Structural organization found in many examples from nature provides an inspiring model of engineering to produce smart materials. This approach is based on exploiting the theme of structure-propertyrelationship to design new materials in which the applications stem from their structural aspects. The work presented in this thesis highlights this idea by exploiting diverse properties of specially designed hybrid Bragg stacks built up from different constituent polymer and nanoparticles. This thesis is a compilation of work done on a variety of multilayered systems involving their fabrication and a detailed analysis of their phononic, mechanical and magnetic properties. In particular, one-dimensional phononic crystals are studied in detail to devise ways to mold the flow of elastic energy and obtain a full description of the phononic band diagram which is instrumental in providing an insight into the fundamental concepts of heat management and acousto-optic interactions. In addition, this provides a way to manipulate and control the propagation of elastic waves in periodic materials.
A number of experimental techniques can be used to characterize the microdomain structure of multiphase polymers at molecular level. They include, for example, transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), fluorescence spectroscopy, and solid state NMR spectroscopy. Among the available techniques, the solid state NMR became an extremely powerful and useful analytical tool for such characterizations in the last few decades. The power of this technique lies in its ability to obtain various kind of information by simply combining different NMR techniques. In particular, it can probe the microphase separation and extract domain thickness with the help of spin-diffusion experiments. These type of experiments in which the proton magnetisation is selectively suppressed in one of the phases with the help of dipolar filters 27-30 and then allowed to re-equilibrate due to a dipolar mediated flip-flop process were successfully applied to various type of systems including polyolefins 24 , nylon fibres 29,30 , block copolymers 29-32 , but also much more complex systems such as confined biomolecules. 33 Generally, the estimated domain sizes by the proton spin- diffusion agree very well with those estimated by X-ray. 24
recent report , where pure phases were reported for up to y = 0.3, nevertheless the given reflection profiles of the diffraction patterns are comparable to the one of the samples reported here. The deviations of lattice parameters are small and there are only Pawley-fit refinements, structure refinements were not carried out. It is well possible that the single phase refinements were done using broader reflections and slightly different lattice parameters. Samples synthesized with nominal compositions of y ≥ 0.1 showed a mixture of two phases, namely, HTB-I (W 5+ is partially replaced) and HTB-II m (W 5+ is more or less fully replaced, oxidized phase, m = mixed phase appearance), both of which conform the space group P6 3 22. The
The term ‘polymer-based nanocomposites’ refers to the group of polymer- inorganic hybrid materials containing two or more phases, in which at least one of them is in the nanometer scale. During the past decades, the research on polymer-based nanocomposites attracts tremendous attention for their various applications not only in the field of conventional engineering, but increasingly also in the fields of microelectronics, organic batteries, optics and catalysis. Related to the small size of the filler particles, polymer-based nanocomposites exhibit remarkable property improvements such as enhanced tensile properties, reduced gas permeability, reduced solvent uptake and improved thermal stability, when compared to conventional polymer-filler composites. In order to design new nanocomposites with desirable properties, an explicit under- standing of the structure-propertyrelationship of the polymer-nanofiller system is required. Many research groups have attributed the obtained improvements on material properties to the extremely high surface to volume ratio of the nanofillers (see Chapter 1).
