Microsegregation: From Basic Concepts to Complexity in Liquid Crystal Self-Assembly

This review is focused on the basic concepts of microsegregation and a fundamental understanding of the formation of positionally ordered LC phases based on micro- and nanophases, interaction parameters and interfaces. Selected examples were chosen from the actual literature to illustrate the concepts. Microsegregation is the basis of classical LC phases and cybotaxis, and most importantly, it paves the way to a huge number of new LC phases. Beside the distinct modes of micellar packing motifs and liquid quasicrystals formed by self-assembly of dendritic molecules, attention is also focused on the specific effects of rigid anisometric units and polyphilicity. Honeycomb LC phases, vesicular LC phases and mesophases with 3D-lattices lead to enhanced complexity of LC self-assembly.     

Polarized recombination of acoustically transported carriers in GaAs nanowires

ABSTRACT: : The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited electrons and holes in GaAs nanowires deposited on a SAW delay line on a LiNbO3 crystal. The carriers generated in the nanowire by a focused light spot are acoustically transferred to a second location where they recombine. We show that the recombination of the transported carriers occurs in a zinc blende section on top of the predominant wurtzite nanowire. This allows contactless control of the linear polarized emission by SAWs which is governed by the crystal structure. Additional polarization-resolved photoluminescence measurements were performed to investigate spin conservation during transport.     

A Systematic Structure–Activity Study of a New Type of Small Peptidic Transfection Vector Reveals the Importance of a Special Oxo-Anion-Binding Motif for Gene Delivery

We discovered a new class of artificial peptidic transfection vectors based on an artificial anion-binding motif, the guanidiniocarbonylpyrrole (GCP) cation. This new type of vector is surprisingly smaller than traditional systems, and our previous work suggested that the GCP group was important for promoting critical endosomal escape. We now present here a systematic comparison of similar DNA ligands featuring our GCP oxo-anion-binding motif with DNA ligands only consisting of naturally occurring amino acids. Structure–activity studies showed that the artificial binding motif clearly outperformed natural amino acids such as histidine, lysine, and arginine. It improved the ability to shuttle foreign genetic material into cells, yet successfully mediated endosomal escape. Also, plasmids that were complexed by our artificial ligands were stabilized against cytosolic degradation to some extent. This resulted in the successful expression of plasmid information (comparable to gold standards such as polyethyleneimine). Hence, our study clearly demonstrates the importance of the tailor-made GCP anion-binding site for efficient gene transfection.     

Modeling the Electrical Conductive Paths within All-Solid-State Battery Electrodes

All-solid-state batteries constitute a very promising energy storage device. Two very important properties of these battery cells are the ionic and the electrical conductivity, which describe the ion and the electron transport through the electrodes, respectively. In this work, a numerical method is presented to model the electrical conductivity, considering the outcome of discrete-element method simulations and the intrinsic conductivities of both the active material particles and the conductive additive particles. The results are calibrated and validated with the help of experimental data of real manufactured electrodes. The tortuosity, which strongly influences the ionic conductivity, is also presented for the analyzed electrodes, taking their microstructure into account.     

Trends in Thermal Separation Technologies – An Industrial Perspective

The article discusses future trends and their implications on separation technologies starting from the main drivers of technological developments. Especially the consequences of the expected energy and raw material change and the increasing international economic competition on process technologies are addressed. Special attention is given to the opportunities of increasing computational power and the availability of high-performance networks for scientific modeling and their use in process industries.     

A Cell-Free Multi-enzyme Cascade Reaction for the Synthesis of CDP-Glycerol

CDP-glycerol is a nucleotide-diphosphate-activated version of glycerol. In nature, it is required for the biosynthesis of teichoic acid in Gram-positive bacteria, which is an appealing target epitope for the development of new vaccines. Here, a cell-free multi-enzyme cascade was developed to synthetize nucleotide-activated glycerol from the inexpensive and readily available substrates cytidine and glycerol. The cascade comprises five recombinant enzymes expressed in Escherichia coli that were purified by immobilized metal affinity chromatography. As part of the cascade, ATP is regenerated in situ from polyphosphate to reduce synthesis costs. The enzymatic cascade was characterized at the laboratory scale, and the products were analyzed by high-performance anion-exchange chromatography (HPAEC)-UV and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). After the successful synthesis had been confirmed, a design-of-experiments approach was used to screen for optimal operation conditions (temperature, pH value and MgCl₂ concentration). Overall, a substrate conversion of 89 % was achieved with respect to the substrate cytidine.     

