16,340 research outputs found
Book Review: Excavations at Lemba Lakkous, 1976-1983: Lemba Lakkous. Excavations at Lemba Lakkous, 1976-1983. By Peltenburg E. J. and others. (Lemba archaeological project, 1: studies in Mediterranean archaeology, 70:1.) Göteborg: Åström, 1985. Pp. xxv + 332, [51] plates, 86 text figs, (some folding). Price not stated
Book Review: The necropolis of Kaloriziki: Benson (J. L.) The necropolis of Kaloriziki. (Studies in Mediterranean Archaeology, xxxvi.) Göteborg: Paul Aströms Förlag. 1973. Pp. 138. 63 Plates. Sw.kr. 150
Book Review: Les objets des niveaux stratifiés d'Enkomi (fouilles C.F.-A. Schaeffer 1947-1970): Alasia. 3. Les objets des niveaux stratifiés d'Enkomi (fouilles C.F.-A. Schaeffer 1947-1970). By Courtois J.-C. and others. (Mission archéologique d'Alasia, 6: Éiditions recherche sur les civilisations, mémoire, 32.) Paris: A.D.P.F., Éditions Recherche sur les Civilisations, 1984. Pp. 244, [70] plates. Fr. 140
Current dependence of grain boundary magnetoresistance in La_0.67Ca_0.33MnO_3 films
We prepared epitaxial ferromagnetic manganite films on bicrystal substrates
by pulsed laser ablation. Their low- and high-field magnetoresistance (MR) was
measured as a function of magnetic field, temperature and current. At low
temperatures hysteretic changes in resistivity up to 70% due to switching of
magnetic domains at the coercitive field are observed. The strongly non-ohmic
behavior of the current-voltage leads to a complete suppression of the MR
effect at high bias currents with the identical current dependence at low and
high magnetic fields. We discuss the data in view of tunneling and mesoscale
magnetic transport models and propose an explicit dependence of the spin
polarization on the applied current in the grain boundary region.Comment: 5 pages, to appear in J. Appl. Phy
Short-Range Ordered Phase of the Double-Exchange Model in Infinite Dimensions
Using dynamical mean-field theory, we have evaluated the magnetic
instabilities and T=0 phase diagram of the double-exchange model on a Bethe
lattice in infinite dimensions. In addition to ferromagnetic (FM) and
antiferromagnetic (AF) phases, we also study a class of disordered phases with
magnetic short-range order (SRO). In the weak-coupling limit, a SRO phase has a
higher transition temperature than the AF phase for all fillings p below 1 and
can even have a higher transition temperature than the FM phase. At T=0 and for
small Hund's coupling J_H, a SRO state has lower energy than either the FM or
AF phases for 0.26\le p 0 limit
but appears for any non-zero value of J_H.Comment: 11 pages, 3 figures, published versio
Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals
The fundamental parameter of the uniaxial liquid crystalline state that governs nearly all of its physical properties is the primary orientational order parameter (S) for the long axes of molecules with respect to the director. The biaxial liquid crystals (LCs) possess biaxial order parameters depending on the phase symmetry of the system. In this paper we show that in the first approximation a biaxial orthogonal smectic phase can be described by two primary order parameters: S for the long axes and C for the ordering of the short axes of molecules. The temperature dependencies of S and C are obtained by the Haller's extrapolation technique through measurements of the optical birefringence and biaxiality on a nontilted polar antiferroelectric (Sm-APA) phase of a homologous series of LCs built from the bent-core achiral molecules. For such a biaxial smectic phase both S and C, particularly the temperature dependency of the latter, are being experimentally determined. Results show that S in the orthogonal smectic phase composed of bent cores is higher than in Sm-A calamatic LCs and C is also significantly large
Surface plasmon enhanced absorption and suppressed transmission in periodic arrays of graphene ribbons
Resonance diffraction in the periodic array of graphene micro-ribbons is
theoretically studied following a recent experiment [L. Ju et al, Nature
Nanotech. 6, 630 (2011)]. Systematic studies over a wide range of parameters
are presented. It is shown that a much richer resonant picture would be
observable for higher relaxation times of charge carriers: more resonances
appear and transmission can be totally suppressed. The comparison with the
absorption cross-section of a single ribbon shows that the resonant features of
the periodic array are associated with leaky plasmonic modes. The
longest-wavelength resonance provides the highest visibility of the
transmission dip and has the strongest spectral shift and broadening with
respect to the single-ribbon resonance, due to collective effects.Comment: 5 pages, 3 figure
Experimental verification of entanglement generated in a plasmonic system
A core process in many quantum tasks is the generation of entanglement. It is
being actively studied in a variety of physical settings - from simple
bipartite systems to complex multipartite systems. In this work we
experimentally study the generation of bipartite entanglement in a nanophotonic
system. Entanglement is generated via the quantum interference of two surface
plasmon polaritons in a beamsplitter structure, i.e. utilising the
Hong-Ou-Mandel (HOM) effect, and its presence is verified using quantum state
tomography. The amount of entanglement is quantified by the concurrence and we
find values of up to 0.77 +/- 0.04. Verifying entanglement in the output state
from HOM interference is a nontrivial task and cannot be inferred from the
visibility alone. The techniques we use to verify entanglement could be applied
to other types of photonic system and therefore may be useful for the
characterisation of a range of different nanophotonic quantum devices.Comment: 7 pages, 4 figure
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Upper ocean climate of the Eastern Mediterranean Sea during the Holocene Insolation Maximum – a model study
ine thousand years ago (9 ka BP), the Northern Hemisphere experienced enhanced seasonality caused by an orbital configuration close to the minimum of the precession index. To assess the impact of this "Holocene Insolation Maximum" (HIM) on the Mediterranean Sea, we use a regional ocean general circulation model forced by atmospheric input derived from global simulations. A stronger seasonal cycle is simulated by the model, which shows a relatively homogeneous winter cooling and a summer warming with well-defined spatial patterns, in particular, a subsurface warming in the Cretan and western Levantine areas.
The comparison between the SST simulated for the HIM and a reconstruction from planktonic foraminifera transfer functions shows a poor agreement, especially for summer, when the vertical temperature gradient is strong. As a novel approach, we propose a reinterpretation of the reconstruction, to consider the conditions throughout the upper water column rather than at a single depth. We claim that such a depth-integrated approach is more adequate for surface temperature comparison purposes in a situation where the upper ocean structure in the past was different from the present-day. In this case, the depth-integrated interpretation of the proxy data strongly improves the agreement between modelled and reconstructed temperature signal with the subsurface summer warming being recorded by both model and proxies, with a small shift to the south in the model results.
The mechanisms responsible for the peculiar subsurface pattern are found to be a combination of enhanced downwelling and wind mixing due to strengthened Etesian winds, and enhanced thermal forcing due to the stronger summer insolation in the Northern Hemisphere. Together, these processes induce a stronger heat transfer from the surface to the subsurface during late summer in the western Levantine; this leads to an enhanced heat piracy in this region, a process never identified before, but potentially characteristic of time slices with enhanced insolation
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