2,592 research outputs found
Cyanobacteria in Spanish reservoirs. How frequently are they toxic?
In this paper we analyse the cyanobacterial occurrence in the Spanish reservoirs, using data obtained from published material or reports of several Spanish institutions. Our analysis shows that potentially toxic cyanobacteria are widespread in the Spanish reservoirs, dominating the phytoplankton community at least once during the study period in a high proportion of the investigated reservoirs (35-48%). The bibliographic data also show that in Europe and in the rest of the World more than 70% of the samples analysed from potentially toxic cyanobacteria were toxic. Extrapolating these data we can assume that a high proportion of the Spanish reservoirs (between 25 and 35 %) present a high probability of developing blooms of toxic cyanobacteria. Finally, the available data about the presence of cyanotoxins in different Spanish Basins show that cyanotoxins are present in all the analysed basins and occasionally show very high toxin concentrations.En este artículo analizamos la presencia de cianobacterias en los embalses españoles, fundamentalmente basándonos en datos presentes en la literatura científica y en informes de distintos organismos. Nuestro análisis demuestra que en un alto porcentaje de los embalses estudiados (entre el 35 y el 48%) las cianobacterias potencialmente tóxicas dominaron la comunidad del fitoplancton en al menos una ocasión durante el periodo de estudio. Los datos bibliográficos también demuestran que en Europa y en el resto del mundo aparecieron cianotoxinas en más del 70% de las muestras analizadas de afloramientos de cianobacterias potencialmente tóxicas. Extrapolando estos datos podemos deducir que al menos entre un 25 y un 35% de los embalses españoles muestran una elevada probabilidad a desarrollar afloramientos tóxicos. Finalmente se analizan los datos disponibles sobre cianotoxinas en España, mostrando que en diversas cuencas hidrográficas las cianotoxinas están presentes y ocasionalmente en altas concentraciones
Nucleon scattering on actinides using a dispersive optical model with extended couplings
Tamura coupling model has been extended to consider the coupling of
additional low-lying rotational bands to the ground state band. Rotational
bands are built on vibrational bandheads (even-even targets) or single particle
bandheads (odd- targets) including both axial and non-axial deformations.
These additional excitations are introduced as a perturbation to the underlying
axially-symmetric rigid rotor structure of the ground state rotational band.
Coupling matrix elements of the generalized optical model are derived for
extended multi-band transitions in even-even and odd- nuclei. Isospin
symmetric formulation of the optical model is employed.
A coupled-channels optical model potential (OMP) containing a dispersive
contribution is used to fit simultaneously all available optical experimental
databases including neutron strength functions for nucleon scattering on
Th, U and Pu nuclei and quasi-elastic (,)
scattering data on Th and U. Lane consistent OMP is derived for
all actinides if corresponding multi-band coupling schemes are defined.
Calculations using the derived OMP potential reproduce measured total
cross-section differences between several actinide pairs within experimental
uncertainty for incident neutron energies from 50 keV up to 150MeV. Multi-band
coupling is stronger in even-even targets due to the collective nature of the
coupling; the impact of extended coupling on predicted compound-nucleus
formation cross section reaches 5% below 3 MeV of incident neutron energy.
