16,493 research outputs found
Рецензия на руководство для врачей «Профессиональные заболевания у работников железнодорожного транспорта»
Рецензія на посібник: Профессиональные заболевания у работников железнодорожного транспорта: учебное пособие / С.И. Ткач, А.И. Гоженко, А.Е. Лукьяненко, Е.Я. Николенко. -Одесса: Пальмира,2008. - 168 с
A new catalog of photometric redshifts in the Hubble Deep Field
Using the newly available infrared images of the Hubble Deep Field in the J,
H, and K bands and an optimal photometric method, we have refined a technique
to estimate the redshifts of 1067 galaxies. A detailed comparison of our
results with the spectroscopic redshifts in those cases where the latter are
available shows that this technique gives very good results for bright enough
objects (AB(8140) < 26.0). From a study of the distribution of residuals
(Dz(rms)/(1+z) ~ 0.1 at all redshifts) we conclude that the observed errors are
mainly due to cosmic variance. This very important result allows for the
assessment of errors in quantities to be directly or indirectly measured from
the catalog. We present some of the statistical properties of the ensemble of
galaxies in the catalog, and finish by presenting a list of bright
high-redshift (z ~ 5) candidates extracted from our catalog, together with
recent spectroscopic redshift determinations confirming that two of them are at
z=5.34 and z=5.60.Comment: 28 pages, 12PS+4JPEG figures, aaspp style. Accepted for publication
in The Astrophysical Journal. The catalog, together with a clickable map of
the HDF, Tables 4 and 5 (HTML, LaTeX or ASCII format), and the figures, are
available at http://bat.phys.unsw.edu.au/~fsoto/hdfcat.htm
A graphene transmon operating at 1 T
A superconducting transmon qubit resilient to strong magnetic fields is an
important component for proposed topological and hybrid quantum computing (QC)
schemes. Transmon qubits consist of a Josephson junction (JJ) shunted by a
large capacitance, coupled to a high quality factor superconducting resonator.
In conventional transmon devices, the JJ is made from an Al/AlO/Al tunnel
junction which ceases operation above the critical magnetic field of Al, 10 mT.
Alternative junction technologies are therefore required to push the operation
of these qubits into strong magnetic fields. Graphene JJs are one such
candidate due to their high quality, ballistic transport and electrically
tunable critical current densities. Importantly the monolayer structure of
graphene protects the JJ from orbital interference effects that would otherwise
inhibit operation at high magnetic field. Here we report the integration of
ballistic graphene JJs into microwave frequency superconducting circuits to
create the first graphene transmons. The electric tunability allows the
characteristic band dispersion of graphene to be resolved via dispersive
microwave spectroscopy. We demonstrate that the device is insensitive to the
applied field and perform energy level spectroscopy of the transmon at 1 T,
more than an order of magnitude higher than previous studies.Comment: attached supplementary materia
Structure of Disk Dominated Galaxies I. Bulge/Disk Parameters, Simulations, and Secular Evolution
(Abridged) A robust analysis of galaxy structural parameters, based on the
modeling of bulge and disk brightnesses in the BVRH bandpasses, is presented
for 121 face-on and moderately inclined late-type spirals. Each surface
brightness (SB) profile is decomposed into a sum of a generalized Sersic bulge
and an exponential disk. The reliability and limitations of our bulge-to-disk
(B/D) decompositions are tested with extensive simulations of galaxy brightness
profiles (1D) and images (2D). Galaxy types are divided into 3 classes
according to their SB profile shapes; Freeman Type-I and Type-II, and a third
``Transition'' class for galaxies whose profiles change from Type-II in the
optical to Type-I in the infrared. We discuss possible interpretations of
Freeman Type-II profiles. The Sersic bulge shape parameter for nearby Type-I
late-type spirals shows a range between n=0.1-2 but, on average, the underlying
surface density profile for the bulge and disk of these galaxies is adequately
described by a double-exponential distribution. We confirm a coupling between
the bulge and disk with a scale length ratio r_e/h=0.22+/-0.09, or
h_bulge/h_disk=0.13+/-0.06 for late-type spirals, in agreement with recent
N-body simulations of disk formation and models of secular evolution. This
ratio increases from ~0.20 for late-type spirals to ~0.24 for earlier types.
The similar scaling relations for early and late-type spirals suggest
comparable formation and/or evolution scenarios for disk galaxies of all Hubble
types.Comment: 78 pages with 23 embedded color figures + tables of galaxy structural
parameters. Accepted for publication in the Astrophysical Journal. The
interested reader is strongly encouraged to ignore some of the low res
figures within; instead, download the high resolution version from
http://www.astro.ubc.ca/people/courteau/public/macarthur02_disks.ps.g
Regulatory Dynamics on Random Networks: Asymptotic Periodicity and Modularity
We study the dynamics of discrete-time regulatory networks on random
digraphs. For this we define ensembles of deterministic orbits of random
regulatory networks, and introduce some statistical indicators related to the
long-term dynamics of the system. We prove that, in a random regulatory
network, initial conditions converge almost surely to a periodic attractor. We
study the subnetworks, which we call modules, where the periodic asymptotic
oscillations are concentrated. We proof that those modules are dynamically
equivalent to independent regulatory networks.Comment: 23 pages, 3 figure
Relativistic Brueckner-Hartree-Fock calculations with explicit intermediate negative energy states
In a relativistic Brueckner-Hartree-Fock calculation we include explicit
negative-energy states in the two-body propagator. This is achieved by using
the Gross spectator-equation, modified by medium effects. Qualitatively our
results compare well with other RBHF calculations. In some details significant
differences occur, e.g, our equation of state is stiffer and the momentum
dependence of the self-energy components is stronger than found in a reference
calculation without intermediate negative energy states.Comment: 13 pages Revtex, 5 figures included seperatel
Shot Noise of Single-Electron Tunneling in 1D Arrays
We have used numerical modeling and a semi-analytical calculation method to
find the low frequency value S_{I}(0) of the spectral density of fluctuations
of current through 1D arrays of small tunnel junctions, using the ``orthodox
theory'' of single-electron tunneling. In all three array types studied, at low
temperature (kT << eV), increasing current induces a crossover from the
Schottky value S_{I}(0)=2e to the ``reduced Schottky value''
S_{I}(0)=2e/N (where N is the array length) at some crossover current I_{c}.
In uniform arrays over a ground plane, I_{c} is proportional to exp(-\lambda
N), where 1/\lambda is the single-electron soliton length. In arrays without a
ground plane, I_{c} decreases slowly with both N and \lambda. Finally, we have
calculated the statistics of I_{c} for ensembles of arrays with random
background charges. The standard deviation of I_{c} from the ensemble average
is quite large, typically between 0.5 and 0.7 of , while the
dependence of on N or \lambda is so weak that it is hidden within the
random fluctuations of the crossover current.Comment: RevTex. 21 pages of text, 10 postscript figure
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