Efficient copper-catalyzed Sonogashira coupling reactions and simulation studies

A practical copper-catalyzed I-substitutions of alkyl-2-iodobenzoates with alkynes have been developed using Cu powder as a catalyst under solvent, cocatalyst, and base-free conditions. This reaction system is new, facile, efficient, and economical that gives Sonogashira coupling products in excellent yields (up to 97%). The coupled products (A–J) were characterized by CHNS, ¹H NMR, and ¹³C NMR and are found soluble in ethyl acetate and dichloromethane. In addition, simulation studies of A–J were performed with aspulvinone dimethylallyltransferase enzyme and observe good binding affinity. The reported compounds may act as anti-cizmatics, anti-fobic in future and also have the inhibition of aspulvinone dimethylallyltransferase properties to control Alzheimer’s, Schizophrenia, etc. diseases.     

A simple and rapid method for determination of boron in fast breeder reactor components

The present paper describes a new analytical method developed for direct determination of boron in steels using radio frequency glow discharge optical emission spectrometer. “Single parameter alternative method” technique has been used to optimize the various experimental conditions of glow discharge plasma such as forward power, gas pressure inside plasma chamber, pre-integration time, and integration time. Different emission lines for boron were studied and inter element interference effect is also discussed in the paper. A complete statistical analysis has been done to validate the developed method. A RSD of less than ±5% is achieved for boron in the range of 0.0010–0.020% in Steels using this method.     

Quorum sensing regulates electric current generation of Pseudomonas aeruginosa PA14 in bioelectrochemical systems

Here, we show that quorum sensing (QS) modulates the current generation of the anode-respiring bacterium Pseudomonas aeruginosa because it controls the production of phenazines, which mediate the electron transfer to the anode. The current generation by a wildtype (WT) strain P. aeruginosa PA14 and the GacS/GacA protein-regulatory mutant retS was investigated under different environmental conditions. The retS mutant generated significantly higher current (45-fold) than the WT under anaerobic conditions. Anaerobic current generation by the WT was 28-fold higher with extraneously supplied lactones (a QS-signaling molecule). Compared to anaerobic conditions, the WT with some oxygen (microaerobic conditions) exhibited enhanced phenazine production (39-fold) and current levels (48-fold). Iron-rich medium and microaerobic conditions had a negative impact on current generation by retS. All these results were directly linked to QS activity in P. aeruginosa, thus, demonstrating the importance of this bacterial communication system for current generation in BESs. We also show that BESs represent a new tool for real-time investigation of phenazine-related QS activity.     

Enhanced Green Emission from Er<Subscript>2</Subscript>WO<Subscript>6</Subscript> Nanocrystals Embedded Composite Tellurite Glasses

A series of tungsten-tellurite glasses activated with different concentrations (0–1.5 mol %) of Er³⁺ has been synthesized. The structural properties of the best luminescent sample and the optical properties of its Er³⁺ ions, are studied both immediate after its preparation as well as after its ageing. On ageing the glass suffers structural reorganization and generates Er₂WO₆—nanocrystals in the matrix, which greatly enhances the normal and upconversion green luminescence efficiency of Er³⁺. The nanocrystal aided enhancement of normal and upconversion luminescence of Er³⁺ of the glass has been attributed to the crystal field effects of the new environment of Er³⁺ in the nanocrystals. A phenomenon of preferential enhancement of red upconversion luminescence at the cost of green upconversion luminescence of Er³⁺ at its higher concentrations in the glass has been observed and the related photo-physics is proposed. The material shows the prospect of being used as NIR solar concentrator.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

Synthesis and characterization of LaB6 thin films on tungsten, rhenium, silicon and other substrates and their investigations as?field emitters

The paper deals with the comparative study of nanocrystalline Lanthanum hexaboride (LaB₆) thin films grown on various substrates by Pulsed laser deposition and Arc plasma method. Field emission studies were carried out on LaB₆ films deposited on various substrates show metallic behavior of the emitters. The high value of field enhancement factors, indicating that the electron emission from LaB₆ nanoscale protrusions deposited on emitter surface. The post field emission surface morphology of the emitters showed no significant erosion of the films during continuous operation. The observed behavior indicates that it is linked with the growth of LaB₆ films on substrate crystal structure. The LaB₆ nanocrystallites/nanowires films were synthesized using arc plasma method shows good emission current stability. The LaB₆ micro/nanocrystallites were also obtained by picosecond laser irradiation which gives high enhancement β factor, and good emission current stability along with high current density. The results reveal that nanocrystalline LaB₆ films, exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for practical applications in field emission based new generation devices.     

Combinatorial Markov chains on linear extensions

We consider generalizations of Schützenberger’s promotion operator on the set $\mathcal{L}$ of linear extensions of a finite poset of size n. This gives rise to a strongly connected graph on $\mathcal{L}$ . By assigning weights to the edges of the graph in two different ways, we study two Markov chains, both of which are irreducible. The stationary state of one gives rise to the uniform distribution, whereas the weights of the stationary state of the other have a nice product formula. This generalizes results by Hendricks on the Tsetlin library, which corresponds to the case when the poset is the anti-chain and hence $\mathcal{L}=S_{n}$ is the full symmetric group. We also provide explicit eigenvalues of the transition matrix in general when the poset is a rooted forest. This is shown by proving that the associated monoid is $\mathcal {R}$ -trivial and then using Steinberg’s extension of Brown’s theory for Markov chains on left regular bands to $\mathcal {R}$ -trivial monoids.     

HPTLC Method for Analysis of Piperine in Fruits of Piper Species

JPC – Journal of Planar Chromatography – Modern TLC - Piperine, an alkaloid with diverse biological activity commonly occurring in fruits of Piper sp., has high commercial, economical,...     

Electron paramagnetic resonance of Er doped in YVO4: hyperfine parameters

X-band (9.60 GHz) electron paramagnetic resonance (EPR) spectra of the Er³⁺ Kramers ion substituting for the Y³⁺ ion in yttrium vanadate (YVO₄) single crystal were recorded at liquid-helium temperatures. Fine and hyperfine EPR transitions were observed for the ¹⁶⁶Er (zero nuclear magnetic moment) and ¹⁶⁷Er (I=7/2) isotopes, respectively. The values of the elements of the anisotropic ²- and ò-tensors of the ¹⁶⁷Er³⁺ ion, and those of the ² tensor for the ¹⁶⁶Er ion, were estimated. The admixture of crystal-field wave functions in the ground-state wave function of Er³⁺ were determined using the experimental g-values.