Integration of D-dimensional 2-factor spaces cosmological models by reducing to the generalized Emden-Fowler equation

The D-dimensional cosmological model on the manifold $M = R \times M_{1} \times M_{2}$ describing the evolution of 2 Einsteinian factor spaces, $M_1$ and $M_2$, in the presence of multicomponent perfect fluid source is considered. The barotropic equation of state for mass-energy densities and the pressures of the components is assumed in each space. When the number of the non Ricci-flat factor spaces and the number of the perfect fluid components are both equal to 2, the Einstein equations for the model are reduced to the generalized Emden-Fowler (second-order ordinary differential) equation, which has been recently investigated by Zaitsev and Polyanin within discrete-group analysis. Using the integrable classes of this equation one generates the integrable cosmological models. The corresponding metrics are presented. The method is demonstrated for the special model with Ricci-flat spaces $M_1,M_2$ and the 2-component perfect fluid source.Comment: LaTeX file, no figure

Toda chains with type A_m Lie algebra for multidimensional m-component perfect fluid cosmology

We consider a D-dimensional cosmological model describing an evolution of Ricci-flat factor spaces, M_1,...M_n (n > 2), in the presence of an m-component perfect fluid source (n > m > 1). We find characteristic vectors, related to the matter constants in the barotropic equations of state for fluid components of all factor spaces. We show that, in the case where we can interpret these vectors as the root vectors of a Lie algebra of Cartan type A_m=sl(m+1,C), the model reduces to the classical open m-body Toda chain. Using an elegant technique by Anderson (J. Math. Phys. 37 (1996) 1349) for solving this system, we integrate the Einstein equations for the model and present the metric in a Kasner-like form.Comment: LaTeX, 2 ps figure

Some exact non-vacuum Bianchi VI0 and VII0 instantons

We report some new exact instantons in general relativity. These solutions are K\"ahler and fall into the symmetry classes of Bianchi types VI0 and VII0, with matter content of a stiff fluid. The qualitative behaviour of the solutions is presented, and we compare it to the known results of the corresponding self-dual Bianchi solutions. We also give axisymmetric Bianchi VII0 solutions with an electromagnetic field.Comment: latex, 15 pages with 3 eps figure

Hyperextended Scalar-Tensor Gravity

We study a general Scalar-Tensor Theory with an arbitrary coupling funtion $\omega (\phi )$ but also an arbitrary dependence of the ``gravitational constant'' $G(\phi )$ in the cases in which either one of them, or both, do not admit an analytical inverse, as in the hyperextended inflationary scenario. We present the full set of field equations and study their cosmological behavior. We show that different scalar-tensor theories can be grouped in classes with the same solution for the scalar field.Comment: latex file, To appear in Physical Review

Multidimensional integrable vacuum cosmology with two curvatures

The vacuum cosmological model on the manifold $R \times M_1 \times \ldots \times M_n$ describing the evolution of $n$ Einstein spaces of non-zero curvatures is considered. For $n = 2$ the Einstein equations are reduced to the Abel (ordinary differential) equation and solved, when $(N_1 =$dim $M_1, N_2 =$ dim$M_2) = (6,3), (5,5), (8,2)$. The Kasner-like behaviour of the solutions near the singularity $t_s \to +0$ is considered ($t_s$ is synchronous time). The exceptional ("Milne-type") solutions are obtained for arbitrary $n$. For $n=2$ these solutions are attractors for other ones, when $t_s \to + \infty$. For dim $M = 10, 11$ and $3 \leq n \leq 5$ certain two-parametric families of solutions are obtained from $n=2$ ones using "curvature-splitting" trick. In the case $n=2$, $(N_1, N_2)= (6,3)$ a family of non-singular solutions with the topology $R^7 \times M_2$ is found.Comment: 21 pages, LaTex. 5 figures are available upon request (hard copy). Submitted to Classical and Quantum Gravit

Avaliação da estratégia de tratamento parcial do rebanho no controle da mosca-dos-chifres.

