Creation of an isolated turbulent blob fed by vortex rings

Turbulence is hard to control. A plethora of experimental methods have been developed to generate this ephemeral state of matter, leading to fundamental insights into its statistical and structural features as well as its onset at ever higher Reynolds numbers. In all cases however, the central role played by the material boundaries of the apparatus poses a challenge on understanding what the turbulence has been fed, and how it would freely evolve. Here, we build and control a confined state of turbulence using only elemental building blocks: vortex rings. We create a stationary and isolated blob of turbulence ($Re_\lambda$=50-300) in a quiescent environment, initiated and sustained solely by vortex rings. We assemble a full picture of its three-dimensional structure, onset, energy budget and tunability. Crucially, the incoming vortex rings can be endowed with conserved quantities, such as helicity, which can then be controllably transferred to the turbulent state. Our `one eddy at a time' approach paves the way for sculpting turbulent flows much as a state of matter, `printing' it at a targeted position, localizing it, and ultimately harnessing it. Our work paves the way to gaining a complete picture of this ephemeral state of flow.Comment: 68 pages, 43 figures, manuscript and supplementary informatio

Cytostatic Factor Proteins Are Present in Male Meiotic Cells and β-Nerve Growth Factor Increases Mos Levels in Rat Late Spermatocytes

Background: In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF regulates the second meiotic division by blocking secondary spermatocytes in metaphase (metaphase II), and thereby lowers round spermatid formation. In vertebrates, mature oocytes are arrested at metaphase II until fertilization, because of the presence of cytostatic factor (CSF) in their cytoplasm. By analogy, we hypothesized the presence of CSF in male germ cells. Methodology/Principal Findings: We show here, that Mos, Emi2, cyclin E and Cdk2, the four proteins of CSF, and their respective mRNAs, are present in male rat meiotic cells; this was assessed by using Western blotting, immunocytochemistry and reverse transcriptase PCR. We measured the relative cellular levels of Mos, Emi2, Cyclin E and Cdk2 in the meiotic cells by flow cytometry and found that the four proteins increased throughout the first meiotic prophase, reaching their highest levels in middle to late pachytene spermatocytes, then decreased following the meiotic divisions. In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF increased the number of metaphases II, while enhancing Mos and Emi2 levels in middle to late pachytene spermatocytes, pachytene spermatocytes in division and secondary spermatocytes. Conclusion/Significance: Our results suggest that CSF is not restricted to the oocyte. In addition, they reinforce the view that NGF, by enhancing Mos in late spermatocytes, is one of the intra-testicular factors which adjusts the number of round spermatids that can be supported by Sertoli cells

Vespinae of Yunnan.

10 p. ; 26 cm. "April 19, 2011."In recent years, five new species of Vespinae have been described from Yunnan Province, China. A thorough assessment of these taxa, including study of color differences and compilation of measurements of specimens from six entomological collections, shows that the new taxa are merely variants of existing, nominal species. Thus, all five are synonymized here, as follows: Vespa hekouensis Dong and Wang, and Vespa maguanensis Dong = Vespa analis Fabricius; Vespula yulongensis Dong and Wang = Vespula flaviceps (Smith); Vespula nujiangensis Dong and Wang = Vespula orbata (du Buysson); and Vespula gongshanensis Dong = Vespula rufa (Linnaeus), all new synonymy. The synonymies bring the current number of vespine species recognized worldwide to 67

National records of 3000 European bee and hoverfly species: A contribution to pollinator conservation

Pollinators play a crucial role in ecosystems globally, ensuring the seed production of most flowering plants. They are threatened by global changes and knowledge of their distribution at the national and continental levels is needed to implement efficient conservation actions, but this knowledge is still fragmented and/or difficult to access. As a step forward, we provide an updated list of around 3000 European bee and hoverfly species, reflecting their current distributional status at the national level (in the form of present, absent, regionally extinct, possibly extinct or non-native). This work was attainable by incorporating both published and unpublished data, as well as knowledge from a large set of taxonomists and ecologists in both groups. After providing the first National species lists for bees and hoverflies for many countries, we examine the current distributional patterns of these species and designate the countries with highest levels of species richness. We also show that many species are recorded in a single European country, highlighting the importance of articulating European and national conservation strategies. Finally, we discuss how the data provided here can be combined with future trait and Red List data to implement research that will further advance pollinator conservation

Biology of the southern giant hornet, Vespa soror: nest architecture, morphological differences among castes, and the genetic structure of colonies.

