2,267 research outputs found
Counterparts to the Nuclear Bulge X-ray source population
We present an initial matching of the source positions of the Chandra Nuclear
Bulge X-ray sources to the new UKIDSS-GPS near-infrared survey of the Nuclear
Bulge. This task is made difficult by the extremely crowded nature of the
region, despite this, we find candidate counterparts to ~50% of the X-ray
sources. We show that detection in the J-band for a candidate counterpart to an
X-ray source preferentially selects those candidate counterparts in the
foreground whereas candidate counterparts with only detections in the H and
K-bands are more likely to be Nuclear Bulge sources. We discuss the planned
follow-up for these candidate counterparts.Comment: 5 pages, 2 figures, 1 table, published in the proceedings of "A
population Explosion", AIP Conference Proceedings Volume 1010, pp. 117-12
The Nuclear Bulge extinction
We present a new, high resolution (5" per pixel) near-infrared extinction map
of the Nuclear Bulge using data from the UKIDSS-GPS. Using photometry from the
J, H and K-bands we show that the extinction law parameter is also highly
variable in this region on similar scales to the absolute extinction. We show
that only when this extinction law variation is taken into account can the
extinction be measured consistently at different wavelengths.Comment: 3 pages, 2 figures, published in the proceedings of "A population
Explosion", AIP Conference Proceedings Volume 1010, pp. 168-17
Adaptive Management for Impacts to Eelgrass Habitat in Gloucester Harbor
The Massachusetts Office of Coastal Zone Management and the Massachusetts Institute of Technology Sea Grant College Program, along with partners, led an effort to create an eelgrass bank, raise awareness of the value of eelgrass habitat, and facilitate transplanting efforts to Boston Harbor in the summer and fall of 2006. A planned impact to eelgrass habitat in Gloucester Harbor warranted efforts to try to save this valuable and declining resource. This unfortunate circumstance was used to educate interested citizens, students and teachers from regional schools, and government employees. Methods to transplant and store eelgrass were researched and tested in attempt to facilitate restoration of the impact area. Two community events were organized at Pavilion Beach to harvest eelgrass from the impact area. These events were attended by a variety of government (city, state, and federal) and non-government employees, along with students and teachers, and attracted much attention of the citizens of Gloucester. Eelgrass was successfully transplanted to Boston Harbor by the Massachusetts Division of Marine Fisheries. Harvested eelgrass was also maintained in a hydroponic raft system for three months (October-December) and used to set-up an interpretative display in a flow-through tank at the Gloucester Maritime Heritage Center. While the harvested eelgrass was ultimately not transplanted back to the impact corridor, experience in storing eelgrass within hydroponic and tank systems could assist future restoration efforts. By teaming up to save the eelgrass at Pavilion Beach in Gloucester Harbor, project partners demonstrated the advantage of creative, adaptive, and cooperative efforts to manage coastal resources. The project was a learning experience in adaptive management for eelgrass habitat and a success in outreach
Instability of a four-dimensional de Sitter black hole with a conformally coupled scalar field
We study the stability of new neutral and electrically charged
four-dimensional black hole solutions of Einstein's equations with a positive
cosmological constant and conformally coupled scalar field. The neutral black
holes are always unstable. The charged black holes are also shown analytically
to be unstable for the vast majority of the parameter space of solutions, and
we argue using numerical techniques that the configurations corresponding to
the remainder of the parameter space are also unstable.Comment: revtex4, 8 pages, 4 figures, minor changes, accepted for publication
in Phys. Rev.
