674 research outputs found
Trastorno por déficit de atención con hiperactividad y potenciales evocados cognitivos. Proyecto de investigación
Quartes Jornades de Foment de la Investigació de la FCHS (Any 1998-1999
Coherent Manipulation of Orbital Feshbach Molecules of Two-Electron Atoms
Ultracold molecules have experienced increasing attention in recent years.
Compared to ultracold atoms, they possess several unique properties that make
them perfect candidates for the implementation of new quantum-technological
applications in several fields, from quantum simulation to quantum sensing and
metrology. In particular, ultracold molecules of two-electron atoms (such as
strontium or ytterbium) also inherit the peculiar properties of these atomic
species, above all the possibility to access metastable electronic states via
direct excitation on optical clock transitions with ultimate sensitivity and
accuracy. In this paper we report on the production and coherent manipulation
of molecular bound states of two fermionic Yb atoms in different
electronic (orbital) states S and P in proximity of a
scattering resonance involving atoms in different spin and electronic states,
called orbital Feshbach resonance. We demonstrate that orbital molecules can be
coherently photoassociated starting from a gas of ground-state atoms in a
three-dimensional optical lattices by observing several photoassociation and
photodissociation cycles. We also show the possibility to coherently control
the molecular internal state by using Raman-assisted transfer to swap the
nuclear spin of one of the atoms forming the molecule, thus demonstrating a
powerful manipulation and detection tool of these molecular bound states.
Finally, by exploiting this peculiar detection technique we provide first
information on the lifetime of the molecular states in a many-body setting,
paving the way towards future investigations of strongly interacting Fermi
gases in a still unexplored regime.Comment: 11 pages, 8 figure
Multi-technique characterisation of MOVPE-grown GaAs on Si
The heterogeneous integration of III-V materials on a Si CMOS platform offers tremendous prospects for future high speed and low power logic applications. That said this integration generates immense scientific and technological challenges. In this work multi-technique characterisation is used to investigate properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Si substrates - (100) with 4⁰ offset towards - under various growth conditions. This being a crucial first step towards the production of III-V template layers with a relatively lower density of defects for selective epitaxial overgrowth of device quality material. The optical and structural properties of heteroepitaxial GaAs are first investigated by micro-Raman spectroscopy and photoluminescence and reflectance measurements. High-resolution X-ray diffraction (HR-XRD) is used to investigate structural properties. Advanced XRD techniques, including double-axis diffraction and X-ray crystallographic mapping are used to evaluate degrees of relaxation and distribution of the grain orientations in the epilayers, respectively. Results obtained from the different methodologies are compared in an attempt to understand growth kinetics of the materials system. The GaAs overlayer grown with annealing at 735⁰C following As predeposition at 500⁰C shows the best crystallinity. Close inspection confirms the growth of epitaxial GaAs preferentially oriented along (100) embedded in a highly-textured polycrystalline structure
Mesa redonda // Impacto de la información sobre salud en la relcación médico/paciente y en la salud pública
La información sobre salud se ha multiplicado en los últimos años. El impacto que provoca variará si el destinatario es un paciente o la sociedad en general. La información disponible en los medios de comunicación e Internet está contribuyendo a modificar la tradicional relación médico/paciente, con un cambio de un modelo paternalista a una actitud más participativa por parte del paciente en la toma de decisiones. Sin duda, el incremento en las fuentes de información, a las que acceden profesionales sanitarios y no sanitarios, ha provocado diversas modificaciones también en la salud pública. Este tema es analizado desde cuatro interesantes perspectivas
Notes on brentidae. I. (Col. Brentidae)
