10,195 research outputs found
Hu(l)man Medi(t)ations: Intercultural explorations in Keri Hulmeâs The Windeater / Te Kaihau
published_or_final_versio
High-temperature ferroelectric order and magnetic field-cooled effect driven magnetoelectric coupling in R2BaCuO5 (R= Er, Dy, Sm)
The high-temperature ferroelectric order and a remarkable magnetoelectric
effect driven by the magnetic field cooling are reported in R2BaCuO5 (R = Er,
Dy, Sm) series. The ferroelectric (FE) orders are observed at much higher
temperatures than their magnetic orders for all three members. The value of FE
Curie temperature (TFE) is considerably high as ~ 235 K with the polarization
value (P) of ~ 1410 {\mu}C/m2 for a 4 kV/cm poling field in case of Er2BaCuO5,
whereas the values of TFE and P are also promising as ~ 232 K and ~ 992
{\mu}C/m2 for Dy2BaCuO5, and ~ 184 K and ~ 980 {\mu}C/m2 for Sm2BaCuO5. The
synchrotron diffraction studies of Dy2BaCuO5 confirm a structural transition at
TFE to a polar Pna21 structure, which correlates the FE order. An unusual
magnetoelectric coupling is observed below the R order for Er and Dy compounds
and below the Cu order for Sm compound, when the pyroelectric current is
recorded only with the magnetic field both in heating and cooling cycles i.e.
typical magnetic field cooled effect. The magnetic field cooled effect driven
emergence of polarization is ferroelectric in nature, as it reverses due to the
opposite poling field. The unexplored R2BaCuO5 series attracts the community
for large TFE, high P value, and strange magnetoelectric consequences.Comment: 9 figures and 2 supporting figure
Anomalous Phase Transition in Strained SrTiO Thin Films
We have studied the cubic to tetragonal phase transition in epitaxial
SrTiO films under various biaxial strain conditions using synchrotron X-ray
diffraction. Measuring the superlattice peak associated with TiO octahedra
rotation in the low temperature tetragonal phase indicates the presence of a
phase transition whose critical temperature is a strong function of strain,
with T as much as 50K above the corresponding bulk temperature.
Surprisingly, the lattice constants evolve smoothly through the transition with
no indication of a phase change. This signals an important change in the nature
of the phase transition due to the epitaxy strain and substrate clamping
effect. The internal degrees of freedom (TiO rotations) have become
uncoupled from the overall lattice shape.Comment: 4 pages, 3 figures, REVTeX
Perturbative Quantum Field Theory at Positive Temperatures: An Axiomatic Approach
It is shown that the perturbative expansions of the correlation functions of
a relativistic quantum field theory at finite temperature are uniquely
determined by the equations of motion and standard axiomatic requirements,
including the KMS condition. An explicit expression as a sum over generalized
Feynman graphs is derived. The canonical formalism is not used, and the
derivation proceeds from the beginning in the thermodynamic limit. No doubling
of fields is invoked. An unsolved problem concerning existence of these
perturbative expressions is pointed out.Comment: 17pages Late
The Frequency Dependence of Critical-velocity Behavior in Oscillatory Flow of Superfluid Helium-4 Through a 2-micrometer by 2-micrometer Aperture in a Thin Foil
The critical-velocity behavior of oscillatory superfluid Helium-4 flow
through a 2-micrometer by 2-micrometer aperture in a 0.1-micrometer-thick foil
has been studied from 0.36 K to 2.10 K at frequencies from less than 50 Hz up
to above 1880 Hz. The pressure remained less than 0.5 bar. In early runs during
which the frequency remained below 400 Hz, the critical velocity was a
nearly-linearly decreasing function of increasing temperature throughout the
region of temperature studied. In runs at the lowest frequencies, isolated 2 Pi
phase slips could be observed at the onset of dissipation. In runs with
frequencies higher than 400 Hz, downward curvature was observed in the decrease
of critical velocity with increasing temperature. In addition, above 500 Hz an
alteration in supercritical behavior was seen at the lower temperatures,
involving the appearance of large energy-loss events. These irregular events
typically lasted a few tens of half-cycles of oscillation and could involve
hundreds of times more energy loss than would have occurred in a single
complete 2 Pi phase slip at maximum flow. The temperatures at which this
altered behavior was observed rose with frequency, from ~ 0.6 K and below, at
500 Hz, to ~ 1.0 K and below, at 1880 Hz.Comment: 35 pages, 13 figures, prequel to cond-mat/050203
OBJECTIVE: a benchmark for object-oriented active database systems
Cataloged from PDF version of article.Although much work in the area of Active Database Management Systems (ADBMSs) has been done, it is not yet clear how the performance of an active DBMS can be evaluated systematically. In this paper, we describe the OBJECTIVE Benchmark for object-oriented ADBMSs, and present experimental results from its implementation in an active database system prototype. OBJECTIVE can be used to identify performance bottlenecks and active functionalities of an ADBMS, and to compare the performance of multiple ADBMSs. (C) 1999 Published by Elsevier Science Inc. All rights reserved
Aspectos biolĂłgicos de Spodoptera cosmioides Walk. (Lepidoptera: Noctuidae) em diferentes plantas hospedeiras.
A Class of Renormalization Group Invariant Scalar Field Cosmologies
We present a class of scalar field cosmologies with a dynamically evolving
Newton parameter and cosmological term . In particular, we discuss
a class of solutions which are consistent with a renormalization group scaling
for and near a fixed point. Moreover, we propose a modified
action for gravity which includes the effective running of and
near the fixed point. A proper understanding of the associated variational
problem is obtained upon considering the four-dimensional gradient of the
Newton parameter.Comment: 10 pages, RevTex4, no figures, to appear on GR
Exponential Renormalization II: Bogoliubov's R-operation and momentum subtraction schemes
This article aims at advancing the recently introduced exponential method for
renormalisation in perturbative quantum field theory. It is shown that this new
procedure provides a meaningful recursive scheme in the context of the
algebraic and group theoretical approach to renormalisation. In particular, we
describe in detail a Hopf algebraic formulation of Bogoliubov's classical
R-operation and counterterm recursion in the context of momentum subtraction
schemes. This approach allows us to propose an algebraic classification of
different subtraction schemes. Our results shed light on the peculiar algebraic
role played by the degrees of Taylor jet expansions, especially the notion of
minimal subtraction and oversubtractions.Comment: revised versio
TLEP: A High-Performance Circular e+e- Collider to Study the Higgs Boson
The recent discovery of a light Higgs boson has opened up considerable
interest in circular e+e- Higgs factories around the world. We report on the
progress of the TLEP concept since last year. TLEP is an e+e- circular collider
capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from
90 to 350 GeV. TLEP could be housed in a new 80 to 100 km tunnel in the Geneva
region. The design can be adapted to different ring circumference (e.g. LEP3 in
the 27 km LHC tunnel). TLEP is an ideal complementary machine to the LHC thanks
to high luminosity, exquisite determination of ECM and the possibility of four
interaction points, both for precision measurements of the Higgs boson
properties and for precision tests of the closure of the Standard Model from
the Z pole to the top threshold.Comment: Contribution to IPAC13, 12-17 May 2013, Shanghai, Chin
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