Signal structure: from manifolds to molecules and structured sparsity

Atom lithography is a technique to structure layers of atoms during deposition, using interactions of near-resonant light fields with neutral atoms. The basic scheme uses a standing wave light field, aligned just above a substrate, while a beam of atoms impinges perpendicularly on the standing wave light field. The interaction of the light field and the atoms focuses the atoms towards the crests or troughs of the standing wave intensity, dependent on the tuning of the light field. The focused atoms are subsequently deposited on the substrate, resulting in an array of lines, whose periodicity is determined by the wavelength of the light field. The standing wave light field can therefore be seen as an array of lenses, focusing the atom beam into an array of lines. The first experiments on atom lithography were performed in the 1990s with sodium and chromium. In this thesis experiments with iron are described, which is a magnetic element and thus allows for the creation of magnetic nanostructures. To focus atom beams into structures using atom lithography, well-colimated atom beams are required. The most common technique to create collimated atom beams is transverse laser cooling, but iron has no closed optical transition suitable for laser cooling. Fortunately Smeets and Te Sligte found that even then atom lithography of iron is possible. If the standing wave light field is considered to be an array of lenses, the focusing of the atom beam on a single lens is determined by the local collimation of the atom beam at that position. This local collimation is determined by the geometry of the beam source and the distance of the beam source to the standing wave lens. Using a small beam source (e.g. 1 mm diameter) positioned far from the standing wave (e.g. 1 m), the geometrically collimated atom beam is suitable for atom lithography. Chapter 3 shows what the implications of geometric collimation are on the structure formation in atom lithography. The geometric effects that locally collimate the atom beam on the sample also introduce local offset angles of the atom beam with respect to the focusing light field. Structure formation has been observed with lines of up to 7 nm high on a background layer of 15 nm average height, over areas of up to 400 µm × 6 mm. This indicates that the offset angles can vary over an 8 mrad range, which is more than an order of magnitude larger than the local angle of collimation. The offset angle influence the local geometry of the deposited structures: an increasing offset angle decreases the local line height, increases the width and creates a skewness in the local line shape. The local geometry of the lines has been modelled with a Monte Carlo particle tracking model and the results were compared to experiments. It was found that the highest and narrowest lines suffer from significant broadening due to surface diffusion in experiments, limiting the achievable structure width of iron on SiOx samples to about 80 nm. We have also found that in atom lithography without laser cooling, each standing wave lens is effectively imaging the source geometry onto the substrate. We therefore propose using structured atom beam sources to image more complex patterns on sub-wavelength scales in a parallel way. The reason to use iron in atom lithography, is the option to create magnetic nanostructures. However, in previous experiments no clear magnetic signature of the atom lithographic structuring of iron was found. Therefore in Chapter 4 firstly the magnetic properties of unstructured layers of iron (Fe), nickel (Ni) and FexNi1-x are investigated. These layers are all ferromagnetic, but with a reduced magnetic moment compared to bulk values due to contaminations and crystal growth effects. As a reference for periodic atom lithography structures, periodic line structures are created with interference lithography in a polymer layer and onto these structures thin layers of FexNi1-x are shadow deposited, thereby creating a layer periodically modulated in both height and elemental composition. This periodic modulation in composition has been observed with SEM-EDX on sub-micron scales. The structures showed a clear magnetic anisotropy with an easy axis along the direction of the lines, in accordance with expectations. In Chapter 5, the magnetic properties of atom lithographic iron line structures are presented. Using MOKE microscopy, direct comparison of structured and unstructured parts of a sample is possible, which allows for the observation of clear magnetic signatures due to the atom lithographic structuring. In layers of an average thickness of about 15 nm, no anisotropy is induced by the line structures, while a magnetic easy axis along the direction of the lines is expected. The line structures introduce an isotropic increase in the coercivity of the layers, indicating that the line structures can be considered as isotropic corrugations instead of directional line structures. For layers of 30 nm average thickness and thus higher line structures, a clear magnetic anisotropy is observed for the highest line structures. This anisotropy can be seen as a magnetic easy axis along the direction of the lines, as expected for line structures. However, we also observe a sharp increase in coercivity for applied fields perpendicular to the lines. This phenomenon is intriguing and may be explained by a pinning of head-to-head domain walls along the direction of the lines. In Chapter 5, we also report on the first results of co-deposition of FexNi1-x, where the Fe is structured into lines using atom lithography, while the Ni is deposited uniformly, thereby creating an alloy of modulating composition. Magnetic analysis of these structures indicates that these structures are anisotropic, both the coercivity and the shape of domain walls is dependent on the angle of the applied field relative to the line structures. Finally in Chapter 6, we investigate the possibilities to focus a thermal beam of atoms into a single 100 nm spot using light fields, thereby creating a nanopencil suitable for deposition of nanostructures. A Monte Carlo particle tracking program was developed to model the all optical focusing or funneling of 10 µm sized atom beams to a 100 nm spot. This model included effects of initial beam divergence, magnetic substructure, laser cooling, and spontaneous as well as stimulated diffusion and it was applied to a number of promising light field configurations. The best results obtained for experimentally realistic settings are a beam focused to a full width at half maximum of FWHM = 0.55 µm in a blue detuned hollow beam where atoms are focused towards the dark center, or a FWHM = 0.31 µm in a red detuned axicon light field, where atoms are focused towards the maximum intensity at the heart line. However, in the latter case the focused beam has a flux only 25 times larger than the background flux, which is unpractical for applications. The limiting factors of all schemes are heating due to stimulated diffusion and the limited interaction time available for a thermal beam of atoms. A nanopencil could be possible if it were based on the focussing of a slow and / or monochromatic atom beam, but this would seriously complicate the practical application of such a device.

