33,514 research outputs found
Negative Specific Heat in a Quasi-2D Generalized Vorticity Model
Negative specific heat is a dramatic phenomenon where processes decrease in
temperature when adding energy. It has been observed in gravo-thermal collapse
of globular clusters. We now report finding this phenomenon in bundles of
nearly parallel, periodic, single-sign generalized vortex filaments in the
electron magnetohydrodynamic (EMH) model for the unbounded plane under strong
magnetic confinement. We derive the specific heat using a steepest descent
method and a mean field property. Our derivations show that as temperature
increases, the overall size of the system increases exponentially and the
energy drops. The implication of negative specific heat is a runaway reaction,
resulting in a collapsing inner core surrounded by an expanding halo of
filaments.Comment: 12 pages, 3 figures; updated with revision
Study of large adaptive arrays for space technology applications
The research in large adaptive antenna arrays for space technology applications is reported. Specifically two tasks were considered. The first was a system design study for accurate determination of the positions and the frequencies of sources radiating from the earth's surface that could be used for the rapid location of people or vehicles in distress. This system design study led to a nonrigid array about 8 km in size with means for locating the array element positions, receiving signals from the earth and determining the source locations and frequencies of the transmitting sources. It is concluded that this system design is feasible, and satisfies the desired objectives. The second task was an experiment to determine the largest earthbound array which could simulate a spaceborne experiment. It was determined that an 800 ft array would perform indistinguishably in both locations and it is estimated that one several times larger also would serve satisfactorily. In addition the power density spectrum of the phase difference fluctuations across a large array was measured. It was found that the spectrum falls off approximately as f to the minus 5/2 power
Consuming Asia: Culinary tourism, soft power and mediation of Peranakan TV
This paper examines the role of East Asian pop culture flows in boosting the soft power of Asian nations. Specifically, it explores the role of television dramas and pop culture in promoting heritage culinary heritage tourism. While much has been discussed on the globalizing appeal of Korean pop culture in boosting Korean tourism and cultural consumption, little has been studied within the context of Southeast Asian countries’ indigenous cultures such as the Peranakan culture in Singapore. This study examines the nostalgic and culinary appeal of The Little Nyonya , a regionally successful locally-produced Peranakan TV drama from Singapore, and suggests that if media and tourism policies were better integrated, Singapore’s unique, multicultural heritage and culture could be a source of soft power and tourism attraction, attracting both viewers and visitors to Singapore
Widely separated binary systems of very low mass stars
In this paper we review some recent detections of wide binary brown dwarf
systems and discuss them in the context of the multiplicity properties of very
low-mass stars and brown dwarfs.Comment: 2 pages, 1 figure (new version with minor corrections); to appear in
the proceedings of the workshop "Ultra-low mass star formation and
evolution", to be published in A
Vortex ring refraction at large Froude numbers
We have experimentally studied the impact of an initially planar axisymmetric
vortex ring, incident at an oblique angle, upon a gravity-induced interface
separating two fluids of differing densities. After impact, the vortex ring was
found to exhibit a variety of subsequent trajectories, which we organize
according to both the incidence angle, , and the interface strength,
defined as the ratio of the Atwood and Froude numbers, . For grazing
incidence angles ( deg.) vortices either penetrate or
reflect from the interface, depending on whether the interface is weak or
strong. In some cases, reflected vortices execute damped oscillations before
finally disintegrating. For smaller incidence angles (
deg.) vortices penetrate the interface. When there is a strong interface, these
vortices are observed to curve back up toward the interface. When there is a
weak interface, these vortices are observed to refract downward, away from the
interface. The critical interface strength below which vortex ring refraction
is observed is given by .Comment: 26 pages, 11 figures; Submitted to Physical Review
Curate and storyspace: an ontology and web-based environment for describing curatorial narratives
Existing metadata schemes and content management systems used by museums focus on describing the heritage objects that the museum holds in its collection. These are used to manage and describe individual heritage objects according to properties such as artist, date and preservation requirements. Curatorial narratives, such as physical or online exhibitions tell a story that spans across heritage objects and have a meaning that does not necessarily reside in the individual heritage objects themselves. Here we present curate, an ontology for describing curatorial narratives. This draws on structuralist accounts that distinguish the narrative from the story and plot, and also a detailed analysis of two museum exhibitions and the curatorial processes that contributed to them. Storyspace, our web based interface and API to the ontology, is being used by curatorial staff in two museums to model curatorial narratives and the processes through which they are constructed
Discovery of Radio Emission from the Tight M8 Binary: LP 349-25
We present radio observations of 8 ultracool dwarfs with a narrow spectral
type range (M8-M9.5) using the Very Large Array at 8.5 GHz. Only the tight M8
binary LP 349-25 was detected. LP 349-25 is the tenth ultracool dwarf system
detected in radio and its trigonometric parallax pi = 67.6 mas, recently
measured by Gatewood et al., makes it the furthest ultracool system detected by
the Very Large Array to date, and the most radio-luminous outside of obvious
flaring activity or variability. With a separation of only 1.8 AU, masses of
the components of LP 349-25 can be measured precisely without any theoretical
assumptions (Forveille et al.), allowing us to clarify their fully-convective
status and hence the kind of magnetic dynamo in these components which may play
an important role to explain our detection of radio emission from these
objects. This also makes LP 349-25 an excellent target for further studies with
better constraints on the correlations between X-ray, radio emission and
stellar parameters such as mass, age, temperature, and luminosity in ultracool
dwarfs.Comment: accepted by ApJ, referee's comments included, typo in equation 1
correcte
A novel haptic model and environment for maxillofacial surgical operation planning and manipulation
This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone
De novo 2.3 Mb microdeletion of 1q32.2 involving the Van der Woude Syndrome locus
10.1186/1755-8166-6-31Molecular Cytogenetics61
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