Thermophysical properties of lysozyme (protein) solutions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76692/1/AIAA-392-587.pd

Thermocapillary convection in lysozyme sessile drops with internal solidification.

The subject of thermocapillary flow has been given serious attention in recent years due to the opportunity of processing material in space. In order to provide the basic information needed for protein crystal growth under a reduced gravity environment, an experimental study was performed on Marangoni convection in a sessile drop of lysozyme solution with internal solidification. The flow was induced by thermocapillary force, resulting from a temperature difference along the free surface, simulating the situation in a reduced gravity environment. Solidification inside the sessile drop was initiated by means of a center coating method. The first part of the study was to investigate some physical properties of lysozyme solutions, such as thermal conductivity, specific heat, viscosity and surface tension. The surface tension coefficient of a lysozyme solution was typically three times larger than that of water. The measured surface tensions are compared with the data in the literature. The second part of the study involves the visualization of Marangoni convection and solidification front movement in the sessile drop by using a microscope-video monitor system. The temperature at the drop edge was monitored by thermocouples. Experimental results are obtained for water, a sodium chloride/sodium acetate buffer, and the lysozyme solutions. The temperatures at the drop edge of the lysozyme solutions were higher compared with the case of water or the buffer. The intensity of Marangoni convection was also stronger for the lysozyme solutions than other cases due to a larger temperature gradient and surface tension coefficient. It was also found that the molecules of lysozyme were able to change the free surface morphology from an unstable to a substable one, thus improving its lense effect. A mathematical model, with appropriate assumptions, was developed to account for the physics of the system. The model was solved by the integral method. The temperature profiles and the location of the interface were found by integrating the simplified governing equation of energy and interface simultaneously using the Runge-Kutta method. The predicted temperature profiles were confirmed by observations involving a relatively higher velocity of a tracer in the lysozyme solution. A distortion of Marangoni convection was observed at the beginning of the solidification process due to the volume expansion of water when it freezes. This behavior may enhance or hamper thermocapillary convection, depending on the density change when a liquid is frozen or crystallized.Ph.D.Macromolecular Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105400/1/9124047.pdfDescription of 9124047.pdf : Restricted to UM users only

Mechanics of transport phenomena in multi-component sessile drops with solidification

An experimental study is performed to determine the mechanics of transport phenomena in multicomponent sessile drops with internal solidification. These drops are cooled at the center of the drop base or over the enter base of the drop. Both the interfacial and internal flow structures are examined by means of laser shadowgraphy, while the microstructures are investigated using a microscope-video system. Three different degrees of cooling rate are imposed on the drops: low, medium and high cooling. It is disclosed that the center cooling at a low rate produces a radial flow induced by component separation but without solidification and Marangoni type (surface-tension induced) flow. In contrast, a high cooling rate results in Marangoni convection accompanied by solidification but no component separation. The effect of Prandtl number on the Marangoni flow velocity is determined. The interfacial disturbance is suppressed by center cooling but not by bulk cooling which induces the formation of Bernard cells. The impact of flow patterns on the mechanical property of melt solidification is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28339/1/0000098.pd

Left Ventricular Systolic and Diastolic Dyssynchrony to Improve Cardiac Resynchronization Therapy Response in Heart Failure Patients with Dilated Cardiomyopathy

Background The systolic and diastolic dyssynchrony is physiologically related, but measure different left ventricular mechanisms. Left ventricular systolic mechanical dyssynchrony (systolic LVMD) has shown significant clinical values in improving cardiac resynchronization therapy (CRT) response in the heart failure patients with dilated cardiomyopathy (DCM). Our recent study demonstrated that LV diastolic dyssynchrony (diastolic LVMD) parameters have important prognostic values for DCM patients. However, there are a limited number of studies about the clinical value of diastolic LVMD for CRT. This study aims to explore the predictive values of both systolic LVMD and diastolic LVMD for CRT in DCM patients. Methods Eighty-four consecutive CRT patients with both DCM and complete left bundle branch block (CLBBB) who received gated resting SPECT MPI at baseline were included in the present study. The phase analysis technique was applied on resting gated short-axis SPECT MPI images to measure systolic LVMD and diastolic LVMD, characterized by phase standard deviation (PSD) and phase histogram bandwidth (PBW). CRT response was defined as ≥ 5% improvement of LVEF at 6-month follow-up. Variables with P \u3c 0.10 in the univariate analysis were included in the multivariate cox analysis. Results During the follow-up period, 59.5% (50 of 84) patients were CRT responders. The univariate cox regression analysis showed that at baseline QRS duration, non-sustained ventricular tachycardia (NS-VT), systolic PSD, systolic PBW, diastolic PSD, diastolic PBW, scar burden and LV lead in the scarred myocardium were statistically significantly associated with CRT response. The multivariate cox regression analysis showed that QRS duration, NS-VT, systolic PSD, systolic PBW, diastolic PSD, and diastolic PBW were independent predictive factors for CRT response. Furthermore, the rate of CRT response was 94.4% (17 of 18) in patients whose LV lead was in the segments with both the first three late contraction and the first three late relaxation; by contrast, the rate of CRT response was only 6.7% (1 of 15, P \u3c 0.000) in patients whose LV lead was in the segments with neither the first three late contraction nor the first three late relaxation. Conclusion Both systolic LVMD and diastolic LVMD from gated SPECT MPI have important predictive values for CRT response in DCM patients. Pacing at LV segments with both late contraction and late relaxation has potential to increase the CRT response