A novel single frequency stabilized Fabry-Perot laser diode at 1590 nm for gas sensing

A novel single frequency stabilized Fabry-Perot (SFP) laser diode with an emission wavelength of lambda = 1590 nm for H2S gas sensing is reported. Sculpting of the multi-mode spectral distribution of a FP laser to achieve single frequency emission is carried out using post growth photolitographic processing of the device. The resulting longitudinal-mode controlled FP laser has a stabilized single frequency emission with a side mode suppression ratio (SMSR) of 40 dB. The application of this device to spectroscopic based H2S sensing is demonstrated by targeting absorption lines in the wavelength range 1588 < or = lambda < or = 1591 nm. Using wavelength modulation spectroscopy (WMS), a low detection limit of 120 ppm x m x Hz(-1/2) was estimated while targeting the absorption line at 1590.08 nm. These initial results demonstrate the potential of the stabilized FP laser diode at this wavelength as a tunable, single frequency source for spectroscopic based gas sensing.     

One-pot selective oxidation/olefination of primary alcohols using TEMPO-BAIB system and stabilized phosphorus ylides

A one-pot process for the synthesis of α,β-unsaturated esters from a variety of alcohols, obtained in good yields and diastereoselectivities, is described. The use of BAIB/TEMPO system at the oxidizing step authorizes the chemoselective homologation of primary alcohols in the presence of secondary ones.     

Hard X-ray phase imaging and tomography using a grating interferometer

An interferometric technique for hard X-rays is presented. It is based on two transmission gratings and a phase-stepping technique, and it provides separate radiographs of the phase and absorption profiles of bulk samples. Tomographic reconstruction yields quantitative three-dimensional maps of the X-ray refractive index and of the attenuation coefficient, with a spatial resolution down to a few microns. The method is mechanically robust, it requires little monochromaticity, and can be scaled up to large fields of view. These are important prerequisites for use with laboratory X-ray sources. Numerous applications ranging from wave front sensing to medical radiography are presently under investigation.     

Water revealed as molecular mirror when measuring low concentrations of sugar with near infrared light

Near infrared spectroscopy is an overtone spectroscopy regarded as a quick and non-destructive method that provides analytical solutions for components that represent approximately 1% or more of the total mass of the investigated composite samples. Aquaphotomics offers the possibility for disentanglement of information remaining hidden in the spectra when conventional data evaluation methods are used, since this concept utilizes changes of the water structure induced by the measured solute as specific molecular vibrations at water bands. Here, near infrared technique and aquaphotomics are applied for non-destructive identification and quantification of mono- and di-saccharide solutes at 100–0.02 mM concentration that is accepted as unachievable with near infrared spectroscopy. The results presented in this study support the aquaphotomics' water molecular mirror concept that explores spectral changes related to water molecular rearrangements caused by minute changes of the solutes in the aqueous systems. The method provides quick and accurate alternative for classical analytical measurements of saccharides even at millimolar concentration levels.     

Preparation of nanodispersed titania using stabilized ammonium nitrate melts

An expedite one-step approach using simple precursors has been proposed to obtain metallic oxide compounds and exemplified by preparation of highly dispersed TiO₂. The technique consists in heating to 400-500 °C of molten ammonium nitrate stabilized with an organic nitrogen-containing compound (urea, melamine, ammonium oxalate) and containing dissolved metal salt precursor (TiOCl₂). The crystallites of the resulting TiO₂ demonstrated variable size and shape as a function of stabilizer used. Their activity in photocatalytic oxidation of formic acid also depends on the nature of the stabilizer. The catalysts as-prepared showed high photocatalytic performance, superior to that of the Degussa P25 reference. Nitrogen containing stabilizers play a double role of increasing the process safety and modifying the properties of the solid products.     

