Stability of diphenylalanine peptide nanotubes in solution

Over the last couple of years, self-organizing nanotubes based on the dipeptide diphenylalanine have received much attention, mainly as possible building blocks for the next generation of biosensors and as drug delivery systems. One of the main reasons for this large interest is that these peptide nanotubes are believed to be very stable both thermally and chemically. Previously, the chemical and thermal stability of self-organizing structures has been investigated after the evaporation of the solvent. However, it was recently discovered that the stability of the structures differed significantly when the tubes were in solution. It has been shown that, in solution, the peptide nanotubes can easily be dissolved in several solvents including water. It is therefore of critical importance that the stability of the nanotubes in solution and not after solvent evaporation be investigated prior to applications in which the nanotube will be submerged in liquid. The present article reports results demonstrating the instability and suggests a possible approach to a stabilization procedure, which drastically improves the stability of the formed structures. The results presented herein provide new information regarding the stability of self-organizing diphenylalanine nanotubes in solution.     

Spatial Heterogeneity of Thermo‐Oxidative Degradation in Impact Poly(propylene) Copolymers

The spatial degradation in impact PP copolymers with different ethylene contents is studied by FTIR microscopy and layer‐by‐layer milling of the sample surfaces, followed by ATR‐FTIR, SEC, and CRYSTAF analysis. FTIR allows for tracking of the rate of degradation, providing information on the depth profiling of the degradation. Results show that samples with lower ethylene content degrade faster at all depths than those with higher ethylene content. The latter show a more uniform degradation from the surface to the bulk of the material at longer degradation times. This is ascribed to the higher amorphous content which results in a larger oxygen diffusion to the centre of the material while its slower rate of degradation is ascribed to the lower tertiary carbon content.

     

Urban Disturbance: Urban Intrusions of the office for subversive architecture (osa)

The work of the office for subversive architecture (osa) ‘crosses boundaries by thinking beyond, or further than others’. For the office's Ulrich Beckefeld and Karsten Huneck , transgression is both a conceptual and practical tool. For the work to communicate effectively, it has to stretch expectations and question norms. The urban public spaces within which they intervene are also the most tightly controlled areas of any city, which requires a subtle but pragmatic disregard for regulations.     

Teilen und Trennen im Recycling-Prozeß

Division and Separation in the Recycling Process. The recycling process comprises a preparation and a reutilization step. This article describes preparation processes which are of importance for the recycling of used products and production wastes. The goal is to provide a clear presentation of the individual processes of division and separation and their mode of functioning with the aid of the systematic classification discussed in the paper. This is important for the overall process of recycling since combinations of various processes are usually employed. A systematic classification thus also provides a basis for new processes and combinations of processes.     

Design Methodology for a DVB Satellite Receiver ASIC

This contribution describes design methodology and implementation of a single-chip timing and carrier synchronizer and channel decoder for digital video broadcasting over satellite (DVB-S). The device consists of an A /D converter with AGC, timing and carrier synchronizer with matched filter, Viterbi decoder including node synchronization, byte and frame synchronizer, convolutional de-interleaver, Reed Solomon decoder, and a descrambler.The system was designed in accordance with the DVB specifications. It is able to perform Viterbi decoding at data rates up to 56 Mbit /s and to sample the analog input values with up to 88 MHz. The chip allows automatic acquisition of the convolutional code rate and the position of the puncturing mask. The symbol synchronization is performed fully digitally by means of interpolation and controlled decimation. Hence, no external analog clock recovery circuit is needed.For algorithm design, system performance evaluation, co-verification of the building blocks, and functional hardware verification an advanced design methodology and the corresponding tool framework are presented which guarantee both short design time and highly reliable results. The chip has been fabricated in a 0.5 µm CMOS technology with three metal layers. A die photograph is included.     

SOI-based optical board technology

A SOI-based optical board technology is presented. Hybrid integration combines the strength of silicon and InP. The SOI board provides passive optical components and acts as the mounting platform. Adapted active III/V devices are integrated using Au/Sn solder technology and passive alignment. Precise mounting of lasers on the board is necessary to ensure low coupling losses.     

Organic field effect transistors with ferroelectric hysteresis

The ferroelectric copolymer Poly(vinylidene fluoride trifluoroethylene) is used as insulating material for capacitor structures and organic field effect transistors. For capacitors, we find the typical hysteresis in the capacitance-voltage characteristic upon increasing the voltage scan window. A writing process with adequate electric fields causes shifts in the flatband voltage. Based on these results, we fabricate organic transistors with regioregular poly(3-hexylthiophene) as organic semiconductor. The transistors are constructed in bottom gate architecture with thin layers (100 nm) of spincoated copolymer as gate insulation. The drain source current of the transistor is reversible affected by the polarized gate, which gives opportunities for fabrication of organic nonvolatile memory elements.     

Punching behavior of biaxial hollow slabs

The invention of a new kind of hollow slab with plastic balls as hollow bodies entailed the necessity to investigate its structural behavior. Because of its main field of application as a flat slab, the punching shear capacity is one of the most interesting properties of this slab. To investigate the influence of the cavities on the punching behavior, tests were carried out at the Institute for Concrete Structures in Darmstadt. In addition to these tests nonlinear computations using the Finite Element Method were performed. The computations allowed parametric studies to get a better understanding of the structural behavior without doing further expensive tests. Finally, necessary modifications of existing design recommendations according to the German design code DIN 1045 [1] were developed.