Dependence of thermo-mechanical and mechanical properties of novel fluorophosphate glass on various rare earth dopants

The dependence of thermo-mechanical, and mechanical properties on various rare earth dopants (RE) including Nd₂O₃, Er₂O₃, and Yb₂O₃ in 0.4MgF₂-0.4BaF₂-0.1Ba(PO₃)₂-0.1Al(PO₃)₃ glasses (MBBA system) is systematically investigated. MBBA system doped with RE dopants presented the potential application in the field of communication and high power layer system in the previous reports. In this work, it is found that the density of the doped glass increases with an increasing of RE concentration, which could be understood in terms of cationic field strength (CFS) effect. The Knoop hardness is found to decrease with the loading time and dopant concentration due to the indentation size effect (ISE) effect. The observed decrease of thermal expansion coefficient and the increase of glass transition temperature T _g with increasing dopant concentration are elucidated in terms of the increasing number of strong covalent bonds with increasing RE dopant concentration. Those results will be of paramount importance before designing optical devices.     

Ring-Fluorinated Analog of Methyl Eugenol: Attractiveness to and Metabolism in the Oriental Fruit Fly, <Emphasis Type="Italic">Bactrocera Dorsalis</Emphasis> (Hendel)

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal functions. Side-chain metabolic activation of ME leading to (E)-coniferyl alcohol has long been recognized as a primary reason for hepatocarcinogenicity of this compound in rodents. Earlier, we demonstrated that introduction of a fluorine atom at the terminal carbon of the ME side chain significantly depressed metabolism and specifically reduced formation of coniferyl alcohol but had little effect on field attractiveness to B. dorsalis. In the current paper, we demonstrate that fluorination of ME at the 4 position of the aromatic ring blocks metabolic ring-hydroxylation but overall enhances side-chain metabolism by increasing production of fluorinated (E)-coniferyl alcohol. In laboratory experiments, oriental fruit fly males were attracted to and readily consumed 1,2-dimethoxy-4-fluoro-5-(2-propenyl)benzene (I) at rates similar to ME but metabolized it faster. Flies that consumed the fluorine analog were as healthy post feeding as ones fed on methyl eugenol. In field trials, the fluorine analog I was ∼50% less attractive to male B. dorsalis than ME.

Consumption and Metabolism of 1,2-Dimethoxy-4-(3-Fluoro-2-Propenyl)Benzene, a Fluorine Analog of Methyl Eugenol, in the Oriental Fruit Fly Bactrocera dorsalis (Hendel)

Methyl eugenol (ME) is a natural phenylpropanoid highly attractive to oriental fruit fly Bactrocera dorsalis (Hendel) males. The flies eagerly feed on ME and produce hydroxylated metabolites with both pheromonal and allomonal functions. Side-chain metabolic activation of ME has long been recognized as a primary reason for hepatocarcinogenicity of this compound on rodents. In an attempt to develop a safer alternative to ME for fruit fly management, we developed a fluorine analog 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene (I), which, in earlier field tests, was as active to the oriental fruit fly as ME. Now we report that B. dorsalis males are not only attracted to, but also eagerly consume (up to ∼1 mg/insect) compound I, thus recognizing this fluorinated benzene as a close kin of the natural ME. The flies metabolized the fluorine analog I in a similar fashion producing mostly two hydroxylated products, 2-(3-fluoro-2-propenyl)-4,5-dimethoxyphenol (II) and (E)-coniferyl alcohol (III), which they stored in rectal glands. However, the introduction of the fluorine atom at the terminal carbon atom of the double bond favors the ring hydroxylation over a side-chain metabolic oxidation pathway, by which coniferyl alcohol is produced. It also appears that fluorination overall impedes the metabolism: at high feed rate (10 μl per 10 males), the flies consumed in total more fluorine analog I than ME but were unable to metabolize it as efficiently as ME.     

Filter Material Effects on Particle Absorption Optical Properties

Absorption enhancement and shadowing effects were investigated for nigrosin-laden quartz (fibrous), Teflon (matted), and polycarbonate (membrane) filters in inert surroundings at different sample steady-state temperatures and particle mass loadings. Sample absorptivity was determined using a novel laser-heating technique, which is based on perturbing the sample steady-state temperature and monitoring the thermal response during decay back to steady state, along with a model for thermal energy conservation. In addition, transmissivity measurements were carried out to enable determination of the sample absorption coefficient. The results indicated that the isolated-nigrosin absorption coefficient decreased with steady-state temperature and increased with mass loading and filter pore size. Comparing the absorption coefficient for both the isolated nigrosin and nigrosin-laden filters, indicated that absorption enhancement was most significant for the Teflon filters and least significant for the polycarbonate filters. The effect became more significant as the pore size decreased, steady-state temperature increased, and particle mass loading decreased. The decrease in the isolated-nigrosin, mass-specific absorption cross-section with heavier sample loadings was attributed to shadowing effects.

Copyright 2014 American Association for Aerosol Research     

On stability of linear all-pass systems

In this paper we analyze the class of all-pass, linear and stable systems. We give a condition on the zero distribution of the transfer function of such a system to guarantee stability and we show that stability is not preserved under cascade decomposition.     

