Segmented polyurethanes using fluorescein

Segmented Polyurethanes were prepared by chain extending the prepolymers based on poly(tetramethylene oxide)glycol and tolylene diisocyanate using fluorescein. The polymers were characterized using FTNMR and FTIR. Thermal stability of the polymers was studied using a thermogravimetric analyzer, and the glass transition temperature of the polymers was determined using a differential scanning calorimeter. Tensile strength and percentage of elongation of these segmented polyurethanes were evaluated using a Universal Testing Machine. © John Wiley & Sons, Inc.     

Cadmium solubility in paddy soils: effects of soil oxidation, metal sulfides and competitive ions

Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) and zinc (Zn) for human nutrition. To find ways of limiting this potential risk, we investigated factors influencing Cd solubility relative to Fe and Zn during pre-harvest drainage of paddy soils, in which soil oxidation is accompanied by the grain-filling stage of rice growth. This was simulated in temperature-controlled “reaction cell” experiments by first excluding oxygen to incubate soil suspensions anaerobically, then inducing aerobic conditions. In treatments without sulfur addition, the ratios of Cd:Fe and Cd:Zn in solution increased during the aerobic phase while Cd concentrations were unaffected and the Fe and Zn concentrations decreased. However, in treatments with added sulfur (as sulfate), up to 34 % of sulfur (S) was precipitated as sulfide minerals during the anaerobic phase and the Cd:Fe and Cd:Zn ratios in solution during the aerobic phase were lower than for treatments without S addition. When S was added, Cd solubility decreased whereas Fe and Zn were unaffected. When soil was spiked with Zn the Cd:Zn ratio was lower in solution during the aerobic phase, due to higher Zn concentrations. Decreased Cd:Fe and Cd:Zn ratios during the grain filling stage could potentially limit Cd enrichment in paddy rice grain due to competitive ion effects for root uptake.     

Phytotoxic and Antifungal Compounds from Two <Emphasis Type="Italic">Apiaceae</Emphasis> Species, <Emphasis Type="Italic">Lomatium californicum</Emphasis> and <Emphasis Type="Italic">Ligusticum hultenii</Emphasis>, Rich Sources of Z-ligustilide and Apiol,Respectively

The seeds of two Apiaceae species, Ligusticum hultenii and Lomatium californicum, were investigated. Preliminary bioassays indicated that methylene chloride extracts of seeds of both species contained selective phytotoxic activity against monocots and antifungal activity against Colletotrichum fragariae. Active constituents were isolated by bioassay-guided fractionation, and the structures were elucidated by NMR and GC-MS as apiol and Z-ligustilide, isolated from L. hultenii and L. californicum, respectively. Apiol and Z-ligustilide had I₅₀ values of about 80 and 600 μM, respectively, for inhibition of the growth of Lemna paucicostata. The methylene chloride (CH₂Cl₂) extracts of the seeds and the isolated and purified compounds were tested against the 2-methylisoborneol-producing cyanobacterium (blue-green alga) Oscillatoria perornata, and the green alga Selenastrum capricornutum. The CH₂Cl₂ extracts of both Apiaceae species and apiol were weakly toxic to both species of phytoplankton, while Z-ligustilide was toxic to both with a lowest complete inhibitory concentration (LCIC) of 53 μM. Seeds of L. californicum and L. hultenii were found to be rich sources of Z-ligustilide (97 mg/g of dry seed) and apiol (40 mg/g of dry seed), respectively.     

Investigations on polyurethane ionomers. II. 3,4-dihydroxycinnamic acid-based anionomers

Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of various polyols and diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were converted to their anionomers by treating with metal acetates. The polyurethanes were characterized using FTIR, FTNMR, TGA, and DSC analysis. The molecular weights of the polymers were determined using GPC. A detailed study of the effect of variation of molecular weight of the polyols and mol ratio of the various reactants on the glass transition temperature and molecular weight of the polyurethanes was made. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2105–2109, 1997     

Positive-negative DC-DC converter using amorphous-InGaZnO TFTs

This paper presents two DC-DC converters capable of generating either positive or negative output DC voltage using amorphous-indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). While one uses conventional diode-connected cross-coupled (design-1), the other employs a bootstrapped cross-coupled (design-2) DC-DC converter, which overcomes the limitations of design-1 but requires boosted clock pulses. Therefore, an on-chip clock booster is proposed to generate all the required signals without any external clock pulses. The performance of the proposed circuits (DC-DC converters and clock booster) has been demonstrated using in-house a-IGZO TFT models in the Cadence environment. The simulation results have shown that design-1 (design-2) generates negative or positive output DC voltage of 7.25 V (7.8 V) or 12.7 V (15.2 V), respectively, for a supply voltage of 8 V, using a single DC-DC converter. Therefore, the output DC voltage of design-2 is close to the theoretical value, and it ensures robust performance against different load currents when compared with design-1. Besides, design-2 has shown a maximum power efficiency of 90%, superior compared with design-1, where power efficiency is 60.7%. Therefore, this circuit finds potential applications in the next generation flexible displays.     

