Surface enhanced Raman scattering of 2,2' biquinoline adsorbed on colloidal silver particles

Surface enhanced Raman scattering (SERS) in silver sol and normal Raman spectra in the bulk and in solution of 2,2' biquinoline (BQ) molecule have been investigated. The observed Raman bands along with their corresponding FTIR bands have been assigned based on the established assignments of the vibrational bands of the parent napthalene and quinoline molecules. Existence of both the cis and trans form of the BQ molecule in solution and in the bulk are inferred from the normal Raman and FTIR spectra, whereas SERS study reveal that in the surface adsorbed state the molecule exists in the cis form. Definite evidence of the charge transfer interaction to the overall contribution in the SER enhancement have been reported. The excitation profile also supports the CT interaction. Estimated enhancement factor of the principal SERS bands indicate that the molecule is adsorbed on the silver surface through both the nitrogen atoms with the molecular plane almost perpendicular to the surface. This preferred orientation of the molecule is in conformity with its existence in the cis form in the surface adsorbed state.     

Dust-acoustic waves in a self-gravitating complex plasma with trapped electrons and nonisothermal ions

It is shown that the nonlinear equations governing the dynamics of the large amplitude waves in a self-gravitating unmagnetized collisionless dust-electron-ion plasma admit stationary dust-acoustic shock solutions. Owing to the adiabaticity of dust-charge variation, inclusion of self-gravitation, and to the departure from the so-called Botzmannian electrons and ions to the trapped electrons and nonthermal ions, the dynamics of the nonlinear wave is found to be governed by a new energy-like integral equation.     

Gain enhancement in Nd:glass laser amplifiers using electro-polished aluminum reflectors

This paper presents a comparative study of single pass gain of a Nd:glass laser amplifier using geometrically identical reflector cavities of different reflector materials or surface treatment. An improvement in the small-signal single-pass gain by a factor of 2 and 1.5 is observed for an electro-polished aluminum cavity over a gold-plated cavity and mechanically polished aluminum cavity, corresponding to an increase of 25% and 15% respectively in the pump coupling efficiency.     

On the envelope soliton near critical density in a plasma with cold ions and two-temperature electrons

Summary We have analysed the formation of envelope soliton near critical density in a plasma consisting of two-temperature electrons and cold ions. The non-linear Schr?dinger-like equation obtained isiφ _t +pφ _xx +q|φ|⁴φ=0 which we call the modified non-linear Schr?dinger equation. It is also observed that this approach leads to a physical situation where a linear combination of both the modified and usual NLS equations holds, in the formiφ _t +pφ _xx +q ₁|φ|²φ +q ₂|φ|⁴φ=0. It is demonstrated through graphical analysis thatq ₁,q ₂, thought of as a function of β(=T _el/T _eh), behave in opposite way. That is, whenq ₁ grows,q ₂ decays, or vice versa. Lastly we demonstrate that this equation can sustain a type of solution other than the usual solitary profile. The form of such a wave is also depicted graphically.     

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Ohne Zusammenfassung     

Synthesis and Characterization of Poly(Methyl Methacrylate) Grafted from Acacia Gum

Graft polymerization of methyl methacrylate onto acacia gum has been studied in detail. The grafting was found to be optimal under the following reaction conditions: gum at 0.4 g/dL, monomer at 7.52 × 10^?;2 mol/dL, ceric ammonium sulfate at 15.81 × 10^?;4 mol/dL, H₂SO₄ at 0.037 mol/dL, temperature at 50 °C and time at 3.0 h. Fourier transform infrared spectroscopy was sed for the confirmation of grafting. Thermal and physical properties of the copolymer were studied. A probable mechanism of polymerization has been suggested based on reaction kinetics.     

Analytical Bethe Ansatz,Canonical Bäcklund Transformation and Q-Operator For A New Discrete Integrable Heirarchy

A new discrete heiarchy of integrable equations is generated from a new Lax Operator and a canonical Bäcklund transformation of the system is derived using Sklyanin’s formalism, based on the classical r-matrix. By quantising the system a quantum analogue of the corresponding canonical Bäcklund transformation is obtained and certain properties of the associated Q-operator are examined. Finally the analytical Bethe Ansatz is used to solve for the spectrum.     

Spatial modulation in cross-linked binary polymer blends

Spatial modulation means that the free energy of the composite mixture is minimized at a finite wavenumber, which defines the primary length scale, the maximum size possible, of the evolving phases. Although spatial modulation may appear in different systems in different ways and is not necessarily a thermodynamic precept, here it is expressed as a thermodynamic consequence of short-range interfacial forces pitted against long-range elastic forces. Cross-linked chains bring about new thermodynamic interactions based on their conformations and the fractal dimensions of the chain networks to which they tether and belong. Interplay among these different interactions during phase ordering brings about the spatial modulation and the spatial pattern. Here, the underlying processes are only succinctly outlined.     

A new maleimide-bound acid-cleavable solid-support reagent for profiling phosphorylation

A new chemical strategy for phosphopeptide profiling is reported in this study. Phosphorylation represents one of the most important classes of posttranslational modifications of proteins. Here we report a generalized strategy that employs solid-phase capture and mass-encoding steps to selectively enrich phosphopeptides from complex mixtures. This method exploits conversion of phosphates into thiols and reactive compounds to selectively isolate products of phosphorylation. Selective isolation of phosphopeptides is achieved with a simple, novel, acid-cleavable, solid-support-bound maleimide reagent. Our chemistry efforts have focused on minimization of linker size and simplification of reagent production with incorporation of common solid-phase peptide synthesis steps. Relative quantitation was demonstrated by modifying phosphopeptides with incorporation of ethanedithiol and propanedithiol. We observed that appropriate normalization is necessary to utilize mass tag strategies for relative quantitation of posttranslational modifications. The utility of solid-phase capture was determined with model phosphopeptides, and the method was demonstrated with enriching phosphopeptides from beta-casein, alpha-casein and ovalbumin. The solid-phase capture and release methods were also demonstrated with unfractionated whole histone protein mixtures to show this compound applicability in real biological samples. The new chemical strategy will ultimately be utilized for high-throughput profiling of phosphorylation and possibly other posttranslational modifications.     

TEM00 terawatt amplification by use of micro-optic spatial mode conversion

Micro-optic technology is used in a terawatt multipass Ti:sapphire amplifier to convert high-multimode, 532-nm radiation from an unstable resonator Nd:YAG laser into a TEM00 amplified output without sacrificing the amplifier-to-pump energy conversion efficiency. Experimental measurements and Fourier analysis of the spatial mode show a 3.8-fold increase in the peak irradiance and an order-of-magnitude improvement in the spatial contrast.