Simultaneous determination of epinephrine and norepinephrine in human blood plasma and urine samples using nanotubes modified edge plane pyrolytic graphite electrode

The simultaneous determination of catecholamines - epinephrine and norepinephrine by square wave voltammetry (SWV) at physiological pH 7.2 is reported using multi-walled carbon nanotubes modified edge plane pyrolytic graphite electrode (MWNT/EPPGE). A broad bump at ∼250 mV is appeared for the oxidation of epinephrine (EP) and norepinephrine (NE) at bare EPPGE whereas at MWNT/EPPGE two well-separated peaks at ∼150 and ∼215 mV are appeared for the oxidation of EP and NE, respectively. The oxidation peak current of both the neurotransmitters also increased significantly along with the negative shift of peak potentials using MWNT/EPPGE. The oxidation of both compounds occurred in a pH dependent, 2e and 2H⁺ process and the electrode reaction followed diffusion controlled pathway. Linear calibration curves were obtained for epinephrine and norepinephrine in the range 0.5-100 nM with limits of detection 0.15 × 10⁻⁹ and 0.90 × 10⁻¹⁰ M, respectively. The developed protocol is implemented for the simultaneous determination of epinephrine and norepinephrine in blood plasma and urine samples of smokers as well as in athletes.     

CsPb3Bi3Te8 and CsPb4Bi3Te9: low-dimensional compounds and the homologous series CsPbmBi3Te5 + m

Two new thermoelectric materials of quaternary bismuth telluride CsPb3Bi3Te8 and CsPb4Bi3Te9 are reported, which are members of a homologous series featuring anionic slabs [PbmBi3Te5 + m]- (m = 1-4) of monotonically increasing thickness.     

Tailoring plasmonic substrates for surface enhanced spectroscopies

Our understanding of how the geometry of metallic nanostructures controls the properties of their surface plasmons, based on plasmon hybridization, is useful for developing high-performance substrates for surface enhanced spectroscopies. In this tutorial review, we outline the design of metallic nanostructures tailored specifically for providing electromagnetic enhancements for surface enhanced Raman scattering (SERS). The concepts developed for nanoshell-based substrates can be generalized to other nanoparticle geometries and scaled to other spectroscopies, such as surface enhanced infrared absorption spectroscopy (SEIRA).     

Reduced systems in Markov chains and their applications in queueing theory

A reduced system is a smaller system derived in the process of analyzing a larger system. While solving for steady-state probabilities of a Markov chain, generally the solution can be found by first solving a reduced system of equations which is obtained by appropriately partitioning the transition probability matrix. In this paper, we catagorize reduced systems as standard and nonstandard and explore the existence of reduced systems and their properties relative to the original system. We also discuss first passage probabilities and means for the standard reduced system relative to the original system. These properties are illustrated while determining the steady-state probabilities and first passage time characteristics of a queueing system.     

On Linear Codes over $${\mathbb{Z}}_{2^{s}}$$

In an earlier paper the authors studied simplex codes of type α and β over and obtained some known binary linear and nonlinear codes as Gray images of these codes. In this correspondence, we study weight distributions of simplex codes of type α and β over The generalized Gray map is then used to construct binary codes. The linear codes meet the Griesmer bound and a few non-linear codes are obtained that meet the Plotkin/Johnson bound. We also give the weight hierarchies of the first order Reed-Muller codes over The above codes are also shown to satisfy the chain condition.A part of this paper is contained in his Ph.D. Thesis from IIT Kanpur, India     

Structural and polarization properties of polyimide/TiO2 nanocomposites

Polyimide (PI)/titanium dioxide (TiO₂) nanocomposite films were prepared by a solution mixing method with different contents of TiO₂ nanoparticles. The structural and thermal properties of pure PI and PI/TiO₂ nanocomposite films were studied by several techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermally stimulated depolarization current (TSDC). The SEM and AFM measurements show the uniform dispersion of TiO₂ nanoparticles in PI matrix, and it is also observed that the value of average roughness increases with increasing the contents of TiO₂ nanoparticles. The XRD pattern shows the presence of TiO₂ nanoparticles in PI matrix. It has been observed that the average crystallite size and percentage of crystallinity increase with content of the TiO₂ nanoparticles. FTIR spectra depict the position of different bonds in PI and nanocomposite samples. The TSDC results represent the modification of polarization phenomenon after filling of PI by titania nanoparticles.     

Highly regioselective ring-opening of aziridines with arenesulfinates on water: a facile access to β-amino/vinyl sulfones

We have developed a LiBr catalyzed efficient synthesis of β-amino sulfones from readily available aziridines and sodium sulfinates in good to excellent yields. The synthetic potential of β-amino sulfones has also been demonstrated by their facile conversion to the corresponding vinyl sulfones. The use of water as reaction media, atom-economy and isolation of products by simple filtration in the case of solid β-amino sulfones are certain green virtues of the synthetic protocol.     

Dynamics and correlations in magnetic colloidal systems studied by X-ray photon correlation spectroscopy

We have studied the static and dynamic behaviour of magnetic colloidal systems (ferrofluids) by Small-Angle X-ray Scattering (SAXS) and X-ray Photon Correlation Spectroscopy (XPCS). The main features of the novel XPCS technique will be illustrated by data taken on a model system, colloidal silica spheres. We will then present the results obtained on an optically opaque suspension of magnetic colloids (maghemite) in the wave vector range from 10^-3 to 10^-2?^-1. Translational diffusion in zero field and anisotropic diffusion under external magnetic fields will be discussed. Received 9 August 1999 and Received in final form 26 July 2000     

Axisymmetric vibrations of polar orthotropic mindlin annular plates of variable thickness

Analysis and numerical results are presented for the axisymmetric vibrations of polar orthotropic annular plates with linear variation in thickness, according to Mindlin's shear theory of plates. A chebyshev collocation technique has been employed to obtain the frequency equations for the transverse motion of such plates, for three different boundary conditions. Frequencies, mode shapes and moments for the first three modes of vibration have been computed for different plate parameters. A comparison of frequencies with the corresponding values obtained by classical plate theory leads to some interesting conclusions.     

A systematic scheme of qualitative analysis for anions. part I

A new and comprehensive scheme for the systematic detection of anions has been put forward. This scheme is based on the precipitation of difficultly soluble salts of anions in groups by basic group reagents in sodium carbonate solution and the subsequent analysis of cach group precipitate or filtrate for the detection of individual members of the group