Infinite-Dilution Binary Diffusion Coefficients of 2-Propanone, 2-Butanone, 2-Pentanone, and 3-Pentanone in CO2 by the Taylor Dispersion Technique from 308.15 to 328.15 K in the Pressure Range from 8 to 35 MPa

Infinite-dilution binary diffusion coefficients of 2-propanone, 2-butanone, 2-pentanone, and 3-pentanone in carbon dioxide were measured by the Taylor dispersion method at temperatures from 308.15 to 328.15 K and pressures from 7.60 to 34.57 MPa. The D ₁₂ values were obtained from the response curves by the method of fitting in the time domain. The accuracy in the fitting error was examined for each measurement. The measured D ₁₂ data were found to be well correlated by the Schmidt number correlation, with AAD%=3.74% for all solutes.     

Development and validation of spectrophotometric and HPTLC methods for simultaneous determination of rosiglitazone maleate and metformin hydrochloride in the presence of interfering matrix excipients

Two simple methods have been developed and validated for the simultaneous determination of rosiglitazone maleate (ROS) and metformin hydrochloride (MET) in synthetic mixtures and coated tablets in a ratio of 1:250 (ROS:MET). The first method was a spectrophotometric one. The minor component, ROS was determined by measuring the values of absorbance at λ_max 312?nm and the D₁ amplitudes at 331?nm where MET shows no absorption contribution. However, absorbance interferences from tablet excipients were successfully corrected by D₁ at 331?nm zero-crossing technique. Study of spectral interference from tablet excipients was included in the text. Standard curves for A_max and D₁ methods were in the concentration range 20.0–80.0?μg?mL^?1. The major component, MET was determined both in binary mixtures and tablets by measuring its A_max at 236?nm. Extensive dilution eliminated any absorption contribution from the coexisting ROS or tablet matrix. Standard curves showed linearity in the concentration range 4.0–12.8?μg?mL^?1. The second method was based on high performance thin layer chromatography (HPTLC) separation of the two drugs followed by densitometric measurements of their spots at 230?nm. The separation was carried out on Merck HPTLC aluminium sheets of silica gel 60 F254 using methanol:water:NH₄Cl 1% w/v (5:4:1 v/v/v) as the mobile phase. Linear calibration graphs of peak area values were obtained versus concentrations in the range of 0.4–2.0?μg?band^?1 and 20.0–100.0?μg?band^?1 for ROS and MET, respectively. According to International Conference on Harmonisation (ICH) guidelines, different validation parameters were verified for the two methods and presented.     

Binary Diffusion Coefficients of Acetone in Carbon Dioxide at 308.2 and 313.2 K in the Pressure Range from 7.9 to 40 MPa

Binary diffusion coefficients of acetone in carbon dioxide were measured by the Taylor dispersion method at 308.2 K and 7.9 to 40 MPa and at 313.2 K and 8.0 to 37 MPa. The D ₁₂ values obtained from the response curves by the method of fitting in the time domain were more accurate than those obtained by the moment method. At pressures lower than about 8.3 MPa at 308.2 K or 9.1 MPa at 313.2 K, the accuracy in the D ₁₂ values was found to decrease significantly with decreasing pressure by examining (peak area)×u _{a, cal}, the values of S ₁₀, the fitting error , and u _{a, cal}/u _{a, exp} as a function of pressure. The D ₁₂ values at pressures higher than 8.3 MPa at 308.2 K or 9.1 MPa at 313.2 K were well represented with the Schmidt number correlation. The D ₁₂ data with larger fitting errors (>0.01) showed larger deviations from the values predicted by this correlation.     

Quinine Actinometry as a Method for Calibrating Ultraviolet Radiation Intensity in Light-Stability Testing of Pharmaceuticals

Abstract

A collaborative study was carried out by seven different laboratories to evaluate quinine actinometry as a universal, standardized method for calibrating UV radiation intensity from light sources used in light-stability testing of pharmaceutical products. Near UV fluorescent lamps, white fluorescent lamps, metal halide lamps and xenon arc lamps were employed as light sources. The increase in absorbance at 400 nm of aqueous quinine solutions was found to be proportional to the integrated UV energy emitted from the light sources. The linearity observed between absorbance and integrated UV energy indictates that quinine actinometry can be used to measure the intensity of UV radiation at wavelengths around 330 nm. The slopes of regression curves of absorbance vs integrated UV energy varied among the lamps used due to differing spectral distributions. Light degradation of nifedipine, a model photosensitive drug, was studied based on quinine actinometry.     

