Singularities and semistable degenerations for symplectic topology

We overview our work [7], [8], [9], [10], [11], [6] defining and studying normal crossings varieties and subvarieties in symplectic topology. This work answers a question of Gromov on the feasibility of introducing singular (sub)varieties into symplectic topology in the case of normal crossings singularities. It also provides a necessary and sufficient condition for smoothing normal crossings symplectic varieties. In addition, we explain some connections with other areas of mathematics and discuss a few directions for further research.     

A Lewis acid-catalyzed formal [3 + 3] cycloaddition of alpha,beta-unsaturated aldehydes with 4-hydroxy-2-pyrone, diketones, and vinylogous esters

[reaction: see text] A Lewis acid-catalyzed formal cycloaddition of alpha,beta-unsaturated aldehydes with 6-methyl-4-hydroxy-2-pyrone, 1,3-diketones, and vinylogous silyl esters is described here.     

High‐power HgGa2S4 optical parametric oscillator pumped at 1064 nm and operating at 100 Hz

The defect chalcopyrite crystal HgGa₂S₄ has been employed in a 1064‐nm pumped optical parametric oscillator operating at 100 Hz, to generate ∼5 ns long idler pulses near 4 µm with energies as high as 6.1 mJ and average power of 610 mW. At crystal dimensions comparable to those available for the commercial AgGaS₂ crystal, operation of the 1064‐nm pumped HgGa₂S₄ OPO is characterized by much lower pump threshold and higher conversion efficiency, with the most important consequence that such a device might become practical at pump levels sufficiently lower than the optical damage threshold.     

Comparative Study of Natural Terpenoid Precursors in Reactive Plasmas for Thin Film Deposition

If plasma polymer thin films are to be synthesised from sustainable and natural precursors of chemically heterogeneous composition, it is important to understand the extent to which this composition influences the mechanism of polymerisation. To this end, a well-studied monoterpene alcohol, terpinen-4-ol, has been targeted for a comparative study with the naturally occurring mix of terpenes (viz. Melaleuca alternifolia oil) from which it is commonly distilled. Positive ion mode mass spectra of both terpinen-4-ol and M. alternifolia oil showed a decrease in disparities between the type and abundance of cationic species formed in their respective plasma environments as applied plasma power was increased. Supplementary biological assay revealed the antibacterial action of both terpinen-4-ol and M. alternifolia derived coatings with respect to S. aureus bacteria, whilst cytocompatibility was demonstrated by comparable eukaryotic cell adhesion to both coatings. Elucidating the processes occurring within the reactive plasmas can enhance the economics of plasma polymer deposition by permitting use of the minimum power, time and precursor pre-processing required to control the extent of monomer fragmentation and fabricate a film of the desired thickness and functionality.     

Size and Shape Effects in Optical Spectra of Silver and Gold Nanoparticles

Journal of Russian Laser Research - We report some theoretical results on the extinction, absorption, and scattering of light by individual silver and gold nanoparticles of different sizes and...     

Biohybrid Organic Heterostructure Based on Chlorophyll-Bacteriochlorophyll Aggregates for Ecofriendly Hydrogen Production

Hydrogen energy is an abundant, clean, sustainable and environmentally friendly renewable energy source. Therefore, the production of hydrogen by photocatalytically splitting water on semiconductors has been considered in recent years as a promising and sustainable strategy for converting solar energy into chemical energy to replace conventional energy sources and to solve the growing problem of environmental pollution and the global energy crisis. However, highly efficient solar-driven photocatalytic hydrogen production remains a huge challenge due to the poor visible light response of available photocatalytic materials and the low efficiency of separation and transfer of photogenerated electron-hole pairs. In the present work, organic heterojunction structures based on bacteriochlorophyll (BChl) and chlorophyll (Chl) molecules were introduced and used for solar-driven photocatalytic hydrogen production from water under visible light. Also, noble metal-free photocatalyst was successfully constructed on Ti₃C₂T_x nanosheets by simple successive deposition of Chl and BChl, which was used for the photocatalytic splitting water to hydrogen evolution reaction (HER). The results show that the optimal BChl@Chl@Ti₃C₂T_x composite has a high HER performance with 114 μmol/h/g_cat, which is much higher than the BChl@Ti₃C₂T_x and Chl@Ti₃C₂T_x composites.     

Polyacrylonitrile molecular weight effect on the structural and magnetic properties of metal–carbon nanomaterial

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Chaotic transients in surface-stabilized smectic C* cells induced by magnetic field

Recent theoretical developments regarding the understanding of weakly chaotic transients in ferroelectric liquid crystals (FLCs), induced by electric field, are studied in terms of the interaction with magnetic field. Our research is related with the nonlinear dynamical system represented by a thin film of surface-stabilized FLC in smectic C* phase, and subjected by the swinging magnetic field. The computation of the Lyapunov exponents from the dynamic equation for the director field reveals that the director dynamics exhibits limit cycle, hyperchaotic attractor and strange attractor behavior in the dissipative nonlinear media. The transients between director’s phase space trajectories can be handled by the magnetic field parameters. The fundamental understanding of the director dynamics may have a valuable contribution to the applications of thin liquid crystal films.     

Microdetermination of carbon in compounds containing alkali metals

Zusammenfassung Wenn organische Verbindungen außer Alkalimetallen auch noch eine zumindest äquivalente Menge Schwefel enthalten, so besteht der Verbrennungsrückstand aus Alkalisulfat. Auf Grund dieser Beobachtung wird darauf hingewiesen, daß sich außer Kaliumdichromat und Vanadiumpentoxyd auch Kaliumpersulfat als oxydierender Zusatz zur organischen Substanz für die Verdrängung des Kohlendioxyds aus der Asche eignet.

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Résumé Quand des composés organiques, outre les métaux alcalins contiennent encore une quantité au moins équivalente de soufre, le résidu de la combustion apparaît sous la forme de sulfate alcalin. Sur la base de cette observation, on a montré, qu'à côté du bichromate de potassium et de l'anhydride vanadique, le persulfate de potassium convenait comme oxydant de la substance organique et pour débarrasser les cendres de l'anhydride carbonique.