Effects of multi-media partitioning of chemicals on Junge's variability-lifetime relationship

Junge's variability-lifetime relationship describes the relation between the tropospheric residence time of a volatile trace gas and the coefficient of variation of the tropospheric mixing ratio at a remote location. However, no unique or universal quantification of this relationship exists. It can only be derived on a case-by-case basis for consistent data sets on substances with similar source and sink patterns. Using a multi-media model of the long-range transport of organic compounds, we determine variability-lifetime relationships for volatile substances. Next, we demonstrate how the variability-lifetime relationship can be obtained for semi-volatile organic compounds (SOCs) with the model and we investigate typical deviations from the Junge relationship for volatile compounds that are caused by the multi-media partitioning of SOCs. One cause of deviation from this relationship is substances undergoing significant transport in water so that their distribution in air is noticeably influenced by their distribution in water. The other, wider, deviation is caused by substances with a strong tendency for deposition and re-volatilization. Finally, we address the comparison of the model results with field data. Preliminary analyses of long-term monitoring data for polychlorinated biphenyls at remote sites have shown that the identification of Junge relationships in field data is not straightforward. We discuss possible strategies for the derivation of Junge relationships from field data on SOCs.     

Phytochrome‐Based Extracellular Matrix with Reversibly Tunable Mechanical Properties

Interrogation and control of cellular fate and function using optogenetics is providing revolutionary insights into biology. Optogenetic control of cells is achieved by coupling genetically encoded photoreceptors to cellular effectors and enables unprecedented spatiotemporal control of signaling processes. Here, a fast and reversibly switchable photoreceptor is used to tune the mechanical properties of polymer materials in a fully reversible, wavelength‐specific, and dose‐ and space‐controlled manner. By integrating engineered cyanobacterial phytochrome 1 into a poly(ethylene glycol) matrix, hydrogel materials responsive to light in the cell‐compatible red/far‐red spectrum are synthesized. These materials are applied to study in human mesenchymal stem cells how different mechanosignaling pathways respond to changing mechanical environments and to control the migration of primary immune cells in 3D. This optogenetics‐inspired matrix allows fundamental questions of how cells react to dynamic mechanical environments to be addressed. Further, remote control of such matrices can create new opportunities for tissue engineering or provide a basis for optically stimulated drug depots.     

Berechnung und Optimierung von Geometrie und Eingriffsverhalten von Zahnformen beliebiger Achslage

The main benefit, the economical manufacturability of traditional gear profiles, such as an involute, are no longer of major importance in times of computer-aided design and production. Due to existing modern production techniques standard and more sophisticated gear types can be produced with high precision and maintainable financial effort. Especially for non-standard gear types modern gear production systems ensure high quality and reliability to the operator with regard to flank and meshing geometry. Depending on the context of application different gear types have advantages and disadvantages concerning load carrying capacity, effectiveness or noise excitation. Developing an optimized gearing for the desired application is thus a complex and elementary goal within the design process.     

Energetic Control of Redox-Active Polymers toward Safe Organic Bioelectronic Materials

Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side-products. This is particularly important for bioelectronic devices, which are designed to operate in biological systems. While redox-active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side-reactions with molecular oxygen during device operation. Here, electrochemical side reactions with molecular oxygen are shown to occur during organic electrochemical transistor (OECT) operation using high-performance, state-of-the-art OECT materials. Depending on the choice of the active material, such reactions yield hydrogen peroxide (H₂O₂), a reactive side-product, which may be harmful to the local biological environment and may also accelerate device degradation. A design strategy is reported for the development of redox-active organic semiconductors based on donor–acceptor copolymers that prevents the formation of H₂O₂ during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte-gated devices in application-relevant environments.     

Periodic mesoporous organosilicas (PMOs): past, present, and future

Periodic mesoporous organosilicas (PMOs) represent a new class of organic-inorganic hybrid materials suitable for a broad range of applications such as chromatography, catalysis, sensing and microelectronics. Unlike in organic functionalized mesoporous silica phases obtained via grafting or co-condensation procedures the organic groups in PMOs are direct parts of the 3D framework structure, thus giving raise to enormous possibilities to tune their chemical and physical properties in designated ways by varying the structure of the precursors. In this review the distinctive features of PMOs are discussed, the latest developments concerning compositions, structures, morphologies and potential applications are figured out and finally a brief outlook of future aspects is given.     

Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [μC^*] and current retentions up to 98% over 700 electrochemical switching cycles are developed.     

DNA‐Modification of Eukaryotic Cells

A novel bioorthogonal method for the modification of cells with single‐stranded DNA oligomers is compared to five alternative methods with respect to labeling efficacy, specificity, and effects on cell viability. The new method is based on oxime ligation of aminooxybiotin to aldehyde groups installed by periodate cleavage of cell‐surface glycans, followed by the coupling of preformed DNA–streptavidin conjugates. As compared with two literature‐reported methods based on direct coupling of N‐hydroxysuccinimidyl (NHS)–DNA or NHS–biotinylation as well as with techniques based on strain‐promoted alkyne‐azide cycloaddition, this method shows the highest labeling densities and is sufficiently mild to avoid cell damage. Functionality of the DNA tags is demonstrated by DNA‐directed immobilization on solid substrates and assembly of small cell aggregates.     

Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on colonization and bone formation in vivo

The reconstruction of large bone defects after injury or tumor resection often requires the use of bone substitution. Artificial scaffolds based on synthetic biomaterials can overcome disadvantages of autologous bone grafts, like limited availability and donor side morbidity. Among them, scaffolds based on nanofibers offer great advantages. They mimic the extracellular matrix, can be used as a carrier for growth factors and allow the differentiation of human mesenchymal stem cells. Differentiation is triggered by a series of signaling processes, including integrin and bone morphogenetic protein (BMP), which act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffolds in vivo. Electrospun matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were implanted in calvarial critical size defects in rats. Cranial CT-scans were taken 4, 8 and 12 weeks after implantation. Specimens obtained after euthanasia were processed for histology and immunostainings on osteocalcin, BMP-2 and Smad5. After implantation the scaffolds were inhomogeneously colonized and cells were only present in wrinkle- or channel-like structures. Ossification was detected only in focal areas of the scaffold. This was independent of whether BMP-2 was incorporated in the scaffold. However, cells that migrated into the scaffold showed an increased ratio of osteocalcin and Smad5 positive cells compared to empty defects. Furthermore, in case of BMP-2 incorporated PLLA-collagen type I scaffolds, 4 weeks after implantation approximately 40?% of the cells stained positive for BMP-2 indicating an autocrine process of the ingrown cells. These findings indicate that a cooperative effect between BMP-2 and collagen type I can be transferred to PLLA nanofibers and furthermore, that this effect is active in vivo. However, this had no effect on bone formation. The reason for this seems to be an unbalanced colonization of the scaffolds with cells, due to insufficient pore size.