge'' of the nudging iterates up to a small termination residual, and this residual is as small as the balance error which is of algebraic order in the time-separation parameter for a lower-dimensional system. Hence, optimal balance is an accurate diagnostic tool in primitive variables and can be implemented on complicated models without fundamental obstacles
Large-Scale 3D Printing - Market Analysis
No full textOne of the main problems brought by large-scale 3D printers is the lack of standardization of machines and the potential of low-quality products. If a company invests in an inexpensive 3D printer then the risk of a bad quality product increases. On the other hand, a high-end Large-scale 3D printer would cost millions of dollars to produce a trustworthy result. Regardless, the traditional manufacturing route will always be preferred by production companies. Many different 3D printers produce very different products, making there a lack of universal standards in 3D printing technologies. Therefore, manufacturers compare their products with other manufacturers' methods worrying that they would vary in terms of quality, strength, and reliability. This causes a continuous wariness in the 3D printing technology, making companies always judge the risks compared to the benefits
A Social-Cognitive Approach to the Socioeconomic Gap in Achievement: The Effects of Growing up in Economically Challenging Environment on Self-Efficacy, Problem-Focused Coping Potential and Attribution of Success and Failure
No full textDespite numerous attempts to reduce socioeconomic disparity in education, the gap in educational attainment and expectations among students with different socioeconomic backgrounds persists. This thesis is an attempt to extend our understanding of the social-psychological mechanisms that could explain this gap and inform solutions that would promote greater equality in education. It presents three manuscripts, which together propose that (1) the link between socioeconomic background and educational attainment can be explained by self-efficacy beliefs, and (2) childhood socioeconomic status and self-efficacy bias the process of judgement that precedes achievement-oriented behaviour. Building on the existing literature and research, in the first study I assess the roles of self-efficacy antecedents in the relationship between socioeconomic background and educational expectations. The findings demonstrate that self-efficacy antecedents fully explain the effects of income, social class, and primary caregiver’s education on educational expectations of students. Further, in a theoretical piece, I propose that pre-existing self-efficacy beliefs guide the selection and interpretation of the immediate information relevant in the process of appraisal of problem-focused coping potential. Finally, building on the results of the first study and the proposed theoretical framework, I test the effects of childhood status on the appraisal of coping potential and attribution of the outcome when people solve cognitive tasks. The findings demonstrate that the effect of childhood status varies across tasks with different difficulty and among people who succeeded and failed. I situate these findings within broader research on socioeconomic disparity in education and discuss their implications for theory, research, and practice
Unraveling the geological history of Chaotic terrains and Floor-Fractured Craters on Mars and the Moon
No full textFor my PhD project I investigated the surface characteristics and
tested a possible formation mechanism of two Martian chaotic terrains: Arsinoes and Pyrrhae Chaos. These regions on Mars are characterized by the disruption of the basaltic bedrock into polygonal blocks, later covered by post-collapse sedimentary units. Such investigation included spectral analyses, that revealed the occurrence of basaltic mineralogies in the bedrock and hydrated minerals within and right outside Arsinoes Chaos, structural observations, that showed a prevalence of volcano-tectonic features in the area, and morpho-stratigraphic mapping, that allowed to have a clearer view on the geological history of these two chaotic terrains. Given the paucity of aqueous-related evidence, I developed a hypothesis for the formation mechanism that generated the collapse of chaotic terrain: a piecemeal caldera collapse. This particular type of collapse, known as chaotic caldera collapse, consists of multiple cycles of inflation and deflation of a buried magma chamber, resulting in the disruption of the overlying brittle materials into polygonal blocks, bounded by intersecting radial and concentric faults. This hypothesis was tested in an analog experiment in laboratory, where the process was reproduced, and the results suggest that piecemeal caldera collapse could in fact explain the peculiar characteristics of chaotic terrains, without involving water (either liquid or ice): this would justify the formation of those chaotic terrains where outflow channels and any fluvial feature are not present, and hydrated minerals are exiguous. In the experiment, the comparison was made also with a similar type of terrain, occurring both on Mars and on the Moon (where aquifers do not exist), the Floor-Fractured craters (FFCs). The last part of my project was dedicated to structural analyses on the faults within Lunar FFCs, providing more insights on the complex geological history of these heavily fractured terrains
Delivery Applications of Cobalt Bis(dicarbollide) Clusters
No full textThis thesis focuses on the delivery applications of cobalt bis(dicarbollide) (COSANs). Inspired by the characters of COSANs which are inorganic boron-based anions and have been previously reported to permeate by themselves through lipid bilayer membranes, a propensity that is related to their superchaotropic character, we decided to study their transport ability toward different cargos, including organic oligopeptides and proteins as well as inorganic ions.
