1,201 research outputs found
Anomalous vortex ring velocities induced by thermally-excited Kelvin waves and counterflow effects in superfluids
Dynamical counterflow effects on vortex evolution under the truncated
Gross-Pitaevskii equation are investigated. Standard longitudinal mutual
friction effects are produced and a dilatation of vortex rings is obtained at
large counterflow. A strong temperature-dependent anomalous slowdown of vortex
rings is observed and attributed to the presence of thermally exited Kelvin
waves. This generic effect of finite-temperature superfluids is estimated using
energy equipartition and orders of magnitude are given for weakly interacting
Bose-Einstein condensates and superfluid
Non trivial generalizations of the Schwinger pair production result
We present new, non trivial generalizations of the recent Tomaras, Tsamis and
Woodard extension of the original Schwinger formula for charged pair production
in a constant field.Comment: 11 page
A feasibility study of a home-based exercise intervention for prostate cancer patients on androgen deprivation therapy
Purpose: Androgen deprivation therapy (ADT) is an effective treatment for advanced-stage prostate cancer. Unfortunately, ADT has several adverse effects that significantly impair health-related quality of life (HRQOL). In patients receiving ADT, resistance training has been shown to improve important physical and psychosocial outcomes. However, little is known about the effects of aerobic exercise in this population. This feasibility study compares the effects of aerobic and resistance exercise interventions on a panel of psychological, physical fitness, and biological outcomes related to prostate cancer and ADT.
Methods: 66 men receiving ADT for prostate cancer were recruited for this prospective, randomized trial. Participants are assigned to either a resistance or aerobic, moderate-intensity exercise 3-5 times per week for 30-60 minutes/session. Participants were provided with equipment so that they could exercise at home. The primary outcomes were related to feasibility for future, large-scale trials. Secondary outcomes included: fatigue, HRQOL, physical fitness, adipokines, insulin-like growth factor axis proteins, and exercise adherence. Outcomes were assessed at baseline and at 3, 6, and 12 months.
Results: Preliminary findings are presented. 205 patients were approached for participation, 66 of which agreed to participate (n=34 in the resistance training group and 32 in the aerobic training group). Over the intervention period we experienced an attrition rate of 33%. There were no adverse events and biweekly booster sessions were poorly attended (n=27 aerobic training participants and n=22 resistance training participants did not attend any booster sessions). Intention-to-treat analyses showed that fatigue and HRQOL were not significantly different between groups; however, in a per-protocol analysis the resistance-training group demonstrated clinically significant improvements in HRQOL. Differential within-groups effects on physical fitness and biomarkers were also observed at various time-points. At all time-points, the aerobic training group engaged in significantly more physical activity than the resistance training group.
Conclusion: Our findings suggest that both resistance and aerobic training can have positive effects on body composition with differential effects on psychosocial and biological outcomes. It appears that the aerobic exercise intervention was more effective at producing long-term, clinically significant increases in physical activity volume than resistance training. Our study has set the framework to conduct future clinical trials investigating the effects of exercise in men treated for prostate cancer
The restoration of Loch Leven, Scotland, UK
This paper reviews the progress made towards the restoration of Loch Leven, the largest lake in lowland Scotland, over the last 20 years. In particular, the importance of direct regulation and of setting water quality objectives and targets is examined. Various means of engaging with stakeholders and the general public are also considered. Success criteria and catchment management initiatives are described and briefly reviewed
Three regularization models of the Navier-Stokes equations
We determine how the differences in the treatment of the subfilter-scale
physics affect the properties of the flow for three closely related
regularizations of Navier-Stokes. The consequences on the applicability of the
regularizations as SGS models are also shown by examining their effects on
superfilter-scale properties. Numerical solutions of the Clark-alpha model are
compared to two previously employed regularizations, LANS-alpha and Leray-alpha
(at Re ~ 3300, Taylor Re ~ 790) and to a DNS. We derive the Karman-Howarth
equation for both the Clark-alpha and Leray-alpha models. We confirm one of two
possible scalings resulting from this equation for Clark as well as its
associated k^(-1) energy spectrum. At sub-filter scales, Clark-alpha possesses
similar total dissipation and characteristic time to reach a statistical
turbulent steady-state as Navier-Stokes, but exhibits greater intermittency. As
a SGS model, Clark reproduces the energy spectrum and intermittency properties
of the DNS. For the Leray model, increasing the filter width decreases the
nonlinearity and the effective Re is substantially decreased. Even for the
smallest value of alpha studied, Leray-alpha was inadequate as a SGS model. The
LANS energy spectrum k^1, consistent with its so-called "rigid bodies,"
precludes a reproduction of the large-scale energy spectrum of the DNS at high
Re while achieving a large reduction in resolution. However, that this same
feature reduces its intermittency compared to Clark-alpha (which shares a
similar Karman-Howarth equation). Clark is found to be the best approximation
for reproducing the total dissipation rate and the energy spectrum at scales
larger than alpha, whereas high-order intermittency properties for larger
values of alpha are best reproduced by LANS-alpha.Comment: 21 pages, 8 figure
Fast Numerical simulations of 2D turbulence using a dynamic model for Subgrid Motions
We present numerical simulation of 2D turbulent flow using a new model for
the subgrid scales which are computed using a dynamic equation linking the
subgrid scales with the resolved velocity. This equation is not postulated, but
derived from the constitutive equations under the assumption that the
non-linear interactions of subgrid scales between themselves are equivalent to
a turbulent viscosity.The performances of our model are compared with Direct
Numerical Simulations of decaying and forced turbulence. For a same resolution,
numerical simulations using our model allow for a significant reduction of the
computational time (of the order of 100 in the case we consider), and allow the
achievement of significantly larger Reynolds number than the direct method.Comment: 35 pages, 9 figure
Transformation kinetics of alloys under non-isothermal conditions
The overall solid-to-solid phase transformation kinetics under non-isothermal
conditions has been modeled by means of a differential equation method. The
method requires provisions for expressions of the fraction of the transformed
phase in equilibrium condition and the relaxation time for transition as
functions of temperature. The thermal history is an input to the model. We have
used the method to calculate the time/temperature variation of the volume
fraction of the favored phase in the alpha-to-beta transition in a zirconium
alloy under heating and cooling, in agreement with experimental results. We
also present a formulation that accounts for both additive and non-additive
phase transformation processes. Moreover, a method based on the concept of path
integral, which considers all the possible paths in thermal histories to reach
the final state, is suggested.Comment: 16 pages, 7 figures. To appear in Modelling Simul. Mater. Sci. En
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