Global Analysis of the Flows of Fluids with Pressure-Dependent Viscosities

 To describe the flows of fluids over a wide range of pressures, it is necessary to take into account the fact that the viscosity of the fluid depends on the pressure. That the viscosity depends on the pressure has been verified by numerous careful experiments. While the existence of solutions local-in-time to the equations governing the flows of such fluids are available for small, special data and rather unrealistic dependence of the viscosity on the pressure, no global existence results are in place. Our interest here is to establish the existence of weak solutions for spatially periodic three-dimensional flows that are global in time, for a large class of physically meaningful viscosity-pressure relationships. (Accepted May 1, 2002) Published online November 15, 2002 Communicated by S. S. ANTMAN     

Stability-indicating high-performance liquid chromatographic assay of buspirone HCl

The United States Pharmacopoeia high-performance liquid chromatographic (HPLC) assay method of buspirone is not able to discriminate buspirone from its degradation products. The purpose of this work is to develop a sensitive, selective, and validated stability-indicating HPLC assay for the analysis of a buspirone hydrochloride in a bulk drug. Buspirone HCI and its potential impurities and degradation products are analyzed on an Ultrasphere C18 column heated to 40 degrees C using a gradient program that contains monobasic potassium phosphate buffer solution (pH 6.9) and acetonitrile-methanol mixture (13:17) of 35% for 5 minutes, then increased to 54% in 5.5 minutes. The samples are monitored using a photo-diode array detector and integrated at 244 and 210 nm. The stress testing of buspirone HCI shows that buspirone acid hydrochloride is the major degradation product. The developed method shows a separation of buspirone degradation product and its potential impurities in one run. The stability of buspirone HCI is studied under accelerated conditions in order to provide a rapid indication of differences that might result from a change in the manufacturing process or source of the sample. The forced degradation conditions include the effect of heat, moisture, light, acid-base hydrolysis, sonication, and oxidation. The compatibility of buspirone HCI with some pharmaceutical excipients is studied under stress conditions. The linear range of buspirone HCI is between 5 and 200 ng/microL with a limit of quantitation of 2.5 ng/microL. The intraassay percentage deviation is not more than 0.38%, and the day-to-day variation was not more than 0.80%. The selectivity, repeatability, linearity, range, accuracy, sample solution stability, ruggedness, and robustness show acceptable values.     

Spectrophotometric determination of nickel(II) in different samples by complexation with some triazolylazo dyes

A new sensitive spectrophotometric method for the determination of nickel(II) with 3-(2-hydroxy-5-acetyl-(L¹),-5-ethoxycarbonyl-(L²),-5-methyl-(L³),-5-formyl-(L⁴),-5-bromophen-1-ylazo)-1,2,4-triazole (L⁵), and 3-(2,4-dihydroxyphen-1-ylazo)-1,2,4-triazole (L⁶) in aqueous media containing 40 vol. % methanol has been developed. The method is based on the formation of stable coloured Ni(II) complexes with stoichiometric ratios 1: 1 and 1: 2 (n(M): n(L)). Linear calibration graphs are obtained up to 7.04 μg cm⁻³ of nickel(II) under optimum conditions attained from investigation of complex formation. The absorption maxima varied from 485 nm to 545 nm and the molar absorptivities ranged from 0.84 × 10⁴ to 4.65 × 10⁴ dm³ mol⁻¹ cm⁻¹ for 1: 1 and 1: 2 (n(M): n(L)) complexes with varying the substituent on the phenolic ring. The optimum ranges for the direct determination of nickel(II) (Ringbom) and the stability constants of the formed complexes are determined. The developed method was applied to the spectrophotometric determination of nickel(II) in some samples with satisfactory results.     

Ultrasound-Assisted Dispersive Microsolid-Phase Extraction for Preconcentration of Trace Cobalt and Nickel in Environmental Samples Prior to their Determination by Flame Atomic Absorption Spectrometry

Journal of Applied Spectroscopy - A new, green, simple, and validated ultrasound-assisted dispersive microsolid-phase extraction method applying unprecedented adsorbent-modified multiwalled carbon...     

Discovery of New Coumarin-Based Lead with Potential Anticancer,CDK4 Inhibition and Selective Radiotheranostic Effect: Synthesis, 2D & 3D QSAR,Molecular Dynamics,In Vitro Cytotoxicity,Radioiodination, and Biodistribution Studies

Novel 6-bromo-coumarin-ethylidene-hydrazonyl-thiazolyl and 6-bromo-coumarin-thiazolyl-based derivatives were synthesized. A quantitative structure activity relationship (QSAR) model with high predictive power r² = 0.92, and RMSE = 0.44 predicted five compounds; 2b, 3b, 5a, 9a and 9i to have potential anticancer activities. Compound 2b achieved the best ΔG of –15.34 kcal/mol with an affinity of 40.05 pki. In a molecular dynamic study 2b showed an equilibrium at 0.8 Å after 3.5 ns, while flavopiridol did so at 0.5 Å after the same time (3.5 ns). 2b showed an IC₅₀ of 0.0136 µM, 0.015 µM, and 0.054 µM against MCF-7, A-549, and CHO-K1 cell lines, respectively. The CDK4 enzyme assay revealed the significant CDK4 inhibitory activity of compound 2b with IC₅₀ of 0.036 µM. The selectivity of the newly discovered lead compound 2b toward localization in tumor cells was confirmed by a radioiodination biological assay that was done via electrophilic substitution reaction utilizing the oxidative effect of chloramine-t. ¹³¹I-2b showed good in vitro stability up to 4 h. In solid tumor bearing mice, the values of tumor uptake reached a height of 5.97 ± 0.82%ID/g at 60 min p.i. ¹³¹I-2b can be considered as a selective radiotheranostic agent for solid tumors with promising anticancer activity.     

