A Parameterization of the Microphysical Processes Forming Many Types of Winter Precipitation

Several types of precipitation, such as freezing rain, ice pellets, and wet snow, are commonly observed during winter storms. The objective of this study is to better understand the formation of these winter precipitation types. To address this issue, detailed melting and refreezing of precipitation was added onto an existing bulk microphysics scheme. These modifications allow the formation of mixed-phase particles and these particles in turn lead to, or affect, the formation of many of the other types of precipitation. The precipitation type characteristics, such as the mass content, liquid fraction, and threshold diameters formed during a storm over St John’s, Newfoundland, Canada, are studied and compared with observations. Many of these features were reproduced by the model. Sensitivity experiments with the model were carried out to examine the dependence of precipitation characteristics in this event on thresholds of particle evolution in the new parameterization

On l-th roots and division by l

We give a characterization of the codomain $[\ell]E(k)$ of the multiplication-by-$\ell$ map $[\ell]$ in the case of elliptic curves over a field $k$ of characteristic $\ne 2,3$ with $\ell$-torsion $E[\ell]=\langle W_1,W_2 \rangle$ fully defined over $k$, for primes $\ell$ different from the characteristic. We show that a point $Q\in E(k)$ lies in $[\ell]E(k)$ if and only if $h_{W_1}(-Q)$ and $h_{W_2}(-Q)$ are $\ell$-powers of $k$, where $h_{W_1}$ and $h_{W_2}$ are functions on $E$ with divisor ${\rm div}(h_{W_i})=\ell W_i- \ell P_{\infty}$. Our characterization leads to an effective procedure to find pre-images of $[\ell]$ by solving an order $\ell$ system of linear equations and computing a polynomial gcd.Comment: 18 pages no figure

Junctions of one-dimensional quantum wires - correlation effects in transport

We investigate transport of spinless fermions through a single site dot junction of M one-dimensional quantum wires. The semi-infinite wires are described by a tight-binding model. Each wire consists of two parts: the non-interacting leads and a region of finite extent in which the fermions interact via a nearest-neighbor interaction. The functional renormalization group method is used to determine the flow of the linear conductance as a function of a low-energy cutoff for a wide range of parameters. Several fixed points are identified and their stability is analyzed. We determine the scaling exponents governing the low-energy physics close to the fixed points. Some of our results can already be derived using the non-self-consistent Hartree-Fock approximation.Comment: version accepted for publication in Phys. Rev. B, 14 pages, 7 figures include

Home for a White Season : Measuring precipitation in the Saint John River Valley

Canada First Research Excellence FundNon-Peer ReviewedPersonal account of a scientist's engagement with government agencies and local citizens to produce new understanding of rain and snow patterns in New Brunswick's Saint John River valley

Erratum to: Spatial spin-up of fine scales in a regional climate model simulation driven by low-resolution boundary condition

The capture of the public servant in a criminal investigation is subject to special rules and different to those for the capture of individuals, since the imprisonment of an official can affect continuity, speed and efficiency of the civil service, an equally important constitutional value. Therefore, as a rule capturing the public servant must be preceded by a request for suspensión by the prosecution, and to proceed without suspension, the prosecutor in his providence should motivate the reasons and arguments why not affects the normal functioning of public administration. The lack of motivation for this essential aspect, affords a fact that becomes appropriate procedural habeas corpus as an effective mechanism guarantees of personal freedom. Similarly appropriate habeas corpus when catching public server ordered by a prosecutor without functional competence to advance research, by setting a path made by organic defect.La captura del servidor público investigado en un proceso penal está sujeta a reglas especiales y diversas a las previstas para la captura de los particulares, por cuanto la privación de la libertad de un funcionario puede afectar la continuidad, celeridad y eficacia de la función pública, como un valor constitucional igualmente relevante. Por tal motivo, como regla general,la captura del servidor público debe estar precedida de la solicitud de suspensión por parte de la Fiscalía General de la Nación y para que proceda sin suspensión previa, el fiscal debe consignar en su providencia las razones y argumentos por los cuales no se afecta el normal funcionamiento de la administración pública. La ausencia de motivación de este aspecto esencial constituye una vía de hecho procedimental que torna procedente la acción de habeas corpus, como mecanismo efectivo de garantía de la libertad personal. De igual manera, procede el habeas corpus cuando la captura del servidor público la ordena un fiscal sin competencia funcional para adelantar la investigación, por configuración de una vía de hecho por defecto orgánico

Spatial spin-up of fine scales in a regional climate model simulation driven by low-resolution boundary conditions