Owing to their high surface area, excellent electrolyte permeability and ample diffusion pathways for charge transport, porous and hollow-structured electrochemically active materials attract more attention as the electrodes. In general, the process of template preparation method is used to achieve hollow structured materials over the last few decades. However, the complicated preparation process including removal of template and surface modification often results in poor uniformity, low reproducibility, and high cost of porous structure. Moreover, it incorporates functional chemicals with specific homogeneity and dispersity into the hollow porous intercrystalline structure. These problems hinder the development and application in energy storage and conversion devices of the diversified porous and hollow-structured materials. The metal-organic frameworks (MOFs), consisting of organic linkers and coordinated inorganic clusters, appear as an excellent collection of porous crystal material series with high surface areas, high porosity, and tunable structures. However, their low conductivity and electrolyte instability limit the further use of MOFs in the field of LIBs. Recently, how electrode materials for Lithium–ion batteries (LIBs) are designed and prepare using MOFs has attracted more attention. The composite materials derived from MOFs including nanostructured porous carbons and metal oxide uaing self-sacrificial template synthetic route not only solves the problem of low conductivity but also maintains the high surface area and porous structure of MOFs, providing abundant active sites for insertion/deinsertion or adsorption/desorption; Furthermore, composite materials derived from MOFs increase the complexity of nanostructures in terms of structural units and chemical components. In particular, large pore volume and open pore structure are critical to loading guest species, accommodating mechanical strains and facilitating mass transport. In this paper, we briefly examined the production of MOF-derived materials for applications in LIBs. The optimization and modification of an MOFs morphology were implemented according to the electrode material requirement for LIBs. Moreover, the preparation of MOFs-derived electrode materials with porous, hollow, or complicated construction and their effects on electrochemical performance were described. Finally, the challenge and trend in production of electrode materials derived from MOFs were analyzed.

