Review of strategies for modelling the environmental fate of pesticides discharged into riverine systems

International audiencePesticides are often produced and stored in large quantities near rivers posing a potential hazard for the aquatic environment. Accidental incidents such as storage facility fires are of major concern as significant amounts of pesticide chemicals can enter the nearby riverine system possibly causing considerable environmental damage (for example the Sandoz fire in Basel in 1986 which polluted the Rhine river). In order to assess the potential impact on the riverine environment of such an incident it is necessary to identify the controlling environmental fate processes that affect pesticides in freshwater systems. A strategy for mathematically modelling these processes to predict the fate of the chemical contaminants then needs to be established. This paper discuss and reviews the major environmental controlling fate processes of selected herbicides in freshwater. Strategies on how to mathematical model the environmental fate of pesticides in rivers are also considered

Systematic Inclusion of High-Order Multi-Spin Correlations for the Spin-121\over2 XXZXXZ Models

We apply the microscopic coupled-cluster method (CCM) to the spin-$1\over2$ $XXZ$ models on both the one-dimensional chain and the two-dimensional square lattice. Based on a systematic approximation scheme of the CCM developed by us previously, we carry out high-order {\it ab initio} calculations using computer-algebraic techniques. The ground-state properties of the models are obtained with high accuracy as functions of the anisotropy parameter. Furthermore, our CCM analysis enables us to study their quantum critical behavior in a systematic and unbiased manner.Comment: (to appear in PRL). 4 pages, ReVTeX, two figures available upon request. UMIST Preprint MA-000-000

Coupled-Cluster Approach to Electron Correlations in the Two-Dimensional Hubbard Model

We have studied electron correlations in the doped two-dimensional (2D) Hubbard model by using the coupled-cluster method (CCM) to investigate whether or not the method can be applied to correct the independent particle approximations actually used in ab-initio band calculations. The double excitation version of the CCM, implemented using the approximate coupled pair (ACP) method, account for most of the correlation energies of the 2D Hubbard model in the weak ($U/t \simeq 1$) and the intermediate $U/t$ regions ($U/t \simeq 4$). The error is always less than 1% there. The ACP approximation gets less accurate for large $U/t$ ($U/t \simeq 8$) and/or near half-filling. Further incorporation of electron correlation effects is necessary in this region. The accuracy does not depend on the system size and the gap between the lowest unoccupied level and the highest occupied level due to the finite size effect. Hence, the CCM may be favorably applied to ab-initio band calculations on metals as well as semiconductors and insulators.Comment: RevTeX3.0, 4 pages, 4 figure

Food protein-induced enterocolitis syndrome – a review of the literature with focus on clinical management

Food protein-induced enterocolitis syndrome (FPIES) is a potentially severe presentation of non-IgE-mediated gastrointestinal food allergy (non-IgE-GI-FA) with heterogeneous clinical manifestations. Acute FPIES is typically characterized by profuse vomiting and lethargy, occurring classically 1-4 hours after ingestion of the offending food. When continuously exposed to the incriminated food, a chronic form has been described with persistent vomiting, diarrhea, and/or failure to thrive. Although affecting mainly infants, FPIES has also been described in adults. Although FPIES is actually one of the most actively studied non-IgE-GI-FAs, epidemiologic data are lacking, and estimation of the prevalence is based on a limited number of prospective studies. The exact pathomechanisms of FPIES remain not well defined, but recent data suggest involvement of neutrophils and mast cells, in addition to T cells. There is a wide range of food allergens that can cause FPIES with some geographical variations. The most frequently incriminated foods are cow milk, soy, and grains in Europe and USA. Furthermore, FPIES can be induced by foods usually considered as hypoallergenic, such as chicken, potatoes or rice. The diagnosis relies currently on typical clinical manifestations, resolving after the elimination of the offending food from the infant's/child's diet and/or an oral food challenge (OFC). The prognosis is usually favorable, with the vast majority of the case resolving before 5 years of age. Usually, assessment of tolerance acquisition by OFC is proposed every 12-18 months. Of note, a switch to an IgE-mediated FA is possible and has been suggested to be associated with a more severe phenotype. Avoiding the offending food requires education of the family of the affected child. A multidisciplinary approach including ideally allergists, gastroenterologists, dieticians, specialized nurses, and caregivers is often useful to optimize the management of these patients, that might be difficult

Update of Estimated Agricultural Benefits Attributable to Drainage and Flood Control in Willacy County, Texas

