Chandra Imaging and Spectroscopy of the Eastern XA Region of the Cygnus Loop Supernova Remnant

The XA region of the Cygnus Loop is a bright knot of X-ray emission on the eastern edge of the supernova remnant resulting from the interaction of the supernova blast wave with density enhancements at the edge of a precursor formed cavity. To study the nature and origin of the X-ray emission we use high spatial resolution images from Chandra. Our goal is to probe the density of various spectral extraction regions to form a picture of the cavity wall and characterize the interaction between this supernova and the local interstellar medium. We find that a series of regions along the edge of the X-ray emission appears to trace out the location of the cavity wall. The best fit plasma models result in two temperature component equilibrium models for each region. The low temperature components have densities that are an order of magnitude higher than the high temperature components. The high density plasma may exist in the cavity wall where it equilibrates rapidly and cools efficiently. The low density plasma is interior to the enhancement and heated further by a reverse shock from the wall. Calculations of shock velocities and timescales since shock heating are consistent with this interpretation. Furthermore, we find a bright knot of emission indicative of a discrete interaction of the blast wave with a high density cloud in the cavity wall with a size scale ~0.1 pc. Aside from this, other extractions made interior to the X-ray edge are confused by line of sight projection of various components. Some of these regions show evidence of detecting the cavity wall but their location makes the interpretation difficult. In general, the softer plasmas are well fit at temperatures kT~0.11 keV, with harder plasmas at temperatures of kT~0.27 keV. All regions display consistent metal depletions most notably in N, O, and Ne at an average of 0.54, 0.55, and 0.36 times solar

The Strength of Occupation Indicators as a Proxy for Skill

Labor economists have long used occupation indicators as a proxy for unobserved skills that a worker possesses. In this paper, we consider whether inter-occupational wage differentials that are unexplained by measured human capital are indeed due to differences in often-unmeasured skill. Using the National Compensation Survey, a large, nationally- representative dataset on jobs and ten different components of requisite skill, we compare the effects on residual wage variation of including occupation indicators and including additional skills measures. We find that although skills do vary across 3-digit occupations, occupation indicators decrease wage residuals by far more than can be explained by skill differentials. This indicates that “controlling for occupation” does not equate to controlling for skill alone, but also for some other factors to a great extent. Additionally, we find that there is considerable within occupation variation in skills, and that the amount of variation is not constant across skill levels. As a result, including occupation indicators in a wage model introduces heteroskedasticity that must be accounted for. We suggest that greater caution be applied when using and interpreting occupation indicators as controls in wage regressions.human capital measurement; job skills; occupation indicator variables

Time resolved observation of resonant and non-resonant contributions to the nonlinear susceptibility χ(3)

The resonant and nonresonant part of χ(3) are distinguished by their different time behavior. The medium is coherently excited by two picosecond light pulses of defined frequency difference and the state of the system is monitored by a third properly delayed probe pulse. Results are presented on neat liquids of carbontetrachloride and cyclohexane and on the mixture of CCl4: C6H12

Spectral imaging in preclinical research and clinical pathology.

Spectral imaging methods are attracting increased interest from researchers and practitioners in basic science, pre-clinical and clinical arenas. A combination of better labeling reagents and better optics creates opportunities to detect and measure multiple parameters at the molecular and cellular level. These tools can provide valuable insights into the basic mechanisms of life, and yield diagnostic and prognostic information for clinical applications. There are many multispectral technologies available, each with its own advantages and limitations. This chapter will present an overview of the rationale for spectral imaging, and discuss the hardware, software and sample labeling strategies that can optimize its usefulness in clinical settings

Where is My Attention?

Attention is the key to all learning. Indeed, it is what will save our lives on a daily basis. In all my Communication courses, it is one of the first things I put forward as a question that students may ask of themselves as a check on their “internal considering.” Philosopher/practitioner George Gurdjieff (1866-1949) called the constant rumble in our minds of random condemnations and re-imaginings of past events as “internal considering.” He felt it was detrimental to ourselves and our relationships with others; it is, I maintain, a constant “self considering” that takes us away from the present and “being here now.” So recognizing that we are often not paying attention to what is happening in the space we are in now, with the people we are with now, is the first step in correcting this distracting state of affairs

Zero supermode-based multipartite entanglement in χ(2)\chi^{(2)} nonlinear waveguides arrays

We show that arrays of $\chi^{(2)}$ nonlinear waveguides in the second harmonic generation regime are a promising source of continuous-variable entanglement. We indeed demonstrate analytically that optical arrays with odd number of waveguides injected with the zero-eigenvalue fundamental supermode entangle this fundamental supermode with a collective harmonic field. Moreover the fundamental individual modes are multipartite entangled and their entanglement grows with propagation length. The device is scalable, robust to losses, does not rely on specific values of nonlinearity and coupling and is easily realized with current technology. It thus stands as an unprecedented candidate for generation of multipartite continuous-variable entanglement for optical quantum information processing.Comment: Main text: 7 pages, 6 figures. Supplemental material: 5 pages, 2 figure. v2 closer to published versio

Environmental Impact on the Southeast Limb of the Cygnus Loop

We analyze observations from the Chandra X-ray Observatory of the southeast knot of the Cygnus Loop supernova remnant. In this region, the blast wave propagates through an inhomogeneous environment. Extrinsic differences and subsequent multiple projections along the line of sight rather than intrinsic shock variations, such as fluid instabilities, account for the apparent complexity of the images. Interactions between the supernova blast wave and density enhancements of a large interstellar cloud can produce the morphological and spectral characteristics. Most of the X-ray flux arises in such interactions, not in the diffuse interior of the supernova remnant. Additional observations at optical and radio wavelengths support this account of the existing interstellar medium and its role in shaping the Cygnus Loop, and they demonstrate that the southeast knot is not a small cloud that the blast wave has engulfed. These data are consistent with rapid equilibration of electron and ion temperatures behind the shock front, and the current blast wave velocity v_{bw} approx 330 km/s. Most of this area does not show strong evidence for non-equilibrium ionization conditions, which may be a consequence of the high densities of the bright emission regions.Comment: To appear in ApJ, April 1, 200

Coupling quasi-phase matching: entanglement buildup in χ(2)\chi^{(2)} nonlinear waveguide arrays

Wavevector quasi-phase matching was devised in the 1960s as a way to boost nonlinear interactions with efficient quantum noise squeezing as one outstanding outcome. In the era of quantum technologies, we propose a new coupling quasi-phase matching for efficient generation of multimode downconverted quantum light in nonlinear waveguide arrays. We highlight this technique achieving multimode quantum entanglement and Einstein-Podolsky-Rosen steering buildup. We discuss the feasibility of this method with current technology and demonstrate its competitiveness as a resource for continuous variables quantum information.Comment: 9 pages, 5 figures, v2 closer to published versio