Stellar Differential Rotation and Coronal Timescales

We investigate the timescales of evolution of stellar coronae in response to surface differential rotation and diffusion. To quantify this we study both the formation time and lifetime of a magnetic flux rope in a decaying bipolar active region. We apply a magnetic flux transport model to prescribe the evolution of the stellar photospheric field, and use this to drive the evolution of the coronal magnetic field via a magnetofrictional technique. Increasing the differential rotation (i.e. decreasing the equator-pole lap time) decreases the flux rope formation time. We find that the formation time is dependent upon the geometric mean of the lap time and the surface diffusion timescale. In contrast, the lifetime of flux ropes are proportional to the lap time. With this, flux ropes on stars with a differential rotation of more than eight times the solar value have a lifetime of less than two days. As a consequence, we propose that features such as solar-like quiescent prominences may not be easily observable on such stars, as the lifetimes of the flux ropes which host the cool plasma are very short. We conclude that such high differential rotation stars may have very dynamical coronae

Is It Just Rock \u27n\u27 Roll? A Comment on Stefan Bielinski\u27s Community History, Popular Music, and Public Audiences

The author comments on I Know It\u27s Only Rock \u27n\u27 Roll But They Like It! Community History, Popular Music, and Public Audiences by Stefan Bielinski

Learning Cast up from the Mire: Archaeological Investigations of Schoolhouses in the Northeastern United States

Common schools, often comprising a single room with one or two teachers, taught millions of children from the 1850s through the 1930s. They have provided source material for objective historical writings on education and inspired subjective literature on the school experiences of teachers and students. But as prominent as one-room schools have been in the North American experience, and in the perceptions of rural 19th- and early 20th-century life, these ubiquitous structures have not found a place in the archaeological literature. This paper examines the archaeological potential of schoolhouse sites for providing useful information not otherwise available to historians, poets, and playwrights

Programming Protocol-Independent Packet Processors

P4 is a high-level language for programming protocol-independent packet processors. P4 works in conjunction with SDN control protocols like OpenFlow. In its current form, OpenFlow explicitly specifies protocol headers on which it operates. This set has grown from 12 to 41 fields in a few years, increasing the complexity of the specification while still not providing the flexibility to add new headers. In this paper we propose P4 as a strawman proposal for how OpenFlow should evolve in the future. We have three goals: (1) Reconfigurability in the field: Programmers should be able to change the way switches process packets once they are deployed. (2) Protocol independence: Switches should not be tied to any specific network protocols. (3) Target independence: Programmers should be able to describe packet-processing functionality independently of the specifics of the underlying hardware. As an example, we describe how to use P4 to configure a switch to add a new hierarchical label

Flat conductor cable termination development program Final report

Development program for methods of terminating flat conductor cable to small electrical components used on electrical displays and control panel

Challenges in the development of the orbiter atmosphere revitalization subsystem

The space shuttle orbiter atmospheric revitalization subsystem provides thermal and contaminant control as well as total- and oxygen partial-pressure control of the environment within the orbiter crew cabin. Challenges that occurred during the development of this subsystem for the space shuttle orbiter are described. The design of the rotating hardware elements of the system (pumps, fans, etc.) required significant development to meet the requirements of long service life, maintainability, and high cycle-fatigue life. As a result, a stringent development program, particularly in the areas of bearing life and heat dissipation, was required. Another area requiring significant development was cabin humidity control and condensate collection

Dense cores in the L1630 molecular cloud: discovering new protostars with SCUBA

Maps of the 450 micron and 850 micron dust continuum emission from three star-forming condensations within the Lynds 1630 molecular cloud, made with the SCUBA bolometer array, reveal the presence of four new submillimetre sources, each of a few solar masses, two of which are probably Class I, two Class 0, as well as several sources whose existence was previously known. The sources are located in filaments and appear elongated when observed at 450 microns. They likely have dust temperatures in the range 10 to 20 K, in good agreement with previous ammonia temperature estimates. Attempts to fit their structures with power-law and Gaussian density distributions suggest that the central distribution is flatter than expected for a simple singular isothermal sphere. Although the statistics are poor, our results suggest that the ratio of `protostellar core' mass to total virial mass may be similar for both large and small condensations.Comment: 10 pages, 9 figures, uses mn.st

A survey of SiO 5-4 emission towards outflows from massive young stellar objects

Results are presented of a survey of SiO 5-4 emission observed with the James Clerk Maxwell Telescope (JCMT) towards a sample of outflows from massive young stellar objects. The sample is drawn from a single-distance study by Ridge & Moore. In a sample of 12 sources, the 5-4 line was detected in 5, a detection rate of 42 per cent. This detection rate is higher than that found for a sample of low-luminosity outflow sources, although for sources of comparable luminosity, it is in good agreement with the results of a previous survey of high luminosity sources. For most of the detected sources, the 5-4 emission is compact or slightly extended along the direction of the outflow. NGC6334I shows a clear bipolar flow in the 5-4 line. Additional data were obtained for W3-IRS5, AFGL5142 and W75N for the 2-1 transition of SiO using the Berkeley-Illinois-Maryland Association (BIMA) millimetre interferometer. There is broad agreement between the appearance of the SiO emission in both lines, though there are some minor differences. The 2-1 emission in AFGL5142 is resolved into two outflow lobes which are spatially coincident on the sky, in good agreement with previous observations. In general the SiO emission is clearly associated with the outflow. The primary indicator of SiO 5-4 detectability is the outflow velocity, i.e. the presence of SiO is an indicator of a high velocity outflow. This result is consistent with the existence of a critical shock velocity required to disrupt dust grains and subsequent SiO formation in post-shock gas. There is also weak evidence that higher luminosity sources and denser outflows are more likely to be detected.Comment: Accepted for publication in MNRA