This study presents an economic analysis of agricultural benefits attributable to a proposed drainage project which includes on farm systems, laterals (ditches) and major canals designed to lower the groundwater table and provide an outlet for floodwater from agricultural land in Willacy county, Texas as provided by the Raymondville Drain. There are benefits to the urban communities that are not included in this update

C4-C5 fused pyrazol-3-amines: when the degree of unsaturation and electronic characteristics of the fused ring controls regioselectivity in Ullmann and acylation reactions

Pyrazol-3-amine is a scaffold present in a large number of compounds with a wide range of biological activities and, in many cases, the heterocycle is C4-C5 fused to a second ring. Among the different reactions used for the decoration of the pyrazole ring, Ullmann and acylation have been widely applied. However, there is some confusion in the literature regarding the regioselectivity of such reactions (substitution at N1 or N2 of the pyrazole ring) and no predictive rule has been so far established. As a part of our work on 3-amino-pyrazolo[3,4-b]pyridones 13, we have studied the regioselectivity of such reactions in different C4-C5 fused pyrazol-3-amines. As a rule of thumb, the Ullmann and acylation reactions take place, predominantly, at the NH and non-protonated nitrogen atom of the pyrazole ring respectively, of the most stable initial tautomer (1H- or 2H-pyrazole), which can be easily predicted by using DFT calculations

Tectonic and climatic controls on rift escarpments: Erosion and flexural rebound of the Dhofar passive margin (Gulf of Aden, Oman)

International audienceWe investigate the respective roles of climatic parameters and the flexural rigidity of the lithosphere in the erosion history and behavior of two adjacent rift escarpments along the northern coast of the Gulf of Aden, in Oman. At this 25 Myr old passive margin, we define a type 1 scarp, which is high, sharp-crested and has retreated 25-30 km inland from its master fault, and a type 2 scarp, which exhibits a more rounded profile, lower relief, and still coincides with its mapped normal fault trace. Since about 15 Ma, the margin has been seasonally affected by monsoon precipitation but with contrasting effects at the type 1 and type 2 escarpments depending on the position of the Intertropical Convergence Zone in the geologic past: during peak monsoon conditions, both scarps experienced heavy rainfall and runoff, whereas during monsoon-starved conditions (such as today), the type 2 scarp experienced a foggy, moist climate while the type 1 scarp remained much drier. In order to assess the relative effects of climate and flexural parameters on the present-day morphology of the Dhofar margin, we present onedimensional numerical models of erosion and flexure along two profiles representative of the type 1 and type 2 scarps. Unlike most surface process models previously published, where present-day topography is the only criterion by which to evaluate the quality of model outputs, model behavior here is additionally constrained by independent estimates of denudation provided by geological cross sections, well-defined fault traces, and other stratigraphic markers. The best fitting models indicate that the type 1 escarpment formed under relatively arid climatic conditions and was affected by significant erosion, recession and flexural uplift due to a low (7 km) effective elastic thickness. In contrast, the morphology of the type 2 fault scarp was smoothed by a more humid climate, but a high effective elastic thickness ( 15 km) prevented it from uplifting or receding. In addition, we show that the sedimentary load acting at the foot of the escarpments exerts significant influence on their morphological evolution, though this parameter is often neglected in other scarp evolution models

An Unequivocal Synthesis of 2-Aryl Substituted 3-Amino-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-ones

The reaction between pyridones (1) and substituted hydrazines 4 can afford two different regioisomeric pyrazolo[3,4-b]pyridin - 6-ones 2 and 3 depending on the initial substitution of the methoxy group and the direction of the cyclization. In the case of phenylhydrazine 4 (R3 = Ph), we have clearly shown that the treatment of pyridones 1a-d with 4 (R3 = Ph) in MeOH at temperatures below 1408C yields, independently of the nature and position of the substituents present in the pyridone ring, the open intermediates 7a-d. When the reaction is carried at 1408C under microwave irradiation, the corresponding 2-aryl substituted pyrazolo[3,4-b]pyridines 3a-d are always formed. We have experimentally determined, using DSC techniques, the activation energies of the two steps involved in the formation of 3: a) substitution of the methoxy group present in pyridones 1 with phenylhydrazine 4 (R3 = Ph) to afford intermediates 7 and b) cyclization of intermediates 7 to yield pyrazolopyridines 3. The results obtained, 15 and 42 kcal·mol 1 respectively, are in agreement with the experimental findings