Elastic properties of nanocrystalline forsterite under high pressure and high temperature

A simple theoretical model is developed to study the pressure–volume–temperature relationship and applied for nanocrystalline forsterite in the temperature range 300–1573 K and pressure range 0–9.6 GPa. The results obtained with the present model are in quite close agreement to the experimental values. The model is therefore extended to study the variation of bulk modulus and the coefficient of volume thermal expansion under high pressure and high temperature. The present study also reveals that the quasi-harmonic approximation, i.e., the product of bulk modulus and the coefficient of volume thermal expansion as constant, is valid at least up to the temperature 1573 K and pressure 9.6 GPa in case of nanocrystalline forsterite.     

Electroanalytical Sensor for Diabetic Foot Ulcer Monitoring with Integrated Electronics for Connected Health Application

L‐tyrosine is an amino acid, the concentration of which is found to be highly elevated in patients suffering from diabetic foot ulcer (DFU). The latter proves to be fatal when it turns out chronic and may lead to amputation. The conventional clinical diagnostic methods are costly and time consuming, in which case, the condition of patient(s) may deteriorate long before proper treatment commences. Herein, we report the development of smart band‐aid for real time monitoring of L‐tyrosine by employing enzymatic bio‐sensor using α‐MnO₂/tyrosinase. The smart band‐aid was further integrated with portable electronics capable of wireless data transmission to a personal digital assistant, and its tyrosine sensing performance was evaluated. Anodic current was found to vary linearly with the concentrations of L‐tyrosine in the range of 5 nM–500 μM. The developed sensor displayed a limit of detection and sensitivity of 0.71 nM and 0.67 μA/nM/mm² respectively, with a stability of 25 days. The developed sensor was validated using a commercial impedance analyzer. The impedance response was found to be consistent with the cyclic voltammogram obtained and demonstrated to be a linear function of tyrosine concentration. The developed sensing platform combines early diagnosis with connected health technologies, thus, fitting well into modern healthcare needs.     

Effects of seasonal growth on ratio dependent delayed prey predator system

The Beddington–DeAngelis ratio dependent prey predator model with time delay has been discussed. The existence of Hopf bifurcation has been established. The numerical simulations have shown that seasonal growth and delay can give rise to variety of attractors including periodic, quasi-periodic as well as chaotic oscillations. The degree of complexity in the system increases with increase in magnitude of delay, or frequency of seasonal variation. The model parameters involved in functional response can also affect the complexity of the system.     

Gold‐Iron Bimetallic Nanoparticles Impregnated Reduced Graphene Oxide Based Nanosensor for Label‐free Detection of Biomarker Related to Non‐alcoholic Fatty Liver Disease

We report for the first time a microwave assisted, one pot, direct, and facile synthesis of monodispersed iron‐gold bimetallic nanoparticles (BNP_Au‐Fe) using glucose as a reducing agent in merely 90 s. The as such synthesized BNP_Au‐Fe were thoroughly characterized using UV‐Vis, XRD, TEM, EDX, elemental mapping, and raman spectroscopy. These BNP_Au‐Fe were further impregnated with reduced graphene oxide (rGO) and coated onto glassy carbon electrode (GCE) to develop a sensor probe for label free electrochemical detection of acetaminophen, which is considered to be a most potent biomarker related to non‐alcoholic fatty liver disease. The sensor probe was systematically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BNP_Au‐Fe‐rGO nanocomposite matrix showed the sensing of acetaminophen with a wide dynamic range between 50 and 800 nM with detection limit (DL) of 0.14 nM (±0.05) nM (RSD<4.12 %) that was lower compared to previously reported acetaminophen sensors. To show the practical application of the sensor probe, acetaminophen was detected in human urine samples, which showed the percentage recovery between 86.65 % and 91.32 %. To the best of our knowledge, this is the first report where BNP_Au‐Fe impregnated rGO was used to detect acetaminophen. Interferences due to various molecules such as glucose, serum albumin, glycine, glutamic acid, alanine, citric acid, and ascorbic acid were tested individually and in mixed sample. Long‐term stability of sensor probe was examined which was found to be stable up to 12 weeks. The sensor fabricated using BNP_Au‐Fe‐rGO nanocomposite has many attractive features such as; simplicity, rapidity, and label free detection, hence it could be a method of choice for acetaminophen detection in clinical settings.     

Programming with a special class of nonlinear functionals

Summary In this paper we consider programming problems in which the constraints are linear and the objective function is the product or the quotient of two functions, each function being a homogeneous form of first degree with a constant added to it.With the proper assumptions of concavity or convexity of the homogeneous forms, this nonlinear programming problem is reduced to that of maximization of a concave function over a convex constraint set.