Giant hornets in the genus Vespa are apex predators that are known throughout Asia for their exceptional size and devastating group attacks on social insect colonies. The giant hornets include Vespa mandarinia, a well-studied and widespread temperate species, and Vespa soror, a poorly known sister species that is limited to subtropical and tropical regions of Southeast Asia. Both species have been recently documented on the west coast of North America, raising urgent questions about their potential impact in novel ecosystems. To better understand the biology of V. soror, we describe the nest architecture, caste morphology, and genetic structure of colonies collected in Vietnam. Comparisons of colony metrics between the two giant hornet species suggest important differences that are likely a consequence of the relatively warmer climate in which V. soror occurs. Like V. mandarinia, V. soror constructs large, underground nests of partially enveloped horizontal combs. However, compared to temperate V. mandarinia colonies, the longer nesting period of subtropical V. soror colonies likely resulted in relatively larger colony sizes and nests by the end of their annual cycle. Vespa soror workers and gynes were larger than males, distinguishable based on wing shape and body size (total length and measures of six body parts), and equivalent in size to female castes of V. mandarinia. We genotyped colony members from three mature nests, which revealed that males and females were offspring of singly mated queens. Two colonies were monogynous, but one colony was comprised of two unrelated matrilines. Polygyny has not been observed for V. mandarinia, but is more common in tropical hornet species. Our study sheds light on essential details about the biology of an understudied species of giant hornet, whose populous colonies and long nesting period suggest the potential for substantial ecological impact wherever they occur

KINETICS OF PRECIPITATION AND DISSOLUTION IN MODEL FeCV AND FeCVNb ALLOY, AND A MICROALLOYED ULTRA HIGH STRENGTH SPRING STEEL

Conference on New Developments on Metallurgy and Applications of High Strength Steels, Buenos Aires, ARGENTINA, MAY 26-28, 2008International audiencePrecipitation kinetics were studied in two model alloys and an industrial spring steel. A combination of selected techniques was used to follow the evolution of precipitates volume fraction and size distribution during austenitisation (FeVC and FeNbVC). This was then modelled, first using a simple model based on the classical nucleation theory and diffusion controlled growth and second with the help of a more complex software developped by one of the authors (MatCalc). A good agreement is obtained when comparing calculations and experimental results obtained on the model alloys. This is less so for the industrial alloy, where dissolution kinetics appear to be faster than expected

Influence de quelques paramètres opératoires sur l'oxydation du phénol par le peroxyde d'hydrogène en présence d'une zéolithe Fe-ZSM5

Wastewater originating in the chemical process industries contain high concentrations of organics that must be treated before discharge. Phenol is one of the most important of these pollutants because it is toxic, even at low concentrations. Recently, hydrogen peroxide treatment has emerged as a viable alternative oxidation technique for treatment. It does not form any harmful or intrusive by-products and it is an ecologically clean and non-toxic chemical. However, the methods for treatment of wastewater with hydrogen peroxide are based mostly on homogeneous catalysis by metal ions inducing additional pollution. From this, it was anticipated that the use of heterogeneous catalysis would be a good alternative, thus opening up a new field of investigation. Previous studies, based on screening tests, evidenced the catalytic activity of an MFI zeolite Fe-ZSM-5 for phenol elimination by H2O2. The oxidation tests are carried out in a batch mode, using a stirred glass reactor. The influence of pH, temperature and H2O2 stoichiometric ratio on the phenol oxidation rate with Fe-ZSM-5 is studied. The temperature is below 100°C in order to avoid pressurization of the treatment reactor. Using a H2O2 stoichiometric ratio equal to 1.5 avoids accumulation of any quinone-like by-products. Under these conditions, the catalytic system H2O2 / Fe-ZSM-5 allows a total elimination of phenol and a significant TOC removal (50%) without leaching-off more than 1 ppm of Fe (III) ions. At the end of the reaction period, only carboxylic acids (maleic, fumaric, oxalic, acetic, accumulate. These latter should not be considered as a drawback of this process. The chemical oxidation process would be used only as a detoxification step and such compounds could be treated with a biological process, in a second step

Turbulence through sustained vortex ring collisions

This paper is associated with a video winner of a 2022 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2022.GFM.V0008