First Principles Investigation of Fluorine Based Strontium Series of Perovskites

Density functional theory is used to explore structural, elastic, and mechanical properties of SrLiF₃, SrNaF₃, SrKF₃ and SrRbF₃ fluoroperovskite compounds by means of an ab-initio Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method. Several lattice parameters are employed to obtain accurate equilibrium volume (V_o). The resultant quantities include ground state energy, elastic constants, shear modulus, bulk modulus, young's modulus, cauchy's pressure, poisson's ratio, shear constant, ratio of elastic anisotropy factor, kleinman's parameter, melting temperature, and lame's coefficient. The calculated structural parameters via DFT as well as analytical methods are found to be consistent with experimental findings. Chemical bonding is used to investigate corresponding chemical trends which authenticate combination of covalent-ionic behavior. Furthermore electron density plots as well as elastic and mechanical properties are reported for the first time which reveals that fluorine based strontium series of perovskites are mechanically stable and posses weak resistance towards shear deformation as compared to resistance towards unidirectional compression while brittleness and ionic behavior is dominated in them which decreases from SrLiF₃ to SrRbF₃. Calculated cauchy's pressure, poisson's ratio and B/G ratio also proves ionic nature in these compounds. The present methodology represents an effective and influential approach to calculate the whole set of elastic and mechanical parameters which would support to understand various physical phenomena and empower device engineers for implementing these materials in numerous applications.     

Langmuir probe characteristics in a high pressure plasma in thepresence of convection and ionization

The current to a Langmuir probe operating in a high pressure flowing plasma is calculated for the case where convection of electrons or ions into the sheath adjacent to the probe and thermal generation of electrons and ions within the sheath can both be significant factors in determining probe current. In addition to generating explicit relations for planar, spherical and cylindrical probes for the asymptotic case in which only generation need be considered, a solution is also obtained for the extensive transition between this state and the purely convective state, for which explicit solutions already exist. The theory, which enables the electron/ion density to be calculated from the probe current is applicable to both positive and negative probes     

Information encoding by spectral anomalies of spatially coherent light diffracted by an annular aperture

Extensive experimental study is carried out to investigate spectral behavior of spatially polychromatic coherent light diffracted by an annular aperture. It is found that the spectrum at the observation plane exhibits anomalous behavior after passing through the annular aperture. Experimental observations show that at a particular diffraction angle, the diffracted spectrum splits into two halves, while at other diffraction angles the spectrum either shifts towards lower wavelengths (blue-shift) or shifts towards higher wavelengths (red-shift). These spectral changes take place in the vicinity of the dark ring of the Airy pattern. Moreover, the behavior of the spectrum in the Fraunhofer region around a small circular loop centered at a critical direction is also studied and it is found that these spectral changes are qualitatively different from the spectral changes of the spectrum of the focused waves on a circle centered at the singular point. It is discussed in detail that such spectral anomalies of spatially coherent light may be exploited for information encoding and information hiding for free-space communications. The possibility to entangle bits in the spectral anomalies is also proposed. Such technique might be very useful to improve the throughput of information transmission in free space.     

Iterative approximation of a common solution of a split equilibrium problem,a variational inequality problem and a fixed point problem

In this paper, we introduce an iterative method to approximate a common solution of a split equilibrium problem, a variational inequality problem and a fixed point problem for a nonexpansive mapping in real Hilbert spaces. We prove that the sequences generated by the iterative scheme converge strongly to a common solution of the split equilibrium problem, the variational inequality problem and the fixed point problem for a nonexpansive mapping. The results presented in this paper extend and generalize many previously known results in this research area.     

Synthesis, Characterization and Photoluminescence Study of Novel Sulfobetaine Polyelectrolytes

A novel sulfobetaine copolymer is developed via polycondensation approach. The comonomers, melamine, condenses with a diketone, 5,5-dimethyl-1,3-cyclohexane (dimedone) to produce polyimine chain based on Schiff base chemistry. Dimedone-[N,N' melaminium] propane sulfonate copolymer crystals were obtained on treatment of the polyimine with sulfopropylating agent, 1,3-propane sultone with a crosslinker, di(ethylene glycol diacrylate) (DEGDA). This crosslinked sulfobetaine polymer yielded fine needle like single crystals and shows strong blue fluorescence and a week green phosphorescence. Multi-exponential fluorescence decay function indicates the presence of different conformers both in solution and crystalline phase. This easy straightforward protocol for synthesis of crystalline, soluble, and luminescent polymer could prove to be a landmark in development of next generation smart functional materials.     

Water-compatible ‘aspartame’-imprinted polymer grafted on silica surface for selective recognition in aqueous solution

Molecularly imprinted polymers selective for aspartame have been prepared using N-[2-ammonium-ethyl-piperazinium) maleimidopropane sulfonate copolymer bearing zwitterionic centres along the backbone via a surface-confined grafting procedure. Aspartame, a dipeptide, is commonly used as an artificial sweetener. Polymerisation on the surface was propagated by means of Michael addition reaction on amino-grafted silica surface. Electrostatic interactions along with complementary H-bonding and other hydrophobic interactions inducing additional synergetic effect between the template (aspartame) and the imprinted surface led to the formation of imprinted sites. The MIP was able to selectively and specifically take up aspartame from aqueous solution and certain pharmaceutical samples quantitatively. Hence, a facile, specific and selective technique using surface-grafted specific molecular contours developed for specific and selective uptake of aspartame in the presence of various interferrants, in different kinds of matrices is presented.     

Ion transport properties of NaPF6- and NaCl-doped poly(N-phenylene N′imino pentyl)imminium propane sulfonate

New polymer-salt systems have been prepared by doping synthesized poly(N-phenylene N′imino pentyl) imminium propane sulfonate with NaPF₆ and NaCl. The higher conductivity of the NaPF₆-doped system in comparison to the NaCl-containing sample indicated that a larger-sized anion is facilitating ion conduction. FTIR spectra confirmed the complexation of salt with polymer. The conductivity power law exponent, studied in the frequency range from 42 Hz to 5 MHz, varies with frequency and has values >1, demonstrating dominance of caged ion movement. The dominance of caged motion is more pronounced in the NaCl-doped sample, signifying that a smaller anion has greater chances of being caged. Anion size signature is also visible in temperature and humidity dependence of exponent n.     

Floccosic Acid,a New Triterpenic Acid from Nepeta floccosa

The isolation and structure elucidation of a new triterpenic acid named floccosic acid ( 1 ) is reported on the basis of the 1D‐ and 2D‐NMR assignments. This secondary metabolite was isolated as a new constituent, along with the known triterpenoids, betulinic acid and β‐amyrin. All these compounds were purified by repeated column chromatography of the MeOH extract of Nepeta floccosa. The structure elucidation of the new compound was accomplished by the combined mass spectrometry (MS), infrared (IR) and ultraviolet (UV) absorption spectroscopy, one‐ (¹H‐ and ¹³C‐) and two‐dimensional (H? C correlations; HMBC and HSQC) NMR techniques. The known compounds were identified by comparison of their physical and spectroscopic data with those reported in the literature.