720 research outputs found
An Agent Based Approach of Collective Foraging
In this paper the behaviour of a bee colony is modeled as a
society of communicating agents acting in parallel and synchroniz-ing
their behaviour. Two computational models for defining the agents
behaviour are introduced and compared and tools developed for these
models are briefly illustrated.Ministerio de Ciencia y Tecnología TIC2002-04220-C03-0
Heterogeneously integrated III-V/Si multi-wavelength laser based on a ring resonator array multiplexer
A 4-channel multi-wavelength laser integrated on a silicon waveguide circuit is realized. Waveguide-coupled output powers of 2mW and a side mode suppression ratio of more than 45dB for all channels is realized
III-V/silicon first order distributed feedback lasers integrated on SOI waveguide circuits
Heterogeneously integrated III-V-on-silicon first order distributed feedback lasers utilizing an ultra-thin DVS-BCB die-to-wafer bonding process are reported. A novel design exploiting high confinement in the active waveguide is demonstrated. 5 mW output power coupled to a silicon waveguide, 40 dB side mode suppression ratio and continuous wave operation up to 60°C is obtained
Control of tuberculosis in large cities in developed countries: an organizational problem
Tuberculosis (TB) is still a serious public health issue, even in large cities in developed countries. Control of this old disease is based on complicated programs that require completion of long treatments and contact tracing. In an accompanying research article published in BMC Public Health, Bothamley and colleagues found that areas with a ratio lower than one nurse per forty notifications had increased rates with respect to TB notifications, smear-positive cases, loss to follow-up and treatment abandonment across the UK. Furthermore, in these areas there was less opportunity for directly observed therapy, assistance with complex needs, educational outreach and new-entrant screening. In this commentary, we discuss the importance of improving organizational aspects and evaluating TB control programs. According to Bothamley and colleagues, a ratio of one nurse per forty notifications is an effective method of reducing the high TB incidences observed in London and in other cities in developed countries, or to maintain the decline in incidence in cities with lower incidences. It is crucial to evaluate TB programs every year to detect gaps early
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Combined sensitivity to the neutrino mass ordering with JUNO, the IceCube Upgrade, and PINGU
The ordering of the neutrino mass eigenstates is one of the fundamental open questions in neutrino physics. While current-generation neutrino oscillation experiments are able to produce moderate indications on this ordering, upcoming experiments of the next generation aim to provide conclusive evidence. In this paper we study the combined performance of the two future multi-purpose neutrino oscillation experiments JUNO and the IceCube Upgrade, which employ two very distinct and complementary routes toward the neutrino mass ordering. The approach pursued by the 20 kt medium-baseline reactor neutrino experiment JUNO consists of a careful investigation of the energy spectrum of oscillated νe produced by ten nuclear reactor cores. The IceCube Upgrade, on the other hand, which consists of seven additional densely instrumented strings deployed in the center of IceCube DeepCore, will observe large numbers of atmospheric neutrinos that have undergone oscillations affected by Earth matter. In a joint fit with both approaches, tension occurs between their preferred mass-squared differences Δm312=m32-m12 within the wrong mass ordering. In the case of JUNO and the IceCube Upgrade, this allows to exclude the wrong ordering at >5σ on a timescale of 3-7 years - even under circumstances that are unfavorable to the experiments' individual sensitivities. For PINGU, a 26-string detector array designed as a potential low-energy extension to IceCube, the inverted ordering could be excluded within 1.5 years (3 years for the normal ordering) in a joint analysis
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Neutrinos below 100 TeV from the southern sky employing refined veto techniques to IceCube data
Many Galactic sources of gamma rays, such as supernova remnants, are expected to produce neutrinos with a typical energy cutoff well below 100 TeV. For the IceCube Neutrino Observatory located at the South Pole, the southern sky, containing the inner part of the Galactic plane and the Galactic Center, is a particularly challenging region at these energies, because of the large background of atmospheric muons. In this paper, we present recent advancements in data selection strategies for track-like muon neutrino events with energies below 100 TeV from the southern sky. The strategies utilize the outer detector regions as veto and features of the signal pattern to reduce the background of atmospheric muons to a level which, for the first time, allows IceCube searching for point-like sources of neutrinos in the southern sky at energies between 100 GeV and several TeV in the muon neutrino charged current channel. No significant clustering of neutrinos above background expectation was observed in four years of data recorded with the completed IceCube detector. Upper limits on the neutrino flux for a number of spectral hypotheses are reported for a list of astrophysical objects in the southern hemisphere
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Time-Integrated Neutrino Source Searches with 10 Years of IceCube Data.
This Letter presents the results from pointlike neutrino source searches using ten years of IceCube data collected between April 6, 2008 and July 10, 2018. We evaluate the significance of an astrophysical signal from a pointlike source looking for an excess of clustered neutrino events with energies typically above ∼1 TeV among the background of atmospheric muons and neutrinos. We perform a full-sky scan, a search within a selected source catalog, a catalog population study, and three stacked Galactic catalog searches. The most significant point in the northern hemisphere from scanning the sky is coincident with the Seyfert II galaxy NGC 1068, which was included in the source catalog search. The excess at the coordinates of NGC 1068 is inconsistent with background expectations at the level of 2.9σ after accounting for statistical trials from the entire catalog. The combination of this result along with excesses observed at the coordinates of three other sources, including TXS 0506+056, suggests that, collectively, correlations with sources in the northern catalog are inconsistent with background at 3.3σ significance. The southern catalog is consistent with background. These results, all based on searches for a cumulative neutrino signal integrated over the 10 years of available data, motivate further study of these and similar sources, including time-dependent analyses, multimessenger correlations, and the possibility of stronger evidence with coming upgrades to the detector
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