Nitrogen-modified carbon-based catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells

Nitrogen-modified carbon-based catalysts for oxygen reduction were synthesized by modifying carbon black with nitrogen-containing organic precursors. The electrocatalytic properties of catalysts were studied as a function of surface pre-treatments, nitrogen and oxygen concentrations, and heat-treatment temperatures. On the optimum catalyst, the onset potential for oxygen reduction is approximately 0.76 V (NHE) and the amount of hydrogen peroxide produced at 0.5 V (NHE) is approximately 3% under our experimental conditions. The characterization studies indicated that pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction. In particular, pyridinic nitrogen, which possesses one lone pair of electrons in addition to the one electron donated to the conjugated π bond, facilitates the reductive oxygen adsorption.     

Influence of modified forms of urea and nitrogen levels on weed growth and grain yield of lowland rice

The growth of weeds and their subsequent reduction of rice yield as affected by N source neem cake coated urea (NCU), dicyandiamide coated urea (DCU), rock phosphate coated urea (RPCU), urea supergranules (USG) and prilled urea (PU) was studied on a clay loam soil at Coimbatore, India. Experiments were conducted in northeast monsoon (NEM) 1981, summer 1982, and southwest monsoon (SWM) 1982 seasons.The crop was associated with eleven weed species, and the dominant weeds wereEchinochloa crus-galli, Cyperus difformis andMarsilea quadrifolia. The weed flora varied between seasons. Deep placement of USG reduced the dry weight of weeds in NEM and summer seasons at 60, 90 and 120 Kg N ha^–1 whereas it increased the dry weight at 60 and 90 but not 120 Kg N ha^–1 in SWM season. The dry weight of weeds decreased with increased N rates for all N sources during NEM and summer seasons. In SWM season, dry weight of weeds increased with increased N rates for all N sources except USG. The grain yield of rice was drastically reduced with the deep placement of USG at 60 but not 120 Kg N ha^–1 in SWM season. The differential effect of the N sources between seasons was due to the change of the weed flora. Dominance ofE. crus-galli during SWM season had greater influence on weed dry weight and grain yield of rice.Nitrogen uptake by weeds was frequently greater in unfertilized plots, particularly in NEM and summer seasons. In SWM season, the apparent fertilizer N recovery by weeds was high for USG. It decreased from 53% for 60 Kg USG-N ha^–1 to 4% for 120 Kg USG-N ha^–1.Contribution from the part of Ph.D. work of the first author at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.     

Biosynthesis of polyunsaturated fatty acids in the developing brain: II. Metabolic transformations of intracranially administered [3-14C] eicosatrienoic acid,evidence for lack of Δ8 desaturasedesaturase

[3-¹⁴C] Eicosatrienoic acid (Δ11,14,17) chemically synthesized from [1-¹⁴C] linolenic acid was injected intracranially into 14-day old rats and sacrificed 8 hr later. The analysis of brain fatty acids by radio-gas liquid chromatography before and after ozonolysis showed that the tetraene fraction consisted of a desaturated product, Δ5,11,17–20∶4, and its elongated product, Δ7,13,16,19–22∶4. Both of these products, with a combined total of 61% of the total radioactivity recovered in the tetraene fraction, contain a nonmethylene interrupted double bond system and, therefore, are unsuitable for further desaturation. The other two components, Δ6,9,12,15–18∶4 and Δ8,11,14,17–20∶4, must have been formed from Δ9,12,15–18∶3, formed by retroconversion of the starting material 20∶3, followed by desaturation and elongation. These results suggest a lack of Δ⁸ desaturase in the developing brain, leading to formation of Δ5,11,14,17–20∶4 rather than Δ8,11,14,17–20∶4. Howeve, the nonmethylene interrupted double bond isomer does not restrict chain elongation.     

