Convergence of the Generalized Volume Averaging Method on a Convection-Diffusion Problem: A Spectral Perspective

A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure diffusion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards −∞ and the other towards +∞, thus resulting in a nonsectorial operator. The decomposition of the convection-diffusion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the infinite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator’s two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization

Laser-enhanced high-intensity focused ultrasound heating in an in vivo small animal model

The enhanced heating effect during the combination of high-intensity focused ultrasound (HIFU) and low-optical-fluence laser illumination was investigated by using an in vivo murine animal model. The thighs of murine animals were synergistically irradiated by HIFU and pulsed nano-second laser light. The temperature increases in the target region were measured by a thermocouple under different HIFU pressures, which were 6.2, 7.9, and 9.8 MPa, in combination with 20 mJ/cm2 laser exposures at 532 nm wavelength. In comparison with conventional laser therapies, the laser fluence used here is at least one order of magnitude lower. The results showed that laser illumination could enhance temperature during HIFU applications. Additionally, cavitation activity was enhanced when laser and HIFU irradiation were concurrently used. Further, a theoretical simulation showed that the inertial cavitation threshold was indeed decreased when laser and HIFU irradiation were utilized concurrentl

Retinoid-induced ossification of the posterior longitudinal ligament

Vitamin A and its synthetic congeners are known to produce a variety of skeletal abnormalities in patients on prolonged treatment with these medications. Two patients are described who developed posterior longitudinal ligament ossification following treatment with the synthetic retinoid 13-cis-retinoic acid. In both cases, this finding became apparent after other retinoid-induced skeletal abnormalities were observed and was less marked than the ossification of the anterior longitudinal ligament. Although spinal cord compression did not occur in our patients, patients on long-term retinoid therapy should be carefully observed for this complication.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46779/1/256_2004_Article_BF00355561.pd

Computed tomography of cortical desmoid

The diagnosis of cortical desmoid in the typical case is easily established using conventional radiography. In atypical cases, the use of computed tomography (CT) may be helpful in diagnosis. We report the use of computed tomography in two patients with cortical desmoids. In one case plain radiographic findings were not diagnostic and the use of CT obviated biopsy. The finding of a desmoid in an atypical location, the insertion site of the medial head of the gastrocnemius tendon, is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46775/1/256_2004_Article_BF00373175.pd

Sonographic identification of an unusual complication of midtrimester pregnancy termination: Unrecognized intra-abdominal extrusion of fetal parts

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38190/1/1870160210_ftp.pd

Carpal ligamentous laxity with bilateral perilunate dislocation in Marfan syndrome

A case of persistent bilateral perilunate dislocation unrelated to trauma in a patient with Marfan syndrome is discussed. This finding is believed to be a manifestation of the generalized ligamentous laxity occurring in this disorder. Radiographs of eight additional Marfan syndrome patients failed to demonstrate similar carpal instability. Because some carpal derangements are dynamic events, stress views or wrist fluoroscopy may be necessary to demonstrate unsuspected carpal instability in Marfan patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46776/1/256_2004_Article_BF00349097.pd

Effect of Fabric Deformation on Thermal Protective Performance of Clothing in a Cylindrical Configuration

Firefighting protective clothing is designed to provide thermal protection for firefighters in fire extinguishing or rescuing operations. However, fabric deformation and stretching due to body movement and different postures could change the clothing\u27s thermal protective performance. Current gaps in our knowledge with regard to fabric deformation often resulted in biased predictions of the thermal protective level that personal protective equipment (PPE) can provide, highlighting the need to improve our understanding in this field. In this study, we developed a device that can be connected to a cylindrical copper calorimeter to simulate fabric deformation due to body movement and different postures and simultaneously measure the fabric\u27s thermal properties. Stretching forces of varying magnitudes (of 0, 1.2, 2.1, and 3.1 psi) were applied to study the effect of fabric deformation on the thermal protective performance of clothing under low- and high-intensity heat exposures. In addition, we analyzed skin burn times with different stretching forces and fabric properties. The selected fabrics were stretched by approximately 15 % under a stretching force of 3.1 psi. Fabric deformation led to a significant reduction of the predicted thermal protective performance of fabrics, mainly due to changes in fabric thickness, porosity, and mass per unit area. Predicted skin burn times decreased for increasing stretching forces, although the decrease was less pronounced under high-intensity heat exposure as a result of fabric shrinkage and degradation. The findings from this study further advance our current understanding of the thermal protective performance of clothing and may lead to the development of a new test to characterize clothing performance under more realistic usage situations

Continuous-mode 448 kHz capacitive resistive monopolar radiofrequency induces greater deep blood flow changes compared to pulsed mode shortwave: a crossover study in healthy adults

This document is the Accepted Manuscript version of the following article: Binoy Kumaran, Anthony Herbland and Tim Watson, ‘Continuous-mode 448 kHz capacitive resistive monopolar radiofrequency induces greater deep blood flow changes compared to pulsed mode shortwave: a crossover study in healthy adults’, European Journal of Physiotheraphy, first published online 20 April 2017. The version of record is available online at doi: http://dx.doi.org/10.1080/21679169.2017.1316310. © 2017 Informa UK Limited, trading as Taylor & Francis Group.Aims: Radiofrequency-based electrophysical agents (EPAs) have been used in therapy practice over several decades (e.g. shortwave therapies). Currently, there is insufficient evidence supporting such EPAs operating below shortwave frequencies. This laboratory-based study investigated the deep physiological effects of 448 kHz capacitive resistive monopolar radiofrequency (CRMRF) and compared them to pulsed shortwave therapy (PSWT). Methods: In a randomized crossover study, 17 healthy volunteers initially received four treatment conditions: high, low and placebo dose conditions receiving 15-min CRMRF treatment and a control condition receiving no intervention. Fifteen participants additionally received high-dose PSWT as fifth condition, for comparison. Pre- and post-treatment measurements of deep blood flow and tissue extensibility were obtained using Doppler ultrasound and sonoelastography. Group data were compared using analysis of variance model. Statistical significance was set at p ≤ .05, 0.8 power, and 95% confidence interval. Results: Significant increases in volume and intensity of deep blood flow were obtained with CRMRF over placebo, control (p = .003) and PSWT (p < .001). No significant changes in blood flow velocity or tissue extensibility were noted for any condition. Conclusions: Deep blood flow changes with CRMRF were more pronounced than that with PSWT, placebo or control. Potential greater therapeutic benefits need to be confirmed with comparative clinical studies.Peer reviewe

Automatic control of finite element models for temperature-controlled radiofrequency ablation

BACKGROUND: The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant. METHODS: We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation. RESULTS: We present results of a temperature controlled 3-D FEM model of a RITA model 30 electrode. The control software effectively controlled applied voltage in the FEM model to obtain, and keep electrodes at target temperature of 100°C. The closed loop system simulation output closely correlated with the FEM model, and allowed us to optimize control parameters. DISCUSSION: The closed loop control of the FEM model allowed us to implement temperature controlled RF ablation with minimal user input