5,122 research outputs found
Phase and Intensity Distributions of Individual Pulses of PSR B0950+08
The distribution of the intensities of individual pulses of PSR B0950+08 as a
function of the longitudes at which they appear is analyzed. The flux density
of the pulsar at 111 MHz varies strongly from day to day (by up to a factor of
13) due to the passage of the radiation through the interstellar plasma
(interstellar scintillation). The intensities of individual pulses can exceed
the amplitude of the mean pulse profile, obtained by accumulating 770 pulses,
by more than an order of magnitude. The intensity distribution along the mean
profile is very different for weak and strong pulses. The differential
distribution function for the intensities is a power law with index n = -1.1 +-
0.06 up to peak flux densities for individual pulses of the order of 160 Jy
The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are
reddened by dust either in their host galaxies or in intervening absorber
galaxies are to a large degree missed by optical color selection criteria like
the one used by the Sloan Digital Sky Survey (SDSS). To overcome this bias
against red QSOs, we employ a combined optical and near-infrared color
selection. In this paper, we present a spectroscopic follow-up campaign of a
sample of red candidate QSOs which were selected from the SDSS and the UKIRT
Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS
photometry are supplemented by mid-infrared photometry from the Wide-field
Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are
confirmed to be QSOs. We use a statistical algorithm to identify sightlines
with plausible intervening absorption systems and identify nine such cases
assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We
find absorption systems toward 30 QSOs, 2 of which are consistent with the
best-fit absorber redshift from the statistical modeling. Furthermore, we
observe a broad range in SED properties of the QSOs as probed by the rest-frame
2 {\mu}m flux. We find QSOs with a strong excess as well as QSOs with a large
deficit at rest-frame 2 {\mu}m relative to a QSO template. Potential solutions
to these discrepancies are discussed. Overall, our study demonstrates the high
efficiency of the optical/near-infrared selection of red QSOs.Comment: 64 pages, 18 figures, 16 pages of tables. Accepted to ApJ
Atlas Data-Challenge 1 on NorduGrid
The first LHC application ever to be executed in a computational Grid
environment is the so-called ATLAS Data-Challenge 1, more specifically, the
part assigned to the Scandinavian members of the ATLAS Collaboration. Taking
advantage of the NorduGrid testbed and tools, physicists from Denmark, Norway
and Sweden were able to participate in the overall exercise starting in July
2002 and continuing through the rest of 2002 and the first part of 2003 using
solely the NorduGrid environment. This allowed to distribute input data over a
wide area, and rely on the NorduGrid resource discovery mechanism to find an
optimal cluster for job submission. During the whole Data-Challenge 1, more
than 2 TB of input data was processed and more than 2.5 TB of output data was
produced by more than 4750 Grid jobs.Comment: Talk from the 2003 Computing in High Energy Physics and Nuclear
Physics (CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, 3 ps figure
The NorduGrid architecture and tools
The NorduGrid project designed a Grid architecture with the primary goal to
meet the requirements of production tasks of the LHC experiments. While it is
meant to be a rather generic Grid system, it puts emphasis on batch processing
suitable for problems encountered in High Energy Physics. The NorduGrid
architecture implementation uses the \globus{} as the foundation for various
components, developed by the project. While introducing new services, the
NorduGrid does not modify the Globus tools, such that the two can eventually
co-exist. The NorduGrid topology is decentralized, avoiding a single point of
failure. The NorduGrid architecture is thus a light-weight, non-invasive and
dynamic one, while robust and scalable, capable of meeting most challenging
tasks of High Energy Physics.Comment: Talk from the 2003 Computing in High Energy Physics and Nuclear
Physics (CHEP03), La Jolla, Ca, USA, March 2003, 9 pages,LaTeX, 4 figures.
