Bioelectrical impedance phase angle as a prognostic indicator in breast cancer

<p>Abstract</p> <p>Background</p> <p>Bioelectrical impedance analysis (BIA) is an easy-to-use, non-invasive, and reproducible technique to evaluate changes in body composition and nutritional status. Phase angle, determined by bioelectrical impedance analysis (BIA), detects changes in tissue electrical properties and has been hypothesized to be a marker of malnutrition. Since malnutrition can be found in patients with breast cancer, we investigated the prognostic role of phase angle in breast cancer.</p> <p>Methods</p> <p>We evaluated a case series of 259 histologically confirmed breast cancer patients treated at Cancer Treatment Centers of America. Kaplan Meier method was used to calculate survival. Cox proportional hazard models were constructed to evaluate the prognostic effect of phase angle independent of stage at diagnosis and prior treatment history. Survival was calculated as the time interval between the date of first patient visit to the hospital and the date of death from any cause or date of last contact/last known to be alive.</p> <p>Results</p> <p>Of 259 patients, 81 were newly diagnosed at our hospital while 178 had received prior treatment elsewhere. 56 had stage I disease at diagnosis, 110 had stage II, 46 had stage III and 34 had stage IV. The median age at diagnosis was 49 years (range 25 – 74 years). The median phase angle score was 5.6 (range = 1.5 – 8.9). Patients with phase angle <= 5.6 had a median survival of 23.1 months (95% CI: 14.2 to 31.9; n = 129), while those > 5.6 had 49.9 months (95% CI: 35.6 to 77.8; n = 130); the difference being statistically significant (p = 0.031). Multivariate Cox modeling, after adjusting for stage at diagnosis and prior treatment history found that every one unit increase in phase angle score was associated with a relative risk of 0.82 (95% CI: 0.68 to 0.99, P = 0.041). Stage at diagnosis (p = 0.006) and prior treatment history (p = 0.001) were also predictive of survival independent of each other and phase angle.</p> <p>Conclusion</p> <p>This study demonstrates that BIA-derived phase angle is an independent prognostic indicator in patients with breast cancer. Nutritional interventions targeted at improving phase angle could potentially lead to an improved survival in patients with breast cancer.</p

A Mesh Adaptation Strategy to Predict Pressure Losses in LES of Swirled Flows

The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP/2007-2013) / ERC Grant Agreement ERC-AdG 319067-INTECOCIS

A new correlation for entropy generation in low reynolds number turbulent shear layers

The need to quantify entropy generation rates is critical to optimizing the performance of many engineered systems. However, accurate predictions and measurement of this quantity are difficult. Recent direct numerical simulations (DNS) are employed to develop a new correlation for the entropy generation at low and moderate Reynolds numbers typical of those found on turbomachinery surfaces for example. Such a correlation is only possible due to advances in computing, that have allowed moderate Reynolds numbers to be simulated. The result illustrates the discrepancies of existing correlations used throughout the literature for predicting entropy generation rates in low Reynolds number turbulent flows. © 2009 Begell House, Inc

Instantaneous fluctuation velocity and skewness distributions upstream of transition onset

The development of streamwise orientated disturbances through the boundary layer thickness prior to transition onset for zero-pressure gradient boundary layer flow under the influence %Tu = 4.2 is presented. The analysis concentrates on the development of the maximum positive and negative of the fluctuation velocity in order to gain further insight into the transition process. The average location of the peak negative fluctuation velocity over a range of Reynolds numbers was measured in the upper portion of the boundary layer at y/δ ≈ 0.6, whereas the location of the peak positive value was measured at y/δ ≈ 0.3. The disturbance magnitude of the negative fluctuation velocity increased beyond that of the positive as transition onset approached. The distribution and disturbance magnitude of the maximum positive and negative fluctuation velocities indicate that the initiation of transition may occur on the low-speed components of the flow that are lifted up to the upper region of the boundary layer. This is in qualitative agreement with recent direct numerical simulations on the breakdown of the flow on the lifted low-speed streaks near the boundary layer edge. The results presented in this investigation also demonstrate the increased physical insight gained by examining the distributions of the maximum positive and negative of the streamwise fluctuation velocity component associated with the low- and high-speed streaks, compared to time-averaged values, in determining what structures cause the breakdown to turbulence. © 2007 Elsevier Inc. All rights reserved

Experimental investigation into the routes to bypass transition and the shear-sheltering phenomenon

