Detection of volatile organic compounds (VOCs) using an optical fibre long period grating with a calixarene anchored mesoporous thin film

A long period grating (LPG) modified with a mesoporous film infused with a functional compound, calix[4]arene, was employed for the detection of volatile organic compounds (VOCs). The mesoporous film consisted of an inorganic part, of SiO2 nanoparticles (NPs) along with an organic moiety of poly(allylamine hydrochloride) polycation PAH, which was finally infused with functional compound, p-sulphanatocalix[4]arene (CA[4]). The LPG sensor was designed to operate at the phase matching turning point to provide the highest sensitivity. The sensing mechanism is based on the measurement of the refractive index (RI) change induced by the complexion of the VOCs with calix[4]arene (CA). The LPG modified with 5 cycles of (SiO2 NPs/PAH)5PAA responded to exposure to chloroform and benzene vapours. The sensitivity to humidity as an interfering parameter was also investigated

Controlling quasiparticle excitations in a trapped Bose-Einstein condensate

We describe an approach to quantum control of the quasiparticle excitations in a trapped Bose-Einstein condensate based on adiabatic and diabatic changes in the trap anisotropy. We describe our approach in the context of Landau-Zener transition at the avoided crossings in the quasiparticle excitation spectrum. We show that there can be population oscillation between different modes at the specific aspect ratios of the trapping potential at which the mode energies are almost degenerate. These effects may have implications in the expansion of an excited condensate as well as the dynamics of a moving condensate in an atomic wave guide with a varying width

Влияние автономного инвертора напряжения с синусоидальной широтно-импульсной модуляцией на устойчивость системы электропривода

A method for calculating conditions subharmonic stable AC systems, taking into account the discrete of voltage autonomous inverter with sinusoidal PWM based on which the stable area of AC engine drive

Imparting gas selective and pressure dependent porosity into a non-porous solid: Via coordination flexibility

Using a simple hard-soft acid-base concept we have deliberately designed gas-specific and pressure dependent porosity into a non-porous solid via coordination flexibility. This creates distinct gate-openings wherein the CO2 molecule opens-up the framework pores by rotating the ligand about the weaker hard-soft bonds (hard-soft gate control). For this, we have studied the CO2 gating behaviour of M(4-PyC)2 (M = Mg, Mn and Cu), which represent metals of varying hardness. A combination of quantum chemical calculations, molecular dynamics and Grand canonical Monte Carlo simulations were performed to examine the gate opening of the isonicotinate ligands in Mg(4-PyC)2. The simulations show that interaction of the CO2 molecules with the isonicotinate ligands at different CO2 loadings can result in pressure-dependent gate opening. Furthermore, the simulated CO2 uptake values calculated using the partially gate-opened structures at different loadings showed good agreement with the experimental uptake values. This provides an effective strategy for designing highly-stable dynamic porous solids employing rigid frameworks