Effects of multiscale geometry on the large-scale coherent structures of an axisymmetric turbulent jet

In this study, the effect of multiscale geometry on the near-field structure of an axisymmetric turbulent jet is examined at a global Reynolds number of ReG=10,000. With the aid of tomographic particle image velocimetry, the suppression of the coherent structures due to this fractal geometry is analysed and the changes to the near-field vorticity are evaluated. This particular geometry leads to the breakup of the azimuthal vortex rings present for round jets and to the formation of radial and streamwise opposite-signed patches of vorticity. The latter are found to be responsible for the axis switching of the jet, a phenomenon observed for some noncircular jets where the major axis shrinks and the minor one expands in the near field, effectively switching the two axes of the jet. This was the first time, to the knowledge of the authors, that axis switching has been observed for a jet where the coherent structures have been suppressed. Following the significant differences found in the near field, the far field is examined. There, the integral lengthscale of the large scale eddies Lur and the size of the jet evaluated in terms of the jet half-width r1/2 are found to evolve in a similar fashion, whilst the ratio Lur/r1/2 is found to be higher for the fractal jet than for the round jet, for which the near-field structures have not been suppressed

Invariants of the velocity gradient tensor in a spatially developing inhomogeneous turbulent flow

Tomographic PIV experiments were performed in the near-fiel d of the turbulent flow past a square cylinder. A classical Reynolds decomposition was p erformed on the resulting velocity fields into a time invariant mean flow and a fluctuatin g velocity field. This fluc- tuating velocity field was then further decomposed into cohe rent and residual/stochastic fluctuations. The statistical distributions of the second a nd third invariants of the ve- locity gradient tensor were then computed at various stream wise locations, along the centre line of the flow and within the shear layers. These inva riants were calculated from both the Reynolds-decomposed fluctuating velocity fields an d the coherent and stochas- tic fluctuating velocity fields. The range of spatial locatio ns probed incorporates regions of contrasting flow physics, including a mean recirculation region and separated shear layers, both upstream and downstream of the location of peak turbulence intensity along the centre line. These different flow physics are also reflecte d in the velocity gradients themselves with different topologies, as characterised by t he statistical distributions of the constituent enstrophy and strain-rate invariants, for the three different fluctuating velocity fields. Despite these differing flow physics the ubiq uitous self-similar “tear drop”- shaped joint probability density function between the seco nd and third invariants of the velocity gradient tensor is observed along the centre line a nd shear layer when calcu- lated from both the Reynolds decomposed and the stochastic v elocity fluctuations. These “tear drop”-shaped joint probability density functions ar e not, however, observed when calculated from the coherent velocity fluctuations. This “t ear drop” shape is classically associated to the statistical distribution of the velocity gradient tensor invariants in fully developed turbulent flows in which there are no coherent dyna mics present, and hence spectral peaks at low wavenumbers. The results presented in this manuscript, however, show that such “tear drops” also exist in spatially developi ng inhomogeneous turbulent flows. This suggests that the “tear drop” shape may not just be a universal feature of fully developed turbulence but of turbulent flows in general

Pseudospectral discretization of nonlinear delay equations: new prospects for numerical bifurcation analysis

We apply the pseudospectral discretization approach to nonlinear delay models described by delay differential equations, renewal equations or systems of coupled renewal equations and delay differential equations. The aim is to derive ordinary differential equations and to investigate the stability and bifurcation of equilibria of the original model by available software packages for continuation and bifurcation for ordinary differential equations. Theoretical and numerical results confirm the effectiveness and the versatility of the approach, opening a new perspective for the bifurcation analysis of delay equations, in particular coupled renewal and delay differential equations

The Sublethal Effects of Insecticides in Insects

Studies related to the effect of insecticides on insect pests and nontarget organisms, such as natural enemies, are traditionally accessed by the estimative of lethal effects, through mortality data. Due to the limitations of the traditional methods, recent studies in the past three decades are assessing the sublethal effects of insecticides upon several important biological traits of insect pests and natural enemies. Besides mortality, the sublethal dose/concentrations of an insecticide can affect insect biology, physiology, behavior and demographic parameters. In this chapter, many sublethal effects of insecticides were addressed for several chemical groups, such as botanical insecticides, carbamate, diamide, insect growth regulators, neonicotinoid, organochlorides, organophosphates, pyrethroid and others. An accurate assessment of these effects is crucial to acquire knowledge on the overall insecticide efficacy in the management of pest insect populations, as well as on their selectivity toward nontarget organisms

Biological Performance of Tetranychus bastosi (Acari: Tetranychidae) on different hosts.

Tetranychus bastosi Tuttle, Baker & Sales (Acari: Tetranychidae) has been observed in more than 36 host species and it is considered a potential pest mite for several crops, however its occurrence is still restricted to Brazil. The present study determined the biological, reproductive parameters and host preference of T. bastosi in three plant species: Morus rubra L. (Moraceae); Ipomoea batatas L. (Convolvulaceae); and Psidium guajava L. (Myrtaceae). The incubation period of T. bastosi eggs was longer in M. rubra (5.9 days), followed by I. batatas and P. guajava (4.0 days for both). The longest larval period was observed in P. guajava (5.7 days). The longest durations of the protonymph and deutonymph stages were recorded in P. guajava (3 days) and M. rubra (2.3 days). However, T. bastosi could not complete its life cicle on P. guajava. The longest period from egg to adult of T. bastosi was observed in I. batatas (30 days). The highest longevity of T. bastosi was observed in the hosts I. batatas and M. rubra (39.8 and 30.2 days, respectively). The longest average duration of a generation (T) was observed on M. rubra 21.3 days. Nevertheless, for the intrinsic capacity for population increase (rm) and finite rate of increase (λ) no differences were observed on I. batatas and M. rubra. In this sense, T. bastosi presents a high biological performance in I. batatas and M. rubra, however P. guajava was not considered a suitable host for the red spider mite

Influência de cultivares de feijão-caupi no crescimento populacional de Callosobruchus maculatus (FABR., 1775) (Coleoptera: Chrysomelidae: Bruchinae).