Structure and stability characteristics of turbulent planar flames with inhomogeneous jet in a concentric flow slot burner

Turbulent flames with compositionally inhomogeneous mixtures are common in many combustion systems. Turbulent jet flames with a circular nozzle burner were used earlier to study the impact of inhomogeneous mixtures, and these studies showed that the nozzle radius affects the flame stability. Accordingly, planar turbulent flames with inhomogeneous turbulent jet are created in a concentric flow slot burner (CFSB) to avoid this effect in the present study. The stability characteristics, the mixing field structure, and the flame front structure were measured, and the correlations between stability and the mixing field structure were investigated. The mixture fraction field was measured in non-reacting jets at the nozzle exit using highly resolved Rayleigh scattering technique, and the flame front was measured in some selected turbulent flames using high-speed Planar Laser-Induced Fluorescence (PLIF) of OH technique. The data show strong correlations between flame stability and the range of mixture fraction fluctuations. The flames are highly stabilized within a mixing field environment with the range of fluctuation in mixture fraction close to the range of the flammability limits. The mixing field structure is also illustrated and discussed using a mixing regime diagram and showed that the scatter of the data of the different cases is consistent with the classified mixing regimes. Lean flames are stabilized in the current slot burner. The flame front structure topology varies consistently from thin, small curvature at the low level of turbulence and higher equivalence ratio to more wrinkled, larger curvature, but a thicker structure at a higher level of turbulence and lower equivalence ratio.     

Guided modes of integrated optical guides. A mathematical study

A waveguide in integrated optics is defined by its refractiveindex. The guide is assumed to be invariant in the propagationdirection while in the transverse direction it is supposed tobe a compact perturbation of an unbounded stratified medium.We are interested in the modes guided by this device, whichare waves with a transverse energy confined in a neighbourhoodof the perturbation. Our goal is to analyse the existence of such guided modes. Underthe assumptions of weak guidance the problem reduces to a two-dimensionaleigenvalue problem for a scalar field. The associated operatoris unbounded, selfadjoint, and bounded from below. Its spectrumconsists of the discrete spectrum corresponding to the guidedmodes and of the essential spectrum corresponding to the radiationmodes. We present existence results of guided modes and an asymptoticstudy at high frequencies, which shows that contrarily to thecase of optical fibers, the number of guided modes can remainbounded. The major tools are the min-max principle and comparisonof results between different eigenvalue problems. The originalityof the present study lies in the stratified character of theunbounded reference medium.     

Spectrophotometric determination of epinephrine and norepinephrine with sodium periodate

A simple and accurate spectrophotometric method is described for the determination of epinephrine (EP), norepinephrine (NE) and their bitartrate salts. The method is based on the development of a red colour (lambda(max) 490 nm) with sodium periodate in aqueous alcoholic medium. The colour is stable for at least 1 hr. The molar reacting ratio of EP or NE to periodate is 1:2. The proposed method is particularly suitable for routine analysis of EP and NE injections. The interference due to the sodium metabisulphite normally used as antioxidant can be overcome by addition of acetone. Results for analysis of bulk drugs and injections agree well with those of official methods.     

Interaction of the mu-opioid receptor with GPR177 (Wntless) inhibits Wnt secretion: potential implications for opioid dependence

Background  

Opioid agonist drugs produce analgesia. However, long-term exposure to opioid agonists may lead to opioid dependence. The analgesic and addictive properties of opioid agonist drugs are mediated primarily via the mu-opioid receptor (MOR). Opioid agonists appear to alter neuronal morphology in key brain regions implicated in the development of opioid dependence. However, the precise role of the MOR in the development of these neuronal alterations remains elusive. We hypothesize that identifying and characterizing novel MOR interacting proteins (MORIPs) may help to elucidate the underlying mechanisms involved in the development of opioid dependence.     

Stability-indicating thin-layer chromatographic method for quantitative determination of ribavirin

A simple and accurate stability-indicating thin-layer chromatographic (TLC) method is developed and validated for the quantitative determination of ribavirin (RBV) in its bulk and with used for development consists of chloroform-methanol-acetic acid (60:15:15, v/v/v). The separated spots are visualized as bluish green spots after being sprayed with anisaldehyde reagent. RBV is subjected to different accelerated stress conditions. The drug is found to undergo degradation under all stress conditions, and the degradation products are well resolved from the pure drug with significantly different Rf values. The optical densities of the separated spots are found to be linear with the amount of RBV in the range of 5-40 microg/spot with a good correlation coefficient (r=0.9980). The limit of detection and limit of quantitation values are 1.40 and 4.67 microg/spot, respectively. Statistical analysis proves that the method is repeatable and accurate for the determination of RBV in the presence of its degradation products. The method meets the International Conference on Harmonisation/Food and Drug Administration regulatory requirements. The proposed TLC method is successfully applied for the determination of RBV, pure and in capsules, with good accuracy and precision; the label claim percentages are 98.8%+/-1.5%. The results obtained by the proposed TLC method are comparable with those obtained by the official method.