1,076 research outputs found
Lyman continuum leaker candidates among highly ionised, low-redshift dwarf galaxies selected from HeII
Contemporary research suggests that the reionisation of the intergalactic
medium (IGM) in the early Universe was predominantly realised by star-forming
(proto-)galaxies (SFGs). Due to observational constraints, our knowledge on the
origins of sufficient amounts of ionising Lyman continuum (LyC) photons and the
mechanisms facilitating their transport into the IGM remains sparse. Recent
efforts have thus focussed on the study of local analogues to these
high-redshift objects.
We used archival spectroscopic SDSS DR12 data to select a sample of low-z He
II 4686 emitters and restricted it to a set of SFGs with an emission line
diagnostic sensitive to the presence of an AGN, which serves as our only
selection criterion. Our final sample consists of eighteen low-mass,
low-metallicity dwarf galaxies which appear to be predominantly ionised by
stellar sources. We find large O32 ratios and [S II] deficiencies, which
provide strong indications for these galaxies to be LyC Emitters (LCEs). At
least 40% of these objects are candidates for featuring cosmologically
significant LyC escape fractions >10%. Their SFHs exhibit strong similarities
and almost all galaxies appear to contain an old (>1 Gyr) stellar component,
while also harbouring a young, two-stage (~10 Myr and <1 Myr) starburst, which
we speculate might be related to LyC escape.
The properties of the compact emission line galaxies presented here align
well with those observed in many local LCEs. In fact, our sample may prove as
an extension to the rather small catalogue of local LCEs, as the extreme
interstellar medium (ISM) conditions we find are assumed to facilitate LyC
leakage. Notably, all of our eighteen candidates are significantly closer
(z<0.1) than most established LCEs. If the inferred LyC photon loss is genuine,
this demonstrates that selecting SFGs from He II 4686 is a powerful selection
criterion in the search for LCEs.Comment: 28 pages, 22 figures. Accepted for publication in Astronomy &
Astrophysic
Электрофизические особенности высокочастотного факельного разряда, горящего в аргоне
На основе измерений характеристик электромагнитного поля ВЧФ-разряда, горящего в аргоне, проведены расчёты его тепловой мощности. Проведены измерения тепловых потерь ВЧФ-разряда, горящего в аргоне, в зависимости от длины его канала и проведено сопоставление расчетных и экспериментальных результатов.Based on measurements of the characteristics of the electromagnetic field of an RF RF discharge burning in argon, its thermal power was calculated. The heat losses of the RF RF discharge burning in argon were measured, depending on the length of its channel, and the calculated and experimental results were compared
Two-phonon 1- state in 112Sn observed in resonant photon scattering
Results of a photon scattering experiment on 112Sn using bremsstrahlung with
an endpoint energy of E_0 = 3.8 MeV are reported. A J = 1 state at E_x =
3434(1) keV has been excited. Its decay width into the ground state amounts to
Gamma_0 = 151(17) meV, making it a candidate for a [2+ x 3-]1- two-phonon
state. The results for 112Sn are compared with quasiparticle-phonon model
calculations as well as the systematics of the lowest-lying 1- states
established in other even-mass tin isotopes. Contrary to findings in the
heavier stable even-mass Sn isotopes, no 2+ states between 2 and 3.5 MeV
excitation energy have been detected in the present experiment.Comment: 10 pages, including 2 figures, Phys. Rev. C, in pres
Deep learning for prediction of population health costs
BACKGROUND: Accurate prediction of healthcare costs is important for optimally managing health costs. However, methods leveraging the medical richness from data such as health insurance claims or electronic health records are missing. METHODS: Here, we developed a deep neural network to predict future cost from health insurance claims records. We applied the deep network and a ridge regression model to a sample of 1.4 million German insurants to predict total one-year health care costs. Both methods were compared to existing models with various performance measures and were also used to predict patients with a change in costs and to identify relevant codes for this prediction. RESULTS: We showed that the neural network outperformed the ridge regression as well as all considered models for cost prediction. Further, the neural network was superior to ridge regression in predicting patients with cost change and identified more specific codes. CONCLUSION: In summary, we showed that our deep neural network can leverage the full complexity of the patient records and outperforms standard approaches. We suggest that the better performance is due to the ability to incorporate complex interactions in the model and that the model might also be used for predicting other health phenotypes
WIRE SCANNERS FOR EMITTANCE MEASUREMENTS AT THE 100 keV SPIN POLARIZED ELECTRON BEAM LINE AT THE S-DALINAC
