Spontaneous symmetry breaking for zero mass

We investigate spontaneous symmetry breaking of a zero mass free Lagrangian within a functional formalism. We find that the boundary conditions of field solutions are responsible for the spontaneous symmetry breaking and this can be incorporated naturally in a functional method.     

Note on the use of reciprocity of chiral recognition in designing liquid chromatographic chiral stationary phases

The effect of methanol, acetone and acetonitrile on the sensitivity, selectivity and the detection limits (LODs) of the determination of chromium species by ion chromatography was investigated. A collinear dual-beam thermal lens spectrometer was used for the direct detection of chromium complexes [pre-column derivatized Cr(III)–pyridine-2,6-dicarboxylic acid, and post-column derivatized Cr(VI)–1,5-diphenylcarbazide] following the ion chromatographic separation on a Dionex HPIC-CS5A solvent compatible column. Different amounts of organic solvents were added directly to the eluent (up to 30%) and to the post-column reagent (up to 60%) to improve the thermooptical properties of the solvents. Consequently, the sensitivity of the technique was increased by a factor of 2–3 and LODs of 0.1 and 10 μg dm⁻³ were achieved for Cr(VI) and Cr(III), respectively, when the eluent reaching the detector contained 30% of acetonitrile. The addition of organic solvents also resulted in significant changes in retention times, which improved the Cr(III)/Cr(VI) separation.     

Phase properties of superposed squeezed states

The phase properties of the superposed squeezed states are studied. The superposed squeezed states are obtained by inserting two squeezers in a Mach-Zehnder interferometer one for each arm. The visibility of the states as a measure of the coherence of the generated photons in the nonlinear interferometer is analyzed. And the mean-square phase fluctuations are also considered to analyze the phase properties of the superposed squeezed states. The quantities are obtained as a function of gain and the input phase, when the amplified input is a coherent state, a number state, a thermal state, a displaced number state, or a coherent thermal state.     

Synthesis of iron chalcogenides from single source precursors

In this review article the synthesis of iron chalcogenides using single source precursors is discussed. The effect on morphology and phase of iron chalcogenides formed is studied by varying single source precursors, reaction temperature, reaction time, surfactants and their concentration. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel 9,9′‐(1,3‐phenylene)bis‐9H‐carbazole‐containing copolymers as hole‐transporting and host materials for blue phosphorescent polymer light‐emitting diodes

Novel photo‐crosslinkable hole‐transport and host materials incorporated into multilayer blue phosphorescent polymer light‐emitting diodes (Ph‐PLEDs) were demonstrated in this study. The oxetane‐containing copolymers, which function as hole‐transport layers (HTL), could be cured by UV irradiation in the presence of a cationic photoinitiator. The composition of the two monomers was varied to yield three different hole‐transporting copolymers, [Poly(9,9′‐(5‐(((4‐(7‐(4‐(((3‐methyloxetan‐3‐yl)methoxy)methyl)phenyl)octan‐3‐yl)benzyl)oxy)methyl)?1,3‐phenylene)bis(9H‐carbazole)) ( P(mCP‐Ox)‐I , ‐II , and ‐III )]. In addition, monomer 1 was copolymerized with styrene to produce copolymer P(mCP‐Ph) as a host material for bis[2‐(4,6‐difluorophenyl)pyridinato‐C²,N](picolinato)iridium(III) (FIrpic), a blue‐emitting dopant. All mCP‐based copolymers displayed high glass transition temperatures (T_g) of up to 130–140 °C and triplet energies of up to 3.00 eV. The blue Ph‐PLEDs exhibited a maximum external quantum efficiency of 2.55%, in addition to a luminous efficiency of 8.75 cd A^?1 when using the device configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/ P(mCP‐OX)‐III / P(mCP‐Ph) :FIrpic(15 wt %)/3,3′‐[5′‐[3‐(3‐pyridinyl)phenyl][1,1′:3′,1′′‐terphenyl]‐3,3′′‐diyl]bispyridine/LiF/Al. The device bearing P(mCP‐Ox)‐III HTL, containing the highest composition of mCP unit, exhibited better performance than the other devices, which is attributed to induction of more balanced charge carriers and carrier recombination in the emissive layer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 707–718     

Oxyallyl exposed: an open-shell singlet with picosecond lifetimes in solution but persistent in crystals of a cyclobutanedione precursor

Photoinduced decarbonylation of 2,4-bis(spirocyclohexyl)-1,3-cyclobutanedione 1 in the crystalline solid state resulted in formation of a deep blue transient with λ(max) = 550 nm and a half-life of 42 min at 298 K, identified as kinetically stabilized oxyallyl. Support for an open-shell singlet species was obtained by spectroscopic analysis and (4/4) CASSCF calculations with the 6-31+G(d) basis set and multireference MP2 corrections. The electronic spectrum of the singlet biradical, confirmed by femtosecond pump-probe studies in solution, was matched by coupled cluster calculations with single and double corrections.     