Transport Properties of Nonelectrolyte Liquid Mixtures. XI. Mutual Diffusion Coefficients for Toluene+n-Hexane and Toluene+Acetonitrile at Temperatures from 273 to 348 K and at Pressures up to 25 MPa

Mutual diffusion coefficients,D ₁₂, have been measured at pressures up to 25 MPa using the chromatographic peak broadening technique (Taylor dispersion method) forxtoluene+(1–x)n-hexane in the temperature range 298 to 348 K and forxtoluene+(1–x) acetonitrile in the temperature range 273 to 348 K. The estimated uncertainty is ±4%. Both systems show negative deviations from straight-line behavior. The fractional decrease inD ₁₂is about 0.8% per MPa. Hard-sphere theory is applied under limiting conditions where one of the components is present in a trace amount. It is shown that the diffusion coefficients can be estimated by the Dullien method from a knowledge of the viscosity and density under the same conditions.     

A comparative analysis of TE and TM guided modes in Tidiffused Er:LiNbO3 waveguide lasers

Abstract

A detailed comparative analysis of TE and TM guided-modes in Z-cut Ti-diffused Er:LiNbO₃ strip waveguide lasers has been performed at laser emission wavelengths 1532, 1563, 1576 nm and pump wavelengths 1480 and 980 nm by the variational method. First, the mode size and corresponding effective refractive index at these five wavelengths as a function of initial Ti-strip width W, diffusion temperatures T, intial Ti-strip thickness H and diffusion time t were calcualted for several lower-order TE and TM modes; their characteristics and the single mode condition were discussed comparatively. Then, the plots of effective pump area and coupling efficiency between the laser and the pump modes under different pump and output mode polarizations were analysed. Finally, the coupling loss of a joint between the waveguide and a fibre in terms of these diffusion parameters were also calculated at these wavelengths. Numerical results are in good agreement with previously published experimental data.     

Acidic Potassium Dichromate Solutions as Ultraviolet Absorbance Standards

The absorbances of five concentrations of potassium dichromate in 0.001 M perchloric acid have been determined at eight wavelengths in the ultraviolet on the National Bureau of Standards Institute for Materials Research high-accuracy spectrophotometer. Four of the wavelengths—235, 257, 313, and 350 nm—correspond to absorbance maxima or minima in the HCrO₄^– spectrum and are useful wavelengths for checking the accuracy of the absorbance scale of narrow bandpass spectrophotometers. Although partial dimerization of HCrO₄^– to Cr₂O₇⁼ produces small positive deviations from Beer’s law at these wavelengths, the apparent absorptivities calculated for each concentration are reproducible to one part in a thousand. The estimated uncertainties in the absorptivity values are ± 0.7 percent at 0.1 absorbance (A) and ± 0.2 percent near A = 1. These uncertainties include all known sources of possible systematic error and the 95 percent confidence level for the mean. The remaining four wavelengths used for measurement are near two predicted isosbestic points in the HCr0₄^–/Cr₂O₇⁼ spectra. The absorptivities at 345 nm are sufficiently independent of concentration that this wavelength can be used for checking absorbance linearity to one part in a thousand over the range A = 0.2–1.     

Application of the three-valence model of photorefraction to rhodium-doped barium titanate

Abstract

Small signal and light induced absorption data taken at 633 nm and 1.06 μm for different samples of rhodium-doped barium titanate (Rh : BaTiO₃) have been analysed. These data have been used in conjunction with the three-valence model theory of photorefraction to determine N _D, the total amount of rhodium in each sample. It is shown that the values of N _D calculated at the two wavelengths for individual samples are inconsistent with each other, although no evidence for other impurities in the samples has been observed. This indicates that a more complex theory than the three-valence model is necessary to explain the photorefractive processes in Rh : BaTiO₃, and that an additional photorefractive centre may not be sufficient to account for the observed discrepancies in N _D.     