In regional climate modelling, it is well known that domains should be neither too large to avoid a large departure from the driving data, nor too small to provide a sufficient distance from the lateral inflow boundary to allow the full development of the small-scale (SS) features permitted by the finer resolution. Although most practitioners of dynamical downscaling are well aware that the jump of resolution between the lateral boundary condition (LBC) driving data and the nested regional climate model affects the simulated climate, this issue has not been fully investigated. In principle, as the jump of resolution becomes larger, the region of interest in the limited-area domain should be located further away from the lateral inflow boundary to allow the full development of the SS features. A careless choice of domain might result in a suboptimal use of the full finer resolution potential to develop fine-scale features. To address this issue, regional climate model (RCM) simulations using various resolution driving data are compared following the perfect-prognostic Big-Brother protocol. Several experiments were carried out to evaluate the width of the spin-up region (i.e. the distance between the lateral inflow boundary and the domain of interest required for the full development of SS transient eddies) as a function of the RCM and LBC resolutions, as well as the resolution jump. The spin-up distance turns out to be a function of the LBC resolution only, independent of the RCM resolution. When varying the RCM resolution for a given resolution jump, it is found that the spin-up distance corresponds to a fixed number of RCM grid points that is a function of resolution jump only. These findings can serve a useful purpose to guide the choice of domain and RCM configuration for an optimal development of the small scales allowed by the increased resolution of the nested model

The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part II: Modeling Particle Trajectories

The use of windshields to reduce the impact of wind on snow measurements is common. This paper investigates the catching performance of shielded and unshielded gauges using numerical simulations. In Part II, the role of the windshield and gauge aerodynamics, as well as the varying flow field due to the turbulence generated by the shield–gauge configuration, in reducing the catch efficiency is investigated. This builds on the computational fluid dynamics results obtained in Part I, where the airflow patterns in the proximity of an unshielded and single Alter shielded Geonor T-200B gauge are obtained using both time-independent [Reynolds-averaged Navier–Stokes (RANS)] and time-dependent [large-eddy simulation (LES)] approaches. A Lagrangian trajectory model is used to track different types of snowflakes (wet and dry snow) and to assess the variation of the resulting gauge catching performance with the wind speed. The collection efficiency obtained with the LES approach is generally lower than the one obtained with the RANS approach. This is because of the impact of the LES-resolved turbulence above the gauge orifice rim. The comparison between the collection efficiency values obtained in case of shielded and unshielded gauge validates the choice of installing a single Alter shield in a windy environment. However, time-dependent simulations show that the propagating turbulent structures produced by the aerodynamic response of the upwind single Alter blades have an impact on the collection efficiency. Comparison with field observations provides the validation background for the model results

Oral colistin sulfate in pigs: pharmacokinetics and effect on fecal Escherichia coli excretion of weaned pigs challenged with Escherichia coli F4 (K88)

Colistin sulfate (CS), a polymyxin antibiotic, is used in Canada for the treatment of post-weaning diarrhea in pigs as an alternative to neomycin. The aim of the present study was to evaluate some pharmcokinetics parameters of CS and its effect on the evolution of the intestinal Escherichia coli population in pigs challenged with enterotoxigenic E. coli (ETEC): F4

Impacts of colistin sulfate on fecal Escherichia coli resistance and on growth performance of piglets in a post-weaning diarrhea model

Colistin sulfate (CS) is used in Canada for the treatment of post weaning diarrhea (PWD), to overcome conventional therapeutic antibiotics failures. The aim of the present study was to determine the effect of a conventional oral regimen of CS for the treatment of PWD, on the development of E. coli CS resistance and to evaluate the effect of ETEC: F4 infection on CS intestinal absorption. A total of 48 pigs were used, challenge was carried out by oral administration of 109CFU of a hemolytic ETEC: F4 strain resistant to nalidixic acid. CS was administered at a dose of 50.000 UI/kg twice a day for 5 days. Feces were examined clinically and bacteriologically before and after challenge to evaluate presence of diarrhea and E. coli fecal excretion. ETEC: F4 virulence factors were monitored and CS plasma concentrations were quantified by an HPLC-MS/MS. From one until six days after CS administration, a significant reduction in the fecal excretion of ETEC: F4, total E. coli, ETEC: F4 virulence factors and in diarrhea scores was observed in the challenged treated group compared to the challenged untreated group (p\u3c0.0001). No significant difference in growth performances was observed in treated compared to non-treated pigs (p\u3e0.71). A significant selection pressure on E. coli total population was observed following CS treatment (p\u3c0.0001). Challenge with ETEC: F4 resulted in an increase in intestinal absorption of CS. Our study is the first to demonstrate in an experimental model of PWD, that CS at a dose of 50,000 IU/kg is effective in reducing fecal excretion of E. coli. However, this regimen was associated with a selection pressure on E. coli CS resistance, and did not improve growth performance in challenged pigs. Thus, the use of this antibiotic in pig should be revised