35 research outputs found
Evidence Against the Sciama Model of Radiative Decay of Massive Neutrinos
We report on spectral observations of the night sky in the band around 900
angstroms where the emission line in the Sciama model of radiatively decaying
massive neutrinos would be present. The data were obtained with a high
resolution, high sensitivity spectrometer flown on the Spanish MINISAT
satellite. The observed emission is far less intense than that expected in the
Sciama model.Comment: 9 pages, accepted to Ap
UV-optical from space
The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments
Inverse Compton Scattering as the Source of Diffuse EUV Emission in the Coma Cluster of Galaxies
We have examined the hypothesis that the majority of the diffuse EUV flux in
the Coma cluster is due to inverse Compton scattering of low energy cosmic ray
electrons (0.16 < epsilon < 0.31 GeV) against the 3K black-body background. We
present data on the two-dimensional spatial distribution of the EUV flux and
show that these data provide strong support for a non-thermal origin for the
EUV flux. However, we show that this emission cannot be produced by an
extrapolation to lower energies of the observed synchrotron radio emitting
electrons and an additional component of low energy cosmic ray electrons is
required.Comment: 11 pages, 5 figure
Machine learning forecasting for COVID-19 pandemic-associated effects on paediatric respiratory infections
OBJECTIVE: The COVID-19 pandemic and subsequent government restrictions have had a major impact on healthcare services and disease transmission, particularly those associated with acute respiratory infection. This study examined non-identifiable routine electronic patient record data from a specialist children's hospital in England, UK, examining the effect of pandemic mitigation measures on seasonal respiratory infection rates compared with forecasts based on open-source, transferable machine learning models. METHODS: We performed a retrospective longitudinal study of respiratory disorder diagnoses between January 2010 and February 2022. All diagnoses were extracted from routine healthcare activity data and diagnosis rates were calculated for several diagnosis groups. To study changes in diagnoses, seasonal forecast models were fit to prerestriction period data and extrapolated. RESULTS: Based on 144 704 diagnoses from 31 002 patients, all but two diagnosis groups saw a marked reduction in diagnosis rates during restrictions. We observed 91%, 89%, 72% and 63% reductions in peak diagnoses of 'respiratory syncytial virus', 'influenza', 'acute nasopharyngitis' and 'acute bronchiolitis', respectively. The machine learning predictive model calculated that total diagnoses were reduced by up to 73% (z-score: -26) versus expected during restrictions and increased by up to 27% (z-score: 8) postrestrictions. CONCLUSIONS: We demonstrate the association between COVID-19 related restrictions and significant reductions in paediatric seasonal respiratory infections. Moreover, while many infection rates have returned to expected levels postrestrictions, others remain supressed or followed atypical winter trends. This study further demonstrates the applicability and efficacy of routine electronic record data and cross-domain time-series forecasting to model, monitor, analyse and address clinically important issues
Far Ultraviolet Absolute Flux of alpha Virginis
We present the far ultraviolet spectrum of alpha Virginis taken with EURD
spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to
1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE
spectra of alpha Vir and compared the extension of the model to our wavelengths
with EURD data. This comparison shows that EURD fluxes are consistent with the
prediction of the model within 20-30%, depending on the reddening assumed. EURD
fluxes are consistent with Voyager observations but are ~60% higher than most
previous rocket observations of alpha Vir.Comment: 13 pages, 4 figures. Submitted to The Astrophysical Journa
Far Ultraviolet Spectra of B Stars near the Ecliptic
Spectra of B stars in the wavelength range of 911-1100 A have been obtained
with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with ~5 A
spectral resolution. IUE spectra of the same stars have been used to normalize
Kurucz models to the distance, reddening and spectral type of the corresponding
star. The comparison of 8 main-sequence stars studied in detail (alpha Vir,
epsilon Tau, lambda Tau, tau Tau, alpha Leo, zeta Lib, theta Oph, and sigma
Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher
than the models in most cases. The difference in flux between observations and
models is higher in the wavelength range between Lyman alpha and Lyman beta. We
suggest that Kurucz models underestimate the FUV flux of main-sequence B stars
between these two Lyman lines. Computation of flux distributions of
line-blanketed model atmospheres including non-LTE effects suggests that this
flux underestimate could be due to departures from LTE, although other causes
cannot be ruled out. We found the common assumption of solar metallicity for
young disk stars should be made with care, since small deviations can have a
significant impact on FUV model fluxes. Two peculiar stars (rho Leo and epsilon
Aqr), and two emission line stars (epsilon Cap and pi Aqr) were also studied.