Keywords: antimicrobial polymers; functional polyethers; structure-propertyrelationship; multifunctional polyglycidol; post-polymerization functionalization
Contamination by microorganisms such as bacteria, fungi, and algae is a key issue in medicine , pharmaceutical production , water purification systems , food packaging , and various other fields [5,6]. Artificial materials lack defense against microbial growth, allowing microbes to attach to the surface and form a biofilm . One way to prevent the biofilm formation is the usage of disinfectants to keep the surface sterile. Common disinfectants include low molecular weight substances such as alcohols, aldehydes, quaternary ammonium compounds, silver compounds, peroxygens, and bisphenols . However, these classes of antimicrobial substances need to be applied regularly, leading to the development of resistance in the microbial strains . Another way to prevent microbial growth is the coating of surfaces with antimicrobial substances that either kill microorganisms on contact or repel the attachment of microbes . Nevertheless, the leaching of biocides from those coatings causes the same previously mentioned problems. An attractive alternative to low molecular weight biocides are antimicrobial polymers, because they are non-volatile, chemically stable, and can be used as non-releasing additives . These polymers are prepared either by (co-)polymerization of functionalized monomers or by post-polymerization functionalization . Though, the antimicrobial properties are derived from a variety of functionalities such as biguanides [13,14], benzoate esters and benzaldehydes , or poly(acrylic acid) , the most common active moieties are based on a combination of quaternary ammonium, pyridinium, or phosphonium groups and hydrophobic functionalities [17–19]. The proposed and commonly accepted mechanism for these types of polymers
Produktionstechnik) eine Anpassung der Produktions verhältnisse (der Property Rights) erzwingt. Hierbei ver sucht man zu zeigen, wie Veränderungen der relativen Faktorknappheit und/oder der Transaktions- und Pro duktionstechnik über ihre Allokations-, Distributions- und Innovationsergebnisse auf den gesamten institutio neilen Rahmen von Wirtschaft und Gesellschaft zurück wirken. Modifizierte Nutzenfunktionen und Transak tionskosten verändern Verhaltensweisen, die ihrerseits neue Allokations- und Verteilungswirkungen und neue Produktions- und Transaktionstechniken hervorbrin gen. In dieser Anwendung wird die Property-Rights- Anaiyse zu einem methodischen Grundkonzept für die Wirtschaftsgeschichte, zu einer allgemeinen Entwick lungstheorie, mit deren Hilfe z. B. zu erklären versucht wird, wieso es in Europa (und da wiederum gerade in England) zur Herausbildung kapitalistischer Strukturen und durch diese zur industriellen Revolution kam. Gleichzeitig wird dabei der Frage nachgegangen, war um frühere Wirtschaftsgesellschaften den von ihnen produzierten Überschuß nicht in einer derart wirksa men, wohistandsfördernden Weise produktiv zu absor bieren willens oder in der Lage waren.
Third, we were unable to match the CD and control groups on IQ in the main analysis. However, because both CD groups in this study had lower IQs compared to controls, IQ differ- ences cannot explain the observed sex-by-diagnosis in- teractions. Fourth, controlling for comorbid disorders reduced the signiଏcance of some of the results. It may be informative for future studies to explicitly investigate the impact of these variables, ideally by comparing CD in- dividuals with versus without comorbidity, or by including a psychiatric control group. Fifth, by design, we matched our groups on pubertal development to reduce the possibility of group or sex differences in brain developmental stages. 72 However, we note that the relationship between pubertal stage and brain development may differ by sex. Future ana- lyses of data from younger children, as well as longitudinal imaging data, are needed to investigate whether the results reported here are stable across development. Finally, using the number of CD symptoms as a measure of severity is suboptimal, as these symptoms are not equivalent to each other, for example, weapon use versus lying.
cortical thickness and surface area and altered gyriﬁcation in frontal and temporal regions in adolescents with conduct disorder (CD). Although there is evidence that the clinical phenotype of CD differs between males and fe- males, no studies have examined whether such sex dif- ferences extend to cortical and subcortical structure. Method: As part of a European multisite study (Fem- NAT-CD), structural magnetic resonance imaging (MRI) data were collected from 48 female and 48 male participants with CD and from 104 sex-, age-, and pubertal-statusmatched controls (14–18 years of age). Data were analyzed using surface-based morphometry, testing for effects of sex, diagnosis, and sex-by-diagnosis interactions, while controlling for age, IQ, scan site, and total gray matter volume.
