Constraining the Sub-AU-Scale Distribution of Hydrogen and Carbon Monoxide Gas around Young Stars with the Keck Interferometer

We present Keck Interferometer observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milliarcseconds and a spectral resolution of ~2000. Our observations span the K-band, and include the Br gamma transition of Hydrogen and the v=2-0 and v=3-1 transitions of carbon monoxide. For several targets we also present data from Keck/NIRSPEC that provide higher spectral resolution, but a seeing-limited spatial resolution, of the same spectral features. We analyze the Br gamma emission in the context of both disk and infall/outflow models, and conclude that the Br gamma emission traces gas at very small stellocentric radii, consistent with the magnetospheric scale. However some Br gamma-emitting gas also seems to be located at radii of >0.1 AU, perhaps tracing the inner regions of magnetically launched outflows. CO emission is detected from several objects, and we generate disk models that reproduce both the KI and NIRSPEC data well. We infer the CO spatial distribution to be coincident with the distribution of continuum emission in most cases. Furthermore the Br gamma emission in these objects is roughly coincident with both the CO and continuum emission. We present potential explanations for the spatial coincidence of continuum, Br gamma, and CO overtone emission, and explore the implications for the low occurrence rate of CO overtone emission in young stars. Finally, we provide additional discussion of V1685 Cyg, which is unusual among our sample in showing large differences in emitting region size and spatial position as a function of wavelength.Comment: Accepted for publication in MNRA

The year 1970-a "modest" beginning for monetary aggregates

Monetary policy - United States

Phase-resolved far-ultraviolet HST spectroscopy of the peculiar magnetic white dwarf RE J0317-853

We present phase resolved FUV HST FOS spectra of the rapidly rotating, highly magnetic white dwarf RE J0317-853. Using these data, we construct a new model for the magnetic field morphology across the stellar surface. From an expansion into spherical harmonics, we find the range of magnetic field strengths present is 180-800MG. For the first time we could identify an absorption feature present at certain phases at 1160A as a ``forbidden'' 1s_0 -> 2s_0 component, due to the combined presence of an electric and magnetic field.Comment: 15 pages including 4 figures. Accepted for publication in ApJ Letter

Model for Cumulative Solar Heavy Ion Energy and Linear Energy Transfer Spectra

A probabilistic model of cumulative solar heavy ion energy and LET spectra is developed for spacecraft design applications. Spectra are given as a function of confidence level, mission time period during solar maximum and shielding thickness. It is shown that long-term solar heavy ion fluxes exceed galactic cosmic ray fluxes during solar maximum for shielding levels of interest. Cumulative solar heavy ion fluences should therefore be accounted for in single event effects rate calculations and in the planning of space missions

Beyond Optimal Linear Tax Mechanisms: An Experimental Examination of Damage-Based Ambient Taxes for Nonpoint Polluters

The regulation of nonpoint source water pollution from agriculture is a complex problem characterized by a multiplicity of polluters, informational asymmetries, complex fate and transport processes, and stochastic environmental factors. Taken together, these characteristics make regulatory policy based on individual firm emissions prohibitively costly. To circumvent this issue, economists, beginning with the seminal work of Segerson (1988), have devised economic incentive instruments that assign liabilities based on deviations between the observed ambient water quality level and a specified pollution threshold (Xepapadeas 1991; Horan, Shortle and Abler 1998, 2002; Hansen 1998, 2002). In the special case of a linear damage function, the regulator can optimally set the parameters of Segerson's (1988) incentive scheme solely with information on the damage function. When the damage function is nonlinear, a depiction that likely represents many watersheds, Segerson's incentive scheme is firm-specific, and the regulator must acquire costly firm-specific data on factors such as input use, land management practice, and soil type. Using a linear damage function setting, recent laboratory experimental economics efforts have investigated the ambient-based mechanisms proposed by Segerson, as well as some simple variants (Spraggon 2002, 2004; Poe et al. 2004; Vossler et al. 2005). A fundamental limitaion of this body of research, however, is that has utilized an "optimal design" in which the threshold pollution level for triggering the abient-based policy is set equal to the social optimum. It is therefore unclear whether subjects are optimally responding to the tax and threshold combination, or simply trying to reacting to the focal point created by the threshold. A second limitation of past experimetnal economics research is that, following Segerson, these investigations have utilized the limited case of a linear tax function. While a tax policy is relatively straightforward to apply when damages are linear, the application to real world situations may be limited. A more believable circumstance is that economic damages increase at an increasing rate as ambient pollution levels rise. This paper advances the experimental literature on ambient based pollution mechanisms in two important ways. First, by employing a range of marginal tax rates and threshold levels, we show that subjects do in fact respond optimally to the tax and cutoff combination. Second, by using the damage based tax proposed Hansen (1998) and Horan et al. (1998), we show that aggregate results when the economic damages from ambient water pollution are nonlinear are not significantly different from corresponding results under the linear tax.Environmental Economics and Policy,

