2,486 research outputs found
Assessment of the risk of tuberculosis transmission for five housing prototypes designed for a Haitian community
The hospitalization of patients affected with tuberculosis (TB) can be particularly long and
burdensome, especially in poor countries where the disease remains a major issue and beds in
health care centres are a precious resource. Therefore a policy of decentralising TB treatment
from hospitals to residential environments is starting to be considered worldwide, and new
guidelines in support of such strategy are needed. This study illustrates a potential “risk
assessment model” for TB transmission in dwellings that might help analysing both existing
building stocks and new designs in order to apply the new policy, utilizing as a reference the
general frame of risk assessment for buildings developed by civil engineering; the model was
then tested on five housing prototypes proposed for the town of Saint Marc, Haiti, showing
that environmental features of a building such as ventilation, crowding, temperature and
relative humidity are among the most important parameters for the estimate of the risk. The
final outcome of the analysis, however, highlighted how he most influential factor on the risk
of spread of infectious diseases is the efficiency of the health care system operating in the
building urban context
Order in de Broglie - Bohm quantum mechanics
A usual assumption in the so-called {\it de Broglie - Bohm} approach to
quantum dynamics is that the quantum trajectories subject to typical `guiding'
wavefunctions turn to be quite irregular, i.e. {\it chaotic} (in the dynamical
systems' sense). In the present paper, we consider mainly cases in which the
quantum trajectories are {\it ordered}, i.e. they have zero Lyapunov
characteristic numbers. We use perturbative methods to establish the existence
of such trajectories from a theoretical point of view, while we analyze their
properties via numerical experiments. Using a 2D harmonic oscillator system, we
first establish conditions under which a trajectory can be shown to avoid close
encounters with a moving nodal point, thus avoiding the source of chaos in this
system. We then consider series expansions for trajectories both in the
interior and the exterior of the domain covered by nodal lines, probing the
domain of convergence as well as how successful the series are in comparison
with numerical computations or regular trajectories. We then examine a
H\'{e}non - Heiles system possessing regular trajectories, thus generalizing
previous results. Finally, we explore a key issue of physical interest in the
context of the de Broglie - Bohm formalism, namely the influence of order in
the so-called {\it quantum relaxation} effect. We show that the existence of
regular trajectories poses restrictions to the quantum relaxation process, and
we give examples in which the relaxation is suppressed even when we consider
initial ensembles of only chaotic trajectories, provided, however, that the
system as a whole is characterized by a certain degree of order.Comment: 25 pages, 12 figure
Existential Contextuality and the Models of Meyer, Kent and Clifton
It is shown that the models recently proposed by Meyer, Kent and Clifton
(MKC) exhibit a novel kind of contextuality, which we term existential
contextuality. In this phenomenon it is not simply the pre-existing value but
the actual existence of an observable which is context dependent. This result
confirms the point made elsewhere, that the MKC models do not, as the authors
claim, ``nullify'' the Kochen-Specker theorem. It may also be of some
independent interest.Comment: Revtex, 7 pages, 1 figure. Replaced with published versio
Bell's Jump Process in Discrete Time
The jump process introduced by J. S. Bell in 1986, for defining a quantum
field theory without observers, presupposes that space is discrete whereas time
is continuous. In this letter, our interest is to find an analogous process in
discrete time. We argue that a genuine analog does not exist, but provide
examples of processes in discrete time that could be used as a replacement.Comment: 7 pages LaTeX, no figure
The nature and evolution of Nova Cygni 2006
AIMS: Nova Cyg 2006 has been intensively observed throughout its full
outburst. We investigate the energetics and evolution of the central source and
of the expanding ejecta, their chemical abundances and ionization structure,
and the formation of dust. METHOD: We recorded low, medium, and/or
high-resolution spectra (calibrated into accurate absolute fluxes) on 39
nights, along with 2353 photometric UBVRcIc measures on 313 nights, and
complemented them with IR data from the literature. RESULTS: The nova displayed
initially the normal photometric and spectroscopic evolution of a fast nova of
the FeII-type. Pre-maximum, principal, diffuse-enhanced, and Orion absorption
systems developed in a normal way. After the initial outburst, the nova
progressively slowed its fading pace until the decline reversed and a second
maximum was reached (eight months later), accompanied by large spectroscopic
changes. Following the rapid decline from second maximum, the nova finally
entered the nebular phase and formed optically thin dust. We computed the
amount of formed dust and performed a photo-ionization analysis of the
emission-line spectrum during the nebular phase, which showed a strong
enrichment of the ejecta in nitrogen and oxygen, and none in neon, in agreement
with theoretical predictions for the estimated 1.0 Msun white dwarf in Nova Cyg
2006. The similarities with the poorly investigated V1493 Nova Aql 1999a are
discussed.Comment: in press in Astronomy and Astrophysic
Pressure dependence of the single particle excitation in the charge-density-wave CeTe system
We present new data on the pressure dependence at 300 K of the optical
reflectivity of CeTe, which undergoes a charge-density-wave (CDW) phase
transition well above room temperature. The collected data cover an
unprecedented broad spectral range from the infrared up to the ultraviolet,
which allows a robust determination of the gap as well as of the fraction of
the Fermi surface affected by the formation of the CDW condensate. Upon
compressing the lattice there is a progressive closing of the gap inducing a
transfer of spectral weight from the gap feature into the Drude component. At
frequencies above the CDW gap we also identify a power-law behavior, consistent
with findings along the Te series (i.e., chemical pressure) and
suggestive of a Tomonaga-Luttinger liquid scenario at high energy scales. This
newest set of data is placed in the context of our previous investigations of
this class of materials and allows us to revisit important concepts for the
physics of CDW state in layered-like two-dimensional systems
Zealots Attack and the Revenge of the Commons: Quality vs Quantity in the Best-of-n
© 2020, Springer Nature Switzerland AG. In this paper we study the effect of inflexible individuals with fixed opinions, or zealots, on the dynamics of the best-of-n collective decision making problem, using both the voter model and the majority rule decision mechanisms. We consider two options with different qualities, where the lower quality option is associated to a higher number of zealots. The aim is to study the trade-off between option quality and zealot quantity for two different scenarios: one in which all agents can modulate dissemination of their current opinion proportionally to the option quality, and one in which this capability is only possessed by the zealots. In both scenarios, our goal is to determine in which conditions consensus is more biased towards the high or low quality option, and to determine the indifference curve separating these two regimes. Using both numerical simulations and ordinary differential equation models, we find that: i) if all agents can modulate the dissemination time based on the option quality, then consensus can be driven to the high quality option when the number of zealots for the other option is not too high; ii) if only zealots can modulate the dissemination time based on the option quality, whil e all normal agents cannot distinguish the two options and cannot differentially disseminate, then consensus no longer depends on the quality and is driven to the low quality option by the zealots
Construction task allocation through the collective perception of a dynamic environment
Building structures is a remarkable collective process but its automation remains an open challenge. Robot swarms provide a promising solution to this challenge. However, collective construction involves a number of difficulties regarding efficient robots allocation to the different activities, particularly if the goal is to reach an optimal construction rate. In this paper, we study an abstract construction scenario, where a swarm of robots is engaged in a collective perception process to estimate the density of building blocks around a construction site. The goal of this perception process is to maintain a minimum density of blocks available to the robots for construction. To maintain this density, the allocation of robots to the foraging task needs to be adjusted such that enough blocks are retrieved. Our results show a robust collective perception that enables the swarm to maintain a minimum block density under different rates of construction and foraging. Our approach leads the system to stabilize around a state in which the robots allocation allows the swarm to maintain a tile density that is close to or above the target minimum.info:eu-repo/semantics/publishedDorigo, M. Stützle, T. Blesa, M. J. Blum, C. Hamann, H. Heinrich, M. K. & Strobel, V. (2020). Swarm Intelligence: 12th International Conference, ANTS 2020, Barcelona, Spain, October 26-28, 2020, Proceedings. Cham: Springer International Publishing AG
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