Enhanced π-π interactions between a C60 fullerene and a buckle bend on a double-walled carbon nanotube

In situ low-voltage aberration corrected transmission electron microscopy (TEM) observations of the dynamic entrapment of a C₆₀ molecule in the saddle of a bent double-walled carbon nanotube is presented. The fullerene interaction is non-covalent, suggesting that enhanced π-π interactions (van der Waals forces) are responsible. Classical molecular dynamics calculations confirm that the increased interaction area associated with a buckle is sufficient to trap a fullerene. Moreover, they show hopping behavior in agreement with our experimental observations. Our findings further our understanding of carbon nanostructure interactions, which are important in the rapidly developing field of low-voltage aberration corrected TEM and nano-carbon device fabrication.      

Macro-crack initiation life for orthotropic steel decks considering weld heterogeneity and random traffic loading

This paper presents a multi-scale approach to predict the macro-crack initiation life (MCIL) of welded joints. This fully adaptive multi-scale technique is designed to take into account micro-scale material heterogeneity due to the existence of defects and to consider the uncertainties regarding defect occurrence and characteristics and traffic loading. The procedure of the proposed approach was introduced along with an orthotropic steel deck. Firstly, a homogenisation method was used to link defects in the heat-affected zone with the macro-scale structure. This allows for estimating the effective Paris constant, required for a Paris Law-based fatigue damage analysis. Secondly, a traffic flow, based on weigh-in-motion measurements, was used to simulate the load effects on the examined joint. Afterwards, the extended finite element method was adopted to calculate the stress intensity factors with respect to the weld geometries. Finally, the damage before macro-crack initiation was obtained using the Paris Law. In addition, Monte Carlo simulation was integrated within this multi-scale crack growth procedure to consider the randomness in pore and inclusion occurrence and characteristics. Hence, the MCIL is expressed in the form of a probability distribution. Results show that the proposed approach enables to provide a rational maintenance and inspection intervention time.     

Detection of 4-aminocarminic acid in beverages and cake glaze from the German market: a food additive not approved in the EU

In the European Union, carminic acid and its ammonium, calcium, potassium or sodium salts and its aluminium lakes are approved as food additive E120. In beverages obtained from the German market 4-aminocarminic acid (“acid-stable carmine”) was detected by HPLC–PDA and LC–MS/MS. Isolation of the colorant from a liquid dye preparation used for the production of a beverage sample and subsequent NMR analysis confirmed the presence of 4-aminocarminic acid. Synthesis of ¹⁵N-4-aminocarminic acid clearly demonstrated that “acid-stable carmine” is not the ammonium salt of carminic acid, which is approved as food additive in the European Union. In fact, nitrogen in “acid-stable carmine” is covalently bound. The molecular structure of carminic acid is chemically modified and 4-aminocarminic acid does not comply with the specifications laid down for E120 in Commission Regulation (EU) No 231/2012. 4-Aminocarminic acid was also detected in the red-colored glaze of a raspberry cake and in the liquid dye preparation used for coloring this glaze.     

A consistent flamelet formulation for a reacting char particle considering curvature effects

In the present work, the combustion of a single char particle in quiescent and convective environments is investigated numerically. Fully resolved CFD calculations are carried out considering heterogeneous reactions at the particle surface and detailed homogeneous reactions in the gas phase. Unity and non-unity Lewis number diffusion modeling approaches are employed and compared to each other. The flame shape of the particle in a quiescent atmosphere shows full symmetry whereas the particle in the convective environment exhibits a stagnation region upstream of the particle and a wake region downstream of the particle. The detailed CFD results are used to analyze the flame structure around the char particle and corresponding flamelet simulations are carried out. For the presently investigated case, curvature effects of mixture fraction, species and temperature are found to be significant in almost all the cases. These curvature effects correspond to diffusion tangential to iso-surfaces of mixture fraction. To describe these processes, new extended flamelet equations are derived. The individual terms in the flamelet equations are analyzed for both the quiescent and the convective environment based on the CFD data and the results confirm the importance of tangential diffusion. Except for the quiescent environment and unity Lewis numbers, curvature cannot be neglected for the investigated char combustion case. For all other cases, significant differences between the standard flamelet model and the detailed CFD results are found. On the other hand, applying the extended flamelet equations yields very good agreement with the CFD results.     

