Cyclic Expansion/Compression of the Air–Liquid Interface as a Simple Method to Produce Silk Fibers

Self‐assembly of recombinant spider silk protein at air–liquid interfaces is used as a starting point to produce homogeneous fiber bundles. The film that is formed on a silk protein solution in a vertically placed syringe is subjected to repeated controlled extension and compression by an oscillating vertical motion. Thereby, a precise breakup of the film can be achieved, followed by transport and roll‐up against the syringe wall prior to extraction. Advantages of the method are that it 1) is simple to use; 2) requires a small volume of protein solution (1 mL) at relatively low concentration (1 mg mL^?1); 3) can be performed under sterile conditions; 4) does not require any use of coagulants; and 5) is compatible with the addition of viable cells during the process, which thereby are integrated uniformly throughout the fiber.     

Binding geometry and photophysical properties of DNA-threading binuclear ruthenium complexes

The DNA binding conformation and the photophysical properties of the semiflexible binuclear ruthenium complex [micro-bidppz(phen)4Ru2]4+ (2) were studied with optical spectroscopy and compared to the rigid, planar homologue in syn conformation [micro-dtpf(phen)4Ru2]4+ (3) and the parent "light-switch" complex [Ru(phen)2dppz]2+ (1). Comparison of calculated and observed absorption bands of the bridging ligand, bidppz, confirm earlier suggestions that 2 is significantly nonplanar, both free in solution and when intercalated into poly(dAdT)2, but the conclusion that the intercalated conformation is an anti rotamer is not substantiated by comparison of linear and circular dichroism spectra of 2 and 3. The behavior of the emission quantum yield as a function of temperature is similar for the two binuclear complexes 2 and 3 in different protic solvents, and a quantitative analysis suggests that, in solution, the solvent is more strongly hydrogen bonded to the excited state of 2 than to 1. However, the observation that for 2 the radiative rate constant increases to a value similar to 1 upon intercalation into DNA suggests that the difference between 1 and 2 in accepting hydrogen bonds is less pronounced when intercalated.     

Synthesis and evaluation of 2-(2-fluoro-4-hydroxymethyl-5-methoxy-phenoxy)acetic acid as a linker in solid-phase synthesis monitored by gel-phase (19)F NMR spectroscopy

Gel-phase (19)F NMR spectroscopy is a useful monitoring technique for solid-phase organic chemistry due to the high information content it delivers and swift acquisition times, using standard NMR spectrometers. This paper describes the synthesis of the novel linker 2-(2-fluoro-4-hydroxymethyl-5-methoxy-phenoxy)acetic acid in 29% yield over seven steps, using nucleophilic aromatic substitutions on 2,4,5-trifluorobenzonitrile as key steps. Following standard solid-phase synthesis a peptide could be cleaved from the linker using 20% TFA in CH(2)Cl(2) in 30 minutes, in contrast to a previously described monoalkoxy linker that requires 90% TFA in water at elevated temperature. A resin-bound peptide could be successfully glycosylated using only two equivalents of a thioglycoside donor, activated with N-iodosuccinimide and trifluoromethanesulfonic acid, and subsequent cleavage and deprotection gave the target glycopeptide. Direct glycosylation of the linker itself followed by mild acidic cleavage gave a fully protected hemiacetal for further chemical manipulation.     

A selective intramolecular 5-exo-dig or 6-endo-dig cyclization en route to 2-furanone or 2-pyrone containing tricyclic scaffolds

Ringfused bicyclic 2-pyridones exhibit interesting biological properties against pili assembly in uropathogenic Escherichia coli (Pinkner, J. S. et al. Proc. Natl. Acad. Sci. U. S. A.2006, 103, 17897-17902; ?berg, V. et al. Org. Biomol. Chem.2007, 5, 1827-1834) as well as curli formation (Cegelski, L. et al. Nat. Chem. Biol.2009, 5, 913-919). In the search for new ring-fused central fragments, highly selective synthetic routes to the 2-furanone or 2-pyrone containing tricyclic scaffolds 1 and 2 have been developed.     

