Chemical modification of poly(2,6-dimethyl-1,4-phenylene oxide) by bromination-alkynylation

The chemical modification of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by bromination of the aromatic ring, followed by displacement of bromine with substituted acetylenes, has been investigated. This pathway leads to a series of novel copolymers containing substituted alkynes on the aromatic ring. The degree of bromination and alkynylation, determined by ¹H-NMR, was in the range of 20–85 and 15–80%, respectively. ¹³C-NMR and FT-IR unambiguously elucidated the structure of the alkynylated polymers. Finally, thermal properties and permeation properties of substituted PPO to carbon dioxide, methane, oxygen, and nitrogen are reported. © 1994 John Wiley & Sons, Inc.     

Evaluating the performance of an inexpensive,commercially available,NFC-powered and smartphone controlled potentiostat for electrochemical sensing

To move electrochemical sensing technology from the laboratory into point-of-care (POC)-based settings, electrochemical platforms must be cost-effective, portable, and user-friendly. Here, we present the comparison of a near-field communication (NFC) potentiostat with a traditional potentiostat. The NFC potentiostat is roughly the size of a credit card and is wirelessly powered by a smartphone with a user-friendly application for electrochemical analysis. The proposed system is portable, affordable, and provides analytical capabilities comparable to traditional benchtop potentiostats. Different redox probes were investigated, including ferricyanide, ruthenium hexamine, and hydroquinone, highlighting the ability of the NFC potentiostat to measure a variety of target analytes. In addition, the NFC potentiostat can perform several electrochemical techniques, such as cyclic voltammetry, differential pulse voltammetry, chronoamperometry and square wave voltammetry. The combination of affordable screen-printed carbon electrodes (SPCE)s with the portable, inexpensive NFC potentiostat highlights this platform‘s promise towards POC electrochemical sensing applications, particularly for medical diagnostics in rural or low-income areas.     

Yield of singlet excitons in organic light-emitting devices: a double modulation photoluminescence-detected magnetic resonance study

Double-modulation (DM) photoluminescence (PL) detected magnetic resonance (PLDMR) measurements on poly(2-methoxy-5-(2(')-ethyl)-hexoxy-1,4-phenylene vinylene) are described. In these measurements, the laser excitation power is modulated at 1相似文献   

Co-production of Fructooligosaccharides and Levan by Levansucrase from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> natto with Potential Application in the Food Industry

Fructooligosaccharides and levan have a wide range of applications in the food industry due to their physiological and functional properties. The enzymatic synthesis of these molecules exhibits great advantages when compared with microbial fermentation. In this study, the production of levansucrase from Bacillus subtilis natto and its utilization in fructooligosaccharides and levan syntheses using different reaction conditions were described. The best condition for levansucrase production was 420.7 g L^?1 of sucrose at pH 7.0, which reached 23.9 U ml^?1 of transfructosylation activity. In a bioreactor, the highest production of fructooligosaccharides was 41.3 g L^?1 using a medium containing 350 g L^?1 sucrose at 35 °C for 36 h. The enzymatic synthesis of levan resulted in 86.9 g L^?1 when conditions similar to those used for fructooligosaccharides synthesis were applied. These results indicate that the levansucrase from B. subtilis natto could be applied for the co-production of fructooligosaccharides and levan, which are biomolecules that have health benefits and are used successfully in the food industry.     

Synthesis of tetraphenyl-substituted [12]cycloparaphenylene: toward a rationally designed ultrashort carbon nanotube

The first phenyl-substituted [n]cycloparaphenylene (1) has been synthesized. The preparation of this structure addresses several challenges toward a more elaborate phenyl-substituted [n]cycloparaphenylene (2), a molecule that may lead to the homogeneous synthesis of armchair carbon nanotubes.     

TR-FRET-based duplex immunoassay reveals an inverse correlation of soluble and aggregated mutant huntingtin in huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder caused by the amplification of a polyglutamine stretch at the N terminus of the huntingtin protein. N-terminal fragments of the mutant huntingtin (mHtt) aggregate and form intracellular inclusions in brain and peripheral tissues. Aggregates are an important hallmark of the disease, translating into a high need to quantify them in?vitro and in?vivo. We developed a one-step TR-FRET-based immunoassay to quantify soluble and aggregated mHtt in?cell and tissue homogenates. Strikingly, quantification revealed a decrease of soluble mHtt correlating with an increase of aggregated protein in primary neuronal cell cultures, transgenic R6/2, and HdhQ150 knock-in HD mice. These results emphasize the assay's efficiency for highly sensitive and quantitative detection of soluble and aggregated mHtt and its application in high-throughput screening and characterization of HD models.     

Transient-evoked otoacoustic emission generators in a nonlinear cochlea

This study focuses on the theoretical prediction and experimental evaluation of the latency of transient-evoked otoacoustic emissions. Response components with different delay have been identified in several studies. The main generator of the transient response is assumed to be coherent reflection from cochlear roughness near the resonant place. Additional components of different latency can be generated by different mechanisms. Experimental data are re-analyzed in this study to evaluate the dependence of the latency on stimulus level, for each component of the response, showing that previous estimates of the otoacoustic emission latency were affected by systematic errors. The latency of the emission from each generator changes very little with stimulus level, whereas their different growth rate causes sharp changes of the single-valued latency, estimated as the time of the absolute maximum of the bandpass filtered response. Results of passive linear models, in which gain and bandwidth of the cochlear amplifier are strictly related, are incompatible with the observations. Although active linear models including delayed stiffness terms do predict much slower dependence of latency on the stimulus level, a suitable nonlinear model should be designed, capable of decoupling more effectively the dependence on stimulus level of amplitude and phase of the otoacoustic response.     

Cu2O island shape transition during Cu-Au alloy oxidation

In situ transmission electron microscopy observations of the oxidation of (001) Cu-Au alloys indicate that the Cu2O islands that form undergo a remarkable transformation from an initially compact morphology to a dendritic structure as growth proceeds. Correspondingly, the surface composition becomes nonuniform and the fractal dimension associated with the islands evolves from 2.0 to a stable value of 1.87, indicating a transition in the rate-limiting mechanism of oxidation from oxygen surface diffusion to diffusion of copper through the increasingly gold-rich regions adjacent to the islands.     

Semi-microscopic model for the effective pairing interaction in atomic nuclei

A model has been proposed in which the ab initio effective pairing interaction in atomic nuclei is supplemented by a small phenomenological term containing one parameter universal for all intermediate-mass and heavy nuclei. The neutron and proton pairing gaps have been calculated for several chains of semimagic nuclei; these calculations demonstrate the applicability of this model.     

A Dirichlet problem for harmonic forms inC 1-domains

A Dirichlet problem for harmonic forms in openC ¹-domains is here investigated with boundary data of classL ^p .Work partially supported by MURST 60% and 40%.