Block copolymer derived three-dimensional ordered hybrid materials for energy storage and conversion

In this thesis, block copolymers are used to rationally structure inorganic and hybrid materials into ordered, percolating nanostructures. The tunability of the microstructure, chemical composition, and porosity is explored and correlated with the materials’ performance in energy storage and conversion applications. Dense and thick mesoporous TiO2/C hybrid monoliths were prepared by co-assembly with a triblock copolymer and characterized as potential lithium ion battery anodes. The structure-directing polymer was carbonized to retain a thin conductive carbon layer at the electrolyte|electrode interface that increases the intrinsic conductivity of the active material. Polymer electrolytes were prepared by tailoring the individual blocks of the block copolymer. A minor conductive block decoupled ionic mobility from slow polymer relaxation, while sufficient mechanical stability was provided by covalently linked, mechanically stronger, insulating blocks. This combination overcomes a common trade-off between high conductivity and strength. Photocatalysis requires direct access of reactants and incident photons to a catalysts’ surface. The final part of the thesis shows that complete thermal removal of the template can create a mesoporous inorganic percolating network. Structuring the catalyst in this way improved the efficiency of photocatalysis as it combines high pore diffusibility with improved charge carrier transport properties.Diese Doktorarbeit untersucht die Herstellung hochgeordneter, perkolierender Nanostrukturen mittels Blockcopolymeren und diskutiert deren Einfluss auf die Leistungsfähigkeit darauf basierender Materialien in Anwendungen der modernen Energiespeicherung und –umwandlung. In einer ersten Studie wurden mesoporöse, monolithische TiO2/C-Hybride mittels eines Triblockcopolymers hergestellt und als Lithium-Ionen-Batterieanode getestet. Die Karbonisierung des strukturgebenden Polymers ergab eine leitfähige Kohlenstoffschicht an der Grenzfläche zum Elektrolyten und erhöhte so die intrinsische Leitfähigkeit. Einzelne Polymerblöcke wurden optimiert, um makroskopische Eigenschaften von Polymerelektrolyten unabhängig voneinander einzustellen. Eine besonders kleine, leitfähige Komponente erlaubte die Entkopplung der ionischen Leitfähigkeit von der Kettenmobilität, während kovalent gebundene, isolierenden Blöcke gleichzeitig hohe mechanische Stabilität gewährleisteten. Der verbreitete Widerspruch zwischen hoher Leitfähigkeit und Stabilität dieser Materialklasse konnte so vermieden werden. Photokatalyse erfordert direkten Zugang der Reaktanden und der Ladungsträger zur katalytisch aktiven Oberfläche. Im letzten Teil der Arbeit wird gezeigt, dass die Entfernung des strukturgebenden Polymers zu mesoporösen, perkolierenden, anorganischen Netzwerken führte. Diese erhöhten die Effizienz der Photokatalyse, da verbesserte Porendiffusivität und hohe Ladungsträgermobilitäten kombiniert wurden

Information Systems Success - A Quantitative Literature Review and Comparison

Despite the outstanding economic relevance of information systems in business and society, there exists no consensus among academics and practitioners how to measure the success of information systems. Therefore this paper makes a contribution to structure and classify the most recent research in IS success. This is done by providing an exhaustive overview of literature in the field of IS success capturing the empirical and non-empirical publications between 2007 and 2011. With regard to theoretical foundation, object of analysis, unit of analysis, evaluation perspective, data gathering method, and data analysis, 26 empirical articles are classified. The 11 non-empirical studies are classified by theoretical foundation, methodological type and object of analysis. The results show that in most cases a type of IT or IT application is investigated by applying the DeLone and McLean IS success model. Most of the studies focus on IS users and the individual perspective of analysis, whereas the most prominent data analysis method is structural equation modeling

User-centered design of power tools: a generic process for evaluation of usability aspects [Die Nutzerzentrierte Produktentwicklung von Power-Tools: Ein generischer Prozess zur Untersuchung von Usability-Aspekten]

