Vibrations of a continuous web on elastic supports

We consider an infinite, homogenous linearly elastic beam resting on a system of linearly elastic supports, as an idealized model for a paper web in the middle of a cylinder-based dryer section. We obtain closed-form analytical expressions for the eigenfrequencies and the eigenmodes. The frequencies increase as the support rigidity is increased. Each frequency is bounded from above by the solution with absolutely rigid supports, and from below by the solution in the limit of vanishing support rigidity. Thus in a real system, the natural frequencies will be lower than predicted by commonly used models with rigid supports.     

Bayesian Variable Selection on Model Spaces Constrained by Heredity Conditions

This article investigates Bayesian variable selection when there is a hierarchical dependence structure on the inclusion of predictors in the model. In particular, we study the type of dependence found in polynomial response surfaces of orders two and higher, whose model spaces are required to satisfy weak or strong heredity conditions. These conditions restrict the inclusion of higher-order terms depending upon the inclusion of lower-order parent terms. We develop classes of priors on the model space, investigate their theoretical and finite sample properties, and provide a Metropolis–Hastings algorithm for searching the space of models. The tools proposed allow fast and thorough exploration of model spaces that account for hierarchical polynomial structure in the predictors and provide control of the inclusion of false positives in high posterior probability models.     

Hyperfine structure in optical spectra of LiYF4-Ho3+: forbidden transitions

The hyperfine lines of the forbidden Γ₃₄?→?Γ₃₄ optical transition are observed in the axially polarized absorption spectra of Ho³⁺ in LiYF₄. They are explained by an admixture of nearby lying Γ₂ and Γ₁ crystal field states by the perpendicular part of the magnetic dipole hyperfine interaction.     

Elastic moduli of η‐Ta2N3, a tough self‐healing material,via laser ultrasonics

The elastic moduli of the dense polycrystalline oxygen‐bearing η‐Ta₂N₃, a novel hard and tough high‐pressure (HP) material, were measured using the laser ultrasonic technique. The bulk modulus was determined to be B₀ = 281(15) GPa which is only ～11% below that from HP compression measurements. Our value of the shear modulus G₀ = 123(2) GPa is below those ones predicted theoretically for model structures. The discrepancies in G₀ could be due to a substitution of an‐ ions and the formation of cation vacancies in η‐Ta₂N₃. Self‐healing behaviour of η‐Ta₂N₃ by mechanical polishing was observed and confirmed by two independent experimental methods. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bulk and surface electron transport in topological insulator candidate YbB6–δ

We report the study of transport and magnetic properties of the YbB_6–δsingle crystals grown by inductive zone melting. A strong disparity in the low temperature resistivity, Seebeck and Hall coefficients is established for the samples with the different level of boron deficiency. The effective parameters of the charge transport in YbB_6–δ are shown to depend on the concentration of intrinsic defects, which is estimated to range from 0.09% to 0.6%. The pronounced variation of Hall mobility μ_H found for bulk holes is induced by the decrease of transport relaxation time from τ ≈ 7.7 fs for YbB_5.994 to τ ≈ 2.2 fs for YbB_5.96. An extra contribution to conductivity from electrons with μ_H≈ –1000 cm² V^–1 s^–1 and the very low concentration n /n_Yb≈ 10^–6 discovered below 20 K for all the single crystals under investigation is suggested to arise from the surface electron states appeared in the inversion layer due to the band bending. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Effect of thermosensitive matrix-phase transition on urease-catalyzed urea hydrolysis

Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing gel is shown to increase in the presence of urea. Below a lower critical solution temperature (LCST) of the polymer, the immobilized u reaseactually has thesame catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content.     

Nature of cationic poly(propylenimine) dendrimers in aqueous solutions as studied using versatile indicator dyes

Aqueous solutions of four cationic poly(propylenimine) low-generation dendrimers of different architecture and hydrophobicity have been examined as media for acid-base reactions of indicator dyes. The cationic dendrimers in solution can be considered as oligomers of cationic polyelectrolytes, or surfactant-like species, able to form micelles through self-association or sometimes even as unimolecular micelles. The dendrimers influence the ionization constants, tautomeric equilibria, and absorption/emission/excitation spectra of indicator dyes. The p K a values of the majority of the indicator dyes decrease in dendrimer solutions, often by 1-2 p K a units, similar to effects registered in micellar solutions of cationic surfactants. Analogously, the shifts of absorption band maxima indicate that the microenvironments of the dyes bound to the dendrimers are less polar than in water. However, some spectral effects denote the specificity of the dendrimers. The greatest difference between the dendrimers and spherical surfactant micelles is revealed by kinetic processes, especially of bromophenol blue alkaline fading in a dendrimer solution but not in a micellar surfactant solution. Within the dendrimer series, the most significant differences were observed for substances possessing n-dodecyl tails on the one hand and those without such hydrophobic portions on the other. For the last-named, the decrease in p K a's of indicators, band shifts of their anions, and in particular displacement of tautomeric equilibria compared with aqueous solutions are much smaller than for more hydrophobic dendrimers.     

Host-guest complexes of carotenoids with beta-glycyrrhizic acid

The structure, stability, and reactivity of the host-guest complexes between a set of carotenoids and the triterpene glycoside, beta-glycyrrhizic acid (GA), were investigated by different physicochemical techniques: high-performance liquid chromatography, optical absorption, and fluorescence spectroscopy. It has been demonstrated recently that the molecular complexes of GA with a number of drugs are characterized by reduced toxicity and increased therapeutic activity of these drugs. In the present work it was found that carotenoids form 1:2 complexes with GA in aqueous solutions as well as in polar organic solvents, methanol, acetonitrile, and dimethylsulfoxide. We assume that the structure of the complex is a cycliclike dimer of GA encapsulating a carotenoid molecule. The stability constants in all solvents are near 10(4) M(-1). In addition, GA forms inclusion complexes with carotenoid radical cations, which results in their stabilization. Complex formation (a) decreases the rate of electron transfer from carotenoids to electron acceptors (Fe3+ or quinone) and (b) considerably increases the lifetime of the carotenoid-quinone charge-transfer complex and the yield of the major product (a carotenoid-quinone adduct). A thermodynamic study shows that hydrophobic interactions are the main driving force of the carotenoid-GA complex formation. These results are important for understanding both the nature of GA complexes and the influence of GA on the therapeutic activity of some drugs. Furthermore, carotenoid-GA complexes could be used for the design of artificial light-harvesting, photoredox, and catalytic systems.     

Structural Studies and Anticancer Activity of a Novel Class of β‐Peptides

Functionalized oligomeric organic compounds with well‐defined β‐proline scaffold have been synthesized by a cycloadditive oligomerization approach in racemic and enantiopure forms. The structure of the novel β‐peptides was investigated by NMR spectroscopic and X‐ray methods determining the conformational shapes of the β‐proline oligomers in solution and solid states. The main structural elements subject to conformational switches are β‐peptide bonds between 5‐arylpyrrolidine‐2‐carboxylic acid units existing in Z/E configurations. The whole library of short β‐peptides and intermediate acrylamides has been tested on antiproliferative activity towards the hormone‐refractory prostate cancer cell line PC‐3 revealing several oligomeric compounds with low micromolar and submicromolar activities. Bromine‐substituted dimeric and trimeric acrylamides induced caspase‐dependent apoptosis of PC‐3 cells through cell‐cycle arrest and mitochondrial damage.