Biocompatible "click" wafer bonding for microfluidic devices

We introduce a novel dry wafer bonding concept designed for permanent attachment of micromolded polymer structures to surface functionalized silicon substrates. The method, designed for simultaneous fabrication of many lab-on-chip devices, utilizes a chemically reactive polymer microfluidic structure, which rapidly bonds to a functionalized substrate via"click" chemistry reactions. The microfluidic structure consists of an off-stoichiometry thiol-ene (OSTE) polymer with a very high density of surface bound thiol groups and the substrate is a silicon wafer that has been functionalized with common bio-linker molecules. We demonstrate here void free, and low temperature (< 37 °C) bonding of a batch of OSTE microfluidic layers to a silane functionalized silicon wafer.     

Rod-like particles matching algorithm based on SOM neural network in dispersed two-phase flow measurements

A matching algorithm based on self-organizing map (SOM) neural network is proposed for tracking rod-like particles in 2D optical measurements of dispersed two-phase flows. It is verified by both synthetic images of elongated particles mimicking 2D suspension flows and direct numerical simulations-based results of prolate particles dispersed in a turbulent channel flow. Furthermore, the potential benefit of this algorithm is evaluated by applying it to the experimental data of rod-like fibers tracking in wall turbulence. The study of the behavior of elongated particles suspended in turbulent flows has a practical importance and covers a wide range of applications in engineering and science. In experimental approach, particle tracking velocimetry of the dispersed phase has a key role together with particle image velocimetry of the carrier phase to obtain the velocities of both phases. The essential parts of particle tracking are to identify and match corresponding particles correctly in consecutive images. The present study is focused on the development of an algorithm for pairing non-spherical particles that have one major symmetry axis. The novel idea in the algorithm is to take the orientation of the particles into account for matching in addition to their positions. The method used is based on the SOM neural network that finds the most likely matching link in images on the basis of feature extraction and clustering. The fundamental concept is finding corresponding particles in the images with the nearest characteristics: position and orientation. The most effective aspect of this two-frame matching algorithm is that it does not require any preliminary knowledge of neither the flow field nor the particle behavior. Furthermore, using one additional characteristic of the non-spherical particles, namely their orientation, in addition to its coordinate vector, the pairing is improved both for more reliable matching at higher concentrations of dispersed particles and for higher robustness against loss of particle pairs between image frames.     

Weil representations associated with finite quadratic modules

To any finite quadratic module, that is, a finite abelian group together with a non-degenerate quadratic form, it is possible to associate a representation of $\mathrm{Mp}_{2}(\mathbb Z )$ , the metaplectic cover of the modular group. This representation is usually referred to as a Weil representation and our main result is a general explicit formula for its matrix coefficients. This result completes earlier work by Scheithauer in the case when the representation factors through $\mathrm{SL}_{2}(\mathbb Z )$ . Furthermore, our formula is given in a such a way that it is easy to implement efficiently on a computer.     

Alternating Projections on Nontangential Manifolds

We consider sequences $(B_{k})_{k=0}^{\infty}$ of points obtained by projecting a given point B=B ₀ back and forth between two manifolds $\mathcal{M}_{1}$ and $\mathcal{M}_{2}$ , and give conditions guaranteeing that the sequence converges to a limit $B_{\infty}\in\mathcal{M}_{1}\cap\mathcal{M}_{2}$ . Our motivation is the study of algorithms based on finding the limit of such sequences, which have proved useful in a number of areas. The intersection is typically a set with desirable properties but for which there is no efficient method for finding the closest point B _opt in $\mathcal{M}_{1}\cap\mathcal{M}_{2}$ . Under appropriate conditions, we prove not only that the sequence of alternating projections converges, but that the limit point is fairly close to B _opt , in a manner relative to the distance ∥B ₀?B _opt ∥, thereby significantly improving earlier results in the field.     

Mathematical Modelling of Diesel-Electric Propulsion Systems for Marine Vessels

This article presents a mathematical model of a complete diesel-electric propulsion system, including components as diesel generators, distribution network, variable speed thruster-drives, and conventional motor loads. The model is split into two parts: One power generating part where the load is specified with an aggregated active and reactive power load demand. Secondly, a power consumption part where the effects of the different load types as thruster drives, motors and other loads are modelled. The model is written in a state-space form suitable for the purpose of simulation and control design. PID-controllers represent speed governors and automatic voltage regulators.