261 research outputs found
Fermat-linked relations for the Boubaker polynomial sequences via Riordan matrices analysis
The Boubaker polynomials are investigated in this paper. Using Riordan
matrices analysis, a sequence of relations outlining the relations with
Chebyshev and Fermat polynomials have been obtained. The obtained expressions
are a meaningful supply to recent applied physics studies using the Boubaker
polynomials expansion scheme (BPES).Comment: 12 pages, LaTe
The role of formalization and organizational trust as antecedents of ambidexterity: An investigation on the organic agro-food industry
This article investigates the influence of specific key organizational factors (i.e., enabling formalization, coercive formalization, and trust) as antecedents of ambidexterity. Moreover, we propose a new way of operationalizing ambidexterity, under a holistic vision, including the synergies between exploration and exploitation. The study has been developed in the Spanish organic agro-food industry; a total of 239 usable responses were received from two respondents from each company\u2014the general manager and the quality manager. The findings show that enabling formalization and organizational trust are positively related to ambidexterity, but contrary to our predictions, we found no evidence to show that coercive formalization is related to ambidexterity. In turn, we found different results for trust as a moderating factor on the types of formalization and ambidexterity
Neutron background at the Canfranc Underground Laboratory and its contribution to the IGEX-DM dark matter experiment
A quantitative study of the neutron environment in the Canfranc Underground
Laboratory has been performed. The analysis is based on a complete set of
simulations and, particularly, it is focused on the IGEX-DM dark matter
experiment. The simulations are compared to the IGEX-DM low energy data
obtained with different shielding conditions. The results of the study allow us
to conclude, with respect to the IGEX-DM background, that the main neutron
population, coming from radioactivity from the surrounding rock, is practically
eliminated after the implementation of a suitable neutron shielding. The
remaining neutron background (muon-induced neutrons in the shielding and in the
rock) is substantially below the present background level thanks to the muon
veto system. In addition, the present analysis gives us a further insight on
the effect of neutrons in other current and future experiments at the Canfranc
Underground Laboratory. The comparison of simulations with the body of data
available has allowed to set the flux of neutrons from radioactivity of the
Canfranc rock, (3.82 +- 0.44) x 10^{-6} cm^{-2} s^{-1}, as well as the flux of
muon-induced neutrons in the rock, (1.73 +- 0.22(stat) \+- 0.69(syst)) x
10^{-9} cm^{-2} s^{-1}, or the rate of neutron production by muons in the lead
shielding, (4.8 +- 0.6 (stat) +- 1.9 (syst)) x 10^{-9} cm^{-3} s^{-1}.Comment: 17 pages, 8 figures, elsart document class; final version to appear
in Astroparticle Physic
Occurrence of the Oribatid Mite Trhypochthoniellus longisetus longisetus (Acari: Trhypochthoniidae) on Tilapia (Oreochromis niloticus).
Mites as parasites infesting fish have been described in a few case reports involving Histiostoma anguillarum, H. papillata, and Schwiebea estradai. We describe the unexpected occurrence of oribatid mites of the genus Trhypochthoniellus on farmed tilapia Oreochromis niloticus. The fish had mites on the skin, fins, and gills, as well as in the mouth. The morphological characteristics of the mites, observed by optical and scanning electron microscopy, were consistent with those described for T. longisetus longisetus. All stages of development were observed, suggesting that the mites were able to actively reproduce on fis
Magnetic interactions in thiazyl-based magnets: The role of the charge and spin densities
The crystal structure of the organic radical p-O2NC6F4CNSSN was
determined at 20 K through a single-crystal neutron-diffraction
experiment. It crystallises in the tetragonal space group P41212,
unchanged from a previous single-crystal X-ray diffraction
experiment at 220 K although there are some changes in molecular
geometry and intermolecular contacts arising from the contraction
of the unit cell. Polarized neutron diffraction at 1.5 K revealed that
the spin distribution is predominantly localised on the N and S
atoms of the heterocyclic ring with a small negative spin density
on the heterocyclic C atom. Spin populations determined using a
multipolar analysis were -0.06, +0.25 and +0.28 on the C, N and S
sites, respectively. These spin populations are in excellent agreement
with both ab-initio DFT calculations (spin populations on the C, N
and S sites of -0.07, 0.22 and 0.31, respectively) and cw-EPR studies
