Multiple junction biasing of superconducting tunnel junction detectors

We describe a new biasing scheme for single photon detectors based on superconducting tunnel junctions. It replaces a single detector junction with a circuit of three junctions and achieves biasing of a detector junction at subgap currents without the use of an external magnetic field. The biasing occurs through the nonlinear interaction of the three junctions, which we demonstrate through numerical simulation. This nonlinear state is numerically stable against external fluctuations and is compatible with high fidelity electrical readout of the photon-induced current. The elimination of the external magnetic field potentially increases the capability of these types of photon detectors and eases constraints involved in the fabrication of large detector arrays.Comment: 15 pages, including 3 figure

Impact of Undocumented Populations on 2010 Congressional Reapportionment.

This report compares the allocation of House of Representative seats in 2010 using two scenarious building from the most defensible 2010 population projections for each of the fifty states. The first scenario assumes that Census 2010 counts all undocumented residents in all states. The second scenario assumes that none of the undocument residents are used as a basis for apportionment distribution.immigration; congressional apportionment; Census Bureau, representation.

Origin of asymmetries in X-ray emission lines from the blast wave of the 2014 outburst of nova V745 Sco

The symbiotic nova V745 Sco was observed in outburst on 2014 February 6. Its observations by the Chandra X-ray Observatory at days 16 and 17 have revealed a spectrum characterized by asymmetric and blue-shifted emission lines. Here we investigate the origin of these asymmetries through three-dimensional hydrodynamic simulations describing the outburst during the first 20 days of evolution. The model takes into account thermal conduction and radiative cooling and assumes a blast wave propagates through an equatorial density enhancement. From the simulations, we synthesize the X-ray emission and derive the spectra as they would be observed with Chandra. We find that both the blast wave and the ejecta distribution are efficiently collimated in polar directions due to the presence of the equatorial density enhancement. The majority of the X-ray emission originates from the interaction of the blast with the equatorial density enhancement and is concentrated on the equatorial plane as a ring-like structure. Our "best-fit" model requires a mass of ejecta in the outburst $M_{ej} \approx 3\times 10^{-7}\,M_{\odot}$ and an explosion energy $E_b \approx 3 \times 10^{43}$ erg and reproduces the distribution of emission measure vs temperature and the evolution of shock velocity and temperature inferred from the observations. The model predicts asymmetric and blue-shifted line profiles similar to those observed and explains their origin as due to substantial X-ray absorption of red-shifted emission by ejecta material. The comparison of predicted and observed Ne and O spectral line ratios reveals no signs of strong Ne enhancement and suggests the progenitor is a CO white dwarf.Comment: 16 pages, 17 Figures; accepted for publication on MNRA

The X-ray cycle in the solar-type star HD 81809

(abridged) Our long-term XMM-Newton program of long-term monitoring of a solar-like star with a well-studied chromospheric cycle, HD 81809 aims to study whether an X-ray cycle is present, along with studying its characteristics and its relation to the chromospheric cycle. Regular observations of HD 81809 were performed with XMM-Newton, spaced by 6 months from 2001 to 2007. We studied the variations in the resulting coronal luminosity and temperature, and compared them with the chromospheric CaII variations. We also modeled the observations in terms of a mixture of active regions, using a methodology originally developed to study the solar corona. Our observations show a well-defined cycle with an amplitude exceeding 1 dex and an average luminosity approximately one order of magnitude higher than in the Sun. The behavior of the corona of HD 81809 can be modeled well in terms of varying coverage of solar-like active regions, with a larger coverage than for the Sun, showing it to be compatible with a simple extension of the solar case.Comment: In press, Astronomy & Astrophysic

Do only big cities innovate? : technological maturity and the location of innovation

Innovation enhances economic performance. High rates of innovation are associated with high rates of productivity growth, and faster productivity growth leads to higher real wages and improvements in standards of living. Consequently, many local policymakers are eager to encourage higher rates of innovation in their areas. Theoretical and empirical studies of the geography of innovation find that relatively populous regions are the most conducive to innovative activity. Large and densely populated places offer more developed markets for the specialized inputs used in innovation. Populous places also offer innovators greater opportunities to learn from one another. On the surface, these findings seem to offer little hope to smaller, more sparsely populated regions—places that would like to compete for innovative activity and the benefits of a knowledge economy. Are large populations a prerequisite for innovation? Orlando and Verba explore this common perception and find it is not always true. More populous regions dominate in relatively new technological fields, where innovations are more original. But less populous regions can compete in relatively mature technological fields, where innovations are more incremental. This finding should be of interest to research and development professionals—and to policymakers who are seeking ways to enhance regional innovative activity.Cities and towns

Non-equilibrium of Ionization and the Detection of Hot Plasma in Nanoflare-heated Coronal Loops

Impulsive nanoflares are expected to transiently heat the plasma confined in coronal loops to temperatures of the order of 10 MK. Such hot plasma is hardly detected in quiet and active regions, outside flares. During rapid and short heat pulses in rarified loops the plasma can be highly out of equilibrium of ionization. Here we investigate the effects of the non-equilibrium of ionization (NEI) on the detection of hot plasma in coronal loops. Time-dependent loop hydrodynamic simulations are specifically devoted to this task, including saturated thermal conduction, and coupled to the detailed solution of the equations of ionization rate for several abundant elements. In our simulations, initially cool and rarified magnetic flux tubes are heated to 10 MK by nanoflares deposited either at the footpoints or at the loop apex. We test for different pulse durations, and find that, due to NEI effects, the loop plasma may never be detected at temperatures above ~5 MK for heat pulses shorter than about 1 min. We discuss some implications in the framework of multi-stranded nanoflare-heated coronal loops.Comment: 22 pages, 7 figures, accepted for publicatio

Curvature from quantum deformations

A Poisson coalgebra analogue of a (non-standard) quantum deformation of sl(2) is shown to generate an integrable geodesic dynamics on certain 2D spaces of non-constant curvature. Such a curvature depends on the quantum deformation parameter z and the flat case is recovered in the limit z\to 0. A superintegrable geodesic dynamics can also be defined in the same framework, and the corresponding spaces turn out to be either Riemannian or relativistic spacetimes (AdS and dS) with constant curvature equal to z. The underlying coalgebra symmetry of this approach ensures the existence of its generalization to arbitrary dimension.Comment: 10 pages, LaTe

Barriers to network-specific innovation

We consider an environment in which participants make payments over a network and can invest in a technology that reduces the marginal cost of using the network. A network effect results in multiple equilibria; either all agents invest and usage of the network is high or no agents invest and usage of the network is low. The high-usage equilibrium can be implemented through introduction of a coordinator. Under monopoly network ownership, however, fixed costs associated with use of the network-specific technology result in a hold-up problem that implements the low-investment equilibrium. And even where subsidies can avoid such hold-up, optimal monopoly pricing of network usage may avoid investment in the network-specific technology if demand for on-network transactions is sufficiently inelastic.Payment systems