O autor estudou algumas espécies de Coleópteros, pertencentes à família Brentidae (tribo Arrhenodini). Descreveu o alótipo fêmea de Schoenfeldtia impressicollis Senna, 1893, e três novas espécies de Vianodes H. Rossi, 1955: Vianodes cyriodontoides, sp. n., Vianodes quadridentaticollis, sp. n., Vianodes spinipennis, sp. n. Considerou também Pararrhenodes misionensis (= misionera) H. Rossi, 1954, como sendo sinônimo de Vianodes appositus (Kleine, 1923), e Vianodes vampyrus (Senna, 1897) - somente os machos eram conhecidos - como sendo sinônimo de Rhynchoneus belti Sharp, 1895 - somente as fêmeas eram conhecidas.The author studied some species of Coleopterous insects belonging to the family Brentidae (tribe Arrhenodini). He describes the female allotype of Schoenfeldtia impressicollis Senna, 1893, and three new species of Vianodes H. Rossi, 1955: Vianodes cyriodontoides, sp. n., Vianodes quadridentaticollis, sp. n., Vianodes spinipennis, sp. n. He also considers Pararrhenodes misionensis (= misionera) H. Rossi, 1954, as synonymous with Vianodes appositus (Kleine, 1923), and Vianodes vampyrus (Senna, 1897) – only males were known - as synonymous with Rhynchoneus belti Sharp, 1895 - only females were known
Un modelo de riesgo de credito basado en opciones compuestas con barrera. Aplicacion al mercado continuo espanol
In this work the valuation methodology of compound option written on a downand-out call option, developed by Ericsson and Reneby (2003), has been applied to deduce a credit risk model. It is supposed that the firm has a debt structure with two maturity dates and that the credit event takes place when the assets firm value falls under a determined level called barrier. An empirical application of the model for 105 firms of Spanish continuous market is carried out. For each one of them its value in the date of analysis, the volatility and the critical value are obtained and from these, the default probability to short and long-term and the implicit probability in the two previous probabilities are deduced. The results are compared with the ones obtained from the Geske model (1977).structural approach, compound barrier option, credit risk, default probability
Lumbosacral plexus in Brazilian Common Opossum
The opossum has been suggested as an animal model for biomedical studies due to its adaptability to captivity and number of births per year. Despite many studies on morphology and experimental neurology using this opossum model, the literature does not offer details of the nerves of the lumbosacral plexus in this species. Ten lumbosacral plexus were dissected to describe the peripheral innervations of the Brazilian Common Opossum (Didelphis aurita) and compare the results with Eutheria clade species. The tensor fasciae latae muscle was absent and there was only one sartorius muscle for each limb. The distribution of the nerves were similar to other mammals, except for the caudal gluteal nerve, sartorius muscle innervations and the position of the pudendal nerve which arose from the major ischiatic foramen together with the ischiatic nerve, the cranial gluteal nerve and the caudal gluteal nerve. No anatomical variation was found. The special position of the pudendal nerve suggested that the Brazilian Common Opossum is a better model than rats or rabbits in surgical procedures with that specific nerve. In addition, the study revealed that the pelvic limb nerves are not an invariable structure of reference for muscle homology and homonym as reported previously. New investigation using other species of opossums are necessary to best comprehend the lumbosacral plexus distribution in the Methatheria clade and to confirm that other opossum species is eligible as a good model for pudendal nerve studies
Valoracion de credit default swaps: Una aplicacion del modelo de Hull-White al mercado espanol
An empirical application of Hull-White model (2000) to the Spanish market is presented. This model provides an expression to calculate the payment made by credit default swap (CDS) buyer when there is no counterparty default risk. Moreover, it is assumed that the yield par curve, the recovery rate (that is constant) and the moment of credit event are independent. Data from Banco Santander Central Hispano bonds are used to calculate risk neutral default probability and then CDS premia for an underlying bond of the same credit rating are calculated. This premia are computed under no arbitrage arguments and are compared with the market credit spreads. This results show that the model premia are similar to credit spreads and the main conclusion of this paper is that Hull-White model is suitable to obtain the CDS premia in Spanish market.credit risk, credit event, default probability, swaps
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