1,944 research outputs found
Facts, Values and Quanta
Quantum mechanics is a fundamentally probabilistic theory (at least so far as
the empirical predictions are concerned). It follows that, if one wants to
properly understand quantum mechanics, it is essential to clearly understand
the meaning of probability statements. The interpretation of probability has
excited nearly as much philosophical controversy as the interpretation of
quantum mechanics. 20th century physicists have mostly adopted a frequentist
conception. In this paper it is argued that we ought, instead, to adopt a
logical or Bayesian conception. The paper includes a comparison of the orthodox
and Bayesian theories of statistical inference. It concludes with a few remarks
concerning the implications for the concept of physical reality.Comment: 30 pages, AMS Late
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
Primordial Power Spectrum Reconstruction
In order to reconstruct the initial conditions of the universe it is
important to devise a method that can efficiently constrain the shape of the
power spectrum of primordial matter density fluctuations in a model-independent
way from data. In an earlier paper we proposed a method based on the wavelet
expansion of the primordial power spectrum. The advantage of this method is
that the orthogonality and multiresolution properties of wavelet basis
functions enable information regarding the shape of to be
encoded in a small number of non-zero coefficients. Any deviation from
scale-invariance can then be easily picked out. Here we apply this method to
simulated data to demonstrate that it can accurately reconstruct an input
, and present a prescription for how this method should be used
on future data.Comment: 4 pages, 2 figures. JCAP accepted versio
Duraznero: situación actual en Uruguay, Brasil y Argentina.
O pessegueiro é uma cultura de grande importância econômica e social nos países do Cone Sul da América do Sul. A evolução desta frutífera tem sido condicionada tanto pelas características edafoclimáticas como culturais e econômicas de cada país. Sintetizar em um único documento a situação atual e os diferentes aspectos que caracterizam o cultivo do pessegueiro no Uruguai, Brasil e Argentina foi o objetivo abordado neste trabalho. A incorporação de tecnologia em todos os sentidos tem permitido uma melhora na produtividade para que a produção seja mantida apesar da redução da área de plantio. Ultimamente tem ocorrido um processo de crescimento em escala e concentração da produção, embora as características da cultura continuem a torná-la muito adequada para pequenos produtores. Grandes esforços de pesquisa canalizados através de Universidades e Institutos especializados têm permitido gerar informações locais e regionais de alto valor e impacto. A importância do material genético para o sucesso do sistema de produção é fundamental e a estratégia de geração de cultivares com adaptação local tem sido adotada pela região, com a disponibilidade de novas cultivares geradas por meio de programas de melhoramento locais. A abordagem da produção integrada vem ganhando grande impulso e cada vez mais alternativas produtivas vêm sendo desenvolvidas, visando a dispensar os agroquímicos, principalmente para o controle de pragas e doenças. A densidade de plantio tem aumentado e os sistemas de condução e poda estão evoluindo para formas mais simples e mecanizáveis. São muitos os desafios pela frente, mas também a convicção, entre as equipes de pesquisa, de poder continuar contribuindo para uma maior e melhor disponibilidade de frutos de Prunus nas mesas dos consumidores.VIII Encuentro Latinoamericano Prunus sin Fronteras
Mass-Varying Neutrinos from a Variable Cosmological Constant
We consider, in a completely model-independent way, the transfer of energy
between the components of the dark energy sector consisting of the cosmological
constant (CC) and that of relic neutrinos. We show that such a cosmological
setup may promote neutrinos to mass-varying particles, thus resembling a
recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without
introducing any acceleronlike scalar fields. Although a formal similarity of
the FNW scenario with the variable CC one can be easily established, one
nevertheless finds different laws for neutrino mass variation in each scenario.
We show that as long as the neutrino number density dilutes canonically, only a
very slow variation of the neutrino mass is possible. For neutrino masses to
vary significantly (as in the FNW scenario), a considerable deviation from the
canonical dilution of the neutrino number density is also needed. We note that
the present `coincidence' between the dark energy density and the neutrino
energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA
Relativistic quantum mechanics and the Bohmian interpretation
Conventional relativistic quantum mechanics, based on the Klein-Gordon
equation, does not possess a natural probabilistic interpretation in
configuration space. The Bohmian interpretation, in which probabilities play a
secondary role, provides a viable interpretation of relativistic quantum
mechanics. We formulate the Bohmian interpretation of many-particle wave
functions in a Lorentz-covariant way. In contrast with the nonrelativistic
case, the relativistic Bohmian interpretation may lead to measurable
predictions on particle positions even when the conventional interpretation
does not lead to such predictions.Comment: 10 pages, revised, to appear in Found. Phys. Let
Expression of interferon-γ, interferon-α and related genes in individuals with Down syndrome and periodontitis
AbstractBackgroundRecently, attenuation of anti-inflammatory and increase of pro-inflammatory mediators was demonstrated in individuals with Down syndrome (DS) in comparison with euploid patients during periodontal disease (PD), suggesting a shift to a more aggressive inflammation in DS.AimTo determine the influence of DS in the modulation of interferons (IFNs) signaling pathway in PD.Materials and methodsClinical periodontal assessment was performed and gingival tissue samples obtained from a total of 51 subjects, including 19 DS individuals with PD, 20 euploid individuals with PD and 12 euploid individuals without PD. Expression levels of interferon-gamma (IFNG) and interferon-alpha (IFNA), and their receptors IFNGR1, IFNGR2, IFNAR1 and IFNAR2, the signaling intermediates Janus kinase 1 (JAK1), signal transducer and activator of transcription 1 (STAT1) and interferon regulatory factor 1 (IRF1) were determined using real time quantitative polymerase chain reaction (qPCR).ResultsClinical signs of periodontal disease were markedly more severe in DS and euploid patients with PD in comparison to euploid and periodontally healthy patients. There was no difference on mRNA levels of IFNA, IFNG, INFGR2, IFNAR1 and IFNAR2 between DS and euploid individuals, even though some of these genes are located on chromosome 21. STAT1 and IRF1 mRNA levels were significantly lower in DS patients in comparison with euploid individuals with PD. In euploid individuals, PD was associated with an increased expression of IFNGR1, IFNGR2, IFNAR1, STAT1 and IRF1.ConclusionsReduced expression of STAT1 and IRF1 genes indicate an impaired activation of IFNs signaling in individuals with DS and PD. Expression of IFNA, IFNG and IFN receptors was not altered in DS patients, indicating that indirect mechanisms are involved in the reduced activation of IFN signaling
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