8,564 research outputs found
Memorable And Secure: How Do You Choose Your PIN?
Managing all your PINs is difficult. Banks acknowledge this by allowing and facilitating PIN
changes. However, choosing secure PINs is a difficult task for humans as they are incapable of
consciously generating randomness. This leads to certain PINs being chosen more frequently
than others, which in turn increases the danger of someone else guessing correctly. We
investigate different methods of supporting PIN changes and report on an evaluation of these
methods in a study with 152 participants. Our contribution is twofold: We introduce an
alternative to system-generated random PINs, which considers people’s preferred
memorisation strategy, and, secondly, we provide indication that presenting guidance on how
to avoid insecure PINs does indeed nudge people towards more secure PIN choices when they
are in the process of changing their PINs
Decentralized Routing on Spatial Networks with Stochastic Edge Weights
We investigate algorithms to find short paths in spatial networks with
stochastic edge weights. Our formulation of the problem of finding short paths
differs from traditional formulations because we specifically do not make two
of the usual simplifying assumptions: (1) we allow edge weights to be
stochastic rather than deterministic; and (2) we do not assume that global
knowledge of a network is available. We develop a decentralized routing
algorithm that provides en route guidance for travelers on a spatial network
with stochastic edge weights without the need to rely on global knowledge about
the network. To guide a traveler, our algorithm uses an estimation function
that evaluates cumulative arrival probability distributions based on distances
between pairs of nodes. The estimation function carries a notion of proximity
between nodes and thereby enables routing without global knowledge. In testing
our decentralized algorithm, we define a criterion that allows one to
discriminate among arrival probability distributions, and we test our algorithm
and this criterion using both synthetic and real networks.Comment: 10 pages, 9 figures (some with multiple parts
Dust emission in powder handling: Free falling particle plume characterisation
Dust generation during solids handling, principally from the free falling of bulk materials and their impact on stockpiles, can be a health threat for operators and a cause of dust explosions. The proper design of a dust emission control system requires knowledge of the behaviour of the free falling jet, in particular the amount of air entrained by the falling powder and the concentration of dust liberated. The focus in this present paper is on the effect of drop height of a free falling jet on segregation by particle size, particle velocity, changes in particle concentration and entrained air in the dust plume. This gives a quantification of the important parameters and the concentration of dust emitted during a free fall
Cosmic-ray acceleration and gamma-ray signals from radio supernovae
In this work the efficiency of particle acceleration at the forward shock
right after the SN outburst for the particular case of the well-known SN 1993J
is analyzed. Plasma instabilities driven by the energetic particles accelerated
at the shock front grow over intraday timescales and drive a fast amplification
of the magnetic field at the shock, that can explain the magnetic field
strengths deduced from the radio monitoring of the source. The maximum particle
energy is found to reach 1-10 PeV depending on the instability dominating the
amplification process. We derive the time dependent particle spectra and the
associated hadronic signatures of secondary particles arising from proton
proton interactions. We find that the Cherenkov Telescope Array (CTA) should
easily detect objects like SN 1993J in particular above 1 TeV, while current
generation of Cherenkov telescopes such as H.E.S.S. could only marginally
detect such events. The gamma-ray signal is found to be heavily absorbed by
pair production process during the first week after the outburst. We predict a
low neutrino flux above 10 TeV, implying a detectability horizon with a
KM3NeT-type telescope of 1 Mpc only. We finally discuss the essential
parameters that control the particle acceleration and gamma-ray emission in
other type of SNe.Comment: 7 pages, 3 figures (Note: conflict of .sty file version explains the
problems with journal title and the abstract, apologies for any
inconvenience). Appears as Nuclear Physics B Proceedings Supplement 2014
Proceedings of the workshop "Cosmic Ray Origin beyond the standard models",
San Vito (2014), ed. by O.Tibolla, L. Drur
Granular flows down inclined channels with a strain-rate dependent friction coefficient. Part I: Non-cohesive materials
The flow of a granular material down an incline of finite width with a strain-rate dependent coefficient of friction and a conical yield criterion is semi-analytically obtained using a characteristic method for flows on a deep layer of grains. This analysis leads to a flow field with three distinct zones: a Bagnold-flow zone below the free surface, a dead zone and a matching zone between the two, linked to slippage at the wall. A good agreement between the computed flow field and experimental data is obtained
Detection of TeV emission from the intriguing composite SNR G327.1-1.1
The shock wave of supernova remnants (SNRs) and the wind termination shock in
pulsar wind nebula (PWNe) are considered as prime candidates to accelerate the
bulk of Galactic cosmic ray (CR) ions and electrons. The SNRs hosting a PWN
(known as composite SNRs) provide excellent laboratories to test these
hypotheses. The SNR G327.1-1.1 belongs to this category and exhibits a shell
and a bright central PWN, both seen in radio and X-rays. Interestingly, the
radio observations of the PWN show an extended blob of emission and a curious
narrow finger structure pointing towards the offset compact X-ray source
indicating a possible fast moving pulsar in the SNR and/or an asymmetric
passage of the reverse shock. We report here on the observations, for a total
of 45 hours, of the SNR G327.1-1.1 with the H.E.S.S. telescope array which
resulted in the detection of TeV gamma-ray emission in spatial coincidence with
the PWN.Comment: Proceeding of the 32nd ICRC, August 11-18 2011, Beijing, Chin
Evaluation of microRNA mmu-miR-31 influence in degenerative retinal models
Retinitis pigmentosa (RP) is a group of inherited dystrophic retinal disease that affects 1 of
4000 people worldwide. It gradually leads to visual loss through retinal neurodegeneration
with a slow and progressive process. The underlying mechanisms of the cell death are now
well studied but their interactions remain uncertain. Just before the death of the
photoreceptor, some of the cell cycle proteins are reactivated and may play an important
role. In the laboratory, some microRNAs have been identified during the photoreceptor
relapse of the Rd1 mouse model of retinal degeneration. The objectives of this study is to
understand the potential role of the miR-31 in the control of specific cell cycle proteins. For
this experiment, a mouse photoreceptor-like cell line (661W) has been cultured and
transfected with a plasmid coding for miR-31 and GFP or a scramble sequence and GFP
(control). Western Blot and qPCR allowed us to evaluate respectively the cell cycle protein
status and the corresponding mRNA status in relation to the miR-31 overexpression.
Our experiment revealed that miR-31 downregulates E2f1 cell cycle protein in 661W cells.
These results must be confirmed with supplementary experiments in vivo studies in Rd1
mouse retina
Inflationary spectra and violations of Bell inequalities
In spite of the macroscopic character of the primordial fluctuations, the
standard inflationary distribution (that obtained using linear mode equations)
exhibits inherently quantum properties, that is, properties which cannot be
mimicked by any stochastic distribution. This is demonstrated by a Gedanken
experiment for which certain Bell inequalities are violated. These violations
are {\it in principle} measurable because, unlike for Hawking radiation from
black holes, in inflationary cosmology we can have access to both members of
correlated pairs of modes delivered in the same state. We then compute the
effect of decoherence and show that the violations persist provided the
decoherence level (and thus the entropy) lies below a certain non-vanishing
threshold. Moreover, there exists a higher threshold above which no violation
of any Bell inequality can occur. In this regime, the distributions are
``separable'' and can be interpreted as stochastic ensembles of fluctuations.
Unfortunately, the precision which is required to have access to the quantum
properties is so high that, {\it in practice}, an observational verification
seems excluded.Comment: 5 pages, 1 figure; new presentation and extended discussio
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