Assessment of a high-order finite difference upwind scheme for the simulation of convection-diffusion problems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Historic of therapeutic efficacy of albendazol sulphoxide administered in different routes, dosages and treatment schemes, against Taenia saginata in cattle experimentally infected

The present study aimed to notify the history of albendazole sulphoxide (ALB-SO) and albendazole (ALBZ) efficacy against Taenia saginata cysticercus (Cysticercus bovis) parasitizing experimentally infected bovines. A total of 11 efficacy trials were performed between the years of 2002 and 2010. In order to perform these trials, animals were individually inoculated with 2 x 104 eggs of T. saginata in each study's day zero (DO). For every trial, a positive control group (untreated infected animals) and a negative control group (animals that were neither infected nor treated) were used. ALB-SO or ALB were administered in the different dosages, in different days of treatments. In a last study with this formulation, this active principle was administered orally, mixed with the mineral supplement, on the 60th DPI, in a dosage of 30 mg/kg. In all trials, on the 100th DPI, all animals were euthanized and submitted to the sequenced slicing of 26 anatomical segments (fragments of approximately five millimeters) for the survey of T. saginata cysticercus. With the obtained results it is possible to verify that in the first trials, conducted in 2002, ALB-SO reached, independently of dosage and treatment scheme, efficacies superior to 98% (arithmetic means). The trials conducted in 2005 (2.5 mg/kg on the 30th, 60th, and 90th DPI) obtained values of efficacy all inferior to 60%. In 2008, the trials with 2.5 and 7.7 mg/kg demonstrated efficacy values inferior to 40%, for both dosages and treatment schemes (30th/60th/90th DPI and 60th DPI). When this formulation was administered orally on the dosage of 30 mg/kg on the 60th DPI, the efficacy against T. saginata cysticercus reached 88.28%. ALB administered orally showed efficacy values of 0.0%, 29.88% and 28.64% in the dosages of 5, 10 and 15 mg/kg, respectively, using the treatment schemes described above for each dosage. Based on the results of these trials, conducted in an eight year period (2002-2010) using the sequenced slicing method for evaluating the efficacy of the aforementioned formulations against T. saginata cysticercus, it is possible to observe that, amongst the few molecules used in the chemotherapic treatment against T. saginata larvae, ALB-SO, administered in varied routes, dosages and treatment schemes, the studies conducted in 2008, 2009, and 2010, have a low therapeutic efficacy against C bovis in Brazil, while ALBZ had insignificant efficacy values against T. saginata larvae parasitizing experimentally infected bovines. However, future studies using molecular biology will be necessary to assess whether the difference on the efficacy of the ALB-SO can be related to strain or another specific factor. (C) 2013 Elsevier Inc. All rights reserved.

Effects of Haematobia irritans infestation on weight gain of Nelore calves assessed with different antiparasitic treatment schemes

Effects of Haematobia irritans infestation on weight gain of 18 to 20 months old non-castrated Nelore calves, were investigated, under field conditions, using different antiparasitic treatments. Sixty animals were divided in three groups, with 20 bovines each: T01 (untreated control); T02 (treated with Cypermethrin 15 g + Chlorpyriphos 25 g + Citronellal 1 g, as a whole body spray, on days 0,30, 60, 90 and 120 post-treatment); and T03 (treated on day zero with an ear tag impregnated with Diazinon 6 g on the left ear). Counts of H. irritans were conducted on day 30, 60, 90, 120 and 150 post-treatment (DPT). On the same experimental dates, animals were individually weighed, seeking to evaluate the effects of parasitism on the development of animals in each group. From this study it is concluded that T03 had significantly higher efficacy (>90%, till 90 DPT), based on H. irritans fly counts, compared to T02 which showed little or no effect. At the specific conditions of the present study, an average of approximately 90 flies (mean difference of flycounts between groups T01 and T03) was associated with a difference of 20 kg/animal in 150 days. (C) 2014 Elsevier B.V. All rights reserved.

Maximum principle preserving high order schemes for convection-dominated diffusion equations

The maximum principle is an important property of solutions to PDE. Correspondingly, it's of great interest for people to design a high order numerical scheme solving PDE with this property maintained. In this thesis, our particular interest is solving convection-dominated diffusion equation. We first review a nonconventional maximum principle preserving(MPP) high order finite volume(FV) WENO scheme, and then propose a new parametrized MPP high order finite difference(FD) WENO framework, which is generalized from the one solving hyperbolic conservation laws. A formal analysis is presented to show that a third order finite difference scheme with this parametrized MPP flux limiters maintains the third order accuracy without extra CFL constraint when the low order monotone flux is chosen appropriately. Numerical tests in both one and two dimensional cases are performed on the simulation of the incompressible Navier-Stokes equations in vorticity stream-function formulation and several other problems to show the effectiveness of the proposed method.

Detailed analysis of a conservative difference approximation for the time fractional diffusion equation

Diffusion equations that use time fractional derivatives are attractive because they describe a wealth of problems involving non-Markovian Random walks. The time fractional diffusion equation (TFDE) is obtained from the standard diffusion equation by replacing the first-order time derivative with a fractional derivative of order α ∈ (0, 1). Developing numerical methods for solving fractional partial differential equations is a new research field and the theoretical analysis of the numerical methods associated with them is not fully developed. In this paper an explicit conservative difference approximation (ECDA) for TFDE is proposed. We give a detailed analysis for this ECDA and generate discrete models of random walk suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation. The stability and convergence of the ECDA for TFDE in a bounded domain are discussed. Finally, some numerical examples are presented to show the application of the present technique.

Implicit difference approximation for the time fractional diffusion equation

In this paper, we consider a time fractional diffusion equation on a finite domain. The equation is obtained from the standard diffusion equation by replacing the first-order time derivative by a fractional derivative (of order $0<\alpha<1$ ). We propose a computationally effective implicit difference approximation to solve the time fractional diffusion equation. Stability and convergence of the method are discussed. We prove that the implicit difference approximation (IDA) is unconditionally stable, and the IDA is convergent with $O(\tau+h^2)$, where $\tau$ and $h$ are time and space steps, respectively. Some numerical examples are presented to show the application of the present technique.