The advent of gravitational wave (GW) astronomy has provided a new window through which to view and understand the Universe. To fully exploit the potential of GW astronomy, an understanding of all the potential electromagnetic counterparts to a gravitational wave detected source will help maximise the science returns. Here I present a study of the electromagnetic emission from relativistic jets that accompany the merger of binary neutron stars or black hole-neutron star systems. These counterparts provide a probe for the structure and dynamics of these relativistic outflows. Binary neutron star, or neutron star-black hole, mergers are thought to be the dominant progenitor of short gamma-ray bursts (GRBs). Here we investigate the possibility that there is a hidden population of low-Lorentz factor jets resulting in failed GRBs, on-axis orphan afterglows, and what kind of counterparts can be expected given a merger-jet population dominated by these failed-GRB jets. I find that for GW detected mergers, ∼ 80% of the population of on-axis events may result in a failed GRB afterglow. The afterglow of a failed GRB is characterised by the lack of any prompt emission; where the γ-rays are emitted within an optically thick region of the low-Lorentz factor (Γ) outflow and significant suppression via pair production and a high opacity results in the photons coupled to the pair plasma. This plasma will undergo adiabatic expansion, and the photons will decouple at the photospheric radius. The energy in the prompt photons, for a sufficiently low-Γ outflow, will have been significantly suppressed. GW detected mergers have a Malmquist bias towards on-axis events (i.e. the rotational axis of the system), where the peak of the probability distribution is an inclination ∼ 30⁰. If the jets from these mergers have an intrinsic structure out to wider angles, then the majority of mergers will be accompanied by electromagnetic counterparts from these various jet structures. By making some simple assumptions about the energetic structure of a jet outside of a bright core region, the various temporal features that result from a given jet structure can be predicted. Where the population of merger jets is dominated by a single structure model, I show the expected fractions of optical counterparts brighter than m_AB = 21. On 17 August 2017, the Light Interferometer Gravitational Wave Observatory (LIGO) in collaboration with Virgo detected the merger of a binary neutron star system. Various electromagnetic counterparts were detected: the GRB 170817A by Fermi/GBM and INTEGRAL; an optical, blue to red, macro/kilo-nova from ∼ 1/2 day post merger to ∼ 5 − 10 days; and a brightening radio, and X-ray counterpart from ∼ 10 days. Optical detection of this counterpart at a magnitude ∼ 26 was made at ∼ 100 days post-merger. Analysis of this counterpart is consistent with the afterglow of a Gaussian structured jet viewed at the system inclination, ∼ 18 ± 8⁰. If all short GRB jets have a similar jet structure, then the rates of orphan afterglows in deep drilling blind surveys e.g. the Large Synoptic Survey Telescope (LSST), will be higher than those expected from a homogeneous, or ‘top-hat’ jet, population. The rates for the various jet structures for orphan afterglows from mergers are discussed, showing that for a population of failed GRBs, or an intrinsic Gaussian structure, an excess in the orphan rate may be apparent. Understanding the dynamics and structure for the jets from black-hole systems born at the merger of a compact binary can help give clues as to the nature of jets from black holes on all scales. As an aside, I show empirically that regardless of black hole mass or system phenomenology, the relativistic jets from such systems share a universal scaling for the jet power and emitted γ-ray luminosity. This scaling could be due to the similar efficiencies of various processes, or alternatively, the scaling may be able to give insights into the emission and physical processes that are responsible for high-energy photons from these outflows. GW astronomy offers a probe of the most extreme relativistic outflows in the Universe, GRBs. The predicted electromagnetic counterparts from these outflows, in association with GW detections, provides a way to probe the Lorentz-factor distribution for merger-jets. Additionally, the phenomenological shape of the afterglows, at various inclinations, gives an indication of the intrinsic structure of these jets. An understanding of these dynamical and structural qualities can be used to constrain the parent population, merger rates, and binary evolution models for compact binary systems.

Laminate zeolite structure prepared using papermaking techniques for carbon dioxide capture: synthesis, characterisation and performance

