Dawei Luo

Trapped water of human erythrocytes and its application in cryopreservation

The novel differential scanning calorimetry method as a technique for determining human red cell volume during freezing process has been reexamined and has been shown to provide a final erythrocyte volume to be 53% of its isotonic value after freezing from 0 to -40 degrees C. A new type of electronic particle counter (Multisizer 3, Beckman Coulter Inc., USA) was used to measure cell volume changes in response to equilibration in anisotonic media, and which gave out an equilibrated volume to be 57% of cell isotonic value in solution of 3186 mOsm. Both of these results indicate that 34-40% of intracellular water is trapped and is unavailable for participation in osmotic shifts. These findings are consistent with the published data that at least 20-32% (v/v) of the isotonic cell water is retained within RBCs. Then the application of trapped water in both simulation of freezing models and freezing-drying control was pointed out.

Determination of Thermal Conductivity of Cryoprotectant Solutions and Cell Suspensions

Determination of thermal conductivity of cryoprotectant solutions is required in modeling and predicting cooling/warming conditions for optimal cryopreservation of cells and tissues. A needle-like ...

Determination of temperature dependent thermal conductivity by solving IHCP in infinite region

The determination of the temperature dependent thermal conductivity inside an infinite region with a constant linear heat source at the center is investigated. Assuming the material has a known constant thermal diffusivity, the heat conduction problem is linearised by employing the Kirchhoff transformation. The analytical solution of this inverse heat conduction problem has been developed by applying H ankel transformation and the corresponding inversion transformation. Based on the solution, the temperature dependent thermal conductivity can be obtained by measuring the temperature profile at an arbitrary space location

Heat pattern simulation of some cryo-protectant agencies using a combined electromagnetic and heat transfer solver

An iteration algorithm is presented to obtain the electromagnetic field distribution and the temperature pattern for arbitrary shaped samples when they are in free space and inside cavities. The iteration involves solving the electromagnetic wave equation and the heat transfer equation alternatively. The electromagnetic solver models the cavity with quadrangle patches and the dielectric tissue by hexahedrons. Hence it can be used to simulate realistic microwave re-warming and heating processes, and provides an accurate and effective tool for virtual experiments, through which we can analyze the heating pattern and the heating rate as functions of samples size, shape, and electric and heat conduction properties. The similar simulation can be performed using the FDTD method. Our preliminary comparison shows that the integral equation method has higher efficiency than the FDTD method for this example. These simulations are essential to determine what kind of cavity and what control process can lead to a desired heating pattern and re-warming history

Heat-Mass Transfer in Large Cell Suspensions (Cells in a Ternary Cryopreservation Medium: Water-NaCl-DMSO) During the Freezing Process

In this research, continuum theory (macroscopic enthalpy model) for multi-component phase change was applied to study the freezing process of bulk sample (cell suspension in a flat blood bag), coupled with the investigation of microscopic mass transfer across cell membrane. Numerical simulation results indicated that distributions of temperature and solute concentration inside the sample are not uniform during the cooling process. As a consequence, the degrees of cell dehydration are different at various locations.Copyright

Numerical Simulation of Freezing of Biological Tissue

Cryosurgery, the use of controlled freezing process to destroy tissues, has become an accepted treatment for many diseases. Knowledge of the temperature transients of tissues during the controlled cooling is critical to the success of cryosurgery. In this article, a transient heat conduction problem involving freezing of biological tissue is investigated. Based on the continuum model for multi-component phase change system, a new unified equation, which can be applied to frozen, partially frozen and unfrozen tissue region has been developed. In this equation, for the unfrozen region, the influence of blood perfusion has been taken into account. A one dimensional problem was solved numerically. The results predict the temperature profile in the tissue with a controlled cooling rate boundary.Copyright