A Comparison of Simple Rheological Parameters and Simulation Data for Zymomonas mobilis Fermentation Broths with High Substrate Loading in a 3-L Bioreactor

Traditionally, as much as 80% or more of an ethanol fermentation broth is water that must be removed. This mixture is not only costly to separate but also produces a large aqueous stream that must then be disposed of or recycled. Integrative approaches to water reduction include increasing the biomass concentration during fermentation. In this paper, experimental results are presented for the rheological behavior of high-solids enzymatic cellulose hydrolysis and ethanol fermentation for biomass conversion using Solka Floc as the model feedstock. The experimental determination of the viscosity, shear stress, and shear rate relationships of the 10 to 20% slurry concentrations with constant enzyme concentrations are performed with a variable speed rotational viscometer (2.0 to 200 rpm) at 40 °C. The viscosities of enzymatic suspension observed were in range of 0.0418 to 0.0144, 0.233 to 0.0348, and 0.292 to 0.0447 Pa s for shear rates up to 100 reciprocal seconds at 10, 15, and 20% initial solids (w/v), respectively. Computational fluid dynamics analysis of bioreactor mixing demonstrates the change in bioreactor mixing with increasing biomass concentration. The portion-loading method is shown to be effective for processing high-solids slurries.     

Aminolysis of O-aryl thionobenzoates: amine basicity combines with modulation of the nature of substituents in the leaving group and thionobenzoate moiety to control the reaction mechanism

A kinetic study is reported for aminolysis of O-Y-substituted phenyl thionobenzoates (1a-f) and O-4-nitrophenyl X-substituted thionobenzoates (2a-f) in 80 mol % H2O/20 mol % DMSO at 25.0 +/- 0.1 degrees C. The reaction proceeds through one or two intermediates (i.e., a zwitterionic tetrahedral intermediate T(+/-) and its deprotonated form T(-)) depending on the basicity difference between the nucleophile and nucleofuge, that is, the reaction proceeds through T(+/-) when the leaving aryloxide is less basic than the attacking amine, but through T(+/-) and T(-) when the leaving group is more basic than the amine. However, the reaction mechanism is not influenced by the electronic nature of the substituent X in the nonleaving group. The Hammett plot for the reactions of 2a-f with benzylamine is consisted of two intersecting straight lines, which might be interpreted as a change in the rate-determining step (RDS). However, the Yukawa-Tsuno plot for the same reactions exhibits an excellent linear correlation, indicating that the nonlinear Hammett plot is not due to a change in the RDS but caused by stabilization of the ground-state of the substrate through resonance interaction between the electron-donating substituent X and the thionocarbonyl moiety.     

Choice of solvent (MeCN vs H(2)O) decides rate-limiting step in S(N)Ar aminolysis of 1-fluoro-2,4-dinitrobenzene with secondary amines: importance of Brønsted-type analysis in acetonitrile

A kinetic study is reported for nucleophilic substitution reactions of 2,4-dinitro-1-fluorobenzene (DNFB) with a series of secondary amines in MeCN and H2O at 25.0 degrees C. The reaction in MeCN results in an upward curvature in the plot of k(obsd) vs [amine], indicating that the reaction proceeds through a rate-limiting proton transfer (RLPT) mechanism. On the contrary, the corresponding plot for the reaction in H2O is linear, implying that general base catalysis is absent. The ratios of the microscopic rate constants for the reactions in MeCN are consistent with the proposed mechanism, e.g., the facts that k2/k(-1) < 1 and k3/k2 > 10(2) suggest that formation of a Meisenheimer complex occurs before the rate-limiting step and the deprotonation by a second amine molecule becomes dominant when [amine] > 0.01 M, respectively. The Br?nsted-type plots for k1k2/k(-1) and k1k3/k(-1) are linear with betanuc values of 0.82 and 0.84, respectively, which supports the proposed mechanism. The Br?nsted-type plot for the reactions in H2O is also linear with betanuc = 0.52 which has been interpreted to indicate that the reaction proceeds through rate-limiting formation of a Meisenheimer complex. DNFB is more reactive toward secondary amines in MeCN than in H2O. The enhanced basicity of amines as well as the increased stability of the intermediate whose charges are delocalized through resonance are responsible for the enhanced reactivity in the aprotic solvent.     

Regiochemical and stereochemical evidence for enzyme-initiated catalysis in dual positional specific maize lipoxygenase-1

Dual positional specific maize lipoxygenase-1 catalyzed the formation of racemic mixtures of four possible regioisomers and was strongly inhibited by the radical scavenger, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoxy radical. Molecular modeling studies indicated that the oxygen-binding cavity is segregated from the substrate-binding cavity. The data suggest that a bis-allylic radical reaction intermediate is generated enzymatically, released from the enzyme active site, and subsequently oxygenated outside of the enzyme active site by a nonenzymatic mechanism.