Of these, only epsilon Aqr has a flux in agreement with the models. The rest
have strong variability in the IUE range and/or uncertain reddening, which
makes the comparison with models difficult.Comment: 25 pages, 6 figures, to be published in The Astrophysical Journa
The EUV Emission in the Coma Cluster of Galaxies and the Underlying Source of this Radiation
Observations with the Extreme Ultraviolet Explorer (EUVE) have shown the Coma
Cluster to be a source of EUV emission in excess of that produced by X-ray gas
in the cluster. We have re-examined the EUVE data on this cluster in an attempt
to obtain clues as to the origin of this emission. We find two important new
results. First, the ratio between the azimuthally averaged EUV excess emission
and the ROSAT hard X-ray flux is constant as a function of distance from the
cluster center outward. Second, a correlation analysis between the EUV excess
emission and the X-ray emission shows that on a detailed level the EUV excess
is spatially closely related to the X-ray emission. These findings contradict
previous suggestions as to the underlying source of the diffuse EUV emission in
Coma and provide important information in regards to the true source of this
emission. We propose a new explanation for the source of this emission: inverse
Compton scattering of microwave background photons by secondary electrons and
positrons. We explore this possibility in some detail and show that it is
consistent with all of the available observational evidence. The parent cosmic
ray protons may have been produced by any of a number of sources, including
supernovae, active galaxies, galactic winds, and cluster formation shocks, but
we believe that the most likely source is cluster formation shocks. If the EUV
emission in the Coma Cluster is, in fact, the result of secondary electrons,
this may be the only direct evidence for secondary electrons in the
intracluster medium of a cluster of galaxies, since recent work suggests that
secondary electrons may not be the cause of radio halos.Comment: 17 pages, 7 eps figures inline, submitted to Ap
Grasping Angle Estimation of Human Forearm with Underactuated Grippers Using Proprioceptive Feedback
In this paper, a method for the estimation of the angle of grasping of a human forearm, when grasped by a robot with an underactuated gripper, using proprioceptive information only, is presented.
Knowing the angle around the forearm’s axis (i.e. roll angle) is key for the safe manipulation of the human limb and biomedical sensor placement among others. The adaptive gripper has two independent underactuated fingers with two phalanges and a single actuator each. The final joint position of the gripper provides information related to the shape of the grasped object without the need for external contact or force sensors.
Regression methods to estimate the roll angle of the grasping have been trained with forearm grasping information from different humans at each angular position. The results show that it is possible to accurately estimate the rolling angle of the human arm, for trained and unknown people.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec
FAUST observations of UV sources toward the Virgo cluster
We analyze three UV images covering a 100 square degree field toward the
Virgo cluster,obtained by the FAUST space experiment. We detect 191 sources to
a signal-to-noise ratio of 4.4 and identify 94% of them. Most sources have
optical counterparts in existing catalogs and about half are identified as
galaxies. Some sources with no listed counterpart were observed at the Wise
Observatory. We present the results of low resolution visible spectrophotometry
and discuss the foreground 101 stellar sources and the 76 detected galaxies,
both in the cluster and in the fore- or background. We derive conclusions on
star-formation properties of galaxies and on the total UV flux from discrete
and diffuse sources in the cluster. We test for the presence of intra-cluster
dust, determine the clustering properties of UV emitting galaxies, and derive
the UV luminosity function of Virgo galaxies.Comment: 60 pages, LaTeX (including 5 Tables) + 8 PostScript figures. To
appear in "The Astrophysical Journal