Modeling the fate and transport of agricultural pollutants and their environmental impact on surface and subsurface water quality

This dissertation describes the modeling efforts that devoted to understand the fate and transport processes of agricultural chemicals (pesticides and fertilizers) in aquatic environments and their impacts on surface and subsurface water quality. The main tasks were to develop and apply a two-dimensional (2D) reservoir toxic model for the fate and transport of toxic substances and to evaluate a field-scale non- point source model, the Erosion Productivity Impact Calculator (EPIC), as a tool for agricultural policy analysis;The 2D toxic model was developed using finite difference method to the laterally integrated hydrodynamics, mass transport, and transformation equations. It was applied to the Shasta Reservoir, California to investigate the effects of reservoir flow regime on the persistence and behavior of a spilled toxicant, methyl isothiocyanate (MITC). The results demonstrated that flow regime can substantially affect the persistence and transport of contaminant in the late stage of the spill. The model was also tested using field data, atrazine [2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine], collected from the Saylorville Reservoir, Iowa. Time-variable half-life of atrazine was estimated using a mass balance concept in the reservoir. The half-life varied monthly from 2 to 58 days depending upon environmental conditions (i.e., sunlight, temperature, and microorganisms). The 2D model accurately simulated the temporal and spatial variations of atrazine concentrations in the reservoir;The EPIC model was tested at two field sites in Iowa. It is concluded that standard curve number values should be adequately reduced to represent the impacts of residue cover on the partition of precipitation between surface runoff and infiltration. The results showed that EPIC is sensitive to variations in tillage and cropping practices and can be used to estimate environmental indicators in response to different management systems. However, clear discrepancies occurred between some model estimates and corresponding measured values, e.g., under-prediction of peak flows and nitrogen losses during storm events. Two potential sources of these errors include: (1) the lack of a preferential flow component, and (2) nitrogen transformation routines that may not adequately reflect all of the processes that occur in the field. EPIC showed a limited capability to reproduce tillage and crop rotation effects on crop yield

Acute urinary retention associated with selective serotonin reuptake inhibitors and ziprasidone [4]

postprin

Cooper-Pair Spin Current in a Strontium Ruthenate Heterostructure

It has been recognized that the condensation of spin-triplet Cooper pairs requires not only the broken gauge symmetry but also the spin ordering as well. One consequence of this is the possibility of the Cooper-pair spin current analogous to the magnon spin current in magnetic insulators, the analogy also extending to the existence of the Gilbert damping of the collective spin-triplet dynamics. The recently fabricated heterostructure of the thin film of the itinerant ferromagnet SrRuO3 on the bulk Sr2RuO4, the best-known candidate material for the spin-triplet superconductor, offers a promising platform for generating such spin current. We will show how such heterostructure allows us to not only realize the long-range spin valve but also electrically drive the collective spin mode of the spin-triplet order parameter. Our proposal represents both a new realization of the spin superfluidity and a transport signature of the spin-triplet superconductivity.Comment: 5 pages, 3 figure

Current-driven motion of magnetic topological defects in ferromagnetic superconductors

Recent years have seen a number of instances where magnetism and superconductivity intrinsically coexist. Our focus is on the case where spin-triplet superconductivity arises out of ferromagnetism, and we make a hydrodynamic analysis of the effect of a charge supercurrent on magnetic topological defects like domain walls and merons. We find that the emergent electromagnetic field that arises out of the superconducting order parameter provides a description for not only the physical quantities such as the local energy flux density and the interaction between current and defects but also the energy dissipation through magnetic dynamics of the Gilbert damping, which becomes more prominent compared to the normal state as superconductivity attenuates the energy dissipation through the charge sector. In particular, we reveal that the current-induced dynamics of domain walls and merons in the presence of the Gilbert damping give rise to the nonsingular $4\pi$ and $2\pi$ phase slips, respectively, revealing the intertwined dynamics of spin and charge degrees of freedom in ferromagnetic superconductors.Comment: 14 pages, 4 figure

Electronic Commerce Strategy for Small and Medium Enterprises: Case Studies of Korean Firms

Business firms are increasingly taking part in online business activities through internet as the size of the e-commerce market is rapidly growing in the recent years. Electronic commerce (EC) activities now become an essential part of the business strategy for survival as well as growth for both large enterprises and small- to medium-sized enterprises (SMEs). Previous studies on e-commerce mostly focused on the adoption of EC by business firms, and also have been carried out with the data from big enterprises. More often than not, the results obtained from the large business firms are used to provide the guidelines for small to medium-sized enterprises (SMEs). SMEs are, however, different from large business firms in many aspects, and need to be studied on their own. This paper extends the previous research on EC in two aspects. Firstly, we study the e-commerce issues in the area of implementation in relation to the business firm\u27s performance, beyond the adoption and diffusion of IT technology which has been the research issues in many previous research. Secondly, we focus on small and medium enterprises which comprise a large portion of national economy with significant influenc

