Subtleties in the quasi-classical calculation of Hawking radiation

he quasi-classical method of deriving Hawking radiation is investigated. In order to recover the original Hawking temperature one must take into account a previously ignored contribution coming from the temporal part of the action. This contribution plus a contribution coming from the spatial part of the action gives the correct temperature.Comment: 6 pages revtex. Honorable Mention in 2008 GRF essay contest, typos fixed, sign errors corrected. To be published in Special Issue of IJMP

Performance Data from a Wind-Tunnel Test of Two Main-rotor Blade Designs for a Utility-Class Helicopter

An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to evaluate an advanced main rotor designed for use on a utility class helicopter, specifically the U.S. Army UH-60A Blackhawk. This rotor design incorporated advanced twist, airfoil cross sections, and geometric planform. For evaluation purposes, the current UH-60A main rotor was also tested and is referred to as the baseline blade set. A total of four blade sets were tested. One set of both the baseline and the advanced rotors were dynamically scaled to represent a full scale helicopter rotor blade design. The remaining advanced and baseline blade sets were not dynamically scaled so as to isolate the effects of structural elasticity. The investigation was conducted in hover and at rotor advance ratios ranging from 0.15 to 0.4 at a range of nominal test medium densities from 0.00238 to 0.009 slugs/cu ft. This range of densities, coupled with varying rotor lift and propulsive force, allowed for the simulation of several vehicle gross weight and density altitude combinations. Performance data are presented for all blade sets without analysis; however, cross referencing of data with flight condition may be useful to the analyst for validating aeroelastic theories and design methodologies as well as for evaluating advanced design parameters

Mine maintenance - the cost of operation

Increasing world competition puts pressure on sales volumes and prices. This in turn increases the focus on costs. This in turn reduces potential profit margins. Increasing demands on quality and service puts pressure on delivery performance -the right product at the right time. \u27[his in turn reduces the scope for errors and delays -and this in turn increases focus on equipment reliability. In the mining industry, both costs and equipment reliability have one significant thing in common -they are driven ~;ubstantially by maintenance. ]~aintenance, once the Cinderella of the boardroom, is a pivotal \u27function and demands management attention and, if Inanaged well, can be a source of competitive advantage. They JlIlade the decision to put maintenance high on their agendas because they realised that good maintenance is a vital factclr in achieving excellence. lv1aintenance, because of its impact on return on capital, is a key drilver of performance. By reducing maintenance coSts, (:ompanies can improve their performance. Top managers are increasingly recognising that maintenance is an area in which they must be involved. As Australian mining and metallw.gical companies look to the year 2000 and beyond, maintenance will become an increasingly strategic function, capable of delivering sustainable competitive advantage to those companies that get it right

A statistical model for the intrinsically broad superconducting to normal transition in quasi-two-dimensional crystalline organic metals

Although quasi-two-dimensional organic superconductors such as $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ seem to be very clean systems, with apparent quasiparticle mean-free paths of several thousand \AA, the superconducting transition is intrinsically broad (e.g $\sim 1$ K wide for $T_c \approx 10$ K). We propose that this is due to the extreme anisotropy of these materials, which greatly exacerbates the statistical effects of spatial variations in the potential experienced by the quasiparticles. Using a statistical model, we are able to account for the experimental observations. A parameter $\bar{x}$, which characterises the spatial potential variations, may be derived from Shubnikov-de Haas oscillation experiments. Using this value, we are able to predict a transition width which is in good agreement with that observed in MHz penetration-depth measurements on the same sample.Comment: 8 pages, 2 figures, submitted to J. Phys. Condens. Matte

Inflation with a graceful exit and entrance driven by Hawking radiation

We present a model for cosmological inflation which has a natural "turn on" and a natural "turn off" mechanism. In our model inflation is driven by the Hawking-like radiation that occurs in Friedman-Robertson-Walker (FRW) space-time. This Hawking-like radiation results in an effective negative pressure "fluid" which leads to a rapid period of expansion in the very early Universe. As the Universe expands the FRW Hawking temperature decreases and the inflationary expansion turns off and makes a natural transition to the power law expansion of a radiation dominated universe. The "turn on" mechanism is more speculative, but is based on the common hypothesis that in a quantum theory of gravity at very high temperatures/high densities Hawking radiation will stop. Applying this speculation to the very early Universe implies that the Hawking-like radiation of the FRW space-time will be turned off and therefore the inflation driven by this radiation will turn off.Comment: 19 pages, 2 figures revtex, matches PRD published versio

