441 research outputs found
Superfluid Suppression in d-Wave Superconductors due to Disordered Magnetism
The influence of static magnetic correlations on the temperature-dependent
superfluid density \rho_s(T) is calculated for d-wave superconductors. In
self-consistent calculations, itinerant holes form incommensurate spin density
waves (SDW) which coexist with superconductivity. In the clean limit, the
density of states is gapped, and \rho_s(T << T_c) is exponentially activated.
In inhomogeneously-doped cases, the SDW are disordered and both the density of
states and \rho_s(T) obtain forms indistinguishable from those in dirty but
pure d-wave superconductors, in accordance with experiments. We conclude that
the observed collapse of \rho_s at x\approx 0.35 in underdoped YBCO may
plausibly be attributed to the coexistence of SDW and superconductivity.Comment: 6 pages, 5 figures. Expanded discussio
Detection of s-Triazine pesticides in natural waters by modified large-volume direct injection HPLC
There is a need for simple and inexpensive methods to quantify potentially harmful persistent pesticides often found in our water-ways and water distribution systems. This paper presents a simple, relatively inexpensive method for the detection of a group of commonly used pesticides (atrazine, simazine and hexazinone) in natural waters using large-volume direct injection high performance liquid chromatography (HPLC) utilizing a monolithic column and a single wavelength ultraviolet–visible light (UV–vis) detector. The best results for this system were obtained with a mobile phase made up of acetonitrile and water in a 30:70 ratio, a flow rate of 2.0 mL min−1, and a detector wavelength of 230 nm. Using this method, we achieved retention times of less than three minutes, and detection limits of 5.7 μg L−1 for atrazine, 4.7 μg L−1 for simazine and 4.0 μg L−1 for hexazinone. The performance of this method was validated with an inter-laboratory trial against a National Association of Testing Authorities (NATA) accredited liquid chromatography–mass spectrometry/mass spectrometry (LC–MS/MS) method commonly used in commercial laboratories
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Large Scale Labelled Video Data Augmentation for Semantic Segmentation in Driving Scenarios
In this paper we present an analysis of the effect of large scale video data augmentation for semantic segmentation in driving scenarios. Our work is motivated by a strong correlation between the high performance of most recent deep learning based methods and the availability of large volumes
of ground truth labels. To generate additional labelled data, we make use of an occlusion-aware and uncertainty-enabled label propagation algorithm. As a result we increase the availability of high-resolution labelled frames by a factor of 20, yielding in a 6.8% to 10.8% rise in average classification accuracy and/or IoU scores for several semantic segmentation networks.
Our key contributions include: (a) augmented CityScapes and CamVid datasets providing 56.2K and 6.5K additional labelled frames of object classes respectively, (b) detailed empirical analysis of the effect of the use of augmented data as well as (c) extension of proposed framework to instance segmentation
Change Management in Large-Scale Enterprise Information Systems
Abstract. The information infrastructure in today’s businesses consists of many interoperating autonomous systems. Changes to a single system can therefore have an unexpected impact on other, dependent systems. In our Caro approach we try to cope with this problem by observing each system participating in the infrastructure and analyzing the impact of any change that occurs. The analysis process is driven by declaratively defined rules and works with a generic and ex-tensible graph model to represent the relevant metadata that is subject to changes. This makes Caro applicable to heterogeneous scenarios and customizable to spe-cial needs.
Functional Brain Imaging with Multi-Objective Multi-Modal Evolutionary Optimization
Functional brain imaging is a source of spatio-temporal data mining problems.