Microwave-hydrothermal synthesis and characterization of nanostructured copper substituted ZnM2O4 (M = Al, Ga) spinels as precursors for thermally stable Cu catalysts

Nanostructured Cu(x)Zn(1-x)Al(2)O(4) with a Cu:Zn ratio of ?:? has been prepared by a microwave-assisted hydrothermal synthesis at 150 °C and used as a precursor for Cu/ZnO/Al(2)O(3)-based catalysts. The spinel nanoparticles exhibit an average size of approximately 5 nm and a high specific surface area (above 250 m(2) g(-1)). Cu nanoparticles of an average size of 3.3 nm can be formed by reduction of the spinel precursor in hydrogen and the accessible metallic Cu(0) surface area of the reduced catalyst was 8 m(2) g(-1). The catalytic performance of the material in CO(2) hydrogenation and methanol steam reforming was compared with conventionally prepared Cu/ZnO/Al(2)O(3) reference catalysts. The observed lower performance of the spinel-based samples is attributed to a lack of synergetic interaction of the Cu nanoparticles with ZnO due to the incorporation of Zn(2+) in the stable spinel lattice. Despite its lower performance, however, the nanostructured nature of the spinel catalyst was stable after thermal treatment up to 500 °C in contrast to other Cu-based catalysts. Furthermore, a large fraction of the re-oxidized copper migrates back into the spinel upon calcination of the reduced catalyst, thereby enabling a regeneration of sintered catalysts after prolonged usage at high temperatures. Similarly prepared samples with Ga instead of Al exhibit a more crystalline catalyst with a spinel particle size around 20 nm. The slightly decreased Cu(0) surface area of 3.2 m(2) g(-1) due to less copper incorporation is not a significant drawback for the methanol steam reforming.     

Influence of the chemical structure on the thermal degradation of the glucosinolates in broccoli sprouts

Glucosinolates are secondary plant metabolites occurring in Brassica vegetables. Food processing significantly reduces glucosinolate content, among other things due to thermal degradation. As there is only little information about thermal glucosinolate breakdown, the influence of the chemical structure as well as the influence of different pH to thermal degradation of individual glucosinolates was studied by analysing desulphoglucosinolates with HPLC-DAD. Thermal degradation was forced by heating broccoli sprouts at 130 °C in dry medium, whereas the influence of the pH was studied by cooking at 100 °C in aqueous medium. Within each group of glucosinolates differences in thermal degradation were revealed. Within the sulphur containing aliphatic glucosinolates the oxidative state of the sulphur atom as well as the side chain length influenced the reactivity. Among the indole glucosinolates great differences in stability were observed. A hydroxyl function in the side chain generally seems to destabilise glucosinolates. Glucosinolates were most stable towards thermal treatment in neutral and slightly acidic medium, whereas they degraded more rapidly in basic medium.     

Arrangement of layered double hydroxide in a polyethylene matrix studied by a combination of complementary methods

Organically modified ZnAl Layered Double Hydroxides (ZnAl-LDH) was synthesized and melt blended with polyethylene to obtain nanocomposites. The resulting morphology was investigated by a combination of Differential Scanning Calorimetry (DSC), Small and Wide-angle X-ray scattering (SAXS and WAXS) and dielectric relaxation spectroscopy (DRS). The arrangement (intercalation) of polyethylene chains between LDH stacks was investigated employing SAXS. The homogeneity of the nanocomposites and average number of stack size (4–6 layers) were determined using scanning microfocus SAXS (BESSY II). DSC and WAXS results show that the degree of crystallinity decreases linearly with the increasing content of LDH. The extrapolation of this dependence to zero estimates a limiting concentration of ca. 45% LDH where the crystallization of PE is completely suppressed by the nanofiller. The dielectric spectra of the nanocomposites show several relaxation processes which are discussed in detail. The intensity of the dynamic glass transition (β-relaxation) increases with the concentration of LDH. This is attributed to the increasing concentration of the exchanged anion sodium dodecylbenzene sulfonate (SDBS) which is adsorbed at the LDH layers. Therefore, a detailed analysis of the β-relaxation provides information about the structure and the molecular dynamics in the interfacial region between the LDH layers and the polyethylene matrix which is otherwise dielectrically invisible (low dipole moment).     

Long COVID: Association of Functional Autoantibodies against G-Protein-Coupled Receptors with an Impaired Retinal Microcirculation

Long COVID (LC) describes the clinical phenotype of symptoms after infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Diagnostic and therapeutic options are limited, as the pathomechanism of LC is elusive. As the number of acute SARS-CoV-2 infections was and is large, LC will be a challenge for the healthcare system. Previous studies revealed an impaired blood flow, the formation of microclots, and autoimmune mechanisms as potential factors in this complex interplay. Since functionally active autoantibodies against G-protein-coupled receptors (GPCR-AAbs) were observed in patients after SARS-CoV-2 infection, this study aimed to correlate the appearance of GPCR-AAbs with capillary microcirculation. The seropositivity of GPCR-AAbs was measured by an established cardiomyocyte bioassay in 42 patients with LC and 6 controls. Retinal microcirculation was measured by OCT–angiography and quantified as macula and peripapillary vessel density (VD) by the Erlangen-Angio Tool. A statistical analysis yielded impaired VD in patients with LC compared to the controls, which was accentuated in female persons. A significant decrease in macula and peripapillary VD for AAbs targeting adrenergic β2-receptor, MAS-receptor angiotensin-II-type-1 receptor, and adrenergic α1-receptor were observed. The present study might suggest that a seropositivity of GPCR-AAbs can be linked to an impaired retinal capillary microcirculation, potentially mirroring the systemic microcirculation with consecutive clinical symptoms.