A mosca-dos-chifres (MDC) destaca-se dentre os principais ectoparasitos que acometem a pecuária de corte nacional. Seu controle é realizado quase exclusivamente com produtos inseticidas, o que tem levado a sérios problemas de resíduos e resistência. Alternativas não químicas e redução do uso de inseticidas tornam-se essenciais ao controle sustentável deste parasito. O presente estudo avaliou a eficiência do tratamento parcial do rebanho como estratégia de controle da MDC. Quatro experimentos foram conduzidos, utilizando produtos de diferentes classes inseticidas: lactona macrocíclica (ivermectina), fenilpirazol (fipronil), piretróide cipermetrina) e organofosforado+piretróide (clorpirifós+cipermetrina), em formulações pour-on. Em cada experimento, 200 vacas Nelore foram distribuídas em quatro grupos, para avaliação do tratamento de 20%, 50% e 100% do rebanho, além de um grupo não tratado. Contagens periódicas da MDC foram realizadas nos dias 0, 3, 7, 14, 21 e 28 em todos os animais. A eficácia dos produtos nos grupos tratados integralmente foi superior a 90% (exceto pela cipermetrina) ao final da 1ª semana pós-tratamento, sendo de modo geral superior a dos tratados parcialmente nas duas semanas iniciais. Nos grupos tratados parcialmente, a eficácia foi geralmente maior nos grupos com maior frequência de animais tratados. Independente da classe inseticida aplicada e do percentual de animais tratados (20% ou 50%), o tratamento parcial do rebanho apresentou três características principais: a) rápida e acentuada redução das infestações em todo o rebanho, b) menores níveis de redução das infestações e c) menor período de proteção, em relação ao tratamento de todo o rebanho. Apesar da redução no uso de inseticidas e do menor custo, a viabilidade do tratamento parcial do rebanho, como estratégia de controle da MDC, se limita a situações onde um menor nível e período de eficácia sejam aceitáveis, caso contrário, tratamentos adicionais podem ser necessários, comprometendo as vantagens da estratégia. As implicações do tratamento parcial do rebanho no desenvolvimento e manejo da resistência a inseticidas devem ser avaliadas. The horn fly stands out among the main ectoparasites that affect national beef cattle. This livestock pest is controlled almost exclusively by insecticide products, which has led to serious residue and resistance issues. Non-chemical alternatives and reduction of insecticide use are essential for a sustainable control of this parasite. This study evaluated the efficiency of partial herd treatment as a strategy for controlling horn flies. Four experiments were conducted using products from different insecticide classes: macrocyclic lactone (ivermectin) phenylpyrazole (fipronil), pyrethroid (cypermethrin), and an organophosphate-pyrethroid mixture (chlorpyrifos + cypermethrin), in pour-on formulations. In each experiment, 200 Nelore cows were distributed in four groups for evaluation of the treatment of 20, 50, and 100% of the herd, besides an untreated group. Periodic fly counts were performed on days 0, 3, 7, 14, 21, and 28 in all animals. Product efficacy in the full-treated herd exceeded 90% (except for cypermethrin) at the end of the 1st week after treatment, being mostly higher than in partially treated groups in the first two weeks. In the groups partially treated, efficacy was generally higher in the groups with the largest frequency of treated animals. Regardless of the insecticide class and the percentage of treated animals (20% or 50%), the partial treatment of the herd showed three main features: a) fast and marked reduction in infestations throughout the herd, b) lower reduction of horn fly infestations, and c) shorter period of protection, when compared to the full herd treatment. Despite reduction in insecticide use and lower costs, viability of partial herd treatment as a strategy for controlling the horn fly is limited to situations where a lower level and protection period are acceptable; otherwise, the need for additional treatments tends to compromise the advantages of the strategy. The implications of partial herd treatment in the development and management of insecticide resistance should be evaluated.bitstream/item/129471/1/BP125.pd

Aumento das infestações pela mosca-dos-chifres em bovinos nelore no Pantanal Sul-Mato-Grossense.

Após sua introdução no norte do país na década de 70, a mosca-dos-chifres (Haematobia irritans) chegou à região Centro-Oeste no início dos anos 90. No Pantanal, sua presença foi registrada pela primeira vez em 1991 (Barros, 1992), demandando conhecimento sobre sua ecologia e controle.bitstream/CPAP-2009-09/56780/1/CT80.pdfFormato eletrônico

Early-career researchers at the 6th European Conference on Permafrost

The 6th European Conference on Permafrost (EUCOP), hosted by the International Permafrost Association (IPA), brought together researchers from all over the world in Puigcerdà, Spain, on 18–22 June 2023. The conference covered relevant aspects of permafrost research, from analysing and modelling the highly dynamic permafrost environment to the assessment of climatic and societal impacts. Approaches and methods were discussed during 3 intensive days of oral presentations and poster sessions, topped with local field trips across the eastern Pyrenees. For the recipients of funding by the German Society for Polar Research (DGP), EUCOP 2023 served as a platform for them to present their research to the international permafrost community, gain insights into current research trends, and establish valuable connections within the field.</p

On the Reaction Diffusion Master Equation in the Microscopic Limit

Stochastic modeling of reaction-diffusion kinetics has emerged as a powerful theoretical tool in the study of biochemical reaction networks. Two frequently employed models are the particle-tracking Smoluchowski framework and the on-lattice Reaction-Diffusion Master Equation (RDME) framework. As the mesh size goes from coarse to fine, the RDME initially becomes more accurate. However, recent developments have shown that it will become increasingly inaccurate compared to the Smoluchowski model as the lattice spacing becomes very fine. In this paper we give a new, general and simple argument for why the RDME breaks down. Our analysis reveals a hard limit on the voxel size for which no local RDME can agree with the Smoluchowski model