On the response of MEMS resonators under generic electrostatic loadings: experiments and applications

Nonlinear Dynamics - We present an investigation of the dynamic behavior of an electrostatically actuated clamped–clamped microbeam, under the simultaneous excitation of primary and...     

Dietary Chlorophyll Metabolites Catalyze the Photoreduction of Plasma Ubiquinone

Ubiquinol is a plasma antioxidant. The mechanisms responsible for maintenance of plasma ubiquinol are poorly understood. Here, we show that metabolites of chlorophyll can be found in blood plasma of animals that are given a chlorophyll‐rich diet. We also show that these metabolites catalyze the reduction of plasma ubiquinone to ubiquinol in the presence of ambient light, in vitro. We propose that dietary chlorophyll or its metabolites, together with light exposure, regulate plasma redox status through maintaining the ubiquinol pool.     

Experimental investigation of natural convection heat transfer characteristics in MWCNT-thermal oil nanofluid

Journal of Thermal Analysis and Calorimetry - The carbon nanotubes are considered as one of the highest thermal conductive material which is having a variety of heat transfer applications. The...     

Ab-initio calculations of structural,electronic,and optical properties of Zn_3(VO_4)_2

The structural, electronic, and optical properties of Zn_3(VO_4)_2 are investigated using full potential linearized augmented plane wave(FP-LAPW) method within the framework of density functional theory(DFT). Various approaches are adopted to treat the exchange and correlation potential energy such as generalized gradient approximation(GGA),GGA+U, and the Tran–Blaha modified Becke–Johnson(TB-mBJ) potential. The calculated band gap of 3.424 eV by TB-mBJ is found to be close to the experimental result(3.3 eV). The optical anisotropy is analyzed through optical constants,such as dielectric function and absorption coefficient along parallel and perpendicular crystal orientations. The absorption coefficient reveals high absorption(1.5 × 10~(6) cm~(-1)) of photons in the ultraviolet region.     

Synthesis and characterization of novel thermally stable aromatic and semiaromatic polyamides derived from thiourea-based flexible diacid dichlorides

Abstract  

New diacid dichlorides bearing phenyl thiourea groups were prepared by a facile synthetic approach and characterized using spectroscopic and elemental analyses. A series of novel aromatic and semiaromatic polyamides were prepared via a condensation route from the synthesized diacid dichlorides with 4,4′-oxydianiline. The polymers were characterized by FT-IR, ¹H NMR, ¹³C NMR, and their physical properties, including their solution viscosities, solubilities and thermal properties, were studied too. Polyamides with phenyl thiourea moieties in the backbone showed good solubilities in amide solvents such as DMAc, DMF, DMSO, and NMP. All of the synthesized polymers had η _inh values of 0.042–0.053 dm³/g, and were obtained in quantitative yield. GPC measurements of the synthesized polyamides indicated M _w values of 64,759–86,172. The crystallinity of the polymers was evaluated via their X-ray diffraction patterns. Their glass transition temperatures were found to be 218–229 °C. Furthermore, thermogravimetric analysis indicated that the polymers were thermally stable in the range 300–398 °C in a N₂ atmosphere.     

Investigation on novel thermoplastic poly(urethane-thiourea-imide)s with enhanced chemical and heat resistance

A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 °C having T₁₀ of 521-543 °C. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability.     

Novel Effectively Carbonaceous and Sulfurated Hydrogen Corrosion Inhibitors on the Basis of Organosulfurphosphorus Compounds

Abstract

Novel ammonium salts of O,O-dialkyl dithiophosphoric acids were obtained by one-pot synthesis from white phosphorus, elemental sulfur, industrial alcohols or phenols, and amines. Long-chain S-alkyl O,O-dialkyldithiophosphonates were prepared by the reaction of red phosphorus with elemental sulfur, alcohols, and the cheap industrial fractions of С₁₆–С₁₈ and С₂₀–С₂₆ of higher α-olefins in the presence of Lewis acid catalyst. The dithiophosphates obtained possess the high anticorrosion activities toward mild steel.     

Interfacial electronic structure of vanadyl naphthalocyanine on highly ordered pyrolytic graphite

We present a core and valence region spectroscopic analysis of the interfacial electronic structure of thin films of vanadyl naphthalocyanine (VONc) deposited onto highly oriented pyrolytic graphite (HOPG). X-ray photoelectron spectroscopy indicates the predominantly ionic character of the vanadyl metal center coordinated by the heterocycle and affords the bandgap in the thin VONc films. Valence band photoelectron spectroscopy points to the existence of three different adsorption geometries of VONc on the HOPG surface. The distribution of the different geometries can be systematically influenced in a simple post-deposition processing step, with an immediate effect on the interfacial electronic environment. We find spectroscopic evidence in the valence levels that VONc grows on HOPG most likely in a 2D-gas fashion rather than by nucleation and growth of islands. These data allow us to predict accurately the interface dipole in the case of a broad class of dipolar organic semiconductors, based simply on molecular dipole moment, polarizability and molecular diameter. This ability provides an important step towards rational optimization of energy level alignment in organic electronics.