Firstly, we introduced COSANs as selective and highly efficient molecular carriers of impermeable hydrophilic oligopeptides through both artificial and cellular membranes, without causing membrane damage at micromolar carrier concentration. Importantly, cobalt bisdicarbollides transport not only arginine but also lysine peptides, while low-molecular weight analytes such as amino acids and neurotransmitters as well as neutral and anionic cargos (phalloidin and BSA) are not transported. By a combination of U-tube experiments and electrophysiology, we establish the transport is mediated by a carrier mechanism. Cellular experiments validate FITCArg8 delivery into the cytosol and nucleus by a combination of direct permeation and endocytosis.
Secondly, the ability of COSAN 2 to selectively transport different types of protein cargos into both artificial vesicles and cells has been demonstrated. Especially, isoelectric points of proteins, that is electronic interaction between COSANs and proteins, presumably were the key factor of their delivery process mediated by COSAN. In relation to the CF assay, we proved that positively charged and neutral proteins are well transported by COSAN 2 at micromolar concentration while negatively charged proteins are not transported.
Finally, we extended the application of COSANs to inorganic ion transport. pH-sensitive HPTS assay in combination with mechanism studies demonstrated that COSAN 4 exhibited the most efficient transport of Na+ and K+ flux by H+/K+ antiport mechanism
On the transport of antibiotics and ions across biological membranes through their channels
No full textDuring my Ph.D. I focused on the characterization of the biological membrane channels that are involved or interfering with the communications between the cells and the environment, or the rest of the organism. My thesis is divided in 3 parts: outer membrane proteins, cell wall channels and toxins. All the pore forming proteins were studied in electrophysiological experiments via their reconstitution into the artificial lipid bilayer.
1 In the first part we studied the transport of ions and antibiotics through the phosphate specific channels OprO and OprP expressed in the outer membrane of Pseudomonas aeruginosa. Fosmidomycin and fosfomycin are phosphonic acid containing antibiotics that we kept in consideration for our studies; they are drugs approved from the FDA very active against Gram-positive and Gram-negative bacteria and even protozoa. Then we produced and analyzed mutants of OprO affecting the lysine cluster in the periplasmic cavity of each OprO monomer. The molecular details of these mechanisms are elucidated via the computational analysis performed by Dr. Vinaya Kumar Golla from the workgroup of Professor Ulrich Kleinekathöfer.
2 In the second part we studied the cell wall channels expressed in Rhodococcus ruber and corynebacterioides. Like for all the MspA homologs, the PorARr, PorBRr, PorARc are synthetized as monomers and are able to form octamers in their active form as channels in which they can allow the passage of nutrients and secondary metabolites, such as antibiotics, driven by concentration gradient.
3 In the third part we studied 3 pore forming toxins (PFTs): the ε-Toxin and β2-Toxin from Clostridium perfringens and the LktA of Mannheimia haemolytica. Bacteria can finalize their virulence through PFTs that make large water-filled holes into the target membrane dissipating its osmotic gradient
Fostering Value Co-creation and Service Innovation on Digital Platforms
No full textDigital platforms (DPs) drastically change how users derive their value from offerings and how corporations interact with each other across fading global and organizational boundaries. The rapid development of DPs has already disrupted industries such as retail, entertainment, hospitality, transportation and fueled social and political controversies across the globe.
To evaluate the design of DPs in this thesis, I mainly rely on the concept engagement platforms (EPs). EPs are physical or virtual touchpoint designed to enable and ease the integration of resources. Thereby, co-creation of value between actors is facilitated. Such EPs utilize functionalities to attract users and build loyalty. As time and attention of users are limited, EPs providing the best fit and experience attract and bind the largest user base, thus further increasing their usefulness to users due to network effects. In an increasingly globalized and digitalized world, this leads to an increased occurrence of “winner takes all environments”. To cement their status and keep users on their EPs, platform operators implement features that constantly seek the user’s attention. Yet, these practices may impact users negatively, e.g., through addictive potential or stress.
Consequently, platform operators and designers who try to create impactful and supportive EPs should not solely focus on traditional marketing metrics, such as retention, and maximizing daily usage. Instead, understanding the intended value that users seek to derive provides more appropriate and sustainable solutions for engagement platforms users. This dissertation derives design knowledge for EPs of both the B2C and the B2B sectors. To derive design knowledge for operators and designers, this dissertation follows the Design Science Research approach to provide practitioners with actionable knowledge on how to inform platform design with insight based on the Service Logic
Synthesis and Characterization of Palladium-Containing Polyoxometalates and Polyoxometalate-Based Extended Networks
No full textPolyoxometalates (POMs) are a class of discrete, anionic and soluble polynuclear metal oxides, which are generally constructed through the connectivity between early d-block metal ions and oxo linkers. The class of polyoxopalladates(II) (POPs) as a new member of POMs were discovered in 2008. In the last 14 years, around 80 POPs of various shapes, sizes and compositions have been prepared and various properties studied, with a focus on catalysis. The focus of this thesis lies in the discovery of novel POPs and their structural as well as catalytic characterization.
