Use-Exposure Relationships of Pesticides for Aquatic Risk Assessment

Field-scale environmental models have been widely used in aquatic exposure assessments of pesticides. Those models usually require a large set of input parameters and separate simulations for each pesticide in evaluation. In this study, a simple use-exposure relationship is developed based on regression analysis of stochastic simulation results generated from the Pesticide Root-Zone Model (PRZM). The developed mathematical relationship estimates edge-of-field peak concentrations of pesticides from aerobic soil metabolism half-life (AERO), organic carbon-normalized soil sorption coefficient (KOC), and application rate (RATE). In a case study of California crop scenarios, the relationships explained 90–95% of the variances in the peak concentrations of dissolved pesticides as predicted by PRZM simulations for a 30-year period. KOC was identified as the governing parameter in determining the relative magnitudes of pesticide exposures in a given crop scenario. The results of model application also indicated that the effects of chemical fate processes such as partitioning and degradation on pesticide exposure were similar among crop scenarios, while the cross-scenario variations were mainly associated with the landscape characteristics, such as organic carbon contents and curve numbers. With a minimum set of input data, the use-exposure relationships proposed in this study could be used in screening procedures for potential water quality impacts from the off-site movement of pesticides

Complexity and integrability in 4D bi-rational maps with two invariants

In this letter we give fourth-order autonomous recurrence relations with two invariants, whose degree growth is cubic or exponential. These examples contradict the common belief that maps with sufficiently many invariants can have at most quadratic growth. Cubic growth may reflect the existence of non-elliptic fibrations of invariants, whereas we conjecture that the exponentially growing cases lack the necessary conditions for the applicability of the discrete Liouville theorem.Comment: 16 pages, 2 figure

Co-expressed immune and metabolic genes in visceral and subcutaneous adipose tissue from severely obese individuals are associated with plasma HDL and glucose levels: a microarray study

<p>Abstract</p> <p>Background</p> <p>Excessive accumulation of body fat, in particular in the visceral fat depot, is a major risk factor to develop a variety of diseases such as type 2 diabetes. The mechanisms underlying the increased risk of obese individuals to develop co-morbid diseases are largely unclear.</p> <p>We aimed to identify genes expressed in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) that are related to blood parameters involved in obesity co-morbidity, such as plasma lipid and glucose levels, and to compare gene expression between the fat depots.</p> <p>Methods</p> <p>Whole-transcriptome SAT and VAT gene expression levels were determined in 75 individuals with a BMI >35 kg/m². Modules of co-expressed genes likely to be functionally related were identified and correlated with BMI, plasma levels of glucose, insulin, HbA_1c, triglycerides, non-esterified fatty acids, ALAT, ASAT, C-reactive protein, and LDL- and HDL cholesterol.</p> <p>Results</p> <p>Of the approximately 70 modules identified in SAT and VAT, three SAT modules were inversely associated with plasma HDL-cholesterol levels, and a fourth module was inversely associated with both plasma glucose and plasma triglyceride levels (p < 5.33 × 10^-5). These modules were markedly enriched in immune and metabolic genes. In VAT, one module was associated with both BMI and insulin, and another with plasma glucose (p < 4.64 × 10^-5). This module was also enriched in inflammatory genes and showed a marked overlap in gene content with the SAT modules related to HDL. Several genes differentially expressed in SAT and VAT were identified.</p> <p>Conclusions</p> <p>In obese subjects, groups of co-expressed genes were identified that correlated with lipid and glucose metabolism parameters; they were enriched with immune genes. A number of genes were identified of which the expression in SAT correlated with plasma HDL cholesterol, while their expression in VAT correlated with plasma glucose. This underlines both the singular importance of these genes for lipid and glucose metabolism and the specific roles of these two fat depots in this respect.</p

RESIDUES OF DETERGENT-DERIVED ORGANIC POLLUTANTS AND POLYCHLORINATED-BIPHENYLS IN SLUDGE-AMENDED SOIL

Linear alkylbenzene sulphonates (LAS) and nonylphenol polyethoxylates (NPnEO, n = 1- 20) are widely used anionic and nonionic synthetic aromatic surfactants. LAS is predomi nantly contained in laundry detergents, whereas NPnEO are mostly employed for industrial and institutional cleaning and various other industrial purposes. Commercial LAS and NPnEO are * Present address: United States Geological Survey, St. Paul, Minnesota, U.S.A. 460 characteristically complex mixtures of many isomers, homologs, and oligo mers. These aromatic surfactants are mainly used directly in water, dis charged into municipal and industrial wastewaters and subsequently released to sewage treatment plants (STP's). Unaltered LAS and nonylphenol (NP), the latter being a highly toxic de-ethox ylation intermediate of NPnEO biodeg radation [1], occur in digested sewage sludges at average levels of 5 and 1 g kg- 1 [w/w, dry weight (d.w.)], respec tively [2-4]

CATALYTIC EPOXIDATION OF CYCLOHEXENE WITH TERT-BUTYLHYDROPEROXIDE USING AN IMMOBILIZED MOLYBDENUM CATALYST

This work describes the synthesis of molybdenum complexes immobilized on a silica support and their performance in the epoxidation reaction of cyclohexene using tert-butylhydroperoxide (TBHP) as the oxidizing agent. The catalyst synthesis included solubilization of variable amounts of bis-oxomolybdenum (VI) acetylacetonate precursor in different solvents such as tetrahydrofuran (THF), ethanol, THF/water and ethanol/water mixtures and contact with the silica support. Characterization techniques demonstrated that the nature of the incorporated molybdenum species depends markedly on the solvent employed. If the solvent employed is an ethanol:water mixture, physical adsorption of the Mo-species onto the support surface occurs; however, when THF is used as the solvent (THF catalyst series), molybdenum is grafted on the silica surface via chemical bonding with the surface hydroxyl groups of silica. Specifically, these latter catalysts show similar performance to that of the homogeneous catalyst, although long-term experiments showed deactivation by leaching of the active phase.Peer reviewe