The curious time lags of PG 1244+026: Discovery of the iron K reverberation lag

High-frequency iron K reverberation lags, where the red wing of the line responds before the line centroid, are a robust signature of relativistic reflection off the inner accretion disc. In this letter, we report the discovery of the Fe K lag in PG 1244+026 from ~120 ks of data (1 orbit of the XMM-Newton telescope). The amplitude of the lag with respect to the continuum is 1000 s at a frequency of ~1e-4 Hz. We also find a possible frequency-dependence of the line: as we probe higher frequencies (i.e. shorter timescales from a smaller emitting region) the Fe K lag peaks at the red wing of the line, while at lower frequencies (from a larger emitting region) we see the dominant reflection lag from the rest frame line centroid. The mean energy spectrum shows a strong soft excess, though interestingly, there is no indication of a soft lag. Given that this source has radio emission and it has little reported correlated variability between the soft excess and the hard band, we explore one possible explanation in which the soft excess in this source is dominated by the steep power-law like emission from a jet, and that a corona (or base of the jet) irradiates the inner accretion disc, creating the blurred reflection features evident in the spectrum and the lag. General Relativistic ray-tracing models fit the Fe K lag well, with the best-fit giving a compact X-ray source at a height of 5 gravitational radii and a black hole mass of 1.3e7 Msun.Comment: 6 pages, 6 figures, resubmitted to MNRAS after moderate revisions. This paper focuses on the discovery of the Fe K reverberation lag in PG 1244+026. We point the interested reader to Alston, Done & Vaughan (See today: arXiv:submit/0851673), which focuses on the soft lags in this sourc

Orbital debris research at NASA Johnson Space Center, 1986-1988

Research on orbital debris has intensified in recent years as the number of debris objects in orbit has grown. The population of small debris has now reached the level that orbital debris has become an important design factor for the Space Station. The most active center of research in this field has been the NASA Lyndon B. Johnson Space Center. Work is being done on the measurement of orbital debris, development of models of the debris population, and development of improved shielding against hypervelocity impacts. Significant advances have been made in these areas. The purpose of this document is to summarize these results and provide references for further study

Embedding creativity in the university computing curriculum

We explore the need for embedding creativity in the UK Higher Education computing curriculum and some of the challenges associated with this. We identify some of the initiatives and movements in this area and discuss some of the work that has been carried out. We then describe some of the ways we have tried to meet these challenges and reflect on our degree of success with respect to the goal of producing graduates who are fit for the myriad of job opportunities they will come across in a rapidly changing technology landscape. Finally, we make a number of recommendations

Eugene: a generic interactive genetic algorithm controller

This paper outlines the development of an open source generic hardware-based interactive Genetic Algorithm controller (Eugene) and explores contexts in which it may be deployed. The system was first applied to the generation of synthetic sound using MIDI and a simple analogue synthesiser with 27 continuous controller values. It was then applied in the area of image evaluation using an image enhancer program with 7 continuous controller values. The system was evaluated by experimental observation of users attempting various tasks with different success criteria. This led to the identification of issues, some of which were specific to, and others divorced from the application domain. These are discussed together with areas for improvement

EEuGene: employing electroencephalograph signals in the rating strategy of a hardware-based interactive genetic algorithm

We describe a novel interface and development platform for an interactive Genetic Algorithm (iGA) that uses Electroencephalograph (EEG) signals as an indication of fitness for selection for successive generations. A gaming headset was used to generate EEG readings corresponding to attention and meditation states from a single electrode. These were communicated via Bluetooth to an embedded iGA implemented on the Arduino platform. The readings were taken to measure subjects’ responses to predetermined short sequences of synthesised sound, although the technique could be applied any appropriate problem domain. The prototype provided sufficient evidence to indicate that use of the technology in this context is viable. However, the approach taken was limited by the technical characteristics of the equipment used and only provides proof of concept at this stage. We discuss some of the limitations of using biofeedback systems and suggest possible improvements that might be made with more sophisticated EEG sensors and other biofeedback mechanisms

Towards a brain controller interface for generating simple Berlin School style music with interactive genetic algorithms

A novel approach to generating music is presented using two interactive Genetic Algorithms with electroencephalogram inputs from two subjects as their fitness functions. Many interactive Genetic Algorithm approaches for generating music employ constrained solution spaces that only utilise notes from a given scale. Our work incorporates the use of mutation to extend the solution space through the inclusion of accidental notes. A thresholding approach is adopted, that allows riffs to be repeated until fitness drops, together with a ‘killswitch’ to ensure unpleasant sounding riffs are removed from the population. The development is ongoing, with more testing and calibration required to ensure that there are no timing errors in communication between the microcontroller boards and to identify the most appropriate threshold and mutation ranges, in addition to determining the most appropriate mixes for the users to hear

The use of physical artefacts in undergraduate computer science teaching

This paper describes the introduction of the use of physical artefacts in the teaching of the undergraduate curriculum in the Department of Computer Science at Middlesex University. The rationale for the change is discussed, together with a description of the various technologies and the areas in which they were deployed. We conclude with a discussion of the outcomes of the work and the conclusions reached, prime amongst which are that the policy has been successful in motivating and engaging students, with a resultant improvement in student progression