Chapter 1 is an introduction of POMs and metal-organic frameworks (MOFs) including the history, structural properties, analytical techniques, properties and applications. In Chapter 2, the class of POPs and polyoxometalate-based metal organic frameworks (POM-MOFs) are presented. Chapter 3 represents the information on the instruments used for the characterization. In Chapter 4, the discovery of the large, neutral 40-palladium(II)-oxo cluster (POC) is presented and their solid state and solution characterization. In Chapter 5, tetranuclear and hexanuclear Pd-oxo units are discovered in the vanado- and chromo(V) capped-4-palladates(II), one dimeric 4-palladium-oxo cluster and a 4-Mn4(IV)O4-capped-6-palladate(II) as well as 10-vanado-14-palladate(II) were isolated and structurally characterized. Their catalytic semi-hydrogenation of 1-octyne and phenylacetylene was investigated as supported catalysts. In Chapter 6 Pd(IV)-containing POP and POM compounds were synthesized, which represents the first mix-valence POP and the tungsten analogue of the known molybdenum specie. In the second part of the work, the (4-triazole-phenyl)- arsonic acid functionalized POM like inverted-Keggin and hexamolybdates and their trasition-metals mediated extended network are discussed in Chapter 7 and Chapter 8 respectively
Synthesis of α-Fluorinated Phosphonates and Related Phosphorus (V) Compounds
No full textFor almost 40 years, difluoromethylene phosphonates – compounds of general formula RCF2P(O)(OR)2 – have attracted much interest as molecular tools to study enzymes and their behavior in biochemical processes.
First, we discuss the chemistry of difluoromethylene phosphonates through the prism of its historical development and with an emphasis on general synthetic methods, highlighting the existing challenges and unsolved problems.
We then explore the formal [3,3]-sigmatropic rearrangements of 2,3,3-trifluoroallyl phosphates leading to isomeric 1,1,2-trifluoroallyl phosphates under thermal and Lewis acid-promoted reaction conditions. Although the products of these rearrangements were unstable, the insights we gained while studying these reactions prompted us to explore similar formal [2,3]-sigmatropic rearrangements of 2,3,3-trifluoroallyl phosphorus (III) compounds.
Finally, we describe the newly developed method for the preparation of CF2–P (V) phos- phonate analogs – difluoromethylene phosphonic and phosphinic amides, and phosphine oxides. The method is based on a formal [2,3]-sigmatropic phospha-Wittig rearrangement of readily available fluoroallyl bis(amido)phosphites, amido(aryl)phosphonites and diarylphosphinites. It allows for the preparation of title compounds in a straightforward fashion on a multigram scale, complementing the existing phosphoryldifluoromethylation methods. A powerful one-pot multistep protocol has been developed based on this method. It utilizes ubiquitous starting materials, such as THP-O-protected 2,2,2-trifluoroethanol, directly furnishing phosphonic, phosphinic and phosphine oxide analogs of α,α-difluoro-β-ketophospho- nates without the need for isolation and purification of the intermediate products. Besides providing access to unique compounds hardly accessible through other routes, the developed method benefits from the fact that, unlike most other existing general methods, it does not rely on ozone-depleting HCF2Cl and CF2Br2
Variational Model Reduction for Non-hydrostatic Stratified Flows in the Mid-latitude and the Equator
No full textThis thesis studies balance models for a rotating stratified three-dimensional fluid on a tangent plane with full Coriolis force. Derivations are done for two different regions, namely mid-latitude and equator, which we considered separately. Each model is studied via a variational approach which is based on Lagrangian dynamics assuming smallness of the Rossby number and allowing for anisotropy in the horizontal length scales. We assume semigeostrophic scaling, akin to the derivation of the L 1 model by Salmon (1985) for the rotating shallow water equations. Contrary to Salmon’s derivation, we start with an arbitrary change of coordinates and then choose the transformation to fix the degeneracy on the first order of the Lagrangian, L 1, as suggested by Oliver (2006). In our setting, the full projection of the rotation vector of the Earth is considered, so that the horizontal component of the Coriolis vector is taken into account. For each model, conservation laws for the energy and the potential vorticity are valid because of the Hamiltonian structure. Our first model on f-plane is the most general model obtained so far in semi-geostrophic scaling. The other model concerns balance model on the equatorial β-plane. Under the additional assumption of construction of zero-meridional velocity as suggested by the leading order dynamics, an equatorial balance model is obtained