State-of-the-art data analysis tools have to deal with high-dimensional data. Fortunately, the inherent dimensionality of data is often much smaller, as it has an internal structure limiting its degrees of freedom. In most cases, this structure can be approximated using a graph, i.e, a set of nodes connected by edges. Based on this idea, graphs have been largely used in semi-supervised and unsupervised learning. The canonical assumption when incorporating a graph prior is to assume that the signal is smooth with respect to the graph, i.e, that connected pieces of data have similar values. Nevertheless, this hypothesis is insufficient to characterize more complex relations between the data and its structure, the graph. To this end, the field of Graph Signal Processing (GSP) extends the graph smoothness hypothesis to a more general assumption. Its key idea is to think of the signal as a sum of harmonic modes, which are obtained from the eigen-decomposition of the Laplacian, an operator representing the second order derivative. Thus, the essence of GSP resides in the Fourier transform defined by the projection on the Laplacian eigenvectors basis, which allows us to filter graph signals. However, GSP suffers from a counterintuitive irregularity. Contrarily to the classical Fourier basis, the graph Laplacian eigenvectors are not spreading uniformly on the vertex set and can be highly concentrated in a region of the graph. This non-uniformity results in a lack of any intuitive translation operator and consequently poses challenges to generalize some of the classical signal processing theory, e.g., stationarity, uncertainty principles, or sampling. In this thesis, we answer these difficulties by accepting that each node is unique and should be treated specially according to its surrounding structure. This is achieved using an operator called localization that shifts a kernel defined in the spectral domain around a specific node while adapting to the local graph structure. In the first part of the thesis, we focus on harmonic analysis in GSP. We start by making use of the norm of localized kernels to capture the spectral local features of the graph vertices. To illustrate the relevance of this analysis we then introduce structural clustering, an algorithm that groups nodes according to the role they play in the graph. Then, we bound the vertex-frequency concentration of graph filter banks atoms. Because of the irregular structure of graphs, we construct a local uncertainty principle that is, again, driven by the norm of a localized kernel. In the second part of the thesis, we tackle GSP problems from a machine learning perspective. We use the localization operator to extend the notion of stationarity to graph signals. It consists of a graph signal probabilistic framework allowing us to optimally solve inverse problems. Finally, we show how the graph total variation can be used in semi-supervised learning and prove its consistency with respect to the underlying graph manifold.

Paroxysmal Atrial Fibrillation (PAF) is a kind of accidental arrhythmia, and its high missed detection rate leads to the increase of heart-related diseases. An automatic detection method is proposed based on kernel sparse coding, which can identify PAF attacks based only on short RR interval data. A special geometric structure is presented to analyze the high-dimensional characteristics of the data, and the covariance matrix is calculated as a feature descriptor to find the Riemannian manifold structure contained in the data; Based on the Log-Euclidean framework, a manifold method is used to map the manifold space to a high-dimensional renewable kernel Hilbert space to obtain a more accurate sparse representation to identify quickly PAF. After verification by the Massa-chusetts Institute of Technology-Beth Israel Hospital atrial fibrillation database, the sensitivity is 98.71%, the specificity is 98.43%, and the total accuracy rate is 98.57%. Therefore, this study has a substantial improvement in the detection of transient PAF and shows good potential for clinical monitoring and treatment.

This thesis describes the extension of the coordination chemistry of triazacyclohexanes to new copper complexes and to new ligands with similar coordination geometry, i.e. the orthoamides 13-alkyl-1,5,9-triazatricyclo[7.3.1.05,13 ]-tridecanes (RTATC) and unsymmetrically substituted triazacyclohexanes. By treatment of the literature known [TATC]+ cation with Li, Na, or K alkylating reagents several new RTATC (R = Ph, Bz, CH2SiMe3, 4-Bu-PhCH2) have been prepared and characterized. With these and the previously known ligands HTATC and MeTATC complexes of Cr(III), Fe(III), Cu(II), and Zn(II) have been made and their properties have been compared with those of the analogous 1,3,5-trialkyl-1,3,5-triazacyclohexane (R3TAC) complexes. It shows that the structural, chemical, and physical properties of the RTATC complexes are quite similar to those of the R3TAC complexes. [(R3TAC)Cu(PPh3)]BF4 complexes with R = iPr, Bz, Cy, and (S)-PhMeCH have been prepared and characterized. The Cu(I) complexes are diamagnetic and therefore ideal for NMR spectroscopical analysis. The η3-coordination of the ligand can be deduced from the discrimination of the endoand exo-protons of the TACring, which are in fast exchange in the free ligand. From the form of the ring signals a more symmetrical η3-coordination for the Pr3TAC complex and a slightly distorted η3-coordination for the Bz3TAC complex can be expected. This could be verified by x-ray crystal structures of both complexes. A new Cu(II) complex was found when excess Me3TAC was reacted with CuCl2: (Me3TAC)2CuCl2. The unusual coordination geometry leads to a slow reduction to Cu(I). A crystal structure of the reduction product revealed an unusual [Cu2Cl4] 2−. It shows the first Cu-Cu cuprophilic interaction in an anion which must be stronger than the electrostatic repulsion within the dianion. Synthesis of triazacyclohexanes with a mixture of two amines in a suitable solvent such as ethanol or exploitation of equilibria between R3TAC and R ′NH2 above 100 ◦C yields mixtures of unsymmetrically substituted R2R′TAC which could be separated by various methods below 100◦C. The pure and dry unsymmetrical R2R′TAC are stable at room temperature and even at higher temperatures for short periods and can best be identified by their very characteristic 13C NMR signals for the ring carbon atoms. This way a couple of examples for basically three different types of unsymmetrically substituted R2R′TAC could be prepared: simple R2R′TAC with small hydrocarbon substituents (Me2BzTAC, Me2OctTAC), R2(R′X)TAC with a substituent bearing a functional group (Me2(EtOH)TAC, Me2(EtCN)TAC), and two triazacyclohexanes linked by a short bridge R2TAC-R’-R2TAC (Me2TAC-CH2PhCH2Me2TAC), Bu2TAC-CH2PhCH2Bu2TAC).

Fiber-reinforced polymer (FRP) composites offer several advantages in relation to traditional materials, such as high specific strength, good corrosion resistance, low thermal conductivity and rapid component installation. Despite the great potential of these materials, two major disadvantages limit their acceptance in civil engineering applications: their lack of inherent ductility and the fact that their fibrous and anisotropic character makes the joining of structural components difficult. The purposes of this research are to develop ductile structures using brittle all-FRP materials and to provide a corresponding design method assuring robustness and structural safety. The proposed concept for all-FRP structures incorporates system ductility through the use of ductile, adhesively-bonded joints and redundant (statically indeterminate) structural systems. The concept envisages adhesives with an initially elastic behavior sufficiently stiff to meet short- and long-term serviceability requirements. When serviceability and ultimate loads are exceeded, however, adhesive behavior should change and become plastic, or at least highly non-linear inelastic, with much lower stiffness. The ductile connections effect a favorable redistribution of internal and external forces in the redundant system in the same way as plastic hinges in statically indeterminate systems with ductile materials. In case of joint failure, the redundant system allows the creation of alternative load paths and redistribution of section forces preventing structural collapse. Numerical and experimental investigations of adhesively-bonded double-lap joints demonstrate that using an appropriate bilinear adhesive is more advantageous than using a traditional structural and stiff epoxy adhesive. These investigations show that ductile adhesives generate a linear axial strain distribution and consequently a constant shear stress distribution along the overlap. Numerical and analytical modelings are validated with experimental results. The numerical modeling allows evaluation of the effect of ductile adhesive behavior on joint behavior and establishment of recommendations for the selection of adhesive mechanical properties, according to serviceability and failure limit state requirements. Based on numerical modeling results, joints can also be classified according to stiffness (stiff or flexible). An analytical model, based on numerical and experimental results, is developed for predicting joint stiffness when using ductile adhesives, assuming that the adhesive deforms only and uniformly in shear and that adherends deform only in tension. The design method is developed in accordance with the new structural concept and Eurocode design philosophy. It is based on both numerical and analytical model results for adhesively-bonded double-lap joints. A case study illustrating the adhesively-bonded joint design and appropriate adhesive selection is carried out on continuous beams with adhesively-bonded joints at mid-support. Corresponding bending experiments on beams with ductile, adhesively-bonded connections demonstrate the new structural concept's feasibility and validate the proposed design method. An energy factor defined as the ultimate strength to serviceability limit state energy ratio is proposed to quantify and compare the robustness and safety of structures built from both ductile and brittle materials.

