3,107 research outputs found
Spatiotemporal rheochaos in nematic hydrodynamics
Motivated by the observation of rheochaos in sheared wormlike micelles
[Bandyopadhyay et al., Phys. Rev. Lett, 84 2022, (2000); Europhys. Lett. 56,
447 (2001); Pramana 53, 223 (1999)] we study the coupled nonlinear partial
differential equations for the hydrodynamic velocity and order parameter fields
in a sheared nematogenic fluid. In a suitable parameter range, we find
irregular, dynamic shear-banding and establish by decisive numerical tests that
the chaos we observe in the model is spatiotemporal in nature.Comment: Slight changes in text, references and Fig. 5 inset; 6 eps figures
(figs 2,3,4 at lower resolution to reduce file size; full files available on
request); accepted for publication in Phys Rev Let
Integrating Offshore Wind and Wave Resource Assessment
The aim of this paper is to review the sources of wind and wave information, the methodologies to assess offshore wind and wave energy resources, and the more relevant results at the European level as a first step to integration of the evaluation of both resources. In situ and remote sensed wind and wave data (using satellite based sensors) are done generally by distinct systems (except for SAR) but numerical atmospheric models and wind - wave models are closely related. Offshore wind resource studies using various types of data are reviewed especially in northern European seas and in the Mediterranean. The wave energy resource assessment at European and national levels is also reviewed and the various atlases are identified
Electronic Raman scattering and photoluminescence from LaSrMnO exhibiting giant magnetoresistance
Raman and Photoluminescence (PL) experiments on correlated metallic
LaSrMnO have been carried out using different excitation
wavelengths as a function of temperature from 15 K to 300 K. Our data suggest a
Raman mode centered at 1800 cm and a PL band at 2.2 eV. The intensities
of the two peaks decrease with increasing temperature. The Raman mode can be
attributed to a plasmon excitation whose frequency and linewidths are
consistent with the measured resistivities. The PL involves intersite
electronic transitions of the manganese ions.Comment: 10 pages + 4 eps figures, Revtex 3.0, figures available on reques
Rapidity distribution as a probe for elliptical flow at intermediate energies
Interplay between the spectator and participant matter in heavy-ion
collisions is investigated within isospin dependent quantum molecular dynamics
(IQMD) model in term of rapidity distribution of light charged particles. The
effect of different types and size rapidity distributions is studied in
elliptical flow. The elliptical flow patterns show important role of the nearby
spectator matter on the participant zone. This role is further explained on the
basis of passing time of the spectator and expansion time of the participant
zone. The transition from the in-plane to out-of-plane is observed only when
the mid-rapidity region is included in the rapidity bin, otherwise no
transition occurs. The transition energy is found to be highly sensitive
towards the size of the rapidity bin, while weakly on the type of the rapidity
distribution. The theoretical results are also compared with the experimental
findings and are found in good agreement.Comment: 8 figure
Low temperature and high pressure Raman and x-ray studies of pyrochlore TbTiO : phonon anomalies and possible phase transition
We have carried out temperature and pressure-dependent Raman and x-ray
measurements on single crystals of TbTiO. We attribute the observed
anomalous temperature dependence of phonons to phonon-phonon anharmonic
interactions. The quasiharmonic and anharmonic contributions to the
temperature-dependent changes in phonon frequencies are estimated
quantitatively using mode Gr\"{u}neisen parameters derived from
pressure-dependent Raman experiments and bulk modulus from high pressure x-ray
measurements. Further, our Raman and x-ray data suggest a subtle structural
deformation of the pyrochlore lattice at 9 GPa. We discuss possible
implications of our results on the spin-liquid behaviour of TbTiO.Comment: 10 figures, 26 pages. Appeared in Physical Review B, vol-79,
pp-134112 (2009
Random elastic networks : strong disorder renormalization approach
For arbitrary networks of random masses connected by random springs, we
define a general strong disorder real-space renormalization (RG) approach that
generalizes the procedures introduced previously by Hastings [Phys. Rev. Lett.
90, 148702 (2003)] and by Amir, Oreg and Imry [Phys. Rev. Lett. 105, 070601
(2010)] respectively. The principle is to eliminate iteratively the elementary
oscillating mode of highest frequency associated with either a mass or a spring
constant. To explain the accuracy of the strong disorder RG rules, we compare
with the Aoki RG rules that are exact at fixed frequency.Comment: 8 pages, v2=final versio
Fractional flow reserve vs. angiography in guiding management to optimize outcomes in non-ST-segment elevation myocardial infarction: the British Heart Foundation FAMOUS-NSTEMI randomized trial
Aim: We assessed the management and outcomes of non-ST segment elevation myocardial infarction (NSTEMI) patients randomly assigned to fractional flow reserve (FFR)-guided management or angiography-guided standard care.
