Expedient Access to Functionalized Furan/3(2H)-furanone Ensembles via Microwave-Assisted Domino Reactions

A one-pot linkage between furan and 3(2H)-furanone rings has been effected via the microwave-assisted Et₃N-catalyzed domino condensation of the furan and benzofuran carboxylic acids with available cyanopropargylic alcohols (MeCN, 100 °C, 1.2 atm, 2–17 h). Despite involving a number of C-H-forming/breaking steps, the assembly is chemoselective and the final products, 5-(2-furyl)-3(2H)-furanones, are formed in 59–96% yields.     

Peroxiredoxin-1 from the Human Hookworm Ancylostoma ceylanicum Forms a Stable Oxidized Decamer and Is Covalently Inhibited by Conoidin A

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Functional and nonlinear optical metasurfaces

Optical metasurfaces are thin‐layer subwavelength‐patterned structures that interact strongly with light. Metasurfaces have become the subject of several rapidly growing areas of research, being a logical extension of the field of metamaterials towards their practical applications. Metasurfaces demonstrate many useful properties of metadevices with engineered resonant electric and magnetic optical responses combined with low losses of thin‐layer structures. Here we introduce the basic concepts of this rapidly growing research field that stem from earlier studies of frequency‐selective surfaces in radiophysics, being enriched by the recent development of metamaterials and subwavelength nanophotonics. We review the most interesting properties of photonic metasurfaces, demonstrating their useful functionalities such as frequency selectivity, wavefront shaping, polarization control, etc. We discuss the ways to achieve tunability of metasurfaces and also demonstrate that nonlinear effects can be enhanced with the help of metasurface engineering.

     

Synthesis,photophysical and electrochemical properties of novel 6,12-di(thiophen-2-yl) substituted indolo[3,2-b]carbazoles

Novel 5,11-dialkyl-6,12-di(thiophen-2-yl) substituted 5,11-dihydroindolo[3,2-b]carbazoles have been obtained and plausible ways for their further modifications via the Friedel–Crafts reaction are presented. The formylation of these indolo[3,2-b]carbazoles with dichloromethyl alkyl esters catalysed by Lewis acids leads to the formation of the corresponding 2,8-diformyl derivatives. Applicability of this formylation method for modification of indolo[3,2-b]carbazoles bearing electron-rich aromatic substituents at C-6 and C-12 has also been demonstrated. The Knoevenagel condensation of 2,8-dialdehydes with active methylene nitriles has been studied. The measurements of optical and redox properties for a number of new indolo[3,2-b]carbazoles have been performed.     

Photosensitizing Antivirals

Antiviral action of various photosensitizers is already summarized in several comprehensive reviews, and various mechanisms have been proposed for it. However, a critical consideration of the matter of the area is complicated, since the exact mechanisms are very difficult to explore and clarify, and most publications are of an empirical and “phenomenological” nature, reporting a dependence of the antiviral action on illumination, or a correlation of activity with the photophysical properties of the substances. Of particular interest is substance-assisted photogeneration of highly reactive singlet oxygen (¹O₂). The damaging action of ¹O₂ on the lipids of the viral envelope can probably lead to a loss of the ability of the lipid bilayer of enveloped viruses to fuse with the lipid membrane of the host cell. Thus, lipid bilayer-affine ¹O₂ photosensitizers have prospects as broad-spectrum antivirals against enveloped viruses. In this short review, we want to point out the main types of antiviral photosensitizers with potential affinity to the lipid bilayer and summarize the data on new compounds over the past three years. Further understanding of the data in the field will spur a targeted search for substances with antiviral activity against enveloped viruses among photosensitizers able to bind to the lipid membranes.     

A study of oleic acid-based hydrothermal preparation of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Nearly monodisperse, well crystalline, superparamagnetic CoFe₂O₄ nanoparticles with diameter of 6 nm were synthesized in oleic acid–water–pentanol system at 180 °C. Hydrothermal procedure, as an efficient and environment friendly alternative to organic decomposition methods, was investigated by variation of reaction conditions, and the particle formation mechanism was finally proposed (i.e., hydrolysis of metal oleates in organic phase, with size of the particles (5–8 nm) controlled by polarity-driven precipitation into water phase). As-prepared particles were hydrophobic due to coating by oleic acid. Further modification with dimercaptosuccinic acid led to water-dispersible particles with hydrodynamic diameter of 20 nm. Prepared particles were investigated by TEM, XRD, ICP-AES, light scattering, SQUID magnetometry, and Mössbauer spectroscopy.     

Generating Signals with Multiscale Time Irreversibility: The Asymmetric Weierstrass Function

Time irreversibility (asymmetry with respect to time reversal) is an important property of many time series derived from processes in nature. Some time series (e.g., healthy heart rate dynamics) demonstrate even more complex, multiscale irreversibility, such that not only the original but also coarse-grained time series are asymmetric over a wide range of scales. Several indices to quantify multiscale asymmetry have been introduced. However, there has been no simple generator of model time series with "tunable" multiscale asymmetry to test such indices. We introduce an asymmetric Weierstrass function W(A) (constructed from asymmetric sawtooth functions instead of cosine waves) that can be used to construct time series with any given value of the multiscale asymmetry. We show that multiscale asymmetry appears to be independent of other multiscale complexity indices, such as fractal dimension and multiscale entropy. We further generalize the concept of multiscale asymmetry by introducing time-dependent (local) multiscale asymmetry and provide examples of such time series. The W(A) function combines two essential features of complex fluctuations, namely fractality (self-similarity) and irreversibility (multiscale time asymmetry); moreover, each of these features can be tuned independently. The proposed family of functions can be used to compare and refine multiscale measures of time series asymmetry.     

Derivation of the Boltzmann equation and entropy production in functional mechanics

A derivation of the Boltzmann equation from the Liouville equation by the use of the Grad limiting procedure in a finite volume is proposed. We introduce two scales of space-time: macro- and microscale and use the BBGKY hierarchy and the functional formulation of classical mechanics. According to the functional approach to mechanics, a state of a system of particles is formed from the measurements, which are rational numbers. Hence, one can speak about the accuracy of the initial probability density function in the Liouville equation. We assume that the initial data for the microscopic density functions are assigned by the macroscopic one (so one can say about a kind of hierarchy and subordination of the microscale to the macroscale) and derive the Boltzmann equation, which leads to the entropy production.     

Trident pair production in strong laser pulses

We calculate the trident pair production amplitude in a strong laser background. We allow for finite pulse durations, while still treating the laser fields nonperturbatively in strong-field QED. Our approach reveals explicitly the individual contributions of the one-step and two-step processes. We also expose the role gauge invariance plays in the amplitudes and discuss the relation between our results and the optical theorem.