A central problem in the study of autonomous cooperating systems is that of how to establish mechanisms for controlling the interactions between different parts (which are called agents) of the system. One way to integrate such mechanisms into a multi-agent system is to exploit the technique of cooperation or negotiation protocols. In a protocol we distinguish to essential layers: the communication layer specifying the possible flow of messages between different agents, and the decision layer, which controls the selection of a message (speech-act) that the agent sends in a specific situation. In this report we first give a short introduction of our agent model InteRRap which provides the basis for the modeling of the different scenarios considered in the AKA-Mod project at the DFKI. The techniques we will discuss in the following are located in the plan based component and in the cooperation component of this model. The domain of application is the MARS scenario (Modeling a Multi-Agent Scenario for Shipping Companies) which implements a group of shipping companies whose goal it is to deliver a set of dynamically given orders, satisfying a set of given time and/or cost constraints. The complexity of the orders may exceed the capacities of a single company. Therefore, cooperation between companies is required in order to achieve the goal in a satisfactory way. This domain is of considerable interest for studies with economical background as well as for research projects. We give a short summary of results from economical studies that are concerned with the real-world situation in Germany in the transportation domain. They show the need for the development of new techniques from the field of computer science to tackle the problems therein. Then, an overview on related research is presented. Two approaches are discussed in more detail: the first one being based on OR-techniques and a second one being based on the concept of partial intelligent agents attempting to integrate techniques from OR and DAI. Both approaches are concerned with the situation in a single company. However, our purpose to handle the case of distributed shipping companies requires additional mechanisms, e.g. to cope with the problems of task allocation and task decomposition in multi-agent systems. Mechanisms for distributed task decomposition and task allocation processes in multi-agent systems belong to the core of our studies. Therefore, we will first discuss techniques for these problems in a general setting and then describe their implementations in the MARS system. In this description, particular emphasis is placed on the cooperation within a shipping company. Here, one company agent has to allocate a set of orders its truck agents. The truck agents support the company agents by giving cost estimations based on their route planning facility. Thus, this procedure provides the basis for the decisions of the company agents and is discussed in very detail. Finally, we present results from a series of benchmark tests. The test sets have also been run with OR-implementations and thus, give us the opportunity to compare our implementation against these approaches.

Selection experiments have frequently been used to optimize or alter the functions of biopolymers and have also proven useful for discerning biopolymer structure. Just as covariations observed in ribosomal RNA phylogeny may pinpoint Watson-Crick base pairs, sequence information recovered from in vitro and in vivo selection experiments can be used to establish and refine the structure of natural and unnatural nucleic acids. For example, RNA molecules selected from partially or completely randomized pools typically fall into a limited number of sequence families; the relationships within and between these families constitute an artificial phylogeny in which relationships are based on function rather than history. Nevertheless, comparative sequence analysis can still be used to identify what portions of primary sequence are essential for function, which residues potentially pair with one another, whether base pairs act as structural stabilizers or contribute directly to function, and even where tertiary structural interactions may occur. Such results can be combined to generate artificial evolutionary models for RNA structure. Although crystal or nuclear magnetic resonance (NMR) structures of molecules provide much greater spatial detail, evolutionary studies delve into function as well as structure and can provide insights into how structures may change through time. Evolutionary models can complement more physical determinations: For example, a detailed knowledge of the structure of rRNA or HIV-1 reverse transcriptase can reveal why particular mutations impart resistance to drugs such as streptomycin or AZT, but cannot yet be used to predict all mutations that will lead to drug resistance. In contrast, selection...

