A CFD based procedure for airspace integration of small unmanned aircraft within congested areas

Future integration of small unmanned aircraft within an urban airspace requires an a posteriori understanding of the building-induced aerodynamics which could negatively impact on vehicle performance. Moving away from generalised building formations, we model the centre of the city of Glasgow using Star-CCMþ, a commercial CFD package. After establishing a critical turbulent kinetic energy for our vehicle, we analyse the CFD results to determine how best to operate a small unmanned aircraft within this environment. As discovered in a previous study, the spatial distribution of turbulence increases with altitude. It was recommended then that UAVs operate at the minimal allowable altitude within a congested area. As the flow characteristics in an environment are similar, regardless of inlet velocity, we can determine areas within a city which will have consistently low or high values of turbulent kinetic energy. As the distribution of turbulence is dependent on prevailing wind directions, some directions are more favourable than others, even if the wind speed is unchanging. Moving forward we should aim to gather more information about integrated aircraft and how they respond to turbulence in a congested area

Particle tunneling through a polarizable insulator

The tunneling probability between two leads connected by a molecule, a chain, a film, or a bulk polarizable insulator is investigated within a model of an electron tunneling from lead A to a state higher in energy, describing the barrier, and from there to lead B. To describe the possibility of energy exchange with excitations of the molecule or the insulator we couple the intermediate state to a single oscillator or to a spectrum of these, respectively. In the single-oscillator case we find for weak coupling that the tunneling is weakly suppressed by a Debye-Waller-type factor. For stronger coupling the oscillator gets 'stiff' and we observe a suppression of tunneling since the effective barrier is increased. The probability for the electron to excite the oscillator increases with the coupling. In the case of a film, or a bulk barrier the behavior is qualitatively the same as in the single oscillator case. An insulating chain, as opposed to a film or a bulk connecting the two leads,shows an 'orthogonality catastrophe' similar to that of an electronic transition in a Fermi gas.Comment: 4 pages, 1 figur

The International Appalachian Trail: the ancient Appalachians as ambassador of the geosciences to modern societies

Throughout human history, the geological foundation of our landscape has determined the location of settlements, trade routes, and human migratory paths, inextricably linking our culture to geology. The International Appalachian Trail (IAT) addresses our common geoheritage by establishing a long-distance walking trail that extends beyond borders to all geographic regions once connected by the “Appalachian Mountain” range, formed more than 300 million years ago on the super-continent Pangaea. In addition to connecting people and places, the goal of the IAT is to promote natural and cultural heritage, health and fitness, environmental stewardship, fellowship and understanding, cross-border cooperation, and rural economic development through eco-recreation. The IAT was founded on “Earth Day” in Maine, USA, in 1994 and currently includes 21 Chapters representing an estimated 12,000 miles of trail along the ancient Appalachian terranes rimming the North Atlantic. A work in progress, the development of the IAT continues as individual Chapters: (1) construct a long-distance walking trail; (2) locate the IAT within areas that have been identified by geologists as having been part of the ancient Appalachian/Caledonian landscape; (3) locate the IAT so that it connects to bordering Chapters; (4) make available to the public map and trail descriptions of the IAT within its jurisdiction via the IAT web site; and (5) produce educational web site trail guides. In Europe, the IAT has been a natural fit, both in terms of mission and geography, with Geoparks. The IAT provides an excellent opportunity for earth scientists to participate in this unique recreational/educational project and to engage the public in a discussion of the geological foundations of modern society

Strain dependence of the acoustic properties of amorphous metals below 1K: Evidence for the interaction between tunneling states

We have conducted a thorough study of the acoustic properties between 10^-4 and 1 Kelvin for the amorphous metal Zr_x Cu_1-x (x=0.3 and x=0.4), by measuring the relative change of sound velocity dv/v and internal friction Q^-1 as a function of temperature and also of the applied strain, in both superconducting and normal state. We have found that when plotted versus the ratio of strain energy to thermal energy, all measurements display the same behavior: a crossover from a linear regime of ``independent'' tunneling systems at very low strains and/or high enough temperatures to a nonlinear regime where dv/v and Q^-1 depend on applied strain and the tunneling systems cannot be considered as independent.Comment: 4 pages, 4 figures (submitted to PRL

