3,229 research outputs found

    Optimising the location of tsunami detection buoys and sea-level monitors in the Indian Ocean

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    In the wake of the 2004 Boxing Day tsunami disaster, a global response to implement a tsunami warning system in the Indian Ocean became imperative. Steps in this direction were initiated in 2005 with plans for the deployment of up to 24 tsunami detection buoys. The purpose of this paper is to investigate the optimal placement of tsunami detection buoys and sea-level monitors, in order to provide warning to the greatest population potentially affected. We adopt a mathematical programming approach to examine this problem. It is determined that 10 sites are essential in ensuring that the maximum population can be warned. This has implications for construction and maintenance of the tsunami warning system in the Indian Ocean. Copyright © 2010 Inderscience Enterprises Ltd

    Entanglement genesis by ancilla-based parity measurement in 2D circuit QED

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    We present an indirect two-qubit parity meter in planar circuit quantum electrodynamics, realized by discrete interaction with an ancilla and a subsequent projective ancilla measurement with a dedicated, dispersively coupled resonator. Quantum process tomography and successful entanglement by measurement demonstrate that the meter is intrinsically quantum non-demolition. Separate interaction and measurement steps allow commencing subsequent data qubit operations in parallel with ancilla measurement, offering time savings over continuous schemes.Comment: 5 pages, 4 figures; supplemental material with 5 figure

    Partial-measurement back-action and non-classical weak values in a superconducting circuit

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    We realize indirect partial measurement of a transmon qubit in circuit quantum electrodynamics by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. Accurate control of the interaction and ancilla measurement basis allows tailoring the measurement strength and operator. The tradeoff between measurement strength and qubit back-action is characterized through the distortion of a qubit Rabi oscillation imposed by ancilla measurement in different bases. Combining partial and projective qubit measurements, we provide the solid-state demonstration of the correspondence between a non-classical weak value and the violation of a Leggett-Garg inequality.Comment: 5 pages, 4 figures, and Supplementary Information (8 figures

    Pathways and nerve densities in cerebrovascular innervation

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    It is gradually becoming clear that cerebrovascular nerves contribute to the control of the cerebral circulation although the knowledge of the functional mechanisms is far from complete. However, many aspects of the morphologic substrate have been identified. The basal cerebral arteries receive sympathetic, parasympathetic and sensory innervation, utilizing the superior cervical and stellate, the pterygopalatine and otic, and the trigeminal ganglia, respectively, as the main peripheral sources. Many of the neural pathways to the cerebral arteries have been elucidated. Those to the supratentorial arterial tree are distributed via the cavernous sinus and surrounding regions. Not only the "classical" neurotransmitters, but also many neuropeptides are found in cerebrovascular nerves. This will lead to new insights since the concepts of cotransmission and neuromodulation have been established now. In the arterial wall, a multilayered organization of nerves has been recognized, consisting of paravascular nerve bundles of passage, a superficial plexus and a terminal plexus located at the adventitial-medial border. Human basal cerebral arteries display a topographical heterogeneity of densities of terminal nerve plexuses. Highest nerve densities are found in arterial segments forming the circle of Willis, in the efferent part of the posterior cerebral artery and in the anterior choroidal artery. Nerve density appears to be determined by locality rather than vascular diameter. Furthermore, local decreases in nerve density are observed with ageing and disease in animals and humans.Biomedical Reviews 1995; 4: 35-46

    The stuff that motor chunks are made of: Spatial instead of motor representations?

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    In order to determine how participants represent practiced, discrete keying sequences in the discrete sequence production task, we had 24 participants practice two six-key sequences on the basis of two pre-learned six-digit numbers. These sequences were carried out by fingers of the left (L) and right (R) hand with between-hand transitions always occurring between the second and third, and the fifth and sixth responses. This yielded the so-called LLRRRL and RRLLLR sequences. Early and late in practice, the keypad used for the right hand was briefly relocated from the front of the participants to 90° at their right side. The results indicate that after 600 practice trials, executing a keying sequence relies heavily on a spatial cross-hand representation in a trunk- or head-based reference frame that after about only 15 trials is fully adjusted to the changed hand location. The hand location effect was not found with the last sequence element. This is attributed to the application of explicit knowledge. The between-hand transitions appeared to induce initial segmentation in some of the participants, but this did not consolidate into a concatenation point of successive motor chunks

    Making sense of real-world scenes

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    To interact with the world, we have to make sense of the continuous sensory input conveying information about our environment. A recent surge of studies has investigated the processes enabling scene understanding, using increasingly complex stimuli and sophisticated analyses to highlight the visual features and brain regions involved. However, there are two major challenges to producing a comprehensive framework for scene understanding. First, scene perception is highly dynamic, subserving multiple behavioral goals. Second, a multitude of different visual properties co-occur across scenes and may be correlated or independent. We synthesize the recent literature and argue that for a complete view of scene understanding, it is necessary to account for both differing observer goals and the contribution of diverse scene properties
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