Received: 5 August 2020; Accepted: 3 September 2020; Published: 4 September 2020 Abstract: When in a particular scientific field, major progress is rapidly reached after a long period of relative stand-still, this is often achieved by the development or exploitation of new techniques and methods. A striking example is the new insights brought into the understanding of the gating mechanism of the transient receptor potential melastatin type 2 cation channel (TRPM2) by cryogenic electron microscopy structure analysis. When conventional methods are complemented by new ones, it is quite natural that established researchers are not fully familiar with the possibilities and limitations of the new method. On the other hand, newcomers may need some assistance in perceiving the previous knowledge in detail; they may not realize that some of their interpretations are at odds with previous results and need refinement. This may in turn trigger further studies with new and promising perspectives, combining the promises of several methodological approaches. With this review, I aim to give a comprehensive overview on functional data of several orthologous of TRPM2 that are nicely explained by structural studies. Moreover, I wish to point out some functional contradictions raised by the structural data. Finally, some open questions and some lines of possible future experimental approaches shall be discussed.
identified in the in silico studies . As seen in figure 1.8, these oxygen entry pathways are close to the active site. Hence, apart from the long range structural changes, another possible reason for the effect of the two mutations (E573Q, I342F) on the activity of ECAO in spite of these being 20-30 ˚ A from the active site can be that these mutations affect the dynamics of the enzyme. This change in dynamics may affect the trafficking of molecular oxygen in E573Q mutant in such a way that its entry channel is blocked leading to inactivation of ECAO. In order to understand the influence of the two mutations on the structure which can then be correlated with the function and hence the change in the activity of ECAO, the X-ray structures of single (E573Q) and double (E573Q/I342F) mutants of ECAO were solved . Surprisingly, no major structural changes were observed in the two mutants. Some of the subtle changes include the change in the side chain conformation of the residue MET-699 which maybe related to hindrance of the pathway of molecular oxygen entry as MET-699 is in close proximity to one of the oxygen entry channels. It was also found that the water which replaces the calcium ion bound in wild-type enzyme is present only in subunit A and not in B. To summarize, the subtle structural changes in the two mutants were insufficient to explain the effect of the mutations on the activity of ECAO. This effect can be attributed either to the changes in long-range electrostatic interactions resulting in the alteration of the protonation state of TPQ or the associated residues, hence inaccessible to X-ray crystallography or to the change in structural dynamics of the enzyme resulting in altered conformational sampling either of the residues involved in O 2 or amine entry channel or those involved in the
These results are in good agreement with the insights obtained from the X-ray crystal structure of MraY from Aquifex aeolicus in complex with muraymycin D2 7 [ 22 , 23 ] (vide supra, Figure 2 ). The well-defined binding pocket for the uracil base indeed seems to preclude the introduction of substituents into this moiety. In the case of 5-fluoro substitution, it is not fully clear though if the loss of inhibitory activity is a result of steric hindrance or electronic effects (with respect to the strong electron-withdrawing nature of fluorine). Key interactions in the uracil binding pocket include hydrogen bonding with Lys70, Asp196, and Asn255 (Figure 2 ). The formation and/or strength of these hydrogen bonds might be hampered by the electron deficiency of the 5-fluorouracil moiety. The non-aromatic nucleobase in analogue 16 is probably not sterically hindered, but cannot undergo the same π–π interaction with Phe262 as uracil, thus resulting in a moderate loss of activity. However, the retention of inhibitory activity for 2 0 -deoxy congener 14 could also be predicted from the X-ray crystal structure as it had indicated no obvious interaction of the 2 0 -hydroxy group (vide supra, Figure 2 ). Overall, our findings demonstrate that X-ray crystal structures of MraY-inhibitor complexes appear to be excellent starting points for the structure-based design of new inhibitors, at the very least with respect to variations in the uridine-derived core unit.