User-centered design focuses on the individual needs of the product users. The aim is to adjust the design of the product according to the requirements of the user and application. Existing methods for evaluation of the perceived usability are often limited to one specific aspect, and it requires a high effort to transfer the respective method to other aspects. A generic process for the evaluation of the perceived usability is missing. This paper presents the generic Usability Study Evaluation Process (USE-Process) that helps product designers to identify and evaluate usability aspects relevant to the suitability of the usage of a product. The process is divided into three sections: 1. A structured field study to identify the relevant usability aspects; 2. A generic study design for the subjective evaluation of usability aspects under objective and reproducible conditions; 3. The use of measurement tools that help to quantify the results of the subjective evaluation. The generic applicability of the process is shown by the example of the evaluation of cordless screwdrivers; several usability aspects were identified, clustered, and evaluated by using subjective evaluation methods and measurement techniques

Identifying Gene Clusters by Discovering Common Intervals in Indeterminate Strings

Dörr D, Stoye J, Böcker S, Jahn K. Identifying Gene Clusters by Discovering Common Intervals in Indeterminate Strings. BMC Genomics. 2014;15(Suppl. 6: Proc. of RECOMB-CG 2014): S2.Background: Comparative analyses of chromosomal gene orders are successfully used to predict gene clusters in bacterial and fungal genomes. Present models for detecting sets of co-localized genes in chromosomal sequences require prior knowledge of gene family assignments of genes in the dataset of interest. These families are often computationally predicted on the basis of sequence similarity or higher order features of gene products. Errors introduced in this process amplify in subsequent gene order analyses and thus may deteriorate gene cluster prediction. Results: In this work, we present a new dynamic model and efficient computational approaches for gene cluster prediction suitable in scenarios ranging from traditional gene family-based gene cluster prediction, via multiple conflicting gene family annotations, to gene family-free analysis, in which gene clusters are predicted solely on the basis of a pairwise similarity measure of the genes of different genomes. We evaluate our gene family-free model against a gene family-based model on a dataset of 93 bacterial genomes. Conclusions: Our model is able to detect gene clusters that would be also detected with well-established gene family-based approaches. Moreover, we show that it is able to detect conserved regions which are missed by gene family-based methods due to wrong or deficient gene family assignments

Ice flow and the conditions of the ice-bed interface at the onset of the Northeast Greenland Ice Stream

The Northeast Greenland Ice Stream (NEGIS) is an important dynamic component contributing to the total mass balance of the Greenland ice sheet, as it reaches up to the central divide and drains 12% of the ice sheet. The ice stream geometry and surface velocities in the onset region of the NEGIS are not yet sufficiently well reproduced by ice sheet models. We present an assessment of the basal conditions of the onset region in a systematic analysis of airborne ultra-wideband radar data. Our data yield a new detailed model of ice-thickness distribution and basal topography in the upstream part of the ice stream. We observe a change from a smooth to a rougher bed where the ice stream widens from 10 to 60 km, and a distinct roughness anisotropy, indicating a preferred orientation of subglacial structures. The observation of off-nadir reflections that are symmetrical to the bed reflection in the radargrams suggests that these structures are elongated subglacial landforms, which in turn indicate potential streamlining of the bed. Together with basal water routing pathways, our observations hint to two different zones in this part of the NEGIS: an accelerating and smooth upstream region, which is collecting water, with reduced basal traction, and in the further downstream part, where the ice stream is slowing down and is widening, with a distribution of basal water towards the shear margins. Our findings support the hypothesis that the NEGIS is strongly interconnected to the subglacial water system in its onset region, but also to the subglacial substrate and morphology

Ordered Mesoporous TiO2 Gyroids: Effects of Pore Architecture and Nb-Doping on Photocatalytic Hydrogen Evolution under UV and Visible Irradiation