Risk management in the automotive supply chain: an exploratory study in Brazil

The main objective of this study was to identify the main characteristics of risk management in the automotive supply chain in Brazil, considering companies in the first and second tiers. This objective was achieved through the proposition of three hypotheses that were tested based on a survey of 211 auto parts producers scattered throughout the country, from which 77 completed forms were received. This research enabled us to conclude that the risks perceived in tier 2 are higher than those observed in tier 1. Also, it was possible to verify that the performance of companies in tier 2 (higher risk) is lower than those in tier 1. Contrary to what was observed in the literature, this research could not find evidence to confirm that risk management tools are prioritized to reduce the risk of companies in the supply chain. Therefore, this research contributes to both theory and practice: this is the first study that performs an analysis of risk management in supply chains with tier 1 and 2 companies in the Brazilian automotive industry, becoming an important complement to recent studies on this topic. For practitioners and business executives who manage risks in automotive supply chains in Brazil, this paper shows the reality of the issue in first- and second-tier companies, which can provide them with important contexts for their decision making in the day-to-day business of the automotive sector.     

Wavelet Neural Network-based Wind-power Forecasting in Economic Dispatch: A Differential Evolution,Bacterial Foraging Technology,and Primal Dual-interior Point Approach

Wind speed and wind-power generation are characterized by their inherent variability and uncertainty. To overcome this drawback, an accurate prediction of wind speed is essential. The purpose of this paper is to develop a hybrid wavelet neural network model for wind-speed forecasting and thus, in turn, for wind-power generation. The combined optimal economic scheduling of the wind generators and conventional generators has also been investigated in this paper. The solution methods, namely primal dual interior point, differential evolution, and bacterial foraging technology, are used for solving the wind-thermal economic dispatch (ED). The feasibility of the proposed algorithms is demonstrated on three-unit, 13-unit, and 40-unit systems and their performances are compared in terms of the generation cost and execution time. The results show that the proposed algorithms are indeed capable of handling ED problems.     

Aqueous dispersions of polyurethane polyacrylic acid multiblock copolymers through living radical polymerization

Polyurethane macroiniferter (PUMI) including tetraphenylethane was synthesized and used to prepare polyurethane–polyacrylic acid multiblock copolymers. Film‐forming aqueous dispersions without any added external emulsifiers were prepared from polyurethane–polyacrylic acid multiblock copolymers. The effect of varying PUMI content, polymerization time, and percent ionization on the properties of multiblock copolymeric dispersions were studied in detail. Interfacial tension of the dispersions and critical surface tension measurements of the films formed thereof have shown that the polymers exhibit a hydrophilic character in the dispersed phase and a hydrophobic character in the solid phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1109–1115, 2003     

Morphological Observations of lead ore (Galena) Grafted Between Polymer Composite Layers and Formulated of Styrenated Methacrylate Vinyl Ester System

Composites based on styrenated methacrylate vinyl ester, quartz, and fused alumina were prepared in a lab model Sigma blender and polymerized at room temperature by catalysis. Lead ore galena was grafted in between as two layers, wetted with the monomer, and compression molded. After complete curing the specimen was cut with a slow-speed diamond cutter and observed at the interfaces for morphology. SEM studies revealed excellent compatibility and some compounding at the interphases.     

Chiral macrocyclic salen Mn(III) complexes catalyzed enantioselective epoxidation of non-functionalized alkenes using NaOCl and urea H2O2 as oxidants

Two new chiral Mn(III) macrocyclic salen complexes 1a and 1b were prepared for the enantioselective epoxidation of non-functionalized alkenes. A 5 mol% loading of these catalysts in the presence of pyridine N-oxide as an axial base and sodium hypochlorite or urea hydrogen peroxide adduct as oxidant worked well to give respective epoxides in high yields and ee (up to >95% in selected cases). The catalyst 1b with urea hydrogen peroxide adduct as an oxidant was recovered by precipitation with hexane and was reused up to four times with retention of enantioselectivity.