Inter- and intradiffusion in liquid mixtures of methane andn-decane

The interdiffusion coefficient,D ₁₂, has been measured by Mach-Zehnder interferometry for liquid mixtures of methane andn-decane at 303 K. The mole fraction of methane was from 0.11 to 0.96 and the pressure was from 30 to 60 MPa. This includes measurements in the critical region, the critical locus being approached from supercritical pressures to within 0.4 MPa. The accuracy inD ₁₂ is estimated to be from 3 to 10%, depending on the composition. Our data are compared with the Sigmund correlation, which is widely used to estimate diffusion coefficients in hydrocarbons at high pressures. The deviation between estimate and measurement is one order of magnitude for some of the states. We have also compared with a more recent correlation used by Erkey, but this one is not found to be applicable to the compositions studied in the present work. Our data were related to recently measured intradiffusion coefficients,D ₁ andD ₂, at the same state points. On this basis, we have evaluated different mixing rules for obtaining the interdiffusion coefficient from intradiffusion coefficients, both close to and away from the critical region. It is found that the so-called Darken and Adamson relations have the right qualitative behavior.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Effective lattice stabilization of gadolinium aluminate garnet (GdAG) via Lu3+ doping and development of highly efficient (Gd,Lu)AG:Eu3+ red phosphors

Abstract

The metastable garnet lattice of Gd₃Al₅O₁₂ is stabilized by doping with smaller Lu³⁺, which then allows an effective incorporation of larger Eu³⁺ activators. The [(Gd_1?xLu_x)_1?yEu_y]₃Al₅O₁₂ (x = 0.1–0.5, y = 0.01–0.09) garnet solid solutions, calcined from their precursors synthesized via carbonate coprecipitation, exhibit strong luminescence at 591 nm (the ⁵D₀ → ⁷F₁ magnetic dipole transition of Eu³⁺) upon UV excitation into the charge transfer band (CTB) at ～239 nm, with CIE chromaticity coordinates of x = 0.620 and y = 0.380 (orange-red). The quenching concentration of Eu³⁺ was estimated at ～5 at.% (y = 0.05), and the quenching was attributed to exchange interactions. Partial replacement of Gd³⁺ with Lu³⁺ up to 50 at.% (x = 0.5) while keeping Eu³⁺ at the optimal content of 5 at.% does not significantly alter the peak positions of the CTB and ⁵D₀ → ⁷F₁ emission bands but slightly weakens both bands owing to the higher electronegativity of Lu³⁺. The effects of processing temperature (1000–1500 °C) and Lu/Eu contents on the intensity, quantum efficiency, lifetime and asymmetry factor of luminescence were thoroughly investigated. The [(Gd_0.7Lu_0.3)_0.95Eu_0.05]₃Al₅O₁₂ phosphor processed at 1500 °C exhibits a high internal quantum efficiency of ～83.2% under 239 nm excitation, which, in combination with the high theoretical density, favors its use as a new type of photoluminescent and scintillation material.     

Catalogue to select the initial guess spectrum during unfolding

A new method to select the initial guess spectrum is presented. Neutron spectra unfolded from Bonner sphere data are dependent on the initial guess spectrum used in the unfolding code. The method is based on a catalogue of detector count rates calculated from a set of reported neutron spectra. The spectra of three isotopic neutron sources ²⁵²Cf, ²³⁹PuBe and ²⁵²Cf/D₂O, were measured to test the method. The unfolding was carried out using the three initial guess options included in the BUNKIUT code. Neutron spectra were also calculated using MCNP code. Unfolded spectra were compared with those calculated; in all the cases our method gives the best results.     

The anisotropic diffusion of water in Kevlar-epoxy composites

The diffusion of water into unidirectional Kevlar fibre reinforced epoxy resins was studied as a function of fibre orientation and, for unidirectional (0°) composites, as a function of volume fraction (V_f). As the angle increased from 0 to 90°, the diffusivity increased dramatically; i.e. as more and more fibre-ends were exposed to the shorter diffusion path, the diffusivity increased. The equilibrium weight gain of water (M) in the composites increased with theV _f of the fibre. M of Kevlar fibre was calculated to be 4.9%. At a constantV _f, specimens of the same thickness and width but different lengths were used to determineD ₂₂, the diffusion coefficient of the composite along the fibre, andD ₂₂, the diffusion coefficient transverse to the fibre. The initial data for the percentage weight gain against the square root of time were non-linear, which was attributed to the anisotropy of the diffusion process. The anisotropy arises from the much higher value ofD ₁₁ as compared toD ₂₂. AsV _f increased from 0.37 to 0.59,D ₁₁ increased from about 0.83 to about 4.2 × 10^–12m² sec^–1, whereasD ₂₂ decreased from 0.21 to 0.033 × 10^–12 m2 sec^–1. Thus, the ratioD ₁₁/D ₂₂ increased from 3 to over 100 as U increased. The experimental sorption data could be fitted satisfactorily with these diffusion coefficients.     