Methods and results: We conducted a prospective, multicentre, parallel group, 1 : 1 randomized, controlled trial in 350 NSTEMI patients with ≥ coronary stenosis ≥30% of the lumen diameter assessed visually (threshold for FFR measurement) (NCT01764334). Enrolment took place in six UK hospitals from October 2011 to May 2013. Fractional flow reserve was disclosed to the operator in the FFR-guided group (n = 176). Fractional flow reserve was measured but not disclosed in the angiography-guided group (n = 174). Fractional flow reserve ≤0.80 was an indication for revascularization by percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG). The median (IQR) time from the index episode of myocardial ischaemia to angiography was 3 (2, 5) days. For the primary outcome, the proportion of patients treated initially by medical therapy was higher in the FFR-guided group than in the angiography-guided group [40 (22.7%) vs. 23 (13.2%), difference 95% (95% CI: 1.4%, 17.7%), P = 0.022]. Fractional flow reserve disclosure resulted in a change in treatment between medical therapy, PCI or CABG in 38 (21.6%) patients. At 12 months, revascularization remained lower in the FFR-guided group [79.0 vs. 86.8%, difference 7.8% (−0.2%, 15.8%), P = 0.054]. There were no statistically significant differences in health outcomes and quality of life between the groups.
Conclusion: In NSTEMI patients, angiography-guided management was associated with higher rates of coronary revascularization compared with FFR-guided management. A larger trial is necessary to assess health outcomes and cost-effectiveness
Random walks on the Apollonian network with a single trap
Explicit determination of the mean first-passage time (MFPT) for trapping
problem on complex media is a theoretical challenge. In this paper, we study
random walks on the Apollonian network with a trap fixed at a given hub node
(i.e. node with the highest degree), which are simultaneously scale-free and
small-world. We obtain the precise analytic expression for the MFPT that is
confirmed by direct numerical calculations. In the large system size limit, the
MFPT approximately grows as a power-law function of the number of nodes, with
the exponent much less than 1, which is significantly different from the
scaling for some regular networks or fractals, such as regular lattices,
Sierpinski fractals, T-graph, and complete graphs. The Apollonian network is
the most efficient configuration for transport by diffusion among all
previously studied structure.Comment: Definitive version accepted for publication in EPL (Europhysics
Letters
Brillouin scattering studies in FeO across the Verwey transition
Brillouin scattering studies have been carried out on high quality single
crystals of FeO with [100] and [110] faces in the temperature range of
300 to 30 K. The room temperature spectrum shows a surface Rayleigh wave (SRW)
mode at 8 GHz and a longitudinal acoustic (LA) mode at 60 GHz. The SRW mode
frequency shows a minimum at the Verwey transition temperature of 123 K.
The softening of the SRW mode frequency from about 250 K to can be
quantitatively understood as a result of a decrease in the shear elastic
constant C, arising from the coupling of shear strain to charge
fluctuations. On the other hand, the LA mode frequency does not show any
significant change around , but shows a large change in its intensity. The
latter shows a maximum at around 120 K in the cooling run and at 165 K in the
heating run, exhibiting a large hysteresis of 45 K. This significant change in
intensity may be related to the presence of stress-induced ordering of
Fe and Fe at the octahedral sites, as well as to stress-induced
domain wall motion.Comment: 14 pages, 3 figures, accepted in Physical Review B 200
Temperature dependent Raman and x-ray studies of spin-ice pyrochlore and non-magnetic pyrochlore
We present here temperature-dependent Raman, x-ray diffraction and specific
heat studies between room temperature and 12 K on single crystals of spin-ice
pyrochlore compound and its non-magnetic analogue .
Raman data show a "new" band not predicted by factor group analysis of
Raman-active modes for the pyrochlore structure in , appearing
below a temperature of 110 K with a concomitant contraction of the cubic
unit cell volume as determined from the powder x-ray diffraction analysis. Low
temperature Raman experiments on O-isotope substituted
confirm the phonon origin of the "new" mode. These findings, absent in
, suggest that the room temperature cubic lattice of the
pyrochlore undergoes a "subtle" structural transformation near
. We find anomalous \textit{red-shift} of some of the phonon modes in both
the and the as the temperature decreases, which is
attributed to strong phonon-phonon anharmonic interactions.Comment: 28 pages, 9 figures (Accepted for publication in Physical Review B
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