10,011 research outputs found
Solar type II radio bursts associated with CME expansions as shown by EUV waves
We investigate the physical conditions of the sources of two metric Type-II
bursts associated with CME expansions with the aim of verifying the
relationship between the shocks and the CMEs, comparing the heights of the
radio sources and the heights of the EUV waves associated with the CMEs. The
heights of the EUV waves associated with the events were determined in relation
to the wave fronts. The heights of the shocks were estimated by applying two
different density models to the frequencies of the Type-II emissions and
compared with the heights of the EUV waves. For the 13 June 2010 event, with
band-splitting, the shock speed was estimated from the frequency drifts of the
upper and lower branches of the harmonic lane, taking into account the H/F
frequency ratio fH/fF = 2. Exponential fits on the intensity maxima of the
branches revealed to be more consistent with the morphology of the spectrum of
this event. For the 6 June 2012 event, with no band-splitting and with a clear
fundamental lane on the spectrum, the shock speed was estimated directly from
the frequency drift of the fundamental emission, determined by linear fit on
the intensity maxima of the lane. For each event, the most appropriate density
model was adopted to estimate the physical parameters of the radio source. The
13 June 2010 event presented a shock speed of 664-719 km/s, consistent with the
average speed of the EUV wave fronts of 609 km/s. The 6 June 2012 event was
related to a shock of speed of 211-461 km/s, also consistent with the average
speed of the EUV wave fronts of 418 km/s. For both events, the heights of the
EUV wave revealed to be compatible with the heights of the radio source,
assuming a radial propagation of the shock.Comment: Accepted for publication in Astronomy and Astrophysic
Quantum computing with incoherent resources and quantum jumps
Spontaneous emission and the inelastic scattering of photons are two natural
processes usually associated with decoherence and the reduction in the capacity
to process quantum information. Here we show that when suitably detected, these
photons are sufficient to build all the fundamental blocks needed to perform
quantum computation in the emitting qubits while protecting them from
deleterious dissipative effects. We exemplify by showing how to teleport an
unknown quantum state and how to efficiently prepare graph states for the
implementation of measurement-based quantum computation.Comment: 5 pages, 5 figure
Epidemiologia molecular de trypanosoma cruzi no estado de Mato Grosso do Sul: resultados preliminares.
A molecular line scan in the Hubble Deep Field North
We present a molecular line scan in the Hubble Deep Field North (HDF-N) that covers the entire 3mm window (79-115 GHz) using the IRAM Plateau de Bure Interferometer. Our CO redshift coverage spans z2. We reach a CO detection limit that is deep enough to detect essentially all z>1 CO lines reported in the literature so far. We have developed and applied different line searching algorithms, resulting in the discovery of 17 line candidates. We estimate that the rate of false positive line detections is ~2/17. We identify optical/NIR counterparts from the deep ancillary database of the HDF-N for seven of these candidates and investigate their available SEDs. Two secure CO detections in our scan are identified with star-forming galaxies at z=1.784 and at z=2.047. These galaxies have colors consistent with the `BzK' color selection and they show relatively bright CO emission compared with galaxies of similar dust continuum luminosity. We also detect two spectral lines in the submillimeter galaxy HDF850.1 at z=5.183. We consider an additional 9 line candidates as high quality. Our observations also provide a deep 3mm continuum map (1-sigma noise level = 8.6 μJy/beam). Via a stacking approach, we find that optical/MIR bright galaxies contribute only to <50% of the SFR density at 1<z<3, unless high dust temperatures are invoked. The present study represents a first, fundamental step towards an unbiased census of molecular gas in `normal' galaxies at high-z, a crucial goal of extragalactic astronomy in the ALMA era
O crescimento de plântulas de tomateiro é afetado por extratos de vermicomposto.
O objetivo desse trabalho foi avaliar o efeito de extratos de vermicomposto sobre a morfologia da parte aérea e radicular de plantulas de tomateiro. Observou-se um aumento linear significativo da área foliar (AF) e massa foliar fresca (MFF)
A Mixed Experimental-numerical Energy-based Approach for Fatigue Life Assessment in Notched Samples under Multiaxial Loading
This paper presents a methodology to predict the fatigue lifetime in notched geometries subjected to multiaxial loading on the basis of the cumulated strain energy density. The modus operandi consists of defining an energy-based fatigue master curve that relates the cumulated strain energy density with the number of cycles to failure using standard cylindrical specimens tested under low-cycle fatigue conditions. After that, an elastic-plastic finite-element model representative of the material behaviour, notched geometry and multiaxial loading scenario is developed and used to account for the strain energy density at the crack initiation site. This energy is then averaged using the Theory of Critical Distances and inserted into the energy- based fatigue master curve to estimate the lifetime expectancy. Overall, the comparison between the experimental and predicted fatigue lives has shown a very good agreement.
Keywords: Multiaxial fatigue, Fatigue life prediction, Strain energy densit
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