Selective Conversion of Glycerol to Propylene Glycol Over Fixed Bed Raney® Cu Catalysts

Net propylene glycol (1,2 propanediol) yields of up to 94% at 100% glycerol conversion have been achieved over a fixed bed Raney^® Cu catalyst in trickle bed mode, at relatively low total pressure, 14 bar (200 psig), and minimal feedstock dilution (20 wt% water). The main identified byproducts are ethylene glycol and ethanol (each <2%), with methanol and 1,3 diol both <1%. The other key operating parameters for high yields are a narrow optimum in temperature (near 205 °C), and a high H₂/liquid flow ratio, about 375/0.05 by volume. The effects of chromium promotion have also been studied for effects on side reactions and rates. Our evidence points to initial dehydrogenation as the rate-limiting step in a likely three step mechanism.     

Modeling the RTD of an industrial overflow ball mill as a function of load volume and slurry concentration

The role of residence time distribution (RTD) in the accuracy of milling simulation is well appreciated in literature. Accordingly, the development of models that can accurately predict the RTD at various mill operating conditions would be of considerable benefit to the milling industry. In this paper, a 3-parameter RTD model has been derived using the concept of serial stirred mixers with a dead zone. The model parameters were optimized by minimizing the error between experimental tracer response data and model predictions using a MATLAB algorithm. Based on the optimum values of the model parameters, the mean residence time of slurry was evaluated and the effects of ball load volume and slurry concentration examined. The results revealed that the mean residence time of slurry inside the mill is affected to a larger extent by slurry concentration than the ball load volume. An empirical correlation was developed to predict the mean residence time as a function of slurry concentration, ball load volume and slurry feed rate. Over the range of conditions investigated, the mean residence time was observed to vary linearly with slurry concentration and ball load volume but inversely with feed flow rate. Lastly, a test case of the simulated mill product size distribution using the predicted RTD is presented displaying a close match with experimental data.     

Synthesis and characterization of highly photoresponsive fullerenyl dyads with a close chromophore antenna-C(60) contact and effective photodynamic potential

We report the synthesis of a new class of photoresponsive C(60)-DCE-diphenylaminofluorene nanostructures and their intramolecular photoinduced energy and electron transfer phenomena. Structural modification was made by chemical conversion of the keto group in C(60)(>DPAF-C(n)) to a stronger electron-withdrawing 1,1-dicyanoethylenyl (DCE) unit leading to C(60)(>CPAF-C(n)) with an increased electronic polarization of the molecule. The modification also led to a large bathochromic shift of the major band in visible spectrum giving measureable absorption up to 600 nm and extended the photoresponsive capability of C(60)-DCE-DPAF nanostructures to longer red wavelengths than C(60)(>DPAF-C(n)). Accordingly, C(60)(>CPAF-C(n)) may allow 2γ-PDT using a light wavelength of 1000-1200 nm for enhanced tissue penetration depth. Production efficiency of singlet oxygen by closely related C(60)(>DPAF-C(2) (M)) was found to be comparable with that of tetraphenylporphyrin photosensitizer. Remarkably, the (1)O(2) quantum yield of C(60)(>CPAF-C(2) (M)) was found to be nearly 6-fold higher than that of C(60)(>DPAF-C(2) (M)), demonstrating the large light-harvesting enhancement of the CPAF-C(2) (M) moiety and leading to more efficient triplet state generation of the C(60)> cage moiety. This led to highly effective killing of HeLa cells by C(60)(>CPAF-C(2) (M)) via photodynamic therapy (200 J cm(-2) white light). We interpret the phenomena in terms of the contributions by the extended π-conjugation and stronger electron-withdrawing capability associated with the 1,1-dicyanoethylenyl group compared to that of the keto group.     

Individual differences in negative affect repair.

The extant literature implicates affect repair ability as one source of individual differences in negative affect. Emerging from this literature are three regulatory traits that should predict repair ability (negative mood regulation expectancies, monitoring, labeling), yet no experimental examination of this possibility exists. Two studies explored this issue. Participants (Ns = 305, 146) watched negative affect-inducing videos and completed a repair or control writing task, before and after which they reported their affect. Results revealed wide individual differences in repair ability. Specifically, participants with high expectancies of repair success and those who attend to and understand their affect experienced the largest decreases in negative affect and largest increases in positive affect following the repair tasks. These findings advance understanding of individual differences in affect regulation and have implications for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanochromic Photonic Gels

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism – a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain‐dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer‐based photonic gels that are directly or indirectly fabricated via self‐assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors.     

Chemical characterisation and speciation of organic selenium in cultivated selenium-enriched Agaricus bisporus

The selenium concentration in Agaricus bisporus cultivated in growth compost irrigated with sodium selenite solution increased by 28- and 43-fold compared to the control mushroom irrigated solely with water. Selenium contents of mushroom proteins increased from 13.8 to 60.1 and 14.1 to 137 μg Se/g in caps and stalks from control and selenised mushrooms, respectively. Selenocystine (SeCys; detected as [SeCys]₂ dimer), selenomethionine (SeMet), and methyl-selenocysteine (MeSeCys) were separated, identified and quantified by liquid chromatography–electrospray ionisation-mass spectrometry from water solubilised and acetone precipitated proteins, and significant increases were observed for the selenised mushrooms. The maximum selenoamino acids concentration in caps and stalks of control/selenised mushrooms was 4.16/9.65 μg/g dried weight (DW) for SeCys, 0.08/0.58 μg/g DW for SeMet, and 0.031/0.10 μg/g DW for MeSeCys, respectively. The most notable result was the much higher levels of SeCys accumulated by A. bisporus compared to SeMet and MeSeCys, for both control and selenised A. bisporus.     

Novel potentiometric sensors for the selective determination of domperidone

The fabrication and electrochemical response characteristics of two novel potentiometric sensors for the selective determination of domperidone (DOM) are described. The two fabricated sensors incorporate DOM–PTA (phosphotungstic acid) ion pair as the electroactive material. The sensors include a PVC membrane sensor and a carbon paste sensor. The sensors showed a linear, stable, and near Nernstian slope of 56.5 and 57.8 mV/decade for PVC membrane and carbon paste sensors, respectively over a relatively wide range of DOM concentration (1.0 × 10^?1–1.0 × 10^?5 and 1.0 × 10^?1–3.55 × 10^?6 M). The response time of DOM–PTA membrane sensor was less than 25 s and that in the case of carbon paste sensor was less than 20 s. A useful pH range of 4–6 was obtained for both types of sensors. A detection limit of 7.36 × 10^?5 M was obtained for PVC membrane sensor and 1.0 × 10^?6 M was obtained for carbon paste sensor. The proposed sensors showed very good selectivity to DOM in the presence of a large number of other interfering ions. The analytical application of the developed sensors in the determination of the drug in pharmaceutical formulations such as tablets was investigated. The results obtained are in good agreement with the values obtained by the standard method. The sensors were also applied for the determination of DOM in real samples such as urine by the standard addition method.