Investigation of aluminum interferences using the stabilized temperature platform furnace

Al was determined in the stabilized temperature platform furnace with very few interferences. No interferences were found for several metal nitrates, sulfates or phosphates, or for NaCl. The Al absorbance signal was delayed in the presence of MgCl₂ but there was no interference. This led to the use of 50 μg Mg(NO₃)₂ as a matrix modifier for Al. There were no interferences for CaCl₂ but it was particularly important to use new pyrolytically coated tubes to avoid “aging” effects. CuCl₂ provided a very persistent interference that was reduced when the Mg(NO₃)₂ matrix modifier was used that permitted a char temperature of 1700°C. Perchloric acid interferences were severe with improperly coated graphite tubes but did not exist up to 0.5 M HClO₄ when the new pyrolytically coated tubes were used. A serum Al method was tested briefly and no problems were found. Al was determined in seawater with no influence from the salinity of the sample and less than 0.6 μg/1 Al in seawater could be detected.     

Simulation of block copolymer stabilized nanoparticles in a two-solvent system

In this paper, by using Brownian Dynamics simulation, we investigate in general terms the behavior of a nanoparticle stabilized by a block copolymer in the presence of an oil-water interface. We investigate the probability of sticking to the interface, the density distribution of the copolymer across the interface and the area occupied by the stabilized nanoparticle at the interface. By using representative snapshots of the stabilized nanoparticle, derived from the density distribution, we find that the nanoparticle stabilized by a block copolymer, with the hydrophobic side of it tethered to the nanoparticle, prefers sitting at the oil-phase, and thus has a contact angle that is tested to be larger than 90 degrees for most of the cases, even if the hydrophobe content is less than 50%. Thus we find the architecture of a block-copolymer attachment to have a significant effect on the emulsion type that would result.     

基于平凸柱面镜的LIBS光束整形系统设计

为改善激光诱导击穿光谱(Laser-Induced Breakdown Spectroscopy, LIBS)技术激光能量不均匀分布的问题,利用仿真软件对半径为12.5 mm的不同焦距型号的平凸柱面镜进行光路成像模拟,模拟显示满足激光器条件的最佳焦距为100 mm,在此基础上搭建基于LIBS光束的整形系统,实验表明：相比于无平凸柱面镜整形,样品中锶元素的焦斑光强均方差系数平均降低了41.91%,焦斑光强峰谷比系数平均降低了41.27%,而能量均匀度平均提高了17.23%,拟合决定系数由0.860提高到了0.914。结果显示使用平凸柱面镜可提高光束能量的均匀性,验证了平凸柱面镜是激光光束整形的一种有效方法。     

Alkalimetric determination of hydrophobic pharmaceuticals using stabilized o/w emulsions

Protolytic properties of (+)-(S)-2-(6-methoxynaphthalen-2-yl)propanoic acid (naproxen), 2-(3-benzoylphenyl)propionic acid (ketoprofen), 4-chloro-N-(2-furylmethyl)-5-sulfamoylanthranilic acid (furosemide), and N-(2,3-dimethylphenyl)anthranilic acid (mefenamic acid) in “oil-in-water” emulsions stabilized by surfactants were studied. The procedures for alkalimetric determination of naproxen, ketoprofen, furosemide, and mefenamic acid in emulsion media with indication of the equivalence point pH-metrically and with the use of indicators were proposed.     

