Origin of Lagrangian Intermittency in Drift-Wave Turbulence

The Lagrangian velocity statistics of dissipative drift-wave turbulence are investigated. For large values of the adiabaticity (or small collisionality), the probability density function of the Lagrangian acceleration shows exponential tails, as opposed to the stretched exponential or algebraic tails, generally observed for the highly intermittent acceleration of Navier-Stokes turbulence. This exponential distribution is shown to be a robust feature independent of the Reynolds number. For small adiabaticity, algebraic tails are observed, suggesting the strong influence of point-vortex-like dynamics on the acceleration. A causal connection is found between the shape of the probability density function and the autocorrelation of the norm of the acceleration

Shuttle/spacelab MMAP/electromagnetic environment experiment phase B definition study

Progress made during the first five months of the Phase B definition study for the MMAP/Electromagnetic Environment Experiment (EEE) was described. An antenna/receiver assembly has been defined and sized for stowing in a three pallet bay area in the shuttle. Six scanning modes for the assembly are analyzed and footprints for various antenna sizes are plotted. Mission profiles have been outlined for a 400 km height, 57 deg inclination angle, circular orbit. Viewing time over 7 geographical areas are listed. Shuttle interfaces have been studied to determine what configuration the antenna assembly must have to be shared with other experiments of the Microwave Multi-Applications Payload (MMAP) and to be stowed in the shuttle bay. Other results reported include a frequency plan, a proposed antenna subsystem design, a proposed receiver design, preliminary outlines of the experiment controls and an analysis of on-board and ground data processing schemes

A relativistically covariant version of Bohm's quantum field theory for the scalar field

We give a relativistically covariant, wave-functional formulation of Bohm's quantum field theory for the scalar field based on a general foliation of space-time by space-like hypersurfaces. The wave functional, which guides the evolution of the field, is space-time-foliation independent but the field itself is not. Hence, in order to have a theory in which the field may be considered a beable, some extra rule must be given to determine the foliation. We suggest one such rule based on the eigen vectors of the energy-momentum tensor of the field itself.Comment: 1 figure. Submitted to J Phys A. 20/05/04 replacement has additional references and a few minor changes made for clarity. Accepted by J Phys

Modus Vivendi Beyond the Social Contract: Peace, Justice, and Survival in Realist Political Theory

This essay examines the promise of the notion of modus vivendi for realist political theory. I interpret recent theories of modus vivendi as affirming the priority of peace over justice, and explore several ways of making sense of this idea. I proceed to identify two key problems for modus vivendi theory, so conceived. Normatively speaking, it remains unclear how this approach can sustain a realist critique of Rawlsian theorizing about justice while avoiding a Hobbesian endorsement of absolutism. And conceptually, the theory remains wedded to a key feature of social contract theory: political order is conceived as based on agreement. This construes the horizontal tensions among individual or group agents in society as prior to the vertical, authoritative relations between authorities and their subjects. Political authority thereby appears from the start as a solution to societal conflict, rather than a problem in itself. I argue that this way of framing the issue abstracts from political experience. Instead I attempt to rethink the notion of modus vivendi from within the lived experience of political conflict, as oriented not primarily toward peace, but political survival. With this shift of perspective, the idea of modus vivendi shows us, pace Bernard Williams, that the “first political question” is not how to achieve order and stability, but rather: what can I live with

The cosmic ray spectrum above 10(17) eV

The final analysis of the data obtained by the Sydney University Giant Airshower Recorder (SUGAR) is presented. The data has been reanalysed to take into account the effects of afterpulsing in the photomultiplier tubes. Event data was used to produce a spectrum of equivalent vertical muon number and from this a model dependent primary energy spectrum was obtained. These spectra show good evidence for the Ankle: a flattening at 10(19) eV. There is no sign of the cut-off which would be expected from the effects of the universal black body radiation

A Near-Deterministic Mutational Hotspot in Pseudomonas fluorescens Is Constructed by Multiple Interacting Genomic Features

Mutation—whilst stochastic—is frequently biased toward certain loci. When combined with selection, this results in highly repeatable and predictable evolutionary outcomes. Immotile variants of the bacterium Pseudomonas fluorescens (SBW25) possess a “mutational hotspot” that facilitates repeated occurrences of an identical de novo single nucleotide polymorphism when re-evolving motility, where ≥95% independent lines fix the mutation ntrB A289C. Identifying hotspots of similar potency in other genes and genomic backgrounds would prove valuable for predictive evolutionary models but to do so we must understand the genomic features that enable such a hotspot to form. Here, we reveal that genomic location, local nucleotide sequence, gene strandedness, and presence of mismatch repair proteins operate in combination to facilitate the formation of this mutational hotspot. Our study therefore provides a framework for utilizing genomic features to predict and identify hotspot positions capable of enforcing near-deterministic evolution

Soil water retention and hydraulic conductivity dynamics following tillage

Soil bulk density (ρb) may be purposely reduced in agricultural fields using tillage to improve hydraulic properties. However, tillage alters the soil structure, resulting in unstable soils. As the soil stabilizes, ρb increases over time. While this is known, studies on soil hydraulic properties in tilled soils, including comparisons between tilled and non-tilled soils, commonly assume a rigid soil structure. This study presents changes in soil water retention and saturated hydraulic conductivity (Ksat) as ρb increased dynamically with time following tillage at a loam-textured field site. Over the summer of 2015, soil cores were collected at several depths below the surface following precipitation events. Soil water retention curves and Ksat were determined using pressure cells and the constant head method, respectively. Tillage reduced ρb to 0.94 g cm−3. Changes in ρb increased with depth, reaching a ρb of 1.11 g cm−3 in the 0–5 cm layer, and a ρb of 1.42 g cm−3 at the deepest tilled layer. Soil water retention curves were markedly steeper for samples with higher ρb, indicating an overall increase in water retained at a soil matric potential (Ψ) of −33 kPa. Evaluation of two modeling approaches for water retention as a function ρbindicated that changes in water retention with increases in ρb could be reasonably estimated if a matching point was used. No clear relationship between Ksat and ρbwas obvious for ρb \u3c 1.06 cm3 cm−3, but for ρb \u3e 1.06 cm3 cm−3, Ksat decreased markedly (order of magnitude) as ρb increased. Hydraulic properties varied strongly depending on time since tillage and soil depth, and results have implications for models of tilled soils, as well as for studies comparing tilled and non-tilled soils

Dynamics of the nearly parametric pendulum

NOTICE: this is the author’s version of a work that was accepted for publication in International Journal of Non-Linear Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in International Journal of Non-Linear Mechanics Vol. 46 (2), pp. 436–442. DOI: 10.1016/j.ijnonlinmec.2010.11.003Copyright © 2010 Elsevie

Extended methodology for determining wetting properties of porous media

[1] Because most methods for assessing the wettability of porous materials are restricted in their applicability, we developed two new methods for measuring contact angles and particle surface energy. The proposed methods (the Wilhelmy plate method (WPM) and the modified capillary rise method (MCRM)) were tested on 24 soils. For comparison, the water drop penetration time test (WDPTT) and the sessile drop method (SDM) were also applied. It was found that advancing contact angles, measured either with WPM or MCRM, agreed well in the range of 0° to 142°. Sessile drop contact angles were within the domain enclosed by the range of advancing and receding contact angles as determined with WPM. WDPTT, however, was only sensitive in the narrow range of 85° to 115°. We conclude that both WPM and MCRM are reliable methods for determining contact angles and particle surface energy over a wide range of porous material wettabilities