Directional synthesis of furfural compounds from holocellulose catalyzed by sulfamic acid

Cellulose - The coproduction of 5-hydroxymethylfurfural (5-HMF) and furfural (FUR) via the direct hydrolysis of holocellulose analogue composed of cellulose and hemicellulose was investigated. The...     

Absorption coefficient measurement of high-resistivity germanium at 2.52 THz by Brewster’s angle method

Brewster’s angle method was adopted to measure the absorption coefficient of a set of high-resistivity germanium samples at 2.52 THz in this paper. Numerical simulations were firstly carried out to evaluate the errors during measurement. The experimental setup was improved, and measurement was carried out based on a CW THz laser at 2.52 THz.     

Slow light in a simple metamaterial structure constructed by cut and continuous metal strips

Recently, slow light in metamaterials has been investigated based on the coupling between two quasi-bound states, in classic analogue of electromagnetically induced transparency in atomic systems. Here we demonstrate the feasibility in achieving slow light in metamaterials, based on the mechanism of coupling between a quasi-bound state and a continuum state. The theoretical prediction by a two-particle model is in good agreement with the experimental result in the metamaterial composed of the cut and continuous metal strips. The present work illustrates the versatility of metamaterials, implying the great potential in many applications.     

Collective dynamics of genetic oscillators with cell-to-cell communication: a study case of signal integration

This paper investigates the effect of integration of intracellular and extracellular signals on collective dynamics based on a multicellular system with cell-to-cell communication. Using a mathematical model of genetic repressilators coupled to quorum sensing, we show that the changes in parameters of a certain kind of cis-regulatory input function that quantifies the signal integration can lead to the change of coupling type from phase-attractive to phase-repulsive coupling or vice versa. Consequently, the multicellular system can exhibit, in both coupling cases, different collective behaviors in terms of synchronization and clustering. We give a general method of determining coupling type, elucidate the mechanism of generating these phenomena and present a criterion for stability of cluster states, mainly by analyzing phase interaction functions.     

Enolesters as chain end-functionalizing agents for the living ring opening metathesis polymerization

Functional enolethers have previously been used to introduce functional end groups at the chain end of ruthenium carbene complex initiated living ring opening metathesis polymers. Here, we investigated whether the weaker π-donating enolesters could equally be used in regio selective reactions with ruthenium carbene complexes and thus as polymer end-functionalization reagents. Enolesters such as vinyl acetate, butenyl acetate, 3-(4-(tert-butoxy)phenyl)propenyl acetate and 6-(((benzyloxy)carbonyl)amino)hex-1-en-1-yl acetate were used as living ROMP terminating agents. All gave the expected end groups proving that enolesters are synthetically easily accessible targets for living ROMP end-functionalization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2983–2990     

Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers

The kinetics and reactivity ratios of styrene‐acrylonitrile (SA) copolymerization have been studied extensively in bulk and in a variety of solution media using conventional free radical polymerizations (FRPs). Due to the significant difference in the two reactivity ratios for this monomer pair, at certain feed ratios the copolymers display composition drift with conversion due to monomer depletion. In this study, the kinetics of SA copolymerization using Reversible Addition‐Fragmentation Chain Transfer (RAFT) has been studied in bulk at 80 °C. The reactivity ratios for the terminal model were calculated from the comonomer sequence distributions for the RAFT process at low conversion for nine different compositions and found to be in the same range as those reported for conventional FRP of SA. The changes in the composition and sequence distribution with conversion were studied for three feed compositions. The copolymers show compositional drift with conversion, except at the azeotropic composition, and match the predictions from the reactivity ratios obtained at low conversion. From quantitative ¹³C NMR the triad distributions of these copolymers were estimated and found to match the predicted triad distributions as conversion increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 919–927     

The Structural Fate of Individual Multicomponent Metal‐Oxide Nanoparticles in Polymer Nanoreactors

Multicomponent nanoparticles can be synthesized with either homogeneous or phase‐segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal‐oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co‐Ni‐O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu‐Ni‐O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher‐ordered structure, Co‐Ni‐Cu‐O, was found to follow the behavior of lower ordered systems.     

Temperature effect on threshold voltage and optical property of twisted nematic liquid crystal with applied different voltages

In this paper, temperature-dependent birefringence theory of liquid crystal is used to investigate the temperature effect on the threshold voltage. An expression for describing the non-linear relationship between the threshold voltage and temperature is deduced. In addition, we theoretically discuss the temperature effect on the transmitted ratio of the namatic twisted liquid crystal without the applied voltage and with the applied voltage. It is found that the transmitted ratio is decreased linearly as temperature is increased when the liquid crystal is not applied with voltage, but the transmitted ratio is increased linearly as temperature is increased when the liquid crystal is applied with voltage. The threshold voltages and the transmitted ratio are measured at different temperatures. The experimental data are consistent with the theoretical calculated results.