3,965 research outputs found
Stability conditions for the solutions of the Half-Projected Hartree-Fock scheme. The lithium-hydride ground state
4 págs.; 1 fig.; 2 tabs.The stability conditions for the solutions of a two-unrestricted-determinant function (the half-projected Hartree-Fock function) are deduced from the necessary requirements for the minimization of the energy functional. The theory is applied to the case of the LiH ground state, in order to investigate the various solutions encountered in the variational problem. It is found that the two lowest solutions are local minima. The number of these solutions is estimated and their significance discussed as a function of the nuclear separation. © 1977 The American Physical Society.Peer Reviewe
IEA SHC Task 42 / ECES Annex 29 WG A1: Engineering and Processing of PCMs, TCMs and Sorption Materials
An overview on the recent results on the engineering and characterization of sorption materials, PCMs and TCMs investigated in the working group WG A1 "Engineering and processing of TES materials" of IEA SHC Task 42 / ECES Annex 29 (Task 4229) entitled "Compact Thermal Energy Storage" is presented
NectarCAM : a camera for the medium size telescopes of the Cherenkov Telescope Array
NectarCAM is a camera proposed for the medium-sized telescopes of the
Cherenkov Telescope Array (CTA) covering the central energy range of ~100 GeV
to ~30 TeV. It has a modular design and is based on the NECTAr chip, at the
heart of which is a GHz sampling Switched Capacitor Array and a 12-bit Analog
to Digital converter. The camera will be equipped with 265 7-photomultiplier
modules, covering a field of view of 8 degrees. Each module includes the
photomultiplier bases, high voltage supply, pre-amplifier, trigger, readout and
Ethernet transceiver. The recorded events last between a few nanoseconds and
tens of nanoseconds. The camera trigger will be flexible so as to minimize the
read-out dead-time of the NECTAr chips. NectarCAM is designed to sustain a data
rate of more than 4 kHz with less than 5\% dead time. The camera concept, the
design and tests of the various subcomponents and results of thermal and
electrical prototypes are presented. The design includes the mechanical
structure, cooling of the electronics, read-out, clock distribution, slow
control, data-acquisition, triggering, monitoring and services.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Papel de las diatomeas como indicadores del grado de afección de embalses receptores de AMD: influencia del PH en el modo de ocurrencia
Este trabajo se basa en el estudio de 23 embalses ubicados en la Faja
Pirítica Ibérica para llevar a cabo una clasificación ambiental basada en
las comunidades de Diatomeas, con especial interés en aquellas
acidófilas o ácido tolerantes, para definer la relación de estas
comunidades con la físico-química de las aguas. Para ello, la
distribución de diatomeas bentónicas se ha caracterizado, en particular
en relación con el pH del medio, que ha permitido entender el papel de
las diatomeas como indicadores de AMD en los embalses. Los resultados obtenidos confirmaron que las comunidades de
diatomeas responden a variaciones en el pH y que el análisis cluster
refleja los cambios en las comunidades de los embalses. Se verificó
una relación de dependencia entre la abundancia y la distribución de
las especies en relación con el pH del agua.Twenty three reservoirs located in the Iberian Pyrite Belt were studied
in order to carry out an environmental assessment based on the
communities of Diatoms, with special interest in those that present an
acidophilic or acid-tolerant profile and to define the relation of these
communities with the physical-chemical characteristics of the water. For
this purpose, the distribution of benthic diatoms has been studied, in
particular in relation to the pH of the medium, which has allowed. understanding the role of diatoms as indicators of AMD in the
reservoirs.
The obtained results confirmed that the diatom communities respond
to variations in pH and that the cluster analysis reflects those changes
in the communities of the reservoirs. A relationship of dependence
between the abundance and distribution of the species under study
with respect to the pH of the water was verified.info:eu-repo/semantics/publishedVersio
The Cherenkov Telescope Array Large Size Telescope
The two arrays of the Very High Energy gamma-ray observatory Cherenkov
Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with
a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA
to achieve a low-energy threshold of 20 GeV, which is critical for important
studies in astrophysics, astroparticle physics and cosmology. This work
presents the key specifications and performance of the current LST design in
the light of the CTA scientific objectives.Comment: 4 pages, 5 figures, In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in
the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent
a series of upgrades, involving the exchange of the MAGIC-I camera and its
trigger system, as well as the upgrade of the readout system of both
telescopes. We use observations of the Crab Nebula taken at low and medium
zenith angles to assess the key performance parameters of the MAGIC stereo
system. For low zenith angle observations, the standard trigger threshold of
the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources
with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula
flux in 50 h of observations. The angular resolution, defined as the sigma of a
2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while
the energy resolution is 16%. We also re-evaluate the effect of the systematic
uncertainty on the data taken with the MAGIC telescopes after the upgrade. We
estimate that the systematic uncertainties can be divided in the following
components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for
the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle
Physic
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