Associated strangeness production in the pp to pK^+K^-p and pp to pK^+ pi^0 Sigma^0 reactions

The total and differential cross sections for associated strangeness production in the $pp \to pK^+K^-p$ and $pp \to pK^+\pi^0\Sigma^0$ reactions have been studied in a unified approach using an effective Lagrangian model. It is assumed that both the $K^-p$ and $\pi^0\Sigma^0$ final states originate from the decay of the $\Lambda(1405)$ resonance which was formed in the production chain $pp\to p(N^*(1535)\to K^+\Lambda(1405))$. The available experimental data are well reproduced, especially the ratio of the two total cross sections, which is much less sensitive to the particular model of the entrance channel. The significant coupling of the $N^*(1535)$ resonance to $\Lambda(1405) K$ is further evidence for large $s \bar{s}$ components in the quark wave function of the $N^*(1535)$ resonance.Comment: Published in Phys. Rev.

Jurassic belemnite geochemistry from Cabo Mondego (Bajocian-Bathonian, Portugal) and Albstadt-Pfeffingen (Bathonian-Callovian, Germany)

Here, I have investigated the stable isotope (δ13C, δ18O) and elemental composition (Mg/Ca, Sr/Ca, Fe/Ca, Mn/Ca) of Jurassic belemnites from Cabo Mondego in Portugal (Bajocian-Bathonian) and Albstadt-Pfeffingen in southern Germany (Bathonian-Callovian). Both localities are stratigraphically significant, with Cabo Mondego representing the Auxiliary Stratotype Section and Point (ASSP) for the Bathonian Stage and Albstadt-Pfeffingen being a potential Global Stratotype Section and Point (GSSP) for the Callovian Stage. Variations in the stable carbon-isotope ratios of macrofossil calcite can reflect changes in fluxes between reservoirs in the palaeo carbon cycle. Cabo Mondego is an important site to link changes in stable isotope ratios directly to ammonite zones and subzones, and thereby allow chronostratigraphic calibration. An abrupt positive δ13C isotope shift is observed in the belemnite stable isotope record from the bomfordi Subzone below the Bajocian-Bathonian boundary. The δ13C shift appears not to have been caused by temperature changes as δ18O ratios remain stable throughout the studied section, nor is there a change in the 13C values of coeval brachiopods. One possible cause of this shift in carbon-isotope ratios is a faunal turnover. Faunal turnovers of ammonites and belemnites are observed elsewhere in Europe within the bomfordi Subzone. The potential of the Jurassic section at Albstadt-Pfeffingen (BadenWürttemberg, Germany) to become a GSSP, an internationally agreed reference point which defines the lower boundary of a stage on the geologic timescale, for the base of the Middle Jurassic Callovian Stage, makes detailed investigations, especially regarding the completeness of the strata, important. The ammonite assemblages of this section have already been studied in detail, but few chemostratigraphic data from the Bathonian and Lower Callovian fossils of the site have been published. Belemnite rostra are relatively abundant in the section and have undergone little diagenetic alteration according to chemical and optical screening techniques, making them a suitable target for isotopic analysis. Chemostratigraphic signals in the rostra across the Bathonian-Callovian boundary show comparatively little change in δ13C values, but a gradual decrease in δ18O may indicate a warming trend into the Callovian. Notably, a distinct stepchange in 87Sr/86Sr ratios across the stage boundary suggests an unconformity, or at least strongly condensed part of the section, confirming strong doubts on the site's suitability as a GSSP

Modeling Nonaxisymmetric Bow Shocks: Solution Method and Exact Analytic Solutions

A new solution method is presented for steady-state, momentum-conserving, non-axisymmetric bow shocks and colliding winds in the thin-shell limit. This is a generalization of previous formulations to include a density gradient in the pre-shock ambient medium, as well as anisotropy in the pre-shock wind. For cases where the wind is unaccelerated, the formalism yields exact, analytic solutions. Solutions are presented for two bow shock cases: (1) that due to a star moving supersonically with respect to an ambient medium with a density gradient perpendicular to the stellar velocity, and (2) that due to a star with a misaligned, axisymmetric wind moving in a uniform medium. It is also shown under quite general circumstances that the total rate of energy thermalization in the bow shock is independent of the details of the wind asymmetry, including the orientation of the non-axisymmetric driving wind, provided the wind is non-accelerating and point-symmetric. A typical feature of the solutions is that the region near the standoff point is tilted, so that the star does not lie along the bisector of a parabolic fit to the standoff region. The principal use of this work is to infer the origin of bow shock asymmetries, whether due to the wind or ambient medium, or both.Comment: 26 pages and 6 figures accepted to ap

Small scale noise and wind tunnel tests of upper surface blowing nozzle flap concepts. Volume 1. Aerodynamic test results

The results and analyses of aerodynamic and acoustic studies conducted on the small scale noise and wind tunnel tests of upper surface blowing nozzle flap concepts are presented. Various types of nozzle flap concepts were tested. These are an upper surface blowing concept with a multiple slot arrangement with seven slots (seven slotted nozzle), an upper surface blowing type with a large nozzle exit at approximately mid-chord location in conjunction with a powered trailing edge flap with multiple slots (split flow or partially slotted nozzle). In addition, aerodynamic tests were continued on a similar multi-slotted nozzle flap, but with 14 slots. All three types of nozzle flap concepts tested appear to be about equal in overall aerodynamic performance but with the split flow nozzle somewhat better than the other two nozzle flaps in the landing approach mode. All nozzle flaps can be deflected to a large angle to increase drag without significant loss in lift. The nozzle flap concepts appear to be viable aerodynamic drag modulation devices for landing

Radiocarbon dating results from the Beakers and Bodies Project

The Beakers and Bodies Project is a two-year project based in Marischal Museum, University of Aberdeen, funded by the Leverhulme Trust. It is assessing the beaker-related evidence from North-East Scotland (between the Moray Firth and the Firth of Tay), including the dating and stable isotope analyses of some 40 human skeletons from museum collections. The project builds on the North-East dates resulting from the Beaker People Project (Parker Pearson, 2006; Sheridan et al., 2006) and earlier programmes and studies (e.g. Shepherd, 1986). It also includes a consideration of beaker typology and manufacture, burial contexts, grave goods, human osteology and evidence for diet from stable isotope analysis

Anomalous hydrodynamics and "normal" fluids in rapidly rotating BECs

In rapidly rotating bose systems we show that there is a region of anomalous hydrodynamics whilst the system is still condensed, which coincides with the mean field quantum Hall regime. An immediate consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show there are kinematic constraints which connect spatial variations of density and phase, that the positions of vortices are not the simplest description of the dynamics of such a fluid (despite their utility in describing the instantaneous state of the condensate) and that the most compact description allows solution of some illuminating examples of motion. We demonstrate, inter alia, a very simple relation between vortices and surface waves. We show the surface waves can form a "normal fluid" which absorbs energy and angular momentum from vortex motion in the trap. The time scale of this process is sensitive to the initial configuration of the vortices, which can lead to long-lived vortex patches - perhaps related to those observed at JILA.Comment: 4 pages; 1 sentence and references modifie

Exact vortex nucleation and cooperative vortex tunneling in dilute BECs

With the imminent advent of mesoscopic rotating BECs in the lowest Landau level (LLL) regime, we explore LLL vortex nucleation. An exact many-body analysis is presented in a weakly elliptical trap for up to 400 particles. Striking non-mean field features are exposed at filling factors >>1 . Eg near the critical rotation frequency pairs of energy levels approach each other with exponential accuracy. A physical interpretation is provided by requantising a mean field theory, where 1/N plays the role of Planck's constant, revealing two vortices cooperatively tunneling between classically degenerate energy minima. The tunnel splitting variation is described in terms of frequency, particle number and ellipticity.Comment: 4 pages,4 figure

Energy cost associated with vortex crossing in superconductors

Starting from the Ginzburg-Landau free energy of a type II superconductor in a magnetic field we estimate the energy associated with two vortices crossing. The calculations are performed by assuming that we are in a part of the phase diagram where the lowest Landau level approximation is valid. We consider only two vortices but with two markedly different sets of boundary conditions: on a sphere and on a plane with quasi-periodic boundary conditions. We find that the answers are very similar suggesting that the energy is localised to the crossing point. The crossing energy is found to be field and temperature dependent -- with a value at the experimentally measured melting line of $U_\times \simeq 7.5 k T_m \simeq 1.16/c_L^2$, where $c_L$ is the Lindemann melting criterion parameter. The crossing energy is then used with an extension of the Marchetti, Nelson and Cates hydrodynamic theory to suggest an explanation of the recent transport experiments of Safar {{\em et al.}\ }.Comment: 15 pages, RevTex v3.0, followed by 5 postscript figure