Transport properties of nonelectrolyte liquid mixtures. X. Limiting mutual diffusion coefficients of fluorinated benzenes inn-hexane

Mutual diffusion coefficients.D ₁₂. have been measured for benzene, seven fluorinated benzenes. and octafluorotoluene diffusing inn-hexane at trace concentration in the temperature range 213.2–333.2 K by the chromatographic peak-broadening, technique with an estimated accuracy of ±2.5% These results are compared with the predictions of rough hard-sphere theory (RHS). The results are reproducible to within ±10% with the translational rotational coupling factor equal to the value for the solvent. The activation energy of diffusionE _D, computed from Arrhenius plots. is almost constant for these solutes.     

Effect of inter-ionic interaction on photoluminescence property of yttrium aluminate garnet phosphors

The photoluminescence of Terbium-activated yttrium aluminate with the general formula Y_3-xTb_XAl₅O₁₂was investigated as a function of Tb³⁺concentration. The main attention is focused on the ⁵D₃/⁵D₄fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb³⁺concentration and analyzed in view of the application for plasma display panel (PDP). Also, the diffuse reflectance spectra were measured and analyzed in the range from VUV to UV. As a result, the yttrium aluminate was found to have a broad excitation band extending from VUV to UV range and to show the typical concentration quenching behaviors both for ⁵D₃and ⁵D₄fluorescence. The energy transfer was investigated by analyzing the decay curve of ⁵D₃and ⁵D₄emission based on the multipolar interaction or the exchange interaction. The decay curves of ⁵D₃emission, for which well known cross relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula based on the direct quenching scheme. The decay curves of ⁵D₄emission were analyzed by Yokota and Tanimoto's formula based on the diffusion limited quenching scheme.     

A simple and sensitive method for determination of vitamins D3 and K1 in rat plasma: application for an in vivo pharmacokinetic study

Purpose: To develop and to validate a simple but sensitive method for determination of vitamins D₃ and K₁ in rat plasma.

Methods: The sample treatment included protein precipitation by cold acetonitrile, evaporation, reconstitution with methanol and filtration. The chromatography conditions included Xterra RP18 3.5?µm 4.6?×?100?mm column at ambient temperature and mobile phase consisting of methanol/water (93/7, v/v) at 0.5?mL/min flow rate. Vitamin D₃ and probucol were detected at 265?nm and vitamin K₁ at 239?nm. Rats were administered intravenously by 0.1?mg/kg of vitamin D₃ or K₁ and the blood samples were withdrawn pre-administration and at pre-determined time points post-administration. The pharmacokinetic analysis was performed using a non-compartmental approach.

Results: The calibration curves in rat plasma were linear up to 5000?ng/mL for both vitamins. The limit of quantification (LOQ) was 20?ng/mL for vitamin D₃ and 40?ng/mL for K₁. Inter- and intra-day precision and accuracy were below 15%. The pharmacokinetic parameters of vitamin D₃ following intravenous administration were: AUC_0?∞?=?11323?±?1081?h?×?ng/mL, V_d?=?218?±?80?mL/kg, CL?=?8.9?±?0.8?mL/h/kg, t_1/2?=?16.8?±?5?h; and of vitamin K₁: AUC_0?∞?=?2495?±?297?h?×?ng/mL, V_d?=?60?±24?mL/kg, CL?=?40.5?±?5.1?mL/h/kg, t_1/2?=?1.1?±0.5?h.

Conclusion: The developed HPLC–UV assay is a simple and sensitive method for the determination of vitamins D₃ and K₁ in rat plasma. A higher dose of vitamin K₁ should be used in future studies for accurate estimation of pharmacokinetic parameters. The data show the suitability of the assay for pharmacokinetic studies in rats.     

Quinine Actinometry as a Method for Calibrating Ultraviolet Radiation Intensity in Light-Stability Testing of Pharmaceuticals

A collaborative study was carried out by seven different laboratories to evaluate quinine actinometry as a universal, standardized method for calibrating UV radiation intensity from light sources used in light-stability testing of pharmaceutical products. Near UV fluorescent lamps, white fluorescent lamps, metal halide lamps and xenon arc lamps were employed as light sources. The increase in absorbance at 400 nm of aqueous quinine solutions was found to be proportional to the integrated UV energy emitted from the light sources. The linearity observed between absorbance and integrated UV energy indictates that quinine actinometry can be used to measure the intensity of UV radiation at wavelengths around 330 nm. The slopes of regression curves of absorbance vs integrated UV energy varied among the lamps used due to differing spectral distributions. Light degradation of nifedipine, a model photosensitive drug, was studied based on quinine actinometry.     

