Non-gaussian Noise in Quantum Spin Glasses and Interacting Two-level Systems

We study a general model for non-gaussian $1/f$ noise based on an infinite range quantum Ising spin system in the paramagnetic state, or equivalently, interacting two-level classical fluctuators. We identify a dilatation interaction term in the dynamics which survives the thermodynamic limit and circumvents the central limit theorem to produce non-gaussian noise even when the equilibrium distribution is that of {\em non-interacting} spins. The resulting second spectrum (`noise of the noise') itself has a universal $1/f$ form which we analyze within a dynamical mean field approximation.Comment: 4 pages, 3 figure

Assessment of assimilating SMOS soil moisture information into a distributed hydrologic model

The role that soil moisture plays in terms of modulating hydrologic processes including infiltration and runoff generation makes it an essential component to capture for hydrologic modeling. This work aims to leverage information gained from SMOS to improve surface soil moisture simulations in the Russian River Basin (California, U.S.A). The basin's complex terrain offers a rigorous testing ground for SMOS soil moisture products. Data from seven in situ observation sites are used to assess model performance after assimilating SMOS-based soil saturation ratios. For a comparison of "best case" scenarios, the in situ observations themselves are assimilated. Results show that SMOS assimilated simulations shows modest improvement at most in situ locations. Despite the observed decrease in model performance at some locations, overall performance of simulations assimilated with SMOS-based saturation ratios remains high. Findings suggest that even in a complex environment, useful information may be extracted from SMOS estimates for hydrologic modeling

Non-linear generation of acoustic noise in the IAR spacecraft

The requirement to produce high level acoustic noise fields with increasing accuracy in environmental test facilities dictates that a more precise understanding is required of the factors controlling nonlinear noise generation. Details are given of various nonlinear effects found in acoustic performance data taken from the IAR Spacecraft Acoustic Chamber. This type of data has enabled the IAR to test large spacecraft to relatively tight acoustic tolerances over a wide frequency range using manually set controls. An analog random noise automatic control system was available and modified to provide automatic selection of the chamber's spectral sound pressure levels. The automatic control system when used to complete a typical qualification test appeared to equal the accuracy of the manual system and had the added advantage that parallel spectra could be easily achieved during preset tests

Fluorescent optical fibre chemosensor for the detection of mercury

This work aims to develop a stable, compact and portable fibre optic sensing system which is capable of real time detection of the mercury ion (II), Hg2+. A novel fluorescent polymeric material for Hg2+ detection, based on a coumarin derivative (acting as the fluorophore) and an azathia crown ether moiety (acting as the mercury ion receptor), has been designed and synthesized. The material was covalently attached to the distal end of an optical fibre and exhibited a significant increase in fluorescence intensity in response to Hg2+ in the μM concentration range via a photoinduced electron transfer (PET) mechanism. The sensor has also demonstrated a high selectivity for Hg2+ over other metal ions. A washing protocol was identified for sensor regeneration, allowing the probe to be re-used. The approach developed in this work can also be used for the preparation of sensors for other heavy metals

Jet Fragmentation in Vacuum and Medium with gamma-hadron Correlations in PHENIX

Jet fragmentation in p+p and Au+Au collisions is studied via back-to-back correlations of direct photons and charged hadrons. The direct photon correlations are obtained by statical subtraction of the background from decay photons. Results on the nuclear modification to the associated charged hadron yields are reviewed. Further studies of jet fragmentation in p+p using isolated direct photons are also presented. A kT-smeared LO pQCD calculation is used to interpret the data. The sensitivity of the data to the underlying fragmentation function is tested and the results are found to be compatible with expectations of a sample dominated by quark jet fragmentation.Comment: Talk presented at Hot Quarks 2010, June 21-26, La Londe Les Maures, France. To be published in Journal of Physics: Conference Series (JPCS

Pilot Human Factors in Stall/Spin Accidents of Supersonic Fighter Aircraft

A study has been made of pilot human factors related to stall/spin accidents of supersonic fighter aircraft. The military specifications for flight at high angles of attack are examined. Several pilot human factors problems related to stall/spin are discussed. These problems include (1) unsatisfactory nonvisual warning cues; (2) the inability of the pilot to quickly determine if the aircraft is spinning out of control, or to recognize the type of spin; (3) the inability of the pilot to decide on and implement the correct spin recovery technique; (4) the inability of the pilot to move, caused by high angular rotation; and (5) the tendency of pilots to wait too long in deciding to abandon the irrecoverable aircraft. Psycho-physiological phenomena influencing pilot's behavior in stall/spin situations include (1) channelization of sensory inputs, (2) limitations in precisely controlling several muscular inputs, (3) inaccurate judgment of elapsed time, and (4) disorientation of vestibulo-ocular inputs. Results are given of pilot responses to all these problems in the F14A, F16/AB, and F/A-18A aircraft. The use of departure spin resistance and automatic spin prevention systems incorporated on recent supersonic fighters are discussed. These systems should help to improve the stall/spin accident record with some compromise in maneuverability

SLS Processing Studies of Nylon 11 Nanocomposites

Selective Laser Sintering (SLS) is widely used for rapid prototyping/manufacturing of nylon 11 and nylon 12 parts. This processing technique has not been explored for nylon nanocomposites. This study investigates the technicalities of processing nylon 11-clay and nylon-carbon nanofiber nanocomposites with SLS. Microstructural analyses of the SLS powders and parts were conducted under SEM. Results suggest that SLS processing is possible with the new nylon 11 nanocomposites. Yet the SLS parts built have inferior properties relative to those of injection molding, suggesting that more fine tuning for the processing is required.Mechanical Engineerin

New insights on the dense molecular gas in NGC253 as traced by HCN and HCO+

We have imaged the central ~1kpc of the circumnuclear starburst disk in the galaxy NGC253 in the HCN(1-0), HCO+(1-0), and CO(1-0) transitions at 60pc resolution using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO). We have also obtained Atacama Pathfinder Experiment (APEX) observations of the HCN(4-3) and the HCO+(4-3) lines of the starburst disk. We find that the emission from the HCN(1-0) and HCO+(1-0) transitions, both indicators of dense molecular gas, trace regions which are non-distinguishable within the uncertainties of our observations. Even though the continuum flux varies by more than a factor 10 across the starburst disk, the HCN/HCO+ ratio is constant throughout the disk, and we derive an average ratio of 1.1+/-0.2. From an excitation analysis we find that all lines from both molecules are subthermally excited and that they are optically thick. This subthermal excitation implies that the observed HCN/HCO+ line ratio is sensitive to the underlying chemistry. The constant line ratio thus implies that there are no strong abundance gradients across the starburst disk of NGC253. This finding may also explain the variations in L'(HCN)/L'(HCO+) between different star forming galaxies both nearby and at high redshifts.Comment: 9 pages, 12 figures, ApJ in press (volume 666 September