The objective of this investigation is to give experimental support to recent direct numerical simulation (DNS) results which demonstrated that in bypass transition the flow first breaks down to turbulence on the low-speed streaks (or so-called negative jets) that are lifted up towards the boundary-layer edge region. In order to do this, wall-normal profiles of the streamwise fluctuation velocity are presented in terms of maximum positive and negative values over a range of turbulence intensities (1.3-6%) and Reynolds numbers for zero pressure gradient flow upstream of, and including, transition onset. For all turbulence intensities considered, it was found that the peak negative fluctuation velocity increased in magnitude above the peak positive fluctuations and their positions relative to the wall shifted as transition onset approached; the peak negative value moved towards the boundary-layer edge and the peak positive value moved toward the wall. An experimental measure of the penetration depth (PD) of free-stream disturbances into the boundary layer has been gained through the use of the skewness function. The penetration depth (measured from the boundary-layer edge) scales as PD ∝ (ω Re τ ) ), where ω is the frequency of the largest eddies in the free stream, Re is the Reynolds number of the flow based on the streamwise distance from the leading edge and τ is the wall shear stress. The parameter dependence demonstrated by this scaling compares favourably with recent solutions to the Orr-Sommerfeld equation on the penetration depth of disturbances into the boundary layer. The findings illustrate the importance of negative fluctuation velocities in the transition process, giving experimental support to suggestions from recent DNS predictions that the breakdown to turbulence is initiated on the low-speed regions of the flow in the upper portion of the boundary layer. The representation of pre-transitional disturbances in time-averaged form is shown to be inadequate in elucidating which disturbances grow to cause the breakdown to turbulence. © 2007 Cambridge University Press

Quadrant analysis of a transitional boundary layer subject to free-stream turbulence

This paper presents analyses of particle image velocimetry measurements from a boundary layer on a flat plate subject to grid-generated free-stream turbulence. The pre-transition region and early stages of breakdown to turbulent spots are explored by means of quadrant analysis and quadrant hole analysis. By isolating the contributors to the Reynolds shear stresses, it is possible to identify coherent structures within the flow that are responsible for the production of TKE. It is found that so called ejection events are the most significant form of disturbance, exhibiting the largest amplitude behaviour with increased negative spanwise vorticity. Sweep events become increasingly large close to the wall with increased Reynolds number and intermittency. © 2010 Cambridge University Press

EVOLUTION OF THE LAMINAR BOUNDARY LAYER OVER A FLAT PLATE UNDER A FREE STREAM TURBULENCE INTENSITY OF 1.3%

The evolution of the laminar boundary layer over a flat plate under a free stream turbulence intensity of 1.3% is analysed. The effect of free stream turbulence on the onset of transition is one of the important sources leading to bypass transition. Such disturbances are of great interest in engineering for the prediction of transition on turbine blades. The study concentrates on the early part of the boundary layer, starting from the leading edge, and is characterised by the presence of streamwise elongated regions of high and low streamwise velocity. It is demonstrated that the so called "Klebanoff modes" are not entirely representative of the flow structures, due to the time-averaged representations used in most studies. For the conditions of this investigation it is found that the urms and the peak disturbances remain constant in the early stages of the transition development. This region, in which the streaks strength is constant, is problematic for many theories as it is not known where on a surface to initiate a growth theory calculation, and hence the prediction of transition onset is difficult. The observation that a constant urms region exists within the boundary layer under these conditions may be the source of great difficulty in predicting transition onset under turbulence levels around l%. This region suggests that the streaks are either continuously generated and damped, or do not grow during the early stage of transition, and highlights the importance of continuous influence of the free stream turbulence along the boundary layer edge. This work concludes that the first is more likely, and furthermore the measurements are shown to agree with recent direct numerical simulations. © 2008 by ASME

Criteria for boundary layer transition

New results are deduced to assess the validity of proposed transition indicators when applied to situations other than boundary layers on smooth surfaces. The geometry employed utilizes a two-dimensional square rib to disrupt the boundary layer flow. The objective is to determine whether some available criteria are consistent with the present measurements of laminar recovery and transition for the flow downstream of this rib. For the present data - the proposed values of thresholds for transition in existing literature that are based on the freestream turbulence level at the leading edge are not reached in the recovering laminar run but they are not exceeded in the transitioning run either. Of the pointwise proposals examined, values of the suggested quantity were consistent for three of the criteria; that is, they were less than the threshold in laminar recovery and greater than it in the transitioning case. Copyright © 2011 by ASME