Catalytically Doped Semiconductors for Chemical Gas Sensing: Aerogel‐Like Aluminum‐Containing Zinc Oxide Materials Prepared in the Gas Phase

Atmospheric contamination with organic compounds is undesired in industry and in society because of odor nuisance or potential toxicity. Resistive gas sensors made of semiconducting metal oxides are effective in the detection of gases even at low concentration. Major drawbacks are low selectivity and missing sensitivity toward a targeted compound. Acetaldehyde is selected due to its high relevance in chemical industry and its toxic character. Considering the similarity between gas‐sensing and heterogeneous catalysis (surface reactions, activity, selectivity), it is tempting to transfer concepts. A question of importance is how doping and the resulting change in electronic properties of a metal‐oxide support with semiconducting properties alters reactivity of the surfaces and the functionality in gas‐sensing and in heterogeneous catalysis. A gas‐phase synthesis method is employed for aerogel‐like zinc oxide materials with a defined content of aluminum (n‐doping), which were then used for the assembly of gas sensors. It is shown that only Al‐doped ZnO represents an effective sensor material that is sensitive down to very low concentrations (<350 ppb). The advance in properties relates to a catalytic effect for the doped semiconductor nanomaterial.     

Mass + retention time = structure: a strategy for the analysis of N-glycans by carbon LC-ESI-MS and its application to fibrin N-glycans

Analysis of the numerous possible, often isobaric structures of protein-bound oligosaccharides calls for a high-performance two-dimensional method that combines liquid chromatography's ability to separate isomers and mass spectrometry's ability to determine glycan composition. Here we investigate the usefulness of porous graphitic carbon columns coupled to ESI-MS for the separation of N-glycans with two or more sialic acids. Internal standards helped to rectify retention time fluctuations and thus allowed elution times to play an essential role in the structural assignment of peaks. For generation of a retention time library, standards representing the possible isomers of diantennary non-, mono-, and disialylated N-glycans, differing in the linkage of galactose and sialic acids as well as isobaric hybrid-type N-glycans, were produced using recombinant glycosyltransferases. Once the retention times library was established, isomers could be identified by LC-ESI-MS in the positive mode without additional MS/MS experiments. The method was applied for the detailed structural analysis of fibrin(ogen) N-glycans from various species (human, cow, pig, mouse, rat, cat, dog, Chinese hamster, horse, sheep, and chicken). All fibrins contained diantennary N-glycans. They differed in the occurrence of beta1,3-linked galactose, alpha2,3-linked sialic acids, and N-glycolylneuraminic acid, in the mono/diantennary glycan ratio, and in the O-acetylation of neuraminic acids. The separation system's potential for analyzing tri- and tetrasialylated N-glycans was demonstrated.     

Measuring Local Crystallization Fouling in a Double-Pipe Heat Exchanger

Abstract

Although fouling is a problem varying in space and time, sizing and assessment of a process apparatus is almost always based on one single integral fouling resistance value. Furthermore, the integral fluid dynamic behavior, e.g. the development of time-dependent pressure drop in a heat exchanger, can be influenced by local constrictions. While it is generally possible to determine the time dependency of the integral fouling behavior, local differences are not taken into consideration at present. Therefore, this paper introduces a metrological, an incremental and a segmental approach to study the local development of crystallization fouling by calcium sulfate in a countercurrent double-pipe heat exchanger. The consecutive approaches allow for thermal, volumetric, gravimetric, and optical fouling investigations, aiming to examine the axial distribution of deposit as well as local differences in the deposit morphology. All methods provided congruent results and local fouling could be described properly. An almost clean surface at the colder end of the heat exchanger and an exponential increase of deposit thickness were observed towards the hot end. Hence, the section near to the hot water inlet turned out to be a key area with regards to increasing fouling mass and structural changes of the layer.     

Detwinning Phenomenon and Its Effect on Resulting Twinning Structure of an Austenitic Hadfield Steel

Metallurgical and Materials Transactions A - Hadfield Steel shows high strain hardening which can be linked to its ability to form twins during mechanical loading. Twinning in Hadfield Steel is...     

Genome-Wide Mutation Scoring for Machine-Learning-Based Antimicrobial Resistance Prediction

The prediction of antimicrobial resistance (AMR) based on genomic information can improve patient outcomes. Genetic mechanisms have been shown to explain AMR with accuracies in line with standard microbiology laboratory testing. To translate genetic mechanisms into phenotypic AMR, machine learning has been successfully applied. AMR machine learning models typically use nucleotide k-mer counts to represent genomic sequences. While k-mer representation efficiently captures sequence variation, it also results in high-dimensional and sparse data. With limited training data available, achieving acceptable model performance or model interpretability is challenging. In this study, we explore the utility of feature engineering with several biologically relevant signals. We propose to predict the functional impact of observed mutations with PROVEAN to use the predicted impact as a new feature for each protein in an organism’s proteome. The addition of the new features was tested on a total of 19,521 isolates across nine clinically relevant pathogens and 30 different antibiotics. The new features significantly improved the predictive performance of trained AMR models for Pseudomonas aeruginosa, Citrobacter freundii, and Escherichia coli. The balanced accuracy of the respective models of those three pathogens improved by 6.0% on average.     

