UV line diagnostics of accretion disk winds in cataclysmic variables

The IUE data base is used to analyze the UV line shapes of cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating bi-conical winds from accretion disks. The wind model calculates the wind ionization structure self-consistently including photoionization from the disk and boundary layer and treats 3-D line radiation transfer in the Sobolev approximation. It is found that winds from accretion disks provide a good fit for reasonable parameters to the observed UV lines which include the P Cygni profiles for low inclination systems and pure emission at large inclination. Disk winds are preferable to spherical winds which originate on the white dwarf because they (1) require a much lower ratio of mass loss rate to accretion rate and are therefore more plausible energetically, (2) provide a natural source for a bi-conical distribution of mass outflow which produces strong scattering far above the disk leading to P Cygni profiles for low inclination systems, and pure line emission profiles at high inclination with the absence of eclipses in UV lines, and (3) produce rotation broadened pure emission lines at high inclination

Rotating Winds from Accretion Disks in Cataclysmic Variables: Eclipse Modeling of V347 Puppis

We study the eclipsing nova-like variable V347 Pup by matching its UV emission line profiles in and out of eclipse to synthetic lines using a 3D kinematic and radiation transfer model. Our results support the accretion disk origin of winds in non-magnetic CVs as opposite to the WD origin. Our main point concerns the importance of rotation for the UV emission line shapes in such systems. In particular, we show that the narrowing of the UV emission lines in V347 Pup during eclipse can be easily explained by the eclipse of the innermost part of the wind by the secondary and the resulting reduction in the contribution of rotational broadening to the width of the lines. During the eclipse, the residual line flux is very sensitive to the maximal temperature of disk radiation. Good fits for reasonable mass-loss rates have been obtained for maximum disk temperatures of 50,000 degrees. This constraint was imposed either by leveling off the inner disk temperature profiles, in agreement with recent observations of some nova-like objects, or by assuming that the accretion disk does not extend to the surface of the white dwarf, in which case V347 up would be an intermediate polar. In anticipation of high-speed spectrophotometry of CVs by the HST, we provide numerical model of a time-resolved eclipse of V347 Pup or similar such system to be verified by future observations.Comment: x pages, postscrip, compressed uuencoded. 11 figures available by anonymous ftp from ftp://asta.pa.uky.edu/shlosman/puppis/ (get *.PS.Z). To appear in Ap

Demand for cooking fuels in a developing country. To what extent do taste and preferences matter?

Overreliance on biomass energy, such as firewood and charcoal, for cooking in developing countries has contributed to high rates of deforestation and resulted in substantial indoor pollution which has negatively impacted the health of many individuals. However, the effectiveness of public policies aimed at encouraging households to switch to cleaner fuels, such as liquefied petroleum gas (LPG) and kerosene, hinges on the extent to which they are mentally committed to specific fuels. Using data on four cooking fuels (charcoal, firewood, LPG, and kerosene) from the Ghana living standards survey, we found strong evidence that the most preferred fuel is LPG, followed by charcoal, with kerosene the least preferred. In addition, with the exception of kerosene that has price-elastic demand, the price elasticities of demand for the fuel types examined are inelastic. This finding suggests the so-called fuel-ladder is not robust.Demand for fuel Taste and preferences Ghana

Finite geometry models of electric field noise from patch potentials in ion traps

We model electric field noise from fluctuating patch potentials on conducting surfaces by taking into account the finite geometry of the ion trap electrodes to gain insight into the origin of anomalous heating in ion traps. The scaling of anomalous heating rates with surface distance, $d$, is obtained for several generic geometries of relevance to current ion trap designs, ranging from planar to spheroidal electrodes. The influence of patch size is studied both by solving Laplace's equation in terms of the appropriate Green's function as well as through an eigenfunction expansion. Scaling with surface distance is found to be highly dependent on the choice of geometry and the relative scale between the spatial extent of the electrode, the ion-electrode distance, and the patch size. Our model generally supports the $d^{-4}$ dependence currently found by most experiments and models, but also predicts geometry-driven deviations from this trend

Cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging

The implementation challenges of cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging are discussed and work on the subject is reviewed. System architecture and sensor fusion are identified as key challenges. A partially decentralized system architecture based on step-wise inertial navigation and step-wise dead reckoning is presented. This architecture is argued to reduce the computational cost and required communication bandwidth by around two orders of magnitude while only giving negligible information loss in comparison with a naive centralized implementation. This makes a joint global state estimation feasible for up to a platoon-sized group of agents. Furthermore, robust and low-cost sensor fusion for the considered setup, based on state space transformation and marginalization, is presented. The transformation and marginalization are used to give the necessary flexibility for presented sampling based updates for the inter-agent ranging and ranging free fusion of the two feet of an individual agent. Finally, characteristics of the suggested implementation are demonstrated with simulations and a real-time system implementation.Comment: 14 page

Surface-electrode ion trap with integrated light source

An atomic ion is trapped at the tip of a single-mode optical fiber in a cryogenic (8 K) surface-electrode ion trap. The fiber serves as an integrated source of laser light, which drives the quadrupole qubit transition of $^{88}$Sr$^+$. Through \emph{in situ} translation of the nodal point of the trapping field, the Gaussian beam profile of the fiber output is imaged, and the fiber-ion displacement, in units of the mode waist at the ion, is optimized to within $0.13\pm0.10$ of the mode center despite an initial offset of $3.30\pm0.10$. Fiber-induced charging at $125 \mu$W is observed to be ${\sim}10$ V/m at an ion height of $670 \mu$m, with charging and discharging time constants of $1.6\pm0.3$ s and $4.7\pm0.6$ s respectively. This work is of importance to large-scale, ion-based quantum information processing, where optics integration in surface-electrode designs may be a crucial enabling technology.Comment: 4 pages, 4 figure