Epoxidation of natural rubber studied by nmr spectroscopy

Epoxidation of natural rubber with peroxyacids in homogeneous solution (CHCl₃, benzene) and in latex occurs without main chain fission or isomerization of the cis configuration. There are two possible modes of addition of oxygen to the double bond, which gives rise to diastereoisomers in dyad structures, as shown by the occurrence of splitting of ¹³C NMR resonances in 100% epoxidized rubber. In partially epoxidized rubber the ¹³C NMR resonances of the methylene carbon atoms have been fully assigned using pulse sequences and lanthanide shift reagents, in terms of triad sequences. Resonances in the olefinic region of the spectrum require assignment in terms of pentad sequences whereas those from the oxirane region are much more closely spaced and are assigned using triads. Intensity measurements on the methylene carbon NMR resonances show that the epoxidation reaction is a random process in both homogeneous solution and in latex particles.     

The Effect of Moisture Content on the Conversion of Ergosterol to Vitamin D in Shiitake Mushrooms

The distribution of ergosterol in different parts of shiitake mushrooms was studied in order to optimize the conversion of ergosterol to vitamin D₂ during drying. The effect of moisture on the conversion of ergosterol to vitamin D₂ was also investigated by adjusting the moisture content of fresh mushrooms to different levels in a large vacuum desiccator and subjecting them to UV irradiation at 290-320 nm wavelength, for 2 h. The moisture, ergosterol and vitamin D₂ contents were determined using standard procedures. It was found that the ergosterol content on a dry matter basis of fresh shiitake mushroom was highest in the gills (10.6 ± 0.99 mg/g DM), followed by the cap or pileus (5.34 ± 0.64 mg/g DM) and was least in the stalk or stipe (2.97 ± 0.56). The moisture content had a marked influence on the conversion of ergosterol to vitamin D₂, the best conversion taking place at a moisture content of about 70% on a wet basis.     

Performance of a Yeast-mediated Biological Fuel Cell

Saccharomyces cerevisiae present in common Baker’s yeast was used in a microbial fuel cell in which glucose was the carbon source. Methylene blue was used as the electronophore in the anode compartment, while potassium ferricyanide and methylene blue were tested as electron acceptors in the cathode compartment. Microbes in a mediator-free environment were used as the control. The experiment was performed in both open and closed circuit configurations under different loads ranging from 100 kΩ to 400Ω. The eukaryotic S. cerevisiae-based fuel cell showed improved performance when methylene blue and ferricyanide were used as electron mediators, rendering a maximum power generation of 146.71±7.7 mW/m³. The fuel cell generated a maximum open circuit voltage of 383.6±1.5 mV and recorded a maximum efficiency of 28±1.8 % under 100 kΩ of external load.     

Rates of reinfection with Echinococcus granulosus, Taenia hydatigena, taenia ovis and other cestodes in a rural dog population in Uruguay

Forced thinking is an incompletely understood and rarely described epileptic aura. We studied three patients with forced thinking from left frontal lesions, two neoplastic and one vascular. All three experienced repetitive, intrusive thoughts at the onset of seizures. Their forced thinking was associated with the desire to vocalize, orobuccal movements, and speech arrest. The episodes occurred with other ictal manifestations and responded to antiseizure therapy. These patients suggest that epileptic forced thinking is a heterogeneous phenomenon; forced thinking from left frontal lesions is a manifestation of expressive language and is distinct from experiential thoughts arising from temporal limbic foci.     

Surface modification of natural rubber laces

Epoxidation has been applied to modify the surface of natural rubber laces. When very thin laces of fractionated bleached rubber are used, about 6% of the double bonds could be modified. Using ¹H nuclear magnetic resonance (NMR) and infrared (IR) analysis the best condition for the reaction was worked out. Both ¹³C NMR and differential scanning calorimetry (DSC) results indicate that the 6% epoxide groups are placed in a predominantly block manner. Modification in yellow fraction rubber however gives lower epoxy contents. Increase in glass transition tempreature by epoxidation results in more damping and better abrasion resistance. The resultant polymer acts very similar to a 90/10 natural rubber/50% epoxidized natural rubber (NR/ENR-50) blend.     

Maximum quasi-likelihood estimation for the near(2) model

Abstract.  Maximum quasi-likelihood estimation is investigated for the NEAR(2) model, an autoregressive time series model with marginal exponential distributions. In certain regions of the parameter space, simulations indicate that maximum quasi-likelihood estimators perform better than two-stage conditional least squares estimators in terms of the per cent of estimates falling in the parameter space. The problem of out-of-range estimates is shown to be caused by the lack of information in the data rather than the characteristics of the method of estimation.     

Nitrogen-containing aluminium titanate

In the Ti-Al-O-N system a phase isostructural to aluminium titanate but with expanded unit cell dimensions was observed. It was stable between 1400 and 1700 °C and has unit cell dimensions of a=0.3719 nm, b=0.9703 nm and c=0.9869 nm with a composition of Ti _1.00 ⁴⁺ Al _0.54 ³⁺ Ti _1.46 ³⁺ N _0.28 ^3– O _4.58 ^2– _0.14 Several samples were prepared by reaction sintering mixtures of TiN, Al₂O₃ and AlN powders at 1400 to 1470 °C for 4 h in a nitrogen atmosphere to maximize this phase. One specific advantage of the nitrogen-containing aluminium titanate over aluminium titanate is that the former is unchanged at 1150 °C in a nitrogen atmosphere whereas the latter decomposes. In the Al₂O₃-TiO₂ oxide system Al₂TiO₅ solid solution extends to approximately Al_0.75Ti_2.25O₅ at 1470 °C under the mildly reducing conditions of a graphite furnace. The unit cell volume increases linearly with the increasing replacement of Al³⁺ by Ti³⁺.     

Modelling of interfacial mass transfer in microfluidic solvent extraction: part II. Heterogeneous transport with chemical reaction

The use of a microfluidic device in determining the extraction kinetics of Co^II ions by di-(2-ethylhexyl) phosphoric acid (DEHPA) was demonstrated. Experimental data obtained using a Y-Y-shaped microchannel were modelled using a finite volume method. The contributions of diffusion and reaction transport resistances to the overall rate of mass transfer were obtained. A diffusion-controlled transfer assumption could not account for the experimental data, confirming that transport occurs under a mixed reaction–diffusion resistance regime. The reaction rate constant was determined to be $(2.4 \pm 0.6) \times 10^{-10}$  m/s, in good agreement with corresponding Lewis cell measurements from the literature.     

Supporting the creative drive: investigating paralinguistic voice as a mode of interaction for artists with upper limb disabilities

For people with upper limb disabilities visual art is an important activity that allows for expression of individuality and independence. They show remarkable endurance, patience and determination to adapt their remaining capabilities to create visual art. There are significant advantages of digital technologies in assisting artists with upper limb disabilities. Paralinguistic voice recognition technologies have proven to be a particularly promising mode of interaction. Despite these benefits, technological support for people with upper limb disabilities to create visual art is scarce. This paper reports on a number of case studies of several artists with upper limb disabilities. These case studies illustrate the struggles they face to be creative and also show the significant advantages of digital technologies in assisting such artists. An investigation into people’s ability to use the volume of their voice to control cursor movement to create drawings on the screen is also reported. With motivation, training and practise, use of volume to control drawing tasks shows great promise. It is believed that paralinguistic voice has wider implications beyond assisting artists with upper limb disabilities, such as: an alternative mode of interaction for disabled people to perform tasks other than creating visual art, alternative mode of interaction for hands busy environments and as a voice training system for people with speech impairments.