Three-dimensional analysis of modulated photoreflectance in a silicon wafer

The effects of probe and pumping beam size and modulation frequency on photoreflectance were investigated for a silicon wafer by considering one- and three-dimensional generation and propagation of thermal and plasma waves,PR _1D andPR _3D. The magnitude ofPR _1D decreased as the inverse square of the effective beam radius and that ofPR _3D was 100 times smaller thanPR _1D at 0.1 m effective beam radius and decreased with the effective beam radius. The phase shift ofPR _1D was nearly constant at 225°, whereas that ofPR _3D increased with the effective beam radius from 0° to 225°. The magnitude and phase ofPR _3D become the same as those ofPR _1D by satisfying the equivalence conditions, where the probe and pumping beam radii are larger than the thermal and plasma wavelengths, when the effective beam radius was larger than 112 m.PR _1D decreased with modulation frequency as ^–1/2, whereas the magnitude ofPR _3D was nearly constant and 100 times smaller than that ofPR _1D at 1 kHz modulation frequency. ThePR _1D phase varied from 180° to 225°, but that of thePR _3D increased from 0° to that ofPR _1D with increase of the modulation frequency. As the modulation frequency increased, the magnitude and phase ofPR _3D approached to those ofPR _1D by approaching the equivalence conditions, owing to the decrease of the thermal and plasma wavelengths. The good agreements in the modulation frequency dependence of the magnitude and phase ofPR _3D with those measured, justified the three-dimensional analysis of the photoreflectance.     

Photoelectrochemical investigation on spray depositedn-CdIn2S4 thin films

Polycrystalline thin films ofn-CdIn₂S₄ have been spray deposited onto amorphous and fluorinedoped tin oxide (FTO) coated glass substrates at the optimized substrate temperature of 380°C. The films were characterized by X-ray diffraction (XRD) and optical absorption studies. XRD studies revealed that the films were polycrystalline with spinel cubic structure. The optical absorption studies showed the band gap energy to be 2·14 eV. Photoelectrochemical (PEC) investigations were carried out using cell configurationn-CdIn₂S₄/1 M NaOH+1 M Na₂S+1 M S/C. Using Butler model, the optical band gap and minority carrier diffusion length (L _P) were found to be 2·22 eV and 0·07 μm, respectively. Gartner’s model was used to calculate the minority carrier diffusion length and the donor concentration (N _D) for CdIn₂S₄ films at three different wavelengths.N _D was found to be of the order of 10¹⁶ cm⁻³.     

Thermophysical Properties of Low-Density Pure Alkanes and Their Binary Mixtures Calculated by Means of an (n-6) Lennard-Jones Temperature-Dependent Potential

Self-consistent calculations of interaction pVT-virial coefficients B ₁₂(T), viscosities η _mix (T), and diffusion coefficients D ₁₂(T) of binary mixtures of the alkanes C _n H_{2n + 2} (n < 6) are presented. This study is based on the recently developed model of the (n-6) Lennard-Jones temperature-dependent potential (LJTDP) and uses already obtained potential parameters of the pure alkanes as input data. The well-known and simple Lorentz-Berthelot (LB) and the more laborate Tang-Toennies (TT) mixing rules are applied to the potential parameters of the pure alkanes in order to determine those of the mixtures. The new Hohm–Zarkova–Damyanova (HZD) mixing rule, which is an extension of the TT-mixing rule, is also considered. The HZD takes into account that for the LJTDP model, in general, the repulsive parameter is an independent variable whose value n ≠ 12. As in a recent examination of binary mixtures of globular molecules, the LB-mixing rule is superior to TT- and HZD-mixing rules when calculating equilibrium properties such as B ₁₂(T). For the transport properties η _mix (T) and D ₁₂(T), the new mixing rule performs slightly better.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Ultra-thin TaN Films for Superconducting Nanowire Single-Photon Detectors

Ultra-thin films of superconducting tantalum nitride are deposited by reactive magnetron sputtering on heated sapphire substrates. The critical temperature T _C=10.25 K is reached for films thicker than 10 nm. A superconducting nanowire single-photon detector in the form of a meander line with a width of 110 nm was made from 5 nm thick TaN film. The detector had a transition temperature of 8.3 K and a critical current density of 4 MA/cm² at 4.2 K. A photon detection efficiency of 20% has been obtained for the detector with a filling factor of 0.55 at wavelengths up to 700 nm.