16,612 research outputs found

    Kounis Syndrome Associated With Selective Anaphylaxis to Cefazolin.

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    Alternate islands of multiple isochronous chains in wave-particle interactions

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    We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous island chains varies as a function of the wave parameters. We observe that in all the resonances, the number of chains is related to the amplitude of the various resonant terms. We determine analytically the position of the periodic points and the number of island chains as a function of the wave number and wave period. Such information is very important when one is concerned with regular particle acceleration, since it is necessary to adjust the initial conditions of the particle to obtain the maximum acceleration.Comment: Submitte

    Quantum critical point in the spin glass-antiferromagnetism competition in Kondo-lattice systems

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    A theory is proposed to describe the competition among antiferromagnetism (AF), spin glass (SG) and Kondo effect. The model describes two Kondo sublattices with an intrasite Kondo interaction strength JKJ_{K} and an interlattice quantum Ising interaction in the presence of a transverse field Γ\Gamma. The interlattice coupling is a random Gaussian distributed variable (with average −2J0/N-2J_0/N and variance 32J2/N32 J^{2}/N) while the Γ\Gamma field is introduced as a quantum mechanism to produce spin flipping. The path integral formalism is used to study this fermionic problem where the spin operators are represented by bilinear combinations of Grassmann fields. The disorder is treated within the framework of the replica trick. The free energy and the order parameters of the problem are obtained by using the static ansatz and by choosing both J0/JJ_0/J and Γ/J≈(Jk/J)2\Gamma/J \approx (J_k/J)^2 to allow, as previously, a better comparison with the experimental findings. The results indicate the presence of a SG solution at low JK/JJ_K/J and for temperature T<TfT<T_{f} (TfT_{f} is the freezing temperature). When JK/JJ_K/J is increased, a mixed phase AF+SG appears, then an AF solution and finally a Kondo state is obtained for high values of JK/JJ_{K}/J. Moreover, the behaviors of the freezing and Neel temperatures are also affected by the relationship between JKJ_{K} and the transverse field Γ\Gamma. The first one presents a slight decrease while the second one decreases towards a Quantum Critical Point (QCP). The obtained phase diagram has the same sequence as the experimental one for Ce2Au1−xCoxSi3Ce_{2}Au_{1-x}Co_{x}Si_{3}, if JKJ_{K} is assumed to increase with xx, and in addition, it also shows a qualitative agreement concerning the behavior of the freezing and the Neel temperatures.Comment: 11 pages, 3 figures, accepted for publication in J. Phys.

    Decoherence of Semiclassical Wigner Functions

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    The Lindblad equation governs general markovian evolution of the density operator in an open quantum system. An expression for the rate of change of the Wigner function as a sum of integrals is one of the forms of the Weyl representation for this equation. The semiclassical description of the Wigner function in terms of chords, each with its classically defined amplitude and phase, is thus inserted in the integrals, which leads to an explicit differential equation for the Wigner function. All the Lindblad operators are assumed to be represented by smooth phase space functions corresponding to classical variables. In the case that these are real, representing hermitian operators, the semiclassical Lindblad equation can be integrated. There results a simple extension of the unitary evolution of the semiclassical Wigner function, which does not affect the phase of each chord contribution, while dampening its amplitude. This decreases exponentially, as governed by the time integral of the square difference of the Lindblad functions along the classical trajectories of both tips of each chord. The decay of the amplitudes is shown to imply diffusion in energy for initial states that are nearly pure. Projecting the Wigner function onto an orthogonal position or momentum basis, the dampening of long chords emerges as the exponential decay of off-diagonal elements of the density matrix.Comment: 23 pg, 2 fi

    Critical Lines and Massive Phases in Quantum Spin Ladders with Dimerization

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    We determine the existence of critical lines in dimerized quantum spin ladders in their phase diagram of coupling constants using the finite-size DMRG algorithm. We consider both staggered and columnar dimerization patterns, and antiferromagnetic and ferromagnetic inter-leg couplings. The existence of critical phases depends on the precise combination of these patterns. The nature of the massive phases separating the critical lines are characterized with generalized string order parameters that determine their valence bond solid (VBS) content.Comment: 9 pages 10 figure

    Shifting to green economy: Hype or hope for entrepreneurs into medicinal and aromatic plants?

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    This research aimed at finding out if rural development concerning medicinal and aromatic plants (MAP), in Portugal, was sufficiently consolidated to be considered an alternative lifestyle. Secondary data collected from a panel of 12 high-level experts enabled to picture the sector. Operations were the core knowledge area that helped to find out the implementation of the existing social platform into a technological solution to support a virtual collaborative effort among the stakeholders, as the main requirement to consolidate the sector. The required role of State was also defined as holistic, integrative, supportive, despite not-regulative, to implement a broad MAP policy

    Towards artistic education with textiles: a sustainable challenge with K-10 children

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    Making art with textiles has become part of the development process of creative potential that has led to the acquisition of different types of skills strongly correlated to the success of the textile and clothing industry. There are objectives defined in the curricula of basic education and pre-school education (K10 children) that tackle the artisanal process of transforming raw textile materials: these include acquiring knowledge of textile materials, highlighting the importance of handicrafts in culture and heritage, textile arts and the development of fine motor skills. The objective of this study is to learn about the practices of K10 children using textiles in schools, and to understand how these practices contribute to the development of their creative potential with regard to the area of textiles and clothing. Integrating the activities with textiles makes sensitization to the ma-terials and techniques of the textile arts possible, and paves the way for greater sustainability of this sector in Portuguese society.info:eu-repo/semantics/acceptedVersio

    Creative Teaching of New Product Development to Operations Managers

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    New Product Development (NPD) has got its roots on an Engineering background. Thus, one might wonder about the interest, opportunity, contents and delivery process, if students from soft sciences were involved. This paper addressed «What to teach?» and «How to do it?», as the preliminary research questions that originated the introduced propositions. The curriculum-developer model that was purposefully chosen to adapt the coursebook by pursuing macro/micro strategies was found significant by an exploratory qualitative case study. Moreover, learning was developed and value created by implementing the institutional curriculum through a creative, hands-on, experiencing, problem-solving, problem-based but organized teamwork approach. Product design of an orange squeezer complying with ill-defined requirements, including drafts, sketches, prototypes, CAD simulations and a business plan, plus a website, written reports and presentations were the deliverables that confirmed an innovative contribution towards research and practice of teaching and learning of engineering subjects to non-specialist operations managers candidates
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