Radiation Emitted from Rocket Plumes

The signature of rocket plumes can be used for detection, identification and guidance of rockets. The objective was to investigate the signature of various types of solid rocket propellants by application of spectroscopic methods. The emission and transmission characteristics of plumes were studied experimentally, the results were analyzed based on molecular bands and continuum radiation. The model formulations include a nitramine propellant, a double-base propellant and a composite propellant. Applied were rapid-scanning filter wheel spectrometers for the wavelength region from 1.2 μm to 14 μm with a time resolution of 50 spectra/s and a wavelengths resolution of 1% of actual wavelength. The UV/VIS wavelengths region was recorded by an OMA system with wavelength resolution of 0.1 nm and 1 nm and time resolution of 10 spectra/s. Molecular bands of water and carbon dioxide dominate in the near infrared and infrared. Depending on composition, continuous radiation indicates particles in the rocket exhaust. A code was developed to calculate molecular bands and continuous radiation using temperature and species distributions found by thermodynamic estimation to obtain the radiance of the plume. Comparison with experimental data delivered plume temperatures.     

Subsurface Raman imaging with nanoscale resolution

We report on chemically specific, subsurface imaging with high spatial resolution. Using tip-enhanced Raman spectroscopy, we probe carbon nanotubes buried beneath a host dielectric media. We demonstrate our ability to map and resolve specific vibrational modes with 30 nm spatial resolution for dielectric layers with different thicknesses.     

Bisubstrate inhibitors of catechol O-methyltransferase (COMT): the crucial role of the ribose structural unit for inhibitor binding affinity

Inhibition of the enzyme catechol O-methyltransferase offers a therapeutic handle to regulate the catabolism of catecholamine neurotransmitters, providing valuable assistance in the treatment of CNS disorders such as Parkinson's disease. A series of ribose-modified bisubstrate inhibitors of COMT featuring 2'-deoxy-, 3'-deoxy-, 2'-aminodeoxy-3'-deoxy-, and 2'-deoxy-3'-aminodeoxyribose-derived central moieties and analogues containing the carbocyclic skeleton of the natural product aristeromycin were synthesized and evaluated to investigate the molecular recognition properties of the ribose binding site in the enzyme. Key synthetic intermediates in the ribose-derived series were obtained by deoxygenative [1,2]-hydride shift rearrangement of adenosine derivatives; highlights in the synthesis of carbocyclic aristeromycin analogues include a diastereoselective cyclopropanation step and nucleobase introduction with a modified Mitsunobu protocol. In vitro biological evaluation and kinetic studies revealed dramatic effects of the ribose modification on binding affinity: 3'-deoxygenation of the ribose gave potent inhibitors (IC50 values in the nanomolar range), which stands in sharp contrast to the remarkable decrease in potency observed for 2'-deoxy derivatives (IC50 values in the micromolar range). Aminodeoxy analogues were only weakly active, whereas the change of the tetrahydrofuran skeleton to a carbocycle unexpectedly led to a complete loss of biological activity. These results confirm that the ribose structural unit of the bisubstrate inhibitors of COMT is a key element of molecular recognition and that modifications thereof are delicate and may lead to surprises.     

The effect of hyaluronan combined with KI3 complex (Hyiodine wound dressing) on keratinocytes and immune cells

Hyiodine (high molecular weight hyaluronan combined with KI₃ complex) is a new non-adhesive wound dressing which significantly improves the healing process. The aim of the study was to investigate the effects of Hyoidine on functional properties of isolated human keratinocytes and leukocytes, and on those of U937 and HL60 cell lines. While KI₃ complex inhibited the viability and proliferation of the cells tested, Hyiodine did not have any significant effect. The expression of CD11b, CD62L and CD69 on PMNL, monocytes and lymphocytes, as well as the oxidative burst of blood neutrophils, were not changed. On the contrary, Hyiodine inhibited the PMA-activated oxidative burst and significantly increased the production of IL-6 and TNF-α by lymphocytes. It was concluded that hyaluronan content of Hyiodine reduces the toxic effect of KI₃ complex on cells and speeds up the wound healing process by increasing the production of inflammatory cytokines.