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.     

Bispidine as a β-strand nucleator: from a β-arch to self-assembled cages and vesicles

The development of synthetic scaffolds that nucleate well-folded secondary structures is highly challenging. Herein, we designed and synthesized a series of core-modified peptides (F1, F2, F3, and F4) that fold into β-strand structures. These bispidine-scaffolded peptides were studied by CD, IR, NMR, single crystal XRD, and Molecular Dynamics (MD) simulations to investigate their conformational preferences. Solid-state and solution studies revealed that bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating the β-strand structure. Scaffolds that nucleate an isolated β-strand conformation are rare. Bispidine placed at the C-terminus of the peptide chain could nucleate a β-strand conformation, while bispidine placed at the middle resulted in a β-arch conformation. This nucleation activity stems from the ability to restrict the psi torsion angle (ψ) through intramolecular C5 hydrogen bonding between the equatorial hydrogen(s) of bispidine and the carbonyl oxygen(s) of the amino acid close to the scaffold. Furthermore, the bispidine peptidomimetic with a super secondary structure, namely β-arch, assembled into single-hole submicron cages and spherical vesicles as evident from microscopic studies. The design logic defined here will be a significant strategy for the development of β-strand mimetics and super secondary structures.

Bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating β-strand structures. These β-strand mimetics self-assemble to single hole submicron cages and vesicles.     

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.     

Intersalation Reactions of Trisdiimine Metal Complexes with Montmorillonite Clay: A New Approach

Intersalation reactions of the complexes [Ni(L-L)(3)]SO(4) and [Ni(L-L)(3)]Cl(2) (L-L=1,10-phenanthroline (phen), 2,2'-bipyridyl (bpy)), with Na-montmorillonite carried out under different dynamic conditions such as ultrasonic irradiation, refluxing, autoclaving, and vigorous stirring showed that under ultrasonic irradiation, maximum adsorption of the metal complexes occurred within a period of 30 min. Metal complexes containing the phen ligand showed higher adsorption than those containing bpy. Maximum adsorption up to about three times the cation exchange capacity (CEC) of the clay was observed. Aggregated (basal spacing d(001) 12.5 ?) Na-montmorillonite, in treatment with a higher amount (>CEC) of metal complexes, formed monolayered (basal spacing d(001) 17.6 ?) species, while with predispersed clay, bilayered (basal spacing d(001)>28 ?) or pseudo-trilayer (basal spacing d(001)>32 ?) species were formed. The bilayered species were thermally stable up to 250 degrees C and above this temperature monolayered species were formed. The thermal stability of the intersalated species was higher than that of the intercalated ones. X-ray diffraction, UV-visible, IR-spectroscopy, thermal analyses, and surface area measurements were used for characterization of the products. Copyright 2001 Academic Press.     

On the Single-machine Scheduling Problem with Tardiness Penalties

The n-job, single-machine total tardiness problem is considered in this paper. A branching algorithm based on three theorems is proposed to generate a reduced set of candidate sequences. The computational results indicate that the proposed algorithm provides a smaller set of candidate sequences than the DP algorithm of Schrage and Baker.