3,090 research outputs found
Exploring Consumers’ Attitudes of Smart TV Related Privacy Risks
A number of privacy risks are inherent in the Smart TV ecosystem. It is likely that many consumers are unaware of these privacy risks. Alternatively, they might be aware but consider the privacy risks acceptable. In order to explore this, we carried out an online survey with 200 participants to determine whether consumers were aware of Smart TV related privacy risks. The responses revealed a meagre level of awareness. We also explored consumers’ attitudes towards specific Smart TV related privacy risks.
We isolated a number of factors that influenced rankings and used these to develop awareness-raising messages. We tested these messages in an online survey with 155 participants. The main finding was that participants were generally unwilling to disconnect their Smart TVs from the Internet because they valued the Smart TV’s Internet functionality more than their privacy. We subsequently evaluated the awareness-raising messages in a second survey with 169 participants, framing the question differently. We asked participants to choose between five different Smart TV Internet connection options, two of which retained functionality but entailed expending time and/or effort to preserve privacy
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
Induced Anticlinic Ordering and Nanophase Segregation of Bow-Shaped Molecules in a Smectic Solvent
Recent experiments indicate that doping low concentrations of bent-core
molecules into calamitic smectic solvents can induce anticlinic and biaxial
smectic phases. We have carried out Monte Carlo (MC) simulations of mixtures of
rodlike molecules (hard spherocylinders with length/breadth ratio ) and bow- or banana-shaped molecules (hard spherocylinder dimers
with length/breadth ratio or 2.5 and opening angle ) to
probe the molecular-scale organization and phase behavior of rod/banana
mixtures. We find that a low concentration (3%) of dimers
induces anticlinic (SmC) ordering in an untilted smectic (SmA) phase for
. For smaller , half of each bow-shaped
molecule is nanophase segregated between smectic layers, and the smectic layers
are untilted. For , no tilted phases are induced. However,
with decreasing we observe a sharp transition from {\sl intralamellar}
nanophase segregation (bow-shaped molecules segregated within smectic layers)
to {\sl interlamellar} nanophase segregation (bow-shaped molecules concentrated
between smectic layers) near . These results demonstrate that
purely entropic effects can lead to surprisingly complex behavior in rod/banana
mixtures.Comment: 5 pages Revtex, 7 postscript figure
Theory of Banana Liquid Crystal Phases and Phase Transitions
We study phases and phase transitions that can take place in the newly
discovered banana (bow-shaped or bent-core) liquid crystal molecules. We show
that to completely characterize phases exhibited by such bent-core molecules a
third-rank tensor order parameter is necessary in addition to the
vector and the nematic (second-rank) tensor order parameters. We present an
exhaustive list of possible liquid phases, characterizing them by their
space-symmetry group and order parameters, and catalog the universality classes
of the corresponding phase transitions that we expect to take place in such
bent-core molecular liquid crystals. In addition to the conventional
liquid-crystal phases such as the nematic phase, we predict the existence of
novel liquid phases, including the spontaneously chiral nematic
and chiral polar phases, the orientationally-ordered but
optically isotropic tetrahedratic phase, and a novel nematic phase
with symmetry that is neither uniaxial nor biaxial. Interestingly, the
Isotropic-Tetrahedratic transition is {\em continuous} in mean-field theory,
but is likely driven first-order by thermal fluctuations. We conclude with a
discussion of smectic analogs of these phases and their experimental
signatures.Comment: 28 pgs. RevTex, 32 eps figures, submitted to Phys. Rev.
Using ISS Telescopes for Electromagnetic Follow-up of Gravitational Wave Detections of NS-NS and NS-BH Mergers
The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of ground-based gravitational wave detections of neutron star and black hole mergers. We describe this possibility for OpTIIX, an ISS technology demonstration of a 1.5 m diffraction limited optical telescope assembled in space, and ISS-Lobster, a wide-field imaging X-ray telescope now under study as a potential NASA mission. Both telescopes will be mounted on pointing platforms, allowing rapid positioning to the source of a gravitational wave event. Electromagnetic follow-up rates of several per year appear likely, offering a wealth of complementary science on the mergers of black holes and neutron stars
Hydrodynamic interactions in colloidal ferrofluids: A lattice Boltzmann study
We use lattice Boltzmann simulations, in conjunction with Ewald summation
methods, to investigate the role of hydrodynamic interactions in colloidal
suspensions of dipolar particles, such as ferrofluids. Our work addresses
volume fractions of up to 0.20 and dimensionless dipolar interaction
parameters of up to 8. We compare quantitatively with Brownian
dynamics simulations, in which many-body hydrodynamic interactions are absent.
