A meshless method based on the moving least squares (MLS) approximation for the numerical solution of two-dimensional nonlinear integral equations of the second kind on non-rectangular domains

This paper investigates a numerical method for solving two-dimensional nonlinear Fredholm integral equations of the second kind on non-rectangular domains. The scheme utilizes the shape functions of the moving least squares (MLS) approximation constructed on scattered points as a basis in the discrete collocation method. The MLS methodology is an effective technique for approximating unknown functions which involves a locally weighted least square polynomial fitting. The proposed method is meshless, since it does not need any background mesh or cell structures and so it is independent of the geometry of the domain. The scheme reduces the solution of two-dimensional nonlinear integral equations to the solution of nonlinear systems of algebraic equations. The error analysis of the proposed method is provided. The efficiency and accuracy of the new technique are illustrated by several numerical examples.     

Selective and efficient oxidation of sulfides and thiols with benzyltriphenylphosphonium peroxymonosulfate in aprotic solvent

Benzyltriphenylphosphonium peroxymonosulfate could be used for selective oxidation of aromatic and aliphatic sulfides and thiols to their corresponding sulfoxides and disulfides under nonaqueous and aprotic conditions without catalyst.     

Sensitivity improvement in two-center holographic recording

Persistent holograms are recorded with green light in LiNbO(3) crystals doped with Mn and Fe. The recording sensitivity is 20 times better than that obtained by recording with red light. Partial loss of persistence is caused by using green light for recording.     

Metal-free oxidative dehydrogenation of imidazolines and pyrazolines using silica-adsorbed peroxymonosulfate under aprotic and almost neutral conditions

Oxidative dehydrogenation of 1,3,5-trisubstituted pyrazolines and 2-substituted imidazolines to their corresponding pyrazoles and imidazoles is carried out effectively by treatment with benzyltriphenylphosphonium peroxymonosulfate as an oxidant silica-adsorbed under aprotic and almost neutral conditions. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 1003–1008, June, 2008.     

Hybrid photonic surface-plasmon-polariton ring resonators for sensing applications

We introduce a hybrid photonic surface plasmon ring resonator which consists of a silicon nitride (Si₃N₄) dielectric traveling-wave ring resonator vertically coupled to a thin layer of metallic strip ring resonator made of Silver (Ag) on top. The cladding is assumed to be porous alumina on top of the metal layer, which provides more surface area for the adsorption of target molecules and their efficient interaction with the surface plasmon wave excited at the metal-cladding interface. Simulations show that this hybrid structure has a large refractive index sensitivity due to the excitation of surface plasmon waves and also a relatively narrow resonance linewidth due to the large quality factor of the photonic ring resonator. The Finite Element method is used to systematically design the hybrid structure and to investigate the performance of the hybrid resonator as a refractive index sensor. The proposed structure is very compact and can be implemented on a chip in an integrated platform. Thus, it can be used for lab-on-a-chip sensing applications and is capable of being spectrally and spatially multiplexed for muti-analyte sensing.     

One-Pot,Three-Component Synthesis of 4H-Pyrans Using Cu(II) Oxymetasilicate

4H-Pyrans are synthesized through one-pot, three-component reaction of benzaldehyde, malononitrile, and ethyl acetoacetate using Cu(II) oxymetasilicate as an efficient, reusable catalyst. The procedure offers advantages in terms of better yields, short reaction times, mild reaction conditions, and reusability of the catalyst.     

Modified Borohydride Agents1a-d Methyltriphenylphosphonium Tetrahydroborate; MePh3P+BH4 − as a Selective and An Efficient Reducing Agent

Abstract

MePh₃P⁺BH₄ ^? is able to reduce aldehydes and ketones to their corresponding alcohols in CH₂Cl₂. Aldehydes are reduced with high selectivity in the presence of ketones. α,β-Unsaturated carbonyl compounds undergo 1,2-reduction and produce their corresponding allylic alcohols in high yields. Carboxylic acid chlorides are also converted to their alcohols with high yields.     

Expansion of the relative time delay by switching between slow and fast light using coherent population oscillation with semiconductors

The slow-light effect based on free-carrier population oscillation in semiconductors is analyzed using generalized macroscopic Bloch equations. Using this model, we are able to investigate the relation between the fractional time delay and the intensity of control laser beams for semiconductors. It is found that although increasing the control-beam intensity can enlarge the fractional time delay, the maximum delay that can be achieved is limited and determined by a critical value of the separation between the quasi-Fermi levels of electrons and holes. We also show that there is an intensity threshold for the control beam above which the probe signal becomes gain-assisted fast light rather than slow light. We therefore suggest a method to expand the relative time delay by switching between the fast-light region and the slow-light region through changing the intensity of the control laser beams. PACS 42.25.Bs; 42.70.Nq; 42.79.-e     

Multiplexing holograms in LiNbO3:Fe:Mn crystals

Persistent holograms are recorded with red light in lithium niobate crystals doped with manganese and iron. Different erasure mechanisms are investigated, and a recording schedule for multiplexing holograms with equal diffraction efficiencies is proposed. To test the recording schedule experimentally, we multiplex 50 plane-wave holograms with the proposed recording schedule.     

Wet silica-supported permanganate for the cleavage of semicarbazones and phenylhydrazones under solvent-free conditions

Wet silica-supported potassium permanganate was used as an inexpensive and efficient reagent for conversion of semicarbazones and phenylhydrazones to the corresponding carbonyl compounds under solid-state conditions.