Multi-parameter evaluation of fast sol–gel process by terahertz measurements

We present a feasibility study to apply terahertz (THz) spectroscopy and THz imaging as non-destructive diagnostic tools for sol–gel analysis, manufacturing and quality control. By performing THz spectroscopy on liquid and solid samples we were able to follow several key parameters during the sol–gel formation process and of the final product. Sol–gel transformations were monitored by THz absorption, whereas density changes have been observed through changes in refractive indices. Time domain spectroscopy (TDS), both in transmission and reflection geometries, was used to monitor the properties of fast sol–gel resins. THz imaging of gold coated, thin-film sol–gel enables us to determine inhomogeneities and defects in their internal structure. We demonstrated that THz spectroscopy can be implemented as an online analytical tool for multi-parameter evaluation of the sol–gel process during fabrication, and of the final product.     

Convergent chemoenzymatic synthesis of O-GalNAc rare cores 5, 7, 8 and their sialylated forms

All O-GalNAc glycans are derived from 8 cores with 2 or 3 monosaccharides linked via α- or β-glycosidic bonds. While chemical and chemoenzymatic syntheses of β-linked cores 1–4 and 6 and derived glycans have been well developed, the preparation of α-linked rare cores 5, 7, and 8 is challenging due to the presence of this 1,2-cis linkage. Meanwhile, the biosynthesis and functional roles of these structures are poorly understood. Herein, we synthesize 3 α-linked rare cores with exclusive α-configuration from a versatile precursor through multifaceted chemical modulations. Efficient regioselective α2-6sialylion of the rare cores was then achieved by Photobacterium damselae α2-6sialyltransferase-catalyzed reactions. These structures, together with β-linked cores 1–4 and 6, and their sialylated forms, were fabricated into a comprehensive O-GalNAc core microarray to profile the binding of clinically important GalNAc-specific lectins. It is found that only Tn, (sialyl-)core 5, and core 7 are the binders of WFL, VVL, and SBA, while DBA only recognized (sialyl-)core 5, and Jacalin is the only lectin that binds core 8. In addition, activity assays of human α-N-acetylgalactosaminide α2-6sialyltransferases (ST6GalNAcTs) towards the cores suggested that ST6GalNAc1 may be involved in the biosynthesis of previously identified sialyl-core 5 and sialyl-core 8 glycans. In conclusion, we provide efficient routes to access α-linked O-GalNAc rare cores and derived structures, which are valuable tools for functional glycomics studies of mucin O-glycans.

Mucin rare cores 5, 7, and 8 with 1,2-cis glycosidic bonds were prepared with exclusive stereo-selectivity from a versatile precursor. Enzyme-catalyzed regio-selective sialylation was then achieved, yielding natural sialylated rare cores.     

Size direction games over the real line. III

We prove, using the continuum hypothesis, thatD (the direction player) has a winning strategy in {ie442-1} for some uncountableX, and that there is an uncountableX which intersects each perfect nowhere-dense set of reals in a countable set such thatD does not win in {ie442-2} for everya. We also give another proof to the fact that Γ^S (X) is a win forD is countable.     

Self-focusing in the presence of small time dispersion and nonparaxiality

We analyze the combined effect of small time dispersion and nonparaxiality on self-focusing and its ability to arrest the blowup of laser pulses by deriving reduced equations that depend on only the propagation distance and time. We calculate the pulse duration for which time dispersion dominates over nonparaxiality, or vice versa. We identify additional terms (shock term, group-velocity nonparaxiality, etc.)that should be retained when time dispersion and nonparaxiality are of comparable magnitude. These additional terms lead to temporal asymmetry, and in the visible spectrum they can dominate over both time dispersion and nonparaxiality.     

Conversion of CO2 by non-Thermal Inductively-Coupled Plasma Catalysis

CO\begin{document}$ _2 $\end{document} decomposition is a very strongly endothermic reaction where very high temperatures are required to thermally dissociate CO\begin{document}$ _2 $\end{document}. Radio frequency inductively-coupled plasma enables to selectively activate and dissociate CO\begin{document}$ _2 $\end{document} at room temperature. Tuning the flow rate and the frequency of the radio frequency inductively-coupled plasma gives high yields of CO under mild conditions. Finally the discovery of a plasma catalytic effect has been demonstrated for CO\begin{document}$ _2 $\end{document} dissociation that shows a significant increase of the CO yield by metallic meshes. The metallic meshes become catalysts under exposure to plasma to activate the recombination reaction of atomic O to yield O\begin{document}$ _2 $\end{document}, thereby reducing the reaction to convert CO back to CO\begin{document}$ _2 $\end{document}. Inductively-coupled hybrid plasma catalysis allows access to study and to utilize high CO\begin{document}$ _2 $\end{document} conversion in a non-thermal plasma regime. This advance offers opportunities to investigate the possibility to use radio frequency inductively-coupled plasma to store superfluous renewable electricity into high-valuable CO in time where the price of renewable electricity is plunging.     

Instability of bound states of a nonlinear Schrödinger equation with a Dirac potential

We study analytically and numerically the stability of the standing waves for a nonlinear Schrödinger equation with a point defect and a power type nonlinearity. A major difficulty is to compute the number of negative eigenvalues of the linearized operator around the standing waves. This is overcome by a perturbation method and continuation arguments. Among others, in the case of a repulsive defect, we show that the standing-wave solution is stable in and unstable in under subcritical nonlinearity. Further we investigate the nature of instability: under critical or supercritical nonlinear interaction, we prove the instability by blowup in the repulsive case by showing a virial theorem and using a minimization method involving two constraints. In the subcritical radial case, unstable bound states cannot collapse, but rather narrow down until they reach the stable regime (a finite-width instability). In the nonradial repulsive case, all bound states are unstable, and the instability is manifested by a lateral drift away from the defect, sometimes in combination with a finite-width instability or a blowup instability.     

Collapse of optical vortices

We theoretically and experimentally investigate the self-focusing of optical vortices in Kerr media. We observe collapse to a distinct self-similar profile, which becomes unstable to azimuthal perturbations. We analyze the azimuthal modulational instability for ring-shaped vortices and predict the number of azimuthal maxima solely as a function of power and topological charge. In our experiments, the observed multiple-filamentation patterns are in excellent agreement with our theoretical analysis.     

In-situ UV-visible study of Pd nanocluster formation in solution

The formation of Pd nanoclusters in solution is studied. This system has two types of light-absorbing species: Pd ions which absorb light via electronic transitions and Pd clusters and aggregates which absorb light via valence-conduction transitions and also scatter light due to their nanometric dimensions. Here we monitor these dynamic changes using UV-visible spectroscopy. The reduction and clustering concentration profiles are extracted from the raw data using a combination of net analyte signal (NAS) and principal component analysis (PCA) methods. PdCl2, Pd(OAc)2 and Pd(NO3)2 are used as Pd2+ precursors and various tetra-n-octylammonium carboxylates are applied as reducing and stabilising agents. This in situ approach enables the quantification of both the reduction of the Pd2+ ions and the growth of the Pd clusters. Kinetic models that account for ion reduction, cluster growth and aggregation are presented and the influence of the counteranions and the reducing agents on these processes is discussed.