Dissipative Effects on Inertial-Range Statistics at High Reynolds numbers

Using the unique capabilities of the Variable Density Turbulence Tunnel at the Max Planck Institute for Dynamics and Self-Organization, G\"{o}ttingen, we report experimental result on classical grid turbulence that uncover fine, yet important details of the structure functions in the inertial range. This was made possible by measuring extremely long time series of up to $10^{10}$ samples of the turbulent fluctuating velocity, which corresponds to $\mathcal{O}\left(10^5\right)$ large eddy turnover times. These classical grid measurements were conducted in a well-controlled environment at a wide range of high Reynolds numbers from $R_\lambda=110$ up to $R_\lambda=1600$, using both traditional hot-wire probes as well as NSTAP probes developed at Princeton University. We found that deviations from ideal scaling are anchored to the small scales and that dissipation influences the inertial-range statistics at scales larger than the near-dissipation range.Comment: 6 pages, 5 figure

Non-Kolmogorov probability models and modified Bell's inequality

We analyse the proof of Bell's inequality and demonstrate that this inequality is related to one particular model of probability theory, namely Kolmogorov measure-theoretical axiomatics, 1933. We found a (numerical) statistical correction to Bell's inequality. Such an additional term in the right hand side of Bell's inequality can be considered as a probability invariant of a quantum state. This is a measure of nonreproducibility of hidden variables in different runs of experiments. Experiments to verify Bell's inequality can be considered as just experiments to estimate this constant. It seems that Bell's inequality could not be used as a crucial reason to deny local realism. We consider deterministic as well as stochastic hidden variables models

Control of long-range correlations in turbulence

The character of turbulence depends on where it develops. Turbulence near boundaries, for instance, is different than in a free stream. To elucidate the differences between flows, it is instructive to vary the structure of turbulence systematically, but there are few ways of stirring turbulence that make this possible. In other words, an experiment typically examines either a boundary layer or a free stream, say, and the structure of the turbulence is fixed by the geometry of the experiment. We introduce a new active grid with many more degrees of freedom than previous active grids. The additional degrees of freedom make it possible to control various properties of the turbulence. We show how long-range correlations in the turbulent velocity fluctuations can be shaped by changing the way the active grid moves. Specifically, we show how not only the correlation length but also the detailed shape of the correlation function depends on the correlations imposed in the motions of the grid. Until now, large-scale structure had not been adjustable in experiments. This new capability makes possible new systematic investigations into turbulence dissipation and dispersion, for example, and perhaps in flows that mimic features of boundary layers, free streams, and flows of intermediate character.Comment: This paper has been accepted to Experiments in Fluids. 25 pages, 10 figure

Scientific results of the Bryotrop expedition to Zaire and Rwanda : 3., photosynthetic gas exchange of bryophytes from different forest types in eastern Central Africa.

During the BRYOTROP-Expedition to Zaire and Rwanda bryophytes were collected from a rainforest habitat at 800 m a.s.l. and from bamboo forest and tree-heath environments between 2200 and 3200 m. The microclimates influencing the mosses are different at the altitudinally separated locations. Conditions are rather constant with 24 °C, 100 % rel. hum. and PAR below 100 μmol photons m-2 sec-1 at the lowland station, rather versatile in the mountains with six times higher daily sums of PAR, temperatures between 10 and 25 °C and relative humidities between 60 and 1oo %. In the bamboo forest epiphytic mosses dry out during the day to less than 70 % of their water content, but regain saturation from the vapor-saturated air during night. Bryophyte photosynthesis and respiration were studied by Warburg manometry with moisture saturated samples. Temperature curves of gas exchange peaked between 22 and 30 °C. Optima of the lowland species were somewhat higher than those from samples collected at the mountain sites. Habitat separation of characteristics of photosynthesis was more pronounced with respect to light responses. Saturation gas exchange rates were reached by all species still below 400 μmol photons m-2 sec-1. But the slopes of the curves in the low-light range were distinctly steeper, and the light compensation points smaller in the lowland than in the highland species (compensation points of the former: 3 - 12 μmol photons m-2 sec-1, of the latter: 8 - 20 μmol photons m-2 sec-1). It is emphasized that bryophytes in the rainforest understory experience extremely high ambient C02 concentrations near the floor. This, their low light requirements for photosynthesis, and the permanently optimal temperature and humidity conditions for maximal carbon gain enable them to live successfully, but with less biomass development in this dark and damp environment. By contrast, bryophytes from the bamboo forest and tree-heath environments can utilize light conditions combined with variable temperatures and humidities similarly as species from extratropical vegetation types