Nuclear relocalisation of cytoplasmic poly(A)-binding proteins PABP1 and PABP4 in response to UV irradiation reveals mRNA-dependent export of metazoan PABPs

Poly(A)-binding protein 1 (PABP1) has a fundamental role in the regulation of mRNA translation and stability, both of which are crucial for a wide variety of cellular processes. Although generally a diffuse cytoplasmic protein, it can be found in discrete foci such as stress and neuronal granules. Mammals encode several additional cytoplasmic PABPs that remain poorly characterised, and with the exception of PABP4, appear to be restricted in their expression to a small number of cell types. We have found that PABP4, similarly to PABP1, is a diffusely cytoplasmic protein that can be localised to stress granules. However, UV exposure unexpectedly relocalised both proteins to the nucleus. Nuclear relocalisation of PABPs was accompanied by a reduction in protein synthesis but was not linked to apoptosis. In examining the mechanism of PABP relocalisation, we found that it was related to a change in the distribution of poly(A) RNA within cells. Further investigation revealed that this change in RNA distribution was not affected by PABP knockdown but that perturbations that block mRNA export recapitulate PABP relocalisation. Our results support a model in which nuclear export of PABPs is dependent on ongoing mRNA export, and that a block in this process following UV exposure leads to accumulation of cytoplasmic PABPs in the nucleus. These data also provide mechanistic insight into reports that transcriptional inhibitors and expression of certain viral proteins cause relocation of PABP to the nucleus. © 2011. Published by The Company of Biologists Ltd

Effect of bilayer coupling on tunneling conductance of double-layer high T_c cuprates

Physical effects of bilayer coupling on the tunneling spectroscopy of high T$_{c}$ cuprates are investigated. The bilayer coupling separates the bonding and antibonding bands and leads to a splitting of the coherence peaks in the tunneling differential conductance. However, the coherence peak of the bonding band is strongly suppressed and broadened by the particle-hole asymmetry in the density of states and finite quasiparticle life-time, and is difficult to resolve by experiments. This gives a qualitative account why the bilayer splitting of the coherence peaks was not clearly observed in tunneling measurements of double-layer high-T$_c$ oxides.Comment: 4 pages, 3 figures, to be published in PR

Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors

The electromagnetic response of a system with two planes per unit cell involves, in addition to the usual intraband contribution, an added interband term. These transitions affect the temperature dependence and the magnitude of the zero temperature c-axis penetration depth. When the interplane hopping is sufficiently small, the interband transitions dominate the low temperature behaviour of the penetration depth which then does not reflect the linear temperature dependence of the intraband term and in comparison becomes quite flat even for a d-wave gap. It is in this regime that the pseudogap was found in our previous normal state calculations of the c-axis conductivity, and the effects are connected.Comment: 8 pages, 5 figure

Derivation of fluid dynamics from kinetic theory with the 14--moment approximation

We review the traditional derivation of the fluid-dynamical equations from kinetic theory according to Israel and Stewart. We show that their procedure to close the fluid-dynamical equations of motion is not unique. Their approach contains two approximations, the first being the so-called 14-moment approximation to truncate the single-particle distribution function. The second consists in the choice of equations of motion for the dissipative currents. Israel and Stewart used the second moment of the Boltzmann equation, but this is not the only possible choice. In fact, there are infinitely many moments of the Boltzmann equation which can serve as equations of motion for the dissipative currents. All resulting equations of motion have the same form, but the transport coefficients are different in each case.Comment: 15 pages, 3 figures, typos fixed and discussions added; EPJA: Topical issue on "Relativistic Hydro- and Thermodynamics

Stability of the Scalar Potential and Symmetry Breaking in the Economical 3-3-1 Model

A detailed study of the criteria for stability of the scalar potential and the proper electroweak symmetry breaking pattern in the economical 3-3-1 model, is presented. For the analysis we use, and improve, a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. A new theorem related to the stability of the potential is stated. As a consequence of this study, the consistency of the economical 3-3-1 model emerges.Comment: to be published in EPJ C, 13 page

Antimicrobial activity of a continuous visible light disinfection system

We evaluated the ability of high-intensity visible violet light with a peak output of 405 nm to kill epidemiologically important pathogens. The high irradiant light significantly reduced both vegetative bacteria and spores at some time points over a 72-hour exposure period