Lamellar miscibility gap in a binary catanionic surfactant-water system

The coexistence of two lamellar liquid-crystalline phases in equilibrium for binary surfactant-water systems is a rare and still puzzling phenomenon. In the few binary systems where it has been demonstrated experimentally, the surfactant is invariably ionic and the miscibility gap is thought to stem from a subtle balance between attractive and repulsive interbilayer forces. In this paper, we report for the first time a miscibility gap for a catanionic lamellar phase formed by the surfactant hexadecyltrimethylammonium octylsulfonate (TASo) in water. Synchrotron small-angle X-ray scattering, polarizing light microscopy, and 2H NMR unequivocally show the coexistence of a dilute (or swollen) lamellar phase, Lalpha', and a concentrated (or collapsed) lamellar phase, Lalpha' '. Furthermore, linear swelling is observed for each of the phases, with the immiscibility region occurring for 15-54 wt % surfactant. In the dilute region, the swollen lamellar phase is in equilibrium with an isotropic micellar region. Vesicles can be observed in this two-phase region as a dispersion of Lalpha' in the solution phase. A theoretical cell model based on combined DLVO and short-range repulsive potentials is presented in order to provide physical insight into the miscibility gap. The surfactant TASo is net uncharged, but it undergoes partial dissociation owing to the higher aqueous solubility of the short octylsulfonate chain. Thus, a residual positive charge in the bilayer is originated and, consequently, an electrostatic repulsive force, whose magnitude is dependent on surfactant concentration. For physically reasonable values of the solubility of the octyl chain, assumed to be constant with surfactant volume fraction, a fairly good agreement is observed between the experimental miscibility gap and the theoretical one.     

Research on measuring thermophysical properties using parameter estimation

In this paper a new prompt method is proposed for the measurement of thermal conductivityk and thermal diffusivity which are functions of temperature. This method is based on parameter estimation. Thek and can be got by measurement of the temperature on sample and heat-flow through the sample. The experiment has also confirmed that the method is feasible.

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Zusammenfassung Es wird ein neues Verfahren zur Schnellbestimmung der Wärmeleitfähigkeitk und der Temperaturleitfähigkeita beschrieben, welche beides eine Funktion der Temperatur darstellen. Diesem Verfahren liegt eine Parameterschätzung zugrunde.k und können durch Messung der Temperatur an einer Probe bzw. des Wärmeflusses durch eine Probe ermittelt werden. Die Experimente erwiesen die Anwendbarkeit dieses Verfahrens.

     

Hydrothermal synthesis of yttria stabilized ZrO2 nanoparticles in subcritical and supercritical water using a flow reaction system

Yttria stabilized zirconia nanoparticles have been prepared by hydrothermal flow reaction system under subcritical and supercritical conditions. ZrO(NO₃)₂/Y(NO₃)₃ mixed solutions were used as starting materials. Reaction temperature was 300–400 °C. Reaction time was adjusted to 0.17–0.35 s. Based on the residual Zr and Y concentrations, the complete conversion of zirconium was achieved irrespective of pH and hydrothermal temperature, whereas the conversion of yttrium increased with an increase in pH and hydrothermal temperature. Stoichiometric solid solution was achieved at pH>8. XRD results revealed that tetragonal zirconia can be formed regardless of yttrium content, where the tetragonality was confirmed by Raman spectroscopy. The average particle size estimated from BET surface area was around 4–6 nm. Dynamic light scattering particle size increased with the solution pH owing to the aggregation of primary particles. TG-DTA analyses revealed that weight losses for adsorbed water and hydroxyl groups decreased with hydrothermal temperature.     

Measurements of heat transfer from an isothermal rotating disk using a Mach-Zehnder interferometer

Results are presented for the heat transfer from an horizontal disk rotating in still air. The investigation was carried out using a Mach-Zehnder interferometer, after the system was calibrated by verifying the empirical expression for an horizontal isothermal disk in natural convection. The results have extended the range of already known solutions, and experimental data, for rotational Reynold numbers below 10⁴. The orientation of the rotating disk, appears to have no effect on the heat transfer, which is of the mixed convection mode.     

The application of a piezoelectric scanning Fabry-Perot interferometer to the study of atomic line sources—II: Line-widths for calcium in air-acetylene and nitrous oxide-acetylene flames

The variation in observed half-width of the calcium 422.7 nm line with calcium concentration has been studied interferometrically in air-acetylene and nitrous oxide-acetylene flames supported as cylindrical flames, with and without flame shielding and inert gas separation, and at a long path burner. Extrapolation of the curves obtained to zero added calcium concentration is shown to permit correction for self-absorption and calculation of interaction broadening half-width and damping constants (a-parameters).     