Variable Density Turbulence Tunnel Facility

The Variable Density Turbulence Tunnel (VDTT) at the Max Planck Institute for Dynamics and Self-Organization in G\"ottingen, Germany produces very high turbulence levels at moderate flow velocities, low power consumption and adjustable kinematic viscosity between $10^{-4} m^2/s$ and $10^{-7} m^2/s$. The Reynolds number can be varied by changing the pressure or flow rate of the gas or by using different non-flammable gases including air. The highest kinematic viscosities, and hence lowest Reynolds numbers, are reached with air or nitrogen at 0.1 bar. To reach the highest Reynolds numbers the tunnel is pressurized to 15 bar with the dense gas sulfur hexafluoride (SF$_6$). Turbulence is generated at the upstream ends of two measurement sections with grids, and the evolution of this turbulence is observed as it moves down the length of the sections. We describe the instrumentation presently in operation, which consists of the tunnel itself, classical grid turbulence generators, and state-of-the-art nano-fabricated hot-wire anemometers provided by Princeton University [Vallikivi et al. (2011) Exp. Fluids 51, 1521]. We report measurements of the characteristic scales of the flow and of turbulent spectra up to Taylor Reynolds number $R_\lambda \approx 1600$, higher than any other grid-turbulence experiment. We also describe instrumentation under development, which includes an active grid and a Lagrangian particle tracking system that moves down the length of the tunnel with the mean flow. In this configuration, the properties of the turbulence are adjustable and its structure is resolvable up to $R_\lambda \approx 8000$.Comment: 45 pages, 31 figure

Multidimensional Leadership: Masculine and Feminine Leadership Approaches in Public Education

With two-thirds of new leaders being women, it has become increasingly more clear that the face of our educational organizations is changing both symbolically and substantively. The demands placed on public education have also grown exponentially. If society demands that schools become better, then it is necessary to investigate the approaches that school leaders utilize in making decisions. The purpose of this research was to explore the different approaches that educational leaders implement during their decision-making processes. The present study asked 20 school leaders within Miami Dade County Public Schools to report and explain their personal approaches to leadership to determine if these individuals utilize the reporting categories of masculine, feminine, or multidimensional decision making. Following a four-round modified electronic Delphi technique, involving an open-ended questionnaire, a situation specific decision making survey, and two subsequent rounds of reflection, it was determined that the majority of school leaders use a multidimensional approach in making decisions; however, these individuals did not adhere strictly to any one of the specific reporting categories discussed. The study showed that the incorporation of several approaches contributed to the decision-making processes of educational leaders. Although contrary to relevant literature in the field, participants’ leadership approaches were not stringently tied to whether they happened to be male or female. The results of the current study suggest that research in sex-role orientations and gender studies, especially in the fields of organizational and educational leadership, may be evolving. The complex nature surrounding leadership in schools may imply that the infusion of a diverse or multidimensional approach to decision making is a necessary part of steering an organization towards a path that meets contemporary education demands. The environment particular to each school determines the leadership approach that is appropriate. Environmental variables may include the school’s history, the demographics of students and personnel, and details involving the type of organizational culture that has been fostered. Practical implications of the current study include exploring appropriate leadership and the role that multidimensional leadership approaches have in fulfilling the needs of specific schools. These leadership styles not only incorporate masculine and feminine leadership approaches, but also integrate approaches that can be considered androgynous and multidimensional

FREEDOM OF THE PRESS AND OF THE MAILS

It should be unnecessary to amend the Federal Constitution to accommodate the facilities of government to the needs of society, as those needs develop with the social and scientific advance of civilization. But the trend of legislative effort to reach beyond constitutional limits to satisfy fleeting economic or political expediencies, without regard for the vital distinction between sound and substance, and of courts to seek justification for such excursions, under the benefit of constitutional doubt due solemn expressions of legislative will, may lead to highly dangerous situations. As this trend is permitted to reach extremes, the erasure of the well-defined lines of demarcation segregating the departments of government, and the approach of totalitarianism, are inevitable