A new framework hybridizing multi-objective and multi-modal optimization is
proposed to formalize these data mining problems, and addressed through
Evolutionary Computation (EC). The merits of EC for spatio-temporal data mining
are demonstrated as the approach facilitates the modelling of the experts'
requirements, and flexibly accommodates their changing goals
Temporal inflection points in decorated pottery: a bayesian refinement of the late formative chronology in the Southern Lake Titicaca Basin, Bolivia
The Late Formative period immediately precedes the emergence of Tiwanaku, one of the earliest South American states, yet it is one of the most poorly understood periods in the southern Lake Titicaca Basin (Bolivia). In this article, we refine the ceramic chronology of this period with large sets of dates from eight sites, focusing on temporal inflection points in decorated ceramic styles. These points, estimated here by Bayesian models, index specific moments of change: (1) cal AD 120 (60-170, 95% probability): the first deposition of Kalasasaya red-rimmed and zonally incised styles; (2) cal AD 240 (190-340, 95% probability): a tentative estimate of the final deposition of Kalasasaya zonally incised vessels; (3) cal AD 420 (380-470, 95% probability): the final deposition of Kalasasaya red-rimmed vessels; and (4) cal AD 590 (500-660, 95% probability): the first deposition of Tiwanaku Redwares. These four modeled boundaries anchor an updated Late Formative chronology, which includes the Initial Late Formative phase, a newly identified decorative hiatus between the Middle and Late Formative periods. The models place Qeya and transitional vessels between inflection points 3 and 4 based on regionally consistent stratigraphic sequences. This more precise chronology will enable researchers to explore the trajectories of other contemporary shifts during this crucial period in Lake Titicaca Basin's prehistory.Fil: Marsh, Erik Johnson. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología Humana; ArgentinaFil: Roddick, Andrew P.. Mc Master University; CanadáFil: Bruno, Maria C.. Dickinson College; Estados UnidosFil: Smith, Scott C.. Franklin & Marshall College; Estados UnidosFil: Janusek, John W.. Vanderbilt University; Estados UnidosFil: Hastorf, Christine A.. University of California at Berkeley; Estados Unido
The Bose Metal: gauge field fluctuations and scaling for field tuned quantum phase transitions
In this paper, we extend our previous discussion of the Bose metal to the
field tuned case. We point out that the recent observation of the metallic
state as an intermediate phase between the superconductor and the insulator in
the field tuned experiments on MoGe films is in perfect consistency with the
Bose metal scenario. We establish a connection between general dissipation
models and gauge field fluctuations and apply this to a discussion of scaling
across the quantum phase boundaries of the Bose metallic state. Interestingly,
we find that the Bose metal scenario implies a possible {\em two} parameter
scaling for resistivity across the Bose metal-insulator transition, which is
remarkably consistent with the MoGe data. Scaling at the superconductor-metal
transition is also proposed, and a phenomenolgical model for the metallic state
is discussed. The effective action of the Bose metal state is described and its
low energy excitation spectrum is found to be .Comment: 15 pages, 1 figur
Phase separation in supersolids
We study quantum phase transitions in the ground state of the two dimensional
hard-core boson Hubbard Hamiltonian. Recent work on this and related models has
suggested ``supersolid'' phases with simultaneous diagonal and off-diagonal
long range order. We show numerically that, contrary to the generally held
belief, the most commonly discussed ``checkerboard'' supersolid is
thermodynamically unstable. Furthermore, this supersolid cannot be stabilized
by next near neighbour interaction. We obtain the correct phase diagram using
the Maxwell construction. We demonstrate the ``striped'' supersolid is
thermodynamically stable and is separated from the superfluid phase by a
continuous phase transition.Comment: 4 pages, 4 eps figures, include
Phase fluctuations in superconductors: from Galilean invariant to quantum XY models
We analyze the corrections to the superfluid density due to phase
fluctuations within both a continuum and a lattice model for - and d-wave
superconductors. We expand the phase-only action beyond the Gaussian level and
compare our results with the quantum XY model both in the quantum and in the
classical regime. We find new dynamic anharmonic vertices, absent in the
quantum XY model, which are responsible for the vanishing of the correction to
the superfluid density at zero temperature in a continuum (Galilean invariant)
model. Moreover the phase-fluctuation effects are reduced with respect to the
XY model by a factor at least of order .Comment: 4 pages; shorter version, accepted for publication on Phys. Rev. B
Rapid Com
One-dimensional Josephson arrays as superlattices for single Cooper pairs
We investigate uniform one-dimensional arrays of small Josephson junctions
(, ) with a realistic Coulomb interaction (here is the screening length
in units of the lattice constant of the array). At low energies this system can
be described in terms of interacting Bose particles (extra single Cooper pairs)
on the lattice. With increasing concentration of extra Cooper pairs, a
crossover from the Bose gas phase to the Wigner crystal phase and then to the
superlattice regime occurs. The phase diagram in the superlattice regime
consists of commensurable insulating phases with ( is integer)
separated by superconducting regions where the current is carried by
excitations with {\em fractional} electric charge . The Josephson
current through a ring-shaped array pierced by magnetic flux is calculated for
all of the phases.Comment: 4 pages (LATEX), 2 figure
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