Fak. 2 Mathematik und Naturwissenschaften

1815 Items

Recent Submissions
Property-performance correlations in the oxidative coupling of methane

Wang, Huan (2018)

The oxidative coupling of methane is a “dream reaction” in heterogeneous catalysis to achieve direct conversion for natural gas towards value-added and easily transportable C2 products with high economic relevance. Although extensive academic papers and patents have been reported over the last three decades, no economically viable industrial-scale application is yet achieved because of the limi...

Enzymes as modular catalysts for redox halfreactions in H2-powered chemical synthesis: from biology to technology

Reeve, Holly A. ; Ash, Philip A. ; Park, HyunSeo ; Huang, Ailun ; Posidias, Michalis ; Tomlinson, Chloe ; Lenz, Oliver ; Vincent, Kylie A. (2017-01-06)

The present study considers the ways in which redox enzyme modules are coupled in living cells for linking reductive and oxidative half-reactions, and then reviews examples in which this concept can be exploited technologically in applications of coupled enzyme pairs. We discuss many examples in which enzymes are interfaced with electronically conductive particles to build up heterogeneous cata...

Facile Control over the Supramolecular Ordering of Selfassembled Peptide Scaffolds by Simultaneous Assembly with a Polysacharride

Li, Rui ; Boyd-Moss, Mitchell ; Long, Benjamin ; Martel, Anne ; Parnell, Andrew ; Dennison, Andrew J. C. ; Barrow, Colin J. ; Nisbet, David R. ; Williams, Richard J. (2017-07-06)

Enabling control over macromolecular ordering and the spatial distribution of structures formed via the mechanisms of molecular self-assembly is a challenge that could yield a range of new functional materials. In particular, using the self-assembly of minimalist peptides, to drive the incorporation of large complex molecules will allow a functionalization strategy for the next generation of bi...

Enantioselektive Reduktionen mit Ru–S-Komplexen und Untersuchung der zugrundeliegenden Mechanismen

Bähr, Susanne (2018)

Die vorliegende Dissertation widmet sich der Synthese und Charakterisierung chiraler, kationischer Ruthenium(II)-Thiolatkomplexe und deren Anwendung in enantioselektiven Reduktionen. Die Aufklärung der Mechanismen dieser katalytischen Umsetzungen ist ein weiterer Schwerpunkt. Der erste Teil der Arbeit besteht in der mechanistischen Aufklärung der zuvor entwickelten 1,4-Hydrosilylierung von Py...

Growth and characterization of antimony-based quantum dots in GaP matrix for nanomemories

Sala, Elisa Maddalena (2018)

Self-assembled Quantum Dots (QDs) have recently attracted great attention for enabling a novel type of non-volatile electronic nanomemory, the QD-Flash. Such a memory architecture represents the ultimate memory cell, exhibiting endurance and fast access times (~ns). To ensure non-volatile operation, the storage time for carriers has to be of the order of 10 years (or longer) at room temperature...

Stable marriage and roommates problems with restricted edges: complexity and approximability

Cseh, Ágnes ; Manlove, David F. (2016-04-16)

In the Stable Marriage and Roommates problems, a set of agents is given, each of them having a strictly ordered preference list over some or all of the other agents. A matching is a set of disjoint pairs of mutually acceptable agents. If any two agents mutually prefer each other to their partner, then they block the matching, otherwise, the matching is said to be stable. We investigate the comp...

Tropicalization of del Pezzo surfaces

Ren, Qingchun ; Shaw, Kristin ; Sturmfels, Bernd (2016-03-30)

We determine the tropicalizations of very affine surfaces over a valued field that are obtained from del Pezzo surfaces of degree 5, 4 and 3 by removing their (-1)-curves. On these tropical surfaces, the boundary divisors are represented by trees at infinity. These trees are glued together according to the Petersen, Clebsch and Schläfli graphs, respectively. There are 27 trees on each tropical ...

Investigating the trimethylaluminium/water ALD process on mesoporous silica by in situ gravimetric monitoring

Strempel, Verena E. ; Knemeyer, Kristian ; Naumann d’Alnoncourt, Raoul ; Rosowski, Frank (2018-05-24)

A low amount of AlOx was successfully deposited on an unordered, mesoporous SiO2 powder using 1–3 ALD (Atomic Layer Deposition) cycles of trimethylaluminium and water. The process was realized in a self-built ALD setup featuring a microbalanceand a fixed particle bed. The reactor temperature was varied between 75, 120, and 200 °C. The self-limiting nature of the deposition was verified by in si...

Presolving techniques and linear relaxations for cumulative scheduling

Heinz, Stefan (2018)

In the mathematical optimization community the term scheduling usually describes the computation of a sequential plan for a set of jobs w.r.t. a set of side conditions such as precedence constraints and resource restrictions. Thereby, a certain objective should be fulfilled which can be for example to minimize the latest completion time of all jobs. The sequential plan can be an ordering of the...

On the dimension of posets with cover graphs of treewidth 2

Joret, Gwenael ; Micek, Piotr ; Trotter, William T. ; Wang, Ruidong ; Wiechert, Veit (2016-06-01)

In 1977, Trotter and Moore proved that a poset has dimension at most 3 whenever its cover graph is a forest, or equivalently, has treewidth at most 1. On the other hand, a well-known construction of Kelly shows that there are posets of arbitrarily large dimension whose cover graphs have treewidth 3. In this paper we focus on the boundary case of treewidth 2. It was recently shown that the dimen...