Highly sensitive impedance-based propene sensor using stabilized zirconia and zinc oxide sensing-electrode

Aimed at an environmental monitoring of hydrocarbons (HCs), a new-type impedancemetric sensor was fabricated by using an yttria-stabilized zirconia (YSZ) tube and ZnO sensing-electrode (SE). The fabricated tubular sensor was examined for detection of low concentrations of propene (C₃H₆) in the presence of 1.35 vol.% H₂O and 400 ppm CO₂ at 600 °C. As a result, it was found that the present sensor could detect the low concentrations of C₃H₆ in the range of 0.05–0.8 ppm and the sensitivity varied linearly with C₃H₆ concentration. In addition, the C₃H₆ sensitivity was almost invariant with the changes in the concentration of water vapor and the interferences to other gases, such as NO₂, NO, H₂, CO and CH₄, were insignificant.     

Preparation of stable direct emulsions stabilized with a system of phospholipid emulsifiers

The conditions of formation of stable highly dispersed direct emulsions water-soybean oil-mineral oil-emulsifier (base of “natural” creams), stabilized with natural emulsifiers, soybean lecithin and lysolecithin, were examined. The effect of 1,2-pentanediol and 1,2-octanediol on the stability of the emulsions and on the particle size and charge was analyzed from the viewpoint of oriented wedge theory.     

Desolvation of BSA-ligand complexes measured using the quartz crystal microbalance and dual polarization interferometer

By taking advantage of their unique difference in hydration sensitivity, we have shown that dual polarization interferometer (DPI) and quartz-crystal microbalance with dissipation monitoring (QCM-D) measurements can be used together to explore the degree of desolvation involved in the binding of small drug molecules to an immobilized bovine serum albumin film in real time. Results with DPI and QCM-D show significantly different mass values for three ligands of varying hydrophobicities that may be attributed to changes in the degree of hydration of the ligand-protein complexes in accordance with the physicochemical properties of the ligands. Furthermore, our data suggest that masses measured by QCM-D can be overwhelmed by changes in water content of ligand-protein, binary complexes, which has important consequences for future studies using mechanical resonators to study protein-binding events.     

A computer system for measuring fast-scan lowresolution mass spectra

A microprocessor-based satellite computer system (MASDAT) controls a low-resolution, fast-scan mass spectrometer for the measurement of series of spectra. Special digitization hardware (logarithmic A/D converter) and software algorithms are necessary to achieve a dynamic range (ratio of highest to lowest intensity) of about 10⁵ in peak heights. Up to three MASDAT satellites can be connected to a host computer. Synchronized parallel programs in the host system communicate with the operator, calibrate the mass scale, print an interscan report, and store final spectra and, optionally, unreduced data on mass storage devices. Host software is described for a RSX11M and for a VAX/VMS operating system.     

Frequency characteristics of amplitude and phase of oscillating bubble systems in a closed measuring cell

The amplitude- and phase-frequency characteristics of oscillating bubble systems with a closed measuring cell are analyzed. The shape of the frequency characteristics is qualitatively different for bubbles smaller or larger than a hemisphere, respectively, and also for diluted and concentrated surfactant solutions. Moreover, the presence of a surfactant in the solution strongly influences the characteristic frequencies of the system. The experiments performed under ground and microgravity conditions show a good qualitative agreement with theoretically predicted amplitude- and phase-frequency characteristics and confirm the adequacy of the proposed theory. The comparison of high-frequency limits of the surface dilatational elasticity with the theoretical Gibbs elasticities calculated according to the respective adsorption isotherm shows good agreement for small surfactant concentrations. At higher concentrations large discrepancies are observed which can possibly be explained by the violation of the linearity condition for the surface layer.