A Dynamic, Distributed Hydrologic Model for the Blue Earth River Watershed, Minnesota With Implications Regarding Land Use and Water Quality

The Blue Earth River (BER) watershed covers approximately one million acres of south-central Minnesota and northern Iowa. Modern farming practices have led to the loss of over 90 percent of the watershed\u27s original wetlands. Corresponding changes in runoff and stream flow have led to dramatically reduced water quality in the BER\u27s main stem following most precipitation events. The purpose of this research is to examine the relationships among precipitation, infiltration, base flow, and runoff in the Blue Earth River watershed basin. This study developed a calibrated numerical hydrologic model for BER watershed using the distributed flow model, Vflo™. The model was developed the seven major runoff events for the 2008 monitoring season (March – June). The research showed the importance of soil depth, hydrologic conductivity, and initial saturation in simulating peak flow volume. Where as overland roughness and channel roughness were found to attenuate the timing of the peak flow volume within the channel. The calibrated model is able to simulate flows where flows have not been observed in the field in both temporal v and spatial dimensions. The model is able to accurately depict the onset of the rising limb event and peak discharges to within ten percent of each event. Results of this research provide a better understanding of the hydrologic regime, prediction of flow rate, depth, and flow-weight total contaminant loads, of the BER watershed. These results therefore provide an objective means for improving best management practices within the Blue Earth River watershed

Spatial focalization of pheromone/MAPK signaling triggers commitment to cell-cell fusion.

Cell fusion is universal in eukaryotes for fertilization and development, but what signals this process is unknown. Here, we show in Schizosaccharomyces pombe that fusion does not require a dedicated signal but is triggered by spatial focalization of the same pheromone-GPCR (G-protein-coupled receptor)-MAPK signaling cascade that drives earlier mating events. Autocrine cells expressing the receptor for their own pheromone trigger fusion attempts independently of cell-cell contact by concentrating pheromone release at the fusion focus, a dynamic actin aster underlying the secretion of cell wall hydrolases. Pheromone receptor and MAPK cascade are similarly enriched at the fusion focus, concomitant with fusion commitment in wild-type mating pairs. This focalization promotes cell fusion by immobilizing the fusion focus, thus driving local cell wall dissolution. We propose that fusion commitment is imposed by a local increase in MAPK concentration at the fusion focus, driven by a positive feedback between fusion focus formation and focalization of pheromone release and perception

On a Low-Frequency and Contrast Stabilized Full-Wave Volume Integral Equation Solver for Lossy Media

In this article, we present a new regularized electric flux volume integral equation (D-VIE) for modeling high-contrast conductive dielectric objects in a broad frequency range. This new formulation is particularly suitable for modeling biological tissues at low frequencies, as it is required by brain epileptogenic area imaging, but also at higher ones, as it is required by several applications, including, but not limited to, deep brain stimulation (DBS). When modeling inhomogeneous objects with high complex permittivities at low frequencies, the traditional D-VIE is ill-conditioned and suffers from numerical instabilities that result in slower convergence and less accurate solutions. In this work, we address these shortcomings by leveraging a new set of volume quasi-Helmholtz projectors. Their scaling by the material permittivity matrix allows for the rebalancing of the equation when applied to inhomogeneous scatterers and, thereby, makes the proposed method accurate and stable even for high complex permittivity objects until arbitrarily low frequencies. Numerical results, canonical and realistic, corroborate the theory and confirm the stability and the accuracy of this new method both in the quasi-static regime and at higher frequencies

Exploration and stabilization of Ras1 mating zone: A mechanism with positive and negative feedbacks.

In mating fission yeast cells, sensing and response to extracellular pheromone concentrations occurs through an exploratory Cdc42 patch that stochastically samples the cell cortex before stabilizing towards a mating partner. Active Ras1 (Ras1-GTP), an upstream regulator of Cdc42, and Gap1, the GTPase-activating protein for Ras1, localize at the patch. We developed a reaction-diffusion model of Ras1 patch appearance and disappearance with a positive feedback by a Guanine nucleotide Exchange Factor (GEF) and Gap1 inhibition. The model is based on new estimates of Ras1-GDP, Ras1-GTP and Gap1 diffusion coefficients and rates of cytoplasmic exchange studied by FRAP. The model reproduces exploratory patch behavior and lack of Ras1 patch in cells lacking Gap1. Transition to a stable patch can occur by change of Gap1 rates constants or local increase of the positive feedback rate constants. The model predicts that the patch size and number of patches depend on the strength of positive and negative feedbacks. Measurements of Ras1 patch size and number in cells overexpressing the Ras1 GEF or Gap1 are consistent with the model

Cell cycle-dependent and independent mating blocks ensure fungal zygote survival and ploidy maintenance.

