Polymer-doped ferroelectric liquid crystal: UV absorbance,fluorescence and electro-optical study

In this study, UV absorption, fluorescence and electro-optical study have been performed for pure ferroelectric liquid crystal (FLC) and its three different concentrations, i.e. 1%, 3% and 5% of fluorescent polymer in the pure FLC. We observed that there is higher value of UV absorption for fluorescent polymer-doped system in comparison to the pure system. We have found excitation wavelength, emission wavelength and quantum yield for all the mixtures. Quantum yield shows the probability of excited state being deactivated by fluorescence rather than non-radiative mechanism. The higher value of spontaneous polarization and faster response has been observed for fluorescent polymer-doped system compared to the pure FLC system. The electro-optical study also suggests that there exists an optimum concentration of fluorescent polymer for which we have found highest spontaneous polarization and least response time.     

Flow boiling heat transfer study of R-134a/R-290/R-600a mixture in 9.52 and 12.7 mm smooth horizontal tubes: Experimental investigation

A detailed experimental investigation is carried out to study the flow boiling heat transfer behavior of R-134a/R-290/R-600a (91%/4.068%/4.932% by mass) refrigerant mixture in smooth horizontal tubes of diameter 9.52 and 12.7 mm. The heat transfer coefficients of the mixture are experimentally measured under varied heat flux conditions for stratified flow patterns using a coaxial counter-current heat exchanger test section. The tests are conducted for refrigerant inlet temperatures between ?9 and 5 °C and mass flow rates ranging from 3 to 5 g s^?1. Kattan–Thome–Favrat maps are used to confirm the flow patterns for the tested conditions. The magnitude of the heat transfer coefficient with respect to flow patterns and different mechanisms of boiling are discussed. The heat transfer coefficient of the refrigerant mixture is also compared with that of R-134a for selected working conditions. The significance of nucleate boiling in the overall heat transfer process under these testing conditions is highlighted.     

Synthesis of highly functionalized piperidines by one-pot multicomponent reaction using tetrabutylammonium tribromide (TBATB)

Tetrabutylammonium tribromide (TBATB) has been found to be an efficient catalyst for the one-pot synthesis of highly substituted piperidines through a combination of 1,3-dicarbonyl compounds, aromatic aldehydes, and various amines in ethanol at room temperature. Atom economy, good yields, environmentally benign, and mild reaction conditions are some of the important features of this protocol.     

Analysis and optimization of numerical sponge layers as a nonreflective boundary treatment

The aim of this work is to provide practical guidelines for designing sponge layers considering applications in computational fluid dynamics and computational aeroacoustics. We present the analysis of sponge/flow interactions and provide a characterization of its basic reflectivity mechanisms. While sponges are perfect absorbers in one-dimensional systems, they can cause their own reflection when encountering oblique sound or oblique vorticity waves. To minimize this adverse effect, sponge strength and profile need to be selected optimally. Also for a fixed desired accuracy, sponge length should be above a minimum threshold. Our analysis quantifies these requirements for a wide range of conditions in terms of inflow/outflow Mach number, incident frequencies, incident angles, and desired accuracy, and covers main concerns with sponges such as sound/sponge interactions and vortex/sponge interactions. As a test case, we present a nonlinear Euler calculation of a convecting vortex interacting with sponges with different lengths. We show that sponges designed by our guidelines achieve accuracies comparable to perfectly matched layers for the same cost, over moderate to high accuracy demands. The results of the presented analysis can be used to determine sponge requirements for a wide range of CFD applications. A summary of these guidelines are listed in the paper.     

K5.76Ga5.76Si10.24O32·3.4H2O,a gallosilicate with the zeolite gismondine topology

The title compound, K–GaSi–GIS, potassium gallium silicon oxide hydrate, was synthesized hydro­thermally and its crystal structure was determined from data collected on a single crystal of dimensions 10 × 10 × 8 µm at a synchrotron X‐ray source. The compound, which has the aluminosilicate (AlSi) zeolite gismondine (GIS) topology, Ca₄[Al₈Si₈O₃₂]·16H₂O, crystallizes in the tetragonal space group I4₁/a. A disordered distribution of the framework Si/Ga sites leads to higher symmetry of the GIS‐type network compared with the usual monoclinic symmetry in AlSi–GIS. Framework Ga substitution for Al in AlSi–GIS leads to substantial distortion of the crankshaft chains, reducing the effective pore dimensions and suggesting the possibility of pore‐dimension control via partial framework‐cation substitution.     

Molybdenum(VI), (V) and (IV) complexes with chiral benzoin thiosemicarbazone

The chiral (ONS) dianionic Schiff base ligand benzoin thiosemicarbazone (H₂L) reacts with MoO₂(acac)₂ to give the polymeric complex [(MoO₂L) _n ] (1) (Type 1). The reaction of MoO₂L with pyridine (py), 3-picoline (3-pic) or 4-picoline (4-pic) gives [Mo^VIO₂LD] (D = py, 3-pic or 4-pic) (Type 1). Further, the reaction of [MoO₂L] or [MoO₂LD] with PPh₃ or reaction of [MoO₂L] with PPh₃ (plus bpy or phen, D) in the presence of donor reagents D gives [Mo^IVOL] or [Mo^IVOLD] (Type 2). On the other hand, the reaction of [MoO₂L] with hydrazides (zdhH₃) such as benzoylhydrazine (bhH₃), isonicotinoylhydrazine (inhH₃), nicotinoylhydrazine (nhH₃), salicyloylhydrazine (slhH₃) and thiosemicarbazide (tscH₃) produced non-oxo–diazenido complexes [MoL(zdh)] (Type 3). The complexes have been characterized by elemental analyses, molar conductance, magnetic moment, electronic, i.r. and e.s.r. spectroscopic measurements.     

Thermal and mechanical damage of GaAs in picosecond regime

An in-depth study of the single pulse and multiple pulse laser (35 ps, 10 Hz and 1064 nm) damage for threshold fluence and greater fluence of GaAs 1 0 0 single crystal is presented. Damage which starts at a power 2×10¹¹ W/cm² in the form of pits occurs due to accumulation of laser induced microscopic defects. Effect of multiple pulse at first makes the pits more prominent in the form of Ga emission. Then the topmost layer is removed. If the number of pulses is further increased new pits are formed in the new surface (beneath the removed surface) and the above process is repeated. The thermal model is sufficient to explain this morphology. However, for larger fluences, a large cracking and fracture and the possibility of both Ga and As emission in different ratios suggest that mechanical damage is a dominant feature for higher fluences which arises due to generation of shock waves and rapid vaporization of material. Damage threshold has been calculated with the help of the thermal model given by Meyer et al. which is in good agreement with our experimental results.