Development of enhanced three-dimensional printed packings for scale-up of distillation columns: A successful case study

This publication presents a general approach for the enhancement of packings regarding scalability, separation efficiency, and fluid dynamic properties using three-dimensional (3D) printing. The methodology is used to develop miniaturized, scalable packings for process development, and scale-up applications. For this purpose, a 3D printable computer-aided design version of the Rombopak 9M industrial packing (RP9M-3D), which is known for its positive scalability properties, was created. An initial characterization by means of computational fluid dynamics simulations and mass transfer measurements reveals positive but also negative design properties. These findings are used to create a more advanced, miniaturized packing structure, the XW-Pak. The evolved structure is compared to the RP9M-3D. The simulation and experimental results show that the enhanced packing, which is still in the early stages of development, exhibits higher separation efficiencies with improved scalability properties at the same void fraction and surface area than the RP9M-3D.     

Influence of preheating of fly ash precursors to produce geopolymers

This study has been focused on the effect of pretreatment of FA and POFA after geopolymerization on the mechanical properties. The aim of this work was to simplify the pretreatment that it can easily industrial be applied, using existing technology. Previous work has shown that a reduction in particle size increases the mechanical properties. However, this method involves a milling process which is not applicable for a wide industrial application. Hence, FA and POFA particles have been heated to 300°C, 500°C, and 800°C but applying different pretreatments: (i) predried at 110°C (reference sample); (ii) as received; (iii) prewetted; (iv) prewetted and later quenched in cold water. It was found that during the treatment the particle size increased due to thermal stress cracking. During fast heating, trapped pore water cannot be removed as fast as it evaporates and hence the particles crack. This increase in particle size caused an increase in compressive strength. In addition, heating to 300°C and 500°C caused a dehydroxylation of FA and POFA. This dehydroxylation resulted in a higher initial reactivity, reducing the setting time and improved mechanical strength.     

Metal Organic Frameworks for Natural Gas Storage in Vehicles

With the increasing demand for alternative fuels the storage of natural gas (NG) in adsorbents like metal organic frameworks (MOFs) will become more important. In order to use MOFs as storage media in fuel delivery systems, the optimization of mass and energy transfer of the system is crucial. For rapid NG filling of a tank, molecules need to reach the adsorption sites within a reasonable time while the heat of adsorption should be dissipated to the environment. In this article, mass transfer in shaped bodies of MOFs was determined by permeability measurements and pulsed field gradient (PFG) NMR spectroscopy. The heat dissipation was also experimentally measured and both data sets were used to set up a theoretical density function theory model to predict the behavior of MOFs for NG storage.     

Measurement of Aerosol Organic Compounds Using a Novel Collection/Thermal-Desorption PTR-ITMS Instrument

We report the development and characterization of a proton-transfer-reaction ion trap mass spectrometer for the speciated measurement of organic compounds in atmospheric aerosols and show results from its first field deployment. The instrument uses an aerosol collection inlet to accumulate aerosol mass followed by rapid thermal desorption to volatilize the organic compounds for in situ analysis. We have performed laboratory studies to characterize instrument performance and the instrument was deployed aboard a NOAA research vessel during the Texas Air Quality Study 2006/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS 2006/GoMACCS) in August–September 2006. The laboratory-determined detection limit for glutaric acid in mixed glutaric acid/NH ₄ HSO ₄ test aerosols was 0.22 ng collected mass, which corresponds to an estimated detection limit of 12 ng m^?3 for a 10 min sample based on the instrument sample flow rate of 1.8 L min^?1. During TexAQS 2006/GoMACCS, signals well above the detection limit were observed at a number of mass to charge ratios, mostly occurring during an extended period of active pollution photochemistry, but also including detection of possible primary emissions of aerosol-phase pyridine.