Current Algebra of Super WZNW Models

We derive the current algebra of supersymmetric principal chiral models with a Wess-Zumino term. At the critical point one obtains two commuting super Kac-Moody algebra as expected, but in general there are intertwining fields connecting both right and left sectors, analogously to the bosonic case. Moreover, in the present supersymmetric extension we have a quadratic algebra, rather than an affine Lie algebra, due to the mixing between bosonic and fermionic fields since the purely fermionic sector displays a Lie algebra as well.Comment: 13 page

Long-term field metal extraction by pelargonium:phytoextraction efficiency in relation to plant maturity

The long length of periods required for effective soil remediation via phytoextraction constitutes a weak point that reduces its industrial use. However, these calculated periods are mainly based on short-term and/or hydroponic controlled experiments. Moreover, only a few studies concern more than one metal, although soils are scarcely polluted by only one element.In this scientific context, the phytoextraction of metals and metalloids (Pb, Cd, Zn, Cu,and As) by Pelargonium was measured after a long-term field experiment. Both bulk and rhizosphere soils were analyzed in order to determine the mechanisms involved in soil-root transfer. First, a strong increase in lead phytoextraction was observed with plant maturity, significantly reducing the length of the period required for remediation. Rhizosphere Pb, Zn, Cu, Cd, and As accumulation was observed (compared to bulk soil), indicating metal mobilization by the plant, perhaps in relation to root activity. Moreover, metal phytoextraction and translocation were found to be a function of the metals’ nature. These results, taken altogether, suggest that Pelargonium could be used as a multi-metal hyperaccumulator under multi-metal soil contamination conditions, and they also provide an interesting insight for improving field phytoextraction remediation in terms of the length of time required, promoting this biological technique

Social change and the family: Comparative perspectives from the west, China, and South Asia

This paper examines the influence of social and economic change on family structure and relationships: How do such economic and social transformations as industrialization, urbanization, demographic change, the expansion of education, and the long-term growth of income influence the family? We take a comparative and historical approach, reviewing the experiences of three major sociocultural regions: the West, China, and South Asia. Many of the changes that have occurred in family life have been remarkably similar in the three settings—the separation of the workplace from the home, increased training of children in nonfamilial institutions, the development of living arrangements outside the family household, increased access of children to financial and other productive resources, and increased participation by children in the selection of a mate. While the similarities of family change in diverse cultural settings are striking, specific aspects of change have varied across settings because of significant pre-existing differences in family structure, residential patterns of marriage, autonomy of children, and the role of marriage within kinship systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45661/1/11206_2005_Article_BF01124383.pd

Heterogeneous Superacidic Catalyst for Friedel-Crafts Alkylation

Long-chain alkylbenzenes are industrially synthesized precursors to commercial surfactants such as laundry detergent. The process of benzene alkylation currently utilizes homogeneous acidic catalysts (HF, AlCl3, etc.), which cause a multitude of problems such as production of toxic waste, hazards to workers, and corrosion of expensive industrial equipment. These problems can be avoided by the use of heterogeneous highly acidic catalysts. Solid catalysts do not corrode equipment and are relatively simple to remove from the post-reaction mixture. Phosphotungstic acid (PTA) supported on silica gel could be a possible catalyst due to its high acidity with an estimated pKa ≈ -13. However, it is soluble in many solvents and can be leached from silica gel during the process. The objective of this research is to obtain a superacidic stable heterogeneous catalyst containing covalently immobilized PTA, and evaluate its activity and stability in the alkylation of benzene by long-chain alkenes. The catalyst PTA/SiO2 was prepared via the sol-gel method by co-condensation of PTA with tetraethoxysilane in acidic media. Surfactant Pluronic P123 was used as a template to form porous structure. Then the catalyst was granulated to prevent caking of the powder during reaction. For granulation, the powder PTA/SiO2 was mixed with aluminum oxide (an inert adhesive agent) and pressured at 7 t to make tablets. The tablets were converted to granules of 1-2 mm diameter and calcined at 400 °C to remove moisture. FT-IR spectra confirmed the presence of PTA in the obtained material. Analysis by atomic absorption spectroscopy showed PTA contents of 0.027 mmol/g. The catalyst was mesoporous with BET surface area of 168 m2/g and mean particle size of 856 nm. The reaction of alkylation of benzene by octene-1 and decene-1 was carried out in a fixed bed flow reactor at 200-250 °C where mixtures of benzene and an alkene flowed through the catalyst with constant rate. Products were collected and analyzed on a GC chromatograph. The catalyst demonstrated good catalytic activity at temperatures above 200 °C. In all experiments mixtures of isomeric alkylbenzenes were obtained with 2-phenylalkanes as main products. Decreasing of flow rate and ratio alkene:benzene favored conversion of alkenes. Characterization of the catalyst after the reaction showed little changes in porosity and particle size. No leaching of PTA was observed. However, carbon deposits were found on the catalyst that requires regeneration before next use in catalysis