Indefinite Least Squares Problem with Quadratic Constraint and Its Condition Numbers

In this paper,we consider the indefinite least squares problem with quadratic constraint and its condition numbers.The conditions under which the problem has the unique solution are first presented.Then,the normwise,mixed,and componentwise condition numbers for solution and residual of this problem are derived.Numerical example is also provided to illustrate these results.     

Synthesis of nano-phase TiO2 crystalline films over premixed stagnation flames

A new method is proposed to fabricate nanocrystalline titania (TiO₂) films of controlled crystalline size and film thickness. The method uses the laminar, premixed, stagnation flame approach, combining particle synthesis and film deposition in a single step. A rotating disc serves as a combination of substrate-holder and stagnation-surface that stabilizes the flame. Disc rotation repetitively passes the substrates over a thin-sheet, fuel-lean ethylene–oxygen–argon flame doped with titanium tetraisopropoxide. Convective cooling of the back side of the disc keeps the substrate well below the flame temperature, allowing thermophoretic forces to deposit a uniform film of particles that are nucleated and grown via the flame stabilized just below the surface. The particle film grows typically at 1 μm/s. The film is made of narrowly distributed, crystalline TiO₂ several nanometers in diameter and forms with a 90% porosity. Analysis shows that the rotation of the stagnation-surface does not reduce the stability of a stagnation flame, nor does it affect the fundamental chemistry of particle nucleation and growth that occurs between the flame and the stagnation surface.     

Common fixed points of four maps in partially ordered metric spaces

In this paper, common fixed points of four mappings satisfying a generalized weak contractive condition in the framework of partially ordered metric space are obtained. We also provide examples of new concepts introduced herein.     

Development and Validation of a Stability-Indicating High-Performance Thin-Layer Chromatographic Method for the Simultaneous Quantification of Sparfloxacin and Flurbiprofen in Nanoparticulate Formulation

JPC – Journal of Planar Chromatography – Modern TLC - A simple, sensitive, precise, rapid, and reliable high-performance thin-layer chromatographic (HPTLC) method for the simultaneous...     

Physiological assessment of in vivo human knee articular cartilage using sodium MR imaging at 1.5 T

Osteoarthritis is a common joint disorder that is most prevalent in the knee joint. Knee osteoarthritis (OA) can be characterized by the gradual loss of articular cartilage (AC). Formation of lesion, fissures and cracks on the cartilage surface has been associated with degenerative AC and can be measured by morphological assessment. In addition, loss of proteoglycan from extracellular matrix of the AC can be measured at early stage of cartilage degradation by physiological assessment. In this case, a biochemical phenomenon of cartilage is used to assess the changes at early degeneration of AC. In this paper, a method to measure local sodium concentration in AC due to proteoglycan has been investigated. A clinical 1.5-T magnetic resonance imaging (MRI) with multinuclear spectroscopic facility is used to acquire sodium images and quantify local sodium content of AC. An optimised 3D gradient-echo sequence with low echo time has been used for MR scan. The estimated sodium concentration in AC region from four different data sets is found to be ~ 225 ± 19 mmol/l, which matches the values that has been reported for the normal AC. This study shows that sodium images acquired at clinical 1.5-T MRI system can generate an adequate quantitative data that enable the estimation of sodium concentration in AC. We conclude that this method is potentially suitable for non-invasive physiological (sodium content) measurement of articular cartilage.     

Equilibrium molecular dynamics simulation of shear viscosity of two-dimensional complex (dusty) plasmas

Shear viscosity is examined throughout the entire range of strongly coupled states of two-dimensional complex (dusty) plasma liquids (CDPLs). We have employed equilibrium molecular dynamics (EMD) simulation to compute the shear viscosity coefficients of CDPLs. In the strongly coupled liquid region, the values of valid viscosity coefficient can be estimated only in order of magnitude. The variations in the valid viscosity coefficients with screening strength (κ) and Coulomb coupling strengths (Γ) are observed. A systematic dependence of shear viscosity on κ is observed for an intermediate and higher Γ. The investigations showed that the position of the minimum viscosity coefficient shifts towards higher Γ as κ increases. The computational results for the entire range of liquid states of the strongly coupled dusty plasma obtained using the shear autocorrelation functions are in good agreement with the available simulation results and experimental data. It is shown that new simulations extended the range of plasma states (Γ, κ) used in our earlier simulation results for the existence of a finite minimum possible viscosity coefficient and it is also dependent on plasma states.     

