Design and operation characteristics of a high power transverse flow pulser sustained cw CO2 laser

A transverse flow, transverse discharge cw CO₂ laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO₂, 16 mbar of N₂ and 38.5 mbar of He. Design details and operational characteristics of this laser are presented.     

SYNTHESIS AND SEMIEMPIRICAL CALCULATIONS OF THIAZOLIDINONE AND IMIDAZOLIDINONE DERIVATIVES OF α-DIONES

The condensation reactions of α-diones with rhodanine and creatinine to give acenaphthylidene, isatylidene and thioisatylidene derivatives, which may act as potential bioactive compounds, are described. The synthesized compounds have been characterized by elemental analysis and spectral studies, as well as by molecular modelling using PCWIN model.     

NHC-Pd complex heterogenized on graphene oxide for cross-coupling reactions and supercapacitor applications

N-heterocyclic carbene (NHC)-palladium(II) complex (GO@NHC-Pd) was synthesized on graphene oxide (GO) support via a simple and cost-effective multistep approach. The spectroscopic, microscopic, thermal, and surface analyses of GO@NHC-Pd confirmed the successful formation of the catalyst. The investigation of catalytic activity showed that GO@NHC-Pd was very effective in Suzuki–Miyaura as well as Hiyama cross-coupling. Being heterogeneous in nature, GO@NHC-Pd was recovered after each reaction cycle easily and reused for up to nine and six cycles in Suzuki–Miyaura and Hiyama cross-coupling, respectively, without significant loss of activity. Further exploration of the supercapacitor performance of GO@NHC-Pd catalyst assembled in a two-electrode cell configuration shown a maximum attained capacitance of 105.26 F/g at a current density of 0.1 A/g with good cycling stability of 96.89% over 2,500 cycles.     

3D zinc(II) coordination polymers built up by triazole and benzene-polycarboxylate anions: Synthesis,crystal structure,thermal and photoluminescence characterization

Two coordination polymers of the formula [Zn₅(tmaH)₄(trz)₂(H₂O)₄] (1) and [Zn₃(bta)(trz)₂(H₂O)₄]·2H₂O (2) [tmaH₃ = benzene-1,3,5-tricarboxylic acid/trimesic acid, trzH = 1,2,4-triazole, btaH₄ = benzene-1,2,4,5-tetracarboxylic acid] have been synthesized and structurally characterized by X-ray single crystal diffraction analysis. Both complexes are 3D coordination polymers containing [Zn₄(trz)₂] units connected by benzene-carboxylate anions. In particular, an undulated layer containing 6- and 18-membered rings is outlined in the network of 1. Hydrogen bonds, involving the coordinated and lattice water molecules with carboxylate oxygen atoms, contribute to the stabilization of the networks. Their thermal stability was investigated by thermogravimetric analysis. The fluorescence spectrum of 1 features two peaks at 419 and 323 nm, originating from a π–π∗ intraligand transition and LMCT, respectively. For 2 a broad band at 410 nm is assigned solely as a π–π∗ intraligand transition.     

Improved Mucoadhesion,Permeation and In Vitro Anticancer Potential of Synthesized Thiolated Acacia and Karaya Gum Combination: A Systematic Study

Thiolation of polymers is one of the most appropriate approaches to impart higher mechanical strength and mucoadhesion. Thiol modification of gum karaya and gum acacia was carried out by esterification with 80% thioglycolic acid. FTIR, DSC and XRD confirmed the completion of thiolation reaction. Anticancer potential of developed thiomer was studied on cervical cancer cell lines (HeLa) and more than 60% of human cervical cell lines (HeLa) were inhibited at concentration of 5 µg/100 µL. Immobilized thiol groups were found to be 0.8511 mmol/g as determined by Ellman’s method. Cytotoxicity studies on L929 fibroblast cell lines indicated thiomers were biocompatible. Bilayered tablets were prepared using Ivabradine hydrochloride as the model drug and synthesized thiolated gums as mucoadhesive polymer. Tablets prepared using thiolated polymers in combination showed more swelling, mucoadhesion and residence time as compared to unmodified gums. Thiol modification controlled the release of the drug for 24 h and enhanced permeation of the drug up to 3 fold through porcine buccal mucosa as compared to tablets with unmodified gums. Thiolated polymer showed increased mucoadhesion and permeation, anticancer potential, controlled release and thus can be utilized as a novel excipient in formulation development.     

