Structure of the O-Specific Polysaccharide of Hafnia Alvei 23 Having an Oligosaccharide-Phosphate Repeating Unit

ABSTRACT

Lipopolysaccharide (LPS) of Hafnia alvei 23 has an acid-labile O-specific polysaccharide (OPS) with a pentasaccharide-phosphate repeating unit containing D-Glc1P, D-GlcNAc, L-Fuc, 6-deoxy-D-talose (D-6dTal), 4-acetamido-4,6-dideoxy-D-glucose (D-Qui4NAc), and an O-acetyl group. A partially degraded OPS was obtained by hydrolysis of LPS with 0.25 M sodium acetate in aqueous 0.5% acetic acid. Fractionation of LPS on Sephadex G-200 in DOC buffer allowed isolation of long-chain LPS species which, together with OPS, were studied by methylation analysis, chemical degradations (O-deacetylation, dephosphorylation with 48% hydrofluoric acid, Smith degradation), and ¹H and ¹³C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, and H-detected ¹H,¹³C heteronuclear single-quantum coherence (HSQC) experiments. The following structure of the repeating unit of OPS was established:     

Heats of displacement of hydrogen from palladium by noble gases

It has been observed that noble gases, such as helium, neon and argon produce heat evolution when contacted with Pd powder partially saturated with hydrogen. These phenomena have been studied with flow-through adsorption microcalorimetry. The observed exothermic effects are comparable to those usually associated with the heat of sorption of hydrogen in palladium. It is suggested that the noble gases displace the adsorbed H species from the surface of Pd, causing their reabsorption in the Pd lattice with the exothermic heat of PdH bonds formation, or the formation of H₂, both heat evolutions being observed with a flow-through microcalorimeter.     

Time-resolved streak camera system with solid state laser and optical parametric generator in different spectroscopic applications

Apparatus to study time-evolution of emission spectra over very wide time and spectral range is described. Excitation part of the equipment consists of solid state Nd:YAG laser and optical parametric generator. The heart of the detection system consists of spectrograph and streak camera. The significance of optics and electronics built in the system for proper, fast and convenient measurements is underlined. The results of donor-acceptor energy transfer in a rigid polyvinyl alcohol matrix serve here as an example of application our equipment to study complex systems.     

The formation of oxide nanoparticles on the surface of natural clinoptilolite

Nanoparticles of NiO, ZnO and Cu₂O crystallize when the Ni-, Zn- and Cu-exchanged natural clinoptilolite, respectively, are dehydrated by heating in air at 550 °C. The dehydration of Mn-exchanged clinoptilolite does not lead to the crystallization of manganese oxide but affects the crystallinity of the host clinoptilolite lattice, which becomes amorphous. The NiO, ZnO and Cu₂O nanoparticles are found to be randomly dispersed in the clinoptilolite matrix. The particle size varies from 2 to 5 nm and exceeds the aperture of the clinoptilolite channel (approximately 0.4 nm), suggesting that the crystallization of the oxide phases takes place on the surfaces of clinoptilolite microcrystals.     

The fixed point property in ordered sets of width two

We consider the fixed point property (FPP) in an ordered set of width two (every antichain contains at most two elements). The necessary condition of the FPP and a number of equivalent conditions to the FPP in such sets is established. The product theorem is proved, as well.     

Tests of discrete symmetries with the neutral kaon system at the KLOE and KLOE-2 experiments

The KLOE-2 experiment continues and extends the program of its predecessor KLOE in the field of discrete symmetry tests with the K meson system, among other studies which comprise light meson spectroscopy, dark matter searches and γγ physics. Together, KLOE and KLOE-2 have recorded the largest sample (almost 8 fb^??1) of e⁺e^? collisions at the energy equal to ? meson mass, amounting to 2.4 × 10¹⁰ of produced ? mesons. We report on the latest results and ongoing analyses of KLOE and KLOE-2 concerning discrete symmetry tests and measurements of symmetry-violating observables. A measurement of the CPT violation sensitive asymmetry in semileptonic decays of K˙S with 1.7 fb^??1 of KLOE data will be presented, which improves the sensitivity w.r.t. previous measurements about twice. Moreover, status of direct tests of T and CPT in transitions of neutral kaons performed with the ? →K˙SK˙L → πeν, 3π⁰(2π) processes will be reported, followed by the search of the CP-violating decay K˙S → 3π⁰ using the data recently acquired by KLOE-2.     

Dilation theorems for positive definite operator kernels having majorants

Dilation theorems for Banach space valued stochastic processes and operator valued positive definite kernels are considered. It is shown, e.g., that a Banach space valued stochastic process X can be dilated to another process Y, if and only if the covariance kernel of Y is a majorant of the covariance kernel of X. Positive definite operator kernels having majorants of certain special type are characterized.     

Numerical study of light correlations in a random medium close to the Anderson localization threshold

We applied a finite-difference time domain algorithm to the study of field and intensity correlations in random media. Close to the onset of Anderson localization, we observe deviations of the correlation functions, in both shape and magnitude, from those predicted by the diffusion theory. Physical implications of the observed phenomena are discussed.     

Comparison of Proton Acceptor and Proton Donor Properties of H2O and H2O2 in Organic Crystals of Drug-like Compounds: Peroxosolvates vs. Crystallohydrates

Two new peroxosolvates of drug-like compounds were synthesized and studied by a combination of X-ray crystallographic, Raman spectroscopic methods, and periodic DFT computations. The enthalpies of H-bonds formed by hydrogen peroxide (H₂O₂) as a donor and an acceptor of protons were compared with the enthalpies of analogous H-bonds formed by water (H₂O) in isomorphic (isostructural) hydrates. The enthalpies of H-bonds formed by H₂O₂ as a proton donor turned out to be higher than the values of the corresponding H-bonds formed by H₂O. In the case of H₂O₂ as a proton acceptor in H-bonds, the ratio appeared reversed. The neutral O∙∙∙H-O/O∙∙∙H-N bonds formed by the lone electron pair of the oxygen atom of water were the strongest H-bonds in the considered crystals. In the paper, it was found out that the low-frequency Raman spectra of isomorphous crystalline hydrate and peroxosolvate of N-(5-Nitro-2-furfurylidene)-1-aminohydantoin are similar. As for the isostructural hydrate and peroxosolvate of the salt of protonated 2-amino-nicotinic acid and maleic acid monoanion, the Raman spectra are different.