Simulating the complex cell design of Trypanosoma brucei and its motility

Alizadehrad, Davod ; Krüger, Timothy ; Engstler, Markus ; Stark, Holger (2015)

The flagellate Trypanosoma brucei, which causes the sleeping sickness when infecting a mammalian host, goes through an intricate life cycle. It has a rather complex propulsion mechanism and swims in diverse microenvironments. These continuously exert selective pressure, to which the trypanosome adjusts with its architecture and behavior. As a result, the trypanosome assumes a diversity of compl...

Higher alcohol synthesis over Rh catalysts: conditioning of Rh/N-CNTs by Co and Mn entrapped in the support

Xie, Zailai ; Frank, Benjamin ; Huang, Xing ; Schlögl, Robert ; Trunschke, Annette (2016-10-13)

Rh nanoparticles supported on commercial non-purified N-doped CNTs (NCNTs) containing residual CNT growth catalyst have been studied in hydrogenation of CO to higher alcohols. It has been found that Co and Mn residues in NCNTs are not inert, but change the catalyst under reaction conditions and efficiently promote the catalyst resulting in both increasing activity and selectivity to C2+ alcohol...

Matchings with lower quotas: algorithms and complexity

Arulselvan, Ashwin ; Cseh, Ágnes ; Groß, Martin ; Manlove, David F. ; Matuschke, Jannik (2016-11-21)

We study a natural generalization of the maximum weight many-to-one matching problem. We are given an undirected bipartite graph G=(A∪˙P,E) with weights on the edges in E, and with lower and upper quotas on the vertices in P. We seek a maximum weight many-to-one matching satisfying two sets of constraints: vertices in A are incident to at most one matching edge, while vertices in P are either u...

Deliquescence‐induced wetting and RSL‐like darkening of a Mars analogue soil containing various perchlorate and chloride salts

Heinz, Jacob ; Schulze‐Makuch, Dirk ; Kounaves, Samuel P. (2016-05-13)

Recurring slope lineae (RSL) are flow‐like features on Mars characterized by a local darkening of the soil thought to be generated by the formation and flow of liquid brines. One possible mechanism responsible for forming these brines could be the deliquescence of salts present in the Martian soil. We show that the JSC Mars‐1a analogue soil undergoes a darkening process when salts dispersed in ...

A small-angle neutron scattering environment for in-situ observation of chemical processes

Hayward, Dominic W. ; Chiappisi, Leonardo ; Prévost, Sylvain ; Schweins, Ralf ; Gradzielski, Michael (2018-05-08)

A new sample environment for the observation of ongoing chemical reactions is introduced for small-angle neutron scattering (SANS) experiments which enables structural changes to be followed continuously across a wide Q-range in response to changes in the chemical environment. The approach is demonstrated and validated by performing single and multiple potentiometric titrations on an aqueous an...

Algorithm and mechanism design for congested networks

Bjelde, Antje (2018)

We are tackling the problem of reducing high congestion in networks from a mathematical point of view. First, we consider resource allocation problems where a set of commodities jointly uses a set of resources. The feasible allocations for each commodity are a commodity specific set of subsets of resources. The cost of each resource is determined by a polynomial function with maximum degree d...

Photo- and thermo-responsive poly (ethylene glycol)-based biomaterials

Rahman, Rahima (2018)

Chemically incorporated azobenzenes (AZO) with in a matrix can generate multi-responsive materials that exhibit both temperature and light responsivity; hence act as multi-responsive system. The main aim of the work presented here was to design novel multi-responsive gels having chemically crosslinked azobenzene moiety incorporated into Poly (Ethylene Glycol) (PEG) matrix. The chemically bonded...

Low frequency dynamics of the nitrogenase MoFe protein via femtosecond pump probe spectroscopy

Maiuri, Margherita ; Delfino, Ines ; Cerullo, Giulio ; Manzoni, Cristian ; Pelmenschikov, Vladimir ; Guo, Yisong ; Wang, Hongxin ; Gee, Leland B. ; Dapper, Christie H. ; Newton, William E. ; Cramer, Stephen P. (2015)

We have used femtosecond pump-probe spectroscopy (FPPS) to study the FeMo-cofactor within the nitrogenase (N2ase) MoFe protein from Azotobacter vinelandii. A sub-20-fs visible laser pulse was used to pump the sample to an excited electronic state, and a second sub-10-fs pulse was used to probe changes in transmission as a function of probe wavelength and delay time. The excited protein relaxes ...

Dendronylation: Residue-specific chemoselective attachment of oligoglycerol dendrimers on proteins with noncanonical amino acids

Ma, Ying ; Thota, Bala N. S. ; Haag, Rainer ; Budisa, Nediljko (2015)

Polyglycerol dendrimers as an important class of polymeric materials especially attractive for covalent attachment to therapeutic proteins as a useful alternative to traditional PEGylation procedures. Herein, we combine in vivo noncanonical amino acid (ncAA) incorporation and chemoselective conjugation in vitro to produce novel hybrid protein–dendrimer conjugates with the defined architectures....

Spectroelectrochemical study of biomolecules in artificial membrane systems

Gonzalez, Barbara Daiana (2018)

This work presents a spectroeletrochemical approach combining electrochemical impedance spectroscopy (EIS) and surface-enhanced infrared absorption (SEIRA) spectroscopy to characterise the interaction of proteins and peptides with model membranes. The artificial membrane systems are assembled on a nanostructured Au-film, which is deposited on an attenuated total reflectance (ATR) crystal as a p...