which estimated the spin population on the N site as 0.24. The DFT
calculated spin density revealed less than 1% spin delocalisation
onto the perfluoroaryl ring, several orders of magnitude lower than
the density on the heterocyclic ring. cw-ENDOR studies at both
X-band (9 GHz) and Q-band (34 GHz) frequencies probed the spin
populations at the two chemically distinct F atoms. These spin
populations on the F atoms ortho and meta to the dithiadiazolyl
ring are of magnitude 10-3 and 10-4 respectively. Additional high-resolution single-crystal X-ray diffraction studies at 100 K analysed
within the atoms-in-molecules (AIM) framework gave detailed
information on the charge density distributio
Spin canting in a Dy-based Single-Chain Magnet with dominant next-nearest neighbor antiferromagnetic interactions
We investigate theoretically and experimentally the static magnetic
properties of single crystals of the molecular-based Single-Chain Magnet (SCM)
of formula [Dy(hfac)NIT(CHOPh)] comprising
alternating Dy and organic radicals. A peculiar inversion between maxima
and minima in the angular dependence of the magnetic molar susceptibility
occurs on increasing temperature. Using information regarding the
monomeric building block as well as an {\it ab initio} estimation of the
magnetic anisotropy of the Dy ion, this anisotropy-inversion phenomenon
can be assigned to weak one-dimensional ferromagnetism along the chain axis.
This indicates that antiferromagnetic next-nearest-neighbor interactions
between Dy ions dominate, despite the large Dy-Dy separation, over the
nearest-neighbor interactions between the radicals and the Dy ions.
Measurements of the field dependence of the magnetization, both along and
perpendicularly to the chain, and of the angular dependence of in a
strong magnetic field confirm such an interpretation. Transfer matrix
simulations of the experimental measurements are performed using a classical
one-dimensional spin model with antiferromagnetic Heisenberg exchange
interaction and non-collinear uniaxial single-ion anisotropies favoring a
canted antiferromagnetic spin arrangement, with a net magnetic moment along the
chain axis. The fine agreement obtained with experimental data provides
estimates of the Hamiltonian parameters, essential for further study of the
dynamics of rare-earths based molecular chains.Comment: 11 pages, 8 figure
A Micromegas-based low-background x-ray detector coupled to a slumped-glass telescope for axion research
We report on the design, construction and operation of a low background x-ray
detection line composed of a shielded Micromegas (micromesh gaseous structure)
detector of the microbulk technique. The detector is made from radiopure
materials and is placed at the focal point of a ~5 cm diameter, 1.3 m
focal-length, cone-approximation Wolter I x-ray telescope (XRT) comprised of
thermally-formed (or "slumped") glass substrates deposited with multilayer
coatings. The system has been conceived as a technological pathfinder for the
future International Axion Observatory (IAXO), as it combines two of the
techniques (optic and detector) proposed in the conceptual design of the
project. It is innovative for two reasons: it is the first time an x-ray optic
has been designed and fabricated specifically for axion research, and the first
time a Micromegas detector has been operated with an x-ray optic. The line has
been installed at one end of the CERN Axion Solar Telescope (CAST) magnet and
is currently looking for solar axions. The combination of the XRT and
Micromegas detector provides the best signal-to-noise ratio obtained so far by
any detection system of the CAST experiment with a background rate of
5.410counts per hour in the energy region-of-interest and
signal spot area.Comment: 21 pages, 16 figure
Status of IGEX dark matter search at Canfranc Underground Laboratory
One IGEX 76Ge double-beta decay detector is currently operating in the
Canfranc Underground Laboratory in a search for dark matter WIMPs, through the
Ge nuclear recoil produced by the WIMP elastic scattering. In this talk we
report on the on-going efforts to understand and eventually reject the
background at low energy. These efforts have led to the improvement of the
neutron shielding and to partial reduction of the background, but still the
remaining events are not totally identified. A tritium contamination or
muon-induced neutrons are considered as possible sources, simulations and
experimental test being still under progress. According to the success of this
study we comment the prospects of the experiment as well as those of its future
extension, the GEDEON dark matter experiment.Comment: 6 pages, 3 figures, talk given at 4th International Workshop on the
Identification of Dark Matter, York, September 200
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