1,257 research outputs found
Excited states of beryllium atom from explicitly correlated wave functions
A study of the first excited states of beryllium atom starting from
explicitly correlated wave functions is carried out. Several properties are
obtained and discussed focusing on the analysis of the Hund's rules in terms of
the single--particle and electron pair intracule and extracule densities. A
systematic study of the differences on the electronic distributions of the
singlet and triplet states is carried out. The trial wave function used to
describe the different bound states consists of a generalized Jastrow-type
correlation factor times a configuration interaction model wave function. This
model wave function has been fixed by using a generalization of the optimized
effective potential method to deal with multiconfiguration wave functions. The
optimization of the wave function and the calculation of the different
quantities is carried out by means of the Variational Monte Carlo method.Comment: 28 pages, 6 figure
Primeval very low-mass stars and brown dwarfs - VI. Population properties of metal-poor degenerate brown dwarfs
© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy, and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near infrared spectra obtained with the Very Large Telescope and the Gran Telescopio Canarias. One of these new T dwarfs is mildly metal-poor with slightly suppressed -band flux. We presented a new X-shooter spectrum of a known benchmark sdT5.5 subdwarf, HIP 73786B. To better understand observational properties of brown dwarfs, we discussed transition zones (mass ranges) with low-rate hydrogen, lithium, and deuterium burning in brown dwarf population. The hydrogen burning transition zone is also the substellar transition zone that separates very low-mass stars, transitional, and degenerate brown dwarfs. Transitional brown dwarfs have been discussed in previous works of the Primeval series. Degenerate brown dwarfs without hydrogen fusion are the majority of brown dwarfs. Metal-poor degenerate brown dwarfs of the Galactic thick disc and halo have become T5+ subdwarfs. We selected 41 T5+ subdwarfs from the literature by their suppressed -band flux. We studied the spectral-type - colour correlations, spectral-type - absolute magnitude correlations, colour-colour plots, and HR diagrams of T5+ subdwarfs, in comparison to these of L-T dwarfs and L subdwarfs. We discussed the T5+ subdwarf discovery capability of deep sky surveys in the 2020s.Peer reviewe
Dynamical Localization: Hydrogen Atoms in Magnetic and Microwave fields
We show that dynamical localization for excited hydrogen atoms in magnetic
and microwave fields takes place at quite low microwave frequency much lower
than the Kepler frequency. The estimates of localization length are given for
different parameter regimes, showing that the quantum delocalization border
drops significantly as compared to the case of zero magnetic field. This opens
up broad possibilities for laboratory investigations.Comment: revtex, 11 pages, 3 figures, to appear in Phys. Rev. A, Feb (1997
Purple dwarfs : New L subdwarfs from UKIDSS and SDSS
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The first L subdwarf was a discovered only ten years ago. Less than ten L subdwarfs been published in the literature to date. Metal-poor ultracool atmospheres has not been well understood. Halo mass function cross substellar limit has not been measured. We used UKIDSS and SDSS to search for L subdwarfs. We have confirmed some new L subdwarfs and are following up more candidates with ground based large telescopes. We discussed spectral features of L subdwarfs and halo brown dwarfs
Experimental realization of smectic phase in vortex matter induced by symmetric potentials arranged in two-fold symmetry arrays
Smectic order has been generated in superconducting Nb films with two-fold
symmetry arrays of symmetric pinning centers. Magnetic fields applied
perpendicularly to the films develop a vortex matter smectic phase that is
easily detected when the vortices commensurate with the pinning center array.
The smectic phase can be turned on and off with external parameters.Comment: 15 pages, 5 figure
Stochastic ionization through noble tori: Renormalization results
We find that chaos in the stochastic ionization problem develops through the
break-up of a sequence of noble tori. In addition to being very accurate, our
method of choice, the renormalization map, is ideally suited for analyzing
properties at criticality. Our computations of chaos thresholds agree closely
with the widely used empirical Chirikov criterion
Frequency Dependence of Quantum Localization in a Periodically Driven System
We study the quantum localization phenomena for a random matrix model
belonging to the Gaussian orthogonal ensemble (GOE). An oscillating external
field is applied on the system. After the transient time evolution, energy is
saturated to various values depending on the frequencies. We investigate the
frequency dependence of the saturated energy. This dependence cannot be
explained by a naive picture of successive independent Landau-Zener transitions
at avoided level crossing points. The effect of quantum interference is
essential. We define the number of Floquet states which have large overlap with
the initial state, and calculate its frequency dependence. The number of
Floquet states shows approximately linear dependence on the frequency, when the
frequency is small. Comparing the localization length in Floquet states and
that in energy states from the viewpoint of the Anderson localization, we
conclude that the Landau-Zener picture works for the local transition processes
between levels.Comment: 12 pages and 6 figure
Description of the BRIGHTLIGHT cohort: the evaluation of teenage and young adult cancer services in England
Objective International recognition of the unique needs
of young people with cancer is growing. Many countries
have developed specialist age-appropriate cancer services
believing them to be of value. In England, 13 specialist
principal treatment centres (PTCs) deliver cancer care to
young people. Despite this expansion of specialist care,
systematic investigation of associated outcomes and
costs has, to date, been lacking. The aim of this paper is
to describe recruitment and baseline characteristics of the
BRIGHTLIGHT cohort and the development of the bespoke
measures of levels of care and disease severity, which will
inform the evaluation of cancer services in England.
Design Prospective, longitudinal, observational study.
Setting Ninety-seven National Health Service hospitals in
England.
Participants A total of 1114 participants were recruited and
diagnosed between July 2012 and December 2014: 55%
(n=618) were men, mean age was 20.1 years (SD=3.3),
most (86%) were white and most common diagnoses were
lymphoma (31%), germ cell tumour (19%) and leukaemia
(13%).
Results At diagnosis, median quality of life score was
significantly lower than a published control threshold (69.7
points); 40% had borderline to severe anxiety, and 21%
had borderline to severe depression. There was minimal
variation in other patient-reported outcomes according to
age, diagnosis or severity of illness. Survival was lower in
the cohort than for young people diagnosed during the same
period who were not recruited (cumulative survival probability
4 years after diagnosis: 88% vs 92%).
Conclusions Data collection was completed in March 2018.
Longitudinal comparisons will determine outcomes and costs
associated with access/exposure to PTCs. Findings will inform
international intervention and policy initiatives to improve
outcomes for young people with cancer
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