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focused on the formation of the scales of butterflies, which are closely related to weevil scales and often display vivid colors as well. In butterfly scales, it is known that similar inner lattice structures only start to form after the formation of external structures (lower and upper lamina, ridges and ribs) is finished (Ghiradella, 1989). Under the assumption that the formation of 3D lattice structures in the scales of E. imperialis is similar to the one of butterfly scales, this structured core is most probably formed after the formation of the shell and thus belongs to the procuticle. The observation of chitin-protein fibrils inside the struts of the core would directly prove the assignment of the core to procuticle. Fibrils have been described in the outer lamina or the inner structures during the development of the scales of moths (Overton, 1966) and butterflies (Ghiradella, 1989), but were not distinguishable in TEM micrographs of the cross section of scales from E. imperialis (Wilts et al., 2011). The observations on mechanically fractured (Fig. 6.2.2) or polished (Fig. 6.2.4) and FIB polished (Fig. 6.2.7) surfaces of the core show no indication of fibrillar structures. However, even if there are fibrils, whose center to center spacing of the constituting chitin rods is normally about 6 nm (Neville, 1975), they are most probably obscured because of the coating (2-3 nm) or the drying effect during the SEM observation and become undistinguishable. Therefore, additional characterization methods, such as TEM, X-ray analysis, and Raman spectroscopy are needed to further elucidate the chemical nature of the core and thus provide information for the determination of the refractive index of this optically active structure.
The aggregation number, i.e. the number of surfactants making up a micelle, is a structurally relevant parameter which contains indirect information on the micelle size and shape. The aggregation number is known to be affected by the chemical nature of the surfactant, its concentration , the temperature [38-41] and the addition of electrolytes [39, 42-44] or organic compounds [45-48]. Many methods can be used to determine the aggregation numbers , for instance, static light scattering (SLS), small angle neutron scattering (SANS) or fluorescence probing techniques. Light scattering requires extrapolation to low concentrations, close to the CMC (owing to intermicellar interactions) [50-51]. But by decreasing the concentration, the micelle size is possibly modified, as it is concentration dependent in most surfactant systems. Moreover, exploratory static light scattering measurements performed on micellar solutions of the surfactant dimer EO-2 (in analogy to experiments reported in reference ) were unsuccessful as the intensities were too low for reliable analysis. Likewise, small angle neutron scattering (at high scattering vectors) allows the determination of micelle aggregation numbers and also yields information on the micelle shape in the actual experimental conditions . Nevertheless, neutron scattering is very costly and the facilities are not generally available. Most problems evoked before can be avoided by using fluorescence probing methods [12, 33, 53-59]. This determination is affected neither by intermicellar interactions nor by the micellar shape. However, the fluorescence probes (and other necessary additives, such as quenchers) must be chosen carefully, and their concentration must be kept very low, in order to avoid possible changes of the micelle structure induced by the probe.
These patents didn’t sound like something people had made up in a pub, but struck me much more like the description of something that someone had seen that was already out there working. This was almost unprecedented. As has been known forever amongst people in the intellectual property world: most patents applied for and granted describe things that are both obvious, and not possible to make, things that are so baroque in their strange combinations, but so quotidian in their applications, that they must have involved intoxicants and a major triumph of hope over sense and sensibility. I’m not proud or prejudiced, but to be honest, I was only doing this job because it paid the rent while I felt in the force.
tions in linolenic acid content and fluorescence in duction in vivo .
Calculations in  propose that in appressed re gions, there is a minimum set-up of acyl lipids which favour energy transfer between pigment protein complexes. All our data suggest that the am ount of linolenic acid in glycolipids is strongly correlated (significance 0.1—5% ) with excitation, trapping and dissipation of both PS II and PS I, with grouping of PS II-LH C-units, but not with spillover. From these findings we conclude that a relationship exists be tween the structural organization of the lipid matrix and the functional state of energy distribution in thylakoids.
The data available for Czechoslovakia during the period of Communist rule are limited to political risk indexes held by private rating agencies PRS Group (dataset ICRG) and BERI (dataset HRRP).