Abstract A source of 100 keV spin polarized electrons has been installed at the 130 MeV superconducting Darmstadt linear accelerator S-DALINAC. Circularly polarized laser light excites a GaAs cathode, producing spin polarized electrons in bunches with pulse lengths in the region of 50 ps and smaller at a repetition frequency of 3 GHz. A Wienfilter for spin manipulation and a Mott polarimeter for polarization measurements are installed in the low-energy beam line. Polarizations up to 86% have been shown with strained superlattice GaAs cathodes. Installed wire scanners in the beam line measure beam radius and position and in conjunction with a solenoid with variable focal length a parameter set of beam sizes depending on the focal length can be obtained, allowing for an emittance calculation. The scanning unit, two perpendicular 50 ➭ m tungsten wires for x and y measurements mounted on an insulated frame, is installed at an angle of 45 in a plane perpendicular to the beam. Pneumatic as well as electric translation is used while the data read-out is done by a 24-bit ADC with variable reading speed. Measurements at the S-DALINAC give an indication of the beam quality of the spin polarized electron source, permit a comparison with the already installed thermionic electron source, and allow the measurement of a possible emittance growth from the Wien-filter that is to be excluded. Furthermore, the knowledge of the beam size renders a slit measurement of the beam pulse length possible. S-DALINAC The S-DALINAC [1] is a recirculating superconducting electron linear accelerator capable of producing electron beams at beam energies from 2.5 MeV up to typically 80-90 Mev, with a design value of up to 130 MeV. Around the S-DALINAC, a multifacetted nuclear-physics program is realized in Darmstadt. Research topics are nuclear structure, nuclear astrophysics, fundamental studies and the continuous upgrade of the accelerator, all being the focus of a center of excellence funded by the German Research Foundation (DFG) about eight years ago. Since the S-DALINAC's first commissioning around 1990, nuclear resonance fluorescence experiment
F-spin as a Partial Symmetry
We use the empirical evidence that F-spin multiplets exist in nuclei for only
selected states as an indication that F-spin can be regarded as a partial
symmetry. We show that there is a class of non-F-scalar IBM-2 Hamiltonians with
partial F-spin symmetry, which reproduce the known systematics of collective
bands in nuclei. These Hamiltonians predict that the scissors states have good
F-spin and form F-spin multiplets, which is supported by the existing data.Comment: 14 pages, 1 figur
Transition Rates between Mixed Symmetry States: First Measurement in 94Mo
The nucleus 94Mo was investigated using a powerful combination of
gamma-singles photon scattering experiments and gamma-gamma-coincidence studies
following the beta-decay of 94mTc. The data survey short-lived J^pi=1+,2+
states and include branching ratios, E2/M1 mixing ratios, lifetimes, and
transition strengths. The mixed-symmetry (MS) 1+ scissors mode and the 2+ MS
state are identified from M1 strengths. A gamma transition between MS states
was observed and its rate was measured. Nine M1 and E2 strengths involving MS
states agree with the O(6) limit of the interacting boson model-2 using the
proton boson E2 charge as the only free parameter.Comment: 9 pages, 3 PostScript figures included, ReVTeX, accepted for
publication in Physical Review Letters, tentatively scheduled for August 9,
199
Strong fragmentation of low-energy electromagnetic excitation strength in Sn
Results of nuclear resonance fluorescence experiments on Sn are
reported. More than 50 transitions with MeV were
detected indicating a strong fragmentation of the electromagnetic excitation
strength. For the first time microscopic calculations making use of a complete
configuration space for low-lying states are performed in heavy odd-mass
spherical nuclei. The theoretical predictions are in good agreement with the
data. It is concluded that although the E1 transitions are the strongest ones
also M1 and E2 decays contribute substantially to the observed spectra. In
contrast to the neighboring even Sn, in Sn the
component of the two-phonon quintuplet built on top of
the 1/2 ground state is proved to be strongly fragmented.Comment: 4 pages, 3 figure
The damping width of giant dipole resonances of cold and hot nuclei: a macroscopic model
A phenomenological macroscopic model of the Giant Dipole Resonance (GDR)
damping width of cold- and hot-nuclei with ground-state spherical and
near-spherical shapes is developed. The model is based on a generalized Fermi
Liquid model which takes into account the nuclear surface dynamics. The
temperature dependence of the GDR damping width is accounted for in terms of
surface- and volume-components. Parameter-free expressions for the damping
width and the effective deformation are obtained. The model is validated with
GDR measurements of the following nuclides, K, Ca, Sc,
Cu, Sn,Eu, Hg, and Pb, and is
compared with the predictions of other models.Comment: 10 pages, 5 figure
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