A Census of the Carina Nebula -- II. Energy Budget and Global Properties of the Nebulosity

The first paper in this series took a direct census of energy input from the known OB stars in the Carina Nebula, and in this paper we study the global properties of the surrounding nebulosity. We find that the total IR luminosity of Carina is about 1.2E7 Lsun, accounting for only about 50-60% of the known stellar luminosity from Paper I. Similarly, the ionizing photon luminosity -- (abridged; many important details omitted). Synchronized star formation around the periphery of Carina provides a strong case that star formation here was indeed triggered by stellar winds and UV radiation. This second generation appears to involve a cascade toward preferentially intermediate- and low-mass stars, but this may soon change when eta Car and its siblings explode. If the current reservoir of atomic and molecular gas can be tapped at that time, massive star formation may be rejuvinated around the periphery of Carina much as if it were a young version of Gould's Belt. Also, when these multiple SNe occur, the triggered second generation will be pelted repeatedly with SN ejecta bearing short-lived radioactive nuclides. Carina may therefore represent the most observable analog to the cradle of our own Solar System.Comment: MNRAS accepted, 14 pages, fig 1 in colo

Analytical investigation of solid rocket nozzle failure

On April 5, 1983, an Inertial Upper Stage (IUS) spacecraft experienced loss of control during the burn of the second of two solid rocket motors. The anomaly investigation showed the cause to be a malfunction of the solid rocket motor. This paper presents a description of the IUS system, a failure analysis summary, an account of the thermal testing and computer modeling done at Marshall Space Flight Center, a comparison of analysis results with thermal data obtained from motor static tests, and describes some of the design enhancement incorporated to prevent recurrence of the anomaly

Break up of returning plasma after the 7 June 2011 filament eruption by Rayleigh-Taylor instabilities

A prominence eruption on 7 June 2011 produced spectacular curtains of plasma falling through the lower corona. At the solar surface they created an incredible display of extreme ultraviolet brightenings. The aim is to identify and analyze some of the local instabilities which produce structure in the falling plasma. The structures were investigated using SDO/AIA 171A and 193A images in which the falling plasma appeared dark against the bright coronal emission. Several instances of the Rayleigh-Taylor instability were investigated. In two cases the Alfven velocity associated with the dense plasma could be estimated from the separation of the Rayleigh-Taylor fingers. A second type of feature, which has the appearance of self-similar branching horns, is also discussed.Comment: 6 pages, 7 figures, submitted A&A. Movies are at http://www.mps.mpg.de/data/outgoing/innes/arcs_movie.avi and http://www.mps.mpg.de/data/outgoing/innes/horns_movie.av

Deep Reinforcement Learning for Join Order Enumeration

Join order selection plays a significant role in query performance. However, modern query optimizers typically employ static join enumeration algorithms that do not receive any feedback about the quality of the resulting plan. Hence, optimizers often repeatedly choose the same bad plan, as they do not have a mechanism for "learning from their mistakes". In this paper, we argue that existing deep reinforcement learning techniques can be applied to address this challenge. These techniques, powered by artificial neural networks, can automatically improve decision making by incorporating feedback from their successes and failures. Towards this goal, we present ReJOIN, a proof-of-concept join enumerator, and present preliminary results indicating that ReJOIN can match or outperform the PostgreSQL optimizer in terms of plan quality and join enumeration efficiency

Time Synchronisation for Wireless Sensors using Low-cost GPS module and Arduino (article)

This is the final version. Available on open access from Frontiers Media via the DOI in this recordThe dataset associated with this article is located in ORE at: https://doi.org/10.24378/exe.1063Time synchronisation for wireless sensors is important for a proper interpretation of measurements, particularly for acceleration measurements to estimate mode-shapes correctly. This paper presents a new time synchronisation method working independently on each node without exchanging time-sync packets among nodes. This stand-along operation can make field measurement campaigns very time-efficient without a need of constructing and validating the wireless sensor network. The proposed method firstly time-stamps measurements using the accurate time-source from a GPS module on each node, and secondly re-samples the time-stamped data to get time-synchronised data. The time-stamping method proposed in the study utilises Pulse-Per-Second (PPS) signals and NMEA (National Marine Electronics Association) sentences generated by a low-cost GPS module, and the internal timer/counter unit of Arduino. Error analysis on the proposed time-stamping method was carried out and derived an analytical expression for the maximum variance of time-stamping error of the proposed method. Four experiments have been carried out to observe 1) the long-term operational stability of the GPS module, 2) the accuracy of the PPS signals, 3) the accuracy of the proposed time-stamping method, and 4) the validity of the proposed time-synchronisation method for output-only modal analysis on a laboratory floor structure. The GPS module was found to operate or to resume operating stably for the entire test period of seven days even with the limited field of view to the sky. The relative time errors of two PPS signals from four GPS modules were found to be within +/-400 nsec. The time-stamping error measured by two identical time-stamping Arduinos for common trigger signals was found to have a standard deviation of 40.8 nsec, which agreed well with the maximum value of 42.0 nsec predicted by the error analysis. From the output-only modal analysis, the estimated modal parameters were found to agree well with that from the wired acceleration sensors. The phase angle of the cross spectral density of the two wireless accelerations showed that there was no apparent time-synchronisation error observable. These observations indicated a successful operation of the proposed time-synchronisation method

Obsidian Artifacts from East Texas Archaeological Sites

Obsidian artifacts are one of the few material culture remains on East Texas sites that provide direct evidence of distant links between East Texas’s native American peoples and native American communities in the Southwest or the Northwestern Plains. Other such material culture items include marine shells from the Gulf of California, turquoise from New Mexico sources, and sherds from ceramic vessels made in the Puebloan Southwest. Such artifacts, however, are rarely recovered in East Texas archaeological sites. In this article, we summarize the available information on obsidian artifacts from East Texas archaeological sites, much of it gathered from Hester’s Texas Obsidian Project (TOP), including obsidian source data when it is available

Leadership, job satisfaction and intention to leave among registered nurses in the North West and Free State provinces of South Africa

Background: The nurse leadership of a hospital is identified as the single most important aspect of the practice environment that impacts nurse outcomes. When nurses are satisfied with their jobs, they tend to remain with their employers and become more productive in their workplaces. Objectives: This study aimed to investigate the relationship between leadership, job satisfaction and intentions to leave among registered nurses (RNs) working in hospitals in the North West and Free State provinces of South Africa. Methods: A cross-sectional survey design was adopted. The population (N = 680) with the sample (n = 204) included RNs in medical–surgical units in both private and public hospitals in the two provinces. Data were collected using the RN4CAST questionnaire. Results: RNs were satisfied with the items pertaining to leadership except for praise and recognition (55.7%). They also indicated high levels of overall job satisfaction (70.5%) but were dissatisfied with wages (50%), study leave (40.9%) and opportunities for advancement (40.1%). Furthermore, 46.1% of the RNs intended to leave their current hospitals. The results indicated a relationship between leadership and job satisfaction (r = 0.47; p = 0.00) and between intention to leave and job satisfaction (d = 0.50). Conclusion: The nurse managers played a significant role influencing RN’s level of job satisfaction, while job satisfaction was highly correlated with intention to leave. The nurse leadership can improve job satisfaction by giving praise and recognition to the RNs for jobs well done, and RNs should be afforded the opportunity to advance their careers through further studies. Keywords: Leadership,  job satisfaction, intention to leave, Nurs