319 research outputs found
Energy and Heat Fluctuations in a Temperature Quench
Fluctuations of energy and heat are investigated during the relaxation
following the instantaneous temperature quench of an extended system. Results
are obtained analytically for the Gaussian model and for the large model
quenched below the critical temperature . The main finding is that
fluctuations exceeding a critical threshold do condense. Though driven by a
mechanism similar to that of Bose-Einstein condensation, this phenomenon is an
out-of-equilibrium feature produced by the breaking of energy equipartition
occurring in the transient regime. The dynamical nature of the transition is
illustrated by phase diagrams extending in the time direction.Comment: To be published in the Proceedings of the Research Program "Small
system non equilibrium fluctuations, dynamics and stochastics, and anomalous
behavior", Kavli Institute for Theoretical Physics China, July 2013. 40
pages, 9 figure
The N-Vortex Problem on a Symmetric Ellipsoid: A Perturbation Approach
We consider the N-vortex problem on a ellipsoid of revolution. Applying
standard techniques of classical perturbation theory we construct a sequence of
conformal transformations from the ellipsoid into the complex plane. Using
these transformations the equations of motion for the N-vortex problem on the
ellipsoid are written as a formal series on the eccentricity of the ellipsoid's
generating ellipse. First order equations are obtained explicitly. We show
numerically that the truncated first order system for the three-vortices system
on the symmetric ellipsoid is non-integrable.Comment: 14 pages, 1 figur
Set of Boundary Conditions for Aerodynamic Design
Robust and flexible numerical methodologies for the imposition of boundary conditions are required to formulate well-posed problems. A boundary condition should be Robust and flexible numerical methodologies for the imposition of boundary conditions are required to formulate well-posed problems. A boundary condition should be nonreflecting, to avoid spurious perturbations that can provocate unsteadiness or instabilities. The reflectiveness of various boundary conditions is analyzed in the context of the Godunov methods. A nonlinear, isentropic wave propagation model is used to investigate the reflection mechanism on the flowfield borders, and a parameter τ is defined to give a measure of the boundary reflectiveness. A new set of boundary conditions, in which τ =0, that is, totally nonreflecting, is then proposed. The approach has been integrated in an aerodynamic design procedure using a distributed boundary control
Does the Presence of an Iliac Aneurysm Affect Outcome of Endoluminal AAA Repair? An Analysis of 336 Cases
AbstractObjective: to determine whether the presence of an iliac aneurysm compromises outcome of endovascular exclusion of AAA and to ascertain the fate of the iliac aneurysmal sac.Patients and methods: between April 1997 and March 2001, data on 336 consecutive patients undergoing endovascular repair for AAA were entered in a prospective database. Suitability for endovascular repair was assessed by preoperative contrast-enhanced computed tomography. A maximum common iliac artery (CIA) diameter ≥20mm was defined as iliac aneurysm. Patients with and without iliac aneurysms were compared to early (immediate conversion or perioperative death) and late failure (increase in aneurysm diameter or persisting graft-related endoleak, or late AAA rupture or conversion).Results: fifty-nine patients (18%) had iliac aneurysms, 19 were bilateral, for a total of 78 aneurysmal iliac arteries (median diameter 23mm; range 20–50mm). A distal seal was achieved by landing in 33 external iliac arteries, in 20 ectatic CIAs, and in 25 normal CIAs. Operating time differed significantly between patients with and without CIA aneurysms (153±71 vs 123±55min,p =0.0001), whereas no statistically significant differences were found with respect to early and late failure (2% vs 3%, p=0.5 and 14% vs 8%, p=0.11, respectively). There were no cases of buttock or colon necrosis. At a median follow-up of 14 months (range 0–46; i.q.r. 7–27 months) common iliac diameter decreased ≥2mm in 49 cases, remained stable in 25, and increased ≥2mm in 3.Conclusion: the presence of iliac aneurysm rendered endoluminal AAA repair more complex but did not affect feasibility and long-term outcome of the procedure. In our experience internal iliac exclusion was never associated with significant morbidity. These data may be useful when considering endovascular repair in high-risk patients with challenging anatomy
Control of the urban pigeon Columba livia population and the preservation of common swift Apus apus and bats Chiroptera during the restoration of the Ghirlandina tower in the city of Modena (Italy)
Ferri, M., Ferraresi, M., Gelati, A., Zannetti, G., Domenichini, A., Ravizza, L., Cadignani, R
Effects of an external drive on the fluctuation-dissipation relation of phase-ordering systems
The relation between the autocorrelation and the integrated linear
response function is studied in the context of the large-N model
for phase-ordering systems subjected to a shear flow. In the high temperature
phase a non-equilibrium stationary state is entered which is
characterized by a non-trivial fluctuation-dissipation relation . For quenches below the splitting of the
order parameter field into two statistically independent components,
