Jeans Instability of Self Gravitating Dust Cloud in Presence of Effective Electrostatic Pressure

The role of viscosity coefficient (η'), coulomb coupling parameter (Γ) and dust mass on the growth of jeans mode is investigated in strongly coupled dusty plasma using equations of Generalized Hydrodynamics (GH) Model. The novel aspect of this work is that the force arising due to electrostatic pressure caused by grain grain interaction has been included in the dynamics of dust particles. This force is found to play a significant role in counter balancing the self gravity effect, thereby reducing the growth rate of jeans instability. The present work may provide more physical insight in understanding the mechanisms behind formation of planetesimals, stars etc.     

The privileged spectrum of cnoidal ion holes and its extension by imperfect ion trapping

The fundamental properties of nonlinear ion hole modes propagating in current-driven collisionless plasmas are derived. Making use of Schamel's alternative method their spatial structure $?(x)$ and phase velocities $u_0$ are analyzed and found to depend crucially on the used trapped ion distribution $f_{it}$. A regular $f_{it}$ represents a continuous spectrum, which is called privileged or perfect since it yields a definite $u_0$ and appears most realistic. A singular $f_{it}$, on the other hand, involving jumps and moderate slope singularities at the separatrix, does reveal further classes of hole equilibria at the cost, however, of a well-defined $u_0$. This explains why Bernstein, Greene, Kruskal (BGK)-solutions of the Vlasov–Poisson system, exhibiting a strong slope singularity of their derived trapped particle distribution, can principally not provide definite $u_{0}s$. The nonlinear dispersion relation (or $u_0$) of privileged ion holes, on the other hand, is equivalent with that of cnoidal electron holes, i.e. in addition to the ordinary ion acoustic branch there exists a correspondence to the “Langmuir” branch and to the multiple “slow electron acoustic” branches, reflecting different trapping scenarios.     

A conductivity study of polyelectrolytes based on 4-vinyl pyridine and butylmethacrylate

Abstract  In this paper, the chain flexibility of P4-VP was tried to increase by lowering its glass transition temperature (T _g) and by increasing its amorphous region by copolymerizing with butyl methacrylate. The copolymers were prepared in five different feed molar ratios to optimize the required properties such as higher room temperature conductivity and film-forming capacity. The conductivity and conduction behavior of the copolymers, as well as their hydrochloride and hydrobromide salts, have been reported. The copolymers were prepared by solution polymerization technique, using tetrahydrofuran as solvent at 60 °C, and the salts were prepared by simple acidification. The copolymers and their salts were characterized by scanning electron micrographs, infrared, proton nuclear magnetic resonance, thermogravimetric, differential scanning calorimetry and AC impedance measurements. There was about 10³- to 10⁴-fold increase in room temperature conductivity of these plasticized polyelectrolytes. The conduction behavior was found to be predominantly ionic. The scientific importance of this paper is that, unlike polymer electrolytes, no external salt is used; instead the virgin polymer and polyelectrolytes are used for conductivity measurements.     

Optimization of plasma parameters for high rate deposition of titanium nitride films as protective coating on bell-metal by reactive sputtering in cylindrical magnetron device

Nano-structured titanium nitride (TiN) thin film coating is deposited by reactive sputtering in cylindrical magnetron device in argon and nitrogen gas mixtures at low temperature. This method of deposition using DC cylindrical magnetron configuration provides high uniform yield of film coating over large substrate area of different shapes desirous for various technological applications. The influence of nitrogen gas on the properties of TiN thin film as suitable surface protective coating on bell-metal has been studied. Structural morphological study of the deposited thin film carried out by employing X-ray diffraction exhibits a strong (2 0 0) lattice texture corresponding to TiN in single phase. The surface morphology of the film coating is studied using scanning electron microscope and atomic force microscope techniques. The optimized condition for the deposition of good quality TiN film coating is found to be at Ar:N₂ gas partial pressure ratio of 1:1. This coating of TiN serves a dual purpose of providing an anti-corrosive and hard protective layer over the bell-metal surface which is used for various commercial applications. The TiN film's radiant golden colour at proper deposition condition makes it a very suitable candidate for decorative applications.     

Jeans Instability of Self Gravitating Dust Cloud in Presence of Effective Electrostatic Pressure

The role of viscosity coefficient(η′), coulomb coupling parameter(Γ) and dust mass on the growth of jeans mode is investigated in strongly coupled dusty plasma using equations of Generalized Hydrodynamics(GH) Model. The novel aspect of this work is that the force arising due to electrostatic pressure caused by grain grain interaction has been included in the dynamics of dust particles. This force is found to play a significant role in counter balancing the self gravity effect, thereby reducing the growth rate of jeans instability. The present work may provide more physical insight in understanding the mechanisms behind formation of planetesimals, stars etc.     

Phosphine-free Suzuki cross-coupling reaction: a mild and selective method for the carbon–carbon bond formation in aqueous tea extract

A mild and selective protocol has been developed for the palladium-catalyzed phosphine-free Suzuki cross-coupling reaction of aryl bromides with arylboronic acids in aqueous tea extract at room temperature. It is noteworthy that the aqueous tea extract plays an important role in the reaction, and various functional groups are tolerated under the optimized conditions. The reactions proceeded with very good chemoselectivity in favor of the bromo instead of the chloro group even at higher temperatures. Furthermore, this protocol could be applied to the cross-coupling of 4-bromoindole without protecting the base sensitive amine group with arylboronic acids in moderate to excellent yields.     

Effect of Gd3+ doping on structural,optical and frequency-dependent dielectric response properties of pseudo-cubic BaTiO3 nanostructures

We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd³⁺) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd³⁺ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ～10–15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition (n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0–7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tanδ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ～ω ^s approaches ideal Debye behavior (s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd³⁺) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers.     

The cytidinium—cytidine complex: infrared and Raman spectroscopic studies

Using IR and Raman spectra, it is shown that the sytidinium cation hydrogen bonds to cytidine to form a stable 1:1 complex, in both aqueous solution (pH ~ 3.3) and as a solid. The spectra indicate that the proton is located asymmetrically in the NH?N bond of the complex, on the vibrational time scale, in both solution and the solid. The perdeuterated systems were also examined; their spectra support these conclusions.