Study of Micellar Behavior of SDS and CTAB in Aqueous Media Containing Furosemide—A Cardiovascular Drug

Sound velocity and density measurements of aqueous solutions of the anionic surfactant SDS (sodium dodecyl sulfate) and the cationic surfactant CTAB (cetyltrimethylammonium bromide) with the drug furosemide (0.002 and 0.02 mol⋅dm⁻³) have been carried out in the temperature range 20–40 °C. From these measurements, the compressibility coefficient (β), apparent molar volume (φ _v ) and apparent molar compressibility (φ _κ ) have been computed. From electrical conductivity measurements, the critical micelle concentrations (CMCs) of SDS and CTAB has been determined in the above aqueous furosemide solutions. From the CMC values as a function of temperature, various thermodynamic parameters have been evaluated: the standard enthalpy change (DH_m^o\Delta H_{\mathrm{m}}^{\mathrm{o}}), standard entropy change (DS_m^o\Delta S_{\mathrm{m}}^{\mathrm{o}}), and standard Gibbs energy change (DG_m^o\Delta G_{\mathrm{m}}^{\mathrm{o}}) for micellization. This work also included viscosity studies of aqueous solutions of SDS and CTAB with the drug in order to determine the relative viscosity (η _r). UV-Vis studies have also been carried for the ternary drug/surfactant/water system having SDS in the concentration range 0.002–0.014 mol⋅dm⁻³. All of these parameters are discussed in terms of drug–drug, drug–solvent and drug–surfactant interactions resulting from of various electrostatic and hydrophobic interactions.     

Infrared and permittivity studies on alkali perchlorates

The infrared spectroscopic studies and the dielectric constant measurements during the orthorhombic to cubic transformation of NaClO₄, KClO₄, RbClO₄, and CsClO₄ are reported here to investigate the possibility or not of rotation of ClO₄⁻ in the cubic form. The multiplicity of ν₃, the triply degenerate stretching frequency, change at T_t as it should go from a triplet to a singlet when the crystal structure changes from Cmcm to . The symmetric stretching frequency of ClO₄⁻ is active in Cmcm but symmetry forbidden in . At the respective transition temperature there is a sharp increase in the dielectric constants of these perchlorates proving the transition to be of order-disorder type with the possibility of rotation of ClO₄⁻ at least in NaClO₄ and KClO₄, but involves the discontinuity of properties characteristic of a first-order transition     

The zeta potential of PMMA in contact with electrolytes of various conditions: Theoretical and experimental investigation

Many unit operations required in microfluidics can be realised by electrokinetic phenomena. Electrokinetic phenomena are related to the presence of electrical surface charges of microfluidic substrates in contact with a liquid. As surface charges cannot be directly measured, the zeta potential is considered as the relevant parameter instead. PMMA is an attractive microfluidic substrate since micron‐sized features can be manufactured at low costs. However, the existence of PMMA surface charges is not well understood and the zeta potential data found in the literature show significant disagreement. In this article, we present a thorough investigation on the zeta potential of PMMA. We use computations of the potential distribution in the electrical double layer to predict the influence of various electrolyte parameters. The generated knowledge is compared to extensive experiments where we investigate the influence of ionic strength, pH, temperature and the nature of the electrolyte. Our findings imply that two different mechanisms influence the zeta potential depending on the pH value. We propose pure shielding in the acidic and neutral milieus while adsorption of co‐ions occurs along with shielding in the alkaline milieu.     

Au(III)-catalyzed regio- and stereoselective tandem synthesis of oxazolo fused naphthyridines and isoquinolines from o-alkynylaldehydes

An efficient tandem approach for the regio- and stereoselective synthesis of oxazolo-fused naphthyridines 3a–g, 3i–l and isoquinolines 3h, 3m via the reaction of o-alkynylaldehydes 1a–i with chiral amino alcohols 2a–c under mild reaction conditions is described. The stereochemistry and structures of the products were assigned via NOESY and X-ray crystallographic studies.