Chromatic and opto-mechanical dispersion of some characteristic parameters of optical fiber undergoing macrobending

Bending of optical fiber leads to an induced-anisotropy in the index profile that influences many important guiding fiber parameters. An analytical method is described for the measurement of refractive-index-wavelength dispersion in bent optical fibers. Multiple-beam Fizeau fringes technique at transmission is used to analyze the opto-mechanical properties and induced-index anisotropy in a standard single-mode fiber undergoes pure mechanical macrobending. The shift in Fizeau fringes is employed to evaluate the dispersion of the cladding material of the bent fiber. The radial variations in Cauchy’s coefficients and the associated variations of some fiber parameters due to macrobending are carried out. The radial profiles of some material parameters such as oscillation energy, dispersion energy, lattice energy and material dispersion are measured as well. The presented method is capable to achieve quantitative and qualitative measurements, which is not available with other methods. The method has a good index resolution in the order of 10⁻⁴ and spatial resolution of 1.3 μm.     

Study of the dehydration of Portland Cement by Mössbauer spectrometry

Egyptian Portland Cement in the form of one inch cube was hydrated at different times of hydration. Nine cubes of each period of hydration were heated for five minutes 200, 300, 400 up to 1000°C then were quenched in air. The compressive strength was measured for these samples and related to unheated ones. These cubes were ground and measured by Mössbauer spectrometry to correlate the effect of dehydration of cement pastes on the states of iron, with the decrease of compressive strength. It was observed that starting from 400°C the central doublet characteristic of the hydration process decreased as the dehydration temperature was increased. At 1000°C the dehydration process was complete, the central doublet disappeared and the compressive strength vanished. The hydration process was found to be reversible. The application of Mössbauer spectrometry to estimate the degree of fire in concrete building was demonstrated.     

Mössbauer study of iron reduction in hematite containing mineral originated from Aswan area in Egypt

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.     

Thermal Study of the Cr-Mo-O System in Air

The phase diagram of the ternary system Cr-Mo-O in air was established from the results of thermal analysis of mixtures with different initial CrO3 to MoO3 ratios. It was found that MoO3 did not take any chromium oxide into solid solution. The presence of Cr2O3 destabilized MoO3 causing it to decompose to MoO2 in the temperature range 723-958 K depending on the initial Cr/Mo ratio. The decomposition of pure MoO3 MoO2 did not occur in air at any temperature. However, this decomposition took place through the formation of the compound Cr2O3·3MoO3(ss) and its decomposition to Cr2O3·3MoO2(ss). The latter compound has never been reported before and the X-ray data for this compound are given. The previously reported catalytic activity of Cr2O3·3MoO3(ss), at high temperatures, is presumably due to its reduction to Cr2O3·3MoO2(ss). This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel Cyanine Dyes: Synthesis,Characterization and Photosensitization‐Structure Correlation

Novel furo, thieno and pyrrolo[2,3‐b]pyrazole cyanine dyes were synthesized. The structure‐photosensitization properties correlation of the dyes were examined in 95% ethanol solution by absorption spectroscopy. The chemical structure of the starting biheterocyclic compounds and their derived cyanine dyes were confirmed by elemental analysis, IR and ¹H NMR spectroscopy.     

A note on the two-stage hybrid flow shop problem with dedicated machines

In this paper we introduce a new dominance rule for the two-stage hybrid flow shop problem with dedicated machines. The rule is then used to construct a dominating set. The efficiency of the proposed rule is shown through an analysis of the dominating set cardinality.     

Attraction behaviour of Anagrus nilaparvatae to remote lemongrass (Cymbopogon distans) oil and its volatile compounds

Utilisation of Anagrus nilaparvatae is a promising and effective method for planthoppers manipulation. Twenty-seven components of remote lemongrass (Cymbopogon distans) oil were identified by GC/MS and nine volatiles were selected for behavioural experiments. In this study, we noted that the remote lemongrass oil was attractive to female A. nilaparvatae at concentrations of 0.1 and 1 mg/L. α-Pinene, β-pinene, eucalyptol, carveol and D-carvone attracted female wasps in the dose-dependent bioassays. Blend 1 (a mixture of eucalyptol, D-carvone, carveol, α-pinene, and β-pinene with ratios of remote lemongrass oil volatiles of 625:80:11:5:3) attracted female wasps at 10 mg/L, while blend 2 (a mixture of the same five volatiles at the same loading ratio) attracted them at 0.1 and 1 mg/L. These results suggested that plant essential oils could be attractants for natural enemies to control pests. The ratios of volatiles in the mixtures affect the attractiveness of the synthetic mixtures.     

Disappearing Polymorphs in Metal–Organic Framework Chemistry: Unexpected Stabilization of a Layered Polymorph over an Interpenetrated Three-Dimensional Structure in Mercury Imidazolate

The “disappearing polymorph” phenomenon is well established in organic solids, and has had a profound effect in pharmaceutical materials science. The first example of this effect in metal-containing systems in general, and in coordination-network solids in particular, is here reported. Specifically, attempts to mechanochemically synthesize a known interpenetrated diamondoid (dia) mercury(II) imidazolate metal–organic framework (MOF) yielded a novel, more stable polymorph based on square-grid (sql) layers. Simultaneously, the dia-form was found to be highly elusive, observed only as a short-lived intermediate in monitoring solvent-free synthesis and not at all from solution. The destabilization of a dense dia-framework relative to a lower dimensionality one is in contrast to the behavior of other imidazolate MOFs, with periodic density functional theory (DFT) calculations showing that it arises from weak interactions, including structure-stabilizing agostic C−H⋅⋅⋅Hg contacts. While providing a new link between MOFs and crystal engineering of organic solids, these findings highlight a possible role for agostic interactions in directing topology and stability of MOF polymorphs.     

Cyclodesulfurization of Substituted Thiosemicarbazides into 1,3,4-Oxadiazoles via Hydrazonoyl Chlorides

Abstract

The reaction of thiosemicarbazides 1a–h with hydrazonoyl chlorides 2a–g at ambient temperature, in the presence of triethylamine yielded, in each case, two products. The structure of these compounds was confirmed as 1,3,4-oxadiazoles 14a–h and hydrazonothioates 15a–g. The structure of 15b was confirmed through single crystal X-ray diffraction. A mechanism was proposed for this cyclodesulfurization reaction.