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Zusammenfassung In der vorliegenden Arbeit werden Programme untersucht, bei denen die Nebenbedingungen linear sind und die Zielfunktion als Produkt bzw. Quotient zweier Funktionen darstellbar ist, die bis auf additive Konstanten homogen von 1. Grad sind. Bei geeigneten Konvexitäts- oder Konkavitätsannahmen für diese Funktionen lassen sich solche Programme auf die Maximierung einer konkaven Funktion in einem konvexen Gebiet zurückführen.

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Prepared with the partial support of the C.S.I.R., India.

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Vorgel. v.:J. Nitsche.     

Synthesis, Characterization and X-Ray Structure of Bis(O-propyldithiocarbonato-κ2S,S′)bis(4-cyanopyridine-κN)nickel(II)

Abstract  

The [Ni(S₂COCH₂CH₂CH₃)₂(C₆H₄N₂)₂] adduct of 4-cyanopyridine with [Ni(S₂COCH₂CH₂CH₃)₂] was synthesized and characterized by elemental analysis, magnetic susceptibility measurement, IR, electronic spectral data, Thermogravimetric analysis/DTA techniques and X-ray diffraction analysis. The Ni atom in the title complex is octahedrally coordinated within a trans-N₂S₄ donor set, with the Ni atom located on a centre of inversion. The title complex crystallizes in the monoclinic space group P2 ₁ /c with unit cell parameters a = 11.75(4), b = 11.62(3), c = 9.20(2) ?, β = 104.99(3)°. Crystal structure was solved by direct methods and refined by full matrix least squares procedures to a final R-value of 0.0294 for 1895 observed reflections. The packing of layers of molecules is stabilized by weak C–H···N and C–H···π interactions.     

Synthesis and characterization of nanostructured (Pb1− x Sr x )TiO3 thin films by a modified chemical route

The coating solutions of nanostructured (Pb_{1– x} Sr _x )TiO₃ (PST) thin films have been prepared by the sol–gel combined metallo-organic decomposition method. The coating solutions were deposited on Pt/Ti/SiO₂/Si substrates using a spin-coating technique with spinning speed of 4300 rpm and annealed at 650°C. The effect of Sr content in reducing the grain size and tetragonal distortion of PST films has been studied. The optimum conditions for crystalline phase formation in the films have been analyzed by thermogravimetric, differential thermal analysis and Fourier transform infrared spectroscopy. The phase and microstructure of the films were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD pattern shows that the PST thin films are crystallized into tetragonal structures without any impurity phase and the distortion ratio reduces with increasing Sr concentration. The AFM results indicate an increase in grain size with increasing annealing temperature of the film and reduction in grain size with increasing Sr concentration.     

Highly Sensitive Synchronous Fluorescence Measurement of Danofloxacin in Pharmaceutical and Milk Samples Using Aluminium (III) Enhanced Fluorescence

A simple, rapid and sensitive constant wavelength synchronous fluorescence method is developed for the determination of danofloxacin (DAN) in pharmaceutical formulations and its residue in milk based on Al(III) enhanced fluorescence. The synchronous fluorescence intensity of the system is measured at 435?nm using ? λ?=?80?nm and an excitation wavelength of 280?nm. A good linear relationship between enhanced fluorescence intensity and DAN concentration is obtained in the range of 3-100?ng?mL(-1)(r (2)?=?0.9991). The limit of detection (LOD, S/N?=?3) of the present method is 0.9?ng?mL(-1). The proposed method can be successfully applied to the determination of DAN in pharmaceutical formulations and in milk without serious interferences from common excipients, metal ions and other co-existing substances. The method can be used as a rapid screening to judge whether the DAN residues in milk exceed Maximum Residue Limits (MRLs) or not.     

Study on the Fluorescence Quenching Reaction of Amitriptyline and Clomipramine Hydrochlorides with Eosin Y and its Analytical Application

Amitriptyline.HCl (AMI) and clomipramine.HCl (CMI) react with eosin Y (EY) in pH 3.8 NaAc-AcH buffer solution to form ion association complex which results in quenching of fluorescence of EY and appearance of a new resonance Rayleigh scattering (RSS) spectrum at 620 nm. The spectral characteristics of absorption, fluorescence and RSS spectra have been investigated. The factors influencing the reaction were studied and optimum conditions for the reaction have been determined. Based on fluorescence quenching, a simple and sensitive spectrofluorimetric method for determination of AMI and CMI has been developed. The fluorescence quenching intensity was measured at 550 nm using an excitation wavelength of 310 nm. The calibration graph was found to be rectilinear in the range 0.08–2.0 μg?mL^?1 with detection limit of 0.017 μg?mL^?1 for AMI and 0.06–2.0 μg?mL^?1 with detection limit of 0.015 μg?mL^?1 for CMI. The method can be satisfactorily applied to the determination of AMI and CMI in tablets without interference from commonly occurring exicipients. The recovery and RSD values obtained indicate good accuracy and precision of the method. The mechanism of the reaction and fluorescence quenching has also been discussed.