Sensitivity of Bragg grating imprinted in a three-mode elliptical core fiber to temperature and to strain

Sensing characteristics of Bragg grating imprinted in a three-mode elliptical core fiber were investigated in details. The grating sensitivity to temperature and to strain was measured for each polarization and spatial mode. The experimental results show very small difference in the grating sensitivity vs. mode order and polarization. We also modeled the sensitivity of the host elliptical core fiber to these two parameters. We demonstrated relatively good agreement between the sensitivity of the grating determined in our experiment and the calculated sensitivity of the host fiber for respective modes.     

On Kirk's asymptotic contractions

Recently Kirk introduced the notion of asymptotic contractions on a metric space and using ultrapower techniques he obtained an asymptotic version of the Boyd-Wong fixed point theorem. In this paper we extend this result and moreover, we give a constructive proof of it. Furthermore, we obtain a complete characterization of asymptotic contractions on a compact metric space. As a by-product we establish a separation theorem for upper semicontinuous functions satisfying some limit condition.     

Alkylation of the inverted porphyrin nickel(II) complex by dihalogenalkanes: formation of monomeric and dimeric derivatives

An efficient and simple method of modification of "inverted" porphyrin is provided by reactions of 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrinatonickel(II) 2 with dihalogenalkanes under basic conditions. The substituents are bound to the internal carbon or external nitrogen of the inverted pyrrole depending on dihalogenalkane and basic catalyst. The monomeric 2- or 21-ethoxymethyl-substituted species are formed in the reaction of 2 with dihalomethanes and sodium ethoxide or ethanol in the presence of K(2)CO(3). A novel, dimeric 21,21'-ethylene-linked derivative 11 is obtained from 2 and ethylene bromide in dichloromethane in the presence of potassium carbonate end ethanol, while application of potassium tert-butoxide promotes formation of N-bromoethyl-substituted monomer 12. Reaction of 2 with propylene bromide in the presence of proton scavenger efficiently leads to the 21-allyl-substituted monomer 14 that is a product of the HBr elimination from a transient 21-bromopropyl-substituted species. The new compounds have been identified and characterized by means of mass spectrometry and optical and NMR spectroscopies. A single-crystal X-ray analysis performed for 12 allows discussion of structural parameters concerning the macrocycle and coordination core. Formation of deprotonated species [2](-), which is proposed as a key intermediate in the alkylation reaction, has been observed spectroscopically. Chirality of the N-substituted derivatives induced by protonation of the internal carbon is observed by NMR at low temperatures.     

The effect of solvent on the reactions of allyltin (IV) compounds with singlet oxygen, 4-phenyl-1,2,4-triazoline-3,5-dione and diethyl azodicarboxylate

The effect of the influence on the increase of polarity of the solvent on the selectivity and rate of metalloene reactions of different allyltin compounds with singlet oxygen, 4-phenyl-1,2,4-triazoline-3,5-dione (TD) and diethyl azodicarboxylate has been studied.     

Comparative Analysis of Acyclovir Esters Stability in Solutions: The Influence of the Substituent Structure,Kinetics, and Steric Effects

Reversed‐phase high‐performance liquid chromatography has been applied to the determination of acyclovir (ACV) esters such as acetate, isobutyrate, pivalate, ethoxycarbonate, and nicotinate. All analyses were carried out at laboratory temperature using a column LiChrospher RP‐18 (250 × 4 mm, 5 µm) and a proper mobile phase consisting of acetonitrile and phosphate buffer (pH 6 or 6.7) or acetonitrile and potassium dihydrogen phosphate, and acetic acid. The methods were validated by the determination of the following parameters: selectivity, precision, accuracy, and linearity. Kinetic studies on the hydrolysis were investigated in solutions at 310 K over the pH range 0.42–1.38. The pH‐profiles indicated specific acid‐catalyzed and spontaneous water‐catalyzed degradation. The stability of the studied ACV esters were determined not only by steric factors. In the case of ethoxycarbonyl ester of ACV, the hydrolysis was a two‐step reaction.     

USAXS study of influence of gelator polarity on organogel structure

Organogels, formed of polar and apolar glucose-based gelators with organic solvents, were studied using USAXS. The polarity was introduced by attaching the NO₂ group to the gelator molecule. The USAXS data were processed using fractal analysis, pair distribution function and Guinier approximation. It was found that the number of molecules, i.e. also the size of the primary aggregates in these gels structure, were strongly dependent on the gelator polarity, while several other structural parameters, e.g. the shape of the aggregates and the mechanism of their aggregation to the secondary structure, remained unsusceptible to it.     

RP-HPLC method with electrochemical detection for the determination of metoclopramide in serum and its use in pharmacokinetic studies.

A rapid and sensitive reversed-phase high performance liquid chromatographic method has been developed for the determination of metoclopramide in serum. The assay was performed after single extraction with ethyl ether using methyl parahydroxybenzoate as internal standard. Chromatographic separations were performed on C(18) stationary phase with a mobile phase composed of methanol-phosphate buffer pH 3 (30:70 v/v). Analytes were detected electrochemically. The quantification limit for metoclopramide in serum was 2 ng mL(-1). Linearity of the method was confirmed in the range of 5-120 ng mL(-1) (correlation coefficient 0.9998). Within-day relative standard deviations (RSDs) ranged from 0.3 to 5.5% and between-day RSDs from 0.8 to 6.0%. The analytical method was successfully applied for the determination of pharmacokinetic parameters after ingestion of 10 mg dose of metoclopramide. Studies were performed on 18 healthy volunteers of both sexes.     

Synthesis,characterisation, crystal structure and biological activity of metal(II) complexes with theophylline

Three metal complexes with empirical formulae [Mn(theop)₂(H₂O)₄] (1), [Co(theop)₂(H₂O)₄] (2), [Ni(theop)₂(H₂O)₄] (3), (where: theop?=?theophylline) were synthesized and characterized by elemental analysis, FTIR- spectroscopy and thermal decomposition techniques. Their crystal structures were determined by single crystal Xray diffraction analysis. Complexes are isomorphous and crystallise in the monocyclic space group P21/c. Their thermal behavior was studied by TGA methods under non-isothermal condition in air. Upon heating all compounds decompose progressively to metal oxides, which are the final products of pyrolysis. Furthermore, antimicrobial and antioxidant activity of the complexes was examined.