462 research outputs found
Distribution and abundance of early life stages of squid (Illex argentinus) in the south-west Atlantic
A joint research cruise (Japan-Argentina-Uruguay) was carried out in the South-western Atlantic during August-September 1989 in order to study the winter-spawning and hatchery areas of Illex argentinus, and also the migration pattern of the juveniles towards the continental shelf. A few Rhynchoteuthion larvae were found in subtropical waters of the Brazil Current, next to the Brazil-Malvinas confluence, and in the frontal zone with shelf water, but never at temperatures below 14°C. Large numbers of juveniles found in subantarctic waters (6–10°C) on the shelf were probably migrating southward from their hatchery grounds following the zooplankton concentrations on which they were feeding
Nonlinear quantum state transformation of spin-1/2
A non-linear quantum state transformation is presented. The transformation,
which operates on pairs of spin-1/2, can be used to distinguish optimally
between two non-orthogonal states. Similar transformations applied locally on
each component of an entangled pair of spin-1/2 can be used to transform a
mixed nonlocal state into a quasi-pure maximally entangled singlet state. In
both cases the transformation makes use of the basic building block of the
quantum computer, namely the quantum-XOR gate.Comment: 12 pages, LaTeX, amssym, epsfig (2 figures included
CP^n, or, entanglement illustrated
We show that many topological and geometrical properties of complex
projective space can be understood just by looking at a suitably constructed
picture. The idea is to view CP^n as a set of flat tori parametrized by the
positive octant of a round sphere. We pay particular attention to submanifolds
of constant entanglement in CP^3 and give a few new results concerning them.Comment: 28 pages, 9 figure
Lattice relaxation around arsenic and selenium in CdTe
We have investigated the lattice relaxation around impurity atoms at the anion sublattice in CdTe, such as As acting as acceptor and Se which is isovalent to Te, with fluorescence detected EXAFS. We experimentally verify the lattice relaxation with a bond length being reduced by 8% around the As atom as inferred indirectly from ab-initio calculations of the electric field gradient in comparison with the measured value in a PAC experiment (S. Lany et al., Phys. Rev. B 62, R2259 (2000)). In the case of the isovalent impurity atom Se, the bond length is similarly reduced as determined experimentally by EXAFS and by model calculations with the density functional theory implemented in the WIEN97 program. In contrast to this inward relaxation, preliminary calculations for Br in CdTe, the next element in the series As, Se, and Br, which acts as donor at the Te sublattice, indicate an increase in bond length, an interesting prediction waiting for experimental verification
Structural stability and local electronic properties of some EC synthesized magnetite nanopowders
Structural and electronic properties, oxidation and aging effect of electrochemically (EC) synthesized magnetite nanopowders (NPs) are studied by means of X–ray diffraction (XRD), X–ray absorption fine structure (XAFS) and X–ray magnetic circular dichroism (XMCD). The obtained results enabled to get a direct insight into the structure and electronic properties of Fe immediate surrounding and to elucidate the influence of preparation conditions on stoichiometry of NPs and their stability in ambient conditions. All investigated NPs are produced as non–stoichiometric FeO oxide phases, with the lattice constant and the Fe/Fe ratio both in–between the values for bulk maghemite and magnetite. NPs synthesized under smaller current density (J = 200 mA/dm) are more magnetite–alike, whereas larger current density (J = 1000 mA/dm) has led to formation of NPs closer to maghemite. Oxidation of magnetite–like NPs is slower, although in the course of time particles agglomerate and oxide penetrates into the core. Maghemite–like NPs oxidize much faster and the oxide layer which is confined close to the particles' surface protects the core from further oxidation. In all NPs the fist coordination around Fe is pretty stable against both temperature and oxidation process. The temperature change from 293 K to 20 K considerably affects the second coordination around Fe, which is most likely a consequence of the Verwey transition present in all investigated samples
Binary Weighted DAC with 2-ξ Resistor Ratio
In this paper we present a new digital analog converter (DAC) design, based on the binary weighted resistor network. The proposed design ensures high conversion accuracy using low precision resistors with ±1% ±2%, ±5%, ±10% and ±20% resistor tolerance. High accuracy is achieved due to better coverage of the analog domain of the transfer characteristic. In binary weighted converters the imprecision of resistors introduces positive and negative differential nonlinearities (DNL). Positive DNL causes gap in the analog domain of the transfer characteristic and negative DNL causes non-monotonicity. In the proposed solution we change the resistor ratio of the two consecutive DAC branches from 2 to 2-ξ, where ξ is small positive number. With this change, we intentionally introduce an additional negative DNL in order to entirely avoid the positive gap. Simulation results confirm that even with resistors tolerance of up to ±10%, we can achieve a converter with maximal gap in the transfer characteristic less than or around one LSB
Exploring Apprenticeship Learning for Player Modelling in Interactive Narratives
In this paper we present an early Apprenticeship Learning approach to mimic
the behaviour of different players in a short adaption of the interactive
fiction Anchorhead. Our motivation is the need to understand and simulate
player behaviour to create systems to aid the design and personalisation of
Interactive Narratives (INs). INs are partially observable for the players and
their goals are dynamic as a result. We used Receding Horizon IRL (RHIRL) to
learn players' goals in the form of reward functions, and derive policies to
imitate their behaviour. Our preliminary results suggest that RHIRL is able to
learn action sequences to complete a game, and provided insights towards
generating behaviour more similar to specific players.Comment: Extended Abstracts of the 2019 Annual Symposium on Computer-Human
Interaction in Play (CHI Play
Unambiguous state discrimination in quantum cryptography with weak coherent states
The use of linearly independent signal states in realistic implementations of
quantum key distribution (QKD) enables an eavesdropper to perform unambiguous
state discrimination. We explore quantitatively the limits for secure QKD
imposed by this fact taking into account that the receiver can monitor to some
extend the photon number statistics of the signals even with todays standard
detection schemes. We compare our attack to the beamsplitting attack and show
that security against beamsplitting attack does not necessarily imply security
against the attack considered here.Comment: 10 pages, 6 figures, updated version with added discussion of
beamsplitting attac
Strategies and Networks for State-Dependent Quantum Cloning
State-dependent cloning machines that have so far been considered either
deterministically copy a set of states approximately, or probablistically copy
them exactly. In considering the case of two equiprobable pure states, we
derive the maximum global fidelity of approximate clones given initial
exact copies, where . We also consider strategies which interpolate
between approximate and exact cloning. A tight inequality is obtained which
expresses a trade-off between the global fidelity and success probability. This
inequality is found to tend, in the limit as , to a known
inequality which expresses the trade-off between error and inconclusive result
probabilities for state-discrimination measurements. Quantum-computational
networks are also constructed for the kinds of cloning machine we describe. For
this purpose, we introduce two gates: the distinguishability transfer and state
separation gates. Their key properties are describedComment: 12 pages, 6 eps figures, submitted to Phys. Rev.
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