Na região Nordeste do Brasil a cultura do feijão-caupi tem grande importância socioeconômica, exercendo função no suprimento das necessidades nutricionais e fixação de mão-de-obra. Dentre as pragas que atacam os grãos de feijão-caupi durante o armazenamento, destaca-se Callosobruchus maculatus, por provocar perdas quantitativas e qualitativas. O controle deste inseto é feito principalmente com inseticidas sintéticos, no entanto, com os problemas decorrentes da intoxicação de aplicadores e seleção de insetos resistentes, formas alternativas de controle têm sido buscadas. Neste contexto, o objetivo deste trabalho foi avaliar a influência de cultivares de caupi no crescimento populacional de C. maculatus. Para realização do experimento utilizou-se cultivares de caupi provenientes da Embrapa Semiárido: BRS Guariba, BRS Maratoã, BRS Milênio, BRS Paraguaçu e BRS Pujante, além da testemunha Sempre Verde. Realizou-se teste sem chance de escolha, avaliando-se número de insetos emergidos e a taxa instantânea de crescimento populacional. A cultivar BRS Pujante apresentou os melhores resultados em relação aos parâmetros biológicos testados, apresentando possivelmente resistência do tipo antibiose.CONAC 2012. Disponível em: http://www.conac2012.org/resumos/pdf/241a.pdf. Acesso em: 08 ago. 2013

The Sodium and Potassium Content of the Most Commonly Available Street Foods in Tajikistan and Kyrgyzstan in the Context of the FEEDCities Project

This cross-sectional study is aimed at assessing sodium (Na) and potassium (K) content and the molar Na:K ratios of the most commonly available ready-to-eat street foods in Tajikistan and Kyrgyzstan. Four different samples of each of these foods were collected and 62 food categories were evaluated through bromatological analysis. Flame photometry was used to quantify sodium and potassium concentrations. The results show that home-made foods can be important sources of sodium. In particular, main dishes and sandwiches, respectively, contain more than 1400 and nearly 1000 mg Na in an average serving and provide approximately 70% and 50% of the maximum daily recommended values. Wide ranges of sodium content were found between individual samples of the same home-made food collected from different vending sites from both countries. In industrial foods, sodium contents ranged from 1 to 1511 mg/serving in Tajikistan, and from 19 to 658 mg/serving in Kyrgyzstan. Most Na:K ratios exceeded the recommended level of 1.0 and the highest ratios were found in home-made snacks (21.2) from Tajikistan and industrial beverages (16.4) from Kyrgyzstan. These findings not only improve data on the nutritional composition of foods in these countries, but may also serve as baseline information for future policies and interventions.The project is funded by the World Health Organization Europe (WHO registration 2015/591370-0) and, in particular, work on FEEDCities project is funded by a voluntary contribution of the Ministry of Health of the Russian Federation. The authors would like to thank the staff from WHO Country Offices in Tajikistan and Kyrgyzstan as well as local authorities. The authors would also like to thank Andreia Lemos and Eulália Mendes for carrying out laboratory analysis

Electron-phonon interaction in C70

The matrix elements of the deformation potential of C$_{70}$ are calculated by means of a simple, yet accurate solution of the electron-phonon coupling problem in fullerenes, based on a parametrization of the ground state electronic density of the system in terms of $sp^{2+x}$ hybridized orbitals. The value of the calculated dimensionless total electron-phonon coupling constant is $\lambda\approx0.1$, an order of magnitude smaller than in C$_{60}$, consistent with the lack of a superconducting phase transition in C$_{70}$A$_3$ fullerite, and in overall agreement with measurements of the broadening of Raman peaks in C$_{70}$K$_4$. We also calculate the photoemission cross section of C$_{70}^-$, which is found to display less structure than that associated with C$_{60}^-$, in overall agreement with the experimental findings.Comment: To be published in Phys. Rev.

Long-term data for endemic frog genera reveal potential conservation crisis in the Bale Mountains, Ethiopia

Populations of many frogs have declined alarmingly in recent years, placing nearly one third of the \u3e 6,000 species under threat of extinction. Declines have been attributed largely to habitat loss, environmental degradation and/or infectious diseases such as chytridiomycosis. Many frogs undergo dramatic natural population fluctuations such that long-term data are required to determine population trends without undue influence of stochastic factors. We present long-term quantitative data (individuals encountered per person hour of searching) for four monotypic frog genera endemic to an Afromontane region of exceptional importance but growing conservation concern: one endemic to the Ethiopian highlands (Spinophrynoides osgoodi) and three endemic to the Bale Mountains (Altiphrynoides malcolmi, Balebreviceps hillmani, Ericabatrachus baleensis), collected during 15 field trips to the Bale Mountains between 1971 and 2009. Only a single confirmed sighting of S. osgoodi has been made since 1995. The other three species have also declined, at least locally. E. baleensis appears to have been extirpated at its type locality and at the same site B. hillmani has declined. These declines are in association with substantial habitat degradation caused by a growing human population. Chytrid fungus has been found on several frog species in Bale, although no dead or moribund frogs have been encountered. These results expose an urgent need for more amphibian surveys in the Bale Mountains. Additionally, we argue that detrimental human exploitation must be halted immediately in at least some parts of the Harenna Forest if a conservation crisis is to be averted