Gold catalysis in organic transformations: A review

This review updates the explosive development of gold catalysis for organic transformation focusing on the current literature over last 3 years. Recent investigations have shown that gold catalysis provides catalytically active systems, whereas selectivity and reusability are advantages over noncatalyzed organic transformations. The collected literature is focusing for new organic reactions and synthetic methodologies. Gold can also be suggested for green processes dedicated to fine chemicals, pharmaceuticals, and the food industry due to its recognized biocompatibility. The current review is focused on new methods in the organic synthesis that could be of interest in the wide area of organic chemistry for developing new catalytic pathways.     

Combustion behavior of ammonia blended with diethyl ether

Ammonia (NH₃) is recognized as a carbon-free hydrogen-carrier fuel with a high content of hydrogen atoms per unit volume. Recently, ammonia has received increasing attention as a promising alternative fuel for internal combustion engine and gas turbine applications. However, the viability of ammonia fueling future combustion devices has several barriers to overcome. To overcome the challenge of its low reactivity, it is proposed to blend it with a high-reactivity fuel. In this work, we have investigated the combustion characteristics of ammonia/diethyl ether (NH₃/DEE) blends using a rapid compression machine (RCM) and a constant volume spherical reactor (CVSR). Ignition delay times (IDTs) of NH₃/DEE blends were measured using the RCM over a temperature range of 620 to 942 K, pressures near 20 and 40 bar, equivalence ratios (Φ) of 1 and 0.5, and a range of mole fractions of DEE, χ_DEE, from 0.05 to 0.2 (DEE/NH₃ = 5 – 20%). Laminar burning velocities of NH₃/DEE premixed flames were measured using the CVSR at 298 K, 1 bar, Φ of 0.9 to 1.3, and χ_DEE from 0.1 to 0.4. Our results indicate that DEE promotes the reactivity of fuel blends resulting in significant shortening of the ignition delay times of ammonia under RCM conditions. IDTs expectedly exhibited strong dependence on pressure and equivalence ratio for a given blend. Laminar burning velocity was found to increase with increasing fraction of DEE. The burnt gas Markstein length increased with equivalence ratio for χ_DEE = 0.1 as seen in NH₃-air flames, while the opposite evolution of Markstein length was observed with Φ for 0.1 < χ_DEE ≤ 0.4, as observed in isooctane-air flames. A detailed chemical kinetics model was assembled to analyze and understand the combustion characteristics of NH₃/DEE blends.     

Trace analysis of some organophosphorus pesticides in rice samples using ultrasound‐assisted dispersive liquid–liquid microextraction and high‐performance liquid chromatography

An ultrasound‐assisted dispersive liquid–liquid microextraction based on solidification of a floating organic drop method followed by high‐performance liquid chromatography was developed for the extraction, preconcentration, and determination of trace amounts of organophosphorus pesticides in rice samples. Variables affecting the performance of both steps were thoroughly investigated. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, recoveries for rice sample are in the range of 58.0–66.0%. The calibration graphs are linear in the range of 4–800 μg/kg and, limits of detection and limits of quantification are in the range of 1.5–3 and 4.2–8.5 μg/kg, respectively. The relative standard deviation for 50.0 μg/kg of organophosphorus pesticides in rice sample are in the range of 4.4–5.1% (n = 5). The obtained results show that proposed method is a fast and simple method for the determination of pesticides in cereals.     

Sensitive determination of methadone in human serum and urine by dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet followed by HPLC–UV

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high‐performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1‐Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34 ng/mmL in serum and 1.67 ng/mL in urine samples. Compared with the traditional dispersive liquid–liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high‐density and toxic solvents of traditional dispersive liquid–liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy.