34,026 research outputs found
Theoretical analysis of the electrical aspects of the basic electro-impulse problem in aircraft de-icing applications
A summary of modeling the electrical system aspects of a coil and metal target configuration resembling a practical electro-impulse deicing (EIDI) installation, and a simple circuit for providing energy to the coil, was presented. The model was developed in sufficient theoretical detail to allow the generation of computer algorithms for the current in the coil, the magnetic induction on both surfaces of the target, the force between the coil and target, and the impulse delivered to the target. These algorithms were applied to a specific prototype EIDI test system for which the current, magnetic fields near the target surfaces, and impulse were previously measured
Coordination polymers and isomerism; a study using silver(I) and a ∏-stacked ligand
The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl)pyrazine. This new ligand was treated with AgClO₄ in a 1 1 metal-to-ligand ratio and with AgNO₃in a 2 1 metal-to-ligand ratio to give coordination polymers. The crystal structures of {[Ag(L)]ClO₄}∞ ( 1) and {[Ag₂(L)](NO₃)₂}∞ ( 2) were determined. The Ag(I) ions in the one-dimensional polymeric chains of 1 adopted square-pyramidal geometries with the pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in the donor atoms about the Ag(I) ions and in the arrangement of adjacent ligands along the chain. A feature of both structures was that L adopted a three-layer ∏-stacked arrangement
On Quantum Algorithms
Quantum computers use the quantum interference of different computational
paths to enhance correct outcomes and suppress erroneous outcomes of
computations. In effect, they follow the same logical paradigm as
(multi-particle) interferometers. We show how most known quantum algorithms,
including quantum algorithms for factorising and counting, may be cast in this
manner. Quantum searching is described as inducing a desired relative phase
between two eigenvectors to yield constructive interference on the sought
elements and destructive interference on the remaining terms.Comment: 15 pages, 8 figure
Perturbation theory of structure in classical liquid mixtures: Application to metallic systems near phase separation
The partial structure factors of classical simple liquid mixtures near phase separation are dicussed. The theory is developed for particles interacting through pair potentials, and is thus appropriate both to insulating fluids, and also to metallic systems if these may be described by an effective ion-ion pair interaction. The motivation arose from consideration of metallic liquid mixtures, in which resistive anomalies have been observed near phase separation. A mean field theory correction appropriate to 3 pair potential for the effects of correlated motions in the reference fluid is studied. The work is cast in terms of functions which are closely related to the direct correlation functions of Ornstein and Zernike. The results are qualitatively in accord with physical expectations. Quantitative agreement with experiment seems to turn on the selection of the hard core reference potential in terms of the metallic effective pair potential. It is suggested that the present effective pair potentials are perhaps not properly used to calculate the metallic structure factors at long wavelength
Struggling to a monumental triumph : Re-assessing the final stages of the smallpox eradication program in India, 1960-1980
The global smallpox program is generally presented as the brainchild of a handful of actors from the WHO headquarters in Geneva and at the agency's regional offices. This article attempts to present a more complex description of the drive to eradicate smallpox. Based on the example of India, a major focus of the campaign, it is argued that historians and public health officials should recognize the varying roles played by a much wider range of participants. Highlighting the significance of both Indian and international field officials, the author shows how bureaucrats and politicians at different levels of administration and society managed to strengthen—yet sometimes weaken—important program components. Centrally dictated strategies developed at WHO offices in Geneva and New Delhi, often in association with Indian federal authorities, were reinterpreted by many actors and sometimes changed beyond recognition
An extended model of the quantum free-electron laser
Previous models of the quantum regime of operation of the Free Electron Laser
(QFEL) have performed an averaging and the application of periodic boundary
conditions to the coupled Maxwell - Schrodinger equations over short, resonant
wavelength intervals of the interaction. Here, an extended, one-dimensional
model of the QFEL interaction is presented in the absence of any such averaging
or application of periodic boundary conditions, the absence of the latter
allowing electron diffusion processes to be modeled throughout the pulse. The
model is used to investigate how both the steady-state (CW) and pulsed regimes
of QFEL operation are affected. In the steady-state regime it is found that the
electrons are confined to evolve as a 2-level system, similar to the previous
QFEL models. In the pulsed regime Coherent Spontaneous Emission (CSE) due to
the shape of the electron pulse current distribution is shown to be present in
the QFEL regime for the first time. However, unlike the classical case, CSE in
the QFEL is damped by the effects of quantum diffusion of the electron
wavefunction. Electron recoil from the QFEL interaction can also cause a
diffusive drift between the recoiled and non-recoiled parts of the electron
pulse wavefunction, effectively removing the recoiled part from the primary
electron-radiation interaction.Comment: Submitted to Optics Expres
Orthogonal measurements are {\it almost} sufficient for quantum discord of two qubits
The common use in literature of orthogonal measurements in obtaining quantum
discord for two-qubit states is discussed and compared with more general
measurements. We prove the optimality of orthogonal measurements for rank 2
states. While for rank 3 and 4 mixed states they are not optimal, we present
strong numerical evidence showing that they give the correct quantum discord up
to minimal corrections. Based on the connection, through purification with an
ancilla, between discord and entanglement of formation (EoF), we give a tight
upper bound for the EoF of a mixed state of rank 2, given by an
optimal decomposition of 2 elements. We also provide an alternative way to
compute the quantum discord for two qubits based on the Bloch vectors of the
state.Comment: EPL 96, 40005 (2011
Agricultural Biotechnology as an Intangible Asset: Incentives for Transnational Vertical Integration in Agribusiness
Exact date of working paper unknown.An emerging global phenomenon is the application of biotechnology to food and agricultural production. How individual firms will relate to biotechnological advances and the decisions made regarding the commercialization of biotechnology will influence the structure of the industrial landscape in global markets and international trade. The scope of biotechnology in the United States and Europe and the economic incentives for transnational vertical integration of biotechnological products or processes is examined. An economic model is used to assess the nature of incentives for the transnational vertical integration of biotechnology. The analysis argues that rights to commercial biotechnology products or processes are intangible assets which may provide incentives for vertical foreign direct investment by the firms holding such rights. The transnational character of intellectual property as an intangible asset is explored briefly. Implications are drawn from the analysis concerning transnational vertical integration of biotechnology
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