A Cluster of Compact Radio Sources in W40

We present deep 3.6 cm radio continuum observations of the HII region W40 obtained using the Very Large Array in its A and B configurations. We detect a total of 20 compact radio sources in a region of 4 x 4 arcmin, with 11 of them concentrated in a band with 30 arcsec of extent. We also present JHK photometry of the W40 cluster taken with the QUIRC instrument on the University of Hawaii 2.2 meter telescope. These data reveal that 15 of the 20 VLA sources have infrared counterparts, and 10 show radio variability with periods less than 20 days. Based on these combined radio and IR data, we propose that 8 of the radio sources are candidate ultracompact HII regions, 7 are likely to be young stellar objects, and 2 may be shocked interstellar gas.Comment: Accepted for publication in the Astronomical Journal. 10 pages, 4 figures, plus online table in electronic versio

Work and pay in flexible and regulated labor markets: A generalized perspective on institutional evolution and inequality trends in Europe and the US

In den letzten Jahren hat sich eine unified theory aus der Arbeitsökonomik heraus-gebildet, in der die Meinung vorherrscht, dass die Kombination makroökonomi- scher Schocks und flexibler Arbeitsmarktinstitutionen in den USA eine starke Zu-nahme der Lohnungleichheit verursacht habe, während die gleichen Schocks in Europa vor allem für gering qualifizierte Arbeitnehmer eine hohe Arbeitslosigkeit und geringe Beschäftigungsniveaus gebracht hätten als (unerwünschter) Nebeneffekt der durch die strikten institutionellen Regelungen des Arbeitsmarkts in Europa rigiden Löhne. In der vorliegenden Analyse wird hingegen argumentiert, dass Institutionen in Europa eigene Formen der Flexibilität entwickelt hätten, die im Gefolge der in der unified theory beschriebenen Schocks ebenfalls zu einer zunehmenden Un-gleichheit in Europa geführt hätten, aber eben in anderer Gestalt. In Frankreich sei beispielsweise die Ungleichheit bei der Arbeitsplatzsicherheit schneller gewachsen als in den USA. Darüber hinaus hätten Entwicklungen auf dem französischen Ar-beitsmarkt dazu geführt, dass sich gering qualifizierte Arbeitnehmer in unsicheren Beschäftigungsverhältnissen konzentrierten. -- In recent years a unified theory has emerged out of labor economics, which argues that a combination of macroeconomic shocks and flexible labor market institutions in the U.S. has produced strong upward trends in wage inequality, while these same shocks have produced high unemployment and low employment growth in Europe as a side effect of the wage stability preserved by that continents rigid labor market in-stitutions. This paper argues instead that European institutions in fact have evolved their own form of flexibility, which, in combination with the macroeconomic shocks described in the unified theory, have also led to rising inequality in Europe, but of a different form. Taking France as an example, inequality of employment security has risen faster here than in the U.S. Furthermore, trends in the French labor market have led to increased concentration of low-skill workers in these insecure job statuses. These results challenge the view that unemployment is the main mecha-nism through which European labor markets absorbed asymmetric shocks to their demand for labor. They also challenge the view that Europeans have intolerance for inequality, but instead suggest that the main difference between the two sides of the Atlantic concerns the nature of the inequalities that each society is willing to tolerate.

Smearing of the 2D Kohn anomaly in a nonquantizing magnetic field: Implications for the interaction effects

Thermodynamic and transport characteristics of a clean two-dimensional interacting electron gas are shown to be sensitive to the weak perpendicular magnetic field even at temperatures much higher than the cyclotron energy, when the quantum oscillations are completely washed out. We demonstrate this sensitivity for two interaction-related characteristics: electron lifetime and the tunnel density of states. The origin of the sensitivity is traced to the field-induced smearing of the Kohn anomaly; this smearing is the result of curving of the semiclassical electron trajectories in magnetic field.Comment: 4.5 pages, 3 figures, published versio

An O(M(n) log n) algorithm for the Jacobi symbol

The best known algorithm to compute the Jacobi symbol of two n-bit integers runs in time O(M(n) log n), using Sch\"onhage's fast continued fraction algorithm combined with an identity due to Gauss. We give a different O(M(n) log n) algorithm based on the binary recursive gcd algorithm of Stehl\'e and Zimmermann. Our implementation - which to our knowledge is the first to run in time O(M(n) log n) - is faster than GMP's quadratic implementation for inputs larger than about 10000 decimal digits.Comment: Submitted to ANTS IX (Nancy, July 2010

Heap Reference Analysis Using Access Graphs

Despite significant progress in the theory and practice of program analysis, analysing properties of heap data has not reached the same level of maturity as the analysis of static and stack data. The spatial and temporal structure of stack and static data is well understood while that of heap data seems arbitrary and is unbounded. We devise bounded representations which summarize properties of the heap data. This summarization is based on the structure of the program which manipulates the heap. The resulting summary representations are certain kinds of graphs called access graphs. The boundedness of these representations and the monotonicity of the operations to manipulate them make it possible to compute them through data flow analysis. An important application which benefits from heap reference analysis is garbage collection, where currently liveness is conservatively approximated by reachability from program variables. As a consequence, current garbage collectors leave a lot of garbage uncollected, a fact which has been confirmed by several empirical studies. We propose the first ever end-to-end static analysis to distinguish live objects from reachable objects. We use this information to make dead objects unreachable by modifying the program. This application is interesting because it requires discovering data flow information representing complex semantics. In particular, we discover four properties of heap data: liveness, aliasing, availability, and anticipability. Together, they cover all combinations of directions of analysis (i.e. forward and backward) and confluence of information (i.e. union and intersection). Our analysis can also be used for plugging memory leaks in C/C++ languages.Comment: Accepted for printing by ACM TOPLAS. This version incorporates referees' comment

Allosterically Tunable, DNA-Based Switches Triggered by Heavy Metals

Here we demonstrate the rational design of allosterically controllable, metal-ion-triggered molecular switches. Specifically, we designed DNA sequences that adopt two low energy conformations, one of which does not bind to the target ion and the other of which contains mismatch sites serving as specific recognition elements for mercury(II) or silver(I) ions. Both switches contain multiple metal binding sites and thus exhibit homotropic allosteric (cooperative) responses. As heterotropic allosteric effectors we employ single-stranded DNA sequences that either stabilize or destabilize the nonbinding state, enabling dynamic range tuning over several orders of magnitude. The ability to rationally introduce these effects into target-responsive switches could be of value in improving the functionality of DNA-based nanomachines

On the Detection of Magnetic Helicity

Magnetic fields in various astrophysical settings may be helical and, in the cosmological context, may provide a measure of primordial CP violation during baryogenesis. Yet it is difficult, even in principle, to devise a scheme by which magnetic helicity may be detected, except in some very special systems. We propose that charged cosmic rays originating from known sources may be useful for this purpose. We show that the correlator of the arrival momenta of the cosmic rays is sensitive to the helicity of an intervening magnetic field. If the sources themselves are not known, the method may still be useful provided we have some knowledge of their spatial distribution.Comment: 5 pages, 1 figure, discussions and references added, submited to Phys. Rev.