PSN MOAT00
The Dialogue as a Means of Spiritual Development of a Pupil at the Lesson of Music
При финансовой поддержке Российского гуманитарного научного фонда, проект № 08-06-14134
Theory of high-order harmonic generation from molecules by intense laser pulses
We show that high-order harmonics generated from molecules by intense laser
pulses can be expressed as the product of a returning electron wave packet and
the photo-recombination cross section (PRCS) where the electron wave packet can
be obtained from simple strong-field approximation (SFA) or from a companion
atomic target. Using these wave packets but replacing the PRCS obtained from
SFA or from the atomic target by the accurate PRCS from molecules, the
resulting HHG spectra are shown to agree well with the benchmark results from
direct numerical solution of the time-dependent Schr\"odinger equation, for the
case of H in laser fields. The result illustrates that these powerful
theoretical tools can be used for obtaining high-order harmonic spectra from
molecules. More importantly, the results imply that the PRCS extracted from
laser-induced HHG spectra can be used for time-resolved dynamic chemical
imaging of transient molecules with temporal resolutions down to a few
femtoseconds.Comment: 10 pages, 5 figure
Professions, governance and citizenship through the global looking glass
The state-professions relationship and the role of professionalism as facilitator of public sector services are key issues of the professions studies. This makes the study of professions an important source of understanding how to create a “better world,” with more efficient public sectors and accessible services for all citizens. Currently, the relationships between professions and the state face a number of fundamental transformations involving different governance reforms, stakeholders, and professional groups. First, state regulation expands towards “governance” with plural actors and market logics; second, globalization and new economies add new forms of “state” and “citizenship”; and third, austerity politics curb prospering markets and public funding for professional services.info:eu-repo/semantics/publishedVersio
On the origin of 140 GHz emission from the 4 July 2012 solar flare
The sub-THz event observed on the 4 July 2012 with the Bauman Moscow State
Technical University Radio Telescope RT-7.5 at 93 and 140~GHz as well as
Kislovodsk and Mets\"ahovi radio telescopes, Radio Solar Telescope Network
(RSTN), GOES, RHESSI, and SDO orbital stations is analyzed. The spectral flux
between 93 and 140 GHz has been observed increasing with frequency. On the
basis of the SDO/AIA data the differential emission measure has been
calculated. It is shown that the thermal coronal plasma with the temperature
above 0.5~MK cannot be responsible for the observed sub-THz flare emission. The
non-thermal gyrosynchrotron mechanism can be responsible for the microwave
emission near ~GHz but the observed millimeter spectral characteristics are
likely to be produced by the thermal bremsstrahlung emission from plasma with a
temperature of about 0.1~MK.Comment: 18 pages, 6 figure
Asymmetry Function of Interstellar Scintillations of Pulsars
A new method for separating intensity variations of a source's radio emission
having various physical natures is proposed. The method is based on a joint
analysis of the structure function of the intensity variations and the
asymmetry function, which is a generalization of the asymmetry coefficient and
characterizes the asymmetry of the distribution function of the intensity
fluctuations on various scales for the inhomogeneities in the diffractive
scintillation pattern. Relationships for the asymmetry function in the cases of
a logarithmic normal distribution of the intensity fluctuations and a normal
distribution of the field fluctuations are derived. Theoretical relationships
and observational data on interstellar scintillations of pulsars (refractive,
diffractive, and weak scintillations) are compared. Pulsar scintillations match
the behavior expected for a normal distribution of the field fluctuations
(diffractive scintillation) or logarithmic normal distribution of the intensity
fluctuations (refractive and weak scintillation). Analysis of the asymmetry
function is a good test for distinguishing scintillations against the
background of variations that have different origins
Interpreting Attoclock Measurements of Tunnelling Times
Resolving in time the dynamics of light absorption by atoms and molecules,
and the electronic rearrangement this induces, is among the most challenging
goals of attosecond spectroscopy. The attoclock is an elegant approach to this
problem, which encodes ionization times in the strong-field regime. However,
the accurate reconstruction of these times from experimental data presents a
formidable theoretical challenge. Here, we solve this problem by combining
analytical theory with ab-initio numerical simulations. We apply our theory to
numerical attoclock experiments on the hydrogen atom to extract ionization time
delays and analyse their nature. Strong field ionization is often viewed as
optical tunnelling through the barrier created by the field and the core
potential. We show that, in the hydrogen atom, optical tunnelling is
instantaneous. By calibrating the attoclock using the hydrogen atom, our method
opens the way to identify possible delays associated with multielectron
dynamics during strong-field ionization.Comment: 33 pages, 10 figures, 3 appendixe
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