Flight and wind-tunnel calibrations of a flush airdata sensor at high angles of attack and sideslip and at supersonic Mach numbers

A nonintrusive airdata-sensing system was calibrated in flight and wind-tunnel experiments to an angle of attack of 70 deg and to angles of sideslip of +/- 15 deg. Flight-calibration data have also been obtained to Mach 1.2. The sensor, known as the flush airdata sensor, was installed on the nosecap of an F-18 aircraft for flight tests and on a full-scale F-18 forebody for wind-tunnel tests. Flight tests occurred at the NASA Dryden Flight Research Facility, Edwards, California, using the F-18 High Alpha Research Vehicle. Wind-tunnel tests were conducted in the 30- by 60-ft wind tunnel at the NASA LaRC, Hampton, Virginia. The sensor consisted of 23 flush-mounted pressure ports arranged in concentric circles and located within 1.75 in. of the tip of the nosecap. An overdetermined mathematical model was used to relate the pressure measurements to the local airdata quantities. The mathematical model was based on potential flow over a sphere and was empirically adjusted based on flight and wind-tunnel data. For quasi-steady maneuvering, the mathematical model worked well throughout the subsonic, transonic, and low supersonic flight regimes. The model also worked well throughout the angles-of-attack and -sideslip regions studied

Thermal correlators of anyons in two dimensions

The anyon fields have trivial $\alpha$-commutator for $\alpha$ not integer. For integer $\alpha$ the commutators become temperature-dependent operator valued distributions. The $n$-point functions do not factorize as for quasifree states.Comment: 14 pages, LaTeX (misprints corrected, a reference added

Quantum logic as superbraids of entangled qubit world lines

Presented is a topological representation of quantum logic that views entangled qubit spacetime histories (or qubit world lines) as a generalized braid, referred to as a superbraid. The crossing of world lines is purely quantum in nature, most conveniently expressed analytically with ladder-operator-based quantum gates. At a crossing, independent world lines can become entangled. Complicated superbraids are systematically reduced by recursively applying novel quantum skein relations. If the superbraid is closed (e.g. representing quantum circuits with closed-loop feedback, quantum lattice gas algorithms, loop or vacuum diagrams in quantum field theory), then one can decompose the resulting superlink into an entangled superposition of classical links. In turn, for each member link, one can compute a link invariant, e.g. the Jones polynomial. Thus, a superlink possesses a unique link invariant expressed as an entangled superposition of classical link invariants.Comment: 4 page

Tip-enhanced fluorescence microscopy at 10 nanometer resolution

Journal ArticleWe demonstrate unambiguously that the field enhancement near the apex of a laser-illuminated silicon tip decays according to a power law that is moderated by a single parameter characterizing the tip sharpness. Oscillating the probe in intermittent contact with a semiconductor nanocrystal strongly modulates the fluorescence excitation rate, providing robust optical contrast and enabling excellent background rejection. Laterally encoded demodulation yields images with <10 nm spatial resolution, consistent with independent measurements of tip sharpness