Derivatives of biomacromolecules as stabilizers of aqueous alumina suspensions

The stabilization of alumina suspensions is key to the development of high‐performance materials for the ceramic industry, which has motivated extensive research into synthetic polymers used as stabilizers. In this study, mimosa tannin extract and a chitosan derivative, that is, macromolecules obtained from renewable resources, are shown to be promising to replace synthetic polymers, yielding less viscous suspensions with smaller particles and greater fluidity, that is, more homogeneous suspensions that may lead to better‐quality products. The functional groups of tannin present in mimosa extract and N,N,N‐trimethylchitosan (TMC) are capable of establishing interactions with the alumina surface, thus leading to repulsion between the particles mainly due to steric and electrosteric mechanisms, respectively. The stabilization of the suspension induced by either TMC or mimosa tannin was confirmed by a considerable decrease in viscosity and average particle size, in comparison with alumina suspensions without stabilizing agents. The viscosity/average particle size decreased by 49/84% and 52/87% for suspensions with TMC and mimosa tannin, respectively. In addition, the increase in the absolute zeta potential upon addition of either TMC or mimosa tannin extract, especially at high pHs, points to an increased stability of the suspension. The feasibility of using derivatives of macromolecules from renewable sources to stabilize aqueous alumina suspensions was therefore demonstrated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A methodology for unveiling global innovation networks: patent citations as clues to cross border knowledge flows

This paper presents a new methodology to describe global innovations networks. Using 167,315 USPTO patents granted in 2009 and the papers they cited, this methodology shows “scientific footprints of technology” that cross national boundaries, and how multinational enterprises interact globally with universities and other firms. The data and the map of these flows provide insights to support a tentative taxonomy of global innovation networks.     

The recognition of handwritten numeral strings using a two-stage HMM-based method

In this paper, a two-stage HMM-based recognition method allows us to compensate for the possible loss in terms of recognition performance caused by the necessary trade-off between segmentation and recognition in an implicit segmentation-based strategy. The first stage consists of an implicit segmentation process that takes into account some contextual information to provide multiple segmentation-recognition hypotheses for a given preprocessed string. These hypotheses are verified and re-ranked in a second stage by using an isolated digit classifier. This method enables the use of two sets of features and numeral models: one taking into account both the segmentation and recognition aspects in an implicit segmentation-based strategy, and the other considering just the recognition aspects of isolated digits. These two stages have been shown to be complementary, in the sense that the verification stage compensates for the loss in terms of recognition performance brought about by the necessary tradeoff between segmentation and recognition carried out in the first stage. The experiments on 12,802 handwritten numeral strings of different lengths have shown that the use of a two-stage recognition strategy is a promising idea. The verification stage brought about an average improvement of 9.9% on the string recognition rates. On touching digit pairs, the method achieved a recognition rate of 89.6%. Received June 28, 2002 / Revised July 03, 2002     

Low-density polyethylene modified by thermal polymerization of 4-vinylpyridine and methyl methacrylate: Structural studies

The structures of low-density polyethylene (LDPE) modified by in situ sorption and thermal polymerization of 4-vinylpyridine (4VP) and of methyl methacrylate (MMA) were studied. The phase behavior of these materials was investigated by means of X-ray diffraction, scanning electron microscopy (SEM), and by thermal measurements (DSC). The diffraction studies indicated that the polymerization occurs at the amorphous domains of the matrix, except for the case of 4VP (168.0%), in which polymerization at the crystalline domains of LDPE matrix was also observed. These materials showed at least two T_g values, indicating microphase separation. The morphology of LDPE-P4VP was different from that of LDPE-PMMA.     

