Effect of viscosity on internal waves from a source in a wall

The solution for a line source of oscillatory strength kept at the origin in a wall bounding a semi-infinite viscous imcompressible stratified fluid is presented in an integral form. The behaviour of the flow at far field and near field is studied by an asymptotic expansion procedure. The streamlines for different parameters are drawn and discussed. The real characteristic straight lines present in the inviscid problem are modified by the viscosity and the solutions obtained are valid even at the resonance frequency.     

Multiple ionic-plasmon resonances in naturally occurring multiwall nanotubes: infrared spectra of chrysotile asbestos

Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of Mg(3)Si(2)O(5)(OH)(4). We show by experiment and theory that the infrared spectra of chrysotile present multiple ionic-plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.     

Markov jump random c.d.f.’s and their posterior distributions

In this article we introduce the class of Markov jump random c.d.f.’s as a sub-class of the Q$Q$-Markov prior distributions studied in R.M. Balan [Q$Q$-Markov random probability measures and their posterior distributions, Stochastic Process. Appl. 109 (2004) 296–316]. Our main result states that if the prior distribution of a sample is a Markov jump process, then the posterior distribution can also be viewed as the distribution of a Markov jump process, whose transition mechanism and infinitesimal behavior have been updated in the light of the new data.     

One-dimensional confinement of a nanosized metal organic framework in carbon nanofibers for improved gas adsorption

The loading of a Zn-terephthalate based MOF in the inner cavity as well as on the outer walls of a hollow carbon nanofiber (CNF) creates MOF@CNF hybrids. This hybrid 'MOF@CNF' displayed improved thermal stability as well as gas adsorption compared to the individual counterparts.     

Photo‐Hydrogen‐Evolving Molecular Catalysts Consisting of Polypyridyl Ruthenium(II) Photosensitizers and Platinum(II) Catalysts: Insights into the Reaction Mechanism

The mechanism of photoinduced hydrogen evolution from water driven by the first photo‐hydrogen‐evolving molecular catalyst ( 1 ), given by a coupling of [Ru(bpy)₂(5‐amino‐phen)]²⁺ and [PtCl₂(4,4′‐dicarboxy‐bpy)] (bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline), was investigated in detail. The H₂ evolution rate was found to obey Michaelis–Menten enzymatic kinetics with regard to the concentration of EDTA (ethylenediamine tetra‐acetic acid disodium salt, sacrificial electron donor), which indicates that an ion‐pair formation between the dicationic 1 and the dianionic form of EDTA (pH 5) is a key step leading to H₂ formation. A 2:1 coupling product of 1 and ethylenediamine (i.e., a {Ru^II₂Pt^II₂} complex 2 ) was found to show significantly higher photo‐hydrogen‐evolving (PHE) activity than 1 , which revealed the validity of the bimolecular activation proposed in our previous study. The PHE activity of 2 was also observed to be linear to the concentration of 2 , which indicates that H₂ formation through the intermolecular path competes with the intramolecular path. Molecular orbital diagrams, conformational features, and Pt???H(water or acetic acid) hydrogen bonds were characterized by DFT calculations.     

Determination of the non-linear parameter (mobility factor) of the Giesekus constitutive model using LAOS procedure

The paper introduces a novel procedure to determine the non-linear parameter of the Giesekus model, in relation to the characterization of the non-linear oscillatory shear regime of viscoelastic polymer solutions based on polyacrylamide. Instead of using the shear-thinning viscosity as the representative non-linear effect, the third harmonic in the Fourier spectrum of the shear stress response signal is considered for computing the mobility factor. The fluid is subjected to large amplitude oscillatory shear (LAOS) and its response is recorded. Deviations of this signal from the sinusoidal form are specific to each material and gives both qualitative and quantitative measures of the non-linearity. By fitting the material response with the corresponding numerical solutions of the n-modes Giesekus constitutive relation, one can extract the values of the non-linear α_i-parameters that describe the fluid rheology. It is demonstrated that this procedure, which can be successfully applied to semi-concentrated polymer solutions, provides better results than the classical viscosity-fit method.     

Neutral additives enhance the metal-chelate affinity adsorption of nucleic acids: role of water activity

Immobilized metal-chelate affinity chromatography has been widely used in the purification of proteins, and we have recently found that it can also be applied to purification of nucleic acids through interactions involving exposed bases, especially purines. Here we report that the inclusion of moderate quantities of neutral solutes in the buffer substantially enhances the binding affinity of nucleic acids for immobilized metal-chelate affinity adsorbents. Addition of 20% (v/v) of solutes such as ethanol, methanol, isopropanol, n-propanol, and dimethyl sulfoxide enhances the initial affinity of binding of total yeast RNA by 4.4-, 3.8-, 3.7-, 3.0-, and 2.8-fold, respectively for Cu(II)-iminodiacetic acid (IDA) agarose adsorbent, and the weaker adsorption by Cu(II)-nitrilotriacetic acid (NTA) agarose was even more strongly enhanced. The adsorption affinities of the smaller oligodeoxynucleotide molecules A20, G20, C20 and T20 also increase with the addition of ethanol, suggesting that the effect is not significantly mediated by conformational changes. Binding enhancement generally correlates with reduction of water activity by the various solutes, as predicted by several models of solution thermodynamics, consistent with an entropic contribution by displacement of waters from the metal-chelate. Interestingly, the enhancement was not seen with the proteins bovine serum albumin and lysozyme.     

A Cascade Strategy Enables a Total Synthesis of (±)‐Morphine

Morphine has been a target for synthetic chemists since Robinson proposed its correct structure in 1925, resulting in a large number of total syntheses of morphine alkaloids. Here we report a total synthesis of (±)‐morphine that employs two key strategic cyclizations: 1) a diastereoselective light‐mediated cyclization of an O‐arylated butyrolactone to form a tricyclic cis‐fused benzofuran and 2) a cascade ene–yne–ene ring closing metathesis to forge the tetracyclic morphine core. This approach enables a short and stereoselective synthesis of morphine in an overall yield of 6.6 %.     

Parabolic Anderson Model with Space-Time Homogeneous Gaussian Noise and Rough Initial Condition

In this article, we study the parabolic Anderson model driven by a space-time homogeneous Gaussian noise on \(\mathbb {R}_{+} \times \mathbb {R}^d\), whose covariance kernels in space and time are locally integrable nonnegative functions which are nonnegative definite (in the sense of distributions). We assume that the initial condition is given by a signed Borel measure on \(\mathbb {R}^d\), and the spectral measure of the noise satisfies Dalang’s (Electron J Probab 4(6):29, 1999) condition. Under these conditions, we prove that this equation has a unique solution, and we investigate the magnitude of the p-th moments of the solution, for any \(p \ge 2\). In addition, we show that this solution has a Hölder continuous modification with the same regularity and under the same condition as in the case of the white noise in time, regardless of the temporal covariance function of the noise.