Precipitation behavior in a medium carbon,ti-v-n microalloyed steel

The precipitation behavior of a medium carbon steel microalloyed with Ti, V, and N has been studied by analytical transmission electron microscopy in the as-cast and isothermally heat-treated states, as well as at different stages in the thermomechanical processing of the steel. Mixed (Ti,V) nitrides were found in all the structures, but there was no evidence for mixed carbonitride formation. The Hillert-Staffansson model was used to predict the composition of the nitrides as a function of tem-perature. Upon prolonged aging many of the precipitates became “fragmented” and were no longer single crystals. At the same time, the volume fraction of precipitates dropped, while their average Ti content increased. Possible explanations for this unexpected behavior are discussed in this article.     

A study on the behaviour of steel braced barrel vaults

The computer analysis of steel braced barrel vaults is presented. This analysis is compared with the approximate method of analysis suggested by Baer. The drawbacks of Baer's method are discussed. The behaviour of these frames due to the effect of laterals, edge trusses and different types of bracing systems is predicted. Based on this parametric study an economic system of braced barrel vault is suggested for practical applications.     

A Microprocessor-Based Full Voltage Starting of Induction Motor with Switched Capacitors

ABSTRACT

Increasing concerns over the starting of induction motors with high starting torque requirements have prompted engineers to seek methods of starting with full voltage and switched capacitors. This method provides ample acceleration torque with minimum voltage disturbances on the main bus. A highly reliable microprocessor-based starter with high performance has been developed. The hardware and software architecture of this starter and its starting aspects are described. The programmable automation provided here allows a flexibility in algorithms which can be altered or expanded easily. The performance goals designed also include protection of induction motor against overload, phase loss, wrong phase sequence and severe over voltage due to self-excitation.     

Log-convexity of rate region in 802.11e WLANs

In this paper we establish the log-convexity of the rate region in 802.11 WLANs. This generalises previous results for Aloha networks and has immediate implications for optimisation based approaches to the analysis and design of 802.11 wireless networks.     

Synthesis and characterization of Y (In,Mn) O3 blue pigment using the complex polymerization method (CPM)

In this paper, a new synthetic pathway is proposed for the system YIn_1-xMn_xO₃, a bright blue inorganic pigment, discovered in 2009. Blue pigment samples with increasing concentration of Mn³⁺ (x?=?0.08, 0.12 and 0.16) were prepared using the complex polymerization method (CPM) and compared with those synthesized via solid state reaction. All powders, the amorphous precursor from CPM and the starting materials for solid state method, were calcined at 1000, 1100, 1200 and 1300?°C for 12?h, and the resulting blue pigments were characterized by X-ray diffraction (XRD), colorimetric system CIE L*a*b* and Near infrared (NIR) reflectance measurements. XRD patterns and Rietveld Refinement show that the lowest temperature at which single hexagonal phase (isostructural to YInO₃) is formed is 1000?°C for CPM method and 1300?°C for conventional solid state method, respectively. The L*a*b* values demonstrate that the coloration of powders prepared by CPM exhibit temperature dependence below 1300?°C, a color shade shift from grayish blue to intense deep blue is observed when heating the samples from 1000 to 1300?°C. Blue pigments obtained by CPM have smaller particle size due to low temperatures and excellent near-infrared reflectance comparable to those by solid state method. Thus, providing advantages for application process and energy efficiency.     

Self-Assembly and Neurotoxicity of β-Amyloid (21–40) Peptide Fragment: The Regulatory Role of GxxxG Motifs

The three GxxxG repeating motifs from the C-terminal region of β-amyloid (Aβ) peptide play a significant role in regulating the aggregation kinetics of the peptide. Mutation of these glycine residues to leucine greatly accelerates the fibrillation process but generates a varied toxicity profile. Using an array of biophysical techniques, we demonstrated the uniqueness of the composite glycine residues in these structural repeats. We used solvent relaxation NMR spectroscopy to investigate the role played by the surrounding water molecules in determining the corresponding aggregation pathway. Notably, the conformational changes induced by Gly³³ and Gly³⁷ mutations result in significantly decreased toxicity in a neuronal cell line. Our results indicate that G³³xxxG³⁷ is the primary motif responsible for Aβ neurotoxicity, hence providing a direct structure–function correlation. Targeting this motif, therefore, can be a promising strategy to prevent neuronal cell death associated with Alzheimer's and other related diseases, such as type II diabetes and Parkinson's.