Maternal viral genotypic zidovudine resistance and infrequent failure of zidovudine therapy to prevent perinatal transmission of human immunodeficiency virus type 1 in pediatric AIDS Clinical Trials Group Protocol 076

Maternal samples were assessed from 96 women enrolled in Pediatric AIDS Clinical Trials Group protocol 076 to determine the prevalence of human immunodeficiency virus type 1 (HIV-1) genotypic zidovudine resistance at entry, if zidovudine resistance developed on study, and the role of zidovudine resistance in vertical transmission of HIV-1 despite zidovudine therapy. Low and high levels of genotypic resistance were assessed by differential hybridization, oligoligation, or direct sequencing of plasma HIV-1 RNA for codons K70R and T215Y/F. None of the women had high-level genotypic resistance to zidovudine at study entry or delivery. For low-level zidovudine resistance, the 95% confidence intervals were 0.3%-6.8% for baseline prevalence and 0.3%-14% for delivery incidence. Low-level zidovudine resistance, adjusted for plasma viral RNA level at delivery, was not strongly associated with an increase in vertical transmission risk (odds ratio, 4.8; 95% confidence interval, 0.2-131; P = .35).     

Calretinin in the mouse superior colliculus originates from retinal ganglion cells

We investigated the origin of the calretinin-immunoreactive fibers in the mouse superior colliculus. The dense plexus of calretinin-positive fibers in the superficial layers of the colliculus was completely eliminated after eye enucleation. Retrograde tracing combined with immunohistochemistry revealed many calretinin-positive small-to-medium retinal ganglion cells projecting to the colliculus. These results indicate that calretinin-containing ganglion cells are the source of this calcium-binding protein in the superficial layers of the superior colliculus.     

Comparative investigation of the effects of lower and higher alcohols/bio-diesel blends on engine performance and emissions characteristics of a diesel engine

ABSTRACT

The use of lower alcohol (such as methanol and ethanol) blends in diesel engines shows problems like phase separation, miscibility, higher NO_x emissions etc. The addition of higher alcohols with either diesel or biodiesel is relatively new and only a little information is available on the effects of higher alcohols. In this work, the engine performance and emissions characteristics were compared between the lower and higher alcohol blended with biodiesel. Conventional diesel and biodiesel are considered as the reference fuels. Three lower alcohols (methanol, ethanol and propanol) and three higher alcohols (butanol, pentanol and octanol) of each 50% by volume were mixed with biodiesel of 50% by volume. Experiments were conducted on a single cylinder compression ignition diesel engine by varying the load conditions at a constant speed. Engine performance and emissions of CO, CO₂, NO_x and HC were determined. The results are discussed.     

Experimental investigation of the influence of isobutanol addition on engine performance and emissions of a direct ignition diesel engine fuelled by biodiesel blends derived from waste vegetable oil

Biodiesel has become one of the potential alternative sources to replace diesel. Some of the limitations of biodiesel include high NO _x , poor atomization, poor oxidation stability, cold-flow problems, long-term storage problems, etc. Various strategies were discussed to overcome the limitations of biodiesels. Recent research is on effects of fuel additives or fuel composition modification to reformulate the fuel properties. This article is aimed at presenting the experimental investigation of the effects of isobutanol additive on the engine performance and emission characteristics of biodiesel blends derived from waste vegetable oils. The experimental investigation was conducted on a direct injection four-stroke diesel engine with different blends, B10, B20, B30, B10 (10% ISB), B20 (10% ISB), B30 (10% ISB), B10 (20% ISB), B20 (20% ISB) and B30 (20% ISB), and engine performance and emission characteristics are evaluated and discussed.     

Growth and characterization of dl-Alanine — A new NLO material from the amino acid family

Single crystals of dl-Alanine (C₃H₇NO₂), one among the rare amino acid racemates crystallizing in a non-centrosymmetric space group and a new NLO material, were grown from aqueous solution by slow evaporation method. They were characterized by single crystal X-ray diffraction. Fourier transform infrared spectroscopy (FTIR) showed the presence of the different functional groups. The thermal stability and decomposition of the sample was studied by thermal analysis (TGA/DTA). The optical transparency was studied by UV–Vis–NIR spectral analysis. The above experimental results showed that dl-Alanine is stable up to 280 °C and transparent in the region of 220 nm–1100 nm. The second harmonic generation (SHG) efficiency was determined using Kurtz and Perry method and found to be 1.7 times higher than that of standard KDP.