Coupling of ground-state rotational band levels in odd- nuclei is sufficient
for a good description of the compound-nucleus formation cross sections as long
as the coupling is saturated (a minimum of 7 coupled levels are typically
needed).Comment: 30 pages, 4 figures, 8 tables, 3 appendice
Predicting the optical observables for nucleon scattering on even-even actinides
Previously derived Lane consistent dispersive coupled-channel optical model
for nucleon scattering on Th and U nuclei is extended to
describe scattering on even-even actinides with 90--98. A
soft-rotator-model (SRM) description of the low-lying nuclear structure is
used, where SRM Hamiltonian parameters are adjusted to the observed collective
levels of the target nucleus. SRM nuclear wave functions (mixed in quantum
number) have been used to calculate coupling matrix elements of the generalized
optical model. The "effective" deformations that define inter-band couplings
are derived from SRM Hamiltonian parameters. Conservation of nuclear volume is
enforced by introducing a dynamic monopolar term to the deformed potential
leading to additional couplings between rotational bands. Fitted static
deformation parameters are in very good agreement with those derived by Wang
and collaborators using the Weizs\"acker-Skyrme global mass model (WS4),
allowing to use the latter to predict cross section for nuclei without
experimental data. A good description of scarce "optical" experimental database
is achieved. SRM couplings and volume conservation allow a precise calculation
of the compound-nucleus formation cross sections, which is significantly
different from the one calculated with rigid-rotor potentials coupling the
ground-state rotational band. Derived parameters can be used to describe both
neutron and proton induced reactions.Comment: 6 pages, 4 figures, 5 table
A novel route to Pt-Bi2O3 composite thin films and their application in photo-reduction of water
A novel homoleptic bismuth(III) β-diketonate (dibenzoylmethane – dbm) complex [Bi(dbm)3]2 has been used as a precursor to thin films of crystalline β-Bi2O3, and hexachloroplatinic acid (H2PtCl6·6H2O) has been demonstrated as a suitable precursor for deposition of platinum nanoparticles, both deposited via aerosol-assisted chemical vapour deposition (AACVD). Thin films of Pt–Bi2O3 were co-deposited from a mixture of [Bi(dbm)3]2 and H2PtCl6·6H2O; the introduction of Pt particles into β-Bi2O3 causes hydrogen to be evolved during photolysis of water over the composite material, a property not found for Pt particles or β-Bi2O3 alone
Hydrogen bonding in substituted nitroanilines : isolated nets in 1,3-diamino-4-nitrobenzene and continuously interwoven nets in 3,5-dinitroaniline
Peer reviewedPublisher PD
Thermodynamic functions within the van Hove BCS model: Symmetry mixing effects
All the new layer perovskite superconductors seem to show a phenomenon of
symmetry mixing with repect to the order parameter. An analysis of the
different alternative of mixing and how far could them be presented is carried
out. For the particular case of s+id symmetry of the gap, the temperature
dependence of the specific heat () and the thermodynamic critical
magnetic field () are calculated. A double peak transition is observed
on in the mixed regime while the single peak behavior is recovered
for a purely symmetric state (s or d). presents a quadratic law at low
tempeartures for a d-wave gap and for the s-wave one the typical exponential
attenuation. The temperature dependence of shows a clear phase
transition of second order at temperatures where the d-wave component becomes
negligible. A comparison with other results and experiments is done.Comment: Revised version and accepted to be published in Physica
A new generation of real-time simulation techniques
This work presents a novel methodology for the development of real-time simulation techniques. They are focused on the PGD method, which allows the solution of complex problems by pre-calculating all the possible results. Subsequently, applications efficiently process these data to show particular results on demand
Integral measurement of the 12C(n, p)12B reaction up to 10 GeV
The integral measurement of the 12C(n, p)12B reaction was performed at the neutron time-offlight facility n TOF at CERN. The total number of 12B nuclei produced per neutron pulse of the n TOF
beam was determined using the activation technique in combination with a time-of-flight technique. The
cross section is integrated over the n TOF neutron energy spectrum from reaction threshold at 13.6 MeV
to 10 GeV. Having been measured up to 1 GeV on basis of the 235U(n, f) reaction, the neutron energy
spectrum above 200 MeV has been re-evaluated due to the recent extension of the cross section reference
for this particular reaction, which is otherwise considered a standard up to 200 MeV. The results from the
dedicated GEANT4 simulations have been used to evaluate the neutron flux from 1 GeV up to 10 GeV. The
experimental results related to the 12C(n, p)12B reaction are compared with the evaluated cross sections
from major libraries and with the predictions of different GEANT4 models, which mostly underestimate
the 12B production. On the contrary, a good reproduction of the integral cross section derived from measurements is obtained with TALYS-1.6 calculations, with optimized parameters.European Atomic Energy Communitys (Euratom) Seventh Framework Programme FP7/2007-2011-CHANDA (No. 605203)Narodowe Centrum Nauki (NCN)-UMO-2012/04/M/ST2/00700Croatian Science Foundation-No. 168
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