A silent speech system based on permanent magnet articulography and direct synthesis
In this paper we present a silent speech interface (SSI) system aimed at restoring speech communication for individuals who have lost their voice due to laryngectomy or diseases affecting the vocal folds. In the proposed system, articulatory data captured from the lips and tongue using permanent magnet articulography (PMA) are converted into audible speech using a speaker-dependent transformation learned from simultaneous recordings of PMA and audio signals acquired before laryngectomy. The transformation is represented using a mixture of factor analysers, which is a generative model that allows us to efficiently model non-linear behaviour and perform dimensionality reduction at the same time. The learned transformation is then deployed during normal usage of the SSI to restore the acoustic speech signal associated with the captured PMA data. The proposed system is evaluated using objective quality measures and listening tests on two databases containing PMA and audio recordings for normal speakers. Results show that it is possible to reconstruct speech from articulator movements captured by an unobtrusive technique without an intermediate recognition step. The SSI is capable of producing speech of sufficient intelligibility and naturalness that the speaker is clearly identifiable, but problems remain in scaling up the process to function consistently for phonetically rich vocabularies
Speleothem evidence for C3 dominated vegetation during the Late Miocene (Messinian) of South Africa
During the Late Miocene, Africa experienced a number of ecological transitions including the spread of C4 grasslands, the expansion of the Sahara Desert, the Messinian Salinity Crisis and a number of mammalian migrations and expansions, including the origin of the hominin clade. A detailed understanding of the relationship between environmental change and hominin evolution is hampered by the paucity of data available from terrestrial localities, especially in southern Africa. Here, we present a stable isotope and trace element record from a speleothem from the South African cave site of Hoogland. Uranium-lead dating and magnetostratigraphy places the speleothem within the Messinian Age (7.25–5.33 Ma) of the Late Miocene, making it the oldest known cave deposit from the region near the UNESCO Fossil Hominids of South Africa World Heritage Site (locally known as the “Cradle of Humankind”). Low carbon isotope values indicate a predominantly C3 vegetation in the vicinity of the cave throughout the period of speleothem growth. It is not possible to determine if this represents a C3 grassland or a C3 woodland, but it is clear that an equivalent C3-rich environment has yet to be found during the Messinian of east Africa. We conclude that the C4 grass expansion occurred millions of years later in South Africa than it did in eastern Africa, and that this vegetation shift should be considered when comparing African vegetation change with the late Miocene hominin fossil record
An evaluation of airborne laser scan data for coalmine subsidence mapping
The accurate mapping of coalmine subsidence is necessary for the continued management of potential subsidence impacts. The use of airborne laser scan (ALS) data for subsidence mapping provides an alternative method to traditional ground-based approaches that affords increased accessibility and complete spatial coverage. This paper evaluates the suitability and potential of ALS data for subsidence mapping, primarily through the examination of two pre-mining surveys in a rugged, densely vegetated study site. Data quality, in terms of mean point spacing and coverage, is evaluated, along with the impact of interpolation methods, resolution, and terrain. It was assumed that minimal surface height changes occurred between the two pre-mining surfaces. Therefore any height changes between digital elevation models of the two ALS surveys were interpreted as errors associated with the use of ALS data for subsidence mapping. A mean absolute error of 0.23 m was observed, though this error may be exaggerated by the presence of a systematic 0.15 m offset between the two surveys. Very large (several metres) errors occur in areas of steep or dynamic terrain, such as along cliff lines and watercourses. Despite these errors, preliminary subsidence mapping, performed using a third, post-mining dataset, clearly demonstrates the potential benefits of ALS data for subsidence mapping, as well as some potential limitations and the need for further careful assessment and validation concerning data errors
Integrating user-centred design in the development of a silent speech interface based on permanent magnetic articulography
Abstract: A new wearable silent speech interface (SSI) based on Permanent Magnetic Articulography (PMA) was developed with the involvement of end users in the design process. Hence, desirable features such as appearance, port-ability, ease of use and light weight were integrated into the prototype. The aim of this paper is to address the challenges faced and the design considerations addressed during the development. Evaluation on both hardware and speech recognition performances are presented here. The new prototype shows a com-parable performance with its predecessor in terms of speech recognition accuracy (i.e. ~95% of word accuracy and ~75% of sequence accuracy), but significantly improved appearance, portability and hardware features in terms of min-iaturization and cost
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