Uniform semiclassical wave function for coherent 2D electron flow

We find a uniform semiclassical (SC) wave function describing coherent branched flow through a two-dimensional electron gas (2DEG), a phenomenon recently discovered by direct imaging of the current using scanned probed microscopy. The formation of branches has been explained by classical arguments, but the SC simulations necessary to account for the coherence are made difficult by the proliferation of catastrophes in the phase space. In this paper, expansion in terms of "replacement manifolds" is used to find a uniform SC wave function for a cusp singularity. The method is then generalized and applied to calculate uniform wave functions for a quantum-map model of coherent flow through a 2DEG. Finally, the quantum-map approximation is dropped and the method is shown to work for a continuous-time model as well.Comment: 9 pages, 7 figure

Dew point, internal gas pressure, and chemical composition of the gas within the free volume of DWPF canistered waste forms

The Defense Waste Processing Facility (DWPF) produced 55 canistered waste forms containing simulated waste glass during the four Waste Qualification campaigns of the DWPF Startup Test Program. Testing of the gas within the free volume of these canisters for dew point, internal gas pressure, and chemical composition was performed as part of a continuing effort to demonstrate compliance with the Waste Acceptance Product Specifications. Results are presented for six glass-filled canisters. The dew points within the canisters met the acceptance criterion of < 20{degrees}C for all six canisters. Factors influencing the magnitude of the dew point are presented. The chemical composition of the free volume gas was indistinguishable from air for all six canisters. Hence, no foreign materials were present in the gas phase of these canisters. The internal gas pressures within the sealed canisters were < 1 atm at 25{degrees}C for all six canisters which readily met the acceptance criterion of an internal gas pressure of less than 1.5 atm at 25{degrees}C. These results provided the evidence required to demonstrate compliance with the Waste Acceptance Product Specifications

Variations of Hadron Masses and Matter Properties in Dense Nuclear Matter

Using a self-consistent quark model for nuclear matter we investigate variations of the masses of the non-strange vector mesons, the hyperons and the nucleon in dense nuclear matter (up to four times the normal nuclear density). We find that the changes in the hadron masses can be described in terms of the value of the scalar mean-field in matter. The model is then used to calculate the density dependence of the quark condensate in-medium, which turns out to be well approximated by a linear function of the nuclear density. Some relations among the hadron properties and the in-medium quark condensate are discussed.Comment: 22 pages, University of Adelaide preperint ADP-94-20/T160, submitted to Physical Review

Three applications of path integrals: equilibrium and kinetic isotope effects, and the temperature dependence of the rate constant of the [1,5] sigmatropic hydrogen shift in (Z)-1,3-pentadiene

Recent experiments have confirmed the importance of nuclear quantum effects even in large biomolecules at physiological temperature. Here we describe how the path integral formalism can be used to describe rigorously the nuclear quantum effects on equilibrium and kinetic properties of molecules. Specifically, we explain how path integrals can be employed to evaluate the equilibrium (EIE) and kinetic (KIE) isotope effects, and the temperature dependence of the rate constant. The methodology is applied to the [1,5] sigmatropic hydrogen shift in pentadiene. Both the KIE and the temperature dependence of the rate constant confirm the importance of tunneling and other nuclear quantum effects as well as of the anharmonicity of the potential energy surface. Moreover, previous results on the KIE were improved by using a combination of a high level electronic structure calculation within the harmonic approximation with a path integral anharmonicity correction using a lower level method.Comment: 9 pages, 4 figure

Losing the media battle, waging the policy war: The pharmaceutical industry’s response to the access to medicines crisis in the Global South

This article sheds new light on the pharmaceutical industry’s response to the public relations crisis generated by the global civil society campaign for access to HIV/AIDS medicines since the early 2000s – one of the most contentious policy areas of global trade and health governance. Drawing on interviews with industry insiders, the article explores the industry’s communicative agency in both the media sphere and key sites of power, with a focus on the European Union (EU) policy sphere. The analysis shows that the industry has focused primarily on maintaining access to policymakers and sustaining elite consensus around the existing global intellectual property rights regime through political communication activities that largely bypass mediated public arenas – from strategically promoting its corporate social responsibility (CSR) programmes and mobilizing third-party endorsement to direct lobbying. The article concludes by reflecting on the implications of the findings for critical investigations of the interplay between media and political power in relation to global economic governance

