628 research outputs found
Domino: exploring mobile collaborative software adaptation
Social Proximity Applications (SPAs) are a promising new area for ubicomp software that exploits the everyday changes in the proximity of mobile users. While a number of applications facilitate simple file sharing between co–present users, this paper explores opportunities for recommending and sharing software between users. We describe an architecture that allows the recommendation of new system components from systems with similar histories of use. Software components and usage histories are exchanged between mobile users who are in proximity with each other. We apply this architecture in a mobile strategy game in which players adapt and upgrade their game using components from other players, progressing through the game through sharing tools and history. More broadly, we discuss the general application of this technique as well as the security and privacy challenges to such an approach
Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms
Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical
Journal, January, 200
Emergence behaviour of Phobocampe sp. (Hymenoptera: Ichneumonidae), a larval eudoparasitoid of Operophtera spp. (Lepidoptera: Geometridae)
Seasonal activity of Ichneumonid pupal parasitoids of Operophtera spp. (Lepidoptera: Geometridae)
Field placement of cocoons of Operophtera spp. was used to determine the timing of attack by pupal parasitoids of the winter moth, Operophtera brumata (L.), and the Bruce spanworm, O. bruceata (Hulst). Coccygomimus hesperus Tow. & Tow., the most abundant parasitoid recovered, attacked Operophtera pupae from early June until the end of August. At least two generations of C. hesperus occur each season. Buathra dorsicarinata (Pratt) was not recovered in numbers large enough to determine its timing of attack and no pupae parasitized by Cratichneumon sp. were recovered
An Improved Model for Relativistic Solar Proton Acceleration applied to the 2005 January 20 and Earlier Events
This paper presents results on modelling the ground level response of the
higher energy protons for the 2005 January 20 ground level enhancement (GLE).
This event, known as GLE 69, produced the highest intensity of relativistic
solar particles since the famous event on 1956 February 23. The location of
recent X-ray and gamma-ray emission (N14 W61) was near to Sun-Earth connecting
magnetic field lines, thus providing the opportunity to directly observe the
acceleration source from Earth. We restrict our analysis to protons of energy
greater than 450 MeV to avoid complications arising from transport processes
that can affect the propagation of low energy protons. In light of this revised
approach we have reinvestigated two previous GLEs: those of 2000 July 14 (GLE
59) and 2001 April 15 (GLE 60). Within the limitations of the spectral forms
employed, we find that from the peak (06:55 UT) to the decline (07:30 UT)
phases of GLE 69, neutron monitor observations from 450 MeV to 10 GeV are best
fitted by the Gallegos-Cruz & Perez-Peraza stochastic acceleration model. In
contrast, the Ellison & Ramaty spectra did not fit the neutron monitor
observations as well. This result suggests that for GLE 69, a stochastic
process cannot be discounted as a mechanism for relativistic particle
acceleration, particularly during the initial stages of this solar event. For
GLE 59 we find evidence that more than one acceleration mechanism was present,
consistent with both shock and stochastic acceleration processes dominating at
different times of the event. For GLE 60 we find that Ellison & Ramaty spectra
better represent the neutron monitor observations compared to stochastic
acceleration spectra. The results for GLEs 59 and 60 are in agreement with our
previous work.Comment: 42 pages, 10 figures, 10 tables, published in ApJ, August 200
Drymus brunneus (Sahlberg) (Hemiptera: Rhyparochromidae): a seed bug introduced into North America
The occurrence of the adventive Drymus brunneus (Sahlberg) in North America is documented, and characteristics to distinguish this Old World species from D. unus (Say) are described and illustrated. A revised key to the Western Hemisphere species of Drymus is included
An investigation of the cross-language transfer of reading skills: Evidence from a study in Nigerian Government Primary Schools
This paper investigates the linguistic interdependence of grade 3 children studying in government primary schools in northern Nigeria who are learning to read in Hausa (L1) and English (L2) simultaneously. There are few studies in the African context that consider linguistic interdependence and the bidirectional influences of literacy skills in multilingual contexts. To do so a total of 2,328 grade 3 children were tested on their Hausa and English letter sound knowledge (phonemes) and reading decoding skills (word) after participating in a two-year English structured reading intervention programme as part of their school day. In grade 4 these children will become English immersion learners, with English becoming the medium of instruction. Carrying out bivariate correlations we find a large and strongly positively significant correlation between L1 and L2 test scores. Concerning bidirectionality a feedback path model illustrates that L1 word predicts L2 word and vice versa. Multi-level modelling is then used to consider the variation in test scores. Almost two thirds of the variation in the word score is attributable to the pupil level and one third to the school level. Hausa word score is significantly predicted through Hausa sound and English word score. English word score is significantly predicted through Hausa word and English sound score. The findings have implications for language policy and classroom instruction showing the importance of cross-language transfer between reading skills. The overall results support bidirectionality and linguistic interdependence
Preliminary analysis of three cycles for nuclear propulsion of aircraft
A preliminary study was made of the feasibility of three cycles for nuclear propulsion of aircraft: a direct-air-turbojet, a binary liquid-metal turbojet, and a helium compressor jet. All three cycles appeared feasible for flight at a Mach number of 0.9 and altitudes up to 50,000 feet; the liquid-metal cycle appeared feasible for flight at a Mach number of 1.5. The air and helium cycles resulted in heavier aircraft than did the liquid-metal cycle, particularly at a Mach number of 1.5. The relative advantage of the liquid-metal cycle became greater as the flight speed and altitude increased, and as the reactor wall temperature decreased
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