Effect of Natural Deep Eutectic Solvents on trans-Resveratrol Photo-Chemical Induced Isomerization and 2,4,6-Trihydroxyphenanthrene Electro-Cyclic Formation

trans-Resveratrol is a natural bioactive compound with well-recognized health promoting effects. When exposed to UV light, this compound can undergo a photochemically induced trans/cis isomerization and a 6π electrochemical cyclization with the subsequent formation of 2,4,6-trihydroxyphenanthrene (THP). THP is a potentially harmful compound which can exert genotoxic effects. In this work we improved the chromatographic separation and determination of the two resveratrol isomers and of THP by using a non-commercial pentafluorophenyl stationary phase. We assessed the effect of natural deep eutectic solvents (NaDES) as possible photo-protective agents by evaluating cis-resveratrol isomer and THP formation under different UV-light exposure conditions with the aim of enhancing resveratrol photostability and inhibiting THP production. Our results demonstrate a marked photoprotective effect exerted by glycerol-containing NaDES, and in particular by proline/glycerol NaDES, which exerts a strong inhibitory effect on the photochemical isomerization of resveratrol and significantly limits the formation of the toxic derivative THP. Considering the presence of resveratrol in various commercial products, these results are of note in view of the potential genotoxic risk associated with its photochemical degradation products and in view of the need for the development of green, eco-sustainable and biocompatible resveratrol photo-stable formulations.     

Effect of temperature on the photophysics of rhodamine 101 in a polar solvent

The absorption and emission properties of rhodamine 101 in polar, aprotic propionitrile-butyronitrile (4:5 v/v) solvent have been investigated. The equilibrium between the neutral zwitterionic and lactonic (colourless) forms is strongly affected by the temperature in the range 293–144 K. In dilute solution (1.12×10⁻⁵M), at room temperature the lactonic form is 98%, while at 144 K the zwitterionic form predominates, being 79%. These findings are discussed in terms of differential stabilization of the lactonic and zwitterionic forms through non-specific solute-solvent interactions involving the COO⁻¹ group.     

Theoretical study of the interaction between sodium ion and a cyclopeptidic tubular structure

DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure.     

On the similarity solutions of the KdV equation with variable coefficients

In this paper we apply the similarity methods to a modified Korteweg-deVries equation containing an arbitrary function of time which describes the inhomogeneity effects. Some classes of functional forms for this arbitrary function are characterized and the related similarity solutions are determined.     

A semi-analytical finite element formulation for modeling stress wave propagation in axisymmetric damped waveguides

A semi-analytical finite element (SAFE) method is presented for analyzing the wave propagation in viscoelastic axisymmetric waveguides. The approach extends a recent study presented by the authors, in which the general SAFE method was extended to account for material damping. The formulation presented in this paper uses the cylindrical coordinates to reduce the finite element discretization over the waveguide cross-section to a mono-dimensional mesh. The algorithm is validated by comparing the dispersion results with viscoelastic cases for which a Superposition of Partial Bulk Waves solution is known. The formulation accurately predicts dispersion properties and does not show any missing root. Applications to viscoelastic axisymmetric waveguides with varying mechanical and geometrical properties are presented.     

Unprecedented Diastereoselective Arylogous Michael Addition of Unactivated Phthalides

The first highly enantioselective arylogous Michael reaction (AMR) of 3-unsubstituted phthalides has been described. This phase-transfer methodology, which uses catalytic amounts of KOH/18-crown-6 catalyst in mesitylene in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), gives access to a broad range of 3-monosubstituted phthalides with high levels of syn diastereoselectivity and good yields, starting from 3-unsubstituted derivatives and diverse α,β-unsaturated carbonyl compounds. The reaction also applies to unactivated 3-alkyl phthalides to afford 3,3-dialkyl derivatives. A plausible mechanism has been suggested. DFT analysis of possible transition states gives a rationale of the high syn diastereoselectivity observed and its correlation with the solvent's dielectric constant.     

Preface to the special topic: New advances in water and water systems

<正>Water and related systems play a central role in science and technology. Although water has unusual and anomalous behaviors,if compared with normal liquids, it is of fundamental interest in many research fields going from chemical-physics to life sciences. The first and well known example of these anomalies is the density maximum, at 277 K, intuited by Galilei [1] in 1612and lately discovered in Florence [2].     

Nonlinear vibration of the spiral bevel gear with a novel tooth surface modification method

Meccanica - The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly...