13,989 research outputs found
An Introduction to Ontologies and Ontology Engineering
In the last decades, the use of ontologies in information systems has become more and more popular in various fields, such as web technologies, database integration, multi agent systems, natural language processing, etc. Artificial intelligent researchers have initially borrowed the word âontologyâ from Philosophy, then the word spread in many scientific domain and ontologies are now used in several developments. The main goal of this chapter is to answer generic questions about ontologies, such as: Which are the different kinds of ontologies? What is the purpose of the use of ontologies in an application? Which methods can I use to build an ontology
Whirling Waves and the Aharonov-Bohm Effect for Relativistic Spinning Particles
The formulation of Berry for the Aharonov-Bohm effect is generalized to the
relativistic regime. Then, the problem of finding the self-adjoint extensions
of the (2+1)-dimensional Dirac Hamiltonian, in an Aharonov-Bohm background
potential, is solved in a novel way. The same treatment also solves the problem
of finding the self-adjoint extensions of the Dirac Hamiltonian in a background
Aharonov-Casher
Dynamics and control of the expansion of finite-size plasmas produced in ultraintense laser-matter interactions
The strong influence of the electron dynamics provides the possibility of
controlling the expansion of laser-produced plasmas by appropriately shaping
the laser pulse. A simple irradiation scheme is proposed to tailor the
explosion of large deuterium clusters, inducing the formation of shock
structures, capable of driving nuclear fusion reactions. Such a scenario has
been thoroughly investigated, resorting to two- and three-dimensional
particle-in-cell simulations. Furthermore, the intricate dynamics of ions and
electrons during the collisionless expansion of spherical nanoplasmas has been
analyzed in detail using a self-consistent ergodic-kinetic model. This study
clarifies the transition from hydrodynamic-like to Coulomb-explosion regimes
Riemann-Cartan Space-times of G\"odel Type
A class of Riemann-Cartan G\"odel-type space-times are examined in the light
of the equivalence problem techniques. The conditions for local space-time
homogeneity are derived, generalizing previous works on Riemannian G\"odel-type
space-times. The equivalence of Riemann-Cartan G\"odel-type space-times of this
class is studied. It is shown that they admit a five-dimensional group of
affine-isometries and are characterized by three essential parameters : identical triads () correspond to locally
equivalent manifolds. The algebraic types of the irreducible parts of the
curvature and torsion tensors are also presented.Comment: 24 pages, LaTeX fil
Photodisintegration of the triton with realistic potentials
The process is treated by means of three-body integral
equations employing in their kernel the W-Matrix representation of the
subsystem amplitudes. As compared to the plane wave (Born) approximation the
full solution of the integral equations, which takes into account the final
state interaction, shows at low energies a 24% enhancement. The calculations
are based on the semirealistic Malfliet-Tjon and the realistic Paris and Bonn B
potentials. For comparison with earlier calculations we also present results
for the Yamaguchi potential. In the low-energy region a remarkable potential
dependence is observed, which vanishes at higher energies.Comment: 16 pages REVTeX, 8 postscript figures included, uses epsfig.st
Indução de estro em cabras da raça Toggenburg com dois diferentes dispositivos intravaginais.
Doze cabras nuliparas da raça Toggenburg foram distribuidas em dois tratamentos (Tl e T2) para induçao do estro. 0 T1 (n=6) consistiu na inserçao da esponja imnpregnada com 60mg de acetato de medroxiprogesterona, associado a aplicaçao de 50mg do analogo sintetico d-cloprostenol (PGF). No quarto dia, foram aplicadas 250UI de gonadotropina corionica equina (eCG) e, no quinto, a esponja foi retirada. 0 T2 (n=6) diferiu somente quanto ao dispositivo empregado, que foi 0 CIDR-G@. Seis cabras do Tl e seis do T2 entraram em estro depois da retirada dos dispositivos, sendo que 83,3 (5/6) e 33,3% (2/6) ficaram gestantes em Tl e T2, respectivamente. 0 intervalo da retirada do dispositivo ao inicio do estro nao diferiu entre tratamentos (P>O,O5). As caracteristicas ovulatorias nao foram influenciadas pelos tratamentos. 0 intervalo da retirada do dispositivo a ovulaçao, para ambos os protocolos de induçao do estro, nao diferiu (P>O,O5) entre tratamentos. Ambos os dispositivos foram eficientes em induzir O estro. [Estrous induction in Toggenburg goats using intravaginal devices]. Abstract: Twelve Toggenburg breed nuliparous female goats were randomly assigned to two treatments intended to induce estrus. On day zero, animals on T1 (n=6) were treated with an intravaginal sponge impregnated with 60mg of medroxyprogesterone acetate plus 50”g of PGF analogue. The T1 goats received eCG (250IU) on day 4, and on day 5 the sponge was removed. The T2 goats (n=6) received CIDR-GŸ as intravaginal sponge plus 50mg of PGF analogue. All goats expressed behavioral estrus, and the pregnancy rates were 83.3 (5/6) and 33.3% (2/6) for T1 and T2, respectively. The interval from withdrawal of the device to onset of estrus did not differ between treatments (P>0.05). Ovulatory traits also were not affected by treatments. The interval between CIDR-GŸ removal and ovulation for T1 and T2 goats were similar (P>0.05). Both sponge and CIDR-G were equally efficient in inducing the estrus behavior in goats
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