Association of glutathione-S-transferase polymorphisms with atopic dermatitis risk in preschool age children

Background: Glutathione S-transferase (GST) enzymes are critical for detoxifying reactive oxygen species (ROS) and their products which have been implicated in the pathology of inflammatory diseases such as atopic dermatitis (AD). Methods: We investigated the effects of genetic polymorphisms of GST on the risk of AD in preschool age children. Biomarkers for oxidative stress were also evaluated with respect to GST genotype. Results: The GSTP1 Val105 allele was significantly associated with an increased risk of AD [odds ratio (OR)=1.62, p<0.05]. The combination of the GSTP1 Val105 allele and the GSTT1 null genotype further increased this risk by 2.3-fold (p<0.01). No association was observed for the GSTM1 null or GSTT1 null genotype alone. In children with AD, blood total antioxidant capacity was significantly less (p<0.001), while malondialdehyde was higher (p=0.12). Children with the GSTP1 Val105 allele had significantly lower concentrations of erythrocyte glutathione compared to GSTP1 Ile/Ile homozygotes (p=0.03). Conclusions: Our study suggests that the GSTP1 Val105 allele is an important determinant of susceptibility to AD in preschool age children and increased oxidative stress may play a role in the pathogenesis of AD. Clin Chem Lab Med 2009;47:1475–81.Peer Reviewe

The biological significance of non-enzymatic reaction of menadione with plasma thiols: enhancement of menadione-induced cytotoxicity to platelets by the presence of blood plasma

AbstractTo test the hypothesis that the non-enzymatic reaction of quinones with thiols in plasma can generate reactive oxygens (ROS), thereby leading to potentiated cellular toxicity, we have studied the effect of a representative quinone compound, menadione, on plasma isolated from rats. The experimental results are as follows: (1) menadione generated ROS via non-enzymatic reaction with protein thiols in plasma; (2) the presence of plasma increased menadione-induced cytotoxicity to platelets; (3) pretreatment of plasma with a thiol-depleting agent significantly suppressed menadione-induced ROS and cytotoxicity. These results suggest that the non-enzymatic reaction of menadione with plasma thiols could be an important process in quinone-induced cellular toxicity

Cabergoline reduces 3-methoxytyramine in a SDHC patient with metastatic paraganglioma and prolactinoma.

Summary: We observed a novel therapeutic response with cabergoline in a male patient with a dopamine-secreting head and neck paraganglioma (HNPGL), macroprolactinoma and germline succinate dehydrogenase C mutation (SDHC). The macroprolactinoma was treated with cabergoline which gave an excellent response. He was found to have raised plasma 3-methoxytyramine of 1014 pmol/L (NR: 0-180 pmol/L); but it was unclear if this was a drug-induced phenomenon from dopamine agonist (DA) therapy. Cabergoline was stopped for 4 weeks and the 3-methoxytyramine level increased significantly to 2185 pmol/L, suggesting a biochemical response of his HNPGL. Subsequently, Gallium-68 Dotatate PET and MRI (Gallium-68 Dotatate PET/MRI) demonstrated a second lesion in the sacrum. Both the HNPGL and metastatic sacral deposit received external beam radiotherapy with a good biochemical and radiological response. Conclusion: Our case report highlights the rare potential of germline SDHC mutations causing metastatic paraganglioma and concurrent pituitary tumours. Cabergoline treatment may lower elevated 3-methoxytyramine levels and, therefore, mask the biochemical evidence of metastatic disease but also may have therapeutic relevance in dopamine-secreting pheochromocytomas/paragangliomas (PPGLs). Learning points: Several neuroendocrine tumours (NETs) express dopamine D2 and D4 receptors. In this case report, cabergoline significantly reduced plasma 3-methoxytyramine level in a patient with functional HNPGL. Cabergoline might have therapeutic relevance in dopamine-secreting PPGLs. Paragangliomas associated with SDHC mutation classically present with asymptomatic non-functional HNPGL and have rare metastatic potential. The association of pheochromocytoma or paraganglioma and pituitary adenoma is now a well-described rare association (<1%), designated as the three P association. While the three P association is most commonly seen with succinate dehydrogenase B and D mutations, it has also been described in patients with SDHA and SDHC mutations. Cabergoline treatment may lower elevated 3-methoxytyramine levels and mask the biochemical evidence of metastatic disease. Regular functional imaging with Gallium-68 Dotatate PET/MRI provides better evidence of metastatic disease