Pure and Nb-doped TiO2 photocatalysts with highly ordered alternating gyroid architecture and well-controllable mesopore size of 15 nm via co-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) block copolymer are synthesized. A combined effort by electron microscopy, X-ray scattering, photoluminescence, X-ray photoelectron spectroscopy, Raman spectroscopy, and density functional theory simulations reveals that the addition of small amounts of Nb results in the substitution of Ti4+ with isolated Nb5+ species that introduces inter-bandgap states, while at high concentrations, Nb prefers to cluster forming shallow trap states within the conduction band minimum of TiO2. The gyroidal photocatalysts are remarkably active toward hydrogen evolution under UV and visible light due to the open 3D network, where large mesopores ensure efficient pore diffusion and high photon harvesting. The gyroids yield unprecedented high evolution rates beyond 1000 µmol h−1 (per 10 mg catalyst), outperforming even the benchmark P25-TiO2 more than fivefold. Under UV light, the Nb-doping reduces the activity due to the introduction of charge recombination centers, while the activity in the visible triple upon incorporation is owed to a more efficient absorption due to inter-bandgap states. This unique pore architecture may further offer hitherto undiscovered optical benefits to photocatalysis, related to chiral and metamaterial-like behavior, which will stimulate further studies focusing on novel light–matter interactions

Correlates of Adverse Outcomes in Abdominally Obese Individuals: Findings from the Five-Year Followup of the Population-Based Study of Health in Pomerania

Background. Abdominal obesity is a major risk factor of cardiovascular disease (CVD), type 2 diabetes (T2DM), and premature death. However, it has not been resolved which factors predispose for the development of these adverse obesity-related outcomes in otherwise healthy individuals with abdominal obesity. Methods. We studied 1,506 abdominal obese individuals (waist-to-height ratio (WHtR) ≥ 0.5) free of CVD or T2DM from the population-based Study of Health in Pomerania and assessed the incidence of CVD or T2DM after a five-year followup. Logistic regression models were adjusted for major cardiovascular risk factors and liver, kidney diseases, and sociodemographic status. Results. During follow-up time, we observed 114 and 136 new T2DM and CVD cases, respectively. Regression models identified age, waist circumference, serum glucose, and liver disease as predictors of T2DM. Regarding CVD, only age, unemployment, and a divorced or widowed marital status were significantly associated with incident CVD. In this subgroup of obese individuals blood pressure, serum glucose, or lipids did not influence incidence of T2DM or CVD. Conclusion. We identified various factors associated with an increased risk of incident T2DM and CVD among abdominally obese individuals. These findings may improve the detection of high-risk individuals and help to advance prevention strategies in abdominal obesity

Mitoxantrone Induces Natural Killer Cell Maturation in Patients with Secondary Progressive Multiple Sclerosis

Mitoxantrone is one of the few drugs approved for the treatment of progressive multiple sclerosis (MS). However, the prolonged use of this potent immunosuppressive agent is limited by the appearance of severe side effects. Apart from its general cytotoxic effect, the mode of action of mitoxantrone on the immune system is poorly understood. Thus, to develop safe therapeutic approaches for patients with progressive MS, it is essential to elucidate how mitoxantrone exerts it benefits. Accordingly, we initiated a prospective single-arm open-label study with 19 secondary progressive MS patients. We investigated long-term effects of mitoxantrone on patient peripheral immune subsets using flow cytometry. While we corroborate that mitoxantrone persistently suppresses B cells in vivo, we show for the first time that treatment led to an enrichment of neutrophils and immunomodulatory CD8low T cells. Moreover, sustained mitoxantrone applications promoted not only persistent NK cell enrichment but also NK cell maturation. Importantly, this mitoxantrone-induced NK cell maturation was seen only in patients that showed a clinical response to treatment. Our data emphasize the complex immunomodulatory role of mitoxantrone, which may account for its benefit in MS. In particular, these results highlight the contribution of NK cells to mitoxantrone efficacy in progressive MS