The Birth of the Modern Era of Parkinson's Disease Genetics

Genetic understanding in Parkinson’s disease (PD) has followed a path of hard won evolution occasionally punctuated by revolution. While it was suggested early on by both Leroux and Gowers that heredity had a role to play in PD, this was a view that wasn’t widely enough held to even be unpopular. The dogma was that the disease was one of environmental provenance and while the evidence for this is still rather scarce, this view pervades in the minds of patients, clinicians, and scientists. Conversely the evidence linking genetics to PD is both overwhelming and growing. Here we describe the growth of genetics in PD from backwater to driving force, and the structure and shape of its future. The localization and identification of α-synuclein mutations as a cause of PD in the mid 1990’s was perhaps the first concrete and revolutionary finding in PD genetics [1]. This came about as a result of the intuition and hard work of a clinical team from New Jersey, followed by the linkage and positional cloning efforts of a genetic team at NIH, orchestrated by the then director of NINDS, Zach Hall. This effort (described by Bob Nussbaum in another article in this issue) was an extraordinary success. The discovery of α-synuclein mutations as a rare cause of PD was an invigorating and welcome progression for myriad reasons. Most prominently, it gave us the mutation as a tool with which to attempt to understand the disease process. Perhaps more importantly, at least in the short term, it provided empirical evidence that there was a genetic basis for rare forms of the disease and because α-synuclein was a major component of all Lewy bodies, that these findings were directly relevant to all cases of PD. This in fact, prompted one of us to say, tongue in cheek “If you’re not working on synuclein, you’re not working on Parkinson’s disease”

Gravitational Flux Tubes

By studying multidimensional Kaluza-Klein theories, or gravity plus U(1) or SU(2) gauge fields it is shown that these theories possess similar flux tube solutions. The gauge field which fills the tube geometry of these solutions leads to a comparision with the flux tube structures in QCD. These solutions also carry a ``magnetic'' charge, Q, which for the SU(2) Einstein-Yang-Mills (EYM) system exhibits a dual relationship with the Yang-Mills gauge coupling, g, ($Q=1/g$). As $Q \to 0$ or $Q \to \infty$, $g \to \infty$ or $g \to 0$ respectively. Thus within this classical EYM field theory we find solutions which have features - flux tubes, magnetic charges, large value of the gauge coupling - that are similar to the key ingredients of confinement in QCD.Comment: REVTEX, 12 p

The Stac Fada “impact ejecta” layer: not what it seems

The Stac Fada Member (SFM) forms part of the Stoer Group of the Torridonian of NW Scotland. The SFM is unique in the Torridonian, being characterized by the presence of greenish altered glass clasts. Its origin has been debated for decades with several hypotheses being proposed but all invoking some connection with volcanic activity in the region. More recently, Amor et al. suggested that the SFM represents “a chord section through the continuous ejecta blanket surrounding an impact crater”. Here, we confirm the presence of shocked material within the SFM and then discuss its origin

Charged Particle Stopping Power Effects on Ignition: Some Results from an Exact Calculation

A completely rigorous first-principles calculation of the charged particle stopping power has recently been performed by Brown, Preston, and Singleton (BPS). This calculation is exact to leading and next-to-leading order in the plasma number density, including an exact treatment of two-body quantum scattering. The BPS calculation is therefore extremely accurate in the plasma regime realized during the ignition and burn of an inertial confinement fusion capsule. For deuterium-tritium fusion, the 3.5 MeV alpha particle range tends to be 20-30% longer than most models in the literature have predicted, and the energy deposition into the ions tends to be smaller. Preliminary numerical simulations indicate that this increases the rho-R required to achieve ignition.Comment: 19 pages, 3 Figures, Published in the proceedings for the 49th Annual meeting of the APS Division of Plasma Physics, Orlando FL, 12-16 November 2007. Added more details about numeric

Influence of Temporary Chemical Immobilization of Boar Spermatozoa Upon In Vitro Survival

The use of artificial insemination (AI) in swine has been restricted because of the inability to store semen. It is usually recommended that for AI use boar semen not be stored more than 48 hours. Obviously, the goal is to develop a technique whereby boar semen could be stored indefinitely such as is the case with bull semen. However, until such a technique is developed, a method of storing boar semen for a few days would be of value for promoting AI in swine