Italian has five epistemic forms that can be considered as grammaticalized, at least to an extent: the epistemic future, the indicative and the conditional forms of dovere (MUST); the indicative and the conditional forms of potere (CAN). This article studies the semantic oppositions between such forms, with a twofold objective: to describe the internal structure of the epistemic domain in Italian and to characterize it typologically. The Italian epistemic domain appears to be structured around three axes: the gradation of certainty, the opposition between preminently deontic and preminently epistemic meanings, the opposition between epistemic/evidential and genuinely epistemic meanings. The structure of Italian epistemic domain is characterized according to four typological parameters relevant for the semantic classification of epistemic systems. This typological characterization highlights the peculiar complexity of the relationship between epistemicity and evidentiality in Italian, and suggests interesting differences between Italian and other European languages

Detailed knowledge of the structure of bio molecules with atomic resolution is essential for the understanding of their function. Moreover the identification and quantification of their dynamic processes are important, as they are the origin of molecular functionalities. Different spectroscopic methods like X-ray crystallography (limited to structure elucidation, no dynamics), mass spectroscopy, electron spin resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy can deliver this detailed structural information. Especially NMR spectroscopy has found its application in the identification of dynamic processes. This thesis was focused on the characterization of dynamic processes, the structure elucidation of natural products available in nanograms and the synthesis of lanthanide chelating tags for the study of protein-ligand and protein-protein interactions in solution. The thesis is divided into three chapters addressing a specific task of the mentioned topic. A: The influences of different donors and linkers on lanthanide chelating tags were investigated. A 4S-Tetramethylcyclen was used as enantiomerically pure core molecule. The side chains were based on enantiopure lactic acid derivatives. The carboxylic acids of lactic acid were transformed into different functional groups like thiols, nitrogens, and carbonyl. These different donor groups are expected to change the magnetic susceptibility tensor of the lanthanide cation in complex with the synthesized tags. Special protection protocols for the introduction of heteroatoms are presented. On this basis also two new linkers were introduced. These linkers bind in a selective way to cysteins on a protein surface as thioethers. The alpha-bromoketones are very selective for the coupling to cysteins, nevertheless they have a tendency to hydrolyse under Lewis acidic conditions. Vinylsulfones require harsher tagging conditions but they are much more stable against hydrolysis. All new tags were attached to proteins and tested as PCS reagents in protein NMR spectroscopy. B: The effects of para-substituents on the rotation barrier of 2,2«-propyl and 2,2«-butyl-bridged biphenyls were studied by dynamic NMR spectroscopy and dynamic HPLC measurements. Gibbs free activation energies of the rotation about the central biphenyl bond were estimated by variable temperature 1H-NMR experiments for the propyl bridged biphenyl. The resulting data were correlated to Hammett-parameters ?P as a measure of electron donor and acceptor strength. It was demonstrated that the electronic effects influence the activation barrier significantly, whereas sterics had only minor influence. Rate constants were calculated from line shape analysis and analysed by Eyring plots to calculate the entropic and enthalpic contributions. Thermodynamic data for the butyl-bridged biphenyls were directly obtained from dynamic HPLC chromatograms. DFT calculations delivered different transition states for the two series of biphenyls. The calculation of the activation parameters showed a similar trend and therefore the model is validated. The differences in the enthalpic and entropic contributions between HPLC, NMR and DFT calculations are method dependent, which was proven by changes of the solvent in NMR experiments that led to alteration of these contributions. C: The identification and total synthesis of a novel methylated lipid antigen (mLPA) was performed. The presented mLPA shows potent inhibition properties against human leukaemia. A combination of extraction protocols, activation essays and HPLC-MS measurements were used to identify the different antigen molecules from cell extracts. Three different candidates were identified. MS-MS experiments delivered structural insights, which were further confirmed by NMR spectroscopy and allowed the characterization of two of these structures. Total syntheses of the identified structures were performed in 6 linear steps. The high biological activity of the synthesized structures corroborated the identity of the active molecule.

The structure of the monomeric insulin analogue des(B26—B30) insulin is presented.; A detailed comparison with the 2Zn insulin structures shows that while there are some large changes in the structure, the basic secondary structural units maintain their integrity. The DPI structure is broadly similar to molecule Ⅰ in the 2Zn structure, and in this respect is like other crystal forms of insulin. In addition to changes on the surface of the structure there are some subtle but extensive changes in the heart of the molecule. The molecules are closely packed in the crystal with many and varied contacts, including a complex network of protein-cadmium interactions and a considerable number of water mediated contacts. The molecular surface has an unusually large number of hydrophobic groups which tend to cluster in a thick band running around the protein. The crystal structure is well ordered, indeed the clarity of some side chains and the definition of the water molecules is superior to that found in the more liquid rhombohedral crystals of 2Zn insulin hexamers.

