Dimensional transition in rotating turbulence

In this work we investigate, by means of direct numerical simulations, how rotation affects the bi-dimensionalization of a turbulent flow. We study a thin layer of fluid, forced by a two-dimensional forcing, within the framework of the "split cascade" in which the injected energy flows both to small scales (generating the direct cascade) and to large scale (to form the inverse cascade). It is shown that rotation reinforces the inverse cascade at the expense of the direct one, thus promoting bi-dimensionalization of the flow. This is achieved by a suppression of the enstrophy production at large scales. Nonetheless, we find that, in the range of rotation rates investigated, increasing the the vertical scale causes a reduction of the flux of the inverse cascade. Our results suggest that, even in rotating flows, the inverse cascade may eventually disappear when the vertical scale is sufficiently large with respect to the forcing scale

Transient inverse energy cascade in free surface turbulence

We study the statistics of free-surface turbulence at large Reynolds numbers produced by direct numerical simulations in a fluid layer at different thickness with fixed characteristic forcing scale. We observe the production of a transient inverse cascade, with a duration which depends on the thickness of the layer, followed by a transition to three-dimensional turbulence initially produced close to the bottom, no-slip boundary. By switching off the forcing, we study the decaying turbulent regime and we find that it cannot be described by an exponential law. Our results show that boundary conditions play a fundamental role in the nature of turbulence produced in thin layers and give limits on the conditions to produce a two-dimensional phenomenology.Comment: 9 pages, 8 figure

Recent Developments in Individual Taxation

The article focuses on developments affecting individual taxation in the U.S. It says that the Small Business and Work Opportunity Tax Act of 2007 raised the age requirements for Sec. 1(g) effective for tax years after May 2007. It notes that final regulations on the child and dependent care credit clarify that expenses for a child in kindergarten or higher grades do not qualify for the credit. Recommendations in the report Reducing the Federal Tax Gap: A Report on Improving Voluntary Compliance are cited, such as enhancement of taxpayer service

Two-dimensional elastic turbulence

We investigate the effect of polymer additives on a two-dimensional Kolmogorov flow at very low Reynolds numbers by direct numerical simulations of the Oldroyd-B viscoelastic model. We find that above the elastic instability threshold the flow develops the elastic turbulence regime recently observed in experiments. We observe that both the turbulent drag and the Lyapunov exponent increase with Weissenberg, indicating the presence of a disordered, turbulent-like mixing flow. The energy spectrum develops a power-law scaling range with an exponent close to the experimental and theoretical expectations

Comment on "A centrosome-independent role for gamma-TuRC proteins in the spindle assembly checkpoint"

Müller et al. (Reports, 27 October 2006, p. 654) showed that inhibition of the γ-tubulin ring complex (γ-TuRC) activates the spindle assembly checkpoint (SAC), which led them to suggest that γ-TuRC proteins play molecular roles in SAC activation. Because γ-TuRC inhibition leads to pleiotropic spindle defects, which are well known to activate kinetochore-derived checkpoint signaling, we believe that this conclusion is premature

Reproductive Versus Floral Isolation Among Morphologically Similar Serapias L. Species (Orchidaceae)

Flowers of the Mediterranean orchid genus Serapias L. form small, dark tubes that vary among taxa in diameter and depth. Visiting insects use the floral tube as shelter and act as pollinators if they touch the sticky viscidium at the rear of the tube and remove the pollinarium. It has been assumed that floral tube size and shape limit access to the flowers and thus may act as a barrier to gene flow between different Serapias species. Here we investigated floral characters and nuclear microsatellite markers in populations belonging to three morphologically similar Serapias species to test whether these species show evidence for floral or reproductive isolation. We found strong overlap of floral traits between two species, suggesting that floral isolation is nonexistent between them. Microsatellite markers applied to the same populations were highly polymorphic and revealed clear genetic differentiation among all three species. These results suggest that reproductive isolation exists, despite the lack of floral isolation between two of the species. In contrast to morphological characters, diagnostic microsatellite alleles were found for all Serapias species. The microsatellite markers could thus provide a useful tool to identify Serapias species and further investigate evolutionary relationships in this fascinating orchid lineag

Survey archaeology and regional analysis. A conceptual model on the selection of past dynamics during the Holocene in Wadi Abiod, Aures, Eastern Algeria

This paper inserted within a geoarchaeological study, provides a model for the investigation and the support of past dynamics of a mountainous landscape in the Aures region (Algeria) during the Holocene. It introduces the first analysis based on the detailed mapping of morphological features of the study area in relation with a typomorphology theoretical model that was confronted with data from archaeological research. Our results suggest that the choice of the prehistorical movement processes has been driven by the outcrop of some deposits and the presence of specific landforms, such as high and low-relief areas. This approach was applied to a sector with controversial archaeological evidences (the valley of Wadi Abiod), where geological and morphological analyses support archaeological research in the reconstruction of the ancient pathways during the Holocene. This integrated approach can help archaeologists to understand and then discover ancient courses crossing complex in impervious landscapes such as the intramountain Lands

Lagrangian Statistics and Temporal Intermittency in a Shell Model of Turbulence

We study the statistics of single particle Lagrangian velocity in a shell model of turbulence. We show that the small scale velocity fluctuations are intermittent, with scaling exponents connected to the Eulerian structure function scaling exponents. The observed reduced scaling range is interpreted as a manifestation of the intermediate dissipative range, as it disappears in a Gaussian model of turbulence.Comment: 4 pages, 5 figure

Individual Taxation Report

Recent developments affecting taxation of individuals, including legislation, regulations, and IRS guidance, are presented in Code section order