To ensure genome stability, sexually reproducing organisms require that mating brings together exactly 2 haploid gametes and that meiosis occurs only in diploid zygotes. In the fission yeast Schizosaccharomyces pombe, fertilization triggers the Mei3-Pat1-Mei2 signaling cascade, which represses subsequent mating and initiates meiosis. Here, we establish a degron system to specifically degrade proteins postfusion and demonstrate that mating blocks not only safeguard zygote ploidy but also prevent lysis caused by aberrant fusion attempts. Using long-term imaging and flow-cytometry approaches, we identify previously unrecognized and independent roles for Mei3 and Mei2 in zygotes. We show that Mei3 promotes premeiotic S-phase independently of Mei2 and that cell cycle progression is both necessary and sufficient to reduce zygotic mating behaviors. Mei2 not only imposes the meiotic program and promotes the meiotic cycle, but also blocks mating behaviors independently of Mei3 and cell cycle progression. Thus, we find that fungi preserve zygote ploidy and survival by at least 2 mechanisms where the zygotic fate imposed by Mei2 and the cell cycle reentry triggered by Mei3 synergize to prevent zygotic mating

A systematic screen for morphological abnormalities during fission yeast sexual reproduction identifies a mechanism of actin aster formation for cell fusion.

In non-motile fungi, sexual reproduction relies on strong morphogenetic changes in response to pheromone signaling. We report here on a systematic screen for morphological abnormalities of the mating process in fission yeast Schizosaccharomyces pombe. We derived a homothallic (self-fertile) collection of viable deletions, which, upon visual screening, revealed a plethora of phenotypes affecting all stages of the mating process, including cell polarization, cell fusion and sporulation. Cell fusion relies on the formation of the fusion focus, an aster-like F-actin structure that is marked by strong local accumulation of the myosin V Myo52, which concentrates secretion at the fusion site. A secondary screen for fusion-defective mutants identified the myosin V Myo51-associated coiled-coil proteins Rng8 and Rng9 as critical for the coalescence of the fusion focus. Indeed, rng8Δ and rng9Δ mutant cells exhibit multiple stable dots at the cell-cell contact site, instead of the single focus observed in wildtype. Rng8 and Rng9 accumulate on the fusion focus, dependent on Myo51 and tropomyosin Cdc8. A tropomyosin mutant allele, which compromises Rng8/9 localization but not actin binding, similarly leads to multiple stable dots instead of a single focus. By contrast, myo51 deletion does not strongly affect fusion focus coalescence. We propose that focusing of the actin filaments in the fusion aster primarily relies on Rng8/9-dependent cross-linking of tropomyosin-actin filaments

Intermediate scapolite: behavior at non-ambient conditions and unusual symmetry

The scapolite series of minerals represents a complex non-binary solid solution, which end members are: marialite [Na4Al3Si9O24Cl], meionite [Ca4Al6Si6O24CO3] and silvialite [Ca4Al6Si6O24SO4]. The members which composition falls on the marialite-meionite joint appears to be the most common in natural occurrences [1,2]. The members close to marialite on one side and to meionite on the other side, are usually reported to crystallize in the tetragonal I4/m space group, whereas intermediate scapolites are usually found in the primitive space group P42/n. In this study, we report a scapolite of intermediate composition (Na1.86Ca1.86K0.23Fe0.01)(Al4.36Si7.64)O24[Cl0.48(CO3)0.48(SO4)0.01], which, based on both X-ray and neutron single-crystal diffraction data, shows an anomalous I-centered lattice (Figure 1), possibly due to anti-phase domains too small to be detected by diffraction techniques. The behavior at non-ambient conditions of the same sample has been investigated at high-P (ambient-T) by single-crystal XRD at the former ID09 beamline of ESRF (Grenoble) and at high-T (ambient-P) by powder XRD at the MCX beamline of the Elettra synchrotron (Trieste), providing the following thermodynamic parameters: \uf020\uf062V0 = 0.0143(4) GPa-1 and \u3b1V0 = 1.87(4)\ub710-5 K-1, respectively, which confirm that compressibility and thermal expansivity increase, along the solid solution series, from meionite to marialite [3-6]. A P-induced phase transition towards a triclinic polymorph has been observed at 9.87 GPa at ambient-T. An in situ single-crystal XRD experiment at combined high P and T (using a resistive-heated DAC), performed at the P02.2 beamline of the Petra-III synchrotron (Hamburg), allowed to detect the occurrence of the same phase transition at 10.51 GPa at 650 \ub0C

Infertility and hypergonadotropic hypogonadism as first evidence of hereditary apolipoprotein A-I amyloidosis

Purpose: We report that primary infertility and hypergonadotropic hypogonadism in young patients may be caused by testicular amyloidosis and it is associated with the presence of a mutation in the apoA-I gene, resulting in the replacement of proline for leucine at residue 75 of the protein. Materials and Methods: Ten patients presenting with infertility, gynecomastia, decreased libido, erectile dysfunction or a family history of amyloidosis underwent clinical evaluation, hormone assays, semen analysis, ultrasonographic investigation of the testicles, testicular biopsy and DNA sequencing of the apoA-I gene. Results: All patients showed azoospermia and 9 had increased testicular volume. Massive amyloid deposition was observed in all testicular biopsies and the apoA-I mutation of replacement of proline for leucine at residue 75 of the protein was noted. Five patients showed hypergonadotropic hypogonadism and 5 had normal testosterone values with high gonadotropin levels. Conclusions: Nonobstructive azoospermia and macro-orchidism with or without hypogonadism may be caused by hereditary apoA-I amyloidosis in young patients. Testicular amyloidosis can be the first manifestation of this systemic disease. Specific staining for amyloid deposits and genetic analysis of apoA-I mutations are recommended in young, infertile patients with macro-orchidism. Finally, surveillance in asymptomatic mutation carriers is suggested to evaluate the opportunity to implement sperm retrieval and start androgen replacement therapy when necessary