The data from the International Country Risk Guide (ICRG) are among the most com- monly used in economic literature approximating property rights protection and the institutional environment in general (Adámek, 2014). Both indexes provide annual political risk ratings. The ICRG data are available for the period beginning 1984 for eight countries of the Eastern Bloc, while the BERI data start in 1980 and include four of the countries, including Czechoslovakia. These ratings are not based on an analysis of formal provisions, but rather reflect the real behaviour of the authorities in power (Glaeser, La Porta, Lopez-de-Silanes, & Shleifer, 2004), i.e. de facto institutions. Although these indexes are standardly used, they often meet with justified criticism. The data are expert ratings, and the methods used for their calculation are not publicly avail- able, which calls their credibility into question. Furthermore, Jellema & Roland (2011) assess the ICRG time series data as “suspiciously volatile” (e.g. see the IPI index in Figure 1 3 ). This claim must be regarded as fundamental. The institutional environment is generally considered to be a very stable variable and thus the volatility of these indi- cators may suggest an inappropriate proxy was used for the institutional environment. On the other hand, the higher volatility in the ICRG data seems to have a significant effect on the real economy (Berggren, Bergh, & Bjørnskov, 2012, 2015; Mikula, 2011). This, on the contrary would be proof of its credibility. The relatively volatile behaviour of the ICRG data stands in direct contrast to the very stable BERI time series (see Fig- ure 2).
A plate-like, porous structure of the calcined 0.75% Pd/ZnO sample with crystallite diameters of about 40 nm can be observed in the SEM micrograph presented in figure 3.5a. The HAADF-STEM image of the same sample after reduction in hydrogen atmosphere at 323 K is presented in figure 3.5b. In that mode, it is possible to distinguish the metallic palladium from the oxide support due to its much higher atomic number. The particles are depicted as bright grey spheres with almost uniform size in the image and are homogeneously distributed. The size of about 2-3 nm for the lowest loading confirms the CO-chemisorption results, presented in table 3.1. Since the size and distribution of the palladium particles in that sample was found to be appropriate to study the processes previously discovered by the TPR and catalytic measurements in greater detail, some amount of the sample has been reduced at 623 K in 5% CO/Ar gas mixture, similar to the kinetic experiment (Fig. 3.3) and transferred to the TEM without air-contact. Figure 3.5 c-e presents a series of images taken from one specific region of the sample, where a palladium particle in exposed position at the support surface could be found. By variation of the focus of the microscope, we were able to identify a zinc oxide over-layer covering the palladium particle as well as parts of the support. That would be an explanation for the further decrease in activity found in the kinetic studies in that state. A slight astigmatism might also be present in panels c-e. Though it was not possible to directly study the PdZn lattice parameter by microscopy, according to our XRD-experiments and supported by the kinetic studies, such small Pd particles should be alloyed already almost completely. Based on that observation we propose a model scheme in figure 3.5f, where the palladium after 623 K reduction is present as PdZn, covered by a partially reduced ZnO x
2.1 Principle of the Direct Methanol Fuel Cell
The fuel cell is an electrochemical device that converts chemical energy into electricity and heat without combustion. Alike batteries, fuel cells contain electrodes, an electrolyte and positive and negative terminals. In contrast to batteries, the chemical energy is not stored in the cell. Instead of this, the chemical energy in form of the fuel and the oxidant are continuously fed to the fuel cell and converted into electricity. The process of the conversion continues as long as the fuel and the oxidant are fed to the system. All fuel cells have the same basic operating principle and structure. As shown in Fig. 2-1, fuel cells consist of an electrolyte material, which is sandwiched between two thin porous electrodes, the anode and the cathode. The fuel is electrochemically oxidized in the porous anode and the oxidant is electrochemically reduced in the cathode. Because the cathode potential established by the oxidant reaction is more positive than the anode potential, the electrons delivered by the fuel are flowing through an external circuit from the anode to the cathode. The electrical current can be utilized by connecting an electrical load. If a proton conducting electrolyte is used, the protons formed by the fuel oxidation migrate through the electrolyte from the anode to the cathode. At the cathode, the protons recombine with oxygen to form water as a reaction product. If a hydrocarbon fuel is used, carbon dioxide is formed at the anode. Depending on the fuel, the oxidant and the electrolyte, different chemical reactions will occur. In the case of