Spectroscopic properties of Yb in heavy metal contained fluorophosphate glasses

A new series of 20Bi(PO₃)₃–10Sr(PO₃)₂–35BaF₂–35MgF₂ doped with Yb³⁺ is introduced for fiber and waveguide laser applications. The stimulated emission cross-section σ_emi, which was found to be 1.37 pm² at the lasing wavelength of 996 nm, is the highest one among fluorophosphate glasses. It has been found that an extremely high gain coefficient of G = 1.65 ms pm⁴ and high quantum efficiency of η = 93% for 1 wt.% Yb₂O₃ doped systems. The various concentration effects on laser performance properties including minimum pumping intensity I_min, the minimum fraction of excited ions β_min and the saturation pumping intensity I_sat are analyzed as a function of Yb₂O₃ concentration. Those results obtained in current system had advantage over some fluorophosphate glasses reported.     

A modified variable structure control algorithm for stabilization of uncertain dynamical systems

A modified VS feedback is suggested for robust stabilization of continuous-time dynamical systems in the presence of parametric and external time-varying disturbances satisfying the ‘matching conditions’. The main feature of the proposed algorithm is that it contains additional switching ‘integral’ terms which track the unknown disturbances and make it possible to achieve the typical VSS robustness by using switching terms in the control law with arbitrarily small amplitude. This result can be achieved only if the derivatives of the disturbances are bounded.     

Novel alkaline-free Er-doped fluorophosphate glasses for broadband optical fiber lasers and amplifiers

Two sets of Er³⁺-doped alkaline-free glass systems, MgF₂–BaF₂–Ba(PO₃)₂–Al(PO₃)₃ (MBBA) and Bi(PO₃)₃–Ba(PO₃)₂–BaF₂–MgF₂ (BBBM), have been prepared and investigated with the aim of using them as active media. Radiative lifetimes (τ_rad) and branching ratios (β) have been obtained for the excited states of Er³⁺. The absorption spectra were recorded to obtain the intensity parameters (Ω_t) which are found to be Ω₂ = 4.47 × 10⁻²⁰ cm², Ω₄ = 1.31 × 10⁻²⁰ cm², Ω₆ = 0.81 × 10⁻²⁰ cm² for the MBBA system and Ω₂ = 4.03 × 10⁻²⁰ cm², Ω₄ = 1.34 × 10⁻²⁰ cm², Ω₆ = 0.53 × 10⁻²⁰ for the BBBM system, respectively. The emission cross-section for the ⁴I_13/2 → ⁴I_15/2 transition is determined by the Fuchtbauer–Ladenburg method and found to be 2.35 × 10⁻²⁰ cm² and 3.54 × 10⁻²⁰ cm² for the MBBA and BBBM system, respectively. Comparison of the measured values to those of Er³⁺ transitions in other glass hosts suggests that our new glass systems are good candidates for broadband compact optical fiber and waveguide amplifier applications.     

Simultaneous transmission and absorption photometry of carbon-black absorption from drop-cast particle-laden filters

Simultaneous transmissivity and absorptivity measurements were carried out in the visible at a laser wavelength of 532?nm on drop-cast, carbon-black-laden filters under ambient (laboratory) conditions. The focus of this investigation was to establish the feasibility of this approach to estimate the mass absorption coefficient of the isolated particles and compare results to earlier work with the same carbon-black source. Transmissivity measurements were carried out with a laser probe beam positioned normal to the particle-laden filter surface. Absorptivity measurements were carried out using a laser-heating approach to record in time the sample temperature rise to steady-state and decay back to the ambient temperature. The sample temperature was recorded using a fine-wire thermocouple that was integrated into the transmission arrangement by placing the thermocouple flush with the filter back surface. The advantage of this approach is that the sample absorptivity can be determined directly (using laser heating) instead of resolving the difference between reflectivity (filter surface scattering) and transmissivity. The current approach also provides the filter optical characteristics, as well as an estimate of filter effects on the absorption coefficient due to particle absorption enhancement or shadowing. The approach may also be incorporated into other filter-based techniques, like the particle/soot absorption photometer, with the simple addition of a thermocouple to the commercial instrument. For this investigation, measurements were carried out with several blank uncoated quartz filters. A range of solution concentrations was prepared with a well-characterized carbon black in deionized water (i.e., a water-soluble carbonaceous material referred to as a surrogate black carbon or ‘carbon black’). The solution was then drop cast using a calibrated syringe onto blank filters to vary particle loading. After evaporation of the water, the measurements were repeated with the coated filters. The measurement repeatability (95% confidence level) was better than 0.3?K for temperature and 3?×?10^?5 mW for laser power. From the measurements with both the blank and coated filters, the absorption coefficient was determined for the isolated particles. The results were then compared with an earlier investigation by You et al. and Zangmeister and Radney, who used the same carbon-black material. The measurements were also compared with Lorenz–Mie computations for a polydispersion of spherical particles dispersed throughout a volume representative of the actual particles. The mass absorption coefficient for the polydispersion of carbon-black particles was estimated to be about 7.7?±?1.4?m² g^?1, which was consistent with the results expected for these carbon black particles.     

Site Selective Synthesis of Pentaarylpyridines via Multiple Suzuki–Miyaura Cross‐Coupling Reactions

Pentaarylpyridines were conveniently prepared in one step by pentafold Suzuki–Miyaura reactions of pentachloropyridine. Moreover, site selective reactions were performed, leading to various substituted arylpyridines. Pentaarylpyridines were studied in detail by means of DFT calculations and by optical spectroscopy.