2,732 research outputs found
Security and privacy in online social networking: Risk perceptions and precautionary behaviour
A quantitative behavioural online study examined a set of hazards that correspond with security- and privacy settings of the major global online social network (Facebook). These settings concern access to a user's account and access to the user's shared information (both security) as well as regulation of the user's information-sharing and user's regulation of others' information-sharing in relation to the user (both privacy). We measured 201 non-student UK users' perceptions of risk and other risk dimensions, and precautionary behaviour. First, perceptions of risk and dread were highest and precautionary behaviour was most common for hazards related to users' regulation of information-sharing. Other hazards were perceived as less risky and less precaution was taken against these, even though they can lead to breaches of users' security or privacy. Second, consistent with existing theory, significant predictors of perceived risk were attitude towards sharing information on Facebook, dread, voluntariness, catastrophic potential and Internet experience; and significant predictors of precautionary behaviour were perceived risk, control, voluntariness and Internet experience. Methodological implications emphasise the need for non-aggregated analysis and practical implications emphasise interventions to promote safe online social-network use
Separating climate-induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements
We estimate the signature of the climate-induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3–4 nm/s^2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long-term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake
Bounds on gravitational wave backgrounds from large distance clock comparisons
Our spacetime is filled with gravitational wave backgrounds that constitute a
fluctuating environment created by astrophysical and cosmological sources.
Bounds on these backgrounds are obtained from cosmological and astrophysical
data but also by analysis of ranging and Doppler signals from distant
spacecraft. We propose here a new way to set bounds on those backgrounds by
performing clock comparisons between a ground clock and a remote spacecraft
equipped with an ultra-stable clock, rather than only ranging to an onboard
transponder. This technique can then be optimized as a function of the signal
to be measured and the dominant noise sources, leading to significant
improvements on present bounds in a promising frequency range where different
theoretical models are competing. We illustrate our approach using the SAGAS
project which aims to fly an ultra stable optical clock in the outer solar
system.Comment: 10 pages, 8 figures, minor amendment
Influence of electron correlations on ground-state properties of III-V semiconductors
Lattice constants and bulk moduli of eleven cubic III-V semiconductors are
calculated using an ab initio scheme. Correlation contributions of the valence
electrons, in particular, are determined using increments for localized bonds
and for pairs and triples of such bonds; individual increments, in turn, are
evaluated using the coupled cluster approach with single and double
excitations. Core-valence correlation is taken into account by means of a core
polarization potential. Combining the results at the correlated level with
corresponding Hartree-Fock data, we obtain lattice constants which agree with
experiment within an average error of -0.2%; bulk moduli are accurate to +4%.
We discuss in detail the influence of the various correlation contributions on
lattice constants and bulk moduli.Comment: 4 pages, Latex, no figures, Phys. Rev. B, accepte
Updated tests of scaling and universality for the spin-spin correlations in the 2D and 3D spin-S Ising models using high-temperature expansions
We have extended, from order 12 through order 25, the high-temperature series
expansions (in zero magnetic field) for the spin-spin correlations of the
spin-S Ising models on the square, simple-cubic and body-centered-cubic
lattices. On the basis of this large set of data, we confirm accurately the
validity of the scaling and universality hypotheses by resuming several tests
which involve the correlation function, its moments and the exponential or the
second-moment correlation-lengths.Comment: 21 pages, 8 figure
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