responsible for the stationary and aging part
of the autocorrelation function, can be explicitly exhibited in close analogy
with the undriven case. In the regime the same relation is found between the response and
, as for . The aging part of is
negligible for , as without drive, resulting in a flat in the aging regime .Comment: 8 pages, 2 figure
Role of Duplex Scan in Endoleak Detection After Endoluminal Abdominal Aortic Aneurysm Repair
AbstractObjective: to validate the role of duplex scan in endoleak detection in postoperative surveillance of endoluminal abdominal aneurysm repair (EAAR). Patients and methods between April 1997 and March 1999, 103 patients were eligible for duplex and computed tomography (CT) scan after EAAR. Mean follow-up was 8 months (range 1–24 months). The study protocol comprised concurrent examination with colour-duplex and CT scan at 1, 6, and 12 months after EAAR, for a total of 198 concurrent examinations. All duplex scan examinations were performed by two vascular surgeons with the same machine (ATL HDI 3000). Interobserver agreement in endoleak detection (κ=1) and in type of endoleak (κ=0.7) was evaluated in 50 random duplex examinations. Endoleak detection was examined comparatively in duplex and CT scan, the latter being the gold standard. Sensitivity and specificity tests together with negative- and positive-predictive values (NPV and PPV) were calculated. Results duplex scan was not feasible in one patient. On CT scan the endoleak rate was 4% at one month, 3% at 6 months, and 4% at one year. Overall, CT scan detected 12 endoleaks. With respect to endoleak detection, duplex scan revealed a great ability in ruling out false-negative results (sensitivity 91.7%, NPV 99.4%), but overestimated the presence of endoleak (specificity 98.4%, PPV 78.6%). Regarding type of endoleak, the ability of duplex scan to identify the source of endoleak was low (sensitivity 66.7%). Conclusions duplex scan, if validated, appears to be a reliable means for excluding the presence of endoleak after EAAR
Interface fluctuations, bulk fluctuations and dimensionality in the off-equilibrium response of coarsening systems
The relationship between statics and dynamics proposed by Franz, Mezard,
Parisi and Peliti (FMPP) for slowly relaxing systems [Phys.Rev.Lett. {\bf 81},
1758 (1998)] is investigated in the framework of non disordered coarsening
systems. Separating the bulk from interface response we find that for statics
to be retrievable from dynamics the interface contribution must be
asymptotically negligible. How fast this happens depends on dimensionality.
There exists a critical dimensionality above which the interface response
vanishes like the interface density and below which it vanishes more slowly. At
the interface response does not vanish leading to the violation of the
FMPP scheme. This behavior is explained in terms of the competition between
curvature driven and field driven interface motion.Comment: 11 pages, 3 figures. Significantly improved version of the paper with
new results, new numerical simulations and new figure
Influence of thermal fluctuations on the geometry of the interfaces of the quenched Ising model
We study the role of the quench temperature in the phase-ordering
kinetics of the Ising model with single spin flip in . Equilibrium
interfaces are flat at , whereas at they are curved and rough
(above the roughening temperature in ). We show, by means of scaling
arguments and numerical simulations, that this geometrical difference is
important for the phase-ordering kinetics as well. In particular, while the
growth exponent of the size of domains is unaffected
by , other exponents related to the interface geometry take different
values at or . For a crossover phenomenon is observed
from an early stage where interfaces are still flat and the system behaves as
at , to the asymptotic regime with curved interfaces characteristic of
. Furthermore, it is shown that the roughening length, although
sub-dominant with respect to , produces appreciable correction to scaling
up to very long times in .Comment: 21 pages, 15 figures. To be published in Phys. Rev.
Development and testing of a new instrument to measure self-care in patients with osteoporosis: the self-care of osteoporosis scale
Purpose: The aim of this study was to develop and test the Self-Care of Osteoporosis Scale (SCOS), a new instrument
to measure self-care in postmenopausal women with osteoporosis.
Methods: A cross-sectional study was conducted. The SCOS was developed by a panel of experts and it was theory-driven. Confirmatory factor analysis (N = 544) was used to test the instrument’s factorial validity; Cronbach’s alpha and
McDonald’s omega were used to derive the measure’s internal consistency reliability; an intraclass correlation coefficient
was used to evaluate test-retest reliability.
Results: Confirmatory factor analysis resulted in supportive fit indices for the hypothesized three-factor structure of the
SCOS (RMSEA = 0.065; CFI = 0.99). The SCOS was demonstrated to have content validity, internal consistency and
test-retest reliability.
Conclusions: The SCOS demonstrated excellent psychometric characteristics in terms of validity and reliability. It may
be used by healthcare providers to identify if patients show lower self-care and require educational interventions
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