Excitation of weakly bound Rydberg electrons by half-cycle pulses

The interaction of a weakly bound Rydberg electron with an electromagnetic half-cycle pulse (HCP) is described with the help of a multidimensional semiclassical treatment. This approach relates the quantum evolution of the electron to its underlying classical dynamics. The method is nonperturbative and is valid for arbitrary spatial and temporal shapes of the applied HCP. On the basis of this approach angle- and energy-resolved spectra resulting from the ionization of Rydberg atoms by HCPs are analyzed. The different types of spectra obtainable in the sudden-impact approximation are characterized in terms of the appearing semiclassical scattering phenomena. Typical modifications of the spectra originating from finite pulse effects are discussed.Comment: Submitted to Phys. Rev.

Theory of Circle Maps and the Problem of One-Dimensional Optical Resonator with a Periodically Moving Wall

We consider the electromagnetic field in a cavity with a periodically oscillating perfectly reflecting boundary and show that the mathematical theory of circle maps leads to several physical predictions. Notably, well-known results in the theory of circle maps (which we review briefly) imply that there are intervals of parameters where the waves in the cavity get concentrated in wave packets whose energy grows exponentially. Even if these intervals are dense for typical motions of the reflecting boundary, in the complement there is a positive measure set of parameters where the energy remains bounded.Comment: 34 pages LaTeX (revtex) with eps figures, PACS: 02.30.Jr, 42.15.-i, 42.60.Da, 42.65.Y

Structure and flexibility of the endosomal Vps34 complex reveals the basis of its function on membranes

Phosphatidylinositol 3-kinase Vps34 complexes regulate intracellular membrane trafficking in endocytic sorting, cytokinesis and autophagy. We present the 4.4 Å crystal structure of the 385 kDa endosomal complex II (PIK3C3-CII), consisting of Vps34, Vps15 (p150), Vps30/Atg6 (Beclin 1) and Vps38 (UVRAG). The subunits form a Y-shaped complex, centered on the Vps34 C2 domain. Vps34 and Vps15 intertwine in one arm where the Vps15 kinase domain engages the Vps34 activation loop to regulate its activity. Vps30 and Vps38 form the other arm that brackets the Vps15/Vps34 heterodimer, suggesting a path for complex assembly. Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) revealed conformational changes accompanying membrane binding and identified a Vps30 loop that is critical for the ability of complex II to phosphorylate giant liposomes on which complex I is inactive

The air raids that never were and the war that nobody won: government propaganda in conflict reporting and how journalists should respond to it

During the bombing campaign against Libya in the spring of 2011, the fog of war enveloped not only the shifting frontlines of the battles between forces loyal to the then Libyan leader, Muammar Gaddafi, but also the more comfortable surroundings of British government ministries. A news story of an aborted air raid reflected the huge importance which governments increasingly place upon getting their message across in the international media in times of conflict. Looking at that example from the conflict in Libya, and studying in detail others from Russia’s 2008 war with Georgia, this article argues that journalists must correspondingly be increasingly aware of attempts by governments, and their hired public relations hands, to influence reporting

Semiclassical Approximations in Phase Space with Coherent States

We present a complete derivation of the semiclassical limit of the coherent state propagator in one dimension, starting from path integrals in phase space. We show that the arbitrariness in the path integral representation, which follows from the overcompleteness of the coherent states, results in many different semiclassical limits. We explicitly derive two possible semiclassical formulae for the propagator, we suggest a third one, and we discuss their relationships. We also derive an initial value representation for the semiclassical propagator, based on an initial gaussian wavepacket. It turns out to be related to, but different from, Heller's thawed gaussian approximation. It is very different from the Herman--Kluk formula, which is not a correct semiclassical limit. We point out errors in two derivations of the latter. Finally we show how the semiclassical coherent state propagators lead to WKB-type quantization rules and to approximations for the Husimi distributions of stationary states.Comment: 80 pages, 4 figure