Monte Carlo data are also used to check the accuracy of static properties
measured with the lattice Boltzmann technique. At equilibrium, hydrodynamic
interactions slow down both the long-time and the short-time decays of the
intermediate scattering function , for wavevectors close to the peak of
the static structure factor , by a factor of roughly two. The long-time
slowing is diminished at high interaction strengths whereas the short-time
slowing (quantified via the hydrodynamic factor ) is less affected by the
dipolar interactions, despite their strong effect on the pair distribution
function arising from cluster formation. Cluster formation is also studied in
transient data following a quench from ; hydrodynamic interactions
slow the formation rate, again by a factor of roughly two
Renormalized couplings and scaling correction amplitudes in the N-vector spin models on the sc and the bcc lattices
For the classical N-vector model, with arbitrary N, we have computed through
order \beta^{17} the high temperature expansions of the second field derivative
of the susceptibility \chi_4(N,\beta) on the simple cubic and on the body
centered cubic lattices. (The N-vector model is also known as the O(N)
symmetric classical spin Heisenberg model or, in quantum field theory, as the
lattice
O(N) nonlinear sigma model.) By analyzing the expansion of \chi_4(N,\beta) on
the two lattices, and by carefully allowing for the corrections to scaling, we
obtain updated estimates of the critical parameters and more accurate tests of
the hyperscaling relation d\nu(N) +\gamma(N) -2\Delta_4(N)=0 for a range of
values of the spin dimensionality N, including
N=0 [the self-avoiding walk model], N=1 [the Ising spin 1/2 model],
N=2 [the XY model], N=3 [the classical Heisenberg model]. Using the recently
extended series for the susceptibility and for the second correlation moment,
we also compute the dimensionless renormalized four point coupling constants
and some universal ratios of scaling correction amplitudes in fair agreement
with recent renormalization group estimates.Comment: 23 pages, latex, no figure
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
Teachers as writers: a systematic review
This paper is a critical literature review of empirical work from 1990-2015 on teachers as writers. It interrogates the evidence on teachers’ attitudes to writing, their sense of themselves as writers and the potential impact of teacher writing on pedagogy or student outcomes in writing. The methodology was carried out in four stages. Firstly, educational databases keyword searches located 438 papers. Secondly, initial screening identified 159 for further scrutiny, 43 of which were found to specifically address teachers’ writing identities and practices. Thirdly, these sources were screened further using inclusion/exclusion criteria. Fourthly, the 22 papers judged to satisfy the criteria were subject to in-depth analysis and synthesis. The findings reveal that the evidence base in relation to teachers as writers is not strong, particularly with regard to the impact of teachers’ writing on student outcomes. The review indicates that teachers have narrow conceptions of what counts as writing and being a writer and that multiple tensions exist, relating to low self-confidence, negative writing histories, and the challenge of composing and enacting teacher and writer positions in school. However, initial training and professional development programmes do appear to afford opportunities for reformulation of attitudes and sense of self as writer
SALL4 Expression in Gonocytes and Spermatogonial Clones of Postnatal Mouse Testes
The spermatogenic lineage is established after birth when gonocytes migrate to the basement membrane of seminiferous tubules and give rise to spermatogonial stem cells (SSC). In adults, SSCs reside within the population of undifferentiated spermatogonia (Aundiff) that expands clonally from single cells (Asingle) to form pairs (Apaired) and chains of 4, 8 and 16 Aaligned spermatogonia. Although stem cell activity is thought to reside in the population of Asingle spermatogonia, new research suggests that clone size alone does not define the stem cell pool. The mechanisms that regulate self-renewal and differentiation fate decisions are poorly understood due to limited availability of experimental tools that distinguish the products of those fate decisions. The pluripotency factor SALL4 (sal-like protein 4) is implicated in stem cell maintenance and patterning in many organs during embryonic development, but expression becomes restricted to the gonads after birth. We analyzed the expression of SALL4 in the mouse testis during the first weeks after birth and in adult seminiferous tubules. In newborn mice, the isoform SALL4B is expressed in quiescent gonocytes at postnatal day 0 (PND0) and SALL4A is upregulated at PND7 when gonocytes have colonized the basement membrane and given rise to spermatogonia. During steady-state spermatogenesis in adult testes, SALL4 expression overlapped substantially with PLZF and LIN28 in Asingle, Apaired and Aaligned spermatogonia and therefore appears to be a marker of undifferentiated spermatogonia in mice. In contrast, co-expression of SALL4 with GFRα1 and cKIT identified distinct subpopulations of Aundiff in all clone sizes that might provide clues about SSC regulation. Collectively, these results indicate that 1) SALL4 isoforms are differentially expressed at the initiation of spermatogenesis, 2) SALL4 is expressed in undifferentiated spermatogonia in adult testes and 3) SALL4 co-staining with GFRα1 and cKIT reveals distinct subpopulations of Aundiff spermatogonia that merit further investigation. © 2013 Gassei, Orwig
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