569 research outputs found
Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9
The shape of the UV ionizing background is reconstructed from optically thin
metal absorption-line systems identified in spectra of HE2347-4342, Q1157+3143,
and HS1700+6416 in the redshift interval 1.8 < z < 2.9. The systems are
analyzed by means of the Monte Carlo Inversion method completed with the
spectral shape recovering procedure. The UVB spectral shape fluctuates at 2.4 <
z < 2.9 mostly due to radiative transfer processes in the clumpy IGM. At z <
1.8, the IGM becomes almost transparent both in the HI and HeII Lyman continua
and the variability of the spectral shape comes from diversity of spectral
indices describing the QSO/AGN intrinsic radiation. At z > 2.4, the recovered
spectral shapes show intensity depression between 3 and 4 Ryd due to HeII
Ly-alpha absorption in the IGM clouds (line blanketing) and continuous medium
(true Gunn-Petersen effect). The mean HeII Ly-alpha opacity estimated from the
depth of this depression corresponds within 1-2sigma to the values directly
measured from the HI/HeII Ly-alpha forest towards the quasars studied. The
observed scatter in eta = N(HeII)/N(HI) and anti-correlation between N(HI) and
eta can be explained by the combined action of variable spectral softness and
differences in the mean gas density between the absorbing clouds. Neither of
the recovered spectral shapes show features which can be attributed to the
putative input of radiation from soft sources like starburst galaxies.Comment: 20 pages, 20 figures. Accepted for publication in A&
Conditions of the Development of Logistic Centers in Poland in the Context of European States Experiences
The article is, for the most part, the aftermath of his own examinations carried out in years 2007-2010 and concerning logistic centers development conditioning.Artykuł jest w znacznej mierze pokłosiem badań własnych autora przeprowadzonych w latach: 2007-2010 dotyczących uwarunkowań rozwoju centrów logistycznych
Nitrogen-deficient and iron-rich associated absorbers with oversolar metallicities towards the quasar HE0141-3932
HE0141-3932 (zem=1.80) is a bright blue radio-quite quasar which reveals an
emission line spectrum with an unusually weak Ly-alpha line. In addition, large
redshift differences (Delta z=0.05) are observed between high ionization and
low ionization emission lines. Absorption systems identified at z=1.78, 1.71,
and 1.68 show mild oversolar metallicities (Z ~= 1-2Zsolar) and can be
attributed to the associated gas clouds ejected from the circumnuclear region.
The joint analysis of the emission and absorption lines leads to the conclusion
that this quasar is seen almost pole-on. Its apparent luminosity may be Doppler
boosted by ~10 times. The absorbing gas shows high abundance of Fe, Mg, and Al
([Fe, Mg, Al/C] ~= 0.15+/-0.10) along with underabundance of N ([N/C]<=-0.5).
This abundance pattern is at variance with current chemical evolution models of
QSOs predicting [N/C]>0 and [Fe/C]<0 at Z ~ Zsolar. Full details of this work
are given in Reimers et al. (2005).Comment: 2 pages, to appear in the Proceed. of IAU Symp.228 "From Lithium to
Uranium: Elemental Tracers of Early Cosmic Evolution", eds. V.Hill,
P.Francois and F.Prima
Unusually large polarizabilities and "new" atomic states in Ba
Electric polarizabilities of four low-J even-parity states and three low-J
odd-parity states of atomic barium in the range to $36,000\
^{-1}6s8p
^3P_{0,2}$ is suggested.Comment: 29 pages, 12 figure
HE 0141-3932: a bright QSO with an unusual emission line spectrum and associated absorption
HE 0141-3932 (zem = 1.80) is a bright blue radio-quite quasar with an
unusually weak Ly-alpha emission line. Large redshift differences (Delta z =
0.05) are observed between high ionization and low ionization emission lines.
Absorption systems identified at zabs = 1.78, 1.71, and 1.68 show mild
oversolar metallicities (Z ~= 1-2Zsolar) and can be attributed to the
associated gas clouds ejected from the circumnuclear region. The joint analysis
of the emission and absorption lines leads to the conclusion that this quasar
is seen almost pole-on. Its apparent luminosity may be Doppler boosted by ~10
times. The absorbing gas shows a high abundance of Fe, Mg and Al ([Fe, Mg,
Al/C] ~= 0.15 +/- 0.10) along with underabundance of N ([N/C] <= -0.5). This
abundance pattern is at variance with current chemical evolution models of QSOs
predicting [N/C] >= 0$ and [Fe/C] < 0 at Z ~ Zsolar.Comment: 12 pages, 6 figures, accepted for publication in A&
Strong influence of the complex bandstructure on the tunneling electroresistance: A combined model and ab-initio study
The tunneling electroresistance (TER) for ferroelectric tunnel junctions
(FTJs) with BaTiO_{3} (BTO) and PbTiO}_{3} (PTO) barriers is calculated by
combining the microscopic electronic structure of the barrier material with a
macroscopic model for the electrostatic potential which is caused by the
ferroelectric polarization. The TER ratio is investigated in dependence on the
intrinsic polarization, the chemical potential, and the screening properties of
the electrodes. A change of sign in the TER ratio is obtained for both barrier
materials in dependence on the chemical potential. The inverse imaginary Fermi
velocity describes the microscopic origin of this effect; it qualitatively
reflects the variation and the sign reversal of the TER. The quantity of the
imaginary Fermi velocity allows to obtain detailed information on the transport
properties of FTJs by analyzing the complex bandstructure of the barrier
material.Comment: quality of figures reduce
Application of Volcano Plots in Analyses of mRNA Differential Expressions with Microarrays
Volcano plot displays unstandardized signal (e.g. log-fold-change) against
noise-adjusted/standardized signal (e.g. t-statistic or -log10(p-value) from
the t test). We review the basic and an interactive use of the volcano plot,
and its crucial role in understanding the regularized t-statistic. The joint
filtering gene selection criterion based on regularized statistics has a curved
discriminant line in the volcano plot, as compared to the two perpendicular
lines for the "double filtering" criterion. This review attempts to provide an
unifying framework for discussions on alternative measures of differential
expression, improved methods for estimating variance, and visual display of a
microarray analysis result. We also discuss the possibility to apply volcano
plots to other fields beyond microarray.Comment: 8 figure
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