Discovery of kHz Fluctuations in Centaurus X-3: Evidence for Photon Bubble Oscillations (PBO) and Turbulence in a High Mass X-ray Binary Pulsar

We report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at ~330 Hz and ~760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3. These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to $f^{-2}$ behavior between a few Hz and ~100 Hz. Above a hundred Hz, the spectrum shows the QPO features, plus a flat continuum extending to ~1200 Hz and then falling out to ~1800 Hz. These results, which required the co-adding three days of observations of Cen X-3, are at least as fast as the fastest known variations in X-ray emission from an accreting compact object (kHz QPO in LMXB sources) and probably faster since extension to ~1800 Hz is indicated by the most likely parameterization of the data. Multi-dimensional radiation hydrodynamics simulations of optically thick plasma flow onto the magnetic poles of an accreting neutron star show that the fluctuations at frequencies above 100 Hz are consistent with photon bubble turbulence and oscillations (PBO) previously predicted to be observable in this source. For a polar cap opening angle of 0.25 radians, we show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kHz continuum. This has resulted in the first model-dependent measurement of the polar cap size of an X-ray pulsar.Comment: received ApJ: April 1, 1999 accepted ApJ: September 1, 199

Paint gun incorporating a laser device

A spray gun for applying a liquid spray coating, such as paint, to a surface incorporates a light source and detection system for analyzing the position of the spray gun relative to a worksurface in order to optimize application of the coating to the surface. The light source is preferably in the form of a laser which emits a beam of light toward the worksurface. The laser is interconnected with the housing of the spray gun in a location over the spray gun handle so as not to effect the center of gravity of the spray gun. Optical sensors are mounted to the spray gun housing for receiving light reflected from the work-surface, and the sensors are interconnected with a processor for providing the operator with a real time visual indication as to compliance with predetermined paint application criteria. In addition, information can be stored to memory and downloaded for subsequent analysis

Molecular Line Emission from Massive Protostellar Disks: Predictions for ALMA and the EVLA

We compute the molecular line emission of massive protostellar disks by solving the equation of radiative transfer through the cores and disks produced by the recent radiation-hydrodynamic simulations of Krumholz, Klein, & McKee. We find that in several representative lines the disks show brightness temperatures of hundreds of Kelvin over velocity channels ~10 km s^-1 wide, extending over regions hundreds of AU in size. We process the computed intensities to model the performance of next-generation radio and submillimeter telescopes. Our calculations show that observations using facilities such as the EVLA and ALMA should be able to detect massive protostellar disks and measure their rotation curves, at least in the nearest massive star-forming regions. They should also detect significant sub-structure and non-axisymmetry in the disks, and in some cases may be able to detect star-disk velocity offsets of a few km s^-1, both of which are the result of strong gravitational instability in massive disks. We use our simulations to explore the strengths and weaknesses of different observational techniques, and we also discuss how observations of massive protostellar disks may be used to distinguish between alternative models of massive star formation.Comment: 15 pages, 9 figures, emulateapj format, accepted for publication in ApJ. Resolution of figures severely degraded to fit within size limits. Download the full paper from http://www.astro.princeton.edu/~krumholz/recent.htm

Climate change adaptation and the Least Developed Countries Fund (LDCF): qualitative insights from policy implementation in the Asia-Pacific

Least developed countries often lack the requisite capacity to implement climate change adaptation projects. The Least Developed Countries Fund (LDCF) is a scheme where industrialized countries have (as of early 2016) disbursed $934.5 million in voluntary contributions, raised more than four times that amount in co-financing, and supported 213 adaptation projects across 51 least developed countries. But what sorts of challenges have arisen during implementation? Based on extensive field research in five least developed countries—Bangladesh, Bhutan, Cambodia, the Maldives, and Vanuatu—and original data collected from almost 150 research interviews, this article qualitatively explores both the benefits and challenges of LDCF projects in the Asia-Pacific. It finds that while LDCF projects do contribute to enhancing multiple types of infrastructural, institutional, and community-based adaptive capacity, they also suffer from uncertainty, a convoluted management structure, and an inability to fully respond to climate risks. Based on these findings, the study concludes that adaptation must be pursued as a multidimensional process; and that LDCF activities have tended to promote marginal rather than more radical or systematic transformations

Optical spray painting practice and training system

An optical spray painting practice gun emits a shaped optical beam onto a practice surface to simulate an actual paint spray on the surface. The gun preferably uses a class 2 diode laser to generate a laser beam which is reshaped by a collimating lens into a diverging beam that illuminates the practice surface. The collimating lens creates an elongated image on the practice surface having a length corresponding linearly to the distance of the practice gun nozzle to the practice surface as with a conventional spray gun. The illuminated image distorts when the practice gun is not perpendicular to the practice surface. The collimating lens is located in a rotatable collar so that the orientation of the elongated image on the practice surface can be adjusted. In other respects, the structure of the practice gun is preferably the same as a conventional spray gun. A DC battery is contained in the removable paint container for the practice gun and supplies power to the laser when a trigger-actuated electric switch is engaged. Placing the battery in the removable container helps to simulate proper spray gun weight and weight distribution