Molecular self-assembly at metal surfaces has been recognized as an efficient strategy to create supramolecular nanoarchitectures with promising functionalities. The focus of this thesis lies on the strong electron accepting molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ). The self-assembly of TCNQ and metal-TCNQ coordination networks on metal surfaces were investigated. The structural formation is directed by non-covalent interactions. By controlling fabrication parameters, surface coordination nanostructures with different chemical composition or molecular packing have been synthesized and characterized by scanning tunneling microscopy (STM). The electronic and magnetic properties of the surface organic or metal-organic nanostructures were studied by a combination of x-ray absorption spectroscopy (XAS) and x-ray photoelectron spectroscopy (XPS). The thesis is organized into three parts. In the first part, the self-assembly of TCNQ molecules on Cu(100) and Ag(100) surfaces will be discussed. The two substrates provide different chemical environments as exhibited by the surface mobility of TCNQ. Charge transfer from either Cu(100) or Ag(100) substrate induces conformational bending of the -C≡N cyano groups of TCNQ, which consequently facilitates the bonding of molecules to surfaces via nitrogen lone pairs. As shown by density functional theory (DFT) calculations, on Cu(100), the substrate-cyano interaction leads to local substrate reconstructions at the proximity of cyano groups. These charge-transfer induced structural modifications at the TCNQ/Cu(100) interface and the electrostatic interaction between molecules determine the self-assembly of TCNQ into long-range ordered domains. The adsorption and self-assembly of TCNQ on Ag(100) is presumably governed by a similar mechanism as concluded from the molecular packing and charge transfer phenomenon. In the second part of this thesis, the fabrication of MTCNQx (M = Mn, Fe, Co, and Ni) coordination complexes on metal surfaces is presented. The molecular adsorption geometry in all structures indicates the participation of the cyano-substrate interaction in determining the final structures, except the x = 1 case in which all cyano groups are coordinated to metal adatoms. The competition between the coordination of TCNQ to metal adatom and TCNQ to substrate is shown by the growth phenomena on the Cu(100) and Ag(100) substrates. The weaker substrate interaction provided by the Ag(100) substrate results in multiple ordered phases (x = 1, 2, or 4), in contrast to the single ordered x = 2 phase on Cu(100). The MTCNQ2 networks synthesized on both substrates are isostructural apart from a rotation of the network orientation to adapt the substrate periodicities. This highlights the importance of the substrate lattice in guiding the growth of supramolecular networks as well as the robust intra-network interaction to obtain a stable structure. The inherent chemical reactivity of Mn, Fe, Co and Ni atoms, which can be further modified upon adsorption due to substrate hybridization, strongly influences the resultant coordination structures. In addition to metal coordination, hydrogen bonding also plays a role in the stabilization of metal-TCNQ networks. Adjusting the substrate temperature has been an important and effective method to tune the interplay between adsorbate-adsorbate and adsorbate-substrate interactions. These experiments provide a systematic investigation on the formation of metal-TCNQ coordination structures on metal surfaces. In the last part of this thesis, the electronic and magnetic properties of the MTCNQx complexes on metal surfaces will be discussed. XPS measurements and DFT calculations show that both the substrate and metal coordination atoms contribute to the electron donation to TCNQ molecules. The magnetic properties of the metal coordination centers were studied in x-ray magnetic circular dichroism (XMCD) measurements. The Mn centers are found to be paramagnetic from 300 K to 8 K. The Mn-coordinated networks represent ordered arrays of magnetic atoms carrying a high spin moment of S = 5/2. In the case of Ni-coordinated networks, the magnetism of Ni centers is induced by TCNQ coordination and dehybridization from the substrate. These results show the interesting physical phenomena emerging in two-dimensional metal-organic coordination systems.

Protein adsorption at oil-water interfaces interfacial structure and function of proteins in emulsions