6,502 research outputs found
Data protection: the challenges facing social networking
The popularity of social networking sites has increased dramatically over the past decade. A recent report indicated that thirty-eight percent of online users have a social networking profile. Many of these social networking site users (SNS users) post or provide personal information over the internet every day. According to the latest OfCom study, the average adult SNS user has profiles on 1.6 sites and most check their profiles at least once every other day. However, the recent rise in social networking activity has opened the door to the misuse and abuse of personal information through identity theft, cyber stalking, and undesirable screenings by prospective employers. Behavioral advertising programs have also misused personal information available on social networking sites. Society is now facing an important question: what level of privacy should be expected and required within the social networking environment
Bridging the gap: parkour athletes provide new insights into locomotion energetics of arboreal apes
The tree canopy is an energetically challenging environment to traverse. Along with compliant vegetation, gaps in the canopy can prove energetically costly if they force a route-extending detour. Arboreal apes exhibit diverse locomotion strategies, including for gap crossing. Which one they employ in any given scenario may be influenced by the energy costs to do so, which are affected by the details of the immediate environment in combination with their body size. Measuring energetics of arboreal apes is not tractable; thus our knowledge in this area is limited. We devised a novel, custom-made experimental set-up to record the energy expenditure of parkour athletes tree-swaying, jumping and vertical climbing. The latter strategy was vastly more expensive, indicating that when energy economy is the focus arboreal apes will prioritize routes that limit height changes. Whether tree-swaying or jumping was most economical for the athletes depended upon interactions between tree stiffness, the distance to cross, number of tree-sways required and their own mass. Updated analysis of previous interspecific correlations suggests that whether the relative costs to vertical climb are size-invariant across primate species is complicated by details of the climbing context
Plasma electrons above Saturn's main rings: CAPS observations
We present observations of thermal ( similar to 0.6 - 100eV) electrons observed near Saturn's main rings during Cassini's Saturn Orbit Insertion (SOI) on 1 July 2004. We find that the intensity of electrons is broadly anticorrelated with the ring optical depth at the magnetic footprint of the field line joining the spacecraft to the rings. We see enhancements corresponding to the Cassini division and Encke gap. We suggest that some of the electrons are generated by photoemission from ring particle surfaces on the illuminated side of the rings, the far side from the spacecraft. Structure in the energy spectrum over the Cassini division and A-ring may be related to photoelectron emission followed by acceleration, or, more likely, due to photoelectron production in the ring atmosphere or ionosphere
Measurements of Rate Coefficients for Reactions of OH with Ethanol and Propan-2-ol at Very Low Temperatures.
The low temperature kinetics of the reactions of OH with ethanol and propan-2-ol have been studied using a pulsed Laval nozzle apparatus coupled with pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) spectroscopy. The rate coefficients for both reactions have been found to increase significantly as the temperature is lowered, by approximately a factor of 18 between 293 and 54 K for ethanol, and by âŒ10 between 298 and 88 K for OH + propan-2-ol. The pressure dependence of the rate coefficients provides evidence for two reaction channels: a zero pressure bimolecular abstraction channel leading to products and collisional stabilization of a weakly bound OH-alcohol complex. The presence of the abstraction channel at low temperatures is rationalized by a quantum mechanical tunneling mechanism, most likely through the barrier to hydrogen abstraction from the OH moiety on the alcohol
Dissociating performance from learning: An empirical evaluation of a computational model
This paper presents a follow-up to the ATM-Soar models presented at 1993 Meeting of the Cognitive Science Society and the CHI 1994 Research Symposium. The original work described the use of the Soar cognitive architecture to simulate user learning with different ATM interfaces. In particular, it focused on the relative effects of interface instructions (e.g., 'Insert card into slot') and perceptual attentional cues (e.g., a flashing area around the card slot) on learning and performance. The study described here involves getting human data on the same tasks to test the predictions of the computational models. The ATM task is simulated on a PC in order to contrast three types of interface conditions: just instructions, instructions plus flashing, and just flashing. Subjects must insert a bank card, check the account balance, and withdraw money. They are asked to repeat the task four times so that the effects of training on performance and learning can be observed. The data suggests that subjects learn to perform the task faster with attentional attractors, as the Soar model predicted. More interestingly, the Soar model also predicted that people would do better without instructions when there are attentional attractors. This prediction was supported as well.published_or_final_versio
Radio-optical orientation of E/S0 galaxies: APM versus FIRST
We searched for extended radio sources in isolated E/S0 galaxies comparing
the FIRST and APM catalogues for a single POSS plate. The 35 most promising
candidates were visually inspected on the Digitized Sky Survey (DSS) and on
FIRST images: we find several spirals and interacting galaxies and a few E/S0s
with very weak, marginally extended radio cores. The only double-lobed
(previously known) radio source is a dumbbell. For the rest of the objects, all
hosting small and weak radio sources, the DSS is inadequate to determine
morphological types. Thus a significant increase in sample size will be a major
effort.Comment: 2 pages; no figures; to appear in Proc. "Observational Cosmology with
the New Radio Surveys", eds. M. Bremer, N. Jackson & I. Perez-Fournon, Kluwer
Acad. Pres
Searching (the) FIRST radio arcs near ACO clusters
Gravitational lensing (GL) of distant radio sources by galaxy clusters should
produce radio arc(let)s. We extracted radio sources from the FIRST survey near
Abell cluster cores and found their radio position angles to be uniformly
distributed with respect to the cluster centres. This result holds even when we
restrict the sample to the richest or most centrally condensed clusters, and to
sources with high S/N and large axial ratio. Our failure to detect GL with
statistical methods may be due to poor cluster centre positions. We did not
find convincing candidates for arcs either. Our result agrees with theoretical
estimates predicting that surveys much deeper than FIRST are required to detect
the effect. This is in apparent conflict with the detection of such an effect
claimed by Bagchi & Kapahi (1995).Comment: 6 pages; 8 figures and 1 style file are included; to appear in Proc.
"Observational Cosmology with the New Radio Surveys", eds. M. Bremer, N.
Jackson & I. Perez-Fournon, Kluwer Acad. Pres
A massive reservoir of low-excitation molecular gas at high redshift
Molecular hydrogen is an important component of galaxies because it fuels
star formation and accretion onto AGN, the two processes that generate the
large infrared luminosities of gas-rich galaxies. Observations of spectral-line
emission from the tracer molecule CO are used to probe the properties of this
gas. But the lines that have been studied in the local Universe, mostly the
lower rotational transitions of J = 1-0 and J = 2-1, have hitherto been
unobservable in high-redshift galaxies. Instead, higher transitions have been
used, although the densities and temperatures required to excite these higher
transitions may not be reached by much of the gas. As a result, past
observations may have underestimated the total amount of molecular gas by a
substantial amount. Here we report the discovery of large amounts of
low-excitation molecular gas around the infrared-luminous quasar, APM
08279+5255 at z = 3.91, using the two lowest excitation lines of 12CO (J = 1-0
and J = 2-1). The maps confirm the presence of hot and dense gas near the
nucleus, and reveal an extended reservoir of molecular gas with low excitation
that is 10 to 100 times more massive than the gas traced by higher-excitation
observations. This raises the possibility that significant amounts of
low-excitation molecular gas may lurk in the environments of high-redshift (z >
3) galaxies.Comment: To appear as a Letter to Nature, 4th January 200
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