Burst diaphragm flow initiator Patent

Burst diaphragm flow initiator for installation in short duration wind tunnel

Magnetic pressure support and accretion disk spectra

Stellar atmosphere models of ionized accretion disks have generally neglected the contribution of magnetic fields to the vertical hydrostatic support, although magnetic fields are widely believed to play a critical role in the transport of angular momentum. Simulations of magnetorotational turbulence in a vertically stratified shearing box geometry show that magnetic pressure support can be dominant in the upper layers of the disk. We present calculations of accretion disk spectra that include this magnetic pressure support, as well as a vertical dissipation profile based on simulation. Magnetic pressure support generically produces a more vertically extended disk atmosphere with a larger density scale height. This acts to harden the spectrum compared to models that neglect magnetic pressure support. We estimate the significance of this effect on disk-integrated spectra by calculating an illustrative disk model for a stellar mass black hole, assuming that similar magnetic pressure support exists at all radii.Comment: submitted to Ap

Two-photon laser-induced fluorescence detection of OH

The TP-LIF OH sensor is based on the principle that a molecule having multiple energy states, all of which are bonding, can be pumped into the highest state with the resulting fluorescence being blue-shifted relative to all pumping wavelengths. In this way, one can successfully discriminate against virtually all noise sources in the system using long wavelength blocking filters in conjunction with solar-blind photomultiplier tubes. Thus, these systems tend to be signal limited rather than signal-to-noise limited as is true of the SP-LIF technique as well as other conventional analytical methods. The trick to achieving the above sampling scheme, with high efficiency, is in the use of high photon fluxes of short time duration. Obviously, the latter type of light source is fulfilled nicely by available pulsed lasers. From an operational point of view, however, this laser source needs to be tunable. The latter characteristic permits extremely high selectivity for the detection of a diatomic or simple polyatomic molecule by taking advantage of the high-resolution spectroscopic features of these type species

Long Strings, Anomaly Cancellation, Phase Transitions, T-duality and Locality in the 2d Heterotic String

We study the noncritical two-dimensional heterotic string. Long fundamental strings play a crucial role in the dynamics. They cancel anomalies and lead to phase transitions when the system is compactified on a Euclidean circle. A careful analysis of the gauge symmetries of the system uncovers new subtleties leading to modifications of the worldsheet results. The compactification on a Euclidean thermal circle is particularly interesting. It leads us to an incompatibility between T-duality (and its corresponding gauge symmetry) and locality.Comment: 36 pages, 2 figure

The Chameleonic Contribution to the SZ Radial Profile of the Coma Cluster

We constrain the chameleonic Sunyaev--Zel'dovich (CSZ) effect in the Coma cluster from measurements of the Coma radial profile presented in the WMAP 7-year results. The CSZ effect arises from the interaction of a scalar (or pseudoscalar) particle with the cosmic microwave background in the magnetic field of galaxy clusters. We combine this radial profile data with SZ measurements towards the centre of the Coma cluster in different frequency bands, to find Delta T_{SZ,RJ}(0)=-400+/-40 microKelvin and Delta T_{CSZ}^{204 GHz}(0)=-20+/-15 microKelvin (68% CL) for the thermal SZ and CSZ effects in the cluster respectively. The central value leads to an estimate of the photon to scalar (or pseudoscalar) coupling strength of g = (5.2 - 23.8) x 10^{-10} GeV^{-1}, while the 95% confidence bound is estimated to be